[llvm] [LLVM][GlobalISel] Make CSEMIRBuilder::buildConstant scalable vector aware. (PR #158299)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm updated https://github.com/llvm/llvm-project/pull/158299

>From 444914436c201437f106dacaa21c4ed72d2bb9aa Mon Sep 17 00:00:00 2001
From: Paul Walker <paul.walker at arm.com>
Date: Fri, 12 Sep 2025 14:52:27 +0100
Subject: [PATCH] [LLVM][GlobalISel] Make CSEMIRBuilder::buildConstant scalable
 vector aware.

---
 llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp               | 4 +++-
 llvm/test/CodeGen/AArch64/GlobalISel/select-splat-vector.ll | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp
index 59c62cf106482..3a47d59a9029c 100644
--- a/llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CSEMIRBuilder.cpp
@@ -339,8 +339,10 @@ MachineInstrBuilder CSEMIRBuilder::buildConstant(const DstOp &Res,
 
   // For vectors, CSE the element only for now.
   LLT Ty = Res.getLLTTy(*getMRI());
-  if (Ty.isVector())
+  if (Ty.isFixedVector())
     return buildSplatBuildVector(Res, buildConstant(Ty.getElementType(), Val));
+  if (Ty.isScalableVector())
+    return buildSplatVector(Res, buildConstant(Ty.getElementType(), Val));
 
   FoldingSetNodeID ID;
   GISelInstProfileBuilder ProfBuilder(ID, *getMRI());
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/select-splat-vector.ll b/llvm/test/CodeGen/AArch64/GlobalISel/select-splat-vector.ll
index 770035c34812c..8705e3aa2c305 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/select-splat-vector.ll
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/select-splat-vector.ll
@@ -1,8 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 3
 ; RUN: llc < %s -mtriple aarch64 -mattr=+sve -aarch64-enable-gisel-sve=1  | FileCheck %s  --check-prefixes=CHECK,CHECK-SDAG
+; RUN: llc < %s -mtriple aarch64 -mattr=+sve -aarch64-enable-gisel-sve=1  -use-constant-int-for-scalable-splat | FileCheck %s  --check-prefixes=CHECK,CHECK-SDAG
 ; RUN: llc < %s -mtriple aarch64 -mattr=+sve -global-isel -aarch64-enable-gisel-sve=1 | FileCheck %s --check-prefixes=CHECK,CHECK-GS
-
-; REQUIRES: asserts
+; RUN: llc < %s -mtriple aarch64 -mattr=+sve -global-isel -aarch64-enable-gisel-sve=1 -use-constant-int-for-scalable-splat | FileCheck %s --check-prefixes=CHECK,CHECK-GS
 
 ;; add
 define <vscale x 2 x i64> @addnxv2i64(<vscale x 2 x i64> %a, <vscale x 2 x i64> %b) {