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SimplifyIndVar: teach widenLoopCompare about samesign #125851

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merged 2 commits into from
Feb 6, 2025
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SimplifyIndVar: teach widenLoopCompare about samesign #125851

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963ec33
IndVarSimplify: pre-commit samesign tests
artagnon Feb 4, 2025
46ff022
SimplifyIndVar: teach widenLoopCompare about samesign
artagnon Feb 4, 2025
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5 changes: 3 additions & 2 deletions llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1614,7 +1614,8 @@ bool WidenIV::widenLoopCompare(WidenIV::NarrowIVDefUse DU) {
// (A) == icmp slt i32 sext(%narrow), sext(%val)
// == icmp slt i32 zext(%narrow), sext(%val)
bool IsSigned = getExtendKind(DU.NarrowDef) == ExtendKind::Sign;
if (!(DU.NeverNegative || IsSigned == Cmp->isSigned()))
bool CmpPreferredSign = Cmp->hasSameSign() ? IsSigned : Cmp->isSigned();
if (!DU.NeverNegative && IsSigned != CmpPreferredSign)
return false;

Value *Op = Cmp->getOperand(Cmp->getOperand(0) == DU.NarrowDef ? 1 : 0);
Expand All @@ -1627,7 +1628,7 @@ bool WidenIV::widenLoopCompare(WidenIV::NarrowIVDefUse DU) {

// Widen the other operand of the compare, if necessary.
if (CastWidth < IVWidth) {
Value *ExtOp = createExtendInst(Op, WideType, Cmp->isSigned(), Cmp);
Value *ExtOp = createExtendInst(Op, WideType, CmpPreferredSign, Cmp);
DU.NarrowUse->replaceUsesOfWith(Op, ExtOp);
}
return true;
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