Bug 21610: Canonicalize min/max fcmp selects to use ordered comparisons

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222705 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -928,8 +928,22 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
              !CFPf->getValueAPF().isZero()))
         return ReplaceInstUsesWith(SI, TrueVal);
       }
-      // NOTE: if we wanted to, this is where to detect MIN/MAX
 
+      // Canonicalize to use ordered comparisons by swapping the select
+      // operands.
+      //
+      // e.g.
+      // (X ugt Y) ? X : Y -> (X ole Y) ? Y : X
+      if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
+        FCmpInst::Predicate InvPred = FCI->getInversePredicate();
+        Value *NewCond = Builder->CreateFCmp(InvPred, TrueVal, FalseVal,
+                                             FCI->getName() + ".inv");
+
+        return SelectInst::Create(NewCond, FalseVal, TrueVal,
+                                  SI.getName() + ".p");
+      }
+
+      // NOTE: if we wanted to, this is where to detect MIN/MAX
     } else if (FCI->getOperand(0) == FalseVal && FCI->getOperand(1) == TrueVal){
       // Transform (X == Y) ? Y : X  -> X
       if (FCI->getPredicate() == FCmpInst::FCMP_OEQ) {
@@ -955,6 +969,21 @@ Instruction *InstCombiner::visitSelectInst(SelectInst &SI) {
              !CFPf->getValueAPF().isZero()))
           return ReplaceInstUsesWith(SI, TrueVal);
       }
+
+      // Canonicalize to use ordered comparisons by swapping the select
+      // operands.
+      //
+      // e.g.
+      // (X ugt Y) ? X : Y -> (X ole Y) ? X : Y
+      if (FCI->hasOneUse() && FCmpInst::isUnordered(FCI->getPredicate())) {
+        FCmpInst::Predicate InvPred = FCI->getInversePredicate();
+        Value *NewCond = Builder->CreateFCmp(InvPred, FalseVal, TrueVal,
+                                             FCI->getName() + ".inv");
+
+        return SelectInst::Create(NewCond, FalseVal, TrueVal,
+                                  SI.getName() + ".p");
+      }
+
       // NOTE: if we wanted to, this is where to detect MIN/MAX
     }
     // NOTE: if we wanted to, this is where to detect ABS

test/Transforms/InstCombine/unordered-fcmp-select.ll

@@ -0,0 +1,125 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+; CHECK-LABEL: @select_max_ugt(
+; CHECK: %cmp.inv = fcmp ole float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_max_ugt(float %a, float %b) {
+  %cmp = fcmp ugt float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_max_uge(
+; CHECK: %cmp.inv = fcmp olt float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_max_uge(float %a, float %b) {
+  %cmp = fcmp uge float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_min_ugt(
+; CHECK: %cmp.inv = fcmp ole float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %a, float %b
+; CHECK-NEXT: ret float %sel
+define float @select_min_ugt(float %a, float %b) {
+  %cmp = fcmp ugt float %a, %b
+  %sel = select i1 %cmp, float %b, float %a
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_min_uge(
+; CHECK: %cmp.inv = fcmp olt float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %a, float %b
+; CHECK-NEXT: ret float %sel
+define float @select_min_uge(float %a, float %b) {
+  %cmp = fcmp uge float %a, %b
+  %sel = select i1 %cmp, float %b, float %a
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_max_ult(
+; CHECK: %cmp.inv = fcmp oge float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %a, float %b
+; CHECK-NEXT: ret float %sel
+define float @select_max_ult(float %a, float %b) {
+  %cmp = fcmp ult float %a, %b
+  %sel = select i1 %cmp, float %b, float %a
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_max_ule(
+; CHECK: %cmp.inv = fcmp ogt float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %a, float %b
+; CHECK: ret float %sel
+define float @select_max_ule(float %a, float %b) {
+  %cmp = fcmp ule float %a, %b
+  %sel = select i1 %cmp, float %b, float %a
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_min_ult(
+; CHECK: %cmp.inv = fcmp oge float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_min_ult(float %a, float %b) {
+  %cmp = fcmp ult float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_min_ule(
+; CHECK: %cmp.inv = fcmp ogt float %a, %b
+; CHECK-NEXT: %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_min_ule(float %a, float %b) {
+  %cmp = fcmp ule float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_fcmp_une(
+; CHECK:  %cmp.inv = fcmp oeq float %a, %b
+; CHECK-NEXT:  %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_fcmp_une(float %a, float %b) {
+  %cmp = fcmp une float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_fcmp_ueq
+; CHECK:  %cmp.inv = fcmp one float %a, %b
+; CHECK-NEXT:  %sel = select i1 %cmp.inv, float %b, float %a
+; CHECK-NEXT: ret float %sel
+define float @select_fcmp_ueq(float %a, float %b) {
+  %cmp = fcmp ueq float %a, %b
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+declare void @foo(i1)
+
+; CHECK-LABEL: @select_max_ugt_2_use_cmp(
+; CHECK: fcmp ugt
+; CHECK-NOT: fcmp
+; CHECK: ret
+define float @select_max_ugt_2_use_cmp(float %a, float %b) {
+  %cmp = fcmp ugt float %a, %b
+  call void @foo(i1 %cmp)
+  %sel = select i1 %cmp, float %a, float %b
+  ret float %sel
+}
+
+; CHECK-LABEL: @select_min_uge_2_use_cmp(
+; CHECK: fcmp uge
+; CHECK-NOT: fcmp
+; CHECK: ret
+define float @select_min_uge_2_use_cmp(float %a, float %b) {
+  %cmp = fcmp uge float %a, %b
+  call void @foo(i1 %cmp)
+  %sel = select i1 %cmp, float %b, float %a
+  ret float %sel
+}

test/Transforms/LoopVectorize/minmax_reduction.ll

@@ -516,7 +516,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @unordered_max_red_float(
-; CHECK: fcmp ugt <2 x float>
+; CHECK: fcmp ole <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp ogt <2 x float>
@@ -542,7 +542,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @unordered_max_red_float_ge(
-; CHECK: fcmp uge <2 x float>
+; CHECK: fcmp olt <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp ogt <2 x float>
@@ -568,7 +568,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @inverted_unordered_max_red_float(
-; CHECK: fcmp ult <2 x float>
+; CHECK: fcmp oge <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp ogt <2 x float>
@@ -594,7 +594,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @inverted_unordered_max_red_float_le(
-; CHECK: fcmp ule <2 x float>
+; CHECK: fcmp ogt <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp ogt <2 x float>
@@ -727,7 +727,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @unordered_min_red_float(
-; CHECK: fcmp ult <2 x float>
+; CHECK: fcmp oge <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp olt <2 x float>
@@ -753,7 +753,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @unordered_min_red_float_le(
-; CHECK: fcmp ule <2 x float>
+; CHECK: fcmp ogt <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp olt <2 x float>
@@ -779,7 +779,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @inverted_unordered_min_red_float(
-; CHECK: fcmp ugt <2 x float>
+; CHECK: fcmp ole <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp olt <2 x float>
@@ -805,7 +805,7 @@ for.end:
 }
 
 ; CHECK-LABEL: @inverted_unordered_min_red_float_ge(
-; CHECK: fcmp uge <2 x float>
+; CHECK: fcmp olt <2 x float>
 ; CHECK: select <2 x i1>
 ; CHECK: middle.block
 ; CHECK: fcmp olt <2 x float>