diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -1334,7 +1334,8 @@
 void CodeGenFunction::EmitAggregateStore(llvm::Value *Val, Address Dest,
                                          bool DestIsVolatile) {
   // Prefer scalar stores to first-class aggregate stores.
-  if (llvm::StructType *STy = dyn_cast<llvm::StructType>(Val->getType())) {
+  llvm::StructType *STy = dyn_cast<llvm::StructType>(Val->getType());
+  if (STy && STy->isLayoutIdentical(cast<llvm::StructType>(Dest.getElementType()))) {
     for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
       Address EltPtr = Builder.CreateStructGEP(Dest, i);
       llvm::Value *Elt = Builder.CreateExtractValue(Val, i);