Revert "[InstCombine] Remove nnan requirement for transformation to fabs from select" (946fd4ea) · Commits · llvm-doe / llvm-project

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

+9 −5

Original line number	Diff line number	Diff line
		@@ -2863,12 +2863,14 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
		}

		// Canonicalize select with fcmp to fabs(). -0.0 makes this tricky. We need
		// fast-math-flags (nsz) or fsub with +0.0 (not fneg) for this to work.
		// fast-math-flags (nsz) or fsub with +0.0 (not fneg) for this to work. We
		// also require nnan because we do not want to unintentionally change the
		// sign of a NaN value.
		// (X <= +/-0.0) ? (0.0 - X) : X --> fabs(X)
		Instruction *FSub;
		if (match(CondVal, m_FCmp(Pred, m_Specific(FalseVal), m_AnyZeroFP())) &&
		match(TrueVal, m_FSub(m_PosZeroFP(), m_Specific(FalseVal))) &&
		match(TrueVal, m_Instruction(FSub)) &&
		match(TrueVal, m_Instruction(FSub)) && FSub->hasNoNaNs() &&
		(Pred == FCmpInst::FCMP_OLE \|\| Pred == FCmpInst::FCMP_ULE)) {
		Value *Fabs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, FalseVal, &SI);
		return replaceInstUsesWith(SI, Fabs);
		@@ -2876,7 +2878,7 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
		// (X > +/-0.0) ? X : (0.0 - X) --> fabs(X)
		if (match(CondVal, m_FCmp(Pred, m_Specific(TrueVal), m_AnyZeroFP())) &&
		match(FalseVal, m_FSub(m_PosZeroFP(), m_Specific(TrueVal))) &&
		match(FalseVal, m_Instruction(FSub)) &&
		match(FalseVal, m_Instruction(FSub)) && FSub->hasNoNaNs() &&
		(Pred == FCmpInst::FCMP_OGT \|\| Pred == FCmpInst::FCMP_UGT)) {
		Value *Fabs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, TrueVal, &SI);
		return replaceInstUsesWith(SI, Fabs);
		@@ -2887,7 +2889,8 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
		Instruction *FNeg;
		if (match(CondVal, m_FCmp(Pred, m_Specific(FalseVal), m_AnyZeroFP())) &&
		match(TrueVal, m_FNeg(m_Specific(FalseVal))) &&
		match(TrueVal, m_Instruction(FNeg)) && SI.hasNoSignedZeros() &&
		match(TrueVal, m_Instruction(FNeg)) && FNeg->hasNoNaNs() &&
		FNeg->hasNoSignedZeros() && SI.hasNoSignedZeros() &&
		(Pred == FCmpInst::FCMP_OLT \|\| Pred == FCmpInst::FCMP_OLE \|\|
		Pred == FCmpInst::FCMP_ULT \|\| Pred == FCmpInst::FCMP_ULE)) {
		Value *Fabs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, FalseVal, &SI);
		@@ -2898,7 +2901,8 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
		// (X >= +/-0.0) ? X : -X --> fabs(X)
		if (match(CondVal, m_FCmp(Pred, m_Specific(TrueVal), m_AnyZeroFP())) &&
		match(FalseVal, m_FNeg(m_Specific(TrueVal))) &&
		match(FalseVal, m_Instruction(FNeg)) && SI.hasNoSignedZeros() &&
		match(FalseVal, m_Instruction(FNeg)) && FNeg->hasNoNaNs() &&
		FNeg->hasNoSignedZeros() && SI.hasNoSignedZeros() &&
		(Pred == FCmpInst::FCMP_OGT \|\| Pred == FCmpInst::FCMP_OGE \|\|
		Pred == FCmpInst::FCMP_UGT \|\| Pred == FCmpInst::FCMP_UGE)) {
		Value *Fabs = Builder.CreateUnaryIntrinsic(Intrinsic::fabs, TrueVal, &SI);

llvm/test/Transforms/InstCombine/fabs.ll

+16 −8

Original line number	Diff line number	Diff line
		@@ -254,8 +254,10 @@ define double @multi_use_fabs_fpext(float %x) {

		define double @select_fcmp_ole_zero(double %x) {
		; CHECK-LABEL: @select_fcmp_ole_zero(
		; CHECK-NEXT: [[TMP1:%.]] = call double @llvm.fabs.f64(double [[X:%.]])
		; CHECK-NEXT: ret double [[TMP1]]
		; CHECK-NEXT: [[LEZERO:%.]] = fcmp ole double [[X:%.]], 0.000000e+00
		; CHECK-NEXT: [[NEGX:%.*]] = fsub double 0.000000e+00, [[X]]
		; CHECK-NEXT: [[FABS:%.*]] = select i1 [[LEZERO]], double [[NEGX]], double [[X]]
		; CHECK-NEXT: ret double [[FABS]]
		;
		%lezero = fcmp ole double %x, 0.0
		%negx = fsub double 0.0, %x
		@@ -343,8 +345,10 @@ define <2 x float> @select_nnan_fcmp_nnan_ole_negzero(<2 x float> %x) {

		define fp128 @select_fcmp_ogt_zero(fp128 %x) {
		; CHECK-LABEL: @select_fcmp_ogt_zero(
		; CHECK-NEXT: [[TMP1:%.]] = call fp128 @llvm.fabs.f128(fp128 [[X:%.]])
		; CHECK-NEXT: ret fp128 [[TMP1]]
		; CHECK-NEXT: [[GTZERO:%.]] = fcmp ogt fp128 [[X:%.]], 0xL00000000000000000000000000000000
		; CHECK-NEXT: [[NEGX:%.*]] = fsub fp128 0xL00000000000000000000000000000000, [[X]]
		; CHECK-NEXT: [[FABS:%.*]] = select i1 [[GTZERO]], fp128 [[X]], fp128 [[NEGX]]
		; CHECK-NEXT: ret fp128 [[FABS]]
		;
		%gtzero = fcmp ogt fp128 %x, zeroinitializer
		%negx = fsub fp128 zeroinitializer, %x
		@@ -430,8 +434,10 @@ define half @select_fcmp_nnan_oge_negzero(half %x) {

		define double @select_fcmp_olt_zero_unary_fneg(double %x) {
		; CHECK-LABEL: @select_fcmp_olt_zero_unary_fneg(
		; CHECK-NEXT: [[TMP1:%.]] = call nsz double @llvm.fabs.f64(double [[X:%.]])
		; CHECK-NEXT: ret double [[TMP1]]
		; CHECK-NEXT: [[LTZERO:%.]] = fcmp olt double [[X:%.]], 0.000000e+00
		; CHECK-NEXT: [[NEGX:%.*]] = fneg double [[X]]
		; CHECK-NEXT: [[FABS:%.*]] = select nsz i1 [[LTZERO]], double [[NEGX]], double [[X]]
		; CHECK-NEXT: ret double [[FABS]]
		;
		%ltzero = fcmp olt double %x, 0.0
		%negx = fneg double %x
		@@ -717,8 +723,10 @@ define float @select_fcmp_nnan_nsz_ule_negzero_unary_fneg(float %x) {

		define <2 x float> @select_fcmp_ogt_zero_unary_fneg(<2 x float> %x) {
		; CHECK-LABEL: @select_fcmp_ogt_zero_unary_fneg(
		; CHECK-NEXT: [[TMP1:%.]] = call nsz <2 x float> @llvm.fabs.v2f32(<2 x float> [[X:%.]])
		; CHECK-NEXT: ret <2 x float> [[TMP1]]
		; CHECK-NEXT: [[GTZERO:%.]] = fcmp ogt <2 x float> [[X:%.]], zeroinitializer
		; CHECK-NEXT: [[NEGX:%.*]] = fneg <2 x float> [[X]]
		; CHECK-NEXT: [[FABS:%.*]] = select nsz <2 x i1> [[GTZERO]], <2 x float> [[X]], <2 x float> [[NEGX]]
		; CHECK-NEXT: ret <2 x float> [[FABS]]
		;
		%gtzero = fcmp ogt <2 x float> %x, zeroinitializer
		%negx = fneg <2 x float> %x

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