[PATCH] D65898: [InstCombine] x / fabs(x) -> copysign(1.0, x)

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 updated this revision to Diff 213971.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65898/new/

https://reviews.llvm.org/D65898

Files:
  lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  test/Transforms/InstCombine/fabs-copysign.ll


Index: test/Transforms/InstCombine/fabs-copysign.ll
===================================================================
--- test/Transforms/InstCombine/fabs-copysign.ll
+++ test/Transforms/InstCombine/fabs-copysign.ll
@@ -10,9 +10,8 @@
 
 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
@@ -22,9 +21,8 @@
 
 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
@@ -33,9 +31,8 @@
 
 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:    [[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
@@ -47,11 +44,11 @@
 define double @fabs_copysign_mismatch(double %x, double %y) {
 ; CHECK-LABEL: @fabs_copysign_mismatch(
 ; CHECK-NEXT:    [[F:%.*]] = tail call double @llvm.fabs.f64(double [[Y:%.*]])
-; CHECK-NEXT:    [[DIV:%.*]] = fdiv double [[X:%.*]], [[F]]
+; CHECK-NEXT:    [[DIV:%.*]] = fdiv nnan ninf double [[X:%.*]], [[F]]
 ; CHECK-NEXT:    ret double [[DIV]]
 ;
   %f = tail call double @llvm.fabs.f64(double %y)
-  %div = fdiv double %x, %f
+  %div = fdiv nnan ninf double %x, %f
   ret double %div
 }
 
Index: lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1234,6 +1234,14 @@
     return &I;
   }
 
+  // X / fabs(X) -> copysign(1.0, X)
+  if (I.hasNoNaNs() && I.hasNoInfs() &&
+      match(Op1, m_Intrinsic<Intrinsic::fabs>(m_Specific(Op0))) &&
+      Op1->hasOneUse()) {
+    Value *V = Builder.CreateBinaryIntrinsic(
+        Intrinsic::copysign, ConstantFP::get(I.getType(), 1.0), Op0, &I);
+    return replaceInstUsesWith(I, V);
+  }
   return nullptr;
 }
 


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