[llvm] DAG: Preserve poison in combineConcatVectorOfScalars (PR #168220)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/168220

None

>From e8222f8a8f68ab3f2c3a99ab9dcba99dd28b1926 Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Sat, 15 Nov 2025 09:54:38 -0800
Subject: [PATCH] DAG: Preserve poison in combineConcatVectorOfScalars

---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 70005ba7051cc..6fbac0f8c8cdf 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -25465,7 +25465,7 @@ static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
         !Op.getOperand(0).getValueType().isVector())
       Ops.push_back(Op.getOperand(0));
     else if (Op.isUndef())
-      Ops.push_back(DAG.getNode(ISD::UNDEF, DL, SVT));
+      Ops.push_back(DAG.getNode(Op.getOpcode(), DL, SVT));
     else
       return SDValue();
 
@@ -25487,7 +25487,7 @@ static SDValue combineConcatVectorOfScalars(SDNode *N, SelectionDAG &DAG) {
       if (Op.getValueType() == SVT)
         continue;
       if (Op.isUndef())
-        Op = DAG.getNode(ISD::UNDEF, DL, SVT);
+        Op = DAG.getNode(Op.getOpcode(), DL, SVT);
       else
         Op = DAG.getBitcast(SVT, Op);
     }