1 files changed, 8 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/ObjCARC/ObjCARCAliasAnalysis.cpp b/llvm/lib/Transforms/ObjCARC/ObjCARCAliasAnalysis.cpp
index 46b2de71374..1a3f383d4c0 100644
--- a/llvm/lib/Transforms/ObjCARC/ObjCARCAliasAnalysis.cpp
+++ b/llvm/lib/Transforms/ObjCARC/ObjCARCAliasAnalysis.cpp
@@ -150,6 +150,14 @@ ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
     break;
   }
 
+  // Handle special objective c calls defaulting to chaining.
+  const Function *F = CS.getCalledFunction();
+  if (F)
+    return StringSwitch<AliasAnalysis::ModRefResult>(F->getName())
+      .Case("objc_sync_start", NoModRef)
+      .Case("objc_sync_stop", NoModRef)
+      .Default(AliasAnalysis::getModRefInfo(CS, Loc));
+
   return AliasAnalysis::getModRefInfo(CS, Loc);
 }