[llvm] [LLVM][X86InstCombine] Extend mask combines to cover ConstantInt/FP based splats. (PR #195090)
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Thu Apr 30 08:51:34 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Paul Walker (paulwalker-arm)
<details>
<summary>Changes</summary>
---
Full diff: https://github.com/llvm/llvm-project/pull/195090.diff
3 Files Affected:
- (modified) llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp (+4-4)
- (modified) llvm/test/Transforms/InstCombine/X86/blend_x86.ll (+50-1)
- (modified) llvm/test/Transforms/InstCombine/X86/x86-masked-memops.ll (+19-1)
``````````diff
diff --git a/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp b/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp
index ff4b96e0e6935..932b4a416a8d3 100644
--- a/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp
+++ b/llvm/lib/Target/X86/X86InstCombineIntrinsic.cpp
@@ -40,8 +40,8 @@ static Constant *getNegativeIsTrueBoolVec(Constant *V, const DataLayout &DL) {
/// each element's most significant bit (the sign bit).
static Value *getBoolVecFromMask(Value *Mask, const DataLayout &DL) {
// Fold Constant Mask.
- if (auto *ConstantMask = dyn_cast<ConstantDataVector>(Mask))
- return getNegativeIsTrueBoolVec(ConstantMask, DL);
+ if (isa<ConstantInt, ConstantFP, ConstantDataVector>(Mask))
+ return getNegativeIsTrueBoolVec(cast<Constant>(Mask), DL);
// Mask was extended from a boolean vector.
Value *ExtMask;
@@ -2973,9 +2973,9 @@ X86TTIImpl::instCombineIntrinsic(InstCombiner &IC, IntrinsicInst &II) const {
}
// Constant Mask - select 1st/2nd argument lane based on top bit of mask.
- if (auto *ConstantMask = dyn_cast<ConstantDataVector>(Mask)) {
+ if (isa<ConstantInt, ConstantFP, ConstantDataVector>(Mask)) {
Constant *NewSelector =
- getNegativeIsTrueBoolVec(ConstantMask, IC.getDataLayout());
+ getNegativeIsTrueBoolVec(cast<Constant>(Mask), IC.getDataLayout());
return SelectInst::Create(NewSelector, Op1, Op0, "blendv");
}
unsigned BitWidth = Mask->getType()->getScalarSizeInBits();
diff --git a/llvm/test/Transforms/InstCombine/X86/blend_x86.ll b/llvm/test/Transforms/InstCombine/X86/blend_x86.ll
index 90fa512d306a2..75d1a693d4264 100644
--- a/llvm/test/Transforms/InstCombine/X86/blend_x86.ll
+++ b/llvm/test/Transforms/InstCombine/X86/blend_x86.ll
@@ -1,5 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=instcombine -mtriple=x86_64-apple-macosx -mcpu=core-avx2 -S | FileCheck %s
+; RUN: opt < %s -passes=instcombine -mtriple=x86_64-apple-macosx -mcpu=core-avx2 -use-constant-int-for-fixed-length-splat=false -use-constant-fp-for-fixed-length-splat=false -S | FileCheck %s
+; RUN: opt < %s -passes=instcombine -mtriple=x86_64-apple-macosx -mcpu=core-avx2 -use-constant-int-for-fixed-length-splat -use-constant-fp-for-fixed-length-splat -S | FileCheck %s
define <2 x double> @constant_blendvpd(<2 x double> %xy, <2 x double> %ab) {
; CHECK-LABEL: @constant_blendvpd(
@@ -18,6 +19,14 @@ define <2 x double> @constant_blendvpd_zero(<2 x double> %xy, <2 x double> %ab)
ret <2 x double> %1
}
+define <2 x double> @constant_blendvpd_one(<2 x double> %ab) {
+; CHECK-LABEL: @constant_blendvpd_one(
+; CHECK-NEXT: ret <2 x double> zeroinitializer
+;
+ %1 = tail call <2 x double> @llvm.x86.sse41.blendvpd(<2 x double> zeroinitializer, <2 x double> %ab, <2 x double> splat (double 1.000000e+00))
+ ret <2 x double> %1
+}
+
define <2 x double> @constant_blendvpd_dup(<2 x double> %xy, <2 x double> %sel) {
; CHECK-LABEL: @constant_blendvpd_dup(
; CHECK-NEXT: ret <2 x double> [[XY:%.*]]
@@ -43,6 +52,14 @@ define <4 x float> @constant_blendvps_zero(<4 x float> %xyzw, <4 x float> %abcd)
ret <4 x float> %1
}
+define <4 x float> @constant_blendvps_one(<4 x float> %abcd) {
+; CHECK-LABEL: @constant_blendvps_one(
+; CHECK-NEXT: ret <4 x float> zeroinitializer
+;
+ %1 = tail call <4 x float> @llvm.x86.sse41.blendvps(<4 x float> zeroinitializer, <4 x float> %abcd, <4 x float> splat (float 1.000000e+00))
+ ret <4 x float> %1
+}
+
define <4 x float> @constant_blendvps_dup(<4 x float> %xyzw, <4 x float> %sel) {
; CHECK-LABEL: @constant_blendvps_dup(
; CHECK-NEXT: ret <4 x float> [[XYZW:%.*]]
@@ -68,6 +85,14 @@ define <16 x i8> @constant_pblendvb_zero(<16 x i8> %xyzw, <16 x i8> %abcd) {
ret <16 x i8> %1
}
+define <16 x i8> @constant_pblendvb_one(<16 x i8> %abcd) {
+; CHECK-LABEL: @constant_pblendvb_one(
+; CHECK-NEXT: ret <16 x i8> zeroinitializer
+;
+ %1 = tail call <16 x i8> @llvm.x86.sse41.pblendvb(<16 x i8> zeroinitializer, <16 x i8> %abcd, <16 x i8> splat (i8 1))
+ ret <16 x i8> %1
+}
+
define <16 x i8> @constant_pblendvb_dup(<16 x i8> %xyzw, <16 x i8> %sel) {
; CHECK-LABEL: @constant_pblendvb_dup(
; CHECK-NEXT: ret <16 x i8> [[XYZW:%.*]]
@@ -93,6 +118,14 @@ define <4 x double> @constant_blendvpd_avx_zero(<4 x double> %xy, <4 x double> %
ret <4 x double> %1
}
+define <4 x double> @constant_blendvpd_avx_one(<4 x double> %ab) {
+; CHECK-LABEL: @constant_blendvpd_avx_one(
+; CHECK-NEXT: ret <4 x double> zeroinitializer
+;
+ %1 = tail call <4 x double> @llvm.x86.avx.blendv.pd.256(<4 x double> zeroinitializer, <4 x double> %ab, <4 x double> splat (double 1.000000e+00))
+ ret <4 x double> %1
+}
+
define <4 x double> @constant_blendvpd_avx_dup(<4 x double> %xy, <4 x double> %sel) {
; CHECK-LABEL: @constant_blendvpd_avx_dup(
; CHECK-NEXT: ret <4 x double> [[XY:%.*]]
@@ -118,6 +151,14 @@ define <8 x float> @constant_blendvps_avx_zero(<8 x float> %xyzw, <8 x float> %a
ret <8 x float> %1
}
+define <8 x float> @constant_blendvps_avx_one(<8 x float> %abcd) {
+; CHECK-LABEL: @constant_blendvps_avx_one(
+; CHECK-NEXT: ret <8 x float> zeroinitializer
+;
+ %1 = tail call <8 x float> @llvm.x86.avx.blendv.ps.256(<8 x float> zeroinitializer, <8 x float> %abcd, <8 x float> splat (float 1.000000e+00))
+ ret <8 x float> %1
+}
+
define <8 x float> @constant_blendvps_avx_dup(<8 x float> %xyzw, <8 x float> %sel) {
; CHECK-LABEL: @constant_blendvps_avx_dup(
; CHECK-NEXT: ret <8 x float> [[XYZW:%.*]]
@@ -147,6 +188,14 @@ define <32 x i8> @constant_pblendvb_avx2_zero(<32 x i8> %xyzw, <32 x i8> %abcd)
ret <32 x i8> %1
}
+define <32 x i8> @constant_pblendvb_avx2_one(<32 x i8> %abcd) {
+; CHECK-LABEL: @constant_pblendvb_avx2_one(
+; CHECK-NEXT: ret <32 x i8> zeroinitializer
+;
+ %1 = tail call <32 x i8> @llvm.x86.avx2.pblendvb(<32 x i8> zeroinitializer, <32 x i8> %abcd, <32 x i8> splat (i8 1))
+ ret <32 x i8> %1
+}
+
define <32 x i8> @constant_pblendvb_avx2_dup(<32 x i8> %xyzw, <32 x i8> %sel) {
; CHECK-LABEL: @constant_pblendvb_avx2_dup(
; CHECK-NEXT: ret <32 x i8> [[XYZW:%.*]]
diff --git a/llvm/test/Transforms/InstCombine/X86/x86-masked-memops.ll b/llvm/test/Transforms/InstCombine/X86/x86-masked-memops.ll
index 297d2b6522611..05976214ca179 100644
--- a/llvm/test/Transforms/InstCombine/X86/x86-masked-memops.ll
+++ b/llvm/test/Transforms/InstCombine/X86/x86-masked-memops.ll
@@ -1,5 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt < %s -passes=instcombine -mtriple=x86_64-unknown-unknown -S | FileCheck %s
+; RUN: opt < %s -passes=instcombine -mtriple=x86_64-unknown-unknown -use-constant-int-for-fixed-length-splat=false -S | FileCheck %s
+; RUN: opt < %s -passes=instcombine -mtriple=x86_64-unknown-unknown -use-constant-int-for-fixed-length-splat -S | FileCheck %s
;; MASKED LOADS
@@ -48,6 +49,14 @@ define <4 x float> @mload_fake_ones(ptr %f) {
ret <4 x float> %ld
}
+define <4 x float> @mload_fake_ones_splat(ptr %f) {
+; CHECK-LABEL: @mload_fake_ones_splat(
+; CHECK-NEXT: ret <4 x float> zeroinitializer
+;
+ %ld = tail call <4 x float> @llvm.x86.avx.maskload.ps(ptr %f, <4 x i32> splat(i32 1))
+ ret <4 x float> %ld
+}
+
; All mask bits are set, so this is just a vector load.
define <4 x float> @mload_real_ones(ptr %f) {
@@ -59,6 +68,15 @@ define <4 x float> @mload_real_ones(ptr %f) {
ret <4 x float> %ld
}
+define <4 x float> @mload_real_ones_splat(ptr %f) {
+; CHECK-LABEL: @mload_real_ones_splat(
+; CHECK-NEXT: [[UNMASKEDLOAD:%.*]] = load <4 x float>, ptr [[F:%.*]], align 1
+; CHECK-NEXT: ret <4 x float> [[UNMASKEDLOAD]]
+;
+ %ld = tail call <4 x float> @llvm.x86.avx.maskload.ps(ptr %f, <4 x i32> splat(i32 -1))
+ ret <4 x float> %ld
+}
+
; It's a constant mask, so convert to an LLVM intrinsic. The backend should optimize further.
define <4 x float> @mload_one_one(ptr %f) {
``````````
</details>
https://github.com/llvm/llvm-project/pull/195090
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