Added debug message for ObjCARC when we zap an objc_autoreleaseReturnValue/objc_retainAutoreleasedValue pair.

llvm-svn: 171628
diff --git a/llvm/lib/Transforms/Scalar/ObjCARC.cpp b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
index 1e9b08e..de09713 100644
--- a/llvm/lib/Transforms/Scalar/ObjCARC.cpp
+++ b/llvm/lib/Transforms/Scalar/ObjCARC.cpp
@@ -2247,6 +2247,11 @@
         GetObjCArg(I) == Arg) {
       Changed = true;
       ++NumPeeps;
+      
+      DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
+                   << "                                  Erasing " << *RetainRV
+                   << "\n");
+      
       EraseInstruction(I);
       EraseInstruction(RetainRV);
       return true;