[DAG] use !isUndef() ; NFCI

llvm-svn: 263453
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 9edded8..7eab758 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -6256,7 +6256,7 @@
     return false;
 
   RLI.Ptr = LD->getBasePtr();
-  if (LD->isIndexed() && LD->getOffset().getOpcode() != ISD::UNDEF) {
+  if (LD->isIndexed() && !LD->getOffset().isUndef()) {
     assert(LD->getAddressingMode() == ISD::PRE_INC &&
            "Non-pre-inc AM on PPC?");
     RLI.Ptr = DAG.getNode(ISD::ADD, dl, RLI.Ptr.getValueType(), RLI.Ptr,