[llvm] DAG: Use poison instead of undef in WidenVector (PR #206940)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/206940

None

>From ad58e5b5bbfc9b7605595589f3a3fe88c819a79a Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 1 Jul 2026 12:39:19 +0200
Subject: [PATCH] DAG: Use poison instead of undef in WidenVector

---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index c542f8e7cc20b..fa0b564b25006 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -14498,7 +14498,7 @@ SDValue SelectionDAG::WidenVector(const SDValue &N, const SDLoc &DL) {
   EVT VT = N.getValueType();
   EVT WideVT = EVT::getVectorVT(*getContext(), VT.getVectorElementType(),
                                 NextPowerOf2(VT.getVectorNumElements()));
-  return getInsertSubvector(DL, getUNDEF(WideVT), N, 0);
+  return getInsertSubvector(DL, getPOISON(WideVT), N, 0);
 }
 
 void SelectionDAG::ExtractVectorElements(SDValue Op,