Define weak and __weak to mean ARC-style weak references, even in MRC.

Previously, __weak was silently accepted and ignored in MRC mode.
That makes this a potentially source-breaking change that we have to
roll out cautiously.  Accordingly, for the time being, actual support
for __weak references in MRC is experimental, and the compiler will
reject attempts to actually form such references.  The intent is to
eventually enable the feature by default in all non-GC modes.
(It is, of course, incompatible with ObjC GC's interpretation of
__weak.)

If you like, you can enable this feature with
  -Xclang -fobjc-weak
but like any -Xclang option, this option may be removed at any point,
e.g. if/when it is eventually enabled by default.

This patch also enables the use of the ARC __unsafe_unretained qualifier
in MRC.  Unlike __weak, this is being enabled immediately.  Since
variables are essentially __unsafe_unretained by default in MRC,
the only practical uses are (1) communication and (2) changing the
default behavior of by-value block capture.

As an implementation matter, this means that the ObjC ownership
qualifiers may appear in any ObjC language mode, and so this patch
removes a number of checks for getLangOpts().ObjCAutoRefCount
that were guarding the processing of these qualifiers.  I don't
expect this to be a significant drain on performance; it may even
be faster to just check for these qualifiers directly on a type
(since it's probably in a register anyway) than to do N dependent
loads to grab the LangOptions.

rdar://9674298

llvm-svn: 251041

3 files changed, 145 insertions, 3 deletions

diff --git a/clang/test/CodeGenObjC/blocks.m b/clang/test/CodeGenObjC/blocks.m
index 091331e8b2b..d485bb4053b 100644
--- a/clang/test/CodeGenObjC/blocks.m
+++ b/clang/test/CodeGenObjC/blocks.m
@@ -84,7 +84,7 @@ void test2(Test2 *x) {
   // CHECK:      [[T0:%.*]] = bitcast [[WEAK_T]]* [[WEAKX]] to i8*
   // CHECK:      call void @_Block_object_dispose(i8* [[T0]], i32 8)
 
-  __weak __block Test2 *weakX = x;
+  __attribute__((objc_gc(weak))) __block Test2 *weakX = x;
   test2_helper(^{ [weakX destroy]; });
 }
 
diff --git a/clang/test/CodeGenObjC/mrc-weak.m b/clang/test/CodeGenObjC/mrc-weak.m
new file mode 100644
index 00000000000..f9c4ff1b123
--- /dev/null
+++ b/clang/test/CodeGenObjC/mrc-weak.m
@@ -0,0 +1,142 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -fobjc-runtime=macosx-10.10 -emit-llvm -fblocks -fobjc-weak -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-MODERN
+// RUN: %clang_cc1 -triple i386-apple-darwin10 -fobjc-runtime=macosx-fragile-10.10 -emit-llvm -fblocks -fobjc-weak -o - %s | FileCheck %s -check-prefix=CHECK -check-prefix=CHECK-FRAGILE
+
+@interface Object
+- (instancetype) retain;
+- (void) run;
+@end
+
+// CHECK-MODERN: @OBJC_CLASS_NAME_{{.*}} = {{.*}} c"\01\00"
+// CHECK-MODERN: @"\01l_OBJC_CLASS_RO_$_Foo" = {{.*}} { i32 772
+//   772 == 0x304
+//            ^ HasMRCWeakIvars
+//            ^ HasCXXDestructorOnly
+//              ^ HasCXXStructors
+
+// CHECK-FRAGILE: @OBJC_CLASS_NAME_{{.*}} = {{.*}} c"\01\00"
+// CHECK-FRAGILE: @OBJC_CLASS_Foo = {{.*}} i32 134225921,
+//   134225921 == 0x08002001
+//                   ^ HasMRCWeakIvars
+//                      ^ HasCXXStructors
+//                         ^ Factory
+@interface Foo : Object {
+  __weak id ivar;
+}
+@end
+
+@implementation Foo
+// CHECK-LABEL: define internal void @"\01-[Foo .cxx_destruct]"
+// CHECK: call void @objc_destroyWeak
+@end
+
+
+void test1(__weak id x) {}
+// CHECK-LABEL: define void @test1
+// CHECK:      [[X:%.*]] = alloca i8*,
+// CHECK-NEXT: objc_initWeak
+// CHECK-NEXT: objc_destroyWeak
+// CHECK-NEXT: ret void
+
+void test2(id y) {
+  __weak id z = y;
+}
+// CHECK-LABEL: define void @test2
+// CHECK:      [[Y:%.*]] = alloca i8*,
+// CHECK-NEXT: [[Z:%.*]] = alloca i8*,
+// CHECK-NEXT: store
+// CHECK-NEXT: [[T0:%.*]] = load i8*, i8** [[Y]]
+// CHECK-NEXT: call i8* @objc_initWeak(i8** [[Z]], i8* [[T0]])
+// CHECK-NEXT: call void @objc_destroyWeak(i8** [[Z]])
+// CHECK-NEXT: ret void
+
+void test3(id y) {
+  __weak id z;
+  z = y;
+}
+// CHECK-LABEL: define void @test3
+// CHECK:      [[Y:%.*]] = alloca i8*,
+// CHECK-NEXT: [[Z:%.*]] = alloca i8*,
+// CHECK-NEXT: store
+// CHECK-NEXT: store i8* null, i8** [[Z]]
+// CHECK-NEXT: [[T0:%.*]] = load i8*, i8** [[Y]]
+// CHECK-NEXT: call i8* @objc_storeWeak(i8** [[Z]], i8* [[T0]])
+// CHECK-NEXT: call void @objc_destroyWeak(i8** [[Z]])
+// CHECK-NEXT: ret void
+
+void test4(__weak id *p) {
+  id y = *p;
+}
+// CHECK-LABEL: define void @test4
+// CHECK:      [[P:%.*]] = alloca i8**,
+// CHECK-NEXT: [[Y:%.*]] = alloca i8*,
+// CHECK-NEXT: store
+// CHECK-NEXT: [[T0:%.*]] = load i8**, i8*** [[P]]
+// CHECK-NEXT: [[T1:%.*]] = call i8* @objc_loadWeak(i8** [[T0]])
+// CHECK-NEXT: store i8* [[T1]], i8** [[Y]]
+// CHECK-NEXT: ret void
+
+void test5(__weak id *p) {
+  id y = [*p retain];
+}
+// CHECK-LABEL: define void @test5
+// CHECK:      [[P:%.*]] = alloca i8**,
+// CHECK-NEXT: [[Y:%.*]] = alloca i8*,
+// CHECK-NEXT: store
+// CHECK-NEXT: [[T0:%.*]] = load i8**, i8*** [[P]]
+// CHECK-NEXT: [[T1:%.*]] = call i8* @objc_loadWeakRetained(i8** [[T0]])
+// CHECK-NEXT: store i8* [[T1]], i8** [[Y]]
+// CHECK-NEXT: ret void
+
+void test6(__weak Foo **p) {
+  Foo *y = [*p retain];
+}
+// CHECK-LABEL: define void @test6
+// CHECK:      [[P:%.*]] = alloca [[FOO:%.*]]**,
+// CHECK-NEXT: [[Y:%.*]] = alloca [[FOO]]*,
+// CHECK-NEXT: store
+// CHECK-NEXT: [[T0:%.*]] = load [[FOO]]**, [[FOO]]*** [[P]]
+// CHECK-NEXT: [[T1:%.*]] = bitcast [[FOO]]** [[T0]] to i8**
+// CHECK-NEXT: [[T2:%.*]] = call i8* @objc_loadWeakRetained(i8** [[T1]])
+// CHECK-NEXT: [[T3:%.*]] = bitcast i8* [[T2]] to [[FOO]]*
+// CHECK-NEXT: store [[FOO]]* [[T3]], [[FOO]]** [[Y]]
+// CHECK-NEXT: ret void
+
+extern id get_object(void);
+extern void use_block(void (^)(void));
+
+void test7(void) {
+  __weak Foo *p = get_object();
+  use_block(^{ [p run ]; });
+}
+// CHECK-LABEL: define void @test7
+// CHECK:       [[P:%.*]] = alloca [[FOO]]*,
+// CHECK:       [[T0:%.*]] = call i8* @get_object()
+// CHECK-NEXT:  [[T1:%.*]] = bitcast i8* [[T0]] to [[FOO]]*
+// CHECK-NEXT:  [[T2:%.*]] = bitcast [[FOO]]** [[P]] to i8**
+// CHECK-NEXT:  [[T3:%.*]] = bitcast [[FOO]]* [[T1]] to i8*
+// CHECK-NEXT:  call i8* @objc_initWeak(i8** [[T2]], i8* [[T3]])
+// CHECK:       call void @objc_copyWeak
+// CHECK:       call void @use_block
+// CHECK:       call void @objc_destroyWeak
+
+// CHECK-LABEL: define internal void @__copy_helper_block
+// CHECK:       @objc_copyWeak
+
+// CHECK-LABEL: define internal void @__destroy_helper_block
+// CHECK:       @objc_destroyWeak
+
+void test8(void) {
+  __block __weak Foo *p = get_object();
+  use_block(^{ [p run ]; });
+}
+// CHECK-LABEL: define void @test8
+// CHECK:       call i8* @objc_initWeak
+// CHECK-NOT:   call void @objc_copyWeak
+// CHECK:       call void @use_block
+// CHECK:       call void @objc_destroyWeak
+
+// CHECK-LABEL: define internal void @__Block_byref_object_copy
+// CHECK:       call void @objc_moveWeak
+
+// CHECK-LABEL: define internal void @__Block_byref_object_dispose
+// CHECK:       call void @objc_destroyWeak
diff --git a/clang/test/CodeGenObjC/mrr-captured-block-var-inlined-layout.m b/clang/test/CodeGenObjC/mrr-captured-block-var-inlined-layout.m
index c87140a87d8..76b7cfd118b 100644
--- a/clang/test/CodeGenObjC/mrr-captured-block-var-inlined-layout.m
+++ b/clang/test/CodeGenObjC/mrr-captured-block-var-inlined-layout.m
@@ -1,6 +1,6 @@
-// RUN: %clang_cc1 -fblocks -fobjc-runtime-has-weak -triple x86_64-apple-darwin -print-ivar-layout -emit-llvm -o /dev/null %s > %t-64.layout
+// RUN: %clang_cc1 -fblocks -fobjc-runtime-has-weak -fobjc-arc -triple x86_64-apple-darwin -print-ivar-layout -emit-llvm -o /dev/null %s > %t-64.layout
 // RUN: FileCheck -check-prefix=CHECK -check-prefix=CHECK-64 --input-file=%t-64.layout %s
-// RUN: %clang_cc1 -fblocks -fobjc-runtime-has-weak -triple i386-apple-darwin -print-ivar-layout -emit-llvm -o /dev/null %s > %t-32.layout
+// RUN: %clang_cc1 -fblocks -fobjc-runtime-has-weak -fobjc-arc -triple i386-apple-darwin -print-ivar-layout -emit-llvm -o /dev/null %s > %t-32.layout
 // RUN: FileCheck -check-prefix=CHECK -check-prefix=CHECK-32 --input-file=%t-32.layout %s
 // rdar://12184410
 // rdar://12184410