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Merged
merged 3 commits into from
Aug 5, 2025
+53 −30
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Java: Improve a couple of join-orders #20127

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e3021f4
Java: Untangle code a bit to improve join order.
aschackmull Jul 25, 2025
5ca35af
Java: Improve joinorder in getErasedRepr.
aschackmull Jul 25, 2025
6c82752
Java: Improve ObjFlow performance.
aschackmull Jul 25, 2025
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Java: Improve ObjFlow performance.
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@aschackmull
aschackmull committed Jul 25, 2025
commit 6c8275298b4366c66d5b00e1f3f0a620683cb5ee
35 changes: 23 additions & 12 deletions java/ql/lib/semmle/code/java/dispatch/ObjFlow.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -214,24 +214,35 @@ private predicate relevantNode(ObjNode n) {
exists(ObjNode mid | relevantNode(mid) and objStep(mid, n) and relevantNodeBack(n))
}

pragma[noinline]
private predicate objStepPruned(ObjNode n1, ObjNode n2) {
objStep(n1, n2) and relevantNode(n1) and relevantNode(n2)
private newtype TObjFlowNode =
TObjNode(ObjNode n) { relevantNode(n) } or
TObjType(RefType t) { source(t, _) }

private predicate objStepPruned(TObjFlowNode node1, TObjFlowNode node2) {
exists(ObjNode n1, ObjNode n2 |
node1 = TObjNode(n1) and
node2 = TObjNode(n2) and
objStep(n1, n2)
)
or
exists(RefType t, ObjNode n |
node1 = TObjType(t) and
node2 = TObjNode(n) and
source(t, n)
)
}

private predicate stepPlus(Node n1, Node n2) = fastTC(objStepPruned/2)(n1, n2)
private predicate flowSrc(TObjFlowNode src) { src instanceof TObjType }

private predicate flowSink(TObjFlowNode sink) { exists(ObjNode n | sink = TObjNode(n) and sink(n)) }

private predicate stepPlus(TObjFlowNode n1, TObjFlowNode n2) =
doublyBoundedFastTC(objStepPruned/2, flowSrc/1, flowSink/1)(n1, n2)

/**
* Holds if the qualifier `n` of an `Object.toString()` call might have type `t`.
*/
pragma[noopt]
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Very nice to get rid of this.

private predicate objType(ObjNode n, RefType t) {
exists(ObjNode n2 |
sink(n) and
(stepPlus(n2, n) or n2 = n) and
source(t, n2)
)
}
private predicate objType(ObjNode n, RefType t) { stepPlus(TObjType(t), TObjNode(n)) }

private VirtualMethodCall objectToString(ObjNode n) {
result.getQualifier() = n.asExpr() and sink(n)
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