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Data flow: Track access path singleton info in stages 2 and 3 #22383

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57 changes: 39 additions & 18 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImpl.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -2859,12 +2859,17 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
Typ getTyp(Type t) { any() }

bindingset[c, tail]
Ap apCons(Content c, Ap tail) { result.getAHead() = c and exists(tail) }
Ap apCons(Content c, Ap tail) {
exists(boolean isSingleton |
result.getAHead(isSingleton) = c and
if tail instanceof ApNil then isSingleton = true else isSingleton = false
)
}

class ApHeadContent = ContentApprox;

pragma[noinline]
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead() }
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead(_) }

predicate projectToHeadContent = getContentApproxCached/1;

Expand Down Expand Up @@ -2910,7 +2915,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
PrevStage::revFlow(node) and
PrevStage::readStepCand(_, c, _) and
Stage1::expectsContentEx(node, c) and
c = ap.getAHead()
c = ap.getAHead(_)
)
}

Expand Down Expand Up @@ -2961,12 +2966,17 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
Typ getTyp(Type t) { any() }

bindingset[c, tail]
Ap apCons(Content c, Ap tail) { result.getHead() = c and exists(tail) }
Ap apCons(Content c, Ap tail) {
exists(boolean isSingleton |
result.getHead(isSingleton) = c and
if tail instanceof ApNil then isSingleton = true else isSingleton = false
)
}

class ApHeadContent = Content;

pragma[noinline]
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead() }
ApHeadContent getHeadContent(Ap ap) { result = ap.getHead(_) }

ApHeadContent projectToHeadContent(Content c) { result = c }

Expand Down Expand Up @@ -3012,19 +3022,19 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
// When `node` is the target of a store, we interpret `clearsContent` as
// only pertaining to _earlier_ store steps. In this case, we need to postpone
// checking `clearsContent` to the step creation.
clearContent(node, ap.getHead(), false)
clearContent(node, ap.getHead(_), false)
}

pragma[nomagic]
private predicate clearExceptStore(Nd node, Ap ap) { clearContent(node, ap.getHead(), true) }
private predicate clearExceptStore(Nd node, Ap ap) { clearContent(node, ap.getHead(_), true) }

pragma[nomagic]
private predicate expectsContentCand(Nd node, Ap ap) {
exists(Content c |
PrevStage::revFlow(node) and
PrevStage::readStepCand(_, c, _) and
Stage1::expectsContentEx(node, c) and
c = ap.getHead()
c = ap.getHead(_)
)
}

Expand Down Expand Up @@ -3059,9 +3069,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tails = strictcount(AccessPathFront apf | Stage4::consCand(c, apf)) and
nodes =
strictcount(Nd n |
Stage4::revFlow(n, any(AccessPathFrontHead apf | apf.getHead() = c))
Stage4::revFlow(n, any(AccessPathFrontHead apf | apf.getHead(_) = c))
or
Stage4::nodeMayUseSummary(n, any(AccessPathFrontHead apf | apf.getHead() = c))
Stage4::nodeMayUseSummary(n, any(AccessPathFrontHead apf | apf.getHead(_) = c))
) and
accessPathApproxCostLimits(apLimit, tupleLimit) and
apLimit < tails and
Expand All @@ -3077,7 +3087,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
not expensiveLen2unfolding(c)
} or
TConsCons(Content c1, Content c2, int len) {
Stage4::consCand(c1, TFrontHead(c2)) and
Stage4::consCand(c1, TFrontHead(c2, _)) and
len in [2 .. Config::accessPathLimit()] and
not expensiveLen2unfolding(c1)
} or
Expand Down Expand Up @@ -3131,7 +3141,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = 1 }

override AccessPathFront getFront() { result = TFrontHead(c) }
override AccessPathFront getFront() { result = TFrontHead(c, true) }

override predicate isCons(Content head, AccessPathApprox tail) { head = c and tail = TNil() }
}
Expand All @@ -3153,7 +3163,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = len }

override AccessPathFront getFront() { result = TFrontHead(c1) }
override AccessPathFront getFront() { result = TFrontHead(c1, false) }

override predicate isCons(Content head, AccessPathApprox tail) {
head = c1 and
Expand Down Expand Up @@ -3184,12 +3194,17 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override int len() { result = len }

override AccessPathFront getFront() { result = TFrontHead(c) }
override AccessPathFront getFront() {
if len = 1 then result = TFrontHead(c, true) else result = TFrontHead(c, false)
}

override predicate isCons(Content head, AccessPathApprox tail) {
head = c and
(
exists(Content c2 | Stage4::consCand(c, TFrontHead(c2)) |
exists(Content c2, boolean isSingleton |
Stage4::consCand(c, TFrontHead(c2, isSingleton)) and
if len > 2 then isSingleton = false else isSingleton = true
|
tail = TConsCons(c2, _, len - 1)
or
len = 2 and
Expand Down Expand Up @@ -3531,7 +3546,11 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {

override predicate isCons(Content head, AccessPath tail) { head = head_ and tail = tail_ }

override AccessPathFrontHead getFront() { result = TFrontHead(head_) }
override AccessPathFrontHead getFront() {
if this.length() = 1
then result = TFrontHead(head_, true)
else result = TFrontHead(head_, false)
}

override AccessPathApproxCons getApprox() {
result = TConsNil(head_) and tail_ = TAccessPathNil()
Expand Down Expand Up @@ -3586,7 +3605,7 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tail.length() = len - 1
}

override AccessPathFrontHead getFront() { result = TFrontHead(head1) }
override AccessPathFrontHead getFront() { result = TFrontHead(head1, false) }

override AccessPathApproxCons getApprox() {
result = TConsCons(head1, head2, len) or
Expand Down Expand Up @@ -3618,7 +3637,9 @@ module MakeImpl<LocationSig Location, InputSig<Location> Lang> {
tail.length() = len - 1
}

override AccessPathFrontHead getFront() { result = TFrontHead(head_) }
override AccessPathFrontHead getFront() {
if len = 1 then result = TFrontHead(head_, true) else result = TFrontHead(head_, false)
}

override AccessPathApproxCons getApprox() { result = TCons1(head_, len) }

Expand Down
31 changes: 17 additions & 14 deletions shared/dataflow/codeql/dataflow/internal/DataFlowImplCommon.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -1797,12 +1797,12 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {
cached
newtype TAccessPathFront =
TFrontNil() or
TFrontHead(Content c)
TFrontHead(Content c, Boolean isSingleton)

cached
newtype TApproxAccessPathFront =
TApproxFrontNil() or
TApproxFrontHead(ContentApprox c)
TApproxFrontHead(ContentApprox c, Boolean isSingleton)

cached
newtype TAccessPathFrontOption =
Expand Down Expand Up @@ -2505,14 +2505,11 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract boolean toBoolNonEmpty();

ContentApprox getHead() { this = TApproxFrontHead(result) }
ContentApprox getHead(boolean isSingleton) { this = TApproxFrontHead(result, isSingleton) }

pragma[nomagic]
Content getAHead() {
exists(ContentApprox cont |
this = TApproxFrontHead(cont) and
cont = getContentApproxCached(result)
)
Content getAHead(boolean isSingleton) {
this.getHead(isSingleton) = getContentApproxCached(result)
}
}

Expand All @@ -2524,10 +2521,13 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

class ApproxAccessPathFrontHead extends ApproxAccessPathFront, TApproxFrontHead {
private ContentApprox c;
private boolean isSingleton;

ApproxAccessPathFrontHead() { this = TApproxFrontHead(c) }
ApproxAccessPathFrontHead() { this = TApproxFrontHead(c, isSingleton) }

override string toString() { result = c.toString() }
override string toString() {
if isSingleton = true then result = c.toString() + " (singleton)" else result = c.toString()
}

override boolean toBoolNonEmpty() { result = true }
}
Expand All @@ -2549,7 +2549,7 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

abstract ApproxAccessPathFront toApprox();

Content getHead() { this = TFrontHead(result) }
Content getHead(boolean isSingleton) { this = TFrontHead(result, isSingleton) }
}

class AccessPathFrontNil extends AccessPathFront, TFrontNil {
Expand All @@ -2560,12 +2560,15 @@ module MakeImplCommon<LocationSig Location, InputSig<Location> Lang> {

class AccessPathFrontHead extends AccessPathFront, TFrontHead {
private Content c;
private boolean isSingleton;

AccessPathFrontHead() { this = TFrontHead(c) }
AccessPathFrontHead() { this = TFrontHead(c, isSingleton) }

override string toString() { result = c.toString() }
override string toString() {
if isSingleton = true then result = c.toString() + " (singleton)" else result = c.toString()
}

override ApproxAccessPathFront toApprox() { result.getAHead() = c }
override ApproxAccessPathFront toApprox() { result.getAHead(isSingleton) = c }
}

/** An optional access path front. */
Expand Down
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