Fix an Obj-C++ miscompile when calling an Obj-C method that returns a C++ reference.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@106477 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGExpr.cpp

@@ -1981,10 +1981,17 @@ CodeGenFunction::EmitCXXBindTemporaryLValue(const CXXBindTemporaryExpr *E) {
 }
 
 LValue CodeGenFunction::EmitObjCMessageExprLValue(const ObjCMessageExpr *E) {
-  // Can only get l-value for message expression returning aggregate type
   RValue RV = EmitObjCMessageExpr(E);
-  // FIXME: can this be volatile?
-  return LValue::MakeAddr(RV.getAggregateAddr(), MakeQualifiers(E->getType()));
+  
+  if (!RV.isScalar())
+    return LValue::MakeAddr(RV.getAggregateAddr(),
+                            MakeQualifiers(E->getType()));
+  
+  assert(E->getMethodDecl()->getResultType()->isReferenceType() &&
+         "Can't have a scalar return unless the return type is a "
+         "reference type!");
+  
+  return LValue::MakeAddr(RV.getScalarVal(), MakeQualifiers(E->getType()));
 }
 
 LValue CodeGenFunction::EmitObjCSelectorLValue(const ObjCSelectorExpr *E) {

lib/CodeGen/CGObjC.cpp

@@ -90,11 +90,14 @@ RValue CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E,
   CallArgList Args;
   EmitCallArgs(Args, E->getMethodDecl(), E->arg_begin(), E->arg_end());
 
+  QualType ResultType =
+    E->getMethodDecl() ? E->getMethodDecl()->getResultType() : E->getType();
+
   if (isSuperMessage) {
     // super is only valid in an Objective-C method
     const ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(CurFuncDecl);
     bool isCategoryImpl = isa<ObjCCategoryImplDecl>(OMD->getDeclContext());
-    return Runtime.GenerateMessageSendSuper(*this, Return, E->getType(),
+    return Runtime.GenerateMessageSendSuper(*this, Return, ResultType,
                                             E->getSelector(),
                                             OMD->getClassInterface(),
                                             isCategoryImpl,
@@ -104,7 +107,7 @@ RValue CodeGenFunction::EmitObjCMessageExpr(const ObjCMessageExpr *E,
                                             E->getMethodDecl());
   }
 
-  return Runtime.GenerateMessageSend(*this, Return, E->getType(),
+  return Runtime.GenerateMessageSend(*this, Return, ResultType,
                                      E->getSelector(),
                                      Receiver, Args, OID,
                                      E->getMethodDecl());

lib/CodeGen/CGObjCMac.cpp

@@ -1634,6 +1634,11 @@ CGObjCCommonMac::EmitLegacyMessageSend(CodeGen::CodeGenFunction &CGF,
   const llvm::FunctionType *FTy =
     Types.GetFunctionType(FnInfo, Method ? Method->isVariadic() : false);
 
+  if (Method)
+    assert(CGM.getContext().getCanonicalType(Method->getResultType()) ==
+           CGM.getContext().getCanonicalType(ResultType) &&
+           "Result type mismatch!");
+
   llvm::Constant *Fn = NULL;
   if (CGM.ReturnTypeUsesSret(FnInfo)) {
     Fn = (ObjCABI == 2) ?  ObjCTypes.getSendStretFn2(IsSuper)

test/CodeGenObjCXX/references.mm

@@ -0,0 +1,25 @@
+// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
+
+struct A { ~A(); };
+
+@interface B {
+  A a;
+}
+
+- (const A&)getA;
+@end
+
+@implementation B 
+
+- (const A&)getA {
+  return a;
+}
+
+@end
+
+// CHECK: define void @_Z1fP1B
+// CHECK: objc_msgSend to
+// CHECK: ret void
+void f(B* b) {
+  (void)[b getA];
+}