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[InstSimplify] fold fcmp using isKnownNeverInfinity + isKnownNeverNaN 

Follow-up to D84035 / rG7393d7574c09.
This sidesteps a question of FMF/poison on fcmp raised in PR46077:
http://bugs.llvm.org/PR46077

https://alive2.llvm.org/ce/z/TCsyzD
  define i1 @src(float %x) {
  %0:
    %x42 = fadd nnan ninf float %x, 42.000000
    %r = fcmp ueq float %x42, inf
    ret i1 %r
  }
  =>
  define i1 @tgt(float %x) {
  %0:
    ret i1 0
  }
  Transformation seems to be correct!

https://alive2.llvm.org/ce/z/FQaH7a
  define i1 @src(i8 %x) {
  %0:
    %cast = uitofp i8 %x to float
    %r = fcmp one float inf, %cast
    ret i1 %r
  }
  =>
  define i1 @tgt(i8 %x) {
  %0:
    ret i1 1
  }
  Transformation seems to be correct!
This commit is contained in:
Sanjay Patel 2020-07-24 15:11:02 -04:00
parent 912e9e5262
commit b89ae102e6
2 changed files with 12 additions and 13 deletions
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8
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -3701,6 +3701,14 @@ static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
// LHS != Inf
if (Pred == FCmpInst::FCMP_UNE && isKnownNeverInfinity(LHS, Q.TLI))
return getTrue(RetTy);
// LHS == Inf || LHS == NaN
if (Pred == FCmpInst::FCMP_UEQ && isKnownNeverInfinity(LHS, Q.TLI) &&
isKnownNeverNaN(LHS, Q.TLI))
return getFalse(RetTy);
// LHS != Inf && LHS != NaN
if (Pred == FCmpInst::FCMP_ONE && isKnownNeverInfinity(LHS, Q.TLI) &&
isKnownNeverNaN(LHS, Q.TLI))
return getTrue(RetTy);
}
if (C->isNegative() && !C->isNegZero()) {
assert(!C->isNaN() && "Unexpected NaN constant!");

17
llvm/test/Transforms/InstSimplify/floating-point-compare.ll
View File

@ -1072,9 +1072,7 @@ define i1 @is_infinite_or_nan(float %x) {
define i1 @is_infinite_or_nan2(float %x) {
; CHECK-LABEL: @is_infinite_or_nan2(
; CHECK-NEXT: [[XABS:%.*]] = call nnan ninf float @llvm.fabs.f32(float [[X:%.*]])
; CHECK-NEXT: [[R:%.*]] = fcmp ueq float [[XABS]], 0x7FF0000000000000
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 false
;
%xabs = call nnan ninf float @llvm.fabs.f32(float %x)
%r = fcmp ueq float %xabs, 0x7FF0000000000000
@ -1083,9 +1081,7 @@ define i1 @is_infinite_or_nan2(float %x) {
define <2 x i1> @is_infinite_neg_or_nan(<2 x float> %x) {
; CHECK-LABEL: @is_infinite_neg_or_nan(
; CHECK-NEXT: [[X42:%.*]] = fadd nnan ninf <2 x float> [[X:%.*]], <float 4.200000e+01, float 4.200000e+01>
; CHECK-NEXT: [[R:%.*]] = fcmp ueq <2 x float> [[X42]], <float 0xFFF0000000000000, float 0xFFF0000000000000>
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> zeroinitializer
;
%x42 = fadd nnan ninf <2 x float> %x, <float 42.0, float 42.0>
%r = fcmp ueq <2 x float> %x42, <float 0xFFF0000000000000, float 0xFFF0000000000000>
@ -1126,10 +1122,7 @@ define i1 @is_finite_and_ordered(double %x) {
define i1 @is_finite(i1 %c, double %x) {
; CHECK-LABEL: @is_finite(
; CHECK-NEXT: [[XX:%.*]] = fmul nnan ninf double [[X:%.*]], [[X]]
; CHECK-NEXT: [[S:%.*]] = select i1 [[C:%.*]], double 4.200000e+01, double [[XX]]
; CHECK-NEXT: [[R:%.*]] = fcmp one double [[S]], 0x7FF0000000000000
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 true
;
%xx = fmul nnan ninf double %x, %x
%s = select i1 %c, double 42.0, double %xx
@ -1139,9 +1132,7 @@ define i1 @is_finite(i1 %c, double %x) {
define <2 x i1> @is_finite_commute(<2 x i8> %x) {
; CHECK-LABEL: @is_finite_commute(
; CHECK-NEXT: [[CAST:%.*]] = uitofp <2 x i8> [[X:%.*]] to <2 x float>
; CHECK-NEXT: [[R:%.*]] = fcmp one <2 x float> <float 0x7FF0000000000000, float 0x7FF0000000000000>, [[CAST]]
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> <i1 true, i1 true>
;
%cast = uitofp <2 x i8> %x to <2 x float>
%r = fcmp one <2 x float> <float 0x7FF0000000000000, float 0x7FF0000000000000>, %cast