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[InstCombine] add restrict reassoc for the powi(X,Y) / X #86428

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Merged
vfdff merged 2 commits into from
Mar 27, 2024
Merged

[InstCombine] add restrict reassoc for the powi(X,Y) / X #86428

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2938f1c
[InstCombine] Refactor powi(X,Y) / X to call foldPowiReassoc, NFC
vfdff Mar 24, 2024
bd9bb31
[InstCombine] add restrict reassoc for the powi(X,Y) / X
vfdff Mar 24, 2024
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28 changes: 14 additions & 14 deletions llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -611,6 +611,18 @@ Instruction *InstCombinerImpl::foldPowiReassoc(BinaryOperator &I) {
Y->getType() == Z->getType())
return createPowiExpr(I, *this, X, Y, Z);

// powi(X, Y) / X --> powi(X, Y-1)
// This is legal when (Y - 1) can't wraparound, in which case reassoc and nnan
// are required.
// TODO: Multi-use may be also better off creating Powi(x,y-1)
if (I.hasAllowReassoc() && I.hasNoNaNs() &&
match(Op0, m_OneUse(m_AllowReassoc(m_Intrinsic<Intrinsic::powi>(
m_Specific(Op1), m_Value(Y))))) &&
willNotOverflowSignedSub(Y, ConstantInt::get(Y->getType(), 1), I)) {
Constant *NegOne = ConstantInt::getAllOnesValue(Y->getType());
return createPowiExpr(I, *this, Op1, Y, NegOne);
}

return nullptr;
}

Expand Down Expand Up @@ -1904,20 +1916,8 @@ Instruction *InstCombinerImpl::visitFDiv(BinaryOperator &I) {
return replaceInstUsesWith(I, Pow);
}

// powi(X, Y) / X --> powi(X, Y-1)
// This is legal when (Y - 1) can't wraparound, in which case reassoc and nnan
// are required.
// TODO: Multi-use may be also better off creating Powi(x,y-1)
if (I.hasAllowReassoc() && I.hasNoNaNs() &&
match(Op0, m_OneUse(m_Intrinsic<Intrinsic::powi>(m_Specific(Op1),
m_Value(Y)))) &&
willNotOverflowSignedSub(Y, ConstantInt::get(Y->getType(), 1), I)) {
Constant *NegOne = ConstantInt::getAllOnesValue(Y->getType());
Value *Y1 = Builder.CreateAdd(Y, NegOne);
Type *Types[] = {Op1->getType(), Y1->getType()};
Value *Pow = Builder.CreateIntrinsic(Intrinsic::powi, Types, {Op1, Y1}, &I);
return replaceInstUsesWith(I, Pow);
}
if (Instruction *FoldedPowi = foldPowiReassoc(I))
return FoldedPowi;

return nullptr;
}
Expand Down
17 changes: 14 additions & 3 deletions llvm/test/Transforms/InstCombine/powi.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -313,7 +313,7 @@ define double @fdiv_pow_powi(double %x) {
; CHECK-NEXT: [[DIV:%.*]] = fmul reassoc nnan double [[X:%.*]], [[X]]
; CHECK-NEXT: ret double [[DIV]]
;
%p1 = call double @llvm.powi.f64.i32(double %x, i32 3)
%p1 = call reassoc double @llvm.powi.f64.i32(double %x, i32 3)
%div = fdiv reassoc nnan double %p1, %x
ret double %div
}
Expand All @@ -323,7 +323,7 @@ define float @fdiv_powf_powi(float %x) {
; CHECK-NEXT: [[DIV:%.*]] = call reassoc nnan float @llvm.powi.f32.i32(float [[X:%.*]], i32 99)
; CHECK-NEXT: ret float [[DIV]]
;
%p1 = call float @llvm.powi.f32.i32(float %x, i32 100)
%p1 = call reassoc float @llvm.powi.f32.i32(float %x, i32 100)
%div = fdiv reassoc nnan float %p1, %x
ret float %div
}
Expand All @@ -347,10 +347,21 @@ define double @fdiv_pow_powi_multi_use(double %x) {
define float @fdiv_powf_powi_missing_reassoc(float %x) {
; CHECK-LABEL: @fdiv_powf_powi_missing_reassoc(
; CHECK-NEXT: [[P1:%.*]] = call float @llvm.powi.f32.i32(float [[X:%.*]], i32 100)
; CHECK-NEXT: [[DIV:%.*]] = fdiv nnan float [[P1]], [[X]]
; CHECK-NEXT: [[DIV:%.*]] = fdiv reassoc nnan float [[P1]], [[X]]
; CHECK-NEXT: ret float [[DIV]]
;
%p1 = call float @llvm.powi.f32.i32(float %x, i32 100)
%div = fdiv reassoc nnan float %p1, %x
ret float %div
}

define float @fdiv_powf_powi_missing_reassoc1(float %x) {
; CHECK-LABEL: @fdiv_powf_powi_missing_reassoc1(
; CHECK-NEXT: [[P1:%.*]] = call reassoc float @llvm.powi.f32.i32(float [[X:%.*]], i32 100)
; CHECK-NEXT: [[DIV:%.*]] = fdiv nnan float [[P1]], [[X]]
; CHECK-NEXT: ret float [[DIV]]
;
%p1 = call reassoc float @llvm.powi.f32.i32(float %x, i32 100)
%div = fdiv nnan float %p1, %x
ret float %div
}
Expand Down