From 20d37fab82968d45c00f85023bb329aa836221ad Mon Sep 17 00:00:00 2001
From: David Bolvansky <david.bolvansky@gmail.com>
Date: Mon, 12 Aug 2019 13:43:35 +0000
Subject: [PATCH] [InstCombine] x /c fabs(x) -> copysign(1.0, x)

Summary:
x / fabs(x) -> copysign(1.0, x)
fabs(x) / x -> copysign(1.0, x)

Reviewers: spatel, foad, RKSimon, efriedma

Reviewed By: spatel

Subscribers: lebedev.ri, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D65898

llvm-svn: 368570
---
 .../InstCombine/InstCombineMulDivRem.cpp           | 11 ++++++
 llvm/test/Transforms/InstCombine/fabs-copysign.ll  | 39 ++++++++++++++++------
 2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 0469448..7f152aa 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1234,6 +1234,17 @@ Instruction *InstCombiner::visitFDiv(BinaryOperator &I) {
     return &I;
   }
 
+  // X / fabs(X) -> copysign(1.0, X)
+  // fabs(X) / X -> copysign(1.0, X)
+  if (I.hasNoNaNs() && I.hasNoInfs() &&
+      (match(&I,
+             m_FDiv(m_Value(X), m_Intrinsic<Intrinsic::fabs>(m_Deferred(X)))) ||
+       match(&I, m_FDiv(m_Intrinsic<Intrinsic::fabs>(m_Value(X)),
+                        m_Deferred(X))))) {
+    Value *V = Builder.CreateBinaryIntrinsic(
+        Intrinsic::copysign, ConstantFP::get(I.getType(), 1.0), X, &I);
+    return replaceInstUsesWith(I, V);
+  }
   return nullptr;
 }
 
diff --git a/llvm/test/Transforms/InstCombine/fabs-copysign.ll b/llvm/test/Transforms/InstCombine/fabs-copysign.ll
index 9523b5c..b95969e 100644
--- a/llvm/test/Transforms/InstCombine/fabs-copysign.ll
+++ b/llvm/test/Transforms/InstCombine/fabs-copysign.ll
@@ -3,6 +3,7 @@
 
 declare double @llvm.fabs.f64(double)
 declare float @llvm.fabs.f32(float)
+declare <4 x double> @llvm.fabs.v4f64(<4 x double>)
 declare void @use(double)
 
 declare double @llvm.copysign.f64(double, double)
@@ -10,9 +11,8 @@ declare float @llvm.copysign.f32(float, float)
 
 define double @fabs_copysign(double %x) {
 ; CHECK-LABEL: @fabs_copysign(
-; CHECK-NEXT:    [[F:%.*]] = tail call double @llvm.fabs.f64(double [[X:%.*]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv nnan ninf double [[X]], [[F]]
-; CHECK-NEXT:    ret double [[DIV]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf double @llvm.copysign.f64(double 1.000000e+00, double [[X:%.*]])
+; CHECK-NEXT:    ret double [[TMP1]]
 ;
   %f = tail call double @llvm.fabs.f64(double %x)
   %div = fdiv nnan ninf double %x, %f
@@ -21,21 +21,38 @@ define double @fabs_copysign(double %x) {
 
 define double @fabs_copysign_commuted(double %x) {
 ; CHECK-LABEL: @fabs_copysign_commuted(
-; CHECK-NEXT:    [[F:%.*]] = tail call double @llvm.fabs.f64(double [[X:%.*]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv nnan ninf double [[F]], [[X]]
-; CHECK-NEXT:    ret double [[DIV]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf double @llvm.copysign.f64(double 1.000000e+00, double [[X:%.*]])
+; CHECK-NEXT:    ret double [[TMP1]]
 ;
   %f = tail call double @llvm.fabs.f64(double %x)
   %div = fdiv nnan ninf double %f, %x
   ret double %div
 }
 
+define <4 x double> @fabs_copysign_vec(<4 x double> %x) {
+; CHECK-LABEL: @fabs_copysign_vec(
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf <4 x double> @llvm.copysign.v4f64(<4 x double> <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>, <4 x double> [[X:%.*]])
+; CHECK-NEXT:    ret <4 x double> [[TMP1]]
+;
+  %f = call <4 x double> @llvm.fabs.v4f64(<4 x double> %x)
+  %div = fdiv nnan ninf <4 x double> %x, %f
+  ret <4 x double> %div
+}
+
+define <4 x double> @fabs_copysign_vec_commuted(<4 x double> %x) {
+; CHECK-LABEL: @fabs_copysign_vec_commuted(
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf <4 x double> @llvm.copysign.v4f64(<4 x double> <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>, <4 x double> [[X:%.*]])
+; CHECK-NEXT:    ret <4 x double> [[TMP1]]
+;
+  %f = call <4 x double> @llvm.fabs.v4f64(<4 x double> %x)
+  %div = fdiv nnan ninf <4 x double> %f, %x
+  ret <4 x double> %div
+}
 
 define float @fabs_copysignf(float %x) {
 ; CHECK-LABEL: @fabs_copysignf(
-; CHECK-NEXT:    [[F:%.*]] = tail call float @llvm.fabs.f32(float [[X:%.*]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv nnan ninf float [[X]], [[F]]
-; CHECK-NEXT:    ret float [[DIV]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf float @llvm.copysign.f32(float 1.000000e+00, float [[X:%.*]])
+; CHECK-NEXT:    ret float [[TMP1]]
 ;
   %f = tail call float @llvm.fabs.f32(float %x)
   %div = fdiv nnan ninf float %x, %f
@@ -46,8 +63,8 @@ define double @fabs_copysign_use(double %x) {
 ; CHECK-LABEL: @fabs_copysign_use(
 ; CHECK-NEXT:    [[F:%.*]] = tail call double @llvm.fabs.f64(double [[X:%.*]])
 ; CHECK-NEXT:    call void @use(double [[F]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv nnan ninf double [[X]], [[F]]
-; CHECK-NEXT:    ret double [[DIV]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf double @llvm.copysign.f64(double 1.000000e+00, double [[X]])
+; CHECK-NEXT:    ret double [[TMP1]]
 ;
   %f = tail call double @llvm.fabs.f64(double %x)
   call void @use(double %f)
-- 
2.7.4