Make functions returning a struct indirectly evaluate the returned struct
directly into the sret pointer. This is an optimization in C, but is required
for correctness in C++ for classes with a non-trivial copy constructor.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90526 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 1e952f9..88f02a9 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -179,9 +179,6 @@
AllocaInsertPt->setName("allocapt");
ReturnBlock = createBasicBlock("return");
- ReturnValue = 0;
- if (!RetTy->isVoidType())
- ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
Builder.SetInsertPoint(EntryBB);
@@ -204,6 +201,19 @@
// FIXME: Leaked.
CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
+
+ if (RetTy->isVoidType()) {
+ // Void type; nothing to return.
+ ReturnValue = 0;
+ } else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
+ hasAggregateLLVMType(CurFnInfo->getReturnType())) {
+ // Indirect aggregate return; emit returned value directly into sret slot.
+ // This reduces code size, and is also affects correctness in C++.
+ ReturnValue = CurFn->arg_begin();
+ } else {
+ ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
+ }
+
EmitFunctionProlog(*CurFnInfo, CurFn, Args);
// If any of the arguments have a variably modified type, make sure to