[llvm] 1f69d63 - [InstCombine] Preserve the sign bit of NaN in `SimplifyDemandedUseFPClass` (#137287)
via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 28 02:01:46 PDT 2025
Author: Yingwei Zheng
Date: 2025-04-28T17:01:43+08:00
New Revision: 1f69d6354a4b088bda5ee62c31411a75eead8b0c
URL: https://github.com/llvm/llvm-project/commit/1f69d6354a4b088bda5ee62c31411a75eead8b0c
DIFF: https://github.com/llvm/llvm-project/commit/1f69d6354a4b088bda5ee62c31411a75eead8b0c.diff
LOG: [InstCombine] Preserve the sign bit of NaN in `SimplifyDemandedUseFPClass` (#137287)
Alive2: https://alive2.llvm.org/ce/z/uiUzEf
Closes https://github.com/llvm/llvm-project/issues/137196.
Note: To avoid regression in
`ret_nofpclass_nopositives_copysign_nnan_flag`, the second commit takes
FMF into account.
Added:
Modified:
llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 2c8939b5a0514..a48854a191cae 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1959,9 +1959,11 @@ static Constant *getFPClassConstant(Type *Ty, FPClassTest Mask) {
}
}
-Value *InstCombinerImpl::SimplifyDemandedUseFPClass(
- Value *V, const FPClassTest DemandedMask, KnownFPClass &Known,
- unsigned Depth, Instruction *CxtI) {
+Value *InstCombinerImpl::SimplifyDemandedUseFPClass(Value *V,
+ FPClassTest DemandedMask,
+ KnownFPClass &Known,
+ unsigned Depth,
+ Instruction *CxtI) {
assert(Depth <= MaxAnalysisRecursionDepth && "Limit Search Depth");
Type *VTy = V->getType();
@@ -1985,7 +1987,12 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(
if (!I->hasOneUse())
return nullptr;
- // TODO: Should account for nofpclass/FastMathFlags on current instruction
+ if (auto *FPOp = dyn_cast<FPMathOperator>(I)) {
+ if (FPOp->hasNoNaNs())
+ DemandedMask &= ~fcNan;
+ if (FPOp->hasNoInfs())
+ DemandedMask &= ~fcInf;
+ }
switch (I->getOpcode()) {
case Instruction::FNeg: {
if (SimplifyDemandedFPClass(I, 0, llvm::fneg(DemandedMask), Known,
@@ -2013,13 +2020,13 @@ Value *InstCombinerImpl::SimplifyDemandedUseFPClass(
if (SimplifyDemandedFPClass(I, 0, DemandedMaskAnySign, Known, Depth + 1))
return I;
- if ((DemandedMask & fcPositive) == fcNone) {
+ if ((DemandedMask & fcNegative) == DemandedMask) {
// Roundabout way of replacing with fneg(fabs)
I->setOperand(1, ConstantFP::get(VTy, -1.0));
return I;
}
- if ((DemandedMask & fcNegative) == fcNone) {
+ if ((DemandedMask & fcPositive) == DemandedMask) {
// Roundabout way of replacing with fabs
I->setOperand(1, ConstantFP::getZero(VTy));
return I;
diff --git a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
index ad88287f1d99e..df60078dbf452 100644
--- a/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
+++ b/llvm/test/Transforms/InstCombine/simplify-demanded-fpclass.ll
@@ -678,12 +678,11 @@ define nofpclass(inf) float @ret_nofpclass_inf__copysign_negative_select_pinf_rh
ret float %copysign
}
-; can fold to fneg(fabs(x))
+; can't fold to fneg(fabs(x))
define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_nopositives_copysign(float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_nopositives_copysign
; CHECK-SAME: (float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[X]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%copysign = call float @llvm.copysign.f32(float %x, float %unknown.sign)
@@ -703,6 +702,18 @@ define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_nopositives_copysig
}
; can fold to fneg(fabs(x))
+define nofpclass(pnorm psub pzero) float @ret_nofpclass_nopositive_finites_copysign_nnan_ninf_flag(float %x, float %unknown.sign) {
+; CHECK-LABEL: define nofpclass(pzero psub pnorm) float @ret_nofpclass_nopositive_finites_copysign_nnan_ninf_flag
+; CHECK-SAME: (float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
+; CHECK-NEXT: [[TMP1:%.*]] = call nnan ninf float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg nnan ninf float [[TMP1]]
+; CHECK-NEXT: ret float [[COPYSIGN]]
+;
+ %copysign = call nnan ninf float @llvm.copysign.f32(float %x, float %unknown.sign)
+ ret float %copysign
+}
+
+; can't fold to fneg(fabs(x))
define nofpclass(nan pinf pnorm psub pzero) float @ret_nofpclass_nopositives_nonan_copysign(float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(nan pinf pzero psub pnorm) float @ret_nofpclass_nopositives_nonan_copysign
; CHECK-SAME: (float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
@@ -714,11 +725,11 @@ define nofpclass(nan pinf pnorm psub pzero) float @ret_nofpclass_nopositives_non
ret float %copysign
}
-; can fold to fabs(x)
+; can't fold to fabs(x)
define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_nonegatives_copysign(float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @ret_nofpclass_nonegatives_copysign
; CHECK-SAME: (float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[X]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%copysign = call float @llvm.copysign.f32(float %x, float %unknown.sign)
@@ -763,7 +774,7 @@ define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_nopositives__copysi
define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_no_negatives_noinf__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(inf nzero nsub nnorm) float @ret_nofpclass_no_negatives_noinf__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.fabs.f32(float [[X]])
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[X]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
@@ -775,8 +786,7 @@ define nofpclass(inf nnorm nsub nzero) float @ret_nofpclass_no_negatives_noinf__
define nofpclass(inf pnorm psub pzero) float @ret_nofpclass_no_positives_noinf__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(inf pzero psub pnorm) float @ret_nofpclass_no_positives_noinf__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[COPYSIGN:%.*]] = fneg float [[TMP1]]
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[X]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
@@ -788,8 +798,8 @@ define nofpclass(inf pnorm psub pzero) float @ret_nofpclass_no_positives_noinf__
define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_no_negatives__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(ninf nzero nsub nnorm) float @ret_nofpclass_no_negatives__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[COPYSIGN:%.*]] = select i1 [[COND]], float [[TMP1]], float 0x7FF0000000000000
+; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[COND]], float [[X]], float 0x7FF0000000000000
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[SELECT]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
@@ -801,9 +811,8 @@ define nofpclass(ninf nnorm nsub nzero) float @ret_nofpclass_no_negatives__copys
define nofpclass(pinf pnorm psub pzero) float @ret_nofpclass_no_positives__copysign_unknown_select_pinf_rhs(i1 %cond, float %x, float %unknown.sign) {
; CHECK-LABEL: define nofpclass(pinf pzero psub pnorm) float @ret_nofpclass_no_positives__copysign_unknown_select_pinf_rhs
; CHECK-SAME: (i1 [[COND:%.*]], float [[X:%.*]], float [[UNKNOWN_SIGN:%.*]]) {
-; CHECK-NEXT: [[TMP1:%.*]] = call float @llvm.fabs.f32(float [[X]])
-; CHECK-NEXT: [[DOTNEG:%.*]] = fneg float [[TMP1]]
-; CHECK-NEXT: [[COPYSIGN:%.*]] = select i1 [[COND]], float [[DOTNEG]], float 0xFFF0000000000000
+; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[COND]], float [[X]], float 0x7FF0000000000000
+; CHECK-NEXT: [[COPYSIGN:%.*]] = call float @llvm.copysign.f32(float [[SELECT]], float [[UNKNOWN_SIGN]])
; CHECK-NEXT: ret float [[COPYSIGN]]
;
%select = select i1 %cond, float %x, float 0x7FF0000000000000
More information about the llvm-commits
mailing list