[llvm] r364721 - [InstCombine] canonicalize fcmp+select to minnum/maxnum intrinsics

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Sun Jun 30 06:40:31 2019
New Revision: 364721

URL: http://llvm.org/viewvc/llvm-project?rev=364721&view=rev
Log:
[InstCombine] canonicalize fcmp+select to minnum/maxnum intrinsics

This is the opposite direction of D62158 (we have to choose 1 form or the other).
Now that we have FMF on the select, this becomes more palatable. And the benefits
of having a single IR instruction for this operation (less chances of missing folds
based on extra uses, etc) overcome my previous comments about the potential advantage
of larger pattern matching/analysis.

Differential Revision: https://reviews.llvm.org/D62414

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
    llvm/trunk/test/Transforms/InstCombine/minmax-fp.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=364721&r1=364720&r2=364721&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Sun Jun 30 06:40:31 2019
@@ -2030,6 +2030,19 @@ Instruction *InstCombiner::visitSelectIn
     }
   }
 
+  // Canonicalize select of FP values where NaN and -0.0 are not valid as
+  // minnum/maxnum intrinsics.
+  if (isa<FPMathOperator>(SI) && SI.hasNoNaNs() && SI.hasNoSignedZeros()) {
+    Value *X, *Y;
+    if (match(&SI, m_OrdFMax(m_Value(X), m_Value(Y))))
+      return replaceInstUsesWith(
+          SI, Builder.CreateBinaryIntrinsic(Intrinsic::maxnum, X, Y, &SI));
+
+    if (match(&SI, m_OrdFMin(m_Value(X), m_Value(Y))))
+      return replaceInstUsesWith(
+          SI, Builder.CreateBinaryIntrinsic(Intrinsic::minnum, X, Y, &SI));
+  }
+
   // See if we can fold the select into a phi node if the condition is a select.
   if (auto *PN = dyn_cast<PHINode>(SI.getCondition()))
     // The true/false values have to be live in the PHI predecessor's blocks.

Modified: llvm/trunk/test/Transforms/InstCombine/minmax-fp.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/minmax-fp.ll?rev=364721&r1=364720&r2=364721&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/minmax-fp.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/minmax-fp.ll Sun Jun 30 06:40:31 2019
@@ -313,9 +313,8 @@ define double @fneg_fmin(double %x, doub
 
 define float @maxnum_ogt_fmf_on_select(float %a, float %b) {
 ; CHECK-LABEL: @maxnum_ogt_fmf_on_select(
-; CHECK-NEXT:    [[COND:%.*]] = fcmp ogt float [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[F:%.*]] = select nnan nsz i1 [[COND]], float [[A]], float [[B]]
-; CHECK-NEXT:    ret float [[F]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan nsz float @llvm.maxnum.f32(float [[A:%.*]], float [[B:%.*]])
+; CHECK-NEXT:    ret float [[TMP1]]
 ;
   %cond = fcmp ogt float %a, %b
   %f = select nnan nsz i1 %cond, float %a, float %b
@@ -324,9 +323,8 @@ define float @maxnum_ogt_fmf_on_select(f
 
 define <2 x float> @maxnum_oge_fmf_on_select(<2 x float> %a, <2 x float> %b) {
 ; CHECK-LABEL: @maxnum_oge_fmf_on_select(
-; CHECK-NEXT:    [[COND:%.*]] = fcmp oge <2 x float> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[F:%.*]] = select nnan ninf nsz <2 x i1> [[COND]], <2 x float> [[A]], <2 x float> [[B]]
-; CHECK-NEXT:    ret <2 x float> [[F]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf nsz <2 x float> @llvm.maxnum.v2f32(<2 x float> [[A:%.*]], <2 x float> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x float> [[TMP1]]
 ;
   %cond = fcmp oge <2 x float> %a, %b
   %f = select ninf nnan nsz <2 x i1> %cond, <2 x float> %a, <2 x float> %b
@@ -379,9 +377,8 @@ define float @maxnum_no_nnan(float %a, f
 
 define float @minnum_olt_fmf_on_select(float %a, float %b) {
 ; CHECK-LABEL: @minnum_olt_fmf_on_select(
-; CHECK-NEXT:    [[COND:%.*]] = fcmp olt float [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[F:%.*]] = select nnan nsz i1 [[COND]], float [[A]], float [[B]]
-; CHECK-NEXT:    ret float [[F]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan nsz float @llvm.minnum.f32(float [[A:%.*]], float [[B:%.*]])
+; CHECK-NEXT:    ret float [[TMP1]]
 ;
   %cond = fcmp olt float %a, %b
   %f = select nnan nsz i1 %cond, float %a, float %b
@@ -390,9 +387,8 @@ define float @minnum_olt_fmf_on_select(f
 
 define <2 x float> @minnum_ole_fmf_on_select(<2 x float> %a, <2 x float> %b) {
 ; CHECK-LABEL: @minnum_ole_fmf_on_select(
-; CHECK-NEXT:    [[COND:%.*]] = fcmp ole <2 x float> [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[F:%.*]] = select nnan ninf nsz <2 x i1> [[COND]], <2 x float> [[A]], <2 x float> [[B]]
-; CHECK-NEXT:    ret <2 x float> [[F]]
+; CHECK-NEXT:    [[TMP1:%.*]] = call nnan ninf nsz <2 x float> @llvm.minnum.v2f32(<2 x float> [[A:%.*]], <2 x float> [[B:%.*]])
+; CHECK-NEXT:    ret <2 x float> [[TMP1]]
 ;
   %cond = fcmp ole <2 x float> %a, %b
   %f = select ninf nnan nsz <2 x i1> %cond, <2 x float> %a, <2 x float> %b