vendor/clang/clang-trunk-r300422

11 files changed, 1772 insertions, 593 deletions

diff --git a/lib/Serialization/ASTCommon.cpp b/lib/Serialization/ASTCommon.cpp
index ecd249cc50259..684ec243035e9 100644
--- a/lib/Serialization/ASTCommon.cpp
+++ b/lib/Serialization/ASTCommon.cpp
@@ -147,9 +147,6 @@ serialization::TypeIdxFromBuiltin(const BuiltinType *BT) {
   case BuiltinType::OCLQueue:
     ID = PREDEF_TYPE_QUEUE_ID;
     break;
-  case BuiltinType::OCLNDRange:
-    ID = PREDEF_TYPE_NDRANGE_ID;
-    break;
   case BuiltinType::OCLReserveID:
     ID = PREDEF_TYPE_RESERVE_ID_ID;
     break;
@@ -254,6 +251,7 @@ bool serialization::isRedeclarableDeclKind(unsigned Kind) {
   case Decl::VarTemplateSpecialization:
   case Decl::VarTemplatePartialSpecialization:
   case Decl::Function:
+  case Decl::CXXDeductionGuide:
   case Decl::CXXMethod:
   case Decl::CXXConstructor:
   case Decl::CXXDestructor:
diff --git a/lib/Serialization/ASTReader.cpp b/lib/Serialization/ASTReader.cpp
index 53224e2b493d4..406c4b50d92bc 100644
--- a/lib/Serialization/ASTReader.cpp
+++ b/lib/Serialization/ASTReader.cpp
@@ -26,6 +26,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/NestedNameSpecifier.h"
+#include "clang/AST/ODRHash.h"
 #include "clang/AST/RawCommentList.h"
 #include "clang/AST/Type.h"
 #include "clang/AST/TypeLocVisitor.h"
@@ -36,6 +37,7 @@
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/FileSystemOptions.h"
 #include "clang/Basic/LangOptions.h"
+#include "clang/Basic/MemoryBufferCache.h"
 #include "clang/Basic/ObjCRuntime.h"
 #include "clang/Basic/OperatorKinds.h"
 #include "clang/Basic/Sanitizers.h"
@@ -72,6 +74,7 @@
 #include "llvm/Bitcode/BitstreamReader.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -461,19 +464,9 @@ static bool checkDiagnosticMappings(DiagnosticsEngine &StoredDiags,
   return checkDiagnosticGroupMappings(StoredDiags, Diags, Complain);
 }
 
-bool PCHValidator::ReadDiagnosticOptions(
-    IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts, bool Complain) {
-  DiagnosticsEngine &ExistingDiags = PP.getDiagnostics();
-  IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(ExistingDiags.getDiagnosticIDs());
-  IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
-      new DiagnosticsEngine(DiagIDs, DiagOpts.get()));
-  // This should never fail, because we would have processed these options
-  // before writing them to an ASTFile.
-  ProcessWarningOptions(*Diags, *DiagOpts, /*Report*/false);
-
-  ModuleManager &ModuleMgr = Reader.getModuleManager();
-  assert(ModuleMgr.size() >= 1 && "what ASTFile is this then");
-
+/// Return the top import module if it is implicit, nullptr otherwise.
+static Module *getTopImportImplicitModule(ModuleManager &ModuleMgr,
+                                          Preprocessor &PP) {
   // If the original import came from a file explicitly generated by the user,
   // don't check the diagnostic mappings.
   // FIXME: currently this is approximated by checking whether this is not a
@@ -481,21 +474,41 @@ bool PCHValidator::ReadDiagnosticOptions(
   // Note: ModuleMgr.rbegin() may not be the current module, but it must be in
   // the transitive closure of its imports, since unrelated modules cannot be
   // imported until after this module finishes validation.
-  ModuleFile *TopImport = *ModuleMgr.rbegin();
+  ModuleFile *TopImport = &*ModuleMgr.rbegin();
   while (!TopImport->ImportedBy.empty())
     TopImport = TopImport->ImportedBy[0];
   if (TopImport->Kind != MK_ImplicitModule)
-    return false;
+    return nullptr;
 
   StringRef ModuleName = TopImport->ModuleName;
   assert(!ModuleName.empty() && "diagnostic options read before module name");
 
   Module *M = PP.getHeaderSearchInfo().lookupModule(ModuleName);
   assert(M && "missing module");
+  return M;
+}
+
+bool PCHValidator::ReadDiagnosticOptions(
+    IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts, bool Complain) {
+  DiagnosticsEngine &ExistingDiags = PP.getDiagnostics();
+  IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(ExistingDiags.getDiagnosticIDs());
+  IntrusiveRefCntPtr<DiagnosticsEngine> Diags(
+      new DiagnosticsEngine(DiagIDs, DiagOpts.get()));
+  // This should never fail, because we would have processed these options
+  // before writing them to an ASTFile.
+  ProcessWarningOptions(*Diags, *DiagOpts, /*Report*/false);
+
+  ModuleManager &ModuleMgr = Reader.getModuleManager();
+  assert(ModuleMgr.size() >= 1 && "what ASTFile is this then");
+
+  Module *TopM = getTopImportImplicitModule(ModuleMgr, PP);
+  if (!TopM)
+    return false;
 
   // FIXME: if the diagnostics are incompatible, save a DiagnosticOptions that
   // contains the union of their flags.
-  return checkDiagnosticMappings(*Diags, ExistingDiags, M->IsSystem, Complain);
+  return checkDiagnosticMappings(*Diags, ExistingDiags, TopM->IsSystem,
+                                 Complain);
 }
 
 /// \brief Collect the macro definitions provided by the given preprocessor
@@ -943,6 +956,10 @@ DeclarationNameKey::DeclarationNameKey(DeclarationName Name)
   case DeclarationName::CXXLiteralOperatorName:
     Data = (uint64_t)Name.getCXXLiteralIdentifier();
     break;
+  case DeclarationName::CXXDeductionGuideName:
+    Data = (uint64_t)Name.getCXXDeductionGuideTemplate()
+               ->getDeclName().getAsIdentifierInfo();
+    break;
   case DeclarationName::CXXConstructorName:
   case DeclarationName::CXXDestructorName:
   case DeclarationName::CXXConversionFunctionName:
@@ -959,6 +976,7 @@ unsigned DeclarationNameKey::getHash() const {
   switch (Kind) {
   case DeclarationName::Identifier:
   case DeclarationName::CXXLiteralOperatorName:
+  case DeclarationName::CXXDeductionGuideName:
     ID.AddString(((IdentifierInfo*)Data)->getName());
     break;
   case DeclarationName::ObjCZeroArgSelector:
@@ -1002,6 +1020,8 @@ ASTDeclContextNameLookupTrait::ReadKey(const unsigned char *d, unsigned) {
   uint64_t Data;
   switch (Kind) {
   case DeclarationName::Identifier:
+  case DeclarationName::CXXLiteralOperatorName:
+  case DeclarationName::CXXDeductionGuideName:
     Data = (uint64_t)Reader.getLocalIdentifier(
         F, endian::readNext<uint32_t, little, unaligned>(d));
     break;
@@ -1016,10 +1036,6 @@ ASTDeclContextNameLookupTrait::ReadKey(const unsigned char *d, unsigned) {
   case DeclarationName::CXXOperatorName:
     Data = *d++; // OverloadedOperatorKind
     break;
-  case DeclarationName::CXXLiteralOperatorName:
-    Data = (uint64_t)Reader.getLocalIdentifier(
-        F, endian::readNext<uint32_t, little, unaligned>(d));
-    break;
   case DeclarationName::CXXConstructorName:
   case DeclarationName::CXXDestructorName:
   case DeclarationName::CXXConversionFunctionName:
@@ -1103,7 +1119,7 @@ bool ASTReader::ReadVisibleDeclContextStorage(ModuleFile &M,
   return false;
 }
 
-void ASTReader::Error(StringRef Msg) {
+void ASTReader::Error(StringRef Msg) const {
   Error(diag::err_fe_pch_malformed, Msg);
   if (Context.getLangOpts().Modules && !Diags.isDiagnosticInFlight() &&
       !PP.getHeaderSearchInfo().getModuleCachePath().empty()) {
@@ -1113,7 +1129,7 @@ void ASTReader::Error(StringRef Msg) {
 }
 
 void ASTReader::Error(unsigned DiagID,
-                      StringRef Arg1, StringRef Arg2) {
+                      StringRef Arg1, StringRef Arg2) const {
   if (Diags.isDiagnosticInFlight())
     Diags.SetDelayedDiagnostic(DiagID, Arg1, Arg2);
   else
@@ -1278,10 +1294,15 @@ bool ASTReader::ReadSLocEntry(int ID) {
     unsigned RecCode = SLocEntryCursor.readRecord(Code, Record, &Blob);
 
     if (RecCode == SM_SLOC_BUFFER_BLOB_COMPRESSED) {
+      if (!llvm::zlib::isAvailable()) {
+        Error("zlib is not available");
+        return nullptr;
+      }
       SmallString<0> Uncompressed;
-      if (llvm::zlib::uncompress(Blob, Uncompressed, Record[0]) !=
-          llvm::zlib::StatusOK) {
-        Error("could not decompress embedded file contents");
+      if (llvm::Error E =
+              llvm::zlib::uncompress(Blob, Uncompressed, Record[0])) {
+        Error("could not decompress embedded file contents: " +
+              llvm::toString(std::move(E)));
         return nullptr;
       }
       return llvm::MemoryBuffer::getMemBufferCopy(Uncompressed, Name);
@@ -1575,7 +1596,11 @@ MacroInfo *ASTReader::ReadMacroRecord(ModuleFile &F, uint64_t Offset) {
 }
 
 PreprocessedEntityID
-ASTReader::getGlobalPreprocessedEntityID(ModuleFile &M, unsigned LocalID) const {
+ASTReader::getGlobalPreprocessedEntityID(ModuleFile &M,
+                                         unsigned LocalID) const {
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::const_iterator
     I = M.PreprocessedEntityRemap.find(LocalID - NUM_PREDEF_PP_ENTITY_IDS);
   assert(I != M.PreprocessedEntityRemap.end()
@@ -1707,15 +1732,15 @@ void ASTReader::ReadDefinedMacros() {
   // Note that we are loading defined macros.
   Deserializing Macros(this);
 
-  for (auto &I : llvm::reverse(ModuleMgr)) {
-    BitstreamCursor &MacroCursor = I->MacroCursor;
+  for (ModuleFile &I : llvm::reverse(ModuleMgr)) {
+    BitstreamCursor &MacroCursor = I.MacroCursor;
 
     // If there was no preprocessor block, skip this file.
     if (MacroCursor.getBitcodeBytes().empty())
       continue;
 
     BitstreamCursor Cursor = MacroCursor;
-    Cursor.JumpToBit(I->MacroStartOffset);
+    Cursor.JumpToBit(I.MacroStartOffset);
 
     RecordData Record;
     while (true) {
@@ -1737,7 +1762,7 @@ void ASTReader::ReadDefinedMacros() {
 
         case PP_MACRO_OBJECT_LIKE:
         case PP_MACRO_FUNCTION_LIKE: {
-          IdentifierInfo *II = getLocalIdentifier(*I, Record[0]);
+          IdentifierInfo *II = getLocalIdentifier(I, Record[0]);
           if (II->isOutOfDate())
             updateOutOfDateIdentifier(*II);
           break;
@@ -2149,7 +2174,7 @@ static bool isDiagnosedResult(ASTReader::ASTReadResult ARR, unsigned Caps) {
 ASTReader::ASTReadResult ASTReader::ReadOptionsBlock(
     BitstreamCursor &Stream, unsigned ClientLoadCapabilities,
     bool AllowCompatibleConfigurationMismatch, ASTReaderListener &Listener,
-    std::string &SuggestedPredefines, bool ValidateDiagnosticOptions) {
+    std::string &SuggestedPredefines) {
   if (Stream.EnterSubBlock(OPTIONS_BLOCK_ID))
     return Failure;
 
@@ -2191,15 +2216,6 @@ ASTReader::ASTReadResult ASTReader::ReadOptionsBlock(
       break;
     }
 
-    case DIAGNOSTIC_OPTIONS: {
-      bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
-      if (ValidateDiagnosticOptions &&
-          !AllowCompatibleConfigurationMismatch &&
-          ParseDiagnosticOptions(Record, Complain, Listener))
-        return OutOfDate;
-      break;
-    }
-
     case FILE_SYSTEM_OPTIONS: {
       bool Complain = (ClientLoadCapabilities & ARR_ConfigurationMismatch) == 0;
       if (!AllowCompatibleConfigurationMismatch &&
@@ -2240,6 +2256,23 @@ ASTReader::ReadControlBlock(ModuleFile &F,
     return Failure;
   }
 
+  // Lambda to read the unhashed control block the first time it's called.
+  //
+  // For PCM files, the unhashed control block cannot be read until after the
+  // MODULE_NAME record.  However, PCH files have no MODULE_NAME, and yet still
+  // need to look ahead before reading the IMPORTS record.  For consistency,
+  // this block is always read somehow (see BitstreamEntry::EndBlock).
+  bool HasReadUnhashedControlBlock = false;
+  auto readUnhashedControlBlockOnce = [&]() {
+    if (!HasReadUnhashedControlBlock) {
+      HasReadUnhashedControlBlock = true;
+      if (ASTReadResult Result =
+              readUnhashedControlBlock(F, ImportedBy, ClientLoadCapabilities))
+        return Result;
+    }
+    return Success;
+  };
+
   // Read all of the records and blocks in the control block.
   RecordData Record;
   unsigned NumInputs = 0;
@@ -2252,6 +2285,11 @@ ASTReader::ReadControlBlock(ModuleFile &F,
       Error("malformed block record in AST file");
       return Failure;
     case llvm::BitstreamEntry::EndBlock: {
+      // Validate the module before returning.  This call catches an AST with
+      // no module name and no imports.
+      if (ASTReadResult Result = readUnhashedControlBlockOnce())
+        return Result;
+
       // Validate input files.
       const HeaderSearchOptions &HSOpts =
           PP.getHeaderSearchInfo().getHeaderSearchOpts();
@@ -2323,13 +2361,10 @@ ASTReader::ReadControlBlock(ModuleFile &F,
           // FIXME: Allow this for files explicitly specified with -include-pch.
           bool AllowCompatibleConfigurationMismatch =
               F.Kind == MK_ExplicitModule || F.Kind == MK_PrebuiltModule;
-          const HeaderSearchOptions &HSOpts =
-              PP.getHeaderSearchInfo().getHeaderSearchOpts();
 
           Result = ReadOptionsBlock(Stream, ClientLoadCapabilities,
                                     AllowCompatibleConfigurationMismatch,
-                                    *Listener, SuggestedPredefines,
-                                    HSOpts.ModulesValidateDiagnosticOptions);
+                                    *Listener, SuggestedPredefines);
           if (Result == Failure) {
             Error("malformed block record in AST file");
             return Result;
@@ -2403,12 +2438,13 @@ ASTReader::ReadControlBlock(ModuleFile &F,
       break;
     }
 
-    case SIGNATURE:
-      assert((!F.Signature || F.Signature == Record[0]) && "signature changed");
-      F.Signature = Record[0];
-      break;
-
     case IMPORTS: {
+      // Validate the AST before processing any imports (otherwise, untangling
+      // them can be error-prone and expensive).  A module will have a name and
+      // will already have been validated, but this catches the PCH case.
+      if (ASTReadResult Result = readUnhashedControlBlockOnce())
+        return Result;
+
       // Load each of the imported PCH files.
       unsigned Idx = 0, N = Record.size();
       while (Idx < N) {
@@ -2421,7 +2457,10 @@ ASTReader::ReadControlBlock(ModuleFile &F,
             ReadUntranslatedSourceLocation(Record[Idx++]);
         off_t StoredSize = (off_t)Record[Idx++];
         time_t StoredModTime = (time_t)Record[Idx++];
-        ASTFileSignature StoredSignature = Record[Idx++];
+        ASTFileSignature StoredSignature = {
+            {{(uint32_t)Record[Idx++], (uint32_t)Record[Idx++],
+              (uint32_t)Record[Idx++], (uint32_t)Record[Idx++],
+              (uint32_t)Record[Idx++]}}};
         auto ImportedFile = ReadPath(F, Record, Idx);
 
         // If our client can't cope with us being out of date, we can't cope with
@@ -2473,6 +2512,12 @@ ASTReader::ReadControlBlock(ModuleFile &F,
       F.ModuleName = Blob;
       if (Listener)
         Listener->ReadModuleName(F.ModuleName);
+
+      // Validate the AST as soon as we have a name so we can exit early on
+      // failure.
+      if (ASTReadResult Result = readUnhashedControlBlockOnce())
+        return Result;
+
       break;
 
     case MODULE_DIRECTORY: {
@@ -2513,6 +2558,7 @@ ASTReader::ReadControlBlock(ModuleFile &F,
       F.InputFileOffsets =
           (const llvm::support::unaligned_uint64_t *)Blob.data();
       F.InputFilesLoaded.resize(NumInputs);
+      F.NumUserInputFiles = NumUserInputs;
       break;
     }
   }
@@ -2601,7 +2647,8 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         break;
 
       case SUBMODULE_BLOCK_ID:
-        if (ASTReadResult Result = ReadSubmoduleBlock(F, ClientLoadCapabilities))
+        if (ASTReadResult Result =
+                ReadSubmoduleBlock(F, ClientLoadCapabilities))
           return Result;
         break;
 
@@ -2766,6 +2813,14 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         EagerlyDeserializedDecls.push_back(getGlobalDeclID(F, Record[I]));
       break;
 
+    case MODULAR_CODEGEN_DECLS:
+      // FIXME: Skip reading this record if our ASTConsumer doesn't care about
+      // them (ie: if we're not codegenerating this module).
+      if (F.Kind == MK_MainFile)
+        for (unsigned I = 0, N = Record.size(); I != N; ++I)
+          EagerlyDeserializedDecls.push_back(getGlobalDeclID(F, Record[I]));
+      break;
+
     case SPECIAL_TYPES:
       if (SpecialTypes.empty()) {
         for (unsigned I = 0, N = Record.size(); I != N; ++I)
@@ -2916,80 +2971,9 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       break;
     }
 
-    case MODULE_OFFSET_MAP: {
-      // Additional remapping information.
-      const unsigned char *Data = (const unsigned char*)Blob.data();
-      const unsigned char *DataEnd = Data + Blob.size();
-
-      // If we see this entry before SOURCE_LOCATION_OFFSETS, add placeholders.
-      if (F.SLocRemap.find(0) == F.SLocRemap.end()) {
-        F.SLocRemap.insert(std::make_pair(0U, 0));
-        F.SLocRemap.insert(std::make_pair(2U, 1));
-      }
-
-      // Continuous range maps we may be updating in our module.
-      typedef ContinuousRangeMap<uint32_t, int, 2>::Builder
-          RemapBuilder;
-      RemapBuilder SLocRemap(F.SLocRemap);
-      RemapBuilder IdentifierRemap(F.IdentifierRemap);
-      RemapBuilder MacroRemap(F.MacroRemap);
-      RemapBuilder PreprocessedEntityRemap(F.PreprocessedEntityRemap);
-      RemapBuilder SubmoduleRemap(F.SubmoduleRemap);
-      RemapBuilder SelectorRemap(F.SelectorRemap);
-      RemapBuilder DeclRemap(F.DeclRemap);
-      RemapBuilder TypeRemap(F.TypeRemap);
-
-      while (Data < DataEnd) {
-        using namespace llvm::support;
-        uint16_t Len = endian::readNext<uint16_t, little, unaligned>(Data);
-        StringRef Name = StringRef((const char*)Data, Len);
-        Data += Len;
-        ModuleFile *OM = ModuleMgr.lookup(Name);
-        if (!OM) {
-          Error("SourceLocation remap refers to unknown module");
-          return Failure;
-        }
-
-        uint32_t SLocOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t IdentifierIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t MacroIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t PreprocessedEntityIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t SubmoduleIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t SelectorIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t DeclIDOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-        uint32_t TypeIndexOffset =
-            endian::readNext<uint32_t, little, unaligned>(Data);
-
-        uint32_t None = std::numeric_limits<uint32_t>::max();
-
-        auto mapOffset = [&](uint32_t Offset, uint32_t BaseOffset,
-                             RemapBuilder &Remap) {
-          if (Offset != None)
-            Remap.insert(std::make_pair(Offset,
-                                        static_cast<int>(BaseOffset - Offset)));
-        };
-        mapOffset(SLocOffset, OM->SLocEntryBaseOffset, SLocRemap);
-        mapOffset(IdentifierIDOffset, OM->BaseIdentifierID, IdentifierRemap);
-        mapOffset(MacroIDOffset, OM->BaseMacroID, MacroRemap);
-        mapOffset(PreprocessedEntityIDOffset, OM->BasePreprocessedEntityID,
-                  PreprocessedEntityRemap);
-        mapOffset(SubmoduleIDOffset, OM->BaseSubmoduleID, SubmoduleRemap);
-        mapOffset(SelectorIDOffset, OM->BaseSelectorID, SelectorRemap);
-        mapOffset(DeclIDOffset, OM->BaseDeclID, DeclRemap);
-        mapOffset(TypeIndexOffset, OM->BaseTypeIndex, TypeRemap);
-
-        // Global -> local mappings.
-        F.GlobalToLocalDeclIDs[OM] = DeclIDOffset;
-      }
+    case MODULE_OFFSET_MAP:
+      F.ModuleOffsetMap = Blob;
       break;
-    }
 
     case SOURCE_MANAGER_LINE_TABLE:
       if (ParseLineTable(F, Record))
@@ -3123,14 +3107,6 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       F.ObjCCategories.swap(Record);
       break;
 
-    case DIAG_PRAGMA_MAPPINGS:
-      if (F.PragmaDiagMappings.empty())
-        F.PragmaDiagMappings.swap(Record);
-      else
-        F.PragmaDiagMappings.insert(F.PragmaDiagMappings.end(),
-                                    Record.begin(), Record.end());
-      break;
-
     case CUDA_SPECIAL_DECL_REFS:
       // Later tables overwrite earlier ones.
       // FIXME: Modules will have trouble with this.
@@ -3245,8 +3221,11 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         for (unsigned I = 0, N = Record.size(); I != N; /**/) {
           unsigned GlobalID = getGlobalSubmoduleID(F, Record[I++]);
           SourceLocation Loc = ReadSourceLocation(F, Record, I);
-          if (GlobalID)
+          if (GlobalID) {
             ImportedModules.push_back(ImportedSubmodule(GlobalID, Loc));
+            if (DeserializationListener)
+              DeserializationListener->ModuleImportRead(GlobalID, Loc);
+          }
         }
       }
       break;
@@ -3319,10 +3298,113 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
       }
       ForceCUDAHostDeviceDepth = Record[0];
       break;
+
+    case PACK_PRAGMA_OPTIONS: {
+      if (Record.size() < 3) {
+        Error("invalid pragma pack record");
+        return Failure;
+      }
+      PragmaPackCurrentValue = Record[0];
+      PragmaPackCurrentLocation = ReadSourceLocation(F, Record[1]);
+      unsigned NumStackEntries = Record[2];
+      unsigned Idx = 3;
+      // Reset the stack when importing a new module.
+      PragmaPackStack.clear();
+      for (unsigned I = 0; I < NumStackEntries; ++I) {
+        PragmaPackStackEntry Entry;
+        Entry.Value = Record[Idx++];
+        Entry.Location = ReadSourceLocation(F, Record[Idx++]);
+        PragmaPackStrings.push_back(ReadString(Record, Idx));
+        Entry.SlotLabel = PragmaPackStrings.back();
+        PragmaPackStack.push_back(Entry);
+      }
+      break;
+    }
     }
   }
 }
 
+void ASTReader::ReadModuleOffsetMap(ModuleFile &F) const {
+  assert(!F.ModuleOffsetMap.empty() && "no module offset map to read");
+
+  // Additional remapping information.
+  const unsigned char *Data = (const unsigned char*)F.ModuleOffsetMap.data();
+  const unsigned char *DataEnd = Data + F.ModuleOffsetMap.size();
+  F.ModuleOffsetMap = StringRef();
+
+  // If we see this entry before SOURCE_LOCATION_OFFSETS, add placeholders.
+  if (F.SLocRemap.find(0) == F.SLocRemap.end()) {
+    F.SLocRemap.insert(std::make_pair(0U, 0));
+    F.SLocRemap.insert(std::make_pair(2U, 1));
+  }
+
+  // Continuous range maps we may be updating in our module.
+  typedef ContinuousRangeMap<uint32_t, int, 2>::Builder
+      RemapBuilder;
+  RemapBuilder SLocRemap(F.SLocRemap);
+  RemapBuilder IdentifierRemap(F.IdentifierRemap);
+  RemapBuilder MacroRemap(F.MacroRemap);
+  RemapBuilder PreprocessedEntityRemap(F.PreprocessedEntityRemap);
+  RemapBuilder SubmoduleRemap(F.SubmoduleRemap);
+  RemapBuilder SelectorRemap(F.SelectorRemap);
+  RemapBuilder DeclRemap(F.DeclRemap);
+  RemapBuilder TypeRemap(F.TypeRemap);
+
+  while (Data < DataEnd) {
+    // FIXME: Looking up dependency modules by filename is horrible.
+    using namespace llvm::support;
+    uint16_t Len = endian::readNext<uint16_t, little, unaligned>(Data);
+    StringRef Name = StringRef((const char*)Data, Len);
+    Data += Len;
+    ModuleFile *OM = ModuleMgr.lookup(Name);
+    if (!OM) {
+      std::string Msg =
+          "SourceLocation remap refers to unknown module, cannot find ";
+      Msg.append(Name);
+      Error(Msg);
+      return;
+    }
+
+    uint32_t SLocOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t IdentifierIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t MacroIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t PreprocessedEntityIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t SubmoduleIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t SelectorIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t DeclIDOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+    uint32_t TypeIndexOffset =
+        endian::readNext<uint32_t, little, unaligned>(Data);
+
+    uint32_t None = std::numeric_limits<uint32_t>::max();
+
+    auto mapOffset = [&](uint32_t Offset, uint32_t BaseOffset,
+                         RemapBuilder &Remap) {
+      if (Offset != None)
+        Remap.insert(std::make_pair(Offset,
+                                    static_cast<int>(BaseOffset - Offset)));
+    };
+    mapOffset(SLocOffset, OM->SLocEntryBaseOffset, SLocRemap);
+    mapOffset(IdentifierIDOffset, OM->BaseIdentifierID, IdentifierRemap);
+    mapOffset(MacroIDOffset, OM->BaseMacroID, MacroRemap);
+    mapOffset(PreprocessedEntityIDOffset, OM->BasePreprocessedEntityID,
+              PreprocessedEntityRemap);
+    mapOffset(SubmoduleIDOffset, OM->BaseSubmoduleID, SubmoduleRemap);
+    mapOffset(SelectorIDOffset, OM->BaseSelectorID, SelectorRemap);
+    mapOffset(DeclIDOffset, OM->BaseDeclID, DeclRemap);
+    mapOffset(TypeIndexOffset, OM->BaseTypeIndex, TypeRemap);
+
+    // Global -> local mappings.
+    F.GlobalToLocalDeclIDs[OM] = DeclIDOffset;
+  }
+}
+
 ASTReader::ASTReadResult
 ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
                                   const ModuleFile *ImportedBy,
@@ -3342,8 +3424,7 @@ ASTReader::ReadModuleMapFileBlock(RecordData &Record, ModuleFile &F,
   // usable header search context.
   assert(!F.ModuleName.empty() &&
          "MODULE_NAME should come before MODULE_MAP_FILE");
-  if (F.Kind == MK_ImplicitModule &&
-      (*ModuleMgr.begin())->Kind != MK_MainFile) {
+  if (F.Kind == MK_ImplicitModule && ModuleMgr.begin()->Kind != MK_MainFile) {
     // An implicitly-loaded module file should have its module listed in some
     // module map file that we've already loaded.
     Module *M = PP.getHeaderSearchInfo().lookupModule(F.ModuleName);
@@ -3621,10 +3702,10 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
 
   unsigned NumModules = ModuleMgr.size();
   SmallVector<ImportedModule, 4> Loaded;
-  switch(ASTReadResult ReadResult = ReadASTCore(FileName, Type, ImportLoc,
-                                                /*ImportedBy=*/nullptr, Loaded,
-                                                0, 0, 0,
-                                                ClientLoadCapabilities)) {
+  switch (ASTReadResult ReadResult =
+              ReadASTCore(FileName, Type, ImportLoc,
+                          /*ImportedBy=*/nullptr, Loaded, 0, 0,
+                          ASTFileSignature(), ClientLoadCapabilities)) {
   case Failure:
   case Missing:
   case OutOfDate:
@@ -3635,11 +3716,10 @@ ASTReader::ASTReadResult ASTReader::ReadAST(StringRef FileName,
     for (const ImportedModule &IM : Loaded)
       LoadedSet.insert(IM.Mod);
 
-    ModuleMgr.removeModules(ModuleMgr.begin() + NumModules, ModuleMgr.end(),
-                            LoadedSet,
+    ModuleMgr.removeModules(ModuleMgr.begin() + NumModules, LoadedSet,
                             Context.getLangOpts().Modules
-                              ? &PP.getHeaderSearchInfo().getModuleMap()
-                              : nullptr);
+                                ? &PP.getHeaderSearchInfo().getModuleMap()
+                                : nullptr);
 
     // If we find that any modules are unusable, the global index is going
     // to be out-of-date. Just remove it.
@@ -3986,6 +4066,12 @@ ASTReader::ReadASTCore(StringRef FileName,
       Loaded.push_back(ImportedModule(M, ImportedBy, ImportLoc));
       return Success;
 
+    case UNHASHED_CONTROL_BLOCK_ID:
+      // This block is handled using look-ahead during ReadControlBlock.  We
+      // shouldn't get here!
+      Error("malformed block record in AST file");
+      return Failure;
+
     default:
       if (Stream.SkipBlock()) {
         Error("malformed block record in AST file");
@@ -3998,6 +4084,122 @@ ASTReader::ReadASTCore(StringRef FileName,
   return Success;
 }
 
+ASTReader::ASTReadResult
+ASTReader::readUnhashedControlBlock(ModuleFile &F, bool WasImportedBy,
+                                    unsigned ClientLoadCapabilities) {
+  const HeaderSearchOptions &HSOpts =
+      PP.getHeaderSearchInfo().getHeaderSearchOpts();
+  bool AllowCompatibleConfigurationMismatch =
+      F.Kind == MK_ExplicitModule || F.Kind == MK_PrebuiltModule;
+
+  ASTReadResult Result = readUnhashedControlBlockImpl(
+      &F, F.Data, ClientLoadCapabilities, AllowCompatibleConfigurationMismatch,
+      Listener.get(),
+      WasImportedBy ? false : HSOpts.ModulesValidateDiagnosticOptions);
+
+  // If F was directly imported by another module, it's implicitly validated by
+  // the importing module.
+  if (DisableValidation || WasImportedBy ||
+      (AllowConfigurationMismatch && Result == ConfigurationMismatch))
+    return Success;
+
+  if (Result == Failure) {
+    Error("malformed block record in AST file");
+    return Failure;
+  }
+
+  if (Result == OutOfDate && F.Kind == MK_ImplicitModule) {
+    // If this module has already been finalized in the PCMCache, we're stuck
+    // with it; we can only load a single version of each module.
+    //
+    // This can happen when a module is imported in two contexts: in one, as a
+    // user module; in another, as a system module (due to an import from
+    // another module marked with the [system] flag).  It usually indicates a
+    // bug in the module map: this module should also be marked with [system].
+    //
+    // If -Wno-system-headers (the default), and the first import is as a
+    // system module, then validation will fail during the as-user import,
+    // since -Werror flags won't have been validated.  However, it's reasonable
+    // to treat this consistently as a system module.
+    //
+    // If -Wsystem-headers, the PCM on disk was built with
+    // -Wno-system-headers, and the first import is as a user module, then
+    // validation will fail during the as-system import since the PCM on disk
+    // doesn't guarantee that -Werror was respected.  However, the -Werror
+    // flags were checked during the initial as-user import.
+    if (PCMCache.isBufferFinal(F.FileName)) {
+      Diag(diag::warn_module_system_bit_conflict) << F.FileName;
+      return Success;
+    }
+  }
+
+  return Result;
+}
+
+ASTReader::ASTReadResult ASTReader::readUnhashedControlBlockImpl(
+    ModuleFile *F, llvm::StringRef StreamData, unsigned ClientLoadCapabilities,
+    bool AllowCompatibleConfigurationMismatch, ASTReaderListener *Listener,
+    bool ValidateDiagnosticOptions) {
+  // Initialize a stream.
+  BitstreamCursor Stream(StreamData);
+
+  // Sniff for the signature.
+  if (!startsWithASTFileMagic(Stream))
+    return Failure;
+
+  // Scan for the UNHASHED_CONTROL_BLOCK_ID block.
+  if (SkipCursorToBlock(Stream, UNHASHED_CONTROL_BLOCK_ID))
+    return Failure;
+
+  // Read all of the records in the options block.
+  RecordData Record;
+  ASTReadResult Result = Success;
+  while (1) {
+    llvm::BitstreamEntry Entry = Stream.advance();
+
+    switch (Entry.Kind) {
+    case llvm::BitstreamEntry::Error:
+    case llvm::BitstreamEntry::SubBlock:
+      return Failure;
+
+    case llvm::BitstreamEntry::EndBlock:
+      return Result;
+
+    case llvm::BitstreamEntry::Record:
+      // The interesting case.
+      break;
+    }
+
+    // Read and process a record.
+    Record.clear();
+    switch (
+        (UnhashedControlBlockRecordTypes)Stream.readRecord(Entry.ID, Record)) {
+    case SIGNATURE: {
+      if (F)
+        std::copy(Record.begin(), Record.end(), F->Signature.data());
+      break;
+    }
+    case DIAGNOSTIC_OPTIONS: {
+      bool Complain = (ClientLoadCapabilities & ARR_OutOfDate) == 0;
+      if (Listener && ValidateDiagnosticOptions &&
+          !AllowCompatibleConfigurationMismatch &&
+          ParseDiagnosticOptions(Record, Complain, *Listener))
+        Result = OutOfDate; // Don't return early.  Read the signature.
+      break;
+    }
+    case DIAG_PRAGMA_MAPPINGS:
+      if (!F)
+        break;
+      if (F->PragmaDiagMappings.empty())
+        F->PragmaDiagMappings.swap(Record);
+      else
+        F->PragmaDiagMappings.insert(F->PragmaDiagMappings.end(),
+                                     Record.begin(), Record.end());
+      break;
+    }
+  }
+}
+
 /// Parse a record and blob containing module file extension metadata.
 static bool parseModuleFileExtensionMetadata(
               const SmallVectorImpl<uint64_t> &Record,
@@ -4214,23 +4416,24 @@ void ASTReader::finalizeForWriting() {
 static ASTFileSignature readASTFileSignature(StringRef PCH) {
   BitstreamCursor Stream(PCH);
   if (!startsWithASTFileMagic(Stream))
-    return 0;
+    return ASTFileSignature();
 
-  // Scan for the CONTROL_BLOCK_ID block.
-  if (SkipCursorToBlock(Stream, CONTROL_BLOCK_ID))
-    return 0;
+  // Scan for the UNHASHED_CONTROL_BLOCK_ID block.
+  if (SkipCursorToBlock(Stream, UNHASHED_CONTROL_BLOCK_ID))
+    return ASTFileSignature();
 
-  // Scan for SIGNATURE inside the control block.
+  // Scan for SIGNATURE inside the diagnostic options block.
   ASTReader::RecordData Record;
   while (true) {
     llvm::BitstreamEntry Entry = Stream.advanceSkippingSubblocks();
     if (Entry.Kind != llvm::BitstreamEntry::Record)
-      return 0;
+      return ASTFileSignature();
 
     Record.clear();
     StringRef Blob;
     if (SIGNATURE == Stream.readRecord(Entry.ID, Record, &Blob))
-      return Record[0];
+      return {{{(uint32_t)Record[0], (uint32_t)Record[1], (uint32_t)Record[2],
+                (uint32_t)Record[3], (uint32_t)Record[4]}}};
   }
 }
 
@@ -4349,7 +4552,8 @@ bool ASTReader::readASTFileControlBlock(
   }
 
   // Initialize the stream
-  BitstreamCursor Stream(PCHContainerRdr.ExtractPCH(**Buffer));
+  StringRef Bytes = PCHContainerRdr.ExtractPCH(**Buffer);
+  BitstreamCursor Stream(Bytes);
 
   // Sniff for the signature.
   if (!startsWithASTFileMagic(Stream))
@@ -4377,8 +4581,7 @@ bool ASTReader::readASTFileControlBlock(
         std::string IgnoredSuggestedPredefines;
         if (ReadOptionsBlock(Stream, ARR_ConfigurationMismatch | ARR_OutOfDate,
                              /*AllowCompatibleConfigurationMismatch*/ false,
-                             Listener, IgnoredSuggestedPredefines,
-                             ValidateDiagnosticOptions) != Success)
+                             Listener, IgnoredSuggestedPredefines) != Success)
           return true;
         break;
       }
@@ -4499,6 +4702,7 @@ bool ASTReader::readASTFileControlBlock(
 
   // Look for module file extension blocks, if requested.
   if (FindModuleFileExtensions) {
+    BitstreamCursor SavedStream = Stream;
     while (!SkipCursorToBlock(Stream, EXTENSION_BLOCK_ID)) {
       bool DoneWithExtensionBlock = false;
       while (!DoneWithExtensionBlock) {
@@ -4537,16 +4741,25 @@ bool ASTReader::readASTFileControlBlock(
        }
       }
     }
+    Stream = SavedStream;
   }
 
+  // Scan for the UNHASHED_CONTROL_BLOCK_ID block.
+  if (readUnhashedControlBlockImpl(
+          nullptr, Bytes, ARR_ConfigurationMismatch | ARR_OutOfDate,
+          /*AllowCompatibleConfigurationMismatch*/ false, &Listener,
+          ValidateDiagnosticOptions) != Success)
+    return true;
+
   return false;
 }
 
-bool ASTReader::isAcceptableASTFile(
-    StringRef Filename, FileManager &FileMgr,
-    const PCHContainerReader &PCHContainerRdr, const LangOptions &LangOpts,
-    const TargetOptions &TargetOpts, const PreprocessorOptions &PPOpts,
-    std::string ExistingModuleCachePath) {
+bool ASTReader::isAcceptableASTFile(StringRef Filename, FileManager &FileMgr,
+                                    const PCHContainerReader &PCHContainerRdr,
+                                    const LangOptions &LangOpts,
+                                    const TargetOptions &TargetOpts,
+                                    const PreprocessorOptions &PPOpts,
+                                    StringRef ExistingModuleCachePath) {
   SimplePCHValidator validator(LangOpts, TargetOpts, PPOpts,
                                ExistingModuleCachePath, FileMgr);
   return !readASTFileControlBlock(Filename, FileMgr, PCHContainerRdr,
@@ -4628,8 +4841,9 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
 
       // Retrieve this (sub)module from the module map, creating it if
       // necessary.
-      CurrentModule = ModMap.findOrCreateModule(Name, ParentModule, IsFramework,
-                                                IsExplicit).first;
+      CurrentModule =
+          ModMap.findOrCreateModule(Name, ParentModule, IsFramework, IsExplicit)
+              .first;
 
       // FIXME: set the definition loc for CurrentModule, or call
       // ModMap.setInferredModuleAllowedBy()
@@ -4696,13 +4910,9 @@ ASTReader::ReadSubmoduleBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         if (!CurrentModule->getUmbrellaHeader())
           ModMap.setUmbrellaHeader(CurrentModule, Umbrella, Blob);
         else if (CurrentModule->getUmbrellaHeader().Entry != Umbrella) {
-          // This can be a spurious difference caused by changing the VFS to
-          // point to a different copy of the file, and it is too late to
-          // to rebuild safely.
-          // FIXME: If we wrote the virtual paths instead of the 'real' paths,
-          // after input file validation only real problems would remain and we
-          // could just error. For now, assume it's okay.
-          break;
+          if ((ClientLoadCapabilities & ARR_OutOfDate) == 0)
+            Error("mismatched umbrella headers in submodule");
+          return OutOfDate;
         }
       }
       break;
@@ -5288,48 +5498,128 @@ HeaderFileInfo ASTReader::GetHeaderFileInfo(const FileEntry *FE) {
 }
 
 void ASTReader::ReadPragmaDiagnosticMappings(DiagnosticsEngine &Diag) {
-  // FIXME: Make it work properly with modules.
-  SmallVector<DiagnosticsEngine::DiagState *, 32> DiagStates;
-  for (ModuleIterator I = ModuleMgr.begin(), E = ModuleMgr.end(); I != E; ++I) {
-    ModuleFile &F = *(*I);
+  using DiagState = DiagnosticsEngine::DiagState;
+  SmallVector<DiagState *, 32> DiagStates;
+
+  for (ModuleFile &F : ModuleMgr) {
     unsigned Idx = 0;
+    auto &Record = F.PragmaDiagMappings;
+    if (Record.empty())
+      continue;
+
     DiagStates.clear();
-    assert(!Diag.DiagStates.empty());
-    DiagStates.push_back(&Diag.DiagStates.front()); // the command-line one.
-    while (Idx < F.PragmaDiagMappings.size()) {
-      SourceLocation Loc = ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
-      unsigned DiagStateID = F.PragmaDiagMappings[Idx++];
-      if (DiagStateID != 0) {
-        Diag.DiagStatePoints.push_back(
-                    DiagnosticsEngine::DiagStatePoint(DiagStates[DiagStateID-1],
-                    FullSourceLoc(Loc, SourceMgr)));
-        continue;
-      }
 
-      assert(DiagStateID == 0);
+    auto ReadDiagState =
+        [&](const DiagState &BasedOn, SourceLocation Loc,
+            bool IncludeNonPragmaStates) -> DiagnosticsEngine::DiagState * {
+      unsigned BackrefID = Record[Idx++];
+      if (BackrefID != 0)
+        return DiagStates[BackrefID - 1];
+
       // A new DiagState was created here.
-      Diag.DiagStates.push_back(*Diag.GetCurDiagState());
-      DiagnosticsEngine::DiagState *NewState = &Diag.DiagStates.back();
+      Diag.DiagStates.push_back(BasedOn);
+      DiagState *NewState = &Diag.DiagStates.back();
       DiagStates.push_back(NewState);
-      Diag.DiagStatePoints.push_back(
-          DiagnosticsEngine::DiagStatePoint(NewState,
-                                            FullSourceLoc(Loc, SourceMgr)));
-      while (true) {
-        assert(Idx < F.PragmaDiagMappings.size() &&
-               "Invalid data, didn't find '-1' marking end of diag/map pairs");
-        if (Idx >= F.PragmaDiagMappings.size()) {
-          break; // Something is messed up but at least avoid infinite loop in
-                 // release build.
-        }
-        unsigned DiagID = F.PragmaDiagMappings[Idx++];
-        if (DiagID == (unsigned)-1) {
-          break; // no more diag/map pairs for this location.
+      unsigned Size = Record[Idx++];
+      assert(Idx + Size * 2 <= Record.size() &&
+             "Invalid data, not enough diag/map pairs");
+      while (Size--) {
+        unsigned DiagID = Record[Idx++];
+        unsigned SeverityAndUpgradedFromWarning = Record[Idx++];
+        bool WasUpgradedFromWarning =
+            DiagnosticMapping::deserializeUpgradedFromWarning(
+                SeverityAndUpgradedFromWarning);
+        DiagnosticMapping NewMapping =
+            Diag.makeUserMapping(DiagnosticMapping::deserializeSeverity(
+                                     SeverityAndUpgradedFromWarning),
+                                 Loc);
+        if (!NewMapping.isPragma() && !IncludeNonPragmaStates)
+          continue;
+
+        DiagnosticMapping &Mapping = NewState->getOrAddMapping(DiagID);
+
+        // If this mapping was specified as a warning but the severity was
+        // upgraded due to diagnostic settings, simulate the current diagnostic
+        // settings (and use a warning).
+        if (WasUpgradedFromWarning && !Mapping.isErrorOrFatal()) {
+          Mapping = Diag.makeUserMapping(diag::Severity::Warning, Loc);
+          continue;
         }
-        diag::Severity Map = (diag::Severity)F.PragmaDiagMappings[Idx++];
-        DiagnosticMapping Mapping = Diag.makeUserMapping(Map, Loc);
-        Diag.GetCurDiagState()->setMapping(DiagID, Mapping);
+
+        // Use the deserialized mapping verbatim.
+        Mapping = NewMapping;
+        Mapping.setUpgradedFromWarning(WasUpgradedFromWarning);
+      }
+      return NewState;
+    };
+
+    // Read the first state.
+    DiagState *FirstState;
+    if (F.Kind == MK_ImplicitModule) {
+      // Implicitly-built modules are reused with different diagnostic
+      // settings.  Use the initial diagnostic state from Diag to simulate this
+      // compilation's diagnostic settings.
+      FirstState = Diag.DiagStatesByLoc.FirstDiagState;
+      DiagStates.push_back(FirstState);
+
+      // Skip the initial diagnostic state from the serialized module.
+      assert(Record[0] == 0 &&
+             "Invalid data, unexpected backref in initial state");
+      Idx = 2 + Record[1] * 2;
+      assert(Idx < Record.size() &&
+             "Invalid data, not enough state change pairs in initial state");
+    } else {
+      FirstState = ReadDiagState(
+          F.isModule() ? DiagState() : *Diag.DiagStatesByLoc.CurDiagState,
+          SourceLocation(), F.isModule());
+    }
+
+    // Read the state transitions.
+    unsigned NumLocations = Record[Idx++];
+    while (NumLocations--) {
+      assert(Idx < Record.size() &&
+             "Invalid data, missing pragma diagnostic states");
+      SourceLocation Loc = ReadSourceLocation(F, Record[Idx++]);
+      auto IDAndOffset = SourceMgr.getDecomposedLoc(Loc);
+      assert(IDAndOffset.second == 0 && "not a start location for a FileID");
+      unsigned Transitions = Record[Idx++];
+
+      // Note that we don't need to set up Parent/ParentOffset here, because
+      // we won't be changing the diagnostic state within imported FileIDs
+      // (other than perhaps appending to the main source file, which has no
+      // parent).
+      auto &F = Diag.DiagStatesByLoc.Files[IDAndOffset.first];
+      F.StateTransitions.reserve(F.StateTransitions.size() + Transitions);
+      for (unsigned I = 0; I != Transitions; ++I) {
+        unsigned Offset = Record[Idx++];
+        auto *State =
+            ReadDiagState(*FirstState, Loc.getLocWithOffset(Offset), false);
+        F.StateTransitions.push_back({State, Offset});
       }
     }
+
+    // Read the final state.
+    assert(Idx < Record.size() &&
+           "Invalid data, missing final pragma diagnostic state");
+    SourceLocation CurStateLoc =
+        ReadSourceLocation(F, F.PragmaDiagMappings[Idx++]);
+    auto *CurState = ReadDiagState(*FirstState, CurStateLoc, false);
+
+    if (!F.isModule()) {
+      Diag.DiagStatesByLoc.CurDiagState = CurState;
+      Diag.DiagStatesByLoc.CurDiagStateLoc = CurStateLoc;
+
+      // Preserve the property that the imaginary root file describes the
+      // current state.
+      auto &T = Diag.DiagStatesByLoc.Files[FileID()].StateTransitions;
+      if (T.empty())
+        T.push_back({CurState, 0});
+      else
+        T[0].State = CurState;
+    }
+
+    // Don't try to read these mappings again.
+    Record.clear();
   }
 }
 
@@ -5606,6 +5896,14 @@ QualType ASTReader::readTypeRecord(unsigned Index) {
     return Context.getAutoType(Deduced, Keyword, IsDependent);
   }
 
+  case TYPE_DEDUCED_TEMPLATE_SPECIALIZATION: {
+    TemplateName Name = ReadTemplateName(*Loc.F, Record, Idx);
+    QualType Deduced = readType(*Loc.F, Record, Idx);
+    bool IsDependent = Deduced.isNull() ? Record[Idx++] : false;
+    return Context.getDeducedTemplateSpecializationType(Name, Deduced,
+                                                        IsDependent);
+  }
+
   case TYPE_RECORD: {
     if (Record.size() != 2) {
       Error("incorrect encoding of record type");
@@ -5840,6 +6138,17 @@ QualType ASTReader::readTypeRecord(unsigned Index) {
     return Context.getPipeType(ElementType, ReadOnly);
   }
 
+  case TYPE_DEPENDENT_SIZED_EXT_VECTOR: {
+    unsigned Idx = 0;
+
+    // DependentSizedExtVectorType
+    QualType ElementType = readType(*Loc.F, Record, Idx);
+    Expr *SizeExpr = ReadExpr(*Loc.F);
+    SourceLocation AttrLoc = ReadSourceLocation(*Loc.F, Record, Idx);
+
+    return Context.getDependentSizedExtVectorType(ElementType, SizeExpr,
+                                                  AttrLoc);
+  }
   }
   llvm_unreachable("Invalid TypeCode!");
 }
@@ -6037,6 +6346,11 @@ void TypeLocReader::VisitAutoTypeLoc(AutoTypeLoc TL) {
   TL.setNameLoc(ReadSourceLocation());
 }
 
+void TypeLocReader::VisitDeducedTemplateSpecializationTypeLoc(
+    DeducedTemplateSpecializationTypeLoc TL) {
+  TL.setTemplateNameLoc(ReadSourceLocation());
+}
+
 void TypeLocReader::VisitRecordTypeLoc(RecordTypeLoc TL) {
   TL.setNameLoc(ReadSourceLocation());
 }
@@ -6304,9 +6618,6 @@ QualType ASTReader::GetType(TypeID ID) {
     case PREDEF_TYPE_QUEUE_ID:
       T = Context.OCLQueueTy;
       break;
-    case PREDEF_TYPE_NDRANGE_ID:
-      T = Context.OCLNDRangeTy;
-      break;
     case PREDEF_TYPE_RESERVE_ID_ID:
       T = Context.OCLReserveIDTy;
       break;
@@ -6363,6 +6674,9 @@ ASTReader::getGlobalTypeID(ModuleFile &F, unsigned LocalID) const {
   if (LocalIndex < NUM_PREDEF_TYPE_IDS)
     return LocalID;
 
+  if (!F.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(F);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = F.TypeRemap.find(LocalIndex - NUM_PREDEF_TYPE_IDS);
   assert(I != F.TypeRemap.end() && "Invalid index into type index remap");
@@ -6437,12 +6751,6 @@ Decl *ASTReader::GetExternalDecl(uint32_t ID) {
   return GetDecl(ID);
 }
 
-template<typename TemplateSpecializationDecl>
-static void completeRedeclChainForTemplateSpecialization(Decl *D) {
-  if (auto *TSD = dyn_cast<TemplateSpecializationDecl>(D))
-    TSD->getSpecializedTemplate()->LoadLazySpecializations();
-}
-
 void ASTReader::CompleteRedeclChain(const Decl *D) {
   if (NumCurrentElementsDeserializing) {
     // We arrange to not care about the complete redeclaration chain while we're
@@ -6543,6 +6851,9 @@ ASTReader::getGlobalDeclID(ModuleFile &F, LocalDeclID LocalID) const {
   if (LocalID < NUM_PREDEF_DECL_IDS)
     return LocalID;
 
+  if (!F.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(F);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = F.DeclRemap.find(LocalID - NUM_PREDEF_DECL_IDS);
   assert(I != F.DeclRemap.end() && "Invalid index into decl index remap");
@@ -6728,6 +7039,9 @@ Stmt *ASTReader::GetExternalDeclStmt(uint64_t Offset) {
   // Offset here is a global offset across the entire chain.
   RecordLocation Loc = getLocalBitOffset(Offset);
   Loc.F->DeclsCursor.JumpToBit(Loc.Offset);
+  assert(NumCurrentElementsDeserializing == 0 &&
+         "should not be called while already deserializing");
+  Deserializing D(this);
   return ReadStmtFromStream(*Loc.F);
 }
 
@@ -6920,31 +7234,6 @@ static void PassObjCImplDeclToConsumer(ObjCImplDecl *ImplD,
   Consumer->HandleInterestingDecl(DeclGroupRef(ImplD));
 }
 
-void ASTReader::PassInterestingDeclsToConsumer() {
-  assert(Consumer);
-
-  if (PassingDeclsToConsumer)
-    return;
-
-  // Guard variable to avoid recursively redoing the process of passing
-  // decls to consumer.
-  SaveAndRestore<bool> GuardPassingDeclsToConsumer(PassingDeclsToConsumer,
-                                                   true);
-
-  // Ensure that we've loaded all potentially-interesting declarations
-  // that need to be eagerly loaded.
-  for (auto ID : EagerlyDeserializedDecls)
-    GetDecl(ID);
-  EagerlyDeserializedDecls.clear();
-
-  while (!InterestingDecls.empty()) {
-    Decl *D = InterestingDecls.front();
-    InterestingDecls.pop_front();
-
-    PassInterestingDeclToConsumer(D);
-  }
-}
-
 void ASTReader::PassInterestingDeclToConsumer(Decl *D) {
   if (ObjCImplDecl *ImplD = dyn_cast<ObjCImplDecl>(D))
     PassObjCImplDeclToConsumer(ImplD, Consumer);
@@ -7062,7 +7351,7 @@ void ASTReader::PrintStats() {
 }
 
 template<typename Key, typename ModuleFile, unsigned InitialCapacity>
-static void
+LLVM_DUMP_METHOD static void
 dumpModuleIDMap(StringRef Name,
                 const ContinuousRangeMap<Key, ModuleFile *,
                                          InitialCapacity> &Map) {
@@ -7092,18 +7381,15 @@ LLVM_DUMP_METHOD void ASTReader::dump() {
                   GlobalPreprocessedEntityMap);
 
   llvm::errs() << "\n*** PCH/Modules Loaded:";
-  for (ModuleManager::ModuleConstIterator M = ModuleMgr.begin(),
-                                       MEnd = ModuleMgr.end();
-       M != MEnd; ++M)
-    (*M)->dump();
+  for (ModuleFile &M : ModuleMgr)
+    M.dump();
 }
 
 /// Return the amount of memory used by memory buffers, breaking down
 /// by heap-backed versus mmap'ed memory.
 void ASTReader::getMemoryBufferSizes(MemoryBufferSizes &sizes) const {
-  for (ModuleConstIterator I = ModuleMgr.begin(),
-      E = ModuleMgr.end(); I != E; ++I) {
-    if (llvm::MemoryBuffer *buf = (*I)->Buffer.get()) {
+  for (ModuleFile &I : ModuleMgr) {
+    if (llvm::MemoryBuffer *buf = I.Buffer) {
       size_t bytes = buf->getBufferSize();
       switch (buf->getBufferKind()) {
         case llvm::MemoryBuffer::MemoryBuffer_Malloc:
@@ -7132,7 +7418,7 @@ void ASTReader::InitializeSema(Sema &S) {
   // FIXME: What happens if these are changed by a module import?
   if (!FPPragmaOptions.empty()) {
     assert(FPPragmaOptions.size() == 1 && "Wrong number of FP_PRAGMA_OPTIONS");
-    SemaObj->FPFeatures.fp_contract = FPPragmaOptions[0];
+    SemaObj->FPFeatures = FPOptions(FPPragmaOptions[0]);
   }
 
   SemaObj->OpenCLFeatures.copy(OpenCLExtensions);
@@ -7173,6 +7459,34 @@ void ASTReader::UpdateSema() {
         PointersToMembersPragmaLocation);
   }
   SemaObj->ForceCUDAHostDeviceDepth = ForceCUDAHostDeviceDepth;
+
+  if (PragmaPackCurrentValue) {
+    // The bottom of the stack might have a default value. It must be adjusted
+    // to the current value to ensure that the packing state is preserved after
+    // popping entries that were included/imported from a PCH/module.
+    bool DropFirst = false;
+    if (!PragmaPackStack.empty() &&
+        PragmaPackStack.front().Location.isInvalid()) {
+      assert(PragmaPackStack.front().Value == SemaObj->PackStack.DefaultValue &&
+             "Expected a default alignment value");
+      SemaObj->PackStack.Stack.emplace_back(
+          PragmaPackStack.front().SlotLabel, SemaObj->PackStack.CurrentValue,
+          SemaObj->PackStack.CurrentPragmaLocation);
+      DropFirst = true;
+    }
+    for (const auto &Entry :
+         llvm::makeArrayRef(PragmaPackStack).drop_front(DropFirst ? 1 : 0))
+      SemaObj->PackStack.Stack.emplace_back(Entry.SlotLabel, Entry.Value,
+                                            Entry.Location);
+    if (PragmaPackCurrentLocation.isInvalid()) {
+      assert(*PragmaPackCurrentValue == SemaObj->PackStack.DefaultValue &&
+             "Expected a default alignment value");
+      // Keep the current values.
+    } else {
+      SemaObj->PackStack.CurrentValue = *PragmaPackCurrentValue;
+      SemaObj->PackStack.CurrentPragmaLocation = PragmaPackCurrentLocation;
+    }
+  }
 }
 
 IdentifierInfo *ASTReader::get(StringRef Name) {
@@ -7720,6 +8034,9 @@ IdentifierID ASTReader::getGlobalIdentifierID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_IDENT_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.IdentifierRemap.find(LocalID - NUM_PREDEF_IDENT_IDS);
   assert(I != M.IdentifierRemap.end()
@@ -7758,6 +8075,9 @@ MacroID ASTReader::getGlobalMacroID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_MACRO_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.MacroRemap.find(LocalID - NUM_PREDEF_MACRO_IDS);
   assert(I != M.MacroRemap.end() && "Invalid index into macro index remap");
@@ -7770,6 +8090,9 @@ ASTReader::getGlobalSubmoduleID(ModuleFile &M, unsigned LocalID) {
   if (LocalID < NUM_PREDEF_SUBMODULE_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.SubmoduleRemap.find(LocalID - NUM_PREDEF_SUBMODULE_IDS);
   assert(I != M.SubmoduleRemap.end()
@@ -7833,7 +8156,8 @@ ASTReader::getSourceDescriptor(unsigned ID) {
 
   // If there is only a single PCH, return it instead.
   // Chained PCH are not suported.
-  if (ModuleMgr.size() == 1) {
+  const auto &PCHChain = ModuleMgr.pch_modules();
+  if (std::distance(std::begin(PCHChain), std::end(PCHChain))) {
     ModuleFile &MF = ModuleMgr.getPrimaryModule();
     StringRef ModuleName = llvm::sys::path::filename(MF.OriginalSourceFileName);
     StringRef FileName = llvm::sys::path::filename(MF.FileName);
@@ -7843,6 +8167,13 @@ ASTReader::getSourceDescriptor(unsigned ID) {
   return None;
 }
 
+ExternalASTSource::ExtKind ASTReader::hasExternalDefinitions(const Decl *FD) {
+  auto I = BodySource.find(FD);
+  if (I == BodySource.end())
+    return EK_ReplyHazy;
+  return I->second ? EK_Never : EK_Always;
+}
+
 Selector ASTReader::getLocalSelector(ModuleFile &M, unsigned LocalID) {
   return DecodeSelector(getGlobalSelectorID(M, LocalID));
 }
@@ -7886,6 +8217,9 @@ ASTReader::getGlobalSelectorID(ModuleFile &M, unsigned LocalID) const {
   if (LocalID < NUM_PREDEF_SELECTOR_IDS)
     return LocalID;
 
+  if (!M.ModuleOffsetMap.empty())
+    ReadModuleOffsetMap(M);
+
   ContinuousRangeMap<uint32_t, int, 2>::iterator I
     = M.SelectorRemap.find(LocalID - NUM_PREDEF_SELECTOR_IDS);
   assert(I != M.SelectorRemap.end()
@@ -7915,6 +8249,10 @@ ASTReader::ReadDeclarationName(ModuleFile &F,
     return Context.DeclarationNames.getCXXDestructorName(
                           Context.getCanonicalType(readType(F, Record, Idx)));
 
+  case DeclarationName::CXXDeductionGuideName:
+    return Context.DeclarationNames.getCXXDeductionGuideName(
+                          ReadDeclAs<TemplateDecl>(F, Record, Idx));
+
   case DeclarationName::CXXConversionFunctionName:
     return Context.DeclarationNames.getCXXConversionFunctionName(
                           Context.getCanonicalType(readType(F, Record, Idx)));
@@ -7962,6 +8300,7 @@ void ASTReader::ReadDeclarationNameLoc(ModuleFile &F,
   case DeclarationName::ObjCOneArgSelector:
   case DeclarationName::ObjCMultiArgSelector:
   case DeclarationName::CXXUsingDirective:
+  case DeclarationName::CXXDeductionGuideName:
     break;
   }
 }
@@ -8406,11 +8745,11 @@ CXXTemporary *ASTReader::ReadCXXTemporary(ModuleFile &F,
   return CXXTemporary::Create(Context, Decl);
 }
 
-DiagnosticBuilder ASTReader::Diag(unsigned DiagID) {
+DiagnosticBuilder ASTReader::Diag(unsigned DiagID) const {
   return Diag(CurrentImportLoc, DiagID);
 }
 
-DiagnosticBuilder ASTReader::Diag(SourceLocation Loc, unsigned DiagID) {
+DiagnosticBuilder ASTReader::Diag(SourceLocation Loc, unsigned DiagID) const {
   return Diags.Report(Loc, DiagID);
 }
 
@@ -8493,6 +8832,21 @@ void ASTReader::ReadComments() {
   }
 }
 
+void ASTReader::visitInputFiles(serialization::ModuleFile &MF,
+                                bool IncludeSystem, bool Complain,
+                    llvm::function_ref<void(const serialization::InputFile &IF,
+                                            bool isSystem)> Visitor) {
+  unsigned NumUserInputs = MF.NumUserInputFiles;
+  unsigned NumInputs = MF.InputFilesLoaded.size();
+  assert(NumUserInputs <= NumInputs);
+  unsigned N = IncludeSystem ? NumInputs : NumUserInputs;
+  for (unsigned I = 0; I < N; ++I) {
+    bool IsSystem = I >= NumUserInputs;
+    InputFile IF = getInputFile(MF, I+1, Complain);
+    Visitor(IF, IsSystem);
+  }
+}
+
 std::string ASTReader::getOwningModuleNameForDiagnostic(const Decl *D) {
   // If we know the owning module, use it.
   if (Module *M = D->getImportedOwningModule())
@@ -8651,9 +9005,9 @@ void ASTReader::finishPendingActions() {
       // FIXME: Check for =delete/=default?
       // FIXME: Complain about ODR violations here?
       const FunctionDecl *Defn = nullptr;
-      if (!getContext().getLangOpts().Modules || !FD->hasBody(Defn))
+      if (!getContext().getLangOpts().Modules || !FD->hasBody(Defn)) {
         FD->setLazyBody(PB->second);
-      else
+      } else
         mergeDefinitionVisibility(const_cast<FunctionDecl*>(Defn), FD);
       continue;
     }
@@ -8789,24 +9143,504 @@ void ASTReader::diagnoseOdrViolations() {
       continue;
 
     bool Diagnosed = false;
-    for (auto *RD : Merge.second) {
+    CXXRecordDecl *FirstRecord = Merge.first;
+    std::string FirstModule = getOwningModuleNameForDiagnostic(FirstRecord);
+    for (CXXRecordDecl *SecondRecord : Merge.second) {
       // Multiple different declarations got merged together; tell the user
       // where they came from.
-      if (Merge.first != RD) {
-        // FIXME: Walk the definition, figure out what's different,
-        // and diagnose that.
-        if (!Diagnosed) {
-          std::string Module = getOwningModuleNameForDiagnostic(Merge.first);
-          Diag(Merge.first->getLocation(),
-               diag::err_module_odr_violation_different_definitions)
-            << Merge.first << Module.empty() << Module;
-          Diagnosed = true;
+      if (FirstRecord == SecondRecord)
+        continue;
+
+      std::string SecondModule = getOwningModuleNameForDiagnostic(SecondRecord);
+      using DeclHashes = llvm::SmallVector<std::pair<Decl *, unsigned>, 4>;
+      DeclHashes FirstHashes;
+      DeclHashes SecondHashes;
+      ODRHash Hash;
+
+      auto PopulateHashes = [&Hash, FirstRecord](DeclHashes &Hashes,
+                                                 CXXRecordDecl *Record) {
+        for (auto *D : Record->decls()) {
+          // Due to decl merging, the first CXXRecordDecl is the parent of
+          // Decls in both records.
+          if (!ODRHash::isWhitelistedDecl(D, FirstRecord))
+            continue;
+          Hash.clear();
+          Hash.AddSubDecl(D);
+          Hashes.emplace_back(D, Hash.CalculateHash());
+        }
+      };
+      PopulateHashes(FirstHashes, FirstRecord);
+      PopulateHashes(SecondHashes, SecondRecord);
+
+      // Used with err_module_odr_violation_mismatch_decl and
+      // note_module_odr_violation_mismatch_decl
+      enum {
+        EndOfClass,
+        PublicSpecifer,
+        PrivateSpecifer,
+        ProtectedSpecifer,
+        StaticAssert,
+        Field,
+        CXXMethod,
+        Other
+      } FirstDiffType = Other,
+        SecondDiffType = Other;
+
+      auto DifferenceSelector = [](Decl *D) {
+        assert(D && "valid Decl required");
+        switch (D->getKind()) {
+        default:
+          return Other;
+        case Decl::AccessSpec:
+          switch (D->getAccess()) {
+          case AS_public:
+            return PublicSpecifer;
+          case AS_private:
+            return PrivateSpecifer;
+          case AS_protected:
+            return ProtectedSpecifer;
+          case AS_none:
+            break;
+          }
+          llvm_unreachable("Invalid access specifier");
+        case Decl::StaticAssert:
+          return StaticAssert;
+        case Decl::Field:
+          return Field;
+        case Decl::CXXMethod:
+          return CXXMethod;
+        }
+      };
+
+      Decl *FirstDecl = nullptr;
+      Decl *SecondDecl = nullptr;
+      auto FirstIt = FirstHashes.begin();
+      auto SecondIt = SecondHashes.begin();
+
+      // If there is a diagnoseable difference, FirstDiffType and
+      // SecondDiffType will not be Other and FirstDecl and SecondDecl will be
+      // filled in if not EndOfClass.
+      while (FirstIt != FirstHashes.end() || SecondIt != SecondHashes.end()) {
+        if (FirstIt != FirstHashes.end() && SecondIt != SecondHashes.end() &&
+            FirstIt->second == SecondIt->second) {
+          ++FirstIt;
+          ++SecondIt;
+          continue;
         }
 
-        Diag(RD->getLocation(),
+        FirstDecl = FirstIt == FirstHashes.end() ? nullptr : FirstIt->first;
+        SecondDecl = SecondIt == SecondHashes.end() ? nullptr : SecondIt->first;
+
+        FirstDiffType = FirstDecl ? DifferenceSelector(FirstDecl) : EndOfClass;
+        SecondDiffType =
+            SecondDecl ? DifferenceSelector(SecondDecl) : EndOfClass;
+
+        break;
+      }
+
+      if (FirstDiffType == Other || SecondDiffType == Other) {
+        // Reaching this point means an unexpected Decl was encountered
+        // or no difference was detected.  This causes a generic error
+        // message to be emitted.
+        Diag(FirstRecord->getLocation(),
+             diag::err_module_odr_violation_different_definitions)
+            << FirstRecord << FirstModule.empty() << FirstModule;
+
+        Diag(SecondRecord->getLocation(),
              diag::note_module_odr_violation_different_definitions)
-          << getOwningModuleNameForDiagnostic(RD);
+            << SecondModule;
+        Diagnosed = true;
+        break;
+      }
+
+      if (FirstDiffType != SecondDiffType) {
+        SourceLocation FirstLoc;
+        SourceRange FirstRange;
+        if (FirstDiffType == EndOfClass) {
+          FirstLoc = FirstRecord->getBraceRange().getEnd();
+        } else {
+          FirstLoc = FirstIt->first->getLocation();
+          FirstRange = FirstIt->first->getSourceRange();
+        }
+        Diag(FirstLoc, diag::err_module_odr_violation_mismatch_decl)
+            << FirstRecord << FirstModule.empty() << FirstModule << FirstRange
+            << FirstDiffType;
+
+        SourceLocation SecondLoc;
+        SourceRange SecondRange;
+        if (SecondDiffType == EndOfClass) {
+          SecondLoc = SecondRecord->getBraceRange().getEnd();
+        } else {
+          SecondLoc = SecondDecl->getLocation();
+          SecondRange = SecondDecl->getSourceRange();
+        }
+        Diag(SecondLoc, diag::note_module_odr_violation_mismatch_decl)
+            << SecondModule << SecondRange << SecondDiffType;
+        Diagnosed = true;
+        break;
+      }
+
+      assert(FirstDiffType == SecondDiffType);
+
+      // Used with err_module_odr_violation_mismatch_decl_diff and
+      // note_module_odr_violation_mismatch_decl_diff
+      enum ODRDeclDifference{
+        StaticAssertCondition,
+        StaticAssertMessage,
+        StaticAssertOnlyMessage,
+        FieldName,
+        FieldTypeName,
+        FieldSingleBitField,
+        FieldDifferentWidthBitField,
+        FieldSingleMutable,
+        FieldSingleInitializer,
+        FieldDifferentInitializers,
+        MethodName,
+        MethodDeleted,
+        MethodVirtual,
+        MethodStatic,
+        MethodVolatile,
+        MethodConst,
+        MethodInline,
+      };
+
+      // These lambdas have the common portions of the ODR diagnostics.  This
+      // has the same return as Diag(), so addition parameters can be passed
+      // in with operator<<
+      auto ODRDiagError = [FirstRecord, &FirstModule, this](
+          SourceLocation Loc, SourceRange Range, ODRDeclDifference DiffType) {
+        return Diag(Loc, diag::err_module_odr_violation_mismatch_decl_diff)
+               << FirstRecord << FirstModule.empty() << FirstModule << Range
+               << DiffType;
+      };
+      auto ODRDiagNote = [&SecondModule, this](
+          SourceLocation Loc, SourceRange Range, ODRDeclDifference DiffType) {
+        return Diag(Loc, diag::note_module_odr_violation_mismatch_decl_diff)
+               << SecondModule << Range << DiffType;
+      };
+
+      auto ComputeODRHash = [&Hash](const Stmt* S) {
+        assert(S);
+        Hash.clear();
+        Hash.AddStmt(S);
+        return Hash.CalculateHash();
+      };
+
+      auto ComputeDeclNameODRHash = [&Hash](const DeclarationName Name) {
+        Hash.clear();
+        Hash.AddDeclarationName(Name);
+        return Hash.CalculateHash();
+      };
+
+      switch (FirstDiffType) {
+      case Other:
+      case EndOfClass:
+      case PublicSpecifer:
+      case PrivateSpecifer:
+      case ProtectedSpecifer:
+        llvm_unreachable("Invalid diff type");
+
+      case StaticAssert: {
+        StaticAssertDecl *FirstSA = cast<StaticAssertDecl>(FirstDecl);
+        StaticAssertDecl *SecondSA = cast<StaticAssertDecl>(SecondDecl);
+
+        Expr *FirstExpr = FirstSA->getAssertExpr();
+        Expr *SecondExpr = SecondSA->getAssertExpr();
+        unsigned FirstODRHash = ComputeODRHash(FirstExpr);
+        unsigned SecondODRHash = ComputeODRHash(SecondExpr);
+        if (FirstODRHash != SecondODRHash) {
+          ODRDiagError(FirstExpr->getLocStart(), FirstExpr->getSourceRange(),
+                       StaticAssertCondition);
+          ODRDiagNote(SecondExpr->getLocStart(),
+                      SecondExpr->getSourceRange(), StaticAssertCondition);
+          Diagnosed = true;
+          break;
+        }
+
+        StringLiteral *FirstStr = FirstSA->getMessage();
+        StringLiteral *SecondStr = SecondSA->getMessage();
+        assert((FirstStr || SecondStr) && "Both messages cannot be empty");
+        if ((FirstStr && !SecondStr) || (!FirstStr && SecondStr)) {
+          SourceLocation FirstLoc, SecondLoc;
+          SourceRange FirstRange, SecondRange;
+          if (FirstStr) {
+            FirstLoc = FirstStr->getLocStart();
+            FirstRange = FirstStr->getSourceRange();
+          } else {
+            FirstLoc = FirstSA->getLocStart();
+            FirstRange = FirstSA->getSourceRange();
+          }
+          if (SecondStr) {
+            SecondLoc = SecondStr->getLocStart();
+            SecondRange = SecondStr->getSourceRange();
+          } else {
+            SecondLoc = SecondSA->getLocStart();
+            SecondRange = SecondSA->getSourceRange();
+          }
+          ODRDiagError(FirstLoc, FirstRange, StaticAssertOnlyMessage)
+              << (FirstStr == nullptr);
+          ODRDiagNote(SecondLoc, SecondRange, StaticAssertOnlyMessage)
+              << (SecondStr == nullptr);
+          Diagnosed = true;
+          break;
+        }
+
+        if (FirstStr && SecondStr &&
+            FirstStr->getString() != SecondStr->getString()) {
+          ODRDiagError(FirstStr->getLocStart(), FirstStr->getSourceRange(),
+                       StaticAssertMessage);
+          ODRDiagNote(SecondStr->getLocStart(), SecondStr->getSourceRange(),
+                      StaticAssertMessage);
+          Diagnosed = true;
+          break;
+        }
+        break;
+      }
+      case Field: {
+        FieldDecl *FirstField = cast<FieldDecl>(FirstDecl);
+        FieldDecl *SecondField = cast<FieldDecl>(SecondDecl);
+        IdentifierInfo *FirstII = FirstField->getIdentifier();
+        IdentifierInfo *SecondII = SecondField->getIdentifier();
+        if (FirstII->getName() != SecondII->getName()) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldName)
+              << FirstII;
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldName)
+              << SecondII;
+
+          Diagnosed = true;
+          break;
+        }
+
+        assert(
+            Context.hasSameType(FirstField->getType(), SecondField->getType()));
+
+        QualType FirstType = FirstField->getType();
+        QualType SecondType = SecondField->getType();
+        const TypedefType *FirstTypedef = dyn_cast<TypedefType>(FirstType);
+        const TypedefType *SecondTypedef = dyn_cast<TypedefType>(SecondType);
+
+        if ((FirstTypedef && !SecondTypedef) ||
+            (!FirstTypedef && SecondTypedef)) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldTypeName)
+              << FirstII << FirstType;
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldTypeName)
+              << SecondII << SecondType;
+
+          Diagnosed = true;
+          break;
+        }
+
+        if (FirstTypedef && SecondTypedef) {
+          unsigned FirstHash = ComputeDeclNameODRHash(
+              FirstTypedef->getDecl()->getDeclName());
+          unsigned SecondHash = ComputeDeclNameODRHash(
+              SecondTypedef->getDecl()->getDeclName());
+          if (FirstHash != SecondHash) {
+            ODRDiagError(FirstField->getLocation(),
+                         FirstField->getSourceRange(), FieldTypeName)
+                << FirstII << FirstType;
+            ODRDiagNote(SecondField->getLocation(),
+                        SecondField->getSourceRange(), FieldTypeName)
+                << SecondII << SecondType;
+
+            Diagnosed = true;
+            break;
+          }
+        }
+
+        const bool IsFirstBitField = FirstField->isBitField();
+        const bool IsSecondBitField = SecondField->isBitField();
+        if (IsFirstBitField != IsSecondBitField) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldSingleBitField)
+              << FirstII << IsFirstBitField;
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldSingleBitField)
+              << SecondII << IsSecondBitField;
+          Diagnosed = true;
+          break;
+        }
+
+        if (IsFirstBitField && IsSecondBitField) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldDifferentWidthBitField)
+              << FirstII << FirstField->getBitWidth()->getSourceRange();
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldDifferentWidthBitField)
+              << SecondII << SecondField->getBitWidth()->getSourceRange();
+          Diagnosed = true;
+          break;
+        }
+
+        const bool IsFirstMutable = FirstField->isMutable();
+        const bool IsSecondMutable = SecondField->isMutable();
+        if (IsFirstMutable != IsSecondMutable) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldSingleMutable)
+              << FirstII << IsFirstMutable;
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldSingleMutable)
+              << SecondII << IsSecondMutable;
+          Diagnosed = true;
+          break;
+        }
+
+        const Expr *FirstInitializer = FirstField->getInClassInitializer();
+        const Expr *SecondInitializer = SecondField->getInClassInitializer();
+        if ((!FirstInitializer && SecondInitializer) ||
+            (FirstInitializer && !SecondInitializer)) {
+          ODRDiagError(FirstField->getLocation(), FirstField->getSourceRange(),
+                       FieldSingleInitializer)
+              << FirstII << (FirstInitializer != nullptr);
+          ODRDiagNote(SecondField->getLocation(), SecondField->getSourceRange(),
+                      FieldSingleInitializer)
+              << SecondII << (SecondInitializer != nullptr);
+          Diagnosed = true;
+          break;
+        }
+
+        if (FirstInitializer && SecondInitializer) {
+          unsigned FirstInitHash = ComputeODRHash(FirstInitializer);
+          unsigned SecondInitHash = ComputeODRHash(SecondInitializer);
+          if (FirstInitHash != SecondInitHash) {
+            ODRDiagError(FirstField->getLocation(),
+                         FirstField->getSourceRange(),
+                         FieldDifferentInitializers)
+                << FirstII << FirstInitializer->getSourceRange();
+            ODRDiagNote(SecondField->getLocation(),
+                        SecondField->getSourceRange(),
+                        FieldDifferentInitializers)
+                << SecondII << SecondInitializer->getSourceRange();
+            Diagnosed = true;
+            break;
+          }
+        }
+
+        break;
       }
+      case CXXMethod: {
+        const CXXMethodDecl *FirstMethod = cast<CXXMethodDecl>(FirstDecl);
+        const CXXMethodDecl *SecondMethod = cast<CXXMethodDecl>(SecondDecl);
+        auto FirstName = FirstMethod->getDeclName();
+        auto SecondName = SecondMethod->getDeclName();
+        if (FirstName != SecondName) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodName)
+              << FirstName;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodName)
+              << SecondName;
+
+          Diagnosed = true;
+          break;
+        }
+
+        const bool FirstDeleted = FirstMethod->isDeleted();
+        const bool SecondDeleted = SecondMethod->isDeleted();
+        if (FirstDeleted != SecondDeleted) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodDeleted)
+              << FirstName << FirstDeleted;
+
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodDeleted)
+              << SecondName << SecondDeleted;
+          Diagnosed = true;
+          break;
+        }
+
+        const bool FirstVirtual = FirstMethod->isVirtualAsWritten();
+        const bool SecondVirtual = SecondMethod->isVirtualAsWritten();
+        const bool FirstPure = FirstMethod->isPure();
+        const bool SecondPure = SecondMethod->isPure();
+        if ((FirstVirtual || SecondVirtual) &&
+            (FirstVirtual != SecondVirtual || FirstPure != SecondPure)) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodVirtual)
+              << FirstName << FirstPure << FirstVirtual;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodVirtual)
+              << SecondName << SecondPure << SecondVirtual;
+          Diagnosed = true;
+          break;
+        }
+
+        // CXXMethodDecl::isStatic uses the canonical Decl.  With Decl merging,
+        // FirstDecl is the canonical Decl of SecondDecl, so the storage
+        // class needs to be checked instead.
+        const auto FirstStorage = FirstMethod->getStorageClass();
+        const auto SecondStorage = SecondMethod->getStorageClass();
+        const bool FirstStatic = FirstStorage == SC_Static;
+        const bool SecondStatic = SecondStorage == SC_Static;
+        if (FirstStatic != SecondStatic) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodStatic)
+              << FirstName << FirstStatic;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodStatic)
+              << SecondName << SecondStatic;
+          Diagnosed = true;
+          break;
+        }
+
+        const bool FirstVolatile = FirstMethod->isVolatile();
+        const bool SecondVolatile = SecondMethod->isVolatile();
+        if (FirstVolatile != SecondVolatile) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodVolatile)
+              << FirstName << FirstVolatile;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodVolatile)
+              << SecondName << SecondVolatile;
+          Diagnosed = true;
+          break;
+        }
+
+        const bool FirstConst = FirstMethod->isConst();
+        const bool SecondConst = SecondMethod->isConst();
+        if (FirstConst != SecondConst) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodConst)
+              << FirstName << FirstConst;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodConst)
+              << SecondName << SecondConst;
+          Diagnosed = true;
+          break;
+        }
+
+        const bool FirstInline = FirstMethod->isInlineSpecified();
+        const bool SecondInline = SecondMethod->isInlineSpecified();
+        if (FirstInline != SecondInline) {
+          ODRDiagError(FirstMethod->getLocation(),
+                       FirstMethod->getSourceRange(), MethodInline)
+              << FirstName << FirstInline;
+          ODRDiagNote(SecondMethod->getLocation(),
+                      SecondMethod->getSourceRange(), MethodInline)
+              << SecondName << SecondInline;
+          Diagnosed = true;
+          break;
+        }
+
+        break;
+      }
+      }
+
+      if (Diagnosed == true)
+        continue;
+
+      Diag(FirstRecord->getLocation(),
+           diag::err_module_odr_violation_different_definitions)
+          << FirstRecord << FirstModule.empty() << FirstModule;
+
+      Diag(SecondRecord->getLocation(),
+           diag::note_module_odr_violation_different_definitions)
+          << SecondModule;
+      Diagnosed = true;
     }
 
     if (!Diagnosed) {
@@ -8905,8 +9739,10 @@ ASTReader::ASTReader(Preprocessor &PP, ASTContext &Context,
                    : cast<ASTReaderListener>(new PCHValidator(PP, *this))),
       SourceMgr(PP.getSourceManager()), FileMgr(PP.getFileManager()),
       PCHContainerRdr(PCHContainerRdr), Diags(PP.getDiagnostics()), PP(PP),
-      Context(Context), ModuleMgr(PP.getFileManager(), PCHContainerRdr),
-      DummyIdResolver(PP), ReadTimer(std::move(ReadTimer)), isysroot(isysroot),
+      Context(Context),
+      ModuleMgr(PP.getFileManager(), PP.getPCMCache(), PCHContainerRdr),
+      PCMCache(PP.getPCMCache()), DummyIdResolver(PP),
+      ReadTimer(std::move(ReadTimer)), isysroot(isysroot),
       DisableValidation(DisableValidation),
       AllowASTWithCompilerErrors(AllowASTWithCompilerErrors),
       AllowConfigurationMismatch(AllowConfigurationMismatch),
diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index 707a9249dd96d..e0304d22fe50c 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -119,7 +119,8 @@ namespace clang {
     }
 
     void ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update);
-    void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data);
+    void ReadCXXDefinitionData(struct CXXRecordDecl::DefinitionData &Data,
+                               const CXXRecordDecl *D);
     void MergeDefinitionData(CXXRecordDecl *D,
                              struct CXXRecordDecl::DefinitionData &&NewDD);
     void ReadObjCDefinitionData(struct ObjCInterfaceDecl::DefinitionData &Data);
@@ -240,6 +241,7 @@ namespace clang {
     /// \brief Determine whether this declaration has a pending body.
     bool hasPendingBody() const { return HasPendingBody; }
 
+    void ReadFunctionDefinition(FunctionDecl *FD);
     void Visit(Decl *D);
 
     void UpdateDecl(Decl *D);
@@ -292,6 +294,7 @@ namespace clang {
     void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
     void VisitDeclaratorDecl(DeclaratorDecl *DD);
     void VisitFunctionDecl(FunctionDecl *FD);
+    void VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *GD);
     void VisitCXXMethodDecl(CXXMethodDecl *D);
     void VisitCXXConstructorDecl(CXXConstructorDecl *D);
     void VisitCXXDestructorDecl(CXXDestructorDecl *D);
@@ -421,6 +424,19 @@ uint64_t ASTDeclReader::GetCurrentCursorOffset() {
   return Loc.F->DeclsCursor.GetCurrentBitNo() + Loc.F->GlobalBitOffset;
 }
 
+void ASTDeclReader::ReadFunctionDefinition(FunctionDecl *FD) {
+  if (Record.readInt())
+    Reader.BodySource[FD] = Loc.F->Kind == ModuleKind::MK_MainFile;
+  if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
+    CD->NumCtorInitializers = Record.readInt();
+    if (CD->NumCtorInitializers)
+      CD->CtorInitializers = ReadGlobalOffset();
+  }
+  // Store the offset of the body so we can lazily load it later.
+  Reader.PendingBodies[FD] = GetCurrentCursorOffset();
+  HasPendingBody = true;
+}
+
 void ASTDeclReader::Visit(Decl *D) {
   DeclVisitor<ASTDeclReader, void>::Visit(D);
 
@@ -457,15 +473,8 @@ void ASTDeclReader::Visit(Decl *D) {
     // We only read it if FD doesn't already have a body (e.g., from another
     // module).
     // FIXME: Can we diagnose ODR violations somehow?
-    if (Record.readInt()) {
-      if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
-        CD->NumCtorInitializers = Record.readInt();
-        if (CD->NumCtorInitializers)
-          CD->CtorInitializers = ReadGlobalOffset();
-      }
-      Reader.PendingBodies[FD] = GetCurrentCursorOffset();
-      HasPendingBody = true;
-    }
+    if (Record.readInt())
+      ReadFunctionDefinition(FD);
   }
 }
 
@@ -592,6 +601,11 @@ ASTDeclReader::VisitTypedefNameDecl(TypedefNameDecl *TD) {
     TD->setModedTypeSourceInfo(TInfo, modedT);
   } else
     TD->setTypeSourceInfo(TInfo);
+  // Read and discard the declaration for which this is a typedef name for
+  // linkage, if it exists. We cannot rely on our type to pull in this decl,
+  // because it might have been merged with a type from another module and
+  // thus might not refer to our version of the declaration.
+  ReadDecl();
   return Redecl;
 }
 
@@ -738,6 +752,7 @@ void ASTDeclReader::VisitFunctionDecl(FunctionDecl *FD) {
   FD->SClass = (StorageClass)Record.readInt();
   FD->IsInline = Record.readInt();
   FD->IsInlineSpecified = Record.readInt();
+  FD->IsExplicitSpecified = Record.readInt();
   FD->IsVirtualAsWritten = Record.readInt();
   FD->IsPure = Record.readInt();
   FD->HasInheritedPrototype = Record.readInt();
@@ -1112,8 +1127,12 @@ void ASTDeclReader::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
       (ObjCPropertyDecl::PropertyAttributeKind)Record.readInt());
   D->setPropertyImplementation(
       (ObjCPropertyDecl::PropertyControl)Record.readInt());
-  D->setGetterName(Record.readDeclarationName().getObjCSelector());
-  D->setSetterName(Record.readDeclarationName().getObjCSelector());
+  DeclarationName GetterName = Record.readDeclarationName();
+  SourceLocation GetterLoc = ReadSourceLocation();
+  D->setGetterName(GetterName.getObjCSelector(), GetterLoc);
+  DeclarationName SetterName = Record.readDeclarationName();
+  SourceLocation SetterLoc = ReadSourceLocation();
+  D->setSetterName(SetterName.getObjCSelector(), SetterLoc);
   D->setGetterMethodDecl(ReadDeclAs<ObjCMethodDecl>());
   D->setSetterMethodDecl(ReadDeclAs<ObjCMethodDecl>());
   D->setPropertyIvarDecl(ReadDeclAs<ObjCIvarDecl>());
@@ -1126,7 +1145,6 @@ void ASTDeclReader::VisitObjCImplDecl(ObjCImplDecl *D) {
 
 void ASTDeclReader::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
   VisitObjCImplDecl(D);
-  D->setIdentifier(Record.getIdentifierInfo());
   D->CategoryNameLoc = ReadSourceLocation();
 }
 
@@ -1473,7 +1491,7 @@ void ASTDeclReader::VisitUnresolvedUsingTypenameDecl(
 }
 
 void ASTDeclReader::ReadCXXDefinitionData(
-                                   struct CXXRecordDecl::DefinitionData &Data) {
+    struct CXXRecordDecl::DefinitionData &Data, const CXXRecordDecl *D) {
   // Note: the caller has deserialized the IsLambda bit already.
   Data.UserDeclaredConstructor = Record.readInt();
   Data.UserDeclaredSpecialMembers = Record.readInt();
@@ -1512,10 +1530,19 @@ void ASTDeclReader::ReadCXXDefinitionData(
   Data.ComputedVisibleConversions = Record.readInt();
   Data.UserProvidedDefaultConstructor = Record.readInt();
   Data.DeclaredSpecialMembers = Record.readInt();
-  Data.ImplicitCopyConstructorHasConstParam = Record.readInt();
+  Data.ImplicitCopyConstructorCanHaveConstParamForVBase = Record.readInt();
+  Data.ImplicitCopyConstructorCanHaveConstParamForNonVBase = Record.readInt();
   Data.ImplicitCopyAssignmentHasConstParam = Record.readInt();
   Data.HasDeclaredCopyConstructorWithConstParam = Record.readInt();
   Data.HasDeclaredCopyAssignmentWithConstParam = Record.readInt();
+  Data.ODRHash = Record.readInt();
+  Data.HasODRHash = true;
+
+  if (Record.readInt()) {
+    Reader.BodySource[D] = Loc.F->Kind == ModuleKind::MK_MainFile
+                               ? ExternalASTSource::EK_Never
+                               : ExternalASTSource::EK_Always;
+  }
 
   Data.NumBases = Record.readInt();
   if (Data.NumBases)
@@ -1641,7 +1668,8 @@ void ASTDeclReader::MergeDefinitionData(
   // ComputedVisibleConversions is handled below.
   MATCH_FIELD(UserProvidedDefaultConstructor)
   OR_FIELD(DeclaredSpecialMembers)
-  MATCH_FIELD(ImplicitCopyConstructorHasConstParam)
+  MATCH_FIELD(ImplicitCopyConstructorCanHaveConstParamForVBase)
+  MATCH_FIELD(ImplicitCopyConstructorCanHaveConstParamForNonVBase)
   MATCH_FIELD(ImplicitCopyAssignmentHasConstParam)
   OR_FIELD(HasDeclaredCopyConstructorWithConstParam)
   OR_FIELD(HasDeclaredCopyAssignmentWithConstParam)
@@ -1669,6 +1697,10 @@ void ASTDeclReader::MergeDefinitionData(
     // when they occur within the body of a function template specialization).
   }
 
+  if (D->getODRHash() != MergeDD.ODRHash) {
+    DetectedOdrViolation = true;
+  }
+
   if (DetectedOdrViolation)
     Reader.PendingOdrMergeFailures[DD.Definition].push_back(MergeDD.Definition);
 }
@@ -1686,7 +1718,7 @@ void ASTDeclReader::ReadCXXRecordDefinition(CXXRecordDecl *D, bool Update) {
   else
     DD = new (C) struct CXXRecordDecl::DefinitionData(D);
 
-  ReadCXXDefinitionData(*DD);
+  ReadCXXDefinitionData(*DD, D);
 
   // We might already have a definition for this record. This can happen either
   // because we're reading an update record, or because we've already done some
@@ -1775,6 +1807,10 @@ ASTDeclReader::VisitCXXRecordDeclImpl(CXXRecordDecl *D) {
   return Redecl;
 }
 
+void ASTDeclReader::VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D) {
+  VisitFunctionDecl(D);
+}
+
 void ASTDeclReader::VisitCXXMethodDecl(CXXMethodDecl *D) {
   VisitFunctionDecl(D);
 
@@ -1804,8 +1840,6 @@ void ASTDeclReader::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
   }
 
   VisitCXXMethodDecl(D);
-
-  D->IsExplicitSpecified = Record.readInt();
 }
 
 void ASTDeclReader::VisitCXXDestructorDecl(CXXDestructorDecl *D) {
@@ -1821,7 +1855,6 @@ void ASTDeclReader::VisitCXXDestructorDecl(CXXDestructorDecl *D) {
 
 void ASTDeclReader::VisitCXXConversionDecl(CXXConversionDecl *D) {
   VisitCXXMethodDecl(D);
-  D->IsExplicitSpecified = Record.readInt();
 }
 
 void ASTDeclReader::VisitImportDecl(ImportDecl *D) {
@@ -1831,7 +1864,7 @@ void ASTDeclReader::VisitImportDecl(ImportDecl *D) {
   SourceLocation *StoredLocs = D->getTrailingObjects<SourceLocation>();
   for (unsigned I = 0, N = Record.back(); I != N; ++I)
     StoredLocs[I] = ReadSourceLocation();
-  (void)Record.readInt(); // The number of stored source locations.
+  Record.skipInts(1); // The number of stored source locations.
 }
 
 void ASTDeclReader::VisitAccessSpecDecl(AccessSpecDecl *D) {
@@ -1873,6 +1906,7 @@ DeclID ASTDeclReader::VisitTemplateDecl(TemplateDecl *D) {
   DeclID PatternID = ReadDeclID();
   NamedDecl *TemplatedDecl = cast_or_null<NamedDecl>(Reader.GetDecl(PatternID));
   TemplateParameterList *TemplateParams = Record.readTemplateParameterList();
+  // FIXME handle associated constraints
   D->init(TemplatedDecl, TemplateParams);
 
   return PatternID;
@@ -2471,12 +2505,11 @@ void ASTDeclReader::VisitOMPCapturedExprDecl(OMPCapturedExprDecl *D) {
 //===----------------------------------------------------------------------===//
 
 /// \brief Reads attributes from the current stream position.
-void ASTReader::ReadAttributes(ModuleFile &F, AttrVec &Attrs,
-                               const RecordData &Record, unsigned &Idx) {
-  for (unsigned i = 0, e = Record[Idx++]; i != e; ++i) {
+void ASTReader::ReadAttributes(ASTRecordReader &Record, AttrVec &Attrs) {
+  for (unsigned i = 0, e = Record.readInt(); i != e; ++i) {
     Attr *New = nullptr;
-    attr::Kind Kind = (attr::Kind)Record[Idx++];
-    SourceRange Range = ReadSourceRange(F, Record, Idx);
+    attr::Kind Kind = (attr::Kind)Record.readInt();
+    SourceRange Range = Record.readSourceRange();
 
 #include "clang/Serialization/AttrPCHRead.inc"
 
@@ -2531,7 +2564,11 @@ static bool isConsumerInterestedIn(ASTContext &Ctx, Decl *D, bool HasBody) {
            Var->isThisDeclarationADefinition() == VarDecl::Definition;
   if (FunctionDecl *Func = dyn_cast<FunctionDecl>(D))
     return Func->doesThisDeclarationHaveABody() || HasBody;
-  
+
+  if (auto *ES = D->getASTContext().getExternalSource())
+    if (ES->hasExternalDefinitions(D) == ExternalASTSource::EK_Never)
+      return true;
+
   return false;
 }
 
@@ -2648,6 +2685,45 @@ static bool isSameTemplateParameterList(const TemplateParameterList *X,
   return true;
 }
 
+/// Determine whether the attributes we can overload on are identical for A and
+/// B. Will ignore any overloadable attrs represented in the type of A and B.
+static bool hasSameOverloadableAttrs(const FunctionDecl *A,
+                                     const FunctionDecl *B) {
+  // Note that pass_object_size attributes are represented in the function's
+  // ExtParameterInfo, so we don't need to check them here.
+
+  SmallVector<const EnableIfAttr *, 4> AEnableIfs;
+  // Since this is an equality check, we can ignore that enable_if attrs show up
+  // in reverse order.
+  for (const auto *EIA : A->specific_attrs<EnableIfAttr>())
+    AEnableIfs.push_back(EIA);
+
+  SmallVector<const EnableIfAttr *, 4> BEnableIfs;
+  for (const auto *EIA : B->specific_attrs<EnableIfAttr>())
+    BEnableIfs.push_back(EIA);
+
+  // Two very common cases: either we have 0 enable_if attrs, or we have an
+  // unequal number of enable_if attrs.
+  if (AEnableIfs.empty() && BEnableIfs.empty())
+    return true;
+
+  if (AEnableIfs.size() != BEnableIfs.size())
+    return false;
+
+  llvm::FoldingSetNodeID Cand1ID, Cand2ID;
+  for (unsigned I = 0, E = AEnableIfs.size(); I != E; ++I) {
+    Cand1ID.clear();
+    Cand2ID.clear();
+
+    AEnableIfs[I]->getCond()->Profile(Cand1ID, A->getASTContext(), true);
+    BEnableIfs[I]->getCond()->Profile(Cand2ID, B->getASTContext(), true);
+    if (Cand1ID != Cand2ID)
+      return false;
+  }
+
+  return true;
+}
+
 /// \brief Determine whether the two declarations refer to the same entity.
 static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
   assert(X->getDeclName() == Y->getDeclName() && "Declaration name mismatch!");
@@ -2703,8 +2779,24 @@ static bool isSameEntity(NamedDecl *X, NamedDecl *Y) {
                         CtorY->getInheritedConstructor().getConstructor()))
         return false;
     }
-    return (FuncX->getLinkageInternal() == FuncY->getLinkageInternal()) &&
-      FuncX->getASTContext().hasSameType(FuncX->getType(), FuncY->getType());
+    ASTContext &C = FuncX->getASTContext();
+    if (!C.hasSameType(FuncX->getType(), FuncY->getType())) {
+      // We can get functions with different types on the redecl chain in C++17
+      // if they have differing exception specifications and at least one of
+      // the excpetion specs is unresolved.
+      // FIXME: Do we need to check for C++14 deduced return types here too?
+      auto *XFPT = FuncX->getType()->getAs<FunctionProtoType>();
+      auto *YFPT = FuncY->getType()->getAs<FunctionProtoType>();
+      if (C.getLangOpts().CPlusPlus1z && XFPT && YFPT &&
+          (isUnresolvedExceptionSpec(XFPT->getExceptionSpecType()) ||
+           isUnresolvedExceptionSpec(YFPT->getExceptionSpecType())) &&
+          C.hasSameFunctionTypeIgnoringExceptionSpec(FuncX->getType(),
+                                                     FuncY->getType()))
+        return true;
+      return false;
+    }
+    return FuncX->getLinkageInternal() == FuncY->getLinkageInternal() &&
+           hasSameOverloadableAttrs(FuncX, FuncY);
   }
 
   // Variables with the same type and linkage match.
@@ -3323,6 +3415,9 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   case DECL_CXX_RECORD:
     D = CXXRecordDecl::CreateDeserialized(Context, ID);
     break;
+  case DECL_CXX_DEDUCTION_GUIDE:
+    D = CXXDeductionGuideDecl::CreateDeserialized(Context, ID);
+    break;
   case DECL_CXX_METHOD:
     D = CXXMethodDecl::CreateDeserialized(Context, ID);
     break;
@@ -3531,12 +3626,37 @@ Decl *ASTReader::ReadDeclRecord(DeclID ID) {
   // AST consumer might need to know about, queue it.
   // We don't pass it to the consumer immediately because we may be in recursive
   // loading, and some declarations may still be initializing.
-  if (isConsumerInterestedIn(Context, D, Reader.hasPendingBody()))
-    InterestingDecls.push_back(D);
+  PotentiallyInterestingDecls.push_back(
+      InterestingDecl(D, Reader.hasPendingBody()));
 
   return D;
 }
 
+void ASTReader::PassInterestingDeclsToConsumer() {
+  assert(Consumer);
+
+  if (PassingDeclsToConsumer)
+    return;
+
+  // Guard variable to avoid recursively redoing the process of passing
+  // decls to consumer.
+  SaveAndRestore<bool> GuardPassingDeclsToConsumer(PassingDeclsToConsumer,
+                                                   true);
+
+  // Ensure that we've loaded all potentially-interesting declarations
+  // that need to be eagerly loaded.
+  for (auto ID : EagerlyDeserializedDecls)
+    GetDecl(ID);
+  EagerlyDeserializedDecls.clear();
+
+  while (!PotentiallyInterestingDecls.empty()) {
+    InterestingDecl D = PotentiallyInterestingDecls.front();
+    PotentiallyInterestingDecls.pop_front();
+    if (isConsumerInterestedIn(Context, D.getDecl(), D.hasPendingBody()))
+      PassInterestingDeclToConsumer(D.getDecl());
+  }
+}
+
 void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
   // The declaration may have been modified by files later in the chain.
   // If this is the case, read the record containing the updates from each file
@@ -3547,6 +3667,9 @@ void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
     auto UpdateOffsets = std::move(UpdI->second);
     DeclUpdateOffsets.erase(UpdI);
 
+    // FIXME: This call to isConsumerInterestedIn is not safe because
+    // we could be deserializing declarations at the moment. We should
+    // delay calling this in the same way as done in D30793.
     bool WasInteresting = isConsumerInterestedIn(Context, D, false);
     for (auto &FileAndOffset : UpdateOffsets) {
       ModuleFile *F = FileAndOffset.first;
@@ -3568,7 +3691,8 @@ void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
       // we need to hand it off to the consumer.
       if (!WasInteresting &&
           isConsumerInterestedIn(Context, D, Reader.hasPendingBody())) {
-        InterestingDecls.push_back(D);
+        PotentiallyInterestingDecls.push_back(
+            InterestingDecl(D, Reader.hasPendingBody()));
         WasInteresting = true;
       }
     }
@@ -3858,14 +3982,7 @@ void ASTDeclReader::UpdateDecl(Decl *D) {
         });
       }
       FD->setInnerLocStart(ReadSourceLocation());
-      if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
-        CD->NumCtorInitializers = Record.readInt();
-        if (CD->NumCtorInitializers)
-          CD->CtorInitializers = ReadGlobalOffset();
-      }
-      // Store the offset of the body so we can lazily load it later.
-      Reader.PendingBodies[FD] = GetCurrentCursorOffset();
-      HasPendingBody = true;
+      ReadFunctionDefinition(FD);
       assert(Record.getIdx() == Record.size() && "lazy body must be last");
       break;
     }
diff --git a/lib/Serialization/ASTReaderStmt.cpp b/lib/Serialization/ASTReaderStmt.cpp
index 686a69bbbcd2d..a12fb8cf95a09 100644
--- a/lib/Serialization/ASTReaderStmt.cpp
+++ b/lib/Serialization/ASTReaderStmt.cpp
@@ -381,6 +381,11 @@ void ASTStmtReader::VisitCoawaitExpr(CoawaitExpr *S) {
   llvm_unreachable("unimplemented");
 }
 
+void ASTStmtReader::VisitDependentCoawaitExpr(DependentCoawaitExpr *S) {
+  // FIXME: Implement coroutine serialization.
+  llvm_unreachable("unimplemented");
+}
+
 void ASTStmtReader::VisitCoyieldExpr(CoyieldExpr *S) {
   // FIXME: Implement coroutine serialization.
   llvm_unreachable("unimplemented");
@@ -665,7 +670,7 @@ void ASTStmtReader::VisitBinaryOperator(BinaryOperator *E) {
   E->setRHS(Record.readSubExpr());
   E->setOpcode((BinaryOperator::Opcode)Record.readInt());
   E->setOperatorLoc(ReadSourceLocation());
-  E->setFPContractable((bool)Record.readInt());
+  E->setFPFeatures(FPOptions(Record.readInt()));
 }
 
 void ASTStmtReader::VisitCompoundAssignOperator(CompoundAssignOperator *E) {
@@ -1220,7 +1225,7 @@ void ASTStmtReader::VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
   VisitCallExpr(E);
   E->Operator = (OverloadedOperatorKind)Record.readInt();
   E->Range = Record.readSourceRange();
-  E->setFPContractable((bool)Record.readInt());
+  E->setFPFeatures(FPOptions(Record.readInt()));
 }
 
 void ASTStmtReader::VisitCXXConstructExpr(CXXConstructExpr *E) {
@@ -1928,7 +1933,8 @@ OMPClause *OMPClauseReader::readClause() {
 }
 
 void OMPClauseReader::VisitOMPClauseWithPreInit(OMPClauseWithPreInit *C) {
-  C->setPreInitStmt(Reader->Record.readSubStmt());
+  C->setPreInitStmt(Reader->Record.readSubStmt(),
+                    static_cast<OpenMPDirectiveKind>(Reader->Record.readInt()));
 }
 
 void OMPClauseReader::VisitOMPClauseWithPostUpdate(OMPClauseWithPostUpdate *C) {
@@ -1937,6 +1943,7 @@ void OMPClauseReader::VisitOMPClauseWithPostUpdate(OMPClauseWithPostUpdate *C) {
 }
 
 void OMPClauseReader::VisitOMPIfClause(OMPIfClause *C) {
+  VisitOMPClauseWithPreInit(C);
   C->setNameModifier(static_cast<OpenMPDirectiveKind>(Reader->Record.readInt()));
   C->setNameModifierLoc(Reader->ReadSourceLocation());
   C->setColonLoc(Reader->ReadSourceLocation());
@@ -1950,6 +1957,7 @@ void OMPClauseReader::VisitOMPFinalClause(OMPFinalClause *C) {
 }
 
 void OMPClauseReader::VisitOMPNumThreadsClause(OMPNumThreadsClause *C) {
+  VisitOMPClauseWithPreInit(C);
   C->setNumThreads(Reader->Record.readSubExpr());
   C->setLParenLoc(Reader->ReadSourceLocation());
 }
@@ -2297,11 +2305,13 @@ void OMPClauseReader::VisitOMPMapClause(OMPMapClause *C) {
 }
 
 void OMPClauseReader::VisitOMPNumTeamsClause(OMPNumTeamsClause *C) {
+  VisitOMPClauseWithPreInit(C);
   C->setNumTeams(Reader->Record.readSubExpr());
   C->setLParenLoc(Reader->ReadSourceLocation());
 }
 
 void OMPClauseReader::VisitOMPThreadLimitClause(OMPThreadLimitClause *C) {
+  VisitOMPClauseWithPreInit(C);
   C->setThreadLimit(Reader->Record.readSubExpr());
   C->setLParenLoc(Reader->ReadSourceLocation());
 }
@@ -2566,6 +2576,8 @@ void ASTStmtReader::VisitOMPLoopDirective(OMPLoopDirective *D) {
   if (isOpenMPLoopBoundSharingDirective(D->getDirectiveKind())) {
     D->setPrevLowerBoundVariable(Record.readSubExpr());
     D->setPrevUpperBoundVariable(Record.readSubExpr());
+    D->setDistInc(Record.readSubExpr());
+    D->setPrevEnsureUpperBound(Record.readSubExpr());
   }
   SmallVector<Expr *, 4> Sub;
   unsigned CollapsedNum = D->getCollapsedNumber();
@@ -2909,7 +2921,7 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
   llvm::BitstreamCursor &Cursor = F.DeclsCursor;
 
   // Map of offset to previously deserialized stmt. The offset points
-  /// just after the stmt record.
+  // just after the stmt record.
   llvm::DenseMap<uint64_t, Stmt *> StmtEntries;
 
 #ifndef NDEBUG
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 886523ea94319..bb869077f4cda 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -18,8 +18,8 @@
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/ASTUnresolvedSet.h"
 #include "clang/AST/Decl.h"
-#include "clang/AST/DeclContextInternals.h"
 #include "clang/AST/DeclCXX.h"
+#include "clang/AST/DeclContextInternals.h"
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclTemplate.h"
 #include "clang/AST/Expr.h"
@@ -33,8 +33,9 @@
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/FileSystemOptions.h"
-#include "clang/Basic/LangOptions.h"
 #include "clang/Basic/LLVM.h"
+#include "clang/Basic/LangOptions.h"
+#include "clang/Basic/MemoryBufferCache.h"
 #include "clang/Basic/Module.h"
 #include "clang/Basic/ObjCRuntime.h"
 #include "clang/Basic/SourceManager.h"
@@ -64,20 +65,22 @@
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ADT/IntrusiveRefCntPtr.h"
 #include "llvm/ADT/Optional.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SmallString.h"
-#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/Bitcode/BitCodes.h"
 #include "llvm/Bitcode/BitstreamWriter.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/EndianStream.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/OnDiskHashTable.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
+#include "llvm/Support/SHA1.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cassert>
@@ -348,6 +351,15 @@ void ASTTypeWriter::VisitAutoType(const AutoType *T) {
   Code = TYPE_AUTO;
 }
 
+void ASTTypeWriter::VisitDeducedTemplateSpecializationType(
+    const DeducedTemplateSpecializationType *T) {
+  Record.AddTemplateName(T->getTemplateName());
+  Record.AddTypeRef(T->getDeducedType());
+  if (T->getDeducedType().isNull())
+    Record.push_back(T->isDependentType());
+  Code = TYPE_DEDUCED_TEMPLATE_SPECIALIZATION;
+}
+
 void ASTTypeWriter::VisitTagType(const TagType *T) {
   Record.push_back(T->isDependentType());
   Record.AddDeclRef(T->getDecl()->getCanonicalDecl());
@@ -414,8 +426,10 @@ ASTTypeWriter::VisitDependentSizedArrayType(const DependentSizedArrayType *T) {
 void
 ASTTypeWriter::VisitDependentSizedExtVectorType(
                                         const DependentSizedExtVectorType *T) {
-  // FIXME: Serialize this type (C++ only)
-  llvm_unreachable("Cannot serialize dependent sized extended vector types");
+  Record.AddTypeRef(T->getElementType());
+  Record.AddStmt(T->getSizeExpr());
+  Record.AddSourceLocation(T->getAttributeLoc());
+  Code = TYPE_DEPENDENT_SIZED_EXT_VECTOR;
 }
 
 void
@@ -682,6 +696,11 @@ void TypeLocWriter::VisitAutoTypeLoc(AutoTypeLoc TL) {
   Record.AddSourceLocation(TL.getNameLoc());
 }
 
+void TypeLocWriter::VisitDeducedTemplateSpecializationTypeLoc(
+    DeducedTemplateSpecializationTypeLoc TL) {
+  Record.AddSourceLocation(TL.getTemplateNameLoc());
+}
+
 void TypeLocWriter::VisitRecordTypeLoc(RecordTypeLoc TL) {
   Record.AddSourceLocation(TL.getNameLoc());
 }
@@ -1001,7 +1020,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   // Control Block.
   BLOCK(CONTROL_BLOCK);
   RECORD(METADATA);
-  RECORD(SIGNATURE);
   RECORD(MODULE_NAME);
   RECORD(MODULE_DIRECTORY);
   RECORD(MODULE_MAP_FILE);
@@ -1014,7 +1032,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   BLOCK(OPTIONS_BLOCK);
   RECORD(LANGUAGE_OPTIONS);
   RECORD(TARGET_OPTIONS);
-  RECORD(DIAGNOSTIC_OPTIONS);
   RECORD(FILE_SYSTEM_OPTIONS);
   RECORD(HEADER_SEARCH_OPTIONS);
   RECORD(PREPROCESSOR_OPTIONS);
@@ -1029,6 +1046,7 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(IDENTIFIER_OFFSET);
   RECORD(IDENTIFIER_TABLE);
   RECORD(EAGERLY_DESERIALIZED_DECLS);
+  RECORD(MODULAR_CODEGEN_DECLS);
   RECORD(SPECIAL_TYPES);
   RECORD(STATISTICS);
   RECORD(TENTATIVE_DEFINITIONS);
@@ -1049,7 +1067,6 @@ void ASTWriter::WriteBlockInfoBlock() {
   RECORD(UPDATE_VISIBLE);
   RECORD(DECL_UPDATE_OFFSETS);
   RECORD(DECL_UPDATES);
-  RECORD(DIAG_PRAGMA_MAPPINGS);
   RECORD(CUDA_SPECIAL_DECL_REFS);
   RECORD(HEADER_SEARCH_TABLE);
   RECORD(FP_PRAGMA_OPTIONS);
@@ -1242,6 +1259,11 @@ void ASTWriter::WriteBlockInfoBlock() {
   BLOCK(EXTENSION_BLOCK);
   RECORD(EXTENSION_METADATA);
 
+  BLOCK(UNHASHED_CONTROL_BLOCK);
+  RECORD(SIGNATURE);
+  RECORD(DIAGNOSTIC_OPTIONS);
+  RECORD(DIAG_PRAGMA_MAPPINGS);
+
 #undef RECORD
 #undef BLOCK
   Stream.ExitBlock();
@@ -1304,21 +1326,73 @@ adjustFilenameForRelocatableAST(const char *Filename, StringRef BaseDir) {
   return Filename + Pos;
 }
 
-static ASTFileSignature getSignature() {
-  while (true) {
-    if (ASTFileSignature S = llvm::sys::Process::GetRandomNumber())
-      return S;
-    // Rely on GetRandomNumber to eventually return non-zero...
+ASTFileSignature ASTWriter::createSignature(StringRef Bytes) {
+  // Calculate the hash till start of UNHASHED_CONTROL_BLOCK.
+  llvm::SHA1 Hasher;
+  Hasher.update(ArrayRef<uint8_t>(Bytes.bytes_begin(), Bytes.size()));
+  auto Hash = Hasher.result();
+
+  // Convert to an array [5*i32].
+  ASTFileSignature Signature;
+  auto LShift = [&](unsigned char Val, unsigned Shift) {
+    return (uint32_t)Val << Shift;
+  };
+  for (int I = 0; I != 5; ++I)
+    Signature[I] = LShift(Hash[I * 4 + 0], 24) | LShift(Hash[I * 4 + 1], 16) |
+                   LShift(Hash[I * 4 + 2], 8) | LShift(Hash[I * 4 + 3], 0);
+
+  return Signature;
+}
+
+ASTFileSignature ASTWriter::writeUnhashedControlBlock(Preprocessor &PP,
+                                                      ASTContext &Context) {
+  // Flush first to prepare the PCM hash (signature).
+  Stream.FlushToWord();
+  auto StartOfUnhashedControl = Stream.GetCurrentBitNo() >> 3;
+
+  // Enter the block and prepare to write records.
+  RecordData Record;
+  Stream.EnterSubblock(UNHASHED_CONTROL_BLOCK_ID, 5);
+
+  // For implicit modules, write the hash of the PCM as its signature.
+  ASTFileSignature Signature;
+  if (WritingModule &&
+      PP.getHeaderSearchInfo().getHeaderSearchOpts().ModulesHashContent) {
+    Signature = createSignature(StringRef(Buffer.begin(), StartOfUnhashedControl));
+    Record.append(Signature.begin(), Signature.end());
+    Stream.EmitRecord(SIGNATURE, Record);
+    Record.clear();
   }
+
+  // Diagnostic options.
+  const auto &Diags = Context.getDiagnostics();
+  const DiagnosticOptions &DiagOpts = Diags.getDiagnosticOptions();
+#define DIAGOPT(Name, Bits, Default) Record.push_back(DiagOpts.Name);
+#define ENUM_DIAGOPT(Name, Type, Bits, Default)                                \
+  Record.push_back(static_cast<unsigned>(DiagOpts.get##Name()));
+#include "clang/Basic/DiagnosticOptions.def"
+  Record.push_back(DiagOpts.Warnings.size());
+  for (unsigned I = 0, N = DiagOpts.Warnings.size(); I != N; ++I)
+    AddString(DiagOpts.Warnings[I], Record);
+  Record.push_back(DiagOpts.Remarks.size());
+  for (unsigned I = 0, N = DiagOpts.Remarks.size(); I != N; ++I)
+    AddString(DiagOpts.Remarks[I], Record);
+  // Note: we don't serialize the log or serialization file names, because they
+  // are generally transient files and will almost always be overridden.
+  Stream.EmitRecord(DIAGNOSTIC_OPTIONS, Record);
+
+  // Write out the diagnostic/pragma mappings.
+  WritePragmaDiagnosticMappings(Diags, /* IsModule = */ WritingModule);
+
+  // Leave the options block.
+  Stream.ExitBlock();
+  return Signature;
 }
 
 /// \brief Write the control block.
-uint64_t ASTWriter::WriteControlBlock(Preprocessor &PP,
-                                      ASTContext &Context,
-                                      StringRef isysroot,
-                                      const std::string &OutputFile) {
-  ASTFileSignature Signature = 0;
-
+void ASTWriter::WriteControlBlock(Preprocessor &PP, ASTContext &Context,
+                                  StringRef isysroot,
+                                  const std::string &OutputFile) {
   using namespace llvm;
   Stream.EnterSubblock(CONTROL_BLOCK_ID, 5);
   RecordData Record;
@@ -1346,15 +1420,6 @@ uint64_t ASTWriter::WriteControlBlock(Preprocessor &PP,
                               getClangFullRepositoryVersion());
   }
   if (WritingModule) {
-    // For implicit modules we output a signature that we can use to ensure
-    // duplicate module builds don't collide in the cache as their output order
-    // is non-deterministic.
-    // FIXME: Remove this when output is deterministic.
-    if (Context.getLangOpts().ImplicitModules) {
-      Signature = getSignature();
-      RecordData::value_type Record[] = {Signature};
-      Stream.EmitRecord(SIGNATURE, Record);
-    }
 
     // Module name
     auto Abbrev = std::make_shared<BitCodeAbbrev>();
@@ -1420,17 +1485,23 @@ uint64_t ASTWriter::WriteControlBlock(Preprocessor &PP,
     serialization::ModuleManager &Mgr = Chain->getModuleManager();
     Record.clear();
 
-    for (auto *M : Mgr) {
+    for (ModuleFile &M : Mgr) {
       // Skip modules that weren't directly imported.
-      if (!M->isDirectlyImported())
+      if (!M.isDirectlyImported())
         continue;
 
-      Record.push_back((unsigned)M->Kind); // FIXME: Stable encoding
-      AddSourceLocation(M->ImportLoc, Record);
-      Record.push_back(M->File->getSize());
-      Record.push_back(getTimestampForOutput(M->File));
-      Record.push_back(M->Signature);
-      AddPath(M->FileName, Record);
+      Record.push_back((unsigned)M.Kind); // FIXME: Stable encoding
+      AddSourceLocation(M.ImportLoc, Record);
+
+      // If we have calculated signature, there is no need to store
+      // the size or timestamp.
+      Record.push_back(M.Signature ? 0 : M.File->getSize());
+      Record.push_back(M.Signature ? 0 : getTimestampForOutput(M.File));
+
+      for (auto I : M.Signature)
+        Record.push_back(I);
+
+      AddPath(M.FileName, Record);
     }
     Stream.EmitRecord(IMPORTS, Record);
   }
@@ -1492,24 +1563,6 @@ uint64_t ASTWriter::WriteControlBlock(Preprocessor &PP,
   }
   Stream.EmitRecord(TARGET_OPTIONS, Record);
 
-  // Diagnostic options.
-  Record.clear();
-  const DiagnosticOptions &DiagOpts
-    = Context.getDiagnostics().getDiagnosticOptions();
-#define DIAGOPT(Name, Bits, Default) Record.push_back(DiagOpts.Name);
-#define ENUM_DIAGOPT(Name, Type, Bits, Default) \
-  Record.push_back(static_cast<unsigned>(DiagOpts.get##Name()));
-#include "clang/Basic/DiagnosticOptions.def"
-  Record.push_back(DiagOpts.Warnings.size());
-  for (unsigned I = 0, N = DiagOpts.Warnings.size(); I != N; ++I)
-    AddString(DiagOpts.Warnings[I], Record);
-  Record.push_back(DiagOpts.Remarks.size());
-  for (unsigned I = 0, N = DiagOpts.Remarks.size(); I != N; ++I)
-    AddString(DiagOpts.Remarks[I], Record);
-  // Note: we don't serialize the log or serialization file names, because they
-  // are generally transient files and will almost always be overridden.
-  Stream.EmitRecord(DIAGNOSTIC_OPTIONS, Record);
-
   // File system options.
   Record.clear();
   const FileSystemOptions &FSOpts =
@@ -1623,7 +1676,6 @@ uint64_t ASTWriter::WriteControlBlock(Preprocessor &PP,
                   PP.getHeaderSearchInfo().getHeaderSearchOpts(),
                   PP.getLangOpts().Modules);
   Stream.ExitBlock();
-  return Signature;
 }
 
 namespace  {
@@ -1986,6 +2038,30 @@ void ASTWriter::WriteHeaderSearch(const HeaderSearch &HS) {
     free(const_cast<char *>(SavedStrings[I]));
 }
 
+static void emitBlob(llvm::BitstreamWriter &Stream, StringRef Blob,
+                     unsigned SLocBufferBlobCompressedAbbrv,
+                     unsigned SLocBufferBlobAbbrv) {
+  typedef ASTWriter::RecordData::value_type RecordDataType;
+
+  // Compress the buffer if possible. We expect that almost all PCM
+  // consumers will not want its contents.
+  SmallString<0> CompressedBuffer;
+  if (llvm::zlib::isAvailable()) {
+    llvm::Error E = llvm::zlib::compress(Blob.drop_back(1), CompressedBuffer);
+    if (!E) {
+      RecordDataType Record[] = {SM_SLOC_BUFFER_BLOB_COMPRESSED,
+                                 Blob.size() - 1};
+      Stream.EmitRecordWithBlob(SLocBufferBlobCompressedAbbrv, Record,
+                                CompressedBuffer);
+      return;
+    }
+    llvm::consumeError(std::move(E));
+  }
+
+  RecordDataType Record[] = {SM_SLOC_BUFFER_BLOB};
+  Stream.EmitRecordWithBlob(SLocBufferBlobAbbrv, Record, Blob);
+}
+
 /// \brief Writes the block containing the serialized form of the
 /// source manager.
 ///
@@ -2094,20 +2170,8 @@ void ASTWriter::WriteSourceManagerBlock(SourceManager &SourceMgr,
         const llvm::MemoryBuffer *Buffer =
             Content->getBuffer(PP.getDiagnostics(), PP.getSourceManager());
         StringRef Blob(Buffer->getBufferStart(), Buffer->getBufferSize() + 1);
-
-        // Compress the buffer if possible. We expect that almost all PCM
-        // consumers will not want its contents.
-        SmallString<0> CompressedBuffer;
-        if (llvm::zlib::compress(Blob.drop_back(1), CompressedBuffer) ==
-            llvm::zlib::StatusOK) {
-          RecordData::value_type Record[] = {SM_SLOC_BUFFER_BLOB_COMPRESSED,
-                                             Blob.size() - 1};
-          Stream.EmitRecordWithBlob(SLocBufferBlobCompressedAbbrv, Record,
-                                    CompressedBuffer);
-        } else {
-          RecordData::value_type Record[] = {SM_SLOC_BUFFER_BLOB};
-          Stream.EmitRecordWithBlob(SLocBufferBlobAbbrv, Record, Blob);
-        }
+        emitBlob(Stream, Blob, SLocBufferBlobCompressedAbbrv,
+                 SLocBufferBlobAbbrv);
       }
     } else {
       // The source location entry is a macro expansion.
@@ -2516,7 +2580,8 @@ unsigned ASTWriter::getLocalOrImportedSubmoduleID(Module *Mod) {
 
   auto *Top = Mod->getTopLevelModule();
   if (Top != WritingModule &&
-      !Top->fullModuleNameIs(StringRef(getLangOpts().CurrentModule)))
+      (getLangOpts().CompilingPCH ||
+       !Top->fullModuleNameIs(StringRef(getLangOpts().CurrentModule))))
     return 0;
 
   return SubmoduleIDs[Mod] = NextSubmoduleID++;
@@ -2650,11 +2715,17 @@ void ASTWriter::WriteSubmodules(Module *WritingModule) {
 
     // Emit the definition of the block.
     {
-      RecordData::value_type Record[] = {
-          SUBMODULE_DEFINITION, ID, ParentID, Mod->IsFramework, Mod->IsExplicit,
-          Mod->IsSystem, Mod->IsExternC, Mod->InferSubmodules,
-          Mod->InferExplicitSubmodules, Mod->InferExportWildcard,
-          Mod->ConfigMacrosExhaustive};
+      RecordData::value_type Record[] = {SUBMODULE_DEFINITION,
+                                         ID,
+                                         ParentID,
+                                         Mod->IsFramework,
+                                         Mod->IsExplicit,
+                                         Mod->IsSystem,
+                                         Mod->IsExternC,
+                                         Mod->InferSubmodules,
+                                         Mod->InferExplicitSubmodules,
+                                         Mod->InferExportWildcard,
+                                         Mod->ConfigMacrosExhaustive};
       Stream.EmitRecordWithBlob(DefinitionAbbrev, Record, Mod->Name);
     }
 
@@ -2789,43 +2860,68 @@ ASTWriter::inferSubmoduleIDFromLocation(SourceLocation Loc) {
 
 void ASTWriter::WritePragmaDiagnosticMappings(const DiagnosticsEngine &Diag,
                                               bool isModule) {
-  // Make sure set diagnostic pragmas don't affect the translation unit that
-  // imports the module.
-  // FIXME: Make diagnostic pragma sections work properly with modules.
-  if (isModule)
-    return;
-
   llvm::SmallDenseMap<const DiagnosticsEngine::DiagState *, unsigned, 64>
       DiagStateIDMap;
   unsigned CurrID = 0;
-  DiagStateIDMap[&Diag.DiagStates.front()] = ++CurrID; // the command-line one.
   RecordData Record;
-  for (DiagnosticsEngine::DiagStatePointsTy::const_iterator
-         I = Diag.DiagStatePoints.begin(), E = Diag.DiagStatePoints.end();
-         I != E; ++I) {
-    const DiagnosticsEngine::DiagStatePoint &point = *I;
-    if (point.Loc.isInvalid())
-      continue;
 
-    AddSourceLocation(point.Loc, Record);
-    unsigned &DiagStateID = DiagStateIDMap[point.State];
+  auto AddDiagState = [&](const DiagnosticsEngine::DiagState *State,
+                          bool IncludeNonPragmaStates) {
+    unsigned &DiagStateID = DiagStateIDMap[State];
     Record.push_back(DiagStateID);
-    
+  
     if (DiagStateID == 0) {
       DiagStateID = ++CurrID;
-      for (const auto &I : *(point.State)) {
-        if (I.second.isPragma()) {
+
+      // Add a placeholder for the number of mappings.
+      auto SizeIdx = Record.size();
+      Record.emplace_back();
+      for (const auto &I : *State) {
+        if (I.second.isPragma() || IncludeNonPragmaStates) {
           Record.push_back(I.first);
-          Record.push_back((unsigned)I.second.getSeverity());
+          Record.push_back(I.second.serializeBits());
         }
       }
-      Record.push_back(-1); // mark the end of the diag/map pairs for this
-                            // location.
+      // Update the placeholder.
+      Record[SizeIdx] = (Record.size() - SizeIdx) / 2;
+    }
+  };
+
+  AddDiagState(Diag.DiagStatesByLoc.FirstDiagState, isModule);
+
+  // Reserve a spot for the number of locations with state transitions.
+  auto NumLocationsIdx = Record.size();
+  Record.emplace_back();
+
+  // Emit the state transitions.
+  unsigned NumLocations = 0;
+  for (auto &FileIDAndFile : Diag.DiagStatesByLoc.Files) {
+    if (!FileIDAndFile.first.isValid() ||
+        !FileIDAndFile.second.HasLocalTransitions)
+      continue;
+    ++NumLocations;
+    AddSourceLocation(Diag.SourceMgr->getLocForStartOfFile(FileIDAndFile.first),
+                      Record);
+    Record.push_back(FileIDAndFile.second.StateTransitions.size());
+    for (auto &StatePoint : FileIDAndFile.second.StateTransitions) {
+      Record.push_back(StatePoint.Offset);
+      AddDiagState(StatePoint.State, false);
     }
   }
 
-  if (!Record.empty())
-    Stream.EmitRecord(DIAG_PRAGMA_MAPPINGS, Record);
+  // Backpatch the number of locations.
+  Record[NumLocationsIdx] = NumLocations;
+
+  // Emit CurDiagStateLoc.  Do it last in order to match source order.
+  //
+  // This also protects against a hypothetical corner case with simulating
+  // -Werror settings for implicit modules in the ASTReader, where reading
+  // CurDiagState out of context could change whether warning pragmas are
+  // treated as errors.
+  AddSourceLocation(Diag.DiagStatesByLoc.CurDiagStateLoc, Record);
+  AddDiagState(Diag.DiagStatesByLoc.CurDiagState, false);
+
+  Stream.EmitRecord(DIAG_PRAGMA_MAPPINGS, Record);
 }
 
 //===----------------------------------------------------------------------===//
@@ -3559,6 +3655,7 @@ public:
     case DeclarationName::ObjCOneArgSelector:
     case DeclarationName::ObjCMultiArgSelector:
     case DeclarationName::CXXLiteralOperatorName:
+    case DeclarationName::CXXDeductionGuideName:
       KeyLen += 4;
       break;
     case DeclarationName::CXXOperatorName:
@@ -3588,6 +3685,7 @@ public:
     switch (Name.getKind()) {
     case DeclarationName::Identifier:
     case DeclarationName::CXXLiteralOperatorName:
+    case DeclarationName::CXXDeductionGuideName:
       LE.write<uint32_t>(Writer.getIdentifierRef(Name.getIdentifier()));
       return;
     case DeclarationName::ObjCZeroArgSelector:
@@ -3931,7 +4029,7 @@ void ASTWriter::WriteDeclContextVisibleUpdate(const DeclContext *DC) {
 
 /// \brief Write an FP_PRAGMA_OPTIONS block for the given FPOptions.
 void ASTWriter::WriteFPPragmaOptions(const FPOptions &Opts) {
-  RecordData::value_type Record[] = {Opts.fp_contract};
+  RecordData::value_type Record[] = {Opts.getInt()};
   Stream.EmitRecord(FP_PRAGMA_OPTIONS, Record);
 }
 
@@ -4086,6 +4184,25 @@ void ASTWriter::WriteMSPointersToMembersPragmaOptions(Sema &SemaRef) {
   Stream.EmitRecord(POINTERS_TO_MEMBERS_PRAGMA_OPTIONS, Record);
 }
 
+/// \brief Write the state of 'pragma pack' at the end of the module.
+void ASTWriter::WritePackPragmaOptions(Sema &SemaRef) {
+  // Don't serialize pragma pack state for modules, since it should only take
+  // effect on a per-submodule basis.
+  if (WritingModule)
+    return;
+
+  RecordData Record;
+  Record.push_back(SemaRef.PackStack.CurrentValue);
+  AddSourceLocation(SemaRef.PackStack.CurrentPragmaLocation, Record);
+  Record.push_back(SemaRef.PackStack.Stack.size());
+  for (const auto &StackEntry : SemaRef.PackStack.Stack) {
+    Record.push_back(StackEntry.Value);
+    AddSourceLocation(StackEntry.PragmaLocation, Record);
+    AddString(StackEntry.StackSlotLabel, Record);
+  }
+  Stream.EmitRecord(PACK_PRAGMA_OPTIONS, Record);
+}
+
 void ASTWriter::WriteModuleFileExtension(Sema &SemaRef,
                                          ModuleFileExtensionWriter &Writer) {
   // Enter the extension block.
@@ -4223,9 +4340,11 @@ void ASTWriter::SetSelectorOffset(Selector Sel, uint32_t Offset) {
 }
 
 ASTWriter::ASTWriter(llvm::BitstreamWriter &Stream,
+                     SmallVectorImpl<char> &Buffer, MemoryBufferCache &PCMCache,
                      ArrayRef<std::shared_ptr<ModuleFileExtension>> Extensions,
                      bool IncludeTimestamps)
-    : Stream(Stream), IncludeTimestamps(IncludeTimestamps) {
+    : Stream(Stream), Buffer(Buffer), PCMCache(PCMCache),
+      IncludeTimestamps(IncludeTimestamps) {
   for (const auto &Ext : Extensions) {
     if (auto Writer = Ext->createExtensionWriter(*this))
       ModuleFileExtensionWriters.push_back(std::move(Writer));
@@ -4245,9 +4364,10 @@ time_t ASTWriter::getTimestampForOutput(const FileEntry *E) const {
   return IncludeTimestamps ? E->getModificationTime() : 0;
 }
 
-uint64_t ASTWriter::WriteAST(Sema &SemaRef, const std::string &OutputFile,
-                             Module *WritingModule, StringRef isysroot,
-                             bool hasErrors) {
+ASTFileSignature ASTWriter::WriteAST(Sema &SemaRef,
+                                     const std::string &OutputFile,
+                                     Module *WritingModule, StringRef isysroot,
+                                     bool hasErrors) {
   WritingAST = true;
 
   ASTHasCompilerErrors = hasErrors;
@@ -4271,6 +4391,12 @@ uint64_t ASTWriter::WriteAST(Sema &SemaRef, const std::string &OutputFile,
   this->BaseDirectory.clear();
 
   WritingAST = false;
+  if (SemaRef.Context.getLangOpts().ImplicitModules && WritingModule) {
+    // Construct MemoryBuffer and update buffer manager.
+    PCMCache.addBuffer(OutputFile,
+                       llvm::MemoryBuffer::getMemBufferCopy(
+                           StringRef(Buffer.begin(), Buffer.size())));
+  }
   return Signature;
 }
 
@@ -4283,9 +4409,9 @@ static void AddLazyVectorDecls(ASTWriter &Writer, Vector &Vec,
   }
 }
 
-uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
-                                 const std::string &OutputFile,
-                                 Module *WritingModule) {
+ASTFileSignature ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
+                                         const std::string &OutputFile,
+                                         Module *WritingModule) {
   using namespace llvm;
 
   bool isModule = WritingModule != nullptr;
@@ -4433,7 +4559,7 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
   }
 
   // Write the control block
-  uint64_t Signature = WriteControlBlock(PP, Context, isysroot, OutputFile);
+  WriteControlBlock(PP, Context, isysroot, OutputFile);
 
   // Write the remaining AST contents.
   Stream.EnterSubblock(AST_BLOCK_ID, 5);
@@ -4573,10 +4699,10 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
     SmallString<2048> Buffer;
     {
       llvm::raw_svector_ostream Out(Buffer);
-      for (ModuleFile *M : Chain->ModuleMgr) {
+      for (ModuleFile &M : Chain->ModuleMgr) {
         using namespace llvm::support;
         endian::Writer<little> LE(Out);
-        StringRef FileName = M->FileName;
+        StringRef FileName = M.FileName;
         LE.write<uint16_t>(FileName.size());
         Out.write(FileName.data(), FileName.size());
 
@@ -4594,15 +4720,15 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
 
         // These values should be unique within a chain, since they will be read
         // as keys into ContinuousRangeMaps.
-        writeBaseIDOrNone(M->SLocEntryBaseOffset, M->LocalNumSLocEntries);
-        writeBaseIDOrNone(M->BaseIdentifierID, M->LocalNumIdentifiers);
-        writeBaseIDOrNone(M->BaseMacroID, M->LocalNumMacros);
-        writeBaseIDOrNone(M->BasePreprocessedEntityID,
-                          M->NumPreprocessedEntities);
-        writeBaseIDOrNone(M->BaseSubmoduleID, M->LocalNumSubmodules);
-        writeBaseIDOrNone(M->BaseSelectorID, M->LocalNumSelectors);
-        writeBaseIDOrNone(M->BaseDeclID, M->LocalNumDecls);
-        writeBaseIDOrNone(M->BaseTypeIndex, M->LocalNumTypes);
+        writeBaseIDOrNone(M.SLocEntryBaseOffset, M.LocalNumSLocEntries);
+        writeBaseIDOrNone(M.BaseIdentifierID, M.LocalNumIdentifiers);
+        writeBaseIDOrNone(M.BaseMacroID, M.LocalNumMacros);
+        writeBaseIDOrNone(M.BasePreprocessedEntityID,
+                          M.NumPreprocessedEntities);
+        writeBaseIDOrNone(M.BaseSubmoduleID, M.LocalNumSubmodules);
+        writeBaseIDOrNone(M.BaseSelectorID, M.LocalNumSelectors);
+        writeBaseIDOrNone(M.BaseDeclID, M.LocalNumDecls);
+        writeBaseIDOrNone(M.BaseTypeIndex, M.LocalNumTypes);
       }
     }
     RecordData::value_type Record[] = {MODULE_OFFSET_MAP};
@@ -4650,7 +4776,6 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
   WriteOpenCLExtensionTypes(SemaRef);
   WriteOpenCLExtensionDecls(SemaRef);
   WriteCUDAPragmas(SemaRef);
-  WritePragmaDiagnosticMappings(Context.getDiagnostics(), isModule);
 
   // If we're emitting a module, write out the submodule information.  
   if (WritingModule)
@@ -4662,6 +4787,9 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
   if (!EagerlyDeserializedDecls.empty())
     Stream.EmitRecord(EAGERLY_DESERIALIZED_DECLS, EagerlyDeserializedDecls);
 
+  if (!ModularCodegenDecls.empty())
+    Stream.EmitRecord(MODULAR_CODEGEN_DECLS, ModularCodegenDecls);
+
   // Write the record containing tentative definitions.
   if (!TentativeDefinitions.empty())
     Stream.EmitRecord(TENTATIVE_DEFINITIONS, TentativeDefinitions);
@@ -4765,6 +4893,7 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
     WriteMSStructPragmaOptions(SemaRef);
     WriteMSPointersToMembersPragmaOptions(SemaRef);
   }
+  WritePackPragmaOptions(SemaRef);
 
   // Some simple statistics
   RecordData::value_type Record[] = {
@@ -4776,7 +4905,7 @@ uint64_t ASTWriter::WriteASTCore(Sema &SemaRef, StringRef isysroot,
   for (const auto &ExtWriter : ModuleFileExtensionWriters)
     WriteModuleFileExtension(SemaRef, *ExtWriter);
 
-  return Signature;
+  return writeUnhashedControlBlock(PP, Context);
 }
 
 void ASTWriter::WriteDeclUpdatesBlocks(RecordDataImpl &OffsetsRecord) {
@@ -5229,6 +5358,10 @@ void ASTRecordWriter::AddDeclarationName(DeclarationName Name) {
     AddTypeRef(Name.getCXXNameType());
     break;
 
+  case DeclarationName::CXXDeductionGuideName:
+    AddDeclRef(Name.getCXXDeductionGuideTemplate());
+    break;
+
   case DeclarationName::CXXOperatorName:
     Record->push_back(Name.getCXXOverloadedOperator());
     break;
@@ -5290,6 +5423,7 @@ void ASTRecordWriter::AddDeclarationNameLoc(const DeclarationNameLoc &DNLoc,
   case DeclarationName::ObjCOneArgSelector:
   case DeclarationName::ObjCMultiArgSelector:
   case DeclarationName::CXXUsingDirective:
+  case DeclarationName::CXXDeductionGuideName:
     break;
   }
 }
@@ -5651,10 +5785,20 @@ void ASTRecordWriter::AddCXXDefinitionData(const CXXRecordDecl *D) {
   Record->push_back(Data.ComputedVisibleConversions);
   Record->push_back(Data.UserProvidedDefaultConstructor);
   Record->push_back(Data.DeclaredSpecialMembers);
-  Record->push_back(Data.ImplicitCopyConstructorHasConstParam);
+  Record->push_back(Data.ImplicitCopyConstructorCanHaveConstParamForVBase);
+  Record->push_back(Data.ImplicitCopyConstructorCanHaveConstParamForNonVBase);
   Record->push_back(Data.ImplicitCopyAssignmentHasConstParam);
   Record->push_back(Data.HasDeclaredCopyConstructorWithConstParam);
   Record->push_back(Data.HasDeclaredCopyAssignmentWithConstParam);
+
+  // getODRHash will compute the ODRHash if it has not been previously computed.
+  Record->push_back(D->getODRHash());
+  bool ModulesDebugInfo = Writer->Context->getLangOpts().ModulesDebugInfo &&
+                          Writer->WritingModule && !D->isDependentType();
+  Record->push_back(ModulesDebugInfo);
+  if (ModulesDebugInfo)
+    Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(D));
+
   // IsLambda bit is already saved.
 
   Record->push_back(Data.NumBases);
diff --git a/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index d8466e9cbf3ba..812cd9e916d91 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/lib/Serialization/ASTWriterDecl.cpp
@@ -86,6 +86,7 @@ namespace clang {
     void VisitUnresolvedUsingValueDecl(UnresolvedUsingValueDecl *D);
     void VisitDeclaratorDecl(DeclaratorDecl *D);
     void VisitFunctionDecl(FunctionDecl *D);
+    void VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D);
     void VisitCXXMethodDecl(CXXMethodDecl *D);
     void VisitCXXConstructorDecl(CXXConstructorDecl *D);
     void VisitCXXDestructorDecl(CXXDestructorDecl *D);
@@ -368,6 +369,7 @@ void ASTDeclWriter::VisitTypedefNameDecl(TypedefNameDecl *D) {
   Record.push_back(D->isModed());
   if (D->isModed())
     Record.AddTypeRef(D->getUnderlyingType());
+  Record.AddDeclRef(D->getAnonDeclWithTypedefName(false));
 }
 
 void ASTDeclWriter::VisitTypedefDecl(TypedefDecl *D) {
@@ -519,6 +521,7 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
   Record.push_back((int)D->SClass); // FIXME: stable encoding
   Record.push_back(D->IsInline);
   Record.push_back(D->IsInlineSpecified);
+  Record.push_back(D->IsExplicitSpecified);
   Record.push_back(D->IsVirtualAsWritten);
   Record.push_back(D->IsPure);
   Record.push_back(D->HasInheritedPrototype);
@@ -607,6 +610,11 @@ void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
   Code = serialization::DECL_FUNCTION;
 }
 
+void ASTDeclWriter::VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D) {
+  VisitFunctionDecl(D);
+  Code = serialization::DECL_CXX_DEDUCTION_GUIDE;
+}
+
 void ASTDeclWriter::VisitObjCMethodDecl(ObjCMethodDecl *D) {
   VisitNamedDecl(D);
   // FIXME: convert to LazyStmtPtr?
@@ -791,7 +799,9 @@ void ASTDeclWriter::VisitObjCPropertyDecl(ObjCPropertyDecl *D) {
   // FIXME: stable encoding
   Record.push_back((unsigned)D->getPropertyImplementation());
   Record.AddDeclarationName(D->getGetterName());
+  Record.AddSourceLocation(D->getGetterNameLoc());
   Record.AddDeclarationName(D->getSetterName());
+  Record.AddSourceLocation(D->getSetterNameLoc());
   Record.AddDeclRef(D->getGetterMethodDecl());
   Record.AddDeclRef(D->getSetterMethodDecl());
   Record.AddDeclRef(D->getPropertyIvarDecl());
@@ -806,7 +816,6 @@ void ASTDeclWriter::VisitObjCImplDecl(ObjCImplDecl *D) {
 
 void ASTDeclWriter::VisitObjCCategoryImplDecl(ObjCCategoryImplDecl *D) {
   VisitObjCImplDecl(D);
-  Record.AddIdentifierRef(D->getIdentifier());
   Record.AddSourceLocation(D->getCategoryNameLoc());
   Code = serialization::DECL_OBJC_CATEGORY_IMPL;
 }
@@ -1268,8 +1277,6 @@ void ASTDeclWriter::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
 
   VisitCXXMethodDecl(D);
 
-  Record.push_back(D->IsExplicitSpecified);
-
   Code = D->isInheritingConstructor()
              ? serialization::DECL_CXX_INHERITED_CONSTRUCTOR
              : serialization::DECL_CXX_CONSTRUCTOR;
@@ -1285,7 +1292,6 @@ void ASTDeclWriter::VisitCXXDestructorDecl(CXXDestructorDecl *D) {
 
 void ASTDeclWriter::VisitCXXConversionDecl(CXXConversionDecl *D) {
   VisitCXXMethodDecl(D);
-  Record.push_back(D->IsExplicitSpecified);
   Code = serialization::DECL_CXX_CONVERSION;
 }
 
@@ -2023,6 +2029,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // StorageClass
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Inline
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // InlineSpecified
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // ExplicitSpecified
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // VirtualAsWritten
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // Pure
   Abv->Add(BitCodeAbbrevOp(0));                         // HasInheritedProto
@@ -2221,6 +2228,11 @@ void ASTRecordWriter::AddFunctionDefinition(const FunctionDecl *FD) {
   Writer->ClearSwitchCaseIDs();
 
   assert(FD->doesThisDeclarationHaveABody());
+  bool ModulesCodegen = Writer->Context->getLangOpts().ModulesCodegen &&
+                        Writer->WritingModule && !FD->isDependentContext();
+  Record->push_back(ModulesCodegen);
+  if (ModulesCodegen)
+    Writer->ModularCodegenDecls.push_back(Writer->GetDeclRef(FD));
   if (auto *CD = dyn_cast<CXXConstructorDecl>(FD)) {
     Record->push_back(CD->getNumCtorInitializers());
     if (CD->getNumCtorInitializers())
diff --git a/lib/Serialization/ASTWriterStmt.cpp b/lib/Serialization/ASTWriterStmt.cpp
index 01fd98ceadb2c..1a2edac658865 100644
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@@ -315,6 +315,11 @@ void ASTStmtWriter::VisitCoawaitExpr(CoawaitExpr *S) {
   llvm_unreachable("unimplemented");
 }
 
+void ASTStmtWriter::VisitDependentCoawaitExpr(DependentCoawaitExpr *S) {
+  // FIXME: Implement coroutine serialization.
+  llvm_unreachable("unimplemented");
+}
+
 void ASTStmtWriter::VisitCoyieldExpr(CoyieldExpr *S) {
   // FIXME: Implement coroutine serialization.
   llvm_unreachable("unimplemented");
@@ -645,7 +650,7 @@ void ASTStmtWriter::VisitBinaryOperator(BinaryOperator *E) {
   Record.AddStmt(E->getRHS());
   Record.push_back(E->getOpcode()); // FIXME: stable encoding
   Record.AddSourceLocation(E->getOperatorLoc());
-  Record.push_back(E->isFPContractable());
+  Record.push_back(E->getFPFeatures().getInt());
   Code = serialization::EXPR_BINARY_OPERATOR;
 }
 
@@ -1213,7 +1218,7 @@ void ASTStmtWriter::VisitCXXOperatorCallExpr(CXXOperatorCallExpr *E) {
   VisitCallExpr(E);
   Record.push_back(E->getOperator());
   Record.AddSourceRange(E->Range);
-  Record.push_back(E->isFPContractable());
+  Record.push_back(E->getFPFeatures().getInt());
   Code = serialization::EXPR_CXX_OPERATOR_CALL;
 }
 
@@ -1794,6 +1799,7 @@ void OMPClauseWriter::writeClause(OMPClause *C) {
 }
 
 void OMPClauseWriter::VisitOMPClauseWithPreInit(OMPClauseWithPreInit *C) {
+  Record.push_back(C->getCaptureRegion());
   Record.AddStmt(C->getPreInitStmt());
 }
 
@@ -1803,6 +1809,7 @@ void OMPClauseWriter::VisitOMPClauseWithPostUpdate(OMPClauseWithPostUpdate *C) {
 }
 
 void OMPClauseWriter::VisitOMPIfClause(OMPIfClause *C) {
+  VisitOMPClauseWithPreInit(C);
   Record.push_back(C->getNameModifier());
   Record.AddSourceLocation(C->getNameModifierLoc());
   Record.AddSourceLocation(C->getColonLoc());
@@ -1816,6 +1823,7 @@ void OMPClauseWriter::VisitOMPFinalClause(OMPFinalClause *C) {
 }
 
 void OMPClauseWriter::VisitOMPNumThreadsClause(OMPNumThreadsClause *C) {
+  VisitOMPClauseWithPreInit(C);
   Record.AddStmt(C->getNumThreads());
   Record.AddSourceLocation(C->getLParenLoc());
 }
@@ -2064,11 +2072,13 @@ void OMPClauseWriter::VisitOMPMapClause(OMPMapClause *C) {
 }
 
 void OMPClauseWriter::VisitOMPNumTeamsClause(OMPNumTeamsClause *C) {
+  VisitOMPClauseWithPreInit(C);
   Record.AddStmt(C->getNumTeams());
   Record.AddSourceLocation(C->getLParenLoc());
 }
 
 void OMPClauseWriter::VisitOMPThreadLimitClause(OMPThreadLimitClause *C) {
+  VisitOMPClauseWithPreInit(C);
   Record.AddStmt(C->getThreadLimit());
   Record.AddSourceLocation(C->getLParenLoc());
 }
@@ -2236,6 +2246,8 @@ void ASTStmtWriter::VisitOMPLoopDirective(OMPLoopDirective *D) {
   if (isOpenMPLoopBoundSharingDirective(D->getDirectiveKind())) {
     Record.AddStmt(D->getPrevLowerBoundVariable());
     Record.AddStmt(D->getPrevUpperBoundVariable());
+    Record.AddStmt(D->getDistInc());
+    Record.AddStmt(D->getPrevEnsureUpperBound());
   }
   for (auto I : D->counters()) {
     Record.AddStmt(I);
diff --git a/lib/Serialization/GeneratePCH.cpp b/lib/Serialization/GeneratePCH.cpp
index 7f1b75055b455..2e0076521f9c0 100644
--- a/lib/Serialization/GeneratePCH.cpp
+++ b/lib/Serialization/GeneratePCH.cpp
@@ -27,10 +27,11 @@ PCHGenerator::PCHGenerator(
     ArrayRef<std::shared_ptr<ModuleFileExtension>> Extensions,
     bool AllowASTWithErrors, bool IncludeTimestamps)
     : PP(PP), OutputFile(OutputFile), isysroot(isysroot.str()),
-      SemaPtr(nullptr), Buffer(Buffer), Stream(Buffer->Data),
-      Writer(Stream, Extensions, IncludeTimestamps),
+      SemaPtr(nullptr), Buffer(std::move(Buffer)), Stream(this->Buffer->Data),
+      Writer(Stream, this->Buffer->Data, PP.getPCMCache(), Extensions,
+             IncludeTimestamps),
       AllowASTWithErrors(AllowASTWithErrors) {
-  Buffer->IsComplete = false;
+  this->Buffer->IsComplete = false;
 }
 
 PCHGenerator::~PCHGenerator() {
diff --git a/lib/Serialization/GlobalModuleIndex.cpp b/lib/Serialization/GlobalModuleIndex.cpp
index ae5796ede126e..6978e7e09774f 100644
--- a/lib/Serialization/GlobalModuleIndex.cpp
+++ b/lib/Serialization/GlobalModuleIndex.cpp
@@ -376,6 +376,15 @@ namespace {
     /// \brief The set of modules on which this module depends. Each entry is
     /// a module ID.
     SmallVector<unsigned, 4> Dependencies;
+    ASTFileSignature Signature;
+  };
+
+  struct ImportedModuleFileInfo {
+    off_t StoredSize;
+    time_t StoredModTime;
+    ASTFileSignature StoredSignature;
+    ImportedModuleFileInfo(off_t Size, time_t ModTime, ASTFileSignature Sig)
+        : StoredSize(Size), StoredModTime(ModTime), StoredSignature(Sig) {}
   };
 
   /// \brief Builder that generates the global module index file.
@@ -383,12 +392,20 @@ namespace {
     FileManager &FileMgr;
     const PCHContainerReader &PCHContainerRdr;
 
-    /// \brief Mapping from files to module file information.
+    /// Mapping from files to module file information.
     typedef llvm::MapVector<const FileEntry *, ModuleFileInfo> ModuleFilesMap;
 
-    /// \brief Information about each of the known module files.
+    /// Information about each of the known module files.
     ModuleFilesMap ModuleFiles;
 
+    /// \brief Mapping from the imported module file to the imported
+    /// information.
+    typedef std::multimap<const FileEntry *, ImportedModuleFileInfo>
+        ImportedModuleFilesMap;
+
+    /// \brief Information about each importing of a module file.
+    ImportedModuleFilesMap ImportedModuleFiles;
+
     /// \brief Mapping from identifiers to the list of module file IDs that
     /// consider this identifier to be interesting.
     typedef llvm::StringMap<SmallVector<unsigned, 2> > InterestingIdentifierMap;
@@ -424,7 +441,8 @@ namespace {
     bool loadModuleFile(const FileEntry *File);
 
     /// \brief Write the index to the given bitstream.
-    void writeIndex(llvm::BitstreamWriter &Stream);
+    /// \returns true if an error occurred, false otherwise.
+    bool writeIndex(llvm::BitstreamWriter &Stream);
   };
 }
 
@@ -515,7 +533,7 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
   unsigned ID = getModuleFileInfo(File).ID;
 
   // Search for the blocks and records we care about.
-  enum { Other, ControlBlock, ASTBlock } State = Other;
+  enum { Other, ControlBlock, ASTBlock, DiagnosticOptionsBlock } State = Other;
   bool Done = false;
   while (!Done) {
     llvm::BitstreamEntry Entry = InStream.advance();
@@ -553,6 +571,15 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
         continue;
       }
 
+      if (Entry.ID == UNHASHED_CONTROL_BLOCK_ID) {
+        if (InStream.EnterSubBlock(UNHASHED_CONTROL_BLOCK_ID))
+          return true;
+
+        // Found the Diagnostic Options block.
+        State = DiagnosticOptionsBlock;
+        continue;
+      }
+
       if (InStream.SkipBlock())
         return true;
 
@@ -587,7 +614,10 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
 
         // Skip the stored signature.
         // FIXME: we could read the signature out of the import and validate it.
-        Idx++;
+        ASTFileSignature StoredSignature = {
+            {{(uint32_t)Record[Idx++], (uint32_t)Record[Idx++],
+              (uint32_t)Record[Idx++], (uint32_t)Record[Idx++],
+              (uint32_t)Record[Idx++]}}};
 
         // Retrieve the imported file name.
         unsigned Length = Record[Idx++];
@@ -599,11 +629,16 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
         const FileEntry *DependsOnFile
           = FileMgr.getFile(ImportedFile, /*openFile=*/false,
                             /*cacheFailure=*/false);
-        if (!DependsOnFile ||
-            (StoredSize != DependsOnFile->getSize()) ||
-            (StoredModTime != DependsOnFile->getModificationTime()))
+
+        if (!DependsOnFile)
           return true;
 
+        // Save the information in ImportedModuleFileInfo so we can verify after
+        // loading all pcms.
+        ImportedModuleFiles.insert(std::make_pair(
+            DependsOnFile, ImportedModuleFileInfo(StoredSize, StoredModTime,
+                                                  StoredSignature)));
+
         // Record the dependency.
         unsigned DependsOnID = getModuleFileInfo(DependsOnFile).ID;
         getModuleFileInfo(File).Dependencies.push_back(DependsOnID);
@@ -632,6 +667,12 @@ bool GlobalModuleIndexBuilder::loadModuleFile(const FileEntry *File) {
       }
     }
 
+    // Get Signature.
+    if (State == DiagnosticOptionsBlock && Code == SIGNATURE)
+      getModuleFileInfo(File).Signature = {
+          {{(uint32_t)Record[0], (uint32_t)Record[1], (uint32_t)Record[2],
+            (uint32_t)Record[3], (uint32_t)Record[4]}}};
+
     // We don't care about this record.
   }
 
@@ -680,7 +721,20 @@ public:
 
 }
 
-void GlobalModuleIndexBuilder::writeIndex(llvm::BitstreamWriter &Stream) {
+bool GlobalModuleIndexBuilder::writeIndex(llvm::BitstreamWriter &Stream) {
+  for (auto MapEntry : ImportedModuleFiles) {
+    auto *File = MapEntry.first;
+    ImportedModuleFileInfo &Info = MapEntry.second;
+    if (getModuleFileInfo(File).Signature) {
+      if (getModuleFileInfo(File).Signature != Info.StoredSignature)
+        // Verify Signature.
+        return true;
+    } else if (Info.StoredSize != File->getSize() ||
+               Info.StoredModTime != File->getModificationTime())
+      // Verify Size and ModTime.
+      return true;
+  }
+
   using namespace llvm;
   
   // Emit the file header.
@@ -756,6 +810,7 @@ void GlobalModuleIndexBuilder::writeIndex(llvm::BitstreamWriter &Stream) {
   }
 
   Stream.ExitBlock();
+  return false;
 }
 
 GlobalModuleIndex::ErrorCode
@@ -816,7 +871,8 @@ GlobalModuleIndex::writeIndex(FileManager &FileMgr,
   SmallVector<char, 16> OutputBuffer;
   {
     llvm::BitstreamWriter OutputStream(OutputBuffer);
-    Builder.writeIndex(OutputStream);
+    if (Builder.writeIndex(OutputStream))
+      return EC_IOError;
   }
 
   // Write the global index file to a temporary file.
diff --git a/lib/Serialization/Module.cpp b/lib/Serialization/Module.cpp
index 72b08610bb4d3..5a44d26fe3998 100644
--- a/lib/Serialization/Module.cpp
+++ b/lib/Serialization/Module.cpp
@@ -19,28 +19,6 @@ using namespace clang;
 using namespace serialization;
 using namespace reader;
 
-ModuleFile::ModuleFile(ModuleKind Kind, unsigned Generation)
-  : Kind(Kind), File(nullptr), Signature(0), DirectlyImported(false),
-    Generation(Generation), SizeInBits(0),
-    LocalNumSLocEntries(0), SLocEntryBaseID(0),
-    SLocEntryBaseOffset(0), SLocEntryOffsets(nullptr),
-    LocalNumIdentifiers(0),
-    IdentifierOffsets(nullptr), BaseIdentifierID(0),
-    IdentifierTableData(nullptr), IdentifierLookupTable(nullptr),
-    LocalNumMacros(0), MacroOffsets(nullptr),
-    BasePreprocessedEntityID(0),
-    PreprocessedEntityOffsets(nullptr), NumPreprocessedEntities(0),
-    LocalNumHeaderFileInfos(0), 
-    HeaderFileInfoTableData(nullptr), HeaderFileInfoTable(nullptr),
-    LocalNumSubmodules(0), BaseSubmoduleID(0),
-    LocalNumSelectors(0), SelectorOffsets(nullptr), BaseSelectorID(0),
-    SelectorLookupTableData(nullptr), SelectorLookupTable(nullptr),
-    LocalNumDecls(0), DeclOffsets(nullptr), BaseDeclID(0),
-    FileSortedDecls(nullptr), NumFileSortedDecls(0),
-    ObjCCategoriesMap(nullptr), LocalNumObjCCategoriesInMap(0),
-    LocalNumTypes(0), TypeOffsets(nullptr), BaseTypeIndex(0)
-{}
-
 ModuleFile::~ModuleFile() {
   delete static_cast<ASTIdentifierLookupTable *>(IdentifierLookupTable);
   delete static_cast<HeaderFileInfoLookupTable *>(HeaderFileInfoTable);
diff --git a/lib/Serialization/ModuleManager.cpp b/lib/Serialization/ModuleManager.cpp
index 722b547e803e4..1dee4d0698616 100644
--- a/lib/Serialization/ModuleManager.cpp
+++ b/lib/Serialization/ModuleManager.cpp
@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 #include "clang/Serialization/ModuleManager.h"
+#include "clang/Basic/MemoryBufferCache.h"
 #include "clang/Frontend/PCHContainerOperations.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/ModuleMap.h"
@@ -27,7 +28,7 @@
 using namespace clang;
 using namespace serialization;
 
-ModuleFile *ModuleManager::lookup(StringRef Name) {
+ModuleFile *ModuleManager::lookup(StringRef Name) const {
   const FileEntry *Entry = FileMgr.getFile(Name, /*openFile=*/false,
                                            /*cacheFailure=*/false);
   if (Entry)
@@ -36,9 +37,8 @@ ModuleFile *ModuleManager::lookup(StringRef Name) {
   return nullptr;
 }
 
-ModuleFile *ModuleManager::lookup(const FileEntry *File) {
-  llvm::DenseMap<const FileEntry *, ModuleFile *>::iterator Known
-    = Modules.find(File);
+ModuleFile *ModuleManager::lookup(const FileEntry *File) const {
+  auto Known = Modules.find(File);
   if (Known == Modules.end())
     return nullptr;
 
@@ -52,6 +52,30 @@ ModuleManager::lookupBuffer(StringRef Name) {
   return std::move(InMemoryBuffers[Entry]);
 }
 
+static bool checkSignature(ASTFileSignature Signature,
+                           ASTFileSignature ExpectedSignature,
+                           std::string &ErrorStr) {
+  if (!ExpectedSignature || Signature == ExpectedSignature)
+    return false;
+
+  ErrorStr =
+      Signature ? "signature mismatch" : "could not read module signature";
+  return true;
+}
+
+static void updateModuleImports(ModuleFile &MF, ModuleFile *ImportedBy,
+                                SourceLocation ImportLoc) {
+  if (ImportedBy) {
+    MF.ImportedBy.insert(ImportedBy);
+    ImportedBy->Imports.insert(&MF);
+  } else {
+    if (!MF.DirectlyImported)
+      MF.ImportLoc = ImportLoc;
+
+    MF.DirectlyImported = true;
+  }
+}
+
 ModuleManager::AddModuleResult
 ModuleManager::addModule(StringRef FileName, ModuleKind Type,
                          SourceLocation ImportLoc, ModuleFile *ImportedBy,
@@ -84,141 +108,133 @@ ModuleManager::addModule(StringRef FileName, ModuleKind Type,
   }
 
   // Check whether we already loaded this module, before
-  ModuleFile *ModuleEntry = Modules[Entry];
-  bool NewModule = false;
-  if (!ModuleEntry) {
-    // Allocate a new module.
-    NewModule = true;
-    ModuleEntry = new ModuleFile(Type, Generation);
-    ModuleEntry->Index = Chain.size();
-    ModuleEntry->FileName = FileName.str();
-    ModuleEntry->File = Entry;
-    ModuleEntry->ImportLoc = ImportLoc;
-    ModuleEntry->InputFilesValidationTimestamp = 0;
-
-    if (ModuleEntry->Kind == MK_ImplicitModule) {
-      std::string TimestampFilename = ModuleEntry->getTimestampFilename();
-      vfs::Status Status;
-      // A cached stat value would be fine as well.
-      if (!FileMgr.getNoncachedStatValue(TimestampFilename, Status))
-        ModuleEntry->InputFilesValidationTimestamp =
-            llvm::sys::toTimeT(Status.getLastModificationTime());
-    }
-
-    // Load the contents of the module
-    if (std::unique_ptr<llvm::MemoryBuffer> Buffer = lookupBuffer(FileName)) {
-      // The buffer was already provided for us.
-      ModuleEntry->Buffer = std::move(Buffer);
-    } else {
-      // Open the AST file.
-      llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buf(
-          (std::error_code()));
-      if (FileName == "-") {
-        Buf = llvm::MemoryBuffer::getSTDIN();
-      } else {
-        // Leave the FileEntry open so if it gets read again by another
-        // ModuleManager it must be the same underlying file.
-        // FIXME: Because FileManager::getFile() doesn't guarantee that it will
-        // give us an open file, this may not be 100% reliable.
-        Buf = FileMgr.getBufferForFile(ModuleEntry->File,
-                                       /*IsVolatile=*/false,
-                                       /*ShouldClose=*/false);
-      }
-
-      if (!Buf) {
-        ErrorStr = Buf.getError().message();
-        delete ModuleEntry;
-        return Missing;
-      }
-
-      ModuleEntry->Buffer = std::move(*Buf);
-    }
+  if (ModuleFile *ModuleEntry = Modules.lookup(Entry)) {
+    // Check the stored signature.
+    if (checkSignature(ModuleEntry->Signature, ExpectedSignature, ErrorStr))
+      return OutOfDate;
 
-    // Initialize the stream.
-    ModuleEntry->Data = PCHContainerRdr.ExtractPCH(*ModuleEntry->Buffer);
+    Module = ModuleEntry;
+    updateModuleImports(*ModuleEntry, ImportedBy, ImportLoc);
+    return AlreadyLoaded;
   }
 
-  if (ExpectedSignature) {
-    // If we've not read the control block yet, read the signature eagerly now
-    // so that we can check it.
-    if (!ModuleEntry->Signature)
-      ModuleEntry->Signature = ReadSignature(ModuleEntry->Data);
+  // Allocate a new module.
+  auto NewModule = llvm::make_unique<ModuleFile>(Type, Generation);
+  NewModule->Index = Chain.size();
+  NewModule->FileName = FileName.str();
+  NewModule->File = Entry;
+  NewModule->ImportLoc = ImportLoc;
+  NewModule->InputFilesValidationTimestamp = 0;
+
+  if (NewModule->Kind == MK_ImplicitModule) {
+    std::string TimestampFilename = NewModule->getTimestampFilename();
+    vfs::Status Status;
+    // A cached stat value would be fine as well.
+    if (!FileMgr.getNoncachedStatValue(TimestampFilename, Status))
+      NewModule->InputFilesValidationTimestamp =
+          llvm::sys::toTimeT(Status.getLastModificationTime());
+  }
 
-    if (ModuleEntry->Signature != ExpectedSignature) {
-      ErrorStr = ModuleEntry->Signature ? "signature mismatch"
-                                        : "could not read module signature";
+  // Load the contents of the module
+  if (std::unique_ptr<llvm::MemoryBuffer> Buffer = lookupBuffer(FileName)) {
+    // The buffer was already provided for us.
+    NewModule->Buffer = &PCMCache->addBuffer(FileName, std::move(Buffer));
+  } else if (llvm::MemoryBuffer *Buffer = PCMCache->lookupBuffer(FileName)) {
+    NewModule->Buffer = Buffer;
+  } else {
+    // Open the AST file.
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Buf((std::error_code()));
+    if (FileName == "-") {
+      Buf = llvm::MemoryBuffer::getSTDIN();
+    } else {
+      // Leave the FileEntry open so if it gets read again by another
+      // ModuleManager it must be the same underlying file.
+      // FIXME: Because FileManager::getFile() doesn't guarantee that it will
+      // give us an open file, this may not be 100% reliable.
+      Buf = FileMgr.getBufferForFile(NewModule->File,
+                                     /*IsVolatile=*/false,
+                                     /*ShouldClose=*/false);
+    }
 
-      if (NewModule)
-        delete ModuleEntry;
-      return OutOfDate;
+    if (!Buf) {
+      ErrorStr = Buf.getError().message();
+      return Missing;
     }
-  }
 
-  if (ImportedBy) {
-    ModuleEntry->ImportedBy.insert(ImportedBy);
-    ImportedBy->Imports.insert(ModuleEntry);
-  } else {
-    if (!ModuleEntry->DirectlyImported)
-      ModuleEntry->ImportLoc = ImportLoc;
-    
-    ModuleEntry->DirectlyImported = true;
+    NewModule->Buffer = &PCMCache->addBuffer(FileName, std::move(*Buf));
   }
 
-  Module = ModuleEntry;
+  // Initialize the stream.
+  NewModule->Data = PCHContainerRdr.ExtractPCH(*NewModule->Buffer);
+
+  // Read the signature eagerly now so that we can check it.  Avoid calling
+  // ReadSignature unless there's something to check though.
+  if (ExpectedSignature && checkSignature(ReadSignature(NewModule->Data),
+                                          ExpectedSignature, ErrorStr)) {
+    // Try to remove the buffer.  If it can't be removed, then it was already
+    // validated by this process.
+    if (!PCMCache->tryToRemoveBuffer(NewModule->FileName))
+      FileMgr.invalidateCache(NewModule->File);
+    return OutOfDate;
+  }
 
-  if (!NewModule)
-    return AlreadyLoaded;
+  // We're keeping this module.  Store it everywhere.
+  Module = Modules[Entry] = NewModule.get();
 
-  assert(!Modules[Entry] && "module loaded twice");
-  Modules[Entry] = ModuleEntry;
+  updateModuleImports(*NewModule, ImportedBy, ImportLoc);
 
-  Chain.push_back(ModuleEntry);
-  if (!ModuleEntry->isModule())
-    PCHChain.push_back(ModuleEntry);
+  if (!NewModule->isModule())
+    PCHChain.push_back(NewModule.get());
   if (!ImportedBy)
-    Roots.push_back(ModuleEntry);
+    Roots.push_back(NewModule.get());
 
+  Chain.push_back(std::move(NewModule));
   return NewlyLoaded;
 }
 
 void ModuleManager::removeModules(
-    ModuleIterator first, ModuleIterator last,
+    ModuleIterator First,
     llvm::SmallPtrSetImpl<ModuleFile *> &LoadedSuccessfully,
     ModuleMap *modMap) {
-  if (first == last)
+  auto Last = end();
+  if (First == Last)
     return;
 
+
   // Explicitly clear VisitOrder since we might not notice it is stale.
   VisitOrder.clear();
 
   // Collect the set of module file pointers that we'll be removing.
-  llvm::SmallPtrSet<ModuleFile *, 4> victimSet(first, last);
+  llvm::SmallPtrSet<ModuleFile *, 4> victimSet(
+      (llvm::pointer_iterator<ModuleIterator>(First)),
+      (llvm::pointer_iterator<ModuleIterator>(Last)));
 
   auto IsVictim = [&](ModuleFile *MF) {
     return victimSet.count(MF);
   };
   // Remove any references to the now-destroyed modules.
-  for (unsigned i = 0, n = Chain.size(); i != n; ++i) {
-    Chain[i]->ImportedBy.remove_if(IsVictim);
+  for (auto I = begin(); I != First; ++I) {
+    I->Imports.remove_if(IsVictim);
+    I->ImportedBy.remove_if(IsVictim);
   }
   Roots.erase(std::remove_if(Roots.begin(), Roots.end(), IsVictim),
               Roots.end());
 
   // Remove the modules from the PCH chain.
-  for (auto I = first; I != last; ++I) {
-    if (!(*I)->isModule()) {
-      PCHChain.erase(std::find(PCHChain.begin(), PCHChain.end(), *I),
+  for (auto I = First; I != Last; ++I) {
+    if (!I->isModule()) {
+      PCHChain.erase(std::find(PCHChain.begin(), PCHChain.end(), &*I),
                      PCHChain.end());
       break;
     }
   }
 
   // Delete the modules and erase them from the various structures.
-  for (ModuleIterator victim = first; victim != last; ++victim) {
-    Modules.erase((*victim)->File);
+  for (ModuleIterator victim = First; victim != Last; ++victim) {
+    Modules.erase(victim->File);
 
     if (modMap) {
-      StringRef ModuleName = (*victim)->ModuleName;
+      StringRef ModuleName = victim->ModuleName;
       if (Module *mod = modMap->findModule(ModuleName)) {
         mod->setASTFile(nullptr);
       }
@@ -227,14 +243,17 @@ void ModuleManager::removeModules(
     // Files that didn't make it through ReadASTCore successfully will be
     // rebuilt (or there was an error). Invalidate them so that we can load the
     // new files that will be renamed over the old ones.
-    if (LoadedSuccessfully.count(*victim) == 0)
-      FileMgr.invalidateCache((*victim)->File);
-
-    delete *victim;
+    //
+    // The PCMCache tracks whether the module was successfully loaded in another
+    // thread/context; in that case, it won't need to be rebuilt (and we can't
+    // safely invalidate it anyway).
+    if (LoadedSuccessfully.count(&*victim) == 0 &&
+        !PCMCache->tryToRemoveBuffer(victim->FileName))
+      FileMgr.invalidateCache(victim->File);
   }
 
-  // Remove the modules from the chain.
-  Chain.erase(first, last);
+  // Delete the modules.
+  Chain.erase(Chain.begin() + (First - begin()), Chain.end());
 }
 
 void
@@ -274,11 +293,9 @@ void ModuleManager::setGlobalIndex(GlobalModuleIndex *Index) {
 
   // Notify the global module index about all of the modules we've already
   // loaded.
-  for (unsigned I = 0, N = Chain.size(); I != N; ++I) {
-    if (!GlobalIndex->loadedModuleFile(Chain[I])) {
-      ModulesInCommonWithGlobalIndex.push_back(Chain[I]);
-    }
-  }
+  for (ModuleFile &M : *this)
+    if (!GlobalIndex->loadedModuleFile(&M))
+      ModulesInCommonWithGlobalIndex.push_back(&M);
 }
 
 void ModuleManager::moduleFileAccepted(ModuleFile *MF) {
@@ -288,16 +305,12 @@ void ModuleManager::moduleFileAccepted(ModuleFile *MF) {
   ModulesInCommonWithGlobalIndex.push_back(MF);
 }
 
-ModuleManager::ModuleManager(FileManager &FileMgr,
+ModuleManager::ModuleManager(FileManager &FileMgr, MemoryBufferCache &PCMCache,
                              const PCHContainerReader &PCHContainerRdr)
-    : FileMgr(FileMgr), PCHContainerRdr(PCHContainerRdr), GlobalIndex(),
-      FirstVisitState(nullptr) {}
+    : FileMgr(FileMgr), PCMCache(&PCMCache), PCHContainerRdr(PCHContainerRdr),
+      GlobalIndex(), FirstVisitState(nullptr) {}
 
-ModuleManager::~ModuleManager() {
-  for (unsigned i = 0, e = Chain.size(); i != e; ++i)
-    delete Chain[e - i - 1];
-  delete FirstVisitState;
-}
+ModuleManager::~ModuleManager() { delete FirstVisitState; }
 
 void ModuleManager::visit(llvm::function_ref<bool(ModuleFile &M)> Visitor,
                           llvm::SmallPtrSetImpl<ModuleFile *> *ModuleFilesHit) {
@@ -314,11 +327,11 @@ void ModuleManager::visit(llvm::function_ref<bool(ModuleFile &M)> Visitor,
     Queue.reserve(N);
     llvm::SmallVector<unsigned, 4> UnusedIncomingEdges;
     UnusedIncomingEdges.resize(size());
-    for (ModuleFile *M : llvm::reverse(*this)) {
-      unsigned Size = M->ImportedBy.size();
-      UnusedIncomingEdges[M->Index] = Size;
+    for (ModuleFile &M : llvm::reverse(*this)) {
+      unsigned Size = M.ImportedBy.size();
+      UnusedIncomingEdges[M.Index] = Size;
       if (!Size)
-        Queue.push_back(M);
+        Queue.push_back(&M);
     }
 
     // Traverse the graph, making sure to visit a module before visiting any
@@ -433,7 +446,7 @@ namespace llvm {
   struct GraphTraits<ModuleManager> {
     typedef ModuleFile *NodeRef;
     typedef llvm::SetVector<ModuleFile *>::const_iterator ChildIteratorType;
-    typedef ModuleManager::ModuleConstIterator nodes_iterator;
+    typedef pointer_iterator<ModuleManager::ModuleConstIterator> nodes_iterator;
 
     static ChildIteratorType child_begin(NodeRef Node) {
       return Node->Imports.begin();
@@ -444,11 +457,11 @@ namespace llvm {
     }
     
     static nodes_iterator nodes_begin(const ModuleManager &Manager) {
-      return Manager.begin();
+      return nodes_iterator(Manager.begin());
     }
     
     static nodes_iterator nodes_end(const ModuleManager &Manager) {
-      return Manager.end();
+      return nodes_iterator(Manager.end());
     }
   };