[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, 8 insertions, 0 deletions

diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 36c8b106c7b..497ae34895e 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -357,6 +357,14 @@ bool TargetInfo::initFeatureMap(
   return true;
 }
 
+TargetInfo::CallingConvKind
+TargetInfo::getCallingConvKind(bool ClangABICompat4) const {
+  if (getCXXABI() != TargetCXXABI::Microsoft &&
+      (ClangABICompat4 || getTriple().getOS() == llvm::Triple::PS4))
+    return CCK_ClangABI4OrPS4;
+  return CCK_Default;
+}
+
 LangAS TargetInfo::getOpenCLTypeAddrSpace(OpenCLTypeKind TK) const {
   switch (TK) {
   case OCLTK_Image: