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[Reland][SCEV] teach isImpliedViaOperations about samesign #133711

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Merged
merged 3 commits into from
Apr 2, 2025
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[Reland][SCEV] teach isImpliedViaOperations about samesign #133711

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39148ec
SCEV: teach isImpliedViaOperations about samesign (#124270)
artagnon Feb 6, 2025
e3b5501
[SCEV] Add pre-commit tests. NFC.
dtcxzyw Mar 31, 2025
1387a68
[SCEV] Do not preserve samesign after truncation
dtcxzyw Mar 31, 2025
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6 changes: 4 additions & 2 deletions llvm/lib/Analysis/ScalarEvolution.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11804,8 +11804,10 @@ bool ScalarEvolution::isImpliedCond(CmpPredicate Pred, const SCEV *LHS,
MaxValue)) {
const SCEV *TruncFoundLHS = getTruncateExpr(FoundLHS, NarrowType);
const SCEV *TruncFoundRHS = getTruncateExpr(FoundRHS, NarrowType);
if (isImpliedCondBalancedTypes(Pred, LHS, RHS, FoundPred, TruncFoundLHS,
TruncFoundRHS, CtxI))
// We cannot preserve samesign after truncation.
if (isImpliedCondBalancedTypes(
Pred, LHS, RHS, static_cast<ICmpInst::Predicate>(FoundPred),
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@nikic nikic Apr 2, 2025

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I kind of wonder whether we should have some more explicit API for this like FoundPred.withoutSameSign(). Doing this by going through a static_cast is a bit subtle...

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@dtcxzyw dtcxzyw Apr 2, 2025

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I will fix it in a follow up patch.

TruncFoundLHS, TruncFoundRHS, CtxI))
return true;
}
}
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2 changes: 1 addition & 1 deletion llvm/test/Transforms/IndVarSimplify/pr126409.ll
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Expand Up @@ -10,7 +10,7 @@ define void @pr126409() {
; CHECK: [[FOR_BODY_PREHEADER]]:
; CHECK-NEXT: br label %[[FOR_BODY:.*]]
; CHECK: [[FOR_BODY]]:
; CHECK-NEXT: br i1 true, label %[[FOR_BODY]], label %[[IF_END_LOOPEXIT:.*]]
; CHECK-NEXT: br i1 false, label %[[FOR_BODY]], label %[[IF_END_LOOPEXIT:.*]]
; CHECK: [[IF_END_LOOPEXIT]]:
; CHECK-NEXT: br label %[[IF_END]]
; CHECK: [[IF_END]]:
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