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Guards: Improve performance for phi nodes with many incoming constant values. #20569

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Merged
MathiasVP merged 1 commit into from
Oct 1, 2025
Merged

Guards: Improve performance for phi nodes with many incoming constant values. #20569

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10 changes: 7 additions & 3 deletions shared/controlflow/codeql/controlflow/Guards.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -692,6 +692,9 @@ module Make<
* Holds if `e` equals `k` and may be assigned to `v`. The boolean
* `fromBackEdge` indicates whether the flow from `e` to `v` goes through a
* back edge.
*
* This predicate is restricted to cases where all such possible values are
* constants, which means that the `GuardValue`s are singleton values.
*/
private predicate possibleValue(SsaDefinition v, boolean fromBackEdge, Expr e, GuardValue k) {
not hasPossibleUnknownValue(v) and
Expand All @@ -711,9 +714,10 @@ module Make<
private predicate uniqueValue(SsaDefinition v, Expr e, GuardValue k) {
possibleValue(v, false, e, k) and
not possibleValue(v, true, e, k) and
forex(Expr other, GuardValue otherval | possibleValue(v, _, other, otherval) and other != e |
disjointValues(otherval, k)
)
// there's only one expression with the value `k`
1 = strictcount(Expr e0 | possibleValue(v, _, e0, k)) and
// and `v` has at least two possible values
2 <= strictcount(GuardValue k0 | possibleValue(v, _, _, k0))
}

/**
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