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InstCombine: Handle multiple uses fabs in SimplifyDemandedFPClass (llvm#176035)
1 parent a866030 commit 282a065

3 files changed

Lines changed: 119 additions & 0 deletions

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‎llvm/include/llvm/Support/KnownFPClass.h‎

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Original file line numberDiff line numberDiff line change
@@ -192,6 +192,12 @@ struct KnownFPClass {
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signBitMustBeZero();
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}
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static KnownFPClass fabs(const KnownFPClass &Src) {
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KnownFPClass Known = Src;
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Known.fabs();
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return Known;
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}
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// Enum of min/max intrinsics to avoid dependency on IR.
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enum class MinMaxKind {
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minimum,

‎llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp‎

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@@ -2955,6 +2955,16 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Instruction *I,
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Value *InstCombinerImpl::SimplifyMultipleUseDemandedFPClass(
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Instruction *I, FPClassTest DemandedMask, KnownFPClass &Known,
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Instruction *CxtI, unsigned Depth) {
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FastMathFlags FMF;
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if (auto *FPOp = dyn_cast<FPMathOperator>(I)) {
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FMF = FPOp->getFastMathFlags();
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if (FMF.noNaNs())
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DemandedMask &= ~fcNan;
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if (FMF.noInfs())
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DemandedMask &= ~fcInf;
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}
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switch (I->getOpcode()) {
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case Instruction::Select: {
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// TODO: Can we infer which side it came from based on adjusted result
@@ -2981,6 +2991,24 @@ Value *InstCombinerImpl::SimplifyMultipleUseDemandedFPClass(
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const CallInst *CI = cast<CallInst>(I);
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const Intrinsic::ID IID = CI->getIntrinsicID();
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switch (IID) {
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case Intrinsic::fabs: {
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Value *Src = CI->getArgOperand(0);
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KnownFPClass KnownSrc =
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computeKnownFPClass(Src, fcAllFlags, CxtI, Depth + 1);
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if ((DemandedMask & fcNan) == fcNone)
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KnownSrc.knownNot(fcNan);
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if ((DemandedMask & fcInf) == fcNone)
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KnownSrc.knownNot(fcInf);
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// TODO: If the only sign bit difference is due to -0, look at source if
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// nsz.
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if (KnownSrc.SignBit == false || ((DemandedMask & fcNan) == fcNone &&
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KnownSrc.isKnownNever(fcNegative)))
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return Src;
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Known = KnownFPClass::fabs(KnownSrc);
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break;
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}
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case Intrinsic::maximum:
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case Intrinsic::minimum:
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case Intrinsic::maximumnum:

‎llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll‎

Lines changed: 85 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -682,6 +682,91 @@ define nofpclass(nan) float @ret_nonan_fabs_src_known_positive_or_nan(float nofp
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ret float %fabs
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}
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define nofpclass(snan) float @fabs_src_known_positive_multiple_uses(float nofpclass(nan ninf nnorm nsub nzero) %always.positive, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(snan) float @fabs_src_known_positive_multiple_uses
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; CHECK-SAME: (float nofpclass(nan ninf nzero nsub nnorm) [[ALWAYS_POSITIVE:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: store float [[ALWAYS_POSITIVE]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[ALWAYS_POSITIVE]]
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;
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%fabs = call float @llvm.fabs.f32(float %always.positive)
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store float %fabs, ptr %ptr
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ret float %fabs
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}
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define nofpclass(snan) float @fabs_src_known_positive_except_negzero_multiple_uses(float nofpclass(nan ninf nnorm nsub) %always.positive.or.nzero, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(snan) float @fabs_src_known_positive_except_negzero_multiple_uses
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; CHECK-SAME: (float nofpclass(nan ninf nsub nnorm) [[ALWAYS_POSITIVE_OR_NZERO:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NZERO]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[FABS]]
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;
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%fabs = call float @llvm.fabs.f32(float %always.positive.or.nzero)
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store float %fabs, ptr %ptr
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ret float %fabs
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}
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define nofpclass(snan) float @fabs_nsz_src_known_positive_except_negzero_multiple_uses(float nofpclass(nan ninf nnorm nsub) %always.positive.or.nzero, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(snan) float @fabs_nsz_src_known_positive_except_negzero_multiple_uses
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; CHECK-SAME: (float nofpclass(nan ninf nsub nnorm) [[ALWAYS_POSITIVE_OR_NZERO:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: [[FABS:%.*]] = call nsz float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NZERO]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[FABS]]
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;
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%fabs = call nsz float @llvm.fabs.f32(float %always.positive.or.nzero)
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store float %fabs, ptr %ptr
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ret float %fabs
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}
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define nofpclass(snan) float @fabs_src_known_positive_or_nan_multiple_uses(float nofpclass(ninf nnorm nsub nzero) %always.positive.or.nan, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(snan) float @fabs_src_known_positive_or_nan_multiple_uses
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; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ALWAYS_POSITIVE_OR_NAN:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NAN]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[FABS]]
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;
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%fabs = call float @llvm.fabs.f32(float %always.positive.or.nan)
728+
store float %fabs, ptr %ptr
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ret float %fabs
730+
}
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define nofpclass(nan) float @ret_nonan_fabs_src_known_positive_or_nan_multiple_uses(float nofpclass(ninf nnorm nsub nzero) %always.positive.or.nan, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(nan) float @ret_nonan_fabs_src_known_positive_or_nan_multiple_uses
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; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ALWAYS_POSITIVE_OR_NAN:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: [[FABS:%.*]] = call float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NAN]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[ALWAYS_POSITIVE_OR_NAN]]
738+
;
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%fabs = call float @llvm.fabs.f32(float %always.positive.or.nan)
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store float %fabs, ptr %ptr
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ret float %fabs
742+
}
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; Take no-nan from flag
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define nofpclass(nsub) float @ret_fabs_nnan_src_known_positive_or_nan_multiple_uses(float nofpclass(ninf nnorm nsub nzero) %always.positive.or.nan, ptr %ptr) {
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; CHECK-LABEL: define nofpclass(nsub) float @ret_fabs_nnan_src_known_positive_or_nan_multiple_uses
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; CHECK-SAME: (float nofpclass(ninf nzero nsub nnorm) [[ALWAYS_POSITIVE_OR_NAN:%.*]], ptr [[PTR:%.*]]) {
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; CHECK-NEXT: [[FABS:%.*]] = call nnan float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NAN]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[ALWAYS_POSITIVE_OR_NAN]]
751+
;
752+
%fabs = call nnan float @llvm.fabs.f32(float %always.positive.or.nan)
753+
store float %fabs, ptr %ptr
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ret float %fabs
755+
}
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; Take no-infs from flag, which will then imply no neg
758+
define nofpclass(nsub) float @ret_fabs_ninf_src_known_positive_or_ninf_or_nan_multiple_uses(float nofpclass(nan nnorm nsub nzero) %always.positive.or.ninf, ptr %ptr) {
759+
; CHECK-LABEL: define nofpclass(nsub) float @ret_fabs_ninf_src_known_positive_or_ninf_or_nan_multiple_uses
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; CHECK-SAME: (float nofpclass(nan nzero nsub nnorm) [[ALWAYS_POSITIVE_OR_NINF:%.*]], ptr [[PTR:%.*]]) {
761+
; CHECK-NEXT: [[FABS:%.*]] = call ninf float @llvm.fabs.f32(float [[ALWAYS_POSITIVE_OR_NINF]])
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; CHECK-NEXT: store float [[FABS]], ptr [[PTR]], align 4
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; CHECK-NEXT: ret float [[ALWAYS_POSITIVE_OR_NINF]]
764+
;
765+
%fabs = call ninf float @llvm.fabs.f32(float %always.positive.or.ninf)
766+
store float %fabs, ptr %ptr
767+
ret float %fabs
768+
}
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define nofpclass(snan) float @fabs_src_known_negative(float nofpclass(nan pinf pnorm psub pzero) %always.negative) {
686771
; CHECK-LABEL: define nofpclass(snan) float @fabs_src_known_negative
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; CHECK-SAME: (float nofpclass(nan pinf pzero psub pnorm) [[ALWAYS_NEGATIVE:%.*]]) {

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