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[InstCombine] Fix constant swap case of fcmp + fadd + sel xfrm #119419

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Jan 2, 2025
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[InstCombine] Fix constant swap case of fcmp + fadd + sel xfrm #119419

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44 changes: 26 additions & 18 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3769,22 +3769,9 @@ static Value *foldSelectIntoAddConstant(SelectInst &SI,
if (!SIFOp || !SIFOp->hasNoSignedZeros() || !SIFOp->hasNoNaNs())
return nullptr;

// select((fcmp Pred, X, 0), (fadd X, C), C)
// => fadd((select (fcmp Pred, X, 0), X, 0), C)
//
// Pred := OGT, OGE, OLT, OLE, UGT, UGE, ULT, and ULE
Instruction *FAdd;
Constant *C;
Value *X, *Z;
CmpPredicate Pred;

// Note: OneUse check for `Cmp` is necessary because it makes sure that other
// InstCombine folds don't undo this transformation and cause an infinite
// loop. Furthermore, it could also increase the operation count.
if (match(&SI, m_Select(m_OneUse(m_FCmp(Pred, m_Value(X), m_Value(Z))),
m_OneUse(m_Instruction(FAdd)), m_Constant(C))) ||
match(&SI, m_Select(m_OneUse(m_FCmp(Pred, m_Value(X), m_Value(Z))),
m_Constant(C), m_OneUse(m_Instruction(FAdd))))) {
auto TryFoldIntoAddConstant =
[&Builder, &SI](CmpInst::Predicate Pred, Value *X, Value *Z,
Instruction *FAdd, Constant *C, bool Swapped) -> Value * {
// Only these relational predicates can be transformed into maxnum/minnum
// intrinsic.
if (!CmpInst::isRelational(Pred) || !match(Z, m_AnyZeroFP()))
Expand All @@ -3793,7 +3780,8 @@ static Value *foldSelectIntoAddConstant(SelectInst &SI,
if (!match(FAdd, m_FAdd(m_Specific(X), m_Specific(C))))
return nullptr;

Value *NewSelect = Builder.CreateSelect(SI.getCondition(), X, Z, "", &SI);
Value *NewSelect = Builder.CreateSelect(SI.getCondition(), Swapped ? Z : X,
Swapped ? X : Z, "", &SI);
NewSelect->takeName(&SI);

Value *NewFAdd = Builder.CreateFAdd(NewSelect, C);
Expand All @@ -3808,7 +3796,27 @@ static Value *foldSelectIntoAddConstant(SelectInst &SI,
cast<Instruction>(NewSelect)->setFastMathFlags(NewFMF);

return NewFAdd;
}
};

// select((fcmp Pred, X, 0), (fadd X, C), C)
// => fadd((select (fcmp Pred, X, 0), X, 0), C)
//
// Pred := OGT, OGE, OLT, OLE, UGT, UGE, ULT, and ULE
Instruction *FAdd;
Constant *C;
Value *X, *Z;
CmpPredicate Pred;

// Note: OneUse check for `Cmp` is necessary because it makes sure that other
// InstCombine folds don't undo this transformation and cause an infinite
// loop. Furthermore, it could also increase the operation count.
if (match(&SI, m_Select(m_OneUse(m_FCmp(Pred, m_Value(X), m_Value(Z))),
m_OneUse(m_Instruction(FAdd)), m_Constant(C))))
return TryFoldIntoAddConstant(Pred, X, Z, FAdd, C, /*Swapped=*/false);

if (match(&SI, m_Select(m_OneUse(m_FCmp(Pred, m_Value(X), m_Value(Z))),
m_Constant(C), m_OneUse(m_Instruction(FAdd)))))
return TryFoldIntoAddConstant(Pred, X, Z, FAdd, C, /*Swapped=*/true);

return nullptr;
}
Expand Down
16 changes: 8 additions & 8 deletions llvm/test/Transforms/InstCombine/fcmp-fadd-select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ define float @test_fcmp_ogt_fadd_select_constant(float %in) {
define float @test_fcmp_ogt_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_ogt_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.maxnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.minnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -87,7 +87,7 @@ define float @test_fcmp_olt_fadd_select_constant(float %in) {
define float @test_fcmp_olt_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_olt_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.minnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.maxnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -155,7 +155,7 @@ define float @test_fcmp_oge_fadd_select_constant(float %in) {
define float @test_fcmp_oge_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_oge_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.maxnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.minnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -223,7 +223,7 @@ define float @test_fcmp_ole_fadd_select_constant(float %in) {
define float @test_fcmp_ole_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_ole_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.minnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[SEL_NEW:%.*]] = call nsz float @llvm.maxnum.f32(float [[IN]], float 0.000000e+00)
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -293,7 +293,7 @@ define float @test_fcmp_ugt_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_ugt_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[CMP1_INV:%.*]] = fcmp ole float [[IN]], 0.000000e+00
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float 0.000000e+00, float [[IN]]
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float [[IN]], float 0.000000e+00
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -366,7 +366,7 @@ define float @test_fcmp_uge_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_uge_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[CMP1_INV:%.*]] = fcmp olt float [[IN]], 0.000000e+00
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float 0.000000e+00, float [[IN]]
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float [[IN]], float 0.000000e+00
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -439,7 +439,7 @@ define float @test_fcmp_ult_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_ult_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[CMP1_INV:%.*]] = fcmp oge float [[IN]], 0.000000e+00
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float 0.000000e+00, float [[IN]]
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float [[IN]], float 0.000000e+00
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down Expand Up @@ -512,7 +512,7 @@ define float @test_fcmp_ule_fadd_select_constant_swapped(float %in) {
; CHECK-LABEL: define float @test_fcmp_ule_fadd_select_constant_swapped(
; CHECK-SAME: float [[IN:%.*]]) {
; CHECK-NEXT: [[CMP1_INV:%.*]] = fcmp ogt float [[IN]], 0.000000e+00
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float 0.000000e+00, float [[IN]]
; CHECK-NEXT: [[SEL_NEW:%.*]] = select i1 [[CMP1_INV]], float [[IN]], float 0.000000e+00
; CHECK-NEXT: [[ADD_NEW:%.*]] = fadd nnan nsz float [[SEL_NEW]], 1.000000e+00
; CHECK-NEXT: ret float [[ADD_NEW]]
;
Expand Down
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