return std::make_pair(Vector.begin() + Pair.first->second, false);
}
+ iterator find(const KeyT &Key) {
+ typename MapTy::iterator It = Map.find(Key);
+ if (It == Map.end()) return Vector.end();
+ return Vector.begin() + It->second;
+ }
+
const_iterator find(const KeyT &Key) const {
typename MapTy::const_iterator It = Map.find(Key);
if (It == Map.end()) return Vector.end();
return false;
}
+/// This is a wrapper around getUnderlyingObjCPtr along the lines of
+/// GetUnderlyingObjects except that it returns early when it sees the first
+/// alloca.
+static inline bool AreAnyUnderlyingObjectsAnAlloca(const Value *V) {
+ SmallPtrSet<const Value *, 4> Visited;
+ SmallVector<const Value *, 4> Worklist;
+ Worklist.push_back(V);
+ do {
+ const Value *P = Worklist.pop_back_val();
+ P = GetUnderlyingObjCPtr(P);
+
+ if (isa<AllocaInst>(P))
+ return true;
+
+ if (!Visited.insert(P))
+ continue;
+
+ if (const SelectInst *SI = dyn_cast<const SelectInst>(P)) {
+ Worklist.push_back(SI->getTrueValue());
+ Worklist.push_back(SI->getFalseValue());
+ continue;
+ }
+
+ if (const PHINode *PN = dyn_cast<const PHINode>(P)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ Worklist.push_back(PN->getIncomingValue(i));
+ continue;
+ }
+ } while (!Worklist.empty());
+
+ return false;
+}
+
+
/// @}
///
/// \defgroup ARCOpt ARC Optimization.
/// sequence.
SmallPtrSet<Instruction *, 2> ReverseInsertPts;
+ /// Does this pointer have multiple owners?
+ ///
+ /// In the presence of multiple owners with the same provenance caused by
+ /// allocas, we can not assume that the frontend will emit balanced code
+ /// since it could put the release on the pointer loaded from the
+ /// alloca. This confuses the optimizer so we must be more conservative in
+ /// that case.
+ bool MultipleOwners;
+
RRInfo() :
- KnownSafe(false), IsTailCallRelease(false), ReleaseMetadata(0) {}
+ KnownSafe(false), IsTailCallRelease(false), ReleaseMetadata(0),
+ MultipleOwners(false) {}
void clear();
void RRInfo::clear() {
KnownSafe = false;
IsTailCallRelease = false;
+ MultipleOwners = false;
ReleaseMetadata = 0;
Calls.clear();
ReverseInsertPts.clear();
RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
Other.RRI.IsTailCallRelease;
RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
+ RRI.MultipleOwners |= Other.RRI.MultipleOwners;
// Merge the insert point sets. If there are any differences,
// that makes this a partial merge.
return PerPtrBottomUp[Arg];
}
+ /// Attempt to find the PtrState object describing the bottom up state for
+ /// pointer Arg.
+ ptr_iterator findPtrBottomUpState(const Value *Arg) {
+ return PerPtrBottomUp.find(Arg);
+ }
+
void clearBottomUpPointers() {
PerPtrBottomUp.clear();
}
case IC_None:
// These are irrelevant.
return NestingDetected;
+ case IC_User:
+ // If we have a store into an alloca of a pointer we are tracking, the
+ // pointer has multiple owners implying that we must be more conservative.
+ //
+ // This comes up in the context of a pointer being ``KnownSafe''. In the
+ // presense of a block being initialized, the frontend will emit the
+ // objc_retain on the original pointer and the release on the pointer loaded
+ // from the alloca. The optimizer will through the provenance analysis
+ // realize that the two are related, but since we only require KnownSafe in
+ // one direction, will match the inner retain on the original pointer with
+ // the guard release on the original pointer. This is fixed by ensuring that
+ // in the presense of allocas we only unconditionally remove pointers if
+ // both our retain and our release are KnownSafe.
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ if (AreAnyUnderlyingObjectsAnAlloca(SI->getPointerOperand())) {
+ BBState::ptr_iterator I = MyStates.findPtrBottomUpState(
+ StripPointerCastsAndObjCCalls(SI->getValueOperand()));
+ if (I != MyStates.bottom_up_ptr_end())
+ I->second.RRI.MultipleOwners = true;
+ }
+ }
+ break;
default:
break;
}
bool KnownSafe,
bool &AnyPairsCompletelyEliminated) {
// If a pair happens in a region where it is known that the reference count
- // is already incremented, we can similarly ignore possible decrements.
+ // is already incremented, we can similarly ignore possible decrements unless
+ // we are dealing with a retainable object with multiple provenance sources.
bool KnownSafeTD = true, KnownSafeBU = true;
+ bool MultipleOwners = false;
// Connect the dots between the top-down-collected RetainsToMove and
// bottom-up-collected ReleasesToMove to form sets of related calls.
assert(It != Retains.end());
const RRInfo &NewRetainRRI = It->second;
KnownSafeTD &= NewRetainRRI.KnownSafe;
+ MultipleOwners |= NewRetainRRI.MultipleOwners;
for (SmallPtrSet<Instruction *, 2>::const_iterator
LI = NewRetainRRI.Calls.begin(),
LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
if (NewRetains.empty()) break;
}
- // If the pointer is known incremented or nested, we can safely delete the
- // pair regardless of what's between them.
- if (KnownSafeTD || KnownSafeBU) {
+ // If the pointer is known incremented in 1 direction and we do not have
+ // MultipleOwners, we can safely remove the retain/releases. Otherwise we need
+ // to be known safe in both directions.
+ bool UnconditionallySafe = (KnownSafeTD && KnownSafeBU) ||
+ ((KnownSafeTD || KnownSafeBU) && !MultipleOwners);
+ if (UnconditionallySafe) {
RetainsToMove.ReverseInsertPts.clear();
ReleasesToMove.ReverseInsertPts.clear();
NewCount = 0;
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