[X86] In X86DAGToDAGISel::PreprocessISelDAG, make sure we don't access N after we delete it.

If we turn X86ISD::AND into ISD::AND, we delete N. But we were continuing onto the next block of code even though N no longer existed.

Just happened to notice it. I assume asan didn't notice it because we explicitly unpoison deleted nodes and give them a DELETE_NODE opcode.

llvm-svn: 335787

llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

@@ -668,6 +668,7 @@ void X86DAGToDAGISel::PreprocessISelDAG() {
       CurDAG->ReplaceAllUsesOfValueWith(SDValue(N, 0), Res);
       ++I;
       CurDAG->DeleteNode(N);
+      continue;
     }
 
     if (OptLevel != CodeGenOpt::None &&