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SSA: Skip irrelevant phi input nodes.

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This commit is contained in:
Anders Schack-Mulligen
2025-03-14 15:41:20 +01:00
parent c778bf6343
commit 669f9261f1
1 changed files with 35 additions and 2 deletions
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37
shared/ssa/codeql/ssa/Ssa.qll
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@@ -1502,6 +1502,12 @@ module Make<LocationSig Location, InputSig<Location> Input> {
* definition.
*/
default predicate includeWriteDefsInFlowStep() { any() }
/**
* Holds if barrier guards should be supported on input edges to phi
* nodes. Disable this only if barrier guards are not going to be used.
*/
default predicate supportBarrierGuardsOnPhiEdges() { any() }
}
/**
@@ -1533,6 +1539,29 @@ module Make<LocationSig Location, InputSig<Location> Input> {
)
}
/**
* Holds if the input to `phi` from the block `input` might be relevant for
* barrier guards as a separately synthesized `TSsaInputNode`.
*/
private predicate relevantPhiInputNode(SsaPhiExt phi, BasicBlock input) {
DfInput::supportBarrierGuardsOnPhiEdges() and
// If the input isn't explicitly read then a guard cannot check it.
exists(DfInput::getARead(getAPhiInputDef(phi, input))) and
(
exists(DfInput::Guard g | g.controlsBranchEdge(input, phi.getBasicBlock(), _))
or
exists(BasicBlock prev |
AdjacentSsaRefs::adjacentRefPhi(prev, _, input, phi.getBasicBlock(),
phi.getSourceVariable()) and
prev != input and
exists(DfInput::Guard g, boolean branch |
DfInput::guardControlsBlock(g, input, branch) and
not DfInput::guardControlsBlock(g, prev, branch)
)
)
)
}
private newtype TNode =
TParamNode(DfInput::Parameter p) {
exists(WriteDefinition def | DfInput::ssaDefInitializesParam(def, p))
@@ -1546,7 +1575,7 @@ module Make<LocationSig Location, InputSig<Location> Input> {
)
} or
TSsaDefinitionNode(DefinitionExt def) or
TSsaInputNode(SsaPhiExt phi, BasicBlock input) { exists(getAPhiInputDef(phi, input)) }
TSsaInputNode(SsaPhiExt phi, BasicBlock input) { relevantPhiInputNode(phi, input) }
/**
* A data flow node that we need to reference in the value step relation.
@@ -1822,8 +1851,12 @@ module Make<LocationSig Location, InputSig<Location> Input> {
// Flow from definition/read to phi input
exists(BasicBlock input, BasicBlock bbPhi, DefinitionExt phi |
AdjacentSsaRefs::adjacentRefPhi(bb1, i1, input, bbPhi, v) and
nodeTo = TSsaInputNode(phi, input) and
phi.definesAt(v, bbPhi, -1, _)
|
nodeTo = TSsaInputNode(phi, input)
or
not relevantPhiInputNode(phi, input) and
nodeTo.(SsaDefinitionExtNodeImpl).getDefExt() = phi
)
}