[InstCombine] allow sinking fneg operands through an FP min/max

Fundamentally/generally, we should not have to rely on bailouts/crippling of
folds. In this particular case, I think we always recognize the inverted
predicate min/max pattern, so there should not be any loss of optimization.
Codegen looks better because we are eliminating an fneg.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@360180 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp
index ef72f3bbb72e8641c419f4d47afc82ba4eb8a30e..ce6b38c90ca40e1b4ca98eacb1fd1a54effb0b19 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -5518,6 +5518,11 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
     }
   }
 
+  // fcmp pred (fneg X), (fneg Y) -> fcmp swap(pred) X, Y
+  Value *X, *Y;
+  if (match(Op0, m_FNeg(m_Value(X))) && match(Op1, m_FNeg(m_Value(Y))))
+    return new FCmpInst(I.getSwappedPredicate(), X, Y, "", &I);
+
   // Test if the FCmpInst instruction is used exclusively by a select as
   // part of a minimum or maximum operation. If so, refrain from doing
   // any other folding. This helps out other analyses which understand
@@ -5576,12 +5581,7 @@ Instruction *InstCombiner::visitFCmpInst(FCmpInst &I) {
   if (Instruction *R = foldFabsWithFcmpZero(I))
     return R;
 
-  Value *X, *Y;
   if (match(Op0, m_FNeg(m_Value(X)))) {
-    // fcmp pred (fneg X), (fneg Y) -> fcmp swap(pred) X, Y
-    if (match(Op1, m_FNeg(m_Value(Y))))
-      return new FCmpInst(I.getSwappedPredicate(), X, Y, "", &I);
-
     // fcmp pred (fneg X), C --> fcmp swap(pred) X, -C
     Constant *C;
     if (match(Op1, m_Constant(C))) {

diff --git a/test/Transforms/InstCombine/minmax-fp.ll b/test/Transforms/InstCombine/minmax-fp.ll
index 9cdbf4f2d80cefb0885c9b4ec6305997d334d96d..e139137727c2253975a5619f0fa46a3aa16d3e31 100644 (file)
--- a/test/Transforms/InstCombine/minmax-fp.ll
+++ b/test/Transforms/InstCombine/minmax-fp.ll
@@ -257,10 +257,9 @@ define double @t17(i32 %x) {
 
 define float @fneg_fmax(float %x, float %y) {
 ; CHECK-LABEL: @fneg_fmax(
-; CHECK-NEXT:    [[N1:%.*]] = fneg float [[X:%.*]]
-; CHECK-NEXT:    [[N2:%.*]] = fneg float [[Y:%.*]]
-; CHECK-NEXT:    [[COND:%.*]] = fcmp nnan ogt float [[N1]], [[N2]]
-; CHECK-NEXT:    [[MAX:%.*]] = select i1 [[COND]], float [[N1]], float [[N2]]
+; CHECK-NEXT:    [[COND:%.*]] = fcmp nnan olt float [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[MAX_V:%.*]] = select i1 [[COND]], float [[X]], float [[Y]]
+; CHECK-NEXT:    [[MAX:%.*]] = fneg float [[MAX_V]]
 ; CHECK-NEXT:    ret float [[MAX]]
 ;
   %n1 = fneg float %x
@@ -272,10 +271,9 @@ define float @fneg_fmax(float %x, float %y) {
 
 define <2 x float> @fsub_fmax(<2 x float> %x, <2 x float> %y) {
 ; CHECK-LABEL: @fsub_fmax(
-; CHECK-NEXT:    [[N1:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
-; CHECK-NEXT:    [[N2:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[Y:%.*]]
-; CHECK-NEXT:    [[COND_INV:%.*]] = fcmp nnan nsz olt <2 x float> [[N1]], [[N2]]
-; CHECK-NEXT:    [[MAX:%.*]] = select <2 x i1> [[COND_INV]], <2 x float> [[N2]], <2 x float> [[N1]]
+; CHECK-NEXT:    [[COND_INV:%.*]] = fcmp nnan nsz ogt <2 x float> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[MAX_V:%.*]] = select <2 x i1> [[COND_INV]], <2 x float> [[Y]], <2 x float> [[X]]
+; CHECK-NEXT:    [[MAX:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[MAX_V]]
 ; CHECK-NEXT:    ret <2 x float> [[MAX]]
 ;
   %n1 = fsub <2 x float> <float -0.0, float -0.0>, %x
@@ -287,10 +285,9 @@ define <2 x float> @fsub_fmax(<2 x float> %x, <2 x float> %y) {
 
 define <2 x double> @fsub_fmin(<2 x double> %x, <2 x double> %y) {
 ; CHECK-LABEL: @fsub_fmin(
-; CHECK-NEXT:    [[N1:%.*]] = fsub <2 x double> <double -0.000000e+00, double -0.000000e+00>, [[X:%.*]]
-; CHECK-NEXT:    [[N2:%.*]] = fsub <2 x double> <double -0.000000e+00, double -0.000000e+00>, [[Y:%.*]]
-; CHECK-NEXT:    [[COND:%.*]] = fcmp nnan olt <2 x double> [[N1]], [[N2]]
-; CHECK-NEXT:    [[MAX:%.*]] = select <2 x i1> [[COND]], <2 x double> [[N1]], <2 x double> [[N2]]
+; CHECK-NEXT:    [[COND:%.*]] = fcmp nnan ogt <2 x double> [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[MAX_V:%.*]] = select <2 x i1> [[COND]], <2 x double> [[X]], <2 x double> [[Y]]
+; CHECK-NEXT:    [[MAX:%.*]] = fsub <2 x double> <double -0.000000e+00, double -0.000000e+00>, [[MAX_V]]
 ; CHECK-NEXT:    ret <2 x double> [[MAX]]
 ;
   %n1 = fsub <2 x double> <double -0.0, double -0.0>, %x
@@ -302,10 +299,9 @@ define <2 x double> @fsub_fmin(<2 x double> %x, <2 x double> %y) {
 
 define double @fneg_fmin(double %x, double %y) {
 ; CHECK-LABEL: @fneg_fmin(
-; CHECK-NEXT:    [[N1:%.*]] = fneg double [[X:%.*]]
-; CHECK-NEXT:    [[N2:%.*]] = fneg double [[Y:%.*]]
-; CHECK-NEXT:    [[COND_INV:%.*]] = fcmp nnan nsz ogt double [[N1]], [[N2]]
-; CHECK-NEXT:    [[MAX:%.*]] = select i1 [[COND_INV]], double [[N2]], double [[N1]]
+; CHECK-NEXT:    [[COND_INV:%.*]] = fcmp nnan nsz olt double [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[MAX_V:%.*]] = select i1 [[COND_INV]], double [[Y]], double [[X]]
+; CHECK-NEXT:    [[MAX:%.*]] = fneg double [[MAX_V]]
 ; CHECK-NEXT:    ret double [[MAX]]
 ;
   %n1 = fneg double %x