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

Author: paulwalker-arm

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());

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) {