Generate weak read barriers when reading a weak __block

variable inside the block.

llvm-svn: 83729

2 files changed, 31 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index d0c245369b4..dcb5684032b 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "CodeGenFunction.h"
+#include "CGObjCRuntime.h"
 #include "CodeGenModule.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
@@ -748,7 +749,10 @@ Value *ScalarExprEmitter::VisitStmtExpr(const StmtExpr *E) {
 }
 
 Value *ScalarExprEmitter::VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
-  return Builder.CreateLoad(CGF.GetAddrOfBlockDecl(E), false, "tmp");
+  llvm::Value *V = CGF.GetAddrOfBlockDecl(E);
+  if (E->getType().isObjCGCWeak())
+    return CGF.CGM.getObjCRuntime().EmitObjCWeakRead(CGF, V);
+  return Builder.CreateLoad(V, false, "tmp");
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/clang/test/CodeGenObjC/objc-read-weak-byref.m b/clang/test/CodeGenObjC/objc-read-weak-byref.m
new file mode 100644
index 00000000000..7c297be5667
--- /dev/null
+++ b/clang/test/CodeGenObjC/objc-read-weak-byref.m
@@ -0,0 +1,26 @@
+// RUN: clang-cc -fblocks -fobjc-gc -triple x86_64-apple-darwin -S %s -o %t-64.s &&
+// RUN: FileCheck -check-prefix LP64 --input-file=%t-64.s %s &&
+// RUN: clang-cc -fblocks -fobjc-gc -triple i386-apple-darwin -S %s -o %t-32.s &&
+// RUN: FileCheck -check-prefix LP32 --input-file=%t-32.s %s &&
+// RUN: true
+
+@interface NSObject 
+- copy;
+@end
+
+int main() {
+    NSObject *object = 0;
+    __weak __block NSObject* weak_object = object;
+    void (^callback) (void) = [^{
+        if (weak_object)
+                [weak_object copy];
+    } copy];
+    callback();
+    return 0;
+}
+
+// CHECK-LP64: call     _objc_read_weak
+// CHECK-LP64: call     _objc_read_weak
+
+// CHECK-LP32: call     L_objc_read_weak
+// CHECK-LP32: call     L_objc_read_weak