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 knowledge 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/ADT/DenseMap.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/CommandLine.h"
35 #include "llvm/Support/raw_ostream.h"
38 // A handy option to enable/disable all optimizations in this file.
39 static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
41 //===----------------------------------------------------------------------===//
43 //===----------------------------------------------------------------------===//
46 /// MapVector - An associative container with fast insertion-order
47 /// (deterministic) iteration over its elements. Plus the special
49 template<class KeyT, class ValueT>
51 /// Map - Map keys to indices in Vector.
52 typedef DenseMap<KeyT, size_t> MapTy;
55 /// Vector - Keys and values.
56 typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
60 typedef typename VectorTy::iterator iterator;
61 typedef typename VectorTy::const_iterator const_iterator;
62 iterator begin() { return Vector.begin(); }
63 iterator end() { return Vector.end(); }
64 const_iterator begin() const { return Vector.begin(); }
65 const_iterator end() const { return Vector.end(); }
69 assert(Vector.size() >= Map.size()); // May differ due to blotting.
70 for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
72 assert(I->second < Vector.size());
73 assert(Vector[I->second].first == I->first);
75 for (typename VectorTy::const_iterator I = Vector.begin(),
76 E = Vector.end(); I != E; ++I)
78 (Map.count(I->first) &&
79 Map[I->first] == size_t(I - Vector.begin())));
83 ValueT &operator[](const KeyT &Arg) {
84 std::pair<typename MapTy::iterator, bool> Pair =
85 Map.insert(std::make_pair(Arg, size_t(0)));
87 size_t Num = Vector.size();
88 Pair.first->second = Num;
89 Vector.push_back(std::make_pair(Arg, ValueT()));
90 return Vector[Num].second;
92 return Vector[Pair.first->second].second;
95 std::pair<iterator, bool>
96 insert(const std::pair<KeyT, ValueT> &InsertPair) {
97 std::pair<typename MapTy::iterator, bool> Pair =
98 Map.insert(std::make_pair(InsertPair.first, size_t(0)));
100 size_t Num = Vector.size();
101 Pair.first->second = Num;
102 Vector.push_back(InsertPair);
103 return std::make_pair(Vector.begin() + Num, true);
105 return std::make_pair(Vector.begin() + Pair.first->second, false);
108 const_iterator find(const KeyT &Key) const {
109 typename MapTy::const_iterator It = Map.find(Key);
110 if (It == Map.end()) return Vector.end();
111 return Vector.begin() + It->second;
114 /// blot - This is similar to erase, but instead of removing the element
115 /// from the vector, it just zeros out the key in the vector. This leaves
116 /// iterators intact, but clients must be prepared for zeroed-out keys when
118 void blot(const KeyT &Key) {
119 typename MapTy::iterator It = Map.find(Key);
120 if (It == Map.end()) return;
121 Vector[It->second].first = KeyT();
132 //===----------------------------------------------------------------------===//
134 //===----------------------------------------------------------------------===//
136 #include "llvm/ADT/StringSwitch.h"
137 #include "llvm/Analysis/ValueTracking.h"
138 #include "llvm/Intrinsics.h"
139 #include "llvm/Module.h"
140 #include "llvm/Support/CallSite.h"
141 #include "llvm/Transforms/Utils/Local.h"
144 /// InstructionClass - A simple classification for instructions.
145 enum InstructionClass {
146 IC_Retain, ///< objc_retain
147 IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
148 IC_RetainBlock, ///< objc_retainBlock
149 IC_Release, ///< objc_release
150 IC_Autorelease, ///< objc_autorelease
151 IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
152 IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
153 IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
154 IC_NoopCast, ///< objc_retainedObject, etc.
155 IC_FusedRetainAutorelease, ///< objc_retainAutorelease
156 IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
157 IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
158 IC_StoreWeak, ///< objc_storeWeak (primitive)
159 IC_InitWeak, ///< objc_initWeak (derived)
160 IC_LoadWeak, ///< objc_loadWeak (derived)
161 IC_MoveWeak, ///< objc_moveWeak (derived)
162 IC_CopyWeak, ///< objc_copyWeak (derived)
163 IC_DestroyWeak, ///< objc_destroyWeak (derived)
164 IC_StoreStrong, ///< objc_storeStrong (derived)
165 IC_CallOrUser, ///< could call objc_release and/or "use" pointers
166 IC_Call, ///< could call objc_release
167 IC_User, ///< could "use" a pointer
168 IC_None ///< anything else
172 /// IsPotentialUse - Test whether the given value is possible a
173 /// reference-counted pointer.
174 static bool IsPotentialUse(const Value *Op) {
175 // Pointers to static or stack storage are not reference-counted pointers.
176 if (isa<Constant>(Op) || isa<AllocaInst>(Op))
178 // Special arguments are not reference-counted.
179 if (const Argument *Arg = dyn_cast<Argument>(Op))
180 if (Arg->hasByValAttr() ||
181 Arg->hasNestAttr() ||
182 Arg->hasStructRetAttr())
184 // Only consider values with pointer types.
185 // It seemes intuitive to exclude function pointer types as well, since
186 // functions are never reference-counted, however clang occasionally
187 // bitcasts reference-counted pointers to function-pointer type
189 PointerType *Ty = dyn_cast<PointerType>(Op->getType());
192 // Conservatively assume anything else is a potential use.
196 /// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind
197 /// of construct CS is.
198 static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
199 for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
201 if (IsPotentialUse(*I))
202 return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
204 return CS.onlyReadsMemory() ? IC_None : IC_Call;
207 /// GetFunctionClass - Determine if F is one of the special known Functions.
208 /// If it isn't, return IC_CallOrUser.
209 static InstructionClass GetFunctionClass(const Function *F) {
210 Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
214 return StringSwitch<InstructionClass>(F->getName())
215 .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
216 .Default(IC_CallOrUser);
219 const Argument *A0 = AI++;
221 // Argument is a pointer.
222 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
223 Type *ETy = PTy->getElementType();
225 if (ETy->isIntegerTy(8))
226 return StringSwitch<InstructionClass>(F->getName())
227 .Case("objc_retain", IC_Retain)
228 .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
229 .Case("objc_retainBlock", IC_RetainBlock)
230 .Case("objc_release", IC_Release)
231 .Case("objc_autorelease", IC_Autorelease)
232 .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
233 .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
234 .Case("objc_retainedObject", IC_NoopCast)
235 .Case("objc_unretainedObject", IC_NoopCast)
236 .Case("objc_unretainedPointer", IC_NoopCast)
237 .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
238 .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
239 .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
240 .Default(IC_CallOrUser);
243 if (PointerType *Pte = dyn_cast<PointerType>(ETy))
244 if (Pte->getElementType()->isIntegerTy(8))
245 return StringSwitch<InstructionClass>(F->getName())
246 .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
247 .Case("objc_loadWeak", IC_LoadWeak)
248 .Case("objc_destroyWeak", IC_DestroyWeak)
249 .Default(IC_CallOrUser);
252 // Two arguments, first is i8**.
253 const Argument *A1 = AI++;
255 if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
256 if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
257 if (Pte->getElementType()->isIntegerTy(8))
258 if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
259 Type *ETy1 = PTy1->getElementType();
260 // Second argument is i8*
261 if (ETy1->isIntegerTy(8))
262 return StringSwitch<InstructionClass>(F->getName())
263 .Case("objc_storeWeak", IC_StoreWeak)
264 .Case("objc_initWeak", IC_InitWeak)
265 .Case("objc_storeStrong", IC_StoreStrong)
266 .Default(IC_CallOrUser);
267 // Second argument is i8**.
268 if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
269 if (Pte1->getElementType()->isIntegerTy(8))
270 return StringSwitch<InstructionClass>(F->getName())
271 .Case("objc_moveWeak", IC_MoveWeak)
272 .Case("objc_copyWeak", IC_CopyWeak)
273 .Default(IC_CallOrUser);
277 return IC_CallOrUser;
280 /// GetInstructionClass - Determine what kind of construct V is.
281 static InstructionClass GetInstructionClass(const Value *V) {
282 if (const Instruction *I = dyn_cast<Instruction>(V)) {
283 // Any instruction other than bitcast and gep with a pointer operand have a
284 // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
285 // to a subsequent use, rather than using it themselves, in this sense.
286 // As a short cut, several other opcodes are known to have no pointer
287 // operands of interest. And ret is never followed by a release, so it's
288 // not interesting to examine.
289 switch (I->getOpcode()) {
290 case Instruction::Call: {
291 const CallInst *CI = cast<CallInst>(I);
292 // Check for calls to special functions.
293 if (const Function *F = CI->getCalledFunction()) {
294 InstructionClass Class = GetFunctionClass(F);
295 if (Class != IC_CallOrUser)
298 // None of the intrinsic functions do objc_release. For intrinsics, the
299 // only question is whether or not they may be users.
300 switch (F->getIntrinsicID()) {
301 case Intrinsic::returnaddress: case Intrinsic::frameaddress:
302 case Intrinsic::stacksave: case Intrinsic::stackrestore:
303 case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
304 case Intrinsic::objectsize: case Intrinsic::prefetch:
305 case Intrinsic::stackprotector:
306 case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
307 case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
308 case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
309 case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
310 case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
311 case Intrinsic::invariant_start: case Intrinsic::invariant_end:
312 // Don't let dbg info affect our results.
313 case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
314 // Short cut: Some intrinsics obviously don't use ObjC pointers.
320 return GetCallSiteClass(CI);
322 case Instruction::Invoke:
323 return GetCallSiteClass(cast<InvokeInst>(I));
324 case Instruction::BitCast:
325 case Instruction::GetElementPtr:
326 case Instruction::Select: case Instruction::PHI:
327 case Instruction::Ret: case Instruction::Br:
328 case Instruction::Switch: case Instruction::IndirectBr:
329 case Instruction::Alloca: case Instruction::VAArg:
330 case Instruction::Add: case Instruction::FAdd:
331 case Instruction::Sub: case Instruction::FSub:
332 case Instruction::Mul: case Instruction::FMul:
333 case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
334 case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
335 case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
336 case Instruction::And: case Instruction::Or: case Instruction::Xor:
337 case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
338 case Instruction::IntToPtr: case Instruction::FCmp:
339 case Instruction::FPTrunc: case Instruction::FPExt:
340 case Instruction::FPToUI: case Instruction::FPToSI:
341 case Instruction::UIToFP: case Instruction::SIToFP:
342 case Instruction::InsertElement: case Instruction::ExtractElement:
343 case Instruction::ShuffleVector:
344 case Instruction::ExtractValue:
346 case Instruction::ICmp:
347 // Comparing a pointer with null, or any other constant, isn't an
348 // interesting use, because we don't care what the pointer points to, or
349 // about the values of any other dynamic reference-counted pointers.
350 if (IsPotentialUse(I->getOperand(1)))
354 // For anything else, check all the operands.
355 // Note that this includes both operands of a Store: while the first
356 // operand isn't actually being dereferenced, it is being stored to
357 // memory where we can no longer track who might read it and dereference
358 // it, so we have to consider it potentially used.
359 for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
361 if (IsPotentialUse(*OI))
366 // Otherwise, it's totally inert for ARC purposes.
370 /// GetBasicInstructionClass - Determine what kind of construct V is. This is
371 /// similar to GetInstructionClass except that it only detects objc runtine
372 /// calls. This allows it to be faster.
373 static InstructionClass GetBasicInstructionClass(const Value *V) {
374 if (const CallInst *CI = dyn_cast<CallInst>(V)) {
375 if (const Function *F = CI->getCalledFunction())
376 return GetFunctionClass(F);
377 // Otherwise, be conservative.
378 return IC_CallOrUser;
381 // Otherwise, be conservative.
382 return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
385 /// IsRetain - Test if the given class is objc_retain or
387 static bool IsRetain(InstructionClass Class) {
388 return Class == IC_Retain ||
389 Class == IC_RetainRV;
392 /// IsAutorelease - Test if the given class is objc_autorelease or
394 static bool IsAutorelease(InstructionClass Class) {
395 return Class == IC_Autorelease ||
396 Class == IC_AutoreleaseRV;
399 /// IsForwarding - Test if the given class represents instructions which return
400 /// their argument verbatim.
401 static bool IsForwarding(InstructionClass Class) {
402 // objc_retainBlock technically doesn't always return its argument
403 // verbatim, but it doesn't matter for our purposes here.
404 return Class == IC_Retain ||
405 Class == IC_RetainRV ||
406 Class == IC_Autorelease ||
407 Class == IC_AutoreleaseRV ||
408 Class == IC_RetainBlock ||
409 Class == IC_NoopCast;
412 /// IsNoopOnNull - Test if the given class represents instructions which do
413 /// nothing if passed a null pointer.
414 static bool IsNoopOnNull(InstructionClass Class) {
415 return Class == IC_Retain ||
416 Class == IC_RetainRV ||
417 Class == IC_Release ||
418 Class == IC_Autorelease ||
419 Class == IC_AutoreleaseRV ||
420 Class == IC_RetainBlock;
423 /// IsAlwaysTail - Test if the given class represents instructions which are
424 /// always safe to mark with the "tail" keyword.
425 static bool IsAlwaysTail(InstructionClass Class) {
426 // IC_RetainBlock may be given a stack argument.
427 return Class == IC_Retain ||
428 Class == IC_RetainRV ||
429 Class == IC_Autorelease ||
430 Class == IC_AutoreleaseRV;
433 /// IsNoThrow - Test if the given class represents instructions which are always
434 /// safe to mark with the nounwind attribute..
435 static bool IsNoThrow(InstructionClass Class) {
436 // objc_retainBlock is not nounwind because it calls user copy constructors
437 // which could theoretically throw.
438 return Class == IC_Retain ||
439 Class == IC_RetainRV ||
440 Class == IC_Release ||
441 Class == IC_Autorelease ||
442 Class == IC_AutoreleaseRV ||
443 Class == IC_AutoreleasepoolPush ||
444 Class == IC_AutoreleasepoolPop;
447 /// EraseInstruction - Erase the given instruction. Many ObjC calls return their
448 /// argument verbatim, so if it's such a call and the return value has users,
449 /// replace them with the argument value.
450 static void EraseInstruction(Instruction *CI) {
451 Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
453 bool Unused = CI->use_empty();
456 // Replace the return value with the argument.
457 assert(IsForwarding(GetBasicInstructionClass(CI)) &&
458 "Can't delete non-forwarding instruction with users!");
459 CI->replaceAllUsesWith(OldArg);
462 CI->eraseFromParent();
465 RecursivelyDeleteTriviallyDeadInstructions(OldArg);
468 /// GetUnderlyingObjCPtr - This is a wrapper around getUnderlyingObject which
469 /// also knows how to look through objc_retain and objc_autorelease calls, which
470 /// we know to return their argument verbatim.
471 static const Value *GetUnderlyingObjCPtr(const Value *V) {
473 V = GetUnderlyingObject(V);
474 if (!IsForwarding(GetBasicInstructionClass(V)))
476 V = cast<CallInst>(V)->getArgOperand(0);
482 /// StripPointerCastsAndObjCCalls - This is a wrapper around
483 /// Value::stripPointerCasts which also knows how to look through objc_retain
484 /// and objc_autorelease calls, which we know to return their argument verbatim.
485 static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
487 V = V->stripPointerCasts();
488 if (!IsForwarding(GetBasicInstructionClass(V)))
490 V = cast<CallInst>(V)->getArgOperand(0);
495 /// StripPointerCastsAndObjCCalls - This is a wrapper around
496 /// Value::stripPointerCasts which also knows how to look through objc_retain
497 /// and objc_autorelease calls, which we know to return their argument verbatim.
498 static Value *StripPointerCastsAndObjCCalls(Value *V) {
500 V = V->stripPointerCasts();
501 if (!IsForwarding(GetBasicInstructionClass(V)))
503 V = cast<CallInst>(V)->getArgOperand(0);
508 /// GetObjCArg - Assuming the given instruction is one of the special calls such
509 /// as objc_retain or objc_release, return the argument value, stripped of no-op
510 /// casts and forwarding calls.
511 static Value *GetObjCArg(Value *Inst) {
512 return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
515 /// IsObjCIdentifiedObject - This is similar to AliasAnalysis'
516 /// isObjCIdentifiedObject, except that it uses special knowledge of
517 /// ObjC conventions...
518 static bool IsObjCIdentifiedObject(const Value *V) {
519 // Assume that call results and arguments have their own "provenance".
520 // Constants (including GlobalVariables) and Allocas are never
521 // reference-counted.
522 if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
523 isa<Argument>(V) || isa<Constant>(V) ||
527 if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
528 const Value *Pointer =
529 StripPointerCastsAndObjCCalls(LI->getPointerOperand());
530 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
531 // A constant pointer can't be pointing to an object on the heap. It may
532 // be reference-counted, but it won't be deleted.
533 if (GV->isConstant())
535 StringRef Name = GV->getName();
536 // These special variables are known to hold values which are not
537 // reference-counted pointers.
538 if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
539 Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
540 Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
541 Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
542 Name.startswith("\01l_objc_msgSend_fixup_"))
550 /// FindSingleUseIdentifiedObject - This is similar to
551 /// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value
552 /// with multiple uses.
553 static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
554 if (Arg->hasOneUse()) {
555 if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
556 return FindSingleUseIdentifiedObject(BC->getOperand(0));
557 if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
558 if (GEP->hasAllZeroIndices())
559 return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
560 if (IsForwarding(GetBasicInstructionClass(Arg)))
561 return FindSingleUseIdentifiedObject(
562 cast<CallInst>(Arg)->getArgOperand(0));
563 if (!IsObjCIdentifiedObject(Arg))
568 // If we found an identifiable object but it has multiple uses, but they are
569 // trivial uses, we can still consider this to be a single-use value.
570 if (IsObjCIdentifiedObject(Arg)) {
571 for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
574 if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
584 /// ModuleHasARC - Test if the given module looks interesting to run ARC
586 static bool ModuleHasARC(const Module &M) {
588 M.getNamedValue("objc_retain") ||
589 M.getNamedValue("objc_release") ||
590 M.getNamedValue("objc_autorelease") ||
591 M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
592 M.getNamedValue("objc_retainBlock") ||
593 M.getNamedValue("objc_autoreleaseReturnValue") ||
594 M.getNamedValue("objc_autoreleasePoolPush") ||
595 M.getNamedValue("objc_loadWeakRetained") ||
596 M.getNamedValue("objc_loadWeak") ||
597 M.getNamedValue("objc_destroyWeak") ||
598 M.getNamedValue("objc_storeWeak") ||
599 M.getNamedValue("objc_initWeak") ||
600 M.getNamedValue("objc_moveWeak") ||
601 M.getNamedValue("objc_copyWeak") ||
602 M.getNamedValue("objc_retainedObject") ||
603 M.getNamedValue("objc_unretainedObject") ||
604 M.getNamedValue("objc_unretainedPointer");
607 /// DoesObjCBlockEscape - Test whether the given pointer, which is an
608 /// Objective C block pointer, does not "escape". This differs from regular
609 /// escape analysis in that a use as an argument to a call is not considered
611 static bool DoesObjCBlockEscape(const Value *BlockPtr) {
612 // Walk the def-use chains.
613 SmallVector<const Value *, 4> Worklist;
614 Worklist.push_back(BlockPtr);
616 const Value *V = Worklist.pop_back_val();
617 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
619 const User *UUser = *UI;
620 // Special - Use by a call (callee or argument) is not considered
622 switch (GetBasicInstructionClass(UUser)) {
627 case IC_AutoreleaseRV:
628 // These special functions make copies of their pointer arguments.
632 // Use by an instruction which copies the value is an escape if the
633 // result is an escape.
634 if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
635 isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
636 Worklist.push_back(UUser);
639 // Use by a load is not an escape.
640 if (isa<LoadInst>(UUser))
642 // Use by a store is not an escape if the use is the address.
643 if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
644 if (V != SI->getValueOperand())
648 // Regular calls and other stuff are not considered escapes.
651 // Otherwise, conservatively assume an escape.
654 } while (!Worklist.empty());
660 //===----------------------------------------------------------------------===//
661 // ARC AliasAnalysis.
662 //===----------------------------------------------------------------------===//
664 #include "llvm/Analysis/AliasAnalysis.h"
665 #include "llvm/Analysis/Passes.h"
666 #include "llvm/Pass.h"
669 /// ObjCARCAliasAnalysis - This is a simple alias analysis
670 /// implementation that uses knowledge of ARC constructs to answer queries.
672 /// TODO: This class could be generalized to know about other ObjC-specific
673 /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
674 /// even though their offsets are dynamic.
675 class ObjCARCAliasAnalysis : public ImmutablePass,
676 public AliasAnalysis {
678 static char ID; // Class identification, replacement for typeinfo
679 ObjCARCAliasAnalysis() : ImmutablePass(ID) {
680 initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
684 virtual void initializePass() {
685 InitializeAliasAnalysis(this);
688 /// getAdjustedAnalysisPointer - This method is used when a pass implements
689 /// an analysis interface through multiple inheritance. If needed, it
690 /// should override this to adjust the this pointer as needed for the
691 /// specified pass info.
692 virtual void *getAdjustedAnalysisPointer(const void *PI) {
693 if (PI == &AliasAnalysis::ID)
694 return static_cast<AliasAnalysis *>(this);
698 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
699 virtual AliasResult alias(const Location &LocA, const Location &LocB);
700 virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
701 virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
702 virtual ModRefBehavior getModRefBehavior(const Function *F);
703 virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
704 const Location &Loc);
705 virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
706 ImmutableCallSite CS2);
708 } // End of anonymous namespace
710 // Register this pass...
711 char ObjCARCAliasAnalysis::ID = 0;
712 INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
713 "ObjC-ARC-Based Alias Analysis", false, true, false)
715 ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
716 return new ObjCARCAliasAnalysis();
720 ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
721 AU.setPreservesAll();
722 AliasAnalysis::getAnalysisUsage(AU);
725 AliasAnalysis::AliasResult
726 ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
728 return AliasAnalysis::alias(LocA, LocB);
730 // First, strip off no-ops, including ObjC-specific no-ops, and try making a
731 // precise alias query.
732 const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
733 const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
735 AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
736 Location(SB, LocB.Size, LocB.TBAATag));
737 if (Result != MayAlias)
740 // If that failed, climb to the underlying object, including climbing through
741 // ObjC-specific no-ops, and try making an imprecise alias query.
742 const Value *UA = GetUnderlyingObjCPtr(SA);
743 const Value *UB = GetUnderlyingObjCPtr(SB);
744 if (UA != SA || UB != SB) {
745 Result = AliasAnalysis::alias(Location(UA), Location(UB));
746 // We can't use MustAlias or PartialAlias results here because
747 // GetUnderlyingObjCPtr may return an offsetted pointer value.
748 if (Result == NoAlias)
752 // If that failed, fail. We don't need to chain here, since that's covered
753 // by the earlier precise query.
758 ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
761 return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
763 // First, strip off no-ops, including ObjC-specific no-ops, and try making
764 // a precise alias query.
765 const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
766 if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
770 // If that failed, climb to the underlying object, including climbing through
771 // ObjC-specific no-ops, and try making an imprecise alias query.
772 const Value *U = GetUnderlyingObjCPtr(S);
774 return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
776 // If that failed, fail. We don't need to chain here, since that's covered
777 // by the earlier precise query.
781 AliasAnalysis::ModRefBehavior
782 ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
783 // We have nothing to do. Just chain to the next AliasAnalysis.
784 return AliasAnalysis::getModRefBehavior(CS);
787 AliasAnalysis::ModRefBehavior
788 ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
790 return AliasAnalysis::getModRefBehavior(F);
792 switch (GetFunctionClass(F)) {
794 return DoesNotAccessMemory;
799 return AliasAnalysis::getModRefBehavior(F);
802 AliasAnalysis::ModRefResult
803 ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
805 return AliasAnalysis::getModRefInfo(CS, Loc);
807 switch (GetBasicInstructionClass(CS.getInstruction())) {
811 case IC_AutoreleaseRV:
813 case IC_AutoreleasepoolPush:
814 case IC_FusedRetainAutorelease:
815 case IC_FusedRetainAutoreleaseRV:
816 // These functions don't access any memory visible to the compiler.
817 // Note that this doesn't include objc_retainBlock, because it updates
818 // pointers when it copies block data.
824 return AliasAnalysis::getModRefInfo(CS, Loc);
827 AliasAnalysis::ModRefResult
828 ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
829 ImmutableCallSite CS2) {
830 // TODO: Theoretically we could check for dependencies between objc_* calls
831 // and OnlyAccessesArgumentPointees calls or other well-behaved calls.
832 return AliasAnalysis::getModRefInfo(CS1, CS2);
835 //===----------------------------------------------------------------------===//
837 //===----------------------------------------------------------------------===//
839 #include "llvm/Support/InstIterator.h"
840 #include "llvm/Transforms/Scalar.h"
843 /// ObjCARCExpand - Early ARC transformations.
844 class ObjCARCExpand : public FunctionPass {
845 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
846 virtual bool doInitialization(Module &M);
847 virtual bool runOnFunction(Function &F);
849 /// Run - A flag indicating whether this optimization pass should run.
854 ObjCARCExpand() : FunctionPass(ID) {
855 initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
860 char ObjCARCExpand::ID = 0;
861 INITIALIZE_PASS(ObjCARCExpand,
862 "objc-arc-expand", "ObjC ARC expansion", false, false)
864 Pass *llvm::createObjCARCExpandPass() {
865 return new ObjCARCExpand();
868 void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
869 AU.setPreservesCFG();
872 bool ObjCARCExpand::doInitialization(Module &M) {
873 Run = ModuleHasARC(M);
877 bool ObjCARCExpand::runOnFunction(Function &F) {
881 // If nothing in the Module uses ARC, don't do anything.
885 bool Changed = false;
887 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
888 Instruction *Inst = &*I;
890 DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << *Inst << "\n");
892 switch (GetBasicInstructionClass(Inst)) {
896 case IC_AutoreleaseRV:
897 case IC_FusedRetainAutorelease:
898 case IC_FusedRetainAutoreleaseRV:
899 // These calls return their argument verbatim, as a low-level
900 // optimization. However, this makes high-level optimizations
901 // harder. Undo any uses of this optimization that the front-end
902 // emitted here. We'll redo them in the contract pass.
904 Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0));
911 DEBUG(dbgs() << "ObjCARCExpand: Finished Queue.\n\n");
916 //===----------------------------------------------------------------------===//
917 // ARC autorelease pool elimination.
918 //===----------------------------------------------------------------------===//
920 #include "llvm/ADT/STLExtras.h"
921 #include "llvm/Constants.h"
924 /// ObjCARCAPElim - Autorelease pool elimination.
925 class ObjCARCAPElim : public ModulePass {
926 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
927 virtual bool runOnModule(Module &M);
929 static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0);
930 static bool OptimizeBB(BasicBlock *BB);
934 ObjCARCAPElim() : ModulePass(ID) {
935 initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry());
940 char ObjCARCAPElim::ID = 0;
941 INITIALIZE_PASS(ObjCARCAPElim,
943 "ObjC ARC autorelease pool elimination",
946 Pass *llvm::createObjCARCAPElimPass() {
947 return new ObjCARCAPElim();
950 void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const {
951 AU.setPreservesCFG();
954 /// MayAutorelease - Interprocedurally determine if calls made by the
955 /// given call site can possibly produce autoreleases.
956 bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) {
957 if (const Function *Callee = CS.getCalledFunction()) {
958 if (Callee->isDeclaration() || Callee->mayBeOverridden())
960 for (Function::const_iterator I = Callee->begin(), E = Callee->end();
962 const BasicBlock *BB = I;
963 for (BasicBlock::const_iterator J = BB->begin(), F = BB->end();
965 if (ImmutableCallSite JCS = ImmutableCallSite(J))
966 // This recursion depth limit is arbitrary. It's just great
967 // enough to cover known interesting testcases.
969 !JCS.onlyReadsMemory() &&
970 MayAutorelease(JCS, Depth + 1))
979 bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) {
980 bool Changed = false;
982 Instruction *Push = 0;
983 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
984 Instruction *Inst = I++;
985 switch (GetBasicInstructionClass(Inst)) {
986 case IC_AutoreleasepoolPush:
989 case IC_AutoreleasepoolPop:
990 // If this pop matches a push and nothing in between can autorelease,
992 if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) {
994 Inst->eraseFromParent();
995 Push->eraseFromParent();
1000 if (MayAutorelease(ImmutableCallSite(Inst)))
1011 bool ObjCARCAPElim::runOnModule(Module &M) {
1015 // If nothing in the Module uses ARC, don't do anything.
1016 if (!ModuleHasARC(M))
1019 // Find the llvm.global_ctors variable, as the first step in
1020 // identifying the global constructors. In theory, unnecessary autorelease
1021 // pools could occur anywhere, but in practice it's pretty rare. Global
1022 // ctors are a place where autorelease pools get inserted automatically,
1023 // so it's pretty common for them to be unnecessary, and it's pretty
1024 // profitable to eliminate them.
1025 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
1029 assert(GV->hasDefinitiveInitializer() &&
1030 "llvm.global_ctors is uncooperative!");
1032 bool Changed = false;
1034 // Dig the constructor functions out of GV's initializer.
1035 ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
1036 for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
1039 // llvm.global_ctors is an array of pairs where the second members
1040 // are constructor functions.
1041 Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
1042 // If the user used a constructor function with the wrong signature and
1043 // it got bitcasted or whatever, look the other way.
1046 // Only look at function definitions.
1047 if (F->isDeclaration())
1049 // Only look at functions with one basic block.
1050 if (llvm::next(F->begin()) != F->end())
1052 // Ok, a single-block constructor function definition. Try to optimize it.
1053 Changed |= OptimizeBB(F->begin());
1059 //===----------------------------------------------------------------------===//
1060 // ARC optimization.
1061 //===----------------------------------------------------------------------===//
1063 // TODO: On code like this:
1066 // stuff_that_cannot_release()
1067 // objc_autorelease(%x)
1068 // stuff_that_cannot_release()
1070 // stuff_that_cannot_release()
1071 // objc_autorelease(%x)
1073 // The second retain and autorelease can be deleted.
1075 // TODO: It should be possible to delete
1076 // objc_autoreleasePoolPush and objc_autoreleasePoolPop
1077 // pairs if nothing is actually autoreleased between them. Also, autorelease
1078 // calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
1079 // after inlining) can be turned into plain release calls.
1081 // TODO: Critical-edge splitting. If the optimial insertion point is
1082 // a critical edge, the current algorithm has to fail, because it doesn't
1083 // know how to split edges. It should be possible to make the optimizer
1084 // think in terms of edges, rather than blocks, and then split critical
1087 // TODO: OptimizeSequences could generalized to be Interprocedural.
1089 // TODO: Recognize that a bunch of other objc runtime calls have
1090 // non-escaping arguments and non-releasing arguments, and may be
1091 // non-autoreleasing.
1093 // TODO: Sink autorelease calls as far as possible. Unfortunately we
1094 // usually can't sink them past other calls, which would be the main
1095 // case where it would be useful.
1097 // TODO: The pointer returned from objc_loadWeakRetained is retained.
1099 // TODO: Delete release+retain pairs (rare).
1101 #include "llvm/ADT/SmallPtrSet.h"
1102 #include "llvm/ADT/Statistic.h"
1103 #include "llvm/LLVMContext.h"
1104 #include "llvm/Support/CFG.h"
1106 STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
1107 STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
1108 STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
1109 STATISTIC(NumRets, "Number of return value forwarding "
1110 "retain+autoreleaes eliminated");
1111 STATISTIC(NumRRs, "Number of retain+release paths eliminated");
1112 STATISTIC(NumPeeps, "Number of calls peephole-optimized");
1115 /// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it
1116 /// uses many of the same techniques, except it uses special ObjC-specific
1117 /// reasoning about pointer relationships.
1118 class ProvenanceAnalysis {
1121 typedef std::pair<const Value *, const Value *> ValuePairTy;
1122 typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
1123 CachedResultsTy CachedResults;
1125 bool relatedCheck(const Value *A, const Value *B);
1126 bool relatedSelect(const SelectInst *A, const Value *B);
1127 bool relatedPHI(const PHINode *A, const Value *B);
1129 void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
1130 ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
1133 ProvenanceAnalysis() {}
1135 void setAA(AliasAnalysis *aa) { AA = aa; }
1137 AliasAnalysis *getAA() const { return AA; }
1139 bool related(const Value *A, const Value *B);
1142 CachedResults.clear();
1147 bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
1148 // If the values are Selects with the same condition, we can do a more precise
1149 // check: just check for relations between the values on corresponding arms.
1150 if (const SelectInst *SB = dyn_cast<SelectInst>(B))
1151 if (A->getCondition() == SB->getCondition())
1152 return related(A->getTrueValue(), SB->getTrueValue()) ||
1153 related(A->getFalseValue(), SB->getFalseValue());
1155 // Check both arms of the Select node individually.
1156 return related(A->getTrueValue(), B) ||
1157 related(A->getFalseValue(), B);
1160 bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
1161 // If the values are PHIs in the same block, we can do a more precise as well
1162 // as efficient check: just check for relations between the values on
1163 // corresponding edges.
1164 if (const PHINode *PNB = dyn_cast<PHINode>(B))
1165 if (PNB->getParent() == A->getParent()) {
1166 for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
1167 if (related(A->getIncomingValue(i),
1168 PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
1173 // Check each unique source of the PHI node against B.
1174 SmallPtrSet<const Value *, 4> UniqueSrc;
1175 for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
1176 const Value *PV1 = A->getIncomingValue(i);
1177 if (UniqueSrc.insert(PV1) && related(PV1, B))
1181 // All of the arms checked out.
1185 /// isStoredObjCPointer - Test if the value of P, or any value covered by its
1186 /// provenance, is ever stored within the function (not counting callees).
1187 static bool isStoredObjCPointer(const Value *P) {
1188 SmallPtrSet<const Value *, 8> Visited;
1189 SmallVector<const Value *, 8> Worklist;
1190 Worklist.push_back(P);
1193 P = Worklist.pop_back_val();
1194 for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
1196 const User *Ur = *UI;
1197 if (isa<StoreInst>(Ur)) {
1198 if (UI.getOperandNo() == 0)
1199 // The pointer is stored.
1201 // The pointed is stored through.
1204 if (isa<CallInst>(Ur))
1205 // The pointer is passed as an argument, ignore this.
1207 if (isa<PtrToIntInst>(P))
1208 // Assume the worst.
1210 if (Visited.insert(Ur))
1211 Worklist.push_back(Ur);
1213 } while (!Worklist.empty());
1215 // Everything checked out.
1219 bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
1220 // Skip past provenance pass-throughs.
1221 A = GetUnderlyingObjCPtr(A);
1222 B = GetUnderlyingObjCPtr(B);
1228 // Ask regular AliasAnalysis, for a first approximation.
1229 switch (AA->alias(A, B)) {
1230 case AliasAnalysis::NoAlias:
1232 case AliasAnalysis::MustAlias:
1233 case AliasAnalysis::PartialAlias:
1235 case AliasAnalysis::MayAlias:
1239 bool AIsIdentified = IsObjCIdentifiedObject(A);
1240 bool BIsIdentified = IsObjCIdentifiedObject(B);
1242 // An ObjC-Identified object can't alias a load if it is never locally stored.
1243 if (AIsIdentified) {
1244 // Check for an obvious escape.
1245 if (isa<LoadInst>(B))
1246 return isStoredObjCPointer(A);
1247 if (BIsIdentified) {
1248 // Check for an obvious escape.
1249 if (isa<LoadInst>(A))
1250 return isStoredObjCPointer(B);
1251 // Both pointers are identified and escapes aren't an evident problem.
1254 } else if (BIsIdentified) {
1255 // Check for an obvious escape.
1256 if (isa<LoadInst>(A))
1257 return isStoredObjCPointer(B);
1260 // Special handling for PHI and Select.
1261 if (const PHINode *PN = dyn_cast<PHINode>(A))
1262 return relatedPHI(PN, B);
1263 if (const PHINode *PN = dyn_cast<PHINode>(B))
1264 return relatedPHI(PN, A);
1265 if (const SelectInst *S = dyn_cast<SelectInst>(A))
1266 return relatedSelect(S, B);
1267 if (const SelectInst *S = dyn_cast<SelectInst>(B))
1268 return relatedSelect(S, A);
1274 bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
1275 // Begin by inserting a conservative value into the map. If the insertion
1276 // fails, we have the answer already. If it succeeds, leave it there until we
1277 // compute the real answer to guard against recursive queries.
1278 if (A > B) std::swap(A, B);
1279 std::pair<CachedResultsTy::iterator, bool> Pair =
1280 CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
1282 return Pair.first->second;
1284 bool Result = relatedCheck(A, B);
1285 CachedResults[ValuePairTy(A, B)] = Result;
1290 // Sequence - A sequence of states that a pointer may go through in which an
1291 // objc_retain and objc_release are actually needed.
1294 S_Retain, ///< objc_retain(x)
1295 S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
1296 S_Use, ///< any use of x
1297 S_Stop, ///< like S_Release, but code motion is stopped
1298 S_Release, ///< objc_release(x)
1299 S_MovableRelease ///< objc_release(x), !clang.imprecise_release
1303 static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
1307 if (A == S_None || B == S_None)
1310 if (A > B) std::swap(A, B);
1312 // Choose the side which is further along in the sequence.
1313 if ((A == S_Retain || A == S_CanRelease) &&
1314 (B == S_CanRelease || B == S_Use))
1317 // Choose the side which is further along in the sequence.
1318 if ((A == S_Use || A == S_CanRelease) &&
1319 (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
1321 // If both sides are releases, choose the more conservative one.
1322 if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
1324 if (A == S_Release && B == S_MovableRelease)
1332 /// RRInfo - Unidirectional information about either a
1333 /// retain-decrement-use-release sequence or release-use-decrement-retain
1334 /// reverese sequence.
1336 /// KnownSafe - After an objc_retain, the reference count of the referenced
1337 /// object is known to be positive. Similarly, before an objc_release, the
1338 /// reference count of the referenced object is known to be positive. If
1339 /// there are retain-release pairs in code regions where the retain count
1340 /// is known to be positive, they can be eliminated, regardless of any side
1341 /// effects between them.
1343 /// Also, a retain+release pair nested within another retain+release
1344 /// pair all on the known same pointer value can be eliminated, regardless
1345 /// of any intervening side effects.
1347 /// KnownSafe is true when either of these conditions is satisfied.
1350 /// IsRetainBlock - True if the Calls are objc_retainBlock calls (as
1351 /// opposed to objc_retain calls).
1354 /// IsTailCallRelease - True of the objc_release calls are all marked
1355 /// with the "tail" keyword.
1356 bool IsTailCallRelease;
1358 /// ReleaseMetadata - If the Calls are objc_release calls and they all have
1359 /// a clang.imprecise_release tag, this is the metadata tag.
1360 MDNode *ReleaseMetadata;
1362 /// Calls - For a top-down sequence, the set of objc_retains or
1363 /// objc_retainBlocks. For bottom-up, the set of objc_releases.
1364 SmallPtrSet<Instruction *, 2> Calls;
1366 /// ReverseInsertPts - The set of optimal insert positions for
1367 /// moving calls in the opposite sequence.
1368 SmallPtrSet<Instruction *, 2> ReverseInsertPts;
1371 KnownSafe(false), IsRetainBlock(false),
1372 IsTailCallRelease(false),
1373 ReleaseMetadata(0) {}
1379 void RRInfo::clear() {
1381 IsRetainBlock = false;
1382 IsTailCallRelease = false;
1383 ReleaseMetadata = 0;
1385 ReverseInsertPts.clear();
1389 /// PtrState - This class summarizes several per-pointer runtime properties
1390 /// which are propogated through the flow graph.
1392 /// KnownPositiveRefCount - True if the reference count is known to
1394 bool KnownPositiveRefCount;
1396 /// Partial - True of we've seen an opportunity for partial RR elimination,
1397 /// such as pushing calls into a CFG triangle or into one side of a
1401 /// Seq - The current position in the sequence.
1405 /// RRI - Unidirectional information about the current sequence.
1406 /// TODO: Encapsulate this better.
1409 PtrState() : KnownPositiveRefCount(false), Partial(false),
1412 void SetKnownPositiveRefCount() {
1413 KnownPositiveRefCount = true;
1416 void ClearRefCount() {
1417 KnownPositiveRefCount = false;
1420 bool IsKnownIncremented() const {
1421 return KnownPositiveRefCount;
1424 void SetSeq(Sequence NewSeq) {
1428 Sequence GetSeq() const {
1432 void ClearSequenceProgress() {
1433 ResetSequenceProgress(S_None);
1436 void ResetSequenceProgress(Sequence NewSeq) {
1442 void Merge(const PtrState &Other, bool TopDown);
1447 PtrState::Merge(const PtrState &Other, bool TopDown) {
1448 Seq = MergeSeqs(Seq, Other.Seq, TopDown);
1449 KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
1451 // We can't merge a plain objc_retain with an objc_retainBlock.
1452 if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
1455 // If we're not in a sequence (anymore), drop all associated state.
1456 if (Seq == S_None) {
1459 } else if (Partial || Other.Partial) {
1460 // If we're doing a merge on a path that's previously seen a partial
1461 // merge, conservatively drop the sequence, to avoid doing partial
1462 // RR elimination. If the branch predicates for the two merge differ,
1463 // mixing them is unsafe.
1464 ClearSequenceProgress();
1466 // Conservatively merge the ReleaseMetadata information.
1467 if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
1468 RRI.ReleaseMetadata = 0;
1470 RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
1471 RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
1472 Other.RRI.IsTailCallRelease;
1473 RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
1475 // Merge the insert point sets. If there are any differences,
1476 // that makes this a partial merge.
1477 Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
1478 for (SmallPtrSet<Instruction *, 2>::const_iterator
1479 I = Other.RRI.ReverseInsertPts.begin(),
1480 E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
1481 Partial |= RRI.ReverseInsertPts.insert(*I);
1486 /// BBState - Per-BasicBlock state.
1488 /// TopDownPathCount - The number of unique control paths from the entry
1489 /// which can reach this block.
1490 unsigned TopDownPathCount;
1492 /// BottomUpPathCount - The number of unique control paths to exits
1493 /// from this block.
1494 unsigned BottomUpPathCount;
1496 /// MapTy - A type for PerPtrTopDown and PerPtrBottomUp.
1497 typedef MapVector<const Value *, PtrState> MapTy;
1499 /// PerPtrTopDown - The top-down traversal uses this to record information
1500 /// known about a pointer at the bottom of each block.
1501 MapTy PerPtrTopDown;
1503 /// PerPtrBottomUp - The bottom-up traversal uses this to record information
1504 /// known about a pointer at the top of each block.
1505 MapTy PerPtrBottomUp;
1507 /// Preds, Succs - Effective successors and predecessors of the current
1508 /// block (this ignores ignorable edges and ignored backedges).
1509 SmallVector<BasicBlock *, 2> Preds;
1510 SmallVector<BasicBlock *, 2> Succs;
1513 BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
1515 typedef MapTy::iterator ptr_iterator;
1516 typedef MapTy::const_iterator ptr_const_iterator;
1518 ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
1519 ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
1520 ptr_const_iterator top_down_ptr_begin() const {
1521 return PerPtrTopDown.begin();
1523 ptr_const_iterator top_down_ptr_end() const {
1524 return PerPtrTopDown.end();
1527 ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
1528 ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
1529 ptr_const_iterator bottom_up_ptr_begin() const {
1530 return PerPtrBottomUp.begin();
1532 ptr_const_iterator bottom_up_ptr_end() const {
1533 return PerPtrBottomUp.end();
1536 /// SetAsEntry - Mark this block as being an entry block, which has one
1537 /// path from the entry by definition.
1538 void SetAsEntry() { TopDownPathCount = 1; }
1540 /// SetAsExit - Mark this block as being an exit block, which has one
1541 /// path to an exit by definition.
1542 void SetAsExit() { BottomUpPathCount = 1; }
1544 PtrState &getPtrTopDownState(const Value *Arg) {
1545 return PerPtrTopDown[Arg];
1548 PtrState &getPtrBottomUpState(const Value *Arg) {
1549 return PerPtrBottomUp[Arg];
1552 void clearBottomUpPointers() {
1553 PerPtrBottomUp.clear();
1556 void clearTopDownPointers() {
1557 PerPtrTopDown.clear();
1560 void InitFromPred(const BBState &Other);
1561 void InitFromSucc(const BBState &Other);
1562 void MergePred(const BBState &Other);
1563 void MergeSucc(const BBState &Other);
1565 /// GetAllPathCount - Return the number of possible unique paths from an
1566 /// entry to an exit which pass through this block. This is only valid
1567 /// after both the top-down and bottom-up traversals are complete.
1568 unsigned GetAllPathCount() const {
1569 assert(TopDownPathCount != 0);
1570 assert(BottomUpPathCount != 0);
1571 return TopDownPathCount * BottomUpPathCount;
1574 // Specialized CFG utilities.
1575 typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
1576 edge_iterator pred_begin() { return Preds.begin(); }
1577 edge_iterator pred_end() { return Preds.end(); }
1578 edge_iterator succ_begin() { return Succs.begin(); }
1579 edge_iterator succ_end() { return Succs.end(); }
1581 void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); }
1582 void addPred(BasicBlock *Pred) { Preds.push_back(Pred); }
1584 bool isExit() const { return Succs.empty(); }
1588 void BBState::InitFromPred(const BBState &Other) {
1589 PerPtrTopDown = Other.PerPtrTopDown;
1590 TopDownPathCount = Other.TopDownPathCount;
1593 void BBState::InitFromSucc(const BBState &Other) {
1594 PerPtrBottomUp = Other.PerPtrBottomUp;
1595 BottomUpPathCount = Other.BottomUpPathCount;
1598 /// MergePred - The top-down traversal uses this to merge information about
1599 /// predecessors to form the initial state for a new block.
1600 void BBState::MergePred(const BBState &Other) {
1601 // Other.TopDownPathCount can be 0, in which case it is either dead or a
1602 // loop backedge. Loop backedges are special.
1603 TopDownPathCount += Other.TopDownPathCount;
1605 // Check for overflow. If we have overflow, fall back to conservative behavior.
1606 if (TopDownPathCount < Other.TopDownPathCount) {
1607 clearTopDownPointers();
1611 // For each entry in the other set, if our set has an entry with the same key,
1612 // merge the entries. Otherwise, copy the entry and merge it with an empty
1614 for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
1615 ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
1616 std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
1617 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
1621 // For each entry in our set, if the other set doesn't have an entry with the
1622 // same key, force it to merge with an empty entry.
1623 for (ptr_iterator MI = top_down_ptr_begin(),
1624 ME = top_down_ptr_end(); MI != ME; ++MI)
1625 if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
1626 MI->second.Merge(PtrState(), /*TopDown=*/true);
1629 /// MergeSucc - The bottom-up traversal uses this to merge information about
1630 /// successors to form the initial state for a new block.
1631 void BBState::MergeSucc(const BBState &Other) {
1632 // Other.BottomUpPathCount can be 0, in which case it is either dead or a
1633 // loop backedge. Loop backedges are special.
1634 BottomUpPathCount += Other.BottomUpPathCount;
1636 // Check for overflow. If we have overflow, fall back to conservative behavior.
1637 if (BottomUpPathCount < Other.BottomUpPathCount) {
1638 clearBottomUpPointers();
1642 // For each entry in the other set, if our set has an entry with the
1643 // same key, merge the entries. Otherwise, copy the entry and merge
1644 // it with an empty entry.
1645 for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
1646 ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
1647 std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
1648 Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
1652 // For each entry in our set, if the other set doesn't have an entry
1653 // with the same key, force it to merge with an empty entry.
1654 for (ptr_iterator MI = bottom_up_ptr_begin(),
1655 ME = bottom_up_ptr_end(); MI != ME; ++MI)
1656 if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
1657 MI->second.Merge(PtrState(), /*TopDown=*/false);
1661 /// ObjCARCOpt - The main ARC optimization pass.
1662 class ObjCARCOpt : public FunctionPass {
1664 ProvenanceAnalysis PA;
1666 /// Run - A flag indicating whether this optimization pass should run.
1669 /// RetainRVCallee, etc. - Declarations for ObjC runtime
1670 /// functions, for use in creating calls to them. These are initialized
1671 /// lazily to avoid cluttering up the Module with unused declarations.
1672 Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee,
1673 *RetainCallee, *RetainBlockCallee, *AutoreleaseCallee;
1675 /// UsedInThisFunciton - Flags which determine whether each of the
1676 /// interesting runtine functions is in fact used in the current function.
1677 unsigned UsedInThisFunction;
1679 /// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release
1681 unsigned ImpreciseReleaseMDKind;
1683 /// CopyOnEscapeMDKind - The Metadata Kind for clang.arc.copy_on_escape
1685 unsigned CopyOnEscapeMDKind;
1687 /// NoObjCARCExceptionsMDKind - The Metadata Kind for
1688 /// clang.arc.no_objc_arc_exceptions metadata.
1689 unsigned NoObjCARCExceptionsMDKind;
1691 Constant *getRetainRVCallee(Module *M);
1692 Constant *getAutoreleaseRVCallee(Module *M);
1693 Constant *getReleaseCallee(Module *M);
1694 Constant *getRetainCallee(Module *M);
1695 Constant *getRetainBlockCallee(Module *M);
1696 Constant *getAutoreleaseCallee(Module *M);
1698 bool IsRetainBlockOptimizable(const Instruction *Inst);
1700 void OptimizeRetainCall(Function &F, Instruction *Retain);
1701 bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
1702 void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV);
1703 void OptimizeIndividualCalls(Function &F);
1705 void CheckForCFGHazards(const BasicBlock *BB,
1706 DenseMap<const BasicBlock *, BBState> &BBStates,
1707 BBState &MyStates) const;
1708 bool VisitInstructionBottomUp(Instruction *Inst,
1710 MapVector<Value *, RRInfo> &Retains,
1712 bool VisitBottomUp(BasicBlock *BB,
1713 DenseMap<const BasicBlock *, BBState> &BBStates,
1714 MapVector<Value *, RRInfo> &Retains);
1715 bool VisitInstructionTopDown(Instruction *Inst,
1716 DenseMap<Value *, RRInfo> &Releases,
1718 bool VisitTopDown(BasicBlock *BB,
1719 DenseMap<const BasicBlock *, BBState> &BBStates,
1720 DenseMap<Value *, RRInfo> &Releases);
1721 bool Visit(Function &F,
1722 DenseMap<const BasicBlock *, BBState> &BBStates,
1723 MapVector<Value *, RRInfo> &Retains,
1724 DenseMap<Value *, RRInfo> &Releases);
1726 void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
1727 MapVector<Value *, RRInfo> &Retains,
1728 DenseMap<Value *, RRInfo> &Releases,
1729 SmallVectorImpl<Instruction *> &DeadInsts,
1732 bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
1733 MapVector<Value *, RRInfo> &Retains,
1734 DenseMap<Value *, RRInfo> &Releases,
1737 void OptimizeWeakCalls(Function &F);
1739 bool OptimizeSequences(Function &F);
1741 void OptimizeReturns(Function &F);
1743 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
1744 virtual bool doInitialization(Module &M);
1745 virtual bool runOnFunction(Function &F);
1746 virtual void releaseMemory();
1750 ObjCARCOpt() : FunctionPass(ID) {
1751 initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
1756 char ObjCARCOpt::ID = 0;
1757 INITIALIZE_PASS_BEGIN(ObjCARCOpt,
1758 "objc-arc", "ObjC ARC optimization", false, false)
1759 INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
1760 INITIALIZE_PASS_END(ObjCARCOpt,
1761 "objc-arc", "ObjC ARC optimization", false, false)
1763 Pass *llvm::createObjCARCOptPass() {
1764 return new ObjCARCOpt();
1767 void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
1768 AU.addRequired<ObjCARCAliasAnalysis>();
1769 AU.addRequired<AliasAnalysis>();
1770 // ARC optimization doesn't currently split critical edges.
1771 AU.setPreservesCFG();
1774 bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) {
1775 // Without the magic metadata tag, we have to assume this might be an
1776 // objc_retainBlock call inserted to convert a block pointer to an id,
1777 // in which case it really is needed.
1778 if (!Inst->getMetadata(CopyOnEscapeMDKind))
1781 // If the pointer "escapes" (not including being used in a call),
1782 // the copy may be needed.
1783 if (DoesObjCBlockEscape(Inst))
1786 // Otherwise, it's not needed.
1790 Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
1791 if (!RetainRVCallee) {
1792 LLVMContext &C = M->getContext();
1793 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1794 Type *Params[] = { I8X };
1795 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
1796 AttributeSet Attribute =
1797 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
1798 Attribute::get(C, Attribute::NoUnwind));
1800 M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
1803 return RetainRVCallee;
1806 Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
1807 if (!AutoreleaseRVCallee) {
1808 LLVMContext &C = M->getContext();
1809 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
1810 Type *Params[] = { I8X };
1811 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
1812 AttributeSet Attribute =
1813 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
1814 Attribute::get(C, Attribute::NoUnwind));
1815 AutoreleaseRVCallee =
1816 M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
1819 return AutoreleaseRVCallee;
1822 Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
1823 if (!ReleaseCallee) {
1824 LLVMContext &C = M->getContext();
1825 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1826 AttributeSet Attribute =
1827 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
1828 Attribute::get(C, Attribute::NoUnwind));
1830 M->getOrInsertFunction(
1832 FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
1835 return ReleaseCallee;
1838 Constant *ObjCARCOpt::getRetainCallee(Module *M) {
1839 if (!RetainCallee) {
1840 LLVMContext &C = M->getContext();
1841 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1842 AttributeSet Attribute =
1843 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
1844 Attribute::get(C, Attribute::NoUnwind));
1846 M->getOrInsertFunction(
1848 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1851 return RetainCallee;
1854 Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
1855 if (!RetainBlockCallee) {
1856 LLVMContext &C = M->getContext();
1857 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1858 // objc_retainBlock is not nounwind because it calls user copy constructors
1859 // which could theoretically throw.
1861 M->getOrInsertFunction(
1863 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1866 return RetainBlockCallee;
1869 Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
1870 if (!AutoreleaseCallee) {
1871 LLVMContext &C = M->getContext();
1872 Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
1873 AttributeSet Attribute =
1874 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
1875 Attribute::get(C, Attribute::NoUnwind));
1877 M->getOrInsertFunction(
1879 FunctionType::get(Params[0], Params, /*isVarArg=*/false),
1882 return AutoreleaseCallee;
1885 /// IsPotentialUse - Test whether the given value is possible a
1886 /// reference-counted pointer, including tests which utilize AliasAnalysis.
1887 static bool IsPotentialUse(const Value *Op, AliasAnalysis &AA) {
1888 // First make the rudimentary check.
1889 if (!IsPotentialUse(Op))
1892 // Objects in constant memory are not reference-counted.
1893 if (AA.pointsToConstantMemory(Op))
1896 // Pointers in constant memory are not pointing to reference-counted objects.
1897 if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
1898 if (AA.pointsToConstantMemory(LI->getPointerOperand()))
1901 // Otherwise assume the worst.
1905 /// CanAlterRefCount - Test whether the given instruction can result in a
1906 /// reference count modification (positive or negative) for the pointer's
1909 CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
1910 ProvenanceAnalysis &PA, InstructionClass Class) {
1912 case IC_Autorelease:
1913 case IC_AutoreleaseRV:
1915 // These operations never directly modify a reference count.
1920 ImmutableCallSite CS = static_cast<const Value *>(Inst);
1921 assert(CS && "Only calls can alter reference counts!");
1923 // See if AliasAnalysis can help us with the call.
1924 AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
1925 if (AliasAnalysis::onlyReadsMemory(MRB))
1927 if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
1928 for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
1930 const Value *Op = *I;
1931 if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
1937 // Assume the worst.
1941 /// CanUse - Test whether the given instruction can "use" the given pointer's
1942 /// object in a way that requires the reference count to be positive.
1944 CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
1945 InstructionClass Class) {
1946 // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
1947 if (Class == IC_Call)
1950 // Consider various instructions which may have pointer arguments which are
1952 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
1953 // Comparing a pointer with null, or any other constant, isn't really a use,
1954 // because we don't care what the pointer points to, or about the values
1955 // of any other dynamic reference-counted pointers.
1956 if (!IsPotentialUse(ICI->getOperand(1), *PA.getAA()))
1958 } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
1959 // For calls, just check the arguments (and not the callee operand).
1960 for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
1961 OE = CS.arg_end(); OI != OE; ++OI) {
1962 const Value *Op = *OI;
1963 if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
1967 } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
1968 // Special-case stores, because we don't care about the stored value, just
1969 // the store address.
1970 const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
1971 // If we can't tell what the underlying object was, assume there is a
1973 return IsPotentialUse(Op, *PA.getAA()) && PA.related(Op, Ptr);
1976 // Check each operand for a match.
1977 for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
1979 const Value *Op = *OI;
1980 if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op))
1986 /// CanInterruptRV - Test whether the given instruction can autorelease
1987 /// any pointer or cause an autoreleasepool pop.
1989 CanInterruptRV(InstructionClass Class) {
1991 case IC_AutoreleasepoolPop:
1994 case IC_Autorelease:
1995 case IC_AutoreleaseRV:
1996 case IC_FusedRetainAutorelease:
1997 case IC_FusedRetainAutoreleaseRV:
2005 /// DependenceKind - There are several kinds of dependence-like concepts in
2007 enum DependenceKind {
2008 NeedsPositiveRetainCount,
2009 AutoreleasePoolBoundary,
2010 CanChangeRetainCount,
2011 RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
2012 RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
2013 RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
2017 /// Depends - Test if there can be dependencies on Inst through Arg. This
2018 /// function only tests dependencies relevant for removing pairs of calls.
2020 Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
2021 ProvenanceAnalysis &PA) {
2022 // If we've reached the definition of Arg, stop.
2027 case NeedsPositiveRetainCount: {
2028 InstructionClass Class = GetInstructionClass(Inst);
2030 case IC_AutoreleasepoolPop:
2031 case IC_AutoreleasepoolPush:
2035 return CanUse(Inst, Arg, PA, Class);
2039 case AutoreleasePoolBoundary: {
2040 InstructionClass Class = GetInstructionClass(Inst);
2042 case IC_AutoreleasepoolPop:
2043 case IC_AutoreleasepoolPush:
2044 // These mark the end and begin of an autorelease pool scope.
2047 // Nothing else does this.
2052 case CanChangeRetainCount: {
2053 InstructionClass Class = GetInstructionClass(Inst);
2055 case IC_AutoreleasepoolPop:
2056 // Conservatively assume this can decrement any count.
2058 case IC_AutoreleasepoolPush:
2062 return CanAlterRefCount(Inst, Arg, PA, Class);
2066 case RetainAutoreleaseDep:
2067 switch (GetBasicInstructionClass(Inst)) {
2068 case IC_AutoreleasepoolPop:
2069 case IC_AutoreleasepoolPush:
2070 // Don't merge an objc_autorelease with an objc_retain inside a different
2071 // autoreleasepool scope.
2075 // Check for a retain of the same pointer for merging.
2076 return GetObjCArg(Inst) == Arg;
2078 // Nothing else matters for objc_retainAutorelease formation.
2082 case RetainAutoreleaseRVDep: {
2083 InstructionClass Class = GetBasicInstructionClass(Inst);
2087 // Check for a retain of the same pointer for merging.
2088 return GetObjCArg(Inst) == Arg;
2090 // Anything that can autorelease interrupts
2091 // retainAutoreleaseReturnValue formation.
2092 return CanInterruptRV(Class);
2097 return CanInterruptRV(GetBasicInstructionClass(Inst));
2100 llvm_unreachable("Invalid dependence flavor");
2103 /// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and
2104 /// find local and non-local dependencies on Arg.
2105 /// TODO: Cache results?
2107 FindDependencies(DependenceKind Flavor,
2109 BasicBlock *StartBB, Instruction *StartInst,
2110 SmallPtrSet<Instruction *, 4> &DependingInstructions,
2111 SmallPtrSet<const BasicBlock *, 4> &Visited,
2112 ProvenanceAnalysis &PA) {
2113 BasicBlock::iterator StartPos = StartInst;
2115 SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
2116 Worklist.push_back(std::make_pair(StartBB, StartPos));
2118 std::pair<BasicBlock *, BasicBlock::iterator> Pair =
2119 Worklist.pop_back_val();
2120 BasicBlock *LocalStartBB = Pair.first;
2121 BasicBlock::iterator LocalStartPos = Pair.second;
2122 BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
2124 if (LocalStartPos == StartBBBegin) {
2125 pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
2127 // If we've reached the function entry, produce a null dependence.
2128 DependingInstructions.insert(0);
2130 // Add the predecessors to the worklist.
2132 BasicBlock *PredBB = *PI;
2133 if (Visited.insert(PredBB))
2134 Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
2135 } while (++PI != PE);
2139 Instruction *Inst = --LocalStartPos;
2140 if (Depends(Flavor, Inst, Arg, PA)) {
2141 DependingInstructions.insert(Inst);
2145 } while (!Worklist.empty());
2147 // Determine whether the original StartBB post-dominates all of the blocks we
2148 // visited. If not, insert a sentinal indicating that most optimizations are
2150 for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
2151 E = Visited.end(); I != E; ++I) {
2152 const BasicBlock *BB = *I;
2155 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2156 for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
2157 const BasicBlock *Succ = *SI;
2158 if (Succ != StartBB && !Visited.count(Succ)) {
2159 DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
2166 static bool isNullOrUndef(const Value *V) {
2167 return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
2170 static bool isNoopInstruction(const Instruction *I) {
2171 return isa<BitCastInst>(I) ||
2172 (isa<GetElementPtrInst>(I) &&
2173 cast<GetElementPtrInst>(I)->hasAllZeroIndices());
2176 /// OptimizeRetainCall - Turn objc_retain into
2177 /// objc_retainAutoreleasedReturnValue if the operand is a return value.
2179 ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
2180 ImmutableCallSite CS(GetObjCArg(Retain));
2181 const Instruction *Call = CS.getInstruction();
2183 if (Call->getParent() != Retain->getParent()) return;
2185 // Check that the call is next to the retain.
2186 BasicBlock::const_iterator I = Call;
2188 while (isNoopInstruction(I)) ++I;
2192 // Turn it to an objc_retainAutoreleasedReturnValue..
2195 cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
2198 /// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into
2199 /// objc_retain if the operand is not a return value. Or, if it can be paired
2200 /// with an objc_autoreleaseReturnValue, delete the pair and return true.
2202 ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
2203 // Check for the argument being from an immediately preceding call or invoke.
2204 const Value *Arg = GetObjCArg(RetainRV);
2205 ImmutableCallSite CS(Arg);
2206 if (const Instruction *Call = CS.getInstruction()) {
2207 if (Call->getParent() == RetainRV->getParent()) {
2208 BasicBlock::const_iterator I = Call;
2210 while (isNoopInstruction(I)) ++I;
2211 if (&*I == RetainRV)
2213 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
2214 BasicBlock *RetainRVParent = RetainRV->getParent();
2215 if (II->getNormalDest() == RetainRVParent) {
2216 BasicBlock::const_iterator I = RetainRVParent->begin();
2217 while (isNoopInstruction(I)) ++I;
2218 if (&*I == RetainRV)
2224 // Check for being preceded by an objc_autoreleaseReturnValue on the same
2225 // pointer. In this case, we can delete the pair.
2226 BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
2228 do --I; while (I != Begin && isNoopInstruction(I));
2229 if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
2230 GetObjCArg(I) == Arg) {
2233 EraseInstruction(I);
2234 EraseInstruction(RetainRV);
2239 // Turn it to a plain objc_retain.
2242 cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
2246 /// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into
2247 /// objc_autorelease if the result is not used as a return value.
2249 ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) {
2250 // Check for a return of the pointer value.
2251 const Value *Ptr = GetObjCArg(AutoreleaseRV);
2252 SmallVector<const Value *, 2> Users;
2253 Users.push_back(Ptr);
2255 Ptr = Users.pop_back_val();
2256 for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
2258 const User *I = *UI;
2259 if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
2261 if (isa<BitCastInst>(I))
2264 } while (!Users.empty());
2268 cast<CallInst>(AutoreleaseRV)->
2269 setCalledFunction(getAutoreleaseCallee(F.getParent()));
2272 /// OptimizeIndividualCalls - Visit each call, one at a time, and make
2273 /// simplifications without doing any additional analysis.
2274 void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
2275 // Reset all the flags in preparation for recomputing them.
2276 UsedInThisFunction = 0;
2278 // Visit all objc_* calls in F.
2279 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
2280 Instruction *Inst = &*I++;
2282 DEBUG(dbgs() << "ObjCARCOpt: OptimizeIndividualCalls: Visiting: " <<
2285 InstructionClass Class = GetBasicInstructionClass(Inst);
2290 // Delete no-op casts. These function calls have special semantics, but
2291 // the semantics are entirely implemented via lowering in the front-end,
2292 // so by the time they reach the optimizer, they are just no-op calls
2293 // which return their argument.
2295 // There are gray areas here, as the ability to cast reference-counted
2296 // pointers to raw void* and back allows code to break ARC assumptions,
2297 // however these are currently considered to be unimportant.
2301 EraseInstruction(Inst);
2304 // If the pointer-to-weak-pointer is null, it's undefined behavior.
2307 case IC_LoadWeakRetained:
2309 case IC_DestroyWeak: {
2310 CallInst *CI = cast<CallInst>(Inst);
2311 if (isNullOrUndef(CI->getArgOperand(0))) {
2313 Type *Ty = CI->getArgOperand(0)->getType();
2314 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
2315 Constant::getNullValue(Ty),
2317 CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
2318 CI->eraseFromParent();
2325 CallInst *CI = cast<CallInst>(Inst);
2326 if (isNullOrUndef(CI->getArgOperand(0)) ||
2327 isNullOrUndef(CI->getArgOperand(1))) {
2329 Type *Ty = CI->getArgOperand(0)->getType();
2330 new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
2331 Constant::getNullValue(Ty),
2333 CI->replaceAllUsesWith(UndefValue::get(CI->getType()));
2334 CI->eraseFromParent();
2340 OptimizeRetainCall(F, Inst);
2343 if (OptimizeRetainRVCall(F, Inst))
2346 case IC_AutoreleaseRV:
2347 OptimizeAutoreleaseRVCall(F, Inst);
2351 // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
2352 if (IsAutorelease(Class) && Inst->use_empty()) {
2353 CallInst *Call = cast<CallInst>(Inst);
2354 const Value *Arg = Call->getArgOperand(0);
2355 Arg = FindSingleUseIdentifiedObject(Arg);
2360 // Create the declaration lazily.
2361 LLVMContext &C = Inst->getContext();
2363 CallInst::Create(getReleaseCallee(F.getParent()),
2364 Call->getArgOperand(0), "", Call);
2365 NewCall->setMetadata(ImpreciseReleaseMDKind,
2366 MDNode::get(C, ArrayRef<Value *>()));
2367 EraseInstruction(Call);
2373 // For functions which can never be passed stack arguments, add
2375 if (IsAlwaysTail(Class)) {
2377 cast<CallInst>(Inst)->setTailCall();
2380 // Set nounwind as needed.
2381 if (IsNoThrow(Class)) {
2383 cast<CallInst>(Inst)->setDoesNotThrow();
2386 if (!IsNoopOnNull(Class)) {
2387 UsedInThisFunction |= 1 << Class;
2391 const Value *Arg = GetObjCArg(Inst);
2393 // ARC calls with null are no-ops. Delete them.
2394 if (isNullOrUndef(Arg)) {
2397 EraseInstruction(Inst);
2401 // Keep track of which of retain, release, autorelease, and retain_block
2402 // are actually present in this function.
2403 UsedInThisFunction |= 1 << Class;
2405 // If Arg is a PHI, and one or more incoming values to the
2406 // PHI are null, and the call is control-equivalent to the PHI, and there
2407 // are no relevant side effects between the PHI and the call, the call
2408 // could be pushed up to just those paths with non-null incoming values.
2409 // For now, don't bother splitting critical edges for this.
2410 SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
2411 Worklist.push_back(std::make_pair(Inst, Arg));
2413 std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
2417 const PHINode *PN = dyn_cast<PHINode>(Arg);
2420 // Determine if the PHI has any null operands, or any incoming
2422 bool HasNull = false;
2423 bool HasCriticalEdges = false;
2424 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2426 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
2427 if (isNullOrUndef(Incoming))
2429 else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
2430 .getNumSuccessors() != 1) {
2431 HasCriticalEdges = true;
2435 // If we have null operands and no critical edges, optimize.
2436 if (!HasCriticalEdges && HasNull) {
2437 SmallPtrSet<Instruction *, 4> DependingInstructions;
2438 SmallPtrSet<const BasicBlock *, 4> Visited;
2440 // Check that there is nothing that cares about the reference
2441 // count between the call and the phi.
2444 case IC_RetainBlock:
2445 // These can always be moved up.
2448 // These can't be moved across things that care about the retain
2450 FindDependencies(NeedsPositiveRetainCount, Arg,
2451 Inst->getParent(), Inst,
2452 DependingInstructions, Visited, PA);
2454 case IC_Autorelease:
2455 // These can't be moved across autorelease pool scope boundaries.
2456 FindDependencies(AutoreleasePoolBoundary, Arg,
2457 Inst->getParent(), Inst,
2458 DependingInstructions, Visited, PA);
2461 case IC_AutoreleaseRV:
2462 // Don't move these; the RV optimization depends on the autoreleaseRV
2463 // being tail called, and the retainRV being immediately after a call
2464 // (which might still happen if we get lucky with codegen layout, but
2465 // it's not worth taking the chance).
2468 llvm_unreachable("Invalid dependence flavor");
2471 if (DependingInstructions.size() == 1 &&
2472 *DependingInstructions.begin() == PN) {
2475 // Clone the call into each predecessor that has a non-null value.
2476 CallInst *CInst = cast<CallInst>(Inst);
2477 Type *ParamTy = CInst->getArgOperand(0)->getType();
2478 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
2480 StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
2481 if (!isNullOrUndef(Incoming)) {
2482 CallInst *Clone = cast<CallInst>(CInst->clone());
2483 Value *Op = PN->getIncomingValue(i);
2484 Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
2485 if (Op->getType() != ParamTy)
2486 Op = new BitCastInst(Op, ParamTy, "", InsertPos);
2487 Clone->setArgOperand(0, Op);
2488 Clone->insertBefore(InsertPos);
2489 Worklist.push_back(std::make_pair(Clone, Incoming));
2492 // Erase the original call.
2493 EraseInstruction(CInst);
2497 } while (!Worklist.empty());
2499 DEBUG(dbgs() << "ObjCARCOpt: Finished Individual Call Queue.\n\n");
2504 /// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible
2505 /// control flow, or other CFG structures where moving code across the edge
2506 /// would result in it being executed more.
2508 ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
2509 DenseMap<const BasicBlock *, BBState> &BBStates,
2510 BBState &MyStates) const {
2511 // If any top-down local-use or possible-dec has a succ which is earlier in
2512 // the sequence, forget it.
2513 for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(),
2514 E = MyStates.top_down_ptr_end(); I != E; ++I)
2515 switch (I->second.GetSeq()) {
2518 const Value *Arg = I->first;
2519 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2520 bool SomeSuccHasSame = false;
2521 bool AllSuccsHaveSame = true;
2522 PtrState &S = I->second;
2523 succ_const_iterator SI(TI), SE(TI, false);
2525 // If the terminator is an invoke marked with the
2526 // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
2527 // ignored, for ARC purposes.
2528 if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
2531 for (; SI != SE; ++SI) {
2532 Sequence SuccSSeq = S_None;
2533 bool SuccSRRIKnownSafe = false;
2534 // If VisitBottomUp has pointer information for this successor, take
2535 // what we know about it.
2536 DenseMap<const BasicBlock *, BBState>::iterator BBI =
2538 assert(BBI != BBStates.end());
2539 const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
2540 SuccSSeq = SuccS.GetSeq();
2541 SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
2544 case S_CanRelease: {
2545 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
2546 S.ClearSequenceProgress();
2552 SomeSuccHasSame = true;
2556 case S_MovableRelease:
2557 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
2558 AllSuccsHaveSame = false;
2561 llvm_unreachable("bottom-up pointer in retain state!");
2564 // If the state at the other end of any of the successor edges
2565 // matches the current state, require all edges to match. This
2566 // guards against loops in the middle of a sequence.
2567 if (SomeSuccHasSame && !AllSuccsHaveSame)
2568 S.ClearSequenceProgress();
2571 case S_CanRelease: {
2572 const Value *Arg = I->first;
2573 const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
2574 bool SomeSuccHasSame = false;
2575 bool AllSuccsHaveSame = true;
2576 PtrState &S = I->second;
2577 succ_const_iterator SI(TI), SE(TI, false);
2579 // If the terminator is an invoke marked with the
2580 // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
2581 // ignored, for ARC purposes.
2582 if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
2585 for (; SI != SE; ++SI) {
2586 Sequence SuccSSeq = S_None;
2587 bool SuccSRRIKnownSafe = false;
2588 // If VisitBottomUp has pointer information for this successor, take
2589 // what we know about it.
2590 DenseMap<const BasicBlock *, BBState>::iterator BBI =
2592 assert(BBI != BBStates.end());
2593 const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
2594 SuccSSeq = SuccS.GetSeq();
2595 SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
2598 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
2599 S.ClearSequenceProgress();
2605 SomeSuccHasSame = true;
2609 case S_MovableRelease:
2611 if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
2612 AllSuccsHaveSame = false;
2615 llvm_unreachable("bottom-up pointer in retain state!");
2618 // If the state at the other end of any of the successor edges
2619 // matches the current state, require all edges to match. This
2620 // guards against loops in the middle of a sequence.
2621 if (SomeSuccHasSame && !AllSuccsHaveSame)
2622 S.ClearSequenceProgress();
2629 ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
2631 MapVector<Value *, RRInfo> &Retains,
2632 BBState &MyStates) {
2633 bool NestingDetected = false;
2634 InstructionClass Class = GetInstructionClass(Inst);
2635 const Value *Arg = 0;
2639 Arg = GetObjCArg(Inst);
2641 PtrState &S = MyStates.getPtrBottomUpState(Arg);
2643 // If we see two releases in a row on the same pointer. If so, make
2644 // a note, and we'll cicle back to revisit it after we've
2645 // hopefully eliminated the second release, which may allow us to
2646 // eliminate the first release too.
2647 // Theoretically we could implement removal of nested retain+release
2648 // pairs by making PtrState hold a stack of states, but this is
2649 // simple and avoids adding overhead for the non-nested case.
2650 if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease)
2651 NestingDetected = true;
2653 MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
2654 S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release);
2655 S.RRI.ReleaseMetadata = ReleaseMetadata;
2656 S.RRI.KnownSafe = S.IsKnownIncremented();
2657 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
2658 S.RRI.Calls.insert(Inst);
2660 S.SetKnownPositiveRefCount();
2663 case IC_RetainBlock:
2664 // An objc_retainBlock call with just a use may need to be kept,
2665 // because it may be copying a block from the stack to the heap.
2666 if (!IsRetainBlockOptimizable(Inst))
2671 Arg = GetObjCArg(Inst);
2673 PtrState &S = MyStates.getPtrBottomUpState(Arg);
2674 S.SetKnownPositiveRefCount();
2676 switch (S.GetSeq()) {
2679 case S_MovableRelease:
2681 S.RRI.ReverseInsertPts.clear();
2684 // Don't do retain+release tracking for IC_RetainRV, because it's
2685 // better to let it remain as the first instruction after a call.
2686 if (Class != IC_RetainRV) {
2687 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
2688 Retains[Inst] = S.RRI;
2690 S.ClearSequenceProgress();
2695 llvm_unreachable("bottom-up pointer in retain state!");
2697 return NestingDetected;
2699 case IC_AutoreleasepoolPop:
2700 // Conservatively, clear MyStates for all known pointers.
2701 MyStates.clearBottomUpPointers();
2702 return NestingDetected;
2703 case IC_AutoreleasepoolPush:
2705 // These are irrelevant.
2706 return NestingDetected;
2711 // Consider any other possible effects of this instruction on each
2712 // pointer being tracked.
2713 for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
2714 ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
2715 const Value *Ptr = MI->first;
2717 continue; // Handled above.
2718 PtrState &S = MI->second;
2719 Sequence Seq = S.GetSeq();
2721 // Check for possible releases.
2722 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
2726 S.SetSeq(S_CanRelease);
2730 case S_MovableRelease:
2735 llvm_unreachable("bottom-up pointer in retain state!");
2739 // Check for possible direct uses.
2742 case S_MovableRelease:
2743 if (CanUse(Inst, Ptr, PA, Class)) {
2744 assert(S.RRI.ReverseInsertPts.empty());
2745 // If this is an invoke instruction, we're scanning it as part of
2746 // one of its successor blocks, since we can't insert code after it
2747 // in its own block, and we don't want to split critical edges.
2748 if (isa<InvokeInst>(Inst))
2749 S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
2751 S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
2753 } else if (Seq == S_Release &&
2754 (Class == IC_User || Class == IC_CallOrUser)) {
2755 // Non-movable releases depend on any possible objc pointer use.
2757 assert(S.RRI.ReverseInsertPts.empty());
2758 // As above; handle invoke specially.
2759 if (isa<InvokeInst>(Inst))
2760 S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
2762 S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
2766 if (CanUse(Inst, Ptr, PA, Class))
2774 llvm_unreachable("bottom-up pointer in retain state!");
2778 return NestingDetected;
2782 ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
2783 DenseMap<const BasicBlock *, BBState> &BBStates,
2784 MapVector<Value *, RRInfo> &Retains) {
2785 bool NestingDetected = false;
2786 BBState &MyStates = BBStates[BB];
2788 // Merge the states from each successor to compute the initial state
2789 // for the current block.
2790 BBState::edge_iterator SI(MyStates.succ_begin()),
2791 SE(MyStates.succ_end());
2793 const BasicBlock *Succ = *SI;
2794 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
2795 assert(I != BBStates.end());
2796 MyStates.InitFromSucc(I->second);
2798 for (; SI != SE; ++SI) {
2800 I = BBStates.find(Succ);
2801 assert(I != BBStates.end());
2802 MyStates.MergeSucc(I->second);
2806 // Visit all the instructions, bottom-up.
2807 for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
2808 Instruction *Inst = llvm::prior(I);
2810 // Invoke instructions are visited as part of their successors (below).
2811 if (isa<InvokeInst>(Inst))
2814 NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
2817 // If there's a predecessor with an invoke, visit the invoke as if it were
2818 // part of this block, since we can't insert code after an invoke in its own
2819 // block, and we don't want to split critical edges.
2820 for (BBState::edge_iterator PI(MyStates.pred_begin()),
2821 PE(MyStates.pred_end()); PI != PE; ++PI) {
2822 BasicBlock *Pred = *PI;
2823 if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back()))
2824 NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates);
2827 return NestingDetected;
2831 ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst,
2832 DenseMap<Value *, RRInfo> &Releases,
2833 BBState &MyStates) {
2834 bool NestingDetected = false;
2835 InstructionClass Class = GetInstructionClass(Inst);
2836 const Value *Arg = 0;
2839 case IC_RetainBlock:
2840 // An objc_retainBlock call with just a use may need to be kept,
2841 // because it may be copying a block from the stack to the heap.
2842 if (!IsRetainBlockOptimizable(Inst))
2847 Arg = GetObjCArg(Inst);
2849 PtrState &S = MyStates.getPtrTopDownState(Arg);
2851 // Don't do retain+release tracking for IC_RetainRV, because it's
2852 // better to let it remain as the first instruction after a call.
2853 if (Class != IC_RetainRV) {
2854 // If we see two retains in a row on the same pointer. If so, make
2855 // a note, and we'll cicle back to revisit it after we've
2856 // hopefully eliminated the second retain, which may allow us to
2857 // eliminate the first retain too.
2858 // Theoretically we could implement removal of nested retain+release
2859 // pairs by making PtrState hold a stack of states, but this is
2860 // simple and avoids adding overhead for the non-nested case.
2861 if (S.GetSeq() == S_Retain)
2862 NestingDetected = true;
2864 S.ResetSequenceProgress(S_Retain);
2865 S.RRI.IsRetainBlock = Class == IC_RetainBlock;
2866 S.RRI.KnownSafe = S.IsKnownIncremented();
2867 S.RRI.Calls.insert(Inst);
2870 S.SetKnownPositiveRefCount();
2872 // A retain can be a potential use; procede to the generic checking
2877 Arg = GetObjCArg(Inst);
2879 PtrState &S = MyStates.getPtrTopDownState(Arg);
2882 switch (S.GetSeq()) {
2885 S.RRI.ReverseInsertPts.clear();
2888 S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
2889 S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
2890 Releases[Inst] = S.RRI;
2891 S.ClearSequenceProgress();
2897 case S_MovableRelease:
2898 llvm_unreachable("top-down pointer in release state!");
2902 case IC_AutoreleasepoolPop:
2903 // Conservatively, clear MyStates for all known pointers.
2904 MyStates.clearTopDownPointers();
2905 return NestingDetected;
2906 case IC_AutoreleasepoolPush:
2908 // These are irrelevant.
2909 return NestingDetected;
2914 // Consider any other possible effects of this instruction on each
2915 // pointer being tracked.
2916 for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
2917 ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
2918 const Value *Ptr = MI->first;
2920 continue; // Handled above.
2921 PtrState &S = MI->second;
2922 Sequence Seq = S.GetSeq();
2924 // Check for possible releases.
2925 if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
2929 S.SetSeq(S_CanRelease);
2930 assert(S.RRI.ReverseInsertPts.empty());
2931 S.RRI.ReverseInsertPts.insert(Inst);
2933 // One call can't cause a transition from S_Retain to S_CanRelease
2934 // and S_CanRelease to S_Use. If we've made the first transition,
2943 case S_MovableRelease:
2944 llvm_unreachable("top-down pointer in release state!");
2948 // Check for possible direct uses.
2951 if (CanUse(Inst, Ptr, PA, Class))
2960 case S_MovableRelease:
2961 llvm_unreachable("top-down pointer in release state!");
2965 return NestingDetected;
2969 ObjCARCOpt::VisitTopDown(BasicBlock *BB,
2970 DenseMap<const BasicBlock *, BBState> &BBStates,
2971 DenseMap<Value *, RRInfo> &Releases) {
2972 bool NestingDetected = false;
2973 BBState &MyStates = BBStates[BB];
2975 // Merge the states from each predecessor to compute the initial state
2976 // for the current block.
2977 BBState::edge_iterator PI(MyStates.pred_begin()),
2978 PE(MyStates.pred_end());
2980 const BasicBlock *Pred = *PI;
2981 DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
2982 assert(I != BBStates.end());
2983 MyStates.InitFromPred(I->second);
2985 for (; PI != PE; ++PI) {
2987 I = BBStates.find(Pred);
2988 assert(I != BBStates.end());
2989 MyStates.MergePred(I->second);
2993 // Visit all the instructions, top-down.
2994 for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
2995 Instruction *Inst = I;
2996 NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
2999 CheckForCFGHazards(BB, BBStates, MyStates);
3000 return NestingDetected;
3004 ComputePostOrders(Function &F,
3005 SmallVectorImpl<BasicBlock *> &PostOrder,
3006 SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder,
3007 unsigned NoObjCARCExceptionsMDKind,
3008 DenseMap<const BasicBlock *, BBState> &BBStates) {
3009 /// Visited - The visited set, for doing DFS walks.
3010 SmallPtrSet<BasicBlock *, 16> Visited;
3012 // Do DFS, computing the PostOrder.
3013 SmallPtrSet<BasicBlock *, 16> OnStack;
3014 SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack;
3016 // Functions always have exactly one entry block, and we don't have
3017 // any other block that we treat like an entry block.
3018 BasicBlock *EntryBB = &F.getEntryBlock();
3019 BBState &MyStates = BBStates[EntryBB];
3020 MyStates.SetAsEntry();
3021 TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back());
3022 SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI)));
3023 Visited.insert(EntryBB);
3024 OnStack.insert(EntryBB);
3027 BasicBlock *CurrBB = SuccStack.back().first;
3028 TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back());
3029 succ_iterator SE(TI, false);
3031 // If the terminator is an invoke marked with the
3032 // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be
3033 // ignored, for ARC purposes.
3034 if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind))
3037 while (SuccStack.back().second != SE) {
3038 BasicBlock *SuccBB = *SuccStack.back().second++;
3039 if (Visited.insert(SuccBB)) {
3040 TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back());
3041 SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI)));
3042 BBStates[CurrBB].addSucc(SuccBB);
3043 BBState &SuccStates = BBStates[SuccBB];
3044 SuccStates.addPred(CurrBB);
3045 OnStack.insert(SuccBB);
3049 if (!OnStack.count(SuccBB)) {
3050 BBStates[CurrBB].addSucc(SuccBB);
3051 BBStates[SuccBB].addPred(CurrBB);
3054 OnStack.erase(CurrBB);
3055 PostOrder.push_back(CurrBB);
3056 SuccStack.pop_back();
3057 } while (!SuccStack.empty());
3061 // Do reverse-CFG DFS, computing the reverse-CFG PostOrder.
3062 // Functions may have many exits, and there also blocks which we treat
3063 // as exits due to ignored edges.
3064 SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack;
3065 for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
3066 BasicBlock *ExitBB = I;
3067 BBState &MyStates = BBStates[ExitBB];
3068 if (!MyStates.isExit())
3071 MyStates.SetAsExit();
3073 PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin()));
3074 Visited.insert(ExitBB);
3075 while (!PredStack.empty()) {
3076 reverse_dfs_next_succ:
3077 BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end();
3078 while (PredStack.back().second != PE) {
3079 BasicBlock *BB = *PredStack.back().second++;
3080 if (Visited.insert(BB)) {
3081 PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin()));
3082 goto reverse_dfs_next_succ;
3085 ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first);
3090 // Visit - Visit the function both top-down and bottom-up.
3092 ObjCARCOpt::Visit(Function &F,
3093 DenseMap<const BasicBlock *, BBState> &BBStates,
3094 MapVector<Value *, RRInfo> &Retains,
3095 DenseMap<Value *, RRInfo> &Releases) {
3097 // Use reverse-postorder traversals, because we magically know that loops
3098 // will be well behaved, i.e. they won't repeatedly call retain on a single
3099 // pointer without doing a release. We can't use the ReversePostOrderTraversal
3100 // class here because we want the reverse-CFG postorder to consider each
3101 // function exit point, and we want to ignore selected cycle edges.
3102 SmallVector<BasicBlock *, 16> PostOrder;
3103 SmallVector<BasicBlock *, 16> ReverseCFGPostOrder;
3104 ComputePostOrders(F, PostOrder, ReverseCFGPostOrder,
3105 NoObjCARCExceptionsMDKind,
3108 // Use reverse-postorder on the reverse CFG for bottom-up.
3109 bool BottomUpNestingDetected = false;
3110 for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
3111 ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend();
3113 BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains);
3115 // Use reverse-postorder for top-down.
3116 bool TopDownNestingDetected = false;
3117 for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
3118 PostOrder.rbegin(), E = PostOrder.rend();
3120 TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases);
3122 return TopDownNestingDetected && BottomUpNestingDetected;
3125 /// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove.
3126 void ObjCARCOpt::MoveCalls(Value *Arg,
3127 RRInfo &RetainsToMove,
3128 RRInfo &ReleasesToMove,
3129 MapVector<Value *, RRInfo> &Retains,
3130 DenseMap<Value *, RRInfo> &Releases,
3131 SmallVectorImpl<Instruction *> &DeadInsts,
3133 Type *ArgTy = Arg->getType();
3134 Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
3136 // Insert the new retain and release calls.
3137 for (SmallPtrSet<Instruction *, 2>::const_iterator
3138 PI = ReleasesToMove.ReverseInsertPts.begin(),
3139 PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
3140 Instruction *InsertPt = *PI;
3141 Value *MyArg = ArgTy == ParamTy ? Arg :
3142 new BitCastInst(Arg, ParamTy, "", InsertPt);
3144 CallInst::Create(RetainsToMove.IsRetainBlock ?
3145 getRetainBlockCallee(M) : getRetainCallee(M),
3146 MyArg, "", InsertPt);
3147 Call->setDoesNotThrow();
3148 if (RetainsToMove.IsRetainBlock)
3149 Call->setMetadata(CopyOnEscapeMDKind,
3150 MDNode::get(M->getContext(), ArrayRef<Value *>()));
3152 Call->setTailCall();
3154 for (SmallPtrSet<Instruction *, 2>::const_iterator
3155 PI = RetainsToMove.ReverseInsertPts.begin(),
3156 PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
3157 Instruction *InsertPt = *PI;
3158 Value *MyArg = ArgTy == ParamTy ? Arg :
3159 new BitCastInst(Arg, ParamTy, "", InsertPt);
3160 CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
3162 // Attach a clang.imprecise_release metadata tag, if appropriate.
3163 if (MDNode *M = ReleasesToMove.ReleaseMetadata)
3164 Call->setMetadata(ImpreciseReleaseMDKind, M);
3165 Call->setDoesNotThrow();
3166 if (ReleasesToMove.IsTailCallRelease)
3167 Call->setTailCall();
3170 // Delete the original retain and release calls.
3171 for (SmallPtrSet<Instruction *, 2>::const_iterator
3172 AI = RetainsToMove.Calls.begin(),
3173 AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
3174 Instruction *OrigRetain = *AI;
3175 Retains.blot(OrigRetain);
3176 DeadInsts.push_back(OrigRetain);
3178 for (SmallPtrSet<Instruction *, 2>::const_iterator
3179 AI = ReleasesToMove.Calls.begin(),
3180 AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
3181 Instruction *OrigRelease = *AI;
3182 Releases.erase(OrigRelease);
3183 DeadInsts.push_back(OrigRelease);
3187 /// PerformCodePlacement - Identify pairings between the retains and releases,
3188 /// and delete and/or move them.
3190 ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
3192 MapVector<Value *, RRInfo> &Retains,
3193 DenseMap<Value *, RRInfo> &Releases,
3195 bool AnyPairsCompletelyEliminated = false;
3196 RRInfo RetainsToMove;
3197 RRInfo ReleasesToMove;
3198 SmallVector<Instruction *, 4> NewRetains;
3199 SmallVector<Instruction *, 4> NewReleases;
3200 SmallVector<Instruction *, 8> DeadInsts;
3202 // Visit each retain.
3203 for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
3204 E = Retains.end(); I != E; ++I) {
3205 Value *V = I->first;
3206 if (!V) continue; // blotted
3208 Instruction *Retain = cast<Instruction>(V);
3209 Value *Arg = GetObjCArg(Retain);
3211 // If the object being released is in static or stack storage, we know it's
3212 // not being managed by ObjC reference counting, so we can delete pairs
3213 // regardless of what possible decrements or uses lie between them.
3214 bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
3216 // A constant pointer can't be pointing to an object on the heap. It may
3217 // be reference-counted, but it won't be deleted.
3218 if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
3219 if (const GlobalVariable *GV =
3220 dyn_cast<GlobalVariable>(
3221 StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
3222 if (GV->isConstant())
3225 // If a pair happens in a region where it is known that the reference count
3226 // is already incremented, we can similarly ignore possible decrements.
3227 bool KnownSafeTD = true, KnownSafeBU = true;
3229 // Connect the dots between the top-down-collected RetainsToMove and
3230 // bottom-up-collected ReleasesToMove to form sets of related calls.
3231 // This is an iterative process so that we connect multiple releases
3232 // to multiple retains if needed.
3233 unsigned OldDelta = 0;
3234 unsigned NewDelta = 0;
3235 unsigned OldCount = 0;
3236 unsigned NewCount = 0;
3237 bool FirstRelease = true;
3238 bool FirstRetain = true;
3239 NewRetains.push_back(Retain);
3241 for (SmallVectorImpl<Instruction *>::const_iterator
3242 NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
3243 Instruction *NewRetain = *NI;
3244 MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
3245 assert(It != Retains.end());
3246 const RRInfo &NewRetainRRI = It->second;
3247 KnownSafeTD &= NewRetainRRI.KnownSafe;
3248 for (SmallPtrSet<Instruction *, 2>::const_iterator
3249 LI = NewRetainRRI.Calls.begin(),
3250 LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
3251 Instruction *NewRetainRelease = *LI;
3252 DenseMap<Value *, RRInfo>::const_iterator Jt =
3253 Releases.find(NewRetainRelease);
3254 if (Jt == Releases.end())
3256 const RRInfo &NewRetainReleaseRRI = Jt->second;
3257 assert(NewRetainReleaseRRI.Calls.count(NewRetain));
3258 if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
3260 BBStates[NewRetainRelease->getParent()].GetAllPathCount();
3262 // Merge the ReleaseMetadata and IsTailCallRelease values.
3264 ReleasesToMove.ReleaseMetadata =
3265 NewRetainReleaseRRI.ReleaseMetadata;
3266 ReleasesToMove.IsTailCallRelease =
3267 NewRetainReleaseRRI.IsTailCallRelease;
3268 FirstRelease = false;
3270 if (ReleasesToMove.ReleaseMetadata !=
3271 NewRetainReleaseRRI.ReleaseMetadata)
3272 ReleasesToMove.ReleaseMetadata = 0;
3273 if (ReleasesToMove.IsTailCallRelease !=
3274 NewRetainReleaseRRI.IsTailCallRelease)
3275 ReleasesToMove.IsTailCallRelease = false;
3278 // Collect the optimal insertion points.
3280 for (SmallPtrSet<Instruction *, 2>::const_iterator
3281 RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
3282 RE = NewRetainReleaseRRI.ReverseInsertPts.end();
3284 Instruction *RIP = *RI;
3285 if (ReleasesToMove.ReverseInsertPts.insert(RIP))
3286 NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
3288 NewReleases.push_back(NewRetainRelease);
3293 if (NewReleases.empty()) break;
3295 // Back the other way.
3296 for (SmallVectorImpl<Instruction *>::const_iterator
3297 NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
3298 Instruction *NewRelease = *NI;
3299 DenseMap<Value *, RRInfo>::const_iterator It =
3300 Releases.find(NewRelease);
3301 assert(It != Releases.end());
3302 const RRInfo &NewReleaseRRI = It->second;
3303 KnownSafeBU &= NewReleaseRRI.KnownSafe;
3304 for (SmallPtrSet<Instruction *, 2>::const_iterator
3305 LI = NewReleaseRRI.Calls.begin(),
3306 LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
3307 Instruction *NewReleaseRetain = *LI;
3308 MapVector<Value *, RRInfo>::const_iterator Jt =
3309 Retains.find(NewReleaseRetain);
3310 if (Jt == Retains.end())
3312 const RRInfo &NewReleaseRetainRRI = Jt->second;
3313 assert(NewReleaseRetainRRI.Calls.count(NewRelease));
3314 if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
3315 unsigned PathCount =
3316 BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
3317 OldDelta += PathCount;
3318 OldCount += PathCount;
3320 // Merge the IsRetainBlock values.
3322 RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
3323 FirstRetain = false;
3324 } else if (ReleasesToMove.IsRetainBlock !=
3325 NewReleaseRetainRRI.IsRetainBlock)
3326 // It's not possible to merge the sequences if one uses
3327 // objc_retain and the other uses objc_retainBlock.
3330 // Collect the optimal insertion points.
3332 for (SmallPtrSet<Instruction *, 2>::const_iterator
3333 RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
3334 RE = NewReleaseRetainRRI.ReverseInsertPts.end();
3336 Instruction *RIP = *RI;
3337 if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
3338 PathCount = BBStates[RIP->getParent()].GetAllPathCount();
3339 NewDelta += PathCount;
3340 NewCount += PathCount;
3343 NewRetains.push_back(NewReleaseRetain);
3347 NewReleases.clear();
3348 if (NewRetains.empty()) break;
3351 // If the pointer is known incremented or nested, we can safely delete the
3352 // pair regardless of what's between them.
3353 if (KnownSafeTD || KnownSafeBU) {
3354 RetainsToMove.ReverseInsertPts.clear();
3355 ReleasesToMove.ReverseInsertPts.clear();
3358 // Determine whether the new insertion points we computed preserve the
3359 // balance of retain and release calls through the program.
3360 // TODO: If the fully aggressive solution isn't valid, try to find a
3361 // less aggressive solution which is.
3366 // Determine whether the original call points are balanced in the retain and
3367 // release calls through the program. If not, conservatively don't touch
3369 // TODO: It's theoretically possible to do code motion in this case, as
3370 // long as the existing imbalances are maintained.
3374 // Ok, everything checks out and we're all set. Let's move some code!
3376 assert(OldCount != 0 && "Unreachable code?");
3377 AnyPairsCompletelyEliminated = NewCount == 0;
3378 NumRRs += OldCount - NewCount;
3379 MoveCalls(Arg, RetainsToMove, ReleasesToMove,
3380 Retains, Releases, DeadInsts, M);
3383 NewReleases.clear();
3385 RetainsToMove.clear();
3386 ReleasesToMove.clear();
3389 // Now that we're done moving everything, we can delete the newly dead
3390 // instructions, as we no longer need them as insert points.
3391 while (!DeadInsts.empty())
3392 EraseInstruction(DeadInsts.pop_back_val());
3394 return AnyPairsCompletelyEliminated;
3397 /// OptimizeWeakCalls - Weak pointer optimizations.
3398 void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
3399 // First, do memdep-style RLE and S2L optimizations. We can't use memdep
3400 // itself because it uses AliasAnalysis and we need to do provenance
3402 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
3403 Instruction *Inst = &*I++;
3405 DEBUG(dbgs() << "ObjCARCOpt: OptimizeWeakCalls: Visiting: " << *Inst <<
3408 InstructionClass Class = GetBasicInstructionClass(Inst);
3409 if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
3412 // Delete objc_loadWeak calls with no users.
3413 if (Class == IC_LoadWeak && Inst->use_empty()) {
3414 Inst->eraseFromParent();
3418 // TODO: For now, just look for an earlier available version of this value
3419 // within the same block. Theoretically, we could do memdep-style non-local
3420 // analysis too, but that would want caching. A better approach would be to
3421 // use the technique that EarlyCSE uses.
3422 inst_iterator Current = llvm::prior(I);
3423 BasicBlock *CurrentBB = Current.getBasicBlockIterator();
3424 for (BasicBlock::iterator B = CurrentBB->begin(),
3425 J = Current.getInstructionIterator();
3427 Instruction *EarlierInst = &*llvm::prior(J);
3428 InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
3429 switch (EarlierClass) {
3431 case IC_LoadWeakRetained: {
3432 // If this is loading from the same pointer, replace this load's value
3434 CallInst *Call = cast<CallInst>(Inst);
3435 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
3436 Value *Arg = Call->getArgOperand(0);
3437 Value *EarlierArg = EarlierCall->getArgOperand(0);
3438 switch (PA.getAA()->alias(Arg, EarlierArg)) {
3439 case AliasAnalysis::MustAlias:
3441 // If the load has a builtin retain, insert a plain retain for it.
3442 if (Class == IC_LoadWeakRetained) {
3444 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
3448 // Zap the fully redundant load.
3449 Call->replaceAllUsesWith(EarlierCall);
3450 Call->eraseFromParent();
3452 case AliasAnalysis::MayAlias:
3453 case AliasAnalysis::PartialAlias:
3455 case AliasAnalysis::NoAlias:
3462 // If this is storing to the same pointer and has the same size etc.
3463 // replace this load's value with the stored value.
3464 CallInst *Call = cast<CallInst>(Inst);
3465 CallInst *EarlierCall = cast<CallInst>(EarlierInst);
3466 Value *Arg = Call->getArgOperand(0);
3467 Value *EarlierArg = EarlierCall->getArgOperand(0);
3468 switch (PA.getAA()->alias(Arg, EarlierArg)) {
3469 case AliasAnalysis::MustAlias:
3471 // If the load has a builtin retain, insert a plain retain for it.
3472 if (Class == IC_LoadWeakRetained) {
3474 CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
3478 // Zap the fully redundant load.
3479 Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
3480 Call->eraseFromParent();
3482 case AliasAnalysis::MayAlias:
3483 case AliasAnalysis::PartialAlias:
3485 case AliasAnalysis::NoAlias:
3492 // TOOD: Grab the copied value.
3494 case IC_AutoreleasepoolPush:
3497 // Weak pointers are only modified through the weak entry points
3498 // (and arbitrary calls, which could call the weak entry points).
3501 // Anything else could modify the weak pointer.
3508 // Then, for each destroyWeak with an alloca operand, check to see if
3509 // the alloca and all its users can be zapped.
3510 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
3511 Instruction *Inst = &*I++;
3512 InstructionClass Class = GetBasicInstructionClass(Inst);
3513 if (Class != IC_DestroyWeak)
3516 CallInst *Call = cast<CallInst>(Inst);
3517 Value *Arg = Call->getArgOperand(0);
3518 if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
3519 for (Value::use_iterator UI = Alloca->use_begin(),
3520 UE = Alloca->use_end(); UI != UE; ++UI) {
3521 const Instruction *UserInst = cast<Instruction>(*UI);
3522 switch (GetBasicInstructionClass(UserInst)) {
3525 case IC_DestroyWeak:
3532 for (Value::use_iterator UI = Alloca->use_begin(),
3533 UE = Alloca->use_end(); UI != UE; ) {
3534 CallInst *UserInst = cast<CallInst>(*UI++);
3535 switch (GetBasicInstructionClass(UserInst)) {
3538 // These functions return their second argument.
3539 UserInst->replaceAllUsesWith(UserInst->getArgOperand(1));
3541 case IC_DestroyWeak:
3545 llvm_unreachable("alloca really is used!");
3547 UserInst->eraseFromParent();
3549 Alloca->eraseFromParent();
3554 DEBUG(dbgs() << "ObjCARCOpt: Finished visiting weak calls.\n\n");
3558 /// OptimizeSequences - Identify program paths which execute sequences of
3559 /// retains and releases which can be eliminated.
3560 bool ObjCARCOpt::OptimizeSequences(Function &F) {
3561 /// Releases, Retains - These are used to store the results of the main flow
3562 /// analysis. These use Value* as the key instead of Instruction* so that the
3563 /// map stays valid when we get around to rewriting code and calls get
3564 /// replaced by arguments.
3565 DenseMap<Value *, RRInfo> Releases;
3566 MapVector<Value *, RRInfo> Retains;
3568 /// BBStates, This is used during the traversal of the function to track the
3569 /// states for each identified object at each block.
3570 DenseMap<const BasicBlock *, BBState> BBStates;
3572 // Analyze the CFG of the function, and all instructions.
3573 bool NestingDetected = Visit(F, BBStates, Retains, Releases);
3576 return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
3580 /// OptimizeReturns - Look for this pattern:
3582 /// %call = call i8* @something(...)
3583 /// %2 = call i8* @objc_retain(i8* %call)
3584 /// %3 = call i8* @objc_autorelease(i8* %2)
3587 /// And delete the retain and autorelease.
3589 /// Otherwise if it's just this:
3591 /// %3 = call i8* @objc_autorelease(i8* %2)
3594 /// convert the autorelease to autoreleaseRV.
3595 void ObjCARCOpt::OptimizeReturns(Function &F) {
3596 if (!F.getReturnType()->isPointerTy())
3599 SmallPtrSet<Instruction *, 4> DependingInstructions;
3600 SmallPtrSet<const BasicBlock *, 4> Visited;
3601 for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
3602 BasicBlock *BB = FI;
3603 ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
3605 DEBUG(dbgs() << "ObjCARCOpt: OptimizeReturns: Visiting: " << *Ret << "\n");
3609 const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
3610 FindDependencies(NeedsPositiveRetainCount, Arg,
3611 BB, Ret, DependingInstructions, Visited, PA);
3612 if (DependingInstructions.size() != 1)
3616 CallInst *Autorelease =
3617 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3620 InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
3621 if (!IsAutorelease(AutoreleaseClass))
3623 if (GetObjCArg(Autorelease) != Arg)
3626 DependingInstructions.clear();
3629 // Check that there is nothing that can affect the reference
3630 // count between the autorelease and the retain.
3631 FindDependencies(CanChangeRetainCount, Arg,
3632 BB, Autorelease, DependingInstructions, Visited, PA);
3633 if (DependingInstructions.size() != 1)
3638 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3640 // Check that we found a retain with the same argument.
3642 !IsRetain(GetBasicInstructionClass(Retain)) ||
3643 GetObjCArg(Retain) != Arg)
3646 DependingInstructions.clear();
3649 // Convert the autorelease to an autoreleaseRV, since it's
3650 // returning the value.
3651 if (AutoreleaseClass == IC_Autorelease) {
3652 Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
3653 AutoreleaseClass = IC_AutoreleaseRV;
3656 // Check that there is nothing that can affect the reference
3657 // count between the retain and the call.
3658 // Note that Retain need not be in BB.
3659 FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
3660 DependingInstructions, Visited, PA);
3661 if (DependingInstructions.size() != 1)
3666 dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3668 // Check that the pointer is the return value of the call.
3669 if (!Call || Arg != Call)
3672 // Check that the call is a regular call.
3673 InstructionClass Class = GetBasicInstructionClass(Call);
3674 if (Class != IC_CallOrUser && Class != IC_Call)
3677 // If so, we can zap the retain and autorelease.
3680 EraseInstruction(Retain);
3681 EraseInstruction(Autorelease);
3687 DependingInstructions.clear();
3691 DEBUG(dbgs() << "ObjCARCOpt: OptimizeReturns: Finished visiting returns.\n\n");
3695 bool ObjCARCOpt::doInitialization(Module &M) {
3699 // If nothing in the Module uses ARC, don't do anything.
3700 Run = ModuleHasARC(M);
3704 // Identify the imprecise release metadata kind.
3705 ImpreciseReleaseMDKind =
3706 M.getContext().getMDKindID("clang.imprecise_release");
3707 CopyOnEscapeMDKind =
3708 M.getContext().getMDKindID("clang.arc.copy_on_escape");
3709 NoObjCARCExceptionsMDKind =
3710 M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions");
3712 // Intuitively, objc_retain and others are nocapture, however in practice
3713 // they are not, because they return their argument value. And objc_release
3714 // calls finalizers which can have arbitrary side effects.
3716 // These are initialized lazily.
3718 AutoreleaseRVCallee = 0;
3721 RetainBlockCallee = 0;
3722 AutoreleaseCallee = 0;
3727 bool ObjCARCOpt::runOnFunction(Function &F) {
3731 // If nothing in the Module uses ARC, don't do anything.
3737 PA.setAA(&getAnalysis<AliasAnalysis>());
3739 // This pass performs several distinct transformations. As a compile-time aid
3740 // when compiling code that isn't ObjC, skip these if the relevant ObjC
3741 // library functions aren't declared.
3743 // Preliminary optimizations. This also computs UsedInThisFunction.
3744 OptimizeIndividualCalls(F);
3746 // Optimizations for weak pointers.
3747 if (UsedInThisFunction & ((1 << IC_LoadWeak) |
3748 (1 << IC_LoadWeakRetained) |
3749 (1 << IC_StoreWeak) |
3750 (1 << IC_InitWeak) |
3751 (1 << IC_CopyWeak) |
3752 (1 << IC_MoveWeak) |
3753 (1 << IC_DestroyWeak)))
3754 OptimizeWeakCalls(F);
3756 // Optimizations for retain+release pairs.
3757 if (UsedInThisFunction & ((1 << IC_Retain) |
3758 (1 << IC_RetainRV) |
3759 (1 << IC_RetainBlock)))
3760 if (UsedInThisFunction & (1 << IC_Release))
3761 // Run OptimizeSequences until it either stops making changes or
3762 // no retain+release pair nesting is detected.
3763 while (OptimizeSequences(F)) {}
3765 // Optimizations if objc_autorelease is used.
3766 if (UsedInThisFunction & ((1 << IC_Autorelease) |
3767 (1 << IC_AutoreleaseRV)))
3773 void ObjCARCOpt::releaseMemory() {
3777 //===----------------------------------------------------------------------===//
3779 //===----------------------------------------------------------------------===//
3781 // TODO: ObjCARCContract could insert PHI nodes when uses aren't
3782 // dominated by single calls.
3784 #include "llvm/Analysis/Dominators.h"
3785 #include "llvm/InlineAsm.h"
3786 #include "llvm/Operator.h"
3788 STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
3791 /// ObjCARCContract - Late ARC optimizations. These change the IR in a way
3792 /// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late.
3793 class ObjCARCContract : public FunctionPass {
3797 ProvenanceAnalysis PA;
3799 /// Run - A flag indicating whether this optimization pass should run.
3802 /// StoreStrongCallee, etc. - Declarations for ObjC runtime
3803 /// functions, for use in creating calls to them. These are initialized
3804 /// lazily to avoid cluttering up the Module with unused declarations.
3805 Constant *StoreStrongCallee,
3806 *RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee;
3808 /// RetainRVMarker - The inline asm string to insert between calls and
3809 /// RetainRV calls to make the optimization work on targets which need it.
3810 const MDString *RetainRVMarker;
3812 /// StoreStrongCalls - The set of inserted objc_storeStrong calls. If
3813 /// at the end of walking the function we have found no alloca
3814 /// instructions, these calls can be marked "tail".
3815 SmallPtrSet<CallInst *, 8> StoreStrongCalls;
3817 Constant *getStoreStrongCallee(Module *M);
3818 Constant *getRetainAutoreleaseCallee(Module *M);
3819 Constant *getRetainAutoreleaseRVCallee(Module *M);
3821 bool ContractAutorelease(Function &F, Instruction *Autorelease,
3822 InstructionClass Class,
3823 SmallPtrSet<Instruction *, 4>
3824 &DependingInstructions,
3825 SmallPtrSet<const BasicBlock *, 4>
3828 void ContractRelease(Instruction *Release,
3829 inst_iterator &Iter);
3831 virtual void getAnalysisUsage(AnalysisUsage &AU) const;
3832 virtual bool doInitialization(Module &M);
3833 virtual bool runOnFunction(Function &F);
3837 ObjCARCContract() : FunctionPass(ID) {
3838 initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
3843 char ObjCARCContract::ID = 0;
3844 INITIALIZE_PASS_BEGIN(ObjCARCContract,
3845 "objc-arc-contract", "ObjC ARC contraction", false, false)
3846 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
3847 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
3848 INITIALIZE_PASS_END(ObjCARCContract,
3849 "objc-arc-contract", "ObjC ARC contraction", false, false)
3851 Pass *llvm::createObjCARCContractPass() {
3852 return new ObjCARCContract();
3855 void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
3856 AU.addRequired<AliasAnalysis>();
3857 AU.addRequired<DominatorTree>();
3858 AU.setPreservesCFG();
3861 Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
3862 if (!StoreStrongCallee) {
3863 LLVMContext &C = M->getContext();
3864 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3865 Type *I8XX = PointerType::getUnqual(I8X);
3866 Type *Params[] = { I8XX, I8X };
3868 AttributeSet Attribute = AttributeSet()
3869 .addAttr(M->getContext(), AttributeSet::FunctionIndex,
3870 Attribute::get(C, Attribute::NoUnwind))
3871 .addAttr(M->getContext(), 1, Attribute::get(C, Attribute::NoCapture));
3874 M->getOrInsertFunction(
3876 FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
3879 return StoreStrongCallee;
3882 Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
3883 if (!RetainAutoreleaseCallee) {
3884 LLVMContext &C = M->getContext();
3885 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3886 Type *Params[] = { I8X };
3887 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
3888 AttributeSet Attribute =
3889 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
3890 Attribute::get(C, Attribute::NoUnwind));
3891 RetainAutoreleaseCallee =
3892 M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
3894 return RetainAutoreleaseCallee;
3897 Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
3898 if (!RetainAutoreleaseRVCallee) {
3899 LLVMContext &C = M->getContext();
3900 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
3901 Type *Params[] = { I8X };
3902 FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
3903 AttributeSet Attribute =
3904 AttributeSet().addAttr(M->getContext(), AttributeSet::FunctionIndex,
3905 Attribute::get(C, Attribute::NoUnwind));
3906 RetainAutoreleaseRVCallee =
3907 M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
3910 return RetainAutoreleaseRVCallee;
3913 /// ContractAutorelease - Merge an autorelease with a retain into a fused call.
3915 ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
3916 InstructionClass Class,
3917 SmallPtrSet<Instruction *, 4>
3918 &DependingInstructions,
3919 SmallPtrSet<const BasicBlock *, 4>
3921 const Value *Arg = GetObjCArg(Autorelease);
3923 // Check that there are no instructions between the retain and the autorelease
3924 // (such as an autorelease_pop) which may change the count.
3925 CallInst *Retain = 0;
3926 if (Class == IC_AutoreleaseRV)
3927 FindDependencies(RetainAutoreleaseRVDep, Arg,
3928 Autorelease->getParent(), Autorelease,
3929 DependingInstructions, Visited, PA);
3931 FindDependencies(RetainAutoreleaseDep, Arg,
3932 Autorelease->getParent(), Autorelease,
3933 DependingInstructions, Visited, PA);
3936 if (DependingInstructions.size() != 1) {
3937 DependingInstructions.clear();
3941 Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
3942 DependingInstructions.clear();
3945 GetBasicInstructionClass(Retain) != IC_Retain ||
3946 GetObjCArg(Retain) != Arg)
3952 if (Class == IC_AutoreleaseRV)
3953 Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
3955 Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
3957 EraseInstruction(Autorelease);
3961 /// ContractRelease - Attempt to merge an objc_release with a store, load, and
3962 /// objc_retain to form an objc_storeStrong. This can be a little tricky because
3963 /// the instructions don't always appear in order, and there may be unrelated
3964 /// intervening instructions.
3965 void ObjCARCContract::ContractRelease(Instruction *Release,
3966 inst_iterator &Iter) {
3967 LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
3968 if (!Load || !Load->isSimple()) return;
3970 // For now, require everything to be in one basic block.
3971 BasicBlock *BB = Release->getParent();
3972 if (Load->getParent() != BB) return;
3974 // Walk down to find the store and the release, which may be in either order.
3975 BasicBlock::iterator I = Load, End = BB->end();
3977 AliasAnalysis::Location Loc = AA->getLocation(Load);
3978 StoreInst *Store = 0;
3979 bool SawRelease = false;
3980 for (; !Store || !SawRelease; ++I) {
3984 Instruction *Inst = I;
3985 if (Inst == Release) {
3990 InstructionClass Class = GetBasicInstructionClass(Inst);
3992 // Unrelated retains are harmless.
3993 if (IsRetain(Class))
3997 // The store is the point where we're going to put the objc_storeStrong,
3998 // so make sure there are no uses after it.
3999 if (CanUse(Inst, Load, PA, Class))
4001 } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
4002 // We are moving the load down to the store, so check for anything
4003 // else which writes to the memory between the load and the store.
4004 Store = dyn_cast<StoreInst>(Inst);
4005 if (!Store || !Store->isSimple()) return;
4006 if (Store->getPointerOperand() != Loc.Ptr) return;
4010 Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
4012 // Walk up to find the retain.
4014 BasicBlock::iterator Begin = BB->begin();
4015 while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
4017 Instruction *Retain = I;
4018 if (GetBasicInstructionClass(Retain) != IC_Retain) return;
4019 if (GetObjCArg(Retain) != New) return;
4024 LLVMContext &C = Release->getContext();
4025 Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
4026 Type *I8XX = PointerType::getUnqual(I8X);
4028 Value *Args[] = { Load->getPointerOperand(), New };
4029 if (Args[0]->getType() != I8XX)
4030 Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
4031 if (Args[1]->getType() != I8X)
4032 Args[1] = new BitCastInst(Args[1], I8X, "", Store);
4033 CallInst *StoreStrong =
4034 CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
4036 StoreStrong->setDoesNotThrow();
4037 StoreStrong->setDebugLoc(Store->getDebugLoc());
4039 // We can't set the tail flag yet, because we haven't yet determined
4040 // whether there are any escaping allocas. Remember this call, so that
4041 // we can set the tail flag once we know it's safe.
4042 StoreStrongCalls.insert(StoreStrong);
4044 if (&*Iter == Store) ++Iter;
4045 Store->eraseFromParent();
4046 Release->eraseFromParent();
4047 EraseInstruction(Retain);
4048 if (Load->use_empty())
4049 Load->eraseFromParent();
4052 bool ObjCARCContract::doInitialization(Module &M) {
4053 // If nothing in the Module uses ARC, don't do anything.
4054 Run = ModuleHasARC(M);
4058 // These are initialized lazily.
4059 StoreStrongCallee = 0;
4060 RetainAutoreleaseCallee = 0;
4061 RetainAutoreleaseRVCallee = 0;
4063 // Initialize RetainRVMarker.
4065 if (NamedMDNode *NMD =
4066 M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
4067 if (NMD->getNumOperands() == 1) {
4068 const MDNode *N = NMD->getOperand(0);
4069 if (N->getNumOperands() == 1)
4070 if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
4077 bool ObjCARCContract::runOnFunction(Function &F) {
4081 // If nothing in the Module uses ARC, don't do anything.
4086 AA = &getAnalysis<AliasAnalysis>();
4087 DT = &getAnalysis<DominatorTree>();
4089 PA.setAA(&getAnalysis<AliasAnalysis>());
4091 // Track whether it's ok to mark objc_storeStrong calls with the "tail"
4092 // keyword. Be conservative if the function has variadic arguments.
4093 // It seems that functions which "return twice" are also unsafe for the
4094 // "tail" argument, because they are setjmp, which could need to
4095 // return to an earlier stack state.
4096 bool TailOkForStoreStrongs = !F.isVarArg() &&
4097 !F.callsFunctionThatReturnsTwice();
4099 // For ObjC library calls which return their argument, replace uses of the
4100 // argument with uses of the call return value, if it dominates the use. This
4101 // reduces register pressure.
4102 SmallPtrSet<Instruction *, 4> DependingInstructions;
4103 SmallPtrSet<const BasicBlock *, 4> Visited;
4104 for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
4105 Instruction *Inst = &*I++;
4107 DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
4109 // Only these library routines return their argument. In particular,
4110 // objc_retainBlock does not necessarily return its argument.
4111 InstructionClass Class = GetBasicInstructionClass(Inst);
4114 case IC_FusedRetainAutorelease:
4115 case IC_FusedRetainAutoreleaseRV:
4117 case IC_Autorelease:
4118 case IC_AutoreleaseRV:
4119 if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
4123 // If we're compiling for a target which needs a special inline-asm
4124 // marker to do the retainAutoreleasedReturnValue optimization,
4126 if (!RetainRVMarker)
4128 BasicBlock::iterator BBI = Inst;
4129 BasicBlock *InstParent = Inst->getParent();
4131 // Step up to see if the call immediately precedes the RetainRV call.
4132 // If it's an invoke, we have to cross a block boundary. And we have
4133 // to carefully dodge no-op instructions.
4135 if (&*BBI == InstParent->begin()) {
4136 BasicBlock *Pred = InstParent->getSinglePredecessor();
4138 goto decline_rv_optimization;
4139 BBI = Pred->getTerminator();
4143 } while (isNoopInstruction(BBI));
4145 if (&*BBI == GetObjCArg(Inst)) {
4148 InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
4149 /*isVarArg=*/false),
4150 RetainRVMarker->getString(),
4151 /*Constraints=*/"", /*hasSideEffects=*/true);
4152 CallInst::Create(IA, "", Inst);
4154 decline_rv_optimization:
4158 // objc_initWeak(p, null) => *p = null
4159 CallInst *CI = cast<CallInst>(Inst);
4160 if (isNullOrUndef(CI->getArgOperand(1))) {
4162 ConstantPointerNull::get(cast<PointerType>(CI->getType()));
4164 new StoreInst(Null, CI->getArgOperand(0), CI);
4165 CI->replaceAllUsesWith(Null);
4166 CI->eraseFromParent();
4171 ContractRelease(Inst, I);
4174 // Be conservative if the function has any alloca instructions.
4175 // Technically we only care about escaping alloca instructions,
4176 // but this is sufficient to handle some interesting cases.
4177 if (isa<AllocaInst>(Inst))
4178 TailOkForStoreStrongs = false;
4184 DEBUG(dbgs() << "ObjCARCContract: Finished Queue.\n\n");
4186 // Don't use GetObjCArg because we don't want to look through bitcasts
4187 // and such; to do the replacement, the argument must have type i8*.
4188 const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
4190 // If we're compiling bugpointed code, don't get in trouble.
4191 if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
4193 // Look through the uses of the pointer.
4194 for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
4196 Use &U = UI.getUse();
4197 unsigned OperandNo = UI.getOperandNo();
4198 ++UI; // Increment UI now, because we may unlink its element.
4200 // If the call's return value dominates a use of the call's argument
4201 // value, rewrite the use to use the return value. We check for
4202 // reachability here because an unreachable call is considered to
4203 // trivially dominate itself, which would lead us to rewriting its
4204 // argument in terms of its return value, which would lead to
4205 // infinite loops in GetObjCArg.
4206 if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
4208 Instruction *Replacement = Inst;
4209 Type *UseTy = U.get()->getType();
4210 if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
4211 // For PHI nodes, insert the bitcast in the predecessor block.
4212 unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
4213 BasicBlock *BB = PHI->getIncomingBlock(ValNo);
4214 if (Replacement->getType() != UseTy)
4215 Replacement = new BitCastInst(Replacement, UseTy, "",
4217 // While we're here, rewrite all edges for this PHI, rather
4218 // than just one use at a time, to minimize the number of
4219 // bitcasts we emit.
4220 for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
4221 if (PHI->getIncomingBlock(i) == BB) {
4222 // Keep the UI iterator valid.
4223 if (&PHI->getOperandUse(
4224 PHINode::getOperandNumForIncomingValue(i)) ==
4227 PHI->setIncomingValue(i, Replacement);
4230 if (Replacement->getType() != UseTy)
4231 Replacement = new BitCastInst(Replacement, UseTy, "",
4232 cast<Instruction>(U.getUser()));
4238 // If Arg is a no-op casted pointer, strip one level of casts and iterate.
4239 if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
4240 Arg = BI->getOperand(0);
4241 else if (isa<GEPOperator>(Arg) &&
4242 cast<GEPOperator>(Arg)->hasAllZeroIndices())
4243 Arg = cast<GEPOperator>(Arg)->getPointerOperand();
4244 else if (isa<GlobalAlias>(Arg) &&
4245 !cast<GlobalAlias>(Arg)->mayBeOverridden())
4246 Arg = cast<GlobalAlias>(Arg)->getAliasee();
4252 // If this function has no escaping allocas or suspicious vararg usage,
4253 // objc_storeStrong calls can be marked with the "tail" keyword.
4254 if (TailOkForStoreStrongs)
4255 for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
4256 E = StoreStrongCalls.end(); I != E; ++I)
4257 (*I)->setTailCall();
4258 StoreStrongCalls.clear();