1 //===- ObjCARC.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
11 // Automatic Reference Counting and is a system for managing reference counts
12 // for objects in Objective C.
14 // The optimizations performed include elimination of redundant, partially
15 // redundant, and inconsequential reference count operations, elimination of
16 // redundant weak pointer operations, pattern-matching and replacement of
17 // low-level operations into higher-level operations, and numerous minor
20 // This file also defines a simple ARC-aware AliasAnalysis.
22 // WARNING: This file knows about certain library functions. It recognizes them
23 // by name, and hardwires knowedge of their semantics.
25 // WARNING: This file knows about how certain Objective-C library functions are
26 // used. Naive LLVM IR transformations which would otherwise be
27 // behavior-preserving may break these assumptions.
29 //===----------------------------------------------------------------------===//
31 #define DEBUG_TYPE "objc-arc"
32 #include "llvm/Function.h"
33 #include "llvm/Intrinsics.h"
34 #include "llvm/GlobalVariable.h"
35 #include "llvm/DerivedTypes.h"
36 #include "llvm/Module.h"
37 #include "llvm/Analysis/ValueTracking.h"
38 #include "llvm/Transforms/Utils/Local.h"
39 #include "llvm/Support/CallSite.h"
40 #include "llvm/Support/CommandLine.h"
41 #include "llvm/ADT/StringSwitch.h"
42 #include "llvm/ADT/DenseMap.h"
43 #include "llvm/ADT/STLExtras.h"
46 // A handy option to enable/disable all optimizations in this file.
47 static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
49 //===----------------------------------------------------------------------===//
51 //===----------------------------------------------------------------------===//
54 /// MapVector - An associative container with fast insertion-order
55 /// (deterministic) iteration over its elements. Plus the special
57 template<class KeyT, class ValueT>
59 /// Map - Map keys to indices in Vector.
60 typedef DenseMap<KeyT, size_t> MapTy;
63 /// Vector - Keys and values.
64 typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
68 typedef typename VectorTy::iterator iterator;
69 typedef typename VectorTy::const_iterator const_iterator;
70 iterator begin() { return Vector.begin(); }
71 iterator end() { return Vector.end(); }
72 const_iterator begin() const { return Vector.begin(); }
73 const_iterator end() const { return Vector.end(); }
77 assert(Vector.size() >= Map.size()); // May differ due to blotting.
78 for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
80 assert(I->second < Vector.size());
81 assert(Vector[I->second].first == I->first);
83 for (typename VectorTy::const_iterator I = Vector.begin(),
84 E = Vector.end(); I != E; ++I)
86 (Map.count(I->first) &&
87 Map[I->first] == size_t(I - Vector.begin())));
91 ValueT &operator[](KeyT Arg) {
92 std::pair<typename MapTy::iterator, bool> Pair =
93 Map.insert(std::make_pair(Arg, size_t(0)));
95 Pair.first->second = Vector.size();
96 Vector.push_back(std::make_pair(Arg, ValueT()));
97 return Vector.back().second;
99 return Vector[Pair.first->second].second;
102 std::pair<iterator, bool>
103 insert(const std::pair<KeyT, ValueT> &InsertPair) {
104 std::pair<typename MapTy::iterator, bool> Pair =
105 Map.insert(std::make_pair(InsertPair.first, size_t(0)));
107 Pair.first->second = Vector.size();
108 Vector.push_back(InsertPair);
109 return std::make_pair(llvm::prior(Vector.end()), true);
111 return std::make_pair(Vector.begin() + Pair.first->second, false);
114 const_iterator find(KeyT Key) const {
115 typename MapTy::const_iterator It = Map.find(Key);
116 if (It == Map.end()) return Vector.end();
117 return Vector.begin() + It->second;
120 /// blot - This is similar to erase, but instead of removing the element
121 /// from the vector, it just zeros out the key in the vector. This leaves
122 /// iterators intact, but clients must be prepared for zeroed-out keys when
124 void blot(KeyT Key) {
125 typename MapTy::iterator It = Map.find(Key);
126 if (It == Map.end()) return;
127 Vector[It->second].first = KeyT();
138 //===----------------------------------------------------------------------===//
140 //===----------------------------------------------------------------------===//
143 /// InstructionClass - A simple classification for instructions.
144 enum InstructionClass {
145 IC_Retain, ///< objc_retain
146 IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
147 IC_RetainBlock, ///< objc_retainBlock
148 IC_Release, ///< objc_release
149 IC_Autorelease, ///< objc_autorelease
150 IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
151 IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
152 IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
153 IC_NoopCast, ///< objc_retainedObject, etc.
154 IC_FusedRetainAutorelease, ///< objc_retainAutorelease
155 IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
156 IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
157 IC_StoreWeak, ///< objc_storeWeak (primitive)
158 IC_InitWeak, ///< objc_initWeak (derived)
159 IC_LoadWeak, ///< objc_loadWeak (derived)
160 IC_MoveWeak, ///< objc_moveWeak (derived)
161 IC_CopyWeak, ///< objc_copyWeak (derived)
162 IC_DestroyWeak, ///< objc_destroyWeak (derived)
163 IC_CallOrUser, ///< could call objc_release and/or "use" pointers
164 IC_Call, ///< could call objc_release
165 IC_User, ///< could "use" a pointer
166 IC_None ///< anything else
170 /// IsPotentialUse - Test whether the given value is possible a
171 /// reference-counted pointer.
172 static bool IsPotentialUse(const Value *Op) {
173 // Pointers to static or stack storage are not reference-counted pointers.
174 if (isa<Constant>(Op) || isa<AllocaInst>(Op))
176 // Special arguments are not reference-counted.
177 if (const Argument *Arg = dyn_cast<Argument>(Op))
178 if (Arg->hasByValAttr() ||
179 Arg->hasNestAttr() ||
180 Arg->hasStructRetAttr())
182 // Only consider values with pointer types, and not function pointers.
183 PointerType *Ty = dyn_cast<PointerType>(Op->getType());
184 if (!Ty || isa<FunctionType>(Ty->getElementType()))
186 // Conservatively assume anything else is a potential use.
190 /// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind
191 /// of construct CS is.
192 static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
193 for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
195 if (IsPotentialUse(*I))
196 return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
198 return CS.onlyReadsMemory() ? IC_None : IC_Call;
201 /// GetFunctionClass - Determine if F is one of the special known Functions.
202 /// If it isn't, return IC_CallOrUser.
203 static InstructionClass GetFunctionClass(const Function *F) {
204 Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
208 return StringSwitch<InstructionClass>(F->getName())
209 .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
210 .Default(IC_CallOrUser);
213 const Argument *A0 = AI++;
215 // Argument is a pointer.
216 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
217 Type *ETy = PTy->getElementType();
219 if (ETy->isIntegerTy(8))
220 return StringSwitch<InstructionClass>(F->getName())
221 .Case("objc_retain", IC_Retain)
222 .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
223 .Case("objc_retainBlock", IC_RetainBlock)
224 .Case("objc_release", IC_Release)
225 .Case("objc_autorelease", IC_Autorelease)
226 .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
227 .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
228 .Case("objc_retainedObject", IC_NoopCast)
229 .Case("objc_unretainedObject", IC_NoopCast)
230 .Case("objc_unretainedPointer", IC_NoopCast)
231 .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
232 .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
233 .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
234 .Default(IC_CallOrUser);
237 if (PointerType *Pte = dyn_cast<PointerType>(ETy))
238 if (Pte->getElementType()->isIntegerTy(8))
239 return StringSwitch<InstructionClass>(F->getName())
240 .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
241 .Case("objc_loadWeak", IC_LoadWeak)
242 .Case("objc_destroyWeak", IC_DestroyWeak)
243 .Default(IC_CallOrUser);
246 // Two arguments, first is i8**.
247 const Argument *A1 = AI++;
249 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
250 if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
251 if (Pte->getElementType()->isIntegerTy(8))
252 if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
253 Type *ETy1 = PTy1->getElementType();
254 // Second argument is i8*
255 if (ETy1->isIntegerTy(8))
256 return StringSwitch<InstructionClass>(F->getName())
257 .Case("objc_storeWeak", IC_StoreWeak)
258 .Case("objc_initWeak", IC_InitWeak)
259 .Default(IC_CallOrUser);
260 // Second argument is i8**.
261 if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
262 if (Pte1->getElementType()->isIntegerTy(8))
263 return StringSwitch<InstructionClass>(F->getName())
264 .Case("objc_moveWeak", IC_MoveWeak)
265 .Case("objc_copyWeak", IC_CopyWeak)
266 .Default(IC_CallOrUser);
270 return IC_CallOrUser;
273 /// GetInstructionClass - Determine what kind of construct V is.
274 static InstructionClass GetInstructionClass(const Value *V) {
275 if (const Instruction *I = dyn_cast<Instruction>(V)) {
276 // Any instruction other than bitcast and gep with a pointer operand have a
277 // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
278 // to a subsequent use, rather than using it themselves, in this sense.
279 // As a short cut, several other opcodes are known to have no pointer
280 // operands of interest. And ret is never followed by a release, so it's
281 // not interesting to examine.
282 switch (I->getOpcode()) {
283 case Instruction::Call: {
284 const CallInst *CI = cast<CallInst>(I);
285 // Check for calls to special functions.
286 if (const Function *F = CI->getCalledFunction()) {
287 InstructionClass Class = GetFunctionClass(F);
288 if (Class != IC_CallOrUser)
291 // None of the intrinsic functions do objc_release. For intrinsics, the
292 // only question is whether or not they may be users.
293 switch (F->getIntrinsicID()) {
295 case Intrinsic::bswap: case Intrinsic::ctpop:
296 case Intrinsic::ctlz: case Intrinsic::cttz:
297 case Intrinsic::returnaddress: case Intrinsic::frameaddress:
298 case Intrinsic::stacksave: case Intrinsic::stackrestore:
299 case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
300 // Don't let dbg info affect our results.
301 case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
302 // Short cut: Some intrinsics obviously don't use ObjC pointers.
305 for (Function::const_arg_iterator AI = F->arg_begin(),
306 AE = F->arg_end(); AI != AE; ++AI)
307 if (IsPotentialUse(AI))
312 return GetCallSiteClass(CI);
314 case Instruction::Invoke:
315 return GetCallSiteClass(cast<InvokeInst>(I));
316 case Instruction::BitCast:
317 case Instruction::GetElementPtr:
318 case Instruction::Select: case Instruction::PHI:
319 case Instruction::Ret: case Instruction::Br:
320 case Instruction::Switch: case Instruction::IndirectBr:
321 case Instruction::Alloca: case Instruction::VAArg:
322 case Instruction::Add: case Instruction::FAdd:
323 case Instruction::Sub: case Instruction::FSub:
324 case Instruction::Mul: case Instruction::FMul:
325 case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
326 case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
327 case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
328 case Instruction::And: case Instruction::Or: case Instruction::Xor:
329 case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
330 case Instruction::IntToPtr: case Instruction::FCmp:
331 case Instruction::FPTrunc: case Instruction::FPExt:
332 case Instruction::FPToUI: case Instruction::FPToSI:
333 case Instruction::UIToFP: case Instruction::SIToFP:
334 case Instruction::InsertElement: case Instruction::ExtractElement:
335 case Instruction::ShuffleVector:
336 case Instruction::ExtractValue:
338 case Instruction::ICmp:
339 // Comparing a pointer with null, or any other constant, isn't an
340 // interesting use, because we don't care what the pointer points to, or
341 // about the values of any other dynamic reference-counted pointers.
342 if (IsPotentialUse(I->getOperand(1)))
346 // For anything else, check all the operands.
347 // Note that this includes both operands of a Store: while the first
348 // operand isn't actually being dereferenced, it is being stored to
349 // memory where we can no longer track who might read it and dereference
350 // it, so we have to consider it potentially used.
351 for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
353 if (IsPotentialUse(*OI))
358 // Otherwise, it's totally inert for ARC purposes.
362 /// GetBasicInstructionClass - Determine what kind of construct V is. This is
363 /// similar to GetInstructionClass except that it only detects objc runtine
364 /// calls. This allows it to be faster.
365 static InstructionClass GetBasicInstructionClass(const Value *V) {
366 if (const CallInst *CI = dyn_cast<CallInst>(V)) {
367 if (const Function *F = CI->getCalledFunction())
368 return GetFunctionClass(F);
369 // Otherwise, be conservative.
370 return IC_CallOrUser;
373 // Otherwise, be conservative.
377 /// IsRetain - Test if the the given class is objc_retain or
379 static bool IsRetain(InstructionClass Class) {
380 return Class == IC_Retain ||
381 Class == IC_RetainRV;
384 /// IsAutorelease - Test if the the given class is objc_autorelease or
386 static bool IsAutorelease(InstructionClass Class) {
387 return Class == IC_Autorelease ||
388 Class == IC_AutoreleaseRV;
391 /// IsForwarding - Test if the given class represents instructions which return
392 /// their argument verbatim.
393 static bool IsForwarding(InstructionClass Class) {
394 // objc_retainBlock technically doesn't always return its argument
395 // verbatim, but it doesn't matter for our purposes here.
396 return Class == IC_Retain ||
397 Class == IC_RetainRV ||
398 Class == IC_Autorelease ||
399 Class == IC_AutoreleaseRV ||
400 Class == IC_RetainBlock ||
401 Class == IC_NoopCast;
404 /// IsNoopOnNull - Test if the given class represents instructions which do
405 /// nothing if passed a null pointer.
406 static bool IsNoopOnNull(InstructionClass Class) {
407 return Class == IC_Retain ||
408 Class == IC_RetainRV ||
409 Class == IC_Release ||
410 Class == IC_Autorelease ||
411 Class == IC_AutoreleaseRV ||
412 Class == IC_RetainBlock;
415 /// IsAlwaysTail - Test if the given class represents instructions which are
416 /// always safe to mark with the "tail" keyword.
417 static bool IsAlwaysTail(InstructionClass Class) {
418 // IC_RetainBlock may be given a stack argument.
419 return Class == IC_Retain ||
420 Class == IC_RetainRV ||
421 Class == IC_Autorelease ||
422 Class == IC_AutoreleaseRV;
425 /// IsNoThrow - Test if the given class represents instructions which are always
426 /// safe to mark with the nounwind attribute..
427 static bool IsNoThrow(InstructionClass Class) {
428 // objc_retainBlock is not nounwind because it calls user copy constructors
429 // which could theoretically throw.
430 return Class == IC_Retain ||
431 Class == IC_RetainRV ||
432 Class == IC_Release ||
433 Class == IC_Autorelease ||
434 Class == IC_AutoreleaseRV ||
435 Class == IC_AutoreleasepoolPush ||
436 Class == IC_AutoreleasepoolPop;
439 /// EraseInstruction - Erase the given instruction. ObjC calls return their
440 /// argument verbatim, so if it's such a call and the return value has users,
441 /// replace them with the argument value.
442 static void EraseInstruction(Instruction *CI) {
443 Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
445 bool Unused = CI->use_empty();
448 // Replace the return value with the argument.
449 assert(IsForwarding(GetBasicInstructionClass(CI)) &&
450 "Can't delete non-forwarding instruction with users!");
451 CI->replaceAllUsesWith(OldArg);
454 CI->eraseFromParent();
457 RecursivelyDeleteTriviallyDeadInstructions(OldArg);
460 /// GetUnderlyingObjCPtr - This is a wrapper around getUnderlyingObject which
461 /// also knows how to look through objc_retain and objc_autorelease calls, which
462 /// we know to return their argument verbatim.
463 static const Value *GetUnderlyingObjCPtr(const Value *V) {
465 V = GetUnderlyingObject(V);
466 if (!IsForwarding(GetBasicInstructionClass(V)))
468 V = cast<CallInst>(V)->getArgOperand(0);
474 /// StripPointerCastsAndObjCCalls - This is a wrapper around
475 /// Value::stripPointerCasts which also knows how to look through objc_retain
476 /// and objc_autorelease calls, which we know to return their argument verbatim.
477 static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
479 V = V->stripPointerCasts();
480 if (!IsForwarding(GetBasicInstructionClass(V)))
482 V = cast<CallInst>(V)->getArgOperand(0);
487 /// StripPointerCastsAndObjCCalls - This is a wrapper around
488 /// Value::stripPointerCasts which also knows how to look through objc_retain
489 /// and objc_autorelease calls, which we know to return their argument verbatim.
490 static Value *StripPointerCastsAndObjCCalls(Value *V) {
492 V = V->stripPointerCasts();
493 if (!IsForwarding(GetBasicInstructionClass(V)))
495 V = cast<CallInst>(V)->getArgOperand(0);
500 /// GetObjCArg - Assuming the given instruction is one of the special calls such
501 /// as objc_retain or objc_release, return the argument value, stripped of no-op
502 /// casts and forwarding calls.
503 static Value *GetObjCArg(Value *Inst) {
504 return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
507 /// IsObjCIdentifiedObject - This is similar to AliasAnalysis'
508 /// isObjCIdentifiedObject, except that it uses special knowledge of
509 /// ObjC conventions...
510 static bool IsObjCIdentifiedObject(const Value *V) {
511 // Assume that call results and arguments have their own "provenance".
512 // Constants (including GlobalVariables) and Allocas are never
513 // reference-counted.
514 if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
515 isa<Argument>(V) || isa<Constant>(V) ||
519 if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
520 const Value *Pointer =
521 StripPointerCastsAndObjCCalls(LI->getPointerOperand());
522 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
523 // A constant pointer can't be pointing to an object on the heap. It may
524 // be reference-counted, but it won't be deleted.
525 if (GV->isConstant())
527 StringRef Name = GV->getName();
528 // These special variables are known to hold values which are not
529 // reference-counted pointers.
530 if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
531 Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
532 Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
533 Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
534 Name.startswith("\01l_objc_msgSend_fixup_"))
542 /// FindSingleUseIdentifiedObject - This is similar to
543 /// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value
544 /// with multiple uses.
545 static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
546 if (Arg->hasOneUse()) {
547 if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
548 return FindSingleUseIdentifiedObject(BC->getOperand(0));
549 if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
550 if (GEP->hasAllZeroIndices())
551 return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
552 if (IsForwarding(GetBasicInstructionClass(Arg)))
553 return FindSingleUseIdentifiedObject(
554 cast<CallInst>(Arg)->getArgOperand(0));
555 if (!IsObjCIdentifiedObject(Arg))
560 // If we found an identifiable object but it has multiple uses, but they
561 // are trivial uses, we can still consider this to be a single-use
563 if (IsObjCIdentifiedObject(Arg)) {
564 for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
567 if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
577 /// ModuleHasARC - Test if the given module looks interesting to run ARC
579 static bool ModuleHasARC(const Module &M) {
581 M.getNamedValue("objc_retain") ||
582 M.getNamedValue("objc_release") ||
583 M.getNamedValue("objc_autorelease") ||
584 M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
585 M.getNamedValue("objc_retainBlock") ||
586 M.getNamedValue("objc_autoreleaseReturnValue") ||
587 M.getNamedValue("objc_autoreleasePoolPush") ||
588 M.getNamedValue("objc_loadWeakRetained") ||
589 M.getNamedValue("objc_loadWeak") ||
590 M.getNamedValue("objc_destroyWeak") ||
591 M.getNamedValue("objc_storeWeak") ||
592 M.getNamedValue("objc_initWeak") ||
593 M.getNamedValue("objc_moveWeak") ||
594 M.getNamedValue("objc_copyWeak") ||
595 M.getNamedValue("objc_retainedObject") ||
596 M.getNamedValue("objc_unretainedObject") ||
597 M.getNamedValue("objc_unretainedPointer");
600 //===----------------------------------------------------------------------===//
601 // ARC AliasAnalysis.
602 //===----------------------------------------------------------------------===//
604 #include "llvm/Pass.h"
605 #include "llvm/Analysis/AliasAnalysis.h"
606 #include "llvm/Analysis/Passes.h"
609 /// ObjCARCAliasAnalysis - This is a simple alias analysis
610 /// implementation that uses knowledge of ARC constructs to answer queries.
612 /// TODO: This class could be generalized to know about other ObjC-specific
613 /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
614 /// even though their offsets are dynamic.
615 class ObjCARCAliasAnalysis : public ImmutablePass,
616 public AliasAnalysis {
618 static char ID; // Class identification, replacement for typeinfo
619 ObjCARCAliasAnalysis() : ImmutablePass(ID) {
620 initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
624 virtual void initializePass() {
625 InitializeAliasAnalysis(this);
628 /// getAdjustedAnalysisPointer - This method is used when a pass implements
629 /// an analysis interface through multiple inheritance. If needed, it
630 /// should override this to adjust the this pointer as needed for the
631 /// specified pass info.
632 virtual void *getAdjustedAnalysisPointer(const void *PI) {
633 if (PI == &AliasAnalysis::ID)
634 return (AliasAnalysis*)this;
638 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
639 virtual AliasResult alias(const Location &LocA, const Location &LocB);
640 virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
641 virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
642 virtual ModRefBehavior getModRefBehavior(const Function *F);
643 virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
644 const Location &Loc);
645 virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
646 ImmutableCallSite CS2);
648 } // End of anonymous namespace
650 // Register this pass...
651 char ObjCARCAliasAnalysis::ID = 0;
652 INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
653 "ObjC-ARC-Based Alias Analysis", false, true, false)
655 ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
656 return new ObjCARCAliasAnalysis();
660 ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
661 AU.setPreservesAll();
662 AliasAnalysis::getAnalysisUsage(AU);
665 AliasAnalysis::AliasResult
666 ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
668 return AliasAnalysis::alias(LocA, LocB);
670 // First, strip off no-ops, including ObjC-specific no-ops, and try making a
671 // precise alias query.
672 const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
673 const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
675 AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
676 Location(SB, LocB.Size, LocB.TBAATag));
677 if (Result != MayAlias)
680 // If that failed, climb to the underlying object, including climbing through
681 // ObjC-specific no-ops, and try making an imprecise alias query.
682 const Value *UA = GetUnderlyingObjCPtr(SA);
683 const Value *UB = GetUnderlyingObjCPtr(SB);
684 if (UA != SA || UB != SB) {
685 Result = AliasAnalysis::alias(Location(UA), Location(UB));
686 // We can't use MustAlias or PartialAlias results here because
687 // GetUnderlyingObjCPtr may return an offsetted pointer value.
688 if (Result == NoAlias)
692 // If that failed, fail. We don't need to chain here, since that's covered
693 // by the earlier precise query.
698 ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
701 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
703 // First, strip off no-ops, including ObjC-specific no-ops, and try making
704 // a precise alias query.
705 const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
706 if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
710 // If that failed, climb to the underlying object, including climbing through
711 // ObjC-specific no-ops, and try making an imprecise alias query.
712 const Value *U = GetUnderlyingObjCPtr(S);
714 return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
716 // If that failed, fail. We don't need to chain here, since that's covered
717 // by the earlier precise query.
721 AliasAnalysis::ModRefBehavior
722 ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
723 // We have nothing to do. Just chain to the next AliasAnalysis.
724 return AliasAnalysis::getModRefBehavior(CS);
727 AliasAnalysis::ModRefBehavior
728 ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
730 return AliasAnalysis::getModRefBehavior(F);
732 switch (GetFunctionClass(F)) {
734 return DoesNotAccessMemory;
739 return AliasAnalysis::getModRefBehavior(F);
742 AliasAnalysis::ModRefResult
743 ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
745 return AliasAnalysis::getModRefInfo(CS, Loc);
747 switch (GetBasicInstructionClass(CS.getInstruction())) {
751 case IC_AutoreleaseRV:
753 case IC_AutoreleasepoolPush:
754 case IC_FusedRetainAutorelease:
755 case IC_FusedRetainAutoreleaseRV:
756 // These functions don't access any memory visible to the compiler.
757 // Note that this doesn't include objc_retainBlock, becuase it updates
758 // pointers when it copies block data.
764 return AliasAnalysis::getModRefInfo(CS, Loc);
767 AliasAnalysis::ModRefResult
768 ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
769 ImmutableCallSite CS2) {
770 // TODO: Theoretically we could check for dependencies between objc_* calls
771 // and OnlyAccessesArgumentPointees calls or other well-behaved calls.
772 return AliasAnalysis::getModRefInfo(CS1, CS2);
775 //===----------------------------------------------------------------------===//
777 //===----------------------------------------------------------------------===//
779 #include "llvm/Support/InstIterator.h"
780 #include "llvm/Transforms/Scalar.h"
783 /// ObjCARCExpand - Early ARC transformations.
784 class ObjCARCExpand : public FunctionPass {
785 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
786 virtual bool doInitialization(Module &M);
787 virtual bool runOnFunction(Function &F);
789 /// Run - A flag indicating whether this optimization pass should run.
794 ObjCARCExpand() : FunctionPass(ID) {
795 initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
800 char ObjCARCExpand::ID = 0;
801 INITIALIZE_PASS(ObjCARCExpand,
802 "objc-arc-expand", "ObjC ARC expansion", false, false)
804 Pass *llvm::createObjCARCExpandPass() {
805 return new ObjCARCExpand();
808 void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
809 AU.setPreservesCFG();
812 bool ObjCARCExpand::doInitialization(Module &M) {
813 Run = ModuleHasARC(M);
817 bool ObjCARCExpand::runOnFunction(Function &F) {
821 // If nothing in the Module uses ARC, don't do anything.
825 bool Changed = false;
827 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
828 Instruction *Inst = &*I;
830 switch (GetBasicInstructionClass(Inst)) {
834 case IC_AutoreleaseRV:
835 case IC_FusedRetainAutorelease:
836 case IC_FusedRetainAutoreleaseRV:
837 // These calls return their argument verbatim, as a low-level
838 // optimization. However, this makes high-level optimizations
839 // harder. Undo any uses of this optimization that the front-end
840 // emitted here. We'll redo them in a later pass.
842 Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0));
852 //===----------------------------------------------------------------------===//
854 //===----------------------------------------------------------------------===//
856 // TODO: On code like this:
859 // stuff_that_cannot_release()
860 // objc_autorelease(%x)
861 // stuff_that_cannot_release()
863 // stuff_that_cannot_release()
864 // objc_autorelease(%x)
866 // The second retain and autorelease can be deleted.
868 // TODO: It should be possible to delete
869 // objc_autoreleasePoolPush and objc_autoreleasePoolPop
870 // pairs if nothing is actually autoreleased between them. Also, autorelease
871 // calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
872 // after inlining) can be turned into plain release calls.
874 // TODO: Critical-edge splitting. If the optimial insertion point is
875 // a critical edge, the current algorithm has to fail, because it doesn't
876 // know how to split edges. It should be possible to make the optimizer
877 // think in terms of edges, rather than blocks, and then split critical
880 // TODO: OptimizeSequences could generalized to be Interprocedural.
882 // TODO: Recognize that a bunch of other objc runtime calls have
883 // non-escaping arguments and non-releasing arguments, and may be
884 // non-autoreleasing.
886 // TODO: Sink autorelease calls as far as possible. Unfortunately we
887 // usually can't sink them past other calls, which would be the main
888 // case where it would be useful.
890 // TODO: The pointer returned from objc_loadWeakRetained is retained.
892 // TODO: Delete release+retain pairs (rare).
894 #include "llvm/GlobalAlias.h"
895 #include "llvm/Constants.h"
896 #include "llvm/LLVMContext.h"
897 #include "llvm/Support/ErrorHandling.h"
898 #include "llvm/Support/CFG.h"
899 #include "llvm/ADT/PostOrderIterator.h"
900 #include "llvm/ADT/Statistic.h"
902 STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
903 STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
904 STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
905 STATISTIC(NumRets, "Number of return value forwarding "
906 "retain+autoreleaes eliminated");
907 STATISTIC(NumRRs, "Number of retain+release paths eliminated");
908 STATISTIC(NumPeeps, "Number of calls peephole-optimized");
911 /// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it
912 /// uses many of the same techniques, except it uses special ObjC-specific
913 /// reasoning about pointer relationships.
914 class ProvenanceAnalysis {
917 typedef std::pair<const Value *, const Value *> ValuePairTy;
918 typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
919 CachedResultsTy CachedResults;
921 bool relatedCheck(const Value *A, const Value *B);
922 bool relatedSelect(const SelectInst *A, const Value *B);
923 bool relatedPHI(const PHINode *A, const Value *B);
926 void operator=(const ProvenanceAnalysis &);
927 ProvenanceAnalysis(const ProvenanceAnalysis &);
930 ProvenanceAnalysis() {}
932 void setAA(AliasAnalysis *aa) { AA = aa; }
934 AliasAnalysis *getAA() const { return AA; }
936 bool related(const Value *A, const Value *B);
939 CachedResults.clear();
944 bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
945 // If the values are Selects with the same condition, we can do a more precise
946 // check: just check for relations between the values on corresponding arms.
947 if (const SelectInst *SB = dyn_cast<SelectInst>(B))
948 if (A->getCondition() == SB->getCondition()) {
949 if (related(A->getTrueValue(), SB->getTrueValue()))
951 if (related(A->getFalseValue(), SB->getFalseValue()))
956 // Check both arms of the Select node individually.
957 if (related(A->getTrueValue(), B))
959 if (related(A->getFalseValue(), B))
962 // The arms both checked out.
966 bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
967 // If the values are PHIs in the same block, we can do a more precise as well
968 // as efficient check: just check for relations between the values on
969 // corresponding edges.
970 if (const PHINode *PNB = dyn_cast<PHINode>(B))
971 if (PNB->getParent() == A->getParent()) {
972 for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
973 if (related(A->getIncomingValue(i),
974 PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
979 // Check each unique source of the PHI node against B.
980 SmallPtrSet<const Value *, 4> UniqueSrc;
981 for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
982 const Value *PV1 = A->getIncomingValue(i);
983 if (UniqueSrc.insert(PV1) && related(PV1, B))
987 // All of the arms checked out.
991 /// isStoredObjCPointer - Test if the value of P, or any value covered by its
992 /// provenance, is ever stored within the function (not counting callees).
993 static bool isStoredObjCPointer(const Value *P) {
994 SmallPtrSet<const Value *, 8> Visited;
995 SmallVector<const Value *, 8> Worklist;
996 Worklist.push_back(P);
999 P = Worklist.pop_back_val();
1000 for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
1002 const User *Ur = *UI;
1003 if (isa<StoreInst>(Ur)) {
1004 if (UI.getOperandNo() == 0)
1005 // The pointer is stored.
1007 // The pointed is stored through.
1010 if (isa<CallInst>(Ur))
1011 // The pointer is passed as an argument, ignore this.
1013 if (isa<PtrToIntInst>(P))
1014 // Assume the worst.
1016 if (Visited.insert(Ur))
1017 Worklist.push_back(Ur);
1019 } while (!Worklist.empty());
1021 // Everything checked out.
1025 bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
1026 // Skip past provenance pass-throughs.
1027 A = GetUnderlyingObjCPtr(A);
1028 B = GetUnderlyingObjCPtr(B);
1034 // Ask regular AliasAnalysis, for a first approximation.
1035 switch (AA->alias(A, B)) {
1036 case AliasAnalysis::NoAlias:
1038 case AliasAnalysis::MustAlias:
1039 case AliasAnalysis::PartialAlias:
1041 case AliasAnalysis::MayAlias:
1045 bool AIsIdentified = IsObjCIdentifiedObject(A);
1046 bool BIsIdentified = IsObjCIdentifiedObject(B);
1048 // An ObjC-Identified object can't alias a load if it is never locally stored.
1049 if (AIsIdentified) {
1050 if (BIsIdentified) {
1051 // If both pointers have provenance, they can be directly compared.
1055 if (isa<LoadInst>(B))
1056 return isStoredObjCPointer(A);
1059 if (BIsIdentified && isa<LoadInst>(A))
1060 return isStoredObjCPointer(B);
1063 // Special handling for PHI and Select.
1064 if (const PHINode *PN = dyn_cast<PHINode>(A))
1065 return relatedPHI(PN, B);
1066 if (const PHINode *PN = dyn_cast<PHINode>(B))
1067 return relatedPHI(PN, A);
1068 if (const SelectInst *S = dyn_cast<SelectInst>(A))
1069 return relatedSelect(S, B);
1070 if (const SelectInst *S = dyn_cast<SelectInst>(B))
1071 return relatedSelect(S, A);
1077 bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
1078 // Begin by inserting a conservative value into the map. If the insertion
1079 // fails, we have the answer already. If it succeeds, leave it there until we
1080 // compute the real answer to guard against recursive queries.
1081 if (A > B) std::swap(A, B);
1082 std::pair<CachedResultsTy::iterator, bool> Pair =
1083 CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
1085 return Pair.first->second;
1087 bool Result = relatedCheck(A, B);
1088 CachedResults[ValuePairTy(A, B)] = Result;
1093 // Sequence - A sequence of states that a pointer may go through in which an
1094 // objc_retain and objc_release are actually needed.
1097 S_Retain, ///< objc_retain(x)
1098 S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
1099 S_Use, ///< any use of x
1100 S_Stop, ///< like S_Release, but code motion is stopped
1101 S_Release, ///< objc_release(x)
1102 S_MovableRelease ///< objc_release(x), !clang.imprecise_release
1106 static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
1110 if (A == S_None || B == S_None)
1113 if (A > B) std::swap(A, B);
1115 // Choose the side which is further along in the sequence.
1116 if ((A == S_Retain || A == S_CanRelease) &&
1117 (B == S_CanRelease || B == S_Use))
1120 // Choose the side which is further along in the sequence.
1121 if ((A == S_Use || A == S_CanRelease) &&
1122 (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
1124 // If both sides are releases, choose the more conservative one.
1125 if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
1127 if (A == S_Release && B == S_MovableRelease)
1135 /// RRInfo - Unidirectional information about either a
1136 /// retain-decrement-use-release sequence or release-use-decrement-retain
1137 /// reverese sequence.
1139 /// KnownSafe - After an objc_retain, the reference count of the referenced
1140 /// object is known to be positive. Similarly, before an objc_release, the
1141 /// reference count of the referenced object is known to be positive. If
1142 /// there are retain-release pairs in code regions where the retain count
1143 /// is known to be positive, they can be eliminated, regardless of any side
1144 /// effects between them.
1146 /// Also, a retain+release pair nested within another retain+release
1147 /// pair all on the known same pointer value can be eliminated, regardless
1148 /// of any intervening side effects.
1150 /// KnownSafe is true when either of these conditions is satisfied.
1153 /// IsRetainBlock - True if the Calls are objc_retainBlock calls (as
1154 /// opposed to objc_retain calls).
1157 /// IsTailCallRelease - True of the objc_release calls are all marked
1158 /// with the "tail" keyword.
1159 bool IsTailCallRelease;
1161 /// ReleaseMetadata - If the Calls are objc_release calls and they all have
1162 /// a clang.imprecise_release tag, this is the metadata tag.
1163 MDNode *ReleaseMetadata;
1165 /// Calls - For a top-down sequence, the set of objc_retains or
1166 /// objc_retainBlocks. For bottom-up, the set of objc_releases.
1167 SmallPtrSet<Instruction *, 2> Calls;
1169 /// ReverseInsertPts - The set of optimal insert positions for
1170 /// moving calls in the opposite sequence.
1171 SmallPtrSet<Instruction *, 2> ReverseInsertPts;
1174 KnownSafe(false), IsRetainBlock(false), IsTailCallRelease(false),
1175 ReleaseMetadata(0) {}
1181 void RRInfo::clear() {
1183 IsRetainBlock = false;
1184 IsTailCallRelease = false;
1185 ReleaseMetadata = 0;
1187 ReverseInsertPts.clear();
1191 /// PtrState - This class summarizes several per-pointer runtime properties
1192 /// which are propogated through the flow graph.
1194 /// RefCount - The known minimum number of reference count increments.
1197 /// NestCount - The known minimum level of retain+release nesting.
1200 /// Seq - The current position in the sequence.
1204 /// RRI - Unidirectional information about the current sequence.
1205 /// TODO: Encapsulate this better.
1208 PtrState() : RefCount(0), NestCount(0), Seq(S_None) {}
1210 void SetAtLeastOneRefCount() {
1211 if (RefCount == 0) RefCount = 1;
1214 void IncrementRefCount() {
1215 if (RefCount != UINT_MAX) ++RefCount;
1218 void DecrementRefCount() {
1219 if (RefCount != 0) --RefCount;
1222 bool IsKnownIncremented() const {
1223 return RefCount > 0;
1226 void IncrementNestCount() {
1227 if (NestCount != UINT_MAX) ++NestCount;
1230 void DecrementNestCount() {
1231 if (NestCount != 0) --NestCount;
1234 bool IsKnownNested() const {
1235 return NestCount > 0;
1238 void SetSeq(Sequence NewSeq) {
1242 void SetSeqToRelease(MDNode *M) {
1243 if (Seq == S_None || Seq == S_Use) {
1244 Seq = M ? S_MovableRelease : S_Release;
1245 RRI.ReleaseMetadata = M;
1246 } else if (Seq != S_MovableRelease || RRI.ReleaseMetadata != M) {
1248 RRI.ReleaseMetadata = 0;
1252 Sequence GetSeq() const {
1256 void ClearSequenceProgress() {
1261 void Merge(const PtrState &Other, bool TopDown);
1266 PtrState::Merge(const PtrState &Other, bool TopDown) {
1267 Seq = MergeSeqs(Seq, Other.Seq, TopDown);
1268 RefCount = std::min(RefCount, Other.RefCount);
1269 NestCount = std::min(NestCount, Other.NestCount);
1271 // We can't merge a plain objc_retain with an objc_retainBlock.
1272 if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
1275 if (Seq == S_None) {
1278 // Conservatively merge the ReleaseMetadata information.
1279 if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
1280 RRI.ReleaseMetadata = 0;
1282 RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
1283 RRI.IsTailCallRelease = RRI.IsTailCallRelease && Other.RRI.IsTailCallRelease;
1284 RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
1285 RRI.ReverseInsertPts.insert(Other.RRI.ReverseInsertPts.begin(),
1286 Other.RRI.ReverseInsertPts.end());
1291 /// BBState - Per-BasicBlock state.
1293 /// TopDownPathCount - The number of unique control paths from the entry
1294 /// which can reach this block.
1295 unsigned TopDownPathCount;
1297 /// BottomUpPathCount - The number of unique control paths to exits
1298 /// from this block.
1299 unsigned BottomUpPathCount;
1301 /// MapTy - A type for PerPtrTopDown and PerPtrBottomUp.
1302 typedef MapVector<const Value *, PtrState> MapTy;
1304 /// PerPtrTopDown - The top-down traversal uses this to record information
1305 /// known about a pointer at the bottom of each block.
1306 MapTy PerPtrTopDown;
1308 /// PerPtrBottomUp - The bottom-up traversal uses this to record information
1309 /// known about a pointer at the top of each block.
1310 MapTy PerPtrBottomUp;
1313 BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
1315 typedef MapTy::iterator ptr_iterator;
1316 typedef MapTy::const_iterator ptr_const_iterator;
1318 ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
1319 ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
1320 ptr_const_iterator top_down_ptr_begin() const {
1321 return PerPtrTopDown.begin();
1323 ptr_const_iterator top_down_ptr_end() const {
1324 return PerPtrTopDown.end();
1327 ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
1328 ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
1329 ptr_const_iterator bottom_up_ptr_begin() const {
1330 return PerPtrBottomUp.begin();
1332 ptr_const_iterator bottom_up_ptr_end() const {
1333 return PerPtrBottomUp.end();
1336 /// SetAsEntry - Mark this block as being an entry block, which has one
1337 /// path from the entry by definition.
1338 void SetAsEntry() { TopDownPathCount = 1; }
1340 /// SetAsExit - Mark this block as being an exit block, which has one
1341 /// path to an exit by definition.
1342 void SetAsExit() { BottomUpPathCount = 1; }
1344 PtrState &getPtrTopDownState(const Value *Arg) {
1345 return PerPtrTopDown[Arg];
1348 PtrState &getPtrBottomUpState(const Value *Arg) {
1349 return PerPtrBottomUp[Arg];
1352 void clearBottomUpPointers() {
1353 PerPtrBottomUp.clear();
1356 void clearTopDownPointers() {
1357 PerPtrTopDown.clear();
1360 void InitFromPred(const BBState &Other);
1361 void InitFromSucc(const BBState &Other);
1362 void MergePred(const BBState &Other);
1363 void MergeSucc(const BBState &Other);
1365 /// GetAllPathCount - Return the number of possible unique paths from an
1366 /// entry to an exit which pass through this block. This is only valid
1367 /// after both the top-down and bottom-up traversals are complete.
1368 unsigned GetAllPathCount() const {
1369 return TopDownPathCount * BottomUpPathCount;
1372 /// IsVisitedTopDown - Test whether the block for this BBState has been
1373 /// visited by the top-down portion of the algorithm.
1374 bool isVisitedTopDown() const {
1375 return TopDownPathCount != 0;
1380 void BBState::InitFromPred(const BBState &Other) {
1381 PerPtrTopDown = Other.PerPtrTopDown;
1382 TopDownPathCount = Other.TopDownPathCount;
1385 void BBState::InitFromSucc(const BBState &Other) {
1386 PerPtrBottomUp = Other.PerPtrBottomUp;
1387 BottomUpPathCount = Other.BottomUpPathCount;
1390 /// MergePred - The top-down traversal uses this to merge information about
1391 /// predecessors to form the initial state for a new block.
1392 void BBState::MergePred(const BBState &Other) {
1393 // Other.TopDownPathCount can be 0, in which case it is either dead or a
1394 // loop backedge. Loop backedges are special.
1395 TopDownPathCount += Other.TopDownPathCount;
1397 // For each entry in the other set, if our set has an entry with the same key,
1398 // merge the entries. Otherwise, copy the entry and merge it with an empty
1400 for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
1401 ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
1402 std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
1403 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
1407 // For each entry in our set, if the other set doesn't have an entry with the
1408 // same key, force it to merge with an empty entry.
1409 for (ptr_iterator MI = top_down_ptr_begin(),
1410 ME = top_down_ptr_end(); MI != ME; ++MI)
1411 if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
1412 MI->second.Merge(PtrState(), /*TopDown=*/true);
1415 /// MergeSucc - The bottom-up traversal uses this to merge information about
1416 /// successors to form the initial state for a new block.
1417 void BBState::MergeSucc(const BBState &Other) {
1418 // Other.BottomUpPathCount can be 0, in which case it is either dead or a
1419 // loop backedge. Loop backedges are special.
1420 BottomUpPathCount += Other.BottomUpPathCount;
1422 // For each entry in the other set, if our set has an entry with the
1423 // same key, merge the entries. Otherwise, copy the entry and merge
1424 // it with an empty entry.
1425 for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
1426 ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
1427 std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
1428 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
1432 // For each entry in our set, if the other set doesn't have an entry
1433 // with the same key, force it to merge with an empty entry.
1434 for (ptr_iterator MI = bottom_up_ptr_begin(),
1435 ME = bottom_up_ptr_end(); MI != ME; ++MI)
1436 if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
1437 MI->second.Merge(PtrState(), /*TopDown=*/false);
1441 /// ObjCARCOpt - The main ARC optimization pass.
1442 class ObjCARCOpt : public FunctionPass {
1444 ProvenanceAnalysis PA;
1446 /// Run - A flag indicating whether this optimization pass should run.
1449 /// RetainRVCallee, etc. - Declarations for ObjC runtime
1450 /// functions, for use in creating calls to them. These are initialized
1451 /// lazily to avoid cluttering up the Module with unused declarations.
1452 Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee,
1453 *RetainCallee, *RetainBlockCallee, *AutoreleaseCallee;
1455 /// UsedInThisFunciton - Flags which determine whether each of the
1456 /// interesting runtine functions is in fact used in the current function.
1457 unsigned UsedInThisFunction;
1459 /// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release
1461 unsigned ImpreciseReleaseMDKind;
1463 Constant *getRetainRVCallee(Module *M);
1464 Constant *getAutoreleaseRVCallee(Module *M);
1465 Constant *getReleaseCallee(Module *M);
1466 Constant *getRetainCallee(Module *M);
1467 Constant *getRetainBlockCallee(Module *M);
1468 Constant *getAutoreleaseCallee(Module *M);
1470 void OptimizeRetainCall(Function &F, Instruction *Retain);
1471 bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
1472 void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV);
1473 void OptimizeIndividualCalls(Function &F);
1475 void CheckForCFGHazards(const BasicBlock *BB,
1476 DenseMap<const BasicBlock *, BBState> &BBStates,
1477 BBState &MyStates) const;
1478 bool VisitBottomUp(BasicBlock *BB,
1479 DenseMap<const BasicBlock *, BBState> &BBStates,
1480 MapVector<Value *, RRInfo> &Retains);
1481 bool VisitTopDown(BasicBlock *BB,
1482 DenseMap<const BasicBlock *, BBState> &BBStates,
1483 DenseMap<Value *, RRInfo> &Releases);
1484 bool Visit(Function &F,
1485 DenseMap<const BasicBlock *, BBState> &BBStates,
1486 MapVector<Value *, RRInfo> &Retains,
1487 DenseMap<Value *, RRInfo> &Releases);
1489 void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
1490 MapVector<Value *, RRInfo> &Retains,
1491 DenseMap<Value *, RRInfo> &Releases,
1492 SmallVectorImpl<Instruction *> &DeadInsts,
1495 bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
1496 MapVector<Value *, RRInfo> &Retains,
1497 DenseMap<Value *, RRInfo> &Releases,
1500 void OptimizeWeakCalls(Function &F);
1502 bool OptimizeSequences(Function &F);
1504 void OptimizeReturns(Function &F);
1506 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
1507 virtual bool doInitialization(Module &M);
1508 virtual bool runOnFunction(Function &F);
1509 virtual void releaseMemory();
1513 ObjCARCOpt() : FunctionPass(ID) {
1514 initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
1519 char ObjCARCOpt::ID = 0;
1520 INITIALIZE_PASS_BEGIN(ObjCARCOpt,
1521 "objc-arc", "ObjC ARC optimization", false, false)
1522 INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
1523 INITIALIZE_PASS_END(ObjCARCOpt,
1524 "objc-arc", "ObjC ARC optimization", false, false)
1526 Pass *llvm::createObjCARCOptPass() {
1527 return new ObjCARCOpt();
1530 void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
1531 AU.addRequired<ObjCARCAliasAnalysis>();
1532 AU.addRequired<AliasAnalysis>();
1533 // ARC optimization doesn't currently split critical edges.
1534 AU.setPreservesCFG();
1537 Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
1538 if (!RetainRVCallee) {
1539 LLVMContext &C = M->getContext();
1540 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1541 std::vector<Type *> Params;
1542 Params.push_back(I8X);
1544 FunctionType::get(I8X, Params, /*isVarArg=*/false);
1545 AttrListPtr Attributes;
1546 Attributes.addAttr(~0u, Attribute::NoUnwind);
1548 M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
1551 return RetainRVCallee;
1554 Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
1555 if (!AutoreleaseRVCallee) {
1556 LLVMContext &C = M->getContext();
1557 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1558 std::vector<Type *> Params;
1559 Params.push_back(I8X);
1561 FunctionType::get(I8X, Params, /*isVarArg=*/false);
1562 AttrListPtr Attributes;
1563 Attributes.addAttr(~0u, Attribute::NoUnwind);
1564 AutoreleaseRVCallee =
1565 M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
1568 return AutoreleaseRVCallee;
1571 Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
1572 if (!ReleaseCallee) {
1573 LLVMContext &C = M->getContext();
1574 std::vector<Type *> Params;
1575 Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
1576 AttrListPtr Attributes;
1577 Attributes.addAttr(~0u, Attribute::NoUnwind);
1579 M->getOrInsertFunction(
1581 FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
1584 return ReleaseCallee;
1587 Constant *ObjCARCOpt::getRetainCallee(Module *M) {
1588 if (!RetainCallee) {
1589 LLVMContext &C = M->getContext();
1590 std::vector<Type *> Params;
1591 Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
1592 AttrListPtr Attributes;
1593 Attributes.addAttr(~0u, Attribute::NoUnwind);
1595 M->getOrInsertFunction(
1597 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1600 return RetainCallee;
1603 Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
1604 if (!RetainBlockCallee) {
1605 LLVMContext &C = M->getContext();
1606 std::vector<Type *> Params;
1607 Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
1608 AttrListPtr Attributes;
1609 // objc_retainBlock is not nounwind because it calls user copy constructors
1610 // which could theoretically throw.
1612 M->getOrInsertFunction(
1614 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1617 return RetainBlockCallee;
1620 Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
1621 if (!AutoreleaseCallee) {
1622 LLVMContext &C = M->getContext();
1623 std::vector<Type *> Params;
1624 Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C)));
1625 AttrListPtr Attributes;
1626 Attributes.addAttr(~0u, Attribute::NoUnwind);
1628 M->getOrInsertFunction(
1630 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1633 return AutoreleaseCallee;
1636 /// CanAlterRefCount - Test whether the given instruction can result in a
1637 /// reference count modification (positive or negative) for the pointer's
1640 CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
1641 ProvenanceAnalysis &PA, InstructionClass Class) {
1643 case IC_Autorelease:
1644 case IC_AutoreleaseRV:
1646 // These operations never directly modify a reference count.
1651 ImmutableCallSite CS = static_cast<const Value *>(Inst);
1652 assert(CS && "Only calls can alter reference counts!");
1654 // See if AliasAnalysis can help us with the call.
1655 AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
1656 if (AliasAnalysis::onlyReadsMemory(MRB))
1658 if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
1659 for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
1661 const Value *Op = *I;
1662 if (IsPotentialUse(Op) && PA.related(Ptr, Op))
1668 // Assume the worst.
1672 /// CanUse - Test whether the given instruction can "use" the given pointer's
1673 /// object in a way that requires the reference count to be positive.
1675 CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
1676 InstructionClass Class) {
1677 // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
1678 if (Class == IC_Call)
1681 // Consider various instructions which may have pointer arguments which are
1683 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
1684 // Comparing a pointer with null, or any other constant, isn't really a use,
1685 // because we don't care what the pointer points to, or about the values
1686 // of any other dynamic reference-counted pointers.
1687 if (!IsPotentialUse(ICI->getOperand(1)))
1689 } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
1690 // For calls, just check the arguments (and not the callee operand).
1691 for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
1692 OE = CS.arg_end(); OI != OE; ++OI) {
1693 const Value *Op = *OI;
1694 if (IsPotentialUse(Op) && PA.related(Ptr, Op))
1698 } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1699 // Special-case stores, because we don't care about the stored value, just
1700 // the store address.
1701 const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
1702 // If we can't tell what the underlying object was, assume there is a
1704 return IsPotentialUse(Op) && PA.related(Op, Ptr);
1707 // Check each operand for a match.
1708 for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
1710 const Value *Op = *OI;
1711 if (IsPotentialUse(Op) && PA.related(Ptr, Op))
1717 /// CanInterruptRV - Test whether the given instruction can autorelease
1718 /// any pointer or cause an autoreleasepool pop.
1720 CanInterruptRV(InstructionClass Class) {
1722 case IC_AutoreleasepoolPop:
1725 case IC_Autorelease:
1726 case IC_AutoreleaseRV:
1727 case IC_FusedRetainAutorelease:
1728 case IC_FusedRetainAutoreleaseRV:
1736 /// DependenceKind - There are several kinds of dependence-like concepts in
1738 enum DependenceKind {
1739 NeedsPositiveRetainCount,
1740 CanChangeRetainCount,
1741 RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
1742 RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
1743 RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
1747 /// Depends - Test if there can be dependencies on Inst through Arg. This
1748 /// function only tests dependencies relevant for removing pairs of calls.
1750 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
1751 ProvenanceAnalysis &PA) {
1752 // If we've reached the definition of Arg, stop.
1757 case NeedsPositiveRetainCount: {
1758 InstructionClass Class = GetInstructionClass(Inst);
1760 case IC_AutoreleasepoolPop:
1761 case IC_AutoreleasepoolPush:
1765 return CanUse(Inst, Arg, PA, Class);
1769 case CanChangeRetainCount: {
1770 InstructionClass Class = GetInstructionClass(Inst);
1772 case IC_AutoreleasepoolPop:
1773 // Conservatively assume this can decrement any count.
1775 case IC_AutoreleasepoolPush:
1779 return CanAlterRefCount(Inst, Arg, PA, Class);
1783 case RetainAutoreleaseDep:
1784 switch (GetBasicInstructionClass(Inst)) {
1785 case IC_AutoreleasepoolPop:
1786 // Don't merge an objc_autorelease with an objc_retain inside a different
1787 // autoreleasepool scope.
1791 // Check for a retain of the same pointer for merging.
1792 return GetObjCArg(Inst) == Arg;
1794 // Nothing else matters for objc_retainAutorelease formation.
1799 case RetainAutoreleaseRVDep: {
1800 InstructionClass Class = GetBasicInstructionClass(Inst);
1804 // Check for a retain of the same pointer for merging.
1805 return GetObjCArg(Inst) == Arg;
1807 // Anything that can autorelease interrupts
1808 // retainAutoreleaseReturnValue formation.
1809 return CanInterruptRV(Class);
1815 return CanInterruptRV(GetBasicInstructionClass(Inst));
1818 llvm_unreachable("Invalid dependence flavor");
1822 /// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and
1823 /// find local and non-local dependencies on Arg.
1824 /// TODO: Cache results?
1826 FindDependencies(DependenceKind Flavor,
1828 BasicBlock *StartBB, Instruction *StartInst,
1829 SmallPtrSet<Instruction *, 4> &DependingInstructions,
1830 SmallPtrSet<const BasicBlock *, 4> &Visited,
1831 ProvenanceAnalysis &PA) {
1832 BasicBlock::iterator StartPos = StartInst;
1834 SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
1835 Worklist.push_back(std::make_pair(StartBB, StartPos));
1837 std::pair<BasicBlock *, BasicBlock::iterator> Pair =
1838 Worklist.pop_back_val();
1839 BasicBlock *LocalStartBB = Pair.first;
1840 BasicBlock::iterator LocalStartPos = Pair.second;
1841 BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
1843 if (LocalStartPos == StartBBBegin) {
1844 pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
1846 // If we've reached the function entry, produce a null dependence.
1847 DependingInstructions.insert(0);
1849 // Add the predecessors to the worklist.
1851 BasicBlock *PredBB = *PI;
1852 if (Visited.insert(PredBB))
1853 Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
1854 } while (++PI != PE);
1858 Instruction *Inst = --LocalStartPos;
1859 if (Depends(Flavor, Inst, Arg, PA)) {
1860 DependingInstructions.insert(Inst);
1864 } while (!Worklist.empty());
1866 // Determine whether the original StartBB post-dominates all of the blocks we
1867 // visited. If not, insert a sentinal indicating that most optimizations are
1869 for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
1870 E = Visited.end(); I != E; ++I) {
1871 const BasicBlock *BB = *I;
1874 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
1875 for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
1876 const BasicBlock *Succ = *SI;
1877 if (Succ != StartBB && !Visited.count(Succ)) {
1878 DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
1885 static bool isNullOrUndef(const Value *V) {
1886 return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
1889 static bool isNoopInstruction(const Instruction *I) {
1890 return isa<BitCastInst>(I) ||
1891 (isa<GetElementPtrInst>(I) &&
1892 cast<GetElementPtrInst>(I)->hasAllZeroIndices());
1895 /// OptimizeRetainCall - Turn objc_retain into
1896 /// objc_retainAutoreleasedReturnValue if the operand is a return value.
1898 ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
1899 CallSite CS(GetObjCArg(Retain));
1900 Instruction *Call = CS.getInstruction();
1902 if (Call->getParent() != Retain->getParent()) return;
1904 // Check that the call is next to the retain.
1905 BasicBlock::iterator I = Call;
1907 while (isNoopInstruction(I)) ++I;
1911 // Turn it to an objc_retainAutoreleasedReturnValue..
1914 cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
1917 /// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into
1918 /// objc_retain if the operand is not a return value. Or, if it can be
1919 /// paired with an objc_autoreleaseReturnValue, delete the pair and
1922 ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
1923 // Check for the argument being from an immediately preceding call.
1924 Value *Arg = GetObjCArg(RetainRV);
1926 if (Instruction *Call = CS.getInstruction())
1927 if (Call->getParent() == RetainRV->getParent()) {
1928 BasicBlock::iterator I = Call;
1930 while (isNoopInstruction(I)) ++I;
1931 if (&*I == RetainRV)
1935 // Check for being preceded by an objc_autoreleaseReturnValue on the same
1936 // pointer. In this case, we can delete the pair.
1937 BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
1939 do --I; while (I != Begin && isNoopInstruction(I));
1940 if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
1941 GetObjCArg(I) == Arg) {
1944 EraseInstruction(I);
1945 EraseInstruction(RetainRV);
1950 // Turn it to a plain objc_retain.
1953 cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
1957 /// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into
1958 /// objc_autorelease if the result is not used as a return value.
1960 ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) {
1961 // Check for a return of the pointer value.
1962 const Value *Ptr = GetObjCArg(AutoreleaseRV);
1963 SmallVector<const Value *, 2> Users;
1964 Users.push_back(Ptr);
1966 Ptr = Users.pop_back_val();
1967 for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
1969 const User *I = *UI;
1970 if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
1972 if (isa<BitCastInst>(I))
1975 } while (!Users.empty());
1979 cast<CallInst>(AutoreleaseRV)->
1980 setCalledFunction(getAutoreleaseCallee(F.getParent()));
1983 /// OptimizeIndividualCalls - Visit each call, one at a time, and make
1984 /// simplifications without doing any additional analysis.
1985 void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
1986 // Reset all the flags in preparation for recomputing them.
1987 UsedInThisFunction = 0;
1989 // Visit all objc_* calls in F.
1990 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
1991 Instruction *Inst = &*I++;
1992 InstructionClass Class = GetBasicInstructionClass(Inst);
1997 // Delete no-op casts. These function calls have special semantics, but
1998 // the semantics are entirely implemented via lowering in the front-end,
1999 // so by the time they reach the optimizer, they are just no-op calls
2000 // which return their argument.
2002 // There are gray areas here, as the ability to cast reference-counted
2003 // pointers to raw void* and back allows code to break ARC assumptions,
2004 // however these are currently considered to be unimportant.
2008 EraseInstruction(Inst);
2011 // If the pointer-to-weak-pointer is null, it's undefined behavior.
2014 case IC_LoadWeakRetained:
2016 case IC_DestroyWeak: {
2017 CallInst *CI = cast<CallInst>(Inst);
2018 if (isNullOrUndef(CI->getArgOperand(0))) {
2019 Type *Ty = CI->getArgOperand(0)->getType();
2020 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
2021 Constant::getNullValue(Ty),
2023 CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
2024 CI->eraseFromParent();
2031 CallInst *CI = cast<CallInst>(Inst);
2032 if (isNullOrUndef(CI->getArgOperand(0)) ||
2033 isNullOrUndef(CI->getArgOperand(1))) {
2034 Type *Ty = CI->getArgOperand(0)->getType();
2035 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
2036 Constant::getNullValue(Ty),
2038 CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
2039 CI->eraseFromParent();
2045 OptimizeRetainCall(F, Inst);
2048 if (OptimizeRetainRVCall(F, Inst))
2051 case IC_AutoreleaseRV:
2052 OptimizeAutoreleaseRVCall(F, Inst);
2056 // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
2057 if (IsAutorelease(Class) && Inst->use_empty()) {
2058 CallInst *Call = cast<CallInst>(Inst);
2059 const Value *Arg = Call->getArgOperand(0);
2060 Arg = FindSingleUseIdentifiedObject(Arg);
2065 // Create the declaration lazily.
2066 LLVMContext &C = Inst->getContext();
2068 CallInst::Create(getReleaseCallee(F.getParent()),
2069 Call->getArgOperand(0), "", Call);
2070 NewCall->setMetadata(ImpreciseReleaseMDKind,
2071 MDNode::get(C, ArrayRef<Value *>()));
2072 EraseInstruction(Call);
2078 // For functions which can never be passed stack arguments, add
2080 if (IsAlwaysTail(Class)) {
2082 cast<CallInst>(Inst)->setTailCall();
2085 // Set nounwind as needed.
2086 if (IsNoThrow(Class)) {
2088 cast<CallInst>(Inst)->setDoesNotThrow();
2091 if (!IsNoopOnNull(Class)) {
2092 UsedInThisFunction |= 1 << Class;
2096 const Value *Arg = GetObjCArg(Inst);
2098 // ARC calls with null are no-ops. Delete them.
2099 if (isNullOrUndef(Arg)) {
2102 EraseInstruction(Inst);
2106 // Keep track of which of retain, release, autorelease, and retain_block
2107 // are actually present in this function.
2108 UsedInThisFunction |= 1 << Class;
2110 // If Arg is a PHI, and one or more incoming values to the
2111 // PHI are null, and the call is control-equivalent to the PHI, and there
2112 // are no relevant side effects between the PHI and the call, the call
2113 // could be pushed up to just those paths with non-null incoming values.
2114 // For now, don't bother splitting critical edges for this.
2115 SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
2116 Worklist.push_back(std::make_pair(Inst, Arg));
2118 std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
2122 const PHINode *PN = dyn_cast<PHINode>(Arg);
2125 // Determine if the PHI has any null operands, or any incoming
2127 bool HasNull = false;
2128 bool HasCriticalEdges = false;
2129 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2131 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
2132 if (isNullOrUndef(Incoming))
2134 else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
2135 .getNumSuccessors() != 1) {
2136 HasCriticalEdges = true;
2140 // If we have null operands and no critical edges, optimize.
2141 if (!HasCriticalEdges && HasNull) {
2142 SmallPtrSet<Instruction *, 4> DependingInstructions;
2143 SmallPtrSet<const BasicBlock *, 4> Visited;
2145 // Check that there is nothing that cares about the reference
2146 // count between the call and the phi.
2147 FindDependencies(NeedsPositiveRetainCount, Arg,
2148 Inst->getParent(), Inst,
2149 DependingInstructions, Visited, PA);
2150 if (DependingInstructions.size() == 1 &&
2151 *DependingInstructions.begin() == PN) {
2154 // Clone the call into each predecessor that has a non-null value.
2155 CallInst *CInst = cast<CallInst>(Inst);
2156 Type *ParamTy = CInst->getArgOperand(0)->getType();
2157 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2159 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
2160 if (!isNullOrUndef(Incoming)) {
2161 CallInst *Clone = cast<CallInst>(CInst->clone());
2162 Value *Op = PN->getIncomingValue(i);
2163 Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
2164 if (Op->getType() != ParamTy)
2165 Op = new BitCastInst(Op, ParamTy, "", InsertPos);
2166 Clone->setArgOperand(0, Op);
2167 Clone->insertBefore(InsertPos);
2168 Worklist.push_back(std::make_pair(Clone, Incoming));
2171 // Erase the original call.
2172 EraseInstruction(CInst);
2176 } while (!Worklist.empty());
2180 /// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible
2181 /// control flow, or other CFG structures where moving code across the edge
2182 /// would result in it being executed more.
2184 ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
2185 DenseMap<const BasicBlock *, BBState> &BBStates,
2186 BBState &MyStates) const {
2187 // If any top-down local-use or possible-dec has a succ which is earlier in
2188 // the sequence, forget it.
2189 for (BBState::ptr_const_iterator I = MyStates.top_down_ptr_begin(),
2190 E = MyStates.top_down_ptr_end(); I != E; ++I)
2191 switch (I->second.GetSeq()) {
2194 const Value *Arg = I->first;
2195 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2196 bool SomeSuccHasSame = false;
2197 bool AllSuccsHaveSame = true;
2198 PtrState &S = MyStates.getPtrTopDownState(Arg);
2199 for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
2200 PtrState &SuccS = BBStates[*SI].getPtrBottomUpState(Arg);
2201 switch (SuccS.GetSeq()) {
2203 case S_CanRelease: {
2204 if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe)
2205 S.ClearSequenceProgress();
2209 SomeSuccHasSame = true;
2213 case S_MovableRelease:
2214 if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe)
2215 AllSuccsHaveSame = false;
2218 llvm_unreachable("bottom-up pointer in retain state!");
2221 // If the state at the other end of any of the successor edges
2222 // matches the current state, require all edges to match. This
2223 // guards against loops in the middle of a sequence.
2224 if (SomeSuccHasSame && !AllSuccsHaveSame)
2225 S.ClearSequenceProgress();
2227 case S_CanRelease: {
2228 const Value *Arg = I->first;
2229 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2230 bool SomeSuccHasSame = false;
2231 bool AllSuccsHaveSame = true;
2232 PtrState &S = MyStates.getPtrTopDownState(Arg);
2233 for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
2234 PtrState &SuccS = BBStates[*SI].getPtrBottomUpState(Arg);
2235 switch (SuccS.GetSeq()) {
2237 if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe)
2238 S.ClearSequenceProgress();
2242 SomeSuccHasSame = true;
2246 case S_MovableRelease:
2248 if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe)
2249 AllSuccsHaveSame = false;
2252 llvm_unreachable("bottom-up pointer in retain state!");
2255 // If the state at the other end of any of the successor edges
2256 // matches the current state, require all edges to match. This
2257 // guards against loops in the middle of a sequence.
2258 if (SomeSuccHasSame && !AllSuccsHaveSame)
2259 S.ClearSequenceProgress();
2265 ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
2266 DenseMap<const BasicBlock *, BBState> &BBStates,
2267 MapVector<Value *, RRInfo> &Retains) {
2268 bool NestingDetected = false;
2269 BBState &MyStates = BBStates[BB];
2271 // Merge the states from each successor to compute the initial state
2272 // for the current block.
2273 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2274 succ_const_iterator SI(TI), SE(TI, false);
2276 MyStates.SetAsExit();
2279 const BasicBlock *Succ = *SI++;
2282 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
2283 // If we haven't seen this node yet, then we've found a CFG cycle.
2284 // Be optimistic here; it's CheckForCFGHazards' job detect trouble.
2285 if (I == BBStates.end())
2287 MyStates.InitFromSucc(I->second);
2291 I = BBStates.find(Succ);
2292 if (I != BBStates.end())
2293 MyStates.MergeSucc(I->second);
2299 // Visit all the instructions, bottom-up.
2300 for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
2301 Instruction *Inst = llvm::prior(I);
2302 InstructionClass Class = GetInstructionClass(Inst);
2303 const Value *Arg = 0;
2307 Arg = GetObjCArg(Inst);
2309 PtrState &S = MyStates.getPtrBottomUpState(Arg);
2311 // If we see two releases in a row on the same pointer. If so, make
2312 // a note, and we'll cicle back to revisit it after we've
2313 // hopefully eliminated the second release, which may allow us to
2314 // eliminate the first release too.
2315 // Theoretically we could implement removal of nested retain+release
2316 // pairs by making PtrState hold a stack of states, but this is
2317 // simple and avoids adding overhead for the non-nested case.
2318 if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease)
2319 NestingDetected = true;
2321 S.SetSeqToRelease(Inst->getMetadata(ImpreciseReleaseMDKind));
2323 S.RRI.KnownSafe = S.IsKnownNested() || S.IsKnownIncremented();
2324 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
2325 S.RRI.Calls.insert(Inst);
2327 S.IncrementRefCount();
2328 S.IncrementNestCount();
2331 case IC_RetainBlock:
2334 Arg = GetObjCArg(Inst);
2336 PtrState &S = MyStates.getPtrBottomUpState(Arg);
2337 S.DecrementRefCount();
2338 S.SetAtLeastOneRefCount();
2339 S.DecrementNestCount();
2341 // An objc_retainBlock call with just a use still needs to be kept,
2342 // because it may be copying a block from the stack to the heap.
2343 if (Class == IC_RetainBlock && S.GetSeq() == S_Use)
2344 S.SetSeq(S_CanRelease);
2346 switch (S.GetSeq()) {
2349 case S_MovableRelease:
2351 S.RRI.ReverseInsertPts.clear();
2354 // Don't do retain+release tracking for IC_RetainRV, because it's
2355 // better to let it remain as the first instruction after a call.
2356 if (Class != IC_RetainRV) {
2357 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
2358 Retains[Inst] = S.RRI;
2360 S.ClearSequenceProgress();
2365 llvm_unreachable("bottom-up pointer in retain state!");
2369 case IC_AutoreleasepoolPop:
2370 // Conservatively, clear MyStates for all known pointers.
2371 MyStates.clearBottomUpPointers();
2373 case IC_AutoreleasepoolPush:
2375 // These are irrelevant.
2381 // Consider any other possible effects of this instruction on each
2382 // pointer being tracked.
2383 for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
2384 ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
2385 const Value *Ptr = MI->first;
2387 continue; // Handled above.
2388 PtrState &S = MI->second;
2389 Sequence Seq = S.GetSeq();
2391 // Check for possible releases.
2392 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
2393 S.DecrementRefCount();
2396 S.SetSeq(S_CanRelease);
2400 case S_MovableRelease:
2405 llvm_unreachable("bottom-up pointer in retain state!");
2409 // Check for possible direct uses.
2412 case S_MovableRelease:
2413 if (CanUse(Inst, Ptr, PA, Class)) {
2414 assert(S.RRI.ReverseInsertPts.empty());
2415 S.RRI.ReverseInsertPts.insert(Inst);
2417 } else if (Seq == S_Release &&
2418 (Class == IC_User || Class == IC_CallOrUser)) {
2419 // Non-movable releases depend on any possible objc pointer use.
2421 assert(S.RRI.ReverseInsertPts.empty());
2422 S.RRI.ReverseInsertPts.insert(Inst);
2426 if (CanUse(Inst, Ptr, PA, Class))
2434 llvm_unreachable("bottom-up pointer in retain state!");
2439 return NestingDetected;
2443 ObjCARCOpt::VisitTopDown(BasicBlock *BB,
2444 DenseMap<const BasicBlock *, BBState> &BBStates,
2445 DenseMap<Value *, RRInfo> &Releases) {
2446 bool NestingDetected = false;
2447 BBState &MyStates = BBStates[BB];
2449 // Merge the states from each predecessor to compute the initial state
2450 // for the current block.
2451 const_pred_iterator PI(BB), PE(BB, false);
2453 MyStates.SetAsEntry();
2456 const BasicBlock *Pred = *PI++;
2459 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
2460 assert(I != BBStates.end());
2461 // If we haven't seen this node yet, then we've found a CFG cycle.
2462 // Be optimistic here; it's CheckForCFGHazards' job detect trouble.
2463 if (!I->second.isVisitedTopDown())
2465 MyStates.InitFromPred(I->second);
2469 I = BBStates.find(Pred);
2470 assert(I != BBStates.end());
2471 if (I->second.isVisitedTopDown())
2472 MyStates.MergePred(I->second);
2478 // Visit all the instructions, top-down.
2479 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
2480 Instruction *Inst = I;
2481 InstructionClass Class = GetInstructionClass(Inst);
2482 const Value *Arg = 0;
2485 case IC_RetainBlock:
2488 Arg = GetObjCArg(Inst);
2490 PtrState &S = MyStates.getPtrTopDownState(Arg);
2492 // Don't do retain+release tracking for IC_RetainRV, because it's
2493 // better to let it remain as the first instruction after a call.
2494 if (Class != IC_RetainRV) {
2495 // If we see two retains in a row on the same pointer. If so, make
2496 // a note, and we'll cicle back to revisit it after we've
2497 // hopefully eliminated the second retain, which may allow us to
2498 // eliminate the first retain too.
2499 // Theoretically we could implement removal of nested retain+release
2500 // pairs by making PtrState hold a stack of states, but this is
2501 // simple and avoids adding overhead for the non-nested case.
2502 if (S.GetSeq() == S_Retain)
2503 NestingDetected = true;
2507 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
2508 // Don't check S.IsKnownIncremented() here because it's not
2510 S.RRI.KnownSafe = S.IsKnownNested();
2511 S.RRI.Calls.insert(Inst);
2514 S.SetAtLeastOneRefCount();
2515 S.IncrementRefCount();
2516 S.IncrementNestCount();
2520 Arg = GetObjCArg(Inst);
2522 PtrState &S = MyStates.getPtrTopDownState(Arg);
2523 S.DecrementRefCount();
2524 S.DecrementNestCount();
2526 switch (S.GetSeq()) {
2529 S.RRI.ReverseInsertPts.clear();
2532 S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
2533 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
2534 Releases[Inst] = S.RRI;
2535 S.ClearSequenceProgress();
2541 case S_MovableRelease:
2542 llvm_unreachable("top-down pointer in release state!");
2546 case IC_AutoreleasepoolPop:
2547 // Conservatively, clear MyStates for all known pointers.
2548 MyStates.clearTopDownPointers();
2550 case IC_AutoreleasepoolPush:
2552 // These are irrelevant.
2558 // Consider any other possible effects of this instruction on each
2559 // pointer being tracked.
2560 for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
2561 ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
2562 const Value *Ptr = MI->first;
2564 continue; // Handled above.
2565 PtrState &S = MI->second;
2566 Sequence Seq = S.GetSeq();
2568 // Check for possible releases.
2569 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
2570 S.DecrementRefCount();
2573 S.SetSeq(S_CanRelease);
2574 assert(S.RRI.ReverseInsertPts.empty());
2575 S.RRI.ReverseInsertPts.insert(Inst);
2577 // One call can't cause a transition from S_Retain to S_CanRelease
2578 // and S_CanRelease to S_Use. If we've made the first transition,
2587 case S_MovableRelease:
2588 llvm_unreachable("top-down pointer in release state!");
2592 // Check for possible direct uses.
2595 if (CanUse(Inst, Ptr, PA, Class))
2599 // An objc_retainBlock call may be responsible for copying the block
2600 // data from the stack to the heap. Model this by moving it straight
2601 // from S_Retain to S_Use.
2602 if (S.RRI.IsRetainBlock &&
2603 CanUse(Inst, Ptr, PA, Class)) {
2604 assert(S.RRI.ReverseInsertPts.empty());
2605 S.RRI.ReverseInsertPts.insert(Inst);
2614 case S_MovableRelease:
2615 llvm_unreachable("top-down pointer in release state!");
2620 CheckForCFGHazards(BB, BBStates, MyStates);
2621 return NestingDetected;
2624 // Visit - Visit the function both top-down and bottom-up.
2626 ObjCARCOpt::Visit(Function &F,
2627 DenseMap<const BasicBlock *, BBState> &BBStates,
2628 MapVector<Value *, RRInfo> &Retains,
2629 DenseMap<Value *, RRInfo> &Releases) {
2630 // Use reverse-postorder on the reverse CFG for bottom-up, because we
2631 // magically know that loops will be well behaved, i.e. they won't repeatedly
2632 // call retain on a single pointer without doing a release. We can't use
2633 // ReversePostOrderTraversal here because we want to walk up from each
2634 // function exit point.
2635 SmallPtrSet<BasicBlock *, 16> Visited;
2636 SmallVector<std::pair<BasicBlock *, pred_iterator>, 16> Stack;
2637 SmallVector<BasicBlock *, 16> Order;
2638 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
2640 if (BB->getTerminator()->getNumSuccessors() == 0)
2641 Stack.push_back(std::make_pair(BB, pred_begin(BB)));
2643 while (!Stack.empty()) {
2644 pred_iterator End = pred_end(Stack.back().first);
2645 while (Stack.back().second != End) {
2646 BasicBlock *BB = *Stack.back().second++;
2647 if (Visited.insert(BB))
2648 Stack.push_back(std::make_pair(BB, pred_begin(BB)));
2650 Order.push_back(Stack.pop_back_val().first);
2652 bool BottomUpNestingDetected = false;
2653 for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
2654 Order.rbegin(), E = Order.rend(); I != E; ++I) {
2655 BasicBlock *BB = *I;
2656 BottomUpNestingDetected |= VisitBottomUp(BB, BBStates, Retains);
2659 // Use regular reverse-postorder for top-down.
2660 bool TopDownNestingDetected = false;
2661 typedef ReversePostOrderTraversal<Function *> RPOTType;
2663 for (RPOTType::rpo_iterator I = RPOT.begin(), E = RPOT.end(); I != E; ++I) {
2664 BasicBlock *BB = *I;
2665 TopDownNestingDetected |= VisitTopDown(BB, BBStates, Releases);
2668 return TopDownNestingDetected && BottomUpNestingDetected;
2671 /// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove.
2672 void ObjCARCOpt::MoveCalls(Value *Arg,
2673 RRInfo &RetainsToMove,
2674 RRInfo &ReleasesToMove,
2675 MapVector<Value *, RRInfo> &Retains,
2676 DenseMap<Value *, RRInfo> &Releases,
2677 SmallVectorImpl<Instruction *> &DeadInsts,
2679 Type *ArgTy = Arg->getType();
2680 Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
2682 // Insert the new retain and release calls.
2683 for (SmallPtrSet<Instruction *, 2>::const_iterator
2684 PI = ReleasesToMove.ReverseInsertPts.begin(),
2685 PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
2686 Instruction *InsertPt = *PI;
2687 Value *MyArg = ArgTy == ParamTy ? Arg :
2688 new BitCastInst(Arg, ParamTy, "", InsertPt);
2690 CallInst::Create(RetainsToMove.IsRetainBlock ?
2691 getRetainBlockCallee(M) : getRetainCallee(M),
2692 MyArg, "", InsertPt);
2693 Call->setDoesNotThrow();
2694 if (!RetainsToMove.IsRetainBlock)
2695 Call->setTailCall();
2697 for (SmallPtrSet<Instruction *, 2>::const_iterator
2698 PI = RetainsToMove.ReverseInsertPts.begin(),
2699 PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
2700 Instruction *LastUse = *PI;
2701 Instruction *InsertPts[] = { 0, 0, 0 };
2702 if (InvokeInst *II = dyn_cast<InvokeInst>(LastUse)) {
2703 // We can't insert code immediately after an invoke instruction, so
2704 // insert code at the beginning of both successor blocks instead.
2705 // The invoke's return value isn't available in the unwind block,
2706 // but our releases will never depend on it, because they must be
2707 // paired with retains from before the invoke.
2708 InsertPts[0] = II->getNormalDest()->getFirstInsertionPt();
2709 InsertPts[1] = II->getUnwindDest()->getFirstInsertionPt();
2711 // Insert code immediately after the last use.
2712 InsertPts[0] = llvm::next(BasicBlock::iterator(LastUse));
2715 for (Instruction **I = InsertPts; *I; ++I) {
2716 Instruction *InsertPt = *I;
2717 Value *MyArg = ArgTy == ParamTy ? Arg :
2718 new BitCastInst(Arg, ParamTy, "", InsertPt);
2719 CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
2721 // Attach a clang.imprecise_release metadata tag, if appropriate.
2722 if (MDNode *M = ReleasesToMove.ReleaseMetadata)
2723 Call->setMetadata(ImpreciseReleaseMDKind, M);
2724 Call->setDoesNotThrow();
2725 if (ReleasesToMove.IsTailCallRelease)
2726 Call->setTailCall();
2730 // Delete the original retain and release calls.
2731 for (SmallPtrSet<Instruction *, 2>::const_iterator
2732 AI = RetainsToMove.Calls.begin(),
2733 AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
2734 Instruction *OrigRetain = *AI;
2735 Retains.blot(OrigRetain);
2736 DeadInsts.push_back(OrigRetain);
2738 for (SmallPtrSet<Instruction *, 2>::const_iterator
2739 AI = ReleasesToMove.Calls.begin(),
2740 AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
2741 Instruction *OrigRelease = *AI;
2742 Releases.erase(OrigRelease);
2743 DeadInsts.push_back(OrigRelease);
2748 ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
2750 MapVector<Value *, RRInfo> &Retains,
2751 DenseMap<Value *, RRInfo> &Releases,
2753 bool AnyPairsCompletelyEliminated = false;
2754 RRInfo RetainsToMove;
2755 RRInfo ReleasesToMove;
2756 SmallVector<Instruction *, 4> NewRetains;
2757 SmallVector<Instruction *, 4> NewReleases;
2758 SmallVector<Instruction *, 8> DeadInsts;
2760 for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
2761 E = Retains.end(); I != E; ++I) {
2762 Value *V = I->first;
2763 if (!V) continue; // blotted
2765 Instruction *Retain = cast<Instruction>(V);
2766 Value *Arg = GetObjCArg(Retain);
2768 // If the object being released is in static storage, we know it's
2769 // not being managed by ObjC reference counting, so we can delete pairs
2770 // regardless of what possible decrements or uses lie between them.
2771 bool KnownSafe = isa<Constant>(Arg);
2773 // Same for stack storage, unless this is an objc_retainBlock call,
2774 // which is responsible for copying the block data from the stack to
2776 if (!I->second.IsRetainBlock && isa<AllocaInst>(Arg))
2779 // A constant pointer can't be pointing to an object on the heap. It may
2780 // be reference-counted, but it won't be deleted.
2781 if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
2782 if (const GlobalVariable *GV =
2783 dyn_cast<GlobalVariable>(
2784 StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
2785 if (GV->isConstant())
2788 // If a pair happens in a region where it is known that the reference count
2789 // is already incremented, we can similarly ignore possible decrements.
2790 bool KnownSafeTD = true, KnownSafeBU = true;
2792 // Connect the dots between the top-down-collected RetainsToMove and
2793 // bottom-up-collected ReleasesToMove to form sets of related calls.
2794 // This is an iterative process so that we connect multiple releases
2795 // to multiple retains if needed.
2796 unsigned OldDelta = 0;
2797 unsigned NewDelta = 0;
2798 unsigned OldCount = 0;
2799 unsigned NewCount = 0;
2800 bool FirstRelease = true;
2801 bool FirstRetain = true;
2802 NewRetains.push_back(Retain);
2804 for (SmallVectorImpl<Instruction *>::const_iterator
2805 NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
2806 Instruction *NewRetain = *NI;
2807 MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
2808 assert(It != Retains.end());
2809 const RRInfo &NewRetainRRI = It->second;
2810 KnownSafeTD &= NewRetainRRI.KnownSafe;
2811 for (SmallPtrSet<Instruction *, 2>::const_iterator
2812 LI = NewRetainRRI.Calls.begin(),
2813 LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
2814 Instruction *NewRetainRelease = *LI;
2815 DenseMap<Value *, RRInfo>::const_iterator Jt =
2816 Releases.find(NewRetainRelease);
2817 if (Jt == Releases.end())
2819 const RRInfo &NewRetainReleaseRRI = Jt->second;
2820 assert(NewRetainReleaseRRI.Calls.count(NewRetain));
2821 if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
2823 BBStates[NewRetainRelease->getParent()].GetAllPathCount();
2825 // Merge the ReleaseMetadata and IsTailCallRelease values.
2827 ReleasesToMove.ReleaseMetadata =
2828 NewRetainReleaseRRI.ReleaseMetadata;
2829 ReleasesToMove.IsTailCallRelease =
2830 NewRetainReleaseRRI.IsTailCallRelease;
2831 FirstRelease = false;
2833 if (ReleasesToMove.ReleaseMetadata !=
2834 NewRetainReleaseRRI.ReleaseMetadata)
2835 ReleasesToMove.ReleaseMetadata = 0;
2836 if (ReleasesToMove.IsTailCallRelease !=
2837 NewRetainReleaseRRI.IsTailCallRelease)
2838 ReleasesToMove.IsTailCallRelease = false;
2841 // Collect the optimal insertion points.
2843 for (SmallPtrSet<Instruction *, 2>::const_iterator
2844 RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
2845 RE = NewRetainReleaseRRI.ReverseInsertPts.end();
2847 Instruction *RIP = *RI;
2848 if (ReleasesToMove.ReverseInsertPts.insert(RIP))
2849 NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
2851 NewReleases.push_back(NewRetainRelease);
2856 if (NewReleases.empty()) break;
2858 // Back the other way.
2859 for (SmallVectorImpl<Instruction *>::const_iterator
2860 NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
2861 Instruction *NewRelease = *NI;
2862 DenseMap<Value *, RRInfo>::const_iterator It =
2863 Releases.find(NewRelease);
2864 assert(It != Releases.end());
2865 const RRInfo &NewReleaseRRI = It->second;
2866 KnownSafeBU &= NewReleaseRRI.KnownSafe;
2867 for (SmallPtrSet<Instruction *, 2>::const_iterator
2868 LI = NewReleaseRRI.Calls.begin(),
2869 LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
2870 Instruction *NewReleaseRetain = *LI;
2871 MapVector<Value *, RRInfo>::const_iterator Jt =
2872 Retains.find(NewReleaseRetain);
2873 if (Jt == Retains.end())
2875 const RRInfo &NewReleaseRetainRRI = Jt->second;
2876 assert(NewReleaseRetainRRI.Calls.count(NewRelease));
2877 if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
2878 unsigned PathCount =
2879 BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
2880 OldDelta += PathCount;
2881 OldCount += PathCount;
2883 // Merge the IsRetainBlock values.
2885 RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
2886 FirstRetain = false;
2887 } else if (ReleasesToMove.IsRetainBlock !=
2888 NewReleaseRetainRRI.IsRetainBlock)
2889 // It's not possible to merge the sequences if one uses
2890 // objc_retain and the other uses objc_retainBlock.
2893 // Collect the optimal insertion points.
2895 for (SmallPtrSet<Instruction *, 2>::const_iterator
2896 RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
2897 RE = NewReleaseRetainRRI.ReverseInsertPts.end();
2899 Instruction *RIP = *RI;
2900 if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
2901 PathCount = BBStates[RIP->getParent()].GetAllPathCount();
2902 NewDelta += PathCount;
2903 NewCount += PathCount;
2906 NewRetains.push_back(NewReleaseRetain);
2910 NewReleases.clear();
2911 if (NewRetains.empty()) break;
2914 // If the pointer is known incremented or nested, we can safely delete the
2915 // pair regardless of what's between them.
2916 if (KnownSafeTD || KnownSafeBU) {
2917 RetainsToMove.ReverseInsertPts.clear();
2918 ReleasesToMove.ReverseInsertPts.clear();
2921 // Determine whether the new insertion points we computed preserve the
2922 // balance of retain and release calls through the program.
2923 // TODO: If the fully aggressive solution isn't valid, try to find a
2924 // less aggressive solution which is.
2929 // Determine whether the original call points are balanced in the retain and
2930 // release calls through the program. If not, conservatively don't touch
2932 // TODO: It's theoretically possible to do code motion in this case, as
2933 // long as the existing imbalances are maintained.
2937 // Ok, everything checks out and we're all set. Let's move some code!
2939 AnyPairsCompletelyEliminated = NewCount == 0;
2940 NumRRs += OldCount - NewCount;
2941 MoveCalls(Arg, RetainsToMove, ReleasesToMove,
2942 Retains, Releases, DeadInsts, M);
2945 NewReleases.clear();
2947 RetainsToMove.clear();
2948 ReleasesToMove.clear();
2951 // Now that we're done moving everything, we can delete the newly dead
2952 // instructions, as we no longer need them as insert points.
2953 while (!DeadInsts.empty())
2954 EraseInstruction(DeadInsts.pop_back_val());
2956 return AnyPairsCompletelyEliminated;
2959 /// OptimizeWeakCalls - Weak pointer optimizations.
2960 void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
2961 // First, do memdep-style RLE and S2L optimizations. We can't use memdep
2962 // itself because it uses AliasAnalysis and we need to do provenance
2964 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
2965 Instruction *Inst = &*I++;
2966 InstructionClass Class = GetBasicInstructionClass(Inst);
2967 if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
2970 // Delete objc_loadWeak calls with no users.
2971 if (Class == IC_LoadWeak && Inst->use_empty()) {
2972 Inst->eraseFromParent();
2976 // TODO: For now, just look for an earlier available version of this value
2977 // within the same block. Theoretically, we could do memdep-style non-local
2978 // analysis too, but that would want caching. A better approach would be to
2979 // use the technique that EarlyCSE uses.
2980 inst_iterator Current = llvm::prior(I);
2981 BasicBlock *CurrentBB = Current.getBasicBlockIterator();
2982 for (BasicBlock::iterator B = CurrentBB->begin(),
2983 J = Current.getInstructionIterator();
2985 Instruction *EarlierInst = &*llvm::prior(J);
2986 InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
2987 switch (EarlierClass) {
2989 case IC_LoadWeakRetained: {
2990 // If this is loading from the same pointer, replace this load's value
2992 CallInst *Call = cast<CallInst>(Inst);
2993 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
2994 Value *Arg = Call->getArgOperand(0);
2995 Value *EarlierArg = EarlierCall->getArgOperand(0);
2996 switch (PA.getAA()->alias(Arg, EarlierArg)) {
2997 case AliasAnalysis::MustAlias:
2999 // If the load has a builtin retain, insert a plain retain for it.
3000 if (Class == IC_LoadWeakRetained) {
3002 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
3006 // Zap the fully redundant load.
3007 Call->replaceAllUsesWith(EarlierCall);
3008 Call->eraseFromParent();
3010 case AliasAnalysis::MayAlias:
3011 case AliasAnalysis::PartialAlias:
3013 case AliasAnalysis::NoAlias:
3020 // If this is storing to the same pointer and has the same size etc.
3021 // replace this load's value with the stored value.
3022 CallInst *Call = cast<CallInst>(Inst);
3023 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
3024 Value *Arg = Call->getArgOperand(0);
3025 Value *EarlierArg = EarlierCall->getArgOperand(0);
3026 switch (PA.getAA()->alias(Arg, EarlierArg)) {
3027 case AliasAnalysis::MustAlias:
3029 // If the load has a builtin retain, insert a plain retain for it.
3030 if (Class == IC_LoadWeakRetained) {
3032 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
3036 // Zap the fully redundant load.
3037 Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
3038 Call->eraseFromParent();
3040 case AliasAnalysis::MayAlias:
3041 case AliasAnalysis::PartialAlias:
3043 case AliasAnalysis::NoAlias:
3050 // TOOD: Grab the copied value.
3052 case IC_AutoreleasepoolPush:
3055 // Weak pointers are only modified through the weak entry points
3056 // (and arbitrary calls, which could call the weak entry points).
3059 // Anything else could modify the weak pointer.
3066 // Then, for each destroyWeak with an alloca operand, check to see if
3067 // the alloca and all its users can be zapped.
3068 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
3069 Instruction *Inst = &*I++;
3070 InstructionClass Class = GetBasicInstructionClass(Inst);
3071 if (Class != IC_DestroyWeak)
3074 CallInst *Call = cast<CallInst>(Inst);
3075 Value *Arg = Call->getArgOperand(0);
3076 if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
3077 for (Value::use_iterator UI = Alloca->use_begin(),
3078 UE = Alloca->use_end(); UI != UE; ++UI) {
3079 Instruction *UserInst = cast<Instruction>(*UI);
3080 switch (GetBasicInstructionClass(UserInst)) {
3083 case IC_DestroyWeak:
3090 for (Value::use_iterator UI = Alloca->use_begin(),
3091 UE = Alloca->use_end(); UI != UE; ) {
3092 CallInst *UserInst = cast<CallInst>(*UI++);
3093 if (!UserInst->use_empty())
3094 UserInst->replaceAllUsesWith(UserInst->getOperand(1));
3095 UserInst->eraseFromParent();
3097 Alloca->eraseFromParent();
3103 /// OptimizeSequences - Identify program paths which execute sequences of
3104 /// retains and releases which can be eliminated.
3105 bool ObjCARCOpt::OptimizeSequences(Function &F) {
3106 /// Releases, Retains - These are used to store the results of the main flow
3107 /// analysis. These use Value* as the key instead of Instruction* so that the
3108 /// map stays valid when we get around to rewriting code and calls get
3109 /// replaced by arguments.
3110 DenseMap<Value *, RRInfo> Releases;
3111 MapVector<Value *, RRInfo> Retains;
3113 /// BBStates, This is used during the traversal of the function to track the
3114 /// states for each identified object at each block.
3115 DenseMap<const BasicBlock *, BBState> BBStates;
3117 // Analyze the CFG of the function, and all instructions.
3118 bool NestingDetected = Visit(F, BBStates, Retains, Releases);
3121 return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
3125 /// OptimizeReturns - Look for this pattern:
3127 /// %call = call i8* @something(...)
3128 /// %2 = call i8* @objc_retain(i8* %call)
3129 /// %3 = call i8* @objc_autorelease(i8* %2)
3132 /// And delete the retain and autorelease.
3134 /// Otherwise if it's just this:
3136 /// %3 = call i8* @objc_autorelease(i8* %2)
3139 /// convert the autorelease to autoreleaseRV.
3140 void ObjCARCOpt::OptimizeReturns(Function &F) {
3141 if (!F.getReturnType()->isPointerTy())
3144 SmallPtrSet<Instruction *, 4> DependingInstructions;
3145 SmallPtrSet<const BasicBlock *, 4> Visited;
3146 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
3147 BasicBlock *BB = FI;
3148 ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
3151 const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
3152 FindDependencies(NeedsPositiveRetainCount, Arg,
3153 BB, Ret, DependingInstructions, Visited, PA);
3154 if (DependingInstructions.size() != 1)
3158 CallInst *Autorelease =
3159 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3162 InstructionClass AutoreleaseClass =
3163 GetBasicInstructionClass(Autorelease);
3164 if (!IsAutorelease(AutoreleaseClass))
3166 if (GetObjCArg(Autorelease) != Arg)
3169 DependingInstructions.clear();
3172 // Check that there is nothing that can affect the reference
3173 // count between the autorelease and the retain.
3174 FindDependencies(CanChangeRetainCount, Arg,
3175 BB, Autorelease, DependingInstructions, Visited, PA);
3176 if (DependingInstructions.size() != 1)
3181 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3183 // Check that we found a retain with the same argument.
3185 !IsRetain(GetBasicInstructionClass(Retain)) ||
3186 GetObjCArg(Retain) != Arg)
3189 DependingInstructions.clear();
3192 // Convert the autorelease to an autoreleaseRV, since it's
3193 // returning the value.
3194 if (AutoreleaseClass == IC_Autorelease) {
3195 Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
3196 AutoreleaseClass = IC_AutoreleaseRV;
3199 // Check that there is nothing that can affect the reference
3200 // count between the retain and the call.
3201 FindDependencies(CanChangeRetainCount, Arg, BB, Retain,
3202 DependingInstructions, Visited, PA);
3203 if (DependingInstructions.size() != 1)
3208 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3210 // Check that the pointer is the return value of the call.
3211 if (!Call || Arg != Call)
3214 // Check that the call is a regular call.
3215 InstructionClass Class = GetBasicInstructionClass(Call);
3216 if (Class != IC_CallOrUser && Class != IC_Call)
3219 // If so, we can zap the retain and autorelease.
3222 EraseInstruction(Retain);
3223 EraseInstruction(Autorelease);
3229 DependingInstructions.clear();
3234 bool ObjCARCOpt::doInitialization(Module &M) {
3238 Run = ModuleHasARC(M);
3242 // Identify the imprecise release metadata kind.
3243 ImpreciseReleaseMDKind =
3244 M.getContext().getMDKindID("clang.imprecise_release");
3246 // Intuitively, objc_retain and others are nocapture, however in practice
3247 // they are not, because they return their argument value. And objc_release
3248 // calls finalizers.
3250 // These are initialized lazily.
3252 AutoreleaseRVCallee = 0;
3255 RetainBlockCallee = 0;
3256 AutoreleaseCallee = 0;
3261 bool ObjCARCOpt::runOnFunction(Function &F) {
3265 // If nothing in the Module uses ARC, don't do anything.
3271 PA.setAA(&getAnalysis<AliasAnalysis>());
3273 // This pass performs several distinct transformations. As a compile-time aid
3274 // when compiling code that isn't ObjC, skip these if the relevant ObjC
3275 // library functions aren't declared.
3277 // Preliminary optimizations. This also computs UsedInThisFunction.
3278 OptimizeIndividualCalls(F);
3280 // Optimizations for weak pointers.
3281 if (UsedInThisFunction & ((1 << IC_LoadWeak) |
3282 (1 << IC_LoadWeakRetained) |
3283 (1 << IC_StoreWeak) |
3284 (1 << IC_InitWeak) |
3285 (1 << IC_CopyWeak) |
3286 (1 << IC_MoveWeak) |
3287 (1 << IC_DestroyWeak)))
3288 OptimizeWeakCalls(F);
3290 // Optimizations for retain+release pairs.
3291 if (UsedInThisFunction & ((1 << IC_Retain) |
3292 (1 << IC_RetainRV) |
3293 (1 << IC_RetainBlock)))
3294 if (UsedInThisFunction & (1 << IC_Release))
3295 // Run OptimizeSequences until it either stops making changes or
3296 // no retain+release pair nesting is detected.
3297 while (OptimizeSequences(F)) {}
3299 // Optimizations if objc_autorelease is used.
3300 if (UsedInThisFunction &
3301 ((1 << IC_Autorelease) | (1 << IC_AutoreleaseRV)))
3307 void ObjCARCOpt::releaseMemory() {
3311 //===----------------------------------------------------------------------===//
3313 //===----------------------------------------------------------------------===//
3315 // TODO: ObjCARCContract could insert PHI nodes when uses aren't
3316 // dominated by single calls.
3318 #include "llvm/Operator.h"
3319 #include "llvm/InlineAsm.h"
3320 #include "llvm/Analysis/Dominators.h"
3322 STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
3325 /// ObjCARCContract - Late ARC optimizations. These change the IR in a way
3326 /// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late.
3327 class ObjCARCContract : public FunctionPass {
3331 ProvenanceAnalysis PA;
3333 /// Run - A flag indicating whether this optimization pass should run.
3336 /// StoreStrongCallee, etc. - Declarations for ObjC runtime
3337 /// functions, for use in creating calls to them. These are initialized
3338 /// lazily to avoid cluttering up the Module with unused declarations.
3339 Constant *StoreStrongCallee,
3340 *RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee;
3342 /// RetainRVMarker - The inline asm string to insert between calls and
3343 /// RetainRV calls to make the optimization work on targets which need it.
3344 const MDString *RetainRVMarker;
3346 Constant *getStoreStrongCallee(Module *M);
3347 Constant *getRetainAutoreleaseCallee(Module *M);
3348 Constant *getRetainAutoreleaseRVCallee(Module *M);
3350 bool ContractAutorelease(Function &F, Instruction *Autorelease,
3351 InstructionClass Class,
3352 SmallPtrSet<Instruction *, 4>
3353 &DependingInstructions,
3354 SmallPtrSet<const BasicBlock *, 4>
3357 void ContractRelease(Instruction *Release,
3358 inst_iterator &Iter);
3360 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
3361 virtual bool doInitialization(Module &M);
3362 virtual bool runOnFunction(Function &F);
3366 ObjCARCContract() : FunctionPass(ID) {
3367 initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
3372 char ObjCARCContract::ID = 0;
3373 INITIALIZE_PASS_BEGIN(ObjCARCContract,
3374 "objc-arc-contract", "ObjC ARC contraction", false, false)
3375 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
3376 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
3377 INITIALIZE_PASS_END(ObjCARCContract,
3378 "objc-arc-contract", "ObjC ARC contraction", false, false)
3380 Pass *llvm::createObjCARCContractPass() {
3381 return new ObjCARCContract();
3384 void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
3385 AU.addRequired<AliasAnalysis>();
3386 AU.addRequired<DominatorTree>();
3387 AU.setPreservesCFG();
3390 Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
3391 if (!StoreStrongCallee) {
3392 LLVMContext &C = M->getContext();
3393 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3394 Type *I8XX = PointerType::getUnqual(I8X);
3395 std::vector<Type *> Params;
3396 Params.push_back(I8XX);
3397 Params.push_back(I8X);
3399 AttrListPtr Attributes;
3400 Attributes.addAttr(~0u, Attribute::NoUnwind);
3401 Attributes.addAttr(1, Attribute::NoCapture);
3404 M->getOrInsertFunction(
3406 FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
3409 return StoreStrongCallee;
3412 Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
3413 if (!RetainAutoreleaseCallee) {
3414 LLVMContext &C = M->getContext();
3415 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3416 std::vector<Type *> Params;
3417 Params.push_back(I8X);
3419 FunctionType::get(I8X, Params, /*isVarArg=*/false);
3420 AttrListPtr Attributes;
3421 Attributes.addAttr(~0u, Attribute::NoUnwind);
3422 RetainAutoreleaseCallee =
3423 M->getOrInsertFunction("objc_retainAutorelease", FTy, Attributes);
3425 return RetainAutoreleaseCallee;
3428 Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
3429 if (!RetainAutoreleaseRVCallee) {
3430 LLVMContext &C = M->getContext();
3431 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3432 std::vector<Type *> Params;
3433 Params.push_back(I8X);
3435 FunctionType::get(I8X, Params, /*isVarArg=*/false);
3436 AttrListPtr Attributes;
3437 Attributes.addAttr(~0u, Attribute::NoUnwind);
3438 RetainAutoreleaseRVCallee =
3439 M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
3442 return RetainAutoreleaseRVCallee;
3445 /// ContractAutorelease - Merge an autorelease with a retain into a fused
3448 ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
3449 InstructionClass Class,
3450 SmallPtrSet<Instruction *, 4>
3451 &DependingInstructions,
3452 SmallPtrSet<const BasicBlock *, 4>
3454 const Value *Arg = GetObjCArg(Autorelease);
3456 // Check that there are no instructions between the retain and the autorelease
3457 // (such as an autorelease_pop) which may change the count.
3458 CallInst *Retain = 0;
3459 if (Class == IC_AutoreleaseRV)
3460 FindDependencies(RetainAutoreleaseRVDep, Arg,
3461 Autorelease->getParent(), Autorelease,
3462 DependingInstructions, Visited, PA);
3464 FindDependencies(RetainAutoreleaseDep, Arg,
3465 Autorelease->getParent(), Autorelease,
3466 DependingInstructions, Visited, PA);
3469 if (DependingInstructions.size() != 1) {
3470 DependingInstructions.clear();
3474 Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3475 DependingInstructions.clear();
3478 GetBasicInstructionClass(Retain) != IC_Retain ||
3479 GetObjCArg(Retain) != Arg)
3485 if (Class == IC_AutoreleaseRV)
3486 Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
3488 Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
3490 EraseInstruction(Autorelease);
3494 /// ContractRelease - Attempt to merge an objc_release with a store, load, and
3495 /// objc_retain to form an objc_storeStrong. This can be a little tricky because
3496 /// the instructions don't always appear in order, and there may be unrelated
3497 /// intervening instructions.
3498 void ObjCARCContract::ContractRelease(Instruction *Release,
3499 inst_iterator &Iter) {
3500 LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
3501 if (!Load || !Load->isSimple()) return;
3503 // For now, require everything to be in one basic block.
3504 BasicBlock *BB = Release->getParent();
3505 if (Load->getParent() != BB) return;
3507 // Walk down to find the store.
3508 BasicBlock::iterator I = Load, End = BB->end();
3510 AliasAnalysis::Location Loc = AA->getLocation(Load);
3513 IsRetain(GetBasicInstructionClass(I)) ||
3514 !(AA->getModRefInfo(I, Loc) & AliasAnalysis::Mod)))
3516 StoreInst *Store = dyn_cast<StoreInst>(I);
3517 if (!Store || !Store->isSimple()) return;
3518 if (Store->getPointerOperand() != Loc.Ptr) return;
3520 Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
3522 // Walk up to find the retain.
3524 BasicBlock::iterator Begin = BB->begin();
3525 while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
3527 Instruction *Retain = I;
3528 if (GetBasicInstructionClass(Retain) != IC_Retain) return;
3529 if (GetObjCArg(Retain) != New) return;
3534 LLVMContext &C = Release->getContext();
3535 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3536 Type *I8XX = PointerType::getUnqual(I8X);
3538 Value *Args[] = { Load->getPointerOperand(), New };
3539 if (Args[0]->getType() != I8XX)
3540 Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
3541 if (Args[1]->getType() != I8X)
3542 Args[1] = new BitCastInst(Args[1], I8X, "", Store);
3543 CallInst *StoreStrong =
3544 CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
3546 StoreStrong->setDoesNotThrow();
3547 StoreStrong->setDebugLoc(Store->getDebugLoc());
3549 if (&*Iter == Store) ++Iter;
3550 Store->eraseFromParent();
3551 Release->eraseFromParent();
3552 EraseInstruction(Retain);
3553 if (Load->use_empty())
3554 Load->eraseFromParent();
3557 bool ObjCARCContract::doInitialization(Module &M) {
3558 Run = ModuleHasARC(M);
3562 // These are initialized lazily.
3563 StoreStrongCallee = 0;
3564 RetainAutoreleaseCallee = 0;
3565 RetainAutoreleaseRVCallee = 0;
3567 // Initialize RetainRVMarker.
3569 if (NamedMDNode *NMD =
3570 M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
3571 if (NMD->getNumOperands() == 1) {
3572 const MDNode *N = NMD->getOperand(0);
3573 if (N->getNumOperands() == 1)
3574 if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
3581 bool ObjCARCContract::runOnFunction(Function &F) {
3585 // If nothing in the Module uses ARC, don't do anything.
3590 AA = &getAnalysis<AliasAnalysis>();
3591 DT = &getAnalysis<DominatorTree>();
3593 PA.setAA(&getAnalysis<AliasAnalysis>());
3595 // For ObjC library calls which return their argument, replace uses of the
3596 // argument with uses of the call return value, if it dominates the use. This
3597 // reduces register pressure.
3598 SmallPtrSet<Instruction *, 4> DependingInstructions;
3599 SmallPtrSet<const BasicBlock *, 4> Visited;
3600 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
3601 Instruction *Inst = &*I++;
3603 // Only these library routines return their argument. In particular,
3604 // objc_retainBlock does not necessarily return its argument.
3605 InstructionClass Class = GetBasicInstructionClass(Inst);
3608 case IC_FusedRetainAutorelease:
3609 case IC_FusedRetainAutoreleaseRV:
3611 case IC_Autorelease:
3612 case IC_AutoreleaseRV:
3613 if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
3617 // If we're compiling for a target which needs a special inline-asm
3618 // marker to do the retainAutoreleasedReturnValue optimization,
3620 if (!RetainRVMarker)
3622 BasicBlock::iterator BBI = Inst;
3624 while (isNoopInstruction(BBI)) --BBI;
3625 if (&*BBI == GetObjCArg(Inst)) {
3627 InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
3628 /*isVarArg=*/false),
3629 RetainRVMarker->getString(),
3630 /*Constraints=*/"", /*hasSideEffects=*/true);
3631 CallInst::Create(IA, "", Inst);
3636 // objc_initWeak(p, null) => *p = null
3637 CallInst *CI = cast<CallInst>(Inst);
3638 if (isNullOrUndef(CI->getArgOperand(1))) {
3640 ConstantPointerNull::get(cast<PointerType>(CI->getType()));
3642 new StoreInst(Null, CI->getArgOperand(0), CI);
3643 CI->replaceAllUsesWith(Null);
3644 CI->eraseFromParent();
3649 ContractRelease(Inst, I);
3655 // Don't use GetObjCArg because we don't want to look through bitcasts
3656 // and such; to do the replacement, the argument must have type i8*.
3657 const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
3659 // If we're compiling bugpointed code, don't get in trouble.
3660 if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
3662 // Look through the uses of the pointer.
3663 for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
3665 Use &U = UI.getUse();
3666 unsigned OperandNo = UI.getOperandNo();
3667 ++UI; // Increment UI now, because we may unlink its element.
3668 if (Instruction *UserInst = dyn_cast<Instruction>(U.getUser()))
3669 if (Inst != UserInst && DT->dominates(Inst, UserInst)) {
3671 Instruction *Replacement = Inst;
3672 Type *UseTy = U.get()->getType();
3673 if (PHINode *PHI = dyn_cast<PHINode>(UserInst)) {
3674 // For PHI nodes, insert the bitcast in the predecessor block.
3676 PHINode::getIncomingValueNumForOperand(OperandNo);
3678 PHI->getIncomingBlock(ValNo);
3679 if (Replacement->getType() != UseTy)
3680 Replacement = new BitCastInst(Replacement, UseTy, "",
3682 for (unsigned i = 0, e = PHI->getNumIncomingValues();
3684 if (PHI->getIncomingBlock(i) == BB) {
3685 // Keep the UI iterator valid.
3686 if (&PHI->getOperandUse(
3687 PHINode::getOperandNumForIncomingValue(i)) ==
3690 PHI->setIncomingValue(i, Replacement);
3693 if (Replacement->getType() != UseTy)
3694 Replacement = new BitCastInst(Replacement, UseTy, "", UserInst);
3700 // If Arg is a no-op casted pointer, strip one level of casts and
3702 if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
3703 Arg = BI->getOperand(0);
3704 else if (isa<GEPOperator>(Arg) &&
3705 cast<GEPOperator>(Arg)->hasAllZeroIndices())
3706 Arg = cast<GEPOperator>(Arg)->getPointerOperand();
3707 else if (isa<GlobalAlias>(Arg) &&
3708 !cast<GlobalAlias>(Arg)->mayBeOverridden())
3709 Arg = cast<GlobalAlias>(Arg)->getAliasee();