Re-land the fix for PR7139.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@104446 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 1 deletions

diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index d3bf1645a0..222dcc4b8f 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -472,7 +472,23 @@ void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
   CGM.ErrorUnsupported(S, Type, OmitOnError);
 }
 
-void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
+void
+CodeGenFunction::EmitNullInitialization(llvm::Value *DestPtr, QualType Ty) {
+  // If the type contains a pointer to data member we can't memset it to zero.
+  // Instead, create a null constant and copy it to the destination.
+  if (CGM.getTypes().ContainsPointerToDataMember(Ty)) {
+    llvm::Constant *NullConstant = CGM.EmitNullConstant(Ty);
+    
+    llvm::GlobalVariable *NullVariable = 
+      new llvm::GlobalVariable(CGM.getModule(), NullConstant->getType(),
+                               /*isConstant=*/true, 
+                               llvm::GlobalVariable::PrivateLinkage,
+                               NullConstant, llvm::Twine());
+    EmitAggregateCopy(DestPtr, NullVariable, Ty, /*isVolatile=*/false);
+    return;
+  } 
+  
+
   // Ignore empty classes in C++.
   if (getContext().getLangOptions().CPlusPlus) {
     if (const RecordType *RT = Ty->getAs<RecordType>()) {
@@ -481,6 +497,9 @@ void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
     }
   }
   
+  // Otherwise, just memset the whole thing to zero.  This is legal
+  // because in LLVM, all default initializers (other than the ones we just
+  // handled above) are guaranteed to have a bit pattern of all zeros.
   const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
   if (DestPtr->getType() != BP)
     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");