[ObjC][ARC] Honor noescape attribute for -Warc-retain-cycles

rdar://35409566

Differential Revision: https://reviews.llvm.org/D40141

llvm-svn: 318552

1 files changed, 8 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 6b209cdef7c..e662a5c8b97 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -11652,9 +11652,15 @@ void Sema::checkRetainCycles(ObjCMessageExpr *msg) {
   }
 
   // Check whether the receiver is captured by any of the arguments.
-  for (unsigned i = 0, e = msg->getNumArgs(); i != e; ++i)
-    if (Expr *capturer = findCapturingExpr(*this, msg->getArg(i), owner))
+  const ObjCMethodDecl *MD = msg->getMethodDecl();
+  for (unsigned i = 0, e = msg->getNumArgs(); i != e; ++i) {
+    if (Expr *capturer = findCapturingExpr(*this, msg->getArg(i), owner)) {
+      // noescape blocks should not be retained by the method.
+      if (MD && MD->parameters()[i]->hasAttr<NoEscapeAttr>())
+        continue;
       return diagnoseRetainCycle(*this, capturer, owner);
+    }
+  }
 }
 
 /// Check a property assign to see if it's likely to cause a retain cycle.