[llvm] [LLVM][GlobalISel] Ensure G_{F}CONSTANT only store references to scalar Constant{Int,FP}. (PR #137319)

[Paul Walker via llvm-commits]

https://github.com/paulwalker-arm created https://github.com/llvm/llvm-project/pull/137319

This is the GlobalISel equivalent of
https://github.com/llvm/llvm-project/issues/111005.

>From 3141a2ce56ee5b90a5078548ca3069fa3ea577b0 Mon Sep 17 00:00:00 2001
From: Paul Walker <paul.walker at arm.com>
Date: Thu, 24 Apr 2025 14:27:24 +0000
Subject: [PATCH] [LLVM][GlobalISel] Ensure G_{F}CONSTANT only store references
 to scalar Constant{Int,FP}.

This is the GlobalISel equivalent of
https://github.com/llvm/llvm-project/issues/111005.
---
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp     | 12 +++++++++---
 llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp |  2 ++
 llvm/test/CodeGen/AArch64/neon-mov.ll            | 16 ++++++++++++----
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 931e4fe19e69a..5a4ee12d730cc 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -3645,11 +3645,17 @@ bool IRTranslator::translate(const Constant &C, Register Reg) {
   if (auto CurrInstDL = CurBuilder->getDL())
     EntryBuilder->setDebugLoc(DebugLoc());
 
-  if (auto CI = dyn_cast<ConstantInt>(&C))
+  if (auto CI = dyn_cast<ConstantInt>(&C)) {
+    // buildConstant expects a to-be-splatted scalar ConstantInt.
+    if (isa<VectorType>(CI->getType()))
+      CI = ConstantInt::get(CI->getContext(), CI->getValue());
     EntryBuilder->buildConstant(Reg, *CI);
-  else if (auto CF = dyn_cast<ConstantFP>(&C))
+  } else if (auto CF = dyn_cast<ConstantFP>(&C)) {
+    // buildFConstant expects a to-be-splatted scalar ConstantFP.
+    if (isa<VectorType>(CF->getType()))
+      CF = ConstantFP::get(CF->getContext(), CF->getValue());
     EntryBuilder->buildFConstant(Reg, *CF);
-  else if (isa<UndefValue>(C))
+  } else if (isa<UndefValue>(C))
     EntryBuilder->buildUndef(Reg);
   else if (isa<ConstantPointerNull>(C))
     EntryBuilder->buildConstant(Reg, 0);
diff --git a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
index 359677027f52f..47e3351bb33d7 100644
--- a/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/MachineIRBuilder.cpp
@@ -316,6 +316,7 @@ MachineInstrBuilder MachineIRBuilder::buildCopy(const DstOp &Res,
 
 MachineInstrBuilder MachineIRBuilder::buildConstant(const DstOp &Res,
                                                     const ConstantInt &Val) {
+  assert(!isa<VectorType>(Val.getType()) && "Unexpected vector constant!");
   LLT Ty = Res.getLLTTy(*getMRI());
   LLT EltTy = Ty.getScalarType();
   assert(EltTy.getScalarSizeInBits() == Val.getBitWidth() &&
@@ -348,6 +349,7 @@ MachineInstrBuilder MachineIRBuilder::buildConstant(const DstOp &Res,
 
 MachineInstrBuilder MachineIRBuilder::buildFConstant(const DstOp &Res,
                                                      const ConstantFP &Val) {
+  assert(!isa<VectorType>(Val.getType()) && "Unexpected vector constant!");
   LLT Ty = Res.getLLTTy(*getMRI());
   LLT EltTy = Ty.getScalarType();
 
diff --git a/llvm/test/CodeGen/AArch64/neon-mov.ll b/llvm/test/CodeGen/AArch64/neon-mov.ll
index ff80ff097b28f..5be9394f61b30 100644
--- a/llvm/test/CodeGen/AArch64/neon-mov.ll
+++ b/llvm/test/CodeGen/AArch64/neon-mov.ll
@@ -1,8 +1,16 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -verify-machineinstrs -mtriple=aarch64-none-linux-gnu -mattr=+neon | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-SD
-; RUN: llc < %s -verify-machineinstrs -mtriple=aarch64-none-linux-gnu -mattr=+neon,+fullfp16 | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-SD
-; RUN: llc -mtriple=aarch64-none-linux-gnu -mattr=+neon -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-GI
-; RUN: llc -mtriple=aarch64-none-linux-gnu -mattr=+neon,+fullfp16 -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-GI
+; RUN: llc < %s -verify-machineinstrs -mattr=+neon | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-SD
+; RUN: llc < %s -verify-machineinstrs -mattr=+neon,+fullfp16 | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-SD
+; RUN: llc -mattr=+neon -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-GI
+; RUN: llc -mattr=+neon,+fullfp16 -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-GI
+
+; This are copies of the above RUN lines but with vector constants enabled.
+; RUN: llc -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat < %s -verify-machineinstrs -mattr=+neon | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-SD
+; RUN: llc -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat < %s -verify-machineinstrs -mattr=+neon,+fullfp16 | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-SD
+; RUN: llc -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat -mattr=+neon -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-NOFP16,CHECK-NOFP16-GI
+; RUN: llc -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat -mattr=+neon,+fullfp16 -global-isel %s -o - | FileCheck %s --check-prefixes=CHECK,CHECK-FP16,CHECK-FP16-GI
+
+target triple = "aarch64-none-linux-gnu"
 
 define <8 x i8> @movi8b_0() {
 ; CHECK-LABEL: movi8b_0: