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[InstSimplify] fold X +nnan Inf

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If we exclude NaN (and therefore the opposite Inf),
anything plus Inf is Inf:
https://alive2.llvm.org/ce/z/og3dj9
This commit is contained in:
Sanjay Patel
2022-11-10 17:10:46 -05:00
parent 58167f67dc
commit fbc2c8f2fb
2 changed files with 17 additions and 15 deletions
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18
llvm/lib/Analysis/InstructionSimplify.cpp
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@@ -5245,14 +5245,18 @@ simplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF,
if (!isDefaultFPEnvironment(ExBehavior, Rounding))
return nullptr;
// 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()) {
// With nnan: X + {+/-}Inf --> {+/-}Inf
if (match(Op1, m_Inf()))
return Op1;
// 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 (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0))))
return ConstantFP::getNullValue(Op0->getType());

14
llvm/test/Transforms/InstSimplify/floating-point-arithmetic.ll
View File

@@ -818,8 +818,7 @@ define float @maxnum_with_pos_one_op(float %a) {
define double @fadd_nnan_inf_op0(double %x) {
; CHECK-LABEL: @fadd_nnan_inf_op0(
; CHECK-NEXT: [[R:%.*]] = fadd nnan double 0x7FF0000000000000, [[X:%.*]]
; CHECK-NEXT: ret double [[R]]
; CHECK-NEXT: ret double 0x7FF0000000000000
;
%r = fadd nnan double 0x7ff0000000000000, %x
ret double %r
@@ -827,8 +826,7 @@ define double @fadd_nnan_inf_op0(double %x) {
define double @fadd_nnan_inf_op1(double %x) {
; CHECK-LABEL: @fadd_nnan_inf_op1(
; CHECK-NEXT: [[R:%.*]] = fadd nnan double [[X:%.*]], 0x7FF0000000000000
; CHECK-NEXT: ret double [[R]]
; CHECK-NEXT: ret double 0x7FF0000000000000
;
%r = fadd nnan double %x, 0x7ff0000000000000
ret double %r
@@ -836,8 +834,7 @@ define double @fadd_nnan_inf_op1(double %x) {
define <2 x double> @fadd_nnan_neginf_op1(<2 x double> %x) {
; CHECK-LABEL: @fadd_nnan_neginf_op1(
; CHECK-NEXT: [[R:%.*]] = fadd nnan <2 x double> [[X:%.*]], <double 0xFFF0000000000000, double poison>
; CHECK-NEXT: ret <2 x double> [[R]]
; CHECK-NEXT: ret <2 x double> <double 0xFFF0000000000000, double poison>
;
%r = fadd nnan <2 x double> %x, <double 0xfff0000000000000, double poison>
ret <2 x double> %r
@@ -845,13 +842,14 @@ define <2 x double> @fadd_nnan_neginf_op1(<2 x double> %x) {
define double @fadd_nnan_neginf_op0(double %x) {
; CHECK-LABEL: @fadd_nnan_neginf_op0(
; CHECK-NEXT: [[R:%.*]] = fadd nnan double 0xFFF0000000000000, [[X:%.*]]
; CHECK-NEXT: ret double [[R]]
; CHECK-NEXT: ret double 0xFFF0000000000000
;
%r = fadd nnan double 0xfff0000000000000, %x
ret double %r
}
; negative test - requires nnan
define double @fadd_inf_op0(double %x) {
; CHECK-LABEL: @fadd_inf_op0(
; CHECK-NEXT: [[R:%.*]] = fadd double 0x7FF0000000000000, [[X:%.*]]