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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171628 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/ObjCARC.cpp

@@ -2247,6 +2247,11 @@ ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
         GetObjCArg(I) == Arg) {
       Changed = true;
       ++NumPeeps;
+      
+      DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
+                   << "                                  Erasing " << *RetainRV
+                   << "\n");
+      
       EraseInstruction(I);
       EraseInstruction(RetainRV);
       return true;