[llvm] [InstCombine] Add fold for fabs(-x) -> fabs(x) (PR #95627)
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Fri Jun 14 19:37:26 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-transforms
Author: Vaibhav (VaibhavRumale)
<details>
<summary>Changes</summary>
Here is my patch for #<!-- -->94170 for fold transformation for fabs(-x) -> fabs(x)
- [InstCombine] Add tests for fold: fabs(-x) -> fabs(x)
- [InstCombine] Add fold transformation: fabs(-x) -> fabs(x)
Proofs: https://alive2.llvm.org/ce/z/pGzLts
---
Full diff: https://github.com/llvm/llvm-project/pull/95627.diff
2 Files Affected:
- (modified) llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp (+7)
- (added) llvm/test/Transforms/InstCombine/fabs-fneg-fold.ll (+138)
``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
index 436cdbff75669..f91aea35d1aab 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2511,6 +2511,13 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
}
case Intrinsic::fabs: {
Value *Cond, *TVal, *FVal;
+ Value* Arg = II->getArgOperand(0);
+ Value* X;
+ // fabs (-X) --> fabs (X)
+ if (match(Arg, m_FNeg(m_Value(X))))
+ return replaceInstUsesWith(
+ CI, Builder.CreateUnaryIntrinsic(Intrinsic::fabs, X));
+
if (match(II->getArgOperand(0),
m_Select(m_Value(Cond), m_Value(TVal), m_Value(FVal)))) {
// fabs (select Cond, TrueC, FalseC) --> select Cond, AbsT, AbsF
diff --git a/llvm/test/Transforms/InstCombine/fabs-fneg-fold.ll b/llvm/test/Transforms/InstCombine/fabs-fneg-fold.ll
new file mode 100644
index 0000000000000..bc239f207ef42
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/fabs-fneg-fold.ll
@@ -0,0 +1,138 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine %s | FileCheck %s
+
+define float @fabs_fneg_basic(float %x) {
+; CHECK-LABEL: define float @fabs_fneg_basic(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[FABS]]
+;
+ %neg = fneg float %x
+ %fabs = call float @llvm.fabs.f32(float %neg)
+ ret float %fabs
+}
+
+define <2 x float> @fabs_fneg_v2f32(<2 x float> %x) {
+; CHECK-LABEL: define <2 x float> @fabs_fneg_v2f32(
+; CHECK-SAME: <2 x float> [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call <2 x float> @llvm.fabs.v2f32(<2 x float> [[X]])
+; CHECK-NEXT: ret <2 x float> [[FABS]]
+;
+ %neg = fneg <2 x float> %x
+ %fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %neg)
+ ret <2 x float> %fabs
+}
+
+define double @fabs_fneg_f64(double %x) {
+; CHECK-LABEL: define double @fabs_fneg_f64(
+; CHECK-SAME: double [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call double @llvm.fabs.f64(double [[X]])
+; CHECK-NEXT: ret double [[FABS]]
+;
+ %neg = fneg double %x
+ %fabs = call double @llvm.fabs.f64(double %neg)
+ ret double %fabs
+}
+
+define <4 x double> @fabs_fneg_v4f64(<4 x double> %x) {
+; CHECK-LABEL: define <4 x double> @fabs_fneg_v4f64(
+; CHECK-SAME: <4 x double> [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call <4 x double> @llvm.fabs.v4f64(<4 x double> [[X]])
+; CHECK-NEXT: ret <4 x double> [[FABS]]
+;
+ %neg = fneg <4 x double> %x
+ %fabs = call <4 x double> @llvm.fabs.v4f64(<4 x double> %neg)
+ ret <4 x double> %fabs
+}
+
+define half @fabs_fneg_f16(half %x) {
+; CHECK-LABEL: define half @fabs_fneg_f16(
+; CHECK-SAME: half [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call half @llvm.fabs.f16(half [[X]])
+; CHECK-NEXT: ret half [[FABS]]
+;
+ %neg = fneg half %x
+ %fabs = call half @llvm.fabs.f16(half %neg)
+ ret half %fabs
+}
+
+define float @fabs_fneg_nnan(float %x) {
+; CHECK-LABEL: define float @fabs_fneg_nnan(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[FABS]]
+;
+ %neg = fneg nnan float %x
+ %fabs = call nnan float @llvm.fabs.f32(float %neg)
+ ret float %fabs
+}
+
+define float @fabs_fneg_ninf(float %x) {
+; CHECK-LABEL: define float @fabs_fneg_ninf(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[FABS]]
+;
+ %neg = fneg ninf float %x
+ %fabs = call ninf float @llvm.fabs.f32(float %neg)
+ ret float %fabs
+}
+
+define float @fabs_fneg_no_fabs(float %x) {
+; CHECK-LABEL: define float @fabs_fneg_no_fabs(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT: [[NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: ret float [[NEG]]
+;
+ %neg = fneg float %x
+ ret float %neg
+}
+
+define <2 x float> @fabs_fneg_splat_v2f32(<2 x float> %x) {
+; CHECK-LABEL: define <2 x float> @fabs_fneg_splat_v2f32(
+; CHECK-SAME: <2 x float> [[X:%.*]]) {
+; CHECK-NEXT: ret <2 x float> <float 2.000000e+00, float 2.000000e+00>
+;
+ %neg = fneg <2 x float> <float -2.0, float -2.0>
+ %fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %neg)
+ ret <2 x float> %fabs
+}
+
+
+define <2 x float> @fabs_fneg_splat_poison_v2f32(<2 x float> %x) {
+; CHECK-LABEL: define <2 x float> @fabs_fneg_splat_poison_v2f32(
+; CHECK-SAME: <2 x float> [[X:%.*]]) {
+; CHECK-NEXT: [[FABS:%.*]] = call <2 x float> @llvm.fabs.v2f32(<2 x float> <float -2.000000e+00, float poison>)
+; CHECK-NEXT: ret <2 x float> [[FABS]]
+;
+ %neg = fneg <2 x float> <float 2.0, float poison>
+ %fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %neg)
+ ret <2 x float> %fabs
+}
+
+define <2 x float> @fabs_fneg_non_splat_v2f32(<2 x float> %x) {
+; CHECK-LABEL: define <2 x float> @fabs_fneg_non_splat_v2f32(
+; CHECK-SAME: <2 x float> [[X:%.*]]) {
+; CHECK-NEXT: ret <2 x float> <float 2.000000e+00, float 3.000000e+00>
+;
+ %neg = fneg <2 x float> <float 2.0, float 3.0>
+ %fabs = call <2 x float> @llvm.fabs.v2f32(<2 x float> %neg)
+ ret <2 x float> %fabs
+}
+
+declare void @use(float)
+
+define float @fabs_fneg_multi_use(float %x) {
+; CHECK-LABEL: define float @fabs_fneg_multi_use(
+; CHECK-SAME: float [[X:%.*]]) {
+; CHECK-NEXT: [[NEG:%.*]] = fneg float [[X]]
+; CHECK-NEXT: call void @use(float [[NEG]])
+; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: ret float [[FABS]]
+;
+ %neg = fneg float %x
+ call void @use(float %neg)
+ %fabs = call float @llvm.fabs.f32(float %neg)
+ ret float %fabs
+}
+
``````````
</details>
https://github.com/llvm/llvm-project/pull/95627
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