[llvm] [GlobalIsel] Use aext in ctlz_zero_undef expansion (PR #181506)

[Alex MacLean via llvm-commits]

https://github.com/AlexMaclean created https://github.com/llvm/llvm-project/pull/181506

None

>From da9a2d35d046f4da643432f191f9ea91f7b8ea17 Mon Sep 17 00:00:00 2001
From: Alex Maclean <amaclean at nvidia.com>
Date: Sat, 14 Feb 2026 20:48:39 +0000
Subject: [PATCH] [GlobalIsel] Use aext in ctlz_zero_undef expansion

---
 llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 41b79ccb4e4d1..ffd0814f86010 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -2816,6 +2816,7 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
     switch (Opcode) {
     case TargetOpcode::G_CTTZ:
     case TargetOpcode::G_CTTZ_ZERO_UNDEF:
+    case TargetOpcode::G_CTLZ_ZERO_UNDEF: // undef bits shifted out below
       ExtOpc = TargetOpcode::G_ANYEXT;
       break;
     case TargetOpcode::G_CTLS: