[DAG] Use recursivelyDeleteUnusedNodes in PromoteLoad

[deadalnix]

Summary

It simplifies the code overall and removes the need for manual bookkeeping.

[RKSimon]

LGTM

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

ISD::LoadExtType ExtType = ISD::isNON_EXTLoad(LD) ? ISD::EXTLOAD
                                                       : LD->getExtensionType();
     SDValue NewLD = DAG.getExtLoad(ExtType, DL, PVT,
                                    LD->getChain(), LD->getBasePtr(),
                                    MemVT, LD->getMemOperand());
     SDValue Result = DAG.getNode(ISD::TRUNCATE, DL, VT, NewLD);
 
     LLVM_DEBUG(dbgs() << "\nPromoting "; N->dump(&DAG); dbgs() << "\nTo: ";
                Result.dump(&DAG); dbgs() << '\n');
-    WorklistRemover DeadNodes(*this);
+
     DAG.ReplaceAllUsesOfValueWith(SDValue(N, 0), Result);
     DAG.ReplaceAllUsesOfValueWith(SDValue(N, 1), NewLD.getValue(1));
-    deleteAndRecombine(N);
+
     AddToWorklist(Result.getNode());
+    recursivelyDeleteUnusedNodes(N);
     return true;
   }
+
   return false;
 }
 
 /// Recursively delete a node which has no uses and any operands for
 /// which it is the only use.
 ///
 /// Note that this both deletes the nodes and removes them from the worklist.
 /// It also adds any nodes who have had a user deleted to the worklist as they