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[InstCombine] Remove foldSelectWithFrozenICmp() fold #161659

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Merged
merged 1 commit into from
Oct 2, 2025
+0 −29
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[InstCombine] Remove foldSelectWithFrozenICmp() fold #161659

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29 changes: 0 additions & 29 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2934,32 +2934,6 @@ static Instruction *foldSelectWithSRem(SelectInst &SI, InstCombinerImpl &IC,
return nullptr;
}

static Value *foldSelectWithFrozenICmp(SelectInst &Sel, InstCombiner::BuilderTy &Builder) {
FreezeInst *FI = dyn_cast<FreezeInst>(Sel.getCondition());
if (!FI)
return nullptr;

Value *Cond = FI->getOperand(0);
Value *TrueVal = Sel.getTrueValue(), *FalseVal = Sel.getFalseValue();

// select (freeze(x == y)), x, y --> y
// select (freeze(x != y)), x, y --> x
// The freeze should be only used by this select. Otherwise, remaining uses of
// the freeze can observe a contradictory value.
// c = freeze(x == y) ; Let's assume that y = poison & x = 42; c is 0 or 1
// a = select c, x, y ;
// f(a, c) ; f(poison, 1) cannot happen, but if a is folded
// ; to y, this can happen.
CmpPredicate Pred;
if (FI->hasOneUse() &&
match(Cond, m_c_ICmp(Pred, m_Specific(TrueVal), m_Specific(FalseVal))) &&
(Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE)) {
return Pred == ICmpInst::ICMP_EQ ? FalseVal : TrueVal;
}

return nullptr;
}

/// Given that \p CondVal is known to be \p CondIsTrue, try to simplify \p SI.
static Value *simplifyNestedSelectsUsingImpliedCond(SelectInst &SI,
Value *CondVal,
Expand Down Expand Up @@ -4446,9 +4420,6 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
if (Instruction *PN = foldSelectToPhi(SI, DT, Builder))
return replaceInstUsesWith(SI, PN);

if (Value *Fr = foldSelectWithFrozenICmp(SI, Builder))
return replaceInstUsesWith(SI, Fr);

if (Value *V = foldRoundUpIntegerWithPow2Alignment(SI, Builder))
return replaceInstUsesWith(SI, V);

Expand Down