1 files changed, 19 insertions, 4 deletions
diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index c3709bf2e447..38d7344572d3 100644
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -1929,7 +1929,7 @@ void CodeGenModule::ConstructAttributeList(
       RetAttrs.addAttribute(llvm::Attribute::SExt);
     else if (RetTy->hasUnsignedIntegerRepresentation())
       RetAttrs.addAttribute(llvm::Attribute::ZExt);
-    // FALL THROUGH
+    LLVM_FALLTHROUGH;
   case ABIArgInfo::Direct:
     if (RetAI.getInReg())
       RetAttrs.addAttribute(llvm::Attribute::InReg);
@@ -2014,7 +2014,7 @@ void CodeGenModule::ConstructAttributeList(
         else
           Attrs.addAttribute(llvm::Attribute::ZExt);
       }
-      // FALL THROUGH
+      LLVM_FALLTHROUGH;
     case ABIArgInfo::Direct:
       if (ArgNo == 0 && FI.isChainCall())
         Attrs.addAttribute(llvm::Attribute::Nest);
@@ -2758,6 +2758,12 @@ static llvm::StoreInst *findDominatingStoreToReturnValue(CodeGenFunction &CGF) {
 void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
                                          bool EmitRetDbgLoc,
                                          SourceLocation EndLoc) {
+  if (FI.isNoReturn()) {
+    // Noreturn functions don't return.
+    EmitUnreachable(EndLoc);
+    return;
+  }
+
   if (CurCodeDecl && CurCodeDecl->hasAttr<NakedAttr>()) {
     // Naked functions don't have epilogues.
     Builder.CreateUnreachable();
@@ -3718,7 +3724,8 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
                                  const CGCallee &Callee,
                                  ReturnValueSlot ReturnValue,
                                  const CallArgList &CallArgs,
-                                 llvm::Instruction **callOrInvoke) {
+                                 llvm::Instruction **callOrInvoke,
+                                 SourceLocation Loc) {
   // FIXME: We no longer need the types from CallArgs; lift up and simplify.
 
   assert(Callee.isOrdinary());
@@ -4241,7 +4248,15 @@ RValue CodeGenFunction::EmitCall(const CGFunctionInfo &CallInfo,
       EmitLifetimeEnd(llvm::ConstantInt::get(Int64Ty, UnusedReturnSize),
                       SRetPtr.getPointer());
 
-    Builder.CreateUnreachable();
+    // Strip away the noreturn attribute to better diagnose unreachable UB.
+    if (SanOpts.has(SanitizerKind::Unreachable)) {
+      if (auto *F = CS.getCalledFunction())
+        F->removeFnAttr(llvm::Attribute::NoReturn);
+      CS.removeAttribute(llvm::AttributeList::FunctionIndex,
+                         llvm::Attribute::NoReturn);
+    }
+
+    EmitUnreachable(Loc);
     Builder.ClearInsertionPoint();
 
     // FIXME: For now, emit a dummy basic block because expr emitters in