Don't copy or initialize empty classes. Fixes PR7012.

llvm-svn: 102891

clang/lib/CodeGen/CGExprAgg.cpp

@@ -738,6 +738,14 @@ void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
                                         bool isVolatile) {
   assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
 
+  // Ignore empty classes in C++.
+  if (getContext().getLangOptions().CPlusPlus) {
+    if (const RecordType *RT = Ty->getAs<RecordType>()) {
+      if (cast<CXXRecordDecl>(RT->getDecl())->isEmpty())
+        return;
+    }
+  }
+  
   // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
   // C99 6.5.16.1p3, which states "If the value being stored in an object is
   // read from another object that overlaps in anyway the storage of the first

clang/lib/CodeGen/CodeGenFunction.cpp

@@ -473,6 +473,14 @@ void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
 }
 
 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
+  // Ignore empty classes in C++.
+  if (getContext().getLangOptions().CPlusPlus) {
+    if (const RecordType *RT = Ty->getAs<RecordType>()) {
+      if (cast<CXXRecordDecl>(RT->getDecl())->isEmpty())
+        return;
+    }
+  }
+  
   const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
   if (DestPtr->getType() != BP)
     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");

clang/test/CodeGenCXX/new.cpp

@@ -90,7 +90,7 @@ A* t10() {
   return new(1, 2, 3.45, 100) A;
 }
 
-struct B { };
+struct B { int a; };
 void t11() {
   // CHECK: call noalias i8* @_Znwm
   // CHECK: call void @llvm.memset.p0i8.i64(