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Merge pull request #2066 from jbj/dataflow-conditionAlwaysTrue-perf

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C++: Improve join orders for QL CFG
This commit is contained in:
Geoffrey White
2019-10-04 14:16:41 +01:00
committed by GitHub
parent e465f4cc81 3c7d79481f
commit 0e478d1c0e
1 changed files with 13 additions and 17 deletions
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30
cpp/ql/src/semmle/code/cpp/dataflow/internal/FlowVar.qll
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@@ -490,7 +490,7 @@ module FlowVar_internal {
exists(VariableAccess va |
va.getTarget() = result and
readAccess(va) and
bbNotInLoop(va.getBasicBlock())
exists(BasicBlock bb | bb = va.getBasicBlock() | not this.bbInLoop(bb))
)
}
@@ -513,10 +513,8 @@ module FlowVar_internal {
bbInLoopCondition(bb)
}
predicate bbNotInLoop(BasicBlock bb) {
not this.bbInLoop(bb) and
bb.getEnclosingFunction() = this.getEnclosingFunction()
}
/** Holds if `sbb` is inside this loop. */
predicate sbbInLoop(SubBasicBlock sbb) { this.bbInLoop(sbb.getBasicBlock()) }
/**
* Holds if `bb` is a basic block inside this loop where `v` has not been
@@ -537,22 +535,19 @@ module FlowVar_internal {
}
/**
* Holds if some loop always assigns to `v` before leaving through an edge
* from `bbInside` in its condition to `bbOutside` outside the loop, where
* (`sbbDef`, `v`) is a `BlockVar` defined outside the loop. Also, `v` must
* be used outside the loop.
* Holds if `loop` always assigns to `v` before leaving through an edge
* from `bbInside` in its condition to `bbOutside` outside the loop. Also,
* `v` must be used outside the loop.
*/
predicate skipLoop(
SubBasicBlock sbbInside, SubBasicBlock sbbOutside, SubBasicBlock sbbDef, Variable v
SubBasicBlock sbbInside, SubBasicBlock sbbOutside, Variable v, AlwaysTrueUponEntryLoop loop
) {
exists(AlwaysTrueUponEntryLoop loop, BasicBlock bbInside, BasicBlock bbOutside |
exists(BasicBlock bbInside, BasicBlock bbOutside |
loop.alwaysAssignsBeforeLeavingCondition(bbInside, bbOutside, v) and
bbInside = sbbInside.getBasicBlock() and
bbOutside = sbbOutside.getBasicBlock() and
sbbInside.lastInBB() and
sbbOutside.firstInBB() and
loop.bbNotInLoop(sbbDef.getBasicBlock()) and
exists(TBlockVar(sbbDef, v))
sbbOutside.firstInBB()
)
}
@@ -571,7 +566,7 @@ module FlowVar_internal {
start = TBlockVar(sbbDef, v) and
result = mid.getASuccessor() and
variableLiveInSBB(result, v) and
not skipLoop(mid, result, sbbDef, v) and
forall(AlwaysTrueUponEntryLoop loop | skipLoop(mid, result, v, loop) | loop.sbbInLoop(sbbDef)) and
not assignmentLikeOperation(result, v, _, _)
)
}
@@ -679,10 +674,11 @@ module FlowVar_internal {
predicate dominatedByOverwrite(UninitializedLocalVariable v, VariableAccess va) {
exists(BasicBlock bb, int vaIndex |
va = bb.getNode(vaIndex) and
va.getTarget() = v
|
va.getTarget() = v and
vaIndex > indexOfFirstOverwriteInBB(v, bb)
or
va = bb.getNode(vaIndex) and
va.getTarget() = v and
bbStrictlyDominates(getAnOverwritingBB(v), bb)
)
}