1 //===- ObjCARCOpts.cpp - ObjC ARC Optimization ----------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This file defines ObjC ARC optimizations. ARC stands for Automatic
11 /// Reference Counting and is a system for managing reference counts for objects
14 /// The optimizations performed include elimination of redundant, partially
15 /// redundant, and inconsequential reference count operations, elimination of
16 /// redundant weak pointer operations, and numerous minor simplifications.
18 /// WARNING: This file knows about certain library functions. It recognizes them
19 /// by name, and hardwires knowledge of their semantics.
21 /// WARNING: This file knows about how certain Objective-C library functions are
22 /// used. Naive LLVM IR transformations which would otherwise be
23 /// behavior-preserving may break these assumptions.
25 //===----------------------------------------------------------------------===//
27 #define DEBUG_TYPE "objc-arc-opts"
29 #include "DependencyAnalysis.h"
30 #include "ObjCARCAliasAnalysis.h"
31 #include "ProvenanceAnalysis.h"
32 #include "llvm/ADT/DenseMap.h"
33 #include "llvm/ADT/STLExtras.h"
34 #include "llvm/ADT/SmallPtrSet.h"
35 #include "llvm/ADT/Statistic.h"
36 #include "llvm/IR/IRBuilder.h"
37 #include "llvm/IR/LLVMContext.h"
38 #include "llvm/Support/CFG.h"
39 #include "llvm/Support/Debug.h"
40 #include "llvm/Support/raw_ostream.h"
43 using namespace llvm::objcarc;
45 /// \defgroup MiscUtils Miscellaneous utilities that are not ARC specific.
49 /// \brief An associative container with fast insertion-order (deterministic)
50 /// iteration over its elements. Plus the special blot operation.
51 template<class KeyT, class ValueT>
53 /// Map keys to indices in Vector.
54 typedef DenseMap<KeyT, size_t> MapTy;
57 typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
62 typedef typename VectorTy::iterator iterator;
63 typedef typename VectorTy::const_iterator const_iterator;
64 iterator begin() { return Vector.begin(); }
65 iterator end() { return Vector.end(); }
66 const_iterator begin() const { return Vector.begin(); }
67 const_iterator end() const { return Vector.end(); }
71 assert(Vector.size() >= Map.size()); // May differ due to blotting.
72 for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
74 assert(I->second < Vector.size());
75 assert(Vector[I->second].first == I->first);
77 for (typename VectorTy::const_iterator I = Vector.begin(),
78 E = Vector.end(); I != E; ++I)
80 (Map.count(I->first) &&
81 Map[I->first] == size_t(I - Vector.begin())));
85 ValueT &operator[](const KeyT &Arg) {
86 std::pair<typename MapTy::iterator, bool> Pair =
87 Map.insert(std::make_pair(Arg, size_t(0)));
89 size_t Num = Vector.size();
90 Pair.first->second = Num;
91 Vector.push_back(std::make_pair(Arg, ValueT()));
92 return Vector[Num].second;
94 return Vector[Pair.first->second].second;
97 std::pair<iterator, bool>
98 insert(const std::pair<KeyT, ValueT> &InsertPair) {
99 std::pair<typename MapTy::iterator, bool> Pair =
100 Map.insert(std::make_pair(InsertPair.first, size_t(0)));
102 size_t Num = Vector.size();
103 Pair.first->second = Num;
104 Vector.push_back(InsertPair);
105 return std::make_pair(Vector.begin() + Num, true);
107 return std::make_pair(Vector.begin() + Pair.first->second, false);
110 const_iterator find(const KeyT &Key) const {
111 typename MapTy::const_iterator It = Map.find(Key);
112 if (It == Map.end()) return Vector.end();
113 return Vector.begin() + It->second;
116 /// This is similar to erase, but instead of removing the element from the
117 /// vector, it just zeros out the key in the vector. This leaves iterators
118 /// intact, but clients must be prepared for zeroed-out keys when iterating.
119 void blot(const KeyT &Key) {
120 typename MapTy::iterator It = Map.find(Key);
121 if (It == Map.end()) return;
122 Vector[It->second].first = KeyT();
135 /// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
138 /// \brief This is similar to StripPointerCastsAndObjCCalls but it stops as soon
139 /// as it finds a value with multiple uses.
140 static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
141 if (Arg->hasOneUse()) {
142 if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
143 return FindSingleUseIdentifiedObject(BC->getOperand(0));
144 if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
145 if (GEP->hasAllZeroIndices())
146 return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
147 if (IsForwarding(GetBasicInstructionClass(Arg)))
148 return FindSingleUseIdentifiedObject(
149 cast<CallInst>(Arg)->getArgOperand(0));
150 if (!IsObjCIdentifiedObject(Arg))
155 // If we found an identifiable object but it has multiple uses, but they are
156 // trivial uses, we can still consider this to be a single-use value.
157 if (IsObjCIdentifiedObject(Arg)) {
158 for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
161 if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
171 /// \brief Test whether the given retainable object pointer escapes.
173 /// This differs from regular escape analysis in that a use as an
174 /// argument to a call is not considered an escape.
176 static bool DoesRetainableObjPtrEscape(const User *Ptr) {
177 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: Target: " << *Ptr << "\n");
179 // Walk the def-use chains.
180 SmallVector<const Value *, 4> Worklist;
181 Worklist.push_back(Ptr);
182 // If Ptr has any operands add them as well.
183 for (User::const_op_iterator I = Ptr->op_begin(), E = Ptr->op_end(); I != E;
185 Worklist.push_back(*I);
188 // Ensure we do not visit any value twice.
189 SmallPtrSet<const Value *, 8> VisitedSet;
192 const Value *V = Worklist.pop_back_val();
194 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: Visiting: " << *V << "\n");
196 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
198 const User *UUser = *UI;
200 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: User: " << *UUser << "\n");
202 // Special - Use by a call (callee or argument) is not considered
204 switch (GetBasicInstructionClass(UUser)) {
209 case IC_AutoreleaseRV: {
210 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: User copies pointer "
211 "arguments. Pointer Escapes!\n");
212 // These special functions make copies of their pointer arguments.
215 case IC_IntrinsicUser:
216 // Use by the use intrinsic is not an escape.
220 // Use by an instruction which copies the value is an escape if the
221 // result is an escape.
222 if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
223 isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
225 if (VisitedSet.insert(UUser)) {
226 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: User copies value. "
227 "Ptr escapes if result escapes. Adding to list.\n");
228 Worklist.push_back(UUser);
230 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: Already visited node."
235 // Use by a load is not an escape.
236 if (isa<LoadInst>(UUser))
238 // Use by a store is not an escape if the use is the address.
239 if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
240 if (V != SI->getValueOperand())
244 // Regular calls and other stuff are not considered escapes.
247 // Otherwise, conservatively assume an escape.
248 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: Assuming ptr escapes.\n");
251 } while (!Worklist.empty());
254 DEBUG(dbgs() << "DoesRetainableObjPtrEscape: Ptr does not escape.\n");
260 /// \defgroup ARCOpt ARC Optimization.
263 // TODO: On code like this:
266 // stuff_that_cannot_release()
267 // objc_autorelease(%x)
268 // stuff_that_cannot_release()
270 // stuff_that_cannot_release()
271 // objc_autorelease(%x)
273 // The second retain and autorelease can be deleted.
275 // TODO: It should be possible to delete
276 // objc_autoreleasePoolPush and objc_autoreleasePoolPop
277 // pairs if nothing is actually autoreleased between them. Also, autorelease
278 // calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
279 // after inlining) can be turned into plain release calls.
281 // TODO: Critical-edge splitting. If the optimial insertion point is
282 // a critical edge, the current algorithm has to fail, because it doesn't
283 // know how to split edges. It should be possible to make the optimizer
284 // think in terms of edges, rather than blocks, and then split critical
287 // TODO: OptimizeSequences could generalized to be Interprocedural.
289 // TODO: Recognize that a bunch of other objc runtime calls have
290 // non-escaping arguments and non-releasing arguments, and may be
291 // non-autoreleasing.
293 // TODO: Sink autorelease calls as far as possible. Unfortunately we
294 // usually can't sink them past other calls, which would be the main
295 // case where it would be useful.
297 // TODO: The pointer returned from objc_loadWeakRetained is retained.
299 // TODO: Delete release+retain pairs (rare).
301 STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
302 STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
303 STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
304 STATISTIC(NumRets, "Number of return value forwarding "
305 "retain+autoreleaes eliminated");
306 STATISTIC(NumRRs, "Number of retain+release paths eliminated");
307 STATISTIC(NumPeeps, "Number of calls peephole-optimized");
312 /// \brief A sequence of states that a pointer may go through in which an
313 /// objc_retain and objc_release are actually needed.
316 S_Retain, ///< objc_retain(x).
317 S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement.
318 S_Use, ///< any use of x.
319 S_Stop, ///< like S_Release, but code motion is stopped.
320 S_Release, ///< objc_release(x).
321 S_MovableRelease ///< objc_release(x), !clang.imprecise_release.
324 raw_ostream &operator<<(raw_ostream &OS, const Sequence S)
325 LLVM_ATTRIBUTE_UNUSED;
326 raw_ostream &operator<<(raw_ostream &OS, const Sequence S) {
329 return OS << "S_None";
331 return OS << "S_Retain";
333 return OS << "S_CanRelease";
335 return OS << "S_Use";
337 return OS << "S_Release";
338 case S_MovableRelease:
339 return OS << "S_MovableRelease";
341 return OS << "S_Stop";
343 llvm_unreachable("Unknown sequence type.");
347 static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
351 if (A == S_None || B == S_None)
354 if (A > B) std::swap(A, B);
356 // Choose the side which is further along in the sequence.
357 if ((A == S_Retain || A == S_CanRelease) &&
358 (B == S_CanRelease || B == S_Use))
361 // Choose the side which is further along in the sequence.
362 if ((A == S_Use || A == S_CanRelease) &&
363 (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
365 // If both sides are releases, choose the more conservative one.
366 if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
368 if (A == S_Release && B == S_MovableRelease)
376 /// \brief Unidirectional information about either a
377 /// retain-decrement-use-release sequence or release-use-decrement-retain
378 /// reverese sequence.
380 /// After an objc_retain, the reference count of the referenced
381 /// object is known to be positive. Similarly, before an objc_release, the
382 /// reference count of the referenced object is known to be positive. If
383 /// there are retain-release pairs in code regions where the retain count
384 /// is known to be positive, they can be eliminated, regardless of any side
385 /// effects between them.
387 /// Also, a retain+release pair nested within another retain+release
388 /// pair all on the known same pointer value can be eliminated, regardless
389 /// of any intervening side effects.
391 /// KnownSafe is true when either of these conditions is satisfied.
394 /// True if the Calls are objc_retainBlock calls (as opposed to objc_retain
398 /// True of the objc_release calls are all marked with the "tail" keyword.
399 bool IsTailCallRelease;
401 /// If the Calls are objc_release calls and they all have a
402 /// clang.imprecise_release tag, this is the metadata tag.
403 MDNode *ReleaseMetadata;
405 /// For a top-down sequence, the set of objc_retains or
406 /// objc_retainBlocks. For bottom-up, the set of objc_releases.
407 SmallPtrSet<Instruction *, 2> Calls;
409 /// The set of optimal insert positions for moving calls in the opposite
411 SmallPtrSet<Instruction *, 2> ReverseInsertPts;
414 KnownSafe(false), IsRetainBlock(false),
415 IsTailCallRelease(false),
416 ReleaseMetadata(0) {}
422 void RRInfo::clear() {
424 IsRetainBlock = false;
425 IsTailCallRelease = false;
428 ReverseInsertPts.clear();
432 /// \brief This class summarizes several per-pointer runtime properties which
433 /// are propogated through the flow graph.
435 /// True if the reference count is known to be incremented.
436 bool KnownPositiveRefCount;
438 /// True of we've seen an opportunity for partial RR elimination, such as
439 /// pushing calls into a CFG triangle or into one side of a CFG diamond.
442 /// The current position in the sequence.
446 /// Unidirectional information about the current sequence.
448 /// TODO: Encapsulate this better.
451 PtrState() : KnownPositiveRefCount(false), Partial(false),
454 void SetKnownPositiveRefCount() {
455 KnownPositiveRefCount = true;
458 void ClearKnownPositiveRefCount() {
459 KnownPositiveRefCount = false;
462 bool HasKnownPositiveRefCount() const {
463 return KnownPositiveRefCount;
466 void SetSeq(Sequence NewSeq) {
470 Sequence GetSeq() const {
474 void ClearSequenceProgress() {
475 ResetSequenceProgress(S_None);
478 void ResetSequenceProgress(Sequence NewSeq) {
484 void Merge(const PtrState &Other, bool TopDown);
489 PtrState::Merge(const PtrState &Other, bool TopDown) {
490 Seq = MergeSeqs(Seq, Other.Seq, TopDown);
491 KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
493 // We can't merge a plain objc_retain with an objc_retainBlock.
494 if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
497 // If we're not in a sequence (anymore), drop all associated state.
501 } else if (Partial || Other.Partial) {
502 // If we're doing a merge on a path that's previously seen a partial
503 // merge, conservatively drop the sequence, to avoid doing partial
504 // RR elimination. If the branch predicates for the two merge differ,
505 // mixing them is unsafe.
506 ClearSequenceProgress();
508 // Conservatively merge the ReleaseMetadata information.
509 if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
510 RRI.ReleaseMetadata = 0;
512 RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
513 RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
514 Other.RRI.IsTailCallRelease;
515 RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
517 // Merge the insert point sets. If there are any differences,
518 // that makes this a partial merge.
519 Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
520 for (SmallPtrSet<Instruction *, 2>::const_iterator
521 I = Other.RRI.ReverseInsertPts.begin(),
522 E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
523 Partial |= RRI.ReverseInsertPts.insert(*I);
528 /// \brief Per-BasicBlock state.
530 /// The number of unique control paths from the entry which can reach this
532 unsigned TopDownPathCount;
534 /// The number of unique control paths to exits from this block.
535 unsigned BottomUpPathCount;
537 /// A type for PerPtrTopDown and PerPtrBottomUp.
538 typedef MapVector<const Value *, PtrState> MapTy;
540 /// The top-down traversal uses this to record information known about a
541 /// pointer at the bottom of each block.
544 /// The bottom-up traversal uses this to record information known about a
545 /// pointer at the top of each block.
546 MapTy PerPtrBottomUp;
548 /// Effective predecessors of the current block ignoring ignorable edges and
549 /// ignored backedges.
550 SmallVector<BasicBlock *, 2> Preds;
551 /// Effective successors of the current block ignoring ignorable edges and
552 /// ignored backedges.
553 SmallVector<BasicBlock *, 2> Succs;
556 BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
558 typedef MapTy::iterator ptr_iterator;
559 typedef MapTy::const_iterator ptr_const_iterator;
561 ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
562 ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
563 ptr_const_iterator top_down_ptr_begin() const {
564 return PerPtrTopDown.begin();
566 ptr_const_iterator top_down_ptr_end() const {
567 return PerPtrTopDown.end();
570 ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
571 ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
572 ptr_const_iterator bottom_up_ptr_begin() const {
573 return PerPtrBottomUp.begin();
575 ptr_const_iterator bottom_up_ptr_end() const {
576 return PerPtrBottomUp.end();
579 /// Mark this block as being an entry block, which has one path from the
580 /// entry by definition.
581 void SetAsEntry() { TopDownPathCount = 1; }
583 /// Mark this block as being an exit block, which has one path to an exit by
585 void SetAsExit() { BottomUpPathCount = 1; }
587 PtrState &getPtrTopDownState(const Value *Arg) {
588 return PerPtrTopDown[Arg];
591 PtrState &getPtrBottomUpState(const Value *Arg) {
592 return PerPtrBottomUp[Arg];
595 void clearBottomUpPointers() {
596 PerPtrBottomUp.clear();
599 void clearTopDownPointers() {
600 PerPtrTopDown.clear();
603 void InitFromPred(const BBState &Other);
604 void InitFromSucc(const BBState &Other);
605 void MergePred(const BBState &Other);
606 void MergeSucc(const BBState &Other);
608 /// Return the number of possible unique paths from an entry to an exit
609 /// which pass through this block. This is only valid after both the
610 /// top-down and bottom-up traversals are complete.
611 unsigned GetAllPathCount() const {
612 assert(TopDownPathCount != 0);
613 assert(BottomUpPathCount != 0);
614 return TopDownPathCount * BottomUpPathCount;
617 // Specialized CFG utilities.
618 typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
619 edge_iterator pred_begin() { return Preds.begin(); }
620 edge_iterator pred_end() { return Preds.end(); }
621 edge_iterator succ_begin() { return Succs.begin(); }
622 edge_iterator succ_end() { return Succs.end(); }
624 void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); }
625 void addPred(BasicBlock *Pred) { Preds.push_back(Pred); }
627 bool isExit() const { return Succs.empty(); }
631 void BBState::InitFromPred(const BBState &Other) {
632 PerPtrTopDown = Other.PerPtrTopDown;
633 TopDownPathCount = Other.TopDownPathCount;
636 void BBState::InitFromSucc(const BBState &Other) {
637 PerPtrBottomUp = Other.PerPtrBottomUp;
638 BottomUpPathCount = Other.BottomUpPathCount;
641 /// The top-down traversal uses this to merge information about predecessors to
642 /// form the initial state for a new block.
643 void BBState::MergePred(const BBState &Other) {
644 // Other.TopDownPathCount can be 0, in which case it is either dead or a
645 // loop backedge. Loop backedges are special.
646 TopDownPathCount += Other.TopDownPathCount;
648 // Check for overflow. If we have overflow, fall back to conservative
650 if (TopDownPathCount < Other.TopDownPathCount) {
651 clearTopDownPointers();
655 // For each entry in the other set, if our set has an entry with the same key,
656 // merge the entries. Otherwise, copy the entry and merge it with an empty
658 for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
659 ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
660 std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
661 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
665 // For each entry in our set, if the other set doesn't have an entry with the
666 // same key, force it to merge with an empty entry.
667 for (ptr_iterator MI = top_down_ptr_begin(),
668 ME = top_down_ptr_end(); MI != ME; ++MI)
669 if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
670 MI->second.Merge(PtrState(), /*TopDown=*/true);
673 /// The bottom-up traversal uses this to merge information about successors to
674 /// form the initial state for a new block.
675 void BBState::MergeSucc(const BBState &Other) {
676 // Other.BottomUpPathCount can be 0, in which case it is either dead or a
677 // loop backedge. Loop backedges are special.
678 BottomUpPathCount += Other.BottomUpPathCount;
680 // Check for overflow. If we have overflow, fall back to conservative
682 if (BottomUpPathCount < Other.BottomUpPathCount) {
683 clearBottomUpPointers();
687 // For each entry in the other set, if our set has an entry with the
688 // same key, merge the entries. Otherwise, copy the entry and merge
689 // it with an empty entry.
690 for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
691 ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
692 std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
693 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
697 // For each entry in our set, if the other set doesn't have an entry
698 // with the same key, force it to merge with an empty entry.
699 for (ptr_iterator MI = bottom_up_ptr_begin(),
700 ME = bottom_up_ptr_end(); MI != ME; ++MI)
701 if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
702 MI->second.Merge(PtrState(), /*TopDown=*/false);
705 // Only enable ARC Annotations if we are building a debug version of
708 #define ARC_ANNOTATIONS
711 // Define some macros along the lines of DEBUG and some helper functions to make
712 // it cleaner to create annotations in the source code and to no-op when not
713 // building in debug mode.
714 #ifdef ARC_ANNOTATIONS
716 #include "llvm/Support/CommandLine.h"
718 /// Enable/disable ARC sequence annotations.
720 EnableARCAnnotations("enable-objc-arc-annotations", cl::init(false));
722 /// This function appends a unique ARCAnnotationProvenanceSourceMDKind id to an
723 /// instruction so that we can track backwards when post processing via the llvm
724 /// arc annotation processor tool. If the function is an
725 static MDString *AppendMDNodeToSourcePtr(unsigned NodeId,
729 // If pointer is a result of an instruction and it does not have a source
730 // MDNode it, attach a new MDNode onto it. If pointer is a result of
731 // an instruction and does have a source MDNode attached to it, return a
732 // reference to said Node. Otherwise just return 0.
733 if (Instruction *Inst = dyn_cast<Instruction>(Ptr)) {
735 if (!(Node = Inst->getMetadata(NodeId))) {
736 // We do not have any node. Generate and attatch the hash MDString to the
739 // We just use an MDString to ensure that this metadata gets written out
740 // of line at the module level and to provide a very simple format
741 // encoding the information herein. Both of these makes it simpler to
742 // parse the annotations by a simple external program.
744 raw_string_ostream os(Str);
745 os << "(" << Inst->getParent()->getParent()->getName() << ",%"
746 << Inst->getName() << ")";
748 Hash = MDString::get(Inst->getContext(), os.str());
749 Inst->setMetadata(NodeId, MDNode::get(Inst->getContext(),Hash));
751 // We have a node. Grab its hash and return it.
752 assert(Node->getNumOperands() == 1 &&
753 "An ARCAnnotationProvenanceSourceMDKind can only have 1 operand.");
754 Hash = cast<MDString>(Node->getOperand(0));
756 } else if (Argument *Arg = dyn_cast<Argument>(Ptr)) {
758 raw_string_ostream os(str);
759 os << "(" << Arg->getParent()->getName() << ",%" << Arg->getName()
761 Hash = MDString::get(Arg->getContext(), os.str());
767 static std::string SequenceToString(Sequence A) {
769 raw_string_ostream os(str);
774 /// Helper function to change a Sequence into a String object using our overload
775 /// for raw_ostream so we only have printing code in one location.
776 static MDString *SequenceToMDString(LLVMContext &Context,
778 return MDString::get(Context, SequenceToString(A));
781 /// A simple function to generate a MDNode which describes the change in state
782 /// for Value *Ptr caused by Instruction *Inst.
783 static void AppendMDNodeToInstForPtr(unsigned NodeId,
786 MDString *PtrSourceMDNodeID,
790 Value *tmp[3] = {PtrSourceMDNodeID,
791 SequenceToMDString(Inst->getContext(),
793 SequenceToMDString(Inst->getContext(),
795 Node = MDNode::get(Inst->getContext(),
796 ArrayRef<Value*>(tmp, 3));
798 Inst->setMetadata(NodeId, Node);
801 /// Add to the beginning of the basic block llvm.ptr.annotations which show the
802 /// state of a pointer at the entrance to a basic block.
803 static void GenerateARCBBEntranceAnnotation(const char *Name, BasicBlock *BB,
804 Value *Ptr, Sequence Seq) {
805 Module *M = BB->getParent()->getParent();
806 LLVMContext &C = M->getContext();
807 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
808 Type *I8XX = PointerType::getUnqual(I8X);
809 Type *Params[] = {I8XX, I8XX};
810 FunctionType *FTy = FunctionType::get(Type::getVoidTy(C),
811 ArrayRef<Type*>(Params, 2),
813 Constant *Callee = M->getOrInsertFunction(Name, FTy);
815 IRBuilder<> Builder(BB, BB->getFirstInsertionPt());
818 StringRef Tmp = Ptr->getName();
819 if (0 == (PtrName = M->getGlobalVariable(Tmp, true))) {
820 Value *ActualPtrName = Builder.CreateGlobalStringPtr(Tmp,
822 PtrName = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
823 cast<Constant>(ActualPtrName), Tmp);
827 std::string SeqStr = SequenceToString(Seq);
828 if (0 == (S = M->getGlobalVariable(SeqStr, true))) {
829 Value *ActualPtrName = Builder.CreateGlobalStringPtr(SeqStr,
831 S = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
832 cast<Constant>(ActualPtrName), SeqStr);
835 Builder.CreateCall2(Callee, PtrName, S);
838 /// Add to the end of the basic block llvm.ptr.annotations which show the state
839 /// of the pointer at the bottom of the basic block.
840 static void GenerateARCBBTerminatorAnnotation(const char *Name, BasicBlock *BB,
841 Value *Ptr, Sequence Seq) {
842 Module *M = BB->getParent()->getParent();
843 LLVMContext &C = M->getContext();
844 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
845 Type *I8XX = PointerType::getUnqual(I8X);
846 Type *Params[] = {I8XX, I8XX};
847 FunctionType *FTy = FunctionType::get(Type::getVoidTy(C),
848 ArrayRef<Type*>(Params, 2),
850 Constant *Callee = M->getOrInsertFunction(Name, FTy);
852 IRBuilder<> Builder(BB, llvm::prior(BB->end()));
855 StringRef Tmp = Ptr->getName();
856 if (0 == (PtrName = M->getGlobalVariable(Tmp, true))) {
857 Value *ActualPtrName = Builder.CreateGlobalStringPtr(Tmp,
859 PtrName = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
860 cast<Constant>(ActualPtrName), Tmp);
864 std::string SeqStr = SequenceToString(Seq);
865 if (0 == (S = M->getGlobalVariable(SeqStr, true))) {
866 Value *ActualPtrName = Builder.CreateGlobalStringPtr(SeqStr,
868 S = new GlobalVariable(*M, I8X, true, GlobalVariable::InternalLinkage,
869 cast<Constant>(ActualPtrName), SeqStr);
871 Builder.CreateCall2(Callee, PtrName, S);
874 /// Adds a source annotation to pointer and a state change annotation to Inst
875 /// referencing the source annotation and the old/new state of pointer.
876 static void GenerateARCAnnotation(unsigned InstMDId,
882 if (EnableARCAnnotations) {
883 // First generate the source annotation on our pointer. This will return an
884 // MDString* if Ptr actually comes from an instruction implying we can put
885 // in a source annotation. If AppendMDNodeToSourcePtr returns 0 (i.e. NULL),
886 // then we know that our pointer is from an Argument so we put a reference
887 // to the argument number.
889 // The point of this is to make it easy for the
890 // llvm-arc-annotation-processor tool to cross reference where the source
891 // pointer is in the LLVM IR since the LLVM IR parser does not submit such
892 // information via debug info for backends to use (since why would anyone
893 // need such a thing from LLVM IR besides in non standard cases
895 MDString *SourcePtrMDNode =
896 AppendMDNodeToSourcePtr(PtrMDId, Ptr);
897 AppendMDNodeToInstForPtr(InstMDId, Inst, Ptr, SourcePtrMDNode, OldSeq,
902 // The actual interface for accessing the above functionality is defined via
903 // some simple macros which are defined below. We do this so that the user does
904 // not need to pass in what metadata id is needed resulting in cleaner code and
905 // additionally since it provides an easy way to conditionally no-op all
906 // annotation support in a non-debug build.
908 /// Use this macro to annotate a sequence state change when processing
909 /// instructions bottom up,
910 #define ANNOTATE_BOTTOMUP(inst, ptr, old, new) \
911 GenerateARCAnnotation(ARCAnnotationBottomUpMDKind, \
912 ARCAnnotationProvenanceSourceMDKind, (inst), \
913 const_cast<Value*>(ptr), (old), (new))
914 /// Use this macro to annotate a sequence state change when processing
915 /// instructions top down.
916 #define ANNOTATE_TOPDOWN(inst, ptr, old, new) \
917 GenerateARCAnnotation(ARCAnnotationTopDownMDKind, \
918 ARCAnnotationProvenanceSourceMDKind, (inst), \
919 const_cast<Value*>(ptr), (old), (new))
921 #else // !ARC_ANNOTATION
922 // If annotations are off, noop.
923 #define ANNOTATE_BOTTOMUP(inst, ptr, old, new)
924 #define ANNOTATE_TOPDOWN(inst, ptr, old, new)
925 #endif // !ARC_ANNOTATION
928 /// \brief The main ARC optimization pass.
929 class ObjCARCOpt : public FunctionPass {
931 ProvenanceAnalysis PA;
933 /// A flag indicating whether this optimization pass should run.
936 /// Declarations for ObjC runtime functions, for use in creating calls to
937 /// them. These are initialized lazily to avoid cluttering up the Module
938 /// with unused declarations.
940 /// Declaration for ObjC runtime function
941 /// objc_retainAutoreleasedReturnValue.
942 Constant *RetainRVCallee;
943 /// Declaration for ObjC runtime function objc_autoreleaseReturnValue.
944 Constant *AutoreleaseRVCallee;
945 /// Declaration for ObjC runtime function objc_release.
946 Constant *ReleaseCallee;
947 /// Declaration for ObjC runtime function objc_retain.
948 Constant *RetainCallee;
949 /// Declaration for ObjC runtime function objc_retainBlock.
950 Constant *RetainBlockCallee;
951 /// Declaration for ObjC runtime function objc_autorelease.
952 Constant *AutoreleaseCallee;
954 /// Flags which determine whether each of the interesting runtine functions
955 /// is in fact used in the current function.
956 unsigned UsedInThisFunction;
958 /// The Metadata Kind for clang.imprecise_release metadata.
959 unsigned ImpreciseReleaseMDKind;
961 /// The Metadata Kind for clang.arc.copy_on_escape metadata.
962 unsigned CopyOnEscapeMDKind;
964 /// The Metadata Kind for clang.arc.no_objc_arc_exceptions metadata.
965 unsigned NoObjCARCExceptionsMDKind;
967 #ifdef ARC_ANNOTATIONS
968 /// The Metadata Kind for llvm.arc.annotation.bottomup metadata.
969 unsigned ARCAnnotationBottomUpMDKind;
970 /// The Metadata Kind for llvm.arc.annotation.topdown metadata.
971 unsigned ARCAnnotationTopDownMDKind;
972 /// The Metadata Kind for llvm.arc.annotation.provenancesource metadata.
973 unsigned ARCAnnotationProvenanceSourceMDKind;
974 #endif // ARC_ANNOATIONS
976 Constant *getRetainRVCallee(Module *M);
977 Constant *getAutoreleaseRVCallee(Module *M);
978 Constant *getReleaseCallee(Module *M);
979 Constant *getRetainCallee(Module *M);
980 Constant *getRetainBlockCallee(Module *M);
981 Constant *getAutoreleaseCallee(Module *M);
983 bool IsRetainBlockOptimizable(const Instruction *Inst);
985 void OptimizeRetainCall(Function &F, Instruction *Retain);
986 bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
987 void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
988 InstructionClass &Class);
989 bool OptimizeRetainBlockCall(Function &F, Instruction *RetainBlock,
990 InstructionClass &Class);
991 void OptimizeIndividualCalls(Function &F);
993 void CheckForCFGHazards(const BasicBlock *BB,
994 DenseMap<const BasicBlock *, BBState> &BBStates,
995 BBState &MyStates) const;
996 bool VisitInstructionBottomUp(Instruction *Inst,
998 MapVector<Value *, RRInfo> &Retains,
1000 bool VisitBottomUp(BasicBlock *BB,
1001 DenseMap<const BasicBlock *, BBState> &BBStates,
1002 MapVector<Value *, RRInfo> &Retains);
1003 bool VisitInstructionTopDown(Instruction *Inst,
1004 DenseMap<Value *, RRInfo> &Releases,
1006 bool VisitTopDown(BasicBlock *BB,
1007 DenseMap<const BasicBlock *, BBState> &BBStates,
1008 DenseMap<Value *, RRInfo> &Releases);
1009 bool Visit(Function &F,
1010 DenseMap<const BasicBlock *, BBState> &BBStates,
1011 MapVector<Value *, RRInfo> &Retains,
1012 DenseMap<Value *, RRInfo> &Releases);
1014 void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
1015 MapVector<Value *, RRInfo> &Retains,
1016 DenseMap<Value *, RRInfo> &Releases,
1017 SmallVectorImpl<Instruction *> &DeadInsts,
1020 bool ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState> &BBStates,
1021 MapVector<Value *, RRInfo> &Retains,
1022 DenseMap<Value *, RRInfo> &Releases,
1024 SmallVector<Instruction *, 4> &NewRetains,
1025 SmallVector<Instruction *, 4> &NewReleases,
1026 SmallVector<Instruction *, 8> &DeadInsts,
1027 RRInfo &RetainsToMove,
1028 RRInfo &ReleasesToMove,
1031 bool &AnyPairsCompletelyEliminated);
1033 bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
1034 MapVector<Value *, RRInfo> &Retains,
1035 DenseMap<Value *, RRInfo> &Releases,
1038 void OptimizeWeakCalls(Function &F);
1040 bool OptimizeSequences(Function &F);
1042 void OptimizeReturns(Function &F);
1044 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
1045 virtual bool doInitialization(Module &M);
1046 virtual bool runOnFunction(Function &F);
1047 virtual void releaseMemory();
1051 ObjCARCOpt() : FunctionPass(ID) {
1052 initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
1057 char ObjCARCOpt::ID = 0;
1058 INITIALIZE_PASS_BEGIN(ObjCARCOpt,
1059 "objc-arc", "ObjC ARC optimization", false, false)
1060 INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
1061 INITIALIZE_PASS_END(ObjCARCOpt,
1062 "objc-arc", "ObjC ARC optimization", false, false)
1064 Pass *llvm::createObjCARCOptPass() {
1065 return new ObjCARCOpt();
1068 void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
1069 AU.addRequired<ObjCARCAliasAnalysis>();
1070 AU.addRequired<AliasAnalysis>();
1071 // ARC optimization doesn't currently split critical edges.
1072 AU.setPreservesCFG();
1075 bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) {
1076 // Without the magic metadata tag, we have to assume this might be an
1077 // objc_retainBlock call inserted to convert a block pointer to an id,
1078 // in which case it really is needed.
1079 if (!Inst->getMetadata(CopyOnEscapeMDKind))
1082 // If the pointer "escapes" (not including being used in a call),
1083 // the copy may be needed.
1084 if (DoesRetainableObjPtrEscape(Inst))
1087 // Otherwise, it's not needed.
1091 Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
1092 if (!RetainRVCallee) {
1093 LLVMContext &C = M->getContext();
1094 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1095 Type *Params[] = { I8X };
1096 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
1097 AttributeSet Attribute =
1098 AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
1099 Attribute::NoUnwind);
1101 M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
1104 return RetainRVCallee;
1107 Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
1108 if (!AutoreleaseRVCallee) {
1109 LLVMContext &C = M->getContext();
1110 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1111 Type *Params[] = { I8X };
1112 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
1113 AttributeSet Attribute =
1114 AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
1115 Attribute::NoUnwind);
1116 AutoreleaseRVCallee =
1117 M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
1120 return AutoreleaseRVCallee;
1123 Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
1124 if (!ReleaseCallee) {
1125 LLVMContext &C = M->getContext();
1126 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1127 AttributeSet Attribute =
1128 AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
1129 Attribute::NoUnwind);
1131 M->getOrInsertFunction(
1133 FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
1136 return ReleaseCallee;
1139 Constant *ObjCARCOpt::getRetainCallee(Module *M) {
1140 if (!RetainCallee) {
1141 LLVMContext &C = M->getContext();
1142 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1143 AttributeSet Attribute =
1144 AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
1145 Attribute::NoUnwind);
1147 M->getOrInsertFunction(
1149 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1152 return RetainCallee;
1155 Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
1156 if (!RetainBlockCallee) {
1157 LLVMContext &C = M->getContext();
1158 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1159 // objc_retainBlock is not nounwind because it calls user copy constructors
1160 // which could theoretically throw.
1162 M->getOrInsertFunction(
1164 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1167 return RetainBlockCallee;
1170 Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
1171 if (!AutoreleaseCallee) {
1172 LLVMContext &C = M->getContext();
1173 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1174 AttributeSet Attribute =
1175 AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
1176 Attribute::NoUnwind);
1178 M->getOrInsertFunction(
1180 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1183 return AutoreleaseCallee;
1186 /// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
1189 ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
1190 ImmutableCallSite CS(GetObjCArg(Retain));
1191 const Instruction *Call = CS.getInstruction();
1193 if (Call->getParent() != Retain->getParent()) return;
1195 // Check that the call is next to the retain.
1196 BasicBlock::const_iterator I = Call;
1198 while (IsNoopInstruction(I)) ++I;
1202 // Turn it to an objc_retainAutoreleasedReturnValue..
1206 DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainCall: Transforming "
1207 "objc_retain => objc_retainAutoreleasedReturnValue"
1208 " since the operand is a return value.\n"
1210 << *Retain << "\n");
1212 cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
1214 DEBUG(dbgs() << " New: "
1215 << *Retain << "\n");
1218 /// Turn objc_retainAutoreleasedReturnValue into objc_retain if the operand is
1219 /// not a return value. Or, if it can be paired with an
1220 /// objc_autoreleaseReturnValue, delete the pair and return true.
1222 ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
1223 // Check for the argument being from an immediately preceding call or invoke.
1224 const Value *Arg = GetObjCArg(RetainRV);
1225 ImmutableCallSite CS(Arg);
1226 if (const Instruction *Call = CS.getInstruction()) {
1227 if (Call->getParent() == RetainRV->getParent()) {
1228 BasicBlock::const_iterator I = Call;
1230 while (IsNoopInstruction(I)) ++I;
1231 if (&*I == RetainRV)
1233 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
1234 BasicBlock *RetainRVParent = RetainRV->getParent();
1235 if (II->getNormalDest() == RetainRVParent) {
1236 BasicBlock::const_iterator I = RetainRVParent->begin();
1237 while (IsNoopInstruction(I)) ++I;
1238 if (&*I == RetainRV)
1244 // Check for being preceded by an objc_autoreleaseReturnValue on the same
1245 // pointer. In this case, we can delete the pair.
1246 BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
1248 do --I; while (I != Begin && IsNoopInstruction(I));
1249 if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
1250 GetObjCArg(I) == Arg) {
1254 DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
1255 << " Erasing " << *RetainRV
1258 EraseInstruction(I);
1259 EraseInstruction(RetainRV);
1264 // Turn it to a plain objc_retain.
1268 DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Transforming "
1269 "objc_retainAutoreleasedReturnValue => "
1270 "objc_retain since the operand is not a return value.\n"
1272 << *RetainRV << "\n");
1274 cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
1276 DEBUG(dbgs() << " New: "
1277 << *RetainRV << "\n");
1282 /// Turn objc_autoreleaseReturnValue into objc_autorelease if the result is not
1283 /// used as a return value.
1285 ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
1286 InstructionClass &Class) {
1287 // Check for a return of the pointer value.
1288 const Value *Ptr = GetObjCArg(AutoreleaseRV);
1289 SmallVector<const Value *, 2> Users;
1290 Users.push_back(Ptr);
1292 Ptr = Users.pop_back_val();
1293 for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
1295 const User *I = *UI;
1296 if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
1298 if (isa<BitCastInst>(I))
1301 } while (!Users.empty());
1306 DEBUG(dbgs() << "ObjCARCOpt::OptimizeAutoreleaseRVCall: Transforming "
1307 "objc_autoreleaseReturnValue => "
1308 "objc_autorelease since its operand is not used as a return "
1311 << *AutoreleaseRV << "\n");
1313 CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
1315 setCalledFunction(getAutoreleaseCallee(F.getParent()));
1316 AutoreleaseRVCI->setTailCall(false); // Never tail call objc_autorelease.
1317 Class = IC_Autorelease;
1319 DEBUG(dbgs() << " New: "
1320 << *AutoreleaseRV << "\n");
1324 // \brief Attempt to strength reduce objc_retainBlock calls to objc_retain
1327 // Specifically: If an objc_retainBlock call has the copy_on_escape metadata and
1328 // does not escape (following the rules of block escaping), strength reduce the
1329 // objc_retainBlock to an objc_retain.
1331 // TODO: If an objc_retainBlock call is dominated period by a previous
1332 // objc_retainBlock call, strength reduce the objc_retainBlock to an
1335 ObjCARCOpt::OptimizeRetainBlockCall(Function &F, Instruction *Inst,
1336 InstructionClass &Class) {
1337 assert(GetBasicInstructionClass(Inst) == Class);
1338 assert(IC_RetainBlock == Class);
1340 // If we can not optimize Inst, return false.
1341 if (!IsRetainBlockOptimizable(Inst))
1344 CallInst *RetainBlock = cast<CallInst>(Inst);
1345 RetainBlock->setCalledFunction(getRetainCallee(F.getParent()));
1346 // Remove copy_on_escape metadata.
1347 RetainBlock->setMetadata(CopyOnEscapeMDKind, 0);
1353 /// Visit each call, one at a time, and make simplifications without doing any
1354 /// additional analysis.
1355 void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
1356 // Reset all the flags in preparation for recomputing them.
1357 UsedInThisFunction = 0;
1359 // Visit all objc_* calls in F.
1360 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
1361 Instruction *Inst = &*I++;
1363 InstructionClass Class = GetBasicInstructionClass(Inst);
1365 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Visiting: Class: "
1366 << Class << "; " << *Inst << "\n");
1371 // Delete no-op casts. These function calls have special semantics, but
1372 // the semantics are entirely implemented via lowering in the front-end,
1373 // so by the time they reach the optimizer, they are just no-op calls
1374 // which return their argument.
1376 // There are gray areas here, as the ability to cast reference-counted
1377 // pointers to raw void* and back allows code to break ARC assumptions,
1378 // however these are currently considered to be unimportant.
1382 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Erasing no-op cast:"
1383 " " << *Inst << "\n");
1384 EraseInstruction(Inst);
1387 // If the pointer-to-weak-pointer is null, it's undefined behavior.
1390 case IC_LoadWeakRetained:
1392 case IC_DestroyWeak: {
1393 CallInst *CI = cast<CallInst>(Inst);
1394 if (IsNullOrUndef(CI->getArgOperand(0))) {
1396 Type *Ty = CI->getArgOperand(0)->getType();
1397 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
1398 Constant::getNullValue(Ty),
1400 llvm::Value *NewValue = UndefValue::get(CI->getType());
1401 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
1402 "pointer-to-weak-pointer is undefined behavior.\n"
1406 CI->replaceAllUsesWith(NewValue);
1407 CI->eraseFromParent();
1414 CallInst *CI = cast<CallInst>(Inst);
1415 if (IsNullOrUndef(CI->getArgOperand(0)) ||
1416 IsNullOrUndef(CI->getArgOperand(1))) {
1418 Type *Ty = CI->getArgOperand(0)->getType();
1419 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
1420 Constant::getNullValue(Ty),
1423 llvm::Value *NewValue = UndefValue::get(CI->getType());
1424 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
1425 "pointer-to-weak-pointer is undefined behavior.\n"
1430 CI->replaceAllUsesWith(NewValue);
1431 CI->eraseFromParent();
1436 case IC_RetainBlock:
1437 // If we strength reduce an objc_retainBlock to amn objc_retain, continue
1438 // onto the objc_retain peephole optimizations. Otherwise break.
1439 if (!OptimizeRetainBlockCall(F, Inst, Class))
1443 OptimizeRetainCall(F, Inst);
1446 if (OptimizeRetainRVCall(F, Inst))
1449 case IC_AutoreleaseRV:
1450 OptimizeAutoreleaseRVCall(F, Inst, Class);
1454 // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
1455 if (IsAutorelease(Class) && Inst->use_empty()) {
1456 CallInst *Call = cast<CallInst>(Inst);
1457 const Value *Arg = Call->getArgOperand(0);
1458 Arg = FindSingleUseIdentifiedObject(Arg);
1463 // Create the declaration lazily.
1464 LLVMContext &C = Inst->getContext();
1466 CallInst::Create(getReleaseCallee(F.getParent()),
1467 Call->getArgOperand(0), "", Call);
1468 NewCall->setMetadata(ImpreciseReleaseMDKind,
1469 MDNode::get(C, ArrayRef<Value *>()));
1471 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Replacing "
1472 "objc_autorelease(x) with objc_release(x) since x is "
1473 "otherwise unused.\n"
1474 " Old: " << *Call <<
1478 EraseInstruction(Call);
1484 // For functions which can never be passed stack arguments, add
1486 if (IsAlwaysTail(Class)) {
1488 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Adding tail keyword"
1489 " to function since it can never be passed stack args: " << *Inst <<
1491 cast<CallInst>(Inst)->setTailCall();
1494 // Ensure that functions that can never have a "tail" keyword due to the
1495 // semantics of ARC truly do not do so.
1496 if (IsNeverTail(Class)) {
1498 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Removing tail "
1499 "keyword from function: " << *Inst <<
1501 cast<CallInst>(Inst)->setTailCall(false);
1504 // Set nounwind as needed.
1505 if (IsNoThrow(Class)) {
1507 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Found no throw"
1508 " class. Setting nounwind on: " << *Inst << "\n");
1509 cast<CallInst>(Inst)->setDoesNotThrow();
1512 if (!IsNoopOnNull(Class)) {
1513 UsedInThisFunction |= 1 << Class;
1517 const Value *Arg = GetObjCArg(Inst);
1519 // ARC calls with null are no-ops. Delete them.
1520 if (IsNullOrUndef(Arg)) {
1523 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: ARC calls with "
1524 " null are no-ops. Erasing: " << *Inst << "\n");
1525 EraseInstruction(Inst);
1529 // Keep track of which of retain, release, autorelease, and retain_block
1530 // are actually present in this function.
1531 UsedInThisFunction |= 1 << Class;
1533 // If Arg is a PHI, and one or more incoming values to the
1534 // PHI are null, and the call is control-equivalent to the PHI, and there
1535 // are no relevant side effects between the PHI and the call, the call
1536 // could be pushed up to just those paths with non-null incoming values.
1537 // For now, don't bother splitting critical edges for this.
1538 SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
1539 Worklist.push_back(std::make_pair(Inst, Arg));
1541 std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
1545 const PHINode *PN = dyn_cast<PHINode>(Arg);
1548 // Determine if the PHI has any null operands, or any incoming
1550 bool HasNull = false;
1551 bool HasCriticalEdges = false;
1552 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1554 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
1555 if (IsNullOrUndef(Incoming))
1557 else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
1558 .getNumSuccessors() != 1) {
1559 HasCriticalEdges = true;
1563 // If we have null operands and no critical edges, optimize.
1564 if (!HasCriticalEdges && HasNull) {
1565 SmallPtrSet<Instruction *, 4> DependingInstructions;
1566 SmallPtrSet<const BasicBlock *, 4> Visited;
1568 // Check that there is nothing that cares about the reference
1569 // count between the call and the phi.
1572 case IC_RetainBlock:
1573 // These can always be moved up.
1576 // These can't be moved across things that care about the retain
1578 FindDependencies(NeedsPositiveRetainCount, Arg,
1579 Inst->getParent(), Inst,
1580 DependingInstructions, Visited, PA);
1582 case IC_Autorelease:
1583 // These can't be moved across autorelease pool scope boundaries.
1584 FindDependencies(AutoreleasePoolBoundary, Arg,
1585 Inst->getParent(), Inst,
1586 DependingInstructions, Visited, PA);
1589 case IC_AutoreleaseRV:
1590 // Don't move these; the RV optimization depends on the autoreleaseRV
1591 // being tail called, and the retainRV being immediately after a call
1592 // (which might still happen if we get lucky with codegen layout, but
1593 // it's not worth taking the chance).
1596 llvm_unreachable("Invalid dependence flavor");
1599 if (DependingInstructions.size() == 1 &&
1600 *DependingInstructions.begin() == PN) {
1603 // Clone the call into each predecessor that has a non-null value.
1604 CallInst *CInst = cast<CallInst>(Inst);
1605 Type *ParamTy = CInst->getArgOperand(0)->getType();
1606 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
1608 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
1609 if (!IsNullOrUndef(Incoming)) {
1610 CallInst *Clone = cast<CallInst>(CInst->clone());
1611 Value *Op = PN->getIncomingValue(i);
1612 Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
1613 if (Op->getType() != ParamTy)
1614 Op = new BitCastInst(Op, ParamTy, "", InsertPos);
1615 Clone->setArgOperand(0, Op);
1616 Clone->insertBefore(InsertPos);
1618 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Cloning "
1621 "clone at " << *InsertPos << "\n");
1622 Worklist.push_back(std::make_pair(Clone, Incoming));
1625 // Erase the original call.
1626 DEBUG(dbgs() << "Erasing: " << *CInst << "\n");
1627 EraseInstruction(CInst);
1631 } while (!Worklist.empty());
1633 DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Finished List.\n");
1636 /// Check for critical edges, loop boundaries, irreducible control flow, or
1637 /// other CFG structures where moving code across the edge would result in it
1638 /// being executed more.
1640 ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
1641 DenseMap<const BasicBlock *, BBState> &BBStates,
1642 BBState &MyStates) const {
1643 // If any top-down local-use or possible-dec has a succ which is earlier in
1644 // the sequence, forget it.
1645 for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(),
1646 E = MyStates.top_down_ptr_end(); I != E; ++I)
1647 switch (I->second.GetSeq()) {
1650 const Value *Arg = I->first;
1651 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
1652 bool SomeSuccHasSame = false;
1653 bool AllSuccsHaveSame = true;
1654 PtrState &S = I->second;
1655 succ_const_iterator SI(TI), SE(TI, false);
1657 for (; SI != SE; ++SI) {
1658 Sequence SuccSSeq = S_None;
1659 bool SuccSRRIKnownSafe = false;
1660 // If VisitBottomUp has pointer information for this successor, take
1661 // what we know about it.
1662 DenseMap<const BasicBlock *, BBState>::iterator BBI =
1664 assert(BBI != BBStates.end());
1665 const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
1666 SuccSSeq = SuccS.GetSeq();
1667 SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
1670 case S_CanRelease: {
1671 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
1672 S.ClearSequenceProgress();
1678 SomeSuccHasSame = true;
1682 case S_MovableRelease:
1683 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
1684 AllSuccsHaveSame = false;
1687 llvm_unreachable("bottom-up pointer in retain state!");
1690 // If the state at the other end of any of the successor edges
1691 // matches the current state, require all edges to match. This
1692 // guards against loops in the middle of a sequence.
1693 if (SomeSuccHasSame && !AllSuccsHaveSame)
1694 S.ClearSequenceProgress();
1697 case S_CanRelease: {
1698 const Value *Arg = I->first;
1699 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
1700 bool SomeSuccHasSame = false;
1701 bool AllSuccsHaveSame = true;
1702 PtrState &S = I->second;
1703 succ_const_iterator SI(TI), SE(TI, false);
1705 for (; SI != SE; ++SI) {
1706 Sequence SuccSSeq = S_None;
1707 bool SuccSRRIKnownSafe = false;
1708 // If VisitBottomUp has pointer information for this successor, take
1709 // what we know about it.
1710 DenseMap<const BasicBlock *, BBState>::iterator BBI =
1712 assert(BBI != BBStates.end());
1713 const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
1714 SuccSSeq = SuccS.GetSeq();
1715 SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
1718 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
1719 S.ClearSequenceProgress();
1725 SomeSuccHasSame = true;
1729 case S_MovableRelease:
1731 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
1732 AllSuccsHaveSame = false;
1735 llvm_unreachable("bottom-up pointer in retain state!");
1738 // If the state at the other end of any of the successor edges
1739 // matches the current state, require all edges to match. This
1740 // guards against loops in the middle of a sequence.
1741 if (SomeSuccHasSame && !AllSuccsHaveSame)
1742 S.ClearSequenceProgress();
1749 ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
1751 MapVector<Value *, RRInfo> &Retains,
1752 BBState &MyStates) {
1753 bool NestingDetected = false;
1754 InstructionClass Class = GetInstructionClass(Inst);
1755 const Value *Arg = 0;
1759 Arg = GetObjCArg(Inst);
1761 PtrState &S = MyStates.getPtrBottomUpState(Arg);
1763 // If we see two releases in a row on the same pointer. If so, make
1764 // a note, and we'll cicle back to revisit it after we've
1765 // hopefully eliminated the second release, which may allow us to
1766 // eliminate the first release too.
1767 // Theoretically we could implement removal of nested retain+release
1768 // pairs by making PtrState hold a stack of states, but this is
1769 // simple and avoids adding overhead for the non-nested case.
1770 if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease) {
1771 DEBUG(dbgs() << "ObjCARCOpt::VisitInstructionBottomUp: Found nested "
1772 "releases (i.e. a release pair)\n");
1773 NestingDetected = true;
1776 MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
1777 Sequence NewSeq = ReleaseMetadata ? S_MovableRelease : S_Release;
1778 ANNOTATE_BOTTOMUP(Inst, Arg, S.GetSeq(), NewSeq);
1779 S.ResetSequenceProgress(NewSeq);
1780 S.RRI.ReleaseMetadata = ReleaseMetadata;
1781 S.RRI.KnownSafe = S.HasKnownPositiveRefCount();
1782 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
1783 S.RRI.Calls.insert(Inst);
1784 S.SetKnownPositiveRefCount();
1787 case IC_RetainBlock:
1788 // In OptimizeIndividualCalls, we have strength reduced all optimizable
1789 // objc_retainBlocks to objc_retains. Thus at this point any
1790 // objc_retainBlocks that we see are not optimizable.
1794 Arg = GetObjCArg(Inst);
1796 PtrState &S = MyStates.getPtrBottomUpState(Arg);
1797 S.SetKnownPositiveRefCount();
1799 Sequence OldSeq = S.GetSeq();
1803 case S_MovableRelease:
1805 S.RRI.ReverseInsertPts.clear();
1808 // Don't do retain+release tracking for IC_RetainRV, because it's
1809 // better to let it remain as the first instruction after a call.
1810 if (Class != IC_RetainRV) {
1811 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
1812 Retains[Inst] = S.RRI;
1814 S.ClearSequenceProgress();
1819 llvm_unreachable("bottom-up pointer in retain state!");
1821 ANNOTATE_BOTTOMUP(Inst, Arg, OldSeq, S.GetSeq());
1822 return NestingDetected;
1824 case IC_AutoreleasepoolPop:
1825 // Conservatively, clear MyStates for all known pointers.
1826 MyStates.clearBottomUpPointers();
1827 return NestingDetected;
1828 case IC_AutoreleasepoolPush:
1830 // These are irrelevant.
1831 return NestingDetected;
1836 // Consider any other possible effects of this instruction on each
1837 // pointer being tracked.
1838 for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
1839 ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
1840 const Value *Ptr = MI->first;
1842 continue; // Handled above.
1843 PtrState &S = MI->second;
1844 Sequence Seq = S.GetSeq();
1846 // Check for possible releases.
1847 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
1848 S.ClearKnownPositiveRefCount();
1851 S.SetSeq(S_CanRelease);
1852 ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, S.GetSeq());
1856 case S_MovableRelease:
1861 llvm_unreachable("bottom-up pointer in retain state!");
1865 // Check for possible direct uses.
1868 case S_MovableRelease:
1869 if (CanUse(Inst, Ptr, PA, Class)) {
1870 assert(S.RRI.ReverseInsertPts.empty());
1871 // If this is an invoke instruction, we're scanning it as part of
1872 // one of its successor blocks, since we can't insert code after it
1873 // in its own block, and we don't want to split critical edges.
1874 if (isa<InvokeInst>(Inst))
1875 S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
1877 S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
1879 ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, S_Use);
1880 } else if (Seq == S_Release && IsUser(Class)) {
1881 // Non-movable releases depend on any possible objc pointer use.
1883 ANNOTATE_BOTTOMUP(Inst, Ptr, S_Release, S_Stop);
1884 assert(S.RRI.ReverseInsertPts.empty());
1885 // As above; handle invoke specially.
1886 if (isa<InvokeInst>(Inst))
1887 S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
1889 S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
1893 if (CanUse(Inst, Ptr, PA, Class)) {
1895 ANNOTATE_BOTTOMUP(Inst, Ptr, Seq, S_Use);
1903 llvm_unreachable("bottom-up pointer in retain state!");
1907 return NestingDetected;
1911 ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
1912 DenseMap<const BasicBlock *, BBState> &BBStates,
1913 MapVector<Value *, RRInfo> &Retains) {
1914 bool NestingDetected = false;
1915 BBState &MyStates = BBStates[BB];
1917 // Merge the states from each successor to compute the initial state
1918 // for the current block.
1919 BBState::edge_iterator SI(MyStates.succ_begin()),
1920 SE(MyStates.succ_end());
1922 const BasicBlock *Succ = *SI;
1923 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
1924 assert(I != BBStates.end());
1925 MyStates.InitFromSucc(I->second);
1927 for (; SI != SE; ++SI) {
1929 I = BBStates.find(Succ);
1930 assert(I != BBStates.end());
1931 MyStates.MergeSucc(I->second);
1935 #ifdef ARC_ANNOTATIONS
1936 if (EnableARCAnnotations) {
1937 // If ARC Annotations are enabled, output the current state of pointers at the
1938 // bottom of the basic block.
1939 for(BBState::ptr_const_iterator I = MyStates.bottom_up_ptr_begin(),
1940 E = MyStates.bottom_up_ptr_end(); I != E; ++I) {
1941 Value *Ptr = const_cast<Value*>(I->first);
1942 Sequence Seq = I->second.GetSeq();
1943 GenerateARCBBTerminatorAnnotation("llvm.arc.annotation.bottomup.bbend",
1950 // Visit all the instructions, bottom-up.
1951 for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
1952 Instruction *Inst = llvm::prior(I);
1954 // Invoke instructions are visited as part of their successors (below).
1955 if (isa<InvokeInst>(Inst))
1958 DEBUG(dbgs() << "ObjCARCOpt::VisitButtonUp: Visiting " << *Inst << "\n");
1960 NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
1963 // If there's a predecessor with an invoke, visit the invoke as if it were
1964 // part of this block, since we can't insert code after an invoke in its own
1965 // block, and we don't want to split critical edges.
1966 for (BBState::edge_iterator PI(MyStates.pred_begin()),
1967 PE(MyStates.pred_end()); PI != PE; ++PI) {
1968 BasicBlock *Pred = *PI;
1969 if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back()))
1970 NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates);
1973 #ifdef ARC_ANNOTATIONS
1974 if (EnableARCAnnotations) {
1975 // If ARC Annotations are enabled, output the current state of pointers at the
1976 // top of the basic block.
1977 for(BBState::ptr_const_iterator I = MyStates.bottom_up_ptr_begin(),
1978 E = MyStates.bottom_up_ptr_end(); I != E; ++I) {
1979 Value *Ptr = const_cast<Value*>(I->first);
1980 Sequence Seq = I->second.GetSeq();
1981 GenerateARCBBEntranceAnnotation("llvm.arc.annotation.bottomup.bbstart",
1987 return NestingDetected;
1991 ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst,
1992 DenseMap<Value *, RRInfo> &Releases,
1993 BBState &MyStates) {
1994 bool NestingDetected = false;
1995 InstructionClass Class = GetInstructionClass(Inst);
1996 const Value *Arg = 0;
1999 case IC_RetainBlock:
2000 // In OptimizeIndividualCalls, we have strength reduced all optimizable
2001 // objc_retainBlocks to objc_retains. Thus at this point any
2002 // objc_retainBlocks that we see are not optimizable.
2006 Arg = GetObjCArg(Inst);
2008 PtrState &S = MyStates.getPtrTopDownState(Arg);
2010 // Don't do retain+release tracking for IC_RetainRV, because it's
2011 // better to let it remain as the first instruction after a call.
2012 if (Class != IC_RetainRV) {
2013 // If we see two retains in a row on the same pointer. If so, make
2014 // a note, and we'll cicle back to revisit it after we've
2015 // hopefully eliminated the second retain, which may allow us to
2016 // eliminate the first retain too.
2017 // Theoretically we could implement removal of nested retain+release
2018 // pairs by making PtrState hold a stack of states, but this is
2019 // simple and avoids adding overhead for the non-nested case.
2020 if (S.GetSeq() == S_Retain)
2021 NestingDetected = true;
2023 ANNOTATE_TOPDOWN(Inst, Arg, S.GetSeq(), S_Retain);
2024 S.ResetSequenceProgress(S_Retain);
2025 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
2026 S.RRI.KnownSafe = S.HasKnownPositiveRefCount();
2027 S.RRI.Calls.insert(Inst);
2030 S.SetKnownPositiveRefCount();
2032 // A retain can be a potential use; procede to the generic checking
2037 Arg = GetObjCArg(Inst);
2039 PtrState &S = MyStates.getPtrTopDownState(Arg);
2040 S.ClearKnownPositiveRefCount();
2042 switch (S.GetSeq()) {
2045 S.RRI.ReverseInsertPts.clear();
2048 S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
2049 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
2050 Releases[Inst] = S.RRI;
2051 ANNOTATE_TOPDOWN(Inst, Arg, S.GetSeq(), S_None);
2052 S.ClearSequenceProgress();
2058 case S_MovableRelease:
2059 llvm_unreachable("top-down pointer in release state!");
2063 case IC_AutoreleasepoolPop:
2064 // Conservatively, clear MyStates for all known pointers.
2065 MyStates.clearTopDownPointers();
2066 return NestingDetected;
2067 case IC_AutoreleasepoolPush:
2069 // These are irrelevant.
2070 return NestingDetected;
2075 // Consider any other possible effects of this instruction on each
2076 // pointer being tracked.
2077 for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
2078 ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
2079 const Value *Ptr = MI->first;
2081 continue; // Handled above.
2082 PtrState &S = MI->second;
2083 Sequence Seq = S.GetSeq();
2085 // Check for possible releases.
2086 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
2087 S.ClearKnownPositiveRefCount();
2090 S.SetSeq(S_CanRelease);
2091 ANNOTATE_TOPDOWN(Inst, Ptr, Seq, S_CanRelease);
2092 assert(S.RRI.ReverseInsertPts.empty());
2093 S.RRI.ReverseInsertPts.insert(Inst);
2095 // One call can't cause a transition from S_Retain to S_CanRelease
2096 // and S_CanRelease to S_Use. If we've made the first transition,
2105 case S_MovableRelease:
2106 llvm_unreachable("top-down pointer in release state!");
2110 // Check for possible direct uses.
2113 if (CanUse(Inst, Ptr, PA, Class)) {
2115 ANNOTATE_TOPDOWN(Inst, Ptr, Seq, S_Use);
2124 case S_MovableRelease:
2125 llvm_unreachable("top-down pointer in release state!");
2129 return NestingDetected;
2133 ObjCARCOpt::VisitTopDown(BasicBlock *BB,
2134 DenseMap<const BasicBlock *, BBState> &BBStates,
2135 DenseMap<Value *, RRInfo> &Releases) {
2136 bool NestingDetected = false;
2137 BBState &MyStates = BBStates[BB];
2139 // Merge the states from each predecessor to compute the initial state
2140 // for the current block.
2141 BBState::edge_iterator PI(MyStates.pred_begin()),
2142 PE(MyStates.pred_end());
2144 const BasicBlock *Pred = *PI;
2145 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
2146 assert(I != BBStates.end());
2147 MyStates.InitFromPred(I->second);
2149 for (; PI != PE; ++PI) {
2151 I = BBStates.find(Pred);
2152 assert(I != BBStates.end());
2153 MyStates.MergePred(I->second);
2157 #ifdef ARC_ANNOTATIONS
2158 if (EnableARCAnnotations) {
2159 // If ARC Annotations are enabled, output the current state of pointers at the
2160 // top of the basic block.
2161 for(BBState::ptr_const_iterator I = MyStates.top_down_ptr_begin(),
2162 E = MyStates.top_down_ptr_end(); I != E; ++I) {
2163 Value *Ptr = const_cast<Value*>(I->first);
2164 Sequence Seq = I->second.GetSeq();
2165 GenerateARCBBEntranceAnnotation("llvm.arc.annotation.topdown.bbstart",
2171 // Visit all the instructions, top-down.
2172 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
2173 Instruction *Inst = I;
2175 DEBUG(dbgs() << "ObjCARCOpt::VisitTopDown: Visiting " << *Inst << "\n");
2177 NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
2180 #ifdef ARC_ANNOTATIONS
2181 if (EnableARCAnnotations) {
2182 // If ARC Annotations are enabled, output the current state of pointers at the
2183 // bottom of the basic block.
2184 for(BBState::ptr_const_iterator I = MyStates.top_down_ptr_begin(),
2185 E = MyStates.top_down_ptr_end(); I != E; ++I) {
2186 Value *Ptr = const_cast<Value*>(I->first);
2187 Sequence Seq = I->second.GetSeq();
2188 GenerateARCBBTerminatorAnnotation("llvm.arc.annotation.topdown.bbend",
2194 CheckForCFGHazards(BB, BBStates, MyStates);
2195 return NestingDetected;
2199 ComputePostOrders(Function &F,
2200 SmallVectorImpl<BasicBlock *> &PostOrder,
2201 SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder,
2202 unsigned NoObjCARCExceptionsMDKind,
2203 DenseMap<const BasicBlock *, BBState> &BBStates) {
2204 /// The visited set, for doing DFS walks.
2205 SmallPtrSet<BasicBlock *, 16> Visited;
2207 // Do DFS, computing the PostOrder.
2208 SmallPtrSet<BasicBlock *, 16> OnStack;
2209 SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack;
2211 // Functions always have exactly one entry block, and we don't have
2212 // any other block that we treat like an entry block.
2213 BasicBlock *EntryBB = &F.getEntryBlock();
2214 BBState &MyStates = BBStates[EntryBB];
2215 MyStates.SetAsEntry();
2216 TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back());
2217 SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI)));
2218 Visited.insert(EntryBB);
2219 OnStack.insert(EntryBB);
2222 BasicBlock *CurrBB = SuccStack.back().first;
2223 TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back());
2224 succ_iterator SE(TI, false);
2226 while (SuccStack.back().second != SE) {
2227 BasicBlock *SuccBB = *SuccStack.back().second++;
2228 if (Visited.insert(SuccBB)) {
2229 TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back());
2230 SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI)));
2231 BBStates[CurrBB].addSucc(SuccBB);
2232 BBState &SuccStates = BBStates[SuccBB];
2233 SuccStates.addPred(CurrBB);
2234 OnStack.insert(SuccBB);
2238 if (!OnStack.count(SuccBB)) {
2239 BBStates[CurrBB].addSucc(SuccBB);
2240 BBStates[SuccBB].addPred(CurrBB);
2243 OnStack.erase(CurrBB);
2244 PostOrder.push_back(CurrBB);
2245 SuccStack.pop_back();
2246 } while (!SuccStack.empty());
2250 // Do reverse-CFG DFS, computing the reverse-CFG PostOrder.
2251 // Functions may have many exits, and there also blocks which we treat
2252 // as exits due to ignored edges.
2253 SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack;
2254 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
2255 BasicBlock *ExitBB = I;
2256 BBState &MyStates = BBStates[ExitBB];
2257 if (!MyStates.isExit())
2260 MyStates.SetAsExit();
2262 PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin()));
2263 Visited.insert(ExitBB);
2264 while (!PredStack.empty()) {
2265 reverse_dfs_next_succ:
2266 BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end();
2267 while (PredStack.back().second != PE) {
2268 BasicBlock *BB = *PredStack.back().second++;
2269 if (Visited.insert(BB)) {
2270 PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin()));
2271 goto reverse_dfs_next_succ;
2274 ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first);
2279 // Visit the function both top-down and bottom-up.
2281 ObjCARCOpt::Visit(Function &F,
2282 DenseMap<const BasicBlock *, BBState> &BBStates,
2283 MapVector<Value *, RRInfo> &Retains,
2284 DenseMap<Value *, RRInfo> &Releases) {
2286 // Use reverse-postorder traversals, because we magically know that loops
2287 // will be well behaved, i.e. they won't repeatedly call retain on a single
2288 // pointer without doing a release. We can't use the ReversePostOrderTraversal
2289 // class here because we want the reverse-CFG postorder to consider each
2290 // function exit point, and we want to ignore selected cycle edges.
2291 SmallVector<BasicBlock *, 16> PostOrder;
2292 SmallVector<BasicBlock *, 16> ReverseCFGPostOrder;
2293 ComputePostOrders(F, PostOrder, ReverseCFGPostOrder,
2294 NoObjCARCExceptionsMDKind,
2297 // Use reverse-postorder on the reverse CFG for bottom-up.
2298 bool BottomUpNestingDetected = false;
2299 for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
2300 ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend();
2302 BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains);
2304 // Use reverse-postorder for top-down.
2305 bool TopDownNestingDetected = false;
2306 for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
2307 PostOrder.rbegin(), E = PostOrder.rend();
2309 TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases);
2311 return TopDownNestingDetected && BottomUpNestingDetected;
2314 /// Move the calls in RetainsToMove and ReleasesToMove.
2315 void ObjCARCOpt::MoveCalls(Value *Arg,
2316 RRInfo &RetainsToMove,
2317 RRInfo &ReleasesToMove,
2318 MapVector<Value *, RRInfo> &Retains,
2319 DenseMap<Value *, RRInfo> &Releases,
2320 SmallVectorImpl<Instruction *> &DeadInsts,
2322 Type *ArgTy = Arg->getType();
2323 Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
2325 // Insert the new retain and release calls.
2326 for (SmallPtrSet<Instruction *, 2>::const_iterator
2327 PI = ReleasesToMove.ReverseInsertPts.begin(),
2328 PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
2329 Instruction *InsertPt = *PI;
2330 Value *MyArg = ArgTy == ParamTy ? Arg :
2331 new BitCastInst(Arg, ParamTy, "", InsertPt);
2333 CallInst::Create(RetainsToMove.IsRetainBlock ?
2334 getRetainBlockCallee(M) : getRetainCallee(M),
2335 MyArg, "", InsertPt);
2336 Call->setDoesNotThrow();
2337 if (RetainsToMove.IsRetainBlock)
2338 Call->setMetadata(CopyOnEscapeMDKind,
2339 MDNode::get(M->getContext(), ArrayRef<Value *>()));
2341 Call->setTailCall();
2343 DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Release: " << *Call
2345 " At insertion point: " << *InsertPt
2348 for (SmallPtrSet<Instruction *, 2>::const_iterator
2349 PI = RetainsToMove.ReverseInsertPts.begin(),
2350 PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
2351 Instruction *InsertPt = *PI;
2352 Value *MyArg = ArgTy == ParamTy ? Arg :
2353 new BitCastInst(Arg, ParamTy, "", InsertPt);
2354 CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
2356 // Attach a clang.imprecise_release metadata tag, if appropriate.
2357 if (MDNode *M = ReleasesToMove.ReleaseMetadata)
2358 Call->setMetadata(ImpreciseReleaseMDKind, M);
2359 Call->setDoesNotThrow();
2360 if (ReleasesToMove.IsTailCallRelease)
2361 Call->setTailCall();
2363 DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Retain: " << *Call
2365 " At insertion point: " << *InsertPt
2369 // Delete the original retain and release calls.
2370 for (SmallPtrSet<Instruction *, 2>::const_iterator
2371 AI = RetainsToMove.Calls.begin(),
2372 AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
2373 Instruction *OrigRetain = *AI;
2374 Retains.blot(OrigRetain);
2375 DeadInsts.push_back(OrigRetain);
2376 DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting retain: " << *OrigRetain <<
2379 for (SmallPtrSet<Instruction *, 2>::const_iterator
2380 AI = ReleasesToMove.Calls.begin(),
2381 AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
2382 Instruction *OrigRelease = *AI;
2383 Releases.erase(OrigRelease);
2384 DeadInsts.push_back(OrigRelease);
2385 DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting release: " << *OrigRelease
2391 ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
2393 MapVector<Value *, RRInfo> &Retains,
2394 DenseMap<Value *, RRInfo> &Releases,
2396 SmallVector<Instruction *, 4> &NewRetains,
2397 SmallVector<Instruction *, 4> &NewReleases,
2398 SmallVector<Instruction *, 8> &DeadInsts,
2399 RRInfo &RetainsToMove,
2400 RRInfo &ReleasesToMove,
2403 bool &AnyPairsCompletelyEliminated) {
2404 // If a pair happens in a region where it is known that the reference count
2405 // is already incremented, we can similarly ignore possible decrements.
2406 bool KnownSafeTD = true, KnownSafeBU = true;
2408 // Connect the dots between the top-down-collected RetainsToMove and
2409 // bottom-up-collected ReleasesToMove to form sets of related calls.
2410 // This is an iterative process so that we connect multiple releases
2411 // to multiple retains if needed.
2412 unsigned OldDelta = 0;
2413 unsigned NewDelta = 0;
2414 unsigned OldCount = 0;
2415 unsigned NewCount = 0;
2416 bool FirstRelease = true;
2417 bool FirstRetain = true;
2419 for (SmallVectorImpl<Instruction *>::const_iterator
2420 NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
2421 Instruction *NewRetain = *NI;
2422 MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
2423 assert(It != Retains.end());
2424 const RRInfo &NewRetainRRI = It->second;
2425 KnownSafeTD &= NewRetainRRI.KnownSafe;
2426 for (SmallPtrSet<Instruction *, 2>::const_iterator
2427 LI = NewRetainRRI.Calls.begin(),
2428 LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
2429 Instruction *NewRetainRelease = *LI;
2430 DenseMap<Value *, RRInfo>::const_iterator Jt =
2431 Releases.find(NewRetainRelease);
2432 if (Jt == Releases.end())
2434 const RRInfo &NewRetainReleaseRRI = Jt->second;
2435 assert(NewRetainReleaseRRI.Calls.count(NewRetain));
2436 if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
2438 BBStates[NewRetainRelease->getParent()].GetAllPathCount();
2440 // Merge the ReleaseMetadata and IsTailCallRelease values.
2442 ReleasesToMove.ReleaseMetadata =
2443 NewRetainReleaseRRI.ReleaseMetadata;
2444 ReleasesToMove.IsTailCallRelease =
2445 NewRetainReleaseRRI.IsTailCallRelease;
2446 FirstRelease = false;
2448 if (ReleasesToMove.ReleaseMetadata !=
2449 NewRetainReleaseRRI.ReleaseMetadata)
2450 ReleasesToMove.ReleaseMetadata = 0;
2451 if (ReleasesToMove.IsTailCallRelease !=
2452 NewRetainReleaseRRI.IsTailCallRelease)
2453 ReleasesToMove.IsTailCallRelease = false;
2456 // Collect the optimal insertion points.
2458 for (SmallPtrSet<Instruction *, 2>::const_iterator
2459 RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
2460 RE = NewRetainReleaseRRI.ReverseInsertPts.end();
2462 Instruction *RIP = *RI;
2463 if (ReleasesToMove.ReverseInsertPts.insert(RIP))
2464 NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
2466 NewReleases.push_back(NewRetainRelease);
2471 if (NewReleases.empty()) break;
2473 // Back the other way.
2474 for (SmallVectorImpl<Instruction *>::const_iterator
2475 NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
2476 Instruction *NewRelease = *NI;
2477 DenseMap<Value *, RRInfo>::const_iterator It =
2478 Releases.find(NewRelease);
2479 assert(It != Releases.end());
2480 const RRInfo &NewReleaseRRI = It->second;
2481 KnownSafeBU &= NewReleaseRRI.KnownSafe;
2482 for (SmallPtrSet<Instruction *, 2>::const_iterator
2483 LI = NewReleaseRRI.Calls.begin(),
2484 LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
2485 Instruction *NewReleaseRetain = *LI;
2486 MapVector<Value *, RRInfo>::const_iterator Jt =
2487 Retains.find(NewReleaseRetain);
2488 if (Jt == Retains.end())
2490 const RRInfo &NewReleaseRetainRRI = Jt->second;
2491 assert(NewReleaseRetainRRI.Calls.count(NewRelease));
2492 if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
2493 unsigned PathCount =
2494 BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
2495 OldDelta += PathCount;
2496 OldCount += PathCount;
2498 // Merge the IsRetainBlock values.
2500 RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
2501 FirstRetain = false;
2502 } else if (ReleasesToMove.IsRetainBlock !=
2503 NewReleaseRetainRRI.IsRetainBlock)
2504 // It's not possible to merge the sequences if one uses
2505 // objc_retain and the other uses objc_retainBlock.
2508 // Collect the optimal insertion points.
2510 for (SmallPtrSet<Instruction *, 2>::const_iterator
2511 RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
2512 RE = NewReleaseRetainRRI.ReverseInsertPts.end();
2514 Instruction *RIP = *RI;
2515 if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
2516 PathCount = BBStates[RIP->getParent()].GetAllPathCount();
2517 NewDelta += PathCount;
2518 NewCount += PathCount;
2521 NewRetains.push_back(NewReleaseRetain);
2525 NewReleases.clear();
2526 if (NewRetains.empty()) break;
2529 // If the pointer is known incremented or nested, we can safely delete the
2530 // pair regardless of what's between them.
2531 if (KnownSafeTD || KnownSafeBU) {
2532 RetainsToMove.ReverseInsertPts.clear();
2533 ReleasesToMove.ReverseInsertPts.clear();
2536 // Determine whether the new insertion points we computed preserve the
2537 // balance of retain and release calls through the program.
2538 // TODO: If the fully aggressive solution isn't valid, try to find a
2539 // less aggressive solution which is.
2544 // Determine whether the original call points are balanced in the retain and
2545 // release calls through the program. If not, conservatively don't touch
2547 // TODO: It's theoretically possible to do code motion in this case, as
2548 // long as the existing imbalances are maintained.
2553 assert(OldCount != 0 && "Unreachable code?");
2554 NumRRs += OldCount - NewCount;
2555 // Set to true if we completely removed any RR pairs.
2556 AnyPairsCompletelyEliminated = NewCount == 0;
2558 // We can move calls!
2562 /// Identify pairings between the retains and releases, and delete and/or move
2565 ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
2567 MapVector<Value *, RRInfo> &Retains,
2568 DenseMap<Value *, RRInfo> &Releases,
2570 bool AnyPairsCompletelyEliminated = false;
2571 RRInfo RetainsToMove;
2572 RRInfo ReleasesToMove;
2573 SmallVector<Instruction *, 4> NewRetains;
2574 SmallVector<Instruction *, 4> NewReleases;
2575 SmallVector<Instruction *, 8> DeadInsts;
2577 // Visit each retain.
2578 for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
2579 E = Retains.end(); I != E; ++I) {
2580 Value *V = I->first;
2581 if (!V) continue; // blotted
2583 Instruction *Retain = cast<Instruction>(V);
2585 DEBUG(dbgs() << "ObjCARCOpt::PerformCodePlacement: Visiting: " << *Retain
2588 Value *Arg = GetObjCArg(Retain);
2590 // If the object being released is in static or stack storage, we know it's
2591 // not being managed by ObjC reference counting, so we can delete pairs
2592 // regardless of what possible decrements or uses lie between them.
2593 bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
2595 // A constant pointer can't be pointing to an object on the heap. It may
2596 // be reference-counted, but it won't be deleted.
2597 if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
2598 if (const GlobalVariable *GV =
2599 dyn_cast<GlobalVariable>(
2600 StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
2601 if (GV->isConstant())
2604 // Connect the dots between the top-down-collected RetainsToMove and
2605 // bottom-up-collected ReleasesToMove to form sets of related calls.
2606 NewRetains.push_back(Retain);
2607 bool PerformMoveCalls =
2608 ConnectTDBUTraversals(BBStates, Retains, Releases, M, NewRetains,
2609 NewReleases, DeadInsts, RetainsToMove,
2610 ReleasesToMove, Arg, KnownSafe,
2611 AnyPairsCompletelyEliminated);
2613 #ifdef ARC_ANNOTATIONS
2614 // Do not move calls if ARC annotations are requested. If we were to move
2615 // calls in this case, we would not be able
2616 PerformMoveCalls = PerformMoveCalls && !EnableARCAnnotations;
2617 #endif // ARC_ANNOTATIONS
2619 if (PerformMoveCalls) {
2620 // Ok, everything checks out and we're all set. Let's move/delete some
2622 MoveCalls(Arg, RetainsToMove, ReleasesToMove,
2623 Retains, Releases, DeadInsts, M);
2626 // Clean up state for next retain.
2627 NewReleases.clear();
2629 RetainsToMove.clear();
2630 ReleasesToMove.clear();
2633 // Now that we're done moving everything, we can delete the newly dead
2634 // instructions, as we no longer need them as insert points.
2635 while (!DeadInsts.empty())
2636 EraseInstruction(DeadInsts.pop_back_val());
2638 return AnyPairsCompletelyEliminated;
2641 /// Weak pointer optimizations.
2642 void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
2643 // First, do memdep-style RLE and S2L optimizations. We can't use memdep
2644 // itself because it uses AliasAnalysis and we need to do provenance
2646 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
2647 Instruction *Inst = &*I++;
2649 DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Visiting: " << *Inst <<
2652 InstructionClass Class = GetBasicInstructionClass(Inst);
2653 if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
2656 // Delete objc_loadWeak calls with no users.
2657 if (Class == IC_LoadWeak && Inst->use_empty()) {
2658 Inst->eraseFromParent();
2662 // TODO: For now, just look for an earlier available version of this value
2663 // within the same block. Theoretically, we could do memdep-style non-local
2664 // analysis too, but that would want caching. A better approach would be to
2665 // use the technique that EarlyCSE uses.
2666 inst_iterator Current = llvm::prior(I);
2667 BasicBlock *CurrentBB = Current.getBasicBlockIterator();
2668 for (BasicBlock::iterator B = CurrentBB->begin(),
2669 J = Current.getInstructionIterator();
2671 Instruction *EarlierInst = &*llvm::prior(J);
2672 InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
2673 switch (EarlierClass) {
2675 case IC_LoadWeakRetained: {
2676 // If this is loading from the same pointer, replace this load's value
2678 CallInst *Call = cast<CallInst>(Inst);
2679 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
2680 Value *Arg = Call->getArgOperand(0);
2681 Value *EarlierArg = EarlierCall->getArgOperand(0);
2682 switch (PA.getAA()->alias(Arg, EarlierArg)) {
2683 case AliasAnalysis::MustAlias:
2685 // If the load has a builtin retain, insert a plain retain for it.
2686 if (Class == IC_LoadWeakRetained) {
2688 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
2692 // Zap the fully redundant load.
2693 Call->replaceAllUsesWith(EarlierCall);
2694 Call->eraseFromParent();
2696 case AliasAnalysis::MayAlias:
2697 case AliasAnalysis::PartialAlias:
2699 case AliasAnalysis::NoAlias:
2706 // If this is storing to the same pointer and has the same size etc.
2707 // replace this load's value with the stored value.
2708 CallInst *Call = cast<CallInst>(Inst);
2709 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
2710 Value *Arg = Call->getArgOperand(0);
2711 Value *EarlierArg = EarlierCall->getArgOperand(0);
2712 switch (PA.getAA()->alias(Arg, EarlierArg)) {
2713 case AliasAnalysis::MustAlias:
2715 // If the load has a builtin retain, insert a plain retain for it.
2716 if (Class == IC_LoadWeakRetained) {
2718 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
2722 // Zap the fully redundant load.
2723 Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
2724 Call->eraseFromParent();
2726 case AliasAnalysis::MayAlias:
2727 case AliasAnalysis::PartialAlias:
2729 case AliasAnalysis::NoAlias:
2736 // TOOD: Grab the copied value.
2738 case IC_AutoreleasepoolPush:
2740 case IC_IntrinsicUser:
2742 // Weak pointers are only modified through the weak entry points
2743 // (and arbitrary calls, which could call the weak entry points).
2746 // Anything else could modify the weak pointer.
2753 // Then, for each destroyWeak with an alloca operand, check to see if
2754 // the alloca and all its users can be zapped.
2755 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
2756 Instruction *Inst = &*I++;
2757 InstructionClass Class = GetBasicInstructionClass(Inst);
2758 if (Class != IC_DestroyWeak)
2761 CallInst *Call = cast<CallInst>(Inst);
2762 Value *Arg = Call->getArgOperand(0);
2763 if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
2764 for (Value::use_iterator UI = Alloca->use_begin(),
2765 UE = Alloca->use_end(); UI != UE; ++UI) {
2766 const Instruction *UserInst = cast<Instruction>(*UI);
2767 switch (GetBasicInstructionClass(UserInst)) {
2770 case IC_DestroyWeak:
2777 for (Value::use_iterator UI = Alloca->use_begin(),
2778 UE = Alloca->use_end(); UI != UE; ) {
2779 CallInst *UserInst = cast<CallInst>(*UI++);
2780 switch (GetBasicInstructionClass(UserInst)) {
2783 // These functions return their second argument.
2784 UserInst->replaceAllUsesWith(UserInst->getArgOperand(1));
2786 case IC_DestroyWeak:
2790 llvm_unreachable("alloca really is used!");
2792 UserInst->eraseFromParent();
2794 Alloca->eraseFromParent();
2799 DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Finished List.\n\n");
2803 /// Identify program paths which execute sequences of retains and releases which
2804 /// can be eliminated.
2805 bool ObjCARCOpt::OptimizeSequences(Function &F) {
2806 /// Releases, Retains - These are used to store the results of the main flow
2807 /// analysis. These use Value* as the key instead of Instruction* so that the
2808 /// map stays valid when we get around to rewriting code and calls get
2809 /// replaced by arguments.
2810 DenseMap<Value *, RRInfo> Releases;
2811 MapVector<Value *, RRInfo> Retains;
2813 /// This is used during the traversal of the function to track the
2814 /// states for each identified object at each block.
2815 DenseMap<const BasicBlock *, BBState> BBStates;
2817 // Analyze the CFG of the function, and all instructions.
2818 bool NestingDetected = Visit(F, BBStates, Retains, Releases);
2821 return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
2825 /// Look for this pattern:
2827 /// %call = call i8* @something(...)
2828 /// %2 = call i8* @objc_retain(i8* %call)
2829 /// %3 = call i8* @objc_autorelease(i8* %2)
2832 /// And delete the retain and autorelease.
2834 /// Otherwise if it's just this:
2836 /// %3 = call i8* @objc_autorelease(i8* %2)
2839 /// convert the autorelease to autoreleaseRV.
2840 void ObjCARCOpt::OptimizeReturns(Function &F) {
2841 if (!F.getReturnType()->isPointerTy())
2844 SmallPtrSet<Instruction *, 4> DependingInstructions;
2845 SmallPtrSet<const BasicBlock *, 4> Visited;
2846 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
2847 BasicBlock *BB = FI;
2848 ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
2850 DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Visiting: " << *Ret << "\n");
2854 const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
2855 FindDependencies(NeedsPositiveRetainCount, Arg,
2856 BB, Ret, DependingInstructions, Visited, PA);
2857 if (DependingInstructions.size() != 1)
2861 CallInst *Autorelease =
2862 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
2865 InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
2866 if (!IsAutorelease(AutoreleaseClass))
2868 if (GetObjCArg(Autorelease) != Arg)
2871 DependingInstructions.clear();
2874 // Check that there is nothing that can affect the reference
2875 // count between the autorelease and the retain.
2876 FindDependencies(CanChangeRetainCount, Arg,
2877 BB, Autorelease, DependingInstructions, Visited, PA);
2878 if (DependingInstructions.size() != 1)
2883 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
2885 // Check that we found a retain with the same argument.
2887 !IsRetain(GetBasicInstructionClass(Retain)) ||
2888 GetObjCArg(Retain) != Arg)
2891 DependingInstructions.clear();
2894 // Convert the autorelease to an autoreleaseRV, since it's
2895 // returning the value.
2896 if (AutoreleaseClass == IC_Autorelease) {
2897 DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease "
2898 "=> autoreleaseRV since it's returning a value.\n"
2899 " In: " << *Autorelease
2901 Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
2902 DEBUG(dbgs() << " Out: " << *Autorelease
2904 Autorelease->setTailCall(); // Always tail call autoreleaseRV.
2905 AutoreleaseClass = IC_AutoreleaseRV;
2908 // Check that there is nothing that can affect the reference
2909 // count between the retain and the call.
2910 // Note that Retain need not be in BB.
2911 FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
2912 DependingInstructions, Visited, PA);
2913 if (DependingInstructions.size() != 1)
2918 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
2920 // Check that the pointer is the return value of the call.
2921 if (!Call || Arg != Call)
2924 // Check that the call is a regular call.
2925 InstructionClass Class = GetBasicInstructionClass(Call);
2926 if (Class != IC_CallOrUser && Class != IC_Call)
2929 // If so, we can zap the retain and autorelease.
2932 DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Erasing: " << *Retain
2934 << *Autorelease << "\n");
2935 EraseInstruction(Retain);
2936 EraseInstruction(Autorelease);
2942 DependingInstructions.clear();
2946 DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Finished List.\n\n");
2950 bool ObjCARCOpt::doInitialization(Module &M) {
2954 // If nothing in the Module uses ARC, don't do anything.
2955 Run = ModuleHasARC(M);
2959 // Identify the imprecise release metadata kind.
2960 ImpreciseReleaseMDKind =
2961 M.getContext().getMDKindID("clang.imprecise_release");
2962 CopyOnEscapeMDKind =
2963 M.getContext().getMDKindID("clang.arc.copy_on_escape");
2964 NoObjCARCExceptionsMDKind =
2965 M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions");
2966 #ifdef ARC_ANNOTATIONS
2967 ARCAnnotationBottomUpMDKind =
2968 M.getContext().getMDKindID("llvm.arc.annotation.bottomup");
2969 ARCAnnotationTopDownMDKind =
2970 M.getContext().getMDKindID("llvm.arc.annotation.topdown");
2971 ARCAnnotationProvenanceSourceMDKind =
2972 M.getContext().getMDKindID("llvm.arc.annotation.provenancesource");
2973 #endif // ARC_ANNOTATIONS
2975 // Intuitively, objc_retain and others are nocapture, however in practice
2976 // they are not, because they return their argument value. And objc_release
2977 // calls finalizers which can have arbitrary side effects.
2979 // These are initialized lazily.
2981 AutoreleaseRVCallee = 0;
2984 RetainBlockCallee = 0;
2985 AutoreleaseCallee = 0;
2990 bool ObjCARCOpt::runOnFunction(Function &F) {
2994 // If nothing in the Module uses ARC, don't do anything.
3000 DEBUG(dbgs() << "ObjCARCOpt: Visiting Function: " << F.getName() << "\n");
3002 PA.setAA(&getAnalysis<AliasAnalysis>());
3004 // This pass performs several distinct transformations. As a compile-time aid
3005 // when compiling code that isn't ObjC, skip these if the relevant ObjC
3006 // library functions aren't declared.
3008 // Preliminary optimizations. This also computs UsedInThisFunction.
3009 OptimizeIndividualCalls(F);
3011 // Optimizations for weak pointers.
3012 if (UsedInThisFunction & ((1 << IC_LoadWeak) |
3013 (1 << IC_LoadWeakRetained) |
3014 (1 << IC_StoreWeak) |
3015 (1 << IC_InitWeak) |
3016 (1 << IC_CopyWeak) |
3017 (1 << IC_MoveWeak) |
3018 (1 << IC_DestroyWeak)))
3019 OptimizeWeakCalls(F);
3021 // Optimizations for retain+release pairs.
3022 if (UsedInThisFunction & ((1 << IC_Retain) |
3023 (1 << IC_RetainRV) |
3024 (1 << IC_RetainBlock)))
3025 if (UsedInThisFunction & (1 << IC_Release))
3026 // Run OptimizeSequences until it either stops making changes or
3027 // no retain+release pair nesting is detected.
3028 while (OptimizeSequences(F)) {}
3030 // Optimizations if objc_autorelease is used.
3031 if (UsedInThisFunction & ((1 << IC_Autorelease) |
3032 (1 << IC_AutoreleaseRV)))
3035 DEBUG(dbgs() << "\n");
3040 void ObjCARCOpt::releaseMemory() {