Added debug message in ObjCARC when we remove a no-op cast which has only special semantic meaning in the frontend and thus in the optimizer can be deleted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@171670 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/ObjCARC.cpp

@@ -2343,6 +2343,8 @@ void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
     case IC_NoopCast:
       Changed = true;
       ++NumNoops;
+      DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Erasing no-op cast:"
+                   " " << *Inst << "\n");
       EraseInstruction(Inst);
       continue;