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InstCombine: Fold fdiv nnan x, 0 -> copysign(inf, x) 

https://alive2.llvm.org/ce/z/gLBFKB
This commit is contained in:
Matt Arsenault 2022-10-16 22:49:30 -07:00
parent 6ceb607b30
commit e661185fb3
3 changed files with 17 additions and 5 deletions
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1
llvm/lib/Transforms/InstCombine/InstCombineInternal.h
View File

@ -370,6 +370,7 @@ private:
Instruction *foldExtractOfOverflowIntrinsic(ExtractValueInst &EV);
Instruction *foldIntrinsicWithOverflowCommon(IntrinsicInst *II);
Instruction *foldFPSignBitOps(BinaryOperator &I);
Instruction *foldFDivConstantDivisor(BinaryOperator &I);
// Optimize one of these forms:
// and i1 Op, SI / select i1 Op, i1 SI, i1 false (if IsAnd = true)

13
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
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@ -1403,7 +1403,7 @@ Instruction *InstCombinerImpl::visitSDiv(BinaryOperator &I) {
}
/// Remove negation and try to convert division into multiplication.
static Instruction *foldFDivConstantDivisor(BinaryOperator &I) {
Instruction *InstCombinerImpl::foldFDivConstantDivisor(BinaryOperator &I) {
Constant *C;
if (!match(I.getOperand(1), m_Constant(C)))
return nullptr;
@ -1415,6 +1415,17 @@ static Instruction *foldFDivConstantDivisor(BinaryOperator &I) {
if (Constant *NegC = ConstantFoldUnaryOpOperand(Instruction::FNeg, C, DL))
return BinaryOperator::CreateFDivFMF(X, NegC, &I);
// nnan X / +0.0 -> copysign(inf, X)
if (I.hasNoNaNs() && match(I.getOperand(1), m_Zero())) {
IRBuilder<> B(&I);
// TODO: nnan nsz X / -0.0 -> copysign(inf, X)
CallInst *CopySign = B.CreateIntrinsic(
Intrinsic::copysign, {C->getType()},
{ConstantFP::getInfinity(I.getType()), I.getOperand(0)}, &I);
CopySign->takeName(&I);
return replaceInstUsesWith(I, CopySign);
}
// If the constant divisor has an exact inverse, this is always safe. If not,
// then we can still create a reciprocal if fast-math-flags allow it and the
// constant is a regular number (not zero, infinite, or denormal).

8
llvm/test/Transforms/InstCombine/fdiv.ll
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@ -950,7 +950,7 @@ define float @fdiv_zero_f32(float %x) {
; https://alive2.llvm.org/ce/z/gLBFKB
define float @fdiv_nnan_zero_f32(float %x) {
; CHECK-LABEL: @fdiv_nnan_zero_f32(
; CHECK-NEXT: [[FDIV:%.*]] = fdiv nnan float [[X:%.*]], 0.000000e+00
; CHECK-NEXT: [[FDIV:%.*]] = call nnan float @llvm.copysign.f32(float 0x7FF0000000000000, float [[X:%.*]])
; CHECK-NEXT: ret float [[FDIV]]
;
%fdiv = fdiv nnan float %x, 0.0
@ -959,7 +959,7 @@ define float @fdiv_nnan_zero_f32(float %x) {
define <2 x float> @fdiv_nnan_zero_v2f32(<2 x float> %x) {
; CHECK-LABEL: @fdiv_nnan_zero_v2f32(
; CHECK-NEXT: [[FDIV:%.*]] = fdiv nnan <2 x float> [[X:%.*]], zeroinitializer
; CHECK-NEXT: [[FDIV:%.*]] = call nnan <2 x float> @llvm.copysign.v2f32(<2 x float> <float 0x7FF0000000000000, float 0x7FF0000000000000>, <2 x float> [[X:%.*]])
; CHECK-NEXT: ret <2 x float> [[FDIV]]
;
%fdiv = fdiv nnan <2 x float> %x, zeroinitializer
@ -968,7 +968,7 @@ define <2 x float> @fdiv_nnan_zero_v2f32(<2 x float> %x) {
define float @fdiv_nnan_zero_f32_fmf(float %x) {
; CHECK-LABEL: @fdiv_nnan_zero_f32_fmf(
; CHECK-NEXT: [[FDIV:%.*]] = fdiv nnan nsz float [[X:%.*]], 0.000000e+00
; CHECK-NEXT: [[FDIV:%.*]] = call nnan nsz float @llvm.copysign.f32(float 0x7FF0000000000000, float [[X:%.*]])
; CHECK-NEXT: ret float [[FDIV]]
;
%fdiv = fdiv nnan nsz float %x, 0.0
@ -977,7 +977,7 @@ define float @fdiv_nnan_zero_f32_fmf(float %x) {
define <2 x float> @fdiv_nnan_zero_v2f32_fmf(<2 x float> %x) {
; CHECK-LABEL: @fdiv_nnan_zero_v2f32_fmf(
; CHECK-NEXT: [[FDIV:%.*]] = fdiv nnan nsz <2 x float> [[X:%.*]], zeroinitializer
; CHECK-NEXT: [[FDIV:%.*]] = call nnan nsz <2 x float> @llvm.copysign.v2f32(<2 x float> <float 0x7FF0000000000000, float 0x7FF0000000000000>, <2 x float> [[X:%.*]])
; CHECK-NEXT: ret <2 x float> [[FDIV]]
;
%fdiv = fdiv nnan nsz <2 x float> %x, zeroinitializer