[llvm] [LLVM][ValueTracking] Add vector ConstantInt/FP support to isBytewiseValue(). (PR #182519)
Paul Walker via llvm-commits
llvm-commits at lists.llvm.org
Fri Feb 20 08:02:17 PST 2026
https://github.com/paulwalker-arm created https://github.com/llvm/llvm-project/pull/182519
None
>From 3a17ea989d5ba69b6d97035734a258925a1971ca Mon Sep 17 00:00:00 2001
From: Paul Walker <paul.walker at arm.com>
Date: Wed, 18 Feb 2026 18:00:15 +0000
Subject: [PATCH 1/2] Add tests showing missed optimisation/assertion when
using ConstantInt/FP for vector constants.
---
.../store-to-memset-constant-splat.ll | 44 +++++++++++++++++++
1 file changed, 44 insertions(+)
create mode 100644 llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
diff --git a/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll b/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
new file mode 100644
index 0000000000000..b32c245871943
--- /dev/null
+++ b/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
@@ -0,0 +1,44 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt -S -passes=memcpyopt < %s | FileCheck %s --check-prefix=CHECK
+; RUN: opt -S -passes=memcpyopt -use-constant-fp-for-fixed-length-splat < %s | FileCheck %s --check-prefix=CHECK-CFP
+
+; NOTE: -use-constant-int-for-fixed-length-splat triggers an assert.
+define void @store_to_memst_vec_constant_int(ptr %p) {
+; CHECK-LABEL: define void @store_to_memst_vec_constant_int(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
+; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
+; CHECK-NEXT: ret void
+;
+; CHECK-CFP-LABEL: define void @store_to_memst_vec_constant_int(
+; CHECK-CFP-SAME: ptr [[P:%.*]]) {
+; CHECK-CFP-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
+; CHECK-CFP-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
+; CHECK-CFP-NEXT: ret void
+;
+ store <16 x i8> splat (i8 1), ptr %p, align 16
+ %p1 = getelementptr i8, ptr %p, i64 16
+ store <16 x i8> splat (i8 1), ptr %p1, align 16
+ ret void
+}
+
+define void @store_to_memst_vec_constant_fp(ptr %p) {
+; CHECK-LABEL: define void @store_to_memst_vec_constant_fp(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
+; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
+; CHECK-NEXT: ret void
+;
+; CHECK-CFP-LABEL: define void @store_to_memst_vec_constant_fp(
+; CHECK-CFP-SAME: ptr [[P:%.*]]) {
+; CHECK-CFP-NEXT: store <4 x float> splat (float 0x3820202020000000), ptr [[P]], align 16
+; CHECK-CFP-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
+; CHECK-CFP-NEXT: store <4 x float> splat (float 0x3820202020000000), ptr [[P1]], align 16
+; CHECK-CFP-NEXT: ret void
+;
+ store <4 x float> splat (float 2.3694278276172396e-38), ptr %p, align 16
+ %p1 = getelementptr i8, ptr %p, i64 16
+ store <4 x float> splat (float 2.3694278276172396e-38), ptr %p1, align 16
+ ret void
+}
+
>From 3538461964204f34103d051543441e9b848208f4 Mon Sep 17 00:00:00 2001
From: Paul Walker <paul.walker at arm.com>
Date: Thu, 19 Feb 2026 10:54:07 +0000
Subject: [PATCH 2/2] [LLVM][ValueTracking] Add vector ConstantInt/FP support
to isBytewiseValue.
---
llvm/lib/Analysis/ValueTracking.cpp | 16 ++++++----------
.../store-to-memset-constant-splat.ll | 18 ++----------------
2 files changed, 8 insertions(+), 26 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 2d78aa4be3455..3e46b6eb23ad9 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -6282,22 +6282,18 @@ Value *llvm::isBytewiseValue(Value *V, const DataLayout &DL) {
// Constant floating-point values can be handled as integer values if the
// corresponding integer value is "byteable". An important case is 0.0.
if (ConstantFP *CFP = dyn_cast<ConstantFP>(C)) {
- Type *Ty = nullptr;
- if (CFP->getType()->isHalfTy())
- Ty = Type::getInt16Ty(Ctx);
- else if (CFP->getType()->isFloatTy())
- Ty = Type::getInt32Ty(Ctx);
- else if (CFP->getType()->isDoubleTy())
- Ty = Type::getInt64Ty(Ctx);
+ Type *ScalarTy = CFP->getType()->getScalarType();
+ if (ScalarTy->isHalfTy() || ScalarTy->isFloatTy() || ScalarTy->isDoubleTy())
+ return isBytewiseValue(
+ ConstantInt::get(Ctx, CFP->getValue().bitcastToAPInt()), DL);
+
// Don't handle long double formats, which have strange constraints.
- return Ty ? isBytewiseValue(ConstantExpr::getBitCast(CFP, Ty), DL)
- : nullptr;
+ return nullptr;
}
// We can handle constant integers that are multiple of 8 bits.
if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
if (CI->getBitWidth() % 8 == 0) {
- assert(CI->getBitWidth() > 8 && "8 bits should be handled above!");
if (!CI->getValue().isSplat(8))
return nullptr;
return ConstantInt::get(Ctx, CI->getValue().trunc(8));
diff --git a/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll b/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
index b32c245871943..55c68fad8dfaa 100644
--- a/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
+++ b/llvm/test/Transforms/MemCpyOpt/store-to-memset-constant-splat.ll
@@ -1,20 +1,13 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
-; RUN: opt -S -passes=memcpyopt < %s | FileCheck %s --check-prefix=CHECK
-; RUN: opt -S -passes=memcpyopt -use-constant-fp-for-fixed-length-splat < %s | FileCheck %s --check-prefix=CHECK-CFP
+; RUN: opt -S -passes=memcpyopt < %s | FileCheck %s
+; RUN: opt -S -passes=memcpyopt -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat < %s | FileCheck %s
-; NOTE: -use-constant-int-for-fixed-length-splat triggers an assert.
define void @store_to_memst_vec_constant_int(ptr %p) {
; CHECK-LABEL: define void @store_to_memst_vec_constant_int(
; CHECK-SAME: ptr [[P:%.*]]) {
; CHECK-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
; CHECK-NEXT: ret void
-;
-; CHECK-CFP-LABEL: define void @store_to_memst_vec_constant_int(
-; CHECK-CFP-SAME: ptr [[P:%.*]]) {
-; CHECK-CFP-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
-; CHECK-CFP-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
-; CHECK-CFP-NEXT: ret void
;
store <16 x i8> splat (i8 1), ptr %p, align 16
%p1 = getelementptr i8, ptr %p, i64 16
@@ -28,13 +21,6 @@ define void @store_to_memst_vec_constant_fp(ptr %p) {
; CHECK-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
; CHECK-NEXT: call void @llvm.memset.p0.i64(ptr align 16 [[P]], i8 1, i64 32, i1 false)
; CHECK-NEXT: ret void
-;
-; CHECK-CFP-LABEL: define void @store_to_memst_vec_constant_fp(
-; CHECK-CFP-SAME: ptr [[P:%.*]]) {
-; CHECK-CFP-NEXT: store <4 x float> splat (float 0x3820202020000000), ptr [[P]], align 16
-; CHECK-CFP-NEXT: [[P1:%.*]] = getelementptr i8, ptr [[P]], i64 16
-; CHECK-CFP-NEXT: store <4 x float> splat (float 0x3820202020000000), ptr [[P1]], align 16
-; CHECK-CFP-NEXT: ret void
;
store <4 x float> splat (float 2.3694278276172396e-38), ptr %p, align 16
%p1 = getelementptr i8, ptr %p, i64 16
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