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[InstCombine] Generalize select equiv fold for plain condition #85663

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[InstCombine] Generalize select equiv fold for plain condition #85663

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4 changes: 3 additions & 1 deletion llvm/lib/Transforms/InstCombine/InstCombineInternal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -735,9 +735,11 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
Value *A, Value *B, Instruction &Outer,
SelectPatternFlavor SPF2, Value *C);
Instruction *foldSelectInstWithICmp(SelectInst &SI, ICmpInst *ICI);
Instruction *foldSelectValueEquivalence(SelectInst &SI, ICmpInst &ICI);
bool replaceInInstruction(Value *V, Value *Old, Value *New,
unsigned Depth = 0);
Instruction *foldSelectValueEquivalence(SelectInst &Sel,
ICmpInst::Predicate Pred,
Value *CmpLHS, Value *CmpRHS);

Value *insertRangeTest(Value *V, const APInt &Lo, const APInt &Hi,
bool isSigned, bool Inside);
Expand Down
41 changes: 16 additions & 25 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Expand Up @@ -1262,27 +1262,23 @@ bool InstCombinerImpl::replaceInInstruction(Value *V, Value *Old, Value *New,
///
/// We can't replace %sel with %add unless we strip away the flags.
/// TODO: Wrapping flags could be preserved in some cases with better analysis.
Instruction *InstCombinerImpl::foldSelectValueEquivalence(SelectInst &Sel,
ICmpInst &Cmp) {
if (!Cmp.isEquality())
Instruction *InstCombinerImpl::foldSelectValueEquivalence(
SelectInst &Sel, ICmpInst::Predicate Pred, Value *CmpLHS, Value *CmpRHS) {
if (!ICmpInst::isEquality(Pred))
return nullptr;

// Canonicalize the pattern to ICMP_EQ by swapping the select operands.
Value *TrueVal = Sel.getTrueValue(), *FalseVal = Sel.getFalseValue();
bool Swapped = false;
if (Cmp.getPredicate() == ICmpInst::ICMP_NE) {
if (Pred == ICmpInst::ICMP_NE) {
std::swap(TrueVal, FalseVal);
Swapped = true;
}

// In X == Y ? f(X) : Z, try to evaluate f(Y) and replace the operand.
// Make sure Y cannot be undef though, as we might pick different values for
// undef in the icmp and in f(Y). Additionally, take care to avoid replacing
// X == Y ? X : Z with X == Y ? Y : Z, as that would lead to an infinite
// replacement cycle.
Value *CmpLHS = Cmp.getOperand(0), *CmpRHS = Cmp.getOperand(1);
if (TrueVal != CmpLHS &&
isGuaranteedNotToBeUndefOrPoison(CmpRHS, SQ.AC, &Sel, &DT)) {
// undef in the icmp and in f(Y).
if (isGuaranteedNotToBeUndefOrPoison(CmpRHS, SQ.AC, &Sel, &DT)) {
if (Value *V = simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, SQ,
/* AllowRefinement */ true))
// Require either the replacement or the simplification result to be a
Expand All @@ -1299,7 +1295,7 @@ Instruction *InstCombinerImpl::foldSelectValueEquivalence(SelectInst &Sel,
// profitability is not clear for other cases.
// FIXME: Support vectors.
if (match(CmpRHS, m_ImmConstant()) && !match(CmpLHS, m_ImmConstant()) &&
!Cmp.getType()->isVectorTy())
!CmpLHS->getType()->isVectorTy())
if (replaceInInstruction(TrueVal, CmpLHS, CmpRHS))
return &Sel;
}
Expand Down Expand Up @@ -1680,7 +1676,8 @@ static Value *foldSelectInstWithICmpConst(SelectInst &SI, ICmpInst *ICI,
/// Visit a SelectInst that has an ICmpInst as its first operand.
Instruction *InstCombinerImpl::foldSelectInstWithICmp(SelectInst &SI,
ICmpInst *ICI) {
if (Instruction *NewSel = foldSelectValueEquivalence(SI, *ICI))
if (Instruction *NewSel = foldSelectValueEquivalence(
SI, ICI->getPredicate(), ICI->getOperand(0), ICI->getOperand(1)))
return NewSel;

if (Value *V =
Expand Down Expand Up @@ -3376,21 +3373,15 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
if (Instruction *I = canonicalizeScalarSelectOfVecs(SI, *this))
return I;

// If the type of select is not an integer type or if the condition and
// the selection type are not both scalar nor both vector types, there is no
// point in attempting to match these patterns.
Type *CondType = CondVal->getType();
if (!isa<Constant>(CondVal) && SelType->isIntOrIntVectorTy() &&
CondType->isVectorTy() == SelType->isVectorTy()) {
if (Value *S = simplifyWithOpReplaced(TrueVal, CondVal,
ConstantInt::getTrue(CondType), SQ,
/* AllowRefinement */ true))
return replaceOperand(SI, 1, S);
if (!isa<Constant>(CondVal)) {
if (Instruction *I = foldSelectValueEquivalence(
SI, ICmpInst::ICMP_EQ, CondVal, ConstantInt::getTrue(CondType)))
return I;

if (Value *S = simplifyWithOpReplaced(FalseVal, CondVal,
ConstantInt::getFalse(CondType), SQ,
/* AllowRefinement */ true))
return replaceOperand(SI, 2, S);
if (Instruction *I = foldSelectValueEquivalence(
SI, ICmpInst::ICMP_NE, CondVal, ConstantInt::getFalse(CondType)))
return I;
}

if (Instruction *R = foldSelectOfBools(SI))
Expand Down
15 changes: 6 additions & 9 deletions llvm/test/Transforms/InstCombine/select.ll
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Expand Up @@ -3709,9 +3709,8 @@ define i32 @src_select_xxory_eq0_xorxy_y(i32 %x, i32 %y) {

define i32 @sequence_select_with_same_cond_false(i1 %c1, i1 %c2){
; CHECK-LABEL: @sequence_select_with_same_cond_false(
; CHECK-NEXT: [[S1:%.*]] = select i1 [[C1:%.*]], i32 23, i32 45
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], i32 666, i32 [[S1]]
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1]], i32 789, i32 [[S2]]
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], i32 666, i32 45
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1:%.*]], i32 789, i32 [[S2]]
; CHECK-NEXT: ret i32 [[S3]]
;
%s1 = select i1 %c1, i32 23, i32 45
Expand All @@ -3722,9 +3721,8 @@ define i32 @sequence_select_with_same_cond_false(i1 %c1, i1 %c2){

define i32 @sequence_select_with_same_cond_true(i1 %c1, i1 %c2){
; CHECK-LABEL: @sequence_select_with_same_cond_true(
; CHECK-NEXT: [[S1:%.*]] = select i1 [[C1:%.*]], i32 45, i32 23
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], i32 [[S1]], i32 666
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1]], i32 [[S2]], i32 789
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], i32 45, i32 666
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1:%.*]], i32 [[S2]], i32 789
; CHECK-NEXT: ret i32 [[S3]]
;
%s1 = select i1 %c1, i32 45, i32 23
Expand All @@ -3735,9 +3733,8 @@ define i32 @sequence_select_with_same_cond_true(i1 %c1, i1 %c2){

define double @sequence_select_with_same_cond_double(double %a, i1 %c1, i1 %c2, double %r1, double %r2){
; CHECK-LABEL: @sequence_select_with_same_cond_double(
; CHECK-NEXT: [[S1:%.*]] = select i1 [[C1:%.*]], double 1.000000e+00, double 0.000000e+00
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], double [[S1]], double 2.000000e+00
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1]], double [[S2]], double 3.000000e+00
; CHECK-NEXT: [[S2:%.*]] = select i1 [[C2:%.*]], double 1.000000e+00, double 2.000000e+00
; CHECK-NEXT: [[S3:%.*]] = select i1 [[C1:%.*]], double [[S2]], double 3.000000e+00
; CHECK-NEXT: ret double [[S3]]
;
%s1 = select i1 %c1, double 1.0, double 0.0
Expand Down