objc-gc: Adds support for "weak" property attribute under GC.

// rdar://10073896


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@139203 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Sema/SemaObjCProperty.cpp

@@ -594,6 +594,12 @@ Decl *Sema::ActOnPropertyImplDecl(Scope *S,
     ObjCPropertyDecl::PropertyAttributeKind kind 
       = property->getPropertyAttributes();
     QualType PropType = Context.getCanonicalType(property->getType());
+    bool PropertyIsGCWeak = (kind & ObjCPropertyDecl::OBJC_PR_weak &&
+                             !getLangOptions().ObjCAutoRefCount &&
+                             getLangOptions().getGCMode() != 
+                             LangOptions::NonGC);
+    if (PropertyIsGCWeak)
+      PropType = Context.getObjCGCQualType(PropType, Qualifiers::Weak);
     QualType PropertyIvarType = PropType;
     if (PropType->isReferenceType())
       PropertyIvarType = cast<ReferenceType>(PropType)->getPointeeType();

test/CodeGenObjC/gc-weak-attribute.m

@@ -0,0 +1,28 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fobjc-gc -fobjc-nonfragile-abi -emit-llvm -o - %s | FileCheck %s
+// rdar://10073896
+
+@interface I
+{
+  __weak id wObject;
+}
+@property (readwrite, weak) id representedObject;
+@property (readwrite, weak) id wObject;
+@property (readwrite, weak) __weak id wRandom;
+@property (readwrite, assign) __weak id wAnother;
+@end
+
+@implementation I
+@synthesize representedObject;
+@synthesize wObject;
+@synthesize wRandom;
+@synthesize wAnother;
+@end
+// CHECK:  call i8* @objc_read_weak
+// CHECK:  call i8* @objc_assign_weak
+// CHECK:  call i8* @objc_read_weak
+// CHECK:  call i8* @objc_assign_weak
+// CHECK:  call i8* @objc_read_weak
+// CHECK:  call i8* @objc_assign_weak
+// CHECK:  call i8* @objc_read_weak
+// CHECK:  call i8* @objc_assign_weak
+