[llvm] [LLVM][ConstProp] Enable intrinsic simplifications for vector ConstantInt based operands. (PR #159358)
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Wed Sep 17 06:34:29 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Paul Walker (paulwalker-arm)
<details>
<summary>Changes</summary>
Simplifcation of vector.reduce intrinsics are prevented by an early bailout for ConstantInt base operands. This PR removes the bailout and updates the tests to show matching output when -use-constant-int-for-*-splat is used.
No new simplications are added, which is why I only add scalable vector tests for things like bswap and not the vector reductions.
---
Full diff: https://github.com/llvm/llvm-project/pull/159358.diff
6 Files Affected:
- (modified) llvm/lib/Analysis/ConstantFolding.cpp (+3-7)
- (modified) llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/any_all_true.ll (+1)
- (modified) llvm/test/Transforms/InstSimplify/ConstProp/bitcount.ll (+17)
- (added) llvm/test/Transforms/InstSimplify/ConstProp/bitreverse.ll (+51)
- (modified) llvm/test/Transforms/InstSimplify/ConstProp/bswap.ll (+17)
- (modified) llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll (+1)
``````````diff
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index a3b2e62a1b8ba..e50120d345ebe 100755
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -2165,7 +2165,7 @@ Constant *constantFoldVectorReduce(Intrinsic::ID IID, Constant *Op) {
return PoisonValue::get(VT->getElementType());
// TODO: Handle undef.
- if (!isa<ConstantVector>(Op) && !isa<ConstantDataVector>(Op))
+ if (!isa<ConstantVector, ConstantDataVector, ConstantInt>(Op))
return nullptr;
auto *EltC = dyn_cast<ConstantInt>(Op->getAggregateElement(0U));
@@ -3040,9 +3040,6 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
Val = Val | Val << 1;
return ConstantInt::get(Ty, Val);
}
-
- default:
- return nullptr;
}
}
@@ -3063,9 +3060,8 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
}
// Support ConstantVector in case we have an Undef in the top.
- if (isa<ConstantVector>(Operands[0]) ||
- isa<ConstantDataVector>(Operands[0]) ||
- isa<ConstantAggregateZero>(Operands[0])) {
+ if (isa<ConstantVector, ConstantDataVector, ConstantAggregateZero,
+ ConstantInt>(Operands[0])) {
auto *Op = cast<Constant>(Operands[0]);
switch (IntrinsicID) {
default: break;
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/any_all_true.ll b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/any_all_true.ll
index 7b30edbf7792b..71dad41b971b5 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/any_all_true.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/WebAssembly/any_all_true.ll
@@ -1,6 +1,7 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -passes=instsimplify -S < %s | FileCheck %s
+; RUN: opt -passes=instsimplify -use-constant-int-for-fixed-length-splat -S < %s | FileCheck %s
; Test that intrinsics wasm call are constant folded
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/bitcount.ll b/llvm/test/Transforms/InstSimplify/ConstProp/bitcount.ll
index 68b45a94af4bc..f68b85ed4db26 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/bitcount.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/bitcount.ll
@@ -1,5 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+; RUN: opt < %s -passes=instsimplify -use-constant-int-for-fixed-length-splat -use-constant-int-for-scalable-splat -S | FileCheck %s
declare i31 @llvm.ctpop.i31(i31 %val)
declare i32 @llvm.cttz.i32(i32 %val, i1)
@@ -120,6 +121,22 @@ define <2 x i31> @ctpop_vector() {
ret <2 x i31> %x
}
+define <2 x i31> @ctpop_vector_splat_v2i31() {
+; CHECK-LABEL: @ctpop_vector_splat_v2i31(
+; CHECK-NEXT: ret <2 x i31> splat (i31 1)
+;
+ %x = call <2 x i31> @llvm.ctpop.v2i31(<2 x i31> splat(i31 16))
+ ret <2 x i31> %x
+}
+
+define <vscale x 2 x i31> @ctpop_vector_splat_nxv2i31() {
+; CHECK-LABEL: @ctpop_vector_splat_nxv2i31(
+; CHECK-NEXT: ret <vscale x 2 x i31> splat (i31 1)
+;
+ %x = call <vscale x 2 x i31> @llvm.ctpop.nxv2i31(<vscale x 2 x i31> splat(i31 16))
+ ret <vscale x 2 x i31> %x
+}
+
define <2 x i31> @ctpop_vector_undef() {
; CHECK-LABEL: @ctpop_vector_undef(
; CHECK-NEXT: ret <2 x i31> zeroinitializer
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/bitreverse.ll b/llvm/test/Transforms/InstSimplify/ConstProp/bitreverse.ll
new file mode 100644
index 0000000000000..409141a2c872b
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/bitreverse.ll
@@ -0,0 +1,51 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 6
+; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+; RUN: opt < %s -passes=instsimplify -use-constant-int-for-fixed-length-splat -use-constant-int-for-scalable-splat -S | FileCheck %s
+
+define i16 @W() {
+; CHECK-LABEL: define i16 @W() {
+; CHECK-NEXT: ret i16 -32768
+;
+ %Z = call i16 @llvm.bitreverse.i16(i16 1)
+ ret i16 %Z
+}
+
+define i32 @X() {
+; CHECK-LABEL: define i32 @X() {
+; CHECK-NEXT: ret i32 -2147483648
+;
+ %Z = call i32 @llvm.bitreverse.i32(i32 1)
+ ret i32 %Z
+}
+
+define i64 @Y() {
+; CHECK-LABEL: define i64 @Y() {
+; CHECK-NEXT: ret i64 -9223372036854775808
+;
+ %Z = call i64 @llvm.bitreverse.i64(i64 1)
+ ret i64 %Z
+}
+
+define i80 @Z() {
+; CHECK-LABEL: define i80 @Z() {
+; CHECK-NEXT: ret i80 23777929115895377691656
+;
+ %Z = call i80 @llvm.bitreverse.i80(i80 76151636403560493650080)
+ ret i80 %Z
+}
+
+define <4 x i32> @bitreverse_splat_v4i32() {
+; CHECK-LABEL: define <4 x i32> @bitreverse_splat_v4i32() {
+; CHECK-NEXT: ret <4 x i32> splat (i32 -2147483648)
+;
+ %Z = call <4 x i32> @llvm.bitreverse.v4i32(<4 x i32> splat(i32 1))
+ ret <4 x i32> %Z
+}
+
+define <vscale x 4 x i32> @bitreverse_splat_nxv4i32() {
+; CHECK-LABEL: define <vscale x 4 x i32> @bitreverse_splat_nxv4i32() {
+; CHECK-NEXT: ret <vscale x 4 x i32> splat (i32 -2147483648)
+;
+ %Z = call <vscale x 4 x i32> @llvm.bitreverse.v4i32(<vscale x 4 x i32> splat(i32 1))
+ ret <vscale x 4 x i32> %Z
+}
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/bswap.ll b/llvm/test/Transforms/InstSimplify/ConstProp/bswap.ll
index 42bb73344995b..4db8ced58327a 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/bswap.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/bswap.ll
@@ -2,6 +2,7 @@
; bswap should be constant folded when it is passed a constant argument
; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+; RUN: opt < %s -passes=instsimplify -use-constant-int-for-fixed-length-splat -use-constant-int-for-scalable-splat -S | FileCheck %s
declare i16 @llvm.bswap.i16(i16)
@@ -42,3 +43,19 @@ define i80 @Z() {
%Z = call i80 @llvm.bswap.i80( i80 76151636403560493650080 )
ret i80 %Z
}
+
+define <4 x i32> @bswap_splat_v4i32() {
+; CHECK-LABEL: define <4 x i32> @bswap_splat_v4i32() {
+; CHECK-NEXT: ret <4 x i32> splat (i32 16777216)
+;
+ %Z = call <4 x i32> @llvm.bswap.v4i32(<4 x i32> splat(i32 1))
+ ret <4 x i32> %Z
+}
+
+define <vscale x 4 x i32> @bswap_splat_nxv4i32() {
+; CHECK-LABEL: define <vscale x 4 x i32> @bswap_splat_nxv4i32() {
+; CHECK-NEXT: ret <vscale x 4 x i32> splat (i32 16777216)
+;
+ %Z = call <vscale x 4 x i32> @llvm.bswap.v4i32(<vscale x 4 x i32> splat(i32 1))
+ ret <vscale x 4 x i32> %Z
+}
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll b/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
index e994921f62574..9f9e3f9ffc070 100644
--- a/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/vecreduce.ll
@@ -1,5 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instsimplify -S | FileCheck %s
+; RUN: opt < %s -passes=instsimplify -use-constant-int-for-fixed-length-splat -S | FileCheck %s
declare i32 @llvm.vector.reduce.add.v1i32(<1 x i32> %a)
declare i32 @llvm.vector.reduce.add.v8i32(<8 x i32> %a)
``````````
</details>
https://github.com/llvm/llvm-project/pull/159358
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