[llvm] DAG: Use poison for filler values on legalize error paths (PR #170556)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm created https://github.com/llvm/llvm-project/pull/170556

None

>From 7009461dca72e0691adeddb30b786e378b5a590c Mon Sep 17 00:00:00 2001
From: Matt Arsenault <Matthew.Arsenault at amd.com>
Date: Wed, 3 Dec 2025 22:12:40 +0100
Subject: [PATCH] DAG: Use poison for filler values on legalize error paths

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

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 8336e1d1f4134..e739659d68561 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -2130,7 +2130,7 @@ SelectionDAGLegalize::ExpandLibCall(RTLIB::Libcall LC, SDNode *Node,
   if (const char *LibcallName = TLI.getLibcallName(LC))
     Callee = DAG.getExternalSymbol(LibcallName, CodePtrTy);
   else {
-    Callee = DAG.getUNDEF(CodePtrTy);
+    Callee = DAG.getPOISON(CodePtrTy);
     DAG.getContext()->emitError(Twine("no libcall available for ") +
                                 Node->getOperationName(&DAG));
   }
@@ -4992,7 +4992,7 @@ void SelectionDAGLegalize::ConvertNodeToLibcall(SDNode *Node) {
       // If the exponent does not match with sizeof(int) a libcall to
       // RTLIB::POWI would use the wrong type for the argument.
       DAG.getContext()->emitError("POWI exponent does not match sizeof(int)");
-      Results.push_back(DAG.getUNDEF(Node->getValueType(0)));
+      Results.push_back(DAG.getPOISON(Node->getValueType(0)));
       break;
     }
     ExpandFPLibCall(Node, LC, Results);