We should not generate __weak write barrier on indirect reference

of a pointer to object; This patch does this odd behavior according to
gcc.

llvm-svn: 65334

2 files changed, 14 insertions, 3 deletions

diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index a621119daef..3aea3e324ba 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -753,6 +753,8 @@ bool Expr::isOBJCGCCandidate() const {
     return false;
   case ObjCIvarRefExprClass:
     return true;
+  case Expr::UnaryOperatorClass:
+    return cast<UnaryOperator>(this)->getSubExpr()->isOBJCGCCandidate();
   case ParenExprClass:
     return cast<ParenExpr>(this)->getSubExpr()->isOBJCGCCandidate();
   case ImplicitCastExprClass:
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index c96265242ac..0449900a0f8 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -669,10 +669,19 @@ LValue CodeGenFunction::EmitUnaryOpLValue(const UnaryOperator *E) {
   case UnaryOperator::Deref:
     {
       QualType T = E->getSubExpr()->getType()->getAsPointerType()->getPointeeType();
-      return LValue::MakeAddr(EmitScalarExpr(E->getSubExpr()),
-                              ExprTy->getAsPointerType()->getPointeeType()
+      LValue LV = LValue::MakeAddr(EmitScalarExpr(E->getSubExpr()),
+                                   ExprTy->getAsPointerType()->getPointeeType()
                                       .getCVRQualifiers(), 
-                              getContext().getObjCGCAttrKind(T));
+                                   getContext().getObjCGCAttrKind(T));
+     // We should not generate __weak write barrier on indirect reference
+     // of a pointer to object; as in void foo (__weak id *param); *param = 0;
+     // But, we continue to generate __strong write barrier on indirect write
+     // into a pointer to object.
+     if (getContext().getLangOptions().ObjC1 &&
+         getContext().getLangOptions().getGCMode() != LangOptions::NonGC &&
+         LV.isObjCWeak())
+       LValue::SetObjCNonGC(LV, !E->isOBJCGCCandidate());
+     return LV;
     }
   case UnaryOperator::Real:
   case UnaryOperator::Imag: