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Teach InstSimplify -X + X --> 0.0 about unary FNeg
Differential Revision: https://reviews.llvm.org/D61916 llvm-svn: 360777
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@ -4316,17 +4316,23 @@ static Value *SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF,
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(FMF.noSignedZeros() || CannotBeNegativeZero(Op0, Q.TLI)))
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return Op0;
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// With nnan: (+/-0.0 - X) + X --> 0.0 (and commuted variant)
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// With nnan: -X + X --> 0.0 (and commuted variant)
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// We don't have to explicitly exclude infinities (ninf): INF + -INF == NaN.
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// Negative zeros are allowed because we always end up with positive zero:
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// X = -0.0: (-0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
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// X = -0.0: ( 0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
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// X = 0.0: (-0.0 - ( 0.0)) + ( 0.0) == (-0.0) + ( 0.0) == 0.0
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// X = 0.0: ( 0.0 - ( 0.0)) + ( 0.0) == ( 0.0) + ( 0.0) == 0.0
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if (FMF.noNaNs() && (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
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match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0)))))
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if (FMF.noNaNs()) {
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if (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
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match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0))))
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return ConstantFP::getNullValue(Op0->getType());
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if (match(Op0, m_FNeg(m_Specific(Op1))) ||
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match(Op1, m_FNeg(m_Specific(Op0))))
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return ConstantFP::getNullValue(Op0->getType());
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}
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// (X - Y) + Y --> X
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// Y + (X - Y) --> X
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Value *X;
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@ -56,8 +56,8 @@ define float @no_mul_zero_3(float %a) {
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; -X + X --> 0.0 (with nnan on the fadd)
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define float @fadd_fnegx(float %x) {
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; CHECK-LABEL: @fadd_fnegx(
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define float @fadd_binary_fnegx(float %x) {
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; CHECK-LABEL: @fadd_binary_fnegx(
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; CHECK-NEXT: ret float 0.000000e+00
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;
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%negx = fsub float -0.0, %x
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@ -65,10 +65,19 @@ define float @fadd_fnegx(float %x) {
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ret float %r
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}
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define float @fadd_unary_fnegx(float %x) {
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; CHECK-LABEL: @fadd_unary_fnegx(
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; CHECK-NEXT: ret float 0.000000e+00
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;
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%negx = fneg float %x
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%r = fadd nnan float %negx, %x
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ret float %r
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}
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; X + -X --> 0.0 (with nnan on the fadd)
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define <2 x float> @fadd_fnegx_commute_vec(<2 x float> %x) {
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; CHECK-LABEL: @fadd_fnegx_commute_vec(
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define <2 x float> @fadd_binary_fnegx_commute_vec(<2 x float> %x) {
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; CHECK-LABEL: @fadd_binary_fnegx_commute_vec(
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; CHECK-NEXT: ret <2 x float> zeroinitializer
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;
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%negx = fsub <2 x float> <float -0.0, float -0.0>, %x
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@ -76,6 +85,15 @@ define <2 x float> @fadd_fnegx_commute_vec(<2 x float> %x) {
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ret <2 x float> %r
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}
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define <2 x float> @fadd_unary_fnegx_commute_vec(<2 x float> %x) {
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; CHECK-LABEL: @fadd_unary_fnegx_commute_vec(
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; CHECK-NEXT: ret <2 x float> zeroinitializer
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;
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%negx = fneg <2 x float> %x
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%r = fadd nnan <2 x float> %x, %negx
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ret <2 x float> %r
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}
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define <2 x float> @fadd_fnegx_commute_vec_undef(<2 x float> %x) {
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; CHECK-LABEL: @fadd_fnegx_commute_vec_undef(
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; CHECK-NEXT: ret <2 x float> zeroinitializer
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