vendor/llvm-project/llvmorg-10-init-17466-ge26a78e7085

39 files changed, 9087 insertions, 2595 deletions

diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 2c70c0599ecf..04611dadde66 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1174,7 +1174,7 @@ namespace {
     // We analyze lambda bodies separately. Skip them here.
     bool TraverseLambdaExpr(LambdaExpr *LE) {
       // Traverse the captures, but not the body.
-      for (const auto &C : zip(LE->captures(), LE->capture_inits()))
+      for (const auto C : zip(LE->captures(), LE->capture_inits()))
         TraverseLambdaCapture(LE, &std::get<0>(C), std::get<1>(C));
       return true;
     }
diff --git a/clang/lib/Sema/JumpDiagnostics.cpp b/clang/lib/Sema/JumpDiagnostics.cpp
index c8743df90e34..960e62d4a2db 100644
--- a/clang/lib/Sema/JumpDiagnostics.cpp
+++ b/clang/lib/Sema/JumpDiagnostics.cpp
@@ -546,8 +546,8 @@ void JumpScopeChecker::BuildScopeInformation(Stmt *S,
       SmallVector<const Expr *, 4> CommaLHS;
       SmallVector<SubobjectAdjustment, 4> Adjustments;
       const Expr *ExtendedObject =
-          MTE->GetTemporaryExpr()->skipRValueSubobjectAdjustments(
-              CommaLHS, Adjustments);
+          MTE->getSubExpr()->skipRValueSubobjectAdjustments(CommaLHS,
+                                                            Adjustments);
       if (ExtendedObject->getType().isDestructedType()) {
         Scopes.push_back(GotoScope(ParentScope, 0,
                                    diag::note_exits_temporary_dtor,
diff --git a/clang/lib/Sema/MultiplexExternalSemaSource.cpp b/clang/lib/Sema/MultiplexExternalSemaSource.cpp
index b0aa67454a7b..2b0cd6b8c4fc 100644
--- a/clang/lib/Sema/MultiplexExternalSemaSource.cpp
+++ b/clang/lib/Sema/MultiplexExternalSemaSource.cpp
@@ -15,6 +15,8 @@
 
 using namespace clang;
 
+char MultiplexExternalSemaSource::ID;
+
 ///Constructs a new multiplexing external sema source and appends the
 /// given element to it.
 ///
diff --git a/clang/lib/Sema/OpenCLBuiltins.td b/clang/lib/Sema/OpenCLBuiltins.td
index 298614059467..9d6bb411eff8 100644
--- a/clang/lib/Sema/OpenCLBuiltins.td
+++ b/clang/lib/Sema/OpenCLBuiltins.td
@@ -40,6 +40,30 @@ def ConstantAS   : AddressSpace<"clang::LangAS::opencl_constant">;
 def LocalAS      : AddressSpace<"clang::LangAS::opencl_local">;
 def GenericAS    : AddressSpace<"clang::LangAS::opencl_generic">;
 
+// OpenCL language extension.
+class AbstractExtension<string _Ext> {
+  // One or more OpenCL extensions, space separated.  Each extension must be
+  // a valid extension name for the opencl extension pragma.
+  string ExtName = _Ext;
+}
+
+// Extension associated to a builtin function.
+class FunctionExtension<string _Ext> : AbstractExtension<_Ext>;
+
+// FunctionExtension definitions.
+def FuncExtNone                          : FunctionExtension<"">;
+def FuncExtKhrSubgroups                  : FunctionExtension<"cl_khr_subgroups">;
+def FuncExtKhrGlobalInt32BaseAtomics     : FunctionExtension<"cl_khr_global_int32_base_atomics">;
+def FuncExtKhrGlobalInt32ExtendedAtomics : FunctionExtension<"cl_khr_global_int32_extended_atomics">;
+def FuncExtKhrLocalInt32BaseAtomics      : FunctionExtension<"cl_khr_local_int32_base_atomics">;
+def FuncExtKhrLocalInt32ExtendedAtomics  : FunctionExtension<"cl_khr_local_int32_extended_atomics">;
+def FuncExtKhrInt64BaseAtomics           : FunctionExtension<"cl_khr_int64_base_atomics">;
+def FuncExtKhrInt64ExtendedAtomics       : FunctionExtension<"cl_khr_int64_extended_atomics">;
+def FuncExtKhrMipmapImage                : FunctionExtension<"cl_khr_mipmap_image">;
+def FuncExtKhrGlMsaaSharing              : FunctionExtension<"cl_khr_gl_msaa_sharing">;
+
+// Multiple extensions
+def FuncExtKhrMipmapAndWrite3d           : FunctionExtension<"cl_khr_mipmap_image cl_khr_3d_image_writes">;
 
 // Qualified Type.  These map to ASTContext::QualType.
 class QualType<string _Name, bit _IsAbstract=0> {
@@ -180,18 +204,32 @@ class GenericType<string _Ty, TypeList _TypeList, IntList _VectorList> :
   let VecWidth = 0;
 }
 
+// Builtin function attributes.
+def Attr {
+  list<bit> None = [0, 0, 0];
+  list<bit> Pure = [1, 0, 0];
+  list<bit> Const = [0, 1, 0];
+  list<bit> Convergent = [0, 0, 1];
+}
+
 //===----------------------------------------------------------------------===//
 //                      OpenCL C class for builtin functions
 //===----------------------------------------------------------------------===//
-class Builtin<string _Name, list<Type> _Signature> {
+class Builtin<string _Name, list<Type> _Signature, list<bit> _Attributes = Attr.None> {
   // Name of the builtin function
   string Name = _Name;
   // List of types used by the function. The first one is the return type and
   // the following are the arguments. The list must have at least one element
   // (the return type).
   list<Type> Signature = _Signature;
-  // OpenCL Extension to which the function belongs (cl_khr_subgroups, ...)
-  string Extension = "";
+  // Function attribute __attribute__((pure))
+  bit IsPure = _Attributes[0];
+  // Function attribute __attribute__((const))
+  bit IsConst = _Attributes[1];
+  // Function attribute __attribute__((convergent))
+  bit IsConv = _Attributes[2];
+  // OpenCL extensions to which the function belongs.
+  FunctionExtension Extension = FuncExtNone;
   // Version of OpenCL from which the function is available (e.g.: CL10).
   // MinVersion is inclusive.
   Version MinVersion = CL10;
@@ -260,10 +298,25 @@ def Event             : Type<"Event", QualType<"OCLEventTy">>;
 def VecAndScalar: IntList<"VecAndScalar", [1, 2, 3, 4, 8, 16]>;
 def VecNoScalar : IntList<"VecNoScalar", [2, 3, 4, 8, 16]>;
 def Vec1        : IntList<"Vec1", [1]>;
+def Vec2        : IntList<"Vec2", [2]>;
+def Vec4        : IntList<"Vec4", [4]>;
+def Vec8        : IntList<"Vec8", [8]>;
+def Vec16       : IntList<"Vec16", [16]>;
+def Vec1234     : IntList<"Vec1234", [1, 2, 3, 4]>;
 
 // Type lists.
-def TLAll   : TypeList<"TLAll", [Char, UChar, Short, UShort, Int, UInt, Long, ULong, Float, Double, Half]>;
+def TLAll         : TypeList<"TLAll", [Char,  UChar, Short,  UShort, Int,  UInt, Long,  ULong, Float, Double, Half]>;
+def TLAllUnsigned : TypeList<"TLAllUnsigned", [UChar, UChar, UShort, UShort, UInt, UInt, ULong, ULong, UInt,  ULong,  UShort]>;
 def TLFloat : TypeList<"TLFloat", [Float, Double, Half]>;
+def TLSignedInts   : TypeList<"TLSignedInts", [Char, Short, Int, Long]>;
+def TLUnsignedInts : TypeList<"TLUnsignedInts", [UChar, UShort, UInt, ULong]>;
+
+def TLIntLongFloats : TypeList<"TLIntLongFloats", [Int, UInt, Long, ULong, Float, Double, Half]>;
+
+// All unsigned integer types twice, to facilitate unsigned return types for e.g.
+// uchar abs(char) and
+// uchar abs(uchar).
+def TLAllUIntsTwice : TypeList<"TLAllUIntsTwice", [UChar, UChar, UShort, UShort, UInt, UInt, ULong, ULong]>;
 
 def TLAllInts : TypeList<"TLAllInts", [Char, UChar, Short, UShort, Int, UInt, Long, ULong]>;
 
@@ -276,8 +329,16 @@ def AGenTypeNNoScalar      : GenericType<"AGenTypeNNoScalar", TLAll, VecNoScalar
 def AIGenType1             : GenericType<"AIGenType1", TLAllInts, Vec1>;
 def AIGenTypeN             : GenericType<"AIGenTypeN", TLAllInts, VecAndScalar>;
 def AIGenTypeNNoScalar     : GenericType<"AIGenTypeNNoScalar", TLAllInts, VecNoScalar>;
+// All integer to unsigned
+def AI2UGenTypeN           : GenericType<"AI2UGenTypeN", TLAllUIntsTwice, VecAndScalar>;
+// Signed integer
+def SGenTypeN              : GenericType<"SGenTypeN", TLSignedInts, VecAndScalar>;
+// Unsigned integer
+def UGenTypeN              : GenericType<"UGenTypeN", TLUnsignedInts, VecAndScalar>;
 // Float
 def FGenTypeN              : GenericType<"FGenTypeN", TLFloat, VecAndScalar>;
+// (u)int, (u)long, and all floats
+def IntLongFloatGenType1   : GenericType<"IntLongFloatGenType1", TLIntLongFloats, Vec1>;
 
 // GenType definitions for every single base type (e.g. fp32 only).
 // Names are like: GenTypeFloatVecAndScalar.
@@ -292,6 +353,14 @@ foreach Type = [Char, UChar, Short, UShort,
   }
 }
 
+// GenType definitions for vec1234.
+foreach Type = [Float, Double, Half] in {
+  def "GenType" # Type # Vec1234 :
+              GenericType<"GenType" # Type # Vec1234,
+                          TypeList<"GL" # Type.Name, [Type]>,
+                          Vec1234>;
+}
+
 
 //===----------------------------------------------------------------------===//
 //                 Definitions of OpenCL builtin functions
@@ -307,11 +376,12 @@ foreach RType = [Float, Double, Half, Char, UChar, Short,
                    UShort, Int, UInt, Long, ULong] in {
     foreach sat = ["", "_sat"] in {
       foreach rnd = ["", "_rte", "_rtn", "_rtp", "_rtz"] in {
-        def : Builtin<"convert_" # RType.Name # sat # rnd, [RType, IType]>;
+        def : Builtin<"convert_" # RType.Name # sat # rnd, [RType, IType],
+                      Attr.Const>;
         foreach v = [2, 3, 4, 8, 16] in {
           def : Builtin<"convert_" # RType.Name # v # sat # rnd,
-                        [VectorType<RType, v>,
-                         VectorType<IType, v>]>;
+                        [VectorType<RType, v>, VectorType<IType, v>],
+                        Attr.Const>;
         }
       }
     }
@@ -321,11 +391,11 @@ foreach RType = [Float, Double, Half, Char, UChar, Short,
 //--------------------------------------------------------------------
 // OpenCL v1.1 s6.11.1, v1.2 s6.12.1, v2.0 s6.13.1 - Work-item Functions
 // --- Table 7 ---
-def : Builtin<"get_work_dim", [UInt]>;
+def : Builtin<"get_work_dim", [UInt], Attr.Const>;
 foreach name = ["get_global_size", "get_global_id", "get_local_size",
                 "get_local_id", "get_num_groups", "get_group_id",
                 "get_global_offset"] in {
-  def : Builtin<name, [Size, UInt]>;
+  def : Builtin<name, [Size, UInt], Attr.Const>;
 }
 
 let MinVersion = CL20 in {
@@ -335,9 +405,303 @@ let MinVersion = CL20 in {
   }
 }
 
+
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.2, v1.2 s6.12.2, v2.0 s6.13.2 - Math functions
+// OpenCL Extension v2.0 s5.1.2 and s6.1.2 - Math Functions
+// --- Table 8 ---
+// --- 1 argument ---
+foreach name = ["acos", "acosh", "acospi",
+                "asin", "asinh", "asinpi",
+                "atan", "atanh", "atanpi",
+                "cbrt", "ceil",
+                "cos", "cosh", "cospi",
+                "erfc", "erf",
+                "exp", "exp2", "exp10", "expm1",
+                "fabs", "floor",
+                "log", "log2", "log10", "log1p", "logb",
+                "rint", "round", "rsqrt",
+                "sin", "sinh", "sinpi",
+                "sqrt",
+                "tan", "tanh", "tanpi",
+                "tgamma", "trunc",
+                "lgamma"] in {
+    def : Builtin<name, [FGenTypeN, FGenTypeN], Attr.Const>;
+}
+foreach name = ["nan"] in {
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecAndScalar, GenTypeULongVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecAndScalar, GenTypeUShortVecAndScalar], Attr.Const>;
+}
+
+// --- 2 arguments ---
+foreach name = ["atan2", "atan2pi", "copysign", "fdim", "fmod", "hypot",
+                "maxmag", "minmag", "nextafter", "pow", "powr",
+                "remainder"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+}
+foreach name = ["fmax", "fmin"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, GenTypeFloatVecNoScalar, Float], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar, Double], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar, Half], Attr.Const>;
+}
+foreach name = ["ilogb"] in {
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeFloatVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeDoubleVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeHalfVecAndScalar], Attr.Const>;
+}
+foreach name = ["ldexp"] in {
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, GenTypeFloatVecNoScalar, Int], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar, Int], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar, Int], Attr.Const>;
+}
+foreach name = ["pown", "rootn"] in {
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+}
+
+// --- 3 arguments ---
+foreach name = ["fma", "mad"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+}
+
+// --- Version dependent ---
+let MaxVersion = CL20 in {
+  foreach AS = [GlobalAS, LocalAS, PrivateAS] in {
+    foreach name = ["fract", "modf", "sincos"] in {
+      def : Builtin<name, [FGenTypeN, FGenTypeN, PointerType<FGenTypeN, AS>]>;
+    }
+    foreach name = ["frexp", "lgamma_r"] in {
+      foreach Type = [GenTypeFloatVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeHalfVecAndScalar] in {
+        def : Builtin<name, [Type, Type, PointerType<GenTypeIntVecAndScalar, AS>]>;
+      }
+    }
+    foreach name = ["remquo"] in {
+      foreach Type = [GenTypeFloatVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeHalfVecAndScalar] in {
+        def : Builtin<name, [Type, Type, Type, PointerType<GenTypeIntVecAndScalar, AS>]>;
+      }
+    }
+  }
+}
+let MinVersion = CL20 in {
+  foreach name = ["fract", "modf", "sincos"] in {
+    def : Builtin<name, [FGenTypeN, FGenTypeN, PointerType<FGenTypeN, GenericAS>]>;
+  }
+  foreach name = ["frexp", "lgamma_r"] in {
+    foreach Type = [GenTypeFloatVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeHalfVecAndScalar] in {
+      def : Builtin<name, [Type, Type, PointerType<GenTypeIntVecAndScalar, GenericAS>]>;
+    }  }
+  foreach name = ["remquo"] in {
+    foreach Type = [GenTypeFloatVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeHalfVecAndScalar] in {
+      def : Builtin<name, [Type, Type, Type, PointerType<GenTypeIntVecAndScalar, GenericAS>]>;
+    }
+  }
+}
+
+// --- Table 9 ---
+foreach name = ["half_cos",
+                "half_exp", "half_exp2", "half_exp10",
+                "half_log", "half_log2", "half_log10",
+                "half_recip", "half_rsqrt",
+                "half_sin", "half_sqrt", "half_tan",
+                "native_cos",
+                "native_exp", "native_exp2", "native_exp10",
+                "native_log", "native_log2", "native_log10",
+                "native_recip", "native_rsqrt",
+                "native_sin", "native_sqrt", "native_tan"] in {
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar], Attr.Const>;
+}
+foreach name = ["half_divide", "half_powr",
+                "native_divide", "native_powr"] in {
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar], Attr.Const>;
+}
+
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.3, v1.2 s6.12.3, v2.0 s6.13.3 - Integer Functions
+// --- Table 10 ---
+// --- 1 argument ---
+foreach name = ["abs"] in {
+  def : Builtin<name, [AI2UGenTypeN, AIGenTypeN], Attr.Const>;
+}
+foreach name = ["clz", "popcount"] in {
+  def : Builtin<name, [AIGenTypeN, AIGenTypeN], Attr.Const>;
+}
+let MinVersion = CL20 in {
+  foreach name = ["ctz"] in {
+    def : Builtin<name, [AIGenTypeN, AIGenTypeN]>;
+  }
+}
+
+// --- 2 arguments ---
+foreach name = ["abs_diff"] in {
+  def : Builtin<name, [AI2UGenTypeN, AIGenTypeN, AIGenTypeN], Attr.Const>;
+}
+foreach name = ["add_sat", "hadd", "rhadd", "mul_hi", "rotate", "sub_sat"] in {
+  def : Builtin<name, [AIGenTypeN, AIGenTypeN, AIGenTypeN], Attr.Const>;
+}
+foreach name = ["max", "min"] in {
+  def : Builtin<name, [AIGenTypeN, AIGenTypeN, AIGenTypeN], Attr.Const>;
+  def : Builtin<name, [AIGenTypeNNoScalar, AIGenTypeNNoScalar, AIGenType1], Attr.Const>;
+}
+foreach name = ["upsample"] in {
+  def : Builtin<name, [GenTypeShortVecAndScalar, GenTypeCharVecAndScalar, GenTypeUCharVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeUShortVecAndScalar, GenTypeUCharVecAndScalar, GenTypeUCharVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeShortVecAndScalar, GenTypeUShortVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeUIntVecAndScalar, GenTypeUShortVecAndScalar, GenTypeUShortVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeLongVecAndScalar, GenTypeIntVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeULongVecAndScalar, GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+}
+
+// --- 3 arguments ---
+foreach name = ["clamp"] in {
+  def : Builtin<name, [AIGenTypeN, AIGenTypeN, AIGenTypeN, AIGenTypeN], Attr.Const>;
+  def : Builtin<name, [AIGenTypeNNoScalar, AIGenTypeNNoScalar, AIGenType1, AIGenType1], Attr.Const>;
+}
+foreach name = ["mad_hi", "mad_sat"] in {
+  def : Builtin<name, [AIGenTypeN, AIGenTypeN, AIGenTypeN, AIGenTypeN], Attr.Const>;
+}
+
+// --- Table 11 ---
+foreach name = ["mad24"] in {
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeIntVecAndScalar, GenTypeIntVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+}
+foreach name = ["mul24"] in {
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeIntVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+}
+
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.4, v1.2 s6.12.4, v2.0 s6.13.4 - Common Functions
+// OpenCL Extension v2.0 s5.1.3 and s6.1.3 - Common Functions
+// --- Table 12 ---
+// --- 1 argument ---
+foreach name = ["degrees", "radians", "sign"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN], Attr.Const>;
+}
+
+// --- 2 arguments ---
+foreach name = ["max", "min"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, GenTypeFloatVecNoScalar, Float], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar, Double], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar, Half], Attr.Const>;
+}
+foreach name = ["step"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, Float, GenTypeFloatVecNoScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, Double, GenTypeDoubleVecNoScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, Half, GenTypeHalfVecNoScalar], Attr.Const>;
+}
+
+// --- 3 arguments ---
+foreach name = ["clamp", "mix"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, GenTypeFloatVecNoScalar, Float, Float], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar, Double, Double], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar, Half, Half], Attr.Const>;
+}
+foreach name = ["smoothstep"] in {
+  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN, FGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecNoScalar, Float, Float, GenTypeFloatVecNoScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecNoScalar, Double, Double, GenTypeDoubleVecNoScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecNoScalar, Half, Half, GenTypeHalfVecNoScalar], Attr.Const>;
+}
+
+
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.5, v1.2 s6.12.5, v2.0 s6.13.5 - Geometric Functions
+// OpenCL Extension v2.0 s5.1.4 and s6.1.4 - Geometric Functions
+// --- Table 13 ---
+// --- 1 argument ---
+foreach name = ["length"] in {
+  def : Builtin<name, [Float, GenTypeFloatVec1234], Attr.Const>;
+  def : Builtin<name, [Double, GenTypeDoubleVec1234], Attr.Const>;
+  def : Builtin<name, [Half, GenTypeHalfVec1234], Attr.Const>;
+}
+foreach name = ["normalize"] in {
+  def : Builtin<name, [GenTypeFloatVec1234, GenTypeFloatVec1234], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVec1234, GenTypeDoubleVec1234], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVec1234, GenTypeHalfVec1234], Attr.Const>;
+}
+foreach name = ["fast_length"] in {
+  def : Builtin<name, [Float, GenTypeFloatVec1234], Attr.Const>;
+}
+foreach name = ["fast_normalize"] in {
+  def : Builtin<name, [GenTypeFloatVec1234, GenTypeFloatVec1234], Attr.Const>;
+}
+
+// --- 2 arguments ---
+foreach name = ["cross"] in {
+  foreach VSize = [3, 4] in {
+    def : Builtin<name, [VectorType<Float, VSize>, VectorType<Float, VSize>, VectorType<Float, VSize>], Attr.Const>;
+    def : Builtin<name, [VectorType<Double, VSize>, VectorType<Double, VSize>, VectorType<Double, VSize>], Attr.Const>;
+    def : Builtin<name, [VectorType<Half, VSize>, VectorType<Half, VSize>, VectorType<Half, VSize>], Attr.Const>;
+  }
+}
+foreach name = ["dot", "distance"] in {
+  def : Builtin<name, [Float, GenTypeFloatVec1234, GenTypeFloatVec1234], Attr.Const>;
+  def : Builtin<name, [Double, GenTypeDoubleVec1234, GenTypeDoubleVec1234], Attr.Const>;
+  def : Builtin<name, [Half, GenTypeHalfVec1234, GenTypeHalfVec1234], Attr.Const>;
+}
+foreach name = ["fast_distance"] in {
+  def : Builtin<name, [Float, GenTypeFloatVec1234, GenTypeFloatVec1234], Attr.Const>;
+}
+
+
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.6, v1.2 s6.12.6, v2.0 s6.13.6 - Relational Functions
+// OpenCL Extension v2.0 s5.1.5 and s6.1.5 - Relational Functions
+// --- Table 14 ---
+// --- 1 argument ---
+foreach name = ["isfinite", "isinf", "isnan", "isnormal", "signbit"] in {
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeFloatVecAndScalar], Attr.Const>;
+  def : Builtin<name, [Int, Double], Attr.Const>;
+  def : Builtin<name, [GenTypeLongVecNoScalar, GenTypeDoubleVecNoScalar], Attr.Const>;
+  def : Builtin<name, [Int, Half], Attr.Const>;
+  def : Builtin<name, [GenTypeShortVecNoScalar, GenTypeHalfVecNoScalar], Attr.Const>;
+}
+foreach name = ["any", "all"] in {
+  def : Builtin<name, [Int, AIGenTypeN], Attr.Const>;
+}
+
+// --- 2 arguments ---
+foreach name = ["isequal", "isnotequal", "isgreater", "isgreaterequal",
+                "isless", "islessequal", "islessgreater", "isordered",
+                "isunordered"] in {
+  def : Builtin<name, [GenTypeIntVecAndScalar, GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar], Attr.Const>;
+  def : Builtin<name, [Int, Double, Double], Attr.Const>;
+  def : Builtin<name, [GenTypeLongVecNoScalar, GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar], Attr.Const>;
+  def : Builtin<name, [Int, Half, Half], Attr.Const>;
+  def : Builtin<name, [GenTypeShortVecNoScalar, GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar], Attr.Const>;
+}
+
+// --- 3 arguments ---
+foreach name = ["bitselect"] in {
+  def : Builtin<name, [AGenTypeN, AGenTypeN, AGenTypeN, AGenTypeN], Attr.Const>;
+}
+foreach name = ["select"] in {
+  def : Builtin<name, [SGenTypeN, SGenTypeN, SGenTypeN, SGenTypeN], Attr.Const>;
+  def : Builtin<name, [SGenTypeN, SGenTypeN, SGenTypeN, UGenTypeN], Attr.Const>;
+  def : Builtin<name, [UGenTypeN, UGenTypeN, UGenTypeN, UGenTypeN], Attr.Const>;
+  def : Builtin<name, [UGenTypeN, UGenTypeN, UGenTypeN, SGenTypeN], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeFloatVecAndScalar, GenTypeUIntVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeLongVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeDoubleVecAndScalar, GenTypeULongVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeShortVecAndScalar], Attr.Const>;
+  def : Builtin<name, [GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeHalfVecAndScalar, GenTypeUShortVecAndScalar], Attr.Const>;
+}
+
+
 //--------------------------------------------------------------------
 // OpenCL v1.1 s6.11.7, v1.2 s6.12.7, v2.0 s6.13.7 - Vector Data Load and Store Functions
-// OpenCL Extension v1.1 s9.3.6 and s9.6.6, v1.2 s9.5.6, v2.0 s9.4.6, v2.0 s5.1.6 and 6.1.6 - Vector Data Load and Store Functions
+// OpenCL Extension v1.1 s9.3.6 and s9.6.6, v1.2 s9.5.6, v2.0 s5.1.6 and s6.1.6 - Vector Data Load and Store Functions
 // --- Table 15 ---
 // Variants for OpenCL versions below 2.0, using pointers to the global, local
 // and private address spaces.
@@ -448,6 +812,55 @@ foreach VSize = [2, 3, 4, 8, 16] in {
     }
   }
 }
+let MaxVersion = CL20 in {
+  foreach AS = [GlobalAS, LocalAS, PrivateAS] in {
+    def : Builtin<"vload_half", [Float, Size, PointerType<ConstType<Half>, AS>]>;
+    foreach VSize = [2, 3, 4, 8, 16] in {
+      foreach name = ["vload_half" # VSize] in {
+        def : Builtin<name, [VectorType<Float, VSize>, Size, PointerType<ConstType<Half>, AS>]>;
+      }
+    }
+    foreach rnd = ["", "_rte", "_rtz", "_rtp", "_rtn"] in {
+      def : Builtin<"vstore_half" # rnd, [Void, Float, Size, PointerType<Half, AS>]>;
+      def : Builtin<"vstore_half" # rnd, [Void, Double, Size, PointerType<Half, AS>]>;
+      foreach VSize = [2, 3, 4, 8, 16] in {
+        foreach name = ["vstore_half" # VSize # rnd] in {
+          def : Builtin<name, [Void, VectorType<Float, VSize>, Size, PointerType<Half, AS>]>;
+          def : Builtin<name, [Void, VectorType<Double, VSize>, Size, PointerType<Half, AS>]>;
+        }
+      }
+    }
+  }
+}
+let MinVersion = CL20 in {
+  foreach AS = [GenericAS] in {
+    def : Builtin<"vload_half", [Float, Size, PointerType<ConstType<Half>, AS>]>;
+    foreach VSize = [2, 3, 4, 8, 16] in {
+      foreach name = ["vload_half" # VSize] in {
+        def : Builtin<name, [VectorType<Float, VSize>, Size, PointerType<ConstType<Half>, AS>]>;
+      }
+    }
+    foreach rnd = ["", "_rte", "_rtz", "_rtp", "_rtn"] in {
+      def : Builtin<"vstore_half" # rnd, [Void, Float, Size, PointerType<Half, AS>]>;
+      def : Builtin<"vstore_half" # rnd, [Void, Double, Size, PointerType<Half, AS>]>;
+      foreach VSize = [2, 3, 4, 8, 16] in {
+        foreach name = ["vstore_half" # VSize # rnd] in {
+          def : Builtin<name, [Void, VectorType<Float, VSize>, Size, PointerType<Half, AS>]>;
+          def : Builtin<name, [Void, VectorType<Double, VSize>, Size, PointerType<Half, AS>]>;
+        }
+      }
+    }
+  }
+}
+
+foreach AS = [ConstantAS] in {
+  def : Builtin<"vload_half", [Float, Size, PointerType<ConstType<Half>, AS>]>;
+  foreach VSize = [2, 3, 4, 8, 16] in {
+    foreach name = ["vload_half" # VSize] in {
+      def : Builtin<name, [VectorType<Float, VSize>, Size, PointerType<ConstType<Half>, AS>]>;
+    }
+  }
+}
 
 //--------------------------------------------------------------------
 // OpenCL v1.1 s6.11.10, v1.2 s6.12.10, v2.0 s6.13.10: Async Copies from Global to Local Memory, Local to Global Memory, and Prefetch
@@ -473,42 +886,116 @@ foreach name = ["prefetch"] in {
 // Functions that use memory_order and cl_mem_fence_flags enums are not
 // declared here as the TableGen backend does not handle enums.
 
-// OpenCL v1.0 s9.5, s9.6, s9.7 - Atomic Functions for 32-bit integers.
+// OpenCL v1.0 s9.5, s9.6, s9.7 - Atomic Functions for 32-bit integers
 // --- Table 9.1 ---
-foreach Type = [Int, UInt] in {
-  foreach name = ["atom_add", "atom_sub", "atom_xchg"] in {
-    def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>, Type]>;
+let Extension = FuncExtKhrGlobalInt32BaseAtomics in {
+  foreach Type = [Int, UInt] in {
+    foreach name = ["atom_add", "atom_sub", "atom_xchg"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>, Type]>;
+    }
+    foreach name = ["atom_inc", "atom_dec"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>]>;
+    }
+    foreach name = ["atom_cmpxchg"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>, Type, Type]>;
+    }
+  }
+}
+// --- Table 9.3 ---
+let Extension = FuncExtKhrLocalInt32BaseAtomics in {
+  foreach Type = [Int, UInt] in {
+    foreach name = ["atom_add", "atom_sub", "atom_xchg"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, LocalAS>, Type]>;
+    }
+    foreach name = ["atom_inc", "atom_dec"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, LocalAS>]>;
+    }
+    foreach name = ["atom_cmpxchg"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, LocalAS>, Type, Type]>;
+    }
+  }
+}
+// --- Table 9.5 ---
+let Extension = FuncExtKhrInt64BaseAtomics in {
+  foreach AS = [GlobalAS, LocalAS] in {
+    foreach Type = [Long, ULong] in {
+      foreach name = ["atom_add", "atom_sub", "atom_xchg"] in {
+        def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>, Type]>;
+      }
+      foreach name = ["atom_inc", "atom_dec"] in {
+        def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>]>;
+      }
+      foreach name = ["atom_cmpxchg"] in {
+        def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>, Type, Type]>;
+      }
+    }
   }
-  foreach name = ["atom_inc", "atom_dec"] in {
-    def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>]>;
+}
+// --- Table 9.2 ---
+let Extension = FuncExtKhrGlobalInt32ExtendedAtomics in {
+  foreach Type = [Int, UInt] in {
+    foreach name = ["atom_min", "atom_max", "atom_and",
+                    "atom_or", "atom_xor"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>, Type]>;
+    }
   }
-  foreach name = ["atom_cmpxchg"] in {
-    def : Builtin<name, [Type, PointerType<VolatileType<Type>, GlobalAS>, Type, Type]>;
+}
+// --- Table 9.4 ---
+let Extension = FuncExtKhrLocalInt32ExtendedAtomics in {
+  foreach Type = [Int, UInt] in {
+    foreach name = ["atom_min", "atom_max", "atom_and",
+                    "atom_or", "atom_xor"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, LocalAS>, Type]>;
+    }
   }
 }
-
-// OpenCL v1.2 s6.12.2: Math Functions
-foreach name = ["acos", "acosh", "acospi",
-                "asin", "asinh", "asinpi",
-                "atan", "atanh", "atanpi"] in {
-  def : Builtin<name, [FGenTypeN, FGenTypeN]>;
+// --- Table 9.6 ---
+let Extension = FuncExtKhrInt64ExtendedAtomics in {
+  foreach AS = [GlobalAS, LocalAS] in {
+    foreach Type = [Long, ULong] in {
+      foreach name = ["atom_min", "atom_max", "atom_and",
+                      "atom_or", "atom_xor"] in {
+        def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>, Type]>;
+      }
+    }
+  }
 }
-
-foreach name = ["atan2", "atan2pi"] in {
-  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN]>;
+// OpenCL v1.1 s6.11.1, v1.2 s6.12.11 - Atomic Functions
+foreach AS = [GlobalAS, LocalAS] in {
+  foreach Type = [Int, UInt] in {
+    foreach name = ["atomic_add", "atomic_sub", "atomic_xchg",
+                    "atomic_min", "atomic_max", "atomic_and",
+                    "atomic_or", "atomic_xor"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>, Type]>;
+    }
+    foreach name = ["atomic_inc", "atomic_dec"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>]>;
+    }
+    foreach name = ["atomic_cmpxchg"] in {
+      def : Builtin<name, [Type, PointerType<VolatileType<Type>, AS>, Type, Type]>;
+    }
+  }
 }
 
-foreach name = ["fmax", "fmin"] in {
-  def : Builtin<name, [FGenTypeN, FGenTypeN, FGenTypeN]>;
-  def : Builtin<name, [GenTypeFloatVecNoScalar, GenTypeFloatVecNoScalar, Float]>;
-  def : Builtin<name, [GenTypeDoubleVecNoScalar, GenTypeDoubleVecNoScalar, Double]>;
-  def : Builtin<name, [GenTypeHalfVecNoScalar, GenTypeHalfVecNoScalar, Half]>;
+//--------------------------------------------------------------------
+// OpenCL v1.1 s6.11.12, v1.2 s6.12.12, v2.0 s6.13.12 - Miscellaneous Vector Functions
+// --- Table 19 ---
+foreach VSize1 = [Vec2, Vec4, Vec8, Vec16] in {
+  foreach VSize2 = [Vec2, Vec4, Vec8, Vec16] in {
+    def : Builtin<"shuffle", [GenericType<"TLAll" # VSize1.Name, TLAll, VSize1>,
+                              GenericType<"TLAll" # VSize2.Name, TLAll, VSize2>,
+                              GenericType<"TLAllUnsigned" # VSize1.Name, TLAllUnsigned, VSize1>],
+                  Attr.Const>;
+  }
 }
-
-// OpenCL v1.1 s6.11.3, v1.2 s6.12.3, v2.0 s6.13.3 - Integer Functions
-foreach name = ["max", "min"] in {
-  def : Builtin<name, [AIGenTypeN, AIGenTypeN, AIGenTypeN]>;
-  def : Builtin<name, [AIGenTypeNNoScalar, AIGenTypeNNoScalar, AIGenType1]>;
+foreach VSize1 = [Vec2, Vec4, Vec8, Vec16] in {
+  foreach VSize2 = [Vec2, Vec4, Vec8, Vec16] in {
+    def : Builtin<"shuffle2", [GenericType<"TLAll" # VSize1.Name, TLAll, VSize1>,
+                               GenericType<"TLAll" # VSize2.Name, TLAll, VSize2>,
+                               GenericType<"TLAll" # VSize2.Name, TLAll, VSize2>,
+                               GenericType<"TLAllUnsigned" # VSize1.Name, TLAllUnsigned, VSize1>],
+                  Attr.Const>;
+  }
 }
 
 //--------------------------------------------------------------------
@@ -517,49 +1004,49 @@ foreach name = ["max", "min"] in {
 // --- Table 22: Image Read Functions with Samplers ---
 foreach imgTy = [Image1d] in {
   foreach coordTy = [Int, Float] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, coordTy]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, coordTy]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, coordTy]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, coordTy], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, coordTy], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, coordTy], Attr.Pure>;
   }
 }
 foreach imgTy = [Image2d, Image1dArray] in {
   foreach coordTy = [Int, Float] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 2>], Attr.Pure>;
   }
 }
 foreach imgTy = [Image3d, Image2dArray] in {
   foreach coordTy = [Int, Float] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, "RO">, Sampler, VectorType<coordTy, 4>], Attr.Pure>;
   }
 }
 foreach coordTy = [Int, Float] in {
-  def : Builtin<"read_imagef", [Float, ImageType<Image2dDepth, "RO">, Sampler, VectorType<coordTy, 2>]>;
-  def : Builtin<"read_imagef", [Float, ImageType<Image2dArrayDepth, "RO">, Sampler, VectorType<coordTy, 4>]>;
+  def : Builtin<"read_imagef", [Float, ImageType<Image2dDepth, "RO">, Sampler, VectorType<coordTy, 2>], Attr.Pure>;
+  def : Builtin<"read_imagef", [Float, ImageType<Image2dArrayDepth, "RO">, Sampler, VectorType<coordTy, 4>], Attr.Pure>;
 }
 
 // --- Table 23: Sampler-less Read Functions ---
 foreach aQual = ["RO", "RW"] in {
   foreach imgTy = [Image2d, Image1dArray] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>], Attr.Pure>;
   }
   foreach imgTy = [Image3d, Image2dArray] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>], Attr.Pure>;
   }
   foreach imgTy = [Image1d, Image1dBuffer] in {
-    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, Int]>;
-    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, Int]>;
-    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Int]>;
+    def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, Int], Attr.Pure>;
+    def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, Int], Attr.Pure>;
+    def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Int], Attr.Pure>;
   }
-  def : Builtin<"read_imagef", [Float, ImageType<Image2dDepth, aQual>, VectorType<Int, 2>]>;
-  def : Builtin<"read_imagef", [Float, ImageType<Image2dArrayDepth, aQual>, VectorType<Int, 4>]>;
+  def : Builtin<"read_imagef", [Float, ImageType<Image2dDepth, aQual>, VectorType<Int, 2>], Attr.Pure>;
+  def : Builtin<"read_imagef", [Float, ImageType<Image2dArrayDepth, aQual>, VectorType<Int, 4>], Attr.Pure>;
 }
 
 // --- Table 24: Image Write Functions ---
@@ -624,13 +1111,13 @@ foreach aQual = ["RO"] in {
   foreach name = ["read_imageh"] in {
     foreach coordTy = [Int, Float] in {
       foreach imgTy = [Image2d, Image1dArray] in {
-        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<coordTy, 2>]>;
+        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<coordTy, 2>], Attr.Pure>;
       }
       foreach imgTy = [Image3d, Image2dArray] in {
-        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<coordTy, 4>]>;
+        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<coordTy, 4>], Attr.Pure>;
       }
       foreach imgTy = [Image1d] in {
-        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, coordTy]>;
+        def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Sampler, coordTy], Attr.Pure>;
       }
     }
   }
@@ -640,13 +1127,13 @@ foreach aQual = ["RO"] in {
 foreach aQual = ["RO", "RW"] in {
   foreach name = ["read_imageh"] in {
     foreach imgTy = [Image2d, Image1dArray] in {
-      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>]>;
+      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>], Attr.Pure>;
     }
     foreach imgTy = [Image3d, Image2dArray] in {
-      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>]>;
+      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>], Attr.Pure>;
     }
     foreach imgTy = [Image1d, Image1dBuffer] in {
-      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Int]>;
+      def : Builtin<name, [VectorType<Half, 4>, ImageType<imgTy, aQual>, Int], Attr.Pure>;
     }
   }
 }
@@ -664,11 +1151,201 @@ foreach aQual = ["WO", "RW"] in {
 }
 
 
+//--------------------------------------------------------------------
+// OpenCL v2.0 s6.13.15 - Work-group Functions
+// --- Table 26 ---
+let MinVersion = CL20 in {
+  foreach name = ["work_group_all", "work_group_any"] in {
+    def : Builtin<name, [Int, Int], Attr.Convergent>;
+  }
+  foreach name = ["work_group_broadcast"] in {
+    def : Builtin<name, [IntLongFloatGenType1, IntLongFloatGenType1, Size], Attr.Convergent>;
+    def : Builtin<name, [IntLongFloatGenType1, IntLongFloatGenType1, Size, Size], Attr.Convergent>;
+    def : Builtin<name, [IntLongFloatGenType1, IntLongFloatGenType1, Size, Size, Size], Attr.Convergent>;
+  }
+  foreach op = ["add", "min", "max"] in {
+    foreach name = ["work_group_reduce_", "work_group_scan_exclusive_",
+                    "work_group_scan_inclusive_"] in {
+      def : Builtin<name # op, [IntLongFloatGenType1, IntLongFloatGenType1], Attr.Convergent>;
+    }
+  }
+}
+
+
 // OpenCL v2.0 s9.17.3: Additions to section 6.13.1: Work-Item Functions
 let MinVersion = CL20 in {
-  let Extension = "cl_khr_subgroups" in {
+  let Extension = FuncExtKhrSubgroups in {
     def get_sub_group_size : Builtin<"get_sub_group_size", [UInt]>;
     def get_max_sub_group_size : Builtin<"get_max_sub_group_size", [UInt]>;
     def get_num_sub_groups : Builtin<"get_num_sub_groups", [UInt]>;
   }
 }
+
+//--------------------------------------------------------------------
+// End of the builtin functions defined in the OpenCL C specification.
+// Builtin functions defined in the OpenCL C Extension are below.
+//--------------------------------------------------------------------
+
+
+// OpenCL Extension v2.0 s9.18 - Mipmaps
+let Extension = FuncExtKhrMipmapImage in {
+  // Added to section 6.13.14.2.
+  foreach aQual = ["RO"] in {
+    foreach imgTy = [Image2d] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+      foreach name = ["read_imagei"] in {
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+      foreach name = ["read_imageui"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image2dDepth] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [Float, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [Float, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image1d] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imagei"] in {
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imageui"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, Float, Float, Float], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image3d] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 4>, VectorType<Float, 4>], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imagei"] in {
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 4>, VectorType<Float, 4>], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imageui"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 4>, VectorType<Float, 4>], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image1dArray] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imagei"] in {
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float, Float], Attr.Pure>;
+      }
+      foreach name = ["read_imageui"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 2>, Float, Float], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image2dArray] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Float, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+      foreach name = ["read_imagei"] in {
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<Int, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+      foreach name = ["read_imageui"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+    }
+    foreach imgTy = [Image2dArrayDepth] in {
+      foreach name = ["read_imagef"] in {
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, Float], Attr.Pure>;
+        def : Builtin<name, [VectorType<UInt, 4>, ImageType<imgTy, aQual>, Sampler, VectorType<Float, 4>, VectorType<Float, 2>, VectorType<Float, 2>], Attr.Pure>;
+      }
+    }
+  }
+  // Added to section 6.13.14.4.
+  foreach aQual = ["WO"] in {
+    foreach imgTy = [Image2d] in {
+      def : Builtin<"write_imagef", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<Float, 4>]>;
+      def : Builtin<"write_imagei", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<Int, 4>]>;
+      def : Builtin<"write_imageui", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<UInt, 4>]>;
+    }
+    def : Builtin<"write_imagef", [Void, ImageType<Image2dDepth, aQual>, VectorType<Int, 2>, Int, Float]>;
+    foreach imgTy = [Image1d] in {
+      def : Builtin<"write_imagef", [Void, ImageType<imgTy, aQual>, Int, Int, VectorType<Float, 4>]>;
+      def : Builtin<"write_imagei", [Void, ImageType<imgTy, aQual>, Int, Int, VectorType<Int, 4>]>;
+      def : Builtin<"write_imageui", [Void, ImageType<imgTy, aQual>, Int, Int, VectorType<UInt, 4>]>;
+    }
+    foreach imgTy = [Image1dArray] in {
+      def : Builtin<"write_imagef", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<Float, 4>]>;
+      def : Builtin<"write_imagei", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<Int, 4>]>;
+      def : Builtin<"write_imageui", [Void, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int, VectorType<UInt, 4>]>;
+    }
+    foreach imgTy = [Image2dArray] in {
+      def : Builtin<"write_imagef", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<Float, 4>]>;
+      def : Builtin<"write_imagei", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<Int, 4>]>;
+      def : Builtin<"write_imageui", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<UInt, 4>]>;
+    }
+    def : Builtin<"write_imagef", [Void, ImageType<Image2dArrayDepth, aQual>, VectorType<Int, 4>, Int, Float]>;
+    let Extension = FuncExtKhrMipmapAndWrite3d in {
+      foreach imgTy = [Image3d] in {
+        def : Builtin<"write_imagef", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<Float, 4>]>;
+        def : Builtin<"write_imagei", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<Int, 4>]>;
+        def : Builtin<"write_imageui", [Void, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int, VectorType<UInt, 4>]>;
+      }
+    }
+  }
+  // Added to section 6.13.14.5
+  foreach aQual = ["RO", "WO", "RW"] in {
+    foreach imgTy = [Image1d, Image2d, Image3d, Image1dArray, Image2dArray, Image2dDepth, Image2dArrayDepth] in {
+      def : Builtin<"get_image_num_mip_levels", [Int, ImageType<imgTy, aQual>]>;
+    }
+  }
+}
+
+
+//--------------------------------------------------------------------
+// OpenCL Extension v2.0 s18.3 - Creating OpenCL Memory Objects from OpenGL MSAA Textures
+let Extension = FuncExtKhrGlMsaaSharing in {
+  // --- Table 6.13.14.3 ---
+  foreach aQual = ["RO", "RW"] in {
+    foreach imgTy = [Image2dMsaa] in {
+      def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int], Attr.Pure>;
+      def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int], Attr.Pure>;
+      def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 2>, Int], Attr.Pure>;
+    }
+    foreach imgTy = [Image2dArrayMsaa] in {
+      def : Builtin<"read_imagef", [VectorType<Float, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int], Attr.Pure>;
+      def : Builtin<"read_imagei", [VectorType<Int, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int], Attr.Pure>;
+      def : Builtin<"read_imageui", [VectorType<UInt, 4>, ImageType<imgTy, aQual>, VectorType<Int, 4>, Int], Attr.Pure>;
+    }
+    foreach name = ["read_imagef"] in {
+      def : Builtin<name, [Float, ImageType<Image2dMsaaDepth, aQual>, VectorType<Int, 2>, Int], Attr.Pure>;
+      def : Builtin<name, [Float, ImageType<Image2dArrayMsaaDepth, aQual>, VectorType<Int, 4>, Int], Attr.Pure>;
+    }
+  }
+
+  // --- Table 6.13.14.5 ---
+  foreach aQual = ["RO", "WO", "RW"] in {
+    foreach imgTy = [Image2dMsaa, Image2dArrayMsaa, Image2dMsaaDepth, Image2dArrayMsaaDepth] in {
+      foreach name = ["get_image_width", "get_image_height",
+                      "get_image_channel_data_type", "get_image_channel_order",
+                      "get_image_num_samples"] in {
+        def : Builtin<name, [Int, ImageType<imgTy, aQual>], Attr.Const>;
+      }
+      def : Builtin<"get_image_dim", [VectorType<Int, 2>, ImageType<imgTy, aQual>], Attr.Const>;
+    }
+    def : Builtin<"get_image_array_size", [Size, ImageType<Image2dArrayMsaaDepth, aQual>], Attr.Const>;
+  }
+}
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index bedea2167950..2cd158a8b43c 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -137,7 +137,7 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
       OriginalLexicalContext(nullptr), MSStructPragmaOn(false),
       MSPointerToMemberRepresentationMethod(
           LangOpts.getMSPointerToMemberRepresentationMethod()),
-      VtorDispStack(MSVtorDispAttr::Mode(LangOpts.VtorDispMode)), PackStack(0),
+      VtorDispStack(LangOpts.getVtorDispMode()), PackStack(0),
       DataSegStack(nullptr), BSSSegStack(nullptr), ConstSegStack(nullptr),
       CodeSegStack(nullptr), CurInitSeg(nullptr), VisContext(nullptr),
       PragmaAttributeCurrentTargetDecl(nullptr),
@@ -189,6 +189,9 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
   SemaPPCallbackHandler->set(*this);
 }
 
+// Anchor Sema's type info to this TU.
+void Sema::anchor() {}
+
 void Sema::addImplicitTypedef(StringRef Name, QualType T) {
   DeclarationName DN = &Context.Idents.get(Name);
   if (IdResolver.begin(DN) == IdResolver.end())
@@ -921,8 +924,7 @@ void Sema::ActOnEndOfTranslationUnitFragment(TUFragmentKind Kind) {
   }
 
   {
-    llvm::TimeTraceScope TimeScope("PerformPendingInstantiations",
-                                   StringRef(""));
+    llvm::TimeTraceScope TimeScope("PerformPendingInstantiations");
     PerformPendingInstantiations();
   }
 
@@ -1134,6 +1136,13 @@ void Sema::ActOnEndOfTranslationUnit() {
       Consumer.CompleteTentativeDefinition(VD);
   }
 
+  for (auto D : ExternalDeclarations) {
+    if (!D || D->isInvalidDecl() || D->getPreviousDecl() || !D->isUsed())
+      continue;
+
+    Consumer.CompleteExternalDeclaration(D);
+  }
+
   // If there were errors, disable 'unused' warnings since they will mostly be
   // noise. Don't warn for a use from a module: either we should warn on all
   // file-scope declarations in modules or not at all, but whether the
@@ -1287,6 +1296,12 @@ NamedDecl *Sema::getCurFunctionOrMethodDecl() {
   return nullptr;
 }
 
+LangAS Sema::getDefaultCXXMethodAddrSpace() const {
+  if (getLangOpts().OpenCL)
+    return LangAS::opencl_generic;
+  return LangAS::Default;
+}
+
 void Sema::EmitCurrentDiagnostic(unsigned DiagID) {
   // FIXME: It doesn't make sense to me that DiagID is an incoming argument here
   // and yet we also use the current diag ID on the DiagnosticsEngine. This has
@@ -1902,6 +1917,7 @@ void Sema::ActOnComment(SourceRange Comment) {
 
 // Pin this vtable to this file.
 ExternalSemaSource::~ExternalSemaSource() {}
+char ExternalSemaSource::ID;
 
 void ExternalSemaSource::ReadMethodPool(Selector Sel) { }
 void ExternalSemaSource::updateOutOfDateSelector(Selector Sel) { }
diff --git a/clang/lib/Sema/SemaAccess.cpp b/clang/lib/Sema/SemaAccess.cpp
index 9dbb93322b7d..bd15b81cbed0 100644
--- a/clang/lib/Sema/SemaAccess.cpp
+++ b/clang/lib/Sema/SemaAccess.cpp
@@ -1560,21 +1560,24 @@ Sema::AccessResult Sema::CheckUnresolvedMemberAccess(UnresolvedMemberExpr *E,
   return CheckAccess(*this, E->getMemberLoc(), Entity);
 }
 
-/// Is the given special member function accessible for the purposes of
-/// deciding whether to define a special member function as deleted?
-bool Sema::isSpecialMemberAccessibleForDeletion(CXXMethodDecl *decl,
-                                                AccessSpecifier access,
-                                                QualType objectType) {
+/// Is the given member accessible for the purposes of deciding whether to
+/// define a special member function as deleted?
+bool Sema::isMemberAccessibleForDeletion(CXXRecordDecl *NamingClass,
+                                         DeclAccessPair Found,
+                                         QualType ObjectType,
+                                         SourceLocation Loc,
+                                         const PartialDiagnostic &Diag) {
   // Fast path.
-  if (access == AS_public || !getLangOpts().AccessControl) return true;
+  if (Found.getAccess() == AS_public || !getLangOpts().AccessControl)
+    return true;
 
-  AccessTarget entity(Context, AccessTarget::Member, decl->getParent(),
-                      DeclAccessPair::make(decl, access), objectType);
+  AccessTarget Entity(Context, AccessTarget::Member, NamingClass, Found,
+                      ObjectType);
 
   // Suppress diagnostics.
-  entity.setDiag(PDiag());
+  Entity.setDiag(Diag);
 
-  switch (CheckAccess(*this, SourceLocation(), entity)) {
+  switch (CheckAccess(*this, Loc, Entity)) {
   case AR_accessible: return true;
   case AR_inaccessible: return false;
   case AR_dependent: llvm_unreachable("dependent for =delete computation");
diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index 70186c966f8f..cd2a65276b09 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -80,9 +80,9 @@ void Sema::AddMsStructLayoutForRecord(RecordDecl *RD) {
   // FIXME: We should merge AddAlignmentAttributesForRecord with
   // AddMsStructLayoutForRecord into AddPragmaAttributesForRecord, which takes
   // all active pragmas and applies them as attributes to class definitions.
-  if (VtorDispStack.CurrentValue != getLangOpts().VtorDispMode)
-    RD->addAttr(
-        MSVtorDispAttr::CreateImplicit(Context, VtorDispStack.CurrentValue));
+  if (VtorDispStack.CurrentValue != getLangOpts().getVtorDispMode())
+    RD->addAttr(MSVtorDispAttr::CreateImplicit(
+        Context, unsigned(VtorDispStack.CurrentValue)));
 }
 
 template <typename Attribute>
@@ -416,7 +416,7 @@ void Sema::ActOnPragmaMSPointersToMembers(
 
 void Sema::ActOnPragmaMSVtorDisp(PragmaMsStackAction Action,
                                  SourceLocation PragmaLoc,
-                                 MSVtorDispAttr::Mode Mode) {
+                                 MSVtorDispMode Mode) {
   if (Action & PSK_Pop && VtorDispStack.Stack.empty())
     Diag(PragmaLoc, diag::warn_pragma_pop_failed) << "vtordisp"
                                                   << "stack empty";
diff --git a/clang/lib/Sema/SemaCUDA.cpp b/clang/lib/Sema/SemaCUDA.cpp
index d0ddfd040c9c..0c61057e1072 100644
--- a/clang/lib/Sema/SemaCUDA.cpp
+++ b/clang/lib/Sema/SemaCUDA.cpp
@@ -492,6 +492,8 @@ void Sema::checkAllowedCUDAInitializer(VarDecl *VD) {
   const Expr *Init = VD->getInit();
   if (VD->hasAttr<CUDADeviceAttr>() || VD->hasAttr<CUDAConstantAttr>() ||
       VD->hasAttr<CUDASharedAttr>()) {
+    if (LangOpts.GPUAllowDeviceInit)
+      return;
     assert(!VD->isStaticLocal() || VD->hasAttr<CUDASharedAttr>());
     bool AllowedInit = false;
     if (const CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(Init))
diff --git a/clang/lib/Sema/SemaCast.cpp b/clang/lib/Sema/SemaCast.cpp
index 0ebb5c68f7c2..a905ebc67305 100644
--- a/clang/lib/Sema/SemaCast.cpp
+++ b/clang/lib/Sema/SemaCast.cpp
@@ -423,7 +423,7 @@ static bool tryDiagnoseOverloadedCast(Sema &S, CastType CT,
 
   case OR_Ambiguous:
     msg = diag::err_ovl_ambiguous_conversion_in_cast;
-    howManyCandidates = OCD_ViableCandidates;
+    howManyCandidates = OCD_AmbiguousCandidates;
     break;
 
   case OR_Deleted:
@@ -740,7 +740,7 @@ void CastOperation::CheckDynamicCast() {
     assert(DestPointer && "Reference to void is not possible");
   } else if (DestRecord) {
     if (Self.RequireCompleteType(OpRange.getBegin(), DestPointee,
-                                 diag::err_bad_dynamic_cast_incomplete,
+                                 diag::err_bad_cast_incomplete,
                                  DestRange)) {
       SrcExpr = ExprError();
       return;
@@ -763,7 +763,7 @@ void CastOperation::CheckDynamicCast() {
       SrcPointee = SrcPointer->getPointeeType();
     } else {
       Self.Diag(OpRange.getBegin(), diag::err_bad_dynamic_cast_not_ptr)
-        << OrigSrcType << SrcExpr.get()->getSourceRange();
+          << OrigSrcType << this->DestType << SrcExpr.get()->getSourceRange();
       SrcExpr = ExprError();
       return;
     }
@@ -785,7 +785,7 @@ void CastOperation::CheckDynamicCast() {
   const RecordType *SrcRecord = SrcPointee->getAs<RecordType>();
   if (SrcRecord) {
     if (Self.RequireCompleteType(OpRange.getBegin(), SrcPointee,
-                                 diag::err_bad_dynamic_cast_incomplete,
+                                 diag::err_bad_cast_incomplete,
                                  SrcExpr.get())) {
       SrcExpr = ExprError();
       return;
@@ -1182,6 +1182,11 @@ static TryCastResult TryStaticCast(Sema &Self, ExprResult &SrcExpr,
   // The same goes for reverse floating point promotion/conversion and
   // floating-integral conversions. Again, only floating->enum is relevant.
   if (DestType->isEnumeralType()) {
+    if (Self.RequireCompleteType(OpRange.getBegin(), DestType,
+                                 diag::err_bad_cast_incomplete)) {
+      SrcExpr = ExprError();
+      return TC_Failed;
+    }
     if (SrcType->isIntegralOrEnumerationType()) {
       Kind = CK_IntegralCast;
       return TC_Success;
@@ -1301,10 +1306,6 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
   // Because we try the reference downcast before this function, from now on
   // this is the only cast possibility, so we issue an error if we fail now.
   // FIXME: Should allow casting away constness if CStyle.
-  bool DerivedToBase;
-  bool ObjCConversion;
-  bool ObjCLifetimeConversion;
-  bool FunctionConversion;
   QualType FromType = SrcExpr->getType();
   QualType ToType = R->getPointeeType();
   if (CStyle) {
@@ -1312,9 +1313,9 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
     ToType = ToType.getUnqualifiedType();
   }
 
+  Sema::ReferenceConversions RefConv;
   Sema::ReferenceCompareResult RefResult = Self.CompareReferenceRelationship(
-      SrcExpr->getBeginLoc(), ToType, FromType, DerivedToBase, ObjCConversion,
-      ObjCLifetimeConversion, FunctionConversion);
+      SrcExpr->getBeginLoc(), ToType, FromType, &RefConv);
   if (RefResult != Sema::Ref_Compatible) {
     if (CStyle || RefResult == Sema::Ref_Incompatible)
       return TC_NotApplicable;
@@ -1326,7 +1327,7 @@ TryCastResult TryLValueToRValueCast(Sema &Self, Expr *SrcExpr,
     return TC_Failed;
   }
 
-  if (DerivedToBase) {
+  if (RefConv & Sema::ReferenceConversions::DerivedToBase) {
     Kind = CK_DerivedToBase;
     CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                        /*DetectVirtual=*/true);
@@ -1651,7 +1652,7 @@ TryStaticImplicitCast(Sema &Self, ExprResult &SrcExpr, QualType DestType,
                       CastKind &Kind, bool ListInitialization) {
   if (DestType->isRecordType()) {
     if (Self.RequireCompleteType(OpRange.getBegin(), DestType,
-                                 diag::err_bad_dynamic_cast_incomplete) ||
+                                 diag::err_bad_cast_incomplete) ||
         Self.RequireNonAbstractType(OpRange.getBegin(), DestType,
                                     diag::err_allocation_of_abstract_type)) {
       msg = 0;
@@ -2007,7 +2008,7 @@ static bool fixOverloadedReinterpretCastExpr(Sema &Self, QualType DestType,
   // No guarantees that ResolveAndFixSingleFunctionTemplateSpecialization
   // preserves Result.
   Result = E;
-  if (!Self.resolveAndFixAddressOfOnlyViableOverloadCandidate(
+  if (!Self.resolveAndFixAddressOfSingleOverloadCandidate(
           Result, /*DoFunctionPointerConversion=*/true))
     return false;
   return Result.isUsable();
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index dca81d1d275f..74742023d1b3 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -201,6 +201,87 @@ static bool SemaBuiltinPreserveAI(Sema &S, CallExpr *TheCall) {
   return false;
 }
 
+/// Check that the value argument for __builtin_is_aligned(value, alignment) and
+/// __builtin_aligned_{up,down}(value, alignment) is an integer or a pointer
+/// type (but not a function pointer) and that the alignment is a power-of-two.
+static bool SemaBuiltinAlignment(Sema &S, CallExpr *TheCall, unsigned ID) {
+  if (checkArgCount(S, TheCall, 2))
+    return true;
+
+  clang::Expr *Source = TheCall->getArg(0);
+  bool IsBooleanAlignBuiltin = ID == Builtin::BI__builtin_is_aligned;
+
+  auto IsValidIntegerType = [](QualType Ty) {
+    return Ty->isIntegerType() && !Ty->isEnumeralType() && !Ty->isBooleanType();
+  };
+  QualType SrcTy = Source->getType();
+  // We should also be able to use it with arrays (but not functions!).
+  if (SrcTy->canDecayToPointerType() && SrcTy->isArrayType()) {
+    SrcTy = S.Context.getDecayedType(SrcTy);
+  }
+  if ((!SrcTy->isPointerType() && !IsValidIntegerType(SrcTy)) ||
+      SrcTy->isFunctionPointerType()) {
+    // FIXME: this is not quite the right error message since we don't allow
+    // floating point types, or member pointers.
+    S.Diag(Source->getExprLoc(), diag::err_typecheck_expect_scalar_operand)
+        << SrcTy;
+    return true;
+  }
+
+  clang::Expr *AlignOp = TheCall->getArg(1);
+  if (!IsValidIntegerType(AlignOp->getType())) {
+    S.Diag(AlignOp->getExprLoc(), diag::err_typecheck_expect_int)
+        << AlignOp->getType();
+    return true;
+  }
+  Expr::EvalResult AlignResult;
+  unsigned MaxAlignmentBits = S.Context.getIntWidth(SrcTy) - 1;
+  // We can't check validity of alignment if it is type dependent.
+  if (!AlignOp->isInstantiationDependent() &&
+      AlignOp->EvaluateAsInt(AlignResult, S.Context,
+                             Expr::SE_AllowSideEffects)) {
+    llvm::APSInt AlignValue = AlignResult.Val.getInt();
+    llvm::APSInt MaxValue(
+        llvm::APInt::getOneBitSet(MaxAlignmentBits + 1, MaxAlignmentBits));
+    if (AlignValue < 1) {
+      S.Diag(AlignOp->getExprLoc(), diag::err_alignment_too_small) << 1;
+      return true;
+    }
+    if (llvm::APSInt::compareValues(AlignValue, MaxValue) > 0) {
+      S.Diag(AlignOp->getExprLoc(), diag::err_alignment_too_big)
+          << MaxValue.toString(10);
+      return true;
+    }
+    if (!AlignValue.isPowerOf2()) {
+      S.Diag(AlignOp->getExprLoc(), diag::err_alignment_not_power_of_two);
+      return true;
+    }
+    if (AlignValue == 1) {
+      S.Diag(AlignOp->getExprLoc(), diag::warn_alignment_builtin_useless)
+          << IsBooleanAlignBuiltin;
+    }
+  }
+
+  ExprResult SrcArg = S.PerformCopyInitialization(
+      InitializedEntity::InitializeParameter(S.Context, SrcTy, false),
+      SourceLocation(), Source);
+  if (SrcArg.isInvalid())
+    return true;
+  TheCall->setArg(0, SrcArg.get());
+  ExprResult AlignArg =
+      S.PerformCopyInitialization(InitializedEntity::InitializeParameter(
+                                      S.Context, AlignOp->getType(), false),
+                                  SourceLocation(), AlignOp);
+  if (AlignArg.isInvalid())
+    return true;
+  TheCall->setArg(1, AlignArg.get());
+  // For align_up/align_down, the return type is the same as the (potentially
+  // decayed) argument type including qualifiers. For is_aligned(), the result
+  // is always bool.
+  TheCall->setType(IsBooleanAlignBuiltin ? S.Context.BoolTy : SrcTy);
+  return false;
+}
+
 static bool SemaBuiltinOverflow(Sema &S, CallExpr *TheCall) {
   if (checkArgCount(S, TheCall, 3))
     return true;
@@ -340,7 +421,8 @@ void Sema::checkFortifiedBuiltinMemoryFunction(FunctionDecl *FD,
   case Builtin::BI__builtin___strncat_chk:
   case Builtin::BI__builtin___strncpy_chk:
   case Builtin::BI__builtin___stpncpy_chk:
-  case Builtin::BI__builtin___memccpy_chk: {
+  case Builtin::BI__builtin___memccpy_chk:
+  case Builtin::BI__builtin___mempcpy_chk: {
     DiagID = diag::warn_builtin_chk_overflow;
     IsChkVariant = true;
     SizeIndex = TheCall->getNumArgs() - 2;
@@ -379,7 +461,9 @@ void Sema::checkFortifiedBuiltinMemoryFunction(FunctionDecl *FD,
   case Builtin::BImemmove:
   case Builtin::BI__builtin_memmove:
   case Builtin::BImemset:
-  case Builtin::BI__builtin_memset: {
+  case Builtin::BI__builtin_memset:
+  case Builtin::BImempcpy:
+  case Builtin::BI__builtin_mempcpy: {
     DiagID = diag::warn_fortify_source_overflow;
     SizeIndex = TheCall->getNumArgs() - 1;
     ObjectIndex = 0;
@@ -1354,6 +1438,12 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
     if (SemaBuiltinAddressof(*this, TheCall))
       return ExprError();
     break;
+  case Builtin::BI__builtin_is_aligned:
+  case Builtin::BI__builtin_align_up:
+  case Builtin::BI__builtin_align_down:
+    if (SemaBuiltinAlignment(*this, TheCall, BuiltinID))
+      return ExprError();
+    break;
   case Builtin::BI__builtin_add_overflow:
   case Builtin::BI__builtin_sub_overflow:
   case Builtin::BI__builtin_mul_overflow:
@@ -1536,6 +1626,7 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
           return ExprError();
         break;
       case llvm::Triple::aarch64:
+      case llvm::Triple::aarch64_32:
       case llvm::Triple::aarch64_be:
         if (CheckAArch64BuiltinFunctionCall(BuiltinID, TheCall))
           return ExprError();
@@ -1685,6 +1776,7 @@ bool Sema::CheckNeonBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
 
     llvm::Triple::ArchType Arch = Context.getTargetInfo().getTriple().getArch();
     bool IsPolyUnsigned = Arch == llvm::Triple::aarch64 ||
+                          Arch == llvm::Triple::aarch64_32 ||
                           Arch == llvm::Triple::aarch64_be;
     bool IsInt64Long =
         Context.getTargetInfo().getInt64Type() == TargetInfo::SignedLong;
@@ -1717,6 +1809,14 @@ bool Sema::CheckNeonBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   return SemaBuiltinConstantArgRange(TheCall, i, l, u + l);
 }
 
+bool Sema::CheckMVEBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
+  switch (BuiltinID) {
+  default:
+    return false;
+  #include "clang/Basic/arm_mve_builtin_sema.inc"
+  }
+}
+
 bool Sema::CheckARMBuiltinExclusiveCall(unsigned BuiltinID, CallExpr *TheCall,
                                         unsigned MaxWidth) {
   assert((BuiltinID == ARM::BI__builtin_arm_ldrex ||
@@ -1857,6 +1957,8 @@ bool Sema::CheckARMBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
 
   if (CheckNeonBuiltinFunctionCall(BuiltinID, TheCall))
     return true;
+  if (CheckMVEBuiltinFunctionCall(BuiltinID, TheCall))
+    return true;
 
   // For intrinsics which take an immediate value as part of the instruction,
   // range check them here.
@@ -3039,8 +3141,37 @@ bool Sema::CheckHexagonBuiltinFunctionCall(unsigned BuiltinID,
          CheckHexagonBuiltinArgument(BuiltinID, TheCall);
 }
 
+bool Sema::CheckMipsBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
+  return CheckMipsBuiltinCpu(BuiltinID, TheCall) ||
+         CheckMipsBuiltinArgument(BuiltinID, TheCall);
+}
+
+bool Sema::CheckMipsBuiltinCpu(unsigned BuiltinID, CallExpr *TheCall) {
+  const TargetInfo &TI = Context.getTargetInfo();
+
+  if (Mips::BI__builtin_mips_addu_qb <= BuiltinID &&
+      BuiltinID <= Mips::BI__builtin_mips_lwx) {
+    if (!TI.hasFeature("dsp"))
+      return Diag(TheCall->getBeginLoc(), diag::err_mips_builtin_requires_dsp);
+  }
 
-// CheckMipsBuiltinFunctionCall - Checks the constant value passed to the
+  if (Mips::BI__builtin_mips_absq_s_qb <= BuiltinID &&
+      BuiltinID <= Mips::BI__builtin_mips_subuh_r_qb) {
+    if (!TI.hasFeature("dspr2"))
+      return Diag(TheCall->getBeginLoc(),
+                  diag::err_mips_builtin_requires_dspr2);
+  }
+
+  if (Mips::BI__builtin_msa_add_a_b <= BuiltinID &&
+      BuiltinID <= Mips::BI__builtin_msa_xori_b) {
+    if (!TI.hasFeature("msa"))
+      return Diag(TheCall->getBeginLoc(), diag::err_mips_builtin_requires_msa);
+  }
+
+  return false;
+}
+
+// CheckMipsBuiltinArgument - Checks the constant value passed to the
 // intrinsic is correct. The switch statement is ordered by DSP, MSA. The
 // ordering for DSP is unspecified. MSA is ordered by the data format used
 // by the underlying instruction i.e., df/m, df/n and then by size.
@@ -3049,7 +3180,7 @@ bool Sema::CheckHexagonBuiltinFunctionCall(unsigned BuiltinID,
 //        definitions from include/clang/Basic/BuiltinsMips.def.
 // FIXME: GCC is strict on signedness for some of these intrinsics, we should
 //        be too.
-bool Sema::CheckMipsBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
+bool Sema::CheckMipsBuiltinArgument(unsigned BuiltinID, CallExpr *TheCall) {
   unsigned i = 0, l = 0, u = 0, m = 0;
   switch (BuiltinID) {
   default: return false;
@@ -4560,20 +4691,19 @@ ExprResult Sema::BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
       && sizeof(NumVals)/sizeof(NumVals[0]) == NumForm,
       "need to update code for modified forms");
   static_assert(AtomicExpr::AO__c11_atomic_init == 0 &&
-                    AtomicExpr::AO__c11_atomic_fetch_xor + 1 ==
+                    AtomicExpr::AO__c11_atomic_fetch_min + 1 ==
                         AtomicExpr::AO__atomic_load,
                 "need to update code for modified C11 atomics");
   bool IsOpenCL = Op >= AtomicExpr::AO__opencl_atomic_init &&
                   Op <= AtomicExpr::AO__opencl_atomic_fetch_max;
   bool IsC11 = (Op >= AtomicExpr::AO__c11_atomic_init &&
-               Op <= AtomicExpr::AO__c11_atomic_fetch_xor) ||
+               Op <= AtomicExpr::AO__c11_atomic_fetch_min) ||
                IsOpenCL;
   bool IsN = Op == AtomicExpr::AO__atomic_load_n ||
              Op == AtomicExpr::AO__atomic_store_n ||
              Op == AtomicExpr::AO__atomic_exchange_n ||
              Op == AtomicExpr::AO__atomic_compare_exchange_n;
   bool IsAddSub = false;
-  bool IsMinMax = false;
 
   switch (Op) {
   case AtomicExpr::AO__c11_atomic_init:
@@ -4602,8 +4732,6 @@ ExprResult Sema::BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
   case AtomicExpr::AO__c11_atomic_fetch_sub:
   case AtomicExpr::AO__opencl_atomic_fetch_add:
   case AtomicExpr::AO__opencl_atomic_fetch_sub:
-  case AtomicExpr::AO__opencl_atomic_fetch_min:
-  case AtomicExpr::AO__opencl_atomic_fetch_max:
   case AtomicExpr::AO__atomic_fetch_add:
   case AtomicExpr::AO__atomic_fetch_sub:
   case AtomicExpr::AO__atomic_add_fetch:
@@ -4624,12 +4752,14 @@ ExprResult Sema::BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
   case AtomicExpr::AO__atomic_or_fetch:
   case AtomicExpr::AO__atomic_xor_fetch:
   case AtomicExpr::AO__atomic_nand_fetch:
-    Form = Arithmetic;
-    break;
-
+  case AtomicExpr::AO__c11_atomic_fetch_min:
+  case AtomicExpr::AO__c11_atomic_fetch_max:
+  case AtomicExpr::AO__opencl_atomic_fetch_min:
+  case AtomicExpr::AO__opencl_atomic_fetch_max:
+  case AtomicExpr::AO__atomic_min_fetch:
+  case AtomicExpr::AO__atomic_max_fetch:
   case AtomicExpr::AO__atomic_fetch_min:
   case AtomicExpr::AO__atomic_fetch_max:
-    IsMinMax = true;
     Form = Arithmetic;
     break;
 
@@ -4721,16 +4851,8 @@ ExprResult Sema::BuildAtomicExpr(SourceRange CallRange, SourceRange ExprRange,
           << IsC11 << Ptr->getType() << Ptr->getSourceRange();
       return ExprError();
     }
-    if (IsMinMax) {
-      const BuiltinType *BT = ValType->getAs<BuiltinType>();
-      if (!BT || (BT->getKind() != BuiltinType::Int &&
-                  BT->getKind() != BuiltinType::UInt)) {
-        Diag(ExprRange.getBegin(), diag::err_atomic_op_needs_int32_or_ptr);
-        return ExprError();
-      }
-    }
-    if (!IsAddSub && !IsMinMax && !ValType->isIntegerType()) {
-      Diag(ExprRange.getBegin(), diag::err_atomic_op_bitwise_needs_atomic_int)
+    if (!IsAddSub && !ValType->isIntegerType()) {
+      Diag(ExprRange.getBegin(), diag::err_atomic_op_needs_atomic_int)
           << IsC11 << Ptr->getType() << Ptr->getSourceRange();
       return ExprError();
     }
@@ -5506,7 +5628,8 @@ ExprResult Sema::CheckOSLogFormatStringArg(Expr *Arg) {
 static bool checkVAStartABI(Sema &S, unsigned BuiltinID, Expr *Fn) {
   const llvm::Triple &TT = S.Context.getTargetInfo().getTriple();
   bool IsX64 = TT.getArch() == llvm::Triple::x86_64;
-  bool IsAArch64 = TT.getArch() == llvm::Triple::aarch64;
+  bool IsAArch64 = (TT.getArch() == llvm::Triple::aarch64 ||
+                    TT.getArch() == llvm::Triple::aarch64_32);
   bool IsWindows = TT.isOSWindows();
   bool IsMSVAStart = BuiltinID == Builtin::BI__builtin_ms_va_start;
   if (IsX64 || IsAArch64) {
@@ -5723,7 +5846,8 @@ bool Sema::SemaBuiltinUnorderedCompare(CallExpr *TheCall) {
 
   // Do standard promotions between the two arguments, returning their common
   // type.
-  QualType Res = UsualArithmeticConversions(OrigArg0, OrigArg1, false);
+  QualType Res = UsualArithmeticConversions(
+      OrigArg0, OrigArg1, TheCall->getExprLoc(), ACK_Comparison);
   if (OrigArg0.isInvalid() || OrigArg1.isInvalid())
     return true;
 
@@ -5763,36 +5887,41 @@ bool Sema::SemaBuiltinFPClassification(CallExpr *TheCall, unsigned NumArgs) {
            << SourceRange(TheCall->getArg(NumArgs)->getBeginLoc(),
                           (*(TheCall->arg_end() - 1))->getEndLoc());
 
+  // __builtin_fpclassify is the only case where NumArgs != 1, so we can count
+  // on all preceding parameters just being int.  Try all of those.
+  for (unsigned i = 0; i < NumArgs - 1; ++i) {
+    Expr *Arg = TheCall->getArg(i);
+
+    if (Arg->isTypeDependent())
+      return false;
+
+    ExprResult Res = PerformImplicitConversion(Arg, Context.IntTy, AA_Passing);
+
+    if (Res.isInvalid())
+      return true;
+    TheCall->setArg(i, Res.get());
+  }
+
   Expr *OrigArg = TheCall->getArg(NumArgs-1);
 
   if (OrigArg->isTypeDependent())
     return false;
 
+  // Usual Unary Conversions will convert half to float, which we want for
+  // machines that use fp16 conversion intrinsics. Else, we wnat to leave the
+  // type how it is, but do normal L->Rvalue conversions.
+  if (Context.getTargetInfo().useFP16ConversionIntrinsics())
+    OrigArg = UsualUnaryConversions(OrigArg).get();
+  else
+    OrigArg = DefaultFunctionArrayLvalueConversion(OrigArg).get();
+  TheCall->setArg(NumArgs - 1, OrigArg);
+
   // This operation requires a non-_Complex floating-point number.
   if (!OrigArg->getType()->isRealFloatingType())
     return Diag(OrigArg->getBeginLoc(),
                 diag::err_typecheck_call_invalid_unary_fp)
            << OrigArg->getType() << OrigArg->getSourceRange();
 
-  // If this is an implicit conversion from float -> float, double, or
-  // long double, remove it.
-  if (ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(OrigArg)) {
-    // Only remove standard FloatCasts, leaving other casts inplace
-    if (Cast->getCastKind() == CK_FloatingCast) {
-      Expr *CastArg = Cast->getSubExpr();
-      if (CastArg->getType()->isSpecificBuiltinType(BuiltinType::Float)) {
-        assert(
-            (Cast->getType()->isSpecificBuiltinType(BuiltinType::Double) ||
-             Cast->getType()->isSpecificBuiltinType(BuiltinType::Float) ||
-             Cast->getType()->isSpecificBuiltinType(BuiltinType::LongDouble)) &&
-            "promotion from float to either float, double, or long double is "
-            "the only expected cast here");
-        Cast->setSubExpr(nullptr);
-        TheCall->setArg(NumArgs-1, CastArg);
-      }
-    }
-  }
-
   return false;
 }
 
@@ -6235,6 +6364,101 @@ bool Sema::SemaBuiltinConstantArgMultiple(CallExpr *TheCall, int ArgNum,
   return false;
 }
 
+/// SemaBuiltinConstantArgPower2 - Check if argument ArgNum of TheCall is a
+/// constant expression representing a power of 2.
+bool Sema::SemaBuiltinConstantArgPower2(CallExpr *TheCall, int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  // Bit-twiddling to test for a power of 2: for x > 0, x & (x-1) is zero if
+  // and only if x is a power of 2.
+  if (Result.isStrictlyPositive() && (Result & (Result - 1)) == 0)
+    return false;
+
+  return Diag(TheCall->getBeginLoc(), diag::err_argument_not_power_of_2)
+         << Arg->getSourceRange();
+}
+
+static bool IsShiftedByte(llvm::APSInt Value) {
+  if (Value.isNegative())
+    return false;
+
+  // Check if it's a shifted byte, by shifting it down
+  while (true) {
+    // If the value fits in the bottom byte, the check passes.
+    if (Value < 0x100)
+      return true;
+
+    // Otherwise, if the value has _any_ bits in the bottom byte, the check
+    // fails.
+    if ((Value & 0xFF) != 0)
+      return false;
+
+    // If the bottom 8 bits are all 0, but something above that is nonzero,
+    // then shifting the value right by 8 bits won't affect whether it's a
+    // shifted byte or not. So do that, and go round again.
+    Value >>= 8;
+  }
+}
+
+/// SemaBuiltinConstantArgShiftedByte - Check if argument ArgNum of TheCall is
+/// a constant expression representing an arbitrary byte value shifted left by
+/// a multiple of 8 bits.
+bool Sema::SemaBuiltinConstantArgShiftedByte(CallExpr *TheCall, int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  if (IsShiftedByte(Result))
+    return false;
+
+  return Diag(TheCall->getBeginLoc(), diag::err_argument_not_shifted_byte)
+         << Arg->getSourceRange();
+}
+
+/// SemaBuiltinConstantArgShiftedByteOr0xFF - Check if argument ArgNum of
+/// TheCall is a constant expression representing either a shifted byte value,
+/// or a value of the form 0x??FF (i.e. a member of the arithmetic progression
+/// 0x00FF, 0x01FF, ..., 0xFFFF). This strange range check is needed for some
+/// Arm MVE intrinsics.
+bool Sema::SemaBuiltinConstantArgShiftedByteOrXXFF(CallExpr *TheCall,
+                                                   int ArgNum) {
+  llvm::APSInt Result;
+
+  // We can't check the value of a dependent argument.
+  Expr *Arg = TheCall->getArg(ArgNum);
+  if (Arg->isTypeDependent() || Arg->isValueDependent())
+    return false;
+
+  // Check constant-ness first.
+  if (SemaBuiltinConstantArg(TheCall, ArgNum, Result))
+    return true;
+
+  // Check to see if it's in either of the required forms.
+  if (IsShiftedByte(Result) ||
+      (Result > 0 && Result < 0x10000 && (Result & 0xFF) == 0xFF))
+    return false;
+
+  return Diag(TheCall->getBeginLoc(),
+              diag::err_argument_not_shifted_byte_or_xxff)
+         << Arg->getSourceRange();
+}
+
 /// SemaBuiltinARMMemoryTaggingCall - Handle calls of memory tagging extensions
 bool Sema::SemaBuiltinARMMemoryTaggingCall(unsigned BuiltinID, CallExpr *TheCall) {
   if (BuiltinID == AArch64::BI__builtin_arm_irg) {
@@ -9162,7 +9386,7 @@ void Sema::CheckMaxUnsignedZero(const CallExpr *Call,
   auto IsLiteralZeroArg = [](const Expr* E) -> bool {
     const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E);
     if (!MTE) return false;
-    const auto *Num = dyn_cast<IntegerLiteral>(MTE->GetTemporaryExpr());
+    const auto *Num = dyn_cast<IntegerLiteral>(MTE->getSubExpr());
     if (!Num) return false;
     if (Num->getValue() != 0) return false;
     return true;
@@ -11371,32 +11595,6 @@ static const IntegerLiteral *getIntegerLiteral(Expr *E) {
   return IL;
 }
 
-static void CheckConditionalWithEnumTypes(Sema &S, SourceLocation Loc,
-                                          Expr *LHS, Expr *RHS) {
-  QualType LHSStrippedType = LHS->IgnoreParenImpCasts()->getType();
-  QualType RHSStrippedType = RHS->IgnoreParenImpCasts()->getType();
-
-  const auto *LHSEnumType = LHSStrippedType->getAs<EnumType>();
-  if (!LHSEnumType)
-    return;
-  const auto *RHSEnumType = RHSStrippedType->getAs<EnumType>();
-  if (!RHSEnumType)
-    return;
-
-  // Ignore anonymous enums.
-  if (!LHSEnumType->getDecl()->hasNameForLinkage())
-    return;
-  if (!RHSEnumType->getDecl()->hasNameForLinkage())
-    return;
-
-  if (S.Context.hasSameUnqualifiedType(LHSStrippedType, RHSStrippedType))
-    return;
-
-  S.Diag(Loc, diag::warn_conditional_mixed_enum_types)
-      << LHSStrippedType << RHSStrippedType << LHS->getSourceRange()
-      << RHS->getSourceRange();
-}
-
 static void DiagnoseIntInBoolContext(Sema &S, Expr *E) {
   E = E->IgnoreParenImpCasts();
   SourceLocation ExprLoc = E->getExprLoc();
@@ -11737,7 +11935,7 @@ static void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
     return;
 
   if (isObjCSignedCharBool(S, T) && !Source->isCharType() &&
-      !E->isKnownToHaveBooleanValue()) {
+      !E->isKnownToHaveBooleanValue(/*Semantic=*/false)) {
     return adornObjCBoolConversionDiagWithTernaryFixit(
         S, E,
         S.Diag(CC, diag::warn_impcast_int_to_objc_signed_char_bool)
@@ -11888,8 +12086,6 @@ static void CheckConditionalOperator(Sema &S, ConditionalOperator *E,
   bool Suspicious = false;
   CheckConditionalOperand(S, E->getTrueExpr(), T, CC, Suspicious);
   CheckConditionalOperand(S, E->getFalseExpr(), T, CC, Suspicious);
-  CheckConditionalWithEnumTypes(S, E->getBeginLoc(), E->getTrueExpr(),
-                                E->getFalseExpr());
 
   if (T->isBooleanType())
     DiagnoseIntInBoolContext(S, E);
@@ -12360,8 +12556,8 @@ namespace {
 
 /// Visitor for expressions which looks for unsequenced operations on the
 /// same object.
-class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
-  using Base = EvaluatedExprVisitor<SequenceChecker>;
+class SequenceChecker : public ConstEvaluatedExprVisitor<SequenceChecker> {
+  using Base = ConstEvaluatedExprVisitor<SequenceChecker>;
 
   /// A tree of sequenced regions within an expression. Two regions are
   /// unsequenced if one is an ancestor or a descendent of the other. When we
@@ -12431,7 +12627,7 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
   };
 
   /// An object for which we can track unsequenced uses.
-  using Object = NamedDecl *;
+  using Object = const NamedDecl *;
 
   /// Different flavors of object usage which we track. We only track the
   /// least-sequenced usage of each kind.
@@ -12450,17 +12646,19 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
     UK_Count = UK_ModAsSideEffect + 1
   };
 
+  /// Bundle together a sequencing region and the expression corresponding
+  /// to a specific usage. One Usage is stored for each usage kind in UsageInfo.
   struct Usage {
-    Expr *Use;
+    const Expr *UsageExpr;
     SequenceTree::Seq Seq;
 
-    Usage() : Use(nullptr), Seq() {}
+    Usage() : UsageExpr(nullptr), Seq() {}
   };
 
   struct UsageInfo {
     Usage Uses[UK_Count];
 
-    /// Have we issued a diagnostic for this variable already?
+    /// Have we issued a diagnostic for this object already?
     bool Diagnosed;
 
     UsageInfo() : Uses(), Diagnosed(false) {}
@@ -12484,7 +12682,7 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
 
   /// Expressions to check later. We defer checking these to reduce
   /// stack usage.
-  SmallVectorImpl<Expr *> &WorkList;
+  SmallVectorImpl<const Expr *> &WorkList;
 
   /// RAII object wrapping the visitation of a sequenced subexpression of an
   /// expression. At the end of this process, the side-effects of the evaluation
@@ -12498,10 +12696,13 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
     }
 
     ~SequencedSubexpression() {
-      for (auto &M : llvm::reverse(ModAsSideEffect)) {
-        UsageInfo &U = Self.UsageMap[M.first];
-        auto &SideEffectUsage = U.Uses[UK_ModAsSideEffect];
-        Self.addUsage(U, M.first, SideEffectUsage.Use, UK_ModAsValue);
+      for (const std::pair<Object, Usage> &M : llvm::reverse(ModAsSideEffect)) {
+        // Add a new usage with usage kind UK_ModAsValue, and then restore
+        // the previous usage with UK_ModAsSideEffect (thus clearing it if
+        // the previous one was empty).
+        UsageInfo &UI = Self.UsageMap[M.first];
+        auto &SideEffectUsage = UI.Uses[UK_ModAsSideEffect];
+        Self.addUsage(M.first, UI, SideEffectUsage.UsageExpr, UK_ModAsValue);
         SideEffectUsage = M.second;
       }
       Self.ModAsSideEffect = OldModAsSideEffect;
@@ -12545,49 +12746,60 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
 
   /// Find the object which is produced by the specified expression,
   /// if any.
-  Object getObject(Expr *E, bool Mod) const {
+  Object getObject(const Expr *E, bool Mod) const {
     E = E->IgnoreParenCasts();
-    if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
+    if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
       if (Mod && (UO->getOpcode() == UO_PreInc || UO->getOpcode() == UO_PreDec))
         return getObject(UO->getSubExpr(), Mod);
-    } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
+    } else if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
       if (BO->getOpcode() == BO_Comma)
         return getObject(BO->getRHS(), Mod);
       if (Mod && BO->isAssignmentOp())
         return getObject(BO->getLHS(), Mod);
-    } else if (MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
+    } else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
       // FIXME: Check for more interesting cases, like "x.n = ++x.n".
       if (isa<CXXThisExpr>(ME->getBase()->IgnoreParenCasts()))
         return ME->getMemberDecl();
-    } else if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
+    } else if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E))
       // FIXME: If this is a reference, map through to its value.
       return DRE->getDecl();
     return nullptr;
   }
 
-  /// Note that an object was modified or used by an expression.
-  void addUsage(UsageInfo &UI, Object O, Expr *Ref, UsageKind UK) {
+  /// Note that an object \p O was modified or used by an expression
+  /// \p UsageExpr with usage kind \p UK. \p UI is the \p UsageInfo for
+  /// the object \p O as obtained via the \p UsageMap.
+  void addUsage(Object O, UsageInfo &UI, const Expr *UsageExpr, UsageKind UK) {
+    // Get the old usage for the given object and usage kind.
     Usage &U = UI.Uses[UK];
-    if (!U.Use || !Tree.isUnsequenced(Region, U.Seq)) {
+    if (!U.UsageExpr || !Tree.isUnsequenced(Region, U.Seq)) {
+      // If we have a modification as side effect and are in a sequenced
+      // subexpression, save the old Usage so that we can restore it later
+      // in SequencedSubexpression::~SequencedSubexpression.
       if (UK == UK_ModAsSideEffect && ModAsSideEffect)
         ModAsSideEffect->push_back(std::make_pair(O, U));
-      U.Use = Ref;
+      // Then record the new usage with the current sequencing region.
+      U.UsageExpr = UsageExpr;
       U.Seq = Region;
     }
   }
 
-  /// Check whether a modification or use conflicts with a prior usage.
-  void checkUsage(Object O, UsageInfo &UI, Expr *Ref, UsageKind OtherKind,
-                  bool IsModMod) {
+  /// Check whether a modification or use of an object \p O in an expression
+  /// \p UsageExpr conflicts with a prior usage of kind \p OtherKind. \p UI is
+  /// the \p UsageInfo for the object \p O as obtained via the \p UsageMap.
+  /// \p IsModMod is true when we are checking for a mod-mod unsequenced
+  /// usage and false we are checking for a mod-use unsequenced usage.
+  void checkUsage(Object O, UsageInfo &UI, const Expr *UsageExpr,
+                  UsageKind OtherKind, bool IsModMod) {
     if (UI.Diagnosed)
       return;
 
     const Usage &U = UI.Uses[OtherKind];
-    if (!U.Use || !Tree.isUnsequenced(Region, U.Seq))
+    if (!U.UsageExpr || !Tree.isUnsequenced(Region, U.Seq))
       return;
 
-    Expr *Mod = U.Use;
-    Expr *ModOrUse = Ref;
+    const Expr *Mod = U.UsageExpr;
+    const Expr *ModOrUse = UsageExpr;
     if (OtherKind == UK_Use)
       std::swap(Mod, ModOrUse);
 
@@ -12599,47 +12811,79 @@ class SequenceChecker : public EvaluatedExprVisitor<SequenceChecker> {
     UI.Diagnosed = true;
   }
 
-  void notePreUse(Object O, Expr *Use) {
-    UsageInfo &U = UsageMap[O];
+  // A note on note{Pre, Post}{Use, Mod}:
+  //
+  // (It helps to follow the algorithm with an expression such as
+  //  "((++k)++, k) = k" or "k = (k++, k++)". Both contain unsequenced
+  //  operations before C++17 and both are well-defined in C++17).
+  //
+  // When visiting a node which uses/modify an object we first call notePreUse
+  // or notePreMod before visiting its sub-expression(s). At this point the
+  // children of the current node have not yet been visited and so the eventual
+  // uses/modifications resulting from the children of the current node have not
+  // been recorded yet.
+  //
+  // We then visit the children of the current node. After that notePostUse or
+  // notePostMod is called. These will 1) detect an unsequenced modification
+  // as side effect (as in "k++ + k") and 2) add a new usage with the
+  // appropriate usage kind.
+  //
+  // We also have to be careful that some operation sequences modification as
+  // side effect as well (for example: || or ,). To account for this we wrap
+  // the visitation of such a sub-expression (for example: the LHS of || or ,)
+  // with SequencedSubexpression. SequencedSubexpression is an RAII object
+  // which record usages which are modifications as side effect, and then
+  // downgrade them (or more accurately restore the previous usage which was a
+  // modification as side effect) when exiting the scope of the sequenced
+  // subexpression.
+
+  void notePreUse(Object O, const Expr *UseExpr) {
+    UsageInfo &UI = UsageMap[O];
     // Uses conflict with other modifications.
-    checkUsage(O, U, Use, UK_ModAsValue, false);
+    checkUsage(O, UI, UseExpr, /*OtherKind=*/UK_ModAsValue, /*IsModMod=*/false);
   }
 
-  void notePostUse(Object O, Expr *Use) {
-    UsageInfo &U = UsageMap[O];
-    checkUsage(O, U, Use, UK_ModAsSideEffect, false);
-    addUsage(U, O, Use, UK_Use);
+  void notePostUse(Object O, const Expr *UseExpr) {
+    UsageInfo &UI = UsageMap[O];
+    checkUsage(O, UI, UseExpr, /*OtherKind=*/UK_ModAsSideEffect,
+               /*IsModMod=*/false);
+    addUsage(O, UI, UseExpr, /*UsageKind=*/UK_Use);
   }
 
-  void notePreMod(Object O, Expr *Mod) {
-    UsageInfo &U = UsageMap[O];
+  void notePreMod(Object O, const Expr *ModExpr) {
+    UsageInfo &UI = UsageMap[O];
     // Modifications conflict with other modifications and with uses.
-    checkUsage(O, U, Mod, UK_ModAsValue, true);
-    checkUsage(O, U, Mod, UK_Use, false);
+    checkUsage(O, UI, ModExpr, /*OtherKind=*/UK_ModAsValue, /*IsModMod=*/true);
+    checkUsage(O, UI, ModExpr, /*OtherKind=*/UK_Use, /*IsModMod=*/false);
   }
 
-  void notePostMod(Object O, Expr *Use, UsageKind UK) {
-    UsageInfo &U = UsageMap[O];
-    checkUsage(O, U, Use, UK_ModAsSideEffect, true);
-    addUsage(U, O, Use, UK);
+  void notePostMod(Object O, const Expr *ModExpr, UsageKind UK) {
+    UsageInfo &UI = UsageMap[O];
+    checkUsage(O, UI, ModExpr, /*OtherKind=*/UK_ModAsSideEffect,
+               /*IsModMod=*/true);
+    addUsage(O, UI, ModExpr, /*UsageKind=*/UK);
   }
 
 public:
-  SequenceChecker(Sema &S, Expr *E, SmallVectorImpl<Expr *> &WorkList)
+  SequenceChecker(Sema &S, const Expr *E,
+                  SmallVectorImpl<const Expr *> &WorkList)
       : Base(S.Context), SemaRef(S), Region(Tree.root()), WorkList(WorkList) {
     Visit(E);
+    // Silence a -Wunused-private-field since WorkList is now unused.
+    // TODO: Evaluate if it can be used, and if not remove it.
+    (void)this->WorkList;
   }
 
-  void VisitStmt(Stmt *S) {
+  void VisitStmt(const Stmt *S) {
     // Skip all statements which aren't expressions for now.
   }
 
-  void VisitExpr(Expr *E) {
+  void VisitExpr(const Expr *E) {
     // By default, just recurse to evaluated subexpressions.
     Base::VisitStmt(E);
   }
 
-  void VisitCastExpr(CastExpr *E) {
+  void VisitCastExpr(const CastExpr *E) {
     Object O = Object();
     if (E->getCastKind() == CK_LValueToRValue)
       O = getObject(E->getSubExpr(), false);
@@ -12651,7 +12895,8 @@ public:
       notePostUse(O, E);
   }
 
-  void VisitSequencedExpressions(Expr *SequencedBefore, Expr *SequencedAfter) {
+  void VisitSequencedExpressions(const Expr *SequencedBefore,
+                                 const Expr *SequencedAfter) {
     SequenceTree::Seq BeforeRegion = Tree.allocate(Region);
     SequenceTree::Seq AfterRegion = Tree.allocate(Region);
     SequenceTree::Seq OldRegion = Region;
@@ -12671,17 +12916,46 @@ public:
     Tree.merge(AfterRegion);
   }
 
-  void VisitArraySubscriptExpr(ArraySubscriptExpr *ASE) {
+  void VisitArraySubscriptExpr(const ArraySubscriptExpr *ASE) {
     // C++17 [expr.sub]p1:
     //   The expression E1[E2] is identical (by definition) to *((E1)+(E2)). The
     //   expression E1 is sequenced before the expression E2.
     if (SemaRef.getLangOpts().CPlusPlus17)
       VisitSequencedExpressions(ASE->getLHS(), ASE->getRHS());
-    else
-      Base::VisitStmt(ASE);
+    else {
+      Visit(ASE->getLHS());
+      Visit(ASE->getRHS());
+    }
+  }
+
+  void VisitBinPtrMemD(const BinaryOperator *BO) { VisitBinPtrMem(BO); }
+  void VisitBinPtrMemI(const BinaryOperator *BO) { VisitBinPtrMem(BO); }
+  void VisitBinPtrMem(const BinaryOperator *BO) {
+    // C++17 [expr.mptr.oper]p4:
+    //  Abbreviating pm-expression.*cast-expression as E1.*E2, [...]
+    //  the expression E1 is sequenced before the expression E2.
+    if (SemaRef.getLangOpts().CPlusPlus17)
+      VisitSequencedExpressions(BO->getLHS(), BO->getRHS());
+    else {
+      Visit(BO->getLHS());
+      Visit(BO->getRHS());
+    }
   }
 
-  void VisitBinComma(BinaryOperator *BO) {
+  void VisitBinShl(const BinaryOperator *BO) { VisitBinShlShr(BO); }
+  void VisitBinShr(const BinaryOperator *BO) { VisitBinShlShr(BO); }
+  void VisitBinShlShr(const BinaryOperator *BO) {
+    // C++17 [expr.shift]p4:
+    //  The expression E1 is sequenced before the expression E2.
+    if (SemaRef.getLangOpts().CPlusPlus17)
+      VisitSequencedExpressions(BO->getLHS(), BO->getRHS());
+    else {
+      Visit(BO->getLHS());
+      Visit(BO->getRHS());
+    }
+  }
+
+  void VisitBinComma(const BinaryOperator *BO) {
     // C++11 [expr.comma]p1:
     //   Every value computation and side effect associated with the left
     //   expression is sequenced before every value computation and side
@@ -12689,47 +12963,77 @@ public:
     VisitSequencedExpressions(BO->getLHS(), BO->getRHS());
   }
 
-  void VisitBinAssign(BinaryOperator *BO) {
-    // The modification is sequenced after the value computation of the LHS
-    // and RHS, so check it before inspecting the operands and update the
+  void VisitBinAssign(const BinaryOperator *BO) {
+    SequenceTree::Seq RHSRegion;
+    SequenceTree::Seq LHSRegion;
+    if (SemaRef.getLangOpts().CPlusPlus17) {
+      RHSRegion = Tree.allocate(Region);
+      LHSRegion = Tree.allocate(Region);
+    } else {
+      RHSRegion = Region;
+      LHSRegion = Region;
+    }
+    SequenceTree::Seq OldRegion = Region;
+
+    // C++11 [expr.ass]p1:
+    //  [...] the assignment is sequenced after the value computation
+    //  of the right and left operands, [...]
+    //
+    // so check it before inspecting the operands and update the
     // map afterwards.
-    Object O = getObject(BO->getLHS(), true);
-    if (!O)
-      return VisitExpr(BO);
+    Object O = getObject(BO->getLHS(), /*Mod=*/true);
+    if (O)
+      notePreMod(O, BO);
+
+    if (SemaRef.getLangOpts().CPlusPlus17) {
+      // C++17 [expr.ass]p1:
+      //  [...] The right operand is sequenced before the left operand. [...]
+      {
+        SequencedSubexpression SeqBefore(*this);
+        Region = RHSRegion;
+        Visit(BO->getRHS());
+      }
 
-    notePreMod(O, BO);
+      Region = LHSRegion;
+      Visit(BO->getLHS());
 
-    // C++11 [expr.ass]p7:
-    //   E1 op= E2 is equivalent to E1 = E1 op E2, except that E1 is evaluated
-    //   only once.
-    //
-    // Therefore, for a compound assignment operator, O is considered used
-    // everywhere except within the evaluation of E1 itself.
-    if (isa<CompoundAssignOperator>(BO))
-      notePreUse(O, BO);
+      if (O && isa<CompoundAssignOperator>(BO))
+        notePostUse(O, BO);
 
-    Visit(BO->getLHS());
+    } else {
+      // C++11 does not specify any sequencing between the LHS and RHS.
+      Region = LHSRegion;
+      Visit(BO->getLHS());
 
-    if (isa<CompoundAssignOperator>(BO))
-      notePostUse(O, BO);
+      if (O && isa<CompoundAssignOperator>(BO))
+        notePostUse(O, BO);
 
-    Visit(BO->getRHS());
+      Region = RHSRegion;
+      Visit(BO->getRHS());
+    }
 
     // C++11 [expr.ass]p1:
-    //   the assignment is sequenced [...] before the value computation of the
-    //   assignment expression.
+    //  the assignment is sequenced [...] before the value computation of the
+    //  assignment expression.
     // C11 6.5.16/3 has no such rule.
-    notePostMod(O, BO, SemaRef.getLangOpts().CPlusPlus ? UK_ModAsValue
-                                                       : UK_ModAsSideEffect);
+    Region = OldRegion;
+    if (O)
+      notePostMod(O, BO,
+                  SemaRef.getLangOpts().CPlusPlus ? UK_ModAsValue
+                                                  : UK_ModAsSideEffect);
+    if (SemaRef.getLangOpts().CPlusPlus17) {
+      Tree.merge(RHSRegion);
+      Tree.merge(LHSRegion);
+    }
   }
 
-  void VisitCompoundAssignOperator(CompoundAssignOperator *CAO) {
+  void VisitCompoundAssignOperator(const CompoundAssignOperator *CAO) {
     VisitBinAssign(CAO);
   }
 
-  void VisitUnaryPreInc(UnaryOperator *UO) { VisitUnaryPreIncDec(UO); }
-  void VisitUnaryPreDec(UnaryOperator *UO) { VisitUnaryPreIncDec(UO); }
-  void VisitUnaryPreIncDec(UnaryOperator *UO) {
+  void VisitUnaryPreInc(const UnaryOperator *UO) { VisitUnaryPreIncDec(UO); }
+  void VisitUnaryPreDec(const UnaryOperator *UO) { VisitUnaryPreIncDec(UO); }
+  void VisitUnaryPreIncDec(const UnaryOperator *UO) {
     Object O = getObject(UO->getSubExpr(), true);
     if (!O)
       return VisitExpr(UO);
@@ -12738,13 +13042,14 @@ public:
     Visit(UO->getSubExpr());
     // C++11 [expr.pre.incr]p1:
     //   the expression ++x is equivalent to x+=1
-    notePostMod(O, UO, SemaRef.getLangOpts().CPlusPlus ? UK_ModAsValue
-                                                       : UK_ModAsSideEffect);
+    notePostMod(O, UO,
+                SemaRef.getLangOpts().CPlusPlus ? UK_ModAsValue
+                                                : UK_ModAsSideEffect);
   }
 
-  void VisitUnaryPostInc(UnaryOperator *UO) { VisitUnaryPostIncDec(UO); }
-  void VisitUnaryPostDec(UnaryOperator *UO) { VisitUnaryPostIncDec(UO); }
-  void VisitUnaryPostIncDec(UnaryOperator *UO) {
+  void VisitUnaryPostInc(const UnaryOperator *UO) { VisitUnaryPostIncDec(UO); }
+  void VisitUnaryPostDec(const UnaryOperator *UO) { VisitUnaryPostIncDec(UO); }
+  void VisitUnaryPostIncDec(const UnaryOperator *UO) {
     Object O = getObject(UO->getSubExpr(), true);
     if (!O)
       return VisitExpr(UO);
@@ -12754,67 +13059,129 @@ public:
     notePostMod(O, UO, UK_ModAsSideEffect);
   }
 
-  /// Don't visit the RHS of '&&' or '||' if it might not be evaluated.
-  void VisitBinLOr(BinaryOperator *BO) {
-    // The side-effects of the LHS of an '&&' are sequenced before the
-    // value computation of the RHS, and hence before the value computation
-    // of the '&&' itself, unless the LHS evaluates to zero. We treat them
-    // as if they were unconditionally sequenced.
+  void VisitBinLOr(const BinaryOperator *BO) {
+    // C++11 [expr.log.or]p2:
+    //  If the second expression is evaluated, every value computation and
+    //  side effect associated with the first expression is sequenced before
+    //  every value computation and side effect associated with the
+    //  second expression.
+    SequenceTree::Seq LHSRegion = Tree.allocate(Region);
+    SequenceTree::Seq RHSRegion = Tree.allocate(Region);
+    SequenceTree::Seq OldRegion = Region;
+
     EvaluationTracker Eval(*this);
     {
       SequencedSubexpression Sequenced(*this);
+      Region = LHSRegion;
       Visit(BO->getLHS());
     }
 
-    bool Result;
-    if (Eval.evaluate(BO->getLHS(), Result)) {
-      if (!Result)
-        Visit(BO->getRHS());
-    } else {
-      // Check for unsequenced operations in the RHS, treating it as an
-      // entirely separate evaluation.
-      //
-      // FIXME: If there are operations in the RHS which are unsequenced
-      // with respect to operations outside the RHS, and those operations
-      // are unconditionally evaluated, diagnose them.
-      WorkList.push_back(BO->getRHS());
+    // C++11 [expr.log.or]p1:
+    //  [...] the second operand is not evaluated if the first operand
+    //  evaluates to true.
+    bool EvalResult = false;
+    bool EvalOK = Eval.evaluate(BO->getLHS(), EvalResult);
+    bool ShouldVisitRHS = !EvalOK || (EvalOK && !EvalResult);
+    if (ShouldVisitRHS) {
+      Region = RHSRegion;
+      Visit(BO->getRHS());
     }
-  }
-  void VisitBinLAnd(BinaryOperator *BO) {
+
+    Region = OldRegion;
+    Tree.merge(LHSRegion);
+    Tree.merge(RHSRegion);
+  }
+
+  void VisitBinLAnd(const BinaryOperator *BO) {
+    // C++11 [expr.log.and]p2:
+    //  If the second expression is evaluated, every value computation and
+    //  side effect associated with the first expression is sequenced before
+    //  every value computation and side effect associated with the
+    //  second expression.
+    SequenceTree::Seq LHSRegion = Tree.allocate(Region);
+    SequenceTree::Seq RHSRegion = Tree.allocate(Region);
+    SequenceTree::Seq OldRegion = Region;
+
     EvaluationTracker Eval(*this);
     {
       SequencedSubexpression Sequenced(*this);
+      Region = LHSRegion;
       Visit(BO->getLHS());
     }
 
-    bool Result;
-    if (Eval.evaluate(BO->getLHS(), Result)) {
-      if (Result)
-        Visit(BO->getRHS());
-    } else {
-      WorkList.push_back(BO->getRHS());
+    // C++11 [expr.log.and]p1:
+    //  [...] the second operand is not evaluated if the first operand is false.
+    bool EvalResult = false;
+    bool EvalOK = Eval.evaluate(BO->getLHS(), EvalResult);
+    bool ShouldVisitRHS = !EvalOK || (EvalOK && EvalResult);
+    if (ShouldVisitRHS) {
+      Region = RHSRegion;
+      Visit(BO->getRHS());
     }
-  }
 
-  // Only visit the condition, unless we can be sure which subexpression will
-  // be chosen.
-  void VisitAbstractConditionalOperator(AbstractConditionalOperator *CO) {
+    Region = OldRegion;
+    Tree.merge(LHSRegion);
+    Tree.merge(RHSRegion);
+  }
+
+  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO) {
+    // C++11 [expr.cond]p1:
+    //  [...] Every value computation and side effect associated with the first
+    //  expression is sequenced before every value computation and side effect
+    //  associated with the second or third expression.
+    SequenceTree::Seq ConditionRegion = Tree.allocate(Region);
+
+    // No sequencing is specified between the true and false expression.
+    // However since exactly one of both is going to be evaluated we can
+    // consider them to be sequenced. This is needed to avoid warning on
+    // something like "x ? y+= 1 : y += 2;" in the case where we will visit
+    // both the true and false expressions because we can't evaluate x.
+    // This will still allow us to detect an expression like (pre C++17)
+    // "(x ? y += 1 : y += 2) = y".
+    //
+    // We don't wrap the visitation of the true and false expression with
+    // SequencedSubexpression because we don't want to downgrade modifications
+    // as side effect in the true and false expressions after the visition
+    // is done. (for example in the expression "(x ? y++ : y++) + y" we should
+    // not warn between the two "y++", but we should warn between the "y++"
+    // and the "y".
+    SequenceTree::Seq TrueRegion = Tree.allocate(Region);
+    SequenceTree::Seq FalseRegion = Tree.allocate(Region);
+    SequenceTree::Seq OldRegion = Region;
+
     EvaluationTracker Eval(*this);
     {
       SequencedSubexpression Sequenced(*this);
+      Region = ConditionRegion;
       Visit(CO->getCond());
     }
 
-    bool Result;
-    if (Eval.evaluate(CO->getCond(), Result))
-      Visit(Result ? CO->getTrueExpr() : CO->getFalseExpr());
-    else {
-      WorkList.push_back(CO->getTrueExpr());
-      WorkList.push_back(CO->getFalseExpr());
+    // C++11 [expr.cond]p1:
+    // [...] The first expression is contextually converted to bool (Clause 4).
+    // It is evaluated and if it is true, the result of the conditional
+    // expression is the value of the second expression, otherwise that of the
+    // third expression. Only one of the second and third expressions is
+    // evaluated. [...]
+    bool EvalResult = false;
+    bool EvalOK = Eval.evaluate(CO->getCond(), EvalResult);
+    bool ShouldVisitTrueExpr = !EvalOK || (EvalOK && EvalResult);
+    bool ShouldVisitFalseExpr = !EvalOK || (EvalOK && !EvalResult);
+    if (ShouldVisitTrueExpr) {
+      Region = TrueRegion;
+      Visit(CO->getTrueExpr());
+    }
+    if (ShouldVisitFalseExpr) {
+      Region = FalseRegion;
+      Visit(CO->getFalseExpr());
     }
+
+    Region = OldRegion;
+    Tree.merge(ConditionRegion);
+    Tree.merge(TrueRegion);
+    Tree.merge(FalseRegion);
   }
 
-  void VisitCallExpr(CallExpr *CE) {
+  void VisitCallExpr(const CallExpr *CE) {
     // C++11 [intro.execution]p15:
     //   When calling a function [...], every value computation and side effect
     //   associated with any argument expression, or with the postfix expression
@@ -12822,12 +13189,13 @@ public:
     //   expression or statement in the body of the function [and thus before
     //   the value computation of its result].
     SequencedSubexpression Sequenced(*this);
-    Base::VisitCallExpr(CE);
+    SemaRef.runWithSufficientStackSpace(CE->getExprLoc(),
+                                        [&] { Base::VisitCallExpr(CE); });
 
     // FIXME: CXXNewExpr and CXXDeleteExpr implicitly call functions.
   }
 
-  void VisitCXXConstructExpr(CXXConstructExpr *CCE) {
+  void VisitCXXConstructExpr(const CXXConstructExpr *CCE) {
     // This is a call, so all subexpressions are sequenced before the result.
     SequencedSubexpression Sequenced(*this);
 
@@ -12837,8 +13205,8 @@ public:
     // In C++11, list initializations are sequenced.
     SmallVector<SequenceTree::Seq, 32> Elts;
     SequenceTree::Seq Parent = Region;
-    for (CXXConstructExpr::arg_iterator I = CCE->arg_begin(),
-                                        E = CCE->arg_end();
+    for (CXXConstructExpr::const_arg_iterator I = CCE->arg_begin(),
+                                              E = CCE->arg_end();
          I != E; ++I) {
       Region = Tree.allocate(Parent);
       Elts.push_back(Region);
@@ -12851,7 +13219,7 @@ public:
       Tree.merge(Elts[I]);
   }
 
-  void VisitInitListExpr(InitListExpr *ILE) {
+  void VisitInitListExpr(const InitListExpr *ILE) {
     if (!SemaRef.getLangOpts().CPlusPlus11)
       return VisitExpr(ILE);
 
@@ -12859,8 +13227,9 @@ public:
     SmallVector<SequenceTree::Seq, 32> Elts;
     SequenceTree::Seq Parent = Region;
     for (unsigned I = 0; I < ILE->getNumInits(); ++I) {
-      Expr *E = ILE->getInit(I);
-      if (!E) continue;
+      const Expr *E = ILE->getInit(I);
+      if (!E)
+        continue;
       Region = Tree.allocate(Parent);
       Elts.push_back(Region);
       Visit(E);
@@ -12875,11 +13244,11 @@ public:
 
 } // namespace
 
-void Sema::CheckUnsequencedOperations(Expr *E) {
-  SmallVector<Expr *, 8> WorkList;
+void Sema::CheckUnsequencedOperations(const Expr *E) {
+  SmallVector<const Expr *, 8> WorkList;
   WorkList.push_back(E);
   while (!WorkList.empty()) {
-    Expr *Item = WorkList.pop_back_val();
+    const Expr *Item = WorkList.pop_back_val();
     SequenceChecker(*this, Item, WorkList);
   }
 }
@@ -14577,6 +14946,8 @@ void Sema::RefersToMemberWithReducedAlignment(
   bool AnyIsPacked = false;
   do {
     QualType BaseType = ME->getBase()->getType();
+    if (BaseType->isDependentType())
+      return;
     if (ME->isArrow())
       BaseType = BaseType->getPointeeType();
     RecordDecl *RD = BaseType->castAs<RecordType>()->getDecl();
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index f24c3b234ff2..7260977c634d 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -692,18 +692,6 @@ getRequiredQualification(ASTContext &Context, const DeclContext *CurContext,
   return Result;
 }
 
-/// Determine whether \p Id is a name reserved for the implementation (C99
-/// 7.1.3, C++ [lib.global.names]).
-static bool isReservedName(const IdentifierInfo *Id,
-                           bool doubleUnderscoreOnly = false) {
-  if (Id->getLength() < 2)
-    return false;
-  const char *Name = Id->getNameStart();
-  return Name[0] == '_' &&
-         (Name[1] == '_' ||
-          (Name[1] >= 'A' && Name[1] <= 'Z' && !doubleUnderscoreOnly));
-}
-
 // Some declarations have reserved names that we don't want to ever show.
 // Filter out names reserved for the implementation if they come from a
 // system header.
@@ -713,13 +701,13 @@ static bool shouldIgnoreDueToReservedName(const NamedDecl *ND, Sema &SemaRef) {
     return false;
 
   // Ignore reserved names for compiler provided decls.
-  if (isReservedName(Id) && ND->getLocation().isInvalid())
+  if (Id->isReservedName() && ND->getLocation().isInvalid())
     return true;
 
   // For system headers ignore only double-underscore names.
   // This allows for system headers providing private symbols with a single
   // underscore.
-  if (isReservedName(Id, /*doubleUnderscoreOnly=*/true) &&
+  if (Id->isReservedName(/*doubleUnderscoreOnly=*/true) &&
       SemaRef.SourceMgr.isInSystemHeader(
           SemaRef.SourceMgr.getSpellingLoc(ND->getLocation())))
     return true;
@@ -1321,7 +1309,7 @@ void ResultBuilder::AddResult(Result R, DeclContext *CurContext,
         /// Motivating case is const_iterator begin() const vs iterator begin().
         auto &OverloadSet = OverloadMap[std::make_pair(
             CurContext, Method->getDeclName().getAsOpaqueInteger())];
-        for (const DeclIndexPair& Entry : OverloadSet) {
+        for (const DeclIndexPair Entry : OverloadSet) {
           Result &Incumbent = Results[Entry.second];
           switch (compareOverloads(*Method,
                                    *cast<CXXMethodDecl>(Incumbent.Declaration),
@@ -2324,6 +2312,13 @@ static void AddOrdinaryNameResults(Sema::ParserCompletionContext CCC, Scope *S,
         Builder.AddChunk(CodeCompletionString::CK_SemiColon);
         Results.AddResult(Result(Builder.TakeString()));
       }
+      // For pointers, suggest 'return nullptr' in C++.
+      if (SemaRef.getLangOpts().CPlusPlus11 &&
+          (ReturnType->isPointerType() || ReturnType->isMemberPointerType())) {
+        Builder.AddTypedTextChunk("return nullptr");
+        Builder.AddChunk(CodeCompletionString::CK_SemiColon);
+        Results.AddResult(Result(Builder.TakeString()));
+      }
     }
 
     // goto identifier ;
@@ -2991,7 +2986,11 @@ static void AddTemplateParameterChunks(
     if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(*P)) {
       if (TTP->wasDeclaredWithTypename())
         PlaceholderStr = "typename";
-      else
+      else if (const auto *TC = TTP->getTypeConstraint()) {
+        llvm::raw_string_ostream OS(PlaceholderStr);
+        TC->print(OS, Policy);
+        OS.flush();
+      } else
         PlaceholderStr = "class";
 
       if (TTP->getIdentifier()) {
@@ -3327,6 +3326,18 @@ CodeCompletionResult::createCodeCompletionStringForOverride(
   return Result.TakeString();
 }
 
+// FIXME: Right now this works well with lambdas. Add support for other functor
+// types like std::function.
+static const NamedDecl *extractFunctorCallOperator(const NamedDecl *ND) {
+  const auto *VD = dyn_cast<VarDecl>(ND);
+  if (!VD)
+    return nullptr;
+  const auto *RecordDecl = VD->getType()->getAsCXXRecordDecl();
+  if (!RecordDecl || !RecordDecl->isLambda())
+    return nullptr;
+  return RecordDecl->getLambdaCallOperator();
+}
+
 CodeCompletionString *CodeCompletionResult::createCodeCompletionStringForDecl(
     Preprocessor &PP, ASTContext &Ctx, CodeCompletionBuilder &Result,
     bool IncludeBriefComments, const CodeCompletionContext &CCContext,
@@ -3351,9 +3362,8 @@ CodeCompletionString *CodeCompletionResult::createCodeCompletionStringForDecl(
   for (const auto *I : ND->specific_attrs<AnnotateAttr>())
     Result.AddAnnotation(Result.getAllocator().CopyString(I->getAnnotation()));
 
-  AddResultTypeChunk(Ctx, Policy, ND, CCContext.getBaseType(), Result);
-
-  if (const auto *Function = dyn_cast<FunctionDecl>(ND)) {
+  auto AddFunctionTypeAndResult = [&](const FunctionDecl *Function) {
+    AddResultTypeChunk(Ctx, Policy, Function, CCContext.getBaseType(), Result);
     AddQualifierToCompletionString(Result, Qualifier, QualifierIsInformative,
                                    Ctx, Policy);
     AddTypedNameChunk(Ctx, Policy, ND, Result);
@@ -3361,9 +3371,21 @@ CodeCompletionString *CodeCompletionResult::createCodeCompletionStringForDecl(
     AddFunctionParameterChunks(PP, Policy, Function, Result);
     Result.AddChunk(CodeCompletionString::CK_RightParen);
     AddFunctionTypeQualsToCompletionString(Result, Function);
+  };
+
+  if (const auto *Function = dyn_cast<FunctionDecl>(ND)) {
+    AddFunctionTypeAndResult(Function);
+    return Result.TakeString();
+  }
+
+  if (const auto *CallOperator =
+          dyn_cast_or_null<FunctionDecl>(extractFunctorCallOperator(ND))) {
+    AddFunctionTypeAndResult(CallOperator);
     return Result.TakeString();
   }
 
+  AddResultTypeChunk(Ctx, Policy, ND, CCContext.getBaseType(), Result);
+
   if (const FunctionTemplateDecl *FunTmpl =
           dyn_cast<FunctionTemplateDecl>(ND)) {
     AddQualifierToCompletionString(Result, Qualifier, QualifierIsInformative,
@@ -3429,6 +3451,7 @@ CodeCompletionString *CodeCompletionResult::createCodeCompletionStringForDecl(
     Result.AddChunk(CodeCompletionString::CK_RightAngle);
     return Result.TakeString();
   }
+
   if (const auto *Method = dyn_cast<ObjCMethodDecl>(ND)) {
     Selector Sel = Method->getSelector();
     if (Sel.isUnarySelector()) {
@@ -3653,6 +3676,10 @@ CodeCompleteConsumer::OverloadCandidate::CreateSignatureString(
     unsigned CurrentArg, Sema &S, CodeCompletionAllocator &Allocator,
     CodeCompletionTUInfo &CCTUInfo, bool IncludeBriefComments) const {
   PrintingPolicy Policy = getCompletionPrintingPolicy(S);
+  // Show signatures of constructors as they are declared:
+  //   vector(int n) rather than vector<string>(int n)
+  // This is less noisy without being less clear, and avoids tricky cases.
+  Policy.SuppressTemplateArgsInCXXConstructors = true;
 
   // FIXME: Set priority, availability appropriately.
   CodeCompletionBuilder Result(Allocator, CCTUInfo, 1,
@@ -4783,7 +4810,7 @@ void Sema::CodeCompleteMemberReferenceExpr(Scope *S, Expr *Base,
       }
 
       // Add properties from the protocols in a qualified interface.
-      for (auto *I : BaseType->getAs<ObjCObjectPointerType>()->quals())
+      for (auto *I : BaseType->castAs<ObjCObjectPointerType>()->quals())
         AddObjCProperties(CCContext, I, true, /*AllowNullaryMethods=*/true,
                           CurContext, AddedProperties, Results,
                           IsBaseExprStatement, /*IsClassProperty*/ false,
@@ -4796,7 +4823,7 @@ void Sema::CodeCompleteMemberReferenceExpr(Scope *S, Expr *Base,
               BaseType->getAs<ObjCObjectPointerType>())
         Class = ObjCPtr->getInterfaceDecl();
       else
-        Class = BaseType->getAs<ObjCObjectType>()->getInterface();
+        Class = BaseType->castAs<ObjCObjectType>()->getInterface();
 
       // Add all ivars from this class and its superclasses.
       if (Class) {
@@ -5330,18 +5357,21 @@ void Sema::CodeCompleteAfterIf(Scope *S) {
 }
 
 void Sema::CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS,
-                                   bool EnteringContext, QualType BaseType,
+                                   bool EnteringContext,
+                                   bool IsUsingDeclaration, QualType BaseType,
                                    QualType PreferredType) {
   if (SS.isEmpty() || !CodeCompleter)
     return;
 
+  CodeCompletionContext CC(CodeCompletionContext::CCC_Symbol, PreferredType);
+  CC.setIsUsingDeclaration(IsUsingDeclaration);
+  CC.setCXXScopeSpecifier(SS);
+
   // We want to keep the scope specifier even if it's invalid (e.g. the scope
   // "a::b::" is not corresponding to any context/namespace in the AST), since
   // it can be useful for global code completion which have information about
   // contexts/symbols that are not in the AST.
   if (SS.isInvalid()) {
-    CodeCompletionContext CC(CodeCompletionContext::CCC_Symbol, PreferredType);
-    CC.setCXXScopeSpecifier(SS);
     // As SS is invalid, we try to collect accessible contexts from the current
     // scope with a dummy lookup so that the completion consumer can try to
     // guess what the specified scope is.
@@ -5371,10 +5401,8 @@ void Sema::CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS,
   if (!isDependentScopeSpecifier(SS) && RequireCompleteDeclContext(SS, Ctx))
     return;
 
-  ResultBuilder Results(
-      *this, CodeCompleter->getAllocator(),
-      CodeCompleter->getCodeCompletionTUInfo(),
-      CodeCompletionContext(CodeCompletionContext::CCC_Symbol, PreferredType));
+  ResultBuilder Results(*this, CodeCompleter->getAllocator(),
+                        CodeCompleter->getCodeCompletionTUInfo(), CC);
   if (!PreferredType.isNull())
     Results.setPreferredType(PreferredType);
   Results.EnterNewScope();
@@ -5403,23 +5431,21 @@ void Sema::CodeCompleteQualifiedId(Scope *S, CXXScopeSpec &SS,
                        CodeCompleter->loadExternal());
   }
 
-  auto CC = Results.getCompletionContext();
-  CC.setCXXScopeSpecifier(SS);
-
-  HandleCodeCompleteResults(this, CodeCompleter, CC, Results.data(),
-                            Results.size());
+  HandleCodeCompleteResults(this, CodeCompleter, Results.getCompletionContext(),
+                            Results.data(), Results.size());
 }
 
 void Sema::CodeCompleteUsing(Scope *S) {
   if (!CodeCompleter)
     return;
 
+  // This can be both a using alias or using declaration, in the former we
+  // expect a new name and a symbol in the latter case.
+  CodeCompletionContext Context(CodeCompletionContext::CCC_SymbolOrNewName);
+  Context.setIsUsingDeclaration(true);
+
   ResultBuilder Results(*this, CodeCompleter->getAllocator(),
-                        CodeCompleter->getCodeCompletionTUInfo(),
-                        // This can be both a using alias or using
-                        // declaration, in the former we expect a new name and a
-                        // symbol in the latter case.
-                        CodeCompletionContext::CCC_SymbolOrNewName,
+                        CodeCompleter->getCodeCompletionTUInfo(), Context,
                         &ResultBuilder::IsNestedNameSpecifier);
   Results.EnterNewScope();
 
@@ -7721,8 +7747,8 @@ static void AddObjCKeyValueCompletions(ObjCPropertyDecl *Property,
   if (IsInstanceMethod &&
       (ReturnType.isNull() ||
        (ReturnType->isObjCObjectPointerType() &&
-        ReturnType->getAs<ObjCObjectPointerType>()->getInterfaceDecl() &&
-        ReturnType->getAs<ObjCObjectPointerType>()
+        ReturnType->castAs<ObjCObjectPointerType>()->getInterfaceDecl() &&
+        ReturnType->castAs<ObjCObjectPointerType>()
                 ->getInterfaceDecl()
                 ->getName() == "NSArray"))) {
     std::string SelectorName = (Twine(Property->getName()) + "AtIndexes").str();
@@ -8108,8 +8134,8 @@ static void AddObjCKeyValueCompletions(ObjCPropertyDecl *Property,
   if (!IsInstanceMethod &&
       (ReturnType.isNull() ||
        (ReturnType->isObjCObjectPointerType() &&
-        ReturnType->getAs<ObjCObjectPointerType>()->getInterfaceDecl() &&
-        ReturnType->getAs<ObjCObjectPointerType>()
+        ReturnType->castAs<ObjCObjectPointerType>()->getInterfaceDecl() &&
+        ReturnType->castAs<ObjCObjectPointerType>()
                 ->getInterfaceDecl()
                 ->getName() == "NSSet"))) {
     std::string SelectorName =
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 848ccf543445..018ac2d7dc9d 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -11,15 +11,24 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "clang/Sema/SemaConcept.h"
 #include "clang/Sema/Sema.h"
+#include "clang/Sema/SemaInternal.h"
 #include "clang/Sema/SemaDiagnostic.h"
 #include "clang/Sema/TemplateDeduction.h"
 #include "clang/Sema/Template.h"
 #include "clang/AST/ExprCXX.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/OperatorPrecedence.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/PointerUnion.h"
 using namespace clang;
 using namespace sema;
 
-bool Sema::CheckConstraintExpression(Expr *ConstraintExpression) {
+bool
+Sema::CheckConstraintExpression(Expr *ConstraintExpression, Token NextToken,
+                                bool *PossibleNonPrimary,
+                                bool IsTrailingRequiresClause) {
   // C++2a [temp.constr.atomic]p1
   // ..E shall be a constant expression of type bool.
 
@@ -27,99 +36,793 @@ bool Sema::CheckConstraintExpression(Expr *ConstraintExpression) {
 
   if (auto *BinOp = dyn_cast<BinaryOperator>(ConstraintExpression)) {
     if (BinOp->getOpcode() == BO_LAnd || BinOp->getOpcode() == BO_LOr)
-      return CheckConstraintExpression(BinOp->getLHS()) &&
-             CheckConstraintExpression(BinOp->getRHS());
+      return CheckConstraintExpression(BinOp->getLHS(), NextToken,
+                                       PossibleNonPrimary) &&
+             CheckConstraintExpression(BinOp->getRHS(), NextToken,
+                                       PossibleNonPrimary);
   } else if (auto *C = dyn_cast<ExprWithCleanups>(ConstraintExpression))
-    return CheckConstraintExpression(C->getSubExpr());
+    return CheckConstraintExpression(C->getSubExpr(), NextToken,
+                                     PossibleNonPrimary);
+
+  QualType Type = ConstraintExpression->getType();
+
+  auto CheckForNonPrimary = [&] {
+    if (PossibleNonPrimary)
+      *PossibleNonPrimary =
+          // We have the following case:
+          // template<typename> requires func(0) struct S { };
+          // The user probably isn't aware of the parentheses required around
+          // the function call, and we're only going to parse 'func' as the
+          // primary-expression, and complain that it is of non-bool type.
+          (NextToken.is(tok::l_paren) &&
+           (IsTrailingRequiresClause ||
+            (Type->isDependentType() &&
+             IsDependentFunctionNameExpr(ConstraintExpression)) ||
+            Type->isFunctionType() ||
+            Type->isSpecificBuiltinType(BuiltinType::Overload))) ||
+          // We have the following case:
+          // template<typename T> requires size_<T> == 0 struct S { };
+          // The user probably isn't aware of the parentheses required around
+          // the binary operator, and we're only going to parse 'func' as the
+          // first operand, and complain that it is of non-bool type.
+          getBinOpPrecedence(NextToken.getKind(),
+                             /*GreaterThanIsOperator=*/true,
+                             getLangOpts().CPlusPlus11) > prec::LogicalAnd;
+  };
 
   // An atomic constraint!
-  if (ConstraintExpression->isTypeDependent())
+  if (ConstraintExpression->isTypeDependent()) {
+    CheckForNonPrimary();
     return true;
+  }
 
-  QualType Type = ConstraintExpression->getType();
   if (!Context.hasSameUnqualifiedType(Type, Context.BoolTy)) {
     Diag(ConstraintExpression->getExprLoc(),
          diag::err_non_bool_atomic_constraint) << Type
         << ConstraintExpression->getSourceRange();
+    CheckForNonPrimary();
     return false;
   }
+
+  if (PossibleNonPrimary)
+      *PossibleNonPrimary = false;
   return true;
 }
 
-bool
-Sema::CalculateConstraintSatisfaction(ConceptDecl *NamedConcept,
-                                      MultiLevelTemplateArgumentList &MLTAL,
-                                      Expr *ConstraintExpr,
-                                      bool &IsSatisfied) {
+template <typename AtomicEvaluator>
+static bool
+calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
+                                ConstraintSatisfaction &Satisfaction,
+                                AtomicEvaluator &&Evaluator) {
   ConstraintExpr = ConstraintExpr->IgnoreParenImpCasts();
 
   if (auto *BO = dyn_cast<BinaryOperator>(ConstraintExpr)) {
-    if (BO->getOpcode() == BO_LAnd) {
-      if (CalculateConstraintSatisfaction(NamedConcept, MLTAL, BO->getLHS(),
-                                          IsSatisfied))
+    if (BO->getOpcode() == BO_LAnd || BO->getOpcode() == BO_LOr) {
+      if (calculateConstraintSatisfaction(S, BO->getLHS(), Satisfaction,
+                                          Evaluator))
         return true;
-      if (!IsSatisfied)
+
+      bool IsLHSSatisfied = Satisfaction.IsSatisfied;
+
+      if (BO->getOpcode() == BO_LOr && IsLHSSatisfied)
+        // [temp.constr.op] p3
+        //    A disjunction is a constraint taking two operands. To determine if
+        //    a disjunction is satisfied, the satisfaction of the first operand
+        //    is checked. If that is satisfied, the disjunction is satisfied.
+        //    Otherwise, the disjunction is satisfied if and only if the second
+        //    operand is satisfied.
         return false;
-      return CalculateConstraintSatisfaction(NamedConcept, MLTAL, BO->getRHS(),
-                                             IsSatisfied);
-    } else if (BO->getOpcode() == BO_LOr) {
-      if (CalculateConstraintSatisfaction(NamedConcept, MLTAL, BO->getLHS(),
-                                          IsSatisfied))
-        return true;
-      if (IsSatisfied)
+
+      if (BO->getOpcode() == BO_LAnd && !IsLHSSatisfied)
+        // [temp.constr.op] p2
+        //    A conjunction is a constraint taking two operands. To determine if
+        //    a conjunction is satisfied, the satisfaction of the first operand
+        //    is checked. If that is not satisfied, the conjunction is not
+        //    satisfied. Otherwise, the conjunction is satisfied if and only if
+        //    the second operand is satisfied.
         return false;
-      return CalculateConstraintSatisfaction(NamedConcept, MLTAL, BO->getRHS(),
-                                             IsSatisfied);
+
+      return calculateConstraintSatisfaction(S, BO->getRHS(), Satisfaction,
+          std::forward<AtomicEvaluator>(Evaluator));
     }
   }
   else if (auto *C = dyn_cast<ExprWithCleanups>(ConstraintExpr))
-    return CalculateConstraintSatisfaction(NamedConcept, MLTAL, C->getSubExpr(),
-                                           IsSatisfied);
+    return calculateConstraintSatisfaction(S, C->getSubExpr(), Satisfaction,
+        std::forward<AtomicEvaluator>(Evaluator));
 
-  EnterExpressionEvaluationContext ConstantEvaluated(
-      *this, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+  // An atomic constraint expression
+  ExprResult SubstitutedAtomicExpr = Evaluator(ConstraintExpr);
 
-  // Atomic constraint - substitute arguments and check satisfaction.
-  ExprResult E;
-  {
-    TemplateDeductionInfo Info(ConstraintExpr->getBeginLoc());
-    InstantiatingTemplate Inst(*this, ConstraintExpr->getBeginLoc(),
-                               InstantiatingTemplate::ConstraintSubstitution{},
-                               NamedConcept, Info,
-                               ConstraintExpr->getSourceRange());
-    if (Inst.isInvalid())
-      return true;
-    // We do not want error diagnostics escaping here.
-    Sema::SFINAETrap Trap(*this);
+  if (SubstitutedAtomicExpr.isInvalid())
+    return true;
+
+  if (!SubstitutedAtomicExpr.isUsable())
+    // Evaluator has decided satisfaction without yielding an expression.
+    return false;
 
-    E = SubstExpr(ConstraintExpr, MLTAL);
-    if (E.isInvalid() || Trap.hasErrorOccurred()) {
+  EnterExpressionEvaluationContext ConstantEvaluated(
+      S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+  SmallVector<PartialDiagnosticAt, 2> EvaluationDiags;
+  Expr::EvalResult EvalResult;
+  EvalResult.Diag = &EvaluationDiags;
+  if (!SubstitutedAtomicExpr.get()->EvaluateAsRValue(EvalResult, S.Context)) {
       // C++2a [temp.constr.atomic]p1
-      //   ...If substitution results in an invalid type or expression, the
-      //   constraint is not satisfied.
-      IsSatisfied = false;
+      //   ...E shall be a constant expression of type bool.
+    S.Diag(SubstitutedAtomicExpr.get()->getBeginLoc(),
+           diag::err_non_constant_constraint_expression)
+        << SubstitutedAtomicExpr.get()->getSourceRange();
+    for (const PartialDiagnosticAt &PDiag : EvaluationDiags)
+      S.Diag(PDiag.first, PDiag.second);
+    return true;
+  }
+
+  Satisfaction.IsSatisfied = EvalResult.Val.getInt().getBoolValue();
+  if (!Satisfaction.IsSatisfied)
+    Satisfaction.Details.emplace_back(ConstraintExpr,
+                                      SubstitutedAtomicExpr.get());
+
+  return false;
+}
+
+template <typename TemplateDeclT>
+static bool calculateConstraintSatisfaction(
+    Sema &S, TemplateDeclT *Template, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceLocation TemplateNameLoc, MultiLevelTemplateArgumentList &MLTAL,
+    const Expr *ConstraintExpr, ConstraintSatisfaction &Satisfaction) {
+  return calculateConstraintSatisfaction(
+      S, ConstraintExpr, Satisfaction, [&](const Expr *AtomicExpr) {
+        EnterExpressionEvaluationContext ConstantEvaluated(
+            S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
+
+        // Atomic constraint - substitute arguments and check satisfaction.
+        ExprResult SubstitutedExpression;
+        {
+          TemplateDeductionInfo Info(TemplateNameLoc);
+          Sema::InstantiatingTemplate Inst(S, AtomicExpr->getBeginLoc(),
+              Sema::InstantiatingTemplate::ConstraintSubstitution{}, Template,
+              Info, AtomicExpr->getSourceRange());
+          if (Inst.isInvalid())
+            return ExprError();
+          // We do not want error diagnostics escaping here.
+          Sema::SFINAETrap Trap(S);
+          SubstitutedExpression = S.SubstExpr(const_cast<Expr *>(AtomicExpr),
+                                              MLTAL);
+          if (SubstitutedExpression.isInvalid() || Trap.hasErrorOccurred()) {
+            // C++2a [temp.constr.atomic]p1
+            //   ...If substitution results in an invalid type or expression, the
+            //   constraint is not satisfied.
+            if (!Trap.hasErrorOccurred())
+              // A non-SFINAE error has occured as a result of this
+              // substitution.
+              return ExprError();
+
+            PartialDiagnosticAt SubstDiag{SourceLocation(),
+                                          PartialDiagnostic::NullDiagnostic()};
+            Info.takeSFINAEDiagnostic(SubstDiag);
+            // FIXME: Concepts: This is an unfortunate consequence of there
+            //  being no serialization code for PartialDiagnostics and the fact
+            //  that serializing them would likely take a lot more storage than
+            //  just storing them as strings. We would still like, in the
+            //  future, to serialize the proper PartialDiagnostic as serializing
+            //  it as a string defeats the purpose of the diagnostic mechanism.
+            SmallString<128> DiagString;
+            DiagString = ": ";
+            SubstDiag.second.EmitToString(S.getDiagnostics(), DiagString);
+            unsigned MessageSize = DiagString.size();
+            char *Mem = new (S.Context) char[MessageSize];
+            memcpy(Mem, DiagString.c_str(), MessageSize);
+            Satisfaction.Details.emplace_back(
+                AtomicExpr,
+                new (S.Context) ConstraintSatisfaction::SubstitutionDiagnostic{
+                        SubstDiag.first, StringRef(Mem, MessageSize)});
+            Satisfaction.IsSatisfied = false;
+            return ExprEmpty();
+          }
+        }
+
+        if (!S.CheckConstraintExpression(SubstitutedExpression.get()))
+          return ExprError();
+
+        return SubstitutedExpression;
+      });
+}
+
+template<typename TemplateDeclT>
+static bool CheckConstraintSatisfaction(Sema &S, TemplateDeclT *Template,
+                                        ArrayRef<const Expr *> ConstraintExprs,
+                                        ArrayRef<TemplateArgument> TemplateArgs,
+                                        SourceRange TemplateIDRange,
+                                        ConstraintSatisfaction &Satisfaction) {
+  if (ConstraintExprs.empty()) {
+    Satisfaction.IsSatisfied = true;
+    return false;
+  }
+
+  for (auto& Arg : TemplateArgs)
+    if (Arg.isInstantiationDependent()) {
+      // No need to check satisfaction for dependent constraint expressions.
+      Satisfaction.IsSatisfied = true;
       return false;
     }
+
+  Sema::InstantiatingTemplate Inst(S, TemplateIDRange.getBegin(),
+      Sema::InstantiatingTemplate::ConstraintsCheck{}, Template, TemplateArgs,
+      TemplateIDRange);
+  if (Inst.isInvalid())
+    return true;
+
+  MultiLevelTemplateArgumentList MLTAL;
+  MLTAL.addOuterTemplateArguments(TemplateArgs);
+
+  for (const Expr *ConstraintExpr : ConstraintExprs) {
+    if (calculateConstraintSatisfaction(S, Template, TemplateArgs,
+                                        TemplateIDRange.getBegin(), MLTAL,
+                                        ConstraintExpr, Satisfaction))
+      return true;
+    if (!Satisfaction.IsSatisfied)
+      // [temp.constr.op] p2
+      //   [...] To determine if a conjunction is satisfied, the satisfaction
+      //   of the first operand is checked. If that is not satisfied, the
+      //   conjunction is not satisfied. [...]
+      return false;
   }
+  return false;
+}
+
+bool Sema::CheckConstraintSatisfaction(TemplateDecl *Template,
+                                       ArrayRef<const Expr *> ConstraintExprs,
+                                       ArrayRef<TemplateArgument> TemplateArgs,
+                                       SourceRange TemplateIDRange,
+                                       ConstraintSatisfaction &Satisfaction) {
+  return ::CheckConstraintSatisfaction(*this, Template, ConstraintExprs,
+                                       TemplateArgs, TemplateIDRange,
+                                       Satisfaction);
+}
 
-  if (!CheckConstraintExpression(E.get()))
+bool
+Sema::CheckConstraintSatisfaction(ClassTemplatePartialSpecializationDecl* Part,
+                                  ArrayRef<const Expr *> ConstraintExprs,
+                                  ArrayRef<TemplateArgument> TemplateArgs,
+                                  SourceRange TemplateIDRange,
+                                  ConstraintSatisfaction &Satisfaction) {
+  return ::CheckConstraintSatisfaction(*this, Part, ConstraintExprs,
+                                       TemplateArgs, TemplateIDRange,
+                                       Satisfaction);
+}
+
+bool
+Sema::CheckConstraintSatisfaction(VarTemplatePartialSpecializationDecl* Partial,
+                                  ArrayRef<const Expr *> ConstraintExprs,
+                                  ArrayRef<TemplateArgument> TemplateArgs,
+                                  SourceRange TemplateIDRange,
+                                  ConstraintSatisfaction &Satisfaction) {
+  return ::CheckConstraintSatisfaction(*this, Partial, ConstraintExprs,
+                                       TemplateArgs, TemplateIDRange,
+                                       Satisfaction);
+}
+
+bool Sema::CheckConstraintSatisfaction(const Expr *ConstraintExpr,
+                                       ConstraintSatisfaction &Satisfaction) {
+  return calculateConstraintSatisfaction(
+      *this, ConstraintExpr, Satisfaction,
+      [](const Expr *AtomicExpr) -> ExprResult {
+        return ExprResult(const_cast<Expr *>(AtomicExpr));
+      });
+}
+
+bool Sema::EnsureTemplateArgumentListConstraints(
+    TemplateDecl *TD, ArrayRef<TemplateArgument> TemplateArgs,
+    SourceRange TemplateIDRange) {
+  ConstraintSatisfaction Satisfaction;
+  llvm::SmallVector<const Expr *, 3> AssociatedConstraints;
+  TD->getAssociatedConstraints(AssociatedConstraints);
+  if (CheckConstraintSatisfaction(TD, AssociatedConstraints, TemplateArgs,
+                                  TemplateIDRange, Satisfaction))
     return true;
 
-  SmallVector<PartialDiagnosticAt, 2> EvaluationDiags;
-  Expr::EvalResult EvalResult;
-  EvalResult.Diag = &EvaluationDiags;
-  if (!E.get()->EvaluateAsRValue(EvalResult, Context)) {
-    // C++2a [temp.constr.atomic]p1
-    //   ...E shall be a constant expression of type bool.
-    Diag(E.get()->getBeginLoc(),
-         diag::err_non_constant_constraint_expression)
-        << E.get()->getSourceRange();
-    for (const PartialDiagnosticAt &PDiag : EvaluationDiags)
-      Diag(PDiag.first, PDiag.second);
+  if (!Satisfaction.IsSatisfied) {
+    SmallString<128> TemplateArgString;
+    TemplateArgString = " ";
+    TemplateArgString += getTemplateArgumentBindingsText(
+        TD->getTemplateParameters(), TemplateArgs.data(), TemplateArgs.size());
+
+    Diag(TemplateIDRange.getBegin(),
+         diag::err_template_arg_list_constraints_not_satisfied)
+        << (int)getTemplateNameKindForDiagnostics(TemplateName(TD)) << TD
+        << TemplateArgString << TemplateIDRange;
+    DiagnoseUnsatisfiedConstraint(Satisfaction);
+    return true;
+  }
+  return false;
+}
+
+static void diagnoseWellFormedUnsatisfiedConstraintExpr(Sema &S,
+                                                        Expr *SubstExpr,
+                                                        bool First = true) {
+  SubstExpr = SubstExpr->IgnoreParenImpCasts();
+  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(SubstExpr)) {
+    switch (BO->getOpcode()) {
+    // These two cases will in practice only be reached when using fold
+    // expressions with || and &&, since otherwise the || and && will have been
+    // broken down into atomic constraints during satisfaction checking.
+    case BO_LOr:
+      // Or evaluated to false - meaning both RHS and LHS evaluated to false.
+      diagnoseWellFormedUnsatisfiedConstraintExpr(S, BO->getLHS(), First);
+      diagnoseWellFormedUnsatisfiedConstraintExpr(S, BO->getRHS(),
+                                                  /*First=*/false);
+      return;
+    case BO_LAnd:
+      bool LHSSatisfied;
+      BO->getLHS()->EvaluateAsBooleanCondition(LHSSatisfied, S.Context);
+      if (LHSSatisfied) {
+        // LHS is true, so RHS must be false.
+        diagnoseWellFormedUnsatisfiedConstraintExpr(S, BO->getRHS(), First);
+        return;
+      }
+      // LHS is false
+      diagnoseWellFormedUnsatisfiedConstraintExpr(S, BO->getLHS(), First);
+
+      // RHS might also be false
+      bool RHSSatisfied;
+      BO->getRHS()->EvaluateAsBooleanCondition(RHSSatisfied, S.Context);
+      if (!RHSSatisfied)
+        diagnoseWellFormedUnsatisfiedConstraintExpr(S, BO->getRHS(),
+                                                    /*First=*/false);
+      return;
+    case BO_GE:
+    case BO_LE:
+    case BO_GT:
+    case BO_LT:
+    case BO_EQ:
+    case BO_NE:
+      if (BO->getLHS()->getType()->isIntegerType() &&
+          BO->getRHS()->getType()->isIntegerType()) {
+        Expr::EvalResult SimplifiedLHS;
+        Expr::EvalResult SimplifiedRHS;
+        BO->getLHS()->EvaluateAsInt(SimplifiedLHS, S.Context);
+        BO->getRHS()->EvaluateAsInt(SimplifiedRHS, S.Context);
+        if (!SimplifiedLHS.Diag && ! SimplifiedRHS.Diag) {
+          S.Diag(SubstExpr->getBeginLoc(),
+                 diag::note_atomic_constraint_evaluated_to_false_elaborated)
+              << (int)First << SubstExpr
+              << SimplifiedLHS.Val.getInt().toString(10)
+              << BinaryOperator::getOpcodeStr(BO->getOpcode())
+              << SimplifiedRHS.Val.getInt().toString(10);
+          return;
+        }
+      }
+      break;
+
+    default:
+      break;
+    }
+  } else if (auto *CSE = dyn_cast<ConceptSpecializationExpr>(SubstExpr)) {
+    if (CSE->getTemplateArgsAsWritten()->NumTemplateArgs == 1) {
+      S.Diag(
+          CSE->getSourceRange().getBegin(),
+          diag::
+          note_single_arg_concept_specialization_constraint_evaluated_to_false)
+          << (int)First
+          << CSE->getTemplateArgsAsWritten()->arguments()[0].getArgument()
+          << CSE->getNamedConcept();
+    } else {
+      S.Diag(SubstExpr->getSourceRange().getBegin(),
+             diag::note_concept_specialization_constraint_evaluated_to_false)
+          << (int)First << CSE;
+    }
+    S.DiagnoseUnsatisfiedConstraint(CSE->getSatisfaction());
+    return;
+  }
+
+  S.Diag(SubstExpr->getSourceRange().getBegin(),
+         diag::note_atomic_constraint_evaluated_to_false)
+      << (int)First << SubstExpr;
+}
+
+template<typename SubstitutionDiagnostic>
+static void diagnoseUnsatisfiedConstraintExpr(
+    Sema &S, const Expr *E,
+    const llvm::PointerUnion<Expr *, SubstitutionDiagnostic *> &Record,
+    bool First = true) {
+  if (auto *Diag = Record.template dyn_cast<SubstitutionDiagnostic *>()){
+    S.Diag(Diag->first, diag::note_substituted_constraint_expr_is_ill_formed)
+        << Diag->second;
+    return;
+  }
+
+  diagnoseWellFormedUnsatisfiedConstraintExpr(S,
+      Record.template get<Expr *>(), First);
+}
+
+void Sema::DiagnoseUnsatisfiedConstraint(
+    const ConstraintSatisfaction& Satisfaction) {
+  assert(!Satisfaction.IsSatisfied &&
+         "Attempted to diagnose a satisfied constraint");
+  bool First = true;
+  for (auto &Pair : Satisfaction.Details) {
+    diagnoseUnsatisfiedConstraintExpr(*this, Pair.first, Pair.second, First);
+    First = false;
+  }
+}
+
+void Sema::DiagnoseUnsatisfiedConstraint(
+    const ASTConstraintSatisfaction &Satisfaction) {
+  assert(!Satisfaction.IsSatisfied &&
+         "Attempted to diagnose a satisfied constraint");
+  bool First = true;
+  for (auto &Pair : Satisfaction) {
+    diagnoseUnsatisfiedConstraintExpr(*this, Pair.first, Pair.second, First);
+    First = false;
+  }
+}
+
+const NormalizedConstraint *
+Sema::getNormalizedAssociatedConstraints(
+    NamedDecl *ConstrainedDecl, ArrayRef<const Expr *> AssociatedConstraints) {
+  auto CacheEntry = NormalizationCache.find(ConstrainedDecl);
+  if (CacheEntry == NormalizationCache.end()) {
+    auto Normalized =
+        NormalizedConstraint::fromConstraintExprs(*this, ConstrainedDecl,
+                                                  AssociatedConstraints);
+    CacheEntry =
+        NormalizationCache
+            .try_emplace(ConstrainedDecl,
+                         Normalized
+                             ? new (Context) NormalizedConstraint(
+                                 std::move(*Normalized))
+                             : nullptr)
+            .first;
+  }
+  return CacheEntry->second;
+}
+
+static bool substituteParameterMappings(Sema &S, NormalizedConstraint &N,
+    ConceptDecl *Concept, ArrayRef<TemplateArgument> TemplateArgs,
+    const ASTTemplateArgumentListInfo *ArgsAsWritten) {
+  if (!N.isAtomic()) {
+    if (substituteParameterMappings(S, N.getLHS(), Concept, TemplateArgs,
+                                    ArgsAsWritten))
+      return true;
+    return substituteParameterMappings(S, N.getRHS(), Concept, TemplateArgs,
+                                       ArgsAsWritten);
+  }
+  TemplateParameterList *TemplateParams = Concept->getTemplateParameters();
+
+  AtomicConstraint &Atomic = *N.getAtomicConstraint();
+  TemplateArgumentListInfo SubstArgs;
+  MultiLevelTemplateArgumentList MLTAL;
+  MLTAL.addOuterTemplateArguments(TemplateArgs);
+  if (!Atomic.ParameterMapping) {
+    llvm::SmallBitVector OccurringIndices(TemplateParams->size());
+    S.MarkUsedTemplateParameters(Atomic.ConstraintExpr, /*OnlyDeduced=*/false,
+                                 /*Depth=*/0, OccurringIndices);
+    Atomic.ParameterMapping.emplace(
+        MutableArrayRef<TemplateArgumentLoc>(
+            new (S.Context) TemplateArgumentLoc[OccurringIndices.count()],
+            OccurringIndices.count()));
+    for (unsigned I = 0, J = 0, C = TemplateParams->size(); I != C; ++I)
+      if (OccurringIndices[I])
+        new (&(*Atomic.ParameterMapping)[J++]) TemplateArgumentLoc(
+            S.getIdentityTemplateArgumentLoc(TemplateParams->begin()[I],
+                // Here we assume we do not support things like
+                // template<typename A, typename B>
+                // concept C = ...;
+                //
+                // template<typename... Ts> requires C<Ts...>
+                // struct S { };
+                // The above currently yields a diagnostic.
+                // We still might have default arguments for concept parameters.
+                ArgsAsWritten->NumTemplateArgs > I ?
+                ArgsAsWritten->arguments()[I].getLocation() :
+                SourceLocation()));
+  }
+  Sema::InstantiatingTemplate Inst(
+      S, ArgsAsWritten->arguments().front().getSourceRange().getBegin(),
+      Sema::InstantiatingTemplate::ParameterMappingSubstitution{}, Concept,
+      SourceRange(ArgsAsWritten->arguments()[0].getSourceRange().getBegin(),
+                  ArgsAsWritten->arguments().back().getSourceRange().getEnd()));
+  if (S.SubstTemplateArguments(*Atomic.ParameterMapping, MLTAL, SubstArgs))
+    return true;
+  std::copy(SubstArgs.arguments().begin(), SubstArgs.arguments().end(),
+            N.getAtomicConstraint()->ParameterMapping->begin());
+  return false;
+}
+
+Optional<NormalizedConstraint>
+NormalizedConstraint::fromConstraintExprs(Sema &S, NamedDecl *D,
+                                          ArrayRef<const Expr *> E) {
+  assert(E.size() != 0);
+  auto First = fromConstraintExpr(S, D, E[0]);
+  if (E.size() == 1)
+    return First;
+  auto Second = fromConstraintExpr(S, D, E[1]);
+  if (!Second)
+    return None;
+  llvm::Optional<NormalizedConstraint> Conjunction;
+  Conjunction.emplace(S.Context, std::move(*First), std::move(*Second),
+                      CCK_Conjunction);
+  for (unsigned I = 2; I < E.size(); ++I) {
+    auto Next = fromConstraintExpr(S, D, E[I]);
+    if (!Next)
+      return llvm::Optional<NormalizedConstraint>{};
+    NormalizedConstraint NewConjunction(S.Context, std::move(*Conjunction),
+                                        std::move(*Next), CCK_Conjunction);
+    *Conjunction = std::move(NewConjunction);
+  }
+  return Conjunction;
+}
+
+llvm::Optional<NormalizedConstraint>
+NormalizedConstraint::fromConstraintExpr(Sema &S, NamedDecl *D, const Expr *E) {
+  assert(E != nullptr);
+
+  // C++ [temp.constr.normal]p1.1
+  // [...]
+  // - The normal form of an expression (E) is the normal form of E.
+  // [...]
+  E = E->IgnoreParenImpCasts();
+  if (auto *BO = dyn_cast<const BinaryOperator>(E)) {
+    if (BO->getOpcode() == BO_LAnd || BO->getOpcode() == BO_LOr) {
+      auto LHS = fromConstraintExpr(S, D, BO->getLHS());
+      if (!LHS)
+        return None;
+      auto RHS = fromConstraintExpr(S, D, BO->getRHS());
+      if (!RHS)
+        return None;
+
+      return NormalizedConstraint(
+          S.Context, std::move(*LHS), std::move(*RHS),
+          BO->getOpcode() == BO_LAnd ? CCK_Conjunction : CCK_Disjunction);
+    }
+  } else if (auto *CSE = dyn_cast<const ConceptSpecializationExpr>(E)) {
+    const NormalizedConstraint *SubNF;
+    {
+      Sema::InstantiatingTemplate Inst(
+          S, CSE->getExprLoc(),
+          Sema::InstantiatingTemplate::ConstraintNormalization{}, D,
+          CSE->getSourceRange());
+      // C++ [temp.constr.normal]p1.1
+      // [...]
+      // The normal form of an id-expression of the form C<A1, A2, ..., AN>,
+      // where C names a concept, is the normal form of the
+      // constraint-expression of C, after substituting A1, A2, ..., AN for C’s
+      // respective template parameters in the parameter mappings in each atomic
+      // constraint. If any such substitution results in an invalid type or
+      // expression, the program is ill-formed; no diagnostic is required.
+      // [...]
+      ConceptDecl *CD = CSE->getNamedConcept();
+      SubNF = S.getNormalizedAssociatedConstraints(CD,
+                                                   {CD->getConstraintExpr()});
+      if (!SubNF)
+        return None;
+    }
+
+    Optional<NormalizedConstraint> New;
+    New.emplace(S.Context, *SubNF);
+
+    if (substituteParameterMappings(
+            S, *New, CSE->getNamedConcept(),
+            CSE->getTemplateArguments(), CSE->getTemplateArgsAsWritten()))
+      return None;
+
+    return New;
+  }
+  return NormalizedConstraint{new (S.Context) AtomicConstraint(S, E)};
+}
+
+using NormalForm =
+    llvm::SmallVector<llvm::SmallVector<AtomicConstraint *, 2>, 4>;
+
+static NormalForm makeCNF(const NormalizedConstraint &Normalized) {
+  if (Normalized.isAtomic())
+    return {{Normalized.getAtomicConstraint()}};
+
+  NormalForm LCNF = makeCNF(Normalized.getLHS());
+  NormalForm RCNF = makeCNF(Normalized.getRHS());
+  if (Normalized.getCompoundKind() == NormalizedConstraint::CCK_Conjunction) {
+    LCNF.reserve(LCNF.size() + RCNF.size());
+    while (!RCNF.empty())
+      LCNF.push_back(RCNF.pop_back_val());
+    return LCNF;
+  }
+
+  // Disjunction
+  NormalForm Res;
+  Res.reserve(LCNF.size() * RCNF.size());
+  for (auto &LDisjunction : LCNF)
+    for (auto &RDisjunction : RCNF) {
+      NormalForm::value_type Combined;
+      Combined.reserve(LDisjunction.size() + RDisjunction.size());
+      std::copy(LDisjunction.begin(), LDisjunction.end(),
+                std::back_inserter(Combined));
+      std::copy(RDisjunction.begin(), RDisjunction.end(),
+                std::back_inserter(Combined));
+      Res.emplace_back(Combined);
+    }
+  return Res;
+}
+
+static NormalForm makeDNF(const NormalizedConstraint &Normalized) {
+  if (Normalized.isAtomic())
+    return {{Normalized.getAtomicConstraint()}};
+
+  NormalForm LDNF = makeDNF(Normalized.getLHS());
+  NormalForm RDNF = makeDNF(Normalized.getRHS());
+  if (Normalized.getCompoundKind() == NormalizedConstraint::CCK_Disjunction) {
+    LDNF.reserve(LDNF.size() + RDNF.size());
+    while (!RDNF.empty())
+      LDNF.push_back(RDNF.pop_back_val());
+    return LDNF;
+  }
+
+  // Conjunction
+  NormalForm Res;
+  Res.reserve(LDNF.size() * RDNF.size());
+  for (auto &LConjunction : LDNF) {
+    for (auto &RConjunction : RDNF) {
+      NormalForm::value_type Combined;
+      Combined.reserve(LConjunction.size() + RConjunction.size());
+      std::copy(LConjunction.begin(), LConjunction.end(),
+                std::back_inserter(Combined));
+      std::copy(RConjunction.begin(), RConjunction.end(),
+                std::back_inserter(Combined));
+      Res.emplace_back(Combined);
+    }
+  }
+  return Res;
+}
+
+template<typename AtomicSubsumptionEvaluator>
+static bool subsumes(NormalForm PDNF, NormalForm QCNF,
+                     AtomicSubsumptionEvaluator E) {
+  // C++ [temp.constr.order] p2
+  //   Then, P subsumes Q if and only if, for every disjunctive clause Pi in the
+  //   disjunctive normal form of P, Pi subsumes every conjunctive clause Qj in
+  //   the conjuctive normal form of Q, where [...]
+  for (const auto &Pi : PDNF) {
+    for (const auto &Qj : QCNF) {
+      // C++ [temp.constr.order] p2
+      //   - [...] a disjunctive clause Pi subsumes a conjunctive clause Qj if
+      //     and only if there exists an atomic constraint Pia in Pi for which
+      //     there exists an atomic constraint, Qjb, in Qj such that Pia
+      //     subsumes Qjb.
+      bool Found = false;
+      for (const AtomicConstraint *Pia : Pi) {
+        for (const AtomicConstraint *Qjb : Qj) {
+          if (E(*Pia, *Qjb)) {
+            Found = true;
+            break;
+          }
+        }
+        if (Found)
+          break;
+      }
+      if (!Found)
+        return false;
+    }
+  }
+  return true;
+}
+
+template<typename AtomicSubsumptionEvaluator>
+static bool subsumes(Sema &S, NamedDecl *DP, ArrayRef<const Expr *> P,
+                     NamedDecl *DQ, ArrayRef<const Expr *> Q, bool &Subsumes,
+                     AtomicSubsumptionEvaluator E) {
+  // C++ [temp.constr.order] p2
+  //   In order to determine if a constraint P subsumes a constraint Q, P is
+  //   transformed into disjunctive normal form, and Q is transformed into
+  //   conjunctive normal form. [...]
+  auto *PNormalized = S.getNormalizedAssociatedConstraints(DP, P);
+  if (!PNormalized)
+    return true;
+  const NormalForm PDNF = makeDNF(*PNormalized);
+
+  auto *QNormalized = S.getNormalizedAssociatedConstraints(DQ, Q);
+  if (!QNormalized)
     return true;
+  const NormalForm QCNF = makeCNF(*QNormalized);
+
+  Subsumes = subsumes(PDNF, QCNF, E);
+  return false;
+}
+
+bool Sema::IsAtLeastAsConstrained(NamedDecl *D1, ArrayRef<const Expr *> AC1,
+                                  NamedDecl *D2, ArrayRef<const Expr *> AC2,
+                                  bool &Result) {
+  if (AC1.empty()) {
+    Result = AC2.empty();
+    return false;
+  }
+  if (AC2.empty()) {
+    // TD1 has associated constraints and TD2 does not.
+    Result = true;
+    return false;
   }
 
-  IsSatisfied = EvalResult.Val.getInt().getBoolValue();
+  std::pair<NamedDecl *, NamedDecl *> Key{D1, D2};
+  auto CacheEntry = SubsumptionCache.find(Key);
+  if (CacheEntry != SubsumptionCache.end()) {
+    Result = CacheEntry->second;
+    return false;
+  }
 
+  if (subsumes(*this, D1, AC1, D2, AC2, Result,
+        [this] (const AtomicConstraint &A, const AtomicConstraint &B) {
+          return A.subsumes(Context, B);
+        }))
+    return true;
+  SubsumptionCache.try_emplace(Key, Result);
   return false;
-}
\ No newline at end of file
+}
+
+bool Sema::MaybeEmitAmbiguousAtomicConstraintsDiagnostic(NamedDecl *D1,
+    ArrayRef<const Expr *> AC1, NamedDecl *D2, ArrayRef<const Expr *> AC2) {
+  if (isSFINAEContext())
+    // No need to work here because our notes would be discarded.
+    return false;
+
+  if (AC1.empty() || AC2.empty())
+    return false;
+
+  auto NormalExprEvaluator =
+      [this] (const AtomicConstraint &A, const AtomicConstraint &B) {
+        return A.subsumes(Context, B);
+      };
+
+  const Expr *AmbiguousAtomic1 = nullptr, *AmbiguousAtomic2 = nullptr;
+  auto IdenticalExprEvaluator =
+      [&] (const AtomicConstraint &A, const AtomicConstraint &B) {
+        if (!A.hasMatchingParameterMapping(Context, B))
+          return false;
+        const Expr *EA = A.ConstraintExpr, *EB = B.ConstraintExpr;
+        if (EA == EB)
+          return true;
+
+        // Not the same source level expression - are the expressions
+        // identical?
+        llvm::FoldingSetNodeID IDA, IDB;
+        EA->Profile(IDA, Context, /*Cannonical=*/true);
+        EB->Profile(IDB, Context, /*Cannonical=*/true);
+        if (IDA != IDB)
+          return false;
+
+        AmbiguousAtomic1 = EA;
+        AmbiguousAtomic2 = EB;
+        return true;
+      };
+
+  {
+    // The subsumption checks might cause diagnostics
+    SFINAETrap Trap(*this);
+    auto *Normalized1 = getNormalizedAssociatedConstraints(D1, AC1);
+    if (!Normalized1)
+      return false;
+    const NormalForm DNF1 = makeDNF(*Normalized1);
+    const NormalForm CNF1 = makeCNF(*Normalized1);
+
+    auto *Normalized2 = getNormalizedAssociatedConstraints(D2, AC2);
+    if (!Normalized2)
+      return false;
+    const NormalForm DNF2 = makeDNF(*Normalized2);
+    const NormalForm CNF2 = makeCNF(*Normalized2);
+
+    bool Is1AtLeastAs2Normally = subsumes(DNF1, CNF2, NormalExprEvaluator);
+    bool Is2AtLeastAs1Normally = subsumes(DNF2, CNF1, NormalExprEvaluator);
+    bool Is1AtLeastAs2 = subsumes(DNF1, CNF2, IdenticalExprEvaluator);
+    bool Is2AtLeastAs1 = subsumes(DNF2, CNF1, IdenticalExprEvaluator);
+    if (Is1AtLeastAs2 == Is1AtLeastAs2Normally &&
+        Is2AtLeastAs1 == Is2AtLeastAs1Normally)
+      // Same result - no ambiguity was caused by identical atomic expressions.
+      return false;
+  }
+
+  // A different result! Some ambiguous atomic constraint(s) caused a difference
+  assert(AmbiguousAtomic1 && AmbiguousAtomic2);
+
+  Diag(AmbiguousAtomic1->getBeginLoc(), diag::note_ambiguous_atomic_constraints)
+      << AmbiguousAtomic1->getSourceRange();
+  Diag(AmbiguousAtomic2->getBeginLoc(),
+       diag::note_ambiguous_atomic_constraints_similar_expression)
+      << AmbiguousAtomic2->getSourceRange();
+  return true;
+}
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index fd2fd35921ce..6dc9e342beb9 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -18,6 +18,7 @@
 #include "clang/AST/Decl.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/StmtCXX.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/Initialization.h"
 #include "clang/Sema/Overload.h"
@@ -1227,7 +1228,7 @@ bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
     return false;
 
   if (RequiresNoThrowAlloc) {
-    const auto *FT = OperatorNew->getType()->getAs<FunctionProtoType>();
+    const auto *FT = OperatorNew->getType()->castAs<FunctionProtoType>();
     if (!FT->isNothrow(/*ResultIfDependent*/ false)) {
       S.Diag(OperatorNew->getLocation(),
              diag::err_coroutine_promise_new_requires_nothrow)
@@ -1280,7 +1281,7 @@ bool CoroutineStmtBuilder::makeNewAndDeleteExpr() {
 
   // Check if we need to pass the size.
   const auto *OpDeleteType =
-      OpDeleteQualType.getTypePtr()->getAs<FunctionProtoType>();
+      OpDeleteQualType.getTypePtr()->castAs<FunctionProtoType>();
   if (OpDeleteType->getNumParams() > 1)
     DeleteArgs.push_back(FrameSize);
 
@@ -1526,8 +1527,8 @@ bool Sema::buildCoroutineParameterMoves(SourceLocation Loc) {
   auto *FD = cast<FunctionDecl>(CurContext);
 
   auto *ScopeInfo = getCurFunction();
-  assert(ScopeInfo->CoroutineParameterMoves.empty() &&
-         "Should not build parameter moves twice");
+  if (!ScopeInfo->CoroutineParameterMoves.empty())
+    return false;
 
   for (auto *PD : FD->parameters()) {
     if (PD->getType()->isDependentType())
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 62ec83967bff..507e4a6cd436 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -867,6 +867,9 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
   LookupResult Result(*this, Name, NameLoc, LookupOrdinaryName);
   LookupParsedName(Result, S, &SS, !CurMethod);
 
+  if (SS.isInvalid())
+    return NameClassification::Error();
+
   // For unqualified lookup in a class template in MSVC mode, look into
   // dependent base classes where the primary class template is known.
   if (Result.empty() && SS.isEmpty() && getLangOpts().MSVCCompat) {
@@ -879,7 +882,7 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
   // synthesized instance variables), if we're in an Objective-C method.
   // FIXME: This lookup really, really needs to be folded in to the normal
   // unqualified lookup mechanism.
-  if (!SS.isSet() && CurMethod && !isResultTypeOrTemplate(Result, NextToken)) {
+  if (SS.isEmpty() && CurMethod && !isResultTypeOrTemplate(Result, NextToken)) {
     DeclResult Ivar = LookupIvarInObjCMethod(Result, S, Name);
     if (Ivar.isInvalid())
       return NameClassification::Error();
@@ -899,7 +902,7 @@ Corrected:
   case LookupResult::NotFound:
     // If an unqualified-id is followed by a '(', then we have a function
     // call.
-    if (!SS.isSet() && NextToken.is(tok::l_paren)) {
+    if (SS.isEmpty() && NextToken.is(tok::l_paren)) {
       // In C++, this is an ADL-only call.
       // FIXME: Reference?
       if (getLangOpts().CPlusPlus)
@@ -921,7 +924,7 @@ Corrected:
         return NameClassification::NonType(D);
     }
 
-    if (getLangOpts().CPlusPlus2a && !SS.isSet() && NextToken.is(tok::less)) {
+    if (getLangOpts().CPlusPlus2a && SS.isEmpty() && NextToken.is(tok::less)) {
       // In C++20 onwards, this could be an ADL-only call to a function
       // template, and we're required to assume that this is a template name.
       //
@@ -1063,7 +1066,7 @@ Corrected:
        hasAnyAcceptableTemplateNames(
            Result, /*AllowFunctionTemplates=*/true,
            /*AllowDependent=*/false,
-           /*AllowNonTemplateFunctions*/ !SS.isSet() &&
+           /*AllowNonTemplateFunctions*/ SS.isEmpty() &&
                getLangOpts().CPlusPlus2a))) {
     // C++ [temp.names]p3:
     //   After name lookup (3.4) finds that a name is a template-name or that
@@ -1092,7 +1095,7 @@ Corrected:
       IsFunctionTemplate = isa<FunctionTemplateDecl>(TD);
       IsVarTemplate = isa<VarTemplateDecl>(TD);
 
-      if (SS.isSet() && !SS.isInvalid())
+      if (SS.isNotEmpty())
         Template =
             Context.getQualifiedTemplateName(SS.getScopeRep(),
                                              /*TemplateKeyword=*/false, TD);
@@ -1802,6 +1805,13 @@ static bool ShouldDiagnoseUnusedDecl(const NamedDecl *D) {
                 (VD->getInit()->isValueDependent() || !VD->evaluateValue()))
               return false;
           }
+
+          // Suppress the warning if we don't know how this is constructed, and
+          // it could possibly be non-trivial constructor.
+          if (Init->isTypeDependent())
+            for (const CXXConstructorDecl *Ctor : RD->ctors())
+              if (!Ctor->isTrivial())
+                return false;
         }
       }
     }
@@ -2549,7 +2559,7 @@ static bool mergeDeclAttribute(Sema &S, NamedDecl *D,
     NewAttr = S.mergeCodeSegAttr(D, *CSA, CSA->getName());
   else if (const auto *IA = dyn_cast<MSInheritanceAttr>(Attr))
     NewAttr = S.mergeMSInheritanceAttr(D, *IA, IA->getBestCase(),
-                                       IA->getSemanticSpelling());
+                                       IA->getInheritanceModel());
   else if (const auto *AA = dyn_cast<AlwaysInlineAttr>(Attr))
     NewAttr = S.mergeAlwaysInlineAttr(D, *AA,
                                       &S.Context.Idents.get(AA->getSpelling()));
@@ -2675,6 +2685,10 @@ static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) {
       // C's _Noreturn is allowed to be added to a function after it is defined.
       ++I;
       continue;
+    } else if (isa<UuidAttr>(NewAttribute)) {
+      // msvc will allow a subsequent definition to add an uuid to a class
+      ++I;
+      continue;
     } else if (const AlignedAttr *AA = dyn_cast<AlignedAttr>(NewAttribute)) {
       if (AA->isAlignas()) {
         // C++11 [dcl.align]p6:
@@ -2993,28 +3007,6 @@ struct GNUCompatibleParamWarning {
 
 } // end anonymous namespace
 
-/// getSpecialMember - get the special member enum for a method.
-Sema::CXXSpecialMember Sema::getSpecialMember(const CXXMethodDecl *MD) {
-  if (const CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(MD)) {
-    if (Ctor->isDefaultConstructor())
-      return Sema::CXXDefaultConstructor;
-
-    if (Ctor->isCopyConstructor())
-      return Sema::CXXCopyConstructor;
-
-    if (Ctor->isMoveConstructor())
-      return Sema::CXXMoveConstructor;
-  } else if (isa<CXXDestructorDecl>(MD)) {
-    return Sema::CXXDestructor;
-  } else if (MD->isCopyAssignmentOperator()) {
-    return Sema::CXXCopyAssignment;
-  } else if (MD->isMoveAssignmentOperator()) {
-    return Sema::CXXMoveAssignment;
-  }
-
-  return Sema::CXXInvalid;
-}
-
 // Determine whether the previous declaration was a definition, implicit
 // declaration, or a declaration.
 template <typename T>
@@ -3668,6 +3660,11 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD,
     return MergeCompatibleFunctionDecls(New, Old, S, MergeTypeWithOld);
   }
 
+  // Check if the function types are compatible when pointer size address
+  // spaces are ignored.
+  if (Context.hasSameFunctionTypeIgnoringPtrSizes(OldQType, NewQType))
+    return false;
+
   // GNU C permits a K&R definition to follow a prototype declaration
   // if the declared types of the parameters in the K&R definition
   // match the types in the prototype declaration, even when the
@@ -5032,6 +5029,8 @@ Decl *Sema::BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS,
         /*BitWidth=*/nullptr, /*Mutable=*/false,
         /*InitStyle=*/ICIS_NoInit);
     Anon->setAccess(AS);
+    ProcessDeclAttributes(S, Anon, Dc);
+
     if (getLangOpts().CPlusPlus)
       FieldCollector->Add(cast<FieldDecl>(Anon));
   } else {
@@ -5045,6 +5044,7 @@ Decl *Sema::BuildAnonymousStructOrUnion(Scope *S, DeclSpec &DS,
       SC = SC_None;
     }
 
+    assert(DS.getAttributes().empty() && "No attribute expected");
     Anon = VarDecl::Create(Context, Owner, DS.getBeginLoc(),
                            Record->getLocation(), /*IdentifierInfo=*/nullptr,
                            Context.getTypeDeclType(Record), TInfo, SC);
@@ -6139,6 +6139,41 @@ bool Sema::inferObjCARCLifetime(ValueDecl *decl) {
   return false;
 }
 
+void Sema::deduceOpenCLAddressSpace(ValueDecl *Decl) {
+  if (Decl->getType().hasAddressSpace())
+    return;
+  if (VarDecl *Var = dyn_cast<VarDecl>(Decl)) {
+    QualType Type = Var->getType();
+    if (Type->isSamplerT() || Type->isVoidType())
+      return;
+    LangAS ImplAS = LangAS::opencl_private;
+    if ((getLangOpts().OpenCLCPlusPlus || getLangOpts().OpenCLVersion >= 200) &&
+        Var->hasGlobalStorage())
+      ImplAS = LangAS::opencl_global;
+    // If the original type from a decayed type is an array type and that array
+    // type has no address space yet, deduce it now.
+    if (auto DT = dyn_cast<DecayedType>(Type)) {
+      auto OrigTy = DT->getOriginalType();
+      if (!OrigTy.hasAddressSpace() && OrigTy->isArrayType()) {
+        // Add the address space to the original array type and then propagate
+        // that to the element type through `getAsArrayType`.
+        OrigTy = Context.getAddrSpaceQualType(OrigTy, ImplAS);
+        OrigTy = QualType(Context.getAsArrayType(OrigTy), 0);
+        // Re-generate the decayed type.
+        Type = Context.getDecayedType(OrigTy);
+      }
+    }
+    Type = Context.getAddrSpaceQualType(Type, ImplAS);
+    // Apply any qualifiers (including address space) from the array type to
+    // the element type. This implements C99 6.7.3p8: "If the specification of
+    // an array type includes any type qualifiers, the element type is so
+    // qualified, not the array type."
+    if (Type->isArrayType())
+      Type = QualType(Context.getAsArrayType(Type), 0);
+    Decl->setType(Type);
+  }
+}
+
 static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) {
   // Ensure that an auto decl is deduced otherwise the checks below might cache
   // the wrong linkage.
@@ -6496,6 +6531,105 @@ static bool isDeclExternC(const Decl *D) {
 
   llvm_unreachable("Unknown type of decl!");
 }
+/// Returns true if there hasn't been any invalid type diagnosed.
+static bool diagnoseOpenCLTypes(Scope *S, Sema &Se, Declarator &D,
+                                DeclContext *DC, QualType R) {
+  // OpenCL v2.0 s6.9.b - Image type can only be used as a function argument.
+  // OpenCL v2.0 s6.13.16.1 - Pipe type can only be used as a function
+  // argument.
+  if (R->isImageType() || R->isPipeType()) {
+    Se.Diag(D.getIdentifierLoc(),
+            diag::err_opencl_type_can_only_be_used_as_function_parameter)
+        << R;
+    D.setInvalidType();
+    return false;
+  }
+
+  // OpenCL v1.2 s6.9.r:
+  // The event type cannot be used to declare a program scope variable.
+  // OpenCL v2.0 s6.9.q:
+  // The clk_event_t and reserve_id_t types cannot be declared in program
+  // scope.
+  if (NULL == S->getParent()) {
+    if (R->isReserveIDT() || R->isClkEventT() || R->isEventT()) {
+      Se.Diag(D.getIdentifierLoc(),
+              diag::err_invalid_type_for_program_scope_var)
+          << R;
+      D.setInvalidType();
+      return false;
+    }
+  }
+
+  // OpenCL v1.0 s6.8.a.3: Pointers to functions are not allowed.
+  QualType NR = R;
+  while (NR->isPointerType()) {
+    if (NR->isFunctionPointerType()) {
+      Se.Diag(D.getIdentifierLoc(), diag::err_opencl_function_pointer);
+      D.setInvalidType();
+      return false;
+    }
+    NR = NR->getPointeeType();
+  }
+
+  if (!Se.getOpenCLOptions().isEnabled("cl_khr_fp16")) {
+    // OpenCL v1.2 s6.1.1.1: reject declaring variables of the half and
+    // half array type (unless the cl_khr_fp16 extension is enabled).
+    if (Se.Context.getBaseElementType(R)->isHalfType()) {
+      Se.Diag(D.getIdentifierLoc(), diag::err_opencl_half_declaration) << R;
+      D.setInvalidType();
+      return false;
+    }
+  }
+
+  // OpenCL v1.2 s6.9.r:
+  // The event type cannot be used with the __local, __constant and __global
+  // address space qualifiers.
+  if (R->isEventT()) {
+    if (R.getAddressSpace() != LangAS::opencl_private) {
+      Se.Diag(D.getBeginLoc(), diag::err_event_t_addr_space_qual);
+      D.setInvalidType();
+      return false;
+    }
+  }
+
+  // C++ for OpenCL does not allow the thread_local storage qualifier.
+  // OpenCL C does not support thread_local either, and
+  // also reject all other thread storage class specifiers.
+  DeclSpec::TSCS TSC = D.getDeclSpec().getThreadStorageClassSpec();
+  if (TSC != TSCS_unspecified) {
+    bool IsCXX = Se.getLangOpts().OpenCLCPlusPlus;
+    Se.Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
+            diag::err_opencl_unknown_type_specifier)
+        << IsCXX << Se.getLangOpts().getOpenCLVersionTuple().getAsString()
+        << DeclSpec::getSpecifierName(TSC) << 1;
+    D.setInvalidType();
+    return false;
+  }
+
+  if (R->isSamplerT()) {
+    // OpenCL v1.2 s6.9.b p4:
+    // The sampler type cannot be used with the __local and __global address
+    // space qualifiers.
+    if (R.getAddressSpace() == LangAS::opencl_local ||
+        R.getAddressSpace() == LangAS::opencl_global) {
+      Se.Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
+      D.setInvalidType();
+    }
+
+    // OpenCL v1.2 s6.12.14.1:
+    // A global sampler must be declared with either the constant address
+    // space qualifier or with the const qualifier.
+    if (DC->isTranslationUnit() &&
+        !(R.getAddressSpace() == LangAS::opencl_constant ||
+          R.isConstQualified())) {
+      Se.Diag(D.getIdentifierLoc(), diag::err_opencl_nonconst_global_sampler);
+      D.setInvalidType();
+    }
+    if (D.isInvalidType())
+      return false;
+  }
+  return true;
+}
 
 NamedDecl *Sema::ActOnVariableDeclarator(
     Scope *S, Declarator &D, DeclContext *DC, TypeSourceInfo *TInfo,
@@ -6519,95 +6653,6 @@ NamedDecl *Sema::ActOnVariableDeclarator(
     return nullptr;
   }
 
-  if (getLangOpts().OpenCL) {
-    // OpenCL v2.0 s6.9.b - Image type can only be used as a function argument.
-    // OpenCL v2.0 s6.13.16.1 - Pipe type can only be used as a function
-    // argument.
-    if (R->isImageType() || R->isPipeType()) {
-      Diag(D.getIdentifierLoc(),
-           diag::err_opencl_type_can_only_be_used_as_function_parameter)
-          << R;
-      D.setInvalidType();
-      return nullptr;
-    }
-
-    // OpenCL v1.2 s6.9.r:
-    // The event type cannot be used to declare a program scope variable.
-    // OpenCL v2.0 s6.9.q:
-    // The clk_event_t and reserve_id_t types cannot be declared in program scope.
-    if (NULL == S->getParent()) {
-      if (R->isReserveIDT() || R->isClkEventT() || R->isEventT()) {
-        Diag(D.getIdentifierLoc(),
-             diag::err_invalid_type_for_program_scope_var) << R;
-        D.setInvalidType();
-        return nullptr;
-      }
-    }
-
-    // OpenCL v1.0 s6.8.a.3: Pointers to functions are not allowed.
-    QualType NR = R;
-    while (NR->isPointerType()) {
-      if (NR->isFunctionPointerType()) {
-        Diag(D.getIdentifierLoc(), diag::err_opencl_function_pointer);
-        D.setInvalidType();
-        break;
-      }
-      NR = NR->getPointeeType();
-    }
-
-    if (!getOpenCLOptions().isEnabled("cl_khr_fp16")) {
-      // OpenCL v1.2 s6.1.1.1: reject declaring variables of the half and
-      // half array type (unless the cl_khr_fp16 extension is enabled).
-      if (Context.getBaseElementType(R)->isHalfType()) {
-        Diag(D.getIdentifierLoc(), diag::err_opencl_half_declaration) << R;
-        D.setInvalidType();
-      }
-    }
-
-    if (R->isSamplerT()) {
-      // OpenCL v1.2 s6.9.b p4:
-      // The sampler type cannot be used with the __local and __global address
-      // space qualifiers.
-      if (R.getAddressSpace() == LangAS::opencl_local ||
-          R.getAddressSpace() == LangAS::opencl_global) {
-        Diag(D.getIdentifierLoc(), diag::err_wrong_sampler_addressspace);
-      }
-
-      // OpenCL v1.2 s6.12.14.1:
-      // A global sampler must be declared with either the constant address
-      // space qualifier or with the const qualifier.
-      if (DC->isTranslationUnit() &&
-          !(R.getAddressSpace() == LangAS::opencl_constant ||
-          R.isConstQualified())) {
-        Diag(D.getIdentifierLoc(), diag::err_opencl_nonconst_global_sampler);
-        D.setInvalidType();
-      }
-    }
-
-    // OpenCL v1.2 s6.9.r:
-    // The event type cannot be used with the __local, __constant and __global
-    // address space qualifiers.
-    if (R->isEventT()) {
-      if (R.getAddressSpace() != LangAS::opencl_private) {
-        Diag(D.getBeginLoc(), diag::err_event_t_addr_space_qual);
-        D.setInvalidType();
-      }
-    }
-
-    // C++ for OpenCL does not allow the thread_local storage qualifier.
-    // OpenCL C does not support thread_local either, and
-    // also reject all other thread storage class specifiers.
-    DeclSpec::TSCS TSC = D.getDeclSpec().getThreadStorageClassSpec();
-    if (TSC != TSCS_unspecified) {
-      bool IsCXX = getLangOpts().OpenCLCPlusPlus;
-      Diag(D.getDeclSpec().getThreadStorageClassSpecLoc(),
-           diag::err_opencl_unknown_type_specifier)
-          << IsCXX << getLangOpts().getOpenCLVersionTuple().getAsString()
-          << DeclSpec::getSpecifierName(TSC) << 1;
-      D.setInvalidType();
-      return nullptr;
-    }
-  }
 
   DeclSpec::SCS SCSpec = D.getDeclSpec().getStorageClassSpec();
   StorageClass SC = StorageClassSpecToVarDeclStorageClass(D.getDeclSpec());
@@ -6964,6 +7009,13 @@ NamedDecl *Sema::ActOnVariableDeclarator(
     }
   }
 
+  if (getLangOpts().OpenCL) {
+
+    deduceOpenCLAddressSpace(NewVD);
+
+    diagnoseOpenCLTypes(S, *this, D, DC, NewVD->getType());
+  }
+
   // Handle attributes prior to checking for duplicates in MergeVarDecl
   ProcessDeclAttributes(S, NewVD, D);
 
@@ -7039,8 +7091,9 @@ NamedDecl *Sema::ActOnVariableDeclarator(
       }
     }
 
-    NewVD->addAttr(::new (Context) AsmLabelAttr(
-        Context, SE->getStrTokenLoc(0), Label, /*IsLiteralLabel=*/true));
+    NewVD->addAttr(AsmLabelAttr::Create(Context, Label,
+                                        /*IsLiteralLabel=*/true,
+                                        SE->getStrTokenLoc(0)));
   } else if (!ExtnameUndeclaredIdentifiers.empty()) {
     llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
       ExtnameUndeclaredIdentifiers.find(NewVD->getIdentifier());
@@ -7842,7 +7895,13 @@ struct FindOverriddenMethod {
          Path.Decls = Path.Decls.slice(1)) {
       NamedDecl *D = Path.Decls.front();
       if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
-        if (MD->isVirtual() && !S->IsOverload(Method, MD, false))
+        if (MD->isVirtual() &&
+            !S->IsOverload(
+                Method, MD, /*UseMemberUsingDeclRules=*/false,
+                /*ConsiderCudaAttrs=*/true,
+                // C++2a [class.virtual]p2 does not consider requires clauses
+                // when overriding.
+                /*ConsiderRequiresClauses=*/false))
           return true;
       }
     }
@@ -8187,7 +8246,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
 
     NewFD = FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                  R, TInfo, SC, isInline, HasPrototype,
-                                 CSK_unspecified);
+                                 CSK_unspecified,
+                                 /*TrailingRequiresClause=*/nullptr);
     if (D.isInvalidType())
       NewFD->setInvalidDecl();
 
@@ -8204,6 +8264,7 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     ConstexprKind = CSK_unspecified;
     D.getMutableDeclSpec().ClearConstexprSpec();
   }
+  Expr *TrailingRequiresClause = D.getTrailingRequiresClause();
 
   // Check that the return type is not an abstract class type.
   // For record types, this is done by the AbstractClassUsageDiagnoser once
@@ -8223,7 +8284,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     return CXXConstructorDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
         TInfo, ExplicitSpecifier, isInline,
-        /*isImplicitlyDeclared=*/false, ConstexprKind);
+        /*isImplicitlyDeclared=*/false, ConstexprKind, InheritedConstructor(),
+        TrailingRequiresClause);
 
   } else if (Name.getNameKind() == DeclarationName::CXXDestructorName) {
     // This is a C++ destructor declaration.
@@ -8232,8 +8294,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
       CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
       CXXDestructorDecl *NewDD = CXXDestructorDecl::Create(
           SemaRef.Context, Record, D.getBeginLoc(), NameInfo, R, TInfo,
-          isInline,
-          /*isImplicitlyDeclared=*/false, ConstexprKind);
+          isInline, /*isImplicitlyDeclared=*/false, ConstexprKind,
+          TrailingRequiresClause);
 
       // If the destructor needs an implicit exception specification, set it
       // now. FIXME: It'd be nice to be able to create the right type to start
@@ -8253,7 +8315,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
       return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
                                   D.getIdentifierLoc(), Name, R, TInfo, SC,
                                   isInline,
-                                  /*hasPrototype=*/true, ConstexprKind);
+                                  /*hasPrototype=*/true, ConstexprKind,
+                                  TrailingRequiresClause);
     }
 
   } else if (Name.getNameKind() == DeclarationName::CXXConversionFunctionName) {
@@ -8270,9 +8333,14 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     IsVirtualOkay = true;
     return CXXConversionDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
-        TInfo, isInline, ExplicitSpecifier, ConstexprKind, SourceLocation());
+        TInfo, isInline, ExplicitSpecifier, ConstexprKind, SourceLocation(),
+        TrailingRequiresClause);
 
   } else if (Name.getNameKind() == DeclarationName::CXXDeductionGuideName) {
+    if (TrailingRequiresClause)
+      SemaRef.Diag(TrailingRequiresClause->getBeginLoc(),
+                   diag::err_trailing_requires_clause_on_deduction_guide)
+          << TrailingRequiresClause->getSourceRange();
     SemaRef.CheckDeductionGuideDeclarator(D, R, SC);
 
     return CXXDeductionGuideDecl::Create(SemaRef.Context, DC, D.getBeginLoc(),
@@ -8294,7 +8362,8 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     // This is a C++ method declaration.
     CXXMethodDecl *Ret = CXXMethodDecl::Create(
         SemaRef.Context, cast<CXXRecordDecl>(DC), D.getBeginLoc(), NameInfo, R,
-        TInfo, SC, isInline, ConstexprKind, SourceLocation());
+        TInfo, SC, isInline, ConstexprKind, SourceLocation(),
+        TrailingRequiresClause);
     IsVirtualOkay = !Ret->isStatic();
     return Ret;
   } else {
@@ -8308,7 +8377,7 @@ static FunctionDecl *CreateNewFunctionDecl(Sema &SemaRef, Declarator &D,
     //   - we're in C++ (where every function has a prototype),
     return FunctionDecl::Create(SemaRef.Context, DC, D.getBeginLoc(), NameInfo,
                                 R, TInfo, SC, isInline, true /*HasPrototype*/,
-                                ConstexprKind);
+                                ConstexprKind, TrailingRequiresClause);
   }
 }
 
@@ -8332,7 +8401,7 @@ static bool isOpenCLSizeDependentType(ASTContext &C, QualType Ty) {
   QualType DesugaredTy = Ty;
   do {
     ArrayRef<StringRef> Names(SizeTypeNames);
-    auto Match = llvm::find(Names, DesugaredTy.getAsString());
+    auto Match = llvm::find(Names, DesugaredTy.getUnqualifiedType().getAsString());
     if (Names.end() != Match)
       return true;
 
@@ -8943,9 +9012,9 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
   if (Expr *E = (Expr*) D.getAsmLabel()) {
     // The parser guarantees this is a string.
     StringLiteral *SE = cast<StringLiteral>(E);
-    NewFD->addAttr(::new (Context)
-                       AsmLabelAttr(Context, SE->getStrTokenLoc(0),
-                                    SE->getString(), /*IsLiteralLabel=*/true));
+    NewFD->addAttr(AsmLabelAttr::Create(Context, SE->getString(),
+                                        /*IsLiteralLabel=*/true,
+                                        SE->getStrTokenLoc(0)));
   } else if (!ExtnameUndeclaredIdentifiers.empty()) {
     llvm::DenseMap<IdentifierInfo*,AsmLabelAttr*>::iterator I =
       ExtnameUndeclaredIdentifiers.find(NewFD->getIdentifier());
@@ -9551,6 +9620,29 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
     }
   }
 
+  // Diagnose no_builtin attribute on function declaration that are not a
+  // definition.
+  // FIXME: We should really be doing this in
+  // SemaDeclAttr.cpp::handleNoBuiltinAttr, unfortunately we only have access to
+  // the FunctionDecl and at this point of the code
+  // FunctionDecl::isThisDeclarationADefinition() which always returns `false`
+  // because Sema::ActOnStartOfFunctionDef has not been called yet.
+  if (const auto *NBA = NewFD->getAttr<NoBuiltinAttr>())
+    switch (D.getFunctionDefinitionKind()) {
+    case FDK_Defaulted:
+    case FDK_Deleted:
+      Diag(NBA->getLocation(),
+           diag::err_attribute_no_builtin_on_defaulted_deleted_function)
+          << NBA->getSpelling();
+      break;
+    case FDK_Declaration:
+      Diag(NBA->getLocation(), diag::err_attribute_no_builtin_on_non_definition)
+          << NBA->getSpelling();
+      break;
+    case FDK_Definition:
+      break;
+    }
+
   return NewFD;
 }
 
@@ -9687,7 +9779,7 @@ bool Sema::shouldLinkDependentDeclWithPrevious(Decl *D, Decl *PrevDecl) {
 static bool CheckMultiVersionValue(Sema &S, const FunctionDecl *FD) {
   const auto *TA = FD->getAttr<TargetAttr>();
   assert(TA && "MultiVersion Candidate requires a target attribute");
-  TargetAttr::ParsedTargetAttr ParseInfo = TA->parse();
+  ParsedTargetAttr ParseInfo = TA->parse();
   const TargetInfo &TargetInfo = S.Context.getTargetInfo();
   enum ErrType { Feature = 0, Architecture = 1 };
 
@@ -9764,13 +9856,15 @@ bool Sema::areMultiversionVariantFunctionsCompatible(
     Linkage = 5,
   };
 
-  if (OldFD && !OldFD->getType()->getAs<FunctionProtoType>()) {
+  if (NoProtoDiagID.getDiagID() != 0 && OldFD &&
+      !OldFD->getType()->getAs<FunctionProtoType>()) {
     Diag(OldFD->getLocation(), NoProtoDiagID);
     Diag(NoteCausedDiagIDAt.first, NoteCausedDiagIDAt.second);
     return true;
   }
 
-  if (!NewFD->getType()->getAs<FunctionProtoType>())
+  if (NoProtoDiagID.getDiagID() != 0 &&
+      !NewFD->getType()->getAs<FunctionProtoType>())
     return Diag(NewFD->getLocation(), NoProtoDiagID);
 
   if (!TemplatesSupported &&
@@ -9938,7 +10032,7 @@ static bool CheckTargetCausesMultiVersioning(
     bool &Redeclaration, NamedDecl *&OldDecl, bool &MergeTypeWithPrevious,
     LookupResult &Previous) {
   const auto *OldTA = OldFD->getAttr<TargetAttr>();
-  TargetAttr::ParsedTargetAttr NewParsed = NewTA->parse();
+  ParsedTargetAttr NewParsed = NewTA->parse();
   // Sort order doesn't matter, it just needs to be consistent.
   llvm::sort(NewParsed.Features);
 
@@ -9982,8 +10076,7 @@ static bool CheckTargetCausesMultiVersioning(
     return true;
   }
 
-  TargetAttr::ParsedTargetAttr OldParsed =
-      OldTA->parse(std::less<std::string>());
+  ParsedTargetAttr OldParsed = OldTA->parse(std::less<std::string>());
 
   if (OldParsed == NewParsed) {
     S.Diag(NewFD->getLocation(), diag::err_multiversion_duplicate);
@@ -10036,7 +10129,7 @@ static bool CheckMultiVersionAdditionalDecl(
     return true;
   }
 
-  TargetAttr::ParsedTargetAttr NewParsed;
+  ParsedTargetAttr NewParsed;
   if (NewTA) {
     NewParsed = NewTA->parse();
     llvm::sort(NewParsed.Features);
@@ -10063,8 +10156,7 @@ static bool CheckMultiVersionAdditionalDecl(
         return false;
       }
 
-      TargetAttr::ParsedTargetAttr CurParsed =
-          CurTA->parse(std::less<std::string>());
+      ParsedTargetAttr CurParsed = CurTA->parse(std::less<std::string>());
       if (CurParsed == NewParsed) {
         S.Diag(NewFD->getLocation(), diag::err_multiversion_duplicate);
         S.Diag(CurFD->getLocation(), diag::note_previous_declaration);
@@ -10496,6 +10588,11 @@ bool Sema::CheckFunctionDeclaration(Scope *S, FunctionDecl *NewFD,
           }
         }
       }
+      if (Method->isVirtual() && NewFD->getTrailingRequiresClause())
+        // C++2a [class.virtual]p6
+        // A virtual method shall not have a requires-clause.
+        Diag(NewFD->getTrailingRequiresClause()->getBeginLoc(),
+             diag::err_constrained_virtual_method);
 
       if (Method->isStatic())
         checkThisInStaticMemberFunctionType(Method);
@@ -11281,6 +11378,9 @@ bool Sema::DeduceVariableDeclarationType(VarDecl *VDecl, bool DirectInit,
   if (getLangOpts().ObjCAutoRefCount && inferObjCARCLifetime(VDecl))
     VDecl->setInvalidDecl();
 
+  if (getLangOpts().OpenCL)
+    deduceOpenCLAddressSpace(VDecl);
+
   // If this is a redeclaration, check that the type we just deduced matches
   // the previously declared type.
   if (VarDecl *Old = VDecl->getPreviousDecl()) {
@@ -12145,6 +12245,10 @@ void Sema::ActOnUninitializedDecl(Decl *RealDecl) {
         Diag(Var->getLocation(), diag::note_private_extern);
       }
 
+      if (Context.getTargetInfo().allowDebugInfoForExternalVar() &&
+          !Var->isInvalidDecl() && !getLangOpts().CPlusPlus)
+        ExternalDeclarations.push_back(Var);
+
       return;
 
     case VarDecl::TentativeDefinition:
@@ -13103,6 +13207,10 @@ Decl *Sema::ActOnParamDeclarator(Scope *S, Declarator &D) {
   if (New->hasAttr<BlocksAttr>()) {
     Diag(New->getLocation(), diag::err_block_on_nonlocal);
   }
+
+  if (getLangOpts().OpenCL)
+    deduceOpenCLAddressSpace(New);
+
   return New;
 }
 
@@ -13315,8 +13423,10 @@ ShouldWarnAboutMissingPrototype(const FunctionDecl *FD,
     return false;
 
   // Don't warn about 'main'.
-  if (FD->isMain())
-    return false;
+  if (isa<TranslationUnitDecl>(FD->getDeclContext()->getRedeclContext()))
+    if (IdentifierInfo *II = FD->getIdentifier())
+      if (II->isStr("main"))
+        return false;
 
   // Don't warn about inline functions.
   if (FD->isInlined())
@@ -13826,8 +13936,7 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
             LSI->ReturnType.isNull() ? Context.VoidTy : LSI->ReturnType;
 
         // Update the return type to the deduced type.
-        const FunctionProtoType *Proto =
-            FD->getType()->getAs<FunctionProtoType>();
+        const auto *Proto = FD->getType()->castAs<FunctionProtoType>();
         FD->setType(Context.getFunctionType(RetType, Proto->getParamTypes(),
                                             Proto->getExtProtoInfo()));
       }
@@ -16031,7 +16140,7 @@ FieldDecl *Sema::CheckFieldDecl(DeclarationName Name, QualType T,
   }
 
   // TR 18037 does not allow fields to be declared with address space
-  if (T.getQualifiers().hasAddressSpace() || T->isDependentAddressSpaceType() ||
+  if (T.hasAddressSpace() || T->isDependentAddressSpaceType() ||
       T->getBaseElementTypeUnsafe()->isDependentAddressSpaceType()) {
     Diag(Loc, diag::err_field_with_address_space);
     Record->setInvalidDecl();
@@ -16754,7 +16863,7 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
       if (const MSInheritanceAttr *IA = Record->getAttr<MSInheritanceAttr>())
         checkMSInheritanceAttrOnDefinition(cast<CXXRecordDecl>(Record),
                                            IA->getRange(), IA->getBestCase(),
-                                           IA->getSemanticSpelling());
+                                           IA->getInheritanceModel());
     }
 
     // Check if the structure/union declaration is a type that can have zero
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index b2be6245a814..5c51b0f9b8cb 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -23,6 +23,7 @@
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/Basic/TargetBuiltins.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/DeclSpec.h"
@@ -1068,6 +1069,56 @@ static void handleDiagnoseIfAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
       S.Context, AL, Cond, Msg, DiagType, ArgDependent, cast<NamedDecl>(D)));
 }
 
+static void handleNoBuiltinAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  static constexpr const StringRef kWildcard = "*";
+
+  llvm::SmallVector<StringRef, 16> Names;
+  bool HasWildcard = false;
+
+  const auto AddBuiltinName = [&Names, &HasWildcard](StringRef Name) {
+    if (Name == kWildcard)
+      HasWildcard = true;
+    Names.push_back(Name);
+  };
+
+  // Add previously defined attributes.
+  if (const auto *NBA = D->getAttr<NoBuiltinAttr>())
+    for (StringRef BuiltinName : NBA->builtinNames())
+      AddBuiltinName(BuiltinName);
+
+  // Add current attributes.
+  if (AL.getNumArgs() == 0)
+    AddBuiltinName(kWildcard);
+  else
+    for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
+      StringRef BuiltinName;
+      SourceLocation LiteralLoc;
+      if (!S.checkStringLiteralArgumentAttr(AL, I, BuiltinName, &LiteralLoc))
+        return;
+
+      if (Builtin::Context::isBuiltinFunc(BuiltinName))
+        AddBuiltinName(BuiltinName);
+      else
+        S.Diag(LiteralLoc, diag::warn_attribute_no_builtin_invalid_builtin_name)
+            << BuiltinName << AL.getAttrName()->getName();
+    }
+
+  // Repeating the same attribute is fine.
+  llvm::sort(Names);
+  Names.erase(std::unique(Names.begin(), Names.end()), Names.end());
+
+  // Empty no_builtin must be on its own.
+  if (HasWildcard && Names.size() > 1)
+    S.Diag(D->getLocation(),
+           diag::err_attribute_no_builtin_wildcard_or_builtin_name)
+        << AL.getAttrName()->getName();
+
+  if (D->hasAttr<NoBuiltinAttr>())
+    D->dropAttr<NoBuiltinAttr>();
+  D->addAttr(::new (S.Context)
+                 NoBuiltinAttr(S.Context, AL, Names.data(), Names.size()));
+}
+
 static void handlePassObjectSizeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   if (D->hasAttr<PassObjectSizeAttr>()) {
     S.Diag(D->getBeginLoc(), diag::err_attribute_only_once_per_parameter) << AL;
@@ -2549,6 +2600,29 @@ static void handleVisibilityAttr(Sema &S, Decl *D, const ParsedAttr &AL,
     D->addAttr(newAttr);
 }
 
+static void handleObjCDirectAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  // objc_direct cannot be set on methods declared in the context of a protocol
+  if (isa<ObjCProtocolDecl>(D->getDeclContext())) {
+    S.Diag(AL.getLoc(), diag::err_objc_direct_on_protocol) << false;
+    return;
+  }
+
+  if (S.getLangOpts().ObjCRuntime.allowsDirectDispatch()) {
+    handleSimpleAttribute<ObjCDirectAttr>(S, D, AL);
+  } else {
+    S.Diag(AL.getLoc(), diag::warn_objc_direct_ignored) << AL;
+  }
+}
+
+static void handleObjCDirectMembersAttr(Sema &S, Decl *D,
+                                        const ParsedAttr &AL) {
+  if (S.getLangOpts().ObjCRuntime.allowsDirectDispatch()) {
+    handleSimpleAttribute<ObjCDirectMembersAttr>(S, D, AL);
+  } else {
+    S.Diag(AL.getLoc(), diag::warn_objc_direct_ignored) << AL;
+  }
+}
+
 static void handleObjCMethodFamilyAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   const auto *M = cast<ObjCMethodDecl>(D);
   if (!AL.isArgIdent(0)) {
@@ -2839,7 +2913,7 @@ static void handleVecTypeHint(Sema &S, Decl *D, const ParsedAttr &AL) {
   if (!ParmType->isExtVectorType() && !ParmType->isFloatingType() &&
       (ParmType->isBooleanType() ||
        !ParmType->isIntegralType(S.getASTContext()))) {
-    S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument) << 3 << AL;
+    S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument) << 2 << AL;
     return;
   }
 
@@ -2972,7 +3046,7 @@ bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
       return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
              << Unsupported << None << Str;
 
-  TargetAttr::ParsedTargetAttr ParsedAttrs = TargetAttr::parse(AttrStr);
+  ParsedTargetAttr ParsedAttrs = TargetAttr::parse(AttrStr);
 
   if (!ParsedAttrs.Architecture.empty() &&
       !Context.getTargetInfo().isValidCPUName(ParsedAttrs.Architecture))
@@ -2990,6 +3064,19 @@ bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
              << Unsupported << None << CurFeature;
   }
 
+  TargetInfo::BranchProtectionInfo BPI;
+  StringRef Error;
+  if (!ParsedAttrs.BranchProtection.empty() &&
+      !Context.getTargetInfo().validateBranchProtection(
+          ParsedAttrs.BranchProtection, BPI, Error)) {
+    if (Error.empty())
+      return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
+             << Unsupported << None << "branch-protection";
+    else
+      return Diag(LiteralLoc, diag::err_invalid_branch_protection_spec)
+             << Error;
+  }
+
   return false;
 }
 
@@ -3798,7 +3885,7 @@ void Sema::CheckAlignasUnderalignment(Decl *D) {
 
 bool Sema::checkMSInheritanceAttrOnDefinition(
     CXXRecordDecl *RD, SourceRange Range, bool BestCase,
-    MSInheritanceAttr::Spelling SemanticSpelling) {
+    MSInheritanceModel ExplicitModel) {
   assert(RD->hasDefinition() && "RD has no definition!");
 
   // We may not have seen base specifiers or any virtual methods yet.  We will
@@ -3807,14 +3894,14 @@ bool Sema::checkMSInheritanceAttrOnDefinition(
     return false;
 
   // The unspecified model never matches what a definition could need.
-  if (SemanticSpelling == MSInheritanceAttr::Keyword_unspecified_inheritance)
+  if (ExplicitModel == MSInheritanceModel::Unspecified)
     return false;
 
   if (BestCase) {
-    if (RD->calculateInheritanceModel() == SemanticSpelling)
+    if (RD->calculateInheritanceModel() == ExplicitModel)
       return false;
   } else {
-    if (RD->calculateInheritanceModel() <= SemanticSpelling)
+    if (RD->calculateInheritanceModel() <= ExplicitModel)
       return false;
   }
 
@@ -4367,12 +4454,10 @@ static void handleLifetimeCategoryAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
     ParmType = S.GetTypeFromParser(AL.getTypeArg(), &DerefTypeLoc);
 
     unsigned SelectIdx = ~0U;
-    if (ParmType->isVoidType())
+    if (ParmType->isReferenceType())
       SelectIdx = 0;
-    else if (ParmType->isReferenceType())
-      SelectIdx = 1;
     else if (ParmType->isArrayType())
-      SelectIdx = 2;
+      SelectIdx = 1;
 
     if (SelectIdx != ~0U) {
       S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument)
@@ -4830,6 +4915,54 @@ static void handleXRayLogArgsAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
                  XRayLogArgsAttr(S.Context, AL, ArgCount.getSourceIndex()));
 }
 
+static void handlePatchableFunctionEntryAttr(Sema &S, Decl *D,
+                                             const ParsedAttr &AL) {
+  uint32_t Count = 0, Offset = 0;
+  if (!checkUInt32Argument(S, AL, AL.getArgAsExpr(0), Count, 0, true))
+    return;
+  if (AL.getNumArgs() == 2) {
+    Expr *Arg = AL.getArgAsExpr(1);
+    if (!checkUInt32Argument(S, AL, Arg, Offset, 1, true))
+      return;
+    if (Offset) {
+      S.Diag(getAttrLoc(AL), diag::err_attribute_argument_out_of_range)
+          << &AL << 0 << 0 << Arg->getBeginLoc();
+      return;
+    }
+  }
+  D->addAttr(::new (S.Context)
+                 PatchableFunctionEntryAttr(S.Context, AL, Count, Offset));
+}
+
+static bool ArmMveAliasValid(unsigned BuiltinID, StringRef AliasName) {
+  if (AliasName.startswith("__arm_"))
+    AliasName = AliasName.substr(6);
+  switch (BuiltinID) {
+#include "clang/Basic/arm_mve_builtin_aliases.inc"
+  default:
+    return false;
+  }
+}
+
+static void handleArmMveAliasAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (!AL.isArgIdent(0)) {
+    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
+        << AL << 1 << AANT_ArgumentIdentifier;
+    return;
+  }
+
+  IdentifierInfo *Ident = AL.getArgAsIdent(0)->Ident;
+  unsigned BuiltinID = Ident->getBuiltinID();
+
+  if (!ArmMveAliasValid(BuiltinID,
+                        cast<FunctionDecl>(D)->getIdentifier()->getName())) {
+    S.Diag(AL.getLoc(), diag::err_attribute_arm_mve_alias);
+    return;
+  }
+
+  D->addAttr(::new (S.Context) ArmMveAliasAttr(S.Context, AL, Ident));
+}
+
 //===----------------------------------------------------------------------===//
 // Checker-specific attribute handlers.
 //===----------------------------------------------------------------------===//
@@ -5278,9 +5411,11 @@ UuidAttr *Sema::mergeUuidAttr(Decl *D, const AttributeCommonInfo &CI,
   if (const auto *UA = D->getAttr<UuidAttr>()) {
     if (UA->getGuid().equals_lower(Uuid))
       return nullptr;
-    Diag(UA->getLocation(), diag::err_mismatched_uuid);
-    Diag(CI.getLoc(), diag::note_previous_uuid);
-    D->dropAttr<UuidAttr>();
+    if (!UA->getGuid().empty()) {
+      Diag(UA->getLocation(), diag::err_mismatched_uuid);
+      Diag(CI.getLoc(), diag::note_previous_uuid);
+      D->dropAttr<UuidAttr>();
+    }
   }
 
   return ::new (Context) UuidAttr(Context, CI, Uuid);
@@ -5342,8 +5477,7 @@ static void handleMSInheritanceAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
     return;
   }
   MSInheritanceAttr *IA = S.mergeMSInheritanceAttr(
-      D, AL, /*BestCase=*/true,
-      (MSInheritanceAttr::Spelling)AL.getSemanticSpelling());
+      D, AL, /*BestCase=*/true, (MSInheritanceModel)AL.getSemanticSpelling());
   if (IA) {
     D->addAttr(IA);
     S.Consumer.AssignInheritanceModel(cast<CXXRecordDecl>(D));
@@ -5620,6 +5754,47 @@ static void handleAVRSignalAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   handleSimpleAttribute<AVRSignalAttr>(S, D, AL);
 }
 
+static void handleBPFPreserveAIRecord(Sema &S, RecordDecl *RD) {
+  // Add preserve_access_index attribute to all fields and inner records.
+  for (auto D : RD->decls()) {
+    if (D->hasAttr<BPFPreserveAccessIndexAttr>())
+      continue;
+
+    D->addAttr(BPFPreserveAccessIndexAttr::CreateImplicit(S.Context));
+    if (auto *Rec = dyn_cast<RecordDecl>(D))
+      handleBPFPreserveAIRecord(S, Rec);
+  }
+}
+
+static void handleBPFPreserveAccessIndexAttr(Sema &S, Decl *D,
+    const ParsedAttr &AL) {
+  auto *Rec = cast<RecordDecl>(D);
+  handleBPFPreserveAIRecord(S, Rec);
+  Rec->addAttr(::new (S.Context) BPFPreserveAccessIndexAttr(S.Context, AL));
+}
+
+static void handleWebAssemblyExportNameAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (!isFunctionOrMethod(D)) {
+    S.Diag(D->getLocation(), diag::warn_attribute_wrong_decl_type)
+        << "'export_name'" << ExpectedFunction;
+    return;
+  }
+
+  auto *FD = cast<FunctionDecl>(D);
+  if (FD->isThisDeclarationADefinition()) {
+    S.Diag(D->getLocation(), diag::err_alias_is_definition) << FD << 0;
+    return;
+  }
+
+  StringRef Str;
+  SourceLocation ArgLoc;
+  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &ArgLoc))
+    return;
+
+  D->addAttr(::new (S.Context) WebAssemblyExportNameAttr(S.Context, AL, Str));
+  D->addAttr(UsedAttr::CreateImplicit(S.Context));
+}
+
 static void handleWebAssemblyImportModuleAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   if (!isFunctionOrMethod(D)) {
     S.Diag(D->getLocation(), diag::warn_attribute_wrong_decl_type)
@@ -5977,9 +6152,9 @@ static void handleDLLAttr(Sema &S, Decl *D, const ParsedAttr &A) {
 MSInheritanceAttr *
 Sema::mergeMSInheritanceAttr(Decl *D, const AttributeCommonInfo &CI,
                              bool BestCase,
-                             MSInheritanceAttr::Spelling SemanticSpelling) {
+                             MSInheritanceModel Model) {
   if (MSInheritanceAttr *IA = D->getAttr<MSInheritanceAttr>()) {
-    if (IA->getSemanticSpelling() == SemanticSpelling)
+    if (IA->getInheritanceModel() == Model)
       return nullptr;
     Diag(IA->getLocation(), diag::err_mismatched_ms_inheritance)
         << 1 /*previous declaration*/;
@@ -5990,7 +6165,7 @@ Sema::mergeMSInheritanceAttr(Decl *D, const AttributeCommonInfo &CI,
   auto *RD = cast<CXXRecordDecl>(D);
   if (RD->hasDefinition()) {
     if (checkMSInheritanceAttrOnDefinition(RD, CI.getRange(), BestCase,
-                                           SemanticSpelling)) {
+                                           Model)) {
       return nullptr;
     }
   } else {
@@ -6278,6 +6453,45 @@ static void handleOpenCLAccessAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   D->addAttr(::new (S.Context) OpenCLAccessAttr(S.Context, AL));
 }
 
+static void handleSYCLKernelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  // The 'sycl_kernel' attribute applies only to function templates.
+  const auto *FD = cast<FunctionDecl>(D);
+  const FunctionTemplateDecl *FT = FD->getDescribedFunctionTemplate();
+  assert(FT && "Function template is expected");
+
+  // Function template must have at least two template parameters.
+  const TemplateParameterList *TL = FT->getTemplateParameters();
+  if (TL->size() < 2) {
+    S.Diag(FT->getLocation(), diag::warn_sycl_kernel_num_of_template_params);
+    return;
+  }
+
+  // Template parameters must be typenames.
+  for (unsigned I = 0; I < 2; ++I) {
+    const NamedDecl *TParam = TL->getParam(I);
+    if (isa<NonTypeTemplateParmDecl>(TParam)) {
+      S.Diag(FT->getLocation(),
+             diag::warn_sycl_kernel_invalid_template_param_type);
+      return;
+    }
+  }
+
+  // Function must have at least one argument.
+  if (getFunctionOrMethodNumParams(D) != 1) {
+    S.Diag(FT->getLocation(), diag::warn_sycl_kernel_num_of_function_params);
+    return;
+  }
+
+  // Function must return void.
+  QualType RetTy = getFunctionOrMethodResultType(D);
+  if (!RetTy->isVoidType()) {
+    S.Diag(FT->getLocation(), diag::warn_sycl_kernel_return_type);
+    return;
+  }
+
+  handleSimpleAttribute<SYCLKernelAttr>(S, D, AL);
+}
+
 static void handleDestroyAttr(Sema &S, Decl *D, const ParsedAttr &A) {
   if (!cast<VarDecl>(D)->hasGlobalStorage()) {
     S.Diag(D->getLocation(), diag::err_destroy_attr_on_non_static_var)
@@ -6406,6 +6620,50 @@ static void handleMSAllocatorAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   handleSimpleAttribute<MSAllocatorAttr>(S, D, AL);
 }
 
+static void handeAcquireHandleAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  if (AL.isUsedAsTypeAttr())
+    return;
+  // Warn if the parameter is definitely not an output parameter.
+  if (const auto *PVD = dyn_cast<ParmVarDecl>(D)) {
+    if (PVD->getType()->isIntegerType()) {
+      S.Diag(AL.getLoc(), diag::err_attribute_output_parameter)
+          << AL.getRange();
+      return;
+    }
+  }
+  StringRef Argument;
+  if (!S.checkStringLiteralArgumentAttr(AL, 0, Argument))
+    return;
+  D->addAttr(AcquireHandleAttr::Create(S.Context, Argument, AL));
+}
+
+template<typename Attr>
+static void handleHandleAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  StringRef Argument;
+  if (!S.checkStringLiteralArgumentAttr(AL, 0, Argument))
+    return;
+  D->addAttr(Attr::Create(S.Context, Argument, AL));
+}
+
+static void handleCFGuardAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+  // The guard attribute takes a single identifier argument.
+
+  if (!AL.isArgIdent(0)) {
+    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
+        << AL << AANT_ArgumentIdentifier;
+    return;
+  }
+
+  CFGuardAttr::GuardArg Arg;
+  IdentifierInfo *II = AL.getArgAsIdent(0)->Ident;
+  if (!CFGuardAttr::ConvertStrToGuardArg(II->getName(), Arg)) {
+    S.Diag(AL.getLoc(), diag::warn_attribute_type_not_supported) << AL << II;
+    return;
+  }
+
+  D->addAttr(::new (S.Context) CFGuardAttr(S.Context, AL, Arg));
+}
+
 //===----------------------------------------------------------------------===//
 // Top Level Sema Entry Points
 //===----------------------------------------------------------------------===//
@@ -6496,6 +6754,12 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_AVRSignal:
     handleAVRSignalAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_BPFPreserveAccessIndex:
+    handleBPFPreserveAccessIndexAttr(S, D, AL);
+    break;
+  case ParsedAttr::AT_WebAssemblyExportName:
+    handleWebAssemblyExportNameAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_WebAssemblyImportModule:
     handleWebAssemblyImportModuleAttr(S, D, AL);
     break;
@@ -6578,6 +6842,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_DiagnoseIf:
     handleDiagnoseIfAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_NoBuiltin:
+    handleNoBuiltinAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_ExtVectorType:
     handleExtVectorTypeAttr(S, D, AL);
     break;
@@ -6599,6 +6866,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_Flatten:
     handleSimpleAttribute<FlattenAttr>(S, D, AL);
     break;
+  case ParsedAttr::AT_SYCLKernel:
+    handleSYCLKernelAttr(S, D, AL);
+    break;
   case ParsedAttr::AT_Format:
     handleFormatAttr(S, D, AL);
     break;
@@ -6826,6 +7096,13 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_ObjCRootClass:
     handleSimpleAttribute<ObjCRootClassAttr>(S, D, AL);
     break;
+  case ParsedAttr::AT_ObjCDirect:
+    handleObjCDirectAttr(S, D, AL);
+    break;
+  case ParsedAttr::AT_ObjCDirectMembers:
+    handleObjCDirectMembersAttr(S, D, AL);
+    handleSimpleAttribute<ObjCDirectMembersAttr>(S, D, AL);
+    break;
   case ParsedAttr::AT_ObjCNonLazyClass:
     handleSimpleAttribute<ObjCNonLazyClassAttr>(S, D, AL);
     break;
@@ -7015,6 +7292,9 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_AbiTag:
     handleAbiTagAttr(S, D, AL);
     break;
+  case ParsedAttr::AT_CFGuard:
+    handleCFGuardAttr(S, D, AL);
+    break;
 
   // Thread safety attributes:
   case ParsedAttr::AT_AssertExclusiveLock:
@@ -7135,6 +7415,10 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
     handleXRayLogArgsAttr(S, D, AL);
     break;
 
+  case ParsedAttr::AT_PatchableFunctionEntry:
+    handlePatchableFunctionEntryAttr(S, D, AL);
+    break;
+
   // Move semantics attribute.
   case ParsedAttr::AT_Reinitializes:
     handleSimpleAttribute<ReinitializesAttr>(S, D, AL);
@@ -7160,6 +7444,22 @@ static void ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D,
   case ParsedAttr::AT_MSAllocator:
     handleMSAllocatorAttr(S, D, AL);
     break;
+
+  case ParsedAttr::AT_ArmMveAlias:
+    handleArmMveAliasAttr(S, D, AL);
+    break;
+
+  case ParsedAttr::AT_AcquireHandle:
+    handeAcquireHandleAttr(S, D, AL);
+    break;
+
+  case ParsedAttr::AT_ReleaseHandle:
+    handleHandleAttr<ReleaseHandleAttr>(S, D, AL);
+    break;
+
+  case ParsedAttr::AT_UseHandle:
+    handleHandleAttr<UseHandleAttr>(S, D, AL);
+    break;
   }
 }
 
@@ -7238,7 +7538,8 @@ void Sema::ProcessDeclAttributeList(Scope *S, Decl *D,
   }
 }
 
-// Helper for delayed processing TransparentUnion attribute.
+// Helper for delayed processing TransparentUnion or BPFPreserveAccessIndexAttr
+// attribute.
 void Sema::ProcessDeclAttributeDelayed(Decl *D,
                                        const ParsedAttributesView &AttrList) {
   for (const ParsedAttr &AL : AttrList)
@@ -7246,6 +7547,11 @@ void Sema::ProcessDeclAttributeDelayed(Decl *D,
       handleTransparentUnionAttr(*this, D, AL);
       break;
     }
+
+  // For BPFPreserveAccessIndexAttr, we want to populate the attributes
+  // to fields and inner records as well.
+  if (D && D->hasAttr<BPFPreserveAccessIndexAttr>())
+    handleBPFPreserveAIRecord(*this, cast<RecordDecl>(D));
 }
 
 // Annotation attributes are the only attributes allowed after an access
@@ -7308,7 +7614,8 @@ NamedDecl * Sema::DeclClonePragmaWeak(NamedDecl *ND, IdentifierInfo *II,
     NewFD = FunctionDecl::Create(
         FD->getASTContext(), FD->getDeclContext(), Loc, Loc,
         DeclarationName(II), FD->getType(), FD->getTypeSourceInfo(), SC_None,
-        false /*isInlineSpecified*/, FD->hasPrototype(), CSK_unspecified);
+        false /*isInlineSpecified*/, FD->hasPrototype(), CSK_unspecified,
+        FD->getTrailingRequiresClause());
     NewD = NewFD;
 
     if (FD->getQualifier())
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index ff90b9548e29..9916d3be77e1 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -217,8 +217,8 @@ Sema::ImplicitExceptionSpecification::CalledDecl(SourceLocation CallLoc,
       Exceptions.push_back(E);
 }
 
-void Sema::ImplicitExceptionSpecification::CalledExpr(Expr *E) {
-  if (!E || ComputedEST == EST_MSAny)
+void Sema::ImplicitExceptionSpecification::CalledStmt(Stmt *S) {
+  if (!S || ComputedEST == EST_MSAny)
     return;
 
   // FIXME:
@@ -242,7 +242,7 @@ void Sema::ImplicitExceptionSpecification::CalledExpr(Expr *E) {
   // implicit definition. For now, we assume that any non-nothrow expression can
   // throw any exception.
 
-  if (Self->canThrow(E))
+  if (Self->canThrow(S))
     ComputedEST = EST_None;
 }
 
@@ -1501,13 +1501,13 @@ void Sema::MergeVarDeclExceptionSpecs(VarDecl *New, VarDecl *Old) {
   // as pointers to member functions.
   if (const ReferenceType *R = NewType->getAs<ReferenceType>()) {
     NewType = R->getPointeeType();
-    OldType = OldType->getAs<ReferenceType>()->getPointeeType();
+    OldType = OldType->castAs<ReferenceType>()->getPointeeType();
   } else if (const PointerType *P = NewType->getAs<PointerType>()) {
     NewType = P->getPointeeType();
-    OldType = OldType->getAs<PointerType>()->getPointeeType();
+    OldType = OldType->castAs<PointerType>()->getPointeeType();
   } else if (const MemberPointerType *M = NewType->getAs<MemberPointerType>()) {
     NewType = M->getPointeeType();
-    OldType = OldType->getAs<MemberPointerType>()->getPointeeType();
+    OldType = OldType->castAs<MemberPointerType>()->getPointeeType();
   }
 
   if (!NewType->isFunctionProtoType())
@@ -1627,14 +1627,13 @@ static bool CheckConstexprDestructorSubobjects(Sema &SemaRef,
   return true;
 }
 
-// CheckConstexprParameterTypes - Check whether a function's parameter types
-// are all literal types. If so, return true. If not, produce a suitable
-// diagnostic and return false.
+/// Check whether a function's parameter types are all literal types. If so,
+/// return true. If not, produce a suitable diagnostic and return false.
 static bool CheckConstexprParameterTypes(Sema &SemaRef,
                                          const FunctionDecl *FD,
                                          Sema::CheckConstexprKind Kind) {
   unsigned ArgIndex = 0;
-  const FunctionProtoType *FT = FD->getType()->getAs<FunctionProtoType>();
+  const auto *FT = FD->getType()->castAs<FunctionProtoType>();
   for (FunctionProtoType::param_type_iterator i = FT->param_type_begin(),
                                               e = FT->param_type_end();
        i != e; ++i, ++ArgIndex) {
@@ -1649,6 +1648,17 @@ static bool CheckConstexprParameterTypes(Sema &SemaRef,
   return true;
 }
 
+/// Check whether a function's return type is a literal type. If so, return
+/// true. If not, produce a suitable diagnostic and return false.
+static bool CheckConstexprReturnType(Sema &SemaRef, const FunctionDecl *FD,
+                                     Sema::CheckConstexprKind Kind) {
+  if (CheckLiteralType(SemaRef, Kind, FD->getLocation(), FD->getReturnType(),
+                       diag::err_constexpr_non_literal_return,
+                       FD->isConsteval()))
+    return false;
+  return true;
+}
+
 /// Get diagnostic %select index for tag kind for
 /// record diagnostic message.
 /// WARNING: Indexes apply to particular diagnostics only!
@@ -1729,10 +1739,7 @@ bool Sema::CheckConstexprFunctionDefinition(const FunctionDecl *NewFD,
     }
 
     // - its return type shall be a literal type;
-    QualType RT = NewFD->getReturnType();
-    if (CheckLiteralType(*this, Kind, NewFD->getLocation(), RT,
-                         diag::err_constexpr_non_literal_return,
-                         NewFD->isConsteval()))
+    if (!CheckConstexprReturnType(*this, NewFD, Kind))
       return false;
   }
 
@@ -3800,7 +3807,7 @@ namespace {
 
     const CXXRecordDecl *RD = Constructor->getParent();
 
-    if (RD->getDescribedClassTemplate())
+    if (RD->isDependentContext())
       return;
 
     // Holds fields that are uninitialized.
@@ -3861,6 +3868,26 @@ void Sema::ActOnStartCXXInClassMemberInitializer() {
   PushFunctionScope();
 }
 
+void Sema::ActOnStartTrailingRequiresClause(Scope *S, Declarator &D) {
+  if (!D.isFunctionDeclarator())
+    return;
+  auto &FTI = D.getFunctionTypeInfo();
+  if (!FTI.Params)
+    return;
+  for (auto &Param : ArrayRef<DeclaratorChunk::ParamInfo>(FTI.Params,
+                                                          FTI.NumParams)) {
+    auto *ParamDecl = cast<NamedDecl>(Param.Param);
+    if (ParamDecl->getDeclName())
+      PushOnScopeChains(ParamDecl, S, /*AddToContext=*/false);
+  }
+}
+
+ExprResult Sema::ActOnFinishTrailingRequiresClause(ExprResult ConstraintExpr) {
+  if (ConstraintExpr.isInvalid())
+    return ExprError();
+  return CorrectDelayedTyposInExpr(ConstraintExpr);
+}
+
 /// This is invoked after parsing an in-class initializer for a
 /// non-static C++ class member, and after instantiating an in-class initializer
 /// in a class template. Such actions are deferred until the class is complete.
@@ -6084,6 +6111,67 @@ void Sema::propagateDLLAttrToBaseClassTemplate(
   }
 }
 
+/// Determine the kind of defaulting that would be done for a given function.
+///
+/// If the function is both a default constructor and a copy / move constructor
+/// (due to having a default argument for the first parameter), this picks
+/// CXXDefaultConstructor.
+///
+/// FIXME: Check that case is properly handled by all callers.
+Sema::DefaultedFunctionKind
+Sema::getDefaultedFunctionKind(const FunctionDecl *FD) {
+  if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
+    if (const CXXConstructorDecl *Ctor = dyn_cast<CXXConstructorDecl>(FD)) {
+      if (Ctor->isDefaultConstructor())
+        return Sema::CXXDefaultConstructor;
+
+      if (Ctor->isCopyConstructor())
+        return Sema::CXXCopyConstructor;
+
+      if (Ctor->isMoveConstructor())
+        return Sema::CXXMoveConstructor;
+    }
+
+    if (MD->isCopyAssignmentOperator())
+      return Sema::CXXCopyAssignment;
+
+    if (MD->isMoveAssignmentOperator())
+      return Sema::CXXMoveAssignment;
+
+    if (isa<CXXDestructorDecl>(FD))
+      return Sema::CXXDestructor;
+  }
+
+  switch (FD->getDeclName().getCXXOverloadedOperator()) {
+  case OO_EqualEqual:
+    return DefaultedComparisonKind::Equal;
+
+  case OO_ExclaimEqual:
+    return DefaultedComparisonKind::NotEqual;
+
+  case OO_Spaceship:
+    // No point allowing this if <=> doesn't exist in the current language mode.
+    if (!getLangOpts().CPlusPlus2a)
+      break;
+    return DefaultedComparisonKind::ThreeWay;
+
+  case OO_Less:
+  case OO_LessEqual:
+  case OO_Greater:
+  case OO_GreaterEqual:
+    // No point allowing this if <=> doesn't exist in the current language mode.
+    if (!getLangOpts().CPlusPlus2a)
+      break;
+    return DefaultedComparisonKind::Relational;
+
+  default:
+    break;
+  }
+
+  // Not defaultable.
+  return DefaultedFunctionKind();
+}
+
 static void DefineImplicitSpecialMember(Sema &S, CXXMethodDecl *MD,
                                         SourceLocation DefaultLoc) {
   switch (S.getSpecialMember(MD)) {
@@ -6228,7 +6316,11 @@ static bool canPassInRegisters(Sema &S, CXXRecordDecl *D,
 /// Perform semantic checks on a class definition that has been
 /// completing, introducing implicitly-declared members, checking for
 /// abstract types, etc.
-void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
+///
+/// \param S The scope in which the class was parsed. Null if we didn't just
+///        parse a class definition.
+/// \param Record The completed class.
+void Sema::CheckCompletedCXXClass(Scope *S, CXXRecordDecl *Record) {
   if (!Record)
     return;
 
@@ -6330,10 +6422,30 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
   if (HasTrivialABI)
     Record->setHasTrivialSpecialMemberForCall();
 
+  // Explicitly-defaulted secondary comparison functions (!=, <, <=, >, >=).
+  // We check these last because they can depend on the properties of the
+  // primary comparison functions (==, <=>).
+  llvm::SmallVector<FunctionDecl*, 5> DefaultedSecondaryComparisons;
+
+  auto CheckForDefaultedFunction = [&](FunctionDecl *FD) {
+    if (!FD || FD->isInvalidDecl() || !FD->isExplicitlyDefaulted())
+      return;
+
+    DefaultedFunctionKind DFK = getDefaultedFunctionKind(FD);
+    if (DFK.asComparison() == DefaultedComparisonKind::NotEqual ||
+        DFK.asComparison() == DefaultedComparisonKind::Relational)
+      DefaultedSecondaryComparisons.push_back(FD);
+    else
+      CheckExplicitlyDefaultedFunction(S, FD);
+  };
+
   auto CompleteMemberFunction = [&](CXXMethodDecl *M) {
-    // Check whether the explicitly-defaulted special members are valid.
-    if (!M->isInvalidDecl() && M->isExplicitlyDefaulted())
-      CheckExplicitlyDefaultedSpecialMember(M);
+    // Check whether the explicitly-defaulted members are valid.
+    CheckForDefaultedFunction(M);
+
+    // Skip the rest of the checks for a member of a dependent class.
+    if (Record->isDependentType())
+      return;
 
     // For an explicitly defaulted or deleted special member, we defer
     // determining triviality until the class is complete. That time is now!
@@ -6379,40 +6491,52 @@ void Sema::CheckCompletedCXXClass(CXXRecordDecl *Record) {
       DefineImplicitSpecialMember(*this, M, M->getLocation());
   };
 
+  // Check the destructor before any other member function. We need to
+  // determine whether it's trivial in order to determine whether the claas
+  // type is a literal type, which is a prerequisite for determining whether
+  // other special member functions are valid and whether they're implicitly
+  // 'constexpr'.
+  if (CXXDestructorDecl *Dtor = Record->getDestructor())
+    CompleteMemberFunction(Dtor);
+
   bool HasMethodWithOverrideControl = false,
        HasOverridingMethodWithoutOverrideControl = false;
-  if (!Record->isDependentType()) {
-    // Check the destructor before any other member function. We need to
-    // determine whether it's trivial in order to determine whether the claas
-    // type is a literal type, which is a prerequisite for determining whether
-    // other special member functions are valid and whether they're implicitly
-    // 'constexpr'.
-    if (CXXDestructorDecl *Dtor = Record->getDestructor())
-      CompleteMemberFunction(Dtor);
-
-    for (auto *M : Record->methods()) {
-      // See if a method overloads virtual methods in a base
-      // class without overriding any.
-      if (!M->isStatic())
-        DiagnoseHiddenVirtualMethods(M);
-      if (M->hasAttr<OverrideAttr>())
-        HasMethodWithOverrideControl = true;
-      else if (M->size_overridden_methods() > 0)
-        HasOverridingMethodWithoutOverrideControl = true;
+  for (auto *D : Record->decls()) {
+    if (auto *M = dyn_cast<CXXMethodDecl>(D)) {
+      // FIXME: We could do this check for dependent types with non-dependent
+      // bases.
+      if (!Record->isDependentType()) {
+        // See if a method overloads virtual methods in a base
+        // class without overriding any.
+        if (!M->isStatic())
+          DiagnoseHiddenVirtualMethods(M);
+        if (M->hasAttr<OverrideAttr>())
+          HasMethodWithOverrideControl = true;
+        else if (M->size_overridden_methods() > 0)
+          HasOverridingMethodWithoutOverrideControl = true;
+      }
 
       if (!isa<CXXDestructorDecl>(M))
         CompleteMemberFunction(M);
+    } else if (auto *F = dyn_cast<FriendDecl>(D)) {
+      CheckForDefaultedFunction(
+          dyn_cast_or_null<FunctionDecl>(F->getFriendDecl()));
     }
   }
 
   if (HasMethodWithOverrideControl &&
       HasOverridingMethodWithoutOverrideControl) {
     // At least one method has the 'override' control declared.
-    // Diagnose all other overridden methods which do not have 'override' specified on them.
+    // Diagnose all other overridden methods which do not have 'override'
+    // specified on them.
     for (auto *M : Record->methods())
       DiagnoseAbsenceOfOverrideControl(M);
   }
 
+  // Check the defaulted secondary comparisons after any other member functions.
+  for (FunctionDecl *FD : DefaultedSecondaryComparisons)
+    CheckExplicitlyDefaultedFunction(S, FD);
+
   // ms_struct is a request to use the same ABI rules as MSVC.  Check
   // whether this class uses any C++ features that are implemented
   // completely differently in MSVC, and if so, emit a diagnostic.
@@ -6710,20 +6834,50 @@ static bool defaultedSpecialMemberIsConstexpr(
   return true;
 }
 
+namespace {
+/// RAII object to register a defaulted function as having its exception
+/// specification computed.
+struct ComputingExceptionSpec {
+  Sema &S;
+
+  ComputingExceptionSpec(Sema &S, FunctionDecl *FD, SourceLocation Loc)
+      : S(S) {
+    Sema::CodeSynthesisContext Ctx;
+    Ctx.Kind = Sema::CodeSynthesisContext::ExceptionSpecEvaluation;
+    Ctx.PointOfInstantiation = Loc;
+    Ctx.Entity = FD;
+    S.pushCodeSynthesisContext(Ctx);
+  }
+  ~ComputingExceptionSpec() {
+    S.popCodeSynthesisContext();
+  }
+};
+}
+
 static Sema::ImplicitExceptionSpecification
 ComputeDefaultedSpecialMemberExceptionSpec(
     Sema &S, SourceLocation Loc, CXXMethodDecl *MD, Sema::CXXSpecialMember CSM,
     Sema::InheritedConstructorInfo *ICI);
 
 static Sema::ImplicitExceptionSpecification
-computeImplicitExceptionSpec(Sema &S, SourceLocation Loc, CXXMethodDecl *MD) {
-  auto CSM = S.getSpecialMember(MD);
-  if (CSM != Sema::CXXInvalid)
-    return ComputeDefaultedSpecialMemberExceptionSpec(S, Loc, MD, CSM, nullptr);
+ComputeDefaultedComparisonExceptionSpec(Sema &S, SourceLocation Loc,
+                                        FunctionDecl *FD,
+                                        Sema::DefaultedComparisonKind DCK);
 
-  auto *CD = cast<CXXConstructorDecl>(MD);
+static Sema::ImplicitExceptionSpecification
+computeImplicitExceptionSpec(Sema &S, SourceLocation Loc, FunctionDecl *FD) {
+  auto DFK = S.getDefaultedFunctionKind(FD);
+  if (DFK.isSpecialMember())
+    return ComputeDefaultedSpecialMemberExceptionSpec(
+        S, Loc, cast<CXXMethodDecl>(FD), DFK.asSpecialMember(), nullptr);
+  if (DFK.isComparison())
+    return ComputeDefaultedComparisonExceptionSpec(S, Loc, FD,
+                                                   DFK.asComparison());
+
+  auto *CD = cast<CXXConstructorDecl>(FD);
   assert(CD->getInheritedConstructor() &&
-         "only special members have implicit exception specs");
+         "only defaulted functions and inherited constructors have implicit "
+         "exception specs");
   Sema::InheritedConstructorInfo ICI(
       S, Loc, CD->getInheritedConstructor().getShadowDecl());
   return ComputeDefaultedSpecialMemberExceptionSpec(
@@ -6745,34 +6899,46 @@ static FunctionProtoType::ExtProtoInfo getImplicitMethodEPI(Sema &S,
   return EPI;
 }
 
-void Sema::EvaluateImplicitExceptionSpec(SourceLocation Loc, CXXMethodDecl *MD) {
-  const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
+void Sema::EvaluateImplicitExceptionSpec(SourceLocation Loc, FunctionDecl *FD) {
+  const FunctionProtoType *FPT = FD->getType()->castAs<FunctionProtoType>();
   if (FPT->getExceptionSpecType() != EST_Unevaluated)
     return;
 
   // Evaluate the exception specification.
-  auto IES = computeImplicitExceptionSpec(*this, Loc, MD);
+  auto IES = computeImplicitExceptionSpec(*this, Loc, FD);
   auto ESI = IES.getExceptionSpec();
 
   // Update the type of the special member to use it.
-  UpdateExceptionSpec(MD, ESI);
+  UpdateExceptionSpec(FD, ESI);
+}
+
+void Sema::CheckExplicitlyDefaultedFunction(Scope *S, FunctionDecl *FD) {
+  assert(FD->isExplicitlyDefaulted() && "not explicitly-defaulted");
 
-  // A user-provided destructor can be defined outside the class. When that
-  // happens, be sure to update the exception specification on both
-  // declarations.
-  const FunctionProtoType *CanonicalFPT =
-    MD->getCanonicalDecl()->getType()->castAs<FunctionProtoType>();
-  if (CanonicalFPT->getExceptionSpecType() == EST_Unevaluated)
-    UpdateExceptionSpec(MD->getCanonicalDecl(), ESI);
+  DefaultedFunctionKind DefKind = getDefaultedFunctionKind(FD);
+  if (!DefKind) {
+    assert(FD->getDeclContext()->isDependentContext());
+    return;
+  }
+
+  if (DefKind.isSpecialMember()
+          ? CheckExplicitlyDefaultedSpecialMember(cast<CXXMethodDecl>(FD),
+                                                  DefKind.asSpecialMember())
+          : CheckExplicitlyDefaultedComparison(S, FD, DefKind.asComparison()))
+    FD->setInvalidDecl();
 }
 
-void Sema::CheckExplicitlyDefaultedSpecialMember(CXXMethodDecl *MD) {
+bool Sema::CheckExplicitlyDefaultedSpecialMember(CXXMethodDecl *MD,
+                                                 CXXSpecialMember CSM) {
   CXXRecordDecl *RD = MD->getParent();
-  CXXSpecialMember CSM = getSpecialMember(MD);
 
   assert(MD->isExplicitlyDefaulted() && CSM != CXXInvalid &&
          "not an explicitly-defaulted special member");
 
+  // Defer all checking for special members of a dependent type.
+  if (RD->isDependentType())
+    return false;
+
   // Whether this was the first-declared instance of the constructor.
   // This affects whether we implicitly add an exception spec and constexpr.
   bool First = MD == MD->getCanonicalDecl();
@@ -6781,7 +6947,7 @@ void Sema::CheckExplicitlyDefaultedSpecialMember(CXXMethodDecl *MD) {
 
   // C++11 [dcl.fct.def.default]p1:
   //   A function that is explicitly defaulted shall
-  //     -- be a special member function (checked elsewhere),
+  //     -- be a special member function [...] (checked elsewhere),
   //     -- have the same type (except for ref-qualifiers, and except that a
   //        copy operation can take a non-const reference) as an implicit
   //        declaration, and
@@ -6960,8 +7126,1124 @@ void Sema::CheckExplicitlyDefaultedSpecialMember(CXXMethodDecl *MD) {
     }
   }
 
-  if (HadError)
-    MD->setInvalidDecl();
+  return HadError;
+}
+
+namespace {
+/// Helper class for building and checking a defaulted comparison.
+///
+/// Defaulted functions are built in two phases:
+///
+///  * First, the set of operations that the function will perform are
+///    identified, and some of them are checked. If any of the checked
+///    operations is invalid in certain ways, the comparison function is
+///    defined as deleted and no body is built.
+///  * Then, if the function is not defined as deleted, the body is built.
+///
+/// This is accomplished by performing two visitation steps over the eventual
+/// body of the function.
+template<typename Derived, typename ResultList, typename Result,
+         typename Subobject>
+class DefaultedComparisonVisitor {
+public:
+  using DefaultedComparisonKind = Sema::DefaultedComparisonKind;
+
+  DefaultedComparisonVisitor(Sema &S, CXXRecordDecl *RD, FunctionDecl *FD,
+                             DefaultedComparisonKind DCK)
+      : S(S), RD(RD), FD(FD), DCK(DCK) {
+    if (auto *Info = FD->getDefaultedFunctionInfo()) {
+      // FIXME: Change CreateOverloadedBinOp to take an ArrayRef instead of an
+      // UnresolvedSet to avoid this copy.
+      Fns.assign(Info->getUnqualifiedLookups().begin(),
+                 Info->getUnqualifiedLookups().end());
+    }
+  }
+
+  ResultList visit() {
+    // The type of an lvalue naming a parameter of this function.
+    QualType ParamLvalType =
+        FD->getParamDecl(0)->getType().getNonReferenceType();
+
+    ResultList Results;
+
+    switch (DCK) {
+    case DefaultedComparisonKind::None:
+      llvm_unreachable("not a defaulted comparison");
+
+    case DefaultedComparisonKind::Equal:
+    case DefaultedComparisonKind::ThreeWay:
+      getDerived().visitSubobjects(Results, RD, ParamLvalType.getQualifiers());
+      return Results;
+
+    case DefaultedComparisonKind::NotEqual:
+    case DefaultedComparisonKind::Relational:
+      Results.add(getDerived().visitExpandedSubobject(
+          ParamLvalType, getDerived().getCompleteObject()));
+      return Results;
+    }
+    llvm_unreachable("");
+  }
+
+protected:
+  Derived &getDerived() { return static_cast<Derived&>(*this); }
+
+  /// Visit the expanded list of subobjects of the given type, as specified in
+  /// C++2a [class.compare.default].
+  ///
+  /// \return \c true if the ResultList object said we're done, \c false if not.
+  bool visitSubobjects(ResultList &Results, CXXRecordDecl *Record,
+                       Qualifiers Quals) {
+    // C++2a [class.compare.default]p4:
+    //   The direct base class subobjects of C
+    for (CXXBaseSpecifier &Base : Record->bases())
+      if (Results.add(getDerived().visitSubobject(
+              S.Context.getQualifiedType(Base.getType(), Quals),
+              getDerived().getBase(&Base))))
+        return true;
+
+    //   followed by the non-static data members of C
+    for (FieldDecl *Field : Record->fields()) {
+      // Recursively expand anonymous structs.
+      if (Field->isAnonymousStructOrUnion()) {
+        if (visitSubobjects(Results, Field->getType()->getAsCXXRecordDecl(),
+                            Quals))
+          return true;
+        continue;
+      }
+
+      // Figure out the type of an lvalue denoting this field.
+      Qualifiers FieldQuals = Quals;
+      if (Field->isMutable())
+        FieldQuals.removeConst();
+      QualType FieldType =
+          S.Context.getQualifiedType(Field->getType(), FieldQuals);
+
+      if (Results.add(getDerived().visitSubobject(
+              FieldType, getDerived().getField(Field))))
+        return true;
+    }
+
+    //   form a list of subobjects.
+    return false;
+  }
+
+  Result visitSubobject(QualType Type, Subobject Subobj) {
+    //   In that list, any subobject of array type is recursively expanded
+    const ArrayType *AT = S.Context.getAsArrayType(Type);
+    if (auto *CAT = dyn_cast_or_null<ConstantArrayType>(AT))
+      return getDerived().visitSubobjectArray(CAT->getElementType(),
+                                              CAT->getSize(), Subobj);
+    return getDerived().visitExpandedSubobject(Type, Subobj);
+  }
+
+  Result visitSubobjectArray(QualType Type, const llvm::APInt &Size,
+                             Subobject Subobj) {
+    return getDerived().visitSubobject(Type, Subobj);
+  }
+
+protected:
+  Sema &S;
+  CXXRecordDecl *RD;
+  FunctionDecl *FD;
+  DefaultedComparisonKind DCK;
+  UnresolvedSet<16> Fns;
+};
+
+/// Information about a defaulted comparison, as determined by
+/// DefaultedComparisonAnalyzer.
+struct DefaultedComparisonInfo {
+  bool Deleted = false;
+  bool Constexpr = true;
+  ComparisonCategoryType Category = ComparisonCategoryType::StrongOrdering;
+
+  static DefaultedComparisonInfo deleted() {
+    DefaultedComparisonInfo Deleted;
+    Deleted.Deleted = true;
+    return Deleted;
+  }
+
+  bool add(const DefaultedComparisonInfo &R) {
+    Deleted |= R.Deleted;
+    Constexpr &= R.Constexpr;
+    Category = commonComparisonType(Category, R.Category);
+    return Deleted;
+  }
+};
+
+/// An element in the expanded list of subobjects of a defaulted comparison, as
+/// specified in C++2a [class.compare.default]p4.
+struct DefaultedComparisonSubobject {
+  enum { CompleteObject, Member, Base } Kind;
+  NamedDecl *Decl;
+  SourceLocation Loc;
+};
+
+/// A visitor over the notional body of a defaulted comparison that determines
+/// whether that body would be deleted or constexpr.
+class DefaultedComparisonAnalyzer
+    : public DefaultedComparisonVisitor<DefaultedComparisonAnalyzer,
+                                        DefaultedComparisonInfo,
+                                        DefaultedComparisonInfo,
+                                        DefaultedComparisonSubobject> {
+public:
+  enum DiagnosticKind { NoDiagnostics, ExplainDeleted, ExplainConstexpr };
+
+private:
+  DiagnosticKind Diagnose;
+
+public:
+  using Base = DefaultedComparisonVisitor;
+  using Result = DefaultedComparisonInfo;
+  using Subobject = DefaultedComparisonSubobject;
+
+  friend Base;
+
+  DefaultedComparisonAnalyzer(Sema &S, CXXRecordDecl *RD, FunctionDecl *FD,
+                              DefaultedComparisonKind DCK,
+                              DiagnosticKind Diagnose = NoDiagnostics)
+      : Base(S, RD, FD, DCK), Diagnose(Diagnose) {}
+
+  Result visit() {
+    if ((DCK == DefaultedComparisonKind::Equal ||
+         DCK == DefaultedComparisonKind::ThreeWay) &&
+        RD->hasVariantMembers()) {
+      // C++2a [class.compare.default]p2 [P2002R0]:
+      //   A defaulted comparison operator function for class C is defined as
+      //   deleted if [...] C has variant members.
+      if (Diagnose == ExplainDeleted) {
+        S.Diag(FD->getLocation(), diag::note_defaulted_comparison_union)
+          << FD << RD->isUnion() << RD;
+      }
+      return Result::deleted();
+    }
+
+    return Base::visit();
+  }
+
+private:
+  Subobject getCompleteObject() {
+    return Subobject{Subobject::CompleteObject, nullptr, FD->getLocation()};
+  }
+
+  Subobject getBase(CXXBaseSpecifier *Base) {
+    return Subobject{Subobject::Base, Base->getType()->getAsCXXRecordDecl(),
+                     Base->getBaseTypeLoc()};
+  }
+
+  Subobject getField(FieldDecl *Field) {
+    return Subobject{Subobject::Member, Field, Field->getLocation()};
+  }
+
+  Result visitExpandedSubobject(QualType Type, Subobject Subobj) {
+    // C++2a [class.compare.default]p2 [P2002R0]:
+    //   A defaulted <=> or == operator function for class C is defined as
+    //   deleted if any non-static data member of C is of reference type
+    if (Type->isReferenceType()) {
+      if (Diagnose == ExplainDeleted) {
+        S.Diag(Subobj.Loc, diag::note_defaulted_comparison_reference_member)
+            << FD << RD;
+      }
+      return Result::deleted();
+    }
+
+    // [...] Let xi be an lvalue denoting the ith element [...]
+    OpaqueValueExpr Xi(FD->getLocation(), Type, VK_LValue);
+    Expr *Args[] = {&Xi, &Xi};
+
+    // All operators start by trying to apply that same operator recursively.
+    OverloadedOperatorKind OO = FD->getOverloadedOperator();
+    assert(OO != OO_None && "not an overloaded operator!");
+    return visitBinaryOperator(OO, Args, Subobj);
+  }
+
+  Result
+  visitBinaryOperator(OverloadedOperatorKind OO, ArrayRef<Expr *> Args,
+                      Subobject Subobj,
+                      OverloadCandidateSet *SpaceshipCandidates = nullptr) {
+    // Note that there is no need to consider rewritten candidates here if
+    // we've already found there is no viable 'operator<=>' candidate (and are
+    // considering synthesizing a '<=>' from '==' and '<').
+    OverloadCandidateSet CandidateSet(
+        FD->getLocation(), OverloadCandidateSet::CSK_Operator,
+        OverloadCandidateSet::OperatorRewriteInfo(
+            OO, /*AllowRewrittenCandidates=*/!SpaceshipCandidates));
+
+    /// C++2a [class.compare.default]p1 [P2002R0]:
+    ///   [...] the defaulted function itself is never a candidate for overload
+    ///   resolution [...]
+    CandidateSet.exclude(FD);
+
+    S.LookupOverloadedBinOp(CandidateSet, OO, Fns, Args);
+
+    Result R;
+
+    OverloadCandidateSet::iterator Best;
+    switch (CandidateSet.BestViableFunction(S, FD->getLocation(), Best)) {
+    case OR_Success: {
+      // C++2a [class.compare.secondary]p2 [P2002R0]:
+      //   The operator function [...] is defined as deleted if [...] the
+      //   candidate selected by overload resolution is not a rewritten
+      //   candidate.
+      if ((DCK == DefaultedComparisonKind::NotEqual ||
+           DCK == DefaultedComparisonKind::Relational) &&
+          !Best->RewriteKind) {
+        if (Diagnose == ExplainDeleted) {
+          S.Diag(Best->Function->getLocation(),
+                 diag::note_defaulted_comparison_not_rewritten_callee)
+              << FD;
+        }
+        return Result::deleted();
+      }
+
+      // Throughout C++2a [class.compare]: if overload resolution does not
+      // result in a usable function, the candidate function is defined as
+      // deleted. This requires that we selected an accessible function.
+      //
+      // Note that this only considers the access of the function when named
+      // within the type of the subobject, and not the access path for any
+      // derived-to-base conversion.
+      CXXRecordDecl *ArgClass = Args[0]->getType()->getAsCXXRecordDecl();
+      if (ArgClass && Best->FoundDecl.getDecl() &&
+          Best->FoundDecl.getDecl()->isCXXClassMember()) {
+        QualType ObjectType = Subobj.Kind == Subobject::Member
+                                  ? Args[0]->getType()
+                                  : S.Context.getRecordType(RD);
+        if (!S.isMemberAccessibleForDeletion(
+                ArgClass, Best->FoundDecl, ObjectType, Subobj.Loc,
+                Diagnose == ExplainDeleted
+                    ? S.PDiag(diag::note_defaulted_comparison_inaccessible)
+                          << FD << Subobj.Kind << Subobj.Decl
+                    : S.PDiag()))
+          return Result::deleted();
+      }
+
+      // C++2a [class.compare.default]p3 [P2002R0]:
+      //   A defaulted comparison function is constexpr-compatible if [...]
+      //   no overlod resolution performed [...] results in a non-constexpr
+      //   function.
+      if (FunctionDecl *BestFD = Best->Function) {
+        assert(!BestFD->isDeleted() && "wrong overload resolution result");
+        // If it's not constexpr, explain why not.
+        if (Diagnose == ExplainConstexpr && !BestFD->isConstexpr()) {
+          if (Subobj.Kind != Subobject::CompleteObject)
+            S.Diag(Subobj.Loc, diag::note_defaulted_comparison_not_constexpr)
+              << Subobj.Kind << Subobj.Decl;
+          S.Diag(BestFD->getLocation(),
+                 diag::note_defaulted_comparison_not_constexpr_here);
+          // Bail out after explaining; we don't want any more notes.
+          return Result::deleted();
+        }
+        R.Constexpr &= BestFD->isConstexpr();
+      }
+
+      if (OO == OO_Spaceship && FD->getReturnType()->isUndeducedAutoType()) {
+        if (auto *BestFD = Best->Function) {
+          if (auto *Info = S.Context.CompCategories.lookupInfoForType(
+              BestFD->getCallResultType())) {
+            R.Category = Info->Kind;
+          } else {
+            if (Diagnose == ExplainDeleted) {
+              S.Diag(Subobj.Loc, diag::note_defaulted_comparison_cannot_deduce)
+                  << Subobj.Kind << Subobj.Decl
+                  << BestFD->getCallResultType().withoutLocalFastQualifiers();
+              S.Diag(BestFD->getLocation(),
+                     diag::note_defaulted_comparison_cannot_deduce_callee)
+                  << Subobj.Kind << Subobj.Decl;
+            }
+            return Result::deleted();
+          }
+        } else {
+          Optional<ComparisonCategoryType> Cat =
+              getComparisonCategoryForBuiltinCmp(Args[0]->getType());
+          assert(Cat && "no category for builtin comparison?");
+          R.Category = *Cat;
+        }
+      }
+
+      // Note that we might be rewriting to a different operator. That call is
+      // not considered until we come to actually build the comparison function.
+      break;
+    }
+
+    case OR_Ambiguous:
+      if (Diagnose == ExplainDeleted) {
+        unsigned Kind = 0;
+        if (FD->getOverloadedOperator() == OO_Spaceship && OO != OO_Spaceship)
+          Kind = OO == OO_EqualEqual ? 1 : 2;
+        CandidateSet.NoteCandidates(
+            PartialDiagnosticAt(
+                Subobj.Loc, S.PDiag(diag::note_defaulted_comparison_ambiguous)
+                                << FD << Kind << Subobj.Kind << Subobj.Decl),
+            S, OCD_AmbiguousCandidates, Args);
+      }
+      R = Result::deleted();
+      break;
+
+    case OR_Deleted:
+      if (Diagnose == ExplainDeleted) {
+        if ((DCK == DefaultedComparisonKind::NotEqual ||
+             DCK == DefaultedComparisonKind::Relational) &&
+            !Best->RewriteKind) {
+          S.Diag(Best->Function->getLocation(),
+                 diag::note_defaulted_comparison_not_rewritten_callee)
+              << FD;
+        } else {
+          S.Diag(Subobj.Loc,
+                 diag::note_defaulted_comparison_calls_deleted)
+              << FD << Subobj.Kind << Subobj.Decl;
+          S.NoteDeletedFunction(Best->Function);
+        }
+      }
+      R = Result::deleted();
+      break;
+
+    case OR_No_Viable_Function:
+      // If there's no usable candidate, we're done unless we can rewrite a
+      // '<=>' in terms of '==' and '<'.
+      if (OO == OO_Spaceship &&
+          S.Context.CompCategories.lookupInfoForType(FD->getReturnType())) {
+        // For any kind of comparison category return type, we need a usable
+        // '==' and a usable '<'.
+        if (!R.add(visitBinaryOperator(OO_EqualEqual, Args, Subobj,
+                                       &CandidateSet)))
+          R.add(visitBinaryOperator(OO_Less, Args, Subobj, &CandidateSet));
+        break;
+      }
+
+      if (Diagnose == ExplainDeleted) {
+        S.Diag(Subobj.Loc, diag::note_defaulted_comparison_no_viable_function)
+            << FD << Subobj.Kind << Subobj.Decl;
+
+        // For a three-way comparison, list both the candidates for the
+        // original operator and the candidates for the synthesized operator.
+        if (SpaceshipCandidates) {
+          SpaceshipCandidates->NoteCandidates(
+              S, Args,
+              SpaceshipCandidates->CompleteCandidates(S, OCD_AllCandidates,
+                                                      Args, FD->getLocation()));
+          S.Diag(Subobj.Loc,
+                 diag::note_defaulted_comparison_no_viable_function_synthesized)
+              << (OO == OO_EqualEqual ? 0 : 1);
+        }
+
+        CandidateSet.NoteCandidates(
+            S, Args,
+            CandidateSet.CompleteCandidates(S, OCD_AllCandidates, Args,
+                                            FD->getLocation()));
+      }
+      R = Result::deleted();
+      break;
+    }
+
+    return R;
+  }
+};
+
+/// A list of statements.
+struct StmtListResult {
+  bool IsInvalid = false;
+  llvm::SmallVector<Stmt*, 16> Stmts;
+
+  bool add(const StmtResult &S) {
+    IsInvalid |= S.isInvalid();
+    if (IsInvalid)
+      return true;
+    Stmts.push_back(S.get());
+    return false;
+  }
+};
+
+/// A visitor over the notional body of a defaulted comparison that synthesizes
+/// the actual body.
+class DefaultedComparisonSynthesizer
+    : public DefaultedComparisonVisitor<DefaultedComparisonSynthesizer,
+                                        StmtListResult, StmtResult,
+                                        std::pair<ExprResult, ExprResult>> {
+  SourceLocation Loc;
+  unsigned ArrayDepth = 0;
+
+public:
+  using Base = DefaultedComparisonVisitor;
+  using ExprPair = std::pair<ExprResult, ExprResult>;
+
+  friend Base;
+
+  DefaultedComparisonSynthesizer(Sema &S, CXXRecordDecl *RD, FunctionDecl *FD,
+                                 DefaultedComparisonKind DCK,
+                                 SourceLocation BodyLoc)
+      : Base(S, RD, FD, DCK), Loc(BodyLoc) {}
+
+  /// Build a suitable function body for this defaulted comparison operator.
+  StmtResult build() {
+    Sema::CompoundScopeRAII CompoundScope(S);
+
+    StmtListResult Stmts = visit();
+    if (Stmts.IsInvalid)
+      return StmtError();
+
+    ExprResult RetVal;
+    switch (DCK) {
+    case DefaultedComparisonKind::None:
+      llvm_unreachable("not a defaulted comparison");
+
+    case DefaultedComparisonKind::Equal: {
+      // C++2a [class.eq]p3:
+      //   [...] compar[e] the corresponding elements [...] until the first
+      //   index i where xi == yi yields [...] false. If no such index exists,
+      //   V is true. Otherwise, V is false.
+      //
+      // Join the comparisons with '&&'s and return the result. Use a right
+      // fold (traversing the conditions right-to-left), because that
+      // short-circuits more naturally.
+      auto OldStmts = std::move(Stmts.Stmts);
+      Stmts.Stmts.clear();
+      ExprResult CmpSoFar;
+      // Finish a particular comparison chain.
+      auto FinishCmp = [&] {
+        if (Expr *Prior = CmpSoFar.get()) {
+          // Convert the last expression to 'return ...;'
+          if (RetVal.isUnset() && Stmts.Stmts.empty())
+            RetVal = CmpSoFar;
+          // Convert any prior comparison to 'if (!(...)) return false;'
+          else if (Stmts.add(buildIfNotCondReturnFalse(Prior)))
+            return true;
+          CmpSoFar = ExprResult();
+        }
+        return false;
+      };
+      for (Stmt *EAsStmt : llvm::reverse(OldStmts)) {
+        Expr *E = dyn_cast<Expr>(EAsStmt);
+        if (!E) {
+          // Found an array comparison.
+          if (FinishCmp() || Stmts.add(EAsStmt))
+            return StmtError();
+          continue;
+        }
+
+        if (CmpSoFar.isUnset()) {
+          CmpSoFar = E;
+          continue;
+        }
+        CmpSoFar = S.CreateBuiltinBinOp(Loc, BO_LAnd, E, CmpSoFar.get());
+        if (CmpSoFar.isInvalid())
+          return StmtError();
+      }
+      if (FinishCmp())
+        return StmtError();
+      std::reverse(Stmts.Stmts.begin(), Stmts.Stmts.end());
+      //   If no such index exists, V is true.
+      if (RetVal.isUnset())
+        RetVal = S.ActOnCXXBoolLiteral(Loc, tok::kw_true);
+      break;
+    }
+
+    case DefaultedComparisonKind::ThreeWay: {
+      // Per C++2a [class.spaceship]p3, as a fallback add:
+      // return static_cast<R>(std::strong_ordering::equal);
+      QualType StrongOrdering = S.CheckComparisonCategoryType(
+          ComparisonCategoryType::StrongOrdering, Loc,
+          Sema::ComparisonCategoryUsage::DefaultedOperator);
+      if (StrongOrdering.isNull())
+        return StmtError();
+      VarDecl *EqualVD = S.Context.CompCategories.getInfoForType(StrongOrdering)
+                             .getValueInfo(ComparisonCategoryResult::Equal)
+                             ->VD;
+      RetVal = getDecl(EqualVD);
+      if (RetVal.isInvalid())
+        return StmtError();
+      RetVal = buildStaticCastToR(RetVal.get());
+      break;
+    }
+
+    case DefaultedComparisonKind::NotEqual:
+    case DefaultedComparisonKind::Relational:
+      RetVal = cast<Expr>(Stmts.Stmts.pop_back_val());
+      break;
+    }
+
+    // Build the final return statement.
+    if (RetVal.isInvalid())
+      return StmtError();
+    StmtResult ReturnStmt = S.BuildReturnStmt(Loc, RetVal.get());
+    if (ReturnStmt.isInvalid())
+      return StmtError();
+    Stmts.Stmts.push_back(ReturnStmt.get());
+
+    return S.ActOnCompoundStmt(Loc, Loc, Stmts.Stmts, /*IsStmtExpr=*/false);
+  }
+
+private:
+  ExprResult getDecl(ValueDecl *VD) {
+    return S.BuildDeclarationNameExpr(
+        CXXScopeSpec(), DeclarationNameInfo(VD->getDeclName(), Loc), VD);
+  }
+
+  ExprResult getParam(unsigned I) {
+    ParmVarDecl *PD = FD->getParamDecl(I);
+    return getDecl(PD);
+  }
+
+  ExprPair getCompleteObject() {
+    unsigned Param = 0;
+    ExprResult LHS;
+    if (isa<CXXMethodDecl>(FD)) {
+      // LHS is '*this'.
+      LHS = S.ActOnCXXThis(Loc);
+      if (!LHS.isInvalid())
+        LHS = S.CreateBuiltinUnaryOp(Loc, UO_Deref, LHS.get());
+    } else {
+      LHS = getParam(Param++);
+    }
+    ExprResult RHS = getParam(Param++);
+    assert(Param == FD->getNumParams());
+    return {LHS, RHS};
+  }
+
+  ExprPair getBase(CXXBaseSpecifier *Base) {
+    ExprPair Obj = getCompleteObject();
+    if (Obj.first.isInvalid() || Obj.second.isInvalid())
+      return {ExprError(), ExprError()};
+    CXXCastPath Path = {Base};
+    return {S.ImpCastExprToType(Obj.first.get(), Base->getType(),
+                                CK_DerivedToBase, VK_LValue, &Path),
+            S.ImpCastExprToType(Obj.second.get(), Base->getType(),
+                                CK_DerivedToBase, VK_LValue, &Path)};
+  }
+
+  ExprPair getField(FieldDecl *Field) {
+    ExprPair Obj = getCompleteObject();
+    if (Obj.first.isInvalid() || Obj.second.isInvalid())
+      return {ExprError(), ExprError()};
+
+    DeclAccessPair Found = DeclAccessPair::make(Field, Field->getAccess());
+    DeclarationNameInfo NameInfo(Field->getDeclName(), Loc);
+    return {S.BuildFieldReferenceExpr(Obj.first.get(), /*IsArrow=*/false, Loc,
+                                      CXXScopeSpec(), Field, Found, NameInfo),
+            S.BuildFieldReferenceExpr(Obj.second.get(), /*IsArrow=*/false, Loc,
+                                      CXXScopeSpec(), Field, Found, NameInfo)};
+  }
+
+  // FIXME: When expanding a subobject, register a note in the code synthesis
+  // stack to say which subobject we're comparing.
+
+  StmtResult buildIfNotCondReturnFalse(ExprResult Cond) {
+    if (Cond.isInvalid())
+      return StmtError();
+
+    ExprResult NotCond = S.CreateBuiltinUnaryOp(Loc, UO_LNot, Cond.get());
+    if (NotCond.isInvalid())
+      return StmtError();
+
+    ExprResult False = S.ActOnCXXBoolLiteral(Loc, tok::kw_false);
+    assert(!False.isInvalid() && "should never fail");
+    StmtResult ReturnFalse = S.BuildReturnStmt(Loc, False.get());
+    if (ReturnFalse.isInvalid())
+      return StmtError();
+
+    return S.ActOnIfStmt(Loc, false, nullptr,
+                         S.ActOnCondition(nullptr, Loc, NotCond.get(),
+                                          Sema::ConditionKind::Boolean),
+                         ReturnFalse.get(), SourceLocation(), nullptr);
+  }
+
+  StmtResult visitSubobjectArray(QualType Type, llvm::APInt Size,
+                                 ExprPair Subobj) {
+    QualType SizeType = S.Context.getSizeType();
+    Size = Size.zextOrTrunc(S.Context.getTypeSize(SizeType));
+
+    // Build 'size_t i$n = 0'.
+    IdentifierInfo *IterationVarName = nullptr;
+    {
+      SmallString<8> Str;
+      llvm::raw_svector_ostream OS(Str);
+      OS << "i" << ArrayDepth;
+      IterationVarName = &S.Context.Idents.get(OS.str());
+    }
+    VarDecl *IterationVar = VarDecl::Create(
+        S.Context, S.CurContext, Loc, Loc, IterationVarName, SizeType,
+        S.Context.getTrivialTypeSourceInfo(SizeType, Loc), SC_None);
+    llvm::APInt Zero(S.Context.getTypeSize(SizeType), 0);
+    IterationVar->setInit(
+        IntegerLiteral::Create(S.Context, Zero, SizeType, Loc));
+    Stmt *Init = new (S.Context) DeclStmt(DeclGroupRef(IterationVar), Loc, Loc);
+
+    auto IterRef = [&] {
+      ExprResult Ref = S.BuildDeclarationNameExpr(
+          CXXScopeSpec(), DeclarationNameInfo(IterationVarName, Loc),
+          IterationVar);
+      assert(!Ref.isInvalid() && "can't reference our own variable?");
+      return Ref.get();
+    };
+
+    // Build 'i$n != Size'.
+    ExprResult Cond = S.CreateBuiltinBinOp(
+        Loc, BO_NE, IterRef(),
+        IntegerLiteral::Create(S.Context, Size, SizeType, Loc));
+    assert(!Cond.isInvalid() && "should never fail");
+
+    // Build '++i$n'.
+    ExprResult Inc = S.CreateBuiltinUnaryOp(Loc, UO_PreInc, IterRef());
+    assert(!Inc.isInvalid() && "should never fail");
+
+    // Build 'a[i$n]' and 'b[i$n]'.
+    auto Index = [&](ExprResult E) {
+      if (E.isInvalid())
+        return ExprError();
+      return S.CreateBuiltinArraySubscriptExpr(E.get(), Loc, IterRef(), Loc);
+    };
+    Subobj.first = Index(Subobj.first);
+    Subobj.second = Index(Subobj.second);
+
+    // Compare the array elements.
+    ++ArrayDepth;
+    StmtResult Substmt = visitSubobject(Type, Subobj);
+    --ArrayDepth;
+
+    if (Substmt.isInvalid())
+      return StmtError();
+
+    // For the inner level of an 'operator==', build 'if (!cmp) return false;'.
+    // For outer levels or for an 'operator<=>' we already have a suitable
+    // statement that returns as necessary.
+    if (Expr *ElemCmp = dyn_cast<Expr>(Substmt.get())) {
+      assert(DCK == DefaultedComparisonKind::Equal &&
+             "should have non-expression statement");
+      Substmt = buildIfNotCondReturnFalse(ElemCmp);
+      if (Substmt.isInvalid())
+        return StmtError();
+    }
+
+    // Build 'for (...) ...'
+    return S.ActOnForStmt(Loc, Loc, Init,
+                          S.ActOnCondition(nullptr, Loc, Cond.get(),
+                                           Sema::ConditionKind::Boolean),
+                          S.MakeFullDiscardedValueExpr(Inc.get()), Loc,
+                          Substmt.get());
+  }
+
+  StmtResult visitExpandedSubobject(QualType Type, ExprPair Obj) {
+    if (Obj.first.isInvalid() || Obj.second.isInvalid())
+      return StmtError();
+
+    OverloadedOperatorKind OO = FD->getOverloadedOperator();
+    ExprResult Op = S.CreateOverloadedBinOp(
+        Loc, BinaryOperator::getOverloadedOpcode(OO), Fns,
+        Obj.first.get(), Obj.second.get(), /*PerformADL=*/true,
+        /*AllowRewrittenCandidates=*/true, FD);
+    if (Op.isInvalid())
+      return StmtError();
+
+    switch (DCK) {
+    case DefaultedComparisonKind::None:
+      llvm_unreachable("not a defaulted comparison");
+
+    case DefaultedComparisonKind::Equal:
+      // Per C++2a [class.eq]p2, each comparison is individually contextually
+      // converted to bool.
+      Op = S.PerformContextuallyConvertToBool(Op.get());
+      if (Op.isInvalid())
+        return StmtError();
+      return Op.get();
+
+    case DefaultedComparisonKind::ThreeWay: {
+      // Per C++2a [class.spaceship]p3, form:
+      //   if (R cmp = static_cast<R>(op); cmp != 0)
+      //     return cmp;
+      QualType R = FD->getReturnType();
+      Op = buildStaticCastToR(Op.get());
+      if (Op.isInvalid())
+        return StmtError();
+
+      // R cmp = ...;
+      IdentifierInfo *Name = &S.Context.Idents.get("cmp");
+      VarDecl *VD =
+          VarDecl::Create(S.Context, S.CurContext, Loc, Loc, Name, R,
+                          S.Context.getTrivialTypeSourceInfo(R, Loc), SC_None);
+      S.AddInitializerToDecl(VD, Op.get(), /*DirectInit=*/false);
+      Stmt *InitStmt = new (S.Context) DeclStmt(DeclGroupRef(VD), Loc, Loc);
+
+      // cmp != 0
+      ExprResult VDRef = getDecl(VD);
+      if (VDRef.isInvalid())
+        return StmtError();
+      llvm::APInt ZeroVal(S.Context.getIntWidth(S.Context.IntTy), 0);
+      Expr *Zero =
+          IntegerLiteral::Create(S.Context, ZeroVal, S.Context.IntTy, Loc);
+      ExprResult Comp = S.CreateOverloadedBinOp(Loc, BO_NE, Fns, VDRef.get(),
+                                                Zero, true, true, FD);
+      if (Comp.isInvalid())
+        return StmtError();
+      Sema::ConditionResult Cond = S.ActOnCondition(
+          nullptr, Loc, Comp.get(), Sema::ConditionKind::Boolean);
+      if (Cond.isInvalid())
+        return StmtError();
+
+      // return cmp;
+      VDRef = getDecl(VD);
+      if (VDRef.isInvalid())
+        return StmtError();
+      StmtResult ReturnStmt = S.BuildReturnStmt(Loc, VDRef.get());
+      if (ReturnStmt.isInvalid())
+        return StmtError();
+
+      // if (...)
+      return S.ActOnIfStmt(Loc, /*IsConstexpr=*/false, InitStmt, Cond,
+                           ReturnStmt.get(), /*ElseLoc=*/SourceLocation(),
+                           /*Else=*/nullptr);
+    }
+
+    case DefaultedComparisonKind::NotEqual:
+    case DefaultedComparisonKind::Relational:
+      // C++2a [class.compare.secondary]p2:
+      //   Otherwise, the operator function yields x @ y.
+      return Op.get();
+    }
+    llvm_unreachable("");
+  }
+
+  /// Build "static_cast<R>(E)".
+  ExprResult buildStaticCastToR(Expr *E) {
+    QualType R = FD->getReturnType();
+    assert(!R->isUndeducedType() && "type should have been deduced already");
+
+    // Don't bother forming a no-op cast in the common case.
+    if (E->isRValue() && S.Context.hasSameType(E->getType(), R))
+      return E;
+    return S.BuildCXXNamedCast(Loc, tok::kw_static_cast,
+                               S.Context.getTrivialTypeSourceInfo(R, Loc), E,
+                               SourceRange(Loc, Loc), SourceRange(Loc, Loc));
+  }
+};
+}
+
+/// Perform the unqualified lookups that might be needed to form a defaulted
+/// comparison function for the given operator.
+static void lookupOperatorsForDefaultedComparison(Sema &Self, Scope *S,
+                                                  UnresolvedSetImpl &Operators,
+                                                  OverloadedOperatorKind Op) {
+  auto Lookup = [&](OverloadedOperatorKind OO) {
+    Self.LookupOverloadedOperatorName(OO, S, QualType(), QualType(), Operators);
+  };
+
+  // Every defaulted operator looks up itself.
+  Lookup(Op);
+  // ... and the rewritten form of itself, if any.
+  if (OverloadedOperatorKind ExtraOp = getRewrittenOverloadedOperator(Op))
+    Lookup(ExtraOp);
+
+  // For 'operator<=>', we also form a 'cmp != 0' expression, and might
+  // synthesize a three-way comparison from '<' and '=='. In a dependent
+  // context, we also need to look up '==' in case we implicitly declare a
+  // defaulted 'operator=='.
+  if (Op == OO_Spaceship) {
+    Lookup(OO_ExclaimEqual);
+    Lookup(OO_Less);
+    Lookup(OO_EqualEqual);
+  }
+}
+
+bool Sema::CheckExplicitlyDefaultedComparison(Scope *S, FunctionDecl *FD,
+                                              DefaultedComparisonKind DCK) {
+  assert(DCK != DefaultedComparisonKind::None && "not a defaulted comparison");
+
+  CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(FD->getLexicalDeclContext());
+  assert(RD && "defaulted comparison is not defaulted in a class");
+
+  // Perform any unqualified lookups we're going to need to default this
+  // function.
+  if (S) {
+    UnresolvedSet<32> Operators;
+    lookupOperatorsForDefaultedComparison(*this, S, Operators,
+                                          FD->getOverloadedOperator());
+    FD->setDefaultedFunctionInfo(FunctionDecl::DefaultedFunctionInfo::Create(
+        Context, Operators.pairs()));
+  }
+
+  // C++2a [class.compare.default]p1:
+  //   A defaulted comparison operator function for some class C shall be a
+  //   non-template function declared in the member-specification of C that is
+  //    -- a non-static const member of C having one parameter of type
+  //       const C&, or
+  //    -- a friend of C having two parameters of type const C& or two
+  //       parameters of type C.
+  QualType ExpectedParmType1 = Context.getRecordType(RD);
+  QualType ExpectedParmType2 =
+      Context.getLValueReferenceType(ExpectedParmType1.withConst());
+  if (isa<CXXMethodDecl>(FD))
+    ExpectedParmType1 = ExpectedParmType2;
+  for (const ParmVarDecl *Param : FD->parameters()) {
+    if (!Param->getType()->isDependentType() &&
+        !Context.hasSameType(Param->getType(), ExpectedParmType1) &&
+        !Context.hasSameType(Param->getType(), ExpectedParmType2)) {
+      // Don't diagnose an implicit 'operator=='; we will have diagnosed the
+      // corresponding defaulted 'operator<=>' already.
+      if (!FD->isImplicit()) {
+        Diag(FD->getLocation(), diag::err_defaulted_comparison_param)
+            << (int)DCK << Param->getType() << ExpectedParmType1
+            << !isa<CXXMethodDecl>(FD)
+            << ExpectedParmType2 << Param->getSourceRange();
+      }
+      return true;
+    }
+  }
+  if (FD->getNumParams() == 2 &&
+      !Context.hasSameType(FD->getParamDecl(0)->getType(),
+                           FD->getParamDecl(1)->getType())) {
+    if (!FD->isImplicit()) {
+      Diag(FD->getLocation(), diag::err_defaulted_comparison_param_mismatch)
+          << (int)DCK
+          << FD->getParamDecl(0)->getType()
+          << FD->getParamDecl(0)->getSourceRange()
+          << FD->getParamDecl(1)->getType()
+          << FD->getParamDecl(1)->getSourceRange();
+    }
+    return true;
+  }
+
+  // ... non-static const member ...
+  if (auto *MD = dyn_cast<CXXMethodDecl>(FD)) {
+    assert(!MD->isStatic() && "comparison function cannot be a static member");
+    if (!MD->isConst()) {
+      SourceLocation InsertLoc;
+      if (FunctionTypeLoc Loc = MD->getFunctionTypeLoc())
+        InsertLoc = getLocForEndOfToken(Loc.getRParenLoc());
+      // Don't diagnose an implicit 'operator=='; we will have diagnosed the
+      // corresponding defaulted 'operator<=>' already.
+      if (!MD->isImplicit()) {
+        Diag(MD->getLocation(), diag::err_defaulted_comparison_non_const)
+          << (int)DCK << FixItHint::CreateInsertion(InsertLoc, " const");
+      }
+
+      // Add the 'const' to the type to recover.
+      const auto *FPT = MD->getType()->castAs<FunctionProtoType>();
+      FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+      EPI.TypeQuals.addConst();
+      MD->setType(Context.getFunctionType(FPT->getReturnType(),
+                                          FPT->getParamTypes(), EPI));
+    }
+  } else {
+    // A non-member function declared in a class must be a friend.
+    assert(FD->getFriendObjectKind() && "expected a friend declaration");
+  }
+
+  // C++2a [class.eq]p1, [class.rel]p1:
+  //   A [defaulted comparison other than <=>] shall have a declared return
+  //   type bool.
+  if (DCK != DefaultedComparisonKind::ThreeWay &&
+      !FD->getDeclaredReturnType()->isDependentType() &&
+      !Context.hasSameType(FD->getDeclaredReturnType(), Context.BoolTy)) {
+    Diag(FD->getLocation(), diag::err_defaulted_comparison_return_type_not_bool)
+        << (int)DCK << FD->getDeclaredReturnType() << Context.BoolTy
+        << FD->getReturnTypeSourceRange();
+    return true;
+  }
+  // C++2a [class.spaceship]p2 [P2002R0]:
+  //   Let R be the declared return type [...]. If R is auto, [...]. Otherwise,
+  //   R shall not contain a placeholder type.
+  if (DCK == DefaultedComparisonKind::ThreeWay &&
+      FD->getDeclaredReturnType()->getContainedDeducedType() &&
+      !Context.hasSameType(FD->getDeclaredReturnType(),
+                           Context.getAutoDeductType())) {
+    Diag(FD->getLocation(),
+         diag::err_defaulted_comparison_deduced_return_type_not_auto)
+        << (int)DCK << FD->getDeclaredReturnType() << Context.AutoDeductTy
+        << FD->getReturnTypeSourceRange();
+    return true;
+  }
+
+  // For a defaulted function in a dependent class, defer all remaining checks
+  // until instantiation.
+  if (RD->isDependentType())
+    return false;
+
+  // Determine whether the function should be defined as deleted.
+  DefaultedComparisonInfo Info =
+      DefaultedComparisonAnalyzer(*this, RD, FD, DCK).visit();
+
+  bool First = FD == FD->getCanonicalDecl();
+
+  // If we want to delete the function, then do so; there's nothing else to
+  // check in that case.
+  if (Info.Deleted) {
+    if (!First) {
+      // C++11 [dcl.fct.def.default]p4:
+      //   [For a] user-provided explicitly-defaulted function [...] if such a
+      //   function is implicitly defined as deleted, the program is ill-formed.
+      //
+      // This is really just a consequence of the general rule that you can
+      // only delete a function on its first declaration.
+      Diag(FD->getLocation(), diag::err_non_first_default_compare_deletes)
+          << FD->isImplicit() << (int)DCK;
+      DefaultedComparisonAnalyzer(*this, RD, FD, DCK,
+                                  DefaultedComparisonAnalyzer::ExplainDeleted)
+          .visit();
+      return true;
+    }
+
+    SetDeclDeleted(FD, FD->getLocation());
+    if (!inTemplateInstantiation() && !FD->isImplicit()) {
+      Diag(FD->getLocation(), diag::warn_defaulted_comparison_deleted)
+          << (int)DCK;
+      DefaultedComparisonAnalyzer(*this, RD, FD, DCK,
+                                  DefaultedComparisonAnalyzer::ExplainDeleted)
+          .visit();
+    }
+    return false;
+  }
+
+  // C++2a [class.spaceship]p2:
+  //   The return type is deduced as the common comparison type of R0, R1, ...
+  if (DCK == DefaultedComparisonKind::ThreeWay &&
+      FD->getDeclaredReturnType()->isUndeducedAutoType()) {
+    SourceLocation RetLoc = FD->getReturnTypeSourceRange().getBegin();
+    if (RetLoc.isInvalid())
+      RetLoc = FD->getBeginLoc();
+    // FIXME: Should we really care whether we have the complete type and the
+    // 'enumerator' constants here? A forward declaration seems sufficient.
+    QualType Cat = CheckComparisonCategoryType(
+        Info.Category, RetLoc, ComparisonCategoryUsage::DefaultedOperator);
+    if (Cat.isNull())
+      return true;
+    Context.adjustDeducedFunctionResultType(
+        FD, SubstAutoType(FD->getDeclaredReturnType(), Cat));
+  }
+
+  // C++2a [dcl.fct.def.default]p3 [P2002R0]:
+  //   An explicitly-defaulted function that is not defined as deleted may be
+  //   declared constexpr or consteval only if it is constexpr-compatible.
+  // C++2a [class.compare.default]p3 [P2002R0]:
+  //   A defaulted comparison function is constexpr-compatible if it satisfies
+  //   the requirements for a constexpr function [...]
+  // The only relevant requirements are that the parameter and return types are
+  // literal types. The remaining conditions are checked by the analyzer.
+  if (FD->isConstexpr()) {
+    if (CheckConstexprReturnType(*this, FD, CheckConstexprKind::Diagnose) &&
+        CheckConstexprParameterTypes(*this, FD, CheckConstexprKind::Diagnose) &&
+        !Info.Constexpr) {
+      Diag(FD->getBeginLoc(),
+           diag::err_incorrect_defaulted_comparison_constexpr)
+          << FD->isImplicit() << (int)DCK << FD->isConsteval();
+      DefaultedComparisonAnalyzer(*this, RD, FD, DCK,
+                                  DefaultedComparisonAnalyzer::ExplainConstexpr)
+          .visit();
+    }
+  }
+
+  // C++2a [dcl.fct.def.default]p3 [P2002R0]:
+  //   If a constexpr-compatible function is explicitly defaulted on its first
+  //   declaration, it is implicitly considered to be constexpr.
+  // FIXME: Only applying this to the first declaration seems problematic, as
+  // simple reorderings can affect the meaning of the program.
+  if (First && !FD->isConstexpr() && Info.Constexpr)
+    FD->setConstexprKind(CSK_constexpr);
+
+  // C++2a [except.spec]p3:
+  //   If a declaration of a function does not have a noexcept-specifier
+  //   [and] is defaulted on its first declaration, [...] the exception
+  //   specification is as specified below
+  if (FD->getExceptionSpecType() == EST_None) {
+    auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+    FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+    EPI.ExceptionSpec.Type = EST_Unevaluated;
+    EPI.ExceptionSpec.SourceDecl = FD;
+    FD->setType(Context.getFunctionType(FPT->getReturnType(),
+                                        FPT->getParamTypes(), EPI));
+  }
+
+  return false;
+}
+
+void Sema::DeclareImplicitEqualityComparison(CXXRecordDecl *RD,
+                                             FunctionDecl *Spaceship) {
+  Sema::CodeSynthesisContext Ctx;
+  Ctx.Kind = Sema::CodeSynthesisContext::DeclaringImplicitEqualityComparison;
+  Ctx.PointOfInstantiation = Spaceship->getEndLoc();
+  Ctx.Entity = Spaceship;
+  pushCodeSynthesisContext(Ctx);
+
+  if (FunctionDecl *EqualEqual = SubstSpaceshipAsEqualEqual(RD, Spaceship))
+    EqualEqual->setImplicit();
+
+  popCodeSynthesisContext();
+}
+
+void Sema::DefineDefaultedComparison(SourceLocation UseLoc, FunctionDecl *FD,
+                                     DefaultedComparisonKind DCK) {
+  assert(FD->isDefaulted() && !FD->isDeleted() &&
+         !FD->doesThisDeclarationHaveABody());
+  if (FD->willHaveBody() || FD->isInvalidDecl())
+    return;
+
+  SynthesizedFunctionScope Scope(*this, FD);
+
+  // Add a context note for diagnostics produced after this point.
+  Scope.addContextNote(UseLoc);
+
+  {
+    // Build and set up the function body.
+    CXXRecordDecl *RD = cast<CXXRecordDecl>(FD->getLexicalParent());
+    SourceLocation BodyLoc =
+        FD->getEndLoc().isValid() ? FD->getEndLoc() : FD->getLocation();
+    StmtResult Body =
+        DefaultedComparisonSynthesizer(*this, RD, FD, DCK, BodyLoc).build();
+    if (Body.isInvalid()) {
+      FD->setInvalidDecl();
+      return;
+    }
+    FD->setBody(Body.get());
+    FD->markUsed(Context);
+  }
+
+  // The exception specification is needed because we are defining the
+  // function. Note that this will reuse the body we just built.
+  ResolveExceptionSpec(UseLoc, FD->getType()->castAs<FunctionProtoType>());
+
+  if (ASTMutationListener *L = getASTMutationListener())
+    L->CompletedImplicitDefinition(FD);
+}
+
+static Sema::ImplicitExceptionSpecification
+ComputeDefaultedComparisonExceptionSpec(Sema &S, SourceLocation Loc,
+                                        FunctionDecl *FD,
+                                        Sema::DefaultedComparisonKind DCK) {
+  ComputingExceptionSpec CES(S, FD, Loc);
+  Sema::ImplicitExceptionSpecification ExceptSpec(S);
+
+  if (FD->isInvalidDecl())
+    return ExceptSpec;
+
+  // The common case is that we just defined the comparison function. In that
+  // case, just look at whether the body can throw.
+  if (FD->hasBody()) {
+    ExceptSpec.CalledStmt(FD->getBody());
+  } else {
+    // Otherwise, build a body so we can check it. This should ideally only
+    // happen when we're not actually marking the function referenced. (This is
+    // only really important for efficiency: we don't want to build and throw
+    // away bodies for comparison functions more than we strictly need to.)
+
+    // Pretend to synthesize the function body in an unevaluated context.
+    // Note that we can't actually just go ahead and define the function here:
+    // we are not permitted to mark its callees as referenced.
+    Sema::SynthesizedFunctionScope Scope(S, FD);
+    EnterExpressionEvaluationContext Context(
+        S, Sema::ExpressionEvaluationContext::Unevaluated);
+
+    CXXRecordDecl *RD = cast<CXXRecordDecl>(FD->getLexicalParent());
+    SourceLocation BodyLoc =
+        FD->getEndLoc().isValid() ? FD->getEndLoc() : FD->getLocation();
+    StmtResult Body =
+        DefaultedComparisonSynthesizer(S, RD, FD, DCK, BodyLoc).build();
+    if (!Body.isInvalid())
+      ExceptSpec.CalledStmt(Body.get());
+
+    // FIXME: Can we hold onto this body and just transform it to potentially
+    // evaluated when we're asked to define the function rather than rebuilding
+    // it? Either that, or we should only build the bits of the body that we
+    // need (the expressions, not the statements).
+  }
+
+  return ExceptSpec;
 }
 
 void Sema::CheckDelayedMemberExceptionSpecs() {
@@ -7157,7 +8439,8 @@ bool SpecialMemberDeletionInfo::isAccessible(Subobject Subobj,
     objectTy = S.Context.getTypeDeclType(target->getParent());
   }
 
-  return S.isSpecialMemberAccessibleForDeletion(target, access, objectTy);
+  return S.isMemberAccessibleForDeletion(
+      target->getParent(), DeclAccessPair::make(target, access), objectTy);
 }
 
 /// Check whether we should delete a special member due to the implicit
@@ -7568,6 +8851,22 @@ bool Sema::ShouldDeleteSpecialMember(CXXMethodDecl *MD, CXXSpecialMember CSM,
   return false;
 }
 
+void Sema::DiagnoseDeletedDefaultedFunction(FunctionDecl *FD) {
+  DefaultedFunctionKind DFK = getDefaultedFunctionKind(FD);
+  assert(DFK && "not a defaultable function");
+  assert(FD->isDefaulted() && FD->isDeleted() && "not defaulted and deleted");
+
+  if (DFK.isSpecialMember()) {
+    ShouldDeleteSpecialMember(cast<CXXMethodDecl>(FD), DFK.asSpecialMember(),
+                              nullptr, /*Diagnose=*/true);
+  } else {
+    DefaultedComparisonAnalyzer(
+        *this, cast<CXXRecordDecl>(FD->getLexicalDeclContext()), FD,
+        DFK.asComparison(), DefaultedComparisonAnalyzer::ExplainDeleted)
+        .visit();
+  }
+}
+
 /// Perform lookup for a special member of the specified kind, and determine
 /// whether it is trivial. If the triviality can be determined without the
 /// lookup, skip it. This is intended for use when determining whether a
@@ -8187,7 +9486,45 @@ void Sema::ActOnFinishCXXMemberSpecification(
               reinterpret_cast<Decl**>(FieldCollector->getCurFields()),
               FieldCollector->getCurNumFields()), LBrac, RBrac, AttrList);
 
-  CheckCompletedCXXClass(cast<CXXRecordDecl>(TagDecl));
+  CheckCompletedCXXClass(S, cast<CXXRecordDecl>(TagDecl));
+}
+
+/// Find the equality comparison functions that should be implicitly declared
+/// in a given class definition, per C++2a [class.compare.default]p3.
+static void findImplicitlyDeclaredEqualityComparisons(
+    ASTContext &Ctx, CXXRecordDecl *RD,
+    llvm::SmallVectorImpl<FunctionDecl *> &Spaceships) {
+  DeclarationName EqEq = Ctx.DeclarationNames.getCXXOperatorName(OO_EqualEqual);
+  if (!RD->lookup(EqEq).empty())
+    // Member operator== explicitly declared: no implicit operator==s.
+    return;
+
+  // Traverse friends looking for an '==' or a '<=>'.
+  for (FriendDecl *Friend : RD->friends()) {
+    FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(Friend->getFriendDecl());
+    if (!FD) continue;
+
+    if (FD->getOverloadedOperator() == OO_EqualEqual) {
+      // Friend operator== explicitly declared: no implicit operator==s.
+      Spaceships.clear();
+      return;
+    }
+
+    if (FD->getOverloadedOperator() == OO_Spaceship &&
+        FD->isExplicitlyDefaulted())
+      Spaceships.push_back(FD);
+  }
+
+  // Look for members named 'operator<=>'.
+  DeclarationName Cmp = Ctx.DeclarationNames.getCXXOperatorName(OO_Spaceship);
+  for (NamedDecl *ND : RD->lookup(Cmp)) {
+    // Note that we could find a non-function here (either a function template
+    // or a using-declaration). Neither case results in an implicit
+    // 'operator=='.
+    if (auto *FD = dyn_cast<FunctionDecl>(ND))
+      if (FD->isExplicitlyDefaulted())
+        Spaceships.push_back(FD);
+  }
 }
 
 /// AddImplicitlyDeclaredMembersToClass - Adds any implicitly-declared
@@ -8267,6 +9604,20 @@ void Sema::AddImplicitlyDeclaredMembersToClass(CXXRecordDecl *ClassDecl) {
         ClassDecl->needsOverloadResolutionForDestructor())
       DeclareImplicitDestructor(ClassDecl);
   }
+
+  // C++2a [class.compare.default]p3:
+  //   If the member-specification does not explicitly declare any member or
+  //   friend named operator==, an == operator function is declared implicitly
+  //   for each defaulted three-way comparison operator function defined in the
+  //   member-specification
+  // FIXME: Consider doing this lazily.
+  if (getLangOpts().CPlusPlus2a) {
+    llvm::SmallVector<FunctionDecl*, 4> DefaultedSpaceships;
+    findImplicitlyDeclaredEqualityComparisons(Context, ClassDecl,
+                                              DefaultedSpaceships);
+    for (auto *FD : DefaultedSpaceships)
+      DeclareImplicitEqualityComparison(ClassDecl, FD);
+  }
 }
 
 unsigned Sema::ActOnReenterTemplateScope(Scope *S, Decl *D) {
@@ -8478,7 +9829,7 @@ QualType Sema::CheckConstructorDeclarator(Declarator &D, QualType R,
   // Rebuild the function type "R" without any type qualifiers (in
   // case any of the errors above fired) and with "void" as the
   // return type, since constructors don't have return types.
-  const FunctionProtoType *Proto = R->getAs<FunctionProtoType>();
+  const FunctionProtoType *Proto = R->castAs<FunctionProtoType>();
   if (Proto->getReturnType() == Context.VoidTy && !D.isInvalidType())
     return R;
 
@@ -8676,7 +10027,7 @@ QualType Sema::CheckDestructorDeclarator(Declarator &D, QualType R,
   if (!D.isInvalidType())
     return R;
 
-  const FunctionProtoType *Proto = R->getAs<FunctionProtoType>();
+  const FunctionProtoType *Proto = R->castAs<FunctionProtoType>();
   FunctionProtoType::ExtProtoInfo EPI = Proto->getExtProtoInfo();
   EPI.Variadic = false;
   EPI.TypeQuals = Qualifiers();
@@ -8750,7 +10101,7 @@ void Sema::CheckConversionDeclarator(Declarator &D, QualType &R,
     D.setInvalidType();
   }
 
-  const FunctionProtoType *Proto = R->getAs<FunctionProtoType>();
+  const auto *Proto = R->castAs<FunctionProtoType>();
 
   // Make sure we don't have any parameters.
   if (Proto->getNumParams() > 0) {
@@ -9334,22 +10685,37 @@ struct InvalidSTLDiagnoser {
 } // namespace
 
 QualType Sema::CheckComparisonCategoryType(ComparisonCategoryType Kind,
-                                           SourceLocation Loc) {
+                                           SourceLocation Loc,
+                                           ComparisonCategoryUsage Usage) {
   assert(getLangOpts().CPlusPlus &&
          "Looking for comparison category type outside of C++.");
 
+  // Use an elaborated type for diagnostics which has a name containing the
+  // prepended 'std' namespace but not any inline namespace names.
+  auto TyForDiags = [&](ComparisonCategoryInfo *Info) {
+    auto *NNS =
+        NestedNameSpecifier::Create(Context, nullptr, getStdNamespace());
+    return Context.getElaboratedType(ETK_None, NNS, Info->getType());
+  };
+
   // Check if we've already successfully checked the comparison category type
   // before. If so, skip checking it again.
   ComparisonCategoryInfo *Info = Context.CompCategories.lookupInfo(Kind);
-  if (Info && FullyCheckedComparisonCategories[static_cast<unsigned>(Kind)])
+  if (Info && FullyCheckedComparisonCategories[static_cast<unsigned>(Kind)]) {
+    // The only thing we need to check is that the type has a reachable
+    // definition in the current context.
+    if (RequireCompleteType(Loc, TyForDiags(Info), diag::err_incomplete_type))
+      return QualType();
+
     return Info->getType();
+  }
 
   // If lookup failed
   if (!Info) {
     std::string NameForDiags = "std::";
     NameForDiags += ComparisonCategories::getCategoryString(Kind);
     Diag(Loc, diag::err_implied_comparison_category_type_not_found)
-        << NameForDiags;
+        << NameForDiags << (int)Usage;
     return QualType();
   }
 
@@ -9361,18 +10727,10 @@ QualType Sema::CheckComparisonCategoryType(ComparisonCategoryType Kind,
   if (Info->Record->hasDefinition())
     Info->Record = Info->Record->getDefinition();
 
-  // Use an elaborated type for diagnostics which has a name containing the
-  // prepended 'std' namespace but not any inline namespace names.
-  QualType TyForDiags = [&]() {
-    auto *NNS =
-        NestedNameSpecifier::Create(Context, nullptr, getStdNamespace());
-    return Context.getElaboratedType(ETK_None, NNS, Info->getType());
-  }();
-
-  if (RequireCompleteType(Loc, TyForDiags, diag::err_incomplete_type))
+  if (RequireCompleteType(Loc, TyForDiags(Info), diag::err_incomplete_type))
     return QualType();
 
-  InvalidSTLDiagnoser UnsupportedSTLError{*this, Loc, TyForDiags};
+  InvalidSTLDiagnoser UnsupportedSTLError{*this, Loc, TyForDiags(Info)};
 
   if (!Info->Record->isTriviallyCopyable())
     return UnsupportedSTLError(USS_NonTrivial);
@@ -11070,25 +12428,6 @@ void SpecialMemberExceptionSpecInfo::visitSubobjectCall(
     ExceptSpec.CalledDecl(getSubobjectLoc(Subobj), MD);
 }
 
-namespace {
-/// RAII object to register a special member as being currently declared.
-struct ComputingExceptionSpec {
-  Sema &S;
-
-  ComputingExceptionSpec(Sema &S, CXXMethodDecl *MD, SourceLocation Loc)
-      : S(S) {
-    Sema::CodeSynthesisContext Ctx;
-    Ctx.Kind = Sema::CodeSynthesisContext::ExceptionSpecEvaluation;
-    Ctx.PointOfInstantiation = Loc;
-    Ctx.Entity = MD;
-    S.pushCodeSynthesisContext(Ctx);
-  }
-  ~ComputingExceptionSpec() {
-    S.popCodeSynthesisContext();
-  }
-};
-}
-
 bool Sema::tryResolveExplicitSpecifier(ExplicitSpecifier &ExplicitSpec) {
   llvm::APSInt Result;
   ExprResult Converted = CheckConvertedConstantExpression(
@@ -11222,10 +12561,9 @@ void Sema::setupImplicitSpecialMemberType(CXXMethodDecl *SpecialMem,
   // Build an exception specification pointing back at this constructor.
   FunctionProtoType::ExtProtoInfo EPI = getImplicitMethodEPI(*this, SpecialMem);
 
-  if (getLangOpts().OpenCLCPlusPlus) {
-    // OpenCL: Implicitly defaulted special member are of the generic address
-    // space.
-    EPI.TypeQuals.addAddressSpace(LangAS::opencl_generic);
+  LangAS AS = getDefaultCXXMethodAddrSpace();
+  if (AS != LangAS::Default) {
+    EPI.TypeQuals.addAddressSpace(AS);
   }
 
   auto QT = Context.getFunctionType(ResultTy, Args, EPI);
@@ -11384,7 +12722,8 @@ Sema::findInheritingConstructor(SourceLocation Loc,
       BaseCtor->getExplicitSpecifier(), /*isInline=*/true,
       /*isImplicitlyDeclared=*/true,
       Constexpr ? BaseCtor->getConstexprKind() : CSK_unspecified,
-      InheritedConstructor(Shadow, BaseCtor));
+      InheritedConstructor(Shadow, BaseCtor),
+      BaseCtor->getTrailingRequiresClause());
   if (Shadow->isInvalidDecl())
     DerivedCtor->setInvalidDecl();
 
@@ -11635,7 +12974,7 @@ void Sema::ActOnFinishCXXMemberDecls() {
   }
 }
 
-void Sema::ActOnFinishCXXNonNestedClass(Decl *D) {
+void Sema::ActOnFinishCXXNonNestedClass() {
   referenceDLLExportedClassMethods();
 
   if (!DelayedDllExportMemberFunctions.empty()) {
@@ -11676,8 +13015,7 @@ void Sema::AdjustDestructorExceptionSpec(CXXDestructorDecl *Destructor) {
   //   A declaration of a destructor that does not have an exception-
   //   specification is implicitly considered to have the same exception-
   //   specification as an implicit declaration.
-  const FunctionProtoType *DtorType = Destructor->getType()->
-                                        getAs<FunctionProtoType>();
+  const auto *DtorType = Destructor->getType()->castAs<FunctionProtoType>();
   if (DtorType->hasExceptionSpec())
     return;
 
@@ -12135,8 +13473,9 @@ CXXMethodDecl *Sema::DeclareImplicitCopyAssignment(CXXRecordDecl *ClassDecl) {
     return nullptr;
 
   QualType ArgType = Context.getTypeDeclType(ClassDecl);
-  if (Context.getLangOpts().OpenCLCPlusPlus)
-    ArgType = Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
+  LangAS AS = getDefaultCXXMethodAddrSpace();
+  if (AS != LangAS::Default)
+    ArgType = Context.getAddrSpaceQualType(ArgType, AS);
   QualType RetType = Context.getLValueReferenceType(ArgType);
   bool Const = ClassDecl->implicitCopyAssignmentHasConstParam();
   if (Const)
@@ -12237,11 +13576,12 @@ static void diagnoseDeprecatedCopyOperation(Sema &S, CXXMethodDecl *CopyOp) {
     assert(UserDeclaredOperation);
   }
 
-  if (UserDeclaredOperation) {
+  if (UserDeclaredOperation && UserDeclaredOperation->isUserProvided()) {
     S.Diag(UserDeclaredOperation->getLocation(),
-         diag::warn_deprecated_copy_operation)
-      << RD << /*copy assignment*/!isa<CXXConstructorDecl>(CopyOp)
-      << /*destructor*/isa<CXXDestructorDecl>(UserDeclaredOperation);
+           isa<CXXDestructorDecl>(UserDeclaredOperation)
+               ? diag::warn_deprecated_copy_dtor_operation
+               : diag::warn_deprecated_copy_operation)
+        << RD << /*copy assignment*/ !isa<CXXConstructorDecl>(CopyOp);
   }
 }
 
@@ -12460,8 +13800,9 @@ CXXMethodDecl *Sema::DeclareImplicitMoveAssignment(CXXRecordDecl *ClassDecl) {
   // constructor rules.
 
   QualType ArgType = Context.getTypeDeclType(ClassDecl);
-  if (Context.getLangOpts().OpenCLCPlusPlus)
-    ArgType = Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
+  LangAS AS = getDefaultCXXMethodAddrSpace();
+  if (AS != LangAS::Default)
+    ArgType = Context.getAddrSpaceQualType(ArgType, AS);
   QualType RetType = Context.getLValueReferenceType(ArgType);
   ArgType = Context.getRValueReferenceType(ArgType);
 
@@ -12654,8 +13995,8 @@ void Sema::DefineImplicitMoveAssignment(SourceLocation CurrentLocation,
 
   // The parameter for the "other" object, which we are move from.
   ParmVarDecl *Other = MoveAssignOperator->getParamDecl(0);
-  QualType OtherRefType = Other->getType()->
-      getAs<RValueReferenceType>()->getPointeeType();
+  QualType OtherRefType =
+      Other->getType()->castAs<RValueReferenceType>()->getPointeeType();
 
   // Our location for everything implicitly-generated.
   SourceLocation Loc = MoveAssignOperator->getEndLoc().isValid()
@@ -12838,8 +14179,9 @@ CXXConstructorDecl *Sema::DeclareImplicitCopyConstructor(
   if (Const)
     ArgType = ArgType.withConst();
 
-  if (Context.getLangOpts().OpenCLCPlusPlus)
-    ArgType = Context.getAddrSpaceQualType(ArgType, LangAS::opencl_generic);
+  LangAS AS = getDefaultCXXMethodAddrSpace();
+  if (AS != LangAS::Default)
+    ArgType = Context.getAddrSpaceQualType(ArgType, AS);
 
   ArgType = Context.getLValueReferenceType(ArgType);
 
@@ -12970,8 +14312,9 @@ CXXConstructorDecl *Sema::DeclareImplicitMoveConstructor(
   QualType ClassType = Context.getTypeDeclType(ClassDecl);
 
   QualType ArgType = ClassType;
-  if (Context.getLangOpts().OpenCLCPlusPlus)
-    ArgType = Context.getAddrSpaceQualType(ClassType, LangAS::opencl_generic);
+  LangAS AS = getDefaultCXXMethodAddrSpace();
+  if (AS != LangAS::Default)
+    ArgType = Context.getAddrSpaceQualType(ClassType, AS);
   ArgType = Context.getRValueReferenceType(ArgType);
 
   bool Constexpr = defaultedSpecialMemberIsConstexpr(*this, ClassDecl,
@@ -13447,9 +14790,7 @@ Sema::CompleteConstructorCall(CXXConstructorDecl *Constructor,
   unsigned NumArgs = ArgsPtr.size();
   Expr **Args = ArgsPtr.data();
 
-  const FunctionProtoType *Proto
-    = Constructor->getType()->getAs<FunctionProtoType>();
-  assert(Proto && "Constructor without a prototype?");
+  const auto *Proto = Constructor->getType()->castAs<FunctionProtoType>();
   unsigned NumParams = Proto->getNumParams();
 
   // If too few arguments are available, we'll fill in the rest with defaults.
@@ -13512,7 +14853,7 @@ CheckOperatorNewDeleteTypes(Sema &SemaRef, const FunctionDecl *FnDecl,
                             unsigned DependentParamTypeDiag,
                             unsigned InvalidParamTypeDiag) {
   QualType ResultType =
-      FnDecl->getType()->getAs<FunctionType>()->getReturnType();
+      FnDecl->getType()->castAs<FunctionType>()->getReturnType();
 
   // Check that the result type is not dependent.
   if (ResultType->isDependentType())
@@ -13741,7 +15082,7 @@ bool Sema::CheckOverloadedOperatorDeclaration(FunctionDecl *FnDecl) {
 
   // Overloaded operators other than operator() cannot be variadic.
   if (Op != OO_Call &&
-      FnDecl->getType()->getAs<FunctionProtoType>()->isVariadic()) {
+      FnDecl->getType()->castAs<FunctionProtoType>()->isVariadic()) {
     return Diag(FnDecl->getLocation(), diag::err_operator_overload_variadic)
       << FnDecl->getDeclName();
   }
@@ -14010,10 +15351,6 @@ Decl *Sema::ActOnStartLinkageSpecification(Scope *S, SourceLocation ExternLoc,
     Language = LinkageSpecDecl::lang_c;
   else if (Lang == "C++")
     Language = LinkageSpecDecl::lang_cxx;
-  else if (Lang == "C++11")
-    Language = LinkageSpecDecl::lang_cxx_11;
-  else if (Lang == "C++14")
-    Language = LinkageSpecDecl::lang_cxx_14;
   else {
     Diag(LangStr->getExprLoc(), diag::err_language_linkage_spec_unknown)
       << LangStr->getSourceRange();
@@ -14291,8 +15628,16 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc,
       std::string InnerCondDescription;
       std::tie(InnerCond, InnerCondDescription) =
         findFailedBooleanCondition(Converted.get());
-      if (InnerCond && !isa<CXXBoolLiteralExpr>(InnerCond)
-                    && !isa<IntegerLiteral>(InnerCond)) {
+      if (InnerCond && isa<ConceptSpecializationExpr>(InnerCond)) {
+        // Drill down into concept specialization expressions to see why they
+        // weren't satisfied.
+        Diag(StaticAssertLoc, diag::err_static_assert_failed)
+          << !AssertMessage << Msg.str() << AssertExpr->getSourceRange();
+        ConstraintSatisfaction Satisfaction;
+        if (!CheckConstraintSatisfaction(InnerCond, Satisfaction))
+          DiagnoseUnsatisfiedConstraint(Satisfaction);
+      } else if (InnerCond && !isa<CXXBoolLiteralExpr>(InnerCond)
+                           && !isa<IntegerLiteral>(InnerCond)) {
         Diag(StaticAssertLoc, diag::err_static_assert_requirement_failed)
           << InnerCondDescription << !AssertMessage
           << Msg.str() << InnerCond->getSourceRange();
@@ -14974,6 +16319,16 @@ void Sema::SetDeclDeleted(Decl *Dcl, SourceLocation DelLoc) {
   if (Fn->isDeleted())
     return;
 
+  // C++11 [basic.start.main]p3:
+  //   A program that defines main as deleted [...] is ill-formed.
+  if (Fn->isMain())
+    Diag(DelLoc, diag::err_deleted_main);
+
+  // C++11 [dcl.fct.def.delete]p4:
+  //  A deleted function is implicitly inline.
+  Fn->setImplicitlyInline();
+  Fn->setDeletedAsWritten();
+
   // See if we're deleting a function which is already known to override a
   // non-deleted virtual function.
   if (CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Fn)) {
@@ -14990,67 +16345,93 @@ void Sema::SetDeclDeleted(Decl *Dcl, SourceLocation DelLoc) {
     // If this function was implicitly deleted because it was defaulted,
     // explain why it was deleted.
     if (IssuedDiagnostic && MD->isDefaulted())
-      ShouldDeleteSpecialMember(MD, getSpecialMember(MD), nullptr,
-                                /*Diagnose*/true);
+      DiagnoseDeletedDefaultedFunction(MD);
   }
-
-  // C++11 [basic.start.main]p3:
-  //   A program that defines main as deleted [...] is ill-formed.
-  if (Fn->isMain())
-    Diag(DelLoc, diag::err_deleted_main);
-
-  // C++11 [dcl.fct.def.delete]p4:
-  //  A deleted function is implicitly inline.
-  Fn->setImplicitlyInline();
-  Fn->setDeletedAsWritten();
 }
 
 void Sema::SetDeclDefaulted(Decl *Dcl, SourceLocation DefaultLoc) {
-  CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(Dcl);
+  if (!Dcl || Dcl->isInvalidDecl())
+    return;
 
-  if (MD) {
-    if (MD->getParent()->isDependentType()) {
-      MD->setDefaulted();
-      MD->setExplicitlyDefaulted();
-      return;
+  auto *FD = dyn_cast<FunctionDecl>(Dcl);
+  if (!FD) {
+    if (auto *FTD = dyn_cast<FunctionTemplateDecl>(Dcl)) {
+      if (getDefaultedFunctionKind(FTD->getTemplatedDecl()).isComparison()) {
+        Diag(DefaultLoc, diag::err_defaulted_comparison_template);
+        return;
+      }
     }
 
-    CXXSpecialMember Member = getSpecialMember(MD);
-    if (Member == CXXInvalid) {
-      if (!MD->isInvalidDecl())
-        Diag(DefaultLoc, diag::err_default_special_members);
-      return;
-    }
+    Diag(DefaultLoc, diag::err_default_special_members)
+        << getLangOpts().CPlusPlus2a;
+    return;
+  }
 
-    MD->setDefaulted();
-    MD->setExplicitlyDefaulted();
+  // Reject if this can't possibly be a defaultable function.
+  DefaultedFunctionKind DefKind = getDefaultedFunctionKind(FD);
+  if (!DefKind &&
+      // A dependent function that doesn't locally look defaultable can
+      // still instantiate to a defaultable function if it's a constructor
+      // or assignment operator.
+      (!FD->isDependentContext() ||
+       (!isa<CXXConstructorDecl>(FD) &&
+        FD->getDeclName().getCXXOverloadedOperator() != OO_Equal))) {
+    Diag(DefaultLoc, diag::err_default_special_members)
+        << getLangOpts().CPlusPlus2a;
+    return;
+  }
 
-    // Unset that we will have a body for this function. We might not,
-    // if it turns out to be trivial, and we don't need this marking now
-    // that we've marked it as defaulted.
-    MD->setWillHaveBody(false);
+  if (DefKind.isComparison() &&
+      !isa<CXXRecordDecl>(FD->getLexicalDeclContext())) {
+    Diag(FD->getLocation(), diag::err_defaulted_comparison_out_of_class)
+        << (int)DefKind.asComparison();
+    return;
+  }
 
-    // If this definition appears within the record, do the checking when
-    // the record is complete.
-    const FunctionDecl *Primary = MD;
-    if (const FunctionDecl *Pattern = MD->getTemplateInstantiationPattern())
-      // Ask the template instantiation pattern that actually had the
-      // '= default' on it.
-      Primary = Pattern;
+  // Issue compatibility warning. We already warned if the operator is
+  // 'operator<=>' when parsing the '<=>' token.
+  if (DefKind.isComparison() &&
+      DefKind.asComparison() != DefaultedComparisonKind::ThreeWay) {
+    Diag(DefaultLoc, getLangOpts().CPlusPlus2a
+                         ? diag::warn_cxx17_compat_defaulted_comparison
+                         : diag::ext_defaulted_comparison);
+  }
 
-    // If the method was defaulted on its first declaration, we will have
-    // already performed the checking in CheckCompletedCXXClass. Such a
-    // declaration doesn't trigger an implicit definition.
-    if (Primary->getCanonicalDecl()->isDefaulted())
-      return;
+  FD->setDefaulted();
+  FD->setExplicitlyDefaulted();
 
-    CheckExplicitlyDefaultedSpecialMember(MD);
+  // Defer checking functions that are defaulted in a dependent context.
+  if (FD->isDependentContext())
+    return;
 
-    if (!MD->isInvalidDecl())
-      DefineImplicitSpecialMember(*this, MD, DefaultLoc);
-  } else {
-    Diag(DefaultLoc, diag::err_default_special_members);
-  }
+  // Unset that we will have a body for this function. We might not,
+  // if it turns out to be trivial, and we don't need this marking now
+  // that we've marked it as defaulted.
+  FD->setWillHaveBody(false);
+
+  // If this definition appears within the record, do the checking when
+  // the record is complete. This is always the case for a defaulted
+  // comparison.
+  if (DefKind.isComparison())
+    return;
+  auto *MD = cast<CXXMethodDecl>(FD);
+
+  const FunctionDecl *Primary = FD;
+  if (const FunctionDecl *Pattern = FD->getTemplateInstantiationPattern())
+    // Ask the template instantiation pattern that actually had the
+    // '= default' on it.
+    Primary = Pattern;
+
+  // If the method was defaulted on its first declaration, we will have
+  // already performed the checking in CheckCompletedCXXClass. Such a
+  // declaration doesn't trigger an implicit definition.
+  if (Primary->getCanonicalDecl()->isDefaulted())
+    return;
+
+  if (CheckExplicitlyDefaultedSpecialMember(MD, DefKind.asSpecialMember()))
+    MD->setInvalidDecl();
+  else
+    DefineImplicitSpecialMember(*this, MD, DefaultLoc);
 }
 
 static void SearchForReturnInStmt(Sema &Self, Stmt *S) {
@@ -15074,8 +16455,8 @@ void Sema::DiagnoseReturnInConstructorExceptionHandler(CXXTryStmt *TryBlock) {
 
 bool Sema::CheckOverridingFunctionAttributes(const CXXMethodDecl *New,
                                              const CXXMethodDecl *Old) {
-  const auto *NewFT = New->getType()->getAs<FunctionProtoType>();
-  const auto *OldFT = Old->getType()->getAs<FunctionProtoType>();
+  const auto *NewFT = New->getType()->castAs<FunctionProtoType>();
+  const auto *OldFT = Old->getType()->castAs<FunctionProtoType>();
 
   if (OldFT->hasExtParameterInfos()) {
     for (unsigned I = 0, E = OldFT->getNumParams(); I != E; ++I)
@@ -15122,8 +16503,8 @@ bool Sema::CheckOverridingFunctionAttributes(const CXXMethodDecl *New,
 
 bool Sema::CheckOverridingFunctionReturnType(const CXXMethodDecl *New,
                                              const CXXMethodDecl *Old) {
-  QualType NewTy = New->getType()->getAs<FunctionType>()->getReturnType();
-  QualType OldTy = Old->getType()->getAs<FunctionType>()->getReturnType();
+  QualType NewTy = New->getType()->castAs<FunctionType>()->getReturnType();
+  QualType OldTy = Old->getType()->castAs<FunctionType>()->getReturnType();
 
   if (Context.hasSameType(NewTy, OldTy) ||
       NewTy->isDependentType() || OldTy->isDependentType())
@@ -15729,6 +17110,11 @@ bool Sema::checkThisInStaticMemberFunctionType(CXXMethodDecl *Method) {
   if (checkThisInStaticMemberFunctionExceptionSpec(Method))
     return true;
 
+  // Check the trailing requires clause
+  if (Expr *E = Method->getTrailingRequiresClause())
+    if (!Finder.TraverseStmt(E))
+      return true;
+
   return checkThisInStaticMemberFunctionAttributes(Method);
 }
 
diff --git a/clang/lib/Sema/SemaDeclObjC.cpp b/clang/lib/Sema/SemaDeclObjC.cpp
index db594bbd21dd..5fdf6aeed5b4 100644
--- a/clang/lib/Sema/SemaDeclObjC.cpp
+++ b/clang/lib/Sema/SemaDeclObjC.cpp
@@ -2828,6 +2828,9 @@ void Sema::MatchAllMethodDeclarations(const SelectorSet &InsMap,
              "Expected to find the method through lookup as well");
       // ImpMethodDecl may be null as in a @dynamic property.
       if (ImpMethodDecl) {
+        // Skip property accessor function stubs.
+        if (ImpMethodDecl->isSynthesizedAccessorStub())
+          continue;
         if (!WarnCategoryMethodImpl)
           WarnConflictingTypedMethods(ImpMethodDecl, I,
                                       isa<ObjCProtocolDecl>(CDecl));
@@ -2854,6 +2857,9 @@ void Sema::MatchAllMethodDeclarations(const SelectorSet &InsMap,
              "Expected to find the method through lookup as well");
       // ImpMethodDecl may be null as in a @dynamic property.
       if (ImpMethodDecl) {
+        // Skip property accessor function stubs.
+        if (ImpMethodDecl->isSynthesizedAccessorStub())
+          continue;
         if (!WarnCategoryMethodImpl)
           WarnConflictingTypedMethods(ImpMethodDecl, I,
                                       isa<ObjCProtocolDecl>(CDecl));
@@ -3233,6 +3239,9 @@ bool Sema::MatchTwoMethodDeclarations(const ObjCMethodDecl *left,
   if (left->isHidden() || right->isHidden())
     return false;
 
+  if (left->isDirectMethod() != right->isDirectMethod())
+    return false;
+
   if (getLangOpts().ObjCAutoRefCount &&
       (left->hasAttr<NSReturnsRetainedAttr>()
          != right->hasAttr<NSReturnsRetainedAttr>() ||
@@ -3424,6 +3433,9 @@ static bool isAcceptableMethodMismatch(ObjCMethodDecl *chosen,
   if (!chosen->isInstanceMethod())
     return false;
 
+  if (chosen->isDirectMethod() != other->isDirectMethod())
+    return false;
+
   Selector sel = chosen->getSelector();
   if (!sel.isUnarySelector() || sel.getNameForSlot(0) != "length")
     return false;
@@ -3903,6 +3915,25 @@ Decl *Sema::ActOnAtEnd(Scope *S, SourceRange AtEnd, ArrayRef<Decl *> allMethods,
          || isa<ObjCProtocolDecl>(ClassDecl);
   bool checkIdenticalMethods = isa<ObjCImplementationDecl>(ClassDecl);
 
+  // Make synthesized accessor stub functions visible.
+  // ActOnPropertyImplDecl() creates them as not visible in case
+  // they are overridden by an explicit method that is encountered
+  // later.
+  if (auto *OID = dyn_cast<ObjCImplementationDecl>(CurContext)) {
+    for (auto PropImpl : OID->property_impls()) {
+      if (auto *Getter = PropImpl->getGetterMethodDecl())
+        if (Getter->isSynthesizedAccessorStub()) {
+          OID->makeDeclVisibleInContext(Getter);
+          OID->addDecl(Getter);
+        }
+      if (auto *Setter = PropImpl->getSetterMethodDecl())
+        if (Setter->isSynthesizedAccessorStub()) {
+          OID->makeDeclVisibleInContext(Setter);
+          OID->addDecl(Setter);
+        }
+    }
+  }
+
   // FIXME: Remove these and use the ObjCContainerDecl/DeclContext.
   llvm::DenseMap<Selector, const ObjCMethodDecl*> InsMap;
   llvm::DenseMap<Selector, const ObjCMethodDecl*> ClsMap;
@@ -4001,8 +4032,8 @@ Decl *Sema::ActOnAtEnd(Scope *S, SourceRange AtEnd, ArrayRef<Decl *> allMethods,
               continue;
 
           for (const auto *Ext : IDecl->visible_extensions()) {
-            if (ObjCMethodDecl *GetterMethod
-                  = Ext->getInstanceMethod(Property->getGetterName()))
+            if (ObjCMethodDecl *GetterMethod =
+                    Ext->getInstanceMethod(Property->getGetterName()))
               GetterMethod->setPropertyAccessor(true);
             if (!Property->isReadOnly())
               if (ObjCMethodDecl *SetterMethod
@@ -4314,6 +4345,18 @@ private:
 };
 } // end anonymous namespace
 
+void Sema::CheckObjCMethodDirectOverrides(ObjCMethodDecl *method,
+                                          ObjCMethodDecl *overridden) {
+  if (const auto *attr = overridden->getAttr<ObjCDirectAttr>()) {
+    Diag(method->getLocation(), diag::err_objc_override_direct_method);
+    Diag(attr->getLocation(), diag::note_previous_declaration);
+  } else if (const auto *attr = method->getAttr<ObjCDirectAttr>()) {
+    Diag(attr->getLocation(), diag::err_objc_direct_on_override)
+        << isa<ObjCProtocolDecl>(overridden->getDeclContext());
+    Diag(overridden->getLocation(), diag::note_previous_declaration);
+  }
+}
+
 void Sema::CheckObjCMethodOverrides(ObjCMethodDecl *ObjCMethod,
                                     ObjCInterfaceDecl *CurrentClass,
                                     ResultTypeCompatibilityKind RTC) {
@@ -4332,8 +4375,8 @@ void Sema::CheckObjCMethodOverrides(ObjCMethodDecl *ObjCMethod,
       if (isa<ObjCProtocolDecl>(overridden->getDeclContext()) ||
           CurrentClass != overridden->getClassInterface() ||
           overridden->isOverriding()) {
+        CheckObjCMethodDirectOverrides(ObjCMethod, overridden);
         hasOverriddenMethodsInBaseOrProtocol = true;
-
       } else if (isa<ObjCImplDecl>(ObjCMethod->getDeclContext())) {
         // OverrideSearch will return as "overridden" the same method in the
         // interface. For hasOverriddenMethodsInBaseOrProtocol, we need to
@@ -4357,6 +4400,7 @@ void Sema::CheckObjCMethodOverrides(ObjCMethodDecl *ObjCMethod,
               for (ObjCMethodDecl *SuperOverridden : overrides) {
                 if (isa<ObjCProtocolDecl>(SuperOverridden->getDeclContext()) ||
                     CurrentClass != SuperOverridden->getClassInterface()) {
+                  CheckObjCMethodDirectOverrides(ObjCMethod, SuperOverridden);
                   hasOverriddenMethodsInBaseOrProtocol = true;
                   overridden->setOverriding(true);
                   break;
@@ -4551,6 +4595,7 @@ Decl *Sema::ActOnMethodDeclaration(
     Diag(MethodLoc, diag::err_missing_method_context);
     return nullptr;
   }
+
   Decl *ClassDecl = cast<ObjCContainerDecl>(CurContext);
   QualType resultDeclType;
 
@@ -4574,7 +4619,7 @@ Decl *Sema::ActOnMethodDeclaration(
   ObjCMethodDecl *ObjCMethod = ObjCMethodDecl::Create(
       Context, MethodLoc, EndLoc, Sel, resultDeclType, ReturnTInfo, CurContext,
       MethodType == tok::minus, isVariadic,
-      /*isPropertyAccessor=*/false,
+      /*isPropertyAccessor=*/false, /*isSynthesizedAccessorStub=*/false,
       /*isImplicitlyDeclared=*/false, /*isDefined=*/false,
       MethodDeclKind == tok::objc_optional ? ObjCMethodDecl::Optional
                                            : ObjCMethodDecl::Required,
@@ -4666,6 +4711,41 @@ Decl *Sema::ActOnMethodDeclaration(
       ImpDecl->addClassMethod(ObjCMethod);
     }
 
+    // If this method overrides a previous @synthesize declaration,
+    // register it with the property.  Linear search through all
+    // properties here, because the autosynthesized stub hasn't been
+    // made visible yet, so it can be overriden by a later
+    // user-specified implementation.
+    for (ObjCPropertyImplDecl *PropertyImpl : ImpDecl->property_impls()) {
+      if (auto *Setter = PropertyImpl->getSetterMethodDecl())
+        if (Setter->getSelector() == Sel &&
+            Setter->isInstanceMethod() == ObjCMethod->isInstanceMethod()) {
+          assert(Setter->isSynthesizedAccessorStub() && "autosynth stub expected");
+          PropertyImpl->setSetterMethodDecl(ObjCMethod);
+        }
+      if (auto *Getter = PropertyImpl->getGetterMethodDecl())
+        if (Getter->getSelector() == Sel &&
+            Getter->isInstanceMethod() == ObjCMethod->isInstanceMethod()) {
+          assert(Getter->isSynthesizedAccessorStub() && "autosynth stub expected");
+          PropertyImpl->setGetterMethodDecl(ObjCMethod);
+          break;
+        }
+    }
+
+    // A method is either tagged direct explicitly, or inherits it from its
+    // canonical declaration.
+    //
+    // We have to do the merge upfront and not in mergeInterfaceMethodToImpl()
+    // because IDecl->lookupMethod() returns more possible matches than just
+    // the canonical declaration.
+    if (!ObjCMethod->isDirectMethod()) {
+      const ObjCMethodDecl *CanonicalMD = ObjCMethod->getCanonicalDecl();
+      if (const auto *attr = CanonicalMD->getAttr<ObjCDirectAttr>()) {
+        ObjCMethod->addAttr(
+            ObjCDirectAttr::CreateImplicit(Context, attr->getLocation()));
+      }
+    }
+
     // Merge information from the @interface declaration into the
     // @implementation.
     if (ObjCInterfaceDecl *IDecl = ImpDecl->getClassInterface()) {
@@ -4673,12 +4753,64 @@ Decl *Sema::ActOnMethodDeclaration(
                                           ObjCMethod->isInstanceMethod())) {
         mergeInterfaceMethodToImpl(*this, ObjCMethod, IMD);
 
+        // The Idecl->lookupMethod() above will find declarations for ObjCMethod
+        // in one of these places:
+        //
+        // (1) the canonical declaration in an @interface container paired
+        //     with the ImplDecl,
+        // (2) non canonical declarations in @interface not paired with the
+        //     ImplDecl for the same Class,
+        // (3) any superclass container.
+        //
+        // Direct methods only allow for canonical declarations in the matching
+        // container (case 1).
+        //
+        // Direct methods overriding a superclass declaration (case 3) is
+        // handled during overrides checks in CheckObjCMethodOverrides().
+        //
+        // We deal with same-class container mismatches (Case 2) here.
+        if (IDecl == IMD->getClassInterface()) {
+          auto diagContainerMismatch = [&] {
+            int decl = 0, impl = 0;
+
+            if (auto *Cat = dyn_cast<ObjCCategoryDecl>(IMD->getDeclContext()))
+              decl = Cat->IsClassExtension() ? 1 : 2;
+
+            if (isa<ObjCCategoryImplDecl>(ImpDecl))
+              impl = 1 + (decl != 0);
+
+            Diag(ObjCMethod->getLocation(),
+                 diag::err_objc_direct_impl_decl_mismatch)
+                << decl << impl;
+            Diag(IMD->getLocation(), diag::note_previous_declaration);
+          };
+
+          if (const auto *attr = ObjCMethod->getAttr<ObjCDirectAttr>()) {
+            if (ObjCMethod->getCanonicalDecl() != IMD) {
+              diagContainerMismatch();
+            } else if (!IMD->isDirectMethod()) {
+              Diag(attr->getLocation(), diag::err_objc_direct_missing_on_decl);
+              Diag(IMD->getLocation(), diag::note_previous_declaration);
+            }
+          } else if (const auto *attr = IMD->getAttr<ObjCDirectAttr>()) {
+            if (ObjCMethod->getCanonicalDecl() != IMD) {
+              diagContainerMismatch();
+            } else {
+              ObjCMethod->addAttr(
+                  ObjCDirectAttr::CreateImplicit(Context, attr->getLocation()));
+            }
+          }
+        }
+
         // Warn about defining -dealloc in a category.
         if (isa<ObjCCategoryImplDecl>(ImpDecl) && IMD->isOverriding() &&
             ObjCMethod->getSelector().getMethodFamily() == OMF_dealloc) {
           Diag(ObjCMethod->getLocation(), diag::warn_dealloc_in_category)
             << ObjCMethod->getDeclName();
         }
+      } else if (ImpDecl->hasAttr<ObjCDirectMembersAttr>()) {
+        ObjCMethod->addAttr(
+            ObjCDirectAttr::CreateImplicit(Context, ObjCMethod->getLocation()));
       }
 
       // Warn if a method declared in a protocol to which a category or
@@ -4698,6 +4830,42 @@ Decl *Sema::ActOnMethodDeclaration(
           }
     }
   } else {
+    if (!isa<ObjCProtocolDecl>(ClassDecl)) {
+      if (!ObjCMethod->isDirectMethod() &&
+          ClassDecl->hasAttr<ObjCDirectMembersAttr>()) {
+        ObjCMethod->addAttr(
+            ObjCDirectAttr::CreateImplicit(Context, ObjCMethod->getLocation()));
+      }
+
+      // There can be a single declaration in any @interface container
+      // for a given direct method, look for clashes as we add them.
+      //
+      // For valid code, we should always know the primary interface
+      // declaration by now, however for invalid code we'll keep parsing
+      // but we won't find the primary interface and IDecl will be nil.
+      ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(ClassDecl);
+      if (!IDecl)
+        IDecl = cast<ObjCCategoryDecl>(ClassDecl)->getClassInterface();
+
+      if (IDecl)
+        if (auto *IMD = IDecl->lookupMethod(ObjCMethod->getSelector(),
+                                            ObjCMethod->isInstanceMethod(),
+                                            /*shallowCategoryLookup=*/false,
+                                            /*followSuper=*/false)) {
+          if (isa<ObjCProtocolDecl>(IMD->getDeclContext())) {
+            // Do not emit a diagnostic for the Protocol case:
+            // diag::err_objc_direct_on_protocol has already been emitted
+            // during parsing for these with a nicer diagnostic.
+          } else if (ObjCMethod->isDirectMethod() || IMD->isDirectMethod()) {
+            Diag(ObjCMethod->getLocation(),
+                 diag::err_objc_direct_duplicate_decl)
+                << ObjCMethod->isDirectMethod() << IMD->isDirectMethod()
+                << ObjCMethod->getDeclName();
+            Diag(IMD->getLocation(), diag::note_previous_declaration);
+          }
+        }
+    }
+
     cast<DeclContext>(ClassDecl)->addDecl(ObjCMethod);
   }
 
@@ -4783,6 +4951,9 @@ Decl *Sema::ActOnMethodDeclaration(
     }
   }
 
+  // Insert the invisible arguments, self and _cmd!
+  ObjCMethod->createImplicitParams(Context, ObjCMethod->getClassInterface());
+
   ActOnDocumentableDecl(ObjCMethod);
 
   return ObjCMethod;
@@ -5063,6 +5234,9 @@ void Sema::DiagnoseUnusedBackingIvarInAccessor(Scope *S,
     if (!IV)
       continue;
 
+    if (CurMethod->isSynthesizedAccessorStub())
+      continue;
+
     UnusedBackingIvarChecker Checker(*this, CurMethod, IV);
     Checker.TraverseStmt(CurMethod->getBody());
     if (Checker.AccessedIvar)
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index c1abf099e9f2..5aedbe7644e4 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -15,6 +15,7 @@
 #include "clang/AST/CXXInheritance.h"
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
+#include "clang/AST/StmtObjC.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/Diagnostic.h"
 #include "clang/Basic/SourceManager.h"
@@ -80,8 +81,16 @@ ExprResult Sema::ActOnNoexceptSpec(SourceLocation NoexceptLoc,
                                    ExceptionSpecificationType &EST) {
   // FIXME: This is bogus, a noexcept expression is not a condition.
   ExprResult Converted = CheckBooleanCondition(NoexceptLoc, NoexceptExpr);
-  if (Converted.isInvalid())
-    return Converted;
+  if (Converted.isInvalid()) {
+    EST = EST_NoexceptFalse;
+
+    // Fill in an expression of 'false' as a fixup.
+    auto *BoolExpr = new (Context)
+        CXXBoolLiteralExpr(false, Context.BoolTy, NoexceptExpr->getBeginLoc());
+    llvm::APSInt Value{1};
+    Value = 0;
+    return ConstantExpr::Create(Context, BoolExpr, APValue{Value});
+  }
 
   if (Converted.get()->isValueDependent()) {
     EST = EST_DependentNoexcept;
@@ -204,7 +213,7 @@ Sema::ResolveExceptionSpec(SourceLocation Loc, const FunctionProtoType *FPT) {
 
   // Compute or instantiate the exception specification now.
   if (SourceFPT->getExceptionSpecType() == EST_Unevaluated)
-    EvaluateImplicitExceptionSpec(Loc, cast<CXXMethodDecl>(SourceDecl));
+    EvaluateImplicitExceptionSpec(Loc, SourceDecl);
   else
     InstantiateExceptionSpec(Loc, SourceDecl);
 
@@ -970,17 +979,22 @@ bool Sema::CheckOverridingFunctionExceptionSpec(const CXXMethodDecl *New,
                                   New->getLocation());
 }
 
-static CanThrowResult canSubExprsThrow(Sema &S, const Expr *E) {
+static CanThrowResult canSubStmtsThrow(Sema &Self, const Stmt *S) {
   CanThrowResult R = CT_Cannot;
-  for (const Stmt *SubStmt : E->children()) {
-    R = mergeCanThrow(R, S.canThrow(cast<Expr>(SubStmt)));
+  for (const Stmt *SubStmt : S->children()) {
+    if (!SubStmt)
+      continue;
+    R = mergeCanThrow(R, Self.canThrow(SubStmt));
     if (R == CT_Can)
       break;
   }
   return R;
 }
 
-static CanThrowResult canCalleeThrow(Sema &S, const Expr *E, const Decl *D) {
+/// Determine whether the callee of a particular function call can throw.
+/// E and D are both optional, but at least one of E and Loc must be specified.
+static CanThrowResult canCalleeThrow(Sema &S, const Expr *E, const Decl *D,
+                                     SourceLocation Loc = SourceLocation()) {
   // As an extension, we assume that __attribute__((nothrow)) functions don't
   // throw.
   if (D && isa<FunctionDecl>(D) && D->hasAttr<NoThrowAttr>())
@@ -989,7 +1003,7 @@ static CanThrowResult canCalleeThrow(Sema &S, const Expr *E, const Decl *D) {
   QualType T;
 
   // In C++1z, just look at the function type of the callee.
-  if (S.getLangOpts().CPlusPlus17 && isa<CallExpr>(E)) {
+  if (S.getLangOpts().CPlusPlus17 && E && isa<CallExpr>(E)) {
     E = cast<CallExpr>(E)->getCallee();
     T = E->getType();
     if (T->isSpecificPlaceholderType(BuiltinType::BoundMember)) {
@@ -1026,13 +1040,41 @@ static CanThrowResult canCalleeThrow(Sema &S, const Expr *E, const Decl *D) {
   if (!FT)
     return CT_Can;
 
-  FT = S.ResolveExceptionSpec(E->getBeginLoc(), FT);
+  FT = S.ResolveExceptionSpec(Loc.isInvalid() ? E->getBeginLoc() : Loc, FT);
   if (!FT)
     return CT_Can;
 
   return FT->canThrow();
 }
 
+static CanThrowResult canVarDeclThrow(Sema &Self, const VarDecl *VD) {
+  CanThrowResult CT = CT_Cannot;
+
+  // Initialization might throw.
+  if (!VD->isUsableInConstantExpressions(Self.Context))
+    if (const Expr *Init = VD->getInit())
+      CT = mergeCanThrow(CT, Self.canThrow(Init));
+
+  // Destructor might throw.
+  if (VD->needsDestruction(Self.Context) == QualType::DK_cxx_destructor) {
+    if (auto *RD =
+            VD->getType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl()) {
+      if (auto *Dtor = RD->getDestructor()) {
+        CT = mergeCanThrow(
+            CT, canCalleeThrow(Self, nullptr, Dtor, VD->getLocation()));
+      }
+    }
+  }
+
+  // If this is a decomposition declaration, bindings might throw.
+  if (auto *DD = dyn_cast<DecompositionDecl>(VD))
+    for (auto *B : DD->bindings())
+      if (auto *HD = B->getHoldingVar())
+        CT = mergeCanThrow(CT, canVarDeclThrow(Self, HD));
+
+  return CT;
+}
+
 static CanThrowResult canDynamicCastThrow(const CXXDynamicCastExpr *DC) {
   if (DC->isTypeDependent())
     return CT_Dependent;
@@ -1067,13 +1109,13 @@ static CanThrowResult canTypeidThrow(Sema &S, const CXXTypeidExpr *DC) {
   return CT_Can;
 }
 
-CanThrowResult Sema::canThrow(const Expr *E) {
+CanThrowResult Sema::canThrow(const Stmt *S) {
   // C++ [expr.unary.noexcept]p3:
   //   [Can throw] if in a potentially-evaluated context the expression would
   //   contain:
-  switch (E->getStmtClass()) {
+  switch (S->getStmtClass()) {
   case Expr::ConstantExprClass:
-    return canThrow(cast<ConstantExpr>(E)->getSubExpr());
+    return canThrow(cast<ConstantExpr>(S)->getSubExpr());
 
   case Expr::CXXThrowExprClass:
     //   - a potentially evaluated throw-expression
@@ -1082,16 +1124,20 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::CXXDynamicCastExprClass: {
     //   - a potentially evaluated dynamic_cast expression dynamic_cast<T>(v),
     //     where T is a reference type, that requires a run-time check
-    CanThrowResult CT = canDynamicCastThrow(cast<CXXDynamicCastExpr>(E));
+    auto *CE = cast<CXXDynamicCastExpr>(S);
+    // FIXME: Properly determine whether a variably-modified type can throw.
+    if (CE->getType()->isVariablyModifiedType())
+      return CT_Can;
+    CanThrowResult CT = canDynamicCastThrow(CE);
     if (CT == CT_Can)
       return CT;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, CE));
   }
 
   case Expr::CXXTypeidExprClass:
     //   - a potentially evaluated typeid expression applied to a glvalue
     //     expression whose type is a polymorphic class type
-    return canTypeidThrow(*this, cast<CXXTypeidExpr>(E));
+    return canTypeidThrow(*this, cast<CXXTypeidExpr>(S));
 
     //   - a potentially evaluated call to a function, member function, function
     //     pointer, or member function pointer that does not have a non-throwing
@@ -1100,34 +1146,38 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::CXXMemberCallExprClass:
   case Expr::CXXOperatorCallExprClass:
   case Expr::UserDefinedLiteralClass: {
-    const CallExpr *CE = cast<CallExpr>(E);
+    const CallExpr *CE = cast<CallExpr>(S);
     CanThrowResult CT;
-    if (E->isTypeDependent())
+    if (CE->isTypeDependent())
       CT = CT_Dependent;
     else if (isa<CXXPseudoDestructorExpr>(CE->getCallee()->IgnoreParens()))
       CT = CT_Cannot;
     else
-      CT = canCalleeThrow(*this, E, CE->getCalleeDecl());
+      CT = canCalleeThrow(*this, CE, CE->getCalleeDecl());
     if (CT == CT_Can)
       return CT;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, CE));
   }
 
   case Expr::CXXConstructExprClass:
   case Expr::CXXTemporaryObjectExprClass: {
-    CanThrowResult CT = canCalleeThrow(*this, E,
-        cast<CXXConstructExpr>(E)->getConstructor());
+    auto *CE = cast<CXXConstructExpr>(S);
+    // FIXME: Properly determine whether a variably-modified type can throw.
+    if (CE->getType()->isVariablyModifiedType())
+      return CT_Can;
+    CanThrowResult CT = canCalleeThrow(*this, CE, CE->getConstructor());
     if (CT == CT_Can)
       return CT;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, CE));
   }
 
-  case Expr::CXXInheritedCtorInitExprClass:
-    return canCalleeThrow(*this, E,
-                          cast<CXXInheritedCtorInitExpr>(E)->getConstructor());
+  case Expr::CXXInheritedCtorInitExprClass: {
+    auto *ICIE = cast<CXXInheritedCtorInitExpr>(S);
+    return canCalleeThrow(*this, ICIE, ICIE->getConstructor());
+  }
 
   case Expr::LambdaExprClass: {
-    const LambdaExpr *Lambda = cast<LambdaExpr>(E);
+    const LambdaExpr *Lambda = cast<LambdaExpr>(S);
     CanThrowResult CT = CT_Cannot;
     for (LambdaExpr::const_capture_init_iterator
              Cap = Lambda->capture_init_begin(),
@@ -1138,43 +1188,56 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   }
 
   case Expr::CXXNewExprClass: {
+    auto *NE = cast<CXXNewExpr>(S);
     CanThrowResult CT;
-    if (E->isTypeDependent())
+    if (NE->isTypeDependent())
       CT = CT_Dependent;
     else
-      CT = canCalleeThrow(*this, E, cast<CXXNewExpr>(E)->getOperatorNew());
+      CT = canCalleeThrow(*this, NE, NE->getOperatorNew());
     if (CT == CT_Can)
       return CT;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, NE));
   }
 
   case Expr::CXXDeleteExprClass: {
+    auto *DE = cast<CXXDeleteExpr>(S);
     CanThrowResult CT;
-    QualType DTy = cast<CXXDeleteExpr>(E)->getDestroyedType();
+    QualType DTy = DE->getDestroyedType();
     if (DTy.isNull() || DTy->isDependentType()) {
       CT = CT_Dependent;
     } else {
-      CT = canCalleeThrow(*this, E,
-                          cast<CXXDeleteExpr>(E)->getOperatorDelete());
+      CT = canCalleeThrow(*this, DE, DE->getOperatorDelete());
       if (const RecordType *RT = DTy->getAs<RecordType>()) {
         const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
         const CXXDestructorDecl *DD = RD->getDestructor();
         if (DD)
-          CT = mergeCanThrow(CT, canCalleeThrow(*this, E, DD));
+          CT = mergeCanThrow(CT, canCalleeThrow(*this, DE, DD));
       }
       if (CT == CT_Can)
         return CT;
     }
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, DE));
   }
 
   case Expr::CXXBindTemporaryExprClass: {
+    auto *BTE = cast<CXXBindTemporaryExpr>(S);
     // The bound temporary has to be destroyed again, which might throw.
-    CanThrowResult CT = canCalleeThrow(*this, E,
-      cast<CXXBindTemporaryExpr>(E)->getTemporary()->getDestructor());
+    CanThrowResult CT =
+        canCalleeThrow(*this, BTE, BTE->getTemporary()->getDestructor());
     if (CT == CT_Can)
       return CT;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, BTE));
+  }
+
+  case Expr::PseudoObjectExprClass: {
+    auto *POE = cast<PseudoObjectExpr>(S);
+    CanThrowResult CT = CT_Cannot;
+    for (const Expr *E : POE->semantics()) {
+      CT = mergeCanThrow(CT, canThrow(E));
+      if (CT == CT_Can)
+        break;
+    }
+    return CT;
   }
 
     // ObjC message sends are like function calls, but never have exception
@@ -1196,12 +1259,8 @@ CanThrowResult Sema::canThrow(const Expr *E) {
     // Some are simple:
   case Expr::CoawaitExprClass:
   case Expr::ConditionalOperatorClass:
-  case Expr::CompoundLiteralExprClass:
   case Expr::CoyieldExprClass:
-  case Expr::CXXConstCastExprClass:
-  case Expr::CXXReinterpretCastExprClass:
   case Expr::CXXRewrittenBinaryOperatorClass:
-  case Expr::BuiltinBitCastExprClass:
   case Expr::CXXStdInitializerListExprClass:
   case Expr::DesignatedInitExprClass:
   case Expr::DesignatedInitUpdateExprClass:
@@ -1215,9 +1274,19 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::ParenExprClass:
   case Expr::ParenListExprClass:
   case Expr::ShuffleVectorExprClass:
+  case Expr::StmtExprClass:
   case Expr::ConvertVectorExprClass:
   case Expr::VAArgExprClass:
-    return canSubExprsThrow(*this, E);
+    return canSubStmtsThrow(*this, S);
+
+  case Expr::CompoundLiteralExprClass:
+  case Expr::CXXConstCastExprClass:
+  case Expr::CXXReinterpretCastExprClass:
+  case Expr::BuiltinBitCastExprClass:
+      // FIXME: Properly determine whether a variably-modified type can throw.
+    if (cast<Expr>(S)->getType()->isVariablyModifiedType())
+      return CT_Can;
+    return canSubStmtsThrow(*this, S);
 
     // Some might be dependent for other reasons.
   case Expr::ArraySubscriptExprClass:
@@ -1231,29 +1300,32 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::ImplicitCastExprClass:
   case Expr::MaterializeTemporaryExprClass:
   case Expr::UnaryOperatorClass: {
-    CanThrowResult CT = E->isTypeDependent() ? CT_Dependent : CT_Cannot;
-    return mergeCanThrow(CT, canSubExprsThrow(*this, E));
+    // FIXME: Properly determine whether a variably-modified type can throw.
+    if (auto *CE = dyn_cast<CastExpr>(S))
+      if (CE->getType()->isVariablyModifiedType())
+        return CT_Can;
+    CanThrowResult CT =
+        cast<Expr>(S)->isTypeDependent() ? CT_Dependent : CT_Cannot;
+    return mergeCanThrow(CT, canSubStmtsThrow(*this, S));
   }
 
-    // FIXME: We should handle StmtExpr, but that opens a MASSIVE can of worms.
-  case Expr::StmtExprClass:
-    return CT_Can;
-
   case Expr::CXXDefaultArgExprClass:
-    return canThrow(cast<CXXDefaultArgExpr>(E)->getExpr());
+    return canThrow(cast<CXXDefaultArgExpr>(S)->getExpr());
 
   case Expr::CXXDefaultInitExprClass:
-    return canThrow(cast<CXXDefaultInitExpr>(E)->getExpr());
+    return canThrow(cast<CXXDefaultInitExpr>(S)->getExpr());
 
-  case Expr::ChooseExprClass:
-    if (E->isTypeDependent() || E->isValueDependent())
+  case Expr::ChooseExprClass: {
+    auto *CE = cast<ChooseExpr>(S);
+    if (CE->isTypeDependent() || CE->isValueDependent())
       return CT_Dependent;
-    return canThrow(cast<ChooseExpr>(E)->getChosenSubExpr());
+    return canThrow(CE->getChosenSubExpr());
+  }
 
   case Expr::GenericSelectionExprClass:
-    if (cast<GenericSelectionExpr>(E)->isResultDependent())
+    if (cast<GenericSelectionExpr>(S)->isResultDependent())
       return CT_Dependent;
-    return canThrow(cast<GenericSelectionExpr>(E)->getResultExpr());
+    return canThrow(cast<GenericSelectionExpr>(S)->getResultExpr());
 
     // Some expressions are always dependent.
   case Expr::CXXDependentScopeMemberExprClass:
@@ -1274,7 +1346,6 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::ObjCAvailabilityCheckExprClass:
   case Expr::OffsetOfExprClass:
   case Expr::PackExpansionExprClass:
-  case Expr::PseudoObjectExprClass:
   case Expr::SubstNonTypeTemplateParmExprClass:
   case Expr::SubstNonTypeTemplateParmPackExprClass:
   case Expr::FunctionParmPackExprClass:
@@ -1282,7 +1353,7 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::UnresolvedLookupExprClass:
   case Expr::UnresolvedMemberExprClass:
   case Expr::TypoExprClass:
-    // FIXME: Can any of the above throw?  If so, when?
+    // FIXME: Many of the above can throw.
     return CT_Cannot;
 
   case Expr::AddrLabelExprClass:
@@ -1322,14 +1393,170 @@ CanThrowResult Sema::canThrow(const Expr *E) {
   case Expr::MSPropertySubscriptExprClass:
     llvm_unreachable("Invalid class for expression");
 
-#define STMT(CLASS, PARENT) case Expr::CLASS##Class:
-#define STMT_RANGE(Base, First, Last)
-#define LAST_STMT_RANGE(BASE, FIRST, LAST)
-#define EXPR(CLASS, PARENT)
-#define ABSTRACT_STMT(STMT)
-#include "clang/AST/StmtNodes.inc"
-  case Expr::NoStmtClass:
-    llvm_unreachable("Invalid class for expression");
+    // Most statements can throw if any substatement can throw.
+  case Stmt::AttributedStmtClass:
+  case Stmt::BreakStmtClass:
+  case Stmt::CapturedStmtClass:
+  case Stmt::CaseStmtClass:
+  case Stmt::CompoundStmtClass:
+  case Stmt::ContinueStmtClass:
+  case Stmt::CoreturnStmtClass:
+  case Stmt::CoroutineBodyStmtClass:
+  case Stmt::CXXCatchStmtClass:
+  case Stmt::CXXForRangeStmtClass:
+  case Stmt::DefaultStmtClass:
+  case Stmt::DoStmtClass:
+  case Stmt::ForStmtClass:
+  case Stmt::GCCAsmStmtClass:
+  case Stmt::GotoStmtClass:
+  case Stmt::IndirectGotoStmtClass:
+  case Stmt::LabelStmtClass:
+  case Stmt::MSAsmStmtClass:
+  case Stmt::MSDependentExistsStmtClass:
+  case Stmt::NullStmtClass:
+  case Stmt::ObjCAtCatchStmtClass:
+  case Stmt::ObjCAtFinallyStmtClass:
+  case Stmt::ObjCAtSynchronizedStmtClass:
+  case Stmt::ObjCAutoreleasePoolStmtClass:
+  case Stmt::ObjCForCollectionStmtClass:
+  case Stmt::OMPAtomicDirectiveClass:
+  case Stmt::OMPBarrierDirectiveClass:
+  case Stmt::OMPCancelDirectiveClass:
+  case Stmt::OMPCancellationPointDirectiveClass:
+  case Stmt::OMPCriticalDirectiveClass:
+  case Stmt::OMPDistributeDirectiveClass:
+  case Stmt::OMPDistributeParallelForDirectiveClass:
+  case Stmt::OMPDistributeParallelForSimdDirectiveClass:
+  case Stmt::OMPDistributeSimdDirectiveClass:
+  case Stmt::OMPFlushDirectiveClass:
+  case Stmt::OMPForDirectiveClass:
+  case Stmt::OMPForSimdDirectiveClass:
+  case Stmt::OMPMasterDirectiveClass:
+  case Stmt::OMPMasterTaskLoopDirectiveClass:
+  case Stmt::OMPMasterTaskLoopSimdDirectiveClass:
+  case Stmt::OMPOrderedDirectiveClass:
+  case Stmt::OMPParallelDirectiveClass:
+  case Stmt::OMPParallelForDirectiveClass:
+  case Stmt::OMPParallelForSimdDirectiveClass:
+  case Stmt::OMPParallelMasterDirectiveClass:
+  case Stmt::OMPParallelMasterTaskLoopDirectiveClass:
+  case Stmt::OMPParallelMasterTaskLoopSimdDirectiveClass:
+  case Stmt::OMPParallelSectionsDirectiveClass:
+  case Stmt::OMPSectionDirectiveClass:
+  case Stmt::OMPSectionsDirectiveClass:
+  case Stmt::OMPSimdDirectiveClass:
+  case Stmt::OMPSingleDirectiveClass:
+  case Stmt::OMPTargetDataDirectiveClass:
+  case Stmt::OMPTargetDirectiveClass:
+  case Stmt::OMPTargetEnterDataDirectiveClass:
+  case Stmt::OMPTargetExitDataDirectiveClass:
+  case Stmt::OMPTargetParallelDirectiveClass:
+  case Stmt::OMPTargetParallelForDirectiveClass:
+  case Stmt::OMPTargetParallelForSimdDirectiveClass:
+  case Stmt::OMPTargetSimdDirectiveClass:
+  case Stmt::OMPTargetTeamsDirectiveClass:
+  case Stmt::OMPTargetTeamsDistributeDirectiveClass:
+  case Stmt::OMPTargetTeamsDistributeParallelForDirectiveClass:
+  case Stmt::OMPTargetTeamsDistributeParallelForSimdDirectiveClass:
+  case Stmt::OMPTargetTeamsDistributeSimdDirectiveClass:
+  case Stmt::OMPTargetUpdateDirectiveClass:
+  case Stmt::OMPTaskDirectiveClass:
+  case Stmt::OMPTaskgroupDirectiveClass:
+  case Stmt::OMPTaskLoopDirectiveClass:
+  case Stmt::OMPTaskLoopSimdDirectiveClass:
+  case Stmt::OMPTaskwaitDirectiveClass:
+  case Stmt::OMPTaskyieldDirectiveClass:
+  case Stmt::OMPTeamsDirectiveClass:
+  case Stmt::OMPTeamsDistributeDirectiveClass:
+  case Stmt::OMPTeamsDistributeParallelForDirectiveClass:
+  case Stmt::OMPTeamsDistributeParallelForSimdDirectiveClass:
+  case Stmt::OMPTeamsDistributeSimdDirectiveClass:
+  case Stmt::ReturnStmtClass:
+  case Stmt::SEHExceptStmtClass:
+  case Stmt::SEHFinallyStmtClass:
+  case Stmt::SEHLeaveStmtClass:
+  case Stmt::SEHTryStmtClass:
+  case Stmt::SwitchStmtClass:
+  case Stmt::WhileStmtClass:
+    return canSubStmtsThrow(*this, S);
+
+  case Stmt::DeclStmtClass: {
+    CanThrowResult CT = CT_Cannot;
+    for (const Decl *D : cast<DeclStmt>(S)->decls()) {
+      if (auto *VD = dyn_cast<VarDecl>(D))
+        CT = mergeCanThrow(CT, canVarDeclThrow(*this, VD));
+
+      // FIXME: Properly determine whether a variably-modified type can throw.
+      if (auto *TND = dyn_cast<TypedefNameDecl>(D))
+        if (TND->getUnderlyingType()->isVariablyModifiedType())
+          return CT_Can;
+      if (auto *VD = dyn_cast<ValueDecl>(D))
+        if (VD->getType()->isVariablyModifiedType())
+          return CT_Can;
+    }
+    return CT;
+  }
+
+  case Stmt::IfStmtClass: {
+    auto *IS = cast<IfStmt>(S);
+    CanThrowResult CT = CT_Cannot;
+    if (const Stmt *Init = IS->getInit())
+      CT = mergeCanThrow(CT, canThrow(Init));
+    if (const Stmt *CondDS = IS->getConditionVariableDeclStmt())
+      CT = mergeCanThrow(CT, canThrow(CondDS));
+    CT = mergeCanThrow(CT, canThrow(IS->getCond()));
+
+    // For 'if constexpr', consider only the non-discarded case.
+    // FIXME: We should add a DiscardedStmt marker to the AST.
+    if (Optional<const Stmt *> Case = IS->getNondiscardedCase(Context))
+      return *Case ? mergeCanThrow(CT, canThrow(*Case)) : CT;
+
+    CanThrowResult Then = canThrow(IS->getThen());
+    CanThrowResult Else = IS->getElse() ? canThrow(IS->getElse()) : CT_Cannot;
+    if (Then == Else)
+      return mergeCanThrow(CT, Then);
+
+    // For a dependent 'if constexpr', the result is dependent if it depends on
+    // the value of the condition.
+    return mergeCanThrow(CT, IS->isConstexpr() ? CT_Dependent
+                                               : mergeCanThrow(Then, Else));
+  }
+
+  case Stmt::CXXTryStmtClass: {
+    auto *TS = cast<CXXTryStmt>(S);
+    // try /*...*/ catch (...) { H } can throw only if H can throw.
+    // Any other try-catch can throw if any substatement can throw.
+    const CXXCatchStmt *FinalHandler = TS->getHandler(TS->getNumHandlers() - 1);
+    if (!FinalHandler->getExceptionDecl())
+      return canThrow(FinalHandler->getHandlerBlock());
+    return canSubStmtsThrow(*this, S);
+  }
+
+  case Stmt::ObjCAtThrowStmtClass:
+    return CT_Can;
+
+  case Stmt::ObjCAtTryStmtClass: {
+    auto *TS = cast<ObjCAtTryStmt>(S);
+
+    // @catch(...) need not be last in Objective-C. Walk backwards until we
+    // see one or hit the @try.
+    CanThrowResult CT = CT_Cannot;
+    if (const Stmt *Finally = TS->getFinallyStmt())
+      CT = mergeCanThrow(CT, canThrow(Finally));
+    for (unsigned I = TS->getNumCatchStmts(); I != 0; --I) {
+      const ObjCAtCatchStmt *Catch = TS->getCatchStmt(I - 1);
+      CT = mergeCanThrow(CT, canThrow(Catch));
+      // If we reach a @catch(...), no earlier exceptions can escape.
+      if (Catch->hasEllipsis())
+        return CT;
+    }
+
+    // Didn't find an @catch(...). Exceptions from the @try body can escape.
+    return mergeCanThrow(CT, canThrow(TS->getTryBody()));
+  }
+
+  case Stmt::NoStmtClass:
+    llvm_unreachable("Invalid class for statement");
   }
   llvm_unreachable("Bogus StmtClass");
 }
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index e41cd5b6653a..5f4071924d3f 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -25,6 +25,7 @@
 #include "clang/AST/ExprOpenMP.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/TypeLoc.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Basic/FixedPoint.h"
 #include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/SourceManager.h"
@@ -97,21 +98,16 @@ static void DiagnoseUnusedOfDecl(Sema &S, NamedDecl *D, SourceLocation Loc) {
 
 /// Emit a note explaining that this function is deleted.
 void Sema::NoteDeletedFunction(FunctionDecl *Decl) {
-  assert(Decl->isDeleted());
+  assert(Decl && Decl->isDeleted());
 
-  CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Decl);
-
-  if (Method && Method->isDeleted() && Method->isDefaulted()) {
+  if (Decl->isDefaulted()) {
     // If the method was explicitly defaulted, point at that declaration.
-    if (!Method->isImplicit())
+    if (!Decl->isImplicit())
       Diag(Decl->getLocation(), diag::note_implicitly_deleted);
 
     // Try to diagnose why this special member function was implicitly
     // deleted. This might fail, if that reason no longer applies.
-    CXXSpecialMember CSM = getSpecialMember(Method);
-    if (CSM != CXXInvalid)
-      ShouldDeleteSpecialMember(Method, CSM, nullptr, /*Diagnose=*/true);
-
+    DiagnoseDeletedDefaultedFunction(Decl);
     return;
   }
 
@@ -330,6 +326,30 @@ bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
 
   diagnoseUseOfInternalDeclInInlineFunction(*this, D, Loc);
 
+  // [expr.prim.id]p4
+  //   A program that refers explicitly or implicitly to a function with a
+  //   trailing requires-clause whose constraint-expression is not satisfied,
+  //   other than to declare it, is ill-formed. [...]
+  //
+  // See if this is a function with constraints that need to be satisfied.
+  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
+    if (Expr *RC = FD->getTrailingRequiresClause()) {
+      ConstraintSatisfaction Satisfaction;
+      bool Failed = CheckConstraintSatisfaction(RC, Satisfaction);
+      if (Failed)
+        // A diagnostic will have already been generated (non-constant
+        // constraint expression, for example)
+        return true;
+      if (!Satisfaction.IsSatisfied) {
+        Diag(Loc,
+             diag::err_reference_to_function_with_unsatisfied_constraints)
+            << D;
+        DiagnoseUnsatisfiedConstraint(Satisfaction);
+        return true;
+      }
+    }
+  }
+
   return false;
 }
 
@@ -481,16 +501,22 @@ static void CheckForNullPointerDereference(Sema &S, Expr *E) {
   // optimizer will delete, so warn about it.  People sometimes try to use this
   // to get a deterministic trap and are surprised by clang's behavior.  This
   // only handles the pattern "*null", which is a very syntactic check.
-  if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
-    if (UO->getOpcode() == UO_Deref &&
-        UO->getSubExpr()->IgnoreParenCasts()->
-          isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull) &&
+  const auto *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts());
+  if (UO && UO->getOpcode() == UO_Deref &&
+      UO->getSubExpr()->getType()->isPointerType()) {
+    const LangAS AS =
+        UO->getSubExpr()->getType()->getPointeeType().getAddressSpace();
+    if ((!isTargetAddressSpace(AS) ||
+         (isTargetAddressSpace(AS) && toTargetAddressSpace(AS) == 0)) &&
+        UO->getSubExpr()->IgnoreParenCasts()->isNullPointerConstant(
+            S.Context, Expr::NPC_ValueDependentIsNotNull) &&
         !UO->getType().isVolatileQualified()) {
-    S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
-                          S.PDiag(diag::warn_indirection_through_null)
-                            << UO->getSubExpr()->getSourceRange());
-    S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
-                        S.PDiag(diag::note_indirection_through_null));
+      S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
+                            S.PDiag(diag::warn_indirection_through_null)
+                                << UO->getSubExpr()->getSourceRange());
+      S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
+                            S.PDiag(diag::note_indirection_through_null));
+    }
   }
 }
 
@@ -1331,13 +1357,72 @@ static QualType handleFixedPointConversion(Sema &S, QualType LHSTy,
   return ResultTy;
 }
 
+/// Check that the usual arithmetic conversions can be performed on this pair of
+/// expressions that might be of enumeration type.
+static void checkEnumArithmeticConversions(Sema &S, Expr *LHS, Expr *RHS,
+                                           SourceLocation Loc,
+                                           Sema::ArithConvKind ACK) {
+  // C++2a [expr.arith.conv]p1:
+  //   If one operand is of enumeration type and the other operand is of a
+  //   different enumeration type or a floating-point type, this behavior is
+  //   deprecated ([depr.arith.conv.enum]).
+  //
+  // Warn on this in all language modes. Produce a deprecation warning in C++20.
+  // Eventually we will presumably reject these cases (in C++23 onwards?).
+  QualType L = LHS->getType(), R = RHS->getType();
+  bool LEnum = L->isUnscopedEnumerationType(),
+       REnum = R->isUnscopedEnumerationType();
+  bool IsCompAssign = ACK == Sema::ACK_CompAssign;
+  if ((!IsCompAssign && LEnum && R->isFloatingType()) ||
+      (REnum && L->isFloatingType())) {
+    S.Diag(Loc, S.getLangOpts().CPlusPlus2a
+                    ? diag::warn_arith_conv_enum_float_cxx2a
+                    : diag::warn_arith_conv_enum_float)
+        << LHS->getSourceRange() << RHS->getSourceRange()
+        << (int)ACK << LEnum << L << R;
+  } else if (!IsCompAssign && LEnum && REnum &&
+             !S.Context.hasSameUnqualifiedType(L, R)) {
+    unsigned DiagID;
+    if (!L->castAs<EnumType>()->getDecl()->hasNameForLinkage() ||
+        !R->castAs<EnumType>()->getDecl()->hasNameForLinkage()) {
+      // If either enumeration type is unnamed, it's less likely that the
+      // user cares about this, but this situation is still deprecated in
+      // C++2a. Use a different warning group.
+      DiagID = S.getLangOpts().CPlusPlus2a
+                    ? diag::warn_arith_conv_mixed_anon_enum_types_cxx2a
+                    : diag::warn_arith_conv_mixed_anon_enum_types;
+    } else if (ACK == Sema::ACK_Conditional) {
+      // Conditional expressions are separated out because they have
+      // historically had a different warning flag.
+      DiagID = S.getLangOpts().CPlusPlus2a
+                   ? diag::warn_conditional_mixed_enum_types_cxx2a
+                   : diag::warn_conditional_mixed_enum_types;
+    } else if (ACK == Sema::ACK_Comparison) {
+      // Comparison expressions are separated out because they have
+      // historically had a different warning flag.
+      DiagID = S.getLangOpts().CPlusPlus2a
+                   ? diag::warn_comparison_mixed_enum_types_cxx2a
+                   : diag::warn_comparison_mixed_enum_types;
+    } else {
+      DiagID = S.getLangOpts().CPlusPlus2a
+                   ? diag::warn_arith_conv_mixed_enum_types_cxx2a
+                   : diag::warn_arith_conv_mixed_enum_types;
+    }
+    S.Diag(Loc, DiagID) << LHS->getSourceRange() << RHS->getSourceRange()
+                        << (int)ACK << L << R;
+  }
+}
+
 /// UsualArithmeticConversions - Performs various conversions that are common to
 /// binary operators (C99 6.3.1.8). If both operands aren't arithmetic, this
 /// routine returns the first non-arithmetic type found. The client is
 /// responsible for emitting appropriate error diagnostics.
 QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
-                                          bool IsCompAssign) {
-  if (!IsCompAssign) {
+                                          SourceLocation Loc,
+                                          ArithConvKind ACK) {
+  checkEnumArithmeticConversions(*this, LHS.get(), RHS.get(), Loc, ACK);
+
+  if (ACK != ACK_CompAssign) {
     LHS = UsualUnaryConversions(LHS.get());
     if (LHS.isInvalid())
       return QualType();
@@ -1374,7 +1459,7 @@ QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
   QualType LHSBitfieldPromoteTy = Context.isPromotableBitField(LHS.get());
   if (!LHSBitfieldPromoteTy.isNull())
     LHSType = LHSBitfieldPromoteTy;
-  if (LHSType != LHSUnpromotedType && !IsCompAssign)
+  if (LHSType != LHSUnpromotedType && ACK != ACK_CompAssign)
     LHS = ImpCastExprToType(LHS.get(), LHSType, CK_IntegralCast);
 
   // If both types are identical, no conversion is needed.
@@ -1391,24 +1476,24 @@ QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
   // Handle complex types first (C99 6.3.1.8p1).
   if (LHSType->isComplexType() || RHSType->isComplexType())
     return handleComplexFloatConversion(*this, LHS, RHS, LHSType, RHSType,
-                                        IsCompAssign);
+                                        ACK == ACK_CompAssign);
 
   // Now handle "real" floating types (i.e. float, double, long double).
   if (LHSType->isRealFloatingType() || RHSType->isRealFloatingType())
     return handleFloatConversion(*this, LHS, RHS, LHSType, RHSType,
-                                 IsCompAssign);
+                                 ACK == ACK_CompAssign);
 
   // Handle GCC complex int extension.
   if (LHSType->isComplexIntegerType() || RHSType->isComplexIntegerType())
     return handleComplexIntConversion(*this, LHS, RHS, LHSType, RHSType,
-                                      IsCompAssign);
+                                      ACK == ACK_CompAssign);
 
   if (LHSType->isFixedPointType() || RHSType->isFixedPointType())
     return handleFixedPointConversion(*this, LHSType, RHSType);
 
   // Finally, we have two differing integer types.
   return handleIntegerConversion<doIntegralCast, doIntegralCast>
-           (*this, LHS, RHS, LHSType, RHSType, IsCompAssign);
+           (*this, LHS, RHS, LHSType, RHSType, ACK == ACK_CompAssign);
 }
 
 //===----------------------------------------------------------------------===//
@@ -1825,6 +1910,25 @@ Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
       VK, FoundD, TemplateArgs, getNonOdrUseReasonInCurrentContext(D));
   MarkDeclRefReferenced(E);
 
+  // C++ [except.spec]p17:
+  //   An exception-specification is considered to be needed when:
+  //   - in an expression, the function is the unique lookup result or
+  //     the selected member of a set of overloaded functions.
+  //
+  // We delay doing this until after we've built the function reference and
+  // marked it as used so that:
+  //  a) if the function is defaulted, we get errors from defining it before /
+  //     instead of errors from computing its exception specification, and
+  //  b) if the function is a defaulted comparison, we can use the body we
+  //     build when defining it as input to the exception specification
+  //     computation rather than computing a new body.
+  if (auto *FPT = Ty->getAs<FunctionProtoType>()) {
+    if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
+      if (auto *NewFPT = ResolveExceptionSpec(NameInfo.getLoc(), FPT))
+        E->setType(Context.getQualifiedType(NewFPT, Ty.getQualifiers()));
+    }
+  }
+
   if (getLangOpts().ObjCWeak && isa<VarDecl>(D) &&
       Ty.getObjCLifetime() == Qualifiers::OCL_Weak && !isUnevaluatedContext() &&
       !Diags.isIgnored(diag::warn_arc_repeated_use_of_weak, E->getBeginLoc()))
@@ -2704,6 +2808,20 @@ Sema::PerformObjectMemberConversion(Expr *From,
       FromRecordType = FromType;
       DestType = DestRecordType;
     }
+
+    LangAS FromAS = FromRecordType.getAddressSpace();
+    LangAS DestAS = DestRecordType.getAddressSpace();
+    if (FromAS != DestAS) {
+      QualType FromRecordTypeWithoutAS =
+          Context.removeAddrSpaceQualType(FromRecordType);
+      QualType FromTypeWithDestAS =
+          Context.getAddrSpaceQualType(FromRecordTypeWithoutAS, DestAS);
+      if (PointerConversions)
+        FromTypeWithDestAS = Context.getPointerType(FromTypeWithDestAS);
+      From = ImpCastExprToType(From, FromTypeWithDestAS,
+                               CK_AddressSpaceConversion, From->getValueKind())
+                 .get();
+    }
   } else {
     // No conversion necessary.
     return From;
@@ -2993,14 +3111,6 @@ ExprResult Sema::BuildDeclarationNameExpr(
     QualType type = VD->getType();
     if (type.isNull())
       return ExprError();
-    if (auto *FPT = type->getAs<FunctionProtoType>()) {
-      // C++ [except.spec]p17:
-      //   An exception-specification is considered to be needed when:
-      //   - in an expression, the function is the unique lookup result or
-      //     the selected member of a set of overloaded functions.
-      ResolveExceptionSpec(Loc, FPT);
-      type = VD->getType();
-    }
     ExprValueKind valueKind = VK_RValue;
 
     switch (D->getKind()) {
@@ -5231,6 +5341,9 @@ bool Sema::GatherArgumentsForCall(SourceLocation CallLoc, FunctionDecl *FDecl,
       for (Expr *A : Args.slice(ArgIx)) {
         ExprResult Arg = DefaultVariadicArgumentPromotion(A, CallType, FDecl);
         Invalid |= Arg.isInvalid();
+        // Copy blocks to the heap.
+        if (A->getType()->isBlockPointerType())
+          maybeExtendBlockObject(Arg);
         AllArgs.push_back(Arg.get());
       }
     }
@@ -5424,15 +5537,15 @@ static FunctionDecl *rewriteBuiltinFunctionDecl(Sema *Sema, ASTContext &Context,
     Expr *Arg = ArgRes.get();
     QualType ArgType = Arg->getType();
     if (!ParamType->isPointerType() ||
-        ParamType.getQualifiers().hasAddressSpace() ||
+        ParamType.hasAddressSpace() ||
         !ArgType->isPointerType() ||
-        !ArgType->getPointeeType().getQualifiers().hasAddressSpace()) {
+        !ArgType->getPointeeType().hasAddressSpace()) {
       OverloadParams.push_back(ParamType);
       continue;
     }
 
     QualType PointeeType = ParamType->getPointeeType();
-    if (PointeeType.getQualifiers().hasAddressSpace())
+    if (PointeeType.hasAddressSpace())
       continue;
 
     NeedsNewDecl = true;
@@ -7363,7 +7476,8 @@ QualType Sema::CheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
                                /*AllowBothBool*/true,
                                /*AllowBoolConversions*/false);
 
-  QualType ResTy = UsualArithmeticConversions(LHS, RHS);
+  QualType ResTy =
+      UsualArithmeticConversions(LHS, RHS, QuestionLoc, ACK_Conditional);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
@@ -7639,7 +7753,7 @@ static bool IsArithmeticBinaryExpr(Expr *E, BinaryOperatorKind *Opcode,
   E = E->IgnoreConversionOperator();
   E = E->IgnoreImpCasts();
   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E)) {
-    E = MTE->GetTemporaryExpr();
+    E = MTE->getSubExpr();
     E = E->IgnoreImpCasts();
   }
 
@@ -8695,7 +8809,7 @@ namespace {
 struct OriginalOperand {
   explicit OriginalOperand(Expr *Op) : Orig(Op), Conversion(nullptr) {
     if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Op))
-      Op = MTE->GetTemporaryExpr();
+      Op = MTE->getSubExpr();
     if (auto *BTE = dyn_cast<CXXBindTemporaryExpr>(Op))
       Op = BTE->getSubExpr();
     if (auto *ICE = dyn_cast<ImplicitCastExpr>(Op)) {
@@ -8957,6 +9071,12 @@ static bool tryGCCVectorConvertAndSplat(Sema &S, ExprResult *Scalar,
       return true;
 
     ScalarCast = CK_IntegralCast;
+  } else if (VectorEltTy->isIntegralType(S.Context) &&
+             ScalarTy->isRealFloatingType()) {
+    if (S.Context.getTypeSize(VectorEltTy) == S.Context.getTypeSize(ScalarTy))
+      ScalarCast = CK_FloatingToIntegral;
+    else
+      return true;
   } else if (VectorEltTy->isRealFloatingType()) {
     if (ScalarTy->isRealFloatingType()) {
 
@@ -9276,7 +9396,8 @@ QualType Sema::CheckMultiplyDivideOperands(ExprResult &LHS, ExprResult &RHS,
                                /*AllowBothBool*/getLangOpts().AltiVec,
                                /*AllowBoolConversions*/false);
 
-  QualType compType = UsualArithmeticConversions(LHS, RHS, IsCompAssign);
+  QualType compType = UsualArithmeticConversions(
+      LHS, RHS, Loc, IsCompAssign ? ACK_CompAssign : ACK_Arithmetic);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
@@ -9304,7 +9425,8 @@ QualType Sema::CheckRemainderOperands(
     return InvalidOperands(Loc, LHS, RHS);
   }
 
-  QualType compType = UsualArithmeticConversions(LHS, RHS, IsCompAssign);
+  QualType compType = UsualArithmeticConversions(
+      LHS, RHS, Loc, IsCompAssign ? ACK_CompAssign : ACK_Arithmetic);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
@@ -9593,7 +9715,8 @@ QualType Sema::CheckAdditionOperands(ExprResult &LHS, ExprResult &RHS,
     return compType;
   }
 
-  QualType compType = UsualArithmeticConversions(LHS, RHS, CompLHSTy);
+  QualType compType = UsualArithmeticConversions(
+      LHS, RHS, Loc, CompLHSTy ? ACK_CompAssign : ACK_Arithmetic);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
@@ -9687,7 +9810,8 @@ QualType Sema::CheckSubtractionOperands(ExprResult &LHS, ExprResult &RHS,
     return compType;
   }
 
-  QualType compType = UsualArithmeticConversions(LHS, RHS, CompLHSTy);
+  QualType compType = UsualArithmeticConversions(
+      LHS, RHS, Loc, CompLHSTy ? ACK_CompAssign : ACK_Arithmetic);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
 
@@ -10018,35 +10142,6 @@ QualType Sema::CheckShiftOperands(ExprResult &LHS, ExprResult &RHS,
   return LHSType;
 }
 
-/// If two different enums are compared, raise a warning.
-static void checkEnumComparison(Sema &S, SourceLocation Loc, Expr *LHS,
-                                Expr *RHS) {
-  QualType LHSStrippedType = LHS->IgnoreParenImpCasts()->getType();
-  QualType RHSStrippedType = RHS->IgnoreParenImpCasts()->getType();
-
-  const EnumType *LHSEnumType = LHSStrippedType->getAs<EnumType>();
-  if (!LHSEnumType)
-    return;
-  const EnumType *RHSEnumType = RHSStrippedType->getAs<EnumType>();
-  if (!RHSEnumType)
-    return;
-
-  // Ignore anonymous enums.
-  if (!LHSEnumType->getDecl()->getIdentifier() &&
-      !LHSEnumType->getDecl()->getTypedefNameForAnonDecl())
-    return;
-  if (!RHSEnumType->getDecl()->getIdentifier() &&
-      !RHSEnumType->getDecl()->getTypedefNameForAnonDecl())
-    return;
-
-  if (S.Context.hasSameUnqualifiedType(LHSStrippedType, RHSStrippedType))
-    return;
-
-  S.Diag(Loc, diag::warn_comparison_of_mixed_enum_types)
-      << LHSStrippedType << RHSStrippedType
-      << LHS->getSourceRange() << RHS->getSourceRange();
-}
-
 /// Diagnose bad pointer comparisons.
 static void diagnoseDistinctPointerComparison(Sema &S, SourceLocation Loc,
                                               ExprResult &LHS, ExprResult &RHS,
@@ -10085,8 +10180,6 @@ static bool convertPointersToCompositeType(Sema &S, SourceLocation Loc,
     return true;
   }
 
-  LHS = S.ImpCastExprToType(LHS.get(), T, CK_BitCast);
-  RHS = S.ImpCastExprToType(RHS.get(), T, CK_BitCast);
   return false;
 }
 
@@ -10317,7 +10410,6 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
   QualType RHSType = RHS->getType();
   if (LHSType->hasFloatingRepresentation() ||
       (LHSType->isBlockPointerType() && !BinaryOperator::isEqualityOp(Opc)) ||
-      LHS->getBeginLoc().isMacroID() || RHS->getBeginLoc().isMacroID() ||
       S.inTemplateInstantiation())
     return;
 
@@ -10345,45 +10437,64 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
     AlwaysEqual, // std::strong_ordering::equal from operator<=>
   };
 
-  if (Expr::isSameComparisonOperand(LHS, RHS)) {
-    unsigned Result;
-    switch (Opc) {
-    case BO_EQ: case BO_LE: case BO_GE:
-      Result = AlwaysTrue;
-      break;
-    case BO_NE: case BO_LT: case BO_GT:
-      Result = AlwaysFalse;
-      break;
-    case BO_Cmp:
-      Result = AlwaysEqual;
-      break;
-    default:
-      Result = AlwaysConstant;
-      break;
-    }
-    S.DiagRuntimeBehavior(Loc, nullptr,
-                          S.PDiag(diag::warn_comparison_always)
-                              << 0 /*self-comparison*/
-                              << Result);
-  } else if (checkForArray(LHSStripped) && checkForArray(RHSStripped)) {
-    // What is it always going to evaluate to?
-    unsigned Result;
-    switch(Opc) {
-    case BO_EQ: // e.g. array1 == array2
-      Result = AlwaysFalse;
-      break;
-    case BO_NE: // e.g. array1 != array2
-      Result = AlwaysTrue;
-      break;
-    default: // e.g. array1 <= array2
-      // The best we can say is 'a constant'
-      Result = AlwaysConstant;
-      break;
+  // C++2a [depr.array.comp]:
+  //   Equality and relational comparisons ([expr.eq], [expr.rel]) between two
+  //   operands of array type are deprecated.
+  if (S.getLangOpts().CPlusPlus2a && LHSStripped->getType()->isArrayType() &&
+      RHSStripped->getType()->isArrayType()) {
+    S.Diag(Loc, diag::warn_depr_array_comparison)
+        << LHS->getSourceRange() << RHS->getSourceRange()
+        << LHSStripped->getType() << RHSStripped->getType();
+    // Carry on to produce the tautological comparison warning, if this
+    // expression is potentially-evaluated, we can resolve the array to a
+    // non-weak declaration, and so on.
+  }
+
+  if (!LHS->getBeginLoc().isMacroID() && !RHS->getBeginLoc().isMacroID()) {
+    if (Expr::isSameComparisonOperand(LHS, RHS)) {
+      unsigned Result;
+      switch (Opc) {
+      case BO_EQ:
+      case BO_LE:
+      case BO_GE:
+        Result = AlwaysTrue;
+        break;
+      case BO_NE:
+      case BO_LT:
+      case BO_GT:
+        Result = AlwaysFalse;
+        break;
+      case BO_Cmp:
+        Result = AlwaysEqual;
+        break;
+      default:
+        Result = AlwaysConstant;
+        break;
+      }
+      S.DiagRuntimeBehavior(Loc, nullptr,
+                            S.PDiag(diag::warn_comparison_always)
+                                << 0 /*self-comparison*/
+                                << Result);
+    } else if (checkForArray(LHSStripped) && checkForArray(RHSStripped)) {
+      // What is it always going to evaluate to?
+      unsigned Result;
+      switch (Opc) {
+      case BO_EQ: // e.g. array1 == array2
+        Result = AlwaysFalse;
+        break;
+      case BO_NE: // e.g. array1 != array2
+        Result = AlwaysTrue;
+        break;
+      default: // e.g. array1 <= array2
+        // The best we can say is 'a constant'
+        Result = AlwaysConstant;
+        break;
+      }
+      S.DiagRuntimeBehavior(Loc, nullptr,
+                            S.PDiag(diag::warn_comparison_always)
+                                << 1 /*array comparison*/
+                                << Result);
     }
-    S.DiagRuntimeBehavior(Loc, nullptr,
-                          S.PDiag(diag::warn_comparison_always)
-                              << 1 /*array comparison*/
-                              << Result);
   }
 
   if (isa<CastExpr>(LHSStripped))
@@ -10392,7 +10503,7 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
     RHSStripped = RHSStripped->IgnoreParenCasts();
 
   // Warn about comparisons against a string constant (unless the other
-  // operand is null); the user probably wants strcmp.
+  // operand is null); the user probably wants string comparison function.
   Expr *LiteralString = nullptr;
   Expr *LiteralStringStripped = nullptr;
   if ((isa<StringLiteral>(LHSStripped) || isa<ObjCEncodeExpr>(LHSStripped)) &&
@@ -10500,8 +10611,6 @@ static QualType checkArithmeticOrEnumeralThreeWayCompare(Sema &S,
                                                          ExprResult &LHS,
                                                          ExprResult &RHS,
                                                          SourceLocation Loc) {
-  using CCT = ComparisonCategoryType;
-
   QualType LHSType = LHS.get()->getType();
   QualType RHSType = RHS.get()->getType();
   // Dig out the original argument type and expression before implicit casts
@@ -10519,6 +10628,7 @@ static QualType checkArithmeticOrEnumeralThreeWayCompare(Sema &S,
     return QualType();
   }
 
+  // FIXME: Consider combining this with checkEnumArithmeticConversions.
   int NumEnumArgs = (int)LHSStrippedType->isEnumeralType() +
                     RHSStrippedType->isEnumeralType();
   if (NumEnumArgs == 1) {
@@ -10554,12 +10664,17 @@ static QualType checkArithmeticOrEnumeralThreeWayCompare(Sema &S,
 
   // C++2a [expr.spaceship]p4: If both operands have arithmetic types, the
   // usual arithmetic conversions are applied to the operands.
-  QualType Type = S.UsualArithmeticConversions(LHS, RHS);
+  QualType Type =
+      S.UsualArithmeticConversions(LHS, RHS, Loc, Sema::ACK_Comparison);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
   if (Type.isNull())
     return S.InvalidOperands(Loc, LHS, RHS);
-  assert(Type->isArithmeticType() || Type->isEnumeralType());
+
+  Optional<ComparisonCategoryType> CCT =
+      getComparisonCategoryForBuiltinCmp(Type);
+  if (!CCT)
+    return S.InvalidOperands(Loc, LHS, RHS);
 
   bool HasNarrowing = checkThreeWayNarrowingConversion(
       S, Type, LHS.get(), LHSType, LHS.get()->getBeginLoc());
@@ -10570,20 +10685,8 @@ static QualType checkArithmeticOrEnumeralThreeWayCompare(Sema &S,
 
   assert(!Type.isNull() && "composite type for <=> has not been set");
 
-  auto TypeKind = [&]() {
-    if (const ComplexType *CT = Type->getAs<ComplexType>()) {
-      if (CT->getElementType()->hasFloatingRepresentation())
-        return CCT::WeakEquality;
-      return CCT::StrongEquality;
-    }
-    if (Type->isIntegralOrEnumerationType())
-      return CCT::StrongOrdering;
-    if (Type->hasFloatingRepresentation())
-      return CCT::PartialOrdering;
-    llvm_unreachable("other types are unimplemented");
-  }();
-
-  return S.CheckComparisonCategoryType(TypeKind, Loc);
+  return S.CheckComparisonCategoryType(
+      *CCT, Loc, Sema::ComparisonCategoryUsage::OperatorInExpression);
 }
 
 static QualType checkArithmeticOrEnumeralCompare(Sema &S, ExprResult &LHS,
@@ -10594,15 +10697,14 @@ static QualType checkArithmeticOrEnumeralCompare(Sema &S, ExprResult &LHS,
     return checkArithmeticOrEnumeralThreeWayCompare(S, LHS, RHS, Loc);
 
   // C99 6.5.8p3 / C99 6.5.9p4
-  QualType Type = S.UsualArithmeticConversions(LHS, RHS);
+  QualType Type =
+      S.UsualArithmeticConversions(LHS, RHS, Loc, Sema::ACK_Comparison);
   if (LHS.isInvalid() || RHS.isInvalid())
     return QualType();
   if (Type.isNull())
     return S.InvalidOperands(Loc, LHS, RHS);
   assert(Type->isArithmeticType() || Type->isEnumeralType());
 
-  checkEnumComparison(S, Loc, LHS.get(), RHS.get());
-
   if (Type->isAnyComplexType() && BinaryOperator::isRelationalOp(Opc))
     return S.InvalidOperands(Loc, LHS, RHS);
 
@@ -10646,6 +10748,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                     BinaryOperatorKind Opc) {
   bool IsRelational = BinaryOperator::isRelationalOp(Opc);
   bool IsThreeWay = Opc == BO_Cmp;
+  bool IsOrdered = IsRelational || IsThreeWay;
   auto IsAnyPointerType = [](ExprResult E) {
     QualType Ty = E.get()->getType();
     return Ty->isPointerType() || Ty->isMemberPointerType();
@@ -10708,36 +10811,26 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     QualType CompositeTy = LHS.get()->getType();
     assert(!CompositeTy->isReferenceType());
 
-    auto buildResultTy = [&](ComparisonCategoryType Kind) {
-      return CheckComparisonCategoryType(Kind, Loc);
-    };
-
-    // C++2a [expr.spaceship]p7: If the composite pointer type is a function
-    // pointer type, a pointer-to-member type, or std::nullptr_t, the
-    // result is of type std::strong_equality
-    if (CompositeTy->isFunctionPointerType() ||
-        CompositeTy->isMemberPointerType() || CompositeTy->isNullPtrType())
-      // FIXME: consider making the function pointer case produce
-      // strong_ordering not strong_equality, per P0946R0-Jax18 discussion
-      // and direction polls
-      return buildResultTy(ComparisonCategoryType::StrongEquality);
-
-    // C++2a [expr.spaceship]p8: If the composite pointer type is an object
-    // pointer type, p <=> q is of type std::strong_ordering.
-    if (CompositeTy->isPointerType()) {
+    Optional<ComparisonCategoryType> CCT =
+        getComparisonCategoryForBuiltinCmp(CompositeTy);
+    if (!CCT)
+      return InvalidOperands(Loc, LHS, RHS);
+
+    if (CompositeTy->isPointerType() && LHSIsNull != RHSIsNull) {
       // P0946R0: Comparisons between a null pointer constant and an object
-      // pointer result in std::strong_equality
-      if (LHSIsNull != RHSIsNull)
-        return buildResultTy(ComparisonCategoryType::StrongEquality);
-      return buildResultTy(ComparisonCategoryType::StrongOrdering);
+      // pointer result in std::strong_equality, which is ill-formed under
+      // P1959R0.
+      Diag(Loc, diag::err_typecheck_three_way_comparison_of_pointer_and_zero)
+          << (LHSIsNull ? LHS.get()->getSourceRange()
+                        : RHS.get()->getSourceRange());
+      return QualType();
     }
-    // C++2a [expr.spaceship]p9: Otherwise, the program is ill-formed.
-    // TODO: Extend support for operator<=> to ObjC types.
-    return InvalidOperands(Loc, LHS, RHS);
-  };
 
+    return CheckComparisonCategoryType(
+        *CCT, Loc, ComparisonCategoryUsage::OperatorInExpression);
+  };
 
-  if (!IsRelational && LHSIsNull != RHSIsNull) {
+  if (!IsOrdered && LHSIsNull != RHSIsNull) {
     bool IsEquality = Opc == BO_EQ;
     if (RHSIsNull)
       DiagnoseAlwaysNonNullPointer(LHS.get(), RHSNullKind, IsEquality,
@@ -10756,7 +10849,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     // but we allow it as an extension.
     // FIXME: If we really want to allow this, should it be part of composite
     // pointer type computation so it works in conditionals too?
-    if (!IsRelational &&
+    if (!IsOrdered &&
         ((LHSType->isFunctionPointerType() && RHSType->isVoidPointerType()) ||
          (RHSType->isFunctionPointerType() && LHSType->isVoidPointerType()))) {
       // This is a gcc extension compatibility comparison.
@@ -10781,8 +10874,11 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     // C++ [expr.rel]p2:
     //   If both operands are pointers, [...] bring them to their composite
     //   pointer type.
+    // For <=>, the only valid non-pointer types are arrays and functions, and
+    // we already decayed those, so this is really the same as the relational
+    // comparison rule.
     if ((int)LHSType->isPointerType() + (int)RHSType->isPointerType() >=
-            (IsRelational ? 2 : 1) &&
+            (IsOrdered ? 2 : 1) &&
         (!LangOpts.ObjCAutoRefCount || !(LHSType->isObjCObjectPointerType() ||
                                          RHSType->isObjCObjectPointerType()))) {
       if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
@@ -10845,7 +10941,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     // C++ [expr.eq]p4:
     //   Two operands of type std::nullptr_t or one operand of type
     //   std::nullptr_t and the other a null pointer constant compare equal.
-    if (!IsRelational && LHSIsNull && RHSIsNull) {
+    if (!IsOrdered && LHSIsNull && RHSIsNull) {
       if (LHSType->isNullPtrType()) {
         RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
         return computeResultTy();
@@ -10858,12 +10954,12 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
 
     // Comparison of Objective-C pointers and block pointers against nullptr_t.
     // These aren't covered by the composite pointer type rules.
-    if (!IsRelational && RHSType->isNullPtrType() &&
+    if (!IsOrdered && RHSType->isNullPtrType() &&
         (LHSType->isObjCObjectPointerType() || LHSType->isBlockPointerType())) {
       RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
       return computeResultTy();
     }
-    if (!IsRelational && LHSType->isNullPtrType() &&
+    if (!IsOrdered && LHSType->isNullPtrType() &&
         (RHSType->isObjCObjectPointerType() || RHSType->isBlockPointerType())) {
       LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
       return computeResultTy();
@@ -10897,7 +10993,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     // C++ [expr.eq]p2:
     //   If at least one operand is a pointer to member, [...] bring them to
     //   their composite pointer type.
-    if (!IsRelational &&
+    if (!IsOrdered &&
         (LHSType->isMemberPointerType() || RHSType->isMemberPointerType())) {
       if (convertPointersToCompositeType(*this, Loc, LHS, RHS))
         return QualType();
@@ -10907,7 +11003,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
 
   // Handle block pointer types.
-  if (!IsRelational && LHSType->isBlockPointerType() &&
+  if (!IsOrdered && LHSType->isBlockPointerType() &&
       RHSType->isBlockPointerType()) {
     QualType lpointee = LHSType->castAs<BlockPointerType>()->getPointeeType();
     QualType rpointee = RHSType->castAs<BlockPointerType>()->getPointeeType();
@@ -10923,7 +11019,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
 
   // Allow block pointers to be compared with null pointer constants.
-  if (!IsRelational
+  if (!IsOrdered
       && ((LHSType->isBlockPointerType() && RHSType->isPointerType())
           || (LHSType->isPointerType() && RHSType->isBlockPointerType()))) {
     if (!LHSIsNull && !RHSIsNull) {
@@ -10959,6 +11055,9 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
         diagnoseDistinctPointerComparison(*this, Loc, LHS, RHS,
                                           /*isError*/false);
       }
+      // FIXME: If LPtrToVoid, we should presumably convert the LHS rather than
+      // the RHS, but we have test coverage for this behavior.
+      // FIXME: Consider using convertPointersToCompositeType in C++.
       if (LHSIsNull && !RHSIsNull) {
         Expr *E = LHS.get();
         if (getLangOpts().ObjCAutoRefCount)
@@ -10993,12 +11092,12 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
       return computeResultTy();
     }
 
-    if (!IsRelational && LHSType->isBlockPointerType() &&
+    if (!IsOrdered && LHSType->isBlockPointerType() &&
         RHSType->isBlockCompatibleObjCPointerType(Context)) {
       LHS = ImpCastExprToType(LHS.get(), RHSType,
                               CK_BlockPointerToObjCPointerCast);
       return computeResultTy();
-    } else if (!IsRelational &&
+    } else if (!IsOrdered &&
                LHSType->isBlockCompatibleObjCPointerType(Context) &&
                RHSType->isBlockPointerType()) {
       RHS = ImpCastExprToType(RHS.get(), LHSType,
@@ -11015,7 +11114,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
       // since users tend to want to compare addresses.
     } else if ((LHSIsNull && LHSType->isIntegerType()) ||
                (RHSIsNull && RHSType->isIntegerType())) {
-      if (IsRelational) {
+      if (IsOrdered) {
         isError = getLangOpts().CPlusPlus;
         DiagID =
           isError ? diag::err_typecheck_ordered_comparison_of_pointer_and_zero
@@ -11024,7 +11123,7 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
     } else if (getLangOpts().CPlusPlus) {
       DiagID = diag::err_typecheck_comparison_of_pointer_integer;
       isError = true;
-    } else if (IsRelational)
+    } else if (IsOrdered)
       DiagID = diag::ext_typecheck_ordered_comparison_of_pointer_integer;
     else
       DiagID = diag::ext_typecheck_comparison_of_pointer_integer;
@@ -11047,12 +11146,12 @@ QualType Sema::CheckCompareOperands(ExprResult &LHS, ExprResult &RHS,
   }
 
   // Handle block pointers.
-  if (!IsRelational && RHSIsNull
+  if (!IsOrdered && RHSIsNull
       && LHSType->isBlockPointerType() && RHSType->isIntegerType()) {
     RHS = ImpCastExprToType(RHS.get(), LHSType, CK_NullToPointer);
     return computeResultTy();
   }
-  if (!IsRelational && LHSIsNull
+  if (!IsOrdered && LHSIsNull
       && LHSType->isIntegerType() && RHSType->isBlockPointerType()) {
     LHS = ImpCastExprToType(LHS.get(), RHSType, CK_NullToPointer);
     return computeResultTy();
@@ -11129,6 +11228,11 @@ QualType Sema::GetSignedVectorType(QualType V) {
 QualType Sema::CheckVectorCompareOperands(ExprResult &LHS, ExprResult &RHS,
                                           SourceLocation Loc,
                                           BinaryOperatorKind Opc) {
+  if (Opc == BO_Cmp) {
+    Diag(Loc, diag::err_three_way_vector_comparison);
+    return QualType();
+  }
+
   // Check to make sure we're operating on vectors of the same type and width,
   // Allowing one side to be a scalar of element type.
   QualType vType = CheckVectorOperands(LHS, RHS, Loc, /*isCompAssign*/false,
@@ -11318,9 +11422,13 @@ inline QualType Sema::CheckBitwiseOperands(ExprResult &LHS, ExprResult &RHS,
   if (Opc == BO_And)
     diagnoseLogicalNotOnLHSofCheck(*this, LHS, RHS, Loc, Opc);
 
+  if (LHS.get()->getType()->hasFloatingRepresentation() ||
+      RHS.get()->getType()->hasFloatingRepresentation())
+    return InvalidOperands(Loc, LHS, RHS);
+
   ExprResult LHSResult = LHS, RHSResult = RHS;
-  QualType compType = UsualArithmeticConversions(LHSResult, RHSResult,
-                                                 IsCompAssign);
+  QualType compType = UsualArithmeticConversions(
+      LHSResult, RHSResult, Loc, IsCompAssign ? ACK_CompAssign : ACK_BitwiseOp);
   if (LHSResult.isInvalid() || RHSResult.isInvalid())
     return QualType();
   LHS = LHSResult.get();
@@ -13011,6 +13119,14 @@ ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
   if (ResultTy.isNull() || LHS.isInvalid() || RHS.isInvalid())
     return ExprError();
 
+  if (ResultTy->isRealFloatingType() &&
+      (getLangOpts().getFPRoundingMode() != LangOptions::FPR_ToNearest ||
+       getLangOpts().getFPExceptionMode() != LangOptions::FPE_Ignore))
+    // Mark the current function as usng floating point constrained intrinsics
+    if (FunctionDecl *F = dyn_cast<FunctionDecl>(CurContext)) {
+      F->setUsesFPIntrin(true);
+    }
+
   // Some of the binary operations require promoting operands of half vector to
   // float vectors and truncating the result back to half vector. For now, we do
   // this only when HalfArgsAndReturn is set (that is, when the target is arm or
@@ -15268,8 +15384,7 @@ static bool funcHasParameterSizeMangling(Sema &S, FunctionDecl *FD) {
   // These manglings don't do anything on non-Windows or non-x86 platforms, so
   // we don't need parameter type sizes.
   const llvm::Triple &TT = S.Context.getTargetInfo().getTriple();
-  if (!TT.isOSWindows() || (TT.getArch() != llvm::Triple::x86 &&
-                            TT.getArch() != llvm::Triple::x86_64))
+  if (!TT.isOSWindows() || !TT.isX86())
     return false;
 
   // If this is C++ and this isn't an extern "C" function, parameters do not
@@ -15385,9 +15500,8 @@ static OdrUseContext isOdrUseContext(Sema &SemaRef) {
 }
 
 static bool isImplicitlyDefinableConstexprFunction(FunctionDecl *Func) {
-  CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Func);
   return Func->isConstexpr() &&
-         (Func->isImplicitlyInstantiable() || (MD && !MD->isUserProvided()));
+         (Func->isImplicitlyInstantiable() || !Func->isUserProvided());
 }
 
 /// Mark a function referenced, and check whether it is odr-used
@@ -15467,19 +15581,6 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
        Func->getMemberSpecializationInfo()))
     checkSpecializationVisibility(Loc, Func);
 
-  // C++14 [except.spec]p17:
-  //   An exception-specification is considered to be needed when:
-  //   - the function is odr-used or, if it appears in an unevaluated operand,
-  //     would be odr-used if the expression were potentially-evaluated;
-  //
-  // Note, we do this even if MightBeOdrUse is false. That indicates that the
-  // function is a pure virtual function we're calling, and in that case the
-  // function was selected by overload resolution and we need to resolve its
-  // exception specification for a different reason.
-  const FunctionProtoType *FPT = Func->getType()->getAs<FunctionProtoType>();
-  if (FPT && isUnresolvedExceptionSpec(FPT->getExceptionSpecType()))
-    ResolveExceptionSpec(Loc, FPT);
-
   if (getLangOpts().CUDA)
     CheckCUDACall(Loc, Func);
 
@@ -15535,6 +15636,12 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
           MarkVTableUsed(Loc, MethodDecl->getParent());
       }
 
+      if (Func->isDefaulted() && !Func->isDeleted()) {
+        DefaultedComparisonKind DCK = getDefaultedComparisonKind(Func);
+        if (DCK != DefaultedComparisonKind::None)
+          DefineDefaultedComparison(Loc, Func, DCK);
+      }
+
       // Implicit instantiation of function templates and member functions of
       // class templates.
       if (Func->isImplicitlyInstantiable()) {
@@ -15582,6 +15689,19 @@ void Sema::MarkFunctionReferenced(SourceLocation Loc, FunctionDecl *Func,
     });
   }
 
+  // C++14 [except.spec]p17:
+  //   An exception-specification is considered to be needed when:
+  //   - the function is odr-used or, if it appears in an unevaluated operand,
+  //     would be odr-used if the expression were potentially-evaluated;
+  //
+  // Note, we do this even if MightBeOdrUse is false. That indicates that the
+  // function is a pure virtual function we're calling, and in that case the
+  // function was selected by overload resolution and we need to resolve its
+  // exception specification for a different reason.
+  const FunctionProtoType *FPT = Func->getType()->getAs<FunctionProtoType>();
+  if (FPT && isUnresolvedExceptionSpec(FPT->getExceptionSpecType()))
+    ResolveExceptionSpec(Loc, FPT);
+
   // If this is the first "real" use, act on that.
   if (OdrUse == OdrUseContext::Used && !Func->isUsed(/*CheckUsedAttr=*/false)) {
     // Keep track of used but undefined functions.
@@ -17880,7 +18000,7 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
     // No guarantees that ResolveAndFixSingleFunctionTemplateSpecialization
     // leaves Result unchanged on failure.
     Result = E;
-    if (resolveAndFixAddressOfOnlyViableOverloadCandidate(Result))
+    if (resolveAndFixAddressOfSingleOverloadCandidate(Result))
       return Result;
 
     // If that failed, try to recover with a call.
@@ -18017,3 +18137,8 @@ ExprResult Sema::ActOnObjCAvailabilityCheckExpr(
   return new (Context)
       ObjCAvailabilityCheckExpr(Version, AtLoc, RParen, Context.BoolTy);
 }
+
+bool Sema::IsDependentFunctionNameExpr(Expr *E) {
+  assert(E->isTypeDependent());
+  return isa<UnresolvedLookupExpr>(E);
+}
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 9aae9289b514..a73e6906fceb 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -921,7 +921,7 @@ bool Sema::CheckCXXThrowOperand(SourceLocation ThrowLoc,
       // cannot be a simple walk of the class's decls.  Instead, we must perform
       // lookup and overload resolution.
       CXXConstructorDecl *CD = LookupCopyingConstructor(Subobject, 0);
-      if (!CD)
+      if (!CD || CD->isDeleted())
         continue;
 
       // Mark the constructor referenced as it is used by this throw expression.
@@ -2323,7 +2323,7 @@ static bool resolveAllocationOverload(
           PartialDiagnosticAt(R.getNameLoc(),
                               S.PDiag(diag::err_ovl_ambiguous_call)
                                   << R.getLookupName() << Range),
-          S, OCD_ViableCandidates, Args);
+          S, OCD_AmbiguousCandidates, Args);
     }
     return true;
 
@@ -3513,7 +3513,7 @@ static bool resolveBuiltinNewDeleteOverload(Sema &S, CallExpr *TheCall,
         PartialDiagnosticAt(R.getNameLoc(),
                             S.PDiag(diag::err_ovl_ambiguous_call)
                                 << R.getLookupName() << Range),
-        S, OCD_ViableCandidates, Args);
+        S, OCD_AmbiguousCandidates, Args);
     return true;
 
   case OR_Deleted: {
@@ -4095,9 +4095,26 @@ Sema::PerformImplicitConversion(Expr *From, QualType ToType,
             << From->getSourceRange();
     }
 
+    // Defer address space conversion to the third conversion.
+    QualType FromPteeType = From->getType()->getPointeeType();
+    QualType ToPteeType = ToType->getPointeeType();
+    QualType NewToType = ToType;
+    if (!FromPteeType.isNull() && !ToPteeType.isNull() &&
+        FromPteeType.getAddressSpace() != ToPteeType.getAddressSpace()) {
+      NewToType = Context.removeAddrSpaceQualType(ToPteeType);
+      NewToType = Context.getAddrSpaceQualType(NewToType,
+                                               FromPteeType.getAddressSpace());
+      if (ToType->isObjCObjectPointerType())
+        NewToType = Context.getObjCObjectPointerType(NewToType);
+      else if (ToType->isBlockPointerType())
+        NewToType = Context.getBlockPointerType(NewToType);
+      else
+        NewToType = Context.getPointerType(NewToType);
+    }
+
     CastKind Kind;
     CXXCastPath BasePath;
-    if (CheckPointerConversion(From, ToType, Kind, BasePath, CStyle))
+    if (CheckPointerConversion(From, NewToType, Kind, BasePath, CStyle))
       return ExprError();
 
     // Make sure we extend blocks if necessary.
@@ -4108,8 +4125,8 @@ Sema::PerformImplicitConversion(Expr *From, QualType ToType,
       From = E.get();
     }
     if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers())
-      CheckObjCConversion(SourceRange(), ToType, From, CCK);
-    From = ImpCastExprToType(From, ToType, Kind, VK_RValue, &BasePath, CCK)
+      CheckObjCConversion(SourceRange(), NewToType, From, CCK);
+    From = ImpCastExprToType(From, NewToType, Kind, VK_RValue, &BasePath, CCK)
              .get();
     break;
   }
@@ -5730,38 +5747,157 @@ static bool ConvertForConditional(Sema &Self, ExprResult &E, QualType T) {
   return false;
 }
 
+// Check the condition operand of ?: to see if it is valid for the GCC
+// extension.
+static bool isValidVectorForConditionalCondition(ASTContext &Ctx,
+                                                 QualType CondTy) {
+  if (!CondTy->isVectorType() || CondTy->isExtVectorType())
+    return false;
+  const QualType EltTy =
+      cast<VectorType>(CondTy.getCanonicalType())->getElementType();
+
+  assert(!EltTy->isBooleanType() && !EltTy->isEnumeralType() &&
+         "Vectors cant be boolean or enum types");
+  return EltTy->isIntegralType(Ctx);
+}
+
+QualType Sema::CheckGNUVectorConditionalTypes(ExprResult &Cond, ExprResult &LHS,
+                                              ExprResult &RHS,
+                                              SourceLocation QuestionLoc) {
+  LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
+  RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
+
+  QualType CondType = Cond.get()->getType();
+  const auto *CondVT = CondType->getAs<VectorType>();
+  QualType CondElementTy = CondVT->getElementType();
+  unsigned CondElementCount = CondVT->getNumElements();
+  QualType LHSType = LHS.get()->getType();
+  const auto *LHSVT = LHSType->getAs<VectorType>();
+  QualType RHSType = RHS.get()->getType();
+  const auto *RHSVT = RHSType->getAs<VectorType>();
+
+  QualType ResultType;
+
+  // FIXME: In the future we should define what the Extvector conditional
+  // operator looks like.
+  if (LHSVT && isa<ExtVectorType>(LHSVT)) {
+    Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
+        << /*isExtVector*/ true << LHSType;
+    return {};
+  }
+
+  if (RHSVT && isa<ExtVectorType>(RHSVT)) {
+    Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
+        << /*isExtVector*/ true << RHSType;
+    return {};
+  }
+
+  if (LHSVT && RHSVT) {
+    // If both are vector types, they must be the same type.
+    if (!Context.hasSameType(LHSType, RHSType)) {
+      Diag(QuestionLoc, diag::err_conditional_vector_mismatched_vectors)
+          << LHSType << RHSType;
+      return {};
+    }
+    ResultType = LHSType;
+  } else if (LHSVT || RHSVT) {
+    ResultType = CheckVectorOperands(
+        LHS, RHS, QuestionLoc, /*isCompAssign*/ false, /*AllowBothBool*/ true,
+        /*AllowBoolConversions*/ false);
+    if (ResultType.isNull())
+      return {};
+  } else {
+    // Both are scalar.
+    QualType ResultElementTy;
+    LHSType = LHSType.getCanonicalType().getUnqualifiedType();
+    RHSType = RHSType.getCanonicalType().getUnqualifiedType();
+
+    if (Context.hasSameType(LHSType, RHSType))
+      ResultElementTy = LHSType;
+    else
+      ResultElementTy =
+          UsualArithmeticConversions(LHS, RHS, QuestionLoc, ACK_Conditional);
+
+    if (ResultElementTy->isEnumeralType()) {
+      Diag(QuestionLoc, diag::err_conditional_vector_operand_type)
+          << /*isExtVector*/ false << ResultElementTy;
+      return {};
+    }
+    ResultType = Context.getVectorType(
+        ResultElementTy, CondType->getAs<VectorType>()->getNumElements(),
+        VectorType::GenericVector);
+
+    LHS = ImpCastExprToType(LHS.get(), ResultType, CK_VectorSplat);
+    RHS = ImpCastExprToType(RHS.get(), ResultType, CK_VectorSplat);
+  }
+
+  assert(!ResultType.isNull() && ResultType->isVectorType() &&
+         "Result should have been a vector type");
+  QualType ResultElementTy = ResultType->getAs<VectorType>()->getElementType();
+  unsigned ResultElementCount =
+      ResultType->getAs<VectorType>()->getNumElements();
+
+  if (ResultElementCount != CondElementCount) {
+    Diag(QuestionLoc, diag::err_conditional_vector_size) << CondType
+                                                         << ResultType;
+    return {};
+  }
+
+  if (Context.getTypeSize(ResultElementTy) !=
+      Context.getTypeSize(CondElementTy)) {
+    Diag(QuestionLoc, diag::err_conditional_vector_element_size) << CondType
+                                                                 << ResultType;
+    return {};
+  }
+
+  return ResultType;
+}
+
 /// Check the operands of ?: under C++ semantics.
 ///
 /// See C++ [expr.cond]. Note that LHS is never null, even for the GNU x ?: y
 /// extension. In this case, LHS == Cond. (But they're not aliases.)
+///
+/// This function also implements GCC's vector extension for conditionals.
+///  GCC's vector extension permits the use of a?b:c where the type of
+///  a is that of a integer vector with the same number of elements and
+///  size as the vectors of b and c. If one of either b or c is a scalar
+///  it is implicitly converted to match the type of the vector.
+///  Otherwise the expression is ill-formed. If both b and c are scalars,
+///  then b and c are checked and converted to the type of a if possible.
+///  Unlike the OpenCL ?: operator, the expression is evaluated as
+///  (a[0] != 0 ? b[0] : c[0], .. , a[n] != 0 ? b[n] : c[n]).
 QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
                                            ExprResult &RHS, ExprValueKind &VK,
                                            ExprObjectKind &OK,
                                            SourceLocation QuestionLoc) {
-  // FIXME: Handle C99's complex types, vector types, block pointers and Obj-C++
-  // interface pointers.
+  // FIXME: Handle C99's complex types, block pointers and Obj-C++ interface
+  // pointers.
+
+  // Assume r-value.
+  VK = VK_RValue;
+  OK = OK_Ordinary;
+  bool IsVectorConditional =
+      isValidVectorForConditionalCondition(Context, Cond.get()->getType());
 
   // C++11 [expr.cond]p1
   //   The first expression is contextually converted to bool.
-  //
-  // FIXME; GCC's vector extension permits the use of a?b:c where the type of
-  //        a is that of a integer vector with the same number of elements and
-  //        size as the vectors of b and c. If one of either b or c is a scalar
-  //        it is implicitly converted to match the type of the vector.
-  //        Otherwise the expression is ill-formed. If both b and c are scalars,
-  //        then b and c are checked and converted to the type of a if possible.
-  //        Unlike the OpenCL ?: operator, the expression is evaluated as
-  //        (a[0] != 0 ? b[0] : c[0], .. , a[n] != 0 ? b[n] : c[n]).
   if (!Cond.get()->isTypeDependent()) {
-    ExprResult CondRes = CheckCXXBooleanCondition(Cond.get());
+    ExprResult CondRes = IsVectorConditional
+                             ? DefaultFunctionArrayLvalueConversion(Cond.get())
+                             : CheckCXXBooleanCondition(Cond.get());
     if (CondRes.isInvalid())
       return QualType();
     Cond = CondRes;
+  } else {
+    // To implement C++, the first expression typically doesn't alter the result
+    // type of the conditional, however the GCC compatible vector extension
+    // changes the result type to be that of the conditional. Since we cannot
+    // know if this is a vector extension here, delay the conversion of the
+    // LHS/RHS below until later.
+    return Context.DependentTy;
   }
 
-  // Assume r-value.
-  VK = VK_RValue;
-  OK = OK_Ordinary;
 
   // Either of the arguments dependent?
   if (LHS.get()->isTypeDependent() || RHS.get()->isTypeDependent())
@@ -5780,6 +5916,17 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
     //      and value category of the other.
     bool LThrow = isa<CXXThrowExpr>(LHS.get()->IgnoreParenImpCasts());
     bool RThrow = isa<CXXThrowExpr>(RHS.get()->IgnoreParenImpCasts());
+
+    // Void expressions aren't legal in the vector-conditional expressions.
+    if (IsVectorConditional) {
+      SourceRange DiagLoc =
+          LVoid ? LHS.get()->getSourceRange() : RHS.get()->getSourceRange();
+      bool IsThrow = LVoid ? LThrow : RThrow;
+      Diag(DiagLoc.getBegin(), diag::err_conditional_vector_has_void)
+          << DiagLoc << IsThrow;
+      return QualType();
+    }
+
     if (LThrow != RThrow) {
       Expr *NonThrow = LThrow ? RHS.get() : LHS.get();
       VK = NonThrow->getValueKind();
@@ -5802,6 +5949,8 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
   }
 
   // Neither is void.
+  if (IsVectorConditional)
+    return CheckGNUVectorConditionalTypes(Cond, LHS, RHS, QuestionLoc);
 
   // C++11 [expr.cond]p3
   //   Otherwise, if the second and third operand have different types, and
@@ -5845,29 +5994,33 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
   // FIXME:
   //   Resolving a defect in P0012R1: we extend this to cover all cases where
   //   one of the operands is reference-compatible with the other, in order
-  //   to support conditionals between functions differing in noexcept.
+  //   to support conditionals between functions differing in noexcept. This
+  //   will similarly cover difference in array bounds after P0388R4.
+  // FIXME: If LTy and RTy have a composite pointer type, should we convert to
+  //   that instead?
   ExprValueKind LVK = LHS.get()->getValueKind();
   ExprValueKind RVK = RHS.get()->getValueKind();
   if (!Context.hasSameType(LTy, RTy) &&
       LVK == RVK && LVK != VK_RValue) {
     // DerivedToBase was already handled by the class-specific case above.
     // FIXME: Should we allow ObjC conversions here?
-    bool DerivedToBase, ObjCConversion, ObjCLifetimeConversion,
-        FunctionConversion;
-    if (CompareReferenceRelationship(QuestionLoc, LTy, RTy, DerivedToBase,
-                                     ObjCConversion, ObjCLifetimeConversion,
-                                     FunctionConversion) == Ref_Compatible &&
-        !DerivedToBase && !ObjCConversion && !ObjCLifetimeConversion &&
+    const ReferenceConversions AllowedConversions =
+        ReferenceConversions::Qualification |
+        ReferenceConversions::NestedQualification |
+        ReferenceConversions::Function;
+
+    ReferenceConversions RefConv;
+    if (CompareReferenceRelationship(QuestionLoc, LTy, RTy, &RefConv) ==
+            Ref_Compatible &&
+        !(RefConv & ~AllowedConversions) &&
         // [...] subject to the constraint that the reference must bind
         // directly [...]
         !RHS.get()->refersToBitField() && !RHS.get()->refersToVectorElement()) {
       RHS = ImpCastExprToType(RHS.get(), LTy, CK_NoOp, RVK);
       RTy = RHS.get()->getType();
-    } else if (CompareReferenceRelationship(
-                   QuestionLoc, RTy, LTy, DerivedToBase, ObjCConversion,
-                   ObjCLifetimeConversion,
-                   FunctionConversion) == Ref_Compatible &&
-               !DerivedToBase && !ObjCConversion && !ObjCLifetimeConversion &&
+    } else if (CompareReferenceRelationship(QuestionLoc, RTy, LTy, &RefConv) ==
+                   Ref_Compatible &&
+               !(RefConv & ~AllowedConversions) &&
                !LHS.get()->refersToBitField() &&
                !LHS.get()->refersToVectorElement()) {
       LHS = ImpCastExprToType(LHS.get(), RTy, CK_NoOp, LVK);
@@ -5976,7 +6129,8 @@ QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
   //      the usual arithmetic conversions are performed to bring them to a
   //      common type, and the result is of that type.
   if (LTy->isArithmeticType() && RTy->isArithmeticType()) {
-    QualType ResTy = UsualArithmeticConversions(LHS, RHS);
+    QualType ResTy =
+        UsualArithmeticConversions(LHS, RHS, QuestionLoc, ACK_Conditional);
     if (LHS.isInvalid() || RHS.isInvalid())
       return QualType();
     if (ResTy.isNull()) {
@@ -6098,10 +6252,10 @@ mergeExceptionSpecs(Sema &S, FunctionProtoType::ExceptionSpecInfo ESI1,
 
 /// Find a merged pointer type and convert the two expressions to it.
 ///
-/// This finds the composite pointer type (or member pointer type) for @p E1
-/// and @p E2 according to C++1z 5p14. It converts both expressions to this
-/// type and returns it.
-/// It does not emit diagnostics.
+/// This finds the composite pointer type for \p E1 and \p E2 according to
+/// C++2a [expr.type]p3. It converts both expressions to this type and returns
+/// it.  It does not emit diagnostics (FIXME: that's not true if \p ConvertArgs
+/// is \c true).
 ///
 /// \param Loc The location of the operator requiring these two expressions to
 /// be converted to the composite pointer type.
@@ -6154,60 +6308,117 @@ QualType Sema::FindCompositePointerType(SourceLocation Loc,
   assert(!T1->isNullPtrType() && !T2->isNullPtrType() &&
          "nullptr_t should be a null pointer constant");
 
-  //  - if T1 or T2 is "pointer to cv1 void" and the other type is
-  //    "pointer to cv2 T", "pointer to cv12 void", where cv12 is
-  //    the union of cv1 and cv2;
-  //  - if T1 or T2 is "pointer to noexcept function" and the other type is
-  //    "pointer to function", where the function types are otherwise the same,
-  //    "pointer to function";
-  //     FIXME: This rule is defective: it should also permit removing noexcept
-  //     from a pointer to member function.  As a Clang extension, we also
-  //     permit removing 'noreturn', so we generalize this rule to;
-  //     - [Clang] If T1 and T2 are both of type "pointer to function" or
-  //       "pointer to member function" and the pointee types can be unified
-  //       by a function pointer conversion, that conversion is applied
-  //       before checking the following rules.
+  struct Step {
+    enum Kind { Pointer, ObjCPointer, MemberPointer, Array } K;
+    // Qualifiers to apply under the step kind.
+    Qualifiers Quals;
+    /// The class for a pointer-to-member; a constant array type with a bound
+    /// (if any) for an array.
+    const Type *ClassOrBound;
+
+    Step(Kind K, const Type *ClassOrBound = nullptr)
+        : K(K), Quals(), ClassOrBound(ClassOrBound) {}
+    QualType rebuild(ASTContext &Ctx, QualType T) const {
+      T = Ctx.getQualifiedType(T, Quals);
+      switch (K) {
+      case Pointer:
+        return Ctx.getPointerType(T);
+      case MemberPointer:
+        return Ctx.getMemberPointerType(T, ClassOrBound);
+      case ObjCPointer:
+        return Ctx.getObjCObjectPointerType(T);
+      case Array:
+        if (auto *CAT = cast_or_null<ConstantArrayType>(ClassOrBound))
+          return Ctx.getConstantArrayType(T, CAT->getSize(), nullptr,
+                                          ArrayType::Normal, 0);
+        else
+          return Ctx.getIncompleteArrayType(T, ArrayType::Normal, 0);
+      }
+      llvm_unreachable("unknown step kind");
+    }
+  };
+
+  SmallVector<Step, 8> Steps;
+
   //  - if T1 is "pointer to cv1 C1" and T2 is "pointer to cv2 C2", where C1
   //    is reference-related to C2 or C2 is reference-related to C1 (8.6.3),
   //    the cv-combined type of T1 and T2 or the cv-combined type of T2 and T1,
   //    respectively;
   //  - if T1 is "pointer to member of C1 of type cv1 U1" and T2 is "pointer
-  //    to member of C2 of type cv2 U2" where C1 is reference-related to C2 or
-  //    C2 is reference-related to C1 (8.6.3), the cv-combined type of T2 and
-  //    T1 or the cv-combined type of T1 and T2, respectively;
+  //    to member of C2 of type cv2 U2" for some non-function type U, where
+  //    C1 is reference-related to C2 or C2 is reference-related to C1, the
+  //    cv-combined type of T2 and T1 or the cv-combined type of T1 and T2,
+  //    respectively;
   //  - if T1 and T2 are similar types (4.5), the cv-combined type of T1 and
   //    T2;
   //
-  // If looked at in the right way, these bullets all do the same thing.
-  // What we do here is, we build the two possible cv-combined types, and try
-  // the conversions in both directions. If only one works, or if the two
-  // composite types are the same, we have succeeded.
-  // FIXME: extended qualifiers?
-  //
-  // Note that this will fail to find a composite pointer type for "pointer
-  // to void" and "pointer to function". We can't actually perform the final
-  // conversion in this case, even though a composite pointer type formally
-  // exists.
-  SmallVector<unsigned, 4> QualifierUnion;
-  SmallVector<std::pair<const Type *, const Type *>, 4> MemberOfClass;
+  // Dismantle T1 and T2 to simultaneously determine whether they are similar
+  // and to prepare to form the cv-combined type if so.
   QualType Composite1 = T1;
   QualType Composite2 = T2;
   unsigned NeedConstBefore = 0;
   while (true) {
+    assert(!Composite1.isNull() && !Composite2.isNull());
+
+    Qualifiers Q1, Q2;
+    Composite1 = Context.getUnqualifiedArrayType(Composite1, Q1);
+    Composite2 = Context.getUnqualifiedArrayType(Composite2, Q2);
+
+    // Top-level qualifiers are ignored. Merge at all lower levels.
+    if (!Steps.empty()) {
+      // Find the qualifier union: (approximately) the unique minimal set of
+      // qualifiers that is compatible with both types.
+      Qualifiers Quals = Qualifiers::fromCVRUMask(Q1.getCVRUQualifiers() |
+                                                  Q2.getCVRUQualifiers());
+
+      // Under one level of pointer or pointer-to-member, we can change to an
+      // unambiguous compatible address space.
+      if (Q1.getAddressSpace() == Q2.getAddressSpace()) {
+        Quals.setAddressSpace(Q1.getAddressSpace());
+      } else if (Steps.size() == 1) {
+        bool MaybeQ1 = Q1.isAddressSpaceSupersetOf(Q2);
+        bool MaybeQ2 = Q2.isAddressSpaceSupersetOf(Q1);
+        if (MaybeQ1 == MaybeQ2)
+          return QualType(); // No unique best address space.
+        Quals.setAddressSpace(MaybeQ1 ? Q1.getAddressSpace()
+                                      : Q2.getAddressSpace());
+      } else {
+        return QualType();
+      }
+
+      // FIXME: In C, we merge __strong and none to __strong at the top level.
+      if (Q1.getObjCGCAttr() == Q2.getObjCGCAttr())
+        Quals.setObjCGCAttr(Q1.getObjCGCAttr());
+      else
+        return QualType();
+
+      // Mismatched lifetime qualifiers never compatibly include each other.
+      if (Q1.getObjCLifetime() == Q2.getObjCLifetime())
+        Quals.setObjCLifetime(Q1.getObjCLifetime());
+      else
+        return QualType();
+
+      Steps.back().Quals = Quals;
+      if (Q1 != Quals || Q2 != Quals)
+        NeedConstBefore = Steps.size() - 1;
+    }
+
+    // FIXME: Can we unify the following with UnwrapSimilarTypes?
     const PointerType *Ptr1, *Ptr2;
     if ((Ptr1 = Composite1->getAs<PointerType>()) &&
         (Ptr2 = Composite2->getAs<PointerType>())) {
       Composite1 = Ptr1->getPointeeType();
       Composite2 = Ptr2->getPointeeType();
+      Steps.emplace_back(Step::Pointer);
+      continue;
+    }
 
-      // If we're allowed to create a non-standard composite type, keep track
-      // of where we need to fill in additional 'const' qualifiers.
-      if (Composite1.getCVRQualifiers() != Composite2.getCVRQualifiers())
-        NeedConstBefore = QualifierUnion.size();
-
-      QualifierUnion.push_back(
-                 Composite1.getCVRQualifiers() | Composite2.getCVRQualifiers());
-      MemberOfClass.push_back(std::make_pair(nullptr, nullptr));
+    const ObjCObjectPointerType *ObjPtr1, *ObjPtr2;
+    if ((ObjPtr1 = Composite1->getAs<ObjCObjectPointerType>()) &&
+        (ObjPtr2 = Composite2->getAs<ObjCObjectPointerType>())) {
+      Composite1 = ObjPtr1->getPointeeType();
+      Composite2 = ObjPtr2->getPointeeType();
+      Steps.emplace_back(Step::ObjCPointer);
       continue;
     }
 
@@ -6217,34 +6428,79 @@ QualType Sema::FindCompositePointerType(SourceLocation Loc,
       Composite1 = MemPtr1->getPointeeType();
       Composite2 = MemPtr2->getPointeeType();
 
-      // If we're allowed to create a non-standard composite type, keep track
-      // of where we need to fill in additional 'const' qualifiers.
-      if (Composite1.getCVRQualifiers() != Composite2.getCVRQualifiers())
-        NeedConstBefore = QualifierUnion.size();
+      // At the top level, we can perform a base-to-derived pointer-to-member
+      // conversion:
+      //
+      //  - [...] where C1 is reference-related to C2 or C2 is
+      //    reference-related to C1
+      //
+      // (Note that the only kinds of reference-relatedness in scope here are
+      // "same type or derived from".) At any other level, the class must
+      // exactly match.
+      const Type *Class = nullptr;
+      QualType Cls1(MemPtr1->getClass(), 0);
+      QualType Cls2(MemPtr2->getClass(), 0);
+      if (Context.hasSameType(Cls1, Cls2))
+        Class = MemPtr1->getClass();
+      else if (Steps.empty())
+        Class = IsDerivedFrom(Loc, Cls1, Cls2) ? MemPtr1->getClass() :
+                IsDerivedFrom(Loc, Cls2, Cls1) ? MemPtr2->getClass() : nullptr;
+      if (!Class)
+        return QualType();
 
-      QualifierUnion.push_back(
-                 Composite1.getCVRQualifiers() | Composite2.getCVRQualifiers());
-      MemberOfClass.push_back(std::make_pair(MemPtr1->getClass(),
-                                             MemPtr2->getClass()));
+      Steps.emplace_back(Step::MemberPointer, Class);
       continue;
     }
 
+    // Special case: at the top level, we can decompose an Objective-C pointer
+    // and a 'cv void *'. Unify the qualifiers.
+    if (Steps.empty() && ((Composite1->isVoidPointerType() &&
+                           Composite2->isObjCObjectPointerType()) ||
+                          (Composite1->isObjCObjectPointerType() &&
+                           Composite2->isVoidPointerType()))) {
+      Composite1 = Composite1->getPointeeType();
+      Composite2 = Composite2->getPointeeType();
+      Steps.emplace_back(Step::Pointer);
+      continue;
+    }
+
+    // FIXME: arrays
+
     // FIXME: block pointer types?
 
     // Cannot unwrap any more types.
     break;
   }
 
-  // Apply the function pointer conversion to unify the types. We've already
-  // unwrapped down to the function types, and we want to merge rather than
-  // just convert, so do this ourselves rather than calling
+  //  - if T1 or T2 is "pointer to noexcept function" and the other type is
+  //    "pointer to function", where the function types are otherwise the same,
+  //    "pointer to function";
+  //  - if T1 or T2 is "pointer to member of C1 of type function", the other
+  //    type is "pointer to member of C2 of type noexcept function", and C1
+  //    is reference-related to C2 or C2 is reference-related to C1, where
+  //    the function types are otherwise the same, "pointer to member of C2 of
+  //    type function" or "pointer to member of C1 of type function",
+  //    respectively;
+  //
+  // We also support 'noreturn' here, so as a Clang extension we generalize the
+  // above to:
+  //
+  //  - [Clang] If T1 and T2 are both of type "pointer to function" or
+  //    "pointer to member function" and the pointee types can be unified
+  //    by a function pointer conversion, that conversion is applied
+  //    before checking the following rules.
+  //
+  // We've already unwrapped down to the function types, and we want to merge
+  // rather than just convert, so do this ourselves rather than calling
   // IsFunctionConversion.
   //
   // FIXME: In order to match the standard wording as closely as possible, we
   // currently only do this under a single level of pointers. Ideally, we would
   // allow this in general, and set NeedConstBefore to the relevant depth on
-  // the side(s) where we changed anything.
-  if (QualifierUnion.size() == 1) {
+  // the side(s) where we changed anything. If we permit that, we should also
+  // consider this conversion when determining type similarity and model it as
+  // a qualification conversion.
+  if (Steps.size() == 1) {
     if (auto *FPT1 = Composite1->getAs<FunctionProtoType>()) {
       if (auto *FPT2 = Composite2->getAs<FunctionProtoType>()) {
         FunctionProtoType::ExtProtoInfo EPI1 = FPT1->getExtProtoInfo();
@@ -6270,88 +6526,72 @@ QualType Sema::FindCompositePointerType(SourceLocation Loc,
     }
   }
 
-  if (NeedConstBefore) {
-    // Extension: Add 'const' to qualifiers that come before the first qualifier
-    // mismatch, so that our (non-standard!) composite type meets the
-    // requirements of C++ [conv.qual]p4 bullet 3.
-    for (unsigned I = 0; I != NeedConstBefore; ++I)
-      if ((QualifierUnion[I] & Qualifiers::Const) == 0)
-        QualifierUnion[I] = QualifierUnion[I] | Qualifiers::Const;
+  // There are some more conversions we can perform under exactly one pointer.
+  if (Steps.size() == 1 && Steps.front().K == Step::Pointer &&
+      !Context.hasSameType(Composite1, Composite2)) {
+    //  - if T1 or T2 is "pointer to cv1 void" and the other type is
+    //    "pointer to cv2 T", where T is an object type or void,
+    //    "pointer to cv12 void", where cv12 is the union of cv1 and cv2;
+    if (Composite1->isVoidType() && Composite2->isObjectType())
+      Composite2 = Composite1;
+    else if (Composite2->isVoidType() && Composite1->isObjectType())
+      Composite1 = Composite2;
+    //  - if T1 is "pointer to cv1 C1" and T2 is "pointer to cv2 C2", where C1
+    //    is reference-related to C2 or C2 is reference-related to C1 (8.6.3),
+    //    the cv-combined type of T1 and T2 or the cv-combined type of T2 and
+    //    T1, respectively;
+    //
+    // The "similar type" handling covers all of this except for the "T1 is a
+    // base class of T2" case in the definition of reference-related.
+    else if (IsDerivedFrom(Loc, Composite1, Composite2))
+      Composite1 = Composite2;
+    else if (IsDerivedFrom(Loc, Composite2, Composite1))
+      Composite2 = Composite1;
   }
 
-  // Rewrap the composites as pointers or member pointers with the union CVRs.
-  auto MOC = MemberOfClass.rbegin();
-  for (unsigned CVR : llvm::reverse(QualifierUnion)) {
-    Qualifiers Quals = Qualifiers::fromCVRMask(CVR);
-    auto Classes = *MOC++;
-    if (Classes.first && Classes.second) {
-      // Rebuild member pointer type
-      Composite1 = Context.getMemberPointerType(
-          Context.getQualifiedType(Composite1, Quals), Classes.first);
-      Composite2 = Context.getMemberPointerType(
-          Context.getQualifiedType(Composite2, Quals), Classes.second);
-    } else {
-      // Rebuild pointer type
-      Composite1 =
-          Context.getPointerType(Context.getQualifiedType(Composite1, Quals));
-      Composite2 =
-          Context.getPointerType(Context.getQualifiedType(Composite2, Quals));
-    }
-  }
-
-  struct Conversion {
-    Sema &S;
-    Expr *&E1, *&E2;
-    QualType Composite;
-    InitializedEntity Entity;
-    InitializationKind Kind;
-    InitializationSequence E1ToC, E2ToC;
-    bool Viable;
-
-    Conversion(Sema &S, SourceLocation Loc, Expr *&E1, Expr *&E2,
-               QualType Composite)
-        : S(S), E1(E1), E2(E2), Composite(Composite),
-          Entity(InitializedEntity::InitializeTemporary(Composite)),
-          Kind(InitializationKind::CreateCopy(Loc, SourceLocation())),
-          E1ToC(S, Entity, Kind, E1), E2ToC(S, Entity, Kind, E2),
-          Viable(E1ToC && E2ToC) {}
-
-    bool perform() {
-      ExprResult E1Result = E1ToC.Perform(S, Entity, Kind, E1);
-      if (E1Result.isInvalid())
-        return true;
-      E1 = E1Result.getAs<Expr>();
+  // At this point, either the inner types are the same or we have failed to
+  // find a composite pointer type.
+  if (!Context.hasSameType(Composite1, Composite2))
+    return QualType();
 
-      ExprResult E2Result = E2ToC.Perform(S, Entity, Kind, E2);
-      if (E2Result.isInvalid())
-        return true;
-      E2 = E2Result.getAs<Expr>();
+  // Per C++ [conv.qual]p3, add 'const' to every level before the last
+  // differing qualifier.
+  for (unsigned I = 0; I != NeedConstBefore; ++I)
+    Steps[I].Quals.addConst();
 
-      return false;
-    }
-  };
+  // Rebuild the composite type.
+  QualType Composite = Composite1;
+  for (auto &S : llvm::reverse(Steps))
+    Composite = S.rebuild(Context, Composite);
 
-  // Try to convert to each composite pointer type.
-  Conversion C1(*this, Loc, E1, E2, Composite1);
-  if (C1.Viable && Context.hasSameType(Composite1, Composite2)) {
-    if (ConvertArgs && C1.perform())
+  if (ConvertArgs) {
+    // Convert the expressions to the composite pointer type.
+    InitializedEntity Entity =
+        InitializedEntity::InitializeTemporary(Composite);
+    InitializationKind Kind =
+        InitializationKind::CreateCopy(Loc, SourceLocation());
+
+    InitializationSequence E1ToC(*this, Entity, Kind, E1);
+    if (!E1ToC)
       return QualType();
-    return C1.Composite;
-  }
-  Conversion C2(*this, Loc, E1, E2, Composite2);
 
-  if (C1.Viable == C2.Viable) {
-    // Either Composite1 and Composite2 are viable and are different, or
-    // neither is viable.
-    // FIXME: How both be viable and different?
-    return QualType();
-  }
+    InitializationSequence E2ToC(*this, Entity, Kind, E2);
+    if (!E2ToC)
+      return QualType();
 
-  // Convert to the chosen type.
-  if (ConvertArgs && (C1.Viable ? C1 : C2).perform())
-    return QualType();
+    // FIXME: Let the caller know if these fail to avoid duplicate diagnostics.
+    ExprResult E1Result = E1ToC.Perform(*this, Entity, Kind, E1);
+    if (E1Result.isInvalid())
+      return QualType();
+    E1 = E1Result.get();
+
+    ExprResult E2Result = E2ToC.Perform(*this, Entity, Kind, E2);
+    if (E2Result.isInvalid())
+      return QualType();
+    E2 = E2Result.get();
+  }
 
-  return C1.Viable ? C1.Composite : C2.Composite;
+  return Composite;
 }
 
 ExprResult Sema::MaybeBindToTemporary(Expr *E) {
@@ -7780,8 +8020,9 @@ class TransformTypos : public TreeTransform<TransformTypos> {
 
     // If we found a valid result, double check to make sure it's not ambiguous.
     if (!IsAmbiguous && !Res.isInvalid() && !AmbiguousTypoExprs.empty()) {
-      auto SavedTransformCache = std::move(TransformCache);
-      TransformCache.clear();
+      auto SavedTransformCache =
+          llvm::SmallDenseMap<TypoExpr *, ExprResult, 2>(TransformCache);
+
       // Ensure none of the TypoExprs have multiple typo correction candidates
       // with the same edit length that pass all the checks and filters.
       while (!AmbiguousTypoExprs.empty()) {
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index 87114a0fac63..ebfc1ec4b974 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -919,6 +919,18 @@ MemberExpr *Sema::BuildMemberExpr(
                          VK, OK, getNonOdrUseReasonInCurrentContext(Member));
   E->setHadMultipleCandidates(HadMultipleCandidates);
   MarkMemberReferenced(E);
+
+  // C++ [except.spec]p17:
+  //   An exception-specification is considered to be needed when:
+  //   - in an expression the function is the unique lookup result or the
+  //     selected member of a set of overloaded functions
+  if (auto *FPT = Ty->getAs<FunctionProtoType>()) {
+    if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
+      if (auto *NewFPT = ResolveExceptionSpec(MemberNameInfo.getLoc(), FPT))
+        E->setType(Context.getQualifiedType(NewFPT, Ty.getQualifiers()));
+    }
+  }
+
   return E;
 }
 
diff --git a/clang/lib/Sema/SemaExprObjC.cpp b/clang/lib/Sema/SemaExprObjC.cpp
index e18621e42a6b..c61b13cf5980 100644
--- a/clang/lib/Sema/SemaExprObjC.cpp
+++ b/clang/lib/Sema/SemaExprObjC.cpp
@@ -10,13 +10,13 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/Sema/SemaInternal.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Analysis/DomainSpecific/CocoaConventions.h"
+#include "clang/Basic/Builtins.h"
 #include "clang/Edit/Commit.h"
 #include "clang/Edit/Rewriters.h"
 #include "clang/Lex/Preprocessor.h"
@@ -24,6 +24,7 @@
 #include "clang/Sema/Lookup.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/ScopeInfo.h"
+#include "clang/Sema/SemaInternal.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Support/ConvertUTF.h"
 
@@ -288,6 +289,7 @@ static ObjCMethodDecl *getNSNumberFactoryMethod(Sema &S, SourceLocation Loc,
                                S.NSNumberPointer, ReturnTInfo, S.NSNumberDecl,
                                /*isInstance=*/false, /*isVariadic=*/false,
                                /*isPropertyAccessor=*/false,
+                               /*isSynthesizedAccessorStub=*/false,
                                /*isImplicitlyDeclared=*/true,
                                /*isDefined=*/false, ObjCMethodDecl::Required,
                                /*HasRelatedResultType=*/false);
@@ -563,6 +565,7 @@ ExprResult Sema::BuildObjCBoxedExpr(SourceRange SR, Expr *ValueExpr) {
               NSStringPointer, ReturnTInfo, NSStringDecl,
               /*isInstance=*/false, /*isVariadic=*/false,
               /*isPropertyAccessor=*/false,
+              /*isSynthesizedAccessorStub=*/false,
               /*isImplicitlyDeclared=*/true,
               /*isDefined=*/false, ObjCMethodDecl::Required,
               /*HasRelatedResultType=*/false);
@@ -671,20 +674,15 @@ ExprResult Sema::BuildObjCBoxedExpr(SourceRange SR, Expr *ValueExpr) {
         // Debugger needs to work even if NSValue hasn't been defined.
         TypeSourceInfo *ReturnTInfo = nullptr;
         ObjCMethodDecl *M = ObjCMethodDecl::Create(
-                                               Context,
-                                               SourceLocation(),
-                                               SourceLocation(),
-                                               ValueWithBytesObjCType,
-                                               NSValuePointer,
-                                               ReturnTInfo,
-                                               NSValueDecl,
-                                               /*isInstance=*/false,
-                                               /*isVariadic=*/false,
-                                               /*isPropertyAccessor=*/false,
-                                               /*isImplicitlyDeclared=*/true,
-                                               /*isDefined=*/false,
-                                               ObjCMethodDecl::Required,
-                                               /*HasRelatedResultType=*/false);
+            Context, SourceLocation(), SourceLocation(), ValueWithBytesObjCType,
+            NSValuePointer, ReturnTInfo, NSValueDecl,
+            /*isInstance=*/false,
+            /*isVariadic=*/false,
+            /*isPropertyAccessor=*/false,
+            /*isSynthesizedAccessorStub=*/false,
+            /*isImplicitlyDeclared=*/true,
+            /*isDefined=*/false, ObjCMethodDecl::Required,
+            /*HasRelatedResultType=*/false);
 
         SmallVector<ParmVarDecl *, 2> Params;
 
@@ -815,7 +813,7 @@ ExprResult Sema::BuildObjCArrayLiteral(SourceRange SR, MultiExprArg Elements) {
           Context, SourceLocation(), SourceLocation(), Sel, IdT, ReturnTInfo,
           Context.getTranslationUnitDecl(), false /*Instance*/,
           false /*isVariadic*/,
-          /*isPropertyAccessor=*/false,
+          /*isPropertyAccessor=*/false, /*isSynthesizedAccessorStub=*/false,
           /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
           ObjCMethodDecl::Required, false);
       SmallVector<ParmVarDecl *, 2> Params;
@@ -916,16 +914,14 @@ ExprResult Sema::BuildObjCDictionaryLiteral(SourceRange SR,
                                NSAPI::NSDict_dictionaryWithObjectsForKeysCount);
     ObjCMethodDecl *Method = NSDictionaryDecl->lookupClassMethod(Sel);
     if (!Method && getLangOpts().DebuggerObjCLiteral) {
-      Method = ObjCMethodDecl::Create(Context,
-                           SourceLocation(), SourceLocation(), Sel,
-                           IdT,
-                           nullptr /*TypeSourceInfo */,
-                           Context.getTranslationUnitDecl(),
-                           false /*Instance*/, false/*isVariadic*/,
-                           /*isPropertyAccessor=*/false,
-                           /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
-                           ObjCMethodDecl::Required,
-                           false);
+      Method = ObjCMethodDecl::Create(
+          Context, SourceLocation(), SourceLocation(), Sel, IdT,
+          nullptr /*TypeSourceInfo */, Context.getTranslationUnitDecl(),
+          false /*Instance*/, false /*isVariadic*/,
+          /*isPropertyAccessor=*/false,
+          /*isSynthesizedAccessorStub=*/false,
+          /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
+          ObjCMethodDecl::Required, false);
       SmallVector<ParmVarDecl *, 3> Params;
       ParmVarDecl *objects = ParmVarDecl::Create(Context, Method,
                                                  SourceLocation(),
@@ -1174,6 +1170,35 @@ static void DiagnoseMismatchedSelectors(Sema &S, SourceLocation AtLoc,
   }
 }
 
+static void HelperToDiagnoseDirectSelectorsExpr(Sema &S, SourceLocation AtLoc,
+                                                Selector Sel,
+                                                ObjCMethodList &MethList,
+                                                bool &onlyDirect) {
+  ObjCMethodList *M = &MethList;
+  for (M = M->getNext(); M; M = M->getNext()) {
+    ObjCMethodDecl *Method = M->getMethod();
+    if (Method->getSelector() != Sel)
+      continue;
+    if (!Method->isDirectMethod())
+      onlyDirect = false;
+  }
+}
+
+static void DiagnoseDirectSelectorsExpr(Sema &S, SourceLocation AtLoc,
+                                        Selector Sel, bool &onlyDirect) {
+  for (Sema::GlobalMethodPool::iterator b = S.MethodPool.begin(),
+       e = S.MethodPool.end(); b != e; b++) {
+    // first, instance methods
+    ObjCMethodList &InstMethList = b->second.first;
+    HelperToDiagnoseDirectSelectorsExpr(S, AtLoc, Sel, InstMethList,
+                                        onlyDirect);
+
+    // second, class methods
+    ObjCMethodList &ClsMethList = b->second.second;
+    HelperToDiagnoseDirectSelectorsExpr(S, AtLoc, Sel, ClsMethList, onlyDirect);
+  }
+}
+
 ExprResult Sema::ParseObjCSelectorExpression(Selector Sel,
                                              SourceLocation AtLoc,
                                              SourceLocation SelLoc,
@@ -1196,9 +1221,18 @@ ExprResult Sema::ParseObjCSelectorExpression(Selector Sel,
 
     } else
         Diag(SelLoc, diag::warn_undeclared_selector) << Sel;
-  } else
+  } else {
+    bool onlyDirect = Method->isDirectMethod();
+    DiagnoseDirectSelectorsExpr(*this, AtLoc, Sel, onlyDirect);
     DiagnoseMismatchedSelectors(*this, AtLoc, Method, LParenLoc, RParenLoc,
                                 WarnMultipleSelectors);
+    if (onlyDirect) {
+      Diag(AtLoc, diag::err_direct_selector_expression)
+          << Method->getSelector();
+      Diag(Method->getLocation(), diag::note_direct_method_declared_at)
+          << Method->getDeclName();
+    }
+  }
 
   if (Method &&
       Method->getImplementationControl() != ObjCMethodDecl::Optional &&
@@ -1608,15 +1642,14 @@ bool Sema::CheckMessageArgumentTypes(
           << Sel << isClassMessage << SourceRange(SelectorLocs.front(),
                                                 SelectorLocs.back());
       // Find the class to which we are sending this message.
-      if (ReceiverType->isObjCObjectPointerType()) {
-        if (ObjCInterfaceDecl *ThisClass =
-            ReceiverType->getAs<ObjCObjectPointerType>()->getInterfaceDecl()) {
+      if (auto *ObjPT = ReceiverType->getAs<ObjCObjectPointerType>()) {
+        if (ObjCInterfaceDecl *ThisClass = ObjPT->getInterfaceDecl()) {
           Diag(ThisClass->getLocation(), diag::note_receiver_class_declared);
           if (!RecRange.isInvalid())
             if (ThisClass->lookupClassMethod(Sel))
-              Diag(RecRange.getBegin(),diag::note_receiver_expr_here)
-                << FixItHint::CreateReplacement(RecRange,
-                                                ThisClass->getNameAsString());
+              Diag(RecRange.getBegin(), diag::note_receiver_expr_here)
+                  << FixItHint::CreateReplacement(RecRange,
+                                                  ThisClass->getNameAsString());
         }
       }
     }
@@ -2365,7 +2398,6 @@ static void checkFoundationAPI(Sema &S, SourceLocation Loc,
     return;
   QualType Ret = ImpliedMethod->getReturnType();
   if (Ret->isRecordType() || Ret->isVectorType() || Ret->isExtVectorType()) {
-    QualType Ret = ImpliedMethod->getReturnType();
     S.Diag(Loc, diag::warn_objc_unsafe_perform_selector)
         << Method->getSelector()
         << (!Ret->isRecordType()
@@ -2771,9 +2803,6 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
     }
   }
 
-  if (ReceiverType->isObjCIdType() && !isImplicit)
-    Diag(Receiver->getExprLoc(), diag::warn_messaging_unqualified_id);
-
   // There's a somewhat weird interaction here where we assume that we
   // won't actually have a method unless we also don't need to do some
   // of the more detailed type-checking on the receiver.
@@ -2975,6 +3004,30 @@ ExprResult Sema::BuildInstanceMessage(Expr *Receiver,
     (Method && Method->getMethodFamily() == OMF_init)
       ? getEnclosingFunction() : nullptr;
 
+  if (Method && Method->isDirectMethod()) {
+    if (ReceiverType->isObjCIdType() && !isImplicit) {
+      Diag(Receiver->getExprLoc(),
+           diag::err_messaging_unqualified_id_with_direct_method);
+      Diag(Method->getLocation(), diag::note_direct_method_declared_at)
+          << Method->getDeclName();
+    }
+
+    if (ReceiverType->isObjCClassType() && !isImplicit) {
+      Diag(Receiver->getExprLoc(),
+           diag::err_messaging_class_with_direct_method);
+      Diag(Method->getLocation(), diag::note_direct_method_declared_at)
+          << Method->getDeclName();
+    }
+
+    if (SuperLoc.isValid()) {
+      Diag(SuperLoc, diag::err_messaging_super_with_direct_method);
+      Diag(Method->getLocation(), diag::note_direct_method_declared_at)
+          << Method->getDeclName();
+    }
+  } else if (ReceiverType->isObjCIdType() && !isImplicit) {
+    Diag(Receiver->getExprLoc(), diag::warn_messaging_unqualified_id);
+  }
+
   if (DIFunctionScopeInfo &&
       DIFunctionScopeInfo->ObjCIsDesignatedInit &&
       (SuperLoc.isValid() || isSelfExpr(Receiver))) {
@@ -4358,7 +4411,7 @@ Expr *Sema::stripARCUnbridgedCast(Expr *e) {
     SmallVector<TypeSourceInfo *, 4> subTypes;
     subExprs.reserve(n);
     subTypes.reserve(n);
-    for (const GenericSelectionExpr::Association &assoc : gse->associations()) {
+    for (const GenericSelectionExpr::Association assoc : gse->associations()) {
       subTypes.push_back(assoc.getTypeSourceInfo());
       Expr *sub = assoc.getAssociationExpr();
       if (assoc.isSelected())
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 10cb7acad567..785637761e71 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -3877,9 +3877,6 @@ ResolveConstructorOverload(Sema &S, SourceLocation DeclLoc,
     if (!Info.Constructor || Info.Constructor->isInvalidDecl())
       continue;
 
-    if (!AllowExplicit && Info.Constructor->isExplicit())
-      continue;
-
     if (OnlyListConstructors && !S.isInitListConstructor(Info.Constructor))
       continue;
 
@@ -3951,18 +3948,16 @@ ResolveConstructorOverload(Sema &S, SourceLocation DeclLoc,
         else
           Conv = cast<CXXConversionDecl>(D);
 
-        if (AllowExplicit || !Conv->isExplicit()) {
-          if (ConvTemplate)
-            S.AddTemplateConversionCandidate(
-                ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
-                CandidateSet, AllowExplicit, AllowExplicit,
-                /*AllowResultConversion*/ false);
-          else
-            S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
-                                     DestType, CandidateSet, AllowExplicit,
-                                     AllowExplicit,
-                                     /*AllowResultConversion*/ false);
-        }
+        if (ConvTemplate)
+          S.AddTemplateConversionCandidate(
+              ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
+              CandidateSet, AllowExplicit, AllowExplicit,
+              /*AllowResultConversion*/ false);
+        else
+          S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
+                                   DestType, CandidateSet, AllowExplicit,
+                                   AllowExplicit,
+                                   /*AllowResultConversion*/ false);
       }
     }
   }
@@ -4064,7 +4059,7 @@ static void TryConstructorInitialization(Sema &S,
 
     // If the initializer list has no elements and T has a default constructor,
     // the first phase is omitted.
-    if (!(UnwrappedArgs.empty() && DestRecordDecl->hasDefaultConstructor()))
+    if (!(UnwrappedArgs.empty() && S.LookupDefaultConstructor(DestRecordDecl)))
       Result = ResolveConstructorOverload(S, Kind.getLocation(), Args,
                                           CandidateSet, DestType, Ctors, Best,
                                           CopyInitialization, AllowExplicit,
@@ -4229,10 +4224,8 @@ static void TryReferenceListInitialization(Sema &S,
       return;
 
     SourceLocation DeclLoc = Initializer->getBeginLoc();
-    bool dummy1, dummy2, dummy3, dummy4;
     Sema::ReferenceCompareResult RefRelationship
-      = S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2, dummy1,
-                                       dummy2, dummy3, dummy4);
+      = S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2);
     if (RefRelationship >= Sema::Ref_Related) {
       // Try to bind the reference here.
       TryReferenceInitializationCore(S, Entity, Kind, Initializer, cv1T1, T1,
@@ -4350,7 +4343,7 @@ static void TryListInitialization(Sema &S,
       //     value-initialized.
       if (InitList->getNumInits() == 0) {
         CXXRecordDecl *RD = DestType->getAsCXXRecordDecl();
-        if (RD->hasDefaultConstructor()) {
+        if (S.LookupDefaultConstructor(RD)) {
           TryValueInitialization(S, Entity, Kind, Sequence, InitList);
           return;
         }
@@ -4469,18 +4462,8 @@ static OverloadingResult TryRefInitWithConversionFunction(
   QualType cv2T2 = Initializer->getType();
   QualType T2 = cv2T2.getUnqualifiedType();
 
-  bool DerivedToBase;
-  bool ObjCConversion;
-  bool ObjCLifetimeConversion;
-  bool FunctionConversion;
-  assert(!S.CompareReferenceRelationship(
-             Initializer->getBeginLoc(), T1, T2, DerivedToBase, ObjCConversion,
-             ObjCLifetimeConversion, FunctionConversion) &&
+  assert(!S.CompareReferenceRelationship(Initializer->getBeginLoc(), T1, T2) &&
          "Must have incompatible references when binding via conversion");
-  (void)DerivedToBase;
-  (void)ObjCConversion;
-  (void)ObjCLifetimeConversion;
-  (void)FunctionConversion;
 
   // Build the candidate set directly in the initialization sequence
   // structure, so that it will persist if we fail.
@@ -4507,7 +4490,7 @@ static OverloadingResult TryRefInitWithConversionFunction(
         continue;
 
       if (!Info.Constructor->isInvalidDecl() &&
-          Info.Constructor->isConvertingConstructor(AllowExplicitCtors)) {
+          Info.Constructor->isConvertingConstructor(/*AllowExplicit*/true)) {
         if (Info.ConstructorTmpl)
           S.AddTemplateOverloadCandidate(
               Info.ConstructorTmpl, Info.FoundDecl,
@@ -4552,8 +4535,7 @@ static OverloadingResult TryRefInitWithConversionFunction(
       // FIXME: Do we need to make sure that we only consider conversion
       // candidates with reference-compatible results? That might be needed to
       // break recursion.
-      if ((AllowExplicitConvs || !Conv->isExplicit()) &&
-          (AllowRValues ||
+      if ((AllowRValues ||
            Conv->getConversionType()->isLValueReferenceType())) {
         if (ConvTemplate)
           S.AddTemplateConversionCandidate(
@@ -4604,14 +4586,9 @@ static OverloadingResult TryRefInitWithConversionFunction(
 
   // Determine whether we'll need to perform derived-to-base adjustments or
   // other conversions.
-  bool NewDerivedToBase = false;
-  bool NewObjCConversion = false;
-  bool NewObjCLifetimeConversion = false;
-  bool NewFunctionConversion = false;
+  Sema::ReferenceConversions RefConv;
   Sema::ReferenceCompareResult NewRefRelationship =
-      S.CompareReferenceRelationship(
-          DeclLoc, T1, cv3T3, NewDerivedToBase, NewObjCConversion,
-          NewObjCLifetimeConversion, NewFunctionConversion);
+      S.CompareReferenceRelationship(DeclLoc, T1, cv3T3, &RefConv);
 
   // Add the final conversion sequence, if necessary.
   if (NewRefRelationship == Sema::Ref_Incompatible) {
@@ -4641,12 +4618,16 @@ static OverloadingResult TryRefInitWithConversionFunction(
   Sequence.AddReferenceBindingStep(cv1T4, VK == VK_RValue);
   VK = IsLValueRef ? VK_LValue : VK_XValue;
 
-  if (NewDerivedToBase)
+  if (RefConv & Sema::ReferenceConversions::DerivedToBase)
     Sequence.AddDerivedToBaseCastStep(cv1T1, VK);
-  else if (NewObjCConversion)
+  else if (RefConv & Sema::ReferenceConversions::ObjC)
     Sequence.AddObjCObjectConversionStep(cv1T1);
-  else if (NewFunctionConversion)
+  else if (RefConv & Sema::ReferenceConversions::Function)
     Sequence.AddQualificationConversionStep(cv1T1, VK);
+  else if (RefConv & Sema::ReferenceConversions::Qualification) {
+    if (!S.Context.hasSameType(cv1T4, cv1T1))
+      Sequence.AddQualificationConversionStep(cv1T1, VK);
+  }
 
   return OR_Success;
 }
@@ -4700,17 +4681,15 @@ static void TryReferenceInitializationCore(Sema &S,
                                            InitializationSequence &Sequence) {
   QualType DestType = Entity.getType();
   SourceLocation DeclLoc = Initializer->getBeginLoc();
+
   // Compute some basic properties of the types and the initializer.
   bool isLValueRef = DestType->isLValueReferenceType();
   bool isRValueRef = !isLValueRef;
-  bool DerivedToBase = false;
-  bool ObjCConversion = false;
-  bool ObjCLifetimeConversion = false;
-  bool FunctionConversion = false;
   Expr::Classification InitCategory = Initializer->Classify(S.Context);
-  Sema::ReferenceCompareResult RefRelationship = S.CompareReferenceRelationship(
-      DeclLoc, cv1T1, cv2T2, DerivedToBase, ObjCConversion,
-      ObjCLifetimeConversion, FunctionConversion);
+
+  Sema::ReferenceConversions RefConv;
+  Sema::ReferenceCompareResult RefRelationship =
+      S.CompareReferenceRelationship(DeclLoc, cv1T1, cv2T2, &RefConv);
 
   // C++0x [dcl.init.ref]p5:
   //   A reference to type "cv1 T1" is initialized by an expression of type
@@ -4730,19 +4709,25 @@ static void TryReferenceInitializationCore(Sema &S,
           RefRelationship == Sema::Ref_Related))) {
       //   - is an lvalue (but is not a bit-field), and "cv1 T1" is
       //     reference-compatible with "cv2 T2," or
-      if (T1Quals != T2Quals)
-        // Convert to cv1 T2. This should only add qualifiers unless this is a
-        // c-style cast. The removal of qualifiers in that case notionally
-        // happens after the reference binding, but that doesn't matter.
-        Sequence.AddQualificationConversionStep(
-            S.Context.getQualifiedType(T2, T1Quals),
-            Initializer->getValueKind());
-      if (DerivedToBase)
-        Sequence.AddDerivedToBaseCastStep(cv1T1, VK_LValue);
-      else if (ObjCConversion)
-        Sequence.AddObjCObjectConversionStep(cv1T1);
-      else if (FunctionConversion)
-        Sequence.AddQualificationConversionStep(cv1T1, VK_LValue);
+      if (RefConv & (Sema::ReferenceConversions::DerivedToBase |
+                     Sema::ReferenceConversions::ObjC)) {
+        // If we're converting the pointee, add any qualifiers first;
+        // these qualifiers must all be top-level, so just convert to "cv1 T2".
+        if (RefConv & (Sema::ReferenceConversions::Qualification))
+          Sequence.AddQualificationConversionStep(
+              S.Context.getQualifiedType(T2, T1Quals),
+              Initializer->getValueKind());
+        if (RefConv & Sema::ReferenceConversions::DerivedToBase)
+          Sequence.AddDerivedToBaseCastStep(cv1T1, VK_LValue);
+        else
+          Sequence.AddObjCObjectConversionStep(cv1T1);
+      } else if (RefConv & (Sema::ReferenceConversions::Qualification |
+                            Sema::ReferenceConversions::Function)) {
+        // Perform a (possibly multi-level) qualification conversion.
+        // FIXME: Should we use a different step kind for function conversions?
+        Sequence.AddQualificationConversionStep(cv1T1,
+                                                Initializer->getValueKind());
+      }
 
       // We only create a temporary here when binding a reference to a
       // bit-field or vector element. Those cases are't supposed to be
@@ -4873,14 +4858,19 @@ static void TryReferenceInitializationCore(Sema &S,
       T4Quals.addAddressSpace(T1Quals.getAddressSpace());
       QualType cv1T4WithAS = S.Context.getQualifiedType(T2, T4Quals);
       Sequence.AddQualificationConversionStep(cv1T4WithAS, ValueKind);
+      cv1T4 = cv1T4WithAS;
     }
 
     //   In any case, the reference is bound to the resulting glvalue (or to
     //   an appropriate base class subobject).
-    if (DerivedToBase)
+    if (RefConv & Sema::ReferenceConversions::DerivedToBase)
       Sequence.AddDerivedToBaseCastStep(cv1T1, ValueKind);
-    else if (ObjCConversion)
+    else if (RefConv & Sema::ReferenceConversions::ObjC)
       Sequence.AddObjCObjectConversionStep(cv1T1);
+    else if (RefConv & Sema::ReferenceConversions::Qualification) {
+      if (!S.Context.hasSameType(cv1T4, cv1T1))
+        Sequence.AddQualificationConversionStep(cv1T1, ValueKind);
+    }
     return;
   }
 
@@ -5157,7 +5147,7 @@ static void TryUserDefinedConversion(Sema &S,
           continue;
 
         if (!Info.Constructor->isInvalidDecl() &&
-            Info.Constructor->isConvertingConstructor(AllowExplicit)) {
+            Info.Constructor->isConvertingConstructor(/*AllowExplicit*/true)) {
           if (Info.ConstructorTmpl)
             S.AddTemplateOverloadCandidate(
                 Info.ConstructorTmpl, Info.FoundDecl,
@@ -5201,16 +5191,14 @@ static void TryUserDefinedConversion(Sema &S,
         else
           Conv = cast<CXXConversionDecl>(D);
 
-        if (AllowExplicit || !Conv->isExplicit()) {
-          if (ConvTemplate)
-            S.AddTemplateConversionCandidate(
-                ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
-                CandidateSet, AllowExplicit, AllowExplicit);
-          else
-            S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
-                                     DestType, CandidateSet, AllowExplicit,
-                                     AllowExplicit);
-        }
+        if (ConvTemplate)
+          S.AddTemplateConversionCandidate(
+              ConvTemplate, I.getPair(), ActingDC, Initializer, DestType,
+              CandidateSet, AllowExplicit, AllowExplicit);
+        else
+          S.AddConversionCandidate(Conv, I.getPair(), ActingDC, Initializer,
+                                   DestType, CandidateSet, AllowExplicit,
+                                   AllowExplicit);
       }
     }
   }
@@ -6154,7 +6142,7 @@ static ExprResult CopyObject(Sema &S,
                                      << (int)Entity.getKind()
                                      << CurInitExpr->getType()
                                      << CurInitExpr->getSourceRange()),
-        S, OCD_ViableCandidates, CurInitExpr);
+        S, OCD_AmbiguousCandidates, CurInitExpr);
     return ExprError();
 
   case OR_Deleted:
@@ -6295,7 +6283,7 @@ static void CheckCXX98CompatAccessibleCopy(Sema &S,
 
   case OR_Ambiguous:
     CandidateSet.NoteCandidates(PartialDiagnosticAt(Loc, Diag), S,
-                                OCD_ViableCandidates, CurInitExpr);
+                                OCD_AmbiguousCandidates, CurInitExpr);
     break;
 
   case OR_Deleted:
@@ -6653,6 +6641,7 @@ struct IndirectLocalPathEntry {
     VarInit,
     LValToRVal,
     LifetimeBoundCall,
+    GslReferenceInit,
     GslPointerInit
   } Kind;
   Expr *E;
@@ -6783,12 +6772,24 @@ static bool shouldTrackFirstArgument(const FunctionDecl *FD) {
 
 static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
                                     LocalVisitor Visit) {
-  auto VisitPointerArg = [&](const Decl *D, Expr *Arg) {
+  auto VisitPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
     // We are not interested in the temporary base objects of gsl Pointers:
     //   Temp().ptr; // Here ptr might not dangle.
     if (isa<MemberExpr>(Arg->IgnoreImpCasts()))
       return;
-    Path.push_back({IndirectLocalPathEntry::GslPointerInit, Arg, D});
+    // Once we initialized a value with a reference, it can no longer dangle.
+    if (!Value) {
+      for (auto It = Path.rbegin(), End = Path.rend(); It != End; ++It) {
+        if (It->Kind == IndirectLocalPathEntry::GslReferenceInit)
+          continue;
+        if (It->Kind == IndirectLocalPathEntry::GslPointerInit)
+          return;
+        break;
+      }
+    }
+    Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit
+                          : IndirectLocalPathEntry::GslReferenceInit,
+                    Arg, D});
     if (Arg->isGLValue())
       visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
                                             Visit,
@@ -6802,18 +6803,21 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
   if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
     const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());
     if (MD && shouldTrackImplicitObjectArg(MD))
-      VisitPointerArg(MD, MCE->getImplicitObjectArgument());
+      VisitPointerArg(MD, MCE->getImplicitObjectArgument(),
+                      !MD->getReturnType()->isReferenceType());
     return;
   } else if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(Call)) {
     FunctionDecl *Callee = OCE->getDirectCallee();
     if (Callee && Callee->isCXXInstanceMember() &&
         shouldTrackImplicitObjectArg(cast<CXXMethodDecl>(Callee)))
-      VisitPointerArg(Callee, OCE->getArg(0));
+      VisitPointerArg(Callee, OCE->getArg(0),
+                      !Callee->getReturnType()->isReferenceType());
     return;
   } else if (auto *CE = dyn_cast<CallExpr>(Call)) {
     FunctionDecl *Callee = CE->getDirectCallee();
     if (Callee && shouldTrackFirstArgument(Callee))
-      VisitPointerArg(Callee, CE->getArg(0));
+      VisitPointerArg(Callee, CE->getArg(0),
+                      !Callee->getReturnType()->isReferenceType());
     return;
   }
 
@@ -6821,7 +6825,7 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
     const auto *Ctor = CCE->getConstructor();
     const CXXRecordDecl *RD = Ctor->getParent();
     if (CCE->getNumArgs() > 0 && RD->hasAttr<PointerAttr>())
-      VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0]);
+      VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0], true);
   }
 }
 
@@ -6946,8 +6950,8 @@ static void visitLocalsRetainedByReferenceBinding(IndirectLocalPath &Path,
 
   if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(Init)) {
     if (Visit(Path, Local(MTE), RK))
-      visitLocalsRetainedByInitializer(Path, MTE->GetTemporaryExpr(), Visit,
-                                       true, EnableLifetimeWarnings);
+      visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit, true,
+                                       EnableLifetimeWarnings);
   }
 
   if (isa<CallExpr>(Init)) {
@@ -7067,9 +7071,8 @@ static void visitLocalsRetainedByInitializer(IndirectLocalPath &Path,
             }
           } else if (auto *MTE = dyn_cast<MaterializeTemporaryExpr>(L)) {
             if (MTE->getType().isConstQualified())
-              visitLocalsRetainedByInitializer(Path, MTE->GetTemporaryExpr(),
-                                               Visit, true,
-                                               EnableLifetimeWarnings);
+              visitLocalsRetainedByInitializer(Path, MTE->getSubExpr(), Visit,
+                                               true, EnableLifetimeWarnings);
           }
           return false;
         }, EnableLifetimeWarnings);
@@ -7288,6 +7291,7 @@ static SourceRange nextPathEntryRange(const IndirectLocalPath &Path, unsigned I,
     case IndirectLocalPathEntry::AddressOf:
     case IndirectLocalPathEntry::LValToRVal:
     case IndirectLocalPathEntry::LifetimeBoundCall:
+    case IndirectLocalPathEntry::GslReferenceInit:
     case IndirectLocalPathEntry::GslPointerInit:
       // These exist primarily to mark the path as not permitting or
       // supporting lifetime extension.
@@ -7310,7 +7314,8 @@ static bool pathOnlyInitializesGslPointer(IndirectLocalPath &Path) {
       continue;
     if (It->Kind == IndirectLocalPathEntry::AddressOf)
       continue;
-    return It->Kind == IndirectLocalPathEntry::GslPointerInit;
+    return It->Kind == IndirectLocalPathEntry::GslPointerInit ||
+           It->Kind == IndirectLocalPathEntry::GslReferenceInit;
   }
   return false;
 }
@@ -7533,6 +7538,7 @@ void Sema::checkInitializerLifetime(const InitializedEntity &Entity,
 
       case IndirectLocalPathEntry::LifetimeBoundCall:
       case IndirectLocalPathEntry::GslPointerInit:
+      case IndirectLocalPathEntry::GslReferenceInit:
         // FIXME: Consider adding a note for these.
         break;
 
@@ -7835,9 +7841,8 @@ ExprResult InitializationSequence::Perform(Sema &S,
 
   // OpenCL v2.0 s6.13.11.1. atomic variables can be initialized in global scope
   QualType ETy = Entity.getType();
-  Qualifiers TyQualifiers = ETy.getQualifiers();
-  bool HasGlobalAS = TyQualifiers.hasAddressSpace() &&
-                     TyQualifiers.getAddressSpace() == LangAS::opencl_global;
+  bool HasGlobalAS = ETy.hasAddressSpace() &&
+                     ETy.getAddressSpace() == LangAS::opencl_global;
 
   if (S.getLangOpts().OpenCLVersion >= 200 &&
       ETy->isAtomicType() && !HasGlobalAS &&
@@ -8806,7 +8811,7 @@ bool InitializationSequence::Diagnose(Sema &S,
                   : (S.PDiag(diag::err_ref_init_ambiguous)
                      << DestType << OnlyArg->getType()
                      << Args[0]->getSourceRange())),
-          S, OCD_ViableCandidates, Args);
+          S, OCD_AmbiguousCandidates, Args);
       break;
 
     case OR_No_Viable_Function: {
@@ -8906,11 +8911,17 @@ bool InitializationSequence::Diagnose(Sema &S,
       S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
           << NonRefType << SourceType << 1 /*addr space*/
           << Args[0]->getSourceRange();
-    else
+    else if (DroppedQualifiers.hasQualifiers())
       S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
           << NonRefType << SourceType << 0 /*cv quals*/
           << Qualifiers::fromCVRMask(DroppedQualifiers.getCVRQualifiers())
           << DroppedQualifiers.getCVRQualifiers() << Args[0]->getSourceRange();
+    else
+      // FIXME: Consider decomposing the type and explaining which qualifiers
+      // were dropped where, or on which level a 'const' is missing, etc.
+      S.Diag(Kind.getLocation(), diag::err_reference_bind_drops_quals)
+          << NonRefType << SourceType << 2 /*incompatible quals*/
+          << Args[0]->getSourceRange();
     break;
   }
 
@@ -9000,7 +9011,7 @@ bool InitializationSequence::Diagnose(Sema &S,
             PartialDiagnosticAt(Kind.getLocation(),
                                 S.PDiag(diag::err_ovl_ambiguous_init)
                                     << DestType << ArgsRange),
-            S, OCD_ViableCandidates, Args);
+            S, OCD_AmbiguousCandidates, Args);
         break;
 
       case OR_No_Viable_Function:
@@ -9765,9 +9776,8 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
       // C++ [over.match.copy]p1: (non-list copy-initialization from class)
       //   The converting constructors of T are candidate functions.
       if (!AllowExplicit) {
-        // Only consider converting constructors.
-        if (GD->isExplicit())
-          continue;
+        // Overload resolution checks whether the deduction guide is declared
+        // explicit for us.
 
         // When looking for a converting constructor, deduction guides that
         // could never be called with one argument are not interesting to
@@ -9863,7 +9873,7 @@ QualType Sema::DeduceTemplateSpecializationFromInitializer(
             Kind.getLocation(),
             PDiag(diag::err_deduced_class_template_ctor_ambiguous)
                 << TemplateName),
-        *this, OCD_ViableCandidates, Inits);
+        *this, OCD_AmbiguousCandidates, Inits);
     return QualType();
 
   case OR_No_Viable_Function: {
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index c6b19a0b195c..c2d14a44f53d 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -361,7 +361,8 @@ CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
                                            TypeSourceInfo *MethodTypeInfo,
                                            SourceLocation EndLoc,
                                            ArrayRef<ParmVarDecl *> Params,
-                                           ConstexprSpecKind ConstexprKind) {
+                                           ConstexprSpecKind ConstexprKind,
+                                           Expr *TrailingRequiresClause) {
   QualType MethodType = MethodTypeInfo->getType();
   TemplateParameterList *TemplateParams =
       getGenericLambdaTemplateParameterList(getCurLambda(), *this);
@@ -395,7 +396,7 @@ CXXMethodDecl *Sema::startLambdaDefinition(CXXRecordDecl *Class,
       DeclarationNameInfo(MethodName, IntroducerRange.getBegin(),
                           MethodNameLoc),
       MethodType, MethodTypeInfo, SC_None,
-      /*isInline=*/true, ConstexprKind, EndLoc);
+      /*isInline=*/true, ConstexprKind, EndLoc, TrailingRequiresClause);
   Method->setAccess(AS_public);
   if (!TemplateParams)
     Class->addDecl(Method);
@@ -917,6 +918,10 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
         /*IsVariadic=*/false, /*IsCXXMethod=*/true));
     EPI.HasTrailingReturn = true;
     EPI.TypeQuals.addConst();
+    LangAS AS = getDefaultCXXMethodAddrSpace();
+    if (AS != LangAS::Default)
+      EPI.TypeQuals.addAddressSpace(AS);
+
     // C++1y [expr.prim.lambda]:
     //   The lambda return type is 'auto', which is replaced by the
     //   trailing-return type if provided and/or deduced from 'return'
@@ -968,7 +973,8 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
                                                  KnownDependent, Intro.Default);
   CXXMethodDecl *Method =
       startLambdaDefinition(Class, Intro.Range, MethodTyInfo, EndLoc, Params,
-                            ParamInfo.getDeclSpec().getConstexprSpecifier());
+                            ParamInfo.getDeclSpec().getConstexprSpecifier(),
+                            ParamInfo.getTrailingRequiresClause());
   if (ExplicitParams)
     CheckCXXDefaultArguments(Method);
 
@@ -1248,7 +1254,7 @@ void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
   SmallVector<Decl*, 4> Fields(Class->fields());
   ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
               SourceLocation(), ParsedAttributesView());
-  CheckCompletedCXXClass(Class);
+  CheckCompletedCXXClass(nullptr, Class);
 
   PopFunctionScopeInfo();
 }
@@ -1794,7 +1800,7 @@ ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
     SmallVector<Decl*, 4> Fields(Class->fields());
     ActOnFields(nullptr, Class->getLocation(), Class, Fields, SourceLocation(),
                 SourceLocation(), ParsedAttributesView());
-    CheckCompletedCXXClass(Class);
+    CheckCompletedCXXClass(nullptr, Class);
   }
 
   Cleanup.mergeFrom(LambdaCleanup);
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index d56c5980237c..0ed51de0cc13 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -739,6 +739,18 @@ static void GetOpenCLBuiltinFctOverloads(
   }
 }
 
+/// Add extensions to the function declaration.
+/// \param S (in/out) The Sema instance.
+/// \param BIDecl (in) Description of the builtin.
+/// \param FDecl (in/out) FunctionDecl instance.
+static void AddOpenCLExtensions(Sema &S, const OpenCLBuiltinStruct &BIDecl,
+                                FunctionDecl *FDecl) {
+  // Fetch extension associated with a function prototype.
+  StringRef E = FunctionExtensionTable[BIDecl.Extension];
+  if (E != "")
+    S.setOpenCLExtensionForDecl(FDecl, E);
+}
+
 /// When trying to resolve a function name, if isOpenCLBuiltin() returns a
 /// non-null <Index, Len> pair, then the name is referencing an OpenCL
 /// builtin function.  Add all candidate signatures to the LookUpResult.
@@ -765,10 +777,13 @@ static void InsertOCLBuiltinDeclarationsFromTable(Sema &S, LookupResult &LR,
     ASTContext &Context = S.Context;
 
     // Ignore this BIF if its version does not match the language options.
-    if (Context.getLangOpts().OpenCLVersion < OpenCLBuiltin.MinVersion)
+    unsigned OpenCLVersion = Context.getLangOpts().OpenCLVersion;
+    if (Context.getLangOpts().OpenCLCPlusPlus)
+      OpenCLVersion = 200;
+    if (OpenCLVersion < OpenCLBuiltin.MinVersion)
       continue;
     if ((OpenCLBuiltin.MaxVersion != 0) &&
-        (Context.getLangOpts().OpenCLVersion >= OpenCLBuiltin.MaxVersion))
+        (OpenCLVersion >= OpenCLBuiltin.MaxVersion))
       continue;
 
     SmallVector<QualType, 1> RetTypes;
@@ -812,9 +827,20 @@ static void InsertOCLBuiltinDeclarationsFromTable(Sema &S, LookupResult &LR,
         }
         NewOpenCLBuiltin->setParams(ParmList);
       }
-      if (!S.getLangOpts().OpenCLCPlusPlus) {
+
+      // Add function attributes.
+      if (OpenCLBuiltin.IsPure)
+        NewOpenCLBuiltin->addAttr(PureAttr::CreateImplicit(Context));
+      if (OpenCLBuiltin.IsConst)
+        NewOpenCLBuiltin->addAttr(ConstAttr::CreateImplicit(Context));
+      if (OpenCLBuiltin.IsConv)
+        NewOpenCLBuiltin->addAttr(ConvergentAttr::CreateImplicit(Context));
+
+      if (!S.getLangOpts().OpenCLCPlusPlus)
         NewOpenCLBuiltin->addAttr(OverloadableAttr::CreateImplicit(Context));
-      }
+
+      AddOpenCLExtensions(S, OpenCLBuiltin, NewOpenCLBuiltin);
+
       LR.addDecl(NewOpenCLBuiltin);
     }
   }
@@ -3101,11 +3127,10 @@ Sema::SpecialMemberOverloadResult Sema::LookupSpecialMember(CXXRecordDecl *RD,
       });
     }
     CXXDestructorDecl *DD = RD->getDestructor();
-    assert(DD && "record without a destructor");
     Result->setMethod(DD);
-    Result->setKind(DD->isDeleted() ?
-                    SpecialMemberOverloadResult::NoMemberOrDeleted :
-                    SpecialMemberOverloadResult::Success);
+    Result->setKind(DD && !DD->isDeleted()
+                        ? SpecialMemberOverloadResult::Success
+                        : SpecialMemberOverloadResult::NoMemberOrDeleted);
     return *Result;
   }
 
diff --git a/clang/lib/Sema/SemaModule.cpp b/clang/lib/Sema/SemaModule.cpp
index 1fca351bfb09..10de0ca91221 100644
--- a/clang/lib/Sema/SemaModule.cpp
+++ b/clang/lib/Sema/SemaModule.cpp
@@ -31,8 +31,6 @@ static void checkModuleImportContext(Sema &S, Module *M,
         ExternCLoc = LSD->getBeginLoc();
       break;
     case LinkageSpecDecl::lang_cxx:
-    case LinkageSpecDecl::lang_cxx_11:
-    case LinkageSpecDecl::lang_cxx_14:
       break;
     }
     DC = LSD->getParent();
diff --git a/clang/lib/Sema/SemaObjCProperty.cpp b/clang/lib/Sema/SemaObjCProperty.cpp
index ac810745d2f5..f6717f4cbe5e 100644
--- a/clang/lib/Sema/SemaObjCProperty.cpp
+++ b/clang/lib/Sema/SemaObjCProperty.cpp
@@ -306,6 +306,8 @@ makePropertyAttributesAsWritten(unsigned Attributes) {
     attributesAsWritten |= ObjCPropertyDecl::OBJC_PR_atomic;
   if (Attributes & ObjCDeclSpec::DQ_PR_class)
     attributesAsWritten |= ObjCPropertyDecl::OBJC_PR_class;
+  if (Attributes & ObjCDeclSpec::DQ_PR_direct)
+    attributesAsWritten |= ObjCPropertyDecl::OBJC_PR_direct;
 
   return (ObjCPropertyDecl::PropertyAttributeKind)attributesAsWritten;
 }
@@ -705,9 +707,21 @@ ObjCPropertyDecl *Sema::CreatePropertyDecl(Scope *S,
   if (Attributes & ObjCDeclSpec::DQ_PR_null_resettable)
     PDecl->setPropertyAttributes(ObjCPropertyDecl::OBJC_PR_null_resettable);
 
- if (Attributes & ObjCDeclSpec::DQ_PR_class)
+  if (Attributes & ObjCDeclSpec::DQ_PR_class)
     PDecl->setPropertyAttributes(ObjCPropertyDecl::OBJC_PR_class);
 
+  if ((Attributes & ObjCDeclSpec::DQ_PR_direct) ||
+      CDecl->hasAttr<ObjCDirectMembersAttr>()) {
+    if (isa<ObjCProtocolDecl>(CDecl)) {
+      Diag(PDecl->getLocation(), diag::err_objc_direct_on_protocol) << true;
+    } else if (getLangOpts().ObjCRuntime.allowsDirectDispatch()) {
+      PDecl->setPropertyAttributes(ObjCPropertyDecl::OBJC_PR_direct);
+    } else {
+      Diag(PDecl->getLocation(), diag::warn_objc_direct_property_ignored)
+          << PDecl->getDeclName();
+    }
+  }
+
   return PDecl;
 }
 
@@ -1037,6 +1051,33 @@ static bool hasWrittenStorageAttribute(ObjCPropertyDecl *Prop,
   return false;
 }
 
+/// Create a synthesized property accessor stub inside the \@implementation.
+static ObjCMethodDecl *
+RedeclarePropertyAccessor(ASTContext &Context, ObjCImplementationDecl *Impl,
+                          ObjCMethodDecl *AccessorDecl, SourceLocation AtLoc,
+                          SourceLocation PropertyLoc) {
+  ObjCMethodDecl *Decl = AccessorDecl;
+  ObjCMethodDecl *ImplDecl = ObjCMethodDecl::Create(
+      Context, AtLoc.isValid() ? AtLoc : Decl->getBeginLoc(),
+      PropertyLoc.isValid() ? PropertyLoc : Decl->getEndLoc(),
+      Decl->getSelector(), Decl->getReturnType(),
+      Decl->getReturnTypeSourceInfo(), Impl, Decl->isInstanceMethod(),
+      Decl->isVariadic(), Decl->isPropertyAccessor(),
+      /* isSynthesized*/ true, Decl->isImplicit(), Decl->isDefined(),
+      Decl->getImplementationControl(), Decl->hasRelatedResultType());
+  ImplDecl->getMethodFamily();
+  if (Decl->hasAttrs())
+    ImplDecl->setAttrs(Decl->getAttrs());
+  ImplDecl->setSelfDecl(Decl->getSelfDecl());
+  ImplDecl->setCmdDecl(Decl->getCmdDecl());
+  SmallVector<SourceLocation, 1> SelLocs;
+  Decl->getSelectorLocs(SelLocs);
+  ImplDecl->setMethodParams(Context, Decl->parameters(), SelLocs);
+  ImplDecl->setLexicalDeclContext(Impl);
+  ImplDecl->setDefined(false);
+  return ImplDecl;
+}
+
 /// ActOnPropertyImplDecl - This routine performs semantic checks and
 /// builds the AST node for a property implementation declaration; declared
 /// as \@synthesize or \@dynamic.
@@ -1404,6 +1445,18 @@ Decl *Sema::ActOnPropertyImplDecl(Scope *S,
 
   if (ObjCMethodDecl *getterMethod = property->getGetterMethodDecl()) {
     getterMethod->createImplicitParams(Context, IDecl);
+
+    // Redeclare the getter within the implementation as DeclContext.
+    if (Synthesize) {
+      // If the method hasn't been overridden, create a synthesized implementation.
+      ObjCMethodDecl *OMD = ClassImpDecl->getMethod(
+          getterMethod->getSelector(), getterMethod->isInstanceMethod());
+      if (!OMD)
+        OMD = RedeclarePropertyAccessor(Context, IC, getterMethod, AtLoc,
+                                        PropertyLoc);
+      PIDecl->setGetterMethodDecl(OMD);
+    }
+ 
     if (getLangOpts().CPlusPlus && Synthesize && !CompleteTypeErr &&
         Ivar->getType()->isRecordType()) {
       // For Objective-C++, need to synthesize the AST for the IVAR object to be
@@ -1456,8 +1509,20 @@ Decl *Sema::ActOnPropertyImplDecl(Scope *S,
           break;
       }
   }
+
   if (ObjCMethodDecl *setterMethod = property->getSetterMethodDecl()) {
     setterMethod->createImplicitParams(Context, IDecl);
+
+    // Redeclare the setter within the implementation as DeclContext.
+    if (Synthesize) {
+      ObjCMethodDecl *OMD = ClassImpDecl->getMethod(
+          setterMethod->getSelector(), setterMethod->isInstanceMethod());
+      if (!OMD)
+        OMD = RedeclarePropertyAccessor(Context, IC, setterMethod,
+                                        AtLoc, PropertyLoc);
+      PIDecl->setSetterMethodDecl(OMD);
+    }
+
     if (getLangOpts().CPlusPlus && Synthesize && !CompleteTypeErr &&
         Ivar->getType()->isRecordType()) {
       // FIXME. Eventually we want to do this for Objective-C as well.
@@ -1852,10 +1917,12 @@ void Sema::DefaultSynthesizeProperties(Scope *S, ObjCImplDecl *IMPDecl,
     if (IMPDecl->FindPropertyImplDecl(
             Prop->getIdentifier(), Prop->getQueryKind()))
       continue;
-    if (IMPDecl->getInstanceMethod(Prop->getGetterName())) {
+    ObjCMethodDecl *ImpMethod = IMPDecl->getInstanceMethod(Prop->getGetterName());
+    if (ImpMethod && !ImpMethod->getBody()) {
       if (Prop->getPropertyAttributes() & ObjCPropertyDecl::OBJC_PR_readonly)
         continue;
-      if (IMPDecl->getInstanceMethod(Prop->getSetterName()))
+      ImpMethod = IMPDecl->getInstanceMethod(Prop->getSetterName());
+      if (ImpMethod && !ImpMethod->getBody())
         continue;
     }
     if (ObjCPropertyImplDecl *PID =
@@ -2083,7 +2150,6 @@ void Sema::DiagnoseUnimplementedProperties(Scope *S, ObjCImplDecl* IMPDecl,
 void Sema::diagnoseNullResettableSynthesizedSetters(const ObjCImplDecl *impDecl) {
   for (const auto *propertyImpl : impDecl->property_impls()) {
     const auto *property = propertyImpl->getPropertyDecl();
-
     // Warn about null_resettable properties with synthesized setters,
     // because the setter won't properly handle nil.
     if (propertyImpl->getPropertyImplementation()
@@ -2092,16 +2158,16 @@ void Sema::diagnoseNullResettableSynthesizedSetters(const ObjCImplDecl *impDecl)
          ObjCPropertyDecl::OBJC_PR_null_resettable) &&
         property->getGetterMethodDecl() &&
         property->getSetterMethodDecl()) {
-      auto *getterMethod = property->getGetterMethodDecl();
-      auto *setterMethod = property->getSetterMethodDecl();
-      if (!impDecl->getInstanceMethod(setterMethod->getSelector()) &&
-          !impDecl->getInstanceMethod(getterMethod->getSelector())) {
+      auto *getterImpl = propertyImpl->getGetterMethodDecl();
+      auto *setterImpl = propertyImpl->getSetterMethodDecl();
+      if ((!getterImpl || getterImpl->isSynthesizedAccessorStub()) &&
+          (!setterImpl || setterImpl->isSynthesizedAccessorStub())) {
         SourceLocation loc = propertyImpl->getLocation();
         if (loc.isInvalid())
           loc = impDecl->getBeginLoc();
 
         Diag(loc, diag::warn_null_resettable_setter)
-          << setterMethod->getSelector() << property->getDeclName();
+          << setterImpl->getSelector() << property->getDeclName();
       }
     }
   }
@@ -2125,7 +2191,6 @@ Sema::AtomicPropertySetterGetterRules (ObjCImplDecl* IMPDecl,
     const ObjCPropertyDecl *Property = I->second;
     ObjCMethodDecl *GetterMethod = nullptr;
     ObjCMethodDecl *SetterMethod = nullptr;
-    bool LookedUpGetterSetter = false;
 
     unsigned Attributes = Property->getPropertyAttributes();
     unsigned AttributesAsWritten = Property->getPropertyAttributesAsWritten();
@@ -2138,7 +2203,10 @@ Sema::AtomicPropertySetterGetterRules (ObjCImplDecl* IMPDecl,
       SetterMethod = Property->isClassProperty() ?
                      IMPDecl->getClassMethod(Property->getSetterName()) :
                      IMPDecl->getInstanceMethod(Property->getSetterName());
-      LookedUpGetterSetter = true;
+      if (GetterMethod && GetterMethod->isSynthesizedAccessorStub())
+        GetterMethod = nullptr;
+      if (SetterMethod && SetterMethod->isSynthesizedAccessorStub())
+        SetterMethod = nullptr;
       if (GetterMethod) {
         Diag(GetterMethod->getLocation(),
              diag::warn_default_atomic_custom_getter_setter)
@@ -2161,15 +2229,13 @@ Sema::AtomicPropertySetterGetterRules (ObjCImplDecl* IMPDecl,
             Property->getIdentifier(), Property->getQueryKind())) {
       if (PIDecl->getPropertyImplementation() == ObjCPropertyImplDecl::Dynamic)
         continue;
-      if (!LookedUpGetterSetter) {
-        GetterMethod = Property->isClassProperty() ?
-                       IMPDecl->getClassMethod(Property->getGetterName()) :
-                       IMPDecl->getInstanceMethod(Property->getGetterName());
-        SetterMethod = Property->isClassProperty() ?
-                       IMPDecl->getClassMethod(Property->getSetterName()) :
-                       IMPDecl->getInstanceMethod(Property->getSetterName());
-      }
-      if ((GetterMethod && !SetterMethod) || (!GetterMethod && SetterMethod)) {
+      GetterMethod = PIDecl->getGetterMethodDecl();
+      SetterMethod = PIDecl->getSetterMethodDecl();
+      if (GetterMethod && GetterMethod->isSynthesizedAccessorStub())
+        GetterMethod = nullptr;
+      if (SetterMethod && SetterMethod->isSynthesizedAccessorStub())
+        SetterMethod = nullptr;
+      if ((bool)GetterMethod ^ (bool)SetterMethod) {
         SourceLocation MethodLoc =
           (GetterMethod ? GetterMethod->getLocation()
                         : SetterMethod->getLocation());
@@ -2210,8 +2276,10 @@ void Sema::DiagnoseOwningPropertyGetterSynthesis(const ObjCImplementationDecl *D
   for (const auto *PID : D->property_impls()) {
     const ObjCPropertyDecl *PD = PID->getPropertyDecl();
     if (PD && !PD->hasAttr<NSReturnsNotRetainedAttr>() &&
-        !PD->isClassProperty() &&
-        !D->getInstanceMethod(PD->getGetterName())) {
+        !PD->isClassProperty()) {
+      ObjCMethodDecl *IM = PID->getGetterMethodDecl();
+      if (IM && !IM->isSynthesizedAccessorStub())
+        continue;
       ObjCMethodDecl *method = PD->getGetterMethodDecl();
       if (!method)
         continue;
@@ -2396,20 +2464,21 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
       }
     }
 
-    GetterMethod = ObjCMethodDecl::Create(Context, Loc, Loc,
-                             property->getGetterName(),
-                             resultTy, nullptr, CD,
-                             !IsClassProperty, /*isVariadic=*/false,
-                             /*isPropertyAccessor=*/true,
-                             /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
-                             (property->getPropertyImplementation() ==
-                              ObjCPropertyDecl::Optional) ?
-                             ObjCMethodDecl::Optional :
-                             ObjCMethodDecl::Required);
+    GetterMethod = ObjCMethodDecl::Create(
+        Context, Loc, Loc, property->getGetterName(), resultTy, nullptr, CD,
+        !IsClassProperty, /*isVariadic=*/false,
+        /*isPropertyAccessor=*/true, /*isSynthesizedAccessorStub=*/false,
+        /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
+        (property->getPropertyImplementation() == ObjCPropertyDecl::Optional)
+            ? ObjCMethodDecl::Optional
+            : ObjCMethodDecl::Required);
     CD->addDecl(GetterMethod);
 
     AddPropertyAttrs(*this, GetterMethod, property);
 
+    if (property->isDirectProperty())
+      GetterMethod->addAttr(ObjCDirectAttr::CreateImplicit(Context, Loc));
+
     if (property->hasAttr<NSReturnsNotRetainedAttr>())
       GetterMethod->addAttr(NSReturnsNotRetainedAttr::CreateImplicit(Context,
                                                                      Loc));
@@ -2429,6 +2498,9 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
     // A user declared getter will be synthesize when @synthesize of
     // the property with the same name is seen in the @implementation
     GetterMethod->setPropertyAccessor(true);
+
+  GetterMethod->createImplicitParams(Context,
+                                     GetterMethod->getClassInterface());
   property->setGetterMethodDecl(GetterMethod);
 
   // Skip setter if property is read-only.
@@ -2447,6 +2519,7 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
                                nullptr, CD, !IsClassProperty,
                                /*isVariadic=*/false,
                                /*isPropertyAccessor=*/true,
+                               /*isSynthesizedAccessorStub=*/false,
                                /*isImplicitlyDeclared=*/true,
                                /*isDefined=*/false,
                                (property->getPropertyImplementation() ==
@@ -2483,6 +2556,9 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
 
       AddPropertyAttrs(*this, SetterMethod, property);
 
+      if (property->isDirectProperty())
+        SetterMethod->addAttr(ObjCDirectAttr::CreateImplicit(Context, Loc));
+
       CD->addDecl(SetterMethod);
       if (const SectionAttr *SA = property->getAttr<SectionAttr>())
         SetterMethod->addAttr(SectionAttr::CreateImplicit(
@@ -2496,6 +2572,9 @@ void Sema::ProcessPropertyDecl(ObjCPropertyDecl *property) {
       // A user declared setter will be synthesize when @synthesize of
       // the property with the same name is seen in the @implementation
       SetterMethod->setPropertyAccessor(true);
+
+    SetterMethod->createImplicitParams(Context,
+                                       SetterMethod->getClassInterface());
     property->setSetterMethodDecl(SetterMethod);
   }
   // Add any synthesized methods to the global pool. This allows us to
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index c7e0d2aee036..3fce0e27e9b3 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -23,13 +23,17 @@
 #include "clang/AST/StmtVisitor.h"
 #include "clang/AST/TypeOrdering.h"
 #include "clang/Basic/OpenMPKinds.h"
+#include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Sema/Initialization.h"
 #include "clang/Sema/Lookup.h"
 #include "clang/Sema/Scope.h"
 #include "clang/Sema/ScopeInfo.h"
 #include "clang/Sema/SemaInternal.h"
+#include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/PointerEmbeddedInt.h"
+#include "llvm/Frontend/OpenMP/OMPConstants.h"
 using namespace clang;
+using namespace llvm::omp;
 
 //===----------------------------------------------------------------------===//
 // Stack of data-sharing attributes for variables
@@ -48,12 +52,6 @@ enum DefaultDataSharingAttributes {
   DSA_shared = 1 << 1, /// Default data sharing attribute 'shared'.
 };
 
-/// Attributes of the defaultmap clause.
-enum DefaultMapAttributes {
-  DMA_unspecified,   /// Default mapping is not specified.
-  DMA_tofrom_scalar, /// Default mapping is 'tofrom:scalar'.
-};
-
 /// Stack for tracking declarations used in OpenMP directives and
 /// clauses and their data-sharing attributes.
 class DSAStackTy {
@@ -85,7 +83,7 @@ private:
     DeclRefExpr *PrivateCopy = nullptr;
   };
   using DeclSAMapTy = llvm::SmallDenseMap<const ValueDecl *, DSAInfo, 8>;
-  using AlignedMapTy = llvm::SmallDenseMap<const ValueDecl *, const Expr *, 8>;
+  using UsedRefMapTy = llvm::SmallDenseMap<const ValueDecl *, const Expr *, 8>;
   using LCDeclInfo = std::pair<unsigned, VarDecl *>;
   using LoopControlVariablesMapTy =
       llvm::SmallDenseMap<const ValueDecl *, LCDeclInfo, 8>;
@@ -115,17 +113,25 @@ private:
   };
   using DeclReductionMapTy =
       llvm::SmallDenseMap<const ValueDecl *, ReductionData, 4>;
+  struct DefaultmapInfo {
+    OpenMPDefaultmapClauseModifier ImplicitBehavior =
+        OMPC_DEFAULTMAP_MODIFIER_unknown;
+    SourceLocation SLoc;
+    DefaultmapInfo() = default;
+    DefaultmapInfo(OpenMPDefaultmapClauseModifier M, SourceLocation Loc)
+        : ImplicitBehavior(M), SLoc(Loc) {}
+  };
 
   struct SharingMapTy {
     DeclSAMapTy SharingMap;
     DeclReductionMapTy ReductionMap;
-    AlignedMapTy AlignedMap;
+    UsedRefMapTy AlignedMap;
+    UsedRefMapTy NontemporalMap;
     MappedExprComponentsTy MappedExprComponents;
     LoopControlVariablesMapTy LCVMap;
     DefaultDataSharingAttributes DefaultAttr = DSA_unspecified;
     SourceLocation DefaultAttrLoc;
-    DefaultMapAttributes DefaultMapAttr = DMA_unspecified;
-    SourceLocation DefaultMapAttrLoc;
+    DefaultmapInfo DefaultmapMap[OMPC_DEFAULTMAP_unknown];
     OpenMPDirectiveKind Directive = OMPD_unknown;
     DeclarationNameInfo DirectiveName;
     Scope *CurScope = nullptr;
@@ -416,6 +422,10 @@ public:
   /// add it and return NULL; otherwise return previous occurrence's expression
   /// for diagnostics.
   const Expr *addUniqueAligned(const ValueDecl *D, const Expr *NewDE);
+  /// If 'nontemporal' declaration for given variable \a D was not seen yet,
+  /// add it and return NULL; otherwise return previous occurrence's expression
+  /// for diagnostics.
+  const Expr *addUniqueNontemporal(const ValueDecl *D, const Expr *NewDE);
 
   /// Register specified variable as loop control variable.
   void addLoopControlVariable(const ValueDecl *D, VarDecl *Capture);
@@ -592,10 +602,18 @@ public:
     getTopOfStack().DefaultAttr = DSA_shared;
     getTopOfStack().DefaultAttrLoc = Loc;
   }
-  /// Set default data mapping attribute to 'tofrom:scalar'.
-  void setDefaultDMAToFromScalar(SourceLocation Loc) {
-    getTopOfStack().DefaultMapAttr = DMA_tofrom_scalar;
-    getTopOfStack().DefaultMapAttrLoc = Loc;
+  /// Set default data mapping attribute to Modifier:Kind
+  void setDefaultDMAAttr(OpenMPDefaultmapClauseModifier M,
+                         OpenMPDefaultmapClauseKind Kind,
+                         SourceLocation Loc) {
+    DefaultmapInfo &DMI = getTopOfStack().DefaultmapMap[Kind];
+    DMI.ImplicitBehavior = M;
+    DMI.SLoc = Loc;
+  }
+  /// Check whether the implicit-behavior has been set in defaultmap
+  bool checkDefaultmapCategory(OpenMPDefaultmapClauseKind VariableCategory) {
+    return getTopOfStack().DefaultmapMap[VariableCategory].ImplicitBehavior !=
+           OMPC_DEFAULTMAP_MODIFIER_unknown;
   }
 
   DefaultDataSharingAttributes getDefaultDSA() const {
@@ -606,16 +624,53 @@ public:
     return isStackEmpty() ? SourceLocation()
                           : getTopOfStack().DefaultAttrLoc;
   }
-  DefaultMapAttributes getDefaultDMA() const {
-    return isStackEmpty() ? DMA_unspecified
-                          : getTopOfStack().DefaultMapAttr;
+  OpenMPDefaultmapClauseModifier
+  getDefaultmapModifier(OpenMPDefaultmapClauseKind Kind) const {
+    return isStackEmpty()
+               ? OMPC_DEFAULTMAP_MODIFIER_unknown
+               : getTopOfStack().DefaultmapMap[Kind].ImplicitBehavior;
+  }
+  OpenMPDefaultmapClauseModifier
+  getDefaultmapModifierAtLevel(unsigned Level,
+                               OpenMPDefaultmapClauseKind Kind) const {
+    return getStackElemAtLevel(Level).DefaultmapMap[Kind].ImplicitBehavior;
+  }
+  bool isDefaultmapCapturedByRef(unsigned Level,
+                                 OpenMPDefaultmapClauseKind Kind) const {
+    OpenMPDefaultmapClauseModifier M =
+        getDefaultmapModifierAtLevel(Level, Kind);
+    if (Kind == OMPC_DEFAULTMAP_scalar || Kind == OMPC_DEFAULTMAP_pointer) {
+      return (M == OMPC_DEFAULTMAP_MODIFIER_alloc) ||
+             (M == OMPC_DEFAULTMAP_MODIFIER_to) ||
+             (M == OMPC_DEFAULTMAP_MODIFIER_from) ||
+             (M == OMPC_DEFAULTMAP_MODIFIER_tofrom);
+    }
+    return true;
+  }
+  static bool mustBeFirstprivateBase(OpenMPDefaultmapClauseModifier M,
+                                     OpenMPDefaultmapClauseKind Kind) {
+    switch (Kind) {
+    case OMPC_DEFAULTMAP_scalar:
+    case OMPC_DEFAULTMAP_pointer:
+      return (M == OMPC_DEFAULTMAP_MODIFIER_unknown) ||
+             (M == OMPC_DEFAULTMAP_MODIFIER_firstprivate) ||
+             (M == OMPC_DEFAULTMAP_MODIFIER_default);
+    case OMPC_DEFAULTMAP_aggregate:
+      return M == OMPC_DEFAULTMAP_MODIFIER_firstprivate;
+    default:
+      break;
+    }
+    llvm_unreachable("Unexpected OpenMPDefaultmapClauseKind enum");
   }
-  DefaultMapAttributes getDefaultDMAAtLevel(unsigned Level) const {
-    return getStackElemAtLevel(Level).DefaultMapAttr;
+  bool mustBeFirstprivateAtLevel(unsigned Level,
+                                 OpenMPDefaultmapClauseKind Kind) const {
+    OpenMPDefaultmapClauseModifier M =
+        getDefaultmapModifierAtLevel(Level, Kind);
+    return mustBeFirstprivateBase(M, Kind);
   }
-  SourceLocation getDefaultDMALocation() const {
-    return isStackEmpty() ? SourceLocation()
-                          : getTopOfStack().DefaultMapAttrLoc;
+  bool mustBeFirstprivate(OpenMPDefaultmapClauseKind Kind) const {
+    OpenMPDefaultmapClauseModifier M = getDefaultmapModifier(Kind);
+    return mustBeFirstprivateBase(M, Kind);
   }
 
   /// Checks if the specified variable is a threadprivate.
@@ -862,7 +917,7 @@ static const Expr *getExprAsWritten(const Expr *E) {
     E = FE->getSubExpr();
 
   if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(E))
-    E = MTE->GetTemporaryExpr();
+    E = MTE->getSubExpr();
 
   while (const auto *Binder = dyn_cast<CXXBindTemporaryExpr>(E))
     E = Binder->getSubExpr();
@@ -1023,6 +1078,21 @@ const Expr *DSAStackTy::addUniqueAligned(const ValueDecl *D,
   return It->second;
 }
 
+const Expr *DSAStackTy::addUniqueNontemporal(const ValueDecl *D,
+                                             const Expr *NewDE) {
+  assert(!isStackEmpty() && "Data sharing attributes stack is empty");
+  D = getCanonicalDecl(D);
+  SharingMapTy &StackElem = getTopOfStack();
+  auto It = StackElem.NontemporalMap.find(D);
+  if (It == StackElem.NontemporalMap.end()) {
+    assert(NewDE && "Unexpected nullptr expr to be added into aligned map");
+    StackElem.NontemporalMap[D] = NewDE;
+    return nullptr;
+  }
+  assert(It->second && "Unexpected nullptr expr in the aligned map");
+  return It->second;
+}
+
 void DSAStackTy::addLoopControlVariable(const ValueDecl *D, VarDecl *Capture) {
   assert(!isStackEmpty() && "Data-sharing attributes stack is empty");
   D = getCanonicalDecl(D);
@@ -1716,6 +1786,20 @@ void Sema::checkOpenMPDeviceExpr(const Expr *E) {
         << Context.getTargetInfo().getTriple().str() << E->getSourceRange();
 }
 
+static OpenMPDefaultmapClauseKind
+getVariableCategoryFromDecl(const LangOptions &LO, const ValueDecl *VD) {
+  if (LO.OpenMP <= 45) {
+    if (VD->getType().getNonReferenceType()->isScalarType())
+      return OMPC_DEFAULTMAP_scalar;
+    return OMPC_DEFAULTMAP_aggregate;
+  }
+  if (VD->getType().getNonReferenceType()->isAnyPointerType())
+    return OMPC_DEFAULTMAP_pointer;
+  if (VD->getType().getNonReferenceType()->isScalarType())
+    return OMPC_DEFAULTMAP_scalar;
+  return OMPC_DEFAULTMAP_aggregate;
+}
+
 bool Sema::isOpenMPCapturedByRef(const ValueDecl *D, unsigned Level,
                                  unsigned OpenMPCaptureLevel) const {
   assert(LangOpts.OpenMP && "OpenMP is not allowed");
@@ -1834,11 +1918,13 @@ bool Sema::isOpenMPCapturedByRef(const ValueDecl *D, unsigned Level,
     } else {
       // By default, all the data that has a scalar type is mapped by copy
       // (except for reduction variables).
+      // Defaultmap scalar is mutual exclusive to defaultmap pointer
       IsByRef =
           (DSAStack->isForceCaptureByReferenceInTargetExecutable() &&
            !Ty->isAnyPointerType()) ||
           !Ty->isScalarType() ||
-          DSAStack->getDefaultDMAAtLevel(Level) == DMA_tofrom_scalar ||
+          DSAStack->isDefaultmapCapturedByRef(
+              Level, getVariableCategoryFromDecl(LangOpts, D)) ||
           DSAStack->hasExplicitDSA(
               D, [](OpenMPClauseKind K) { return K == OMPC_reduction; }, Level);
     }
@@ -1894,6 +1980,11 @@ VarDecl *Sema::isOpenMPCapturedDecl(ValueDecl *D, bool CheckScopeInfo,
   assert(LangOpts.OpenMP && "OpenMP is not allowed");
   D = getCanonicalDecl(D);
 
+  auto *VD = dyn_cast<VarDecl>(D);
+  // Do not capture constexpr variables.
+  if (VD && VD->isConstexpr())
+    return nullptr;
+
   // If we want to determine whether the variable should be captured from the
   // perspective of the current capturing scope, and we've already left all the
   // capturing scopes of the top directive on the stack, check from the
@@ -1904,7 +1995,6 @@ VarDecl *Sema::isOpenMPCapturedDecl(ValueDecl *D, bool CheckScopeInfo,
   // If we are attempting to capture a global variable in a directive with
   // 'target' we return true so that this global is also mapped to the device.
   //
-  auto *VD = dyn_cast<VarDecl>(D);
   if (VD && !VD->hasLocalStorage() &&
       (getCurCapturedRegion() || getCurBlock() || getCurLambda())) {
     if (isInOpenMPDeclareTargetContext()) {
@@ -2051,9 +2141,8 @@ void Sema::setOpenMPCaptureKind(FieldDecl *FD, const ValueDecl *D,
     if (DSAStack->hasExplicitDirective(isOpenMPTargetExecutionDirective,
                                        NewLevel)) {
       OMPC = OMPC_map;
-      if (D->getType()->isScalarType() &&
-          DSAStack->getDefaultDMAAtLevel(NewLevel) !=
-              DefaultMapAttributes::DMA_tofrom_scalar)
+      if (DSAStack->mustBeFirstprivateAtLevel(
+              NewLevel, getVariableCategoryFromDecl(LangOpts, D)))
         OMPC = OMPC_firstprivate;
       break;
     }
@@ -2141,6 +2230,11 @@ void Sema::EndOpenMPClause() {
 
 static void checkAllocateClauses(Sema &S, DSAStackTy *Stack,
                                  ArrayRef<OMPClause *> Clauses);
+static std::pair<ValueDecl *, bool>
+getPrivateItem(Sema &S, Expr *&RefExpr, SourceLocation &ELoc,
+               SourceRange &ERange, bool AllowArraySection = false);
+static DeclRefExpr *buildCapture(Sema &S, ValueDecl *D, Expr *CaptureExpr,
+                                 bool WithInit);
 
 void Sema::EndOpenMPDSABlock(Stmt *CurDirective) {
   // OpenMP [2.14.3.5, Restrictions, C/C++, p.1]
@@ -2185,6 +2279,31 @@ void Sema::EndOpenMPDSABlock(Stmt *CurDirective) {
           }
         }
         Clause->setPrivateCopies(PrivateCopies);
+        continue;
+      }
+      // Finalize nontemporal clause by handling private copies, if any.
+      if (auto *Clause = dyn_cast<OMPNontemporalClause>(C)) {
+        SmallVector<Expr *, 8> PrivateRefs;
+        for (Expr *RefExpr : Clause->varlists()) {
+          assert(RefExpr && "NULL expr in OpenMP nontemporal clause.");
+          SourceLocation ELoc;
+          SourceRange ERange;
+          Expr *SimpleRefExpr = RefExpr;
+          auto Res = getPrivateItem(*this, SimpleRefExpr, ELoc, ERange);
+          if (Res.second)
+            // It will be analyzed later.
+            PrivateRefs.push_back(RefExpr);
+          ValueDecl *D = Res.first;
+          if (!D)
+            continue;
+
+          const DSAStackTy::DSAVarData DVar =
+              DSAStack->getTopDSA(D, /*FromParent=*/false);
+          PrivateRefs.push_back(DVar.PrivateCopy ? DVar.PrivateCopy
+                                                 : SimpleRefExpr);
+        }
+        Clause->setPrivateRefs(PrivateRefs);
+        continue;
       }
     }
     // Check allocate clauses.
@@ -2759,14 +2878,51 @@ static void reportOriginalDsa(Sema &SemaRef, const DSAStackTy *Stack,
   }
 }
 
+static OpenMPMapClauseKind
+getMapClauseKindFromModifier(OpenMPDefaultmapClauseModifier M,
+                             bool IsAggregateOrDeclareTarget) {
+  OpenMPMapClauseKind Kind = OMPC_MAP_unknown;
+  switch (M) {
+  case OMPC_DEFAULTMAP_MODIFIER_alloc:
+    Kind = OMPC_MAP_alloc;
+    break;
+  case OMPC_DEFAULTMAP_MODIFIER_to:
+    Kind = OMPC_MAP_to;
+    break;
+  case OMPC_DEFAULTMAP_MODIFIER_from:
+    Kind = OMPC_MAP_from;
+    break;
+  case OMPC_DEFAULTMAP_MODIFIER_tofrom:
+    Kind = OMPC_MAP_tofrom;
+    break;
+  case OMPC_DEFAULTMAP_MODIFIER_firstprivate:
+  case OMPC_DEFAULTMAP_MODIFIER_last:
+    llvm_unreachable("Unexpected defaultmap implicit behavior");
+  case OMPC_DEFAULTMAP_MODIFIER_none:
+  case OMPC_DEFAULTMAP_MODIFIER_default:
+  case OMPC_DEFAULTMAP_MODIFIER_unknown:
+    // IsAggregateOrDeclareTarget could be true if:
+    // 1. the implicit behavior for aggregate is tofrom
+    // 2. it's a declare target link
+    if (IsAggregateOrDeclareTarget) {
+      Kind = OMPC_MAP_tofrom;
+      break;
+    }
+    llvm_unreachable("Unexpected defaultmap implicit behavior");
+  }
+  assert(Kind != OMPC_MAP_unknown && "Expect map kind to be known");
+  return Kind;
+}
+
 namespace {
 class DSAAttrChecker final : public StmtVisitor<DSAAttrChecker, void> {
   DSAStackTy *Stack;
   Sema &SemaRef;
   bool ErrorFound = false;
+  bool TryCaptureCXXThisMembers = false;
   CapturedStmt *CS = nullptr;
   llvm::SmallVector<Expr *, 4> ImplicitFirstprivate;
-  llvm::SmallVector<Expr *, 4> ImplicitMap;
+  llvm::SmallVector<Expr *, 4> ImplicitMap[OMPC_MAP_delete];
   Sema::VarsWithInheritedDSAType VarsWithInheritedDSA;
   llvm::SmallDenseSet<const ValueDecl *, 4> ImplicitDeclarations;
 
@@ -2775,12 +2931,26 @@ class DSAAttrChecker final : public StmtVisitor<DSAAttrChecker, void> {
     if (!S->hasAssociatedStmt() || !S->getAssociatedStmt())
       return;
     visitSubCaptures(S->getInnermostCapturedStmt());
+    // Try to capture inner this->member references to generate correct mappings
+    // and diagnostics.
+    if (TryCaptureCXXThisMembers ||
+        (isOpenMPTargetExecutionDirective(Stack->getCurrentDirective()) &&
+         llvm::any_of(S->getInnermostCapturedStmt()->captures(),
+                      [](const CapturedStmt::Capture &C) {
+                        return C.capturesThis();
+                      }))) {
+      bool SavedTryCaptureCXXThisMembers = TryCaptureCXXThisMembers;
+      TryCaptureCXXThisMembers = true;
+      Visit(S->getInnermostCapturedStmt()->getCapturedStmt());
+      TryCaptureCXXThisMembers = SavedTryCaptureCXXThisMembers;
+    }
   }
 
 public:
   void VisitDeclRefExpr(DeclRefExpr *E) {
-    if (E->isTypeDependent() || E->isValueDependent() ||
-        E->containsUnexpandedParameterPack() || E->isInstantiationDependent())
+    if (TryCaptureCXXThisMembers || E->isTypeDependent() ||
+        E->isValueDependent() || E->containsUnexpandedParameterPack() ||
+        E->isInstantiationDependent())
       return;
     if (auto *VD = dyn_cast<VarDecl>(E->getDecl())) {
       // Check the datasharing rules for the expressions in the clauses.
@@ -2825,6 +2995,39 @@ public:
         return;
       }
 
+      // OpenMP 5.0 [2.19.7.2, defaultmap clause, Description]
+      // If implicit-behavior is none, each variable referenced in the
+      // construct that does not have a predetermined data-sharing attribute
+      // and does not appear in a to or link clause on a declare target
+      // directive must be listed in a data-mapping attribute clause, a
+      // data-haring attribute clause (including a data-sharing attribute
+      // clause on a combined construct where target. is one of the
+      // constituent constructs), or an is_device_ptr clause.
+      OpenMPDefaultmapClauseKind ClauseKind =
+          getVariableCategoryFromDecl(SemaRef.getLangOpts(), VD);
+      if (SemaRef.getLangOpts().OpenMP >= 50) {
+        bool IsModifierNone = Stack->getDefaultmapModifier(ClauseKind) ==
+                              OMPC_DEFAULTMAP_MODIFIER_none;
+        if (DVar.CKind == OMPC_unknown && IsModifierNone &&
+            VarsWithInheritedDSA.count(VD) == 0 && !Res) {
+          // Only check for data-mapping attribute and is_device_ptr here
+          // since we have already make sure that the declaration does not
+          // have a data-sharing attribute above
+          if (!Stack->checkMappableExprComponentListsForDecl(
+                  VD, /*CurrentRegionOnly=*/true,
+                  [VD](OMPClauseMappableExprCommon::MappableExprComponentListRef
+                           MapExprComponents,
+                       OpenMPClauseKind) {
+                    auto MI = MapExprComponents.rbegin();
+                    auto ME = MapExprComponents.rend();
+                    return MI != ME && MI->getAssociatedDeclaration() == VD;
+                  })) {
+            VarsWithInheritedDSA[VD] = E;
+            return;
+          }
+        }
+      }
+
       if (isOpenMPTargetExecutionDirective(DKind) &&
           !Stack->isLoopControlVariable(VD).first) {
         if (!Stack->checkMappableExprComponentListsForDecl(
@@ -2854,13 +3057,16 @@ public:
                   VD->getType().getNonReferenceType()->getAsCXXRecordDecl())
             IsFirstprivate = RD->isLambda();
           IsFirstprivate =
-              IsFirstprivate ||
-              (VD->getType().getNonReferenceType()->isScalarType() &&
-               Stack->getDefaultDMA() != DMA_tofrom_scalar && !Res);
-          if (IsFirstprivate)
+              IsFirstprivate || (Stack->mustBeFirstprivate(ClauseKind) && !Res);
+          if (IsFirstprivate) {
             ImplicitFirstprivate.emplace_back(E);
-          else
-            ImplicitMap.emplace_back(E);
+          } else {
+            OpenMPDefaultmapClauseModifier M =
+                Stack->getDefaultmapModifier(ClauseKind);
+            OpenMPMapClauseKind Kind = getMapClauseKindFromModifier(
+                M, ClauseKind == OMPC_DEFAULTMAP_aggregate || Res);
+            ImplicitMap[Kind].emplace_back(E);
+          }
           return;
         }
       }
@@ -2939,7 +3145,11 @@ public:
         if (Stack->isClassPreviouslyMapped(TE->getType()))
           return;
 
-        ImplicitMap.emplace_back(E);
+        OpenMPDefaultmapClauseModifier Modifier =
+            Stack->getDefaultmapModifier(OMPC_DEFAULTMAP_aggregate);
+        OpenMPMapClauseKind Kind = getMapClauseKindFromModifier(
+            Modifier, /*IsAggregateOrDeclareTarget*/ true);
+        ImplicitMap[Kind].emplace_back(E);
         return;
       }
 
@@ -3014,7 +3224,7 @@ public:
               })) {
         Visit(E->getBase());
       }
-    } else {
+    } else if (!TryCaptureCXXThisMembers) {
       Visit(E->getBase());
     }
   }
@@ -3068,7 +3278,9 @@ public:
   ArrayRef<Expr *> getImplicitFirstprivate() const {
     return ImplicitFirstprivate;
   }
-  ArrayRef<Expr *> getImplicitMap() const { return ImplicitMap; }
+  ArrayRef<Expr *> getImplicitMap(OpenMPDefaultmapClauseKind Kind) const {
+    return ImplicitMap[Kind];
+  }
   const Sema::VarsWithInheritedDSAType &getVarsWithInheritedDSA() const {
     return VarsWithInheritedDSA;
   }
@@ -3090,6 +3302,7 @@ void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
   case OMPD_parallel_for:
   case OMPD_parallel_for_simd:
   case OMPD_parallel_sections:
+  case OMPD_parallel_master:
   case OMPD_teams:
   case OMPD_teams_distribute:
   case OMPD_teams_distribute_simd: {
@@ -3282,7 +3495,8 @@ void Sema::ActOnOpenMPRegionStart(OpenMPDirectiveKind DKind, Scope *CurScope) {
             AlwaysInlineAttr::Keyword_forceinline));
     break;
   }
-  case OMPD_parallel_master_taskloop: {
+  case OMPD_parallel_master_taskloop:
+  case OMPD_parallel_master_taskloop_simd: {
     QualType KmpInt32Ty =
         Context.getIntTypeForBitwidth(/*DestWidth=*/32, /*Signed=*/1)
             .withConst();
@@ -3779,7 +3993,10 @@ static bool checkNestingOfRegions(Sema &SemaRef, const DSAStackTy *Stack,
       ShouldBeInTargetRegion,
       ShouldBeInTeamsRegion
     } Recommend = NoRecommend;
-    if (isOpenMPSimdDirective(ParentRegion) && CurrentRegion != OMPD_ordered) {
+    if (isOpenMPSimdDirective(ParentRegion) &&
+        ((SemaRef.LangOpts.OpenMP <= 45 && CurrentRegion != OMPD_ordered) ||
+         (SemaRef.LangOpts.OpenMP >= 50 && CurrentRegion != OMPD_ordered &&
+          CurrentRegion != OMPD_simd && CurrentRegion != OMPD_atomic))) {
       // OpenMP [2.16, Nesting of Regions]
       // OpenMP constructs may not be nested inside a simd region.
       // OpenMP [2.8.1,simd Construct, Restrictions]
@@ -3788,9 +4005,14 @@ static bool checkNestingOfRegions(Sema &SemaRef, const DSAStackTy *Stack,
       // Allowing a SIMD construct nested in another SIMD construct is an
       // extension. The OpenMP 4.5 spec does not allow it. Issue a warning
       // message.
+      // OpenMP 5.0 [2.9.3.1, simd Construct, Restrictions]
+      // The only OpenMP constructs that can be encountered during execution of
+      // a simd region are the atomic construct, the loop construct, the simd
+      // construct and the ordered construct with the simd clause.
       SemaRef.Diag(StartLoc, (CurrentRegion != OMPD_simd)
                                  ? diag::err_omp_prohibited_region_simd
-                                 : diag::warn_omp_nesting_simd);
+                                 : diag::warn_omp_nesting_simd)
+          << (SemaRef.LangOpts.OpenMP >= 50 ? 1 : 0);
       return CurrentRegion != OMPD_simd;
     }
     if (ParentRegion == OMPD_atomic) {
@@ -3888,6 +4110,7 @@ static bool checkNestingOfRegions(Sema &SemaRef, const DSAStackTy *Stack,
       NestingProhibited = isOpenMPWorksharingDirective(ParentRegion) ||
                           isOpenMPTaskingDirective(ParentRegion) ||
                           ParentRegion == OMPD_master ||
+                          ParentRegion == OMPD_parallel_master ||
                           ParentRegion == OMPD_critical ||
                           ParentRegion == OMPD_ordered;
     } else if (isOpenMPWorksharingDirective(CurrentRegion) &&
@@ -3899,6 +4122,7 @@ static bool checkNestingOfRegions(Sema &SemaRef, const DSAStackTy *Stack,
       NestingProhibited = isOpenMPWorksharingDirective(ParentRegion) ||
                           isOpenMPTaskingDirective(ParentRegion) ||
                           ParentRegion == OMPD_master ||
+                          ParentRegion == OMPD_parallel_master ||
                           ParentRegion == OMPD_critical ||
                           ParentRegion == OMPD_ordered;
       Recommend = ShouldBeInParallelRegion;
@@ -3982,13 +4206,17 @@ static bool checkNestingOfRegions(Sema &SemaRef, const DSAStackTy *Stack,
   return false;
 }
 
+struct Kind2Unsigned {
+  using argument_type = OpenMPDirectiveKind;
+  unsigned operator()(argument_type DK) { return unsigned(DK); }
+};
 static bool checkIfClauses(Sema &S, OpenMPDirectiveKind Kind,
                            ArrayRef<OMPClause *> Clauses,
                            ArrayRef<OpenMPDirectiveKind> AllowedNameModifiers) {
   bool ErrorFound = false;
   unsigned NamedModifiersNumber = 0;
-  SmallVector<const OMPIfClause *, OMPC_unknown + 1> FoundNameModifiers(
-      OMPD_unknown + 1);
+  llvm::IndexedMap<const OMPIfClause *, Kind2Unsigned> FoundNameModifiers;
+  FoundNameModifiers.resize(unsigned(OMPD_unknown) + 1);
   SmallVector<SourceLocation, 4> NameModifierLoc;
   for (const OMPClause *C : Clauses) {
     if (const auto *IC = dyn_cast_or_null<OMPIfClause>(C)) {
@@ -4064,9 +4292,10 @@ static bool checkIfClauses(Sema &S, OpenMPDirectiveKind Kind,
   return ErrorFound;
 }
 
-static std::pair<ValueDecl *, bool>
-getPrivateItem(Sema &S, Expr *&RefExpr, SourceLocation &ELoc,
-               SourceRange &ERange, bool AllowArraySection = false) {
+static std::pair<ValueDecl *, bool> getPrivateItem(Sema &S, Expr *&RefExpr,
+                                                   SourceLocation &ELoc,
+                                                   SourceRange &ERange,
+                                                   bool AllowArraySection) {
   if (RefExpr->isTypeDependent() || RefExpr->isValueDependent() ||
       RefExpr->containsUnexpandedParameterPack())
     return std::make_pair(nullptr, true);
@@ -4271,8 +4500,12 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     SmallVector<Expr *, 4> ImplicitFirstprivates(
         DSAChecker.getImplicitFirstprivate().begin(),
         DSAChecker.getImplicitFirstprivate().end());
-    SmallVector<Expr *, 4> ImplicitMaps(DSAChecker.getImplicitMap().begin(),
-                                        DSAChecker.getImplicitMap().end());
+    SmallVector<Expr *, 4> ImplicitMaps[OMPC_MAP_delete];
+    for (unsigned I = 0; I < OMPC_MAP_delete; ++I) {
+      ArrayRef<Expr *> ImplicitMap =
+          DSAChecker.getImplicitMap(static_cast<OpenMPDefaultmapClauseKind>(I));
+      ImplicitMaps[I].append(ImplicitMap.begin(), ImplicitMap.end());
+    }
     // Mark taskgroup task_reduction descriptors as implicitly firstprivate.
     for (OMPClause *C : Clauses) {
       if (auto *IRC = dyn_cast<OMPInReductionClause>(C)) {
@@ -4292,16 +4525,21 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
         ErrorFound = true;
       }
     }
-    if (!ImplicitMaps.empty()) {
+    int ClauseKindCnt = -1;
+    for (ArrayRef<Expr *> ImplicitMap : ImplicitMaps) {
+      ++ClauseKindCnt;
+      if (ImplicitMap.empty())
+        continue;
       CXXScopeSpec MapperIdScopeSpec;
       DeclarationNameInfo MapperId;
+      auto Kind = static_cast<OpenMPMapClauseKind>(ClauseKindCnt);
       if (OMPClause *Implicit = ActOnOpenMPMapClause(
-              llvm::None, llvm::None, MapperIdScopeSpec, MapperId,
-              OMPC_MAP_tofrom, /*IsMapTypeImplicit=*/true, SourceLocation(),
-              SourceLocation(), ImplicitMaps, OMPVarListLocTy())) {
+              llvm::None, llvm::None, MapperIdScopeSpec, MapperId, Kind,
+              /*IsMapTypeImplicit=*/true, SourceLocation(), SourceLocation(),
+              ImplicitMap, OMPVarListLocTy())) {
         ClausesWithImplicit.emplace_back(Implicit);
         ErrorFound |=
-            cast<OMPMapClause>(Implicit)->varlist_size() != ImplicitMaps.size();
+            cast<OMPMapClause>(Implicit)->varlist_size() != ImplicitMap.size();
       } else {
         ErrorFound = true;
       }
@@ -4318,6 +4556,8 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   case OMPD_simd:
     Res = ActOnOpenMPSimdDirective(ClausesWithImplicit, AStmt, StartLoc, EndLoc,
                                    VarsWithInheritedDSA);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_for:
     Res = ActOnOpenMPForDirective(ClausesWithImplicit, AStmt, StartLoc, EndLoc,
@@ -4326,6 +4566,8 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   case OMPD_for_simd:
     Res = ActOnOpenMPForSimdDirective(ClausesWithImplicit, AStmt, StartLoc,
                                       EndLoc, VarsWithInheritedDSA);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_sections:
     Res = ActOnOpenMPSectionsDirective(ClausesWithImplicit, AStmt, StartLoc,
@@ -4358,6 +4600,13 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     Res = ActOnOpenMPParallelForSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
+    break;
+  case OMPD_parallel_master:
+    Res = ActOnOpenMPParallelMasterDirective(ClausesWithImplicit, AStmt,
+                                               StartLoc, EndLoc);
+    AllowedNameModifiers.push_back(OMPD_parallel);
     break;
   case OMPD_parallel_sections:
     Res = ActOnOpenMPParallelSectionsDirective(ClausesWithImplicit, AStmt,
@@ -4466,6 +4715,8 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     Res = ActOnOpenMPTaskLoopSimdDirective(ClausesWithImplicit, AStmt, StartLoc,
                                            EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_taskloop);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_master_taskloop:
     Res = ActOnOpenMPMasterTaskLoopDirective(
@@ -4476,6 +4727,8 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     Res = ActOnOpenMPMasterTaskLoopSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_taskloop);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_parallel_master_taskloop:
     Res = ActOnOpenMPParallelMasterTaskLoopDirective(
@@ -4483,6 +4736,14 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     AllowedNameModifiers.push_back(OMPD_taskloop);
     AllowedNameModifiers.push_back(OMPD_parallel);
     break;
+  case OMPD_parallel_master_taskloop_simd:
+    Res = ActOnOpenMPParallelMasterTaskLoopSimdDirective(
+        ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
+    AllowedNameModifiers.push_back(OMPD_taskloop);
+    AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
+    break;
   case OMPD_distribute:
     Res = ActOnOpenMPDistributeDirective(ClausesWithImplicit, AStmt, StartLoc,
                                          EndLoc, VarsWithInheritedDSA);
@@ -4501,21 +4762,29 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     Res = ActOnOpenMPDistributeParallelForSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_distribute_simd:
     Res = ActOnOpenMPDistributeSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_target_parallel_for_simd:
     Res = ActOnOpenMPTargetParallelForSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_target);
     AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_target_simd:
     Res = ActOnOpenMPTargetSimdDirective(ClausesWithImplicit, AStmt, StartLoc,
                                          EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_target);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_teams_distribute:
     Res = ActOnOpenMPTeamsDistributeDirective(
@@ -4524,11 +4793,15 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
   case OMPD_teams_distribute_simd:
     Res = ActOnOpenMPTeamsDistributeSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_teams_distribute_parallel_for_simd:
     Res = ActOnOpenMPTeamsDistributeParallelForSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_teams_distribute_parallel_for:
     Res = ActOnOpenMPTeamsDistributeParallelForDirective(
@@ -4556,11 +4829,15 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_target);
     AllowedNameModifiers.push_back(OMPD_parallel);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_target_teams_distribute_simd:
     Res = ActOnOpenMPTargetTeamsDistributeSimdDirective(
         ClausesWithImplicit, AStmt, StartLoc, EndLoc, VarsWithInheritedDSA);
     AllowedNameModifiers.push_back(OMPD_target);
+    if (LangOpts.OpenMP >= 50)
+      AllowedNameModifiers.push_back(OMPD_simd);
     break;
   case OMPD_declare_target:
   case OMPD_end_declare_target:
@@ -4586,13 +4863,17 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
       case OMPC_num_threads:
       case OMPC_dist_schedule:
         // Do not analyse if no parent teams directive.
-        if (isOpenMPTeamsDirective(DSAStack->getCurrentDirective()))
+        if (isOpenMPTeamsDirective(Kind))
           break;
         continue;
       case OMPC_if:
-        if (isOpenMPTeamsDirective(DSAStack->getCurrentDirective()) &&
+        if (isOpenMPTeamsDirective(Kind) &&
             cast<OMPIfClause>(C)->getNameModifier() != OMPD_target)
           break;
+        if (isOpenMPParallelDirective(Kind) &&
+            isOpenMPTaskLoopDirective(Kind) &&
+            cast<OMPIfClause>(C)->getNameModifier() != OMPD_parallel)
+          break;
         continue;
       case OMPC_schedule:
         break;
@@ -4601,7 +4882,7 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
       case OMPC_final:
       case OMPC_priority:
         // Do not analyze if no parent parallel directive.
-        if (isOpenMPParallelDirective(DSAStack->getCurrentDirective()))
+        if (isOpenMPParallelDirective(Kind))
           break;
         continue;
       case OMPC_ordered:
@@ -4644,6 +4925,7 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
       case OMPC_from:
       case OMPC_use_device_ptr:
       case OMPC_is_device_ptr:
+      case OMPC_nontemporal:
         continue;
       case OMPC_allocator:
       case OMPC_flush:
@@ -4671,9 +4953,17 @@ StmtResult Sema::ActOnOpenMPExecutableDirective(
     if (P.getFirst()->isImplicit() || isa<OMPCapturedExprDecl>(P.getFirst()))
       continue;
     ErrorFound = true;
-    Diag(P.second->getExprLoc(), diag::err_omp_no_dsa_for_variable)
-        << P.first << P.second->getSourceRange();
-    Diag(DSAStack->getDefaultDSALocation(), diag::note_omp_default_dsa_none);
+    if (DSAStack->getDefaultDSA() == DSA_none) {
+      Diag(P.second->getExprLoc(), diag::err_omp_no_dsa_for_variable)
+          << P.first << P.second->getSourceRange();
+      Diag(DSAStack->getDefaultDSALocation(), diag::note_omp_default_dsa_none);
+    } else if (getLangOpts().OpenMP >= 50) {
+      Diag(P.second->getExprLoc(),
+           diag::err_omp_defaultmap_no_attr_for_variable)
+          << P.first << P.second->getSourceRange();
+      Diag(DSAStack->getDefaultDSALocation(),
+           diag::note_omp_defaultmap_attr_none);
+    }
   }
 
   if (!AllowedNameModifiers.empty())
@@ -4781,8 +5071,9 @@ Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareSimdDirective(
           // OpenMP  [2.8.1, simd construct, Restrictions]
           // A list-item cannot appear in more than one aligned clause.
           if (AlignedArgs.count(CanonPVD) > 0) {
-            Diag(E->getExprLoc(), diag::err_omp_aligned_twice)
-                << 1 << E->getSourceRange();
+            Diag(E->getExprLoc(), diag::err_omp_used_in_clause_twice)
+                << 1 << getOpenMPClauseName(OMPC_aligned)
+                << E->getSourceRange();
             Diag(AlignedArgs[CanonPVD]->getExprLoc(),
                  diag::note_omp_explicit_dsa)
                 << getOpenMPClauseName(OMPC_aligned);
@@ -4804,8 +5095,8 @@ Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareSimdDirective(
       }
     if (isa<CXXThisExpr>(E)) {
       if (AlignedThis) {
-        Diag(E->getExprLoc(), diag::err_omp_aligned_twice)
-            << 2 << E->getSourceRange();
+        Diag(E->getExprLoc(), diag::err_omp_used_in_clause_twice)
+            << 2 << getOpenMPClauseName(OMPC_aligned) << E->getSourceRange();
         Diag(AlignedThis->getExprLoc(), diag::note_omp_explicit_dsa)
             << getOpenMPClauseName(OMPC_aligned);
       }
@@ -4950,6 +5241,29 @@ Sema::DeclGroupPtrTy Sema::ActOnOpenMPDeclareSimdDirective(
   return DG;
 }
 
+static void setPrototype(Sema &S, FunctionDecl *FD, FunctionDecl *FDWithProto,
+                         QualType NewType) {
+  assert(NewType->isFunctionProtoType() &&
+         "Expected function type with prototype.");
+  assert(FD->getType()->isFunctionNoProtoType() &&
+         "Expected function with type with no prototype.");
+  assert(FDWithProto->getType()->isFunctionProtoType() &&
+         "Expected function with prototype.");
+  // Synthesize parameters with the same types.
+  FD->setType(NewType);
+  SmallVector<ParmVarDecl *, 16> Params;
+  for (const ParmVarDecl *P : FDWithProto->parameters()) {
+    auto *Param = ParmVarDecl::Create(S.getASTContext(), FD, SourceLocation(),
+                                      SourceLocation(), nullptr, P->getType(),
+                                      /*TInfo=*/nullptr, SC_None, nullptr);
+    Param->setScopeInfo(0, Params.size());
+    Param->setImplicit();
+    Params.push_back(Param);
+  }
+
+  FD->setParams(Params);
+}
+
 Optional<std::pair<FunctionDecl *, Expr *>>
 Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
                                         Expr *VariantRef, SourceRange SR) {
@@ -5048,7 +5362,9 @@ Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
     if (ICS.isFailure()) {
       Diag(VariantRef->getExprLoc(),
            diag::err_omp_declare_variant_incompat_types)
-          << VariantRef->getType() << FnPtrType << VariantRef->getSourceRange();
+          << VariantRef->getType()
+          << ((Method && !Method->isStatic()) ? FnPtrType : FD->getType())
+          << VariantRef->getSourceRange();
       return None;
     }
     VariantRefCast = PerformImplicitConversion(
@@ -5088,6 +5404,24 @@ Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
     return None;
   }
 
+  // Check if function types are compatible in C.
+  if (!LangOpts.CPlusPlus) {
+    QualType NewType =
+        Context.mergeFunctionTypes(FD->getType(), NewFD->getType());
+    if (NewType.isNull()) {
+      Diag(VariantRef->getExprLoc(),
+           diag::err_omp_declare_variant_incompat_types)
+          << NewFD->getType() << FD->getType() << VariantRef->getSourceRange();
+      return None;
+    }
+    if (NewType->isFunctionProtoType()) {
+      if (FD->getType()->isFunctionNoProtoType())
+        setPrototype(*this, FD, NewFD, NewType);
+      else if (NewFD->getType()->isFunctionNoProtoType())
+        setPrototype(*this, NewFD, FD, NewType);
+    }
+  }
+
   // Check if variant function is not marked with declare variant directive.
   if (NewFD->hasAttrs() && NewFD->hasAttr<OMPDeclareVariantAttr>()) {
     Diag(VariantRef->getExprLoc(),
@@ -5148,10 +5482,9 @@ Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
 
   // Check general compatibility.
   if (areMultiversionVariantFunctionsCompatible(
-          FD, NewFD, PDiag(diag::err_omp_declare_variant_noproto),
-          PartialDiagnosticAt(
-              SR.getBegin(),
-              PDiag(diag::note_omp_declare_variant_specified_here) << SR),
+          FD, NewFD, PartialDiagnostic::NullDiagnostic(),
+          PartialDiagnosticAt(SourceLocation(),
+                              PartialDiagnostic::NullDiagnostic()),
           PartialDiagnosticAt(
               VariantRef->getExprLoc(),
               PDiag(diag::err_omp_declare_variant_doesnt_support)),
@@ -5166,28 +5499,73 @@ Sema::checkOpenMPDeclareVariantFunction(Sema::DeclGroupPtrTy DG,
 
 void Sema::ActOnOpenMPDeclareVariantDirective(
     FunctionDecl *FD, Expr *VariantRef, SourceRange SR,
-    const Sema::OpenMPDeclareVariantCtsSelectorData &Data) {
-  if (Data.CtxSet == OMPDeclareVariantAttr::CtxSetUnknown ||
-      Data.Ctx == OMPDeclareVariantAttr::CtxUnknown)
+    ArrayRef<OMPCtxSelectorData> Data) {
+  if (Data.empty())
     return;
-  Expr *Score = nullptr;
-  OMPDeclareVariantAttr::ScoreType ST = OMPDeclareVariantAttr::ScoreUnknown;
-  if (Data.CtxScore.isUsable()) {
-    ST = OMPDeclareVariantAttr::ScoreSpecified;
-    Score = Data.CtxScore.get();
-    if (!Score->isTypeDependent() && !Score->isValueDependent() &&
-        !Score->isInstantiationDependent() &&
-        !Score->containsUnexpandedParameterPack()) {
-      llvm::APSInt Result;
-      ExprResult ICE = VerifyIntegerConstantExpression(Score, &Result);
-      if (ICE.isInvalid())
-        return;
+  SmallVector<Expr *, 4> CtxScores;
+  SmallVector<unsigned, 4> CtxSets;
+  SmallVector<unsigned, 4> Ctxs;
+  SmallVector<StringRef, 4> ImplVendors, DeviceKinds;
+  bool IsError = false;
+  for (const OMPCtxSelectorData &D : Data) {
+    OpenMPContextSelectorSetKind CtxSet = D.CtxSet;
+    OpenMPContextSelectorKind Ctx = D.Ctx;
+    if (CtxSet == OMP_CTX_SET_unknown || Ctx == OMP_CTX_unknown)
+      return;
+    Expr *Score = nullptr;
+    if (D.Score.isUsable()) {
+      Score = D.Score.get();
+      if (!Score->isTypeDependent() && !Score->isValueDependent() &&
+          !Score->isInstantiationDependent() &&
+          !Score->containsUnexpandedParameterPack()) {
+        Score =
+            PerformOpenMPImplicitIntegerConversion(Score->getExprLoc(), Score)
+                .get();
+        if (Score)
+          Score = VerifyIntegerConstantExpression(Score).get();
+      }
+    } else {
+      // OpenMP 5.0, 2.3.3 Matching and Scoring Context Selectors.
+      // The kind, arch, and isa selectors are given the values 2^l, 2^(l+1) and
+      // 2^(l+2), respectively, where l is the number of traits in the construct
+      // set.
+      // TODO: implement correct logic for isa and arch traits.
+      // TODO: take the construct context set into account when it is
+      // implemented.
+      int L = 0; // Currently set the number of traits in construct set to 0,
+                 // since the construct trait set in not supported yet.
+      if (CtxSet == OMP_CTX_SET_device && Ctx == OMP_CTX_kind)
+        Score = ActOnIntegerConstant(SourceLocation(), std::pow(2, L)).get();
+      else
+        Score = ActOnIntegerConstant(SourceLocation(), 0).get();
     }
+    switch (Ctx) {
+    case OMP_CTX_vendor:
+      assert(CtxSet == OMP_CTX_SET_implementation &&
+             "Expected implementation context selector set.");
+      ImplVendors.append(D.Names.begin(), D.Names.end());
+      break;
+    case OMP_CTX_kind:
+      assert(CtxSet == OMP_CTX_SET_device &&
+             "Expected device context selector set.");
+      DeviceKinds.append(D.Names.begin(), D.Names.end());
+      break;
+    case OMP_CTX_unknown:
+      llvm_unreachable("Unknown context selector kind.");
+    }
+    IsError = IsError || !Score;
+    CtxSets.push_back(CtxSet);
+    Ctxs.push_back(Ctx);
+    CtxScores.push_back(Score);
+  }
+  if (!IsError) {
+    auto *NewAttr = OMPDeclareVariantAttr::CreateImplicit(
+        Context, VariantRef, CtxScores.begin(), CtxScores.size(),
+        CtxSets.begin(), CtxSets.size(), Ctxs.begin(), Ctxs.size(),
+        ImplVendors.begin(), ImplVendors.size(), DeviceKinds.begin(),
+        DeviceKinds.size(), SR);
+    FD->addAttr(NewAttr);
   }
-  auto *NewAttr = OMPDeclareVariantAttr::CreateImplicit(
-      Context, VariantRef, Score, Data.CtxSet, ST, Data.Ctx,
-      Data.ImplVendors.begin(), Data.ImplVendors.size(), SR);
-  FD->addAttr(NewAttr);
 }
 
 void Sema::markOpenMPDeclareVariantFuncsReferenced(SourceLocation Loc,
@@ -5200,7 +5578,7 @@ void Sema::markOpenMPDeclareVariantFuncsReferenced(SourceLocation Loc,
          Func->specific_attrs<OMPDeclareVariantAttr>()) {
       // TODO: add checks for active OpenMP context where possible.
       Expr *VariantRef = A->getVariantFuncRef();
-      auto *DRE = dyn_cast<DeclRefExpr>(VariantRef->IgnoreParenImpCasts());
+      auto *DRE = cast<DeclRefExpr>(VariantRef->IgnoreParenImpCasts());
       auto *F = cast<FunctionDecl>(DRE->getDecl());
       if (!F->isDefined() && F->isTemplateInstantiation())
         InstantiateFunctionDefinition(Loc, F->getFirstDecl());
@@ -6953,7 +7331,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
              "Expected canonical for or range-based for loops.");
       CurStmt = cast<CXXForRangeStmt>(CurStmt)->getBody();
     }
-    CurStmt = CurStmt->IgnoreContainers();
+    CurStmt = OMPLoopDirective::tryToFindNextInnerLoop(
+        CurStmt, SemaRef.LangOpts.OpenMP >= 50);
   }
   for (unsigned Cnt = NestedLoopCount; Cnt < OrderedLoopCount; ++Cnt) {
     if (checkOpenMPIterationSpace(
@@ -6980,7 +7359,8 @@ checkOpenMPLoop(OpenMPDirectiveKind DKind, Expr *CollapseLoopCountExpr,
              "Expected canonical for or range-based for loops.");
       CurStmt = cast<CXXForRangeStmt>(CurStmt)->getBody();
     }
-    CurStmt = CurStmt->IgnoreContainers();
+    CurStmt = OMPLoopDirective::tryToFindNextInnerLoop(
+        CurStmt, SemaRef.LangOpts.OpenMP >= 50);
   }
 
   Built.clear(/* size */ NestedLoopCount);
@@ -7995,6 +8375,28 @@ StmtResult Sema::ActOnOpenMPParallelForSimdDirective(
 }
 
 StmtResult
+Sema::ActOnOpenMPParallelMasterDirective(ArrayRef<OMPClause *> Clauses,
+                                         Stmt *AStmt, SourceLocation StartLoc,
+                                         SourceLocation EndLoc) {
+  if (!AStmt)
+    return StmtError();
+
+  assert(isa<CapturedStmt>(AStmt) && "Captured statement expected");
+  auto *CS = cast<CapturedStmt>(AStmt);
+  // 1.2.2 OpenMP Language Terminology
+  // Structured block - An executable statement with a single entry at the
+  // top and a single exit at the bottom.
+  // The point of exit cannot be a branch out of the structured block.
+  // longjmp() and throw() must not violate the entry/exit criteria.
+  CS->getCapturedDecl()->setNothrow();
+
+  setFunctionHasBranchProtectedScope();
+
+  return OMPParallelMasterDirective::Create(Context, StartLoc, EndLoc, Clauses,
+                                            AStmt);
+}
+
+StmtResult
 Sema::ActOnOpenMPParallelSectionsDirective(ArrayRef<OMPClause *> Clauses,
                                            Stmt *AStmt, SourceLocation StartLoc,
                                            SourceLocation EndLoc) {
@@ -8137,7 +8539,8 @@ StmtResult Sema::ActOnOpenMPOrderedDirective(ArrayRef<OMPClause *> Clauses,
     // OpenMP [2.8.1,simd Construct, Restrictions]
     // An ordered construct with the simd clause is the only OpenMP construct
     // that can appear in the simd region.
-    Diag(StartLoc, diag::err_omp_prohibited_region_simd);
+    Diag(StartLoc, diag::err_omp_prohibited_region_simd)
+        << (LangOpts.OpenMP >= 50 ? 1 : 0);
     ErrorFound = true;
   } else if (DependFound && (TC || SC)) {
     Diag(DependFound->getBeginLoc(), diag::err_omp_depend_clause_thread_simd)
@@ -9467,6 +9870,74 @@ StmtResult Sema::ActOnOpenMPParallelMasterTaskLoopDirective(
       Context, StartLoc, EndLoc, NestedLoopCount, Clauses, AStmt, B);
 }
 
+StmtResult Sema::ActOnOpenMPParallelMasterTaskLoopSimdDirective(
+    ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
+    SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA) {
+  if (!AStmt)
+    return StmtError();
+
+  assert(isa<CapturedStmt>(AStmt) && "Captured statement expected");
+  auto *CS = cast<CapturedStmt>(AStmt);
+  // 1.2.2 OpenMP Language Terminology
+  // Structured block - An executable statement with a single entry at the
+  // top and a single exit at the bottom.
+  // The point of exit cannot be a branch out of the structured block.
+  // longjmp() and throw() must not violate the entry/exit criteria.
+  CS->getCapturedDecl()->setNothrow();
+  for (int ThisCaptureLevel =
+           getOpenMPCaptureLevels(OMPD_parallel_master_taskloop_simd);
+       ThisCaptureLevel > 1; --ThisCaptureLevel) {
+    CS = cast<CapturedStmt>(CS->getCapturedStmt());
+    // 1.2.2 OpenMP Language Terminology
+    // Structured block - An executable statement with a single entry at the
+    // top and a single exit at the bottom.
+    // The point of exit cannot be a branch out of the structured block.
+    // longjmp() and throw() must not violate the entry/exit criteria.
+    CS->getCapturedDecl()->setNothrow();
+  }
+
+  OMPLoopDirective::HelperExprs B;
+  // In presence of clause 'collapse' or 'ordered' with number of loops, it will
+  // define the nested loops number.
+  unsigned NestedLoopCount = checkOpenMPLoop(
+      OMPD_parallel_master_taskloop_simd, getCollapseNumberExpr(Clauses),
+      /*OrderedLoopCountExpr=*/nullptr, CS, *this, *DSAStack,
+      VarsWithImplicitDSA, B);
+  if (NestedLoopCount == 0)
+    return StmtError();
+
+  assert((CurContext->isDependentContext() || B.builtAll()) &&
+         "omp for loop exprs were not built");
+
+  if (!CurContext->isDependentContext()) {
+    // Finalize the clauses that need pre-built expressions for CodeGen.
+    for (OMPClause *C : Clauses) {
+      if (auto *LC = dyn_cast<OMPLinearClause>(C))
+        if (FinishOpenMPLinearClause(*LC, cast<DeclRefExpr>(B.IterationVarRef),
+                                     B.NumIterations, *this, CurScope,
+                                     DSAStack))
+          return StmtError();
+    }
+  }
+
+  // OpenMP, [2.9.2 taskloop Construct, Restrictions]
+  // The grainsize clause and num_tasks clause are mutually exclusive and may
+  // not appear on the same taskloop directive.
+  if (checkGrainsizeNumTasksClauses(*this, Clauses))
+    return StmtError();
+  // OpenMP, [2.9.2 taskloop Construct, Restrictions]
+  // If a reduction clause is present on the taskloop directive, the nogroup
+  // clause must not be specified.
+  if (checkReductionClauseWithNogroup(*this, Clauses))
+    return StmtError();
+  if (checkSimdlenSafelenSpecified(*this, Clauses))
+    return StmtError();
+
+  setFunctionHasBranchProtectedScope();
+  return OMPParallelMasterTaskLoopSimdDirective::Create(
+      Context, StartLoc, EndLoc, NestedLoopCount, Clauses, AStmt, B);
+}
+
 StmtResult Sema::ActOnOpenMPDistributeDirective(
     ArrayRef<OMPClause *> Clauses, Stmt *AStmt, SourceLocation StartLoc,
     SourceLocation EndLoc, VarsWithInheritedDSAType &VarsWithImplicitDSA) {
@@ -10317,6 +10788,7 @@ OMPClause *Sema::ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind, Expr *Expr,
   case OMPC_atomic_default_mem_order:
   case OMPC_device_type:
   case OMPC_match:
+  case OMPC_nontemporal:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -10328,29 +10800,47 @@ OMPClause *Sema::ActOnOpenMPSingleExprClause(OpenMPClauseKind Kind, Expr *Expr,
 // A return value of OMPD_unknown signifies that the expression should not
 // be captured.
 static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
-    OpenMPDirectiveKind DKind, OpenMPClauseKind CKind,
+    OpenMPDirectiveKind DKind, OpenMPClauseKind CKind, unsigned OpenMPVersion,
     OpenMPDirectiveKind NameModifier = OMPD_unknown) {
   OpenMPDirectiveKind CaptureRegion = OMPD_unknown;
   switch (CKind) {
   case OMPC_if:
     switch (DKind) {
+    case OMPD_target_parallel_for_simd:
+      if (OpenMPVersion >= 50 &&
+          (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)) {
+        CaptureRegion = OMPD_parallel;
+        break;
+      }
+      LLVM_FALLTHROUGH;
     case OMPD_target_parallel:
     case OMPD_target_parallel_for:
-    case OMPD_target_parallel_for_simd:
       // If this clause applies to the nested 'parallel' region, capture within
       // the 'target' region, otherwise do not capture.
       if (NameModifier == OMPD_unknown || NameModifier == OMPD_parallel)
         CaptureRegion = OMPD_target;
       break;
-    case OMPD_target_teams_distribute_parallel_for:
     case OMPD_target_teams_distribute_parallel_for_simd:
+      if (OpenMPVersion >= 50 &&
+          (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)) {
+        CaptureRegion = OMPD_parallel;
+        break;
+      }
+      LLVM_FALLTHROUGH;
+    case OMPD_target_teams_distribute_parallel_for:
       // If this clause applies to the nested 'parallel' region, capture within
       // the 'teams' region, otherwise do not capture.
       if (NameModifier == OMPD_unknown || NameModifier == OMPD_parallel)
         CaptureRegion = OMPD_teams;
       break;
-    case OMPD_teams_distribute_parallel_for:
     case OMPD_teams_distribute_parallel_for_simd:
+      if (OpenMPVersion >= 50 &&
+          (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)) {
+        CaptureRegion = OMPD_parallel;
+        break;
+      }
+      LLVM_FALLTHROUGH;
+    case OMPD_teams_distribute_parallel_for:
       CaptureRegion = OMPD_teams;
       break;
     case OMPD_target_update:
@@ -10362,24 +10852,63 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
       if (NameModifier == OMPD_unknown || NameModifier == OMPD_taskloop)
         CaptureRegion = OMPD_parallel;
       break;
+    case OMPD_parallel_master_taskloop_simd:
+      if ((OpenMPVersion <= 45 && NameModifier == OMPD_unknown) ||
+          NameModifier == OMPD_taskloop) {
+        CaptureRegion = OMPD_parallel;
+        break;
+      }
+      if (OpenMPVersion <= 45)
+        break;
+      if (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)
+        CaptureRegion = OMPD_taskloop;
+      break;
+    case OMPD_parallel_for_simd:
+      if (OpenMPVersion <= 45)
+        break;
+      if (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)
+        CaptureRegion = OMPD_parallel;
+      break;
+    case OMPD_taskloop_simd:
+    case OMPD_master_taskloop_simd:
+      if (OpenMPVersion <= 45)
+        break;
+      if (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)
+        CaptureRegion = OMPD_taskloop;
+      break;
+    case OMPD_distribute_parallel_for_simd:
+      if (OpenMPVersion <= 45)
+        break;
+      if (NameModifier == OMPD_unknown || NameModifier == OMPD_simd)
+        CaptureRegion = OMPD_parallel;
+      break;
+    case OMPD_target_simd:
+      if (OpenMPVersion >= 50 &&
+          (NameModifier == OMPD_unknown || NameModifier == OMPD_simd))
+        CaptureRegion = OMPD_target;
+      break;
+    case OMPD_teams_distribute_simd:
+    case OMPD_target_teams_distribute_simd:
+      if (OpenMPVersion >= 50 &&
+          (NameModifier == OMPD_unknown || NameModifier == OMPD_simd))
+        CaptureRegion = OMPD_teams;
+      break;
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
-    case OMPD_parallel_for_simd:
     case OMPD_target:
-    case OMPD_target_simd:
     case OMPD_target_teams:
     case OMPD_target_teams_distribute:
-    case OMPD_target_teams_distribute_simd:
     case OMPD_distribute_parallel_for:
-    case OMPD_distribute_parallel_for_simd:
     case OMPD_task:
     case OMPD_taskloop:
-    case OMPD_taskloop_simd:
     case OMPD_master_taskloop:
-    case OMPD_master_taskloop_simd:
     case OMPD_target_data:
+    case OMPD_simd:
+    case OMPD_for_simd:
+    case OMPD_distribute_simd:
       // Do not capture if-clause expressions.
       break;
     case OMPD_threadprivate:
@@ -10396,9 +10925,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_declare_target:
     case OMPD_end_declare_target:
     case OMPD_teams:
-    case OMPD_simd:
     case OMPD_for:
-    case OMPD_for_simd:
     case OMPD_sections:
     case OMPD_section:
     case OMPD_single:
@@ -10408,9 +10935,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_distribute:
     case OMPD_ordered:
     case OMPD_atomic:
-    case OMPD_distribute_simd:
     case OMPD_teams_distribute:
-    case OMPD_teams_distribute_simd:
     case OMPD_requires:
       llvm_unreachable("Unexpected OpenMP directive with if-clause");
     case OMPD_unknown:
@@ -10431,12 +10956,14 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
       CaptureRegion = OMPD_teams;
       break;
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
     case OMPD_parallel_for_simd:
     case OMPD_distribute_parallel_for:
     case OMPD_distribute_parallel_for_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
       // Do not capture num_threads-clause expressions.
       break;
     case OMPD_target_data:
@@ -10513,12 +11040,14 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop:
     case OMPD_master_taskloop_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
     case OMPD_target_data:
     case OMPD_target_enter_data:
     case OMPD_target_exit_data:
     case OMPD_target_update:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
     case OMPD_parallel_for_simd:
@@ -10583,12 +11112,14 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop:
     case OMPD_master_taskloop_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
     case OMPD_target_data:
     case OMPD_target_enter_data:
     case OMPD_target_exit_data:
     case OMPD_target_update:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
     case OMPD_parallel_for_simd:
@@ -10653,6 +11184,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop:
     case OMPD_master_taskloop_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
     case OMPD_target_data:
     case OMPD_target_enter_data:
     case OMPD_target_exit_data:
@@ -10667,6 +11199,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_target_parallel:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_threadprivate:
     case OMPD_allocate:
@@ -10727,6 +11260,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop:
     case OMPD_master_taskloop_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
     case OMPD_target_data:
     case OMPD_target_enter_data:
     case OMPD_target_exit_data:
@@ -10737,6 +11271,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_target_parallel:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_threadprivate:
     case OMPD_allocate:
@@ -10802,8 +11337,10 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop:
     case OMPD_master_taskloop_simd:
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
     case OMPD_parallel_for_simd:
@@ -10851,6 +11388,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_master_taskloop_simd:
       break;
     case OMPD_parallel_master_taskloop:
+    case OMPD_parallel_master_taskloop_simd:
       CaptureRegion = OMPD_parallel;
       break;
     case OMPD_target_update:
@@ -10876,6 +11414,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
     case OMPD_distribute_parallel_for_simd:
     case OMPD_cancel:
     case OMPD_parallel:
+    case OMPD_parallel_master:
     case OMPD_parallel_sections:
     case OMPD_parallel_for:
     case OMPD_parallel_for_simd:
@@ -10960,6 +11499,7 @@ static OpenMPDirectiveKind getOpenMPCaptureRegionForClause(
   case OMPC_atomic_default_mem_order:
   case OMPC_device_type:
   case OMPC_match:
+  case OMPC_nontemporal:
     llvm_unreachable("Unexpected OpenMP clause.");
   }
   return CaptureRegion;
@@ -10984,8 +11524,8 @@ OMPClause *Sema::ActOnOpenMPIfClause(OpenMPDirectiveKind NameModifier,
     ValExpr = Val.get();
 
     OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
-    CaptureRegion =
-        getOpenMPCaptureRegionForClause(DKind, OMPC_if, NameModifier);
+    CaptureRegion = getOpenMPCaptureRegionForClause(
+        DKind, OMPC_if, LangOpts.OpenMP, NameModifier);
     if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
       ValExpr = MakeFullExpr(ValExpr).get();
       llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -11016,7 +11556,8 @@ OMPClause *Sema::ActOnOpenMPFinalClause(Expr *Condition,
     ValExpr = MakeFullExpr(Val.get()).get();
 
     OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
-    CaptureRegion = getOpenMPCaptureRegionForClause(DKind, OMPC_final);
+    CaptureRegion =
+        getOpenMPCaptureRegionForClause(DKind, OMPC_final, LangOpts.OpenMP);
     if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
       ValExpr = MakeFullExpr(ValExpr).get();
       llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -11101,7 +11642,8 @@ isNonNegativeIntegerValue(Expr *&ValExpr, Sema &SemaRef, OpenMPClauseKind CKind,
     }
     if (!BuildCapture)
       return true;
-    *CaptureRegion = getOpenMPCaptureRegionForClause(DKind, CKind);
+    *CaptureRegion =
+        getOpenMPCaptureRegionForClause(DKind, CKind, SemaRef.LangOpts.OpenMP);
     if (*CaptureRegion != OMPD_unknown &&
         !SemaRef.CurContext->isDependentContext()) {
       ValExpr = SemaRef.MakeFullExpr(ValExpr).get();
@@ -11128,7 +11670,7 @@ OMPClause *Sema::ActOnOpenMPNumThreadsClause(Expr *NumThreads,
 
   OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
   OpenMPDirectiveKind CaptureRegion =
-      getOpenMPCaptureRegionForClause(DKind, OMPC_num_threads);
+      getOpenMPCaptureRegionForClause(DKind, OMPC_num_threads, LangOpts.OpenMP);
   if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
     ValExpr = MakeFullExpr(ValExpr).get();
     llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -11315,9 +11857,8 @@ OMPClause *Sema::ActOnOpenMPSimpleClause(
                                  ArgumentLoc, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_proc_bind:
-    Res = ActOnOpenMPProcBindClause(
-        static_cast<OpenMPProcBindClauseKind>(Argument), ArgumentLoc, StartLoc,
-        LParenLoc, EndLoc);
+    Res = ActOnOpenMPProcBindClause(static_cast<ProcBindKind>(Argument),
+                                    ArgumentLoc, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_atomic_default_mem_order:
     Res = ActOnOpenMPAtomicDefaultMemOrderClause(
@@ -11381,6 +11922,7 @@ OMPClause *Sema::ActOnOpenMPSimpleClause(
   case OMPC_dynamic_allocators:
   case OMPC_device_type:
   case OMPC_match:
+  case OMPC_nontemporal:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -11391,7 +11933,6 @@ getListOfPossibleValues(OpenMPClauseKind K, unsigned First, unsigned Last,
                         ArrayRef<unsigned> Exclude = llvm::None) {
   SmallString<256> Buffer;
   llvm::raw_svector_ostream Out(Buffer);
-  unsigned Bound = Last >= 2 ? Last - 2 : 0;
   unsigned Skipped = Exclude.size();
   auto S = Exclude.begin(), E = Exclude.end();
   for (unsigned I = First; I < Last; ++I) {
@@ -11400,9 +11941,9 @@ getListOfPossibleValues(OpenMPClauseKind K, unsigned First, unsigned Last,
       continue;
     }
     Out << "'" << getOpenMPSimpleClauseTypeName(K, I) << "'";
-    if (I == Bound - Skipped)
+    if (I + Skipped + 2 == Last)
       Out << " or ";
-    else if (I != Bound + 1 - Skipped)
+    else if (I + Skipped + 1 != Last)
       Out << ", ";
   }
   return Out.str();
@@ -11437,15 +11978,16 @@ OMPClause *Sema::ActOnOpenMPDefaultClause(OpenMPDefaultClauseKind Kind,
       OMPDefaultClause(Kind, KindKwLoc, StartLoc, LParenLoc, EndLoc);
 }
 
-OMPClause *Sema::ActOnOpenMPProcBindClause(OpenMPProcBindClauseKind Kind,
+OMPClause *Sema::ActOnOpenMPProcBindClause(ProcBindKind Kind,
                                            SourceLocation KindKwLoc,
                                            SourceLocation StartLoc,
                                            SourceLocation LParenLoc,
                                            SourceLocation EndLoc) {
-  if (Kind == OMPC_PROC_BIND_unknown) {
+  if (Kind == OMP_PROC_BIND_unknown) {
     Diag(KindKwLoc, diag::err_omp_unexpected_clause_value)
-        << getListOfPossibleValues(OMPC_proc_bind, /*First=*/0,
-                                   /*Last=*/OMPC_PROC_BIND_unknown)
+        << getListOfPossibleValues(OMPC_proc_bind,
+                                   /*First=*/unsigned(OMP_PROC_BIND_master),
+                                   /*Last=*/5)
         << getOpenMPClauseName(OMPC_proc_bind);
     return nullptr;
   }
@@ -11561,6 +12103,7 @@ OMPClause *Sema::ActOnOpenMPSingleExprWithArgClause(
   case OMPC_atomic_default_mem_order:
   case OMPC_device_type:
   case OMPC_match:
+  case OMPC_nontemporal:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -11659,8 +12202,8 @@ OMPClause *Sema::ActOnOpenMPScheduleClause(
           return nullptr;
         }
       } else if (getOpenMPCaptureRegionForClause(
-                     DSAStack->getCurrentDirective(), OMPC_schedule) !=
-                     OMPD_unknown &&
+                     DSAStack->getCurrentDirective(), OMPC_schedule,
+                     LangOpts.OpenMP) != OMPD_unknown &&
                  !CurContext->isDependentContext()) {
         ValExpr = MakeFullExpr(ValExpr).get();
         llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -11772,6 +12315,7 @@ OMPClause *Sema::ActOnOpenMPClause(OpenMPClauseKind Kind,
   case OMPC_atomic_default_mem_order:
   case OMPC_device_type:
   case OMPC_match:
+  case OMPC_nontemporal:
     llvm_unreachable("Clause is not allowed.");
   }
   return Res;
@@ -11857,11 +12401,10 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
     OpenMPClauseKind Kind, ArrayRef<Expr *> VarList, Expr *TailExpr,
     const OMPVarListLocTy &Locs, SourceLocation ColonLoc,
     CXXScopeSpec &ReductionOrMapperIdScopeSpec,
-    DeclarationNameInfo &ReductionOrMapperId, OpenMPDependClauseKind DepKind,
-    OpenMPLinearClauseKind LinKind,
+    DeclarationNameInfo &ReductionOrMapperId, int ExtraModifier,
     ArrayRef<OpenMPMapModifierKind> MapTypeModifiers,
-    ArrayRef<SourceLocation> MapTypeModifiersLoc, OpenMPMapClauseKind MapType,
-    bool IsMapTypeImplicit, SourceLocation DepLinMapLoc) {
+    ArrayRef<SourceLocation> MapTypeModifiersLoc, bool IsMapTypeImplicit,
+    SourceLocation DepLinMapLastLoc) {
   SourceLocation StartLoc = Locs.StartLoc;
   SourceLocation LParenLoc = Locs.LParenLoc;
   SourceLocation EndLoc = Locs.EndLoc;
@@ -11874,7 +12417,11 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
     Res = ActOnOpenMPFirstprivateClause(VarList, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_lastprivate:
-    Res = ActOnOpenMPLastprivateClause(VarList, StartLoc, LParenLoc, EndLoc);
+    assert(0 <= ExtraModifier && ExtraModifier <= OMPC_LASTPRIVATE_unknown &&
+           "Unexpected lastprivate modifier.");
+    Res = ActOnOpenMPLastprivateClause(
+        VarList, static_cast<OpenMPLastprivateModifier>(ExtraModifier),
+        DepLinMapLastLoc, ColonLoc, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_shared:
     Res = ActOnOpenMPSharedClause(VarList, StartLoc, LParenLoc, EndLoc);
@@ -11895,8 +12442,12 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
                                        ReductionOrMapperId);
     break;
   case OMPC_linear:
-    Res = ActOnOpenMPLinearClause(VarList, TailExpr, StartLoc, LParenLoc,
-                                  LinKind, DepLinMapLoc, ColonLoc, EndLoc);
+    assert(0 <= ExtraModifier && ExtraModifier <= OMPC_LINEAR_unknown &&
+           "Unexpected linear modifier.");
+    Res = ActOnOpenMPLinearClause(
+        VarList, TailExpr, StartLoc, LParenLoc,
+        static_cast<OpenMPLinearClauseKind>(ExtraModifier), DepLinMapLastLoc,
+        ColonLoc, EndLoc);
     break;
   case OMPC_aligned:
     Res = ActOnOpenMPAlignedClause(VarList, TailExpr, StartLoc, LParenLoc,
@@ -11912,14 +12463,19 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
     Res = ActOnOpenMPFlushClause(VarList, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_depend:
-    Res = ActOnOpenMPDependClause(DepKind, DepLinMapLoc, ColonLoc, VarList,
-                                  StartLoc, LParenLoc, EndLoc);
+    assert(0 <= ExtraModifier && ExtraModifier <= OMPC_DEPEND_unknown &&
+           "Unexpected depend modifier.");
+    Res = ActOnOpenMPDependClause(
+        static_cast<OpenMPDependClauseKind>(ExtraModifier), DepLinMapLastLoc,
+        ColonLoc, VarList, StartLoc, LParenLoc, EndLoc);
     break;
   case OMPC_map:
-    Res = ActOnOpenMPMapClause(MapTypeModifiers, MapTypeModifiersLoc,
-                               ReductionOrMapperIdScopeSpec,
-                               ReductionOrMapperId, MapType, IsMapTypeImplicit,
-                               DepLinMapLoc, ColonLoc, VarList, Locs);
+    assert(0 <= ExtraModifier && ExtraModifier <= OMPC_MAP_unknown &&
+           "Unexpected map modifier.");
+    Res = ActOnOpenMPMapClause(
+        MapTypeModifiers, MapTypeModifiersLoc, ReductionOrMapperIdScopeSpec,
+        ReductionOrMapperId, static_cast<OpenMPMapClauseKind>(ExtraModifier),
+        IsMapTypeImplicit, DepLinMapLastLoc, ColonLoc, VarList, Locs);
     break;
   case OMPC_to:
     Res = ActOnOpenMPToClause(VarList, ReductionOrMapperIdScopeSpec,
@@ -11939,6 +12495,9 @@ OMPClause *Sema::ActOnOpenMPVarListClause(
     Res = ActOnOpenMPAllocateClause(TailExpr, VarList, StartLoc, LParenLoc,
                                     ColonLoc, EndLoc);
     break;
+  case OMPC_nontemporal:
+    Res = ActOnOpenMPNontemporalClause(VarList, StartLoc, LParenLoc, EndLoc);
+    break;
   case OMPC_if:
   case OMPC_final:
   case OMPC_num_threads:
@@ -12442,10 +13001,19 @@ OMPClause *Sema::ActOnOpenMPFirstprivateClause(ArrayRef<Expr *> VarList,
                                        buildPreInits(Context, ExprCaptures));
 }
 
-OMPClause *Sema::ActOnOpenMPLastprivateClause(ArrayRef<Expr *> VarList,
-                                              SourceLocation StartLoc,
-                                              SourceLocation LParenLoc,
-                                              SourceLocation EndLoc) {
+OMPClause *Sema::ActOnOpenMPLastprivateClause(
+    ArrayRef<Expr *> VarList, OpenMPLastprivateModifier LPKind,
+    SourceLocation LPKindLoc, SourceLocation ColonLoc, SourceLocation StartLoc,
+    SourceLocation LParenLoc, SourceLocation EndLoc) {
+  if (LPKind == OMPC_LASTPRIVATE_unknown && LPKindLoc.isValid()) {
+    assert(ColonLoc.isValid() && "Colon location must be valid.");
+    Diag(LPKindLoc, diag::err_omp_unexpected_clause_value)
+        << getListOfPossibleValues(OMPC_lastprivate, /*First=*/0,
+                                   /*Last=*/OMPC_LASTPRIVATE_unknown)
+        << getOpenMPClauseName(OMPC_lastprivate);
+    return nullptr;
+  }
+
   SmallVector<Expr *, 8> Vars;
   SmallVector<Expr *, 8> SrcExprs;
   SmallVector<Expr *, 8> DstExprs;
@@ -12491,6 +13059,19 @@ OMPClause *Sema::ActOnOpenMPLastprivateClause(ArrayRef<Expr *> VarList,
     if (rejectConstNotMutableType(*this, D, Type, OMPC_lastprivate, ELoc))
       continue;
 
+    // OpenMP 5.0 [2.19.4.5 lastprivate Clause, Restrictions]
+    // A list item that appears in a lastprivate clause with the conditional
+    // modifier must be a scalar variable.
+    if (LPKind == OMPC_LASTPRIVATE_conditional && !Type->isScalarType()) {
+      Diag(ELoc, diag::err_omp_lastprivate_conditional_non_scalar);
+      bool IsDecl = !VD || VD->isThisDeclarationADefinition(Context) ==
+                               VarDecl::DeclarationOnly;
+      Diag(D->getLocation(),
+           IsDecl ? diag::note_previous_decl : diag::note_defined_here)
+          << D;
+      continue;
+    }
+
     OpenMPDirectiveKind CurrDir = DSAStack->getCurrentDirective();
     // OpenMP [2.14.1.1, Data-sharing Attribute Rules for Variables Referenced
     // in a Construct]
@@ -12599,6 +13180,7 @@ OMPClause *Sema::ActOnOpenMPLastprivateClause(ArrayRef<Expr *> VarList,
 
   return OMPLastprivateClause::Create(Context, StartLoc, LParenLoc, EndLoc,
                                       Vars, SrcExprs, DstExprs, AssignmentOps,
+                                      LPKind, LPKindLoc, ColonLoc,
                                       buildPreInits(Context, ExprCaptures),
                                       buildPostUpdate(*this, ExprPostUpdates));
 }
@@ -12916,7 +13498,8 @@ buildDeclareReductionRef(Sema &SemaRef, SourceLocation Loc, SourceRange Range,
     }
   }
   if (ReductionIdScopeSpec.isSet()) {
-    SemaRef.Diag(Loc, diag::err_omp_not_resolved_reduction_identifier) << Range;
+    SemaRef.Diag(Loc, diag::err_omp_not_resolved_reduction_identifier)
+        << Ty << Range;
     return ExprError();
   }
   return ExprEmpty();
@@ -13771,8 +14354,8 @@ bool Sema::CheckOpenMPLinearDecl(const ValueDecl *D, SourceLocation ELoc,
   // A list item must be of integral or pointer type.
   Type = Type.getUnqualifiedType().getCanonicalType();
   const auto *Ty = Type.getTypePtrOrNull();
-  if (!Ty || (!Ty->isDependentType() && !Ty->isIntegralType(Context) &&
-              !Ty->isPointerType())) {
+  if (!Ty || (LinKind != OMPC_LINEAR_ref && !Ty->isDependentType() &&
+              !Ty->isIntegralType(Context) && !Ty->isPointerType())) {
     Diag(ELoc, diag::err_omp_linear_expected_int_or_ptr) << Type;
     if (D) {
       bool IsDecl =
@@ -14066,7 +14649,8 @@ OMPClause *Sema::ActOnOpenMPAlignedClause(
     // OpenMP  [2.8.1, simd construct, Restrictions]
     // A list-item cannot appear in more than one aligned clause.
     if (const Expr *PrevRef = DSAStack->addUniqueAligned(D, SimpleRefExpr)) {
-      Diag(ELoc, diag::err_omp_aligned_twice) << 0 << ERange;
+      Diag(ELoc, diag::err_omp_used_in_clause_twice)
+          << 0 << getOpenMPClauseName(OMPC_aligned) << ERange;
       Diag(PrevRef->getExprLoc(), diag::note_omp_explicit_dsa)
           << getOpenMPClauseName(OMPC_aligned);
       continue;
@@ -14437,6 +15021,22 @@ Sema::ActOnOpenMPDependClause(OpenMPDependClauseKind DepKind,
       }
       OpsOffs.emplace_back(RHS, OOK);
     } else {
+      // OpenMP 5.0 [2.17.11, Restrictions]
+      // List items used in depend clauses cannot be zero-length array sections.
+      const auto *OASE = dyn_cast<OMPArraySectionExpr>(SimpleExpr);
+      if (OASE) {
+        const Expr *Length = OASE->getLength();
+        Expr::EvalResult Result;
+        if (Length && !Length->isValueDependent() &&
+            Length->EvaluateAsInt(Result, Context) &&
+            Result.Val.getInt().isNullValue()) {
+          Diag(ELoc,
+               diag::err_omp_depend_zero_length_array_section_not_allowed)
+              << SimpleExpr->getSourceRange();
+          continue;
+        }
+      }
+
       auto *ASE = dyn_cast<ArraySubscriptExpr>(SimpleExpr);
       if (!RefExpr->IgnoreParenImpCasts()->isLValue() ||
           (ASE &&
@@ -14496,7 +15096,7 @@ OMPClause *Sema::ActOnOpenMPDeviceClause(Expr *Device, SourceLocation StartLoc,
 
   OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
   OpenMPDirectiveKind CaptureRegion =
-      getOpenMPCaptureRegionForClause(DKind, OMPC_device);
+      getOpenMPCaptureRegionForClause(DKind, OMPC_device, LangOpts.OpenMP);
   if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
     ValExpr = MakeFullExpr(ValExpr).get();
     llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -14517,7 +15117,7 @@ static bool checkTypeMappable(SourceLocation SL, SourceRange SR, Sema &SemaRef,
     return false;
   }
   if (FullCheck && !SemaRef.CurContext->isDependentContext() &&
-      !QTy.isTrivialType(SemaRef.Context))
+      !QTy.isTriviallyCopyableType(SemaRef.Context))
     SemaRef.Diag(SL, diag::warn_omp_non_trivial_type_mapped) << QTy << SR;
   return true;
 }
@@ -15408,8 +16008,22 @@ static void checkMappableExpressionList(
           return MC.getAssociatedDeclaration();
         });
     assert(I != CurComponents.end() && "Null decl on map clause.");
-    QualType Type =
-        I->getAssociatedDeclaration()->getType().getNonReferenceType();
+    QualType Type;
+    auto *ASE = dyn_cast<ArraySubscriptExpr>(VE->IgnoreParens());
+    auto *OASE = dyn_cast<OMPArraySectionExpr>(VE->IgnoreParens());
+    if (ASE) {
+      Type = ASE->getType().getNonReferenceType();
+    } else if (OASE) {
+      QualType BaseType =
+          OMPArraySectionExpr::getBaseOriginalType(OASE->getBase());
+      if (const auto *ATy = BaseType->getAsArrayTypeUnsafe())
+        Type = ATy->getElementType();
+      else
+        Type = BaseType->getPointeeType();
+      Type = Type.getNonReferenceType();
+    } else {
+      Type = VE->getType();
+    }
 
     // OpenMP 4.5 [2.10.5, target update Construct, Restrictions, p.4]
     // A list item in a to or from clause must have a mappable type.
@@ -15419,6 +16033,8 @@ static void checkMappableExpressionList(
                            DSAS, Type))
       continue;
 
+    Type = I->getAssociatedDeclaration()->getType().getNonReferenceType();
+
     if (CKind == OMPC_map) {
       // target enter data
       // OpenMP [2.10.2, Restrictions, p. 99]
@@ -15948,7 +16564,7 @@ OMPClause *Sema::ActOnOpenMPNumTeamsClause(Expr *NumTeams,
 
   OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
   OpenMPDirectiveKind CaptureRegion =
-      getOpenMPCaptureRegionForClause(DKind, OMPC_num_teams);
+      getOpenMPCaptureRegionForClause(DKind, OMPC_num_teams, LangOpts.OpenMP);
   if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
     ValExpr = MakeFullExpr(ValExpr).get();
     llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -15974,8 +16590,8 @@ OMPClause *Sema::ActOnOpenMPThreadLimitClause(Expr *ThreadLimit,
     return nullptr;
 
   OpenMPDirectiveKind DKind = DSAStack->getCurrentDirective();
-  OpenMPDirectiveKind CaptureRegion =
-      getOpenMPCaptureRegionForClause(DKind, OMPC_thread_limit);
+  OpenMPDirectiveKind CaptureRegion = getOpenMPCaptureRegionForClause(
+      DKind, OMPC_thread_limit, LangOpts.OpenMP);
   if (CaptureRegion != OMPD_unknown && !CurContext->isDependentContext()) {
     ValExpr = MakeFullExpr(ValExpr).get();
     llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -16100,8 +16716,8 @@ OMPClause *Sema::ActOnOpenMPDistScheduleClause(
           return nullptr;
         }
       } else if (getOpenMPCaptureRegionForClause(
-                     DSAStack->getCurrentDirective(), OMPC_dist_schedule) !=
-                     OMPD_unknown &&
+                     DSAStack->getCurrentDirective(), OMPC_dist_schedule,
+                     LangOpts.OpenMP) != OMPD_unknown &&
                  !CurContext->isDependentContext()) {
         ValExpr = MakeFullExpr(ValExpr).get();
         llvm::MapVector<const Expr *, DeclRefExpr *> Captures;
@@ -16120,26 +16736,57 @@ OMPClause *Sema::ActOnOpenMPDefaultmapClause(
     OpenMPDefaultmapClauseModifier M, OpenMPDefaultmapClauseKind Kind,
     SourceLocation StartLoc, SourceLocation LParenLoc, SourceLocation MLoc,
     SourceLocation KindLoc, SourceLocation EndLoc) {
-  // OpenMP 4.5 only supports 'defaultmap(tofrom: scalar)'
-  if (M != OMPC_DEFAULTMAP_MODIFIER_tofrom || Kind != OMPC_DEFAULTMAP_scalar) {
-    std::string Value;
-    SourceLocation Loc;
-    Value += "'";
-    if (M != OMPC_DEFAULTMAP_MODIFIER_tofrom) {
-      Value += getOpenMPSimpleClauseTypeName(OMPC_defaultmap,
-                                             OMPC_DEFAULTMAP_MODIFIER_tofrom);
-      Loc = MLoc;
-    } else {
-      Value += getOpenMPSimpleClauseTypeName(OMPC_defaultmap,
-                                             OMPC_DEFAULTMAP_scalar);
-      Loc = KindLoc;
+  if (getLangOpts().OpenMP < 50) {
+    if (M != OMPC_DEFAULTMAP_MODIFIER_tofrom ||
+        Kind != OMPC_DEFAULTMAP_scalar) {
+      std::string Value;
+      SourceLocation Loc;
+      Value += "'";
+      if (M != OMPC_DEFAULTMAP_MODIFIER_tofrom) {
+        Value += getOpenMPSimpleClauseTypeName(OMPC_defaultmap,
+                                               OMPC_DEFAULTMAP_MODIFIER_tofrom);
+        Loc = MLoc;
+      } else {
+        Value += getOpenMPSimpleClauseTypeName(OMPC_defaultmap,
+                                               OMPC_DEFAULTMAP_scalar);
+        Loc = KindLoc;
+      }
+      Value += "'";
+      Diag(Loc, diag::err_omp_unexpected_clause_value)
+          << Value << getOpenMPClauseName(OMPC_defaultmap);
+      return nullptr;
+    }
+  } else {
+    bool isDefaultmapModifier = (M != OMPC_DEFAULTMAP_MODIFIER_unknown);
+    bool isDefaultmapKind = (Kind != OMPC_DEFAULTMAP_unknown);
+    if (!isDefaultmapKind || !isDefaultmapModifier) {
+      std::string ModifierValue = "'alloc', 'from', 'to', 'tofrom', "
+                                  "'firstprivate', 'none', 'default'";
+      std::string KindValue = "'scalar', 'aggregate', 'pointer'";
+      if (!isDefaultmapKind && isDefaultmapModifier) {
+        Diag(KindLoc, diag::err_omp_unexpected_clause_value)
+            << KindValue << getOpenMPClauseName(OMPC_defaultmap);
+      } else if (isDefaultmapKind && !isDefaultmapModifier) {
+        Diag(MLoc, diag::err_omp_unexpected_clause_value)
+            << ModifierValue << getOpenMPClauseName(OMPC_defaultmap);
+      } else {
+        Diag(MLoc, diag::err_omp_unexpected_clause_value)
+            << ModifierValue << getOpenMPClauseName(OMPC_defaultmap);
+        Diag(KindLoc, diag::err_omp_unexpected_clause_value)
+            << KindValue << getOpenMPClauseName(OMPC_defaultmap);
+      }
+      return nullptr;
+    }
+
+    // OpenMP [5.0, 2.12.5, Restrictions, p. 174]
+    //  At most one defaultmap clause for each category can appear on the
+    //  directive.
+    if (DSAStack->checkDefaultmapCategory(Kind)) {
+      Diag(StartLoc, diag::err_omp_one_defaultmap_each_category);
+      return nullptr;
     }
-    Value += "'";
-    Diag(Loc, diag::err_omp_unexpected_clause_value)
-        << Value << getOpenMPClauseName(OMPC_defaultmap);
-    return nullptr;
   }
-  DSAStack->setDefaultDMAToFromScalar(StartLoc);
+  DSAStack->setDefaultDMAAttr(M, Kind, StartLoc);
 
   return new (Context)
       OMPDefaultmapClause(StartLoc, LParenLoc, MLoc, KindLoc, EndLoc, Kind, M);
@@ -16604,3 +17251,42 @@ OMPClause *Sema::ActOnOpenMPAllocateClause(
   return OMPAllocateClause::Create(Context, StartLoc, LParenLoc, Allocator,
                                    ColonLoc, EndLoc, Vars);
 }
+
+OMPClause *Sema::ActOnOpenMPNontemporalClause(ArrayRef<Expr *> VarList,
+                                              SourceLocation StartLoc,
+                                              SourceLocation LParenLoc,
+                                              SourceLocation EndLoc) {
+  SmallVector<Expr *, 8> Vars;
+  for (Expr *RefExpr : VarList) {
+    assert(RefExpr && "NULL expr in OpenMP nontemporal clause.");
+    SourceLocation ELoc;
+    SourceRange ERange;
+    Expr *SimpleRefExpr = RefExpr;
+    auto Res = getPrivateItem(*this, SimpleRefExpr, ELoc, ERange);
+    if (Res.second)
+      // It will be analyzed later.
+      Vars.push_back(RefExpr);
+    ValueDecl *D = Res.first;
+    if (!D)
+      continue;
+
+    // OpenMP 5.0, 2.9.3.1 simd Construct, Restrictions.
+    // A list-item cannot appear in more than one nontemporal clause.
+    if (const Expr *PrevRef =
+            DSAStack->addUniqueNontemporal(D, SimpleRefExpr)) {
+      Diag(ELoc, diag::err_omp_used_in_clause_twice)
+          << 0 << getOpenMPClauseName(OMPC_nontemporal) << ERange;
+      Diag(PrevRef->getExprLoc(), diag::note_omp_explicit_dsa)
+          << getOpenMPClauseName(OMPC_nontemporal);
+      continue;
+    }
+
+    Vars.push_back(RefExpr);
+  }
+
+  if (Vars.empty())
+    return nullptr;
+
+  return OMPNontemporalClause::Create(Context, StartLoc, LParenLoc, EndLoc,
+                                      Vars);
+}
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 47c1e3cec0ea..0fd932fac970 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -60,14 +60,18 @@ CreateFunctionRefExpr(Sema &S, FunctionDecl *Fn, NamedDecl *FoundDecl,
   // being used.
   if (FoundDecl != Fn && S.DiagnoseUseOfDecl(Fn, Loc))
     return ExprError();
-  if (auto *FPT = Fn->getType()->getAs<FunctionProtoType>())
-    S.ResolveExceptionSpec(Loc, FPT);
   DeclRefExpr *DRE = new (S.Context)
       DeclRefExpr(S.Context, Fn, false, Fn->getType(), VK_LValue, Loc, LocInfo);
   if (HadMultipleCandidates)
     DRE->setHadMultipleCandidates(true);
 
   S.MarkDeclRefReferenced(DRE, Base);
+  if (auto *FPT = DRE->getType()->getAs<FunctionProtoType>()) {
+    if (isUnresolvedExceptionSpec(FPT->getExceptionSpecType())) {
+      S.ResolveExceptionSpec(Loc, FPT);
+      DRE->setType(Fn->getType());
+    }
+  }
   return S.ImpCastExprToType(DRE, S.Context.getPointerType(DRE->getType()),
                              CK_FunctionToPointerDecay);
 }
@@ -591,6 +595,12 @@ namespace {
     TemplateArgumentList *TemplateArgs;
     unsigned CallArgIndex;
   };
+  // Structure used by DeductionFailureInfo to store information about
+  // unsatisfied constraints.
+  struct CNSInfo {
+    TemplateArgumentList *TemplateArgs;
+    ConstraintSatisfaction Satisfaction;
+  };
 }
 
 /// Convert from Sema's representation of template deduction information
@@ -661,6 +671,14 @@ clang::MakeDeductionFailureInfo(ASTContext &Context,
     }
     break;
 
+  case Sema::TDK_ConstraintsNotSatisfied: {
+    CNSInfo *Saved = new (Context) CNSInfo;
+    Saved->TemplateArgs = Info.take();
+    Saved->Satisfaction = Info.AssociatedConstraintsSatisfaction;
+    Result.Data = Saved;
+    break;
+  }
+
   case Sema::TDK_Success:
   case Sema::TDK_NonDependentConversionFailure:
     llvm_unreachable("not a deduction failure");
@@ -701,6 +719,15 @@ void DeductionFailureInfo::Destroy() {
     }
     break;
 
+  case Sema::TDK_ConstraintsNotSatisfied:
+    // FIXME: Destroy the template argument list?
+    Data = nullptr;
+    if (PartialDiagnosticAt *Diag = getSFINAEDiagnostic()) {
+      Diag->~PartialDiagnosticAt();
+      HasDiagnostic = false;
+    }
+    break;
+
   // Unhandled
   case Sema::TDK_MiscellaneousDeductionFailure:
     break;
@@ -726,6 +753,7 @@ TemplateParameter DeductionFailureInfo::getTemplateParameter() {
   case Sema::TDK_NonDeducedMismatch:
   case Sema::TDK_CUDATargetMismatch:
   case Sema::TDK_NonDependentConversionFailure:
+  case Sema::TDK_ConstraintsNotSatisfied:
     return TemplateParameter();
 
   case Sema::TDK_Incomplete:
@@ -769,6 +797,9 @@ TemplateArgumentList *DeductionFailureInfo::getTemplateArgumentList() {
   case Sema::TDK_SubstitutionFailure:
     return static_cast<TemplateArgumentList*>(Data);
 
+  case Sema::TDK_ConstraintsNotSatisfied:
+    return static_cast<CNSInfo*>(Data)->TemplateArgs;
+
   // Unhandled
   case Sema::TDK_MiscellaneousDeductionFailure:
     break;
@@ -789,6 +820,7 @@ const TemplateArgument *DeductionFailureInfo::getFirstArg() {
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_CUDATargetMismatch:
   case Sema::TDK_NonDependentConversionFailure:
+  case Sema::TDK_ConstraintsNotSatisfied:
     return nullptr;
 
   case Sema::TDK_IncompletePack:
@@ -820,6 +852,7 @@ const TemplateArgument *DeductionFailureInfo::getSecondArg() {
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_CUDATargetMismatch:
   case Sema::TDK_NonDependentConversionFailure:
+  case Sema::TDK_ConstraintsNotSatisfied:
     return nullptr;
 
   case Sema::TDK_Inconsistent:
@@ -1104,7 +1137,8 @@ Sema::CheckOverload(Scope *S, FunctionDecl *New, const LookupResult &Old,
 }
 
 bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
-                      bool UseMemberUsingDeclRules, bool ConsiderCudaAttrs) {
+                      bool UseMemberUsingDeclRules, bool ConsiderCudaAttrs,
+                      bool ConsiderRequiresClauses) {
   // C++ [basic.start.main]p2: This function shall not be overloaded.
   if (New->isMain())
     return false;
@@ -1240,19 +1274,36 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
   if (getLangOpts().CUDA && ConsiderCudaAttrs) {
     // Don't allow overloading of destructors.  (In theory we could, but it
     // would be a giant change to clang.)
-    if (isa<CXXDestructorDecl>(New))
-      return false;
-
-    CUDAFunctionTarget NewTarget = IdentifyCUDATarget(New),
-                       OldTarget = IdentifyCUDATarget(Old);
-    if (NewTarget == CFT_InvalidTarget)
-      return false;
+    if (!isa<CXXDestructorDecl>(New)) {
+      CUDAFunctionTarget NewTarget = IdentifyCUDATarget(New),
+                         OldTarget = IdentifyCUDATarget(Old);
+      if (NewTarget != CFT_InvalidTarget) {
+        assert((OldTarget != CFT_InvalidTarget) &&
+               "Unexpected invalid target.");
+
+        // Allow overloading of functions with same signature and different CUDA
+        // target attributes.
+        if (NewTarget != OldTarget)
+          return true;
+      }
+    }
+  }
 
-    assert((OldTarget != CFT_InvalidTarget) && "Unexpected invalid target.");
+  if (ConsiderRequiresClauses) {
+    Expr *NewRC = New->getTrailingRequiresClause(),
+         *OldRC = Old->getTrailingRequiresClause();
+    if ((NewRC != nullptr) != (OldRC != nullptr))
+      // RC are most certainly different - these are overloads.
+      return true;
 
-    // Allow overloading of functions with same signature and different CUDA
-    // target attributes.
-    return NewTarget != OldTarget;
+    if (NewRC) {
+      llvm::FoldingSetNodeID NewID, OldID;
+      NewRC->Profile(NewID, Context, /*Canonical=*/true);
+      OldRC->Profile(OldID, Context, /*Canonical=*/true);
+      if (NewID != OldID)
+        // RCs are not equivalent - these are overloads.
+        return true;
+    }
   }
 
   // The signatures match; this is not an overload.
@@ -1326,7 +1377,7 @@ TryUserDefinedConversion(Sema &S, Expr *From, QualType ToType,
     ICS.Ambiguous.setToType(ToType);
     for (OverloadCandidateSet::iterator Cand = Conversions.begin();
          Cand != Conversions.end(); ++Cand)
-      if (Cand->Viable)
+      if (Cand->Best)
         ICS.Ambiguous.addConversion(Cand->FoundDecl, Cand->Function);
     break;
 
@@ -2802,8 +2853,8 @@ void Sema::HandleFunctionTypeMismatch(PartialDiagnostic &PDiag,
 
   // Get the function type from the pointers.
   if (FromType->isMemberPointerType() && ToType->isMemberPointerType()) {
-    const MemberPointerType *FromMember = FromType->getAs<MemberPointerType>(),
-                            *ToMember = ToType->getAs<MemberPointerType>();
+    const auto *FromMember = FromType->castAs<MemberPointerType>(),
+               *ToMember = ToType->castAs<MemberPointerType>();
     if (!Context.hasSameType(FromMember->getClass(), ToMember->getClass())) {
       PDiag << ft_different_class << QualType(ToMember->getClass(), 0)
             << QualType(FromMember->getClass(), 0);
@@ -2898,8 +2949,12 @@ bool Sema::FunctionParamTypesAreEqual(const FunctionProtoType *OldType,
                                               N = NewType->param_type_begin(),
                                               E = OldType->param_type_end();
        O && (O != E); ++O, ++N) {
-    if (!Context.hasSameType(O->getUnqualifiedType(),
-                             N->getUnqualifiedType())) {
+    // Ignore address spaces in pointee type. This is to disallow overloading
+    // on __ptr32/__ptr64 address spaces.
+    QualType Old = Context.removePtrSizeAddrSpace(O->getUnqualifiedType());
+    QualType New = Context.removePtrSizeAddrSpace(N->getUnqualifiedType());
+
+    if (!Context.hasSameType(Old, New)) {
       if (ArgPos)
         *ArgPos = O - OldType->param_type_begin();
       return false;
@@ -3114,6 +3169,70 @@ static bool isNonTrivialObjCLifetimeConversion(Qualifiers FromQuals,
   return true;
 }
 
+/// Perform a single iteration of the loop for checking if a qualification
+/// conversion is valid.
+///
+/// Specifically, check whether any change between the qualifiers of \p
+/// FromType and \p ToType is permissible, given knowledge about whether every
+/// outer layer is const-qualified.
+static bool isQualificationConversionStep(QualType FromType, QualType ToType,
+                                          bool CStyle,
+                                          bool &PreviousToQualsIncludeConst,
+                                          bool &ObjCLifetimeConversion) {
+  Qualifiers FromQuals = FromType.getQualifiers();
+  Qualifiers ToQuals = ToType.getQualifiers();
+
+  // Ignore __unaligned qualifier if this type is void.
+  if (ToType.getUnqualifiedType()->isVoidType())
+    FromQuals.removeUnaligned();
+
+  // Objective-C ARC:
+  //   Check Objective-C lifetime conversions.
+  if (FromQuals.getObjCLifetime() != ToQuals.getObjCLifetime()) {
+    if (ToQuals.compatiblyIncludesObjCLifetime(FromQuals)) {
+      if (isNonTrivialObjCLifetimeConversion(FromQuals, ToQuals))
+        ObjCLifetimeConversion = true;
+      FromQuals.removeObjCLifetime();
+      ToQuals.removeObjCLifetime();
+    } else {
+      // Qualification conversions cannot cast between different
+      // Objective-C lifetime qualifiers.
+      return false;
+    }
+  }
+
+  // Allow addition/removal of GC attributes but not changing GC attributes.
+  if (FromQuals.getObjCGCAttr() != ToQuals.getObjCGCAttr() &&
+      (!FromQuals.hasObjCGCAttr() || !ToQuals.hasObjCGCAttr())) {
+    FromQuals.removeObjCGCAttr();
+    ToQuals.removeObjCGCAttr();
+  }
+
+  //   -- for every j > 0, if const is in cv 1,j then const is in cv
+  //      2,j, and similarly for volatile.
+  if (!CStyle && !ToQuals.compatiblyIncludes(FromQuals))
+    return false;
+
+  // For a C-style cast, just require the address spaces to overlap.
+  // FIXME: Does "superset" also imply the representation of a pointer is the
+  // same? We're assuming that it does here and in compatiblyIncludes.
+  if (CStyle && !ToQuals.isAddressSpaceSupersetOf(FromQuals) &&
+      !FromQuals.isAddressSpaceSupersetOf(ToQuals))
+    return false;
+
+  //   -- if the cv 1,j and cv 2,j are different, then const is in
+  //      every cv for 0 < k < j.
+  if (!CStyle && FromQuals.getCVRQualifiers() != ToQuals.getCVRQualifiers() &&
+      !PreviousToQualsIncludeConst)
+    return false;
+
+  // Keep track of whether all prior cv-qualifiers in the "to" type
+  // include const.
+  PreviousToQualsIncludeConst =
+      PreviousToQualsIncludeConst && ToQuals.hasConst();
+  return true;
+}
+
 /// IsQualificationConversion - Determines whether the conversion from
 /// an rvalue of type FromType to ToType is a qualification conversion
 /// (C++ 4.4).
@@ -3139,73 +3258,16 @@ Sema::IsQualificationConversion(QualType FromType, QualType ToType,
   bool PreviousToQualsIncludeConst = true;
   bool UnwrappedAnyPointer = false;
   while (Context.UnwrapSimilarTypes(FromType, ToType)) {
-    // Within each iteration of the loop, we check the qualifiers to
-    // determine if this still looks like a qualification
-    // conversion. Then, if all is well, we unwrap one more level of
-    // pointers or pointers-to-members and do it all again
-    // until there are no more pointers or pointers-to-members left to
-    // unwrap.
-    UnwrappedAnyPointer = true;
-
-    Qualifiers FromQuals = FromType.getQualifiers();
-    Qualifiers ToQuals = ToType.getQualifiers();
-
-    // Ignore __unaligned qualifier if this type is void.
-    if (ToType.getUnqualifiedType()->isVoidType())
-      FromQuals.removeUnaligned();
-
-    // Objective-C ARC:
-    //   Check Objective-C lifetime conversions.
-    if (FromQuals.getObjCLifetime() != ToQuals.getObjCLifetime() &&
-        UnwrappedAnyPointer) {
-      if (ToQuals.compatiblyIncludesObjCLifetime(FromQuals)) {
-        if (isNonTrivialObjCLifetimeConversion(FromQuals, ToQuals))
-          ObjCLifetimeConversion = true;
-        FromQuals.removeObjCLifetime();
-        ToQuals.removeObjCLifetime();
-      } else {
-        // Qualification conversions cannot cast between different
-        // Objective-C lifetime qualifiers.
-        return false;
-      }
-    }
-
-    // Allow addition/removal of GC attributes but not changing GC attributes.
-    if (FromQuals.getObjCGCAttr() != ToQuals.getObjCGCAttr() &&
-        (!FromQuals.hasObjCGCAttr() || !ToQuals.hasObjCGCAttr())) {
-      FromQuals.removeObjCGCAttr();
-      ToQuals.removeObjCGCAttr();
-    }
-
-    //   -- for every j > 0, if const is in cv 1,j then const is in cv
-    //      2,j, and similarly for volatile.
-    if (!CStyle && !ToQuals.compatiblyIncludes(FromQuals))
-      return false;
-
-    //   -- if the cv 1,j and cv 2,j are different, then const is in
-    //      every cv for 0 < k < j.
-    if (!CStyle && FromQuals.getCVRQualifiers() != ToQuals.getCVRQualifiers()
-        && !PreviousToQualsIncludeConst)
+    if (!isQualificationConversionStep(FromType, ToType, CStyle,
+                                       PreviousToQualsIncludeConst,
+                                       ObjCLifetimeConversion))
       return false;
-
-    // Keep track of whether all prior cv-qualifiers in the "to" type
-    // include const.
-    PreviousToQualsIncludeConst
-      = PreviousToQualsIncludeConst && ToQuals.hasConst();
-  }
-
-  // Allows address space promotion by language rules implemented in
-  // Type::Qualifiers::isAddressSpaceSupersetOf.
-  Qualifiers FromQuals = FromType.getQualifiers();
-  Qualifiers ToQuals = ToType.getQualifiers();
-  if (!ToQuals.isAddressSpaceSupersetOf(FromQuals) &&
-      !FromQuals.isAddressSpaceSupersetOf(ToQuals)) {
-    return false;
+    UnwrappedAnyPointer = true;
   }
 
   // We are left with FromType and ToType being the pointee types
   // after unwrapping the original FromType and ToType the same number
-  // of types. If we unwrapped any pointers, and if FromType and
+  // of times. If we unwrapped any pointers, and if FromType and
   // ToType have the same unqualified type (since we checked
   // qualifiers above), then this is a qualification conversion.
   return UnwrappedAnyPointer && Context.hasSameUnqualifiedType(FromType,ToType);
@@ -3242,8 +3304,7 @@ static bool tryAtomicConversion(Sema &S, Expr *From, QualType ToType,
 static bool isFirstArgumentCompatibleWithType(ASTContext &Context,
                                               CXXConstructorDecl *Constructor,
                                               QualType Type) {
-  const FunctionProtoType *CtorType =
-      Constructor->getType()->getAs<FunctionProtoType>();
+  const auto *CtorType = Constructor->getType()->castAs<FunctionProtoType>();
   if (CtorType->getNumParams() > 0) {
     QualType FirstArg = CtorType->getParamType(0);
     if (Context.hasSameUnqualifiedType(Type, FirstArg.getNonReferenceType()))
@@ -3265,8 +3326,7 @@ IsInitializerListConstructorConversion(Sema &S, Expr *From, QualType ToType,
       continue;
 
     bool Usable = !Info.Constructor->isInvalidDecl() &&
-                  S.isInitListConstructor(Info.Constructor) &&
-                  (AllowExplicit || !Info.Constructor->isExplicit());
+                  S.isInitListConstructor(Info.Constructor);
     if (Usable) {
       // If the first argument is (a reference to) the target type,
       // suppress conversions.
@@ -3388,11 +3448,9 @@ IsUserDefinedConversion(Sema &S, Expr *From, QualType ToType,
           continue;
 
         bool Usable = !Info.Constructor->isInvalidDecl();
-        if (ListInitializing)
-          Usable = Usable && (AllowExplicit || !Info.Constructor->isExplicit());
-        else
-          Usable = Usable &&
-                   Info.Constructor->isConvertingConstructor(AllowExplicit);
+        if (!ListInitializing)
+          Usable = Usable && Info.Constructor->isConvertingConstructor(
+                                 /*AllowExplicit*/ true);
         if (Usable) {
           bool SuppressUserConversions = !ConstructorsOnly;
           if (SuppressUserConversions && ListInitializing) {
@@ -3446,16 +3504,14 @@ IsUserDefinedConversion(Sema &S, Expr *From, QualType ToType,
         else
           Conv = cast<CXXConversionDecl>(D);
 
-        if (AllowExplicit || !Conv->isExplicit()) {
-          if (ConvTemplate)
-            S.AddTemplateConversionCandidate(
-                ConvTemplate, FoundDecl, ActingContext, From, ToType,
-                CandidateSet, AllowObjCConversionOnExplicit, AllowExplicit);
-          else
-            S.AddConversionCandidate(
-                Conv, FoundDecl, ActingContext, From, ToType, CandidateSet,
-                AllowObjCConversionOnExplicit, AllowExplicit);
-        }
+        if (ConvTemplate)
+          S.AddTemplateConversionCandidate(
+              ConvTemplate, FoundDecl, ActingContext, From, ToType,
+              CandidateSet, AllowObjCConversionOnExplicit, AllowExplicit);
+        else
+          S.AddConversionCandidate(
+              Conv, FoundDecl, ActingContext, From, ToType, CandidateSet,
+              AllowObjCConversionOnExplicit, AllowExplicit);
       }
     }
   }
@@ -3547,7 +3603,10 @@ Sema::DiagnoseMultipleUserDefinedConversion(Expr *From, QualType ToType) {
         (OvResult == OR_No_Viable_Function && !CandidateSet.empty())))
     return false;
 
-  auto Cands = CandidateSet.CompleteCandidates(*this, OCD_AllCandidates, From);
+  auto Cands = CandidateSet.CompleteCandidates(
+      *this,
+      OvResult == OR_Ambiguous ? OCD_AmbiguousCandidates : OCD_AllCandidates,
+      From);
   if (OvResult == OR_Ambiguous)
     Diag(From->getBeginLoc(), diag::err_typecheck_ambiguous_condition)
         << From->getType() << ToType << From->getSourceRange();
@@ -3929,19 +3988,21 @@ CompareStandardConversionSequences(Sema &S, SourceLocation Loc,
     }
   }
 
-  // Compare based on qualification conversions (C++ 13.3.3.2p3,
-  // bullet 3).
-  if (ImplicitConversionSequence::CompareKind QualCK
-        = CompareQualificationConversions(S, SCS1, SCS2))
-    return QualCK;
-
   if (SCS1.ReferenceBinding && SCS2.ReferenceBinding) {
     // Check for a better reference binding based on the kind of bindings.
     if (isBetterReferenceBindingKind(SCS1, SCS2))
       return ImplicitConversionSequence::Better;
     else if (isBetterReferenceBindingKind(SCS2, SCS1))
       return ImplicitConversionSequence::Worse;
+  }
 
+  // Compare based on qualification conversions (C++ 13.3.3.2p3,
+  // bullet 3).
+  if (ImplicitConversionSequence::CompareKind QualCK
+        = CompareQualificationConversions(S, SCS1, SCS2))
+    return QualCK;
+
+  if (SCS1.ReferenceBinding && SCS2.ReferenceBinding) {
     // C++ [over.ics.rank]p3b4:
     //   -- S1 and S2 are reference bindings (8.5.3), and the types to
     //      which the references refer are the same type except for
@@ -3973,7 +4034,7 @@ CompareStandardConversionSequences(Sema &S, SourceLocation Loc,
         T2 = S.Context.getQualifiedType(UnqualT2, T2Quals);
       if (T2.isMoreQualifiedThan(T1))
         return ImplicitConversionSequence::Better;
-      else if (T1.isMoreQualifiedThan(T2))
+      if (T1.isMoreQualifiedThan(T2))
         return ImplicitConversionSequence::Worse;
     }
   }
@@ -4047,22 +4108,16 @@ CompareQualificationConversions(Sema &S,
   QualType T2 = SCS2.getToType(2);
   T1 = S.Context.getCanonicalType(T1);
   T2 = S.Context.getCanonicalType(T2);
+  assert(!T1->isReferenceType() && !T2->isReferenceType());
   Qualifiers T1Quals, T2Quals;
   QualType UnqualT1 = S.Context.getUnqualifiedArrayType(T1, T1Quals);
   QualType UnqualT2 = S.Context.getUnqualifiedArrayType(T2, T2Quals);
 
-  // If the types are the same, we won't learn anything by unwrapped
+  // If the types are the same, we won't learn anything by unwrapping
   // them.
   if (UnqualT1 == UnqualT2)
     return ImplicitConversionSequence::Indistinguishable;
 
-  // If the type is an array type, promote the element qualifiers to the type
-  // for comparison.
-  if (isa<ArrayType>(T1) && T1Quals)
-    T1 = S.Context.getQualifiedType(UnqualT1, T1Quals);
-  if (isa<ArrayType>(T2) && T2Quals)
-    T2 = S.Context.getQualifiedType(UnqualT2, T2Quals);
-
   ImplicitConversionSequence::CompareKind Result
     = ImplicitConversionSequence::Indistinguishable;
 
@@ -4290,14 +4345,10 @@ CompareDerivedToBaseConversions(Sema &S, SourceLocation Loc,
   if (SCS1.Second == ICK_Pointer_Member && SCS2.Second == ICK_Pointer_Member &&
       FromType1->isMemberPointerType() && FromType2->isMemberPointerType() &&
       ToType1->isMemberPointerType() && ToType2->isMemberPointerType()) {
-    const MemberPointerType * FromMemPointer1 =
-                                        FromType1->getAs<MemberPointerType>();
-    const MemberPointerType * ToMemPointer1 =
-                                          ToType1->getAs<MemberPointerType>();
-    const MemberPointerType * FromMemPointer2 =
-                                          FromType2->getAs<MemberPointerType>();
-    const MemberPointerType * ToMemPointer2 =
-                                          ToType2->getAs<MemberPointerType>();
+    const auto *FromMemPointer1 = FromType1->castAs<MemberPointerType>();
+    const auto *ToMemPointer1 = ToType1->castAs<MemberPointerType>();
+    const auto *FromMemPointer2 = FromType2->castAs<MemberPointerType>();
+    const auto *ToMemPointer2 = ToType2->castAs<MemberPointerType>();
     const Type *FromPointeeType1 = FromMemPointer1->getClass();
     const Type *ToPointeeType1 = ToMemPointer1->getClass();
     const Type *FromPointeeType2 = FromMemPointer2->getClass();
@@ -4360,20 +4411,26 @@ static bool isTypeValid(QualType T) {
   return true;
 }
 
+static QualType withoutUnaligned(ASTContext &Ctx, QualType T) {
+  if (!T.getQualifiers().hasUnaligned())
+    return T;
+
+  Qualifiers Q;
+  T = Ctx.getUnqualifiedArrayType(T, Q);
+  Q.removeUnaligned();
+  return Ctx.getQualifiedType(T, Q);
+}
+
 /// CompareReferenceRelationship - Compare the two types T1 and T2 to
-/// determine whether they are reference-related,
-/// reference-compatible, reference-compatible with added
-/// qualification, or incompatible, for use in C++ initialization by
+/// determine whether they are reference-compatible,
+/// reference-related, or incompatible, for use in C++ initialization by
 /// reference (C++ [dcl.ref.init]p4). Neither type can be a reference
 /// type, and the first type (T1) is the pointee type of the reference
 /// type being initialized.
 Sema::ReferenceCompareResult
 Sema::CompareReferenceRelationship(SourceLocation Loc,
                                    QualType OrigT1, QualType OrigT2,
-                                   bool &DerivedToBase,
-                                   bool &ObjCConversion,
-                                   bool &ObjCLifetimeConversion,
-                                   bool &FunctionConversion) {
+                                   ReferenceConversions *ConvOut) {
   assert(!OrigT1->isReferenceType() &&
     "T1 must be the pointee type of the reference type");
   assert(!OrigT2->isReferenceType() && "T2 cannot be a reference type");
@@ -4384,76 +4441,84 @@ Sema::CompareReferenceRelationship(SourceLocation Loc,
   QualType UnqualT1 = Context.getUnqualifiedArrayType(T1, T1Quals);
   QualType UnqualT2 = Context.getUnqualifiedArrayType(T2, T2Quals);
 
-  // C++ [dcl.init.ref]p4:
+  ReferenceConversions ConvTmp;
+  ReferenceConversions &Conv = ConvOut ? *ConvOut : ConvTmp;
+  Conv = ReferenceConversions();
+
+  // C++2a [dcl.init.ref]p4:
   //   Given types "cv1 T1" and "cv2 T2," "cv1 T1" is
-  //   reference-related to "cv2 T2" if T1 is the same type as T2, or
+  //   reference-related to "cv2 T2" if T1 is similar to T2, or
   //   T1 is a base class of T2.
-  DerivedToBase = false;
-  ObjCConversion = false;
-  ObjCLifetimeConversion = false;
+  //   "cv1 T1" is reference-compatible with "cv2 T2" if
+  //   a prvalue of type "pointer to cv2 T2" can be converted to the type
+  //   "pointer to cv1 T1" via a standard conversion sequence.
+
+  // Check for standard conversions we can apply to pointers: derived-to-base
+  // conversions, ObjC pointer conversions, and function pointer conversions.
+  // (Qualification conversions are checked last.)
   QualType ConvertedT2;
   if (UnqualT1 == UnqualT2) {
     // Nothing to do.
   } else if (isCompleteType(Loc, OrigT2) &&
              isTypeValid(UnqualT1) && isTypeValid(UnqualT2) &&
              IsDerivedFrom(Loc, UnqualT2, UnqualT1))
-    DerivedToBase = true;
+    Conv |= ReferenceConversions::DerivedToBase;
   else if (UnqualT1->isObjCObjectOrInterfaceType() &&
            UnqualT2->isObjCObjectOrInterfaceType() &&
            Context.canBindObjCObjectType(UnqualT1, UnqualT2))
-    ObjCConversion = true;
+    Conv |= ReferenceConversions::ObjC;
   else if (UnqualT2->isFunctionType() &&
            IsFunctionConversion(UnqualT2, UnqualT1, ConvertedT2)) {
-    // C++1z [dcl.init.ref]p4:
-    //   cv1 T1" is reference-compatible with "cv2 T2" if [...] T2 is "noexcept
-    //   function" and T1 is "function"
-    //
-    // We extend this to also apply to 'noreturn', so allow any function
-    // conversion between function types.
-    FunctionConversion = true;
+    Conv |= ReferenceConversions::Function;
+    // No need to check qualifiers; function types don't have them.
     return Ref_Compatible;
-  } else
-    return Ref_Incompatible;
-
-  // At this point, we know that T1 and T2 are reference-related (at
-  // least).
-
-  // If the type is an array type, promote the element qualifiers to the type
-  // for comparison.
-  if (isa<ArrayType>(T1) && T1Quals)
-    T1 = Context.getQualifiedType(UnqualT1, T1Quals);
-  if (isa<ArrayType>(T2) && T2Quals)
-    T2 = Context.getQualifiedType(UnqualT2, T2Quals);
-
-  // C++ [dcl.init.ref]p4:
-  //   "cv1 T1" is reference-compatible with "cv2 T2" if T1 is
-  //   reference-related to T2 and cv1 is the same cv-qualification
-  //   as, or greater cv-qualification than, cv2. For purposes of
-  //   overload resolution, cases for which cv1 is greater
-  //   cv-qualification than cv2 are identified as
-  //   reference-compatible with added qualification (see 13.3.3.2).
-  //
-  // Note that we also require equivalence of Objective-C GC and address-space
-  // qualifiers when performing these computations, so that e.g., an int in
-  // address space 1 is not reference-compatible with an int in address
-  // space 2.
-  if (T1Quals.getObjCLifetime() != T2Quals.getObjCLifetime() &&
-      T1Quals.compatiblyIncludesObjCLifetime(T2Quals)) {
-    if (isNonTrivialObjCLifetimeConversion(T2Quals, T1Quals))
-      ObjCLifetimeConversion = true;
-
-    T1Quals.removeObjCLifetime();
-    T2Quals.removeObjCLifetime();
   }
+  bool ConvertedReferent = Conv != 0;
 
-  // MS compiler ignores __unaligned qualifier for references; do the same.
-  T1Quals.removeUnaligned();
-  T2Quals.removeUnaligned();
+  // We can have a qualification conversion. Compute whether the types are
+  // similar at the same time.
+  bool PreviousToQualsIncludeConst = true;
+  bool TopLevel = true;
+  do {
+    if (T1 == T2)
+      break;
 
-  if (T1Quals.compatiblyIncludes(T2Quals))
-    return Ref_Compatible;
-  else
-    return Ref_Related;
+    // We will need a qualification conversion.
+    Conv |= ReferenceConversions::Qualification;
+
+    // Track whether we performed a qualification conversion anywhere other
+    // than the top level. This matters for ranking reference bindings in
+    // overload resolution.
+    if (!TopLevel)
+      Conv |= ReferenceConversions::NestedQualification;
+
+    // MS compiler ignores __unaligned qualifier for references; do the same.
+    T1 = withoutUnaligned(Context, T1);
+    T2 = withoutUnaligned(Context, T2);
+
+    // If we find a qualifier mismatch, the types are not reference-compatible,
+    // but are still be reference-related if they're similar.
+    bool ObjCLifetimeConversion = false;
+    if (!isQualificationConversionStep(T2, T1, /*CStyle=*/false,
+                                       PreviousToQualsIncludeConst,
+                                       ObjCLifetimeConversion))
+      return (ConvertedReferent || Context.hasSimilarType(T1, T2))
+                 ? Ref_Related
+                 : Ref_Incompatible;
+
+    // FIXME: Should we track this for any level other than the first?
+    if (ObjCLifetimeConversion)
+      Conv |= ReferenceConversions::ObjCLifetime;
+
+    TopLevel = false;
+  } while (Context.UnwrapSimilarTypes(T1, T2));
+
+  // At this point, if the types are reference-related, we must either have the
+  // same inner type (ignoring qualifiers), or must have already worked out how
+  // to convert the referent.
+  return (ConvertedReferent || Context.hasSameUnqualifiedType(T1, T2))
+             ? Ref_Compatible
+             : Ref_Incompatible;
 }
 
 /// Look for a user-defined conversion to a value reference-compatible
@@ -4464,8 +4529,7 @@ FindConversionForRefInit(Sema &S, ImplicitConversionSequence &ICS,
                          Expr *Init, QualType T2, bool AllowRvalues,
                          bool AllowExplicit) {
   assert(T2->isRecordType() && "Can only find conversions of record types.");
-  CXXRecordDecl *T2RecordDecl
-    = dyn_cast<CXXRecordDecl>(T2->castAs<RecordType>()->getDecl());
+  auto *T2RecordDecl = cast<CXXRecordDecl>(T2->castAs<RecordType>()->getDecl());
 
   OverloadCandidateSet CandidateSet(
       DeclLoc, OverloadCandidateSet::CSK_InitByUserDefinedConversion);
@@ -4484,17 +4548,7 @@ FindConversionForRefInit(Sema &S, ImplicitConversionSequence &ICS,
     else
       Conv = cast<CXXConversionDecl>(D);
 
-    // If this is an explicit conversion, and we're not allowed to consider
-    // explicit conversions, skip it.
-    if (!AllowExplicit && Conv->isExplicit())
-      continue;
-
     if (AllowRvalues) {
-      bool DerivedToBase = false;
-      bool ObjCConversion = false;
-      bool ObjCLifetimeConversion = false;
-      bool FunctionConversion = false;
-
       // If we are initializing an rvalue reference, don't permit conversion
       // functions that return lvalues.
       if (!ConvTemplate && DeclType->isRValueReferenceType()) {
@@ -4510,9 +4564,8 @@ FindConversionForRefInit(Sema &S, ImplicitConversionSequence &ICS,
               Conv->getConversionType()
                   .getNonReferenceType()
                   .getUnqualifiedType(),
-              DeclType.getNonReferenceType().getUnqualifiedType(),
-              DerivedToBase, ObjCConversion, ObjCLifetimeConversion,
-              FunctionConversion) == Sema::Ref_Incompatible)
+              DeclType.getNonReferenceType().getUnqualifiedType()) ==
+              Sema::Ref_Incompatible)
         continue;
     } else {
       // If the conversion function doesn't return a reference type,
@@ -4571,7 +4624,7 @@ FindConversionForRefInit(Sema &S, ImplicitConversionSequence &ICS,
     ICS.setAmbiguous();
     for (OverloadCandidateSet::iterator Cand = CandidateSet.begin();
          Cand != CandidateSet.end(); ++Cand)
-      if (Cand->Viable)
+      if (Cand->Best)
         ICS.Ambiguous.addConversion(Cand->FoundDecl, Cand->Function);
     return true;
 
@@ -4613,14 +4666,44 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
 
   // Compute some basic properties of the types and the initializer.
   bool isRValRef = DeclType->isRValueReferenceType();
-  bool DerivedToBase = false;
-  bool ObjCConversion = false;
-  bool ObjCLifetimeConversion = false;
-  bool FunctionConversion = false;
   Expr::Classification InitCategory = Init->Classify(S.Context);
-  Sema::ReferenceCompareResult RefRelationship = S.CompareReferenceRelationship(
-      DeclLoc, T1, T2, DerivedToBase, ObjCConversion, ObjCLifetimeConversion,
-      FunctionConversion);
+
+  Sema::ReferenceConversions RefConv;
+  Sema::ReferenceCompareResult RefRelationship =
+      S.CompareReferenceRelationship(DeclLoc, T1, T2, &RefConv);
+
+  auto SetAsReferenceBinding = [&](bool BindsDirectly) {
+    ICS.setStandard();
+    ICS.Standard.First = ICK_Identity;
+    // FIXME: A reference binding can be a function conversion too. We should
+    // consider that when ordering reference-to-function bindings.
+    ICS.Standard.Second = (RefConv & Sema::ReferenceConversions::DerivedToBase)
+                              ? ICK_Derived_To_Base
+                              : (RefConv & Sema::ReferenceConversions::ObjC)
+                                    ? ICK_Compatible_Conversion
+                                    : ICK_Identity;
+    // FIXME: As a speculative fix to a defect introduced by CWG2352, we rank
+    // a reference binding that performs a non-top-level qualification
+    // conversion as a qualification conversion, not as an identity conversion.
+    ICS.Standard.Third = (RefConv &
+                              Sema::ReferenceConversions::NestedQualification)
+                             ? ICK_Qualification
+                             : ICK_Identity;
+    ICS.Standard.FromTypePtr = T2.getAsOpaquePtr();
+    ICS.Standard.setToType(0, T2);
+    ICS.Standard.setToType(1, T1);
+    ICS.Standard.setToType(2, T1);
+    ICS.Standard.ReferenceBinding = true;
+    ICS.Standard.DirectBinding = BindsDirectly;
+    ICS.Standard.IsLvalueReference = !isRValRef;
+    ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
+    ICS.Standard.BindsToRvalue = InitCategory.isRValue();
+    ICS.Standard.BindsImplicitObjectArgumentWithoutRefQualifier = false;
+    ICS.Standard.ObjCLifetimeConversionBinding =
+        (RefConv & Sema::ReferenceConversions::ObjCLifetime) != 0;
+    ICS.Standard.CopyConstructor = nullptr;
+    ICS.Standard.DeprecatedStringLiteralToCharPtr = false;
+  };
 
   // C++0x [dcl.init.ref]p5:
   //   A reference to type "cv1 T1" is initialized by an expression
@@ -4640,25 +4723,7 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
       //   has a type that is a derived class of the parameter type,
       //   in which case the implicit conversion sequence is a
       //   derived-to-base Conversion (13.3.3.1).
-      ICS.setStandard();
-      ICS.Standard.First = ICK_Identity;
-      ICS.Standard.Second = DerivedToBase? ICK_Derived_To_Base
-                         : ObjCConversion? ICK_Compatible_Conversion
-                         : ICK_Identity;
-      ICS.Standard.Third = ICK_Identity;
-      ICS.Standard.FromTypePtr = T2.getAsOpaquePtr();
-      ICS.Standard.setToType(0, T2);
-      ICS.Standard.setToType(1, T1);
-      ICS.Standard.setToType(2, T1);
-      ICS.Standard.ReferenceBinding = true;
-      ICS.Standard.DirectBinding = true;
-      ICS.Standard.IsLvalueReference = !isRValRef;
-      ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
-      ICS.Standard.BindsToRvalue = false;
-      ICS.Standard.BindsImplicitObjectArgumentWithoutRefQualifier = false;
-      ICS.Standard.ObjCLifetimeConversionBinding = ObjCLifetimeConversion;
-      ICS.Standard.CopyConstructor = nullptr;
-      ICS.Standard.DeprecatedStringLiteralToCharPtr = false;
+      SetAsReferenceBinding(/*BindsDirectly=*/true);
 
       // Nothing more to do: the inaccessibility/ambiguity check for
       // derived-to-base conversions is suppressed when we're
@@ -4696,34 +4761,16 @@ TryReferenceInit(Sema &S, Expr *Init, QualType DeclType,
   //               lvalue and "cv1 T1" is reference-compatible with "cv2 T2", or
   if (RefRelationship == Sema::Ref_Compatible &&
       (InitCategory.isXValue() ||
-       (InitCategory.isPRValue() && (T2->isRecordType() || T2->isArrayType())) ||
+       (InitCategory.isPRValue() &&
+          (T2->isRecordType() || T2->isArrayType())) ||
        (InitCategory.isLValue() && T2->isFunctionType()))) {
-    ICS.setStandard();
-    ICS.Standard.First = ICK_Identity;
-    ICS.Standard.Second = DerivedToBase? ICK_Derived_To_Base
-                      : ObjCConversion? ICK_Compatible_Conversion
-                      : ICK_Identity;
-    ICS.Standard.Third = ICK_Identity;
-    ICS.Standard.FromTypePtr = T2.getAsOpaquePtr();
-    ICS.Standard.setToType(0, T2);
-    ICS.Standard.setToType(1, T1);
-    ICS.Standard.setToType(2, T1);
-    ICS.Standard.ReferenceBinding = true;
-    // In C++0x, this is always a direct binding. In C++98/03, it's a direct
+    // In C++11, this is always a direct binding. In C++98/03, it's a direct
     // binding unless we're binding to a class prvalue.
     // Note: Although xvalues wouldn't normally show up in C++98/03 code, we
     // allow the use of rvalue references in C++98/03 for the benefit of
     // standard library implementors; therefore, we need the xvalue check here.
-    ICS.Standard.DirectBinding =
-      S.getLangOpts().CPlusPlus11 ||
-      !(InitCategory.isPRValue() || T2->isRecordType());
-    ICS.Standard.IsLvalueReference = !isRValRef;
-    ICS.Standard.BindsToFunctionLvalue = T2->isFunctionType();
-    ICS.Standard.BindsToRvalue = InitCategory.isRValue();
-    ICS.Standard.BindsImplicitObjectArgumentWithoutRefQualifier = false;
-    ICS.Standard.ObjCLifetimeConversionBinding = ObjCLifetimeConversion;
-    ICS.Standard.CopyConstructor = nullptr;
-    ICS.Standard.DeprecatedStringLiteralToCharPtr = false;
+    SetAsReferenceBinding(/*BindsDirectly=*/S.getLangOpts().CPlusPlus11 ||
+                          !(InitCategory.isPRValue() || T2->isRecordType()));
     return ICS;
   }
 
@@ -5042,13 +5089,8 @@ TryListConversion(Sema &S, InitListExpr *From, QualType ToType,
       }
 
       // Compute some basic properties of the types and the initializer.
-      bool dummy1 = false;
-      bool dummy2 = false;
-      bool dummy3 = false;
-      bool dummy4 = false;
       Sema::ReferenceCompareResult RefRelationship =
-          S.CompareReferenceRelationship(From->getBeginLoc(), T1, T2, dummy1,
-                                         dummy2, dummy3, dummy4);
+          S.CompareReferenceRelationship(From->getBeginLoc(), T1, T2);
 
       if (RefRelationship >= Sema::Ref_Related) {
         return TryReferenceInit(S, Init, ToType, /*FIXME*/ From->getBeginLoc(),
@@ -5218,7 +5260,7 @@ TryObjectArgumentInitialization(Sema &S, SourceLocation Loc, QualType FromType,
     return ICS;
   }
 
-  if (FromTypeCanon.getQualifiers().hasAddressSpace()) {
+  if (FromTypeCanon.hasAddressSpace()) {
     Qualifiers QualsImplicitParamType = ImplicitParamType.getQualifiers();
     Qualifiers QualsFromType = FromTypeCanon.getQualifiers();
     if (!QualsImplicitParamType.isAddressSpaceSupersetOf(QualsFromType)) {
@@ -5367,7 +5409,10 @@ Sema::PerformObjectArgumentInitialization(Expr *From,
 
   if (!Context.hasSameType(From->getType(), DestType)) {
     CastKind CK;
-    if (FromRecordType.getAddressSpace() != DestType.getAddressSpace())
+    QualType PteeTy = DestType->getPointeeType();
+    LangAS DestAS =
+        PteeTy.isNull() ? DestType.getAddressSpace() : PteeTy.getAddressSpace();
+    if (FromRecordType.getAddressSpace() != DestAS)
       CK = CK_AddressSpaceConversion;
     else
       CK = CK_NoOp;
@@ -6046,7 +6091,7 @@ static bool IsAcceptableNonMemberOperatorCandidate(ASTContext &Context,
   if (T1->isRecordType() || (!T2.isNull() && T2->isRecordType()))
     return true;
 
-  const FunctionProtoType *Proto = Fn->getType()->getAs<FunctionProtoType>();
+  const auto *Proto = Fn->getType()->castAs<FunctionProtoType>();
   if (Proto->getNumParams() < 1)
     return false;
 
@@ -6146,6 +6191,15 @@ void Sema::AddOverloadCandidate(
   Candidate.IgnoreObjectArgument = false;
   Candidate.ExplicitCallArguments = Args.size();
 
+  // Explicit functions are not actually candidates at all if we're not
+  // allowing them in this context, but keep them around so we can point
+  // to them in diagnostics.
+  if (!AllowExplicit && ExplicitSpecifier::getFromDecl(Function).isExplicit()) {
+    Candidate.Viable = false;
+    Candidate.FailureKind = ovl_fail_explicit;
+    return;
+  }
+
   if (Function->isMultiVersion() && Function->hasAttr<TargetAttr>() &&
       !Function->getAttr<TargetAttr>()->isDefaultVersion()) {
     Candidate.Viable = false;
@@ -6237,6 +6291,16 @@ void Sema::AddOverloadCandidate(
         return;
       }
 
+  if (Expr *RequiresClause = Function->getTrailingRequiresClause()) {
+    ConstraintSatisfaction Satisfaction;
+    if (CheckConstraintSatisfaction(RequiresClause, Satisfaction) ||
+        !Satisfaction.IsSatisfied) {
+      Candidate.Viable = false;
+      Candidate.FailureKind = ovl_fail_constraints_not_satisfied;
+      return;
+    }
+  }
+
   // Determine the implicit conversion sequences for each of the
   // arguments.
   for (unsigned ArgIdx = 0; ArgIdx < Args.size(); ++ArgIdx) {
@@ -6269,15 +6333,6 @@ void Sema::AddOverloadCandidate(
     }
   }
 
-  if (!AllowExplicit) {
-    ExplicitSpecifier ES = ExplicitSpecifier::getFromDecl(Function);
-    if (ES.getKind() != ExplicitSpecKind::ResolvedFalse) {
-      Candidate.Viable = false;
-      Candidate.FailureKind = ovl_fail_explicit_resolved;
-      return;
-    }
-  }
-
   if (EnableIfAttr *FailedAttr = CheckEnableIf(Function, Args)) {
     Candidate.Viable = false;
     Candidate.FailureKind = ovl_fail_enable_if;
@@ -6753,6 +6808,16 @@ Sema::AddMethodCandidate(CXXMethodDecl *Method, DeclAccessPair FoundDecl,
         return;
       }
 
+  if (Expr *RequiresClause = Method->getTrailingRequiresClause()) {
+    ConstraintSatisfaction Satisfaction;
+    if (CheckConstraintSatisfaction(RequiresClause, Satisfaction) ||
+        !Satisfaction.IsSatisfied) {
+      Candidate.Viable = false;
+      Candidate.FailureKind = ovl_fail_constraints_not_satisfied;
+      return;
+    }
+  }
+
   // Determine the implicit conversion sequences for each of the
   // arguments.
   for (unsigned ArgIdx = 0; ArgIdx < Args.size(); ++ArgIdx) {
@@ -6866,6 +6931,12 @@ void Sema::AddMethodTemplateCandidate(
                      Conversions, PO);
 }
 
+/// Determine whether a given function template has a simple explicit specifier
+/// or a non-value-dependent explicit-specification that evaluates to true.
+static bool isNonDependentlyExplicit(FunctionTemplateDecl *FTD) {
+  return ExplicitSpecifier::getFromDecl(FTD->getTemplatedDecl()).isExplicit();
+}
+
 /// Add a C++ function template specialization as a candidate
 /// in the candidate set, using template argument deduction to produce
 /// an appropriate function template specialization.
@@ -6878,6 +6949,18 @@ void Sema::AddTemplateOverloadCandidate(
   if (!CandidateSet.isNewCandidate(FunctionTemplate, PO))
     return;
 
+  // If the function template has a non-dependent explicit specification,
+  // exclude it now if appropriate; we are not permitted to perform deduction
+  // and substitution in this case.
+  if (!AllowExplicit && isNonDependentlyExplicit(FunctionTemplate)) {
+    OverloadCandidate &Candidate = CandidateSet.addCandidate();
+    Candidate.FoundDecl = FoundDecl;
+    Candidate.Function = FunctionTemplate->getTemplatedDecl();
+    Candidate.Viable = false;
+    Candidate.FailureKind = ovl_fail_explicit;
+    return;
+  }
+
   // C++ [over.match.funcs]p7:
   //   In each case where a candidate is a function template, candidate
   //   function template specializations are generated using template argument
@@ -7065,6 +7148,9 @@ void Sema::AddConversionCandidate(
   // Per C++ [over.match.conv]p1, [over.match.ref]p1, an explicit conversion
   // operator is only a candidate if its return type is the target type or
   // can be converted to the target type with a qualification conversion.
+  //
+  // FIXME: Include such functions in the candidate list and explain why we
+  // can't select them.
   if (Conversion->isExplicit() &&
       !isAllowableExplicitConversion(*this, ConvType, ToType,
                                      AllowObjCConversionOnExplicit))
@@ -7086,6 +7172,15 @@ void Sema::AddConversionCandidate(
   Candidate.Viable = true;
   Candidate.ExplicitCallArguments = 1;
 
+  // Explicit functions are not actually candidates at all if we're not
+  // allowing them in this context, but keep them around so we can point
+  // to them in diagnostics.
+  if (!AllowExplicit && Conversion->isExplicit()) {
+    Candidate.Viable = false;
+    Candidate.FailureKind = ovl_fail_explicit;
+    return;
+  }
+
   // C++ [over.match.funcs]p4:
   //   For conversion functions, the function is considered to be a member of
   //   the class of the implicit implied object argument for the purpose of
@@ -7109,6 +7204,17 @@ void Sema::AddConversionCandidate(
     return;
   }
 
+  Expr *RequiresClause = Conversion->getTrailingRequiresClause();
+  if (RequiresClause) {
+    ConstraintSatisfaction Satisfaction;
+    if (CheckConstraintSatisfaction(RequiresClause, Satisfaction) ||
+        !Satisfaction.IsSatisfied) {
+      Candidate.Viable = false;
+      Candidate.FailureKind = ovl_fail_constraints_not_satisfied;
+      return;
+    }
+  }
+
   // We won't go through a user-defined type conversion function to convert a
   // derived to base as such conversions are given Conversion Rank. They only
   // go through a copy constructor. 13.3.3.1.2-p4 [over.ics.user]
@@ -7199,13 +7305,6 @@ void Sema::AddConversionCandidate(
            "Can only end up with a standard conversion sequence or failure");
   }
 
-  if (!AllowExplicit && Conversion->getExplicitSpecifier().getKind() !=
-                            ExplicitSpecKind::ResolvedFalse) {
-    Candidate.Viable = false;
-    Candidate.FailureKind = ovl_fail_explicit_resolved;
-    return;
-  }
-
   if (EnableIfAttr *FailedAttr = CheckEnableIf(Conversion, None)) {
     Candidate.Viable = false;
     Candidate.FailureKind = ovl_fail_enable_if;
@@ -7236,6 +7335,18 @@ void Sema::AddTemplateConversionCandidate(
   if (!CandidateSet.isNewCandidate(FunctionTemplate))
     return;
 
+  // If the function template has a non-dependent explicit specification,
+  // exclude it now if appropriate; we are not permitted to perform deduction
+  // and substitution in this case.
+  if (!AllowExplicit && isNonDependentlyExplicit(FunctionTemplate)) {
+    OverloadCandidate &Candidate = CandidateSet.addCandidate();
+    Candidate.FoundDecl = FoundDecl;
+    Candidate.Function = FunctionTemplate->getTemplatedDecl();
+    Candidate.Viable = false;
+    Candidate.FailureKind = ovl_fail_explicit;
+    return;
+  }
+
   TemplateDeductionInfo Info(CandidateSet.getLocation());
   CXXConversionDecl *Specialization = nullptr;
   if (TemplateDeductionResult Result
@@ -9440,6 +9551,35 @@ bool clang::isBetterOverloadCandidate(
       return BetterTemplate == Cand1.Function->getPrimaryTemplate();
   }
 
+  //   -— F1 and F2 are non-template functions with the same
+  //      parameter-type-lists, and F1 is more constrained than F2 [...],
+  if (Cand1.Function && Cand2.Function && !Cand1IsSpecialization &&
+      !Cand2IsSpecialization && Cand1.Function->hasPrototype() &&
+      Cand2.Function->hasPrototype()) {
+    auto *PT1 = cast<FunctionProtoType>(Cand1.Function->getFunctionType());
+    auto *PT2 = cast<FunctionProtoType>(Cand2.Function->getFunctionType());
+    if (PT1->getNumParams() == PT2->getNumParams() &&
+        PT1->isVariadic() == PT2->isVariadic() &&
+        S.FunctionParamTypesAreEqual(PT1, PT2)) {
+      Expr *RC1 = Cand1.Function->getTrailingRequiresClause();
+      Expr *RC2 = Cand2.Function->getTrailingRequiresClause();
+      if (RC1 && RC2) {
+        bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+        if (S.IsAtLeastAsConstrained(Cand1.Function, {RC1}, Cand2.Function,
+                                     {RC2}, AtLeastAsConstrained1))
+          return false;
+        if (!AtLeastAsConstrained1)
+          return false;
+        if (S.IsAtLeastAsConstrained(Cand2.Function, {RC2}, Cand1.Function,
+                                     {RC1}, AtLeastAsConstrained2))
+          return false;
+        if (!AtLeastAsConstrained2)
+          return true;
+      } else if (RC1 || RC2)
+        return RC1 != nullptr;
+    }
+  }
+
   //   -- F1 is a constructor for a class D, F2 is a constructor for a base
   //      class B of D, and for all arguments the corresponding parameters of
   //      F1 and F2 have the same type.
@@ -9527,8 +9667,7 @@ bool Sema::isEquivalentInternalLinkageDeclaration(const NamedDecl *A,
   // entity in different modules.
   if (!VA->getDeclContext()->getRedeclContext()->Equals(
           VB->getDeclContext()->getRedeclContext()) ||
-      getOwningModule(const_cast<ValueDecl *>(VA)) ==
-          getOwningModule(const_cast<ValueDecl *>(VB)) ||
+      getOwningModule(VA) == getOwningModule(VB) ||
       VA->isExternallyVisible() || VB->isExternallyVisible())
     return false;
 
@@ -9565,12 +9704,12 @@ void Sema::diagnoseEquivalentInternalLinkageDeclarations(
     SourceLocation Loc, const NamedDecl *D, ArrayRef<const NamedDecl *> Equiv) {
   Diag(Loc, diag::ext_equivalent_internal_linkage_decl_in_modules) << D;
 
-  Module *M = getOwningModule(const_cast<NamedDecl*>(D));
+  Module *M = getOwningModule(D);
   Diag(D->getLocation(), diag::note_equivalent_internal_linkage_decl)
       << !M << (M ? M->getFullModuleName() : "");
 
   for (auto *E : Equiv) {
-    Module *M = getOwningModule(const_cast<NamedDecl*>(E));
+    Module *M = getOwningModule(E);
     Diag(E->getLocation(), diag::note_equivalent_internal_linkage_decl)
         << !M << (M ? M->getFullModuleName() : "");
   }
@@ -9622,11 +9761,13 @@ OverloadCandidateSet::BestViableFunction(Sema &S, SourceLocation Loc,
 
   // Find the best viable function.
   Best = end();
-  for (auto *Cand : Candidates)
+  for (auto *Cand : Candidates) {
+    Cand->Best = false;
     if (Cand->Viable)
       if (Best == end() ||
           isBetterOverloadCandidate(S, *Cand, *Best, Loc, Kind))
         Best = Cand;
+  }
 
   // If we didn't find any viable functions, abort.
   if (Best == end())
@@ -9634,22 +9775,33 @@ OverloadCandidateSet::BestViableFunction(Sema &S, SourceLocation Loc,
 
   llvm::SmallVector<const NamedDecl *, 4> EquivalentCands;
 
+  llvm::SmallVector<OverloadCandidate*, 4> PendingBest;
+  PendingBest.push_back(&*Best);
+  Best->Best = true;
+
   // Make sure that this function is better than every other viable
   // function. If not, we have an ambiguity.
-  for (auto *Cand : Candidates) {
-    if (Cand->Viable && Cand != Best &&
-        !isBetterOverloadCandidate(S, *Best, *Cand, Loc, Kind)) {
-      if (S.isEquivalentInternalLinkageDeclaration(Best->Function,
-                                                   Cand->Function)) {
-        EquivalentCands.push_back(Cand->Function);
-        continue;
+  while (!PendingBest.empty()) {
+    auto *Curr = PendingBest.pop_back_val();
+    for (auto *Cand : Candidates) {
+      if (Cand->Viable && !Cand->Best &&
+          !isBetterOverloadCandidate(S, *Curr, *Cand, Loc, Kind)) {
+        PendingBest.push_back(Cand);
+        Cand->Best = true;
+
+        if (S.isEquivalentInternalLinkageDeclaration(Cand->Function,
+                                                     Curr->Function))
+          EquivalentCands.push_back(Cand->Function);
+        else
+          Best = end();
       }
-
-      Best = end();
-      return OR_Ambiguous;
     }
   }
 
+  // If we found more than one best candidate, this is ambiguous.
+  if (Best == end())
+    return OR_Ambiguous;
+
   // Best is the best viable function.
   if (Best->Function && Best->Function->isDeleted())
     return OR_Deleted;
@@ -9673,6 +9825,7 @@ enum OverloadCandidateKind {
   oc_implicit_move_constructor,
   oc_implicit_copy_assignment,
   oc_implicit_move_assignment,
+  oc_implicit_equality_comparison,
   oc_inherited_constructor
 };
 
@@ -9701,6 +9854,9 @@ ClassifyOverloadCandidate(Sema &S, NamedDecl *Found, FunctionDecl *Fn,
   }();
 
   OverloadCandidateKind Kind = [&]() {
+    if (Fn->isImplicit() && Fn->getOverloadedOperator() == OO_EqualEqual)
+      return oc_implicit_equality_comparison;
+
     if (CRK & CRK_Reversed)
       return oc_reversed_binary_operator;
 
@@ -9791,6 +9947,24 @@ static bool checkAddressOfFunctionIsAvailable(Sema &S, const FunctionDecl *FD,
     return false;
   }
 
+  if (const Expr *RC = FD->getTrailingRequiresClause()) {
+    ConstraintSatisfaction Satisfaction;
+    if (S.CheckConstraintSatisfaction(RC, Satisfaction))
+      return false;
+    if (!Satisfaction.IsSatisfied) {
+      if (Complain) {
+        if (InOverloadResolution)
+          S.Diag(FD->getBeginLoc(),
+                 diag::note_ovl_candidate_unsatisfied_constraints);
+        else
+          S.Diag(Loc, diag::err_addrof_function_constraints_not_satisfied)
+              << FD;
+        S.DiagnoseUnsatisfiedConstraint(Satisfaction);
+      }
+      return false;
+    }
+  }
+
   auto I = llvm::find_if(FD->parameters(), [](const ParmVarDecl *P) {
     return P->hasAttr<PassObjectSizeAttr>();
   });
@@ -9848,6 +10022,55 @@ void Sema::NoteOverloadCandidate(NamedDecl *Found, FunctionDecl *Fn,
   MaybeEmitInheritedConstructorNote(*this, Found);
 }
 
+static void
+MaybeDiagnoseAmbiguousConstraints(Sema &S, ArrayRef<OverloadCandidate> Cands) {
+  // Perhaps the ambiguity was caused by two atomic constraints that are
+  // 'identical' but not equivalent:
+  //
+  // void foo() requires (sizeof(T) > 4) { } // #1
+  // void foo() requires (sizeof(T) > 4) && T::value { } // #2
+  //
+  // The 'sizeof(T) > 4' constraints are seemingly equivalent and should cause
+  // #2 to subsume #1, but these constraint are not considered equivalent
+  // according to the subsumption rules because they are not the same
+  // source-level construct. This behavior is quite confusing and we should try
+  // to help the user figure out what happened.
+
+  SmallVector<const Expr *, 3> FirstAC, SecondAC;
+  FunctionDecl *FirstCand = nullptr, *SecondCand = nullptr;
+  for (auto I = Cands.begin(), E = Cands.end(); I != E; ++I) {
+    if (!I->Function)
+      continue;
+    SmallVector<const Expr *, 3> AC;
+    if (auto *Template = I->Function->getPrimaryTemplate())
+      Template->getAssociatedConstraints(AC);
+    else
+      I->Function->getAssociatedConstraints(AC);
+    if (AC.empty())
+      continue;
+    if (FirstCand == nullptr) {
+      FirstCand = I->Function;
+      FirstAC = AC;
+    } else if (SecondCand == nullptr) {
+      SecondCand = I->Function;
+      SecondAC = AC;
+    } else {
+      // We have more than one pair of constrained functions - this check is
+      // expensive and we'd rather not try to diagnose it.
+      return;
+    }
+  }
+  if (!SecondCand)
+    return;
+  // The diagnostic can only happen if there are associated constraints on
+  // both sides (there needs to be some identical atomic constraint).
+  if (S.MaybeEmitAmbiguousAtomicConstraintsDiagnostic(FirstCand, FirstAC,
+                                                      SecondCand, SecondAC))
+    // Just show the user one diagnostic, they'll probably figure it out
+    // from here.
+    return;
+}
+
 // Notes the location of all overload candidates designated through
 // OverloadedExpr
 void Sema::NoteAllOverloadCandidates(Expr *OverloadedExpr, QualType DestType,
@@ -9916,7 +10139,7 @@ static void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand,
 
   std::string FnDesc;
   std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-      ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->RewriteKind,
+      ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->getRewriteKind(),
                                 FnDesc);
 
   Expr *FromExpr = Conv.Bad.FromExpr;
@@ -9959,10 +10182,17 @@ static void DiagnoseBadConversion(Sema &S, OverloadCandidate *Cand,
     Qualifiers ToQs = CToTy.getQualifiers();
 
     if (FromQs.getAddressSpace() != ToQs.getAddressSpace()) {
-      S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_addrspace)
-          << (unsigned)FnKindPair.first << (unsigned)FnKindPair.second << FnDesc
-          << (FromExpr ? FromExpr->getSourceRange() : SourceRange()) << FromTy
-          << ToTy << (unsigned)isObjectArgument << I + 1;
+      if (isObjectArgument)
+        S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_addrspace_this)
+            << (unsigned)FnKindPair.first << (unsigned)FnKindPair.second
+            << FnDesc << (FromExpr ? FromExpr->getSourceRange() : SourceRange())
+            << FromQs.getAddressSpace() << ToQs.getAddressSpace();
+      else
+        S.Diag(Fn->getLocation(), diag::note_ovl_candidate_bad_addrspace)
+            << (unsigned)FnKindPair.first << (unsigned)FnKindPair.second
+            << FnDesc << (FromExpr ? FromExpr->getSourceRange() : SourceRange())
+            << FromQs.getAddressSpace() << ToQs.getAddressSpace()
+            << ToTy->isReferenceType() << I + 1;
       MaybeEmitInheritedConstructorNote(S, Cand->FoundDecl);
       return;
     }
@@ -10167,7 +10397,7 @@ static void DiagnoseArityMismatch(Sema &S, NamedDecl *Found, Decl *D,
   FunctionDecl *Fn = cast<FunctionDecl>(D);
 
   // TODO: treat calls to a missing default constructor as a special case
-  const FunctionProtoType *FnTy = Fn->getType()->getAs<FunctionProtoType>();
+  const auto *FnTy = Fn->getType()->castAs<FunctionProtoType>();
   unsigned MinParams = Fn->getMinRequiredArguments();
 
   // at least / at most / exactly
@@ -10303,6 +10533,16 @@ static void DiagnoseBadDeduction(Sema &S, NamedDecl *Found, Decl *Templated,
       which = 2;
     }
 
+    // Tweak the diagnostic if the problem is that we deduced packs of
+    // different arities. We'll print the actual packs anyway in case that
+    // includes additional useful information.
+    if (DeductionFailure.getFirstArg()->getKind() == TemplateArgument::Pack &&
+        DeductionFailure.getSecondArg()->getKind() == TemplateArgument::Pack &&
+        DeductionFailure.getFirstArg()->pack_size() !=
+            DeductionFailure.getSecondArg()->pack_size()) {
+      which = 3;
+    }
+
     S.Diag(Templated->getLocation(),
            diag::note_ovl_candidate_inconsistent_deduction)
         << which << ParamD->getDeclName() << *DeductionFailure.getFirstArg()
@@ -10333,6 +10573,23 @@ static void DiagnoseBadDeduction(Sema &S, NamedDecl *Found, Decl *Templated,
     MaybeEmitInheritedConstructorNote(S, Found);
     return;
 
+  case Sema::TDK_ConstraintsNotSatisfied: {
+    // Format the template argument list into the argument string.
+    SmallString<128> TemplateArgString;
+    TemplateArgumentList *Args = DeductionFailure.getTemplateArgumentList();
+    TemplateArgString = " ";
+    TemplateArgString += S.getTemplateArgumentBindingsText(
+        getDescribedTemplate(Templated)->getTemplateParameters(), *Args);
+    if (TemplateArgString.size() == 1)
+      TemplateArgString.clear();
+    S.Diag(Templated->getLocation(),
+           diag::note_ovl_candidate_unsatisfied_constraints)
+        << TemplateArgString;
+
+    S.DiagnoseUnsatisfiedConstraint(
+        static_cast<CNSInfo*>(DeductionFailure.Data)->Satisfaction);
+    return;
+  }
   case Sema::TDK_TooManyArguments:
   case Sema::TDK_TooFewArguments:
     DiagnoseArityMismatch(S, Found, Templated, NumArgs);
@@ -10352,6 +10609,8 @@ static void DiagnoseBadDeduction(Sema &S, NamedDecl *Found, Decl *Templated,
       TemplateArgString = " ";
       TemplateArgString += S.getTemplateArgumentBindingsText(
           getDescribedTemplate(Templated)->getTemplateParameters(), *Args);
+      if (TemplateArgString.size() == 1)
+        TemplateArgString.clear();
     }
 
     // If this candidate was disabled by enable_if, say so.
@@ -10401,6 +10660,8 @@ static void DiagnoseBadDeduction(Sema &S, NamedDecl *Found, Decl *Templated,
       TemplateArgString = " ";
       TemplateArgString += S.getTemplateArgumentBindingsText(
           getDescribedTemplate(Templated)->getTemplateParameters(), *Args);
+      if (TemplateArgString.size() == 1)
+        TemplateArgString.clear();
     }
 
     S.Diag(Templated->getLocation(), diag::note_ovl_candidate_deduced_mismatch)
@@ -10486,8 +10747,8 @@ static void DiagnoseBadTarget(Sema &S, OverloadCandidate *Cand) {
 
   std::string FnDesc;
   std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-      ClassifyOverloadCandidate(S, Cand->FoundDecl, Callee, Cand->RewriteKind,
-                                FnDesc);
+      ClassifyOverloadCandidate(S, Cand->FoundDecl, Callee,
+                                Cand->getRewriteKind(), FnDesc);
 
   S.Diag(Callee->getLocation(), diag::note_ovl_candidate_bad_target)
       << (unsigned)FnKindPair.first << (unsigned)ocs_non_template
@@ -10545,30 +10806,36 @@ static void DiagnoseFailedEnableIfAttr(Sema &S, OverloadCandidate *Cand) {
 }
 
 static void DiagnoseFailedExplicitSpec(Sema &S, OverloadCandidate *Cand) {
-  ExplicitSpecifier ES;
-  const char *DeclName;
+  ExplicitSpecifier ES = ExplicitSpecifier::getFromDecl(Cand->Function);
+  assert(ES.isExplicit() && "not an explicit candidate");
+
+  unsigned Kind;
   switch (Cand->Function->getDeclKind()) {
   case Decl::Kind::CXXConstructor:
-    ES = cast<CXXConstructorDecl>(Cand->Function)->getExplicitSpecifier();
-    DeclName = "constructor";
+    Kind = 0;
     break;
   case Decl::Kind::CXXConversion:
-    ES = cast<CXXConversionDecl>(Cand->Function)->getExplicitSpecifier();
-    DeclName = "conversion operator";
+    Kind = 1;
     break;
   case Decl::Kind::CXXDeductionGuide:
-    ES = cast<CXXDeductionGuideDecl>(Cand->Function)->getExplicitSpecifier();
-    DeclName = "deductiong guide";
+    Kind = Cand->Function->isImplicit() ? 0 : 2;
     break;
   default:
     llvm_unreachable("invalid Decl");
   }
-  assert(ES.getExpr() && "null expression should be handled before");
-  S.Diag(Cand->Function->getLocation(),
-         diag::note_ovl_candidate_explicit_forbidden)
-      << DeclName;
-  S.Diag(ES.getExpr()->getBeginLoc(),
-         diag::note_explicit_bool_resolved_to_true);
+
+  // Note the location of the first (in-class) declaration; a redeclaration
+  // (particularly an out-of-class definition) will typically lack the
+  // 'explicit' specifier.
+  // FIXME: This is probably a good thing to do for all 'candidate' notes.
+  FunctionDecl *First = Cand->Function->getFirstDecl();
+  if (FunctionDecl *Pattern = First->getTemplateInstantiationPattern())
+    First = Pattern->getFirstDecl();
+
+  S.Diag(First->getLocation(),
+         diag::note_ovl_candidate_explicit)
+      << Kind << (ES.getExpr() ? 1 : 0)
+      << (ES.getExpr() ? ES.getExpr()->getSourceRange() : SourceRange());
 }
 
 static void DiagnoseOpenCLExtensionDisabled(Sema &S, OverloadCandidate *Cand) {
@@ -10605,8 +10872,8 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
     if (Fn->isDeleted()) {
       std::string FnDesc;
       std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
-          ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn, Cand->RewriteKind,
-                                    FnDesc);
+          ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn,
+                                    Cand->getRewriteKind(), FnDesc);
 
       S.Diag(Fn->getLocation(), diag::note_ovl_candidate_deleted)
           << (unsigned)FnKindPair.first << (unsigned)FnKindPair.second << FnDesc
@@ -10616,7 +10883,7 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
     }
 
     // We don't really have anything else to say about viable candidates.
-    S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
     return;
   }
 
@@ -10649,7 +10916,7 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
   case ovl_fail_trivial_conversion:
   case ovl_fail_bad_final_conversion:
   case ovl_fail_final_conversion_not_exact:
-    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
 
   case ovl_fail_bad_conversion: {
     unsigned I = (Cand->IgnoreObjectArgument ? 1 : 0);
@@ -10660,7 +10927,7 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
     // FIXME: this currently happens when we're called from SemaInit
     // when user-conversion overload fails.  Figure out how to handle
     // those conditions and diagnose them well.
-    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->RewriteKind);
+    return S.NoteOverloadCandidate(Cand->FoundDecl, Fn, Cand->getRewriteKind());
   }
 
   case ovl_fail_bad_target:
@@ -10669,7 +10936,7 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
   case ovl_fail_enable_if:
     return DiagnoseFailedEnableIfAttr(S, Cand);
 
-  case ovl_fail_explicit_resolved:
+  case ovl_fail_explicit:
     return DiagnoseFailedExplicitSpec(S, Cand);
 
   case ovl_fail_ext_disabled:
@@ -10695,6 +10962,23 @@ static void NoteFunctionCandidate(Sema &S, OverloadCandidate *Cand,
   case ovl_non_default_multiversion_function:
     // Do nothing, these should simply be ignored.
     break;
+
+  case ovl_fail_constraints_not_satisfied: {
+    std::string FnDesc;
+    std::pair<OverloadCandidateKind, OverloadCandidateSelect> FnKindPair =
+        ClassifyOverloadCandidate(S, Cand->FoundDecl, Fn,
+                                  Cand->getRewriteKind(), FnDesc);
+
+    S.Diag(Fn->getLocation(),
+           diag::note_ovl_candidate_constraints_not_satisfied)
+        << (unsigned)FnKindPair.first << (unsigned)ocs_non_template
+        << FnDesc /* Ignored */;
+    ConstraintSatisfaction Satisfaction;
+    if (S.CheckConstraintSatisfaction(Fn->getTrailingRequiresClause(),
+                                      Satisfaction))
+      break;
+    S.DiagnoseUnsatisfiedConstraint(Satisfaction);
+  }
   }
 }
 
@@ -10785,6 +11069,7 @@ static unsigned RankDeductionFailure(const DeductionFailureInfo &DFI) {
 
   case Sema::TDK_SubstitutionFailure:
   case Sema::TDK_DeducedMismatch:
+  case Sema::TDK_ConstraintsNotSatisfied:
   case Sema::TDK_DeducedMismatchNested:
   case Sema::TDK_NonDeducedMismatch:
   case Sema::TDK_MiscellaneousDeductionFailure:
@@ -10816,6 +11101,23 @@ struct CompareOverloadCandidatesForDisplay {
       OverloadCandidateSet::CandidateSetKind CSK)
       : S(S), NumArgs(NArgs), CSK(CSK) {}
 
+  OverloadFailureKind EffectiveFailureKind(const OverloadCandidate *C) const {
+    // If there are too many or too few arguments, that's the high-order bit we
+    // want to sort by, even if the immediate failure kind was something else.
+    if (C->FailureKind == ovl_fail_too_many_arguments ||
+        C->FailureKind == ovl_fail_too_few_arguments)
+      return static_cast<OverloadFailureKind>(C->FailureKind);
+
+    if (C->Function) {
+      if (NumArgs > C->Function->getNumParams() && !C->Function->isVariadic())
+        return ovl_fail_too_many_arguments;
+      if (NumArgs < C->Function->getMinRequiredArguments())
+        return ovl_fail_too_few_arguments;
+    }
+
+    return static_cast<OverloadFailureKind>(C->FailureKind);
+  }
+
   bool operator()(const OverloadCandidate *L,
                   const OverloadCandidate *R) {
     // Fast-path this check.
@@ -10839,34 +11141,37 @@ struct CompareOverloadCandidatesForDisplay {
 
     // Criteria by which we can sort non-viable candidates:
     if (!L->Viable) {
+      OverloadFailureKind LFailureKind = EffectiveFailureKind(L);
+      OverloadFailureKind RFailureKind = EffectiveFailureKind(R);
+
       // 1. Arity mismatches come after other candidates.
-      if (L->FailureKind == ovl_fail_too_many_arguments ||
-          L->FailureKind == ovl_fail_too_few_arguments) {
-        if (R->FailureKind == ovl_fail_too_many_arguments ||
-            R->FailureKind == ovl_fail_too_few_arguments) {
+      if (LFailureKind == ovl_fail_too_many_arguments ||
+          LFailureKind == ovl_fail_too_few_arguments) {
+        if (RFailureKind == ovl_fail_too_many_arguments ||
+            RFailureKind == ovl_fail_too_few_arguments) {
           int LDist = std::abs((int)L->getNumParams() - (int)NumArgs);
           int RDist = std::abs((int)R->getNumParams() - (int)NumArgs);
           if (LDist == RDist) {
-            if (L->FailureKind == R->FailureKind)
+            if (LFailureKind == RFailureKind)
               // Sort non-surrogates before surrogates.
               return !L->IsSurrogate && R->IsSurrogate;
             // Sort candidates requiring fewer parameters than there were
             // arguments given after candidates requiring more parameters
             // than there were arguments given.
-            return L->FailureKind == ovl_fail_too_many_arguments;
+            return LFailureKind == ovl_fail_too_many_arguments;
           }
           return LDist < RDist;
         }
         return false;
       }
-      if (R->FailureKind == ovl_fail_too_many_arguments ||
-          R->FailureKind == ovl_fail_too_few_arguments)
+      if (RFailureKind == ovl_fail_too_many_arguments ||
+          RFailureKind == ovl_fail_too_few_arguments)
         return true;
 
       // 2. Bad conversions come first and are ordered by the number
       // of bad conversions and quality of good conversions.
-      if (L->FailureKind == ovl_fail_bad_conversion) {
-        if (R->FailureKind != ovl_fail_bad_conversion)
+      if (LFailureKind == ovl_fail_bad_conversion) {
+        if (RFailureKind != ovl_fail_bad_conversion)
           return true;
 
         // The conversion that can be fixed with a smaller number of changes,
@@ -10904,17 +11209,17 @@ struct CompareOverloadCandidatesForDisplay {
         if (leftBetter > 0) return true;
         if (leftBetter < 0) return false;
 
-      } else if (R->FailureKind == ovl_fail_bad_conversion)
+      } else if (RFailureKind == ovl_fail_bad_conversion)
         return false;
 
-      if (L->FailureKind == ovl_fail_bad_deduction) {
-        if (R->FailureKind != ovl_fail_bad_deduction)
+      if (LFailureKind == ovl_fail_bad_deduction) {
+        if (RFailureKind != ovl_fail_bad_deduction)
           return true;
 
         if (L->DeductionFailure.Result != R->DeductionFailure.Result)
           return RankDeductionFailure(L->DeductionFailure)
                < RankDeductionFailure(R->DeductionFailure);
-      } else if (R->FailureKind == ovl_fail_bad_deduction)
+      } else if (RFailureKind == ovl_fail_bad_deduction)
         return false;
 
       // TODO: others?
@@ -10943,7 +11248,8 @@ CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
   assert(!Cand->Viable);
 
   // Don't do anything on failures other than bad conversion.
-  if (Cand->FailureKind != ovl_fail_bad_conversion) return;
+  if (Cand->FailureKind != ovl_fail_bad_conversion)
+    return;
 
   // We only want the FixIts if all the arguments can be corrected.
   bool Unfixable = false;
@@ -10969,6 +11275,7 @@ CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
   unsigned ConvIdx = 0;
   unsigned ArgIdx = 0;
   ArrayRef<QualType> ParamTypes;
+  bool Reversed = Cand->RewriteKind & CRK_Reversed;
 
   if (Cand->IsSurrogate) {
     QualType ConvType
@@ -10982,10 +11289,11 @@ CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
     ParamTypes =
         Cand->Function->getType()->castAs<FunctionProtoType>()->getParamTypes();
     if (isa<CXXMethodDecl>(Cand->Function) &&
-        !isa<CXXConstructorDecl>(Cand->Function)) {
+        !isa<CXXConstructorDecl>(Cand->Function) && !Reversed) {
       // Conversion 0 is 'this', which doesn't have a corresponding parameter.
       ConvIdx = 1;
-      if (CSK == OverloadCandidateSet::CSK_Operator)
+      if (CSK == OverloadCandidateSet::CSK_Operator &&
+          Cand->Function->getDeclName().getCXXOverloadedOperator() != OO_Call)
         // Argument 0 is 'this', which doesn't have a corresponding parameter.
         ArgIdx = 1;
     }
@@ -10996,13 +11304,13 @@ CompleteNonViableCandidate(Sema &S, OverloadCandidate *Cand,
   }
 
   // Fill in the rest of the conversions.
-  bool Reversed = Cand->RewriteKind & CRK_Reversed;
   for (unsigned ParamIdx = Reversed ? ParamTypes.size() - 1 : 0;
        ConvIdx != ConvCount;
        ++ConvIdx, ++ArgIdx, ParamIdx += (Reversed ? -1 : 1)) {
+    assert(ArgIdx < Args.size() && "no argument for this arg conversion");
     if (Cand->Conversions[ConvIdx].isInitialized()) {
       // We've already checked this conversion.
-    } else if (ArgIdx < ParamTypes.size()) {
+    } else if (ParamIdx < ParamTypes.size()) {
       if (ParamTypes[ParamIdx]->isDependentType())
         Cand->Conversions[ConvIdx].setAsIdentityConversion(
             Args[ArgIdx]->getType());
@@ -11033,15 +11341,30 @@ SmallVector<OverloadCandidate *, 32> OverloadCandidateSet::CompleteCandidates(
   for (iterator Cand = begin(), LastCand = end(); Cand != LastCand; ++Cand) {
     if (!Filter(*Cand))
       continue;
-    if (Cand->Viable)
-      Cands.push_back(Cand);
-    else if (OCD == OCD_AllCandidates) {
-      CompleteNonViableCandidate(S, Cand, Args, Kind);
-      if (Cand->Function || Cand->IsSurrogate)
-        Cands.push_back(Cand);
-      // Otherwise, this a non-viable builtin candidate.  We do not, in general,
-      // want to list every possible builtin candidate.
+    switch (OCD) {
+    case OCD_AllCandidates:
+      if (!Cand->Viable) {
+        if (!Cand->Function && !Cand->IsSurrogate) {
+          // This a non-viable builtin candidate.  We do not, in general,
+          // want to list every possible builtin candidate.
+          continue;
+        }
+        CompleteNonViableCandidate(S, Cand, Args, Kind);
+      }
+      break;
+
+    case OCD_ViableCandidates:
+      if (!Cand->Viable)
+        continue;
+      break;
+
+    case OCD_AmbiguousCandidates:
+      if (!Cand->Best)
+        continue;
+      break;
     }
+
+    Cands.push_back(Cand);
   }
 
   llvm::stable_sort(
@@ -11062,6 +11385,9 @@ void OverloadCandidateSet::NoteCandidates(PartialDiagnosticAt PD,
   S.Diag(PD.first, PD.second);
 
   NoteCandidates(S, Args, Cands, Opc, OpLoc);
+
+  if (OCD == OCD_AmbiguousCandidates)
+    MaybeDiagnoseAmbiguousConstraints(S, {begin(), end()});
 }
 
 void OverloadCandidateSet::NoteCandidates(Sema &S, ArrayRef<Expr *> Args,
@@ -11710,15 +12036,33 @@ Sema::ResolveAddressOfOverloadedFunction(Expr *AddressOfExpr,
 /// resolve that function to a single function that can have its address taken.
 /// This will modify `Pair` iff it returns non-null.
 ///
-/// This routine can only realistically succeed if all but one candidates in the
-/// overload set for SrcExpr cannot have their addresses taken.
+/// This routine can only succeed if from all of the candidates in the overload
+/// set for SrcExpr that can have their addresses taken, there is one candidate
+/// that is more constrained than the rest.
 FunctionDecl *
-Sema::resolveAddressOfOnlyViableOverloadCandidate(Expr *E,
-                                                  DeclAccessPair &Pair) {
+Sema::resolveAddressOfSingleOverloadCandidate(Expr *E, DeclAccessPair &Pair) {
   OverloadExpr::FindResult R = OverloadExpr::find(E);
   OverloadExpr *Ovl = R.Expression;
+  bool IsResultAmbiguous = false;
   FunctionDecl *Result = nullptr;
   DeclAccessPair DAP;
+  SmallVector<FunctionDecl *, 2> AmbiguousDecls;
+
+  auto CheckMoreConstrained =
+      [&] (FunctionDecl *FD1, FunctionDecl *FD2) -> Optional<bool> {
+        SmallVector<const Expr *, 1> AC1, AC2;
+        FD1->getAssociatedConstraints(AC1);
+        FD2->getAssociatedConstraints(AC2);
+        bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+        if (IsAtLeastAsConstrained(FD1, AC1, FD2, AC2, AtLeastAsConstrained1))
+          return None;
+        if (IsAtLeastAsConstrained(FD2, AC2, FD1, AC1, AtLeastAsConstrained2))
+          return None;
+        if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
+          return None;
+        return AtLeastAsConstrained1;
+      };
+
   // Don't use the AddressOfResolver because we're specifically looking for
   // cases where we have one overload candidate that lacks
   // enable_if/pass_object_size/...
@@ -11730,32 +12074,54 @@ Sema::resolveAddressOfOnlyViableOverloadCandidate(Expr *E,
     if (!checkAddressOfFunctionIsAvailable(FD))
       continue;
 
-    // We have more than one result; quit.
-    if (Result)
-      return nullptr;
+    // We have more than one result - see if it is more constrained than the
+    // previous one.
+    if (Result) {
+      Optional<bool> MoreConstrainedThanPrevious = CheckMoreConstrained(FD,
+                                                                        Result);
+      if (!MoreConstrainedThanPrevious) {
+        IsResultAmbiguous = true;
+        AmbiguousDecls.push_back(FD);
+        continue;
+      }
+      if (!*MoreConstrainedThanPrevious)
+        continue;
+      // FD is more constrained - replace Result with it.
+    }
+    IsResultAmbiguous = false;
     DAP = I.getPair();
     Result = FD;
   }
 
-  if (Result)
+  if (IsResultAmbiguous)
+    return nullptr;
+
+  if (Result) {
+    SmallVector<const Expr *, 1> ResultAC;
+    // We skipped over some ambiguous declarations which might be ambiguous with
+    // the selected result.
+    for (FunctionDecl *Skipped : AmbiguousDecls)
+      if (!CheckMoreConstrained(Skipped, Result).hasValue())
+        return nullptr;
     Pair = DAP;
+  }
   return Result;
 }
 
 /// Given an overloaded function, tries to turn it into a non-overloaded
-/// function reference using resolveAddressOfOnlyViableOverloadCandidate. This
+/// function reference using resolveAddressOfSingleOverloadCandidate. This
 /// will perform access checks, diagnose the use of the resultant decl, and, if
 /// requested, potentially perform a function-to-pointer decay.
 ///
-/// Returns false if resolveAddressOfOnlyViableOverloadCandidate fails.
+/// Returns false if resolveAddressOfSingleOverloadCandidate fails.
 /// Otherwise, returns true. This may emit diagnostics and return true.
-bool Sema::resolveAndFixAddressOfOnlyViableOverloadCandidate(
+bool Sema::resolveAndFixAddressOfSingleOverloadCandidate(
     ExprResult &SrcExpr, bool DoFunctionPointerConverion) {
   Expr *E = SrcExpr.get();
   assert(E->getType() == Context.OverloadTy && "SrcExpr must be an overload");
 
   DeclAccessPair DAP;
-  FunctionDecl *Found = resolveAddressOfOnlyViableOverloadCandidate(E, DAP);
+  FunctionDecl *Found = resolveAddressOfSingleOverloadCandidate(E, DAP);
   if (!Found || Found->isCPUDispatchMultiVersion() ||
       Found->isCPUSpecificMultiVersion())
     return false;
@@ -12406,7 +12772,7 @@ static ExprResult FinishOverloadedCallExpr(Sema &SemaRef, Scope *S, Expr *Fn,
         PartialDiagnosticAt(Fn->getBeginLoc(),
                             SemaRef.PDiag(diag::err_ovl_ambiguous_call)
                                 << ULE->getName() << Fn->getSourceRange()),
-        SemaRef, OCD_ViableCandidates, Args);
+        SemaRef, OCD_AmbiguousCandidates, Args);
     break;
 
   case OR_Deleted: {
@@ -12652,7 +13018,7 @@ Sema::CreateOverloadedUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
                             PDiag(diag::err_ovl_ambiguous_oper_unary)
                                 << UnaryOperator::getOpcodeStr(Opc)
                                 << Input->getType() << Input->getSourceRange()),
-        *this, OCD_ViableCandidates, ArgsArray,
+        *this, OCD_AmbiguousCandidates, ArgsArray,
         UnaryOperator::getOpcodeStr(Opc), OpLoc);
     return ExprError();
 
@@ -12672,6 +13038,70 @@ Sema::CreateOverloadedUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
   return CreateBuiltinUnaryOp(OpLoc, Opc, Input);
 }
 
+/// Perform lookup for an overloaded binary operator.
+void Sema::LookupOverloadedBinOp(OverloadCandidateSet &CandidateSet,
+                                 OverloadedOperatorKind Op,
+                                 const UnresolvedSetImpl &Fns,
+                                 ArrayRef<Expr *> Args, bool PerformADL) {
+  SourceLocation OpLoc = CandidateSet.getLocation();
+
+  OverloadedOperatorKind ExtraOp =
+      CandidateSet.getRewriteInfo().AllowRewrittenCandidates
+          ? getRewrittenOverloadedOperator(Op)
+          : OO_None;
+
+  // Add the candidates from the given function set. This also adds the
+  // rewritten candidates using these functions if necessary.
+  AddNonMemberOperatorCandidates(Fns, Args, CandidateSet);
+
+  // Add operator candidates that are member functions.
+  AddMemberOperatorCandidates(Op, OpLoc, Args, CandidateSet);
+  if (CandidateSet.getRewriteInfo().shouldAddReversed(Op))
+    AddMemberOperatorCandidates(Op, OpLoc, {Args[1], Args[0]}, CandidateSet,
+                                OverloadCandidateParamOrder::Reversed);
+
+  // In C++20, also add any rewritten member candidates.
+  if (ExtraOp) {
+    AddMemberOperatorCandidates(ExtraOp, OpLoc, Args, CandidateSet);
+    if (CandidateSet.getRewriteInfo().shouldAddReversed(ExtraOp))
+      AddMemberOperatorCandidates(ExtraOp, OpLoc, {Args[1], Args[0]},
+                                  CandidateSet,
+                                  OverloadCandidateParamOrder::Reversed);
+  }
+
+  // Add candidates from ADL. Per [over.match.oper]p2, this lookup is not
+  // performed for an assignment operator (nor for operator[] nor operator->,
+  // which don't get here).
+  if (Op != OO_Equal && PerformADL) {
+    DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
+    AddArgumentDependentLookupCandidates(OpName, OpLoc, Args,
+                                         /*ExplicitTemplateArgs*/ nullptr,
+                                         CandidateSet);
+    if (ExtraOp) {
+      DeclarationName ExtraOpName =
+          Context.DeclarationNames.getCXXOperatorName(ExtraOp);
+      AddArgumentDependentLookupCandidates(ExtraOpName, OpLoc, Args,
+                                           /*ExplicitTemplateArgs*/ nullptr,
+                                           CandidateSet);
+    }
+  }
+
+  // Add builtin operator candidates.
+  //
+  // FIXME: We don't add any rewritten candidates here. This is strictly
+  // incorrect; a builtin candidate could be hidden by a non-viable candidate,
+  // resulting in our selecting a rewritten builtin candidate. For example:
+  //
+  //   enum class E { e };
+  //   bool operator!=(E, E) requires false;
+  //   bool k = E::e != E::e;
+  //
+  // ... should select the rewritten builtin candidate 'operator==(E, E)'. But
+  // it seems unreasonable to consider rewritten builtin candidates. A core
+  // issue has been filed proposing to removed this requirement.
+  AddBuiltinOperatorCandidates(Op, OpLoc, Args, CandidateSet);
+}
+
 /// Create a binary operation that may resolve to an overloaded
 /// operator.
 ///
@@ -12688,11 +13118,19 @@ Sema::CreateOverloadedUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
 ///
 /// \param LHS Left-hand argument.
 /// \param RHS Right-hand argument.
+/// \param PerformADL Whether to consider operator candidates found by ADL.
+/// \param AllowRewrittenCandidates Whether to consider candidates found by
+///        C++20 operator rewrites.
+/// \param DefaultedFn If we are synthesizing a defaulted operator function,
+///        the function in question. Such a function is never a candidate in
+///        our overload resolution. This also enables synthesizing a three-way
+///        comparison from < and == as described in C++20 [class.spaceship]p1.
 ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
                                        BinaryOperatorKind Opc,
                                        const UnresolvedSetImpl &Fns, Expr *LHS,
                                        Expr *RHS, bool PerformADL,
-                                       bool AllowRewrittenCandidates) {
+                                       bool AllowRewrittenCandidates,
+                                       FunctionDecl *DefaultedFn) {
   Expr *Args[2] = { LHS, RHS };
   LHS=RHS=nullptr; // Please use only Args instead of LHS/RHS couple
 
@@ -12700,7 +13138,6 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
     AllowRewrittenCandidates = false;
 
   OverloadedOperatorKind Op = BinaryOperator::getOverloadedOperator(Opc);
-  DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
 
   // If either side is type-dependent, create an appropriate dependent
   // expression.
@@ -12722,6 +13159,7 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
     // FIXME: save results of ADL from here?
     CXXRecordDecl *NamingClass = nullptr; // lookup ignores member operators
     // TODO: provide better source location info in DNLoc component.
+    DeclarationName OpName = Context.DeclarationNames.getCXXOperatorName(Op);
     DeclarationNameInfo OpNameInfo(OpName, OpLoc);
     UnresolvedLookupExpr *Fn = UnresolvedLookupExpr::Create(
         Context, NamingClass, NestedNameSpecifierLoc(), OpNameInfo,
@@ -12755,63 +13193,13 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
   if (Opc == BO_PtrMemD)
     return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
 
-  // Build an empty overload set.
+  // Build the overload set.
   OverloadCandidateSet CandidateSet(
       OpLoc, OverloadCandidateSet::CSK_Operator,
       OverloadCandidateSet::OperatorRewriteInfo(Op, AllowRewrittenCandidates));
-
-  OverloadedOperatorKind ExtraOp =
-      AllowRewrittenCandidates ? getRewrittenOverloadedOperator(Op) : OO_None;
-
-  // Add the candidates from the given function set. This also adds the
-  // rewritten candidates using these functions if necessary.
-  AddNonMemberOperatorCandidates(Fns, Args, CandidateSet);
-
-  // Add operator candidates that are member functions.
-  AddMemberOperatorCandidates(Op, OpLoc, Args, CandidateSet);
-  if (CandidateSet.getRewriteInfo().shouldAddReversed(Op))
-    AddMemberOperatorCandidates(Op, OpLoc, {Args[1], Args[0]}, CandidateSet,
-                                OverloadCandidateParamOrder::Reversed);
-
-  // In C++20, also add any rewritten member candidates.
-  if (ExtraOp) {
-    AddMemberOperatorCandidates(ExtraOp, OpLoc, Args, CandidateSet);
-    if (CandidateSet.getRewriteInfo().shouldAddReversed(ExtraOp))
-      AddMemberOperatorCandidates(ExtraOp, OpLoc, {Args[1], Args[0]},
-                                  CandidateSet,
-                                  OverloadCandidateParamOrder::Reversed);
-  }
-
-  // Add candidates from ADL. Per [over.match.oper]p2, this lookup is not
-  // performed for an assignment operator (nor for operator[] nor operator->,
-  // which don't get here).
-  if (Opc != BO_Assign && PerformADL) {
-    AddArgumentDependentLookupCandidates(OpName, OpLoc, Args,
-                                         /*ExplicitTemplateArgs*/ nullptr,
-                                         CandidateSet);
-    if (ExtraOp) {
-      DeclarationName ExtraOpName =
-          Context.DeclarationNames.getCXXOperatorName(ExtraOp);
-      AddArgumentDependentLookupCandidates(ExtraOpName, OpLoc, Args,
-                                           /*ExplicitTemplateArgs*/ nullptr,
-                                           CandidateSet);
-    }
-  }
-
-  // Add builtin operator candidates.
-  //
-  // FIXME: We don't add any rewritten candidates here. This is strictly
-  // incorrect; a builtin candidate could be hidden by a non-viable candidate,
-  // resulting in our selecting a rewritten builtin candidate. For example:
-  //
-  //   enum class E { e };
-  //   bool operator!=(E, E) requires false;
-  //   bool k = E::e != E::e;
-  //
-  // ... should select the rewritten builtin candidate 'operator==(E, E)'. But
-  // it seems unreasonable to consider rewritten builtin candidates. A core
-  // issue has been filed proposing to removed this requirement.
-  AddBuiltinOperatorCandidates(Op, OpLoc, Args, CandidateSet);
+  if (DefaultedFn)
+    CandidateSet.exclude(DefaultedFn);
+  LookupOverloadedBinOp(CandidateSet, Op, Fns, Args, PerformADL);
 
   bool HadMultipleCandidates = (CandidateSet.size() > 1);
 
@@ -13018,6 +13406,15 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
       if (Opc == BO_Comma)
         break;
 
+      // When defaulting an 'operator<=>', we can try to synthesize a three-way
+      // compare result using '==' and '<'.
+      if (DefaultedFn && Opc == BO_Cmp) {
+        ExprResult E = BuildSynthesizedThreeWayComparison(OpLoc, Fns, Args[0],
+                                                          Args[1], DefaultedFn);
+        if (E.isInvalid() || E.isUsable())
+          return E;
+      }
+
       // For class as left operand for assignment or compound assignment
       // operator do not fall through to handling in built-in, but report that
       // no overloaded assignment operator found
@@ -13061,20 +13458,26 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
                                          << Args[1]->getType()
                                          << Args[0]->getSourceRange()
                                          << Args[1]->getSourceRange()),
-          *this, OCD_ViableCandidates, Args, BinaryOperator::getOpcodeStr(Opc),
+          *this, OCD_AmbiguousCandidates, Args, BinaryOperator::getOpcodeStr(Opc),
           OpLoc);
       return ExprError();
 
     case OR_Deleted:
       if (isImplicitlyDeleted(Best->Function)) {
-        CXXMethodDecl *Method = cast<CXXMethodDecl>(Best->Function);
-        Diag(OpLoc, diag::err_ovl_deleted_special_oper)
-          << Context.getRecordType(Method->getParent())
-          << getSpecialMember(Method);
+        FunctionDecl *DeletedFD = Best->Function;
+        DefaultedFunctionKind DFK = getDefaultedFunctionKind(DeletedFD);
+        if (DFK.isSpecialMember()) {
+          Diag(OpLoc, diag::err_ovl_deleted_special_oper)
+            << Args[0]->getType() << DFK.asSpecialMember();
+        } else {
+          assert(DFK.isComparison());
+          Diag(OpLoc, diag::err_ovl_deleted_comparison)
+            << Args[0]->getType() << DeletedFD;
+        }
 
         // The user probably meant to call this special member. Just
         // explain why it's deleted.
-        NoteDeletedFunction(Method);
+        NoteDeletedFunction(DeletedFD);
         return ExprError();
       }
       CandidateSet.NoteCandidates(
@@ -13093,6 +13496,98 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
   return CreateBuiltinBinOp(OpLoc, Opc, Args[0], Args[1]);
 }
 
+ExprResult Sema::BuildSynthesizedThreeWayComparison(
+    SourceLocation OpLoc, const UnresolvedSetImpl &Fns, Expr *LHS, Expr *RHS,
+    FunctionDecl *DefaultedFn) {
+  const ComparisonCategoryInfo *Info =
+      Context.CompCategories.lookupInfoForType(DefaultedFn->getReturnType());
+  // If we're not producing a known comparison category type, we can't
+  // synthesize a three-way comparison. Let the caller diagnose this.
+  if (!Info)
+    return ExprResult((Expr*)nullptr);
+
+  // If we ever want to perform this synthesis more generally, we will need to
+  // apply the temporary materialization conversion to the operands.
+  assert(LHS->isGLValue() && RHS->isGLValue() &&
+         "cannot use prvalue expressions more than once");
+  Expr *OrigLHS = LHS;
+  Expr *OrigRHS = RHS;
+
+  // Replace the LHS and RHS with OpaqueValueExprs; we're going to refer to
+  // each of them multiple times below.
+  LHS = new (Context)
+      OpaqueValueExpr(LHS->getExprLoc(), LHS->getType(), LHS->getValueKind(),
+                      LHS->getObjectKind(), LHS);
+  RHS = new (Context)
+      OpaqueValueExpr(RHS->getExprLoc(), RHS->getType(), RHS->getValueKind(),
+                      RHS->getObjectKind(), RHS);
+
+  ExprResult Eq = CreateOverloadedBinOp(OpLoc, BO_EQ, Fns, LHS, RHS, true, true,
+                                        DefaultedFn);
+  if (Eq.isInvalid())
+    return ExprError();
+
+  ExprResult Less = CreateOverloadedBinOp(OpLoc, BO_LT, Fns, LHS, RHS, true,
+                                          true, DefaultedFn);
+  if (Less.isInvalid())
+    return ExprError();
+
+  ExprResult Greater;
+  if (Info->isPartial()) {
+    Greater = CreateOverloadedBinOp(OpLoc, BO_LT, Fns, RHS, LHS, true, true,
+                                    DefaultedFn);
+    if (Greater.isInvalid())
+      return ExprError();
+  }
+
+  // Form the list of comparisons we're going to perform.
+  struct Comparison {
+    ExprResult Cmp;
+    ComparisonCategoryResult Result;
+  } Comparisons[4] =
+  { {Eq, Info->isStrong() ? ComparisonCategoryResult::Equal
+                          : ComparisonCategoryResult::Equivalent},
+    {Less, ComparisonCategoryResult::Less},
+    {Greater, ComparisonCategoryResult::Greater},
+    {ExprResult(), ComparisonCategoryResult::Unordered},
+  };
+
+  int I = Info->isPartial() ? 3 : 2;
+
+  // Combine the comparisons with suitable conditional expressions.
+  ExprResult Result;
+  for (; I >= 0; --I) {
+    // Build a reference to the comparison category constant.
+    auto *VI = Info->lookupValueInfo(Comparisons[I].Result);
+    // FIXME: Missing a constant for a comparison category. Diagnose this?
+    if (!VI)
+      return ExprResult((Expr*)nullptr);
+    ExprResult ThisResult =
+        BuildDeclarationNameExpr(CXXScopeSpec(), DeclarationNameInfo(), VI->VD);
+    if (ThisResult.isInvalid())
+      return ExprError();
+
+    // Build a conditional unless this is the final case.
+    if (Result.get()) {
+      Result = ActOnConditionalOp(OpLoc, OpLoc, Comparisons[I].Cmp.get(),
+                                  ThisResult.get(), Result.get());
+      if (Result.isInvalid())
+        return ExprError();
+    } else {
+      Result = ThisResult;
+    }
+  }
+
+  // Build a PseudoObjectExpr to model the rewriting of an <=> operator, and to
+  // bind the OpaqueValueExprs before they're (repeatedly) used.
+  Expr *SyntacticForm = new (Context)
+      BinaryOperator(OrigLHS, OrigRHS, BO_Cmp, Result.get()->getType(),
+                     Result.get()->getValueKind(),
+                     Result.get()->getObjectKind(), OpLoc, FPFeatures);
+  Expr *SemanticForm[] = {LHS, RHS, Result.get()};
+  return PseudoObjectExpr::Create(Context, SyntacticForm, SemanticForm, 2);
+}
+
 ExprResult
 Sema::CreateOverloadedArraySubscriptExpr(SourceLocation LLoc,
                                          SourceLocation RLoc,
@@ -13246,7 +13741,7 @@ Sema::CreateOverloadedArraySubscriptExpr(SourceLocation LLoc,
                                         << Args[1]->getType()
                                         << Args[0]->getSourceRange()
                                         << Args[1]->getSourceRange()),
-          *this, OCD_ViableCandidates, Args, "[]", LLoc);
+          *this, OCD_AmbiguousCandidates, Args, "[]", LLoc);
       return ExprError();
 
     case OR_Deleted:
@@ -13438,7 +13933,7 @@ Sema::BuildCallToMemberFunction(Scope *S, Expr *MemExprE,
           PartialDiagnosticAt(UnresExpr->getMemberLoc(),
                               PDiag(diag::err_ovl_ambiguous_member_call)
                                   << DeclName << MemExprE->getSourceRange()),
-          *this, OCD_AllCandidates, Args);
+          *this, OCD_AmbiguousCandidates, Args);
       // FIXME: Leaking incoming expressions!
       return ExprError();
 
@@ -13469,7 +13964,7 @@ Sema::BuildCallToMemberFunction(Scope *S, Expr *MemExprE,
   ResultType = ResultType.getNonLValueExprType(Context);
 
   assert(Method && "Member call to something that isn't a method?");
-  const auto *Proto = Method->getType()->getAs<FunctionProtoType>();
+  const auto *Proto = Method->getType()->castAs<FunctionProtoType>();
   CXXMemberCallExpr *TheCall =
       CXXMemberCallExpr::Create(Context, MemExprE, Args, ResultType, VK,
                                 RParenLoc, Proto->getNumParams());
@@ -13566,7 +14061,6 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
 
   assert(Object.get()->getType()->isRecordType() &&
          "Requires object type argument");
-  const RecordType *Record = Object.get()->getType()->getAs<RecordType>();
 
   // C++ [over.call.object]p1:
   //  If the primary-expression E in the function call syntax
@@ -13583,6 +14077,7 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
                           diag::err_incomplete_object_call, Object.get()))
     return true;
 
+  const auto *Record = Object.get()->getType()->castAs<RecordType>();
   LookupResult R(*this, OpName, LParenLoc, LookupOrdinaryName);
   LookupQualifiedName(R, Record->getDecl());
   R.suppressDiagnostics();
@@ -13670,7 +14165,7 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
                             PDiag(diag::err_ovl_ambiguous_object_call)
                                 << Object.get()->getType()
                                 << Object.get()->getSourceRange()),
-        *this, OCD_ViableCandidates, Args);
+        *this, OCD_AmbiguousCandidates, Args);
     break;
 
   case OR_Deleted:
@@ -13730,9 +14225,7 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
   if (Method->isInvalidDecl())
     return ExprError();
 
-  const FunctionProtoType *Proto =
-    Method->getType()->getAs<FunctionProtoType>();
-
+  const auto *Proto = Method->getType()->castAs<FunctionProtoType>();
   unsigned NumParams = Proto->getNumParams();
 
   DeclarationNameInfo OpLocInfo(
@@ -13853,14 +14346,13 @@ Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
   DeclarationName OpName =
     Context.DeclarationNames.getCXXOperatorName(OO_Arrow);
   OverloadCandidateSet CandidateSet(Loc, OverloadCandidateSet::CSK_Operator);
-  const RecordType *BaseRecord = Base->getType()->getAs<RecordType>();
 
   if (RequireCompleteType(Loc, Base->getType(),
                           diag::err_typecheck_incomplete_tag, Base))
     return ExprError();
 
   LookupResult R(*this, OpName, OpLoc, LookupOrdinaryName);
-  LookupQualifiedName(R, BaseRecord->getDecl());
+  LookupQualifiedName(R, Base->getType()->castAs<RecordType>()->getDecl());
   R.suppressDiagnostics();
 
   for (LookupResult::iterator Oper = R.begin(), OperEnd = R.end();
@@ -13905,7 +14397,7 @@ Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc,
         PartialDiagnosticAt(OpLoc, PDiag(diag::err_ovl_ambiguous_oper_unary)
                                        << "->" << Base->getType()
                                        << Base->getSourceRange()),
-        *this, OCD_ViableCandidates, Base);
+        *this, OCD_AmbiguousCandidates, Base);
     return ExprError();
 
   case OR_Deleted:
@@ -13985,7 +14477,7 @@ ExprResult Sema::BuildLiteralOperatorCall(LookupResult &R,
     CandidateSet.NoteCandidates(
         PartialDiagnosticAt(R.getNameLoc(), PDiag(diag::err_ovl_ambiguous_call)
                                                 << R.getLookupName()),
-        *this, OCD_ViableCandidates, Args);
+        *this, OCD_AmbiguousCandidates, Args);
     return ExprError();
   }
 
@@ -14200,13 +14692,6 @@ Expr *Sema::FixOverloadedFunctionReference(Expr *E, DeclAccessPair Found,
                                        UnOp->getOperatorLoc(), false);
   }
 
-  // C++ [except.spec]p17:
-  //   An exception-specification is considered to be needed when:
-  //   - in an expression the function is the unique lookup result or the
-  //     selected member of a set of overloaded functions
-  if (auto *FPT = Fn->getType()->getAs<FunctionProtoType>())
-    ResolveExceptionSpec(E->getExprLoc(), FPT);
-
   if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
     // FIXME: avoid copy.
     TemplateArgumentListInfo TemplateArgsBuffer, *TemplateArgs = nullptr;
diff --git a/clang/lib/Sema/SemaPseudoObject.cpp b/clang/lib/Sema/SemaPseudoObject.cpp
index 06bcd8d00ded..5587e0d24c7f 100644
--- a/clang/lib/Sema/SemaPseudoObject.cpp
+++ b/clang/lib/Sema/SemaPseudoObject.cpp
@@ -145,7 +145,7 @@ namespace {
         assocExprs.reserve(numAssocs);
         assocTypes.reserve(numAssocs);
 
-        for (const GenericSelectionExpr::Association &assoc :
+        for (const GenericSelectionExpr::Association assoc :
              gse->associations()) {
           Expr *assocExpr = assoc.getAssociationExpr();
           if (assoc.isSelected())
@@ -1190,16 +1190,15 @@ bool ObjCSubscriptOpBuilder::findAtIndexGetter() {
                                              true /*instance*/);
 
   if (!AtIndexGetter && S.getLangOpts().DebuggerObjCLiteral) {
-    AtIndexGetter = ObjCMethodDecl::Create(S.Context, SourceLocation(),
-                           SourceLocation(), AtIndexGetterSelector,
-                           S.Context.getObjCIdType() /*ReturnType*/,
-                           nullptr /*TypeSourceInfo */,
-                           S.Context.getTranslationUnitDecl(),
-                           true /*Instance*/, false/*isVariadic*/,
-                           /*isPropertyAccessor=*/false,
-                           /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
-                           ObjCMethodDecl::Required,
-                           false);
+    AtIndexGetter = ObjCMethodDecl::Create(
+        S.Context, SourceLocation(), SourceLocation(), AtIndexGetterSelector,
+        S.Context.getObjCIdType() /*ReturnType*/, nullptr /*TypeSourceInfo */,
+        S.Context.getTranslationUnitDecl(), true /*Instance*/,
+        false /*isVariadic*/,
+        /*isPropertyAccessor=*/false,
+        /*isSynthesizedAccessorStub=*/false,
+        /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
+        ObjCMethodDecl::Required, false);
     ParmVarDecl *Argument = ParmVarDecl::Create(S.Context, AtIndexGetter,
                                                 SourceLocation(), SourceLocation(),
                                                 arrayRef ? &S.Context.Idents.get("index")
@@ -1303,6 +1302,7 @@ bool ObjCSubscriptOpBuilder::findAtIndexSetter() {
         ReturnType, ReturnTInfo, S.Context.getTranslationUnitDecl(),
         true /*Instance*/, false /*isVariadic*/,
         /*isPropertyAccessor=*/false,
+        /*isSynthesizedAccessorStub=*/false,
         /*isImplicitlyDeclared=*/true, /*isDefined=*/false,
         ObjCMethodDecl::Required, false);
     SmallVector<ParmVarDecl *, 2> Params;
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 6c680f29da4f..d6c3af9e84c8 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -2724,7 +2724,7 @@ static void DiagnoseForRangeReferenceVariableCopies(Sema &SemaRef,
   if (!MTE)
     return;
 
-  const Expr *E = MTE->GetTemporaryExpr()->IgnoreImpCasts();
+  const Expr *E = MTE->getSubExpr()->IgnoreImpCasts();
 
   // Searching for either UnaryOperator for dereference of a pointer or
   // CXXOperatorCallExpr for handling iterators.
@@ -2736,7 +2736,7 @@ static void DiagnoseForRangeReferenceVariableCopies(Sema &SemaRef,
       E = ME->getBase();
     } else {
       const MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(E);
-      E = MTE->GetTemporaryExpr();
+      E = MTE->getSubExpr();
     }
     E = E->IgnoreImpCasts();
   }
@@ -2762,19 +2762,32 @@ static void DiagnoseForRangeReferenceVariableCopies(Sema &SemaRef,
     QualType NewReferenceType =
         SemaRef.Context.getLValueReferenceType(E->getType().withConst());
     SemaRef.Diag(VD->getBeginLoc(), diag::note_use_type_or_non_reference)
-        << NonReferenceType << NewReferenceType << VD->getSourceRange();
-  } else {
+        << NonReferenceType << NewReferenceType << VD->getSourceRange()
+        << FixItHint::CreateRemoval(VD->getTypeSpecEndLoc());
+  } else if (!VariableType->isRValueReferenceType()) {
     // The range always returns a copy, so a temporary is always created.
     // Suggest removing the reference from the loop variable.
+    // If the type is a rvalue reference do not warn since that changes the
+    // semantic of the code.
     SemaRef.Diag(VD->getLocation(), diag::warn_for_range_variable_always_copy)
         << VD << RangeInitType;
     QualType NonReferenceType = VariableType.getNonReferenceType();
     NonReferenceType.removeLocalConst();
     SemaRef.Diag(VD->getBeginLoc(), diag::note_use_non_reference_type)
-        << NonReferenceType << VD->getSourceRange();
+        << NonReferenceType << VD->getSourceRange()
+        << FixItHint::CreateRemoval(VD->getTypeSpecEndLoc());
   }
 }
 
+/// Determines whether the @p VariableType's declaration is a record with the
+/// clang::trivial_abi attribute.
+static bool hasTrivialABIAttr(QualType VariableType) {
+  if (CXXRecordDecl *RD = VariableType->getAsCXXRecordDecl())
+    return RD->hasAttr<TrivialABIAttr>();
+
+  return false;
+}
+
 // Warns when the loop variable can be changed to a reference type to
 // prevent a copy.  For instance, if given "for (const Foo x : Range)" suggest
 // "for (const Foo &x : Range)" if this form does not make a copy.
@@ -2796,10 +2809,13 @@ static void DiagnoseForRangeConstVariableCopies(Sema &SemaRef,
     return;
   }
 
-  // TODO: Determine a maximum size that a POD type can be before a diagnostic
-  // should be emitted.  Also, only ignore POD types with trivial copy
-  // constructors.
-  if (VariableType.isPODType(SemaRef.Context))
+  // Small trivially copyable types are cheap to copy. Do not emit the
+  // diagnostic for these instances. 64 bytes is a common size of a cache line.
+  // (The function `getTypeSize` returns the size in bits.)
+  ASTContext &Ctx = SemaRef.Context;
+  if (Ctx.getTypeSize(VariableType) <= 64 * 8 &&
+      (VariableType.isTriviallyCopyableType(Ctx) ||
+       hasTrivialABIAttr(VariableType)))
     return;
 
   // Suggest changing from a const variable to a const reference variable
@@ -2808,7 +2824,8 @@ static void DiagnoseForRangeConstVariableCopies(Sema &SemaRef,
       << VD << VariableType << InitExpr->getType();
   SemaRef.Diag(VD->getBeginLoc(), diag::note_use_reference_type)
       << SemaRef.Context.getLValueReferenceType(VariableType)
-      << VD->getSourceRange();
+      << VD->getSourceRange()
+      << FixItHint::CreateInsertion(VD->getLocation(), "&");
 }
 
 /// DiagnoseForRangeVariableCopies - Diagnose three cases and fixes for them.
@@ -4184,19 +4201,16 @@ StmtResult Sema::ActOnSEHTryBlock(bool IsCXXTry, SourceLocation TryLoc,
   return SEHTryStmt::Create(Context, IsCXXTry, TryLoc, TryBlock, Handler);
 }
 
-StmtResult
-Sema::ActOnSEHExceptBlock(SourceLocation Loc,
-                          Expr *FilterExpr,
-                          Stmt *Block) {
+StmtResult Sema::ActOnSEHExceptBlock(SourceLocation Loc, Expr *FilterExpr,
+                                     Stmt *Block) {
   assert(FilterExpr && Block);
-
-  if(!FilterExpr->getType()->isIntegerType()) {
-    return StmtError(Diag(FilterExpr->getExprLoc(),
-                     diag::err_filter_expression_integral)
-                     << FilterExpr->getType());
+  QualType FTy = FilterExpr->getType();
+  if (!FTy->isIntegerType() && !FTy->isDependentType()) {
+    return StmtError(
+        Diag(FilterExpr->getExprLoc(), diag::err_filter_expression_integral)
+        << FTy);
   }
-
-  return SEHExceptStmt::Create(Context,Loc,FilterExpr,Block);
+  return SEHExceptStmt::Create(Context, Loc, FilterExpr, Block);
 }
 
 void Sema::ActOnStartSEHFinallyBlock() {
diff --git a/clang/lib/Sema/SemaStmtAsm.cpp b/clang/lib/Sema/SemaStmtAsm.cpp
index 9b051e02d127..93faf2d151f9 100644
--- a/clang/lib/Sema/SemaStmtAsm.cpp
+++ b/clang/lib/Sema/SemaStmtAsm.cpp
@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "clang/AST/ExprCXX.h"
+#include "clang/AST/GlobalDecl.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/TargetInfo.h"
@@ -255,6 +256,10 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
   // The parser verifies that there is a string literal here.
   assert(AsmString->isAscii());
 
+  FunctionDecl *FD = dyn_cast<FunctionDecl>(getCurLexicalContext());
+  llvm::StringMap<bool> FeatureMap;
+  Context.getFunctionFeatureMap(FeatureMap, FD);
+
   for (unsigned i = 0; i != NumOutputs; i++) {
     StringLiteral *Literal = Constraints[i];
     assert(Literal->isAscii());
@@ -325,8 +330,8 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
     }
 
     unsigned Size = Context.getTypeSize(OutputExpr->getType());
-    if (!Context.getTargetInfo().validateOutputSize(Literal->getString(),
-                                                    Size)) {
+    if (!Context.getTargetInfo().validateOutputSize(
+            FeatureMap, Literal->getString(), Size)) {
       targetDiag(OutputExpr->getBeginLoc(), diag::err_asm_invalid_output_size)
           << Info.getConstraintStr();
       return new (Context)
@@ -427,8 +432,8 @@ StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
         return StmtError();
 
     unsigned Size = Context.getTypeSize(Ty);
-    if (!Context.getTargetInfo().validateInputSize(Literal->getString(),
-                                                   Size))
+    if (!Context.getTargetInfo().validateInputSize(FeatureMap,
+                                                   Literal->getString(), Size))
       return StmtResult(
           targetDiag(InputExpr->getBeginLoc(), diag::err_asm_invalid_input_size)
           << Info.getConstraintStr());
@@ -702,8 +707,13 @@ void Sema::FillInlineAsmIdentifierInfo(Expr *Res,
   if (T->isFunctionType() || T->isDependentType())
     return Info.setLabel(Res);
   if (Res->isRValue()) {
-    if (isa<clang::EnumType>(T) && Res->EvaluateAsRValue(Eval, Context))
+    bool IsEnum = isa<clang::EnumType>(T);
+    if (DeclRefExpr *DRE = dyn_cast<clang::DeclRefExpr>(Res))
+      if (DRE->getDecl()->getKind() == Decl::EnumConstant)
+        IsEnum = true;
+    if (IsEnum && Res->EvaluateAsRValue(Eval, Context))
       return Info.setEnum(Eval.Val.getInt().getSExtValue());
+
     return Info.setLabel(Res);
   }
   unsigned Size = Context.getTypeSizeInChars(T).getQuantity();
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 3f2d38630c36..1184446796eb 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -976,20 +976,23 @@ ParsedTemplateArgument Sema::ActOnTemplateTypeArgument(TypeResult ParsedType) {
 /// If the type parameter has a default argument, it will be added
 /// later via ActOnTypeParameterDefault.
 NamedDecl *Sema::ActOnTypeParameter(Scope *S, bool Typename,
-                               SourceLocation EllipsisLoc,
-                               SourceLocation KeyLoc,
-                               IdentifierInfo *ParamName,
-                               SourceLocation ParamNameLoc,
-                               unsigned Depth, unsigned Position,
-                               SourceLocation EqualLoc,
-                               ParsedType DefaultArg) {
+                                    SourceLocation EllipsisLoc,
+                                    SourceLocation KeyLoc,
+                                    IdentifierInfo *ParamName,
+                                    SourceLocation ParamNameLoc,
+                                    unsigned Depth, unsigned Position,
+                                    SourceLocation EqualLoc,
+                                    ParsedType DefaultArg,
+                                    bool HasTypeConstraint) {
   assert(S->isTemplateParamScope() &&
          "Template type parameter not in template parameter scope!");
 
   bool IsParameterPack = EllipsisLoc.isValid();
-  TemplateTypeParmDecl *Param = TemplateTypeParmDecl::Create(
-      Context, Context.getTranslationUnitDecl(), KeyLoc, ParamNameLoc, Depth,
-      Position, ParamName, Typename, IsParameterPack);
+  TemplateTypeParmDecl *Param
+    = TemplateTypeParmDecl::Create(Context, Context.getTranslationUnitDecl(),
+                                   KeyLoc, ParamNameLoc, Depth, Position,
+                                   ParamName, Typename, IsParameterPack,
+                                   HasTypeConstraint);
   Param->setAccess(AS_public);
 
   if (Param->isParameterPack())
@@ -1036,6 +1039,125 @@ NamedDecl *Sema::ActOnTypeParameter(Scope *S, bool Typename,
   return Param;
 }
 
+/// Convert the parser's template argument list representation into our form.
+static TemplateArgumentListInfo
+makeTemplateArgumentListInfo(Sema &S, TemplateIdAnnotation &TemplateId) {
+  TemplateArgumentListInfo TemplateArgs(TemplateId.LAngleLoc,
+                                        TemplateId.RAngleLoc);
+  ASTTemplateArgsPtr TemplateArgsPtr(TemplateId.getTemplateArgs(),
+                                     TemplateId.NumArgs);
+  S.translateTemplateArguments(TemplateArgsPtr, TemplateArgs);
+  return TemplateArgs;
+}
+
+bool Sema::ActOnTypeConstraint(TemplateIdAnnotation *TypeConstr,
+                               TemplateTypeParmDecl *ConstrainedParameter,
+                               SourceLocation EllipsisLoc) {
+  ConceptDecl *CD =
+      cast<ConceptDecl>(TypeConstr->Template.get().getAsTemplateDecl());
+
+  // C++2a [temp.param]p4:
+  //     [...] The concept designated by a type-constraint shall be a type
+  //     concept ([temp.concept]).
+  if (!CD->isTypeConcept()) {
+    Diag(TypeConstr->TemplateNameLoc,
+         diag::err_type_constraint_non_type_concept);
+    return true;
+  }
+
+  bool WereArgsSpecified = TypeConstr->LAngleLoc.isValid();
+
+  if (!WereArgsSpecified &&
+      CD->getTemplateParameters()->getMinRequiredArguments() > 1) {
+    Diag(TypeConstr->TemplateNameLoc,
+         diag::err_type_constraint_missing_arguments) << CD;
+    return true;
+  }
+
+  TemplateArgumentListInfo TemplateArgs;
+  if (TypeConstr->LAngleLoc.isValid()) {
+    TemplateArgs =
+        makeTemplateArgumentListInfo(*this, *TypeConstr);
+  }
+  return AttachTypeConstraint(
+      TypeConstr->SS.isSet() ? TypeConstr->SS.getWithLocInContext(Context) :
+      NestedNameSpecifierLoc(),
+      DeclarationNameInfo(DeclarationName(TypeConstr->Name),
+                          TypeConstr->TemplateNameLoc), CD,
+      TypeConstr->LAngleLoc.isValid() ? &TemplateArgs : nullptr,
+      ConstrainedParameter, EllipsisLoc);
+}
+
+/// Attach a type-constraint to a template parameter.
+/// \returns true if an error occured. This can happen if the
+/// immediately-declared constraint could not be formed (e.g. incorrect number
+/// of arguments for the named concept).
+bool Sema::AttachTypeConstraint(NestedNameSpecifierLoc NS,
+                                DeclarationNameInfo NameInfo,
+                                ConceptDecl *NamedConcept,
+                                const TemplateArgumentListInfo *TemplateArgs,
+                                TemplateTypeParmDecl *ConstrainedParameter,
+                                SourceLocation EllipsisLoc) {
+  // C++2a [temp.param]p4:
+  //     [...] If Q is of the form C<A1, ..., An>, then let E' be
+  //     C<T, A1, ..., An>. Otherwise, let E' be C<T>. [...]
+  const ASTTemplateArgumentListInfo *ArgsAsWritten =
+    TemplateArgs ? ASTTemplateArgumentListInfo::Create(Context,
+                                                       *TemplateArgs) : nullptr;
+
+  QualType ParamAsArgument(ConstrainedParameter->getTypeForDecl(), 0);
+  TemplateArgumentListInfo ConstraintArgs;
+  ConstraintArgs.addArgument(
+    TemplateArgumentLoc(
+        TemplateArgument(ParamAsArgument),
+        TemplateArgumentLocInfo(
+            Context.getTrivialTypeSourceInfo(ParamAsArgument,
+                ConstrainedParameter->getLocation()))));
+  if (TemplateArgs) {
+    ConstraintArgs.setRAngleLoc(TemplateArgs->getRAngleLoc());
+    ConstraintArgs.setLAngleLoc(TemplateArgs->getLAngleLoc());
+    for (const TemplateArgumentLoc &ArgLoc : TemplateArgs->arguments())
+      ConstraintArgs.addArgument(ArgLoc);
+  }
+
+  // C++2a [temp.param]p4:
+  //     [...] This constraint-expression E is called the immediately-declared
+  //     constraint of T. [...]
+  CXXScopeSpec SS;
+  SS.Adopt(NS);
+  ExprResult ImmediatelyDeclaredConstraint = CheckConceptTemplateId(SS,
+      /*TemplateKWLoc=*/SourceLocation(), NameInfo, /*FoundDecl=*/NamedConcept,
+      NamedConcept, &ConstraintArgs);
+  if (ImmediatelyDeclaredConstraint.isInvalid())
+    return true;
+
+  if (ConstrainedParameter->isParameterPack()) {
+    // C++2a [temp.param]p4:
+    //     [...] If T is not a pack, then E is E', otherwise E is (E' && ...).
+    //
+    // We have the following case:
+    //
+    // template<typename T> concept C1 = true;
+    // template<C1... T> struct s1;
+    //
+    // The constraint: (C1<T> && ...)
+    ImmediatelyDeclaredConstraint =
+        BuildCXXFoldExpr(/*LParenLoc=*/SourceLocation(),
+                         ImmediatelyDeclaredConstraint.get(), BO_LAnd,
+                         EllipsisLoc, /*RHS=*/nullptr,
+                         /*RParenLoc=*/SourceLocation(),
+                         /*NumExpansions=*/None).get();
+    if (ImmediatelyDeclaredConstraint.isInvalid())
+      return true;
+  }
+
+  ConstrainedParameter->setTypeConstraint(NS, NameInfo,
+                                          /*FoundDecl=*/NamedConcept,
+                                          NamedConcept, ArgsAsWritten,
+                                          ImmediatelyDeclaredConstraint.get());
+  return false;
+}
+
 /// Check that the type of a non-type template parameter is
 /// well-formed.
 ///
@@ -1120,11 +1242,11 @@ NamedDecl *Sema::ActOnNonTypeTemplateParameter(Scope *S, Declarator &D,
   // Check that we have valid decl-specifiers specified.
   auto CheckValidDeclSpecifiers = [this, &D] {
     // C++ [temp.param]
-    // p1
+    // p1 
     //   template-parameter:
     //     ...
     //     parameter-declaration
-    // p2
+    // p2 
     //   ... A storage class shall not be specified in a template-parameter
     //   declaration.
     // [dcl.typedef]p1:
@@ -1868,7 +1990,23 @@ private:
           SemaRef.Context, DC, TTP->getBeginLoc(), TTP->getLocation(),
           /*Depth*/ 0, Depth1IndexAdjustment + TTP->getIndex(),
           TTP->getIdentifier(), TTP->wasDeclaredWithTypename(),
-          TTP->isParameterPack());
+          TTP->isParameterPack(), TTP->hasTypeConstraint(),
+          TTP->isExpandedParameterPack() ?
+          llvm::Optional<unsigned>(TTP->getNumExpansionParameters()) : None);
+      if (const auto *TC = TTP->getTypeConstraint()) {
+        TemplateArgumentListInfo TransformedArgs;
+        const auto *ArgsAsWritten = TC->getTemplateArgsAsWritten();
+        if (SemaRef.Subst(ArgsAsWritten->getTemplateArgs(),
+                          ArgsAsWritten->NumTemplateArgs, TransformedArgs,
+                          Args))
+          SemaRef.AttachTypeConstraint(
+              TC->getNestedNameSpecifierLoc(), TC->getConceptNameInfo(),
+              TC->getNamedConcept(), &TransformedArgs, NewTTP,
+              NewTTP->isParameterPack()
+                 ? cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
+                     ->getEllipsisLoc()
+                 : SourceLocation());
+      }
       if (TTP->hasDefaultArgument()) {
         TypeSourceInfo *InstantiatedDefaultArg =
             SemaRef.SubstType(TTP->getDefaultArgumentInfo(), Args,
@@ -1894,7 +2032,7 @@ private:
     // Ask the template instantiator to do the heavy lifting for us, then adjust
     // the index of the parameter once it's done.
     auto *NewParam =
-        cast_or_null<TemplateParmDecl>(SemaRef.SubstDecl(OldParam, DC, Args));
+        cast<TemplateParmDecl>(SemaRef.SubstDecl(OldParam, DC, Args));
     assert(NewParam->getDepth() == 0 && "unexpected template param depth");
     NewParam->setPosition(NewParam->getPosition() + Depth1IndexAdjustment);
     return NewParam;
@@ -2177,6 +2315,17 @@ static bool DiagnoseUnexpandedParameterPacks(Sema &S,
   TemplateParameterList *Params = TTP->getTemplateParameters();
   for (unsigned I = 0, N = Params->size(); I != N; ++I) {
     NamedDecl *P = Params->getParam(I);
+    if (TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(P)) {
+      if (!TTP->isParameterPack())
+        if (const TypeConstraint *TC = TTP->getTypeConstraint())
+          if (TC->hasExplicitTemplateArgs())
+            for (auto &ArgLoc : TC->getTemplateArgsAsWritten()->arguments())
+              if (S.DiagnoseUnexpandedParameterPack(ArgLoc,
+                                                    Sema::UPPC_TypeConstraint))
+                return true;
+      continue;
+    }
+
     if (NonTypeTemplateParmDecl *NTTP = dyn_cast<NonTypeTemplateParmDecl>(P)) {
       if (!NTTP->isParameterPack() &&
           S.DiagnoseUnexpandedParameterPack(NTTP->getLocation(),
@@ -2549,6 +2698,9 @@ struct DependencyChecker : RecursiveASTVisitor<DependencyChecker> {
 /// list.
 static bool
 DependsOnTemplateParameters(QualType T, TemplateParameterList *Params) {
+  if (!Params->size())
+    return false;
+
   DependencyChecker Checker(Params, /*IgnoreNonTypeDependent*/false);
   Checker.TraverseType(T);
   return Checker.Match;
@@ -3210,8 +3362,7 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
 
   TemplateDecl *Template = Name.getAsTemplateDecl();
   if (!Template || isa<FunctionTemplateDecl>(Template) ||
-      isa<VarTemplateDecl>(Template) ||
-      isa<ConceptDecl>(Template)) {
+      isa<VarTemplateDecl>(Template) || isa<ConceptDecl>(Template)) {
     // We might have a substituted template template parameter pack. If so,
     // build a template specialization type for it.
     if (Name.getAsSubstTemplateTemplateParmPack())
@@ -3227,7 +3378,8 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
   // template.
   SmallVector<TemplateArgument, 4> Converted;
   if (CheckTemplateArgumentList(Template, TemplateLoc, TemplateArgs,
-                                false, Converted))
+                                false, Converted,
+                                /*UpdateArgsWithConversion=*/true))
     return QualType();
 
   QualType CanonType;
@@ -3235,6 +3387,7 @@ QualType Sema::CheckTemplateIdType(TemplateName Name,
   bool InstantiationDependent = false;
   if (TypeAliasTemplateDecl *AliasTemplate =
           dyn_cast<TypeAliasTemplateDecl>(Template)) {
+
     // Find the canonical type for this type alias template specialization.
     TypeAliasDecl *Pattern = AliasTemplate->getTemplatedDecl();
     if (Pattern->isInvalidDecl())
@@ -3707,17 +3860,6 @@ static bool isSameAsPrimaryTemplate(TemplateParameterList *Params,
   return true;
 }
 
-/// Convert the parser's template argument list representation into our form.
-static TemplateArgumentListInfo
-makeTemplateArgumentListInfo(Sema &S, TemplateIdAnnotation &TemplateId) {
-  TemplateArgumentListInfo TemplateArgs(TemplateId.LAngleLoc,
-                                        TemplateId.RAngleLoc);
-  ASTTemplateArgsPtr TemplateArgsPtr(TemplateId.getTemplateArgs(),
-                                     TemplateId.NumArgs);
-  S.translateTemplateArguments(TemplateArgsPtr, TemplateArgs);
-  return TemplateArgs;
-}
-
 template<typename PartialSpecDecl>
 static void checkMoreSpecializedThanPrimary(Sema &S, PartialSpecDecl *Partial) {
   if (Partial->getDeclContext()->isDependentContext())
@@ -3746,6 +3888,11 @@ static void checkMoreSpecializedThanPrimary(Sema &S, PartialSpecDecl *Partial) {
   }
 
   S.Diag(Template->getLocation(), diag::note_template_decl_here);
+  SmallVector<const Expr *, 3> PartialAC, TemplateAC;
+  Template->getAssociatedConstraints(TemplateAC);
+  Partial->getAssociatedConstraints(PartialAC);
+  S.MaybeEmitAmbiguousAtomicConstraintsDiagnostic(Partial, PartialAC, Template,
+                                                  TemplateAC);
 }
 
 static void
@@ -3872,7 +4019,8 @@ DeclResult Sema::ActOnVarTemplateSpecialization(
   // template.
   SmallVector<TemplateArgument, 4> Converted;
   if (CheckTemplateArgumentList(VarTemplate, TemplateNameLoc, TemplateArgs,
-                                false, Converted))
+                                false, Converted,
+                                /*UpdateArgsWithConversion=*/true))
     return true;
 
   // Find the variable template (partial) specialization declaration that
@@ -3895,7 +4043,9 @@ DeclResult Sema::ActOnVarTemplateSpecialization(
     }
 
     if (isSameAsPrimaryTemplate(VarTemplate->getTemplateParameters(),
-                                Converted)) {
+                                Converted) &&
+        (!Context.getLangOpts().ConceptsTS ||
+         !TemplateParams->hasAssociatedConstraints())) {
       // C++ [temp.class.spec]p9b3:
       //
       //   -- The argument list of the specialization shall not be identical
@@ -3914,8 +4064,8 @@ DeclResult Sema::ActOnVarTemplateSpecialization(
   VarTemplateSpecializationDecl *PrevDecl = nullptr;
 
   if (IsPartialSpecialization)
-    // FIXME: Template parameter list matters too
-    PrevDecl = VarTemplate->findPartialSpecialization(Converted, InsertPos);
+    PrevDecl = VarTemplate->findPartialSpecialization(Converted, TemplateParams,
+                                                      InsertPos);
   else
     PrevDecl = VarTemplate->findSpecialization(Converted, InsertPos);
 
@@ -4043,7 +4193,7 @@ Sema::CheckVarTemplateId(VarTemplateDecl *Template, SourceLocation TemplateLoc,
   if (CheckTemplateArgumentList(
           Template, TemplateNameLoc,
           const_cast<TemplateArgumentListInfo &>(TemplateArgs), false,
-          Converted))
+          Converted, /*UpdateArgsWithConversion=*/true))
     return true;
 
   // Find the variable template specialization declaration that
@@ -4221,20 +4371,20 @@ void Sema::diagnoseMissingTemplateArguments(TemplateName Name,
 ExprResult
 Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
                              SourceLocation TemplateKWLoc,
-                             SourceLocation ConceptNameLoc,
+                             const DeclarationNameInfo &ConceptNameInfo,
                              NamedDecl *FoundDecl,
                              ConceptDecl *NamedConcept,
                              const TemplateArgumentListInfo *TemplateArgs) {
   assert(NamedConcept && "A concept template id without a template?");
 
   llvm::SmallVector<TemplateArgument, 4> Converted;
-  if (CheckTemplateArgumentList(NamedConcept, ConceptNameLoc,
+  if (CheckTemplateArgumentList(NamedConcept, ConceptNameInfo.getLoc(),
                            const_cast<TemplateArgumentListInfo&>(*TemplateArgs),
                                 /*PartialTemplateArgs=*/false, Converted,
                                 /*UpdateArgsWithConversion=*/false))
     return ExprError();
 
-  Optional<bool> IsSatisfied;
+  ConstraintSatisfaction Satisfaction;
   bool AreArgsDependent = false;
   for (TemplateArgument &Arg : Converted) {
     if (Arg.isDependent()) {
@@ -4242,25 +4392,21 @@ Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
       break;
     }
   }
-  if (!AreArgsDependent) {
-    InstantiatingTemplate Inst(*this, ConceptNameLoc,
-        InstantiatingTemplate::ConstraintsCheck{}, NamedConcept, Converted,
-        SourceRange(SS.isSet() ? SS.getBeginLoc() : ConceptNameLoc,
-                    TemplateArgs->getRAngleLoc()));
-    MultiLevelTemplateArgumentList MLTAL;
-    MLTAL.addOuterTemplateArguments(Converted);
-    bool Satisfied;
-    if (CalculateConstraintSatisfaction(NamedConcept, MLTAL,
-                                        NamedConcept->getConstraintExpr(),
-                                        Satisfied))
+  if (!AreArgsDependent &&
+      CheckConstraintSatisfaction(NamedConcept,
+                                  {NamedConcept->getConstraintExpr()},
+                                  Converted,
+                                  SourceRange(SS.isSet() ? SS.getBeginLoc() :
+                                                       ConceptNameInfo.getLoc(),
+                                                TemplateArgs->getRAngleLoc()),
+                                    Satisfaction))
       return ExprError();
-    IsSatisfied = Satisfied;
-  }
+
   return ConceptSpecializationExpr::Create(Context,
       SS.isSet() ? SS.getWithLocInContext(Context) : NestedNameSpecifierLoc{},
-      TemplateKWLoc, ConceptNameLoc, FoundDecl, NamedConcept,
+      TemplateKWLoc, ConceptNameInfo, FoundDecl, NamedConcept,
       ASTTemplateArgumentListInfo::Create(Context, *TemplateArgs), Converted,
-      IsSatisfied);
+      AreArgsDependent ? nullptr : &Satisfaction);
 }
 
 ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
@@ -4304,8 +4450,7 @@ ExprResult Sema::BuildTemplateIdExpr(const CXXScopeSpec &SS,
   }
 
   if (R.getAsSingle<ConceptDecl>()) {
-    return CheckConceptTemplateId(SS, TemplateKWLoc,
-                                  R.getLookupNameInfo().getBeginLoc(),
+    return CheckConceptTemplateId(SS, TemplateKWLoc, R.getLookupNameInfo(),
                                   R.getFoundDecl(),
                                   R.getAsSingle<ConceptDecl>(), TemplateArgs);
   }
@@ -5108,7 +5253,7 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param,
 
   case TemplateArgument::Template:
   case TemplateArgument::TemplateExpansion:
-    if (CheckTemplateTemplateArgument(Params, Arg))
+    if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
       return true;
 
     Converted.push_back(Arg.getArgument());
@@ -5148,6 +5293,12 @@ bool Sema::CheckTemplateArgument(NamedDecl *Param,
 /// In \c A<int,int>::B, \c NTs and \c TTs have expanded pack size 2, and \c Us
 /// is not a pack expansion, so returns an empty Optional.
 static Optional<unsigned> getExpandedPackSize(NamedDecl *Param) {
+  if (TemplateTypeParmDecl *TTP
+        = dyn_cast<TemplateTypeParmDecl>(Param)) {
+    if (TTP->isExpandedParameterPack())
+      return TTP->getNumExpansionParameters();
+  }
+
   if (NonTypeTemplateParmDecl *NTTP
         = dyn_cast<NonTypeTemplateParmDecl>(Param)) {
     if (NTTP->isExpandedParameterPack())
@@ -5206,7 +5357,11 @@ bool Sema::CheckTemplateArgumentList(
     TemplateDecl *Template, SourceLocation TemplateLoc,
     TemplateArgumentListInfo &TemplateArgs, bool PartialTemplateArgs,
     SmallVectorImpl<TemplateArgument> &Converted,
-    bool UpdateArgsWithConversions) {
+    bool UpdateArgsWithConversions, bool *ConstraintsNotSatisfied) {
+
+  if (ConstraintsNotSatisfied)
+    *ConstraintsNotSatisfied = false;
+
   // Make a copy of the template arguments for processing.  Only make the
   // changes at the end when successful in matching the arguments to the
   // template.
@@ -5268,12 +5423,16 @@ bool Sema::CheckTemplateArgumentList(
       bool PackExpansionIntoNonPack =
           NewArgs[ArgIdx].getArgument().isPackExpansion() &&
           (!(*Param)->isTemplateParameterPack() || getExpandedPackSize(*Param));
-      if (PackExpansionIntoNonPack && isa<TypeAliasTemplateDecl>(Template)) {
+      if (PackExpansionIntoNonPack && (isa<TypeAliasTemplateDecl>(Template) ||
+                                       isa<ConceptDecl>(Template))) {
         // Core issue 1430: we have a pack expansion as an argument to an
         // alias template, and it's not part of a parameter pack. This
         // can't be canonicalized, so reject it now.
+        // As for concepts - we cannot normalize constraints where this
+        // situation exists.
         Diag(NewArgs[ArgIdx].getLocation(),
-             diag::err_alias_template_expansion_into_fixed_list)
+             diag::err_template_expansion_into_fixed_list)
+          << (isa<ConceptDecl>(Template) ? 1 : 0)
           << NewArgs[ArgIdx].getSourceRange();
         Diag((*Param)->getLocation(), diag::note_template_param_here);
         return true;
@@ -5321,7 +5480,6 @@ bool Sema::CheckTemplateArgumentList(
       if ((*Param)->isTemplateParameterPack() && !ArgumentPack.empty())
         Converted.push_back(
             TemplateArgument::CreatePackCopy(Context, ArgumentPack));
-
       return false;
     }
 
@@ -5460,6 +5618,15 @@ bool Sema::CheckTemplateArgumentList(
   if (UpdateArgsWithConversions)
     TemplateArgs = std::move(NewArgs);
 
+  if (!PartialTemplateArgs &&
+      EnsureTemplateArgumentListConstraints(
+        Template, Converted, SourceRange(TemplateLoc,
+                                         TemplateArgs.getRAngleLoc()))) {
+    if (ConstraintsNotSatisfied)
+      *ConstraintsNotSatisfied = true;
+    return true;
+  }
+
   return false;
 }
 
@@ -6870,7 +7037,8 @@ static void DiagnoseTemplateParameterListArityMismatch(
 ///
 /// This routine implements the semantics of C++ [temp.arg.template].
 /// It returns true if an error occurred, and false otherwise.
-bool Sema::CheckTemplateTemplateArgument(TemplateParameterList *Params,
+bool Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
+                                         TemplateParameterList *Params,
                                          TemplateArgumentLoc &Arg) {
   TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
   TemplateDecl *Template = Name.getAsTemplateDecl();
@@ -6909,6 +7077,9 @@ bool Sema::CheckTemplateTemplateArgument(TemplateParameterList *Params,
   // C++1z [temp.arg.template]p3: (DR 150)
   //   A template-argument matches a template template-parameter P when P
   //   is at least as specialized as the template-argument A.
+  // FIXME: We should enable RelaxedTemplateTemplateArgs by default as it is a
+  //  defect report resolution from C++17 and shouldn't be introduced by
+  //  concepts.
   if (getLangOpts().RelaxedTemplateTemplateArgs) {
     // Quick check for the common case:
     //   If P contains a parameter pack, then A [...] matches P if each of A's
@@ -6916,12 +7087,39 @@ bool Sema::CheckTemplateTemplateArgument(TemplateParameterList *Params,
     //   the template-parameter-list of P.
     if (TemplateParameterListsAreEqual(
             Template->getTemplateParameters(), Params, false,
-            TPL_TemplateTemplateArgumentMatch, Arg.getLocation()))
+            TPL_TemplateTemplateArgumentMatch, Arg.getLocation()) &&
+        // If the argument has no associated constraints, then the parameter is
+        // definitely at least as specialized as the argument.
+        // Otherwise - we need a more thorough check.
+        !Template->hasAssociatedConstraints())
       return false;
 
     if (isTemplateTemplateParameterAtLeastAsSpecializedAs(Params, Template,
-                                                          Arg.getLocation()))
+                                                          Arg.getLocation())) {
+      // C++2a[temp.func.order]p2
+      //   [...] If both deductions succeed, the partial ordering selects the
+      //   more constrained template as described by the rules in
+      //   [temp.constr.order].
+      SmallVector<const Expr *, 3> ParamsAC, TemplateAC;
+      Params->getAssociatedConstraints(ParamsAC);
+      Template->getAssociatedConstraints(TemplateAC);
+      bool IsParamAtLeastAsConstrained;
+      if (IsAtLeastAsConstrained(Param, ParamsAC, Template, TemplateAC,
+                                 IsParamAtLeastAsConstrained))
+        return true;
+      if (!IsParamAtLeastAsConstrained) {
+        Diag(Arg.getLocation(),
+             diag::err_template_template_parameter_not_at_least_as_constrained)
+            << Template << Param << Arg.getSourceRange();
+        Diag(Param->getLocation(), diag::note_entity_declared_at) << Param;
+        Diag(Template->getLocation(), diag::note_entity_declared_at)
+            << Template;
+        MaybeEmitAmbiguousAtomicConstraintsDiagnostic(Param, ParamsAC, Template,
+                                                      TemplateAC);
+        return true;
+      }
       return false;
+    }
     // FIXME: Produce better diagnostics for deduction failures.
   }
 
@@ -6965,94 +7163,73 @@ Sema::BuildExpressionFromDeclTemplateArgument(const TemplateArgument &Arg,
 
   ValueDecl *VD = Arg.getAsDecl();
 
-  if (VD->getDeclContext()->isRecord() &&
-      (isa<CXXMethodDecl>(VD) || isa<FieldDecl>(VD) ||
-       isa<IndirectFieldDecl>(VD))) {
-    // If the value is a class member, we might have a pointer-to-member.
-    // Determine whether the non-type template template parameter is of
-    // pointer-to-member type. If so, we need to build an appropriate
-    // expression for a pointer-to-member, since a "normal" DeclRefExpr
-    // would refer to the member itself.
-    if (ParamType->isMemberPointerType()) {
-      QualType ClassType
-        = Context.getTypeDeclType(cast<RecordDecl>(VD->getDeclContext()));
-      NestedNameSpecifier *Qualifier
-        = NestedNameSpecifier::Create(Context, nullptr, false,
-                                      ClassType.getTypePtr());
-      CXXScopeSpec SS;
-      SS.MakeTrivial(Context, Qualifier, Loc);
-
-      // The actual value-ness of this is unimportant, but for
-      // internal consistency's sake, references to instance methods
-      // are r-values.
-      ExprValueKind VK = VK_LValue;
-      if (isa<CXXMethodDecl>(VD) && cast<CXXMethodDecl>(VD)->isInstance())
-        VK = VK_RValue;
-
-      ExprResult RefExpr = BuildDeclRefExpr(VD,
-                                            VD->getType().getNonReferenceType(),
-                                            VK,
-                                            Loc,
-                                            &SS);
-      if (RefExpr.isInvalid())
-        return ExprError();
-
-      RefExpr = CreateBuiltinUnaryOp(Loc, UO_AddrOf, RefExpr.get());
-
-      // We might need to perform a trailing qualification conversion, since
-      // the element type on the parameter could be more qualified than the
-      // element type in the expression we constructed.
-      bool ObjCLifetimeConversion;
-      if (IsQualificationConversion(((Expr*) RefExpr.get())->getType(),
-                                    ParamType.getUnqualifiedType(), false,
-                                    ObjCLifetimeConversion))
-        RefExpr = ImpCastExprToType(RefExpr.get(), ParamType.getUnqualifiedType(), CK_NoOp);
-
-      assert(!RefExpr.isInvalid() &&
-             Context.hasSameType(((Expr*) RefExpr.get())->getType(),
-                                 ParamType.getUnqualifiedType()));
-      return RefExpr;
-    }
-  }
-
-  QualType T = VD->getType().getNonReferenceType();
+  CXXScopeSpec SS;
+  if (ParamType->isMemberPointerType()) {
+    // If this is a pointer to member, we need to use a qualified name to
+    // form a suitable pointer-to-member constant.
+    assert(VD->getDeclContext()->isRecord() &&
+           (isa<CXXMethodDecl>(VD) || isa<FieldDecl>(VD) ||
+            isa<IndirectFieldDecl>(VD)));
+    QualType ClassType
+      = Context.getTypeDeclType(cast<RecordDecl>(VD->getDeclContext()));
+    NestedNameSpecifier *Qualifier
+      = NestedNameSpecifier::Create(Context, nullptr, false,
+                                    ClassType.getTypePtr());
+    SS.MakeTrivial(Context, Qualifier, Loc);
+  }
+
+  ExprResult RefExpr = BuildDeclarationNameExpr(
+      SS, DeclarationNameInfo(VD->getDeclName(), Loc), VD);
+  if (RefExpr.isInvalid())
+    return ExprError();
 
-  if (ParamType->isPointerType()) {
-    // When the non-type template parameter is a pointer, take the
-    // address of the declaration.
-    ExprResult RefExpr = BuildDeclRefExpr(VD, T, VK_LValue, Loc);
+  // For a pointer, the argument declaration is the pointee. Take its address.
+  QualType ElemT(RefExpr.get()->getType()->getArrayElementTypeNoTypeQual(), 0);
+  if (ParamType->isPointerType() && !ElemT.isNull() &&
+      Context.hasSimilarType(ElemT, ParamType->getPointeeType())) {
+    // Decay an array argument if we want a pointer to its first element.
+    RefExpr = DefaultFunctionArrayConversion(RefExpr.get());
     if (RefExpr.isInvalid())
       return ExprError();
-
-    if (!Context.hasSameUnqualifiedType(ParamType->getPointeeType(), T) &&
-        (T->isFunctionType() || T->isArrayType())) {
-      // Decay functions and arrays unless we're forming a pointer to array.
-      RefExpr = DefaultFunctionArrayConversion(RefExpr.get());
-      if (RefExpr.isInvalid())
-        return ExprError();
-
-      return RefExpr;
+  } else if (ParamType->isPointerType() || ParamType->isMemberPointerType()) {
+    // For any other pointer, take the address (or form a pointer-to-member).
+    RefExpr = CreateBuiltinUnaryOp(Loc, UO_AddrOf, RefExpr.get());
+    if (RefExpr.isInvalid())
+      return ExprError();
+  } else {
+    assert(ParamType->isReferenceType() &&
+           "unexpected type for decl template argument");
+  }
+
+  // At this point we should have the right value category.
+  assert(ParamType->isReferenceType() == RefExpr.get()->isLValue() &&
+         "value kind mismatch for non-type template argument");
+
+  // The type of the template parameter can differ from the type of the
+  // argument in various ways; convert it now if necessary.
+  QualType DestExprType = ParamType.getNonLValueExprType(Context);
+  if (!Context.hasSameType(RefExpr.get()->getType(), DestExprType)) {
+    CastKind CK;
+    QualType Ignored;
+    if (Context.hasSimilarType(RefExpr.get()->getType(), DestExprType) ||
+        IsFunctionConversion(RefExpr.get()->getType(), DestExprType, Ignored)) {
+      CK = CK_NoOp;
+    } else if (ParamType->isVoidPointerType() &&
+               RefExpr.get()->getType()->isPointerType()) {
+      CK = CK_BitCast;
+    } else {
+      // FIXME: Pointers to members can need conversion derived-to-base or
+      // base-to-derived conversions. We currently don't retain enough
+      // information to convert properly (we need to track a cast path or
+      // subobject number in the template argument).
+      llvm_unreachable(
+          "unexpected conversion required for non-type template argument");
     }
-
-    // Take the address of everything else
-    return CreateBuiltinUnaryOp(Loc, UO_AddrOf, RefExpr.get());
+    RefExpr = ImpCastExprToType(RefExpr.get(), DestExprType, CK,
+                                RefExpr.get()->getValueKind());
   }
 
-  ExprValueKind VK = VK_RValue;
-
-  // If the non-type template parameter has reference type, qualify the
-  // resulting declaration reference with the extra qualifiers on the
-  // type that the reference refers to.
-  if (const ReferenceType *TargetRef = ParamType->getAs<ReferenceType>()) {
-    VK = VK_LValue;
-    T = Context.getQualifiedType(T,
-                              TargetRef->getPointeeType().getQualifiers());
-  } else if (isa<FunctionDecl>(VD)) {
-    // References to functions are always lvalues.
-    VK = VK_LValue;
-  }
-
-  return BuildDeclRefExpr(VD, T, VK, Loc);
+  return RefExpr;
 }
 
 /// Construct a new expression that refers to the given
@@ -7173,50 +7350,73 @@ static bool MatchTemplateParameterKind(Sema &S, NamedDecl *New, NamedDecl *Old,
     // template parameter and one of the non-type template parameter types
     // is dependent, then we must wait until template instantiation time
     // to actually compare the arguments.
-    if (Kind == Sema::TPL_TemplateTemplateArgumentMatch &&
-        (OldNTTP->getType()->isDependentType() ||
-         NewNTTP->getType()->isDependentType()))
-      return true;
-
-    if (!S.Context.hasSameType(OldNTTP->getType(), NewNTTP->getType())) {
-      if (Complain) {
-        unsigned NextDiag = diag::err_template_nontype_parm_different_type;
-        if (TemplateArgLoc.isValid()) {
-          S.Diag(TemplateArgLoc,
-                 diag::err_template_arg_template_params_mismatch);
-          NextDiag = diag::note_template_nontype_parm_different_type;
+    if (Kind != Sema::TPL_TemplateTemplateArgumentMatch ||
+        (!OldNTTP->getType()->isDependentType() &&
+         !NewNTTP->getType()->isDependentType()))
+      if (!S.Context.hasSameType(OldNTTP->getType(), NewNTTP->getType())) {
+        if (Complain) {
+          unsigned NextDiag = diag::err_template_nontype_parm_different_type;
+          if (TemplateArgLoc.isValid()) {
+            S.Diag(TemplateArgLoc,
+                   diag::err_template_arg_template_params_mismatch);
+            NextDiag = diag::note_template_nontype_parm_different_type;
+          }
+          S.Diag(NewNTTP->getLocation(), NextDiag)
+            << NewNTTP->getType()
+            << (Kind != Sema::TPL_TemplateMatch);
+          S.Diag(OldNTTP->getLocation(),
+                 diag::note_template_nontype_parm_prev_declaration)
+            << OldNTTP->getType();
         }
-        S.Diag(NewNTTP->getLocation(), NextDiag)
-          << NewNTTP->getType()
-          << (Kind != Sema::TPL_TemplateMatch);
-        S.Diag(OldNTTP->getLocation(),
-               diag::note_template_nontype_parm_prev_declaration)
-          << OldNTTP->getType();
-      }
 
-      return false;
-    }
-
-    return true;
+        return false;
+      }
   }
-
   // For template template parameters, check the template parameter types.
   // The template parameter lists of template template
   // parameters must agree.
-  if (TemplateTemplateParmDecl *OldTTP
+  else if (TemplateTemplateParmDecl *OldTTP
                                     = dyn_cast<TemplateTemplateParmDecl>(Old)) {
     TemplateTemplateParmDecl *NewTTP = cast<TemplateTemplateParmDecl>(New);
-    return S.TemplateParameterListsAreEqual(NewTTP->getTemplateParameters(),
-                                            OldTTP->getTemplateParameters(),
-                                            Complain,
+    if (!S.TemplateParameterListsAreEqual(NewTTP->getTemplateParameters(),
+                                          OldTTP->getTemplateParameters(),
+                                          Complain,
                                         (Kind == Sema::TPL_TemplateMatch
                                            ? Sema::TPL_TemplateTemplateParmMatch
                                            : Kind),
-                                            TemplateArgLoc);
-  }
+                                          TemplateArgLoc))
+      return false;
+  } else if (Kind != Sema::TPL_TemplateTemplateArgumentMatch) {
+    const Expr *NewC = nullptr, *OldC = nullptr;
+    if (const auto *TC = cast<TemplateTypeParmDecl>(New)->getTypeConstraint())
+      NewC = TC->getImmediatelyDeclaredConstraint();
+    if (const auto *TC = cast<TemplateTypeParmDecl>(Old)->getTypeConstraint())
+      OldC = TC->getImmediatelyDeclaredConstraint();
+
+    auto Diagnose = [&] {
+      S.Diag(NewC ? NewC->getBeginLoc() : New->getBeginLoc(),
+           diag::err_template_different_type_constraint);
+      S.Diag(OldC ? OldC->getBeginLoc() : Old->getBeginLoc(),
+           diag::note_template_prev_declaration) << /*declaration*/0;
+    };
+
+    if (!NewC != !OldC) {
+      if (Complain)
+        Diagnose();
+      return false;
+    }
 
-  // TODO: Concepts: Match immediately-introduced-constraint for type
-  // constraints
+    if (NewC) {
+      llvm::FoldingSetNodeID OldCID, NewCID;
+      OldC->Profile(OldCID, S.Context, /*Canonical=*/true);
+      NewC->Profile(NewCID, S.Context, /*Canonical=*/true);
+      if (OldCID != NewCID) {
+        if (Complain)
+          Diagnose();
+        return false;
+      }
+    }
+  }
 
   return true;
 }
@@ -7243,15 +7443,6 @@ void DiagnoseTemplateParameterListArityMismatch(Sema &S,
     << SourceRange(Old->getTemplateLoc(), Old->getRAngleLoc());
 }
 
-static void
-DiagnoseTemplateParameterListRequiresClauseMismatch(Sema &S,
-                                                    TemplateParameterList *New,
-                                                    TemplateParameterList *Old){
-  S.Diag(New->getTemplateLoc(), diag::err_template_different_requires_clause);
-  S.Diag(Old->getTemplateLoc(),  diag::note_template_prev_declaration)
-      << /*declaration*/0;
-}
-
 /// Determine whether the given template parameter lists are
 /// equivalent.
 ///
@@ -7344,9 +7535,17 @@ Sema::TemplateParameterListsAreEqual(TemplateParameterList *New,
   if (Kind != TPL_TemplateTemplateArgumentMatch) {
     const Expr *NewRC = New->getRequiresClause();
     const Expr *OldRC = Old->getRequiresClause();
+
+    auto Diagnose = [&] {
+      Diag(NewRC ? NewRC->getBeginLoc() : New->getTemplateLoc(),
+           diag::err_template_different_requires_clause);
+      Diag(OldRC ? OldRC->getBeginLoc() : Old->getTemplateLoc(),
+           diag::note_template_prev_declaration) << /*declaration*/0;
+    };
+
     if (!NewRC != !OldRC) {
       if (Complain)
-        DiagnoseTemplateParameterListRequiresClauseMismatch(*this, New, Old);
+        Diagnose();
       return false;
     }
 
@@ -7356,7 +7555,7 @@ Sema::TemplateParameterListsAreEqual(TemplateParameterList *New,
       NewRC->Profile(NewRCID, Context, /*Canonical=*/true);
       if (OldRCID != NewRCID) {
         if (Complain)
-          DiagnoseTemplateParameterListRequiresClauseMismatch(*this, New, Old);
+          Diagnose();
         return false;
       }
     }
@@ -7382,7 +7581,8 @@ Sema::CheckTemplateDeclScope(Scope *S, TemplateParameterList *TemplateParams) {
   // C++ [temp]p4:
   //   A template [...] shall not have C linkage.
   DeclContext *Ctx = S->getEntity();
-  if (Ctx && Ctx->isExternCContext()) {
+  assert(Ctx && "Unknown context");
+  if (Ctx->isExternCContext()) {
     Diag(TemplateParams->getTemplateLoc(), diag::err_template_linkage)
         << TemplateParams->getSourceRange();
     if (const LinkageSpecDecl *LSD = Ctx->getExternCContext())
@@ -7794,7 +7994,8 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
   // template.
   SmallVector<TemplateArgument, 4> Converted;
   if (CheckTemplateArgumentList(ClassTemplate, TemplateNameLoc,
-                                TemplateArgs, false, Converted))
+                                TemplateArgs, false, Converted,
+                                /*UpdateArgsWithConversion=*/true))
     return true;
 
   // Find the class template (partial) specialization declaration that
@@ -7820,8 +8021,9 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
   ClassTemplateSpecializationDecl *PrevDecl = nullptr;
 
   if (isPartialSpecialization)
-    // FIXME: Template parameter list matters, too
-    PrevDecl = ClassTemplate->findPartialSpecialization(Converted, InsertPos);
+    PrevDecl = ClassTemplate->findPartialSpecialization(Converted,
+                                                        TemplateParams,
+                                                        InsertPos);
   else
     PrevDecl = ClassTemplate->findSpecialization(Converted, InsertPos);
 
@@ -7845,7 +8047,9 @@ DeclResult Sema::ActOnClassTemplateSpecialization(
                                                       Converted);
 
     if (Context.hasSameType(CanonType,
-                        ClassTemplate->getInjectedClassNameSpecialization())) {
+                        ClassTemplate->getInjectedClassNameSpecialization()) &&
+        (!Context.getLangOpts().ConceptsTS ||
+         !TemplateParams->hasAssociatedConstraints())) {
       // C++ [temp.class.spec]p9b3:
       //
       //   -- The argument list of the specialization shall not be identical
@@ -9040,7 +9244,8 @@ DeclResult Sema::ActOnExplicitInstantiation(
   // template.
   SmallVector<TemplateArgument, 4> Converted;
   if (CheckTemplateArgumentList(ClassTemplate, TemplateNameLoc,
-                                TemplateArgs, false, Converted))
+                                TemplateArgs, false, Converted,
+                                /*UpdateArgsWithConversion=*/true))
     return true;
 
   // Find the class template specialization declaration that
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 64ef819e30d4..1b9f1b2144d1 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -24,6 +24,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/NestedNameSpecifier.h"
+#include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/TemplateBase.h"
 #include "clang/AST/TemplateName.h"
 #include "clang/AST/Type.h"
@@ -642,6 +643,10 @@ static TemplateParameter makeTemplateParameter(Decl *D) {
 
 /// If \p Param is an expanded parameter pack, get the number of expansions.
 static Optional<unsigned> getExpandedPackSize(NamedDecl *Param) {
+  if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(Param))
+    if (TTP->isExpandedParameterPack())
+      return TTP->getNumExpansionParameters();
+
   if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(Param))
     if (NTTP->isExpandedParameterPack())
       return NTTP->getNumExpansionTypes();
@@ -859,34 +864,31 @@ public:
   /// Finish template argument deduction for a set of argument packs,
   /// producing the argument packs and checking for consistency with prior
   /// deductions.
-  Sema::TemplateDeductionResult
-  finish(bool TreatNoDeductionsAsNonDeduced = true) {
+  Sema::TemplateDeductionResult finish() {
     // Build argument packs for each of the parameter packs expanded by this
     // pack expansion.
     for (auto &Pack : Packs) {
       // Put back the old value for this pack.
       Deduced[Pack.Index] = Pack.Saved;
 
-      // If we are deducing the size of this pack even if we didn't deduce any
-      // values for it, then make sure we build a pack of the right size.
-      // FIXME: Should we always deduce the size, even if the pack appears in
-      // a non-deduced context?
-      if (!TreatNoDeductionsAsNonDeduced)
-        Pack.New.resize(PackElements);
+      // Always make sure the size of this pack is correct, even if we didn't
+      // deduce any values for it.
+      //
+      // FIXME: This isn't required by the normative wording, but substitution
+      // and post-substitution checking will always fail if the arity of any
+      // pack is not equal to the number of elements we processed. (Either that
+      // or something else has gone *very* wrong.) We're permitted to skip any
+      // hard errors from those follow-on steps by the intent (but not the
+      // wording) of C++ [temp.inst]p8:
+      //
+      //   If the function selected by overload resolution can be determined
+      //   without instantiating a class template definition, it is unspecified
+      //   whether that instantiation actually takes place
+      Pack.New.resize(PackElements);
 
       // Build or find a new value for this pack.
       DeducedTemplateArgument NewPack;
-      if (PackElements && Pack.New.empty()) {
-        if (Pack.DeferredDeduction.isNull()) {
-          // We were not able to deduce anything for this parameter pack
-          // (because it only appeared in non-deduced contexts), so just
-          // restore the saved argument pack.
-          continue;
-        }
-
-        NewPack = Pack.DeferredDeduction;
-        Pack.DeferredDeduction = TemplateArgument();
-      } else if (Pack.New.empty()) {
+      if (Pack.New.empty()) {
         // If we deduced an empty argument pack, create it now.
         NewPack = DeducedTemplateArgument(TemplateArgument::getEmptyPack());
       } else {
@@ -2501,6 +2503,30 @@ Sema::getTrivialTemplateArgumentLoc(const TemplateArgument &Arg,
   llvm_unreachable("Invalid TemplateArgument Kind!");
 }
 
+TemplateArgumentLoc
+Sema::getIdentityTemplateArgumentLoc(Decl *TemplateParm,
+                                     SourceLocation Location) {
+  if (auto *TTP = dyn_cast<TemplateTypeParmDecl>(TemplateParm))
+    return getTrivialTemplateArgumentLoc(
+        TemplateArgument(
+            Context.getTemplateTypeParmType(TTP->getDepth(), TTP->getIndex(),
+                                            TTP->isParameterPack(), TTP)),
+        QualType(), Location.isValid() ? Location : TTP->getLocation());
+  else if (auto *TTP = dyn_cast<TemplateTemplateParmDecl>(TemplateParm))
+    return getTrivialTemplateArgumentLoc(TemplateArgument(TemplateName(TTP)),
+                                         QualType(),
+                                         Location.isValid() ? Location :
+                                         TTP->getLocation());
+  auto *NTTP = cast<NonTypeTemplateParmDecl>(TemplateParm);
+  CXXScopeSpec SS;
+  DeclarationNameInfo Info(NTTP->getDeclName(),
+                           Location.isValid() ? Location : NTTP->getLocation());
+  Expr *E = BuildDeclarationNameExpr(SS, Info, NTTP).get();
+  return getTrivialTemplateArgumentLoc(TemplateArgument(E), NTTP->getType(),
+                                       Location.isValid() ? Location :
+                                       NTTP->getLocation());
+}
+
 /// Convert the given deduced template argument and add it to the set of
 /// fully-converted template arguments.
 static bool
@@ -2611,8 +2637,8 @@ static Sema::TemplateDeductionResult ConvertDeducedTemplateArguments(
     //    be deduced to an empty sequence of template arguments.
     // FIXME: Where did the word "trailing" come from?
     if (Deduced[I].isNull() && Param->isTemplateParameterPack()) {
-      if (auto Result = PackDeductionScope(S, TemplateParams, Deduced, Info, I)
-                            .finish(/*TreatNoDeductionsAsNonDeduced*/false))
+      if (auto Result =
+              PackDeductionScope(S, TemplateParams, Deduced, Info, I).finish())
         return Result;
     }
 
@@ -2709,6 +2735,23 @@ struct IsPartialSpecialization<VarTemplatePartialSpecializationDecl> {
   static constexpr bool value = true;
 };
 
+template<typename TemplateDeclT>
+static Sema::TemplateDeductionResult
+CheckDeducedArgumentConstraints(Sema& S, TemplateDeclT *Template,
+                                ArrayRef<TemplateArgument> DeducedArgs,
+                                TemplateDeductionInfo& Info) {
+  llvm::SmallVector<const Expr *, 3> AssociatedConstraints;
+  Template->getAssociatedConstraints(AssociatedConstraints);
+  if (S.CheckConstraintSatisfaction(Template, AssociatedConstraints,
+                                    DeducedArgs, Info.getLocation(),
+                                    Info.AssociatedConstraintsSatisfaction) ||
+      !Info.AssociatedConstraintsSatisfaction.IsSatisfied) {
+    Info.reset(TemplateArgumentList::CreateCopy(S.Context, DeducedArgs));
+    return Sema::TDK_ConstraintsNotSatisfied;
+  }
+  return Sema::TDK_Success;
+}
+
 /// Complete template argument deduction for a partial specialization.
 template <typename T>
 static typename std::enable_if<IsPartialSpecialization<T>::value,
@@ -2767,10 +2810,14 @@ FinishTemplateArgumentDeduction(
     return Sema::TDK_SubstitutionFailure;
   }
 
+  bool ConstraintsNotSatisfied;
   SmallVector<TemplateArgument, 4> ConvertedInstArgs;
   if (S.CheckTemplateArgumentList(Template, Partial->getLocation(), InstArgs,
-                                  false, ConvertedInstArgs))
-    return Sema::TDK_SubstitutionFailure;
+                                  false, ConvertedInstArgs,
+                                  /*UpdateArgsWithConversions=*/true,
+                                  &ConstraintsNotSatisfied))
+    return ConstraintsNotSatisfied ? Sema::TDK_ConstraintsNotSatisfied :
+                                     Sema::TDK_SubstitutionFailure;
 
   TemplateParameterList *TemplateParams = Template->getTemplateParameters();
   for (unsigned I = 0, E = TemplateParams->size(); I != E; ++I) {
@@ -2786,6 +2833,9 @@ FinishTemplateArgumentDeduction(
   if (Trap.hasErrorOccurred())
     return Sema::TDK_SubstitutionFailure;
 
+  if (auto Result = CheckDeducedArgumentConstraints(S, Partial, Builder, Info))
+    return Result;
+
   return Sema::TDK_Success;
 }
 
@@ -2828,10 +2878,13 @@ static Sema::TemplateDeductionResult FinishTemplateArgumentDeduction(
   if (Trap.hasErrorOccurred())
     return Sema::TDK_SubstitutionFailure;
 
+  if (auto Result = CheckDeducedArgumentConstraints(S, Template, Builder,
+                                                    Info))
+    return Result;
+
   return Sema::TDK_Success;
 }
 
-
 /// Perform template argument deduction to determine whether
 /// the given template arguments match the given class template
 /// partial specialization per C++ [temp.class.spec.match].
@@ -3385,6 +3438,23 @@ Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
     return TDK_SubstitutionFailure;
   }
 
+  // C++2a [temp.deduct]p5
+  //   [...] When all template arguments have been deduced [...] all uses of
+  //   template parameters [...] are replaced with the corresponding deduced
+  //   or default argument values.
+  //   [...] If the function template has associated constraints
+  //   ([temp.constr.decl]), those constraints are checked for satisfaction
+  //   ([temp.constr.constr]). If the constraints are not satisfied, type
+  //   deduction fails.
+  if (CheckInstantiatedFunctionTemplateConstraints(Info.getLocation(),
+          Specialization, Builder, Info.AssociatedConstraintsSatisfaction))
+    return TDK_MiscellaneousDeductionFailure;
+
+  if (!Info.AssociatedConstraintsSatisfaction.IsSatisfied) {
+    Info.reset(TemplateArgumentList::CreateCopy(Context, Builder));
+    return TDK_ConstraintsNotSatisfied;
+  }
+
   if (OriginalCallArgs) {
     // C++ [temp.deduct.call]p4:
     //   In general, the deduction process attempts to find template argument
@@ -3505,7 +3575,7 @@ ResolveOverloadForDeduction(Sema &S, TemplateParameterList *TemplateParams,
 
     DeclAccessPair DAP;
     if (FunctionDecl *Viable =
-            S.resolveAddressOfOnlyViableOverloadCandidate(Arg, DAP))
+            S.resolveAddressOfSingleOverloadCandidate(Arg, DAP))
       return GetTypeOfFunction(S, R, Viable);
 
     return {};
@@ -4429,7 +4499,8 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
       /*.IsPack = */ (bool)Type.getAs<PackExpansionTypeLoc>()};
 
   if (!DependentDeductionDepth &&
-      (Type.getType()->isDependentType() || Init->isTypeDependent())) {
+      (Type.getType()->isDependentType() || Init->isTypeDependent() ||
+       Init->containsUnexpandedParameterPack())) {
     Result = SubstituteDeducedTypeTransform(*this, DependentResult).Apply(Type);
     assert(!Result.isNull() && "substituting DependentTy can't fail");
     return DAR_Succeeded;
@@ -4475,11 +4546,12 @@ Sema::DeduceAutoType(TypeLoc Type, Expr *&Init, QualType &Result,
 
   // Build template<class TemplParam> void Func(FuncParam);
   TemplateTypeParmDecl *TemplParam = TemplateTypeParmDecl::Create(
-      Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false);
+      Context, nullptr, SourceLocation(), Loc, Depth, 0, nullptr, false, false,
+      false);
   QualType TemplArg = QualType(TemplParam->getTypeForDecl(), 0);
   NamedDecl *TemplParamPtr = TemplParam;
   FixedSizeTemplateParameterListStorage<1, false> TemplateParamsSt(
-      Loc, Loc, TemplParamPtr, Loc, nullptr);
+      Context, Loc, Loc, TemplParamPtr, Loc, nullptr);
 
   QualType FuncParam =
       SubstituteDeducedTypeTransform(*this, TemplArg, /*UseTypeSugar*/false)
@@ -4905,6 +4977,21 @@ Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
                                  TemplatePartialOrderingContext TPOC,
                                  unsigned NumCallArguments1,
                                  unsigned NumCallArguments2) {
+
+  auto JudgeByConstraints = [&] () -> FunctionTemplateDecl * {
+    llvm::SmallVector<const Expr *, 3> AC1, AC2;
+    FT1->getAssociatedConstraints(AC1);
+    FT2->getAssociatedConstraints(AC2);
+    bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+    if (IsAtLeastAsConstrained(FT1, AC1, FT2, AC2, AtLeastAsConstrained1))
+      return nullptr;
+    if (IsAtLeastAsConstrained(FT2, AC2, FT1, AC1, AtLeastAsConstrained2))
+      return nullptr;
+    if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
+      return nullptr;
+    return AtLeastAsConstrained1 ? FT1 : FT2;
+  };
+
   bool Better1 = isAtLeastAsSpecializedAs(*this, Loc, FT1, FT2, TPOC,
                                           NumCallArguments1);
   bool Better2 = isAtLeastAsSpecializedAs(*this, Loc, FT2, FT1, TPOC,
@@ -4914,7 +5001,7 @@ Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
     return Better1 ? FT1 : FT2;
 
   if (!Better1 && !Better2) // Neither is better than the other
-    return nullptr;
+    return JudgeByConstraints();
 
   // FIXME: This mimics what GCC implements, but doesn't match up with the
   // proposed resolution for core issue 692. This area needs to be sorted out,
@@ -4924,7 +5011,7 @@ Sema::getMoreSpecializedTemplate(FunctionTemplateDecl *FT1,
   if (Variadic1 != Variadic2)
     return Variadic1? FT2 : FT1;
 
-  return nullptr;
+  return JudgeByConstraints();
 }
 
 /// Determine if the two templates are equivalent.
@@ -5119,8 +5206,21 @@ Sema::getMoreSpecializedPartialSpecialization(
   bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
   bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
 
-  if (Better1 == Better2)
-    return nullptr;
+  if (!Better1 && !Better2)
+      return nullptr;
+  if (Better1 && Better2) {
+    llvm::SmallVector<const Expr *, 3> AC1, AC2;
+    PS1->getAssociatedConstraints(AC1);
+    PS2->getAssociatedConstraints(AC2);
+    bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+    if (IsAtLeastAsConstrained(PS1, AC1, PS2, AC2, AtLeastAsConstrained1))
+      return nullptr;
+    if (IsAtLeastAsConstrained(PS2, AC2, PS1, AC1, AtLeastAsConstrained2))
+      return nullptr;
+    if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
+      return nullptr;
+    return AtLeastAsConstrained1 ? PS1 : PS2;
+  }
 
   return Better1 ? PS1 : PS2;
 }
@@ -5132,11 +5232,22 @@ bool Sema::isMoreSpecializedThanPrimary(
   QualType PartialT = Spec->getInjectedSpecializationType();
   if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
     return false;
-  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
-    Info.clearSFINAEDiagnostic();
+  if (!isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info))
+    return true;
+  Info.clearSFINAEDiagnostic();
+  llvm::SmallVector<const Expr *, 3> PrimaryAC, SpecAC;
+  Primary->getAssociatedConstraints(PrimaryAC);
+  Spec->getAssociatedConstraints(SpecAC);
+  bool AtLeastAsConstrainedPrimary, AtLeastAsConstrainedSpec;
+  if (IsAtLeastAsConstrained(Spec, SpecAC, Primary, PrimaryAC,
+                             AtLeastAsConstrainedSpec))
     return false;
-  }
-  return true;
+  if (!AtLeastAsConstrainedSpec)
+    return false;
+  if (IsAtLeastAsConstrained(Primary, PrimaryAC, Spec, SpecAC,
+                             AtLeastAsConstrainedPrimary))
+    return false;
+  return !AtLeastAsConstrainedPrimary;
 }
 
 VarTemplatePartialSpecializationDecl *
@@ -5159,8 +5270,21 @@ Sema::getMoreSpecializedPartialSpecialization(
   bool Better1 = isAtLeastAsSpecializedAs(*this, PT1, PT2, PS2, Info);
   bool Better2 = isAtLeastAsSpecializedAs(*this, PT2, PT1, PS1, Info);
 
-  if (Better1 == Better2)
+  if (!Better1 && !Better2)
     return nullptr;
+  if (Better1 && Better2) {
+    llvm::SmallVector<const Expr *, 3> AC1, AC2;
+    PS1->getAssociatedConstraints(AC1);
+    PS2->getAssociatedConstraints(AC2);
+    bool AtLeastAsConstrained1, AtLeastAsConstrained2;
+    if (IsAtLeastAsConstrained(PS1, AC1, PS2, AC2, AtLeastAsConstrained1))
+      return nullptr;
+    if (IsAtLeastAsConstrained(PS2, AC2, PS1, AC1, AtLeastAsConstrained2))
+      return nullptr;
+    if (AtLeastAsConstrained1 == AtLeastAsConstrained2)
+      return nullptr;
+    return AtLeastAsConstrained1 ? PS1 : PS2;
+  }
 
   return Better1 ? PS1 : PS2;
 }
@@ -5180,13 +5304,25 @@ bool Sema::isMoreSpecializedThanPrimary(
       CanonTemplate, PrimaryArgs);
   QualType PartialT = Context.getTemplateSpecializationType(
       CanonTemplate, Spec->getTemplateArgs().asArray());
+
   if (!isAtLeastAsSpecializedAs(*this, PartialT, PrimaryT, Primary, Info))
     return false;
-  if (isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info)) {
-    Info.clearSFINAEDiagnostic();
+  if (!isAtLeastAsSpecializedAs(*this, PrimaryT, PartialT, Spec, Info))
+    return true;
+  Info.clearSFINAEDiagnostic();
+  llvm::SmallVector<const Expr *, 3> PrimaryAC, SpecAC;
+  Primary->getAssociatedConstraints(PrimaryAC);
+  Spec->getAssociatedConstraints(SpecAC);
+  bool AtLeastAsConstrainedPrimary, AtLeastAsConstrainedSpec;
+  if (IsAtLeastAsConstrained(Spec, SpecAC, Primary, PrimaryAC,
+                             AtLeastAsConstrainedSpec))
     return false;
-  }
-  return true;
+  if (!AtLeastAsConstrainedSpec)
+    return false;
+  if (IsAtLeastAsConstrained(Primary, PrimaryAC, Spec, SpecAC,
+                             AtLeastAsConstrainedPrimary))
+    return false;
+  return !AtLeastAsConstrainedPrimary;
 }
 
 bool Sema::isTemplateTemplateParameterAtLeastAsSpecializedAs(
@@ -5220,7 +5356,8 @@ bool Sema::isTemplateTemplateParameterAtLeastAsSpecializedAs(
     SFINAETrap Trap(*this);
 
     Context.getInjectedTemplateArgs(P, PArgs);
-    TemplateArgumentListInfo PArgList(P->getLAngleLoc(), P->getRAngleLoc());
+    TemplateArgumentListInfo PArgList(P->getLAngleLoc(),
+                                      P->getRAngleLoc());
     for (unsigned I = 0, N = P->size(); I != N; ++I) {
       // Unwrap packs that getInjectedTemplateArgs wrapped around pack
       // expansions, to form an "as written" argument list.
@@ -5252,6 +5389,41 @@ bool Sema::isTemplateTemplateParameterAtLeastAsSpecializedAs(
   return isAtLeastAsSpecializedAs(*this, PType, AType, AArg, Info);
 }
 
+namespace {
+struct MarkUsedTemplateParameterVisitor :
+    RecursiveASTVisitor<MarkUsedTemplateParameterVisitor> {
+  llvm::SmallBitVector &Used;
+  unsigned Depth;
+
+  MarkUsedTemplateParameterVisitor(llvm::SmallBitVector &Used,
+                                   unsigned Depth)
+      : Used(Used), Depth(Depth) { }
+
+  bool VisitTemplateTypeParmType(TemplateTypeParmType *T) {
+    if (T->getDepth() == Depth)
+      Used[T->getIndex()] = true;
+    return true;
+  }
+
+  bool TraverseTemplateName(TemplateName Template) {
+    if (auto *TTP =
+            dyn_cast<TemplateTemplateParmDecl>(Template.getAsTemplateDecl()))
+      if (TTP->getDepth() == Depth)
+        Used[TTP->getIndex()] = true;
+    RecursiveASTVisitor<MarkUsedTemplateParameterVisitor>::
+        TraverseTemplateName(Template);
+    return true;
+  }
+
+  bool VisitDeclRefExpr(DeclRefExpr *E) {
+    if (auto *NTTP = dyn_cast<NonTypeTemplateParmDecl>(E->getDecl()))
+      if (NTTP->getDepth() == Depth)
+        Used[NTTP->getIndex()] = true;
+    return true;
+  }
+};
+}
+
 /// Mark the template parameters that are used by the given
 /// expression.
 static void
@@ -5260,6 +5432,12 @@ MarkUsedTemplateParameters(ASTContext &Ctx,
                            bool OnlyDeduced,
                            unsigned Depth,
                            llvm::SmallBitVector &Used) {
+  if (!OnlyDeduced) {
+    MarkUsedTemplateParameterVisitor(Used, Depth)
+        .TraverseStmt(const_cast<Expr *>(E));
+    return;
+  }
+
   // We can deduce from a pack expansion.
   if (const PackExpansionExpr *Expansion = dyn_cast<PackExpansionExpr>(E))
     E = Expansion->getPattern();
@@ -5278,8 +5456,6 @@ MarkUsedTemplateParameters(ASTContext &Ctx,
       break;
   }
 
-  // FIXME: if !OnlyDeduced, we have to walk the whole subexpression to
-  // find other occurrences of template parameters.
   const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E);
   if (!DRE)
     return;
@@ -5659,6 +5835,20 @@ MarkUsedTemplateParameters(ASTContext &Ctx,
   }
 }
 
+/// Mark which template parameters are used in a given expression.
+///
+/// \param E the expression from which template parameters will be deduced.
+///
+/// \param Used a bit vector whose elements will be set to \c true
+/// to indicate when the corresponding template parameter will be
+/// deduced.
+void
+Sema::MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
+                                 unsigned Depth,
+                                 llvm::SmallBitVector &Used) {
+  ::MarkUsedTemplateParameters(Context, E, OnlyDeduced, Depth, Used);
+}
+
 /// Mark which template parameters can be deduced from a given
 /// template argument list.
 ///
diff --git a/clang/lib/Sema/SemaTemplateInstantiate.cpp b/clang/lib/Sema/SemaTemplateInstantiate.cpp
index 0daa33cfbef5..af41e231134d 100644
--- a/clang/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiate.cpp
@@ -150,7 +150,7 @@ Sema::getTemplateInstantiationArgs(NamedDecl *D,
           break;
 
         // If this function is a generic lambda specialization, we are done.
-        if (isGenericLambdaCallOperatorSpecialization(Function))
+        if (isGenericLambdaCallOperatorOrStaticInvokerSpecialization(Function))
           break;
 
       } else if (FunctionTemplateDecl *FunTmpl
@@ -203,9 +203,12 @@ bool Sema::CodeSynthesisContext::isInstantiationRecord() const {
 
   case DefaultTemplateArgumentChecking:
   case DeclaringSpecialMember:
+  case DeclaringImplicitEqualityComparison:
   case DefiningSynthesizedFunction:
   case ExceptionSpecEvaluation:
   case ConstraintSubstitution:
+  case ParameterMappingSubstitution:
+  case ConstraintNormalization:
   case RewritingOperatorAsSpaceship:
     return false;
 
@@ -363,7 +366,7 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(
 
 Sema::InstantiatingTemplate::InstantiatingTemplate(
     Sema &SemaRef, SourceLocation PointOfInstantiation,
-    ConstraintsCheck, TemplateDecl *Template,
+    ConstraintsCheck, NamedDecl *Template,
     ArrayRef<TemplateArgument> TemplateArgs, SourceRange InstantiationRange)
     : InstantiatingTemplate(
           SemaRef, CodeSynthesisContext::ConstraintsCheck,
@@ -372,13 +375,29 @@ Sema::InstantiatingTemplate::InstantiatingTemplate(
 
 Sema::InstantiatingTemplate::InstantiatingTemplate(
     Sema &SemaRef, SourceLocation PointOfInstantiation,
-    ConstraintSubstitution, TemplateDecl *Template,
+    ConstraintSubstitution, NamedDecl *Template,
     sema::TemplateDeductionInfo &DeductionInfo, SourceRange InstantiationRange)
     : InstantiatingTemplate(
           SemaRef, CodeSynthesisContext::ConstraintSubstitution,
           PointOfInstantiation, InstantiationRange, Template, nullptr,
           {}, &DeductionInfo) {}
 
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    ConstraintNormalization, NamedDecl *Template,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef, CodeSynthesisContext::ConstraintNormalization,
+          PointOfInstantiation, InstantiationRange, Template) {}
+
+Sema::InstantiatingTemplate::InstantiatingTemplate(
+    Sema &SemaRef, SourceLocation PointOfInstantiation,
+    ParameterMappingSubstitution, NamedDecl *Template,
+    SourceRange InstantiationRange)
+    : InstantiatingTemplate(
+          SemaRef, CodeSynthesisContext::ParameterMappingSubstitution,
+          PointOfInstantiation, InstantiationRange, Template) {}
+
 void Sema::pushCodeSynthesisContext(CodeSynthesisContext Ctx) {
   Ctx.SavedInNonInstantiationSFINAEContext = InNonInstantiationSFINAEContext;
   InNonInstantiationSFINAEContext = false;
@@ -671,14 +690,29 @@ void Sema::PrintInstantiationStack() {
         << cast<CXXRecordDecl>(Active->Entity) << Active->SpecialMember;
       break;
 
+    case CodeSynthesisContext::DeclaringImplicitEqualityComparison:
+      Diags.Report(Active->Entity->getLocation(),
+                   diag::note_in_declaration_of_implicit_equality_comparison);
+      break;
+
     case CodeSynthesisContext::DefiningSynthesizedFunction: {
-      // FIXME: For synthesized members other than special members, produce a note.
-      auto *MD = dyn_cast<CXXMethodDecl>(Active->Entity);
-      auto CSM = MD ? getSpecialMember(MD) : CXXInvalid;
-      if (CSM != CXXInvalid) {
+      // FIXME: For synthesized functions that are not defaulted,
+      // produce a note.
+      auto *FD = dyn_cast<FunctionDecl>(Active->Entity);
+      DefaultedFunctionKind DFK =
+          FD ? getDefaultedFunctionKind(FD) : DefaultedFunctionKind();
+      if (DFK.isSpecialMember()) {
+        auto *MD = cast<CXXMethodDecl>(FD);
         Diags.Report(Active->PointOfInstantiation,
                      diag::note_member_synthesized_at)
-          << CSM << Context.getTagDeclType(MD->getParent());
+            << MD->isExplicitlyDefaulted() << DFK.asSpecialMember()
+            << Context.getTagDeclType(MD->getParent());
+      } else if (DFK.isComparison()) {
+        Diags.Report(Active->PointOfInstantiation,
+                     diag::note_comparison_synthesized_at)
+            << (int)DFK.asComparison()
+            << Context.getTagDeclType(
+                   cast<CXXRecordDecl>(FD->getLexicalDeclContext()));
       }
       break;
     }
@@ -691,29 +725,43 @@ void Sema::PrintInstantiationStack() {
     case CodeSynthesisContext::Memoization:
       break;
     
-    case CodeSynthesisContext::ConstraintsCheck:
-      if (auto *CD = dyn_cast<ConceptDecl>(Active->Entity)) {
-        SmallVector<char, 128> TemplateArgsStr;
-        llvm::raw_svector_ostream OS(TemplateArgsStr);
-        CD->printName(OS);
-        printTemplateArgumentList(OS, Active->template_arguments(),
-                                  getPrintingPolicy());
-        Diags.Report(Active->PointOfInstantiation,
-                     diag::note_concept_specialization_here)
-          << OS.str()
-          << Active->InstantiationRange;
-        break;
+    case CodeSynthesisContext::ConstraintsCheck: {
+      unsigned DiagID = 0;
+      if (isa<ConceptDecl>(Active->Entity))
+        DiagID = diag::note_concept_specialization_here;
+      else if (isa<TemplateDecl>(Active->Entity))
+        DiagID = diag::note_checking_constraints_for_template_id_here;
+      else if (isa<VarTemplatePartialSpecializationDecl>(Active->Entity))
+        DiagID = diag::note_checking_constraints_for_var_spec_id_here;
+      else {
+        assert(isa<ClassTemplatePartialSpecializationDecl>(Active->Entity));
+        DiagID = diag::note_checking_constraints_for_class_spec_id_here;
       }
-      // TODO: Concepts - implement this for constrained templates and partial
-      // specializations.
-      llvm_unreachable("only concept constraints are supported right now");
+      SmallVector<char, 128> TemplateArgsStr;
+      llvm::raw_svector_ostream OS(TemplateArgsStr);
+      cast<NamedDecl>(Active->Entity)->printName(OS);
+      printTemplateArgumentList(OS, Active->template_arguments(),
+                                getPrintingPolicy());
+      Diags.Report(Active->PointOfInstantiation, DiagID) << OS.str()
+        << Active->InstantiationRange;
       break;
-      
+    }
     case CodeSynthesisContext::ConstraintSubstitution:
       Diags.Report(Active->PointOfInstantiation,
                    diag::note_constraint_substitution_here)
           << Active->InstantiationRange;
       break;
+    case CodeSynthesisContext::ConstraintNormalization:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_constraint_normalization_here)
+          << cast<NamedDecl>(Active->Entity)->getName()
+          << Active->InstantiationRange;
+      break;
+    case CodeSynthesisContext::ParameterMappingSubstitution:
+      Diags.Report(Active->PointOfInstantiation,
+                   diag::note_parameter_mapping_substitution_here)
+          << Active->InstantiationRange;
+      break;
     }
   }
 }
@@ -738,6 +786,8 @@ Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
     case CodeSynthesisContext::DefaultFunctionArgumentInstantiation:
     case CodeSynthesisContext::ExceptionSpecInstantiation:
     case CodeSynthesisContext::ConstraintsCheck:
+    case CodeSynthesisContext::ParameterMappingSubstitution:
+    case CodeSynthesisContext::ConstraintNormalization:
       // This is a template instantiation, so there is no SFINAE.
       return None;
 
@@ -759,6 +809,7 @@ Optional<TemplateDeductionInfo *> Sema::isSFINAEContext() const {
       return Active->DeductionInfo;
 
     case CodeSynthesisContext::DeclaringSpecialMember:
+    case CodeSynthesisContext::DeclaringImplicitEqualityComparison:
     case CodeSynthesisContext::DefiningSynthesizedFunction:
     case CodeSynthesisContext::RewritingOperatorAsSpaceship:
       // This happens in a context unrelated to template instantiation, so
@@ -1514,8 +1565,12 @@ TemplateInstantiator::TransformFunctionTypeParam(ParmVarDecl *OldParm,
                                                  int indexAdjustment,
                                                Optional<unsigned> NumExpansions,
                                                  bool ExpectParameterPack) {
-  return SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
-                                  NumExpansions, ExpectParameterPack);
+  auto NewParm =
+      SemaRef.SubstParmVarDecl(OldParm, TemplateArgs, indexAdjustment,
+                               NumExpansions, ExpectParameterPack);
+  if (NewParm && SemaRef.getLangOpts().OpenCL)
+    SemaRef.deduceOpenCLAddressSpace(NewParm);
+  return NewParm;
 }
 
 QualType
@@ -2219,11 +2274,13 @@ Sema::InstantiateClass(SourceLocation PointOfInstantiation,
   // Finish checking fields.
   ActOnFields(nullptr, Instantiation->getLocation(), Instantiation, Fields,
               SourceLocation(), SourceLocation(), ParsedAttributesView());
-  CheckCompletedCXXClass(Instantiation);
+  CheckCompletedCXXClass(nullptr, Instantiation);
 
   // Default arguments are parsed, if not instantiated. We can go instantiate
-  // default arg exprs for default constructors if necessary now.
-  ActOnFinishCXXNonNestedClass(Instantiation);
+  // default arg exprs for default constructors if necessary now. Unless we're
+  // parsing a class, in which case wait until that's finished.
+  if (ParsingClassDepth == 0)
+    ActOnFinishCXXNonNestedClass();
 
   // Instantiate late parsed attributes, and attach them to their decls.
   // See Sema::InstantiateAttrs
@@ -2900,6 +2957,17 @@ Sema::SubstStmt(Stmt *S, const MultiLevelTemplateArgumentList &TemplateArgs) {
   return Instantiator.TransformStmt(S);
 }
 
+bool Sema::SubstTemplateArguments(
+    ArrayRef<TemplateArgumentLoc> Args,
+    const MultiLevelTemplateArgumentList &TemplateArgs,
+    TemplateArgumentListInfo &Out) {
+  TemplateInstantiator Instantiator(*this, TemplateArgs,
+                                    SourceLocation(),
+                                    DeclarationName());
+  return Instantiator.TransformTemplateArguments(Args.begin(), Args.end(),
+                                                 Out);
+}
+
 ExprResult
 Sema::SubstExpr(Expr *E, const MultiLevelTemplateArgumentList &TemplateArgs) {
   if (!E)
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index d1ad304e62e4..64500d0a26d5 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -385,12 +385,13 @@ static void instantiateOMPDeclareVariantAttr(
   };
 
   ExprResult VariantFuncRef;
-  if (Expr *E = Attr.getVariantFuncRef())
+  if (Expr *E = Attr.getVariantFuncRef()) {
+    // Do not mark function as is used to prevent its emission if this is the
+    // only place where it is used.
+    EnterExpressionEvaluationContext Unevaluated(
+        S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
     VariantFuncRef = Subst(E);
-
-  ExprResult Score;
-  if (Expr *E = Attr.getScore())
-    Score = Subst(E);
+  }
 
   // Check function/variant ref.
   Optional<std::pair<FunctionDecl *, Expr *>> DeclVarData =
@@ -398,12 +399,41 @@ static void instantiateOMPDeclareVariantAttr(
           S.ConvertDeclToDeclGroup(New), VariantFuncRef.get(), Attr.getRange());
   if (!DeclVarData)
     return;
-  // Instantiate the attribute.
-  Sema::OpenMPDeclareVariantCtsSelectorData Data(
-      Attr.getCtxSelectorSet(), Attr.getCtxSelector(),
-      llvm::makeMutableArrayRef(Attr.implVendors_begin(),
-                                Attr.implVendors_size()),
-      Score);
+  SmallVector<Sema::OMPCtxSelectorData, 4> Data;
+  for (unsigned I = 0, E = Attr.scores_size(); I < E; ++I) {
+    ExprResult Score;
+    if (Expr *E = *std::next(Attr.scores_begin(), I))
+      Score = Subst(E);
+    // Instantiate the attribute.
+    auto CtxSet = static_cast<OpenMPContextSelectorSetKind>(
+        *std::next(Attr.ctxSelectorSets_begin(), I));
+    auto Ctx = static_cast<OpenMPContextSelectorKind>(
+        *std::next(Attr.ctxSelectors_begin(), I));
+    switch (CtxSet) {
+    case OMP_CTX_SET_implementation:
+      switch (Ctx) {
+      case OMP_CTX_vendor:
+        Data.emplace_back(CtxSet, Ctx, Score, Attr.implVendors());
+        break;
+      case OMP_CTX_kind:
+      case OMP_CTX_unknown:
+        llvm_unreachable("Unexpected context selector kind.");
+      }
+      break;
+    case OMP_CTX_SET_device:
+      switch (Ctx) {
+      case OMP_CTX_kind:
+        Data.emplace_back(CtxSet, Ctx, Score, Attr.deviceKinds());
+        break;
+      case OMP_CTX_vendor:
+      case OMP_CTX_unknown:
+        llvm_unreachable("Unexpected context selector kind.");
+      }
+      break;
+    case OMP_CTX_SET_unknown:
+      llvm_unreachable("Unexpected context selector set kind.");
+    }
+  }
   S.ActOnOpenMPDeclareVariantDirective(DeclVarData.getValue().first,
                                        DeclVarData.getValue().second,
                                        Attr.getRange(), Data);
@@ -625,11 +655,10 @@ void Sema::InstantiateAttrs(const MultiLevelTemplateArgumentList &TemplateArgs,
       LateAttrs->push_back(LateInstantiatedAttribute(TmplAttr, Saved, New));
     } else {
       // Allow 'this' within late-parsed attributes.
-      NamedDecl *ND = dyn_cast<NamedDecl>(New);
-      CXXRecordDecl *ThisContext =
-          dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
+      auto *ND = cast<NamedDecl>(New);
+      auto *ThisContext = dyn_cast_or_null<CXXRecordDecl>(ND->getDeclContext());
       CXXThisScopeRAII ThisScope(*this, ThisContext, Qualifiers(),
-                                 ND && ND->isCXXInstanceMember());
+                                 ND->isCXXInstanceMember());
 
       Attr *NewAttr = sema::instantiateTemplateAttribute(TmplAttr, Context,
                                                          *this, TemplateArgs);
@@ -905,6 +934,9 @@ Decl *TemplateDeclInstantiator::VisitVarDecl(VarDecl *D,
       SemaRef.inferObjCARCLifetime(Var))
     Var->setInvalidDecl();
 
+  if (SemaRef.getLangOpts().OpenCL)
+    SemaRef.deduceOpenCLAddressSpace(Var);
+
   // Substitute the nested name specifier, if any.
   if (SubstQualifier(D, Var))
     return nullptr;
@@ -1761,8 +1793,9 @@ static QualType adjustFunctionTypeForInstantiation(ASTContext &Context,
 ///   1) instantiating function templates
 ///   2) substituting friend declarations
 ///   3) substituting deduction guide declarations for nested class templates
-Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
-                                       TemplateParameterList *TemplateParams) {
+Decl *TemplateDeclInstantiator::VisitFunctionDecl(
+    FunctionDecl *D, TemplateParameterList *TemplateParams,
+    RewriteKind FunctionRewriteKind) {
   // Check whether there is already a function template specialization for
   // this declaration.
   FunctionTemplateDecl *FunctionTemplate = D->getDescribedFunctionTemplate();
@@ -1812,6 +1845,18 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
       return nullptr;
   }
 
+  // FIXME: Concepts: Do not substitute into constraint expressions
+  Expr *TrailingRequiresClause = D->getTrailingRequiresClause();
+  if (TrailingRequiresClause) {
+    ExprResult SubstRC = SemaRef.SubstExpr(TrailingRequiresClause,
+                                           TemplateArgs);
+    if (SubstRC.isInvalid())
+      return nullptr;
+    TrailingRequiresClause = SubstRC.get();
+    if (!SemaRef.CheckConstraintExpression(TrailingRequiresClause))
+      return nullptr;
+  }
+
   // If we're instantiating a local function declaration, put the result
   // in the enclosing namespace; otherwise we need to find the instantiated
   // context.
@@ -1832,6 +1877,9 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
   DeclarationNameInfo NameInfo
     = SemaRef.SubstDeclarationNameInfo(D->getNameInfo(), TemplateArgs);
 
+  if (FunctionRewriteKind != RewriteKind::None)
+    adjustForRewrite(FunctionRewriteKind, D, T, TInfo, NameInfo);
+
   FunctionDecl *Function;
   if (auto *DGuide = dyn_cast<CXXDeductionGuideDecl>(D)) {
     Function = CXXDeductionGuideDecl::Create(
@@ -1845,7 +1893,8 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
     Function = FunctionDecl::Create(
         SemaRef.Context, DC, D->getInnerLocStart(), NameInfo, T, TInfo,
         D->getCanonicalDecl()->getStorageClass(), D->isInlineSpecified(),
-        D->hasWrittenPrototype(), D->getConstexprKind());
+        D->hasWrittenPrototype(), D->getConstexprKind(),
+        TrailingRequiresClause);
     Function->setRangeEnd(D->getSourceRange().getEnd());
   }
 
@@ -1872,6 +1921,9 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
       Params[P]->setOwningFunction(Function);
   Function->setParams(Params);
 
+  if (TrailingRequiresClause)
+    Function->setTrailingRequiresClause(TrailingRequiresClause);
+
   if (TemplateParams) {
     // Our resulting instantiation is actually a function template, since we
     // are substituting only the outer template parameters. For example, given
@@ -2049,6 +2101,13 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
     }
   }
 
+  if (D->isExplicitlyDefaulted()) {
+    if (SubstDefaultedFunction(Function, D))
+      return nullptr;
+  }
+  if (D->isDeleted())
+    SemaRef.SetDeclDeleted(Function, D->getLocation());
+
   if (Function->isLocalExternDecl() && !Function->getPreviousDecl())
     DC->makeDeclVisibleInContext(PrincipalDecl);
 
@@ -2056,14 +2115,13 @@ Decl *TemplateDeclInstantiator::VisitFunctionDecl(FunctionDecl *D,
       PrincipalDecl->isInIdentifierNamespace(Decl::IDNS_Ordinary))
     PrincipalDecl->setNonMemberOperator();
 
-  assert(!D->isDefaulted() && "only methods should be defaulted");
   return Function;
 }
 
 Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
     CXXMethodDecl *D, TemplateParameterList *TemplateParams,
-    Optional<const ASTTemplateArgumentListInfo *>
-        ClassScopeSpecializationArgs) {
+    Optional<const ASTTemplateArgumentListInfo *> ClassScopeSpecializationArgs,
+    RewriteKind FunctionRewriteKind) {
   FunctionTemplateDecl *FunctionTemplate = D->getDescribedFunctionTemplate();
   if (FunctionTemplate && !TemplateParams) {
     // We are creating a function template specialization from a function
@@ -2125,6 +2183,18 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
       return nullptr;
   }
 
+  // FIXME: Concepts: Do not substitute into constraint expressions
+  Expr *TrailingRequiresClause = D->getTrailingRequiresClause();
+  if (TrailingRequiresClause) {
+    ExprResult SubstRC = SemaRef.SubstExpr(TrailingRequiresClause,
+                                           TemplateArgs);
+    if (SubstRC.isInvalid())
+      return nullptr;
+    TrailingRequiresClause = SubstRC.get();
+    if (!SemaRef.CheckConstraintExpression(TrailingRequiresClause))
+      return nullptr;
+  }
+
   DeclContext *DC = Owner;
   if (isFriend) {
     if (QualifierLoc) {
@@ -2142,34 +2212,42 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
     if (!DC) return nullptr;
   }
 
+  DeclarationNameInfo NameInfo
+    = SemaRef.SubstDeclarationNameInfo(D->getNameInfo(), TemplateArgs);
+
+  if (FunctionRewriteKind != RewriteKind::None)
+    adjustForRewrite(FunctionRewriteKind, D, T, TInfo, NameInfo);
+
   // Build the instantiated method declaration.
   CXXRecordDecl *Record = cast<CXXRecordDecl>(DC);
   CXXMethodDecl *Method = nullptr;
 
   SourceLocation StartLoc = D->getInnerLocStart();
-  DeclarationNameInfo NameInfo
-    = SemaRef.SubstDeclarationNameInfo(D->getNameInfo(), TemplateArgs);
   if (CXXConstructorDecl *Constructor = dyn_cast<CXXConstructorDecl>(D)) {
     Method = CXXConstructorDecl::Create(
         SemaRef.Context, Record, StartLoc, NameInfo, T, TInfo,
         InstantiatedExplicitSpecifier, Constructor->isInlineSpecified(), false,
-        Constructor->getConstexprKind());
+        Constructor->getConstexprKind(), InheritedConstructor(),
+        TrailingRequiresClause);
     Method->setRangeEnd(Constructor->getEndLoc());
   } else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(D)) {
     Method = CXXDestructorDecl::Create(
         SemaRef.Context, Record, StartLoc, NameInfo, T, TInfo,
-        Destructor->isInlineSpecified(), false, Destructor->getConstexprKind());
+        Destructor->isInlineSpecified(), false, Destructor->getConstexprKind(),
+        TrailingRequiresClause);
     Method->setRangeEnd(Destructor->getEndLoc());
   } else if (CXXConversionDecl *Conversion = dyn_cast<CXXConversionDecl>(D)) {
     Method = CXXConversionDecl::Create(
         SemaRef.Context, Record, StartLoc, NameInfo, T, TInfo,
         Conversion->isInlineSpecified(), InstantiatedExplicitSpecifier,
-        Conversion->getConstexprKind(), Conversion->getEndLoc());
+        Conversion->getConstexprKind(), Conversion->getEndLoc(),
+        TrailingRequiresClause);
   } else {
     StorageClass SC = D->isStatic() ? SC_Static : SC_None;
     Method = CXXMethodDecl::Create(SemaRef.Context, Record, StartLoc, NameInfo,
                                    T, TInfo, SC, D->isInlineSpecified(),
-                                   D->getConstexprKind(), D->getEndLoc());
+                                   D->getConstexprKind(), D->getEndLoc(),
+                                   TrailingRequiresClause);
   }
 
   if (D->isInlined())
@@ -2325,8 +2403,10 @@ Decl *TemplateDeclInstantiator::VisitCXXMethodDecl(
   SemaRef.CheckOverrideControl(Method);
 
   // If a function is defined as defaulted or deleted, mark it as such now.
-  if (D->isExplicitlyDefaulted())
-    SemaRef.SetDeclDefaulted(Method, Method->getLocation());
+  if (D->isExplicitlyDefaulted()) {
+    if (SubstDefaultedFunction(Method, D))
+      return nullptr;
+  }
   if (D->isDeletedAsWritten())
     SemaRef.SetDeclDeleted(Method, Method->getLocation());
 
@@ -2399,13 +2479,68 @@ Decl *TemplateDeclInstantiator::VisitTemplateTypeParmDecl(
   // TODO: don't always clone when decls are refcounted.
   assert(D->getTypeForDecl()->isTemplateTypeParmType());
 
+  Optional<unsigned> NumExpanded;
+
+  if (const TypeConstraint *TC = D->getTypeConstraint()) {
+    if (D->isPackExpansion() && !D->isExpandedParameterPack()) {
+      assert(TC->getTemplateArgsAsWritten() &&
+             "type parameter can only be an expansion when explicit arguments "
+             "are specified");
+      // The template type parameter pack's type is a pack expansion of types.
+      // Determine whether we need to expand this parameter pack into separate
+      // types.
+      SmallVector<UnexpandedParameterPack, 2> Unexpanded;
+      for (auto &ArgLoc : TC->getTemplateArgsAsWritten()->arguments())
+        SemaRef.collectUnexpandedParameterPacks(ArgLoc, Unexpanded);
+
+      // Determine whether the set of unexpanded parameter packs can and should
+      // be expanded.
+      bool Expand = true;
+      bool RetainExpansion = false;
+      if (SemaRef.CheckParameterPacksForExpansion(
+              cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
+                  ->getEllipsisLoc(),
+              SourceRange(TC->getConceptNameLoc(),
+                          TC->hasExplicitTemplateArgs() ?
+                          TC->getTemplateArgsAsWritten()->getRAngleLoc() :
+                          TC->getConceptNameInfo().getEndLoc()),
+              Unexpanded, TemplateArgs, Expand, RetainExpansion, NumExpanded))
+        return nullptr;
+    }
+  }
+
   TemplateTypeParmDecl *Inst = TemplateTypeParmDecl::Create(
       SemaRef.Context, Owner, D->getBeginLoc(), D->getLocation(),
       D->getDepth() - TemplateArgs.getNumSubstitutedLevels(), D->getIndex(),
-      D->getIdentifier(), D->wasDeclaredWithTypename(), D->isParameterPack());
+      D->getIdentifier(), D->wasDeclaredWithTypename(), D->isParameterPack(),
+      D->hasTypeConstraint(), NumExpanded);
+
   Inst->setAccess(AS_public);
   Inst->setImplicit(D->isImplicit());
-
+  if (auto *TC = D->getTypeConstraint()) {
+    // TODO: Concepts: do not instantiate the constraint (delayed constraint
+    // substitution)
+    const ASTTemplateArgumentListInfo *TemplArgInfo
+      = TC->getTemplateArgsAsWritten();
+    TemplateArgumentListInfo InstArgs;
+
+    if (TemplArgInfo) {
+      InstArgs.setLAngleLoc(TemplArgInfo->LAngleLoc);
+      InstArgs.setRAngleLoc(TemplArgInfo->RAngleLoc);
+      if (SemaRef.Subst(TemplArgInfo->getTemplateArgs(),
+                        TemplArgInfo->NumTemplateArgs,
+                        InstArgs, TemplateArgs))
+        return nullptr;
+    }
+    if (SemaRef.AttachTypeConstraint(
+            TC->getNestedNameSpecifierLoc(), TC->getConceptNameInfo(),
+            TC->getNamedConcept(), &InstArgs, Inst,
+            D->isParameterPack()
+                ? cast<CXXFoldExpr>(TC->getImmediatelyDeclaredConstraint())
+                    ->getEllipsisLoc()
+                : SourceLocation()))
+      return nullptr;
+  }
   if (D->hasDefaultArgument() && !D->defaultArgumentWasInherited()) {
     TypeSourceInfo *InstantiatedDefaultArg =
         SemaRef.SubstType(D->getDefaultArgumentInfo(), TemplateArgs,
@@ -3040,7 +3175,9 @@ Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
   }
   if (SubstReductionType.isNull())
     return nullptr;
-  bool IsCorrect = !SubstReductionType.isNull();
+  Expr *Combiner = D->getCombiner();
+  Expr *Init = D->getInitializer();
+  bool IsCorrect = true;
   // Create instantiated copy.
   std::pair<QualType, SourceLocation> ReductionTypes[] = {
       std::make_pair(SubstReductionType, D->getLocation())};
@@ -3055,23 +3192,10 @@ Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
       PrevDeclInScope);
   auto *NewDRD = cast<OMPDeclareReductionDecl>(DRD.get().getSingleDecl());
   SemaRef.CurrentInstantiationScope->InstantiatedLocal(D, NewDRD);
-  if (!RequiresInstantiation) {
-    if (Expr *Combiner = D->getCombiner()) {
-      NewDRD->setCombinerData(D->getCombinerIn(), D->getCombinerOut());
-      NewDRD->setCombiner(Combiner);
-      if (Expr *Init = D->getInitializer()) {
-        NewDRD->setInitializerData(D->getInitOrig(), D->getInitPriv());
-        NewDRD->setInitializer(Init, D->getInitializerKind());
-      }
-    }
-    (void)SemaRef.ActOnOpenMPDeclareReductionDirectiveEnd(
-        /*S=*/nullptr, DRD, IsCorrect && !D->isInvalidDecl());
-    return NewDRD;
-  }
   Expr *SubstCombiner = nullptr;
   Expr *SubstInitializer = nullptr;
   // Combiners instantiation sequence.
-  if (D->getCombiner()) {
+  if (Combiner) {
     SemaRef.ActOnOpenMPDeclareReductionCombinerStart(
         /*S=*/nullptr, NewDRD);
     SemaRef.CurrentInstantiationScope->InstantiatedLocal(
@@ -3083,41 +3207,41 @@ Decl *TemplateDeclInstantiator::VisitOMPDeclareReductionDecl(
     auto *ThisContext = dyn_cast_or_null<CXXRecordDecl>(Owner);
     Sema::CXXThisScopeRAII ThisScope(SemaRef, ThisContext, Qualifiers(),
                                      ThisContext);
-    SubstCombiner = SemaRef.SubstExpr(D->getCombiner(), TemplateArgs).get();
+    SubstCombiner = SemaRef.SubstExpr(Combiner, TemplateArgs).get();
     SemaRef.ActOnOpenMPDeclareReductionCombinerEnd(NewDRD, SubstCombiner);
-    // Initializers instantiation sequence.
-    if (D->getInitializer()) {
-      VarDecl *OmpPrivParm =
-          SemaRef.ActOnOpenMPDeclareReductionInitializerStart(
-              /*S=*/nullptr, NewDRD);
-      SemaRef.CurrentInstantiationScope->InstantiatedLocal(
-          cast<DeclRefExpr>(D->getInitOrig())->getDecl(),
-          cast<DeclRefExpr>(NewDRD->getInitOrig())->getDecl());
-      SemaRef.CurrentInstantiationScope->InstantiatedLocal(
-          cast<DeclRefExpr>(D->getInitPriv())->getDecl(),
-          cast<DeclRefExpr>(NewDRD->getInitPriv())->getDecl());
-      if (D->getInitializerKind() == OMPDeclareReductionDecl::CallInit) {
-        SubstInitializer =
-            SemaRef.SubstExpr(D->getInitializer(), TemplateArgs).get();
-      } else {
-        IsCorrect = IsCorrect && OmpPrivParm->hasInit();
-      }
-      SemaRef.ActOnOpenMPDeclareReductionInitializerEnd(
-          NewDRD, SubstInitializer, OmpPrivParm);
+  }
+  // Initializers instantiation sequence.
+  if (Init) {
+    VarDecl *OmpPrivParm = SemaRef.ActOnOpenMPDeclareReductionInitializerStart(
+        /*S=*/nullptr, NewDRD);
+    SemaRef.CurrentInstantiationScope->InstantiatedLocal(
+        cast<DeclRefExpr>(D->getInitOrig())->getDecl(),
+        cast<DeclRefExpr>(NewDRD->getInitOrig())->getDecl());
+    SemaRef.CurrentInstantiationScope->InstantiatedLocal(
+        cast<DeclRefExpr>(D->getInitPriv())->getDecl(),
+        cast<DeclRefExpr>(NewDRD->getInitPriv())->getDecl());
+    if (D->getInitializerKind() == OMPDeclareReductionDecl::CallInit) {
+      SubstInitializer = SemaRef.SubstExpr(Init, TemplateArgs).get();
+    } else {
+      auto *OldPrivParm =
+          cast<VarDecl>(cast<DeclRefExpr>(D->getInitPriv())->getDecl());
+      IsCorrect = IsCorrect && OldPrivParm->hasInit();
+      if (IsCorrect)
+        SemaRef.InstantiateVariableInitializer(OmpPrivParm, OldPrivParm,
+                                               TemplateArgs);
     }
-    IsCorrect =
-        IsCorrect && SubstCombiner &&
-        (!D->getInitializer() ||
-         (D->getInitializerKind() == OMPDeclareReductionDecl::CallInit &&
-          SubstInitializer) ||
-         (D->getInitializerKind() != OMPDeclareReductionDecl::CallInit &&
-          !SubstInitializer && !SubstInitializer));
-  } else {
-    IsCorrect = false;
+    SemaRef.ActOnOpenMPDeclareReductionInitializerEnd(NewDRD, SubstInitializer,
+                                                      OmpPrivParm);
   }
+  IsCorrect = IsCorrect && SubstCombiner &&
+              (!Init ||
+               (D->getInitializerKind() == OMPDeclareReductionDecl::CallInit &&
+                SubstInitializer) ||
+               (D->getInitializerKind() != OMPDeclareReductionDecl::CallInit &&
+                !SubstInitializer));
 
-  (void)SemaRef.ActOnOpenMPDeclareReductionDirectiveEnd(/*S=*/nullptr, DRD,
-                                                        IsCorrect);
+  (void)SemaRef.ActOnOpenMPDeclareReductionDirectiveEnd(
+      /*S=*/nullptr, DRD, IsCorrect && !D->isInvalidDecl());
 
   return NewDRD;
 }
@@ -3163,7 +3287,8 @@ TemplateDeclInstantiator::VisitOMPDeclareMapperDecl(OMPDeclareMapperDecl *D) {
   } else {
     // Instantiate the mapper variable.
     DeclarationNameInfo DirName;
-    SemaRef.StartOpenMPDSABlock(OMPD_declare_mapper, DirName, /*S=*/nullptr,
+    SemaRef.StartOpenMPDSABlock(llvm::omp::OMPD_declare_mapper, DirName,
+                                /*S=*/nullptr,
                                 (*D->clauselist_begin())->getBeginLoc());
     SemaRef.ActOnOpenMPDeclareMapperDirectiveVarDecl(
         NewDMD, /*S=*/nullptr, SubstMapperTy, D->getLocation(), VN);
@@ -3275,7 +3400,8 @@ TemplateDeclInstantiator::VisitClassTemplateSpecializationDecl(
                                         D->getLocation(),
                                         InstTemplateArgs,
                                         false,
-                                        Converted))
+                                        Converted,
+                                        /*UpdateArgsWithConversion=*/true))
     return nullptr;
 
   // Figure out where to insert this class template explicit specialization
@@ -3396,7 +3522,8 @@ Decl *TemplateDeclInstantiator::VisitVarTemplateSpecializationDecl(
   // Check that the template argument list is well-formed for this template.
   SmallVector<TemplateArgument, 4> Converted;
   if (SemaRef.CheckTemplateArgumentList(InstVarTemplate, D->getLocation(),
-                                        VarTemplateArgsInfo, false, Converted))
+                                        VarTemplateArgsInfo, false, Converted,
+                                        /*UpdateArgsWithConversion=*/true))
     return nullptr;
 
   // Check whether we've already seen a declaration of this specialization.
@@ -3490,6 +3617,73 @@ Decl *Sema::SubstDecl(Decl *D, DeclContext *Owner,
   return SubstD;
 }
 
+void TemplateDeclInstantiator::adjustForRewrite(RewriteKind RK,
+                                                FunctionDecl *Orig, QualType &T,
+                                                TypeSourceInfo *&TInfo,
+                                                DeclarationNameInfo &NameInfo) {
+  assert(RK == RewriteKind::RewriteSpaceshipAsEqualEqual);
+
+  // C++2a [class.compare.default]p3:
+  //   the return type is replaced with bool
+  auto *FPT = T->castAs<FunctionProtoType>();
+  T = SemaRef.Context.getFunctionType(
+      SemaRef.Context.BoolTy, FPT->getParamTypes(), FPT->getExtProtoInfo());
+
+  // Update the return type in the source info too. The most straightforward
+  // way is to create new TypeSourceInfo for the new type. Use the location of
+  // the '= default' as the location of the new type.
+  //
+  // FIXME: Set the correct return type when we initially transform the type,
+  // rather than delaying it to now.
+  TypeSourceInfo *NewTInfo =
+      SemaRef.Context.getTrivialTypeSourceInfo(T, Orig->getEndLoc());
+  auto OldLoc = TInfo->getTypeLoc().getAsAdjusted<FunctionProtoTypeLoc>();
+  assert(OldLoc && "type of function is not a function type?");
+  auto NewLoc = NewTInfo->getTypeLoc().castAs<FunctionProtoTypeLoc>();
+  for (unsigned I = 0, N = OldLoc.getNumParams(); I != N; ++I)
+    NewLoc.setParam(I, OldLoc.getParam(I));
+  TInfo = NewTInfo;
+
+  //   and the declarator-id is replaced with operator==
+  NameInfo.setName(
+      SemaRef.Context.DeclarationNames.getCXXOperatorName(OO_EqualEqual));
+}
+
+FunctionDecl *Sema::SubstSpaceshipAsEqualEqual(CXXRecordDecl *RD,
+                                               FunctionDecl *Spaceship) {
+  if (Spaceship->isInvalidDecl())
+    return nullptr;
+
+  // C++2a [class.compare.default]p3:
+  //   an == operator function is declared implicitly [...] with the same
+  //   access and function-definition and in the same class scope as the
+  //   three-way comparison operator function
+  MultiLevelTemplateArgumentList NoTemplateArgs;
+  TemplateDeclInstantiator Instantiator(*this, RD, NoTemplateArgs);
+  Decl *R;
+  if (auto *MD = dyn_cast<CXXMethodDecl>(Spaceship)) {
+    R = Instantiator.VisitCXXMethodDecl(
+        MD, nullptr, None,
+        TemplateDeclInstantiator::RewriteKind::RewriteSpaceshipAsEqualEqual);
+  } else {
+    assert(Spaceship->getFriendObjectKind() &&
+           "defaulted spaceship is neither a member nor a friend");
+
+    R = Instantiator.VisitFunctionDecl(
+        Spaceship, nullptr,
+        TemplateDeclInstantiator::RewriteKind::RewriteSpaceshipAsEqualEqual);
+    if (!R)
+      return nullptr;
+
+    FriendDecl *FD =
+        FriendDecl::Create(Context, RD, Spaceship->getLocation(),
+                           cast<NamedDecl>(R), Spaceship->getBeginLoc());
+    FD->setAccess(AS_public);
+    RD->addDecl(FD);
+  }
+  return cast_or_null<FunctionDecl>(R);
+}
+
 /// Instantiates a nested template parameter list in the current
 /// instantiation context.
 ///
@@ -3598,7 +3792,8 @@ TemplateDeclInstantiator::InstantiateClassTemplatePartialSpecialization(
   // in the member template's set of class template partial specializations.
   void *InsertPos = nullptr;
   ClassTemplateSpecializationDecl *PrevDecl
-    = ClassTemplate->findPartialSpecialization(Converted, InsertPos);
+    = ClassTemplate->findPartialSpecialization(Converted, InstParams,
+                                               InsertPos);
 
   // Build the canonical type that describes the converted template
   // arguments of the class template partial specialization.
@@ -3722,7 +3917,7 @@ TemplateDeclInstantiator::InstantiateVarTemplatePartialSpecialization(
   // in the member template's set of variable template partial specializations.
   void *InsertPos = nullptr;
   VarTemplateSpecializationDecl *PrevDecl =
-      VarTemplate->findPartialSpecialization(Converted, InsertPos);
+      VarTemplate->findPartialSpecialization(Converted, InstParams, InsertPos);
 
   // Build the canonical type that describes the converted template
   // arguments of the variable template partial specialization.
@@ -4009,6 +4204,48 @@ void Sema::InstantiateExceptionSpec(SourceLocation PointOfInstantiation,
                      TemplateArgs);
 }
 
+bool Sema::CheckInstantiatedFunctionTemplateConstraints(
+    SourceLocation PointOfInstantiation, FunctionDecl *Decl,
+    ArrayRef<TemplateArgument> TemplateArgs,
+    ConstraintSatisfaction &Satisfaction) {
+  // In most cases we're not going to have constraints, so check for that first.
+  FunctionTemplateDecl *Template = Decl->getPrimaryTemplate();
+  // Note - code synthesis context for the constraints check is created
+  // inside CheckConstraintsSatisfaction.
+  SmallVector<const Expr *, 3> TemplateAC;
+  Template->getAssociatedConstraints(TemplateAC);
+  if (TemplateAC.empty()) {
+    Satisfaction.IsSatisfied = true;
+    return false;
+  }
+
+  // Enter the scope of this instantiation. We don't use
+  // PushDeclContext because we don't have a scope.
+  Sema::ContextRAII savedContext(*this, Decl);
+  LocalInstantiationScope Scope(*this);
+
+  MultiLevelTemplateArgumentList MLTAL =
+    getTemplateInstantiationArgs(Decl, nullptr, /*RelativeToPrimary*/true);
+
+  // If this is not an explicit specialization - we need to get the instantiated
+  // version of the template arguments and add them to scope for the
+  // substitution.
+  if (Decl->isTemplateInstantiation()) {
+    InstantiatingTemplate Inst(*this, Decl->getPointOfInstantiation(),
+        InstantiatingTemplate::ConstraintsCheck{}, Decl->getPrimaryTemplate(),
+        MLTAL.getInnermost(), SourceRange());
+    if (Inst.isInvalid())
+      return true;
+    if (addInstantiatedParametersToScope(*this, Decl,
+                                        Decl->getTemplateInstantiationPattern(),
+                                         Scope, MLTAL))
+      return true;
+  }
+
+  return CheckConstraintSatisfaction(Template, TemplateAC, TemplateArgs,
+                                     PointOfInstantiation, Satisfaction);
+}
+
 /// Initializes the common fields of an instantiation function
 /// declaration (New) from the corresponding fields of its template (Tmpl).
 ///
@@ -4016,9 +4253,6 @@ void Sema::InstantiateExceptionSpec(SourceLocation PointOfInstantiation,
 bool
 TemplateDeclInstantiator::InitFunctionInstantiation(FunctionDecl *New,
                                                     FunctionDecl *Tmpl) {
-  if (Tmpl->isDeleted())
-    New->setDeletedAsWritten();
-
   New->setImplicit(Tmpl->isImplicit());
 
   // Forward the mangling number from the template to the instantiated decl.
@@ -4119,6 +4353,34 @@ TemplateDeclInstantiator::InitMethodInstantiation(CXXMethodDecl *New,
   return false;
 }
 
+bool TemplateDeclInstantiator::SubstDefaultedFunction(FunctionDecl *New,
+                                                      FunctionDecl *Tmpl) {
+  // Transfer across any unqualified lookups.
+  if (auto *DFI = Tmpl->getDefaultedFunctionInfo()) {
+    SmallVector<DeclAccessPair, 32> Lookups;
+    Lookups.reserve(DFI->getUnqualifiedLookups().size());
+    bool AnyChanged = false;
+    for (DeclAccessPair DA : DFI->getUnqualifiedLookups()) {
+      NamedDecl *D = SemaRef.FindInstantiatedDecl(New->getLocation(),
+                                                  DA.getDecl(), TemplateArgs);
+      if (!D)
+        return true;
+      AnyChanged |= (D != DA.getDecl());
+      Lookups.push_back(DeclAccessPair::make(D, DA.getAccess()));
+    }
+
+    // It's unlikely that substitution will change any declarations. Don't
+    // store an unnecessary copy in that case.
+    New->setDefaultedFunctionInfo(
+        AnyChanged ? FunctionDecl::DefaultedFunctionInfo::Create(
+                         SemaRef.Context, Lookups)
+                   : DFI);
+  }
+
+  SemaRef.SetDeclDefaulted(New, Tmpl->getLocation());
+  return false;
+}
+
 /// Instantiate (or find existing instantiation of) a function template with a
 /// given set of template arguments.
 ///
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index 975d6620c06f..d947d6d282be 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -937,6 +937,10 @@ bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
     }
   }
 
+  if (Expr *TRC = D.getTrailingRequiresClause())
+    if (TRC->containsUnexpandedParameterPack())
+      return true;
+  
   return false;
 }
 
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index fccdb2bc2e2c..3884fdae8fe7 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -1976,6 +1976,19 @@ bool Sema::CheckQualifiedFunctionForTypeId(QualType T, SourceLocation Loc) {
   return true;
 }
 
+// Helper to deduce addr space of a pointee type in OpenCL mode.
+static QualType deduceOpenCLPointeeAddrSpace(Sema &S, QualType PointeeType) {
+  if (!PointeeType->isUndeducedAutoType() && !PointeeType->isDependentType() &&
+      !PointeeType->isSamplerT() &&
+      !PointeeType.hasAddressSpace())
+    PointeeType = S.getASTContext().getAddrSpaceQualType(
+        PointeeType,
+        S.getLangOpts().OpenCLCPlusPlus || S.getLangOpts().OpenCLVersion == 200
+            ? LangAS::opencl_generic
+            : LangAS::opencl_private);
+  return PointeeType;
+}
+
 /// Build a pointer type.
 ///
 /// \param T The type to which we'll be building a pointer.
@@ -2012,6 +2025,9 @@ QualType Sema::BuildPointerType(QualType T,
   if (getLangOpts().ObjCAutoRefCount)
     T = inferARCLifetimeForPointee(*this, T, Loc, /*reference*/ false);
 
+  if (getLangOpts().OpenCL)
+    T = deduceOpenCLPointeeAddrSpace(*this, T);
+
   // Build the pointer type.
   return Context.getPointerType(T);
 }
@@ -2072,6 +2088,9 @@ QualType Sema::BuildReferenceType(QualType T, bool SpelledAsLValue,
   if (getLangOpts().ObjCAutoRefCount)
     T = inferARCLifetimeForPointee(*this, T, Loc, /*reference*/ true);
 
+  if (getLangOpts().OpenCL)
+    T = deduceOpenCLPointeeAddrSpace(*this, T);
+
   // Handle restrict on references.
   if (LValueRef)
     return Context.getLValueReferenceType(T, SpelledAsLValue);
@@ -2655,6 +2674,9 @@ QualType Sema::BuildBlockPointerType(QualType T,
   if (checkQualifiedFunction(*this, T, Loc, QFK_BlockPointer))
     return QualType();
 
+  if (getLangOpts().OpenCL)
+    T = deduceOpenCLPointeeAddrSpace(*this, T);
+
   return Context.getBlockPointerType(T);
 }
 
@@ -2994,7 +3016,8 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
                 SemaRef.Context, SemaRef.Context.getTranslationUnitDecl(),
                 /*KeyLoc*/ SourceLocation(), /*NameLoc*/ D.getBeginLoc(),
                 TemplateParameterDepth, AutoParameterPosition,
-                /*Identifier*/ nullptr, false, IsParameterPack);
+                /*Identifier*/ nullptr, false, IsParameterPack,
+                /*HasTypeConstraint=*/false);
         CorrespondingTemplateParam->setImplicit();
         LSI->TemplateParams.push_back(CorrespondingTemplateParam);
         // Replace the 'auto' in the function parameter with this invented
@@ -3139,7 +3162,7 @@ static QualType GetDeclSpecTypeForDeclarator(TypeProcessingState &state,
 
       T = SemaRef.Context.IntTy;
       D.setInvalidType(true);
-    } else if (!HaveTrailing &&
+    } else if (Auto && !HaveTrailing &&
                D.getContext() != DeclaratorContext::LambdaExprContext) {
       // If there was a trailing return type, we already got
       // warn_cxx98_compat_trailing_return_type in the parser.
@@ -4788,6 +4811,7 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
         FunctionProtoType::ExtProtoInfo EPI;
         EPI.ExtInfo = EI;
         EPI.Variadic = FTI.isVariadic;
+        EPI.EllipsisLoc = FTI.getEllipsisLoc();
         EPI.HasTrailingReturn = FTI.hasTrailingReturnType();
         EPI.TypeQuals.addCVRUQualifiers(
             FTI.MethodQualifiers ? FTI.MethodQualifiers->getTypeQualifiers()
@@ -4927,7 +4951,9 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
                           .getScopeRep()
                           ->getKind() == NestedNameSpecifier::TypeSpec) ||
                  state.getDeclarator().getContext() ==
-                     DeclaratorContext::MemberContext;
+                     DeclaratorContext::MemberContext ||
+                 state.getDeclarator().getContext() ==
+                     DeclaratorContext::LambdaExprContext;
         };
 
         if (state.getSema().getLangOpts().OpenCLCPlusPlus && IsClassMember()) {
@@ -4946,7 +4972,8 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state,
           // If a class member function's address space is not set, set it to
           // __generic.
           LangAS AS =
-              (ASIdx == LangAS::Default ? LangAS::opencl_generic : ASIdx);
+              (ASIdx == LangAS::Default ? S.getDefaultCXXMethodAddrSpace()
+                                        : ASIdx);
           EPI.TypeQuals.addAddressSpace(AS);
         }
         T = Context.getFunctionType(T, ParamTys, EPI);
@@ -6325,7 +6352,8 @@ namespace {
       Pointer,
       BlockPointer,
       Reference,
-      MemberPointer
+      MemberPointer,
+      MacroQualified,
     };
 
     QualType Original;
@@ -6356,6 +6384,9 @@ namespace {
         } else if (isa<AttributedType>(Ty)) {
           T = cast<AttributedType>(Ty)->getEquivalentType();
           Stack.push_back(Attributed);
+        } else if (isa<MacroQualifiedType>(Ty)) {
+          T = cast<MacroQualifiedType>(Ty)->getUnderlyingType();
+          Stack.push_back(MacroQualified);
         } else {
           const Type *DTy = Ty->getUnqualifiedDesugaredType();
           if (Ty == DTy) {
@@ -6412,6 +6443,9 @@ namespace {
         return C.getParenType(New);
       }
 
+      case MacroQualified:
+        return wrap(C, cast<MacroQualifiedType>(Old)->getUnderlyingType(), I);
+
       case Pointer: {
         QualType New = wrap(C, cast<PointerType>(Old)->getPointeeType(), I);
         return C.getPointerType(New);
@@ -6464,35 +6498,36 @@ static bool handleMSPointerTypeQualifierAttr(TypeProcessingState &State,
     break;
   }
 
+  llvm::SmallSet<attr::Kind, 2> Attrs;
   attr::Kind NewAttrKind = A->getKind();
   QualType Desugared = Type;
   const AttributedType *AT = dyn_cast<AttributedType>(Type);
   while (AT) {
-    attr::Kind CurAttrKind = AT->getAttrKind();
-
-    // You cannot specify duplicate type attributes, so if the attribute has
-    // already been applied, flag it.
-    if (NewAttrKind == CurAttrKind) {
-      S.Diag(PAttr.getLoc(), diag::warn_duplicate_attribute_exact) << PAttr;
-      return true;
-    }
+    Attrs.insert(AT->getAttrKind());
+    Desugared = AT->getModifiedType();
+    AT = dyn_cast<AttributedType>(Desugared);
+  }
 
-    // You cannot have both __sptr and __uptr on the same type, nor can you
-    // have __ptr32 and __ptr64.
-    if ((CurAttrKind == attr::Ptr32 && NewAttrKind == attr::Ptr64) ||
-        (CurAttrKind == attr::Ptr64 && NewAttrKind == attr::Ptr32)) {
-      S.Diag(PAttr.getLoc(), diag::err_attributes_are_not_compatible)
-        << "'__ptr32'" << "'__ptr64'";
-      return true;
-    } else if ((CurAttrKind == attr::SPtr && NewAttrKind == attr::UPtr) ||
-               (CurAttrKind == attr::UPtr && NewAttrKind == attr::SPtr)) {
-      S.Diag(PAttr.getLoc(), diag::err_attributes_are_not_compatible)
-        << "'__sptr'" << "'__uptr'";
-      return true;
-    }
+  // You cannot specify duplicate type attributes, so if the attribute has
+  // already been applied, flag it.
+  if (Attrs.count(NewAttrKind)) {
+    S.Diag(PAttr.getLoc(), diag::warn_duplicate_attribute_exact) << PAttr;
+    return true;
+  }
+  Attrs.insert(NewAttrKind);
 
-    Desugared = AT->getEquivalentType();
-    AT = dyn_cast<AttributedType>(Desugared);
+  // You cannot have both __sptr and __uptr on the same type, nor can you
+  // have __ptr32 and __ptr64.
+  if (Attrs.count(attr::Ptr32) && Attrs.count(attr::Ptr64)) {
+    S.Diag(PAttr.getLoc(), diag::err_attributes_are_not_compatible)
+        << "'__ptr32'"
+        << "'__ptr64'";
+    return true;
+  } else if (Attrs.count(attr::SPtr) && Attrs.count(attr::UPtr)) {
+    S.Diag(PAttr.getLoc(), diag::err_attributes_are_not_compatible)
+        << "'__sptr'"
+        << "'__uptr'";
+    return true;
   }
 
   // Pointer type qualifiers can only operate on pointer types, but not
@@ -6510,7 +6545,26 @@ static bool handleMSPointerTypeQualifierAttr(TypeProcessingState &State,
     return true;
   }
 
-  Type = State.getAttributedType(A, Type, Type);
+  // Add address space to type based on its attributes.
+  LangAS ASIdx = LangAS::Default;
+  uint64_t PtrWidth = S.Context.getTargetInfo().getPointerWidth(0);
+  if (PtrWidth == 32) {
+    if (Attrs.count(attr::Ptr64))
+      ASIdx = LangAS::ptr64;
+    else if (Attrs.count(attr::UPtr))
+      ASIdx = LangAS::ptr32_uptr;
+  } else if (PtrWidth == 64 && Attrs.count(attr::Ptr32)) {
+    if (Attrs.count(attr::UPtr))
+      ASIdx = LangAS::ptr32_uptr;
+    else
+      ASIdx = LangAS::ptr32_sptr;
+  }
+
+  QualType Pointee = Type->getPointeeType();
+  if (ASIdx != LangAS::Default)
+    Pointee = S.Context.getAddrSpaceQualType(
+        S.Context.removeAddrSpaceQualType(Pointee), ASIdx);
+  Type = State.getAttributedType(A, Type, S.Context.getPointerType(Pointee));
   return false;
 }
 
@@ -7215,6 +7269,7 @@ static bool isPermittedNeonBaseType(QualType &Ty,
   // Signed poly is mathematically wrong, but has been baked into some ABIs by
   // now.
   bool IsPolyUnsigned = Triple.getArch() == llvm::Triple::aarch64 ||
+                        Triple.getArch() == llvm::Triple::aarch64_32 ||
                         Triple.getArch() == llvm::Triple::aarch64_be;
   if (VecKind == VectorType::NeonPolyVector) {
     if (IsPolyUnsigned) {
@@ -7232,10 +7287,8 @@ static bool isPermittedNeonBaseType(QualType &Ty,
 
   // Non-polynomial vector types: the usual suspects are allowed, as well as
   // float64_t on AArch64.
-  bool Is64Bit = Triple.getArch() == llvm::Triple::aarch64 ||
-                 Triple.getArch() == llvm::Triple::aarch64_be;
-
-  if (Is64Bit && BTy->getKind() == BuiltinType::Double)
+  if ((Triple.isArch64Bit() || Triple.getArch() == llvm::Triple::aarch64_32) &&
+      BTy->getKind() == BuiltinType::Double)
     return true;
 
   return BTy->getKind() == BuiltinType::SChar ||
@@ -7261,8 +7314,10 @@ static bool isPermittedNeonBaseType(QualType &Ty,
 /// match one of the standard Neon vector types.
 static void HandleNeonVectorTypeAttr(QualType &CurType, const ParsedAttr &Attr,
                                      Sema &S, VectorType::VectorKind VecKind) {
-  // Target must have NEON
-  if (!S.Context.getTargetInfo().hasFeature("neon")) {
+  // Target must have NEON (or MVE, whose vectors are similar enough
+  // not to need a separate attribute)
+  if (!S.Context.getTargetInfo().hasFeature("neon") &&
+      !S.Context.getTargetInfo().hasFeature("mve")) {
     S.Diag(Attr.getLoc(), diag::err_attribute_unsupported) << Attr;
     Attr.setInvalid();
     return;
@@ -7361,137 +7416,6 @@ static void HandleOpenCLAccessAttr(QualType &CurType, const ParsedAttr &Attr,
   }
 }
 
-static void deduceOpenCLImplicitAddrSpace(TypeProcessingState &State,
-                                          QualType &T, TypeAttrLocation TAL) {
-  Declarator &D = State.getDeclarator();
-
-  // Handle the cases where address space should not be deduced.
-  //
-  // The pointee type of a pointer type is always deduced since a pointer always
-  // points to some memory location which should has an address space.
-  //
-  // There are situations that at the point of certain declarations, the address
-  // space may be unknown and better to be left as default. For example, when
-  // defining a typedef or struct type, they are not associated with any
-  // specific address space. Later on, they may be used with any address space
-  // to declare a variable.
-  //
-  // The return value of a function is r-value, therefore should not have
-  // address space.
-  //
-  // The void type does not occupy memory, therefore should not have address
-  // space, except when it is used as a pointee type.
-  //
-  // Since LLVM assumes function type is in default address space, it should not
-  // have address space.
-  auto ChunkIndex = State.getCurrentChunkIndex();
-  bool IsPointee =
-      ChunkIndex > 0 &&
-      (D.getTypeObject(ChunkIndex - 1).Kind == DeclaratorChunk::Pointer ||
-       D.getTypeObject(ChunkIndex - 1).Kind == DeclaratorChunk::Reference ||
-       D.getTypeObject(ChunkIndex - 1).Kind == DeclaratorChunk::BlockPointer);
-  // For pointers/references to arrays the next chunk is always an array
-  // followed by any number of parentheses.
-  if (!IsPointee && ChunkIndex > 1) {
-    auto AdjustedCI = ChunkIndex - 1;
-    if (D.getTypeObject(AdjustedCI).Kind == DeclaratorChunk::Array)
-      AdjustedCI--;
-    // Skip over all parentheses.
-    while (AdjustedCI > 0 &&
-           D.getTypeObject(AdjustedCI).Kind == DeclaratorChunk::Paren)
-      AdjustedCI--;
-    if (D.getTypeObject(AdjustedCI).Kind == DeclaratorChunk::Pointer ||
-        D.getTypeObject(AdjustedCI).Kind == DeclaratorChunk::Reference)
-      IsPointee = true;
-  }
-  bool IsFuncReturnType =
-      ChunkIndex > 0 &&
-      D.getTypeObject(ChunkIndex - 1).Kind == DeclaratorChunk::Function;
-  bool IsFuncType =
-      ChunkIndex < D.getNumTypeObjects() &&
-      D.getTypeObject(ChunkIndex).Kind == DeclaratorChunk::Function;
-  if ( // Do not deduce addr space for function return type and function type,
-       // otherwise it will fail some sema check.
-      IsFuncReturnType || IsFuncType ||
-      // Do not deduce addr space for member types of struct, except the pointee
-      // type of a pointer member type or static data members.
-      (D.getContext() == DeclaratorContext::MemberContext &&
-       (!IsPointee &&
-        D.getDeclSpec().getStorageClassSpec() != DeclSpec::SCS_static)) ||
-      // Do not deduce addr space of non-pointee in type alias because it
-      // doesn't define any object.
-      (D.getContext() == DeclaratorContext::AliasDeclContext && !IsPointee) ||
-      // Do not deduce addr space for types used to define a typedef and the
-      // typedef itself, except the pointee type of a pointer type which is used
-      // to define the typedef.
-      (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_typedef &&
-       !IsPointee) ||
-      // Do not deduce addr space of the void type, e.g. in f(void), otherwise
-      // it will fail some sema check.
-      (T->isVoidType() && !IsPointee) ||
-      // Do not deduce addr spaces for dependent types because they might end
-      // up instantiating to a type with an explicit address space qualifier.
-      // Except for pointer or reference types because the addr space in
-      // template argument can only belong to a pointee.
-      (T->isDependentType() && !T->isPointerType() && !T->isReferenceType()) ||
-      // Do not deduce addr space of decltype because it will be taken from
-      // its argument.
-      T->isDecltypeType() ||
-      // OpenCL spec v2.0 s6.9.b:
-      // The sampler type cannot be used with the __local and __global address
-      // space qualifiers.
-      // OpenCL spec v2.0 s6.13.14:
-      // Samplers can also be declared as global constants in the program
-      // source using the following syntax.
-      //   const sampler_t <sampler name> = <value>
-      // In codegen, file-scope sampler type variable has special handing and
-      // does not rely on address space qualifier. On the other hand, deducing
-      // address space of const sampler file-scope variable as global address
-      // space causes spurious diagnostic about __global address space
-      // qualifier, therefore do not deduce address space of file-scope sampler
-      // type variable.
-      (D.getContext() == DeclaratorContext::FileContext && T->isSamplerT()))
-    return;
-
-  LangAS ImpAddr = LangAS::Default;
-  // Put OpenCL automatic variable in private address space.
-  // OpenCL v1.2 s6.5:
-  // The default address space name for arguments to a function in a
-  // program, or local variables of a function is __private. All function
-  // arguments shall be in the __private address space.
-  if (State.getSema().getLangOpts().OpenCLVersion <= 120 &&
-      !State.getSema().getLangOpts().OpenCLCPlusPlus) {
-    ImpAddr = LangAS::opencl_private;
-  } else {
-    // If address space is not set, OpenCL 2.0 defines non private default
-    // address spaces for some cases:
-    // OpenCL 2.0, section 6.5:
-    // The address space for a variable at program scope or a static variable
-    // inside a function can either be __global or __constant, but defaults to
-    // __global if not specified.
-    // (...)
-    // Pointers that are declared without pointing to a named address space
-    // point to the generic address space.
-    if (IsPointee) {
-      ImpAddr = LangAS::opencl_generic;
-    } else {
-      if (D.getContext() == DeclaratorContext::TemplateArgContext) {
-        // Do not deduce address space for non-pointee type in template arg.
-      } else if (D.getContext() == DeclaratorContext::FileContext) {
-        ImpAddr = LangAS::opencl_global;
-      } else {
-        if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static ||
-            D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_extern) {
-          ImpAddr = LangAS::opencl_global;
-        } else {
-          ImpAddr = LangAS::opencl_private;
-        }
-      }
-    }
-  }
-  T = State.getSema().Context.getAddrSpaceQualType(T, ImpAddr);
-}
-
 static void HandleLifetimeBoundAttr(TypeProcessingState &State,
                                     QualType &CurType,
                                     ParsedAttr &Attr) {
@@ -7504,6 +7428,16 @@ static void HandleLifetimeBoundAttr(TypeProcessingState &State,
   }
 }
 
+static bool isAddressSpaceKind(const ParsedAttr &attr) {
+  auto attrKind = attr.getKind();
+
+  return attrKind == ParsedAttr::AT_AddressSpace ||
+         attrKind == ParsedAttr::AT_OpenCLPrivateAddressSpace ||
+         attrKind == ParsedAttr::AT_OpenCLGlobalAddressSpace ||
+         attrKind == ParsedAttr::AT_OpenCLLocalAddressSpace ||
+         attrKind == ParsedAttr::AT_OpenCLConstantAddressSpace ||
+         attrKind == ParsedAttr::AT_OpenCLGenericAddressSpace;
+}
 
 static void processTypeAttrs(TypeProcessingState &state, QualType &type,
                              TypeAttrLocation TAL,
@@ -7542,11 +7476,11 @@ static void processTypeAttrs(TypeProcessingState &state, QualType &type,
           if (!IsTypeAttr)
             continue;
         }
-      } else if (TAL != TAL_DeclChunk &&
-                 attr.getKind() != ParsedAttr::AT_AddressSpace) {
+      } else if (TAL != TAL_DeclChunk && !isAddressSpaceKind(attr)) {
         // Otherwise, only consider type processing for a C++11 attribute if
         // it's actually been applied to a type.
-        // We also allow C++11 address_space attributes to pass through.
+        // We also allow C++11 address_space and
+        // OpenCL language address space attributes to pass through.
         continue;
       }
     }
@@ -7701,6 +7635,18 @@ static void processTypeAttrs(TypeProcessingState &state, QualType &type,
       else if (!handleFunctionTypeAttr(state, attr, type))
         distributeFunctionTypeAttr(state, attr, type);
       break;
+    case ParsedAttr::AT_AcquireHandle: {
+      if (!type->isFunctionType())
+        return;
+      StringRef HandleType;
+      if (!state.getSema().checkStringLiteralArgumentAttr(attr, 0, HandleType))
+        return;
+      type = state.getAttributedType(
+          AcquireHandleAttr::Create(state.getSema().Context, HandleType, attr),
+          type, type);
+      attr.setUsedAsTypeAttr();
+      break;
+    }
     }
 
     // Handle attributes that are defined in a macro. We do not want this to be
@@ -7721,8 +7667,6 @@ static void processTypeAttrs(TypeProcessingState &state, QualType &type,
   if (!state.getSema().getLangOpts().OpenCL ||
       type.getAddressSpace() != LangAS::Default)
     return;
-
-  deduceOpenCLImplicitAddrSpace(state, type, TAL);
 }
 
 void Sema::completeExprArrayBound(Expr *E) {
@@ -7944,33 +7888,31 @@ bool Sema::hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
 static void assignInheritanceModel(Sema &S, CXXRecordDecl *RD) {
   RD = RD->getMostRecentNonInjectedDecl();
   if (!RD->hasAttr<MSInheritanceAttr>()) {
-    MSInheritanceAttr::Spelling IM;
-
+    MSInheritanceModel IM;
+    bool BestCase = false;
     switch (S.MSPointerToMemberRepresentationMethod) {
     case LangOptions::PPTMK_BestCase:
+      BestCase = true;
       IM = RD->calculateInheritanceModel();
       break;
     case LangOptions::PPTMK_FullGeneralitySingleInheritance:
-      IM = MSInheritanceAttr::Keyword_single_inheritance;
+      IM = MSInheritanceModel::Single;
       break;
     case LangOptions::PPTMK_FullGeneralityMultipleInheritance:
-      IM = MSInheritanceAttr::Keyword_multiple_inheritance;
+      IM = MSInheritanceModel::Multiple;
       break;
     case LangOptions::PPTMK_FullGeneralityVirtualInheritance:
-      IM = MSInheritanceAttr::Keyword_unspecified_inheritance;
+      IM = MSInheritanceModel::Unspecified;
       break;
     }
 
-    SourceRange Loc = 
-    S.ImplicitMSInheritanceAttrLoc.isValid()
-                                 ? S.ImplicitMSInheritanceAttrLoc
-                                 : RD->getSourceRange();
-  RD->addAttr(MSInheritanceAttr::CreateImplicit(
-      S.getASTContext(),
-      /*BestCase=*/S.MSPointerToMemberRepresentationMethod ==
-          LangOptions::PPTMK_BestCase,
-      Loc, AttributeCommonInfo::AS_Microsoft, IM));
-  S.Consumer.AssignInheritanceModel(RD);
+    SourceRange Loc = S.ImplicitMSInheritanceAttrLoc.isValid()
+                          ? S.ImplicitMSInheritanceAttrLoc
+                          : RD->getSourceRange();
+    RD->addAttr(MSInheritanceAttr::CreateImplicit(
+        S.getASTContext(), BestCase, Loc, AttributeCommonInfo::AS_Microsoft,
+        MSInheritanceAttr::Spelling(IM)));
+    S.Consumer.AssignInheritanceModel(RD);
   }
 }
 
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 4b3a6708717c..3b827fbc950b 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -22,6 +22,7 @@
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/ExprObjC.h"
 #include "clang/AST/ExprOpenMP.h"
+#include "clang/AST/OpenMPClause.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/StmtCXX.h"
 #include "clang/AST/StmtObjC.h"
@@ -37,6 +38,8 @@
 #include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
 
+using namespace llvm::omp;
+
 namespace clang {
 using namespace sema;
 
@@ -1613,7 +1616,7 @@ public:
   ///
   /// By default, performs semantic analysis to build the new OpenMP clause.
   /// Subclasses may override this routine to provide different behavior.
-  OMPClause *RebuildOMPProcBindClause(OpenMPProcBindClauseKind Kind,
+  OMPClause *RebuildOMPProcBindClause(ProcBindKind Kind,
                                       SourceLocation KindKwLoc,
                                       SourceLocation StartLoc,
                                       SourceLocation LParenLoc,
@@ -1675,11 +1678,14 @@ public:
   /// By default, performs semantic analysis to build the new OpenMP clause.
   /// Subclasses may override this routine to provide different behavior.
   OMPClause *RebuildOMPLastprivateClause(ArrayRef<Expr *> VarList,
+                                         OpenMPLastprivateModifier LPKind,
+                                         SourceLocation LPKindLoc,
+                                         SourceLocation ColonLoc,
                                          SourceLocation StartLoc,
                                          SourceLocation LParenLoc,
                                          SourceLocation EndLoc) {
-    return getSema().ActOnOpenMPLastprivateClause(VarList, StartLoc, LParenLoc,
-                                                  EndLoc);
+    return getSema().ActOnOpenMPLastprivateClause(
+        VarList, LPKind, LPKindLoc, ColonLoc, StartLoc, LParenLoc, EndLoc);
   }
 
   /// Build a new OpenMP 'shared' clause.
@@ -1984,6 +1990,33 @@ public:
     return getSema().ActOnOpenMPIsDevicePtrClause(VarList, Locs);
   }
 
+  /// Build a new OpenMP 'defaultmap' clause.
+  ///
+  /// By default, performs semantic analysis to build the new OpenMP clause.
+  /// Subclasses may override this routine to provide different behavior.
+  OMPClause *RebuildOMPDefaultmapClause(OpenMPDefaultmapClauseModifier M,
+                                        OpenMPDefaultmapClauseKind Kind,
+                                        SourceLocation StartLoc,
+                                        SourceLocation LParenLoc,
+                                        SourceLocation MLoc,
+                                        SourceLocation KindLoc,
+                                        SourceLocation EndLoc) {
+    return getSema().ActOnOpenMPDefaultmapClause(M, Kind, StartLoc, LParenLoc,
+                                                 MLoc, KindLoc, EndLoc);
+  }
+
+  /// Build a new OpenMP 'nontemporal' clause.
+  ///
+  /// By default, performs semantic analysis to build the new OpenMP clause.
+  /// Subclasses may override this routine to provide different behavior.
+  OMPClause *RebuildOMPNontemporalClause(ArrayRef<Expr *> VarList,
+                                         SourceLocation StartLoc,
+                                         SourceLocation LParenLoc,
+                                         SourceLocation EndLoc) {
+    return getSema().ActOnOpenMPNontemporalClause(VarList, StartLoc, LParenLoc,
+                                                  EndLoc);
+  }
+
   /// Rebuild the operand to an Objective-C \@synchronized statement.
   ///
   /// By default, performs semantic analysis to build the new statement.
@@ -3031,13 +3064,13 @@ public:
   /// By default, performs semantic analysis to build the new expression.
   /// Subclasses may override this routine to provide different behavior.
   ExprResult RebuildConceptSpecializationExpr(NestedNameSpecifierLoc NNS,
-      SourceLocation TemplateKWLoc, SourceLocation ConceptNameLoc,
+      SourceLocation TemplateKWLoc, DeclarationNameInfo ConceptNameInfo,
       NamedDecl *FoundDecl, ConceptDecl *NamedConcept,
       TemplateArgumentListInfo *TALI) {
     CXXScopeSpec SS;
     SS.Adopt(NNS);
     ExprResult Result = getSema().CheckConceptTemplateId(SS, TemplateKWLoc,
-                                                         ConceptNameLoc,
+                                                         ConceptNameInfo,
                                                          FoundDecl,
                                                          NamedConcept, TALI);
     if (Result.isInvalid())
@@ -3455,7 +3488,7 @@ ExprResult TreeTransform<Derived>::TransformInitializer(Expr *Init,
     Init = AIL->getCommonExpr();
 
   if (MaterializeTemporaryExpr *MTE = dyn_cast<MaterializeTemporaryExpr>(Init))
-    Init = MTE->GetTemporaryExpr();
+    Init = MTE->getSubExpr();
 
   while (CXXBindTemporaryExpr *Binder = dyn_cast<CXXBindTemporaryExpr>(Init))
     Init = Binder->getSubExpr();
@@ -4564,14 +4597,6 @@ QualType TreeTransform<Derived>::TransformDecayedType(TypeLocBuilder &TLB,
   return Result;
 }
 
-/// Helper to deduce addr space of a pointee type in OpenCL mode.
-/// If the type is updated it will be overwritten in PointeeType param.
-static void deduceOpenCLPointeeAddrSpace(Sema &SemaRef, QualType &PointeeType) {
-  if (PointeeType.getAddressSpace() == LangAS::Default)
-    PointeeType = SemaRef.Context.getAddrSpaceQualType(PointeeType,
-                                                       LangAS::opencl_generic);
-}
-
 template<typename Derived>
 QualType TreeTransform<Derived>::TransformPointerType(TypeLocBuilder &TLB,
                                                       PointerTypeLoc TL) {
@@ -4580,9 +4605,6 @@ QualType TreeTransform<Derived>::TransformPointerType(TypeLocBuilder &TLB,
   if (PointeeType.isNull())
     return QualType();
 
-  if (SemaRef.getLangOpts().OpenCL)
-    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);
-
   QualType Result = TL.getType();
   if (PointeeType->getAs<ObjCObjectType>()) {
     // A dependent pointer type 'T *' has is being transformed such
@@ -4621,9 +4643,6 @@ TreeTransform<Derived>::TransformBlockPointerType(TypeLocBuilder &TLB,
   if (PointeeType.isNull())
     return QualType();
 
-  if (SemaRef.getLangOpts().OpenCL)
-    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);
-
   QualType Result = TL.getType();
   if (getDerived().AlwaysRebuild() ||
       PointeeType != TL.getPointeeLoc().getType()) {
@@ -4653,9 +4672,6 @@ TreeTransform<Derived>::TransformReferenceType(TypeLocBuilder &TLB,
   if (PointeeType.isNull())
     return QualType();
 
-  if (SemaRef.getLangOpts().OpenCL)
-    deduceOpenCLPointeeAddrSpace(SemaRef, PointeeType);
-
   QualType Result = TL.getType();
   if (getDerived().AlwaysRebuild() ||
       PointeeType != T->getPointeeTypeAsWritten()) {
@@ -7190,8 +7206,12 @@ TreeTransform<Derived>::TransformCoroutineBodyStmt(CoroutineBodyStmt *S) {
   // that may fail.
   ScopeInfo->setNeedsCoroutineSuspends(false);
 
-  // The new CoroutinePromise object needs to be built and put into the current
-  // FunctionScopeInfo before any transformations or rebuilding occurs.
+  // We re-build the coroutine promise object (and the coroutine parameters its
+  // type and constructor depend on) based on the types used in our current
+  // function. We must do so, and set it on the current FunctionScopeInfo,
+  // before attempting to transform the other parts of the coroutine body
+  // statement, such as the implicit suspend statements (because those
+  // statements reference the FunctionScopeInfo::CoroutinePromise).
   if (!SemaRef.buildCoroutineParameterMoves(FD->getLocation()))
     return StmtError();
   auto *Promise = SemaRef.buildCoroutinePromise(FD->getLocation());
@@ -7200,8 +7220,9 @@ TreeTransform<Derived>::TransformCoroutineBodyStmt(CoroutineBodyStmt *S) {
   getDerived().transformedLocalDecl(S->getPromiseDecl(), {Promise});
   ScopeInfo->CoroutinePromise = Promise;
 
-  // Transform the implicit coroutine statements we built during the initial
-  // parse.
+  // Transform the implicit coroutine statements constructed using dependent
+  // types during the previous parse: initial and final suspensions, the return
+  // object, and others. We also transform the coroutine function's body.
   StmtResult InitSuspend = getDerived().TransformStmt(S->getInitSuspendStmt());
   if (InitSuspend.isInvalid())
     return StmtError();
@@ -7228,17 +7249,13 @@ TreeTransform<Derived>::TransformCoroutineBodyStmt(CoroutineBodyStmt *S) {
     return StmtError();
   Builder.ReturnValue = Res.get();
 
+  // If during the previous parse the coroutine still had a dependent promise
+  // statement, we may need to build some implicit coroutine statements
+  // (such as exception and fallthrough handlers) for the first time.
   if (S->hasDependentPromiseType()) {
-    // PR41909: We may find a generic coroutine lambda definition within a
-    // template function that is being instantiated. In this case, the lambda
-    // will have a dependent promise type, until it is used in an expression
-    // that creates an instantiation with a non-dependent promise type. We
-    // should not assert or build coroutine dependent statements for such a
-    // generic lambda.
-    auto *MD = dyn_cast_or_null<CXXMethodDecl>(FD);
-    if (!MD || !MD->getParent()->isGenericLambda()) {
-      assert(!Promise->getType()->isDependentType() &&
-             "the promise type must no longer be dependent");
+    // We can only build these statements, however, if the current promise type
+    // is not dependent.
+    if (!Promise->getType()->isDependentType()) {
       assert(!S->getFallthroughHandler() && !S->getExceptionHandler() &&
              !S->getReturnStmtOnAllocFailure() && !S->getDeallocate() &&
              "these nodes should not have been built yet");
@@ -8046,6 +8063,17 @@ StmtResult TreeTransform<Derived>::TransformOMPParallelForSimdDirective(
 }
 
 template <typename Derived>
+StmtResult TreeTransform<Derived>::TransformOMPParallelMasterDirective(
+    OMPParallelMasterDirective *D) {
+  DeclarationNameInfo DirName;
+  getDerived().getSema().StartOpenMPDSABlock(OMPD_parallel_master, DirName,
+                                             nullptr, D->getBeginLoc());
+  StmtResult Res = getDerived().TransformOMPExecutableDirective(D);
+  getDerived().getSema().EndOpenMPDSABlock(Res.get());
+  return Res;
+}
+
+template <typename Derived>
 StmtResult TreeTransform<Derived>::TransformOMPParallelSectionsDirective(
     OMPParallelSectionsDirective *D) {
   DeclarationNameInfo DirName;
@@ -8310,6 +8338,18 @@ StmtResult TreeTransform<Derived>::TransformOMPParallelMasterTaskLoopDirective(
 }
 
 template <typename Derived>
+StmtResult
+TreeTransform<Derived>::TransformOMPParallelMasterTaskLoopSimdDirective(
+    OMPParallelMasterTaskLoopSimdDirective *D) {
+  DeclarationNameInfo DirName;
+  getDerived().getSema().StartOpenMPDSABlock(
+      OMPD_parallel_master_taskloop_simd, DirName, nullptr, D->getBeginLoc());
+  StmtResult Res = getDerived().TransformOMPExecutableDirective(D);
+  getDerived().getSema().EndOpenMPDSABlock(Res.get());
+  return Res;
+}
+
+template <typename Derived>
 StmtResult TreeTransform<Derived>::TransformOMPDistributeDirective(
     OMPDistributeDirective *D) {
   DeclarationNameInfo DirName;
@@ -8745,7 +8785,8 @@ TreeTransform<Derived>::TransformOMPLastprivateClause(OMPLastprivateClause *C) {
     Vars.push_back(EVar.get());
   }
   return getDerived().RebuildOMPLastprivateClause(
-      Vars, C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+      Vars, C->getKind(), C->getKindLoc(), C->getColonLoc(), C->getBeginLoc(),
+      C->getLParenLoc(), C->getEndLoc());
 }
 
 template <typename Derived>
@@ -9173,7 +9214,15 @@ OMPClause *TreeTransform<Derived>::TransformOMPDistScheduleClause(
 template <typename Derived>
 OMPClause *
 TreeTransform<Derived>::TransformOMPDefaultmapClause(OMPDefaultmapClause *C) {
-  return C;
+  // Rebuild Defaultmap Clause since we need to invoke the checking of
+  // defaultmap(none:variable-category) after template initialization.
+  return getDerived().RebuildOMPDefaultmapClause(C->getDefaultmapModifier(),
+                                                 C->getDefaultmapKind(),
+                                                 C->getBeginLoc(),
+                                                 C->getLParenLoc(),
+                                                 C->getDefaultmapModifierLoc(),
+                                                 C->getDefaultmapKindLoc(),
+                                                 C->getEndLoc());
 }
 
 template <typename Derived>
@@ -9234,6 +9283,21 @@ TreeTransform<Derived>::TransformOMPIsDevicePtrClause(OMPIsDevicePtrClause *C) {
   return getDerived().RebuildOMPIsDevicePtrClause(Vars, Locs);
 }
 
+template <typename Derived>
+OMPClause *
+TreeTransform<Derived>::TransformOMPNontemporalClause(OMPNontemporalClause *C) {
+  llvm::SmallVector<Expr *, 16> Vars;
+  Vars.reserve(C->varlist_size());
+  for (auto *VE : C->varlists()) {
+    ExprResult EVar = getDerived().TransformExpr(cast<Expr>(VE));
+    if (EVar.isInvalid())
+      return nullptr;
+    Vars.push_back(EVar.get());
+  }
+  return getDerived().RebuildOMPNontemporalClause(
+      Vars, C->getBeginLoc(), C->getLParenLoc(), C->getEndLoc());
+}
+
 //===----------------------------------------------------------------------===//
 // Expression transformation
 //===----------------------------------------------------------------------===//
@@ -9368,7 +9432,7 @@ TreeTransform<Derived>::TransformGenericSelectionExpr(GenericSelectionExpr *E) {
 
   SmallVector<Expr *, 4> AssocExprs;
   SmallVector<TypeSourceInfo *, 4> AssocTypes;
-  for (const GenericSelectionExpr::Association &Assoc : E->associations()) {
+  for (const GenericSelectionExpr::Association Assoc : E->associations()) {
     TypeSourceInfo *TSI = Assoc.getTypeSourceInfo();
     if (TSI) {
       TypeSourceInfo *AssocType = getDerived().TransformType(TSI);
@@ -11111,7 +11175,7 @@ TreeTransform<Derived>::TransformConceptSpecializationExpr(
 
   return getDerived().RebuildConceptSpecializationExpr(
       E->getNestedNameSpecifierLoc(), E->getTemplateKWLoc(),
-      E->getConceptNameLoc(), E->getFoundDecl(), E->getNamedConcept(),
+      E->getConceptNameInfo(), E->getFoundDecl(), E->getNamedConcept(),
       &TransArgs);
 }
 
@@ -11488,6 +11552,13 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
                                                         NewCallOpType);
   }
 
+  // Transform the trailing requires clause
+  ExprResult NewTrailingRequiresClause;
+  if (Expr *TRC = E->getCallOperator()->getTrailingRequiresClause())
+    // FIXME: Concepts: Substitution into requires clause should only happen
+    //                  when checking satisfaction.
+    NewTrailingRequiresClause = getDerived().TransformExpr(TRC);
+
   // Create the local class that will describe the lambda.
   CXXRecordDecl *OldClass = E->getLambdaClass();
   CXXRecordDecl *Class
@@ -11508,7 +11579,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
       Class, E->getIntroducerRange(), NewCallOpTSI,
       E->getCallOperator()->getEndLoc(),
       NewCallOpTSI->getTypeLoc().castAs<FunctionProtoTypeLoc>().getParams(),
-      E->getCallOperator()->getConstexprKind());
+      E->getCallOperator()->getConstexprKind(),
+      NewTrailingRequiresClause.get());
 
   LSI->CallOperator = NewCallOperator;
 
@@ -12145,7 +12217,7 @@ template<typename Derived>
 ExprResult
 TreeTransform<Derived>::TransformMaterializeTemporaryExpr(
                                                   MaterializeTemporaryExpr *E) {
-  return getDerived().TransformExpr(E->GetTemporaryExpr());
+  return getDerived().TransformExpr(E->getSubExpr());
 }
 
 template<typename Derived>