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[InstSimplify] enhance fcmp fold with never-nan operand

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This is another step towards correcting our usage of fast-math-flags when applied on an fcmp.
In this case, we are checking for 'nnan' on the fcmp itself rather than the operand of
the fcmp. But I'm leaving that clause in until we're more confident that we can stop
relying on fcmp's FMF.

By using the more general "isKnownNeverNaN()", we gain a simplification shown on the
tests with 'uitofp' regardless of the FMF on the fcmp (uitofp never produces a NaN).
On the tests with 'fabs', we are now relying on the FMF for the call fabs instruction
in addition to the FMF on the fcmp.

This is a continuation of D62979 / rL362879.

llvm-svn: 362903
This commit is contained in:
Sanjay Patel 2019-06-09 13:48:59 +00:00
parent 132a7dcd28
commit 1361930fcb
2 changed files with 6 additions and 14 deletions
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4
lib/Analysis/InstructionSimplify.cpp
View File

@ -3486,8 +3486,8 @@ static Value *SimplifyFCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
return getTrue(RetTy);
break;
case FCmpInst::FCMP_ULT:
// TODO: This should match 'oge'.
if (FMF.noNaNs() && CannotBeOrderedLessThanZero(LHS, Q.TLI))
if ((FMF.noNaNs() || isKnownNeverNaN(LHS, Q.TLI)) &&
CannotBeOrderedLessThanZero(LHS, Q.TLI))
return getFalse(RetTy);
break;
case FCmpInst::FCMP_OLT:

16
test/Transforms/InstSimplify/floating-point-compare.ll
View File

@ -313,9 +313,7 @@ define <2 x i1> @UIToFP_is_not_negative_vec(<2 x i32> %x) {
define i1 @UIToFP_is_not_negative_or_nan(i32 %x) {
; CHECK-LABEL: @UIToFP_is_not_negative_or_nan(
; CHECK-NEXT: [[A:%.*]] = uitofp i32 [[X:%.*]] to float
; CHECK-NEXT: [[R:%.*]] = fcmp ult float [[A]], 0.000000e+00
; CHECK-NEXT: ret i1 [[R]]
; CHECK-NEXT: ret i1 false
;
%a = uitofp i32 %x to float
%r = fcmp ult float %a, 0.000000e+00
@ -324,9 +322,7 @@ define i1 @UIToFP_is_not_negative_or_nan(i32 %x) {
define <2 x i1> @UIToFP_is_not_negative_or_nan_vec(<2 x i32> %x) {
; CHECK-LABEL: @UIToFP_is_not_negative_or_nan_vec(
; CHECK-NEXT: [[A:%.*]] = uitofp <2 x i32> [[X:%.*]] to <2 x float>
; CHECK-NEXT: [[R:%.*]] = fcmp ult <2 x float> [[A]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[R]]
; CHECK-NEXT: ret <2 x i1> zeroinitializer
;
%a = uitofp <2 x i32> %x to <2 x float>
%r = fcmp ult <2 x float> %a, zeroinitializer
@ -425,9 +421,7 @@ define <2 x i1> @fabs_is_not_negative_vec(<2 x double> %x) {
define i1 @fabs_nnan_is_not_negative(double %x) {
; CHECK-LABEL: @fabs_nnan_is_not_negative(
; CHECK-NEXT: [[FABS:%.*]] = tail call nnan double @llvm.fabs.f64(double [[X:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = fcmp ult double [[FABS]], 0.000000e+00
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 false
;
%fabs = tail call nnan double @llvm.fabs.f64(double %x)
%cmp = fcmp ult double %fabs, 0.0
@ -436,9 +430,7 @@ define i1 @fabs_nnan_is_not_negative(double %x) {
define <2 x i1> @fabs_nnan_is_not_negative_vec(<2 x double> %x) {
; CHECK-LABEL: @fabs_nnan_is_not_negative_vec(
; CHECK-NEXT: [[FABS:%.*]] = tail call nnan <2 x double> @llvm.fabs.v2f64(<2 x double> [[X:%.*]])
; CHECK-NEXT: [[CMP:%.*]] = fcmp ult <2 x double> [[FABS]], zeroinitializer
; CHECK-NEXT: ret <2 x i1> [[CMP]]
; CHECK-NEXT: ret <2 x i1> zeroinitializer
;
%fabs = tail call nnan <2 x double> @llvm.fabs.v2f64(<2 x double> %x)
%cmp = fcmp ult <2 x double> %fabs, zeroinitializer