[llvm] [GISel] Use G_ZEXT when widening G_EXTRACT_VECTOR_ELT/G_INSERT_VECTOR_ELT index. (PR #163416)

[Craig Topper via llvm-commits]

https://github.com/topperc created https://github.com/llvm/llvm-project/pull/163416

None

>From 29102e5d777b6510eb51109ab832498a3312585e Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Tue, 14 Oct 2025 08:48:12 -0700
Subject: [PATCH] [GISel] Use G_ZEXT when widening
 G_EXTRACT_VECTOR_ELT/G_INSERT_VECTOR_ELT index.

---
 llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp             | 6 ++----
 .../CodeGen/AArch64/GlobalISel/legalize-vector-compress.mir | 6 ++++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index cffaf7ce5aa06..38ec83f81f471 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -3292,8 +3292,7 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
     if (TypeIdx != 2)
       return UnableToLegalize;
     Observer.changingInstr(MI);
-    // TODO: Probably should be zext
-    widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_SEXT);
+    widenScalarSrc(MI, WideTy, 2, TargetOpcode::G_ZEXT);
     Observer.changedInstr(MI);
     return Legalized;
   }
@@ -3325,8 +3324,7 @@ LegalizerHelper::widenScalar(MachineInstr &MI, unsigned TypeIdx, LLT WideTy) {
 
     if (TypeIdx == 2) {
       Observer.changingInstr(MI);
-      // TODO: Probably should be zext
-      widenScalarSrc(MI, WideTy, 3, TargetOpcode::G_SEXT);
+      widenScalarSrc(MI, WideTy, 3, TargetOpcode::G_ZEXT);
       Observer.changedInstr(MI);
       return Legalized;
     }
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-vector-compress.mir b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-vector-compress.mir
index cc7577473b548..c2bf95ce21adf 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/legalize-vector-compress.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/legalize-vector-compress.mir
@@ -15,8 +15,9 @@ body:             |
     ; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 0
     ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
     ; CHECK-NEXT: [[EVEC:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[COPY]](<4 x s32>), [[C1]](s64)
+    ; CHECK-NEXT: [[COPY2:%[0-9]+]]:_(s64) = COPY [[C1]](s64)
     ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 4
-    ; CHECK-NEXT: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[C1]], [[C2]]
+    ; CHECK-NEXT: [[MUL:%[0-9]+]]:_(s64) = G_MUL [[COPY2]], [[C2]]
     ; CHECK-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[MUL]](s64)
     ; CHECK-NEXT: G_STORE [[EVEC]](s32), [[PTR_ADD]](p0) :: (store (s32))
     ; CHECK-NEXT: [[EVEC1:%[0-9]+]]:_(s16) = G_EXTRACT_VECTOR_ELT [[COPY1]](<4 x s16>), [[C1]](s64)
@@ -91,7 +92,8 @@ body:             |
     ; CHECK-NEXT: [[LOAD:%[0-9]+]]:_(s32) = G_LOAD [[PTR_ADD]](p0) :: (load (s32))
     ; CHECK-NEXT: [[C3:%[0-9]+]]:_(s64) = G_CONSTANT i64 0
     ; CHECK-NEXT: [[EVEC:%[0-9]+]]:_(s32) = G_EXTRACT_VECTOR_ELT [[COPY]](<4 x s32>), [[C3]](s64)
-    ; CHECK-NEXT: [[MUL1:%[0-9]+]]:_(s64) = G_MUL [[C3]], [[C2]]
+    ; CHECK-NEXT: [[COPY3:%[0-9]+]]:_(s64) = COPY [[C3]](s64)
+    ; CHECK-NEXT: [[MUL1:%[0-9]+]]:_(s64) = G_MUL [[COPY3]], [[C2]]
     ; CHECK-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[FRAME_INDEX]], [[MUL1]](s64)
     ; CHECK-NEXT: G_STORE [[EVEC]](s32), [[PTR_ADD1]](p0) :: (store (s32))
     ; CHECK-NEXT: [[EVEC1:%[0-9]+]]:_(s16) = G_EXTRACT_VECTOR_ELT [[COPY1]](<4 x s16>), [[C3]](s64)