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Teach InstSimplify -X + X --> 0.0 about unary FNeg

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Differential Revision: https://reviews.llvm.org/D61916

llvm-svn: 360777
This commit is contained in:
Cameron McInally 2019-05-15 14:31:33 +00:00
parent 9d7e2b79e2
commit 77538a884f
2 changed files with 32 additions and 8 deletions
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12
lib/Analysis/InstructionSimplify.cpp
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@ -4316,17 +4316,23 @@ static Value *SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF,
(FMF.noSignedZeros() || CannotBeNegativeZero(Op0, Q.TLI)))
return Op0;
// With nnan: (+/-0.0 - X) + X --> 0.0 (and commuted variant)
// With nnan: -X + X --> 0.0 (and commuted variant)
// We don't have to explicitly exclude infinities (ninf): INF + -INF == NaN.
// Negative zeros are allowed because we always end up with positive zero:
// X = -0.0: (-0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
// X = -0.0: ( 0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
// X = 0.0: (-0.0 - ( 0.0)) + ( 0.0) == (-0.0) + ( 0.0) == 0.0
// X = 0.0: ( 0.0 - ( 0.0)) + ( 0.0) == ( 0.0) + ( 0.0) == 0.0
if (FMF.noNaNs() && (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0)))))
if (FMF.noNaNs()) {
if (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0))))
return ConstantFP::getNullValue(Op0->getType());
if (match(Op0, m_FNeg(m_Specific(Op1))) ||
match(Op1, m_FNeg(m_Specific(Op0))))
return ConstantFP::getNullValue(Op0->getType());
}
// (X - Y) + Y --> X
// Y + (X - Y) --> X
Value *X;

26
test/Transforms/InstSimplify/fast-math.ll
View File

@ -56,8 +56,8 @@ define float @no_mul_zero_3(float %a) {
; -X + X --> 0.0 (with nnan on the fadd)
define float @fadd_fnegx(float %x) {
; CHECK-LABEL: @fadd_fnegx(
define float @fadd_binary_fnegx(float %x) {
; CHECK-LABEL: @fadd_binary_fnegx(
; CHECK-NEXT: ret float 0.000000e+00
;
%negx = fsub float -0.0, %x
@ -65,10 +65,19 @@ define float @fadd_fnegx(float %x) {
ret float %r
}
define float @fadd_unary_fnegx(float %x) {
; CHECK-LABEL: @fadd_unary_fnegx(
; CHECK-NEXT: ret float 0.000000e+00
;
%negx = fneg float %x
%r = fadd nnan float %negx, %x
ret float %r
}
; X + -X --> 0.0 (with nnan on the fadd)
define <2 x float> @fadd_fnegx_commute_vec(<2 x float> %x) {
; CHECK-LABEL: @fadd_fnegx_commute_vec(
define <2 x float> @fadd_binary_fnegx_commute_vec(<2 x float> %x) {
; CHECK-LABEL: @fadd_binary_fnegx_commute_vec(
; CHECK-NEXT: ret <2 x float> zeroinitializer
;
%negx = fsub <2 x float> <float -0.0, float -0.0>, %x
@ -76,6 +85,15 @@ define <2 x float> @fadd_fnegx_commute_vec(<2 x float> %x) {
ret <2 x float> %r
}
define <2 x float> @fadd_unary_fnegx_commute_vec(<2 x float> %x) {
; CHECK-LABEL: @fadd_unary_fnegx_commute_vec(
; CHECK-NEXT: ret <2 x float> zeroinitializer
;
%negx = fneg <2 x float> %x
%r = fadd nnan <2 x float> %x, %negx
ret <2 x float> %r
}
define <2 x float> @fadd_fnegx_commute_vec_undef(<2 x float> %x) {
; CHECK-LABEL: @fadd_fnegx_commute_vec_undef(
; CHECK-NEXT: ret <2 x float> zeroinitializer