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Merge pull request #1320 from aschackmull/java/guardslogic-perf

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Java: Fix join-order for GuardsLogic::conditionalAssign.
This commit is contained in:
yh-semmle
2019-05-19 22:23:18 -04:00
committed by GitHub
parent 8256f2e736 14cad57960
commit e5f4d475d0
1 changed files with 18 additions and 4 deletions
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22
java/ql/src/semmle/code/java/controlflow/internal/GuardsLogic.qll
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@@ -289,8 +289,25 @@ private ControlFlowNode getAGuardBranchSuccessor(Guard g, boolean branch) {
result = g.(SwitchCase).getControlFlowNode() and branch = true
}
/**
* Holds if `guard` dominates `phi` and `guard` evaluating to `branch` controls the definition
* `upd = e` where `upd` is a possible input to `phi`.
*/
private predicate guardControlsPhiBranch(
SsaExplicitUpdate upd, SsaPhiNode phi, Guard guard, boolean branch, Expr e
) {
guard.directlyControls(upd.getBasicBlock(), branch) and
upd.getDefiningExpr().(VariableAssign).getSource().getProperExpr() = e and
upd = phi.getAPhiInput() and
getBasicBlockOfGuard(guard).bbStrictlyDominates(phi.getBasicBlock())
}
/**
* Holds if `v` is conditionally assigned `e` under the condition that `guard` evaluates to `branch`.
*
* The evaluation of `guard` dominates the definition of `v` and `guard` evaluating to `branch`
* implies that `e` is assigned to `v`. In particular, this allows us to conclude that if `v` has
* a value different from `e` then `guard` must have evaluated to `branch.booleanNot()`.
*/
private predicate conditionalAssign(SsaVariable v, Guard guard, boolean branch, Expr e) {
exists(ConditionalExpr c |
@@ -303,11 +320,8 @@ private predicate conditionalAssign(SsaVariable v, Guard guard, boolean branch,
)
or
exists(SsaExplicitUpdate upd, SsaPhiNode phi |
guard.directlyControls(upd.getBasicBlock(), branch) and
upd.getDefiningExpr().(VariableAssign).getSource().getProperExpr() = e and
phi = v and
upd = phi.getAPhiInput() and
getBasicBlockOfGuard(guard).bbStrictlyDominates(phi.getBasicBlock()) and
guardControlsPhiBranch(upd, phi, guard, branch, e) and
not guard.directlyControls(phi.getBasicBlock(), branch) and
forall(SsaVariable other | other != upd and other = phi.getAPhiInput() |
guard.directlyControls(other.getBasicBlock(), branch.booleanNot())