[llvm] [X86] combineGatherScatter - ensure index / pointer sizes match when converting index shift to scale (PR #140110)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon updated https://github.com/llvm/llvm-project/pull/140110

>From 25eb1059cc26c47e2d3ca68c3e0c83cba43b5990 Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Thu, 15 May 2025 18:43:32 +0100
Subject: [PATCH] [X86] combineGatherScatter - ensure index / pointer sizes
 match when converting index shift to scale

The index value will sext/trunc to the pointer size before being scaled

Noticed while reviewing #139703
---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9be3b39ce16fa..cc45067fbf300 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -56715,7 +56715,8 @@ static SDValue combineGatherScatter(SDNode *N, SelectionDAG &DAG,
   if (DCI.isBeforeLegalize()) {
     // Attempt to move shifted index into the address scale, allows further
     // index truncation below.
-    if (Index.getOpcode() == ISD::SHL && isa<ConstantSDNode>(Scale)) {
+    if (Index.getOpcode() == ISD::SHL && IndexSVT == PtrVT &&
+        isa<ConstantSDNode>(Scale)) {
       unsigned ScaleAmt = Scale->getAsZExtVal();
       assert(isPowerOf2_32(ScaleAmt) && "Scale must be a power of 2");
       unsigned Log2ScaleAmt = Log2_32(ScaleAmt);