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[InstSimplify] use FMF to improve fcmp+select fold 

This is part of a series of patches needed to solve PR39535:
https://bugs.llvm.org/show_bug.cgi?id=39535
This commit is contained in:
Sanjay Patel 2019-11-04 08:29:56 -05:00
parent ad87f244b4
commit 659bd73d13
2 changed files with 18 additions and 31 deletions
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17
llvm/lib/Analysis/InstructionSimplify.cpp
View File

@ -3909,18 +3909,21 @@ static Value *simplifySelectWithICmpCond(Value *CondVal, Value *TrueVal,
/// Try to simplify a select instruction when its condition operand is a
/// floating-point comparison.
static Value *simplifySelectWithFCmp(Value *Cond, Value *T, Value *F) {
static Value *simplifySelectWithFCmp(Value *Cond, Value *T, Value *F,
const SimplifyQuery &Q) {
FCmpInst::Predicate Pred;
if (!match(Cond, m_FCmp(Pred, m_Specific(T), m_Specific(F))) &&
!match(Cond, m_FCmp(Pred, m_Specific(F), m_Specific(T))))
return nullptr;
// TODO: The transform may not be valid with -0.0. An incomplete way of
// testing for that possibility is to check if at least one operand is a
// non-zero constant.
// This transform is safe if we do not have (do not care about) -0.0 or if
// at least one operand is known to not be -0.0. Otherwise, the select can
// change the sign of a zero operand.
bool HasNoSignedZeros = Q.CxtI && isa<FPMathOperator>(Q.CxtI) &&
Q.CxtI->hasNoSignedZeros();
const APFloat *C;
if ((match(T, m_APFloat(C)) && C->isNonZero()) ||
(match(F, m_APFloat(C)) && C->isNonZero())) {
if (HasNoSignedZeros || (match(T, m_APFloat(C)) && C->isNonZero()) ||
(match(F, m_APFloat(C)) && C->isNonZero())) {
// (T == F) ? T : F --> F
// (F == T) ? T : F --> F
if (Pred == FCmpInst::FCMP_OEQ)
@ -3971,7 +3974,7 @@ static Value *SimplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
simplifySelectWithICmpCond(Cond, TrueVal, FalseVal, Q, MaxRecurse))
return V;
if (Value *V = simplifySelectWithFCmp(Cond, TrueVal, FalseVal))
if (Value *V = simplifySelectWithFCmp(Cond, TrueVal, FalseVal, Q))
return V;
if (Value *V = foldSelectWithBinaryOp(Cond, TrueVal, FalseVal))

32
llvm/test/Transforms/InstSimplify/fcmp-select.ll
View File

@ -104,9 +104,7 @@ define double @une_zero_swapped(double %x) {
define double @oeq_zero_nsz(double %x) {
; CHECK-LABEL: @oeq_zero_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp oeq double [[X:%.*]], 0.000000e+00
; CHECK-NEXT: [[COND:%.*]] = select nsz i1 [[CMP]], double [[X]], double 0.000000e+00
; CHECK-NEXT: ret double [[COND]]
; CHECK-NEXT: ret double 0.000000e+00
;
%cmp = fcmp oeq double %x, 0.0
%cond = select nsz i1 %cmp, double %x, double 0.0
@ -117,9 +115,7 @@ define double @oeq_zero_nsz(double %x) {
define float @oeq_zero_swapped_nsz(float %x) {
; CHECK-LABEL: @oeq_zero_swapped_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp oeq float [[X:%.*]], 0.000000e+00
; CHECK-NEXT: [[COND:%.*]] = select fast i1 [[CMP]], float 0.000000e+00, float [[X]]
; CHECK-NEXT: ret float [[COND]]
; CHECK-NEXT: ret float [[X:%.*]]
;
%cmp = fcmp oeq float %x, 0.0
%cond = select fast i1 %cmp, float 0.0, float %x
@ -130,9 +126,7 @@ define float @oeq_zero_swapped_nsz(float %x) {
define double @une_zero_nsz(double %x) {
; CHECK-LABEL: @une_zero_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp une double [[X:%.*]], 0.000000e+00
; CHECK-NEXT: [[COND:%.*]] = select ninf nsz i1 [[CMP]], double [[X]], double 0.000000e+00
; CHECK-NEXT: ret double [[COND]]
; CHECK-NEXT: ret double [[X:%.*]]
;
%cmp = fcmp une double %x, 0.0
%cond = select nsz ninf i1 %cmp, double %x, double 0.0
@ -143,9 +137,7 @@ define double @une_zero_nsz(double %x) {
define <2 x double> @une_zero_swapped_nsz(<2 x double> %x) {
; CHECK-LABEL: @une_zero_swapped_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp une <2 x double> [[X:%.*]], zeroinitializer
; CHECK-NEXT: [[COND:%.*]] = select nsz <2 x i1> [[CMP]], <2 x double> zeroinitializer, <2 x double> [[X]]
; CHECK-NEXT: ret <2 x double> [[COND]]
; CHECK-NEXT: ret <2 x double> zeroinitializer
;
%cmp = fcmp une <2 x double> %x, <double 0.0, double 0.0>
%cond = select nsz <2 x i1> %cmp, <2 x double> <double 0.0, double 0.0>, <2 x double> %x
@ -156,9 +148,7 @@ define <2 x double> @une_zero_swapped_nsz(<2 x double> %x) {
define double @oeq_nsz(double %x, double %y) {
; CHECK-LABEL: @oeq_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp oeq double [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[COND:%.*]] = select fast i1 [[CMP]], double [[X]], double [[Y]]
; CHECK-NEXT: ret double [[COND]]
; CHECK-NEXT: ret double [[Y:%.*]]
;
%cmp = fcmp oeq double %x, %y
%cond = select fast i1 %cmp, double %x, double %y
@ -169,9 +159,7 @@ define double @oeq_nsz(double %x, double %y) {
define <2 x float> @oeq_swapped_nsz(<2 x float> %x, <2 x float> %y) {
; CHECK-LABEL: @oeq_swapped_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp oeq <2 x float> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[COND:%.*]] = select nnan nsz <2 x i1> [[CMP]], <2 x float> [[Y]], <2 x float> [[X]]
; CHECK-NEXT: ret <2 x float> [[COND]]
; CHECK-NEXT: ret <2 x float> [[X:%.*]]
;
%cmp = fcmp oeq <2 x float> %x, %y
%cond = select nsz nnan <2 x i1> %cmp, <2 x float> %y, <2 x float> %x
@ -182,9 +170,7 @@ define <2 x float> @oeq_swapped_nsz(<2 x float> %x, <2 x float> %y) {
define double @une_nsz(double %x, double %y) {
; CHECK-LABEL: @une_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp une double [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[COND:%.*]] = select nsz i1 [[CMP]], double [[X]], double [[Y]]
; CHECK-NEXT: ret double [[COND]]
; CHECK-NEXT: ret double [[X:%.*]]
;
%cmp = fcmp une double %x, %y
%cond = select nsz i1 %cmp, double %x, double %y
@ -195,9 +181,7 @@ define double @une_nsz(double %x, double %y) {
define <2 x double> @une_swapped_nsz(<2 x double> %x, <2 x double> %y) {
; CHECK-LABEL: @une_swapped_nsz(
; CHECK-NEXT: [[CMP:%.*]] = fcmp une <2 x double> [[X:%.*]], [[Y:%.*]]
; CHECK-NEXT: [[COND:%.*]] = select fast <2 x i1> [[CMP]], <2 x double> [[Y]], <2 x double> [[X]]
; CHECK-NEXT: ret <2 x double> [[COND]]
; CHECK-NEXT: ret <2 x double> [[Y:%.*]]
;
%cmp = fcmp une <2 x double> %x, %y
%cond = select fast <2 x i1> %cmp, <2 x double> %y, <2 x double> %x