[llvm] Introducing a new ISD::POISON SDNode to represent the poison value in the IR. (PR #125883)

[zhijian lin via llvm-commits]

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@@ -871,7 +871,7 @@ class SelectionDAG {
   /// for integers, a type wider than) VT's element type.
   SDValue getSplatBuildVector(EVT VT, const SDLoc &DL, SDValue Op) {
     // VerifySDNode (via InsertNode) checks BUILD_VECTOR later.
-    if (Op.getOpcode() == ISD::UNDEF) {
+    if (Op.isUndef()) {
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diggerlin wrote:

the  isUndef() is  `bool isUndef(bool DoNotIncludeExplicitPoison = false)`, it is not a NFC,  do we still need to split off this NFC change?

https://github.com/llvm/llvm-project/pull/125883