[ObjC++] Make parameter passing and function return compatible with ObjC

    
ObjC and ObjC++ pass non-trivial structs in a way that is incompatible
with each other. For example:
    
typedef struct {
  id f0;
  __weak id f1;
} S;
    
// this code is compiled in c++.
extern "C" {
  void foo(S s);
}
    
void caller() {
  // the caller passes the parameter indirectly and destructs it.
  foo(S());
}
    
// this function is compiled in c.
// 'a' is passed directly and is destructed in the callee.
void foo(S a) {
}
    
This patch fixes the incompatibility by passing and returning structs
with __strong or weak fields using the C ABI in C++ mode. __strong and
__weak fields in a struct do not cause the struct to be destructed in
the caller and __strong fields do not cause the struct to be passed
indirectly.
    
Also, this patch fixes the microsoft ABI bug mentioned here:
    
https://reviews.llvm.org/D41039?id=128767#inline-364710
    
rdar://problem/38887866
    
Differential Revision: https://reviews.llvm.org/D44908

llvm-svn: 328731

1 files changed, 5 insertions, 3 deletions

diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 77c06f21dfb..ea96a077631 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -2643,9 +2643,11 @@ void ASTContext::adjustExceptionSpec(
 }
 
 bool ASTContext::isParamDestroyedInCallee(QualType T) const {
-  return getTargetInfo().getCXXABI().areArgsDestroyedLeftToRightInCallee() ||
-         T.hasTrivialABIOverride() ||
-         T.isDestructedType() == QualType::DK_nontrivial_c_struct;
+  if (getTargetInfo().getCXXABI().areArgsDestroyedLeftToRightInCallee())
+    return true;
+  if (const auto *RT = T->getBaseElementTypeUnsafe()->getAs<RecordType>())
+    return RT->getDecl()->isParamDestroyedInCallee();
+  return false;
 }
 
 /// getComplexType - Return the uniqued reference to the type for a complex