[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, 3 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index d70debaf85f..254b5175d7b 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -470,6 +470,7 @@ void ASTDeclWriter::VisitRecordDecl(RecordDecl *D) {
   Record.push_back(D->isNonTrivialToPrimitiveCopy());
   Record.push_back(D->isNonTrivialToPrimitiveDestroy());
   Record.push_back(D->canPassInRegisters());
+  Record.push_back(D->isParamDestroyedInCallee());
 
   if (D->getDeclContext() == D->getLexicalDeclContext() &&
       !D->hasAttrs() &&
@@ -1912,6 +1913,8 @@ void ASTWriter::WriteDeclAbbrevs() {
   // isNonTrivialToPrimitiveDestroy
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // canPassInRegisters
+  // isParamDestroyedInCallee
+  Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1));
 
   // DC
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6));   // LexicalOffset