| //===- ObjCARC.cpp - ObjC ARC Optimization --------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file defines ObjC ARC optimizations. ARC stands for |
| // Automatic Reference Counting and is a system for managing reference counts |
| // for objects in Objective C. |
| // |
| // The optimizations performed include elimination of redundant, partially |
| // redundant, and inconsequential reference count operations, elimination of |
| // redundant weak pointer operations, pattern-matching and replacement of |
| // low-level operations into higher-level operations, and numerous minor |
| // simplifications. |
| // |
| // This file also defines a simple ARC-aware AliasAnalysis. |
| // |
| // WARNING: This file knows about certain library functions. It recognizes them |
| // by name, and hardwires knowledge of their semantics. |
| // |
| // WARNING: This file knows about how certain Objective-C library functions are |
| // used. Naive LLVM IR transformations which would otherwise be |
| // behavior-preserving may break these assumptions. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "objc-arc" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/ADT/DenseMap.h" |
| using namespace llvm; |
| |
| // A handy option to enable/disable all optimizations in this file. |
| static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true)); |
| |
| //===----------------------------------------------------------------------===// |
| // Misc. Utilities |
| //===----------------------------------------------------------------------===// |
| |
| namespace { |
| /// MapVector - An associative container with fast insertion-order |
| /// (deterministic) iteration over its elements. Plus the special |
| /// blot operation. |
| template<class KeyT, class ValueT> |
| class MapVector { |
| /// Map - Map keys to indices in Vector. |
| typedef DenseMap<KeyT, size_t> MapTy; |
| MapTy Map; |
| |
| /// Vector - Keys and values. |
| typedef std::vector<std::pair<KeyT, ValueT> > VectorTy; |
| VectorTy Vector; |
| |
| public: |
| typedef typename VectorTy::iterator iterator; |
| typedef typename VectorTy::const_iterator const_iterator; |
| iterator begin() { return Vector.begin(); } |
| iterator end() { return Vector.end(); } |
| const_iterator begin() const { return Vector.begin(); } |
| const_iterator end() const { return Vector.end(); } |
| |
| #ifdef XDEBUG |
| ~MapVector() { |
| assert(Vector.size() >= Map.size()); // May differ due to blotting. |
| for (typename MapTy::const_iterator I = Map.begin(), E = Map.end(); |
| I != E; ++I) { |
| assert(I->second < Vector.size()); |
| assert(Vector[I->second].first == I->first); |
| } |
| for (typename VectorTy::const_iterator I = Vector.begin(), |
| E = Vector.end(); I != E; ++I) |
| assert(!I->first || |
| (Map.count(I->first) && |
| Map[I->first] == size_t(I - Vector.begin()))); |
| } |
| #endif |
| |
| ValueT &operator[](const KeyT &Arg) { |
| std::pair<typename MapTy::iterator, bool> Pair = |
| Map.insert(std::make_pair(Arg, size_t(0))); |
| if (Pair.second) { |
| size_t Num = Vector.size(); |
| Pair.first->second = Num; |
| Vector.push_back(std::make_pair(Arg, ValueT())); |
| return Vector[Num].second; |
| } |
| return Vector[Pair.first->second].second; |
| } |
| |
| std::pair<iterator, bool> |
| insert(const std::pair<KeyT, ValueT> &InsertPair) { |
| std::pair<typename MapTy::iterator, bool> Pair = |
| Map.insert(std::make_pair(InsertPair.first, size_t(0))); |
| if (Pair.second) { |
| size_t Num = Vector.size(); |
| Pair.first->second = Num; |
| Vector.push_back(InsertPair); |
| return std::make_pair(Vector.begin() + Num, true); |
| } |
| return std::make_pair(Vector.begin() + Pair.first->second, false); |
| } |
| |
| const_iterator find(const KeyT &Key) const { |
| typename MapTy::const_iterator It = Map.find(Key); |
| if (It == Map.end()) return Vector.end(); |
| return Vector.begin() + It->second; |
| } |
| |
| /// blot - This is similar to erase, but instead of removing the element |
| /// from the vector, it just zeros out the key in the vector. This leaves |
| /// iterators intact, but clients must be prepared for zeroed-out keys when |
| /// iterating. |
| void blot(const KeyT &Key) { |
| typename MapTy::iterator It = Map.find(Key); |
| if (It == Map.end()) return; |
| Vector[It->second].first = KeyT(); |
| Map.erase(It); |
| } |
| |
| void clear() { |
| Map.clear(); |
| Vector.clear(); |
| } |
| }; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC Utilities. |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Intrinsics.h" |
| #include "llvm/Module.h" |
| #include "llvm/Analysis/ValueTracking.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/ADT/StringSwitch.h" |
| |
| namespace { |
| /// InstructionClass - A simple classification for instructions. |
| enum InstructionClass { |
| IC_Retain, ///< objc_retain |
| IC_RetainRV, ///< objc_retainAutoreleasedReturnValue |
| IC_RetainBlock, ///< objc_retainBlock |
| IC_Release, ///< objc_release |
| IC_Autorelease, ///< objc_autorelease |
| IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue |
| IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush |
| IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop |
| IC_NoopCast, ///< objc_retainedObject, etc. |
| IC_FusedRetainAutorelease, ///< objc_retainAutorelease |
| IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue |
| IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive) |
| IC_StoreWeak, ///< objc_storeWeak (primitive) |
| IC_InitWeak, ///< objc_initWeak (derived) |
| IC_LoadWeak, ///< objc_loadWeak (derived) |
| IC_MoveWeak, ///< objc_moveWeak (derived) |
| IC_CopyWeak, ///< objc_copyWeak (derived) |
| IC_DestroyWeak, ///< objc_destroyWeak (derived) |
| IC_StoreStrong, ///< objc_storeStrong (derived) |
| IC_CallOrUser, ///< could call objc_release and/or "use" pointers |
| IC_Call, ///< could call objc_release |
| IC_User, ///< could "use" a pointer |
| IC_None ///< anything else |
| }; |
| } |
| |
| /// IsPotentialUse - Test whether the given value is possible a |
| /// reference-counted pointer. |
| static bool IsPotentialUse(const Value *Op) { |
| // Pointers to static or stack storage are not reference-counted pointers. |
| if (isa<Constant>(Op) || isa<AllocaInst>(Op)) |
| return false; |
| // Special arguments are not reference-counted. |
| if (const Argument *Arg = dyn_cast<Argument>(Op)) |
| if (Arg->hasByValAttr() || |
| Arg->hasNestAttr() || |
| Arg->hasStructRetAttr()) |
| return false; |
| // Only consider values with pointer types. |
| // It seemes intuitive to exclude function pointer types as well, since |
| // functions are never reference-counted, however clang occasionally |
| // bitcasts reference-counted pointers to function-pointer type |
| // temporarily. |
| PointerType *Ty = dyn_cast<PointerType>(Op->getType()); |
| if (!Ty) |
| return false; |
| // Conservatively assume anything else is a potential use. |
| return true; |
| } |
| |
| /// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind |
| /// of construct CS is. |
| static InstructionClass GetCallSiteClass(ImmutableCallSite CS) { |
| for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); |
| I != E; ++I) |
| if (IsPotentialUse(*I)) |
| return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser; |
| |
| return CS.onlyReadsMemory() ? IC_None : IC_Call; |
| } |
| |
| /// GetFunctionClass - Determine if F is one of the special known Functions. |
| /// If it isn't, return IC_CallOrUser. |
| static InstructionClass GetFunctionClass(const Function *F) { |
| Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end(); |
| |
| // No arguments. |
| if (AI == AE) |
| return StringSwitch<InstructionClass>(F->getName()) |
| .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush) |
| .Default(IC_CallOrUser); |
| |
| // One argument. |
| const Argument *A0 = AI++; |
| if (AI == AE) |
| // Argument is a pointer. |
| if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) { |
| Type *ETy = PTy->getElementType(); |
| // Argument is i8*. |
| if (ETy->isIntegerTy(8)) |
| return StringSwitch<InstructionClass>(F->getName()) |
| .Case("objc_retain", IC_Retain) |
| .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV) |
| .Case("objc_retainBlock", IC_RetainBlock) |
| .Case("objc_release", IC_Release) |
| .Case("objc_autorelease", IC_Autorelease) |
| .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV) |
| .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop) |
| .Case("objc_retainedObject", IC_NoopCast) |
| .Case("objc_unretainedObject", IC_NoopCast) |
| .Case("objc_unretainedPointer", IC_NoopCast) |
| .Case("objc_retain_autorelease", IC_FusedRetainAutorelease) |
| .Case("objc_retainAutorelease", IC_FusedRetainAutorelease) |
| .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV) |
| .Default(IC_CallOrUser); |
| |
| // Argument is i8** |
| if (PointerType *Pte = dyn_cast<PointerType>(ETy)) |
| if (Pte->getElementType()->isIntegerTy(8)) |
| return StringSwitch<InstructionClass>(F->getName()) |
| .Case("objc_loadWeakRetained", IC_LoadWeakRetained) |
| .Case("objc_loadWeak", IC_LoadWeak) |
| .Case("objc_destroyWeak", IC_DestroyWeak) |
| .Default(IC_CallOrUser); |
| } |
| |
| // Two arguments, first is i8**. |
| const Argument *A1 = AI++; |
| if (AI == AE) |
| if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) |
| if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType())) |
| if (Pte->getElementType()->isIntegerTy(8)) |
| if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) { |
| Type *ETy1 = PTy1->getElementType(); |
| // Second argument is i8* |
| if (ETy1->isIntegerTy(8)) |
| return StringSwitch<InstructionClass>(F->getName()) |
| .Case("objc_storeWeak", IC_StoreWeak) |
| .Case("objc_initWeak", IC_InitWeak) |
| .Case("objc_storeStrong", IC_StoreStrong) |
| .Default(IC_CallOrUser); |
| // Second argument is i8**. |
| if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1)) |
| if (Pte1->getElementType()->isIntegerTy(8)) |
| return StringSwitch<InstructionClass>(F->getName()) |
| .Case("objc_moveWeak", IC_MoveWeak) |
| .Case("objc_copyWeak", IC_CopyWeak) |
| .Default(IC_CallOrUser); |
| } |
| |
| // Anything else. |
| return IC_CallOrUser; |
| } |
| |
| /// GetInstructionClass - Determine what kind of construct V is. |
| static InstructionClass GetInstructionClass(const Value *V) { |
| if (const Instruction *I = dyn_cast<Instruction>(V)) { |
| // Any instruction other than bitcast and gep with a pointer operand have a |
| // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer |
| // to a subsequent use, rather than using it themselves, in this sense. |
| // As a short cut, several other opcodes are known to have no pointer |
| // operands of interest. And ret is never followed by a release, so it's |
| // not interesting to examine. |
| switch (I->getOpcode()) { |
| case Instruction::Call: { |
| const CallInst *CI = cast<CallInst>(I); |
| // Check for calls to special functions. |
| if (const Function *F = CI->getCalledFunction()) { |
| InstructionClass Class = GetFunctionClass(F); |
| if (Class != IC_CallOrUser) |
| return Class; |
| |
| // None of the intrinsic functions do objc_release. For intrinsics, the |
| // only question is whether or not they may be users. |
| switch (F->getIntrinsicID()) { |
| case Intrinsic::returnaddress: case Intrinsic::frameaddress: |
| case Intrinsic::stacksave: case Intrinsic::stackrestore: |
| case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend: |
| case Intrinsic::objectsize: case Intrinsic::prefetch: |
| case Intrinsic::stackprotector: |
| case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64: |
| case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa: |
| case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext: |
| case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline: |
| case Intrinsic::lifetime_start: case Intrinsic::lifetime_end: |
| case Intrinsic::invariant_start: case Intrinsic::invariant_end: |
| // Don't let dbg info affect our results. |
| case Intrinsic::dbg_declare: case Intrinsic::dbg_value: |
| // Short cut: Some intrinsics obviously don't use ObjC pointers. |
| return IC_None; |
| default: |
| break; |
| } |
| } |
| return GetCallSiteClass(CI); |
| } |
| case Instruction::Invoke: |
| return GetCallSiteClass(cast<InvokeInst>(I)); |
| case Instruction::BitCast: |
| case Instruction::GetElementPtr: |
| case Instruction::Select: case Instruction::PHI: |
| case Instruction::Ret: case Instruction::Br: |
| case Instruction::Switch: case Instruction::IndirectBr: |
| case Instruction::Alloca: case Instruction::VAArg: |
| case Instruction::Add: case Instruction::FAdd: |
| case Instruction::Sub: case Instruction::FSub: |
| case Instruction::Mul: case Instruction::FMul: |
| case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv: |
| case Instruction::SRem: case Instruction::URem: case Instruction::FRem: |
| case Instruction::Shl: case Instruction::LShr: case Instruction::AShr: |
| case Instruction::And: case Instruction::Or: case Instruction::Xor: |
| case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc: |
| case Instruction::IntToPtr: case Instruction::FCmp: |
| case Instruction::FPTrunc: case Instruction::FPExt: |
| case Instruction::FPToUI: case Instruction::FPToSI: |
| case Instruction::UIToFP: case Instruction::SIToFP: |
| case Instruction::InsertElement: case Instruction::ExtractElement: |
| case Instruction::ShuffleVector: |
| case Instruction::ExtractValue: |
| break; |
| case Instruction::ICmp: |
| // Comparing a pointer with null, or any other constant, isn't an |
| // interesting use, because we don't care what the pointer points to, or |
| // about the values of any other dynamic reference-counted pointers. |
| if (IsPotentialUse(I->getOperand(1))) |
| return IC_User; |
| break; |
| default: |
| // For anything else, check all the operands. |
| // Note that this includes both operands of a Store: while the first |
| // operand isn't actually being dereferenced, it is being stored to |
| // memory where we can no longer track who might read it and dereference |
| // it, so we have to consider it potentially used. |
| for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end(); |
| OI != OE; ++OI) |
| if (IsPotentialUse(*OI)) |
| return IC_User; |
| } |
| } |
| |
| // Otherwise, it's totally inert for ARC purposes. |
| return IC_None; |
| } |
| |
| /// GetBasicInstructionClass - Determine what kind of construct V is. This is |
| /// similar to GetInstructionClass except that it only detects objc runtine |
| /// calls. This allows it to be faster. |
| static InstructionClass GetBasicInstructionClass(const Value *V) { |
| if (const CallInst *CI = dyn_cast<CallInst>(V)) { |
| if (const Function *F = CI->getCalledFunction()) |
| return GetFunctionClass(F); |
| // Otherwise, be conservative. |
| return IC_CallOrUser; |
| } |
| |
| // Otherwise, be conservative. |
| return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User; |
| } |
| |
| /// IsRetain - Test if the given class is objc_retain or |
| /// equivalent. |
| static bool IsRetain(InstructionClass Class) { |
| return Class == IC_Retain || |
| Class == IC_RetainRV; |
| } |
| |
| /// IsAutorelease - Test if the given class is objc_autorelease or |
| /// equivalent. |
| static bool IsAutorelease(InstructionClass Class) { |
| return Class == IC_Autorelease || |
| Class == IC_AutoreleaseRV; |
| } |
| |
| /// IsForwarding - Test if the given class represents instructions which return |
| /// their argument verbatim. |
| static bool IsForwarding(InstructionClass Class) { |
| // objc_retainBlock technically doesn't always return its argument |
| // verbatim, but it doesn't matter for our purposes here. |
| return Class == IC_Retain || |
| Class == IC_RetainRV || |
| Class == IC_Autorelease || |
| Class == IC_AutoreleaseRV || |
| Class == IC_RetainBlock || |
| Class == IC_NoopCast; |
| } |
| |
| /// IsNoopOnNull - Test if the given class represents instructions which do |
| /// nothing if passed a null pointer. |
| static bool IsNoopOnNull(InstructionClass Class) { |
| return Class == IC_Retain || |
| Class == IC_RetainRV || |
| Class == IC_Release || |
| Class == IC_Autorelease || |
| Class == IC_AutoreleaseRV || |
| Class == IC_RetainBlock; |
| } |
| |
| /// IsAlwaysTail - Test if the given class represents instructions which are |
| /// always safe to mark with the "tail" keyword. |
| static bool IsAlwaysTail(InstructionClass Class) { |
| // IC_RetainBlock may be given a stack argument. |
| return Class == IC_Retain || |
| Class == IC_RetainRV || |
| Class == IC_Autorelease || |
| Class == IC_AutoreleaseRV; |
| } |
| |
| /// IsNoThrow - Test if the given class represents instructions which are always |
| /// safe to mark with the nounwind attribute.. |
| static bool IsNoThrow(InstructionClass Class) { |
| // objc_retainBlock is not nounwind because it calls user copy constructors |
| // which could theoretically throw. |
| return Class == IC_Retain || |
| Class == IC_RetainRV || |
| Class == IC_Release || |
| Class == IC_Autorelease || |
| Class == IC_AutoreleaseRV || |
| Class == IC_AutoreleasepoolPush || |
| Class == IC_AutoreleasepoolPop; |
| } |
| |
| /// EraseInstruction - Erase the given instruction. Many ObjC calls return their |
| /// argument verbatim, so if it's such a call and the return value has users, |
| /// replace them with the argument value. |
| static void EraseInstruction(Instruction *CI) { |
| Value *OldArg = cast<CallInst>(CI)->getArgOperand(0); |
| |
| bool Unused = CI->use_empty(); |
| |
| if (!Unused) { |
| // Replace the return value with the argument. |
| assert(IsForwarding(GetBasicInstructionClass(CI)) && |
| "Can't delete non-forwarding instruction with users!"); |
| CI->replaceAllUsesWith(OldArg); |
| } |
| |
| CI->eraseFromParent(); |
| |
| if (Unused) |
| RecursivelyDeleteTriviallyDeadInstructions(OldArg); |
| } |
| |
| /// GetUnderlyingObjCPtr - This is a wrapper around getUnderlyingObject which |
| /// also knows how to look through objc_retain and objc_autorelease calls, which |
| /// we know to return their argument verbatim. |
| static const Value *GetUnderlyingObjCPtr(const Value *V) { |
| for (;;) { |
| V = GetUnderlyingObject(V); |
| if (!IsForwarding(GetBasicInstructionClass(V))) |
| break; |
| V = cast<CallInst>(V)->getArgOperand(0); |
| } |
| |
| return V; |
| } |
| |
| /// StripPointerCastsAndObjCCalls - This is a wrapper around |
| /// Value::stripPointerCasts which also knows how to look through objc_retain |
| /// and objc_autorelease calls, which we know to return their argument verbatim. |
| static const Value *StripPointerCastsAndObjCCalls(const Value *V) { |
| for (;;) { |
| V = V->stripPointerCasts(); |
| if (!IsForwarding(GetBasicInstructionClass(V))) |
| break; |
| V = cast<CallInst>(V)->getArgOperand(0); |
| } |
| return V; |
| } |
| |
| /// StripPointerCastsAndObjCCalls - This is a wrapper around |
| /// Value::stripPointerCasts which also knows how to look through objc_retain |
| /// and objc_autorelease calls, which we know to return their argument verbatim. |
| static Value *StripPointerCastsAndObjCCalls(Value *V) { |
| for (;;) { |
| V = V->stripPointerCasts(); |
| if (!IsForwarding(GetBasicInstructionClass(V))) |
| break; |
| V = cast<CallInst>(V)->getArgOperand(0); |
| } |
| return V; |
| } |
| |
| /// GetObjCArg - Assuming the given instruction is one of the special calls such |
| /// as objc_retain or objc_release, return the argument value, stripped of no-op |
| /// casts and forwarding calls. |
| static Value *GetObjCArg(Value *Inst) { |
| return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0)); |
| } |
| |
| /// IsObjCIdentifiedObject - This is similar to AliasAnalysis' |
| /// isObjCIdentifiedObject, except that it uses special knowledge of |
| /// ObjC conventions... |
| static bool IsObjCIdentifiedObject(const Value *V) { |
| // Assume that call results and arguments have their own "provenance". |
| // Constants (including GlobalVariables) and Allocas are never |
| // reference-counted. |
| if (isa<CallInst>(V) || isa<InvokeInst>(V) || |
| isa<Argument>(V) || isa<Constant>(V) || |
| isa<AllocaInst>(V)) |
| return true; |
| |
| if (const LoadInst *LI = dyn_cast<LoadInst>(V)) { |
| const Value *Pointer = |
| StripPointerCastsAndObjCCalls(LI->getPointerOperand()); |
| if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) { |
| // A constant pointer can't be pointing to an object on the heap. It may |
| // be reference-counted, but it won't be deleted. |
| if (GV->isConstant()) |
| return true; |
| StringRef Name = GV->getName(); |
| // These special variables are known to hold values which are not |
| // reference-counted pointers. |
| if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") || |
| Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") || |
| Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") || |
| Name.startswith("\01L_OBJC_METH_VAR_NAME_") || |
| Name.startswith("\01l_objc_msgSend_fixup_")) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// FindSingleUseIdentifiedObject - This is similar to |
| /// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value |
| /// with multiple uses. |
| static const Value *FindSingleUseIdentifiedObject(const Value *Arg) { |
| if (Arg->hasOneUse()) { |
| if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg)) |
| return FindSingleUseIdentifiedObject(BC->getOperand(0)); |
| if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg)) |
| if (GEP->hasAllZeroIndices()) |
| return FindSingleUseIdentifiedObject(GEP->getPointerOperand()); |
| if (IsForwarding(GetBasicInstructionClass(Arg))) |
| return FindSingleUseIdentifiedObject( |
| cast<CallInst>(Arg)->getArgOperand(0)); |
| if (!IsObjCIdentifiedObject(Arg)) |
| return 0; |
| return Arg; |
| } |
| |
| // If we found an identifiable object but it has multiple uses, but they are |
| // trivial uses, we can still consider this to be a single-use value. |
| if (IsObjCIdentifiedObject(Arg)) { |
| for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end(); |
| UI != UE; ++UI) { |
| const User *U = *UI; |
| if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg) |
| return 0; |
| } |
| |
| return Arg; |
| } |
| |
| return 0; |
| } |
| |
| /// ModuleHasARC - Test if the given module looks interesting to run ARC |
| /// optimization on. |
| static bool ModuleHasARC(const Module &M) { |
| return |
| M.getNamedValue("objc_retain") || |
| M.getNamedValue("objc_release") || |
| M.getNamedValue("objc_autorelease") || |
| M.getNamedValue("objc_retainAutoreleasedReturnValue") || |
| M.getNamedValue("objc_retainBlock") || |
| M.getNamedValue("objc_autoreleaseReturnValue") || |
| M.getNamedValue("objc_autoreleasePoolPush") || |
| M.getNamedValue("objc_loadWeakRetained") || |
| M.getNamedValue("objc_loadWeak") || |
| M.getNamedValue("objc_destroyWeak") || |
| M.getNamedValue("objc_storeWeak") || |
| M.getNamedValue("objc_initWeak") || |
| M.getNamedValue("objc_moveWeak") || |
| M.getNamedValue("objc_copyWeak") || |
| M.getNamedValue("objc_retainedObject") || |
| M.getNamedValue("objc_unretainedObject") || |
| M.getNamedValue("objc_unretainedPointer"); |
| } |
| |
| /// DoesObjCBlockEscape - Test whether the given pointer, which is an |
| /// Objective C block pointer, does not "escape". This differs from regular |
| /// escape analysis in that a use as an argument to a call is not considered |
| /// an escape. |
| static bool DoesObjCBlockEscape(const Value *BlockPtr) { |
| // Walk the def-use chains. |
| SmallVector<const Value *, 4> Worklist; |
| Worklist.push_back(BlockPtr); |
| do { |
| const Value *V = Worklist.pop_back_val(); |
| for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end(); |
| UI != UE; ++UI) { |
| const User *UUser = *UI; |
| // Special - Use by a call (callee or argument) is not considered |
| // to be an escape. |
| switch (GetBasicInstructionClass(UUser)) { |
| case IC_StoreWeak: |
| case IC_InitWeak: |
| case IC_StoreStrong: |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| // These special functions make copies of their pointer arguments. |
| return true; |
| case IC_User: |
| case IC_None: |
| // Use by an instruction which copies the value is an escape if the |
| // result is an escape. |
| if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) || |
| isa<PHINode>(UUser) || isa<SelectInst>(UUser)) { |
| Worklist.push_back(UUser); |
| continue; |
| } |
| // Use by a load is not an escape. |
| if (isa<LoadInst>(UUser)) |
| continue; |
| // Use by a store is not an escape if the use is the address. |
| if (const StoreInst *SI = dyn_cast<StoreInst>(UUser)) |
| if (V != SI->getValueOperand()) |
| continue; |
| break; |
| default: |
| // Regular calls and other stuff are not considered escapes. |
| continue; |
| } |
| // Otherwise, conservatively assume an escape. |
| return true; |
| } |
| } while (!Worklist.empty()); |
| |
| // No escapes found. |
| return false; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC AliasAnalysis. |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/Passes.h" |
| |
| namespace { |
| /// ObjCARCAliasAnalysis - This is a simple alias analysis |
| /// implementation that uses knowledge of ARC constructs to answer queries. |
| /// |
| /// TODO: This class could be generalized to know about other ObjC-specific |
| /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing |
| /// even though their offsets are dynamic. |
| class ObjCARCAliasAnalysis : public ImmutablePass, |
| public AliasAnalysis { |
| public: |
| static char ID; // Class identification, replacement for typeinfo |
| ObjCARCAliasAnalysis() : ImmutablePass(ID) { |
| initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| private: |
| virtual void initializePass() { |
| InitializeAliasAnalysis(this); |
| } |
| |
| /// getAdjustedAnalysisPointer - This method is used when a pass implements |
| /// an analysis interface through multiple inheritance. If needed, it |
| /// should override this to adjust the this pointer as needed for the |
| /// specified pass info. |
| virtual void *getAdjustedAnalysisPointer(const void *PI) { |
| if (PI == &AliasAnalysis::ID) |
| return static_cast<AliasAnalysis *>(this); |
| return this; |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| virtual AliasResult alias(const Location &LocA, const Location &LocB); |
| virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal); |
| virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS); |
| virtual ModRefBehavior getModRefBehavior(const Function *F); |
| virtual ModRefResult getModRefInfo(ImmutableCallSite CS, |
| const Location &Loc); |
| virtual ModRefResult getModRefInfo(ImmutableCallSite CS1, |
| ImmutableCallSite CS2); |
| }; |
| } // End of anonymous namespace |
| |
| // Register this pass... |
| char ObjCARCAliasAnalysis::ID = 0; |
| INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa", |
| "ObjC-ARC-Based Alias Analysis", false, true, false) |
| |
| ImmutablePass *llvm::createObjCARCAliasAnalysisPass() { |
| return new ObjCARCAliasAnalysis(); |
| } |
| |
| void |
| ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesAll(); |
| AliasAnalysis::getAnalysisUsage(AU); |
| } |
| |
| AliasAnalysis::AliasResult |
| ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) { |
| if (!EnableARCOpts) |
| return AliasAnalysis::alias(LocA, LocB); |
| |
| // First, strip off no-ops, including ObjC-specific no-ops, and try making a |
| // precise alias query. |
| const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr); |
| const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr); |
| AliasResult Result = |
| AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag), |
| Location(SB, LocB.Size, LocB.TBAATag)); |
| if (Result != MayAlias) |
| return Result; |
| |
| // If that failed, climb to the underlying object, including climbing through |
| // ObjC-specific no-ops, and try making an imprecise alias query. |
| const Value *UA = GetUnderlyingObjCPtr(SA); |
| const Value *UB = GetUnderlyingObjCPtr(SB); |
| if (UA != SA || UB != SB) { |
| Result = AliasAnalysis::alias(Location(UA), Location(UB)); |
| // We can't use MustAlias or PartialAlias results here because |
| // GetUnderlyingObjCPtr may return an offsetted pointer value. |
| if (Result == NoAlias) |
| return NoAlias; |
| } |
| |
| // If that failed, fail. We don't need to chain here, since that's covered |
| // by the earlier precise query. |
| return MayAlias; |
| } |
| |
| bool |
| ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc, |
| bool OrLocal) { |
| if (!EnableARCOpts) |
| return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); |
| |
| // First, strip off no-ops, including ObjC-specific no-ops, and try making |
| // a precise alias query. |
| const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr); |
| if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag), |
| OrLocal)) |
| return true; |
| |
| // If that failed, climb to the underlying object, including climbing through |
| // ObjC-specific no-ops, and try making an imprecise alias query. |
| const Value *U = GetUnderlyingObjCPtr(S); |
| if (U != S) |
| return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal); |
| |
| // If that failed, fail. We don't need to chain here, since that's covered |
| // by the earlier precise query. |
| return false; |
| } |
| |
| AliasAnalysis::ModRefBehavior |
| ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) { |
| // We have nothing to do. Just chain to the next AliasAnalysis. |
| return AliasAnalysis::getModRefBehavior(CS); |
| } |
| |
| AliasAnalysis::ModRefBehavior |
| ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) { |
| if (!EnableARCOpts) |
| return AliasAnalysis::getModRefBehavior(F); |
| |
| switch (GetFunctionClass(F)) { |
| case IC_NoopCast: |
| return DoesNotAccessMemory; |
| default: |
| break; |
| } |
| |
| return AliasAnalysis::getModRefBehavior(F); |
| } |
| |
| AliasAnalysis::ModRefResult |
| ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) { |
| if (!EnableARCOpts) |
| return AliasAnalysis::getModRefInfo(CS, Loc); |
| |
| switch (GetBasicInstructionClass(CS.getInstruction())) { |
| case IC_Retain: |
| case IC_RetainRV: |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| case IC_NoopCast: |
| case IC_AutoreleasepoolPush: |
| case IC_FusedRetainAutorelease: |
| case IC_FusedRetainAutoreleaseRV: |
| // These functions don't access any memory visible to the compiler. |
| // Note that this doesn't include objc_retainBlock, because it updates |
| // pointers when it copies block data. |
| return NoModRef; |
| default: |
| break; |
| } |
| |
| return AliasAnalysis::getModRefInfo(CS, Loc); |
| } |
| |
| AliasAnalysis::ModRefResult |
| ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1, |
| ImmutableCallSite CS2) { |
| // TODO: Theoretically we could check for dependencies between objc_* calls |
| // and OnlyAccessesArgumentPointees calls or other well-behaved calls. |
| return AliasAnalysis::getModRefInfo(CS1, CS2); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC expansion. |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Support/InstIterator.h" |
| #include "llvm/Transforms/Scalar.h" |
| |
| namespace { |
| /// ObjCARCExpand - Early ARC transformations. |
| class ObjCARCExpand : public FunctionPass { |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| virtual bool doInitialization(Module &M); |
| virtual bool runOnFunction(Function &F); |
| |
| /// Run - A flag indicating whether this optimization pass should run. |
| bool Run; |
| |
| public: |
| static char ID; |
| ObjCARCExpand() : FunctionPass(ID) { |
| initializeObjCARCExpandPass(*PassRegistry::getPassRegistry()); |
| } |
| }; |
| } |
| |
| char ObjCARCExpand::ID = 0; |
| INITIALIZE_PASS(ObjCARCExpand, |
| "objc-arc-expand", "ObjC ARC expansion", false, false) |
| |
| Pass *llvm::createObjCARCExpandPass() { |
| return new ObjCARCExpand(); |
| } |
| |
| void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| } |
| |
| bool ObjCARCExpand::doInitialization(Module &M) { |
| Run = ModuleHasARC(M); |
| return false; |
| } |
| |
| bool ObjCARCExpand::runOnFunction(Function &F) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| if (!Run) |
| return false; |
| |
| bool Changed = false; |
| |
| for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) { |
| Instruction *Inst = &*I; |
| |
| switch (GetBasicInstructionClass(Inst)) { |
| case IC_Retain: |
| case IC_RetainRV: |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| case IC_FusedRetainAutorelease: |
| case IC_FusedRetainAutoreleaseRV: |
| // These calls return their argument verbatim, as a low-level |
| // optimization. However, this makes high-level optimizations |
| // harder. Undo any uses of this optimization that the front-end |
| // emitted here. We'll redo them in the contract pass. |
| Changed = true; |
| Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0)); |
| break; |
| default: |
| break; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC autorelease pool elimination. |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Constants.h" |
| #include "llvm/ADT/STLExtras.h" |
| |
| namespace { |
| /// ObjCARCAPElim - Autorelease pool elimination. |
| class ObjCARCAPElim : public ModulePass { |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| virtual bool runOnModule(Module &M); |
| |
| static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0); |
| static bool OptimizeBB(BasicBlock *BB); |
| |
| public: |
| static char ID; |
| ObjCARCAPElim() : ModulePass(ID) { |
| initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry()); |
| } |
| }; |
| } |
| |
| char ObjCARCAPElim::ID = 0; |
| INITIALIZE_PASS(ObjCARCAPElim, |
| "objc-arc-apelim", |
| "ObjC ARC autorelease pool elimination", |
| false, false) |
| |
| Pass *llvm::createObjCARCAPElimPass() { |
| return new ObjCARCAPElim(); |
| } |
| |
| void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesCFG(); |
| } |
| |
| /// MayAutorelease - Interprocedurally determine if calls made by the |
| /// given call site can possibly produce autoreleases. |
| bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) { |
| if (const Function *Callee = CS.getCalledFunction()) { |
| if (Callee->isDeclaration() || Callee->mayBeOverridden()) |
| return true; |
| for (Function::const_iterator I = Callee->begin(), E = Callee->end(); |
| I != E; ++I) { |
| const BasicBlock *BB = I; |
| for (BasicBlock::const_iterator J = BB->begin(), F = BB->end(); |
| J != F; ++J) |
| if (ImmutableCallSite JCS = ImmutableCallSite(J)) |
| // This recursion depth limit is arbitrary. It's just great |
| // enough to cover known interesting testcases. |
| if (Depth < 3 && |
| !JCS.onlyReadsMemory() && |
| MayAutorelease(JCS, Depth + 1)) |
| return true; |
| } |
| return false; |
| } |
| |
| return true; |
| } |
| |
| bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) { |
| bool Changed = false; |
| |
| Instruction *Push = 0; |
| for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { |
| Instruction *Inst = I++; |
| switch (GetBasicInstructionClass(Inst)) { |
| case IC_AutoreleasepoolPush: |
| Push = Inst; |
| break; |
| case IC_AutoreleasepoolPop: |
| // If this pop matches a push and nothing in between can autorelease, |
| // zap the pair. |
| if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) { |
| Changed = true; |
| Inst->eraseFromParent(); |
| Push->eraseFromParent(); |
| } |
| Push = 0; |
| break; |
| case IC_CallOrUser: |
| if (MayAutorelease(ImmutableCallSite(Inst))) |
| Push = 0; |
| break; |
| default: |
| break; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| bool ObjCARCAPElim::runOnModule(Module &M) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| if (!ModuleHasARC(M)) |
| return false; |
| |
| // Find the llvm.global_ctors variable, as the first step in |
| // identifying the global constructors. In theory, unnecessary autorelease |
| // pools could occur anywhere, but in practice it's pretty rare. Global |
| // ctors are a place where autorelease pools get inserted automatically, |
| // so it's pretty common for them to be unnecessary, and it's pretty |
| // profitable to eliminate them. |
| GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); |
| if (!GV) |
| return false; |
| |
| assert(GV->hasDefinitiveInitializer() && |
| "llvm.global_ctors is uncooperative!"); |
| |
| bool Changed = false; |
| |
| // Dig the constructor functions out of GV's initializer. |
| ConstantArray *Init = cast<ConstantArray>(GV->getInitializer()); |
| for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end(); |
| OI != OE; ++OI) { |
| Value *Op = *OI; |
| // llvm.global_ctors is an array of pairs where the second members |
| // are constructor functions. |
| Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1)); |
| // If the user used a constructor function with the wrong signature and |
| // it got bitcasted or whatever, look the other way. |
| if (!F) |
| continue; |
| // Only look at function definitions. |
| if (F->isDeclaration()) |
| continue; |
| // Only look at functions with one basic block. |
| if (llvm::next(F->begin()) != F->end()) |
| continue; |
| // Ok, a single-block constructor function definition. Try to optimize it. |
| Changed |= OptimizeBB(F->begin()); |
| } |
| |
| return Changed; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC optimization. |
| //===----------------------------------------------------------------------===// |
| |
| // TODO: On code like this: |
| // |
| // objc_retain(%x) |
| // stuff_that_cannot_release() |
| // objc_autorelease(%x) |
| // stuff_that_cannot_release() |
| // objc_retain(%x) |
| // stuff_that_cannot_release() |
| // objc_autorelease(%x) |
| // |
| // The second retain and autorelease can be deleted. |
| |
| // TODO: It should be possible to delete |
| // objc_autoreleasePoolPush and objc_autoreleasePoolPop |
| // pairs if nothing is actually autoreleased between them. Also, autorelease |
| // calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code |
| // after inlining) can be turned into plain release calls. |
| |
| // TODO: Critical-edge splitting. If the optimial insertion point is |
| // a critical edge, the current algorithm has to fail, because it doesn't |
| // know how to split edges. It should be possible to make the optimizer |
| // think in terms of edges, rather than blocks, and then split critical |
| // edges on demand. |
| |
| // TODO: OptimizeSequences could generalized to be Interprocedural. |
| |
| // TODO: Recognize that a bunch of other objc runtime calls have |
| // non-escaping arguments and non-releasing arguments, and may be |
| // non-autoreleasing. |
| |
| // TODO: Sink autorelease calls as far as possible. Unfortunately we |
| // usually can't sink them past other calls, which would be the main |
| // case where it would be useful. |
| |
| // TODO: The pointer returned from objc_loadWeakRetained is retained. |
| |
| // TODO: Delete release+retain pairs (rare). |
| |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| |
| STATISTIC(NumNoops, "Number of no-op objc calls eliminated"); |
| STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated"); |
| STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases"); |
| STATISTIC(NumRets, "Number of return value forwarding " |
| "retain+autoreleaes eliminated"); |
| STATISTIC(NumRRs, "Number of retain+release paths eliminated"); |
| STATISTIC(NumPeeps, "Number of calls peephole-optimized"); |
| |
| namespace { |
| /// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it |
| /// uses many of the same techniques, except it uses special ObjC-specific |
| /// reasoning about pointer relationships. |
| class ProvenanceAnalysis { |
| AliasAnalysis *AA; |
| |
| typedef std::pair<const Value *, const Value *> ValuePairTy; |
| typedef DenseMap<ValuePairTy, bool> CachedResultsTy; |
| CachedResultsTy CachedResults; |
| |
| bool relatedCheck(const Value *A, const Value *B); |
| bool relatedSelect(const SelectInst *A, const Value *B); |
| bool relatedPHI(const PHINode *A, const Value *B); |
| |
| void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION; |
| ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION; |
| |
| public: |
| ProvenanceAnalysis() {} |
| |
| void setAA(AliasAnalysis *aa) { AA = aa; } |
| |
| AliasAnalysis *getAA() const { return AA; } |
| |
| bool related(const Value *A, const Value *B); |
| |
| void clear() { |
| CachedResults.clear(); |
| } |
| }; |
| } |
| |
| bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) { |
| // If the values are Selects with the same condition, we can do a more precise |
| // check: just check for relations between the values on corresponding arms. |
| if (const SelectInst *SB = dyn_cast<SelectInst>(B)) |
| if (A->getCondition() == SB->getCondition()) |
| return related(A->getTrueValue(), SB->getTrueValue()) || |
| related(A->getFalseValue(), SB->getFalseValue()); |
| |
| // Check both arms of the Select node individually. |
| return related(A->getTrueValue(), B) || |
| related(A->getFalseValue(), B); |
| } |
| |
| bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) { |
| // If the values are PHIs in the same block, we can do a more precise as well |
| // as efficient check: just check for relations between the values on |
| // corresponding edges. |
| if (const PHINode *PNB = dyn_cast<PHINode>(B)) |
| if (PNB->getParent() == A->getParent()) { |
| for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) |
| if (related(A->getIncomingValue(i), |
| PNB->getIncomingValueForBlock(A->getIncomingBlock(i)))) |
| return true; |
| return false; |
| } |
| |
| // Check each unique source of the PHI node against B. |
| SmallPtrSet<const Value *, 4> UniqueSrc; |
| for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) { |
| const Value *PV1 = A->getIncomingValue(i); |
| if (UniqueSrc.insert(PV1) && related(PV1, B)) |
| return true; |
| } |
| |
| // All of the arms checked out. |
| return false; |
| } |
| |
| /// isStoredObjCPointer - Test if the value of P, or any value covered by its |
| /// provenance, is ever stored within the function (not counting callees). |
| static bool isStoredObjCPointer(const Value *P) { |
| SmallPtrSet<const Value *, 8> Visited; |
| SmallVector<const Value *, 8> Worklist; |
| Worklist.push_back(P); |
| Visited.insert(P); |
| do { |
| P = Worklist.pop_back_val(); |
| for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end(); |
| UI != UE; ++UI) { |
| const User *Ur = *UI; |
| if (isa<StoreInst>(Ur)) { |
| if (UI.getOperandNo() == 0) |
| // The pointer is stored. |
| return true; |
| // The pointed is stored through. |
| continue; |
| } |
| if (isa<CallInst>(Ur)) |
| // The pointer is passed as an argument, ignore this. |
| continue; |
| if (isa<PtrToIntInst>(P)) |
| // Assume the worst. |
| return true; |
| if (Visited.insert(Ur)) |
| Worklist.push_back(Ur); |
| } |
| } while (!Worklist.empty()); |
| |
| // Everything checked out. |
| return false; |
| } |
| |
| bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) { |
| // Skip past provenance pass-throughs. |
| A = GetUnderlyingObjCPtr(A); |
| B = GetUnderlyingObjCPtr(B); |
| |
| // Quick check. |
| if (A == B) |
| return true; |
| |
| // Ask regular AliasAnalysis, for a first approximation. |
| switch (AA->alias(A, B)) { |
| case AliasAnalysis::NoAlias: |
| return false; |
| case AliasAnalysis::MustAlias: |
| case AliasAnalysis::PartialAlias: |
| return true; |
| case AliasAnalysis::MayAlias: |
| break; |
| } |
| |
| bool AIsIdentified = IsObjCIdentifiedObject(A); |
| bool BIsIdentified = IsObjCIdentifiedObject(B); |
| |
| // An ObjC-Identified object can't alias a load if it is never locally stored. |
| if (AIsIdentified) { |
| // Check for an obvious escape. |
| if (isa<LoadInst>(B)) |
| return isStoredObjCPointer(A); |
| if (BIsIdentified) { |
| // Check for an obvious escape. |
| if (isa<LoadInst>(A)) |
| return isStoredObjCPointer(B); |
| // Both pointers are identified and escapes aren't an evident problem. |
| return false; |
| } |
| } else if (BIsIdentified) { |
| // Check for an obvious escape. |
| if (isa<LoadInst>(A)) |
| return isStoredObjCPointer(B); |
| } |
| |
| // Special handling for PHI and Select. |
| if (const PHINode *PN = dyn_cast<PHINode>(A)) |
| return relatedPHI(PN, B); |
| if (const PHINode *PN = dyn_cast<PHINode>(B)) |
| return relatedPHI(PN, A); |
| if (const SelectInst *S = dyn_cast<SelectInst>(A)) |
| return relatedSelect(S, B); |
| if (const SelectInst *S = dyn_cast<SelectInst>(B)) |
| return relatedSelect(S, A); |
| |
| // Conservative. |
| return true; |
| } |
| |
| bool ProvenanceAnalysis::related(const Value *A, const Value *B) { |
| // Begin by inserting a conservative value into the map. If the insertion |
| // fails, we have the answer already. If it succeeds, leave it there until we |
| // compute the real answer to guard against recursive queries. |
| if (A > B) std::swap(A, B); |
| std::pair<CachedResultsTy::iterator, bool> Pair = |
| CachedResults.insert(std::make_pair(ValuePairTy(A, B), true)); |
| if (!Pair.second) |
| return Pair.first->second; |
| |
| bool Result = relatedCheck(A, B); |
| CachedResults[ValuePairTy(A, B)] = Result; |
| return Result; |
| } |
| |
| namespace { |
| // Sequence - A sequence of states that a pointer may go through in which an |
| // objc_retain and objc_release are actually needed. |
| enum Sequence { |
| S_None, |
| S_Retain, ///< objc_retain(x) |
| S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement |
| S_Use, ///< any use of x |
| S_Stop, ///< like S_Release, but code motion is stopped |
| S_Release, ///< objc_release(x) |
| S_MovableRelease ///< objc_release(x), !clang.imprecise_release |
| }; |
| } |
| |
| static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) { |
| // The easy cases. |
| if (A == B) |
| return A; |
| if (A == S_None || B == S_None) |
| return S_None; |
| |
| if (A > B) std::swap(A, B); |
| if (TopDown) { |
| // Choose the side which is further along in the sequence. |
| if ((A == S_Retain || A == S_CanRelease) && |
| (B == S_CanRelease || B == S_Use)) |
| return B; |
| } else { |
| // Choose the side which is further along in the sequence. |
| if ((A == S_Use || A == S_CanRelease) && |
| (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease)) |
| return A; |
| // If both sides are releases, choose the more conservative one. |
| if (A == S_Stop && (B == S_Release || B == S_MovableRelease)) |
| return A; |
| if (A == S_Release && B == S_MovableRelease) |
| return A; |
| } |
| |
| return S_None; |
| } |
| |
| namespace { |
| /// RRInfo - Unidirectional information about either a |
| /// retain-decrement-use-release sequence or release-use-decrement-retain |
| /// reverese sequence. |
| struct RRInfo { |
| /// KnownSafe - After an objc_retain, the reference count of the referenced |
| /// object is known to be positive. Similarly, before an objc_release, the |
| /// reference count of the referenced object is known to be positive. If |
| /// there are retain-release pairs in code regions where the retain count |
| /// is known to be positive, they can be eliminated, regardless of any side |
| /// effects between them. |
| /// |
| /// Also, a retain+release pair nested within another retain+release |
| /// pair all on the known same pointer value can be eliminated, regardless |
| /// of any intervening side effects. |
| /// |
| /// KnownSafe is true when either of these conditions is satisfied. |
| bool KnownSafe; |
| |
| /// IsRetainBlock - True if the Calls are objc_retainBlock calls (as |
| /// opposed to objc_retain calls). |
| bool IsRetainBlock; |
| |
| /// IsTailCallRelease - True of the objc_release calls are all marked |
| /// with the "tail" keyword. |
| bool IsTailCallRelease; |
| |
| /// ReleaseMetadata - If the Calls are objc_release calls and they all have |
| /// a clang.imprecise_release tag, this is the metadata tag. |
| MDNode *ReleaseMetadata; |
| |
| /// Calls - For a top-down sequence, the set of objc_retains or |
| /// objc_retainBlocks. For bottom-up, the set of objc_releases. |
| SmallPtrSet<Instruction *, 2> Calls; |
| |
| /// ReverseInsertPts - The set of optimal insert positions for |
| /// moving calls in the opposite sequence. |
| SmallPtrSet<Instruction *, 2> ReverseInsertPts; |
| |
| RRInfo() : |
| KnownSafe(false), IsRetainBlock(false), |
| IsTailCallRelease(false), |
| ReleaseMetadata(0) {} |
| |
| void clear(); |
| }; |
| } |
| |
| void RRInfo::clear() { |
| KnownSafe = false; |
| IsRetainBlock = false; |
| IsTailCallRelease = false; |
| ReleaseMetadata = 0; |
| Calls.clear(); |
| ReverseInsertPts.clear(); |
| } |
| |
| namespace { |
| /// PtrState - This class summarizes several per-pointer runtime properties |
| /// which are propogated through the flow graph. |
| class PtrState { |
| /// KnownPositiveRefCount - True if the reference count is known to |
| /// be incremented. |
| bool KnownPositiveRefCount; |
| |
| /// Partial - True of we've seen an opportunity for partial RR elimination, |
| /// such as pushing calls into a CFG triangle or into one side of a |
| /// CFG diamond. |
| bool Partial; |
| |
| /// Seq - The current position in the sequence. |
| Sequence Seq : 8; |
| |
| public: |
| /// RRI - Unidirectional information about the current sequence. |
| /// TODO: Encapsulate this better. |
| RRInfo RRI; |
| |
| PtrState() : KnownPositiveRefCount(false), Partial(false), |
| Seq(S_None) {} |
| |
| void SetKnownPositiveRefCount() { |
| KnownPositiveRefCount = true; |
| } |
| |
| void ClearRefCount() { |
| KnownPositiveRefCount = false; |
| } |
| |
| bool IsKnownIncremented() const { |
| return KnownPositiveRefCount; |
| } |
| |
| void SetSeq(Sequence NewSeq) { |
| Seq = NewSeq; |
| } |
| |
| Sequence GetSeq() const { |
| return Seq; |
| } |
| |
| void ClearSequenceProgress() { |
| ResetSequenceProgress(S_None); |
| } |
| |
| void ResetSequenceProgress(Sequence NewSeq) { |
| Seq = NewSeq; |
| Partial = false; |
| RRI.clear(); |
| } |
| |
| void Merge(const PtrState &Other, bool TopDown); |
| }; |
| } |
| |
| void |
| PtrState::Merge(const PtrState &Other, bool TopDown) { |
| Seq = MergeSeqs(Seq, Other.Seq, TopDown); |
| KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount; |
| |
| // We can't merge a plain objc_retain with an objc_retainBlock. |
| if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock) |
| Seq = S_None; |
| |
| // If we're not in a sequence (anymore), drop all associated state. |
| if (Seq == S_None) { |
| Partial = false; |
| RRI.clear(); |
| } else if (Partial || Other.Partial) { |
| // If we're doing a merge on a path that's previously seen a partial |
| // merge, conservatively drop the sequence, to avoid doing partial |
| // RR elimination. If the branch predicates for the two merge differ, |
| // mixing them is unsafe. |
| ClearSequenceProgress(); |
| } else { |
| // Conservatively merge the ReleaseMetadata information. |
| if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata) |
| RRI.ReleaseMetadata = 0; |
| |
| RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe; |
| RRI.IsTailCallRelease = RRI.IsTailCallRelease && |
| Other.RRI.IsTailCallRelease; |
| RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end()); |
| |
| // Merge the insert point sets. If there are any differences, |
| // that makes this a partial merge. |
| Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size(); |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| I = Other.RRI.ReverseInsertPts.begin(), |
| E = Other.RRI.ReverseInsertPts.end(); I != E; ++I) |
| Partial |= RRI.ReverseInsertPts.insert(*I); |
| } |
| } |
| |
| namespace { |
| /// BBState - Per-BasicBlock state. |
| class BBState { |
| /// TopDownPathCount - The number of unique control paths from the entry |
| /// which can reach this block. |
| unsigned TopDownPathCount; |
| |
| /// BottomUpPathCount - The number of unique control paths to exits |
| /// from this block. |
| unsigned BottomUpPathCount; |
| |
| /// MapTy - A type for PerPtrTopDown and PerPtrBottomUp. |
| typedef MapVector<const Value *, PtrState> MapTy; |
| |
| /// PerPtrTopDown - The top-down traversal uses this to record information |
| /// known about a pointer at the bottom of each block. |
| MapTy PerPtrTopDown; |
| |
| /// PerPtrBottomUp - The bottom-up traversal uses this to record information |
| /// known about a pointer at the top of each block. |
| MapTy PerPtrBottomUp; |
| |
| /// Preds, Succs - Effective successors and predecessors of the current |
| /// block (this ignores ignorable edges and ignored backedges). |
| SmallVector<BasicBlock *, 2> Preds; |
| SmallVector<BasicBlock *, 2> Succs; |
| |
| public: |
| BBState() : TopDownPathCount(0), BottomUpPathCount(0) {} |
| |
| typedef MapTy::iterator ptr_iterator; |
| typedef MapTy::const_iterator ptr_const_iterator; |
| |
| ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); } |
| ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); } |
| ptr_const_iterator top_down_ptr_begin() const { |
| return PerPtrTopDown.begin(); |
| } |
| ptr_const_iterator top_down_ptr_end() const { |
| return PerPtrTopDown.end(); |
| } |
| |
| ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); } |
| ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); } |
| ptr_const_iterator bottom_up_ptr_begin() const { |
| return PerPtrBottomUp.begin(); |
| } |
| ptr_const_iterator bottom_up_ptr_end() const { |
| return PerPtrBottomUp.end(); |
| } |
| |
| /// SetAsEntry - Mark this block as being an entry block, which has one |
| /// path from the entry by definition. |
| void SetAsEntry() { TopDownPathCount = 1; } |
| |
| /// SetAsExit - Mark this block as being an exit block, which has one |
| /// path to an exit by definition. |
| void SetAsExit() { BottomUpPathCount = 1; } |
| |
| PtrState &getPtrTopDownState(const Value *Arg) { |
| return PerPtrTopDown[Arg]; |
| } |
| |
| PtrState &getPtrBottomUpState(const Value *Arg) { |
| return PerPtrBottomUp[Arg]; |
| } |
| |
| void clearBottomUpPointers() { |
| PerPtrBottomUp.clear(); |
| } |
| |
| void clearTopDownPointers() { |
| PerPtrTopDown.clear(); |
| } |
| |
| void InitFromPred(const BBState &Other); |
| void InitFromSucc(const BBState &Other); |
| void MergePred(const BBState &Other); |
| void MergeSucc(const BBState &Other); |
| |
| /// GetAllPathCount - Return the number of possible unique paths from an |
| /// entry to an exit which pass through this block. This is only valid |
| /// after both the top-down and bottom-up traversals are complete. |
| unsigned GetAllPathCount() const { |
| assert(TopDownPathCount != 0); |
| assert(BottomUpPathCount != 0); |
| return TopDownPathCount * BottomUpPathCount; |
| } |
| |
| // Specialized CFG utilities. |
| typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator; |
| edge_iterator pred_begin() { return Preds.begin(); } |
| edge_iterator pred_end() { return Preds.end(); } |
| edge_iterator succ_begin() { return Succs.begin(); } |
| edge_iterator succ_end() { return Succs.end(); } |
| |
| void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); } |
| void addPred(BasicBlock *Pred) { Preds.push_back(Pred); } |
| |
| bool isExit() const { return Succs.empty(); } |
| }; |
| } |
| |
| void BBState::InitFromPred(const BBState &Other) { |
| PerPtrTopDown = Other.PerPtrTopDown; |
| TopDownPathCount = Other.TopDownPathCount; |
| } |
| |
| void BBState::InitFromSucc(const BBState &Other) { |
| PerPtrBottomUp = Other.PerPtrBottomUp; |
| BottomUpPathCount = Other.BottomUpPathCount; |
| } |
| |
| /// MergePred - The top-down traversal uses this to merge information about |
| /// predecessors to form the initial state for a new block. |
| void BBState::MergePred(const BBState &Other) { |
| // Other.TopDownPathCount can be 0, in which case it is either dead or a |
| // loop backedge. Loop backedges are special. |
| TopDownPathCount += Other.TopDownPathCount; |
| |
| // Check for overflow. If we have overflow, fall back to conservative behavior. |
| if (TopDownPathCount < Other.TopDownPathCount) { |
| clearTopDownPointers(); |
| return; |
| } |
| |
| // For each entry in the other set, if our set has an entry with the same key, |
| // merge the entries. Otherwise, copy the entry and merge it with an empty |
| // entry. |
| for (ptr_const_iterator MI = Other.top_down_ptr_begin(), |
| ME = Other.top_down_ptr_end(); MI != ME; ++MI) { |
| std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI); |
| Pair.first->second.Merge(Pair.second ? PtrState() : MI->second, |
| /*TopDown=*/true); |
| } |
| |
| // For each entry in our set, if the other set doesn't have an entry with the |
| // same key, force it to merge with an empty entry. |
| for (ptr_iterator MI = top_down_ptr_begin(), |
| ME = top_down_ptr_end(); MI != ME; ++MI) |
| if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end()) |
| MI->second.Merge(PtrState(), /*TopDown=*/true); |
| } |
| |
| /// MergeSucc - The bottom-up traversal uses this to merge information about |
| /// successors to form the initial state for a new block. |
| void BBState::MergeSucc(const BBState &Other) { |
| // Other.BottomUpPathCount can be 0, in which case it is either dead or a |
| // loop backedge. Loop backedges are special. |
| BottomUpPathCount += Other.BottomUpPathCount; |
| |
| // Check for overflow. If we have overflow, fall back to conservative behavior. |
| if (BottomUpPathCount < Other.BottomUpPathCount) { |
| clearBottomUpPointers(); |
| return; |
| } |
| |
| // For each entry in the other set, if our set has an entry with the |
| // same key, merge the entries. Otherwise, copy the entry and merge |
| // it with an empty entry. |
| for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(), |
| ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) { |
| std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI); |
| Pair.first->second.Merge(Pair.second ? PtrState() : MI->second, |
| /*TopDown=*/false); |
| } |
| |
| // For each entry in our set, if the other set doesn't have an entry |
| // with the same key, force it to merge with an empty entry. |
| for (ptr_iterator MI = bottom_up_ptr_begin(), |
| ME = bottom_up_ptr_end(); MI != ME; ++MI) |
| if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end()) |
| MI->second.Merge(PtrState(), /*TopDown=*/false); |
| } |
| |
| namespace { |
| /// ObjCARCOpt - The main ARC optimization pass. |
| class ObjCARCOpt : public FunctionPass { |
| bool Changed; |
| ProvenanceAnalysis PA; |
| |
| /// Run - A flag indicating whether this optimization pass should run. |
| bool Run; |
| |
| /// RetainRVCallee, etc. - Declarations for ObjC runtime |
| /// functions, for use in creating calls to them. These are initialized |
| /// lazily to avoid cluttering up the Module with unused declarations. |
| Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee, |
| *RetainCallee, *RetainBlockCallee, *AutoreleaseCallee; |
| |
| /// UsedInThisFunciton - Flags which determine whether each of the |
| /// interesting runtine functions is in fact used in the current function. |
| unsigned UsedInThisFunction; |
| |
| /// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release |
| /// metadata. |
| unsigned ImpreciseReleaseMDKind; |
| |
| /// CopyOnEscapeMDKind - The Metadata Kind for clang.arc.copy_on_escape |
| /// metadata. |
| unsigned CopyOnEscapeMDKind; |
| |
| /// NoObjCARCExceptionsMDKind - The Metadata Kind for |
| /// clang.arc.no_objc_arc_exceptions metadata. |
| unsigned NoObjCARCExceptionsMDKind; |
| |
| Constant *getRetainRVCallee(Module *M); |
| Constant *getAutoreleaseRVCallee(Module *M); |
| Constant *getReleaseCallee(Module *M); |
| Constant *getRetainCallee(Module *M); |
| Constant *getRetainBlockCallee(Module *M); |
| Constant *getAutoreleaseCallee(Module *M); |
| |
| bool IsRetainBlockOptimizable(const Instruction *Inst); |
| |
| void OptimizeRetainCall(Function &F, Instruction *Retain); |
| bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV); |
| void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV); |
| void OptimizeIndividualCalls(Function &F); |
| |
| void CheckForCFGHazards(const BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| BBState &MyStates) const; |
| bool VisitInstructionBottomUp(Instruction *Inst, |
| BasicBlock *BB, |
| MapVector<Value *, RRInfo> &Retains, |
| BBState &MyStates); |
| bool VisitBottomUp(BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| MapVector<Value *, RRInfo> &Retains); |
| bool VisitInstructionTopDown(Instruction *Inst, |
| DenseMap<Value *, RRInfo> &Releases, |
| BBState &MyStates); |
| bool VisitTopDown(BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| DenseMap<Value *, RRInfo> &Releases); |
| bool Visit(Function &F, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases); |
| |
| void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases, |
| SmallVectorImpl<Instruction *> &DeadInsts, |
| Module *M); |
| |
| bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases, |
| Module *M); |
| |
| void OptimizeWeakCalls(Function &F); |
| |
| bool OptimizeSequences(Function &F); |
| |
| void OptimizeReturns(Function &F); |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| virtual bool doInitialization(Module &M); |
| virtual bool runOnFunction(Function &F); |
| virtual void releaseMemory(); |
| |
| public: |
| static char ID; |
| ObjCARCOpt() : FunctionPass(ID) { |
| initializeObjCARCOptPass(*PassRegistry::getPassRegistry()); |
| } |
| }; |
| } |
| |
| char ObjCARCOpt::ID = 0; |
| INITIALIZE_PASS_BEGIN(ObjCARCOpt, |
| "objc-arc", "ObjC ARC optimization", false, false) |
| INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis) |
| INITIALIZE_PASS_END(ObjCARCOpt, |
| "objc-arc", "ObjC ARC optimization", false, false) |
| |
| Pass *llvm::createObjCARCOptPass() { |
| return new ObjCARCOpt(); |
| } |
| |
| void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<ObjCARCAliasAnalysis>(); |
| AU.addRequired<AliasAnalysis>(); |
| // ARC optimization doesn't currently split critical edges. |
| AU.setPreservesCFG(); |
| } |
| |
| bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) { |
| // Without the magic metadata tag, we have to assume this might be an |
| // objc_retainBlock call inserted to convert a block pointer to an id, |
| // in which case it really is needed. |
| if (!Inst->getMetadata(CopyOnEscapeMDKind)) |
| return false; |
| |
| // If the pointer "escapes" (not including being used in a call), |
| // the copy may be needed. |
| if (DoesObjCBlockEscape(Inst)) |
| return false; |
| |
| // Otherwise, it's not needed. |
| return true; |
| } |
| |
| Constant *ObjCARCOpt::getRetainRVCallee(Module *M) { |
| if (!RetainRVCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *Params[] = { I8X }; |
| FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| RetainRVCallee = |
| M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy, |
| Attributes); |
| } |
| return RetainRVCallee; |
| } |
| |
| Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) { |
| if (!AutoreleaseRVCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *Params[] = { I8X }; |
| FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| AutoreleaseRVCallee = |
| M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy, |
| Attributes); |
| } |
| return AutoreleaseRVCallee; |
| } |
| |
| Constant *ObjCARCOpt::getReleaseCallee(Module *M) { |
| if (!ReleaseCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) }; |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| ReleaseCallee = |
| M->getOrInsertFunction( |
| "objc_release", |
| FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false), |
| Attributes); |
| } |
| return ReleaseCallee; |
| } |
| |
| Constant *ObjCARCOpt::getRetainCallee(Module *M) { |
| if (!RetainCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) }; |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| RetainCallee = |
| M->getOrInsertFunction( |
| "objc_retain", |
| FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| Attributes); |
| } |
| return RetainCallee; |
| } |
| |
| Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) { |
| if (!RetainBlockCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) }; |
| // objc_retainBlock is not nounwind because it calls user copy constructors |
| // which could theoretically throw. |
| RetainBlockCallee = |
| M->getOrInsertFunction( |
| "objc_retainBlock", |
| FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| AttrListPtr()); |
| } |
| return RetainBlockCallee; |
| } |
| |
| Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) { |
| if (!AutoreleaseCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) }; |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| AutoreleaseCallee = |
| M->getOrInsertFunction( |
| "objc_autorelease", |
| FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| Attributes); |
| } |
| return AutoreleaseCallee; |
| } |
| |
| /// IsPotentialUse - Test whether the given value is possible a |
| /// reference-counted pointer, including tests which utilize AliasAnalysis. |
| static bool IsPotentialUse(const Value *Op, AliasAnalysis &AA) { |
| // First make the rudimentary check. |
| if (!IsPotentialUse(Op)) |
| return false; |
| |
| // Objects in constant memory are not reference-counted. |
| if (AA.pointsToConstantMemory(Op)) |
| return false; |
| |
| // Pointers in constant memory are not pointing to reference-counted objects. |
| if (const LoadInst *LI = dyn_cast<LoadInst>(Op)) |
| if (AA.pointsToConstantMemory(LI->getPointerOperand())) |
| return false; |
| |
| // Otherwise assume the worst. |
| return true; |
| } |
| |
| /// CanAlterRefCount - Test whether the given instruction can result in a |
| /// reference count modification (positive or negative) for the pointer's |
| /// object. |
| static bool |
| CanAlterRefCount(const Instruction *Inst, const Value *Ptr, |
| ProvenanceAnalysis &PA, InstructionClass Class) { |
| switch (Class) { |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| case IC_User: |
| // These operations never directly modify a reference count. |
| return false; |
| default: break; |
| } |
| |
| ImmutableCallSite CS = static_cast<const Value *>(Inst); |
| assert(CS && "Only calls can alter reference counts!"); |
| |
| // See if AliasAnalysis can help us with the call. |
| AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS); |
| if (AliasAnalysis::onlyReadsMemory(MRB)) |
| return false; |
| if (AliasAnalysis::onlyAccessesArgPointees(MRB)) { |
| for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); |
| I != E; ++I) { |
| const Value *Op = *I; |
| if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op)) |
| return true; |
| } |
| return false; |
| } |
| |
| // Assume the worst. |
| return true; |
| } |
| |
| /// CanUse - Test whether the given instruction can "use" the given pointer's |
| /// object in a way that requires the reference count to be positive. |
| static bool |
| CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA, |
| InstructionClass Class) { |
| // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers. |
| if (Class == IC_Call) |
| return false; |
| |
| // Consider various instructions which may have pointer arguments which are |
| // not "uses". |
| if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) { |
| // Comparing a pointer with null, or any other constant, isn't really a use, |
| // because we don't care what the pointer points to, or about the values |
| // of any other dynamic reference-counted pointers. |
| if (!IsPotentialUse(ICI->getOperand(1), *PA.getAA())) |
| return false; |
| } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) { |
| // For calls, just check the arguments (and not the callee operand). |
| for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(), |
| OE = CS.arg_end(); OI != OE; ++OI) { |
| const Value *Op = *OI; |
| if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op)) |
| return true; |
| } |
| return false; |
| } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| // Special-case stores, because we don't care about the stored value, just |
| // the store address. |
| const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand()); |
| // If we can't tell what the underlying object was, assume there is a |
| // dependence. |
| return IsPotentialUse(Op, *PA.getAA()) && PA.related(Op, Ptr); |
| } |
| |
| // Check each operand for a match. |
| for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end(); |
| OI != OE; ++OI) { |
| const Value *Op = *OI; |
| if (IsPotentialUse(Op, *PA.getAA()) && PA.related(Ptr, Op)) |
| return true; |
| } |
| return false; |
| } |
| |
| /// CanInterruptRV - Test whether the given instruction can autorelease |
| /// any pointer or cause an autoreleasepool pop. |
| static bool |
| CanInterruptRV(InstructionClass Class) { |
| switch (Class) { |
| case IC_AutoreleasepoolPop: |
| case IC_CallOrUser: |
| case IC_Call: |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| case IC_FusedRetainAutorelease: |
| case IC_FusedRetainAutoreleaseRV: |
| return true; |
| default: |
| return false; |
| } |
| } |
| |
| namespace { |
| /// DependenceKind - There are several kinds of dependence-like concepts in |
| /// use here. |
| enum DependenceKind { |
| NeedsPositiveRetainCount, |
| AutoreleasePoolBoundary, |
| CanChangeRetainCount, |
| RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease. |
| RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue. |
| RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue. |
| }; |
| } |
| |
| /// Depends - Test if there can be dependencies on Inst through Arg. This |
| /// function only tests dependencies relevant for removing pairs of calls. |
| static bool |
| Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg, |
| ProvenanceAnalysis &PA) { |
| // If we've reached the definition of Arg, stop. |
| if (Inst == Arg) |
| return true; |
| |
| switch (Flavor) { |
| case NeedsPositiveRetainCount: { |
| InstructionClass Class = GetInstructionClass(Inst); |
| switch (Class) { |
| case IC_AutoreleasepoolPop: |
| case IC_AutoreleasepoolPush: |
| case IC_None: |
| return false; |
| default: |
| return CanUse(Inst, Arg, PA, Class); |
| } |
| } |
| |
| case AutoreleasePoolBoundary: { |
| InstructionClass Class = GetInstructionClass(Inst); |
| switch (Class) { |
| case IC_AutoreleasepoolPop: |
| case IC_AutoreleasepoolPush: |
| // These mark the end and begin of an autorelease pool scope. |
| return true; |
| default: |
| // Nothing else does this. |
| return false; |
| } |
| } |
| |
| case CanChangeRetainCount: { |
| InstructionClass Class = GetInstructionClass(Inst); |
| switch (Class) { |
| case IC_AutoreleasepoolPop: |
| // Conservatively assume this can decrement any count. |
| return true; |
| case IC_AutoreleasepoolPush: |
| case IC_None: |
| return false; |
| default: |
| return CanAlterRefCount(Inst, Arg, PA, Class); |
| } |
| } |
| |
| case RetainAutoreleaseDep: |
| switch (GetBasicInstructionClass(Inst)) { |
| case IC_AutoreleasepoolPop: |
| case IC_AutoreleasepoolPush: |
| // Don't merge an objc_autorelease with an objc_retain inside a different |
| // autoreleasepool scope. |
| return true; |
| case IC_Retain: |
| case IC_RetainRV: |
| // Check for a retain of the same pointer for merging. |
| return GetObjCArg(Inst) == Arg; |
| default: |
| // Nothing else matters for objc_retainAutorelease formation. |
| return false; |
| } |
| |
| case RetainAutoreleaseRVDep: { |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| switch (Class) { |
| case IC_Retain: |
| case IC_RetainRV: |
| // Check for a retain of the same pointer for merging. |
| return GetObjCArg(Inst) == Arg; |
| default: |
| // Anything that can autorelease interrupts |
| // retainAutoreleaseReturnValue formation. |
| return CanInterruptRV(Class); |
| } |
| } |
| |
| case RetainRVDep: |
| return CanInterruptRV(GetBasicInstructionClass(Inst)); |
| } |
| |
| llvm_unreachable("Invalid dependence flavor"); |
| } |
| |
| /// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and |
| /// find local and non-local dependencies on Arg. |
| /// TODO: Cache results? |
| static void |
| FindDependencies(DependenceKind Flavor, |
| const Value *Arg, |
| BasicBlock *StartBB, Instruction *StartInst, |
| SmallPtrSet<Instruction *, 4> &DependingInstructions, |
| SmallPtrSet<const BasicBlock *, 4> &Visited, |
| ProvenanceAnalysis &PA) { |
| BasicBlock::iterator StartPos = StartInst; |
| |
| SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist; |
| Worklist.push_back(std::make_pair(StartBB, StartPos)); |
| do { |
| std::pair<BasicBlock *, BasicBlock::iterator> Pair = |
| Worklist.pop_back_val(); |
| BasicBlock *LocalStartBB = Pair.first; |
| BasicBlock::iterator LocalStartPos = Pair.second; |
| BasicBlock::iterator StartBBBegin = LocalStartBB->begin(); |
| for (;;) { |
| if (LocalStartPos == StartBBBegin) { |
| pred_iterator PI(LocalStartBB), PE(LocalStartBB, false); |
| if (PI == PE) |
| // If we've reached the function entry, produce a null dependence. |
| DependingInstructions.insert(0); |
| else |
| // Add the predecessors to the worklist. |
| do { |
| BasicBlock *PredBB = *PI; |
| if (Visited.insert(PredBB)) |
| Worklist.push_back(std::make_pair(PredBB, PredBB->end())); |
| } while (++PI != PE); |
| break; |
| } |
| |
| Instruction *Inst = --LocalStartPos; |
| if (Depends(Flavor, Inst, Arg, PA)) { |
| DependingInstructions.insert(Inst); |
| break; |
| } |
| } |
| } while (!Worklist.empty()); |
| |
| // Determine whether the original StartBB post-dominates all of the blocks we |
| // visited. If not, insert a sentinal indicating that most optimizations are |
| // not safe. |
| for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(), |
| E = Visited.end(); I != E; ++I) { |
| const BasicBlock *BB = *I; |
| if (BB == StartBB) |
| continue; |
| const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) { |
| const BasicBlock *Succ = *SI; |
| if (Succ != StartBB && !Visited.count(Succ)) { |
| DependingInstructions.insert(reinterpret_cast<Instruction *>(-1)); |
| return; |
| } |
| } |
| } |
| } |
| |
| static bool isNullOrUndef(const Value *V) { |
| return isa<ConstantPointerNull>(V) || isa<UndefValue>(V); |
| } |
| |
| static bool isNoopInstruction(const Instruction *I) { |
| return isa<BitCastInst>(I) || |
| (isa<GetElementPtrInst>(I) && |
| cast<GetElementPtrInst>(I)->hasAllZeroIndices()); |
| } |
| |
| /// OptimizeRetainCall - Turn objc_retain into |
| /// objc_retainAutoreleasedReturnValue if the operand is a return value. |
| void |
| ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) { |
| ImmutableCallSite CS(GetObjCArg(Retain)); |
| const Instruction *Call = CS.getInstruction(); |
| if (!Call) return; |
| if (Call->getParent() != Retain->getParent()) return; |
| |
| // Check that the call is next to the retain. |
| BasicBlock::const_iterator I = Call; |
| ++I; |
| while (isNoopInstruction(I)) ++I; |
| if (&*I != Retain) |
| return; |
| |
| // Turn it to an objc_retainAutoreleasedReturnValue.. |
| Changed = true; |
| ++NumPeeps; |
| cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent())); |
| } |
| |
| /// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into |
| /// objc_retain if the operand is not a return value. Or, if it can be paired |
| /// with an objc_autoreleaseReturnValue, delete the pair and return true. |
| bool |
| ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) { |
| // Check for the argument being from an immediately preceding call or invoke. |
| const Value *Arg = GetObjCArg(RetainRV); |
| ImmutableCallSite CS(Arg); |
| if (const Instruction *Call = CS.getInstruction()) { |
| if (Call->getParent() == RetainRV->getParent()) { |
| BasicBlock::const_iterator I = Call; |
| ++I; |
| while (isNoopInstruction(I)) ++I; |
| if (&*I == RetainRV) |
| return false; |
| } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) { |
| BasicBlock *RetainRVParent = RetainRV->getParent(); |
| if (II->getNormalDest() == RetainRVParent) { |
| BasicBlock::const_iterator I = RetainRVParent->begin(); |
| while (isNoopInstruction(I)) ++I; |
| if (&*I == RetainRV) |
| return false; |
| } |
| } |
| } |
| |
| // Check for being preceded by an objc_autoreleaseReturnValue on the same |
| // pointer. In this case, we can delete the pair. |
| BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin(); |
| if (I != Begin) { |
| do --I; while (I != Begin && isNoopInstruction(I)); |
| if (GetBasicInstructionClass(I) == IC_AutoreleaseRV && |
| GetObjCArg(I) == Arg) { |
| Changed = true; |
| ++NumPeeps; |
| EraseInstruction(I); |
| EraseInstruction(RetainRV); |
| return true; |
| } |
| } |
| |
| // Turn it to a plain objc_retain. |
| Changed = true; |
| ++NumPeeps; |
| cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent())); |
| return false; |
| } |
| |
| /// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into |
| /// objc_autorelease if the result is not used as a return value. |
| void |
| ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) { |
| // Check for a return of the pointer value. |
| const Value *Ptr = GetObjCArg(AutoreleaseRV); |
| SmallVector<const Value *, 2> Users; |
| Users.push_back(Ptr); |
| do { |
| Ptr = Users.pop_back_val(); |
| for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end(); |
| UI != UE; ++UI) { |
| const User *I = *UI; |
| if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV) |
| return; |
| if (isa<BitCastInst>(I)) |
| Users.push_back(I); |
| } |
| } while (!Users.empty()); |
| |
| Changed = true; |
| ++NumPeeps; |
| cast<CallInst>(AutoreleaseRV)-> |
| setCalledFunction(getAutoreleaseCallee(F.getParent())); |
| } |
| |
| /// OptimizeIndividualCalls - Visit each call, one at a time, and make |
| /// simplifications without doing any additional analysis. |
| void ObjCARCOpt::OptimizeIndividualCalls(Function &F) { |
| // Reset all the flags in preparation for recomputing them. |
| UsedInThisFunction = 0; |
| |
| // Visit all objc_* calls in F. |
| for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| Instruction *Inst = &*I++; |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| |
| switch (Class) { |
| default: break; |
| |
| // Delete no-op casts. These function calls have special semantics, but |
| // the semantics are entirely implemented via lowering in the front-end, |
| // so by the time they reach the optimizer, they are just no-op calls |
| // which return their argument. |
| // |
| // There are gray areas here, as the ability to cast reference-counted |
| // pointers to raw void* and back allows code to break ARC assumptions, |
| // however these are currently considered to be unimportant. |
| case IC_NoopCast: |
| Changed = true; |
| ++NumNoops; |
| EraseInstruction(Inst); |
| continue; |
| |
| // If the pointer-to-weak-pointer is null, it's undefined behavior. |
| case IC_StoreWeak: |
| case IC_LoadWeak: |
| case IC_LoadWeakRetained: |
| case IC_InitWeak: |
| case IC_DestroyWeak: { |
| CallInst *CI = cast<CallInst>(Inst); |
| if (isNullOrUndef(CI->getArgOperand(0))) { |
| Changed = true; |
| Type *Ty = CI->getArgOperand(0)->getType(); |
| new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), |
| Constant::getNullValue(Ty), |
| CI); |
| CI->replaceAllUsesWith(UndefValue::get(CI->getType())); |
| CI->eraseFromParent(); |
| continue; |
| } |
| break; |
| } |
| case IC_CopyWeak: |
| case IC_MoveWeak: { |
| CallInst *CI = cast<CallInst>(Inst); |
| if (isNullOrUndef(CI->getArgOperand(0)) || |
| isNullOrUndef(CI->getArgOperand(1))) { |
| Changed = true; |
| Type *Ty = CI->getArgOperand(0)->getType(); |
| new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), |
| Constant::getNullValue(Ty), |
| CI); |
| CI->replaceAllUsesWith(UndefValue::get(CI->getType())); |
| CI->eraseFromParent(); |
| continue; |
| } |
| break; |
| } |
| case IC_Retain: |
| OptimizeRetainCall(F, Inst); |
| break; |
| case IC_RetainRV: |
| if (OptimizeRetainRVCall(F, Inst)) |
| continue; |
| break; |
| case IC_AutoreleaseRV: |
| OptimizeAutoreleaseRVCall(F, Inst); |
| break; |
| } |
| |
| // objc_autorelease(x) -> objc_release(x) if x is otherwise unused. |
| if (IsAutorelease(Class) && Inst->use_empty()) { |
| CallInst *Call = cast<CallInst>(Inst); |
| const Value *Arg = Call->getArgOperand(0); |
| Arg = FindSingleUseIdentifiedObject(Arg); |
| if (Arg) { |
| Changed = true; |
| ++NumAutoreleases; |
| |
| // Create the declaration lazily. |
| LLVMContext &C = Inst->getContext(); |
| CallInst *NewCall = |
| CallInst::Create(getReleaseCallee(F.getParent()), |
| Call->getArgOperand(0), "", Call); |
| NewCall->setMetadata(ImpreciseReleaseMDKind, |
| MDNode::get(C, ArrayRef<Value *>())); |
| EraseInstruction(Call); |
| Inst = NewCall; |
| Class = IC_Release; |
| } |
| } |
| |
| // For functions which can never be passed stack arguments, add |
| // a tail keyword. |
| if (IsAlwaysTail(Class)) { |
| Changed = true; |
| cast<CallInst>(Inst)->setTailCall(); |
| } |
| |
| // Set nounwind as needed. |
| if (IsNoThrow(Class)) { |
| Changed = true; |
| cast<CallInst>(Inst)->setDoesNotThrow(); |
| } |
| |
| if (!IsNoopOnNull(Class)) { |
| UsedInThisFunction |= 1 << Class; |
| continue; |
| } |
| |
| const Value *Arg = GetObjCArg(Inst); |
| |
| // ARC calls with null are no-ops. Delete them. |
| if (isNullOrUndef(Arg)) { |
| Changed = true; |
| ++NumNoops; |
| EraseInstruction(Inst); |
| continue; |
| } |
| |
| // Keep track of which of retain, release, autorelease, and retain_block |
| // are actually present in this function. |
| UsedInThisFunction |= 1 << Class; |
| |
| // If Arg is a PHI, and one or more incoming values to the |
| // PHI are null, and the call is control-equivalent to the PHI, and there |
| // are no relevant side effects between the PHI and the call, the call |
| // could be pushed up to just those paths with non-null incoming values. |
| // For now, don't bother splitting critical edges for this. |
| SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist; |
| Worklist.push_back(std::make_pair(Inst, Arg)); |
| do { |
| std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val(); |
| Inst = Pair.first; |
| Arg = Pair.second; |
| |
| const PHINode *PN = dyn_cast<PHINode>(Arg); |
| if (!PN) continue; |
| |
| // Determine if the PHI has any null operands, or any incoming |
| // critical edges. |
| bool HasNull = false; |
| bool HasCriticalEdges = false; |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| Value *Incoming = |
| StripPointerCastsAndObjCCalls(PN->getIncomingValue(i)); |
| if (isNullOrUndef(Incoming)) |
| HasNull = true; |
| else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back()) |
| .getNumSuccessors() != 1) { |
| HasCriticalEdges = true; |
| break; |
| } |
| } |
| // If we have null operands and no critical edges, optimize. |
| if (!HasCriticalEdges && HasNull) { |
| SmallPtrSet<Instruction *, 4> DependingInstructions; |
| SmallPtrSet<const BasicBlock *, 4> Visited; |
| |
| // Check that there is nothing that cares about the reference |
| // count between the call and the phi. |
| switch (Class) { |
| case IC_Retain: |
| case IC_RetainBlock: |
| // These can always be moved up. |
| break; |
| case IC_Release: |
| // These can't be moved across things that care about the retain |
| // count. |
| FindDependencies(NeedsPositiveRetainCount, Arg, |
| Inst->getParent(), Inst, |
| DependingInstructions, Visited, PA); |
| break; |
| case IC_Autorelease: |
| // These can't be moved across autorelease pool scope boundaries. |
| FindDependencies(AutoreleasePoolBoundary, Arg, |
| Inst->getParent(), Inst, |
| DependingInstructions, Visited, PA); |
| break; |
| case IC_RetainRV: |
| case IC_AutoreleaseRV: |
| // Don't move these; the RV optimization depends on the autoreleaseRV |
| // being tail called, and the retainRV being immediately after a call |
| // (which might still happen if we get lucky with codegen layout, but |
| // it's not worth taking the chance). |
| continue; |
| default: |
| llvm_unreachable("Invalid dependence flavor"); |
| } |
| |
| if (DependingInstructions.size() == 1 && |
| *DependingInstructions.begin() == PN) { |
| Changed = true; |
| ++NumPartialNoops; |
| // Clone the call into each predecessor that has a non-null value. |
| CallInst *CInst = cast<CallInst>(Inst); |
| Type *ParamTy = CInst->getArgOperand(0)->getType(); |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| Value *Incoming = |
| StripPointerCastsAndObjCCalls(PN->getIncomingValue(i)); |
| if (!isNullOrUndef(Incoming)) { |
| CallInst *Clone = cast<CallInst>(CInst->clone()); |
| Value *Op = PN->getIncomingValue(i); |
| Instruction *InsertPos = &PN->getIncomingBlock(i)->back(); |
| if (Op->getType() != ParamTy) |
| Op = new BitCastInst(Op, ParamTy, "", InsertPos); |
| Clone->setArgOperand(0, Op); |
| Clone->insertBefore(InsertPos); |
| Worklist.push_back(std::make_pair(Clone, Incoming)); |
| } |
| } |
| // Erase the original call. |
| EraseInstruction(CInst); |
| continue; |
| } |
| } |
| } while (!Worklist.empty()); |
| } |
| } |
| |
| /// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible |
| /// control flow, or other CFG structures where moving code across the edge |
| /// would result in it being executed more. |
| void |
| ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| BBState &MyStates) const { |
| // If any top-down local-use or possible-dec has a succ which is earlier in |
| // the sequence, forget it. |
| for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(), |
| E = MyStates.top_down_ptr_end(); I != E; ++I) |
| switch (I->second.GetSeq()) { |
| default: break; |
| case S_Use: { |
| const Value *Arg = I->first; |
| const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| bool SomeSuccHasSame = false; |
| bool AllSuccsHaveSame = true; |
| PtrState &S = I->second; |
| succ_const_iterator SI(TI), SE(TI, false); |
| |
| // If the terminator is an invoke marked with the |
| // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be |
| // ignored, for ARC purposes. |
| if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind)) |
| --SE; |
| |
| for (; SI != SE; ++SI) { |
| Sequence SuccSSeq = S_None; |
| bool SuccSRRIKnownSafe = false; |
| // If VisitBottomUp has pointer information for this successor, take |
| // what we know about it. |
| DenseMap<const BasicBlock *, BBState>::iterator BBI = |
| BBStates.find(*SI); |
| assert(BBI != BBStates.end()); |
| const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg); |
| SuccSSeq = SuccS.GetSeq(); |
| SuccSRRIKnownSafe = SuccS.RRI.KnownSafe; |
| switch (SuccSSeq) { |
| case S_None: |
| case S_CanRelease: { |
| if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) { |
| S.ClearSequenceProgress(); |
| break; |
| } |
| continue; |
| } |
| case S_Use: |
| SomeSuccHasSame = true; |
| break; |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) |
| AllSuccsHaveSame = false; |
| break; |
| case S_Retain: |
| llvm_unreachable("bottom-up pointer in retain state!"); |
| } |
| } |
| // If the state at the other end of any of the successor edges |
| // matches the current state, require all edges to match. This |
| // guards against loops in the middle of a sequence. |
| if (SomeSuccHasSame && !AllSuccsHaveSame) |
| S.ClearSequenceProgress(); |
| break; |
| } |
| case S_CanRelease: { |
| const Value *Arg = I->first; |
| const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| bool SomeSuccHasSame = false; |
| bool AllSuccsHaveSame = true; |
| PtrState &S = I->second; |
| succ_const_iterator SI(TI), SE(TI, false); |
| |
| // If the terminator is an invoke marked with the |
| // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be |
| // ignored, for ARC purposes. |
| if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind)) |
| --SE; |
| |
| for (; SI != SE; ++SI) { |
| Sequence SuccSSeq = S_None; |
| bool SuccSRRIKnownSafe = false; |
| // If VisitBottomUp has pointer information for this successor, take |
| // what we know about it. |
| DenseMap<const BasicBlock *, BBState>::iterator BBI = |
| BBStates.find(*SI); |
| assert(BBI != BBStates.end()); |
| const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg); |
| SuccSSeq = SuccS.GetSeq(); |
| SuccSRRIKnownSafe = SuccS.RRI.KnownSafe; |
| switch (SuccSSeq) { |
| case S_None: { |
| if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) { |
| S.ClearSequenceProgress(); |
| break; |
| } |
| continue; |
| } |
| case S_CanRelease: |
| SomeSuccHasSame = true; |
| break; |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| case S_Use: |
| if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) |
| AllSuccsHaveSame = false; |
| break; |
| case S_Retain: |
| llvm_unreachable("bottom-up pointer in retain state!"); |
| } |
| } |
| // If the state at the other end of any of the successor edges |
| // matches the current state, require all edges to match. This |
| // guards against loops in the middle of a sequence. |
| if (SomeSuccHasSame && !AllSuccsHaveSame) |
| S.ClearSequenceProgress(); |
| break; |
| } |
| } |
| } |
| |
| bool |
| ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst, |
| BasicBlock *BB, |
| MapVector<Value *, RRInfo> &Retains, |
| BBState &MyStates) { |
| bool NestingDetected = false; |
| InstructionClass Class = GetInstructionClass(Inst); |
| const Value *Arg = 0; |
| |
| switch (Class) { |
| case IC_Release: { |
| Arg = GetObjCArg(Inst); |
| |
| PtrState &S = MyStates.getPtrBottomUpState(Arg); |
| |
| // If we see two releases in a row on the same pointer. If so, make |
| // a note, and we'll cicle back to revisit it after we've |
| // hopefully eliminated the second release, which may allow us to |
| // eliminate the first release too. |
| // Theoretically we could implement removal of nested retain+release |
| // pairs by making PtrState hold a stack of states, but this is |
| // simple and avoids adding overhead for the non-nested case. |
| if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease) |
| NestingDetected = true; |
| |
| MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind); |
| S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release); |
| S.RRI.ReleaseMetadata = ReleaseMetadata; |
| S.RRI.KnownSafe = S.IsKnownIncremented(); |
| S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall(); |
| S.RRI.Calls.insert(Inst); |
| |
| S.SetKnownPositiveRefCount(); |
| break; |
| } |
| case IC_RetainBlock: |
| // An objc_retainBlock call with just a use may need to be kept, |
| // because it may be copying a block from the stack to the heap. |
| if (!IsRetainBlockOptimizable(Inst)) |
| break; |
| // FALLTHROUGH |
| case IC_Retain: |
| case IC_RetainRV: { |
| Arg = GetObjCArg(Inst); |
| |
| PtrState &S = MyStates.getPtrBottomUpState(Arg); |
| S.SetKnownPositiveRefCount(); |
| |
| switch (S.GetSeq()) { |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| case S_Use: |
| S.RRI.ReverseInsertPts.clear(); |
| // FALL THROUGH |
| case S_CanRelease: |
| // Don't do retain+release tracking for IC_RetainRV, because it's |
| // better to let it remain as the first instruction after a call. |
| if (Class != IC_RetainRV) { |
| S.RRI.IsRetainBlock = Class == IC_RetainBlock; |
| Retains[Inst] = S.RRI; |
| } |
| S.ClearSequenceProgress(); |
| break; |
| case S_None: |
| break; |
| case S_Retain: |
| llvm_unreachable("bottom-up pointer in retain state!"); |
| } |
| return NestingDetected; |
| } |
| case IC_AutoreleasepoolPop: |
| // Conservatively, clear MyStates for all known pointers. |
| MyStates.clearBottomUpPointers(); |
| return NestingDetected; |
| case IC_AutoreleasepoolPush: |
| case IC_None: |
| // These are irrelevant. |
| return NestingDetected; |
| default: |
| break; |
| } |
| |
| // Consider any other possible effects of this instruction on each |
| // pointer being tracked. |
| for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(), |
| ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) { |
| const Value *Ptr = MI->first; |
| if (Ptr == Arg) |
| continue; // Handled above. |
| PtrState &S = MI->second; |
| Sequence Seq = S.GetSeq(); |
| |
| // Check for possible releases. |
| if (CanAlterRefCount(Inst, Ptr, PA, Class)) { |
| S.ClearRefCount(); |
| switch (Seq) { |
| case S_Use: |
| S.SetSeq(S_CanRelease); |
| continue; |
| case S_CanRelease: |
| case S_Release: |
| case S_MovableRelease: |
| case S_Stop: |
| case S_None: |
| break; |
| case S_Retain: |
| llvm_unreachable("bottom-up pointer in retain state!"); |
| } |
| } |
| |
| // Check for possible direct uses. |
| switch (Seq) { |
| case S_Release: |
| case S_MovableRelease: |
| if (CanUse(Inst, Ptr, PA, Class)) { |
| assert(S.RRI.ReverseInsertPts.empty()); |
| // If this is an invoke instruction, we're scanning it as part of |
| // one of its successor blocks, since we can't insert code after it |
| // in its own block, and we don't want to split critical edges. |
| if (isa<InvokeInst>(Inst)) |
| S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt()); |
| else |
| S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst))); |
| S.SetSeq(S_Use); |
| } else if (Seq == S_Release && |
| (Class == IC_User || Class == IC_CallOrUser)) { |
| // Non-movable releases depend on any possible objc pointer use. |
| S.SetSeq(S_Stop); |
| assert(S.RRI.ReverseInsertPts.empty()); |
| // As above; handle invoke specially. |
| if (isa<InvokeInst>(Inst)) |
| S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt()); |
| else |
| S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst))); |
| } |
| break; |
| case S_Stop: |
| if (CanUse(Inst, Ptr, PA, Class)) |
| S.SetSeq(S_Use); |
| break; |
| case S_CanRelease: |
| case S_Use: |
| case S_None: |
| break; |
| case S_Retain: |
| llvm_unreachable("bottom-up pointer in retain state!"); |
| } |
| } |
| |
| return NestingDetected; |
| } |
| |
| bool |
| ObjCARCOpt::VisitBottomUp(BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| MapVector<Value *, RRInfo> &Retains) { |
| bool NestingDetected = false; |
| BBState &MyStates = BBStates[BB]; |
| |
| // Merge the states from each successor to compute the initial state |
| // for the current block. |
| BBState::edge_iterator SI(MyStates.succ_begin()), |
| SE(MyStates.succ_end()); |
| if (SI != SE) { |
| const BasicBlock *Succ = *SI; |
| DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ); |
| assert(I != BBStates.end()); |
| MyStates.InitFromSucc(I->second); |
| ++SI; |
| for (; SI != SE; ++SI) { |
| Succ = *SI; |
| I = BBStates.find(Succ); |
| assert(I != BBStates.end()); |
| MyStates.MergeSucc(I->second); |
| } |
| } |
| |
| // Visit all the instructions, bottom-up. |
| for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) { |
| Instruction *Inst = llvm::prior(I); |
| |
| // Invoke instructions are visited as part of their successors (below). |
| if (isa<InvokeInst>(Inst)) |
| continue; |
| |
| NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates); |
| } |
| |
| // If there's a predecessor with an invoke, visit the invoke as if it were |
| // part of this block, since we can't insert code after an invoke in its own |
| // block, and we don't want to split critical edges. |
| for (BBState::edge_iterator PI(MyStates.pred_begin()), |
| PE(MyStates.pred_end()); PI != PE; ++PI) { |
| BasicBlock *Pred = *PI; |
| if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back())) |
| NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates); |
| } |
| |
| return NestingDetected; |
| } |
| |
| bool |
| ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst, |
| DenseMap<Value *, RRInfo> &Releases, |
| BBState &MyStates) { |
| bool NestingDetected = false; |
| InstructionClass Class = GetInstructionClass(Inst); |
| const Value *Arg = 0; |
| |
| switch (Class) { |
| case IC_RetainBlock: |
| // An objc_retainBlock call with just a use may need to be kept, |
| // because it may be copying a block from the stack to the heap. |
| if (!IsRetainBlockOptimizable(Inst)) |
| break; |
| // FALLTHROUGH |
| case IC_Retain: |
| case IC_RetainRV: { |
| Arg = GetObjCArg(Inst); |
| |
| PtrState &S = MyStates.getPtrTopDownState(Arg); |
| |
| // Don't do retain+release tracking for IC_RetainRV, because it's |
| // better to let it remain as the first instruction after a call. |
| if (Class != IC_RetainRV) { |
| // If we see two retains in a row on the same pointer. If so, make |
| // a note, and we'll cicle back to revisit it after we've |
| // hopefully eliminated the second retain, which may allow us to |
| // eliminate the first retain too. |
| // Theoretically we could implement removal of nested retain+release |
| // pairs by making PtrState hold a stack of states, but this is |
| // simple and avoids adding overhead for the non-nested case. |
| if (S.GetSeq() == S_Retain) |
| NestingDetected = true; |
| |
| S.ResetSequenceProgress(S_Retain); |
| S.RRI.IsRetainBlock = Class == IC_RetainBlock; |
| S.RRI.KnownSafe = S.IsKnownIncremented(); |
| S.RRI.Calls.insert(Inst); |
| } |
| |
| S.SetKnownPositiveRefCount(); |
| |
| // A retain can be a potential use; procede to the generic checking |
| // code below. |
| break; |
| } |
| case IC_Release: { |
| Arg = GetObjCArg(Inst); |
| |
| PtrState &S = MyStates.getPtrTopDownState(Arg); |
| S.ClearRefCount(); |
| |
| switch (S.GetSeq()) { |
| case S_Retain: |
| case S_CanRelease: |
| S.RRI.ReverseInsertPts.clear(); |
| // FALL THROUGH |
| case S_Use: |
| S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind); |
| S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall(); |
| Releases[Inst] = S.RRI; |
| S.ClearSequenceProgress(); |
| break; |
| case S_None: |
| break; |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| llvm_unreachable("top-down pointer in release state!"); |
| } |
| break; |
| } |
| case IC_AutoreleasepoolPop: |
| // Conservatively, clear MyStates for all known pointers. |
| MyStates.clearTopDownPointers(); |
| return NestingDetected; |
| case IC_AutoreleasepoolPush: |
| case IC_None: |
| // These are irrelevant. |
| return NestingDetected; |
| default: |
| break; |
| } |
| |
| // Consider any other possible effects of this instruction on each |
| // pointer being tracked. |
| for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(), |
| ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) { |
| const Value *Ptr = MI->first; |
| if (Ptr == Arg) |
| continue; // Handled above. |
| PtrState &S = MI->second; |
| Sequence Seq = S.GetSeq(); |
| |
| // Check for possible releases. |
| if (CanAlterRefCount(Inst, Ptr, PA, Class)) { |
| S.ClearRefCount(); |
| switch (Seq) { |
| case S_Retain: |
| S.SetSeq(S_CanRelease); |
| assert(S.RRI.ReverseInsertPts.empty()); |
| S.RRI.ReverseInsertPts.insert(Inst); |
| |
| // One call can't cause a transition from S_Retain to S_CanRelease |
| // and S_CanRelease to S_Use. If we've made the first transition, |
| // we're done. |
| continue; |
| case S_Use: |
| case S_CanRelease: |
| case S_None: |
| break; |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| llvm_unreachable("top-down pointer in release state!"); |
| } |
| } |
| |
| // Check for possible direct uses. |
| switch (Seq) { |
| case S_CanRelease: |
| if (CanUse(Inst, Ptr, PA, Class)) |
| S.SetSeq(S_Use); |
| break; |
| case S_Retain: |
| case S_Use: |
| case S_None: |
| break; |
| case S_Stop: |
| case S_Release: |
| case S_MovableRelease: |
| llvm_unreachable("top-down pointer in release state!"); |
| } |
| } |
| |
| return NestingDetected; |
| } |
| |
| bool |
| ObjCARCOpt::VisitTopDown(BasicBlock *BB, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| DenseMap<Value *, RRInfo> &Releases) { |
| bool NestingDetected = false; |
| BBState &MyStates = BBStates[BB]; |
| |
| // Merge the states from each predecessor to compute the initial state |
| // for the current block. |
| BBState::edge_iterator PI(MyStates.pred_begin()), |
| PE(MyStates.pred_end()); |
| if (PI != PE) { |
| const BasicBlock *Pred = *PI; |
| DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred); |
| assert(I != BBStates.end()); |
| MyStates.InitFromPred(I->second); |
| ++PI; |
| for (; PI != PE; ++PI) { |
| Pred = *PI; |
| I = BBStates.find(Pred); |
| assert(I != BBStates.end()); |
| MyStates.MergePred(I->second); |
| } |
| } |
| |
| // Visit all the instructions, top-down. |
| for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { |
| Instruction *Inst = I; |
| NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates); |
| } |
| |
| CheckForCFGHazards(BB, BBStates, MyStates); |
| return NestingDetected; |
| } |
| |
| static void |
| ComputePostOrders(Function &F, |
| SmallVectorImpl<BasicBlock *> &PostOrder, |
| SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder, |
| unsigned NoObjCARCExceptionsMDKind, |
| DenseMap<const BasicBlock *, BBState> &BBStates) { |
| /// Visited - The visited set, for doing DFS walks. |
| SmallPtrSet<BasicBlock *, 16> Visited; |
| |
| // Do DFS, computing the PostOrder. |
| SmallPtrSet<BasicBlock *, 16> OnStack; |
| SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack; |
| |
| // Functions always have exactly one entry block, and we don't have |
| // any other block that we treat like an entry block. |
| BasicBlock *EntryBB = &F.getEntryBlock(); |
| BBState &MyStates = BBStates[EntryBB]; |
| MyStates.SetAsEntry(); |
| TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back()); |
| SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI))); |
| Visited.insert(EntryBB); |
| OnStack.insert(EntryBB); |
| do { |
| dfs_next_succ: |
| BasicBlock *CurrBB = SuccStack.back().first; |
| TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back()); |
| succ_iterator SE(TI, false); |
| |
| // If the terminator is an invoke marked with the |
| // clang.arc.no_objc_arc_exceptions metadata, the unwind edge can be |
| // ignored, for ARC purposes. |
| if (isa<InvokeInst>(TI) && TI->getMetadata(NoObjCARCExceptionsMDKind)) |
| --SE; |
| |
| while (SuccStack.back().second != SE) { |
| BasicBlock *SuccBB = *SuccStack.back().second++; |
| if (Visited.insert(SuccBB)) { |
| TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back()); |
| SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI))); |
| BBStates[CurrBB].addSucc(SuccBB); |
| BBState &SuccStates = BBStates[SuccBB]; |
| SuccStates.addPred(CurrBB); |
| OnStack.insert(SuccBB); |
| goto dfs_next_succ; |
| } |
| |
| if (!OnStack.count(SuccBB)) { |
| BBStates[CurrBB].addSucc(SuccBB); |
| BBStates[SuccBB].addPred(CurrBB); |
| } |
| } |
| OnStack.erase(CurrBB); |
| PostOrder.push_back(CurrBB); |
| SuccStack.pop_back(); |
| } while (!SuccStack.empty()); |
| |
| Visited.clear(); |
| |
| // Do reverse-CFG DFS, computing the reverse-CFG PostOrder. |
| // Functions may have many exits, and there also blocks which we treat |
| // as exits due to ignored edges. |
| SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack; |
| for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { |
| BasicBlock *ExitBB = I; |
| BBState &MyStates = BBStates[ExitBB]; |
| if (!MyStates.isExit()) |
| continue; |
| |
| MyStates.SetAsExit(); |
| |
| PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin())); |
| Visited.insert(ExitBB); |
| while (!PredStack.empty()) { |
| reverse_dfs_next_succ: |
| BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end(); |
| while (PredStack.back().second != PE) { |
| BasicBlock *BB = *PredStack.back().second++; |
| if (Visited.insert(BB)) { |
| PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin())); |
| goto reverse_dfs_next_succ; |
| } |
| } |
| ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first); |
| } |
| } |
| } |
| |
| // Visit - Visit the function both top-down and bottom-up. |
| bool |
| ObjCARCOpt::Visit(Function &F, |
| DenseMap<const BasicBlock *, BBState> &BBStates, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases) { |
| |
| // Use reverse-postorder traversals, because we magically know that loops |
| // will be well behaved, i.e. they won't repeatedly call retain on a single |
| // pointer without doing a release. We can't use the ReversePostOrderTraversal |
| // class here because we want the reverse-CFG postorder to consider each |
| // function exit point, and we want to ignore selected cycle edges. |
| SmallVector<BasicBlock *, 16> PostOrder; |
| SmallVector<BasicBlock *, 16> ReverseCFGPostOrder; |
| ComputePostOrders(F, PostOrder, ReverseCFGPostOrder, |
| NoObjCARCExceptionsMDKind, |
| BBStates); |
| |
| // Use reverse-postorder on the reverse CFG for bottom-up. |
| bool BottomUpNestingDetected = false; |
| for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I = |
| ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend(); |
| I != E; ++I) |
| BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains); |
| |
| // Use reverse-postorder for top-down. |
| bool TopDownNestingDetected = false; |
| for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I = |
| PostOrder.rbegin(), E = PostOrder.rend(); |
| I != E; ++I) |
| TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases); |
| |
| return TopDownNestingDetected && BottomUpNestingDetected; |
| } |
| |
| /// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove. |
| void ObjCARCOpt::MoveCalls(Value *Arg, |
| RRInfo &RetainsToMove, |
| RRInfo &ReleasesToMove, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases, |
| SmallVectorImpl<Instruction *> &DeadInsts, |
| Module *M) { |
| Type *ArgTy = Arg->getType(); |
| Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext())); |
| |
| // Insert the new retain and release calls. |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| PI = ReleasesToMove.ReverseInsertPts.begin(), |
| PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) { |
| Instruction *InsertPt = *PI; |
| Value *MyArg = ArgTy == ParamTy ? Arg : |
| new BitCastInst(Arg, ParamTy, "", InsertPt); |
| CallInst *Call = |
| CallInst::Create(RetainsToMove.IsRetainBlock ? |
| getRetainBlockCallee(M) : getRetainCallee(M), |
| MyArg, "", InsertPt); |
| Call->setDoesNotThrow(); |
| if (RetainsToMove.IsRetainBlock) |
| Call->setMetadata(CopyOnEscapeMDKind, |
| MDNode::get(M->getContext(), ArrayRef<Value *>())); |
| else |
| Call->setTailCall(); |
| } |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| PI = RetainsToMove.ReverseInsertPts.begin(), |
| PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) { |
| Instruction *InsertPt = *PI; |
| Value *MyArg = ArgTy == ParamTy ? Arg : |
| new BitCastInst(Arg, ParamTy, "", InsertPt); |
| CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg, |
| "", InsertPt); |
| // Attach a clang.imprecise_release metadata tag, if appropriate. |
| if (MDNode *M = ReleasesToMove.ReleaseMetadata) |
| Call->setMetadata(ImpreciseReleaseMDKind, M); |
| Call->setDoesNotThrow(); |
| if (ReleasesToMove.IsTailCallRelease) |
| Call->setTailCall(); |
| } |
| |
| // Delete the original retain and release calls. |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| AI = RetainsToMove.Calls.begin(), |
| AE = RetainsToMove.Calls.end(); AI != AE; ++AI) { |
| Instruction *OrigRetain = *AI; |
| Retains.blot(OrigRetain); |
| DeadInsts.push_back(OrigRetain); |
| } |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| AI = ReleasesToMove.Calls.begin(), |
| AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) { |
| Instruction *OrigRelease = *AI; |
| Releases.erase(OrigRelease); |
| DeadInsts.push_back(OrigRelease); |
| } |
| } |
| |
| /// PerformCodePlacement - Identify pairings between the retains and releases, |
| /// and delete and/or move them. |
| bool |
| ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState> |
| &BBStates, |
| MapVector<Value *, RRInfo> &Retains, |
| DenseMap<Value *, RRInfo> &Releases, |
| Module *M) { |
| bool AnyPairsCompletelyEliminated = false; |
| RRInfo RetainsToMove; |
| RRInfo ReleasesToMove; |
| SmallVector<Instruction *, 4> NewRetains; |
| SmallVector<Instruction *, 4> NewReleases; |
| SmallVector<Instruction *, 8> DeadInsts; |
| |
| // Visit each retain. |
| for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(), |
| E = Retains.end(); I != E; ++I) { |
| Value *V = I->first; |
| if (!V) continue; // blotted |
| |
| Instruction *Retain = cast<Instruction>(V); |
| Value *Arg = GetObjCArg(Retain); |
| |
| // If the object being released is in static or stack storage, we know it's |
| // not being managed by ObjC reference counting, so we can delete pairs |
| // regardless of what possible decrements or uses lie between them. |
| bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg); |
| |
| // A constant pointer can't be pointing to an object on the heap. It may |
| // be reference-counted, but it won't be deleted. |
| if (const LoadInst *LI = dyn_cast<LoadInst>(Arg)) |
| if (const GlobalVariable *GV = |
| dyn_cast<GlobalVariable>( |
| StripPointerCastsAndObjCCalls(LI->getPointerOperand()))) |
| if (GV->isConstant()) |
| KnownSafe = true; |
| |
| // If a pair happens in a region where it is known that the reference count |
| // is already incremented, we can similarly ignore possible decrements. |
| bool KnownSafeTD = true, KnownSafeBU = true; |
| |
| // Connect the dots between the top-down-collected RetainsToMove and |
| // bottom-up-collected ReleasesToMove to form sets of related calls. |
| // This is an iterative process so that we connect multiple releases |
| // to multiple retains if needed. |
| unsigned OldDelta = 0; |
| unsigned NewDelta = 0; |
| unsigned OldCount = 0; |
| unsigned NewCount = 0; |
| bool FirstRelease = true; |
| bool FirstRetain = true; |
| NewRetains.push_back(Retain); |
| for (;;) { |
| for (SmallVectorImpl<Instruction *>::const_iterator |
| NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) { |
| Instruction *NewRetain = *NI; |
| MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain); |
| assert(It != Retains.end()); |
| const RRInfo &NewRetainRRI = It->second; |
| KnownSafeTD &= NewRetainRRI.KnownSafe; |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| LI = NewRetainRRI.Calls.begin(), |
| LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) { |
| Instruction *NewRetainRelease = *LI; |
| DenseMap<Value *, RRInfo>::const_iterator Jt = |
| Releases.find(NewRetainRelease); |
| if (Jt == Releases.end()) |
| goto next_retain; |
| const RRInfo &NewRetainReleaseRRI = Jt->second; |
| assert(NewRetainReleaseRRI.Calls.count(NewRetain)); |
| if (ReleasesToMove.Calls.insert(NewRetainRelease)) { |
| OldDelta -= |
| BBStates[NewRetainRelease->getParent()].GetAllPathCount(); |
| |
| // Merge the ReleaseMetadata and IsTailCallRelease values. |
| if (FirstRelease) { |
| ReleasesToMove.ReleaseMetadata = |
| NewRetainReleaseRRI.ReleaseMetadata; |
| ReleasesToMove.IsTailCallRelease = |
| NewRetainReleaseRRI.IsTailCallRelease; |
| FirstRelease = false; |
| } else { |
| if (ReleasesToMove.ReleaseMetadata != |
| NewRetainReleaseRRI.ReleaseMetadata) |
| ReleasesToMove.ReleaseMetadata = 0; |
| if (ReleasesToMove.IsTailCallRelease != |
| NewRetainReleaseRRI.IsTailCallRelease) |
| ReleasesToMove.IsTailCallRelease = false; |
| } |
| |
| // Collect the optimal insertion points. |
| if (!KnownSafe) |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| RI = NewRetainReleaseRRI.ReverseInsertPts.begin(), |
| RE = NewRetainReleaseRRI.ReverseInsertPts.end(); |
| RI != RE; ++RI) { |
| Instruction *RIP = *RI; |
| if (ReleasesToMove.ReverseInsertPts.insert(RIP)) |
| NewDelta -= BBStates[RIP->getParent()].GetAllPathCount(); |
| } |
| NewReleases.push_back(NewRetainRelease); |
| } |
| } |
| } |
| NewRetains.clear(); |
| if (NewReleases.empty()) break; |
| |
| // Back the other way. |
| for (SmallVectorImpl<Instruction *>::const_iterator |
| NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) { |
| Instruction *NewRelease = *NI; |
| DenseMap<Value *, RRInfo>::const_iterator It = |
| Releases.find(NewRelease); |
| assert(It != Releases.end()); |
| const RRInfo &NewReleaseRRI = It->second; |
| KnownSafeBU &= NewReleaseRRI.KnownSafe; |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| LI = NewReleaseRRI.Calls.begin(), |
| LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) { |
| Instruction *NewReleaseRetain = *LI; |
| MapVector<Value *, RRInfo>::const_iterator Jt = |
| Retains.find(NewReleaseRetain); |
| if (Jt == Retains.end()) |
| goto next_retain; |
| const RRInfo &NewReleaseRetainRRI = Jt->second; |
| assert(NewReleaseRetainRRI.Calls.count(NewRelease)); |
| if (RetainsToMove.Calls.insert(NewReleaseRetain)) { |
| unsigned PathCount = |
| BBStates[NewReleaseRetain->getParent()].GetAllPathCount(); |
| OldDelta += PathCount; |
| OldCount += PathCount; |
| |
| // Merge the IsRetainBlock values. |
| if (FirstRetain) { |
| RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock; |
| FirstRetain = false; |
| } else if (ReleasesToMove.IsRetainBlock != |
| NewReleaseRetainRRI.IsRetainBlock) |
| // It's not possible to merge the sequences if one uses |
| // objc_retain and the other uses objc_retainBlock. |
| goto next_retain; |
| |
| // Collect the optimal insertion points. |
| if (!KnownSafe) |
| for (SmallPtrSet<Instruction *, 2>::const_iterator |
| RI = NewReleaseRetainRRI.ReverseInsertPts.begin(), |
| RE = NewReleaseRetainRRI.ReverseInsertPts.end(); |
| RI != RE; ++RI) { |
| Instruction *RIP = *RI; |
| if (RetainsToMove.ReverseInsertPts.insert(RIP)) { |
| PathCount = BBStates[RIP->getParent()].GetAllPathCount(); |
| NewDelta += PathCount; |
| NewCount += PathCount; |
| } |
| } |
| NewRetains.push_back(NewReleaseRetain); |
| } |
| } |
| } |
| NewReleases.clear(); |
| if (NewRetains.empty()) break; |
| } |
| |
| // If the pointer is known incremented or nested, we can safely delete the |
| // pair regardless of what's between them. |
| if (KnownSafeTD || KnownSafeBU) { |
| RetainsToMove.ReverseInsertPts.clear(); |
| ReleasesToMove.ReverseInsertPts.clear(); |
| NewCount = 0; |
| } else { |
| // Determine whether the new insertion points we computed preserve the |
| // balance of retain and release calls through the program. |
| // TODO: If the fully aggressive solution isn't valid, try to find a |
| // less aggressive solution which is. |
| if (NewDelta != 0) |
| goto next_retain; |
| } |
| |
| // Determine whether the original call points are balanced in the retain and |
| // release calls through the program. If not, conservatively don't touch |
| // them. |
| // TODO: It's theoretically possible to do code motion in this case, as |
| // long as the existing imbalances are maintained. |
| if (OldDelta != 0) |
| goto next_retain; |
| |
| // Ok, everything checks out and we're all set. Let's move some code! |
| Changed = true; |
| assert(OldCount != 0 && "Unreachable code?"); |
| AnyPairsCompletelyEliminated = NewCount == 0; |
| NumRRs += OldCount - NewCount; |
| MoveCalls(Arg, RetainsToMove, ReleasesToMove, |
| Retains, Releases, DeadInsts, M); |
| |
| next_retain: |
| NewReleases.clear(); |
| NewRetains.clear(); |
| RetainsToMove.clear(); |
| ReleasesToMove.clear(); |
| } |
| |
| // Now that we're done moving everything, we can delete the newly dead |
| // instructions, as we no longer need them as insert points. |
| while (!DeadInsts.empty()) |
| EraseInstruction(DeadInsts.pop_back_val()); |
| |
| return AnyPairsCompletelyEliminated; |
| } |
| |
| /// OptimizeWeakCalls - Weak pointer optimizations. |
| void ObjCARCOpt::OptimizeWeakCalls(Function &F) { |
| // First, do memdep-style RLE and S2L optimizations. We can't use memdep |
| // itself because it uses AliasAnalysis and we need to do provenance |
| // queries instead. |
| for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| Instruction *Inst = &*I++; |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained) |
| continue; |
| |
| // Delete objc_loadWeak calls with no users. |
| if (Class == IC_LoadWeak && Inst->use_empty()) { |
| Inst->eraseFromParent(); |
| continue; |
| } |
| |
| // TODO: For now, just look for an earlier available version of this value |
| // within the same block. Theoretically, we could do memdep-style non-local |
| // analysis too, but that would want caching. A better approach would be to |
| // use the technique that EarlyCSE uses. |
| inst_iterator Current = llvm::prior(I); |
| BasicBlock *CurrentBB = Current.getBasicBlockIterator(); |
| for (BasicBlock::iterator B = CurrentBB->begin(), |
| J = Current.getInstructionIterator(); |
| J != B; --J) { |
| Instruction *EarlierInst = &*llvm::prior(J); |
| InstructionClass EarlierClass = GetInstructionClass(EarlierInst); |
| switch (EarlierClass) { |
| case IC_LoadWeak: |
| case IC_LoadWeakRetained: { |
| // If this is loading from the same pointer, replace this load's value |
| // with that one. |
| CallInst *Call = cast<CallInst>(Inst); |
| CallInst *EarlierCall = cast<CallInst>(EarlierInst); |
| Value *Arg = Call->getArgOperand(0); |
| Value *EarlierArg = EarlierCall->getArgOperand(0); |
| switch (PA.getAA()->alias(Arg, EarlierArg)) { |
| case AliasAnalysis::MustAlias: |
| Changed = true; |
| // If the load has a builtin retain, insert a plain retain for it. |
| if (Class == IC_LoadWeakRetained) { |
| CallInst *CI = |
| CallInst::Create(getRetainCallee(F.getParent()), EarlierCall, |
| "", Call); |
| CI->setTailCall(); |
| } |
| // Zap the fully redundant load. |
| Call->replaceAllUsesWith(EarlierCall); |
| Call->eraseFromParent(); |
| goto clobbered; |
| case AliasAnalysis::MayAlias: |
| case AliasAnalysis::PartialAlias: |
| goto clobbered; |
| case AliasAnalysis::NoAlias: |
| break; |
| } |
| break; |
| } |
| case IC_StoreWeak: |
| case IC_InitWeak: { |
| // If this is storing to the same pointer and has the same size etc. |
| // replace this load's value with the stored value. |
| CallInst *Call = cast<CallInst>(Inst); |
| CallInst *EarlierCall = cast<CallInst>(EarlierInst); |
| Value *Arg = Call->getArgOperand(0); |
| Value *EarlierArg = EarlierCall->getArgOperand(0); |
| switch (PA.getAA()->alias(Arg, EarlierArg)) { |
| case AliasAnalysis::MustAlias: |
| Changed = true; |
| // If the load has a builtin retain, insert a plain retain for it. |
| if (Class == IC_LoadWeakRetained) { |
| CallInst *CI = |
| CallInst::Create(getRetainCallee(F.getParent()), EarlierCall, |
| "", Call); |
| CI->setTailCall(); |
| } |
| // Zap the fully redundant load. |
| Call->replaceAllUsesWith(EarlierCall->getArgOperand(1)); |
| Call->eraseFromParent(); |
| goto clobbered; |
| case AliasAnalysis::MayAlias: |
| case AliasAnalysis::PartialAlias: |
| goto clobbered; |
| case AliasAnalysis::NoAlias: |
| break; |
| } |
| break; |
| } |
| case IC_MoveWeak: |
| case IC_CopyWeak: |
| // TOOD: Grab the copied value. |
| goto clobbered; |
| case IC_AutoreleasepoolPush: |
| case IC_None: |
| case IC_User: |
| // Weak pointers are only modified through the weak entry points |
| // (and arbitrary calls, which could call the weak entry points). |
| break; |
| default: |
| // Anything else could modify the weak pointer. |
| goto clobbered; |
| } |
| } |
| clobbered:; |
| } |
| |
| // Then, for each destroyWeak with an alloca operand, check to see if |
| // the alloca and all its users can be zapped. |
| for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| Instruction *Inst = &*I++; |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| if (Class != IC_DestroyWeak) |
| continue; |
| |
| CallInst *Call = cast<CallInst>(Inst); |
| Value *Arg = Call->getArgOperand(0); |
| if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) { |
| for (Value::use_iterator UI = Alloca->use_begin(), |
| UE = Alloca->use_end(); UI != UE; ++UI) { |
| const Instruction *UserInst = cast<Instruction>(*UI); |
| switch (GetBasicInstructionClass(UserInst)) { |
| case IC_InitWeak: |
| case IC_StoreWeak: |
| case IC_DestroyWeak: |
| continue; |
| default: |
| goto done; |
| } |
| } |
| Changed = true; |
| for (Value::use_iterator UI = Alloca->use_begin(), |
| UE = Alloca->use_end(); UI != UE; ) { |
| CallInst *UserInst = cast<CallInst>(*UI++); |
| switch (GetBasicInstructionClass(UserInst)) { |
| case IC_InitWeak: |
| case IC_StoreWeak: |
| // These functions return their second argument. |
| UserInst->replaceAllUsesWith(UserInst->getArgOperand(1)); |
| break; |
| case IC_DestroyWeak: |
| // No return value. |
| break; |
| default: |
| llvm_unreachable("alloca really is used!"); |
| } |
| UserInst->eraseFromParent(); |
| } |
| Alloca->eraseFromParent(); |
| done:; |
| } |
| } |
| } |
| |
| /// OptimizeSequences - Identify program paths which execute sequences of |
| /// retains and releases which can be eliminated. |
| bool ObjCARCOpt::OptimizeSequences(Function &F) { |
| /// Releases, Retains - These are used to store the results of the main flow |
| /// analysis. These use Value* as the key instead of Instruction* so that the |
| /// map stays valid when we get around to rewriting code and calls get |
| /// replaced by arguments. |
| DenseMap<Value *, RRInfo> Releases; |
| MapVector<Value *, RRInfo> Retains; |
| |
| /// BBStates, This is used during the traversal of the function to track the |
| /// states for each identified object at each block. |
| DenseMap<const BasicBlock *, BBState> BBStates; |
| |
| // Analyze the CFG of the function, and all instructions. |
| bool NestingDetected = Visit(F, BBStates, Retains, Releases); |
| |
| // Transform. |
| return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) && |
| NestingDetected; |
| } |
| |
| /// OptimizeReturns - Look for this pattern: |
| /// \code |
| /// %call = call i8* @something(...) |
| /// %2 = call i8* @objc_retain(i8* %call) |
| /// %3 = call i8* @objc_autorelease(i8* %2) |
| /// ret i8* %3 |
| /// \endcode |
| /// And delete the retain and autorelease. |
| /// |
| /// Otherwise if it's just this: |
| /// \code |
| /// %3 = call i8* @objc_autorelease(i8* %2) |
| /// ret i8* %3 |
| /// \endcode |
| /// convert the autorelease to autoreleaseRV. |
| void ObjCARCOpt::OptimizeReturns(Function &F) { |
| if (!F.getReturnType()->isPointerTy()) |
| return; |
| |
| SmallPtrSet<Instruction *, 4> DependingInstructions; |
| SmallPtrSet<const BasicBlock *, 4> Visited; |
| for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) { |
| BasicBlock *BB = FI; |
| ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back()); |
| if (!Ret) continue; |
| |
| const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0)); |
| FindDependencies(NeedsPositiveRetainCount, Arg, |
| BB, Ret, DependingInstructions, Visited, PA); |
| if (DependingInstructions.size() != 1) |
| goto next_block; |
| |
| { |
| CallInst *Autorelease = |
| dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| if (!Autorelease) |
| goto next_block; |
| InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease); |
| if (!IsAutorelease(AutoreleaseClass)) |
| goto next_block; |
| if (GetObjCArg(Autorelease) != Arg) |
| goto next_block; |
| |
| DependingInstructions.clear(); |
| Visited.clear(); |
| |
| // Check that there is nothing that can affect the reference |
| // count between the autorelease and the retain. |
| FindDependencies(CanChangeRetainCount, Arg, |
| BB, Autorelease, DependingInstructions, Visited, PA); |
| if (DependingInstructions.size() != 1) |
| goto next_block; |
| |
| { |
| CallInst *Retain = |
| dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| |
| // Check that we found a retain with the same argument. |
| if (!Retain || |
| !IsRetain(GetBasicInstructionClass(Retain)) || |
| GetObjCArg(Retain) != Arg) |
| goto next_block; |
| |
| DependingInstructions.clear(); |
| Visited.clear(); |
| |
| // Convert the autorelease to an autoreleaseRV, since it's |
| // returning the value. |
| if (AutoreleaseClass == IC_Autorelease) { |
| Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent())); |
| AutoreleaseClass = IC_AutoreleaseRV; |
| } |
| |
| // Check that there is nothing that can affect the reference |
| // count between the retain and the call. |
| // Note that Retain need not be in BB. |
| FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain, |
| DependingInstructions, Visited, PA); |
| if (DependingInstructions.size() != 1) |
| goto next_block; |
| |
| { |
| CallInst *Call = |
| dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| |
| // Check that the pointer is the return value of the call. |
| if (!Call || Arg != Call) |
| goto next_block; |
| |
| // Check that the call is a regular call. |
| InstructionClass Class = GetBasicInstructionClass(Call); |
| if (Class != IC_CallOrUser && Class != IC_Call) |
| goto next_block; |
| |
| // If so, we can zap the retain and autorelease. |
| Changed = true; |
| ++NumRets; |
| EraseInstruction(Retain); |
| EraseInstruction(Autorelease); |
| } |
| } |
| } |
| |
| next_block: |
| DependingInstructions.clear(); |
| Visited.clear(); |
| } |
| } |
| |
| bool ObjCARCOpt::doInitialization(Module &M) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| Run = ModuleHasARC(M); |
| if (!Run) |
| return false; |
| |
| // Identify the imprecise release metadata kind. |
| ImpreciseReleaseMDKind = |
| M.getContext().getMDKindID("clang.imprecise_release"); |
| CopyOnEscapeMDKind = |
| M.getContext().getMDKindID("clang.arc.copy_on_escape"); |
| NoObjCARCExceptionsMDKind = |
| M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions"); |
| |
| // Intuitively, objc_retain and others are nocapture, however in practice |
| // they are not, because they return their argument value. And objc_release |
| // calls finalizers which can have arbitrary side effects. |
| |
| // These are initialized lazily. |
| RetainRVCallee = 0; |
| AutoreleaseRVCallee = 0; |
| ReleaseCallee = 0; |
| RetainCallee = 0; |
| RetainBlockCallee = 0; |
| AutoreleaseCallee = 0; |
| |
| return false; |
| } |
| |
| bool ObjCARCOpt::runOnFunction(Function &F) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| if (!Run) |
| return false; |
| |
| Changed = false; |
| |
| PA.setAA(&getAnalysis<AliasAnalysis>()); |
| |
| // This pass performs several distinct transformations. As a compile-time aid |
| // when compiling code that isn't ObjC, skip these if the relevant ObjC |
| // library functions aren't declared. |
| |
| // Preliminary optimizations. This also computs UsedInThisFunction. |
| OptimizeIndividualCalls(F); |
| |
| // Optimizations for weak pointers. |
| if (UsedInThisFunction & ((1 << IC_LoadWeak) | |
| (1 << IC_LoadWeakRetained) | |
| (1 << IC_StoreWeak) | |
| (1 << IC_InitWeak) | |
| (1 << IC_CopyWeak) | |
| (1 << IC_MoveWeak) | |
| (1 << IC_DestroyWeak))) |
| OptimizeWeakCalls(F); |
| |
| // Optimizations for retain+release pairs. |
| if (UsedInThisFunction & ((1 << IC_Retain) | |
| (1 << IC_RetainRV) | |
| (1 << IC_RetainBlock))) |
| if (UsedInThisFunction & (1 << IC_Release)) |
| // Run OptimizeSequences until it either stops making changes or |
| // no retain+release pair nesting is detected. |
| while (OptimizeSequences(F)) {} |
| |
| // Optimizations if objc_autorelease is used. |
| if (UsedInThisFunction & ((1 << IC_Autorelease) | |
| (1 << IC_AutoreleaseRV))) |
| OptimizeReturns(F); |
| |
| return Changed; |
| } |
| |
| void ObjCARCOpt::releaseMemory() { |
| PA.clear(); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ARC contraction. |
| //===----------------------------------------------------------------------===// |
| |
| // TODO: ObjCARCContract could insert PHI nodes when uses aren't |
| // dominated by single calls. |
| |
| #include "llvm/Operator.h" |
| #include "llvm/InlineAsm.h" |
| #include "llvm/Analysis/Dominators.h" |
| |
| STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed"); |
| |
| namespace { |
| /// ObjCARCContract - Late ARC optimizations. These change the IR in a way |
| /// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late. |
| class ObjCARCContract : public FunctionPass { |
| bool Changed; |
| AliasAnalysis *AA; |
| DominatorTree *DT; |
| ProvenanceAnalysis PA; |
| |
| /// Run - A flag indicating whether this optimization pass should run. |
| bool Run; |
| |
| /// StoreStrongCallee, etc. - Declarations for ObjC runtime |
| /// functions, for use in creating calls to them. These are initialized |
| /// lazily to avoid cluttering up the Module with unused declarations. |
| Constant *StoreStrongCallee, |
| *RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee; |
| |
| /// RetainRVMarker - The inline asm string to insert between calls and |
| /// RetainRV calls to make the optimization work on targets which need it. |
| const MDString *RetainRVMarker; |
| |
| /// StoreStrongCalls - The set of inserted objc_storeStrong calls. If |
| /// at the end of walking the function we have found no alloca |
| /// instructions, these calls can be marked "tail". |
| SmallPtrSet<CallInst *, 8> StoreStrongCalls; |
| |
| Constant *getStoreStrongCallee(Module *M); |
| Constant *getRetainAutoreleaseCallee(Module *M); |
| Constant *getRetainAutoreleaseRVCallee(Module *M); |
| |
| bool ContractAutorelease(Function &F, Instruction *Autorelease, |
| InstructionClass Class, |
| SmallPtrSet<Instruction *, 4> |
| &DependingInstructions, |
| SmallPtrSet<const BasicBlock *, 4> |
| &Visited); |
| |
| void ContractRelease(Instruction *Release, |
| inst_iterator &Iter); |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| virtual bool doInitialization(Module &M); |
| virtual bool runOnFunction(Function &F); |
| |
| public: |
| static char ID; |
| ObjCARCContract() : FunctionPass(ID) { |
| initializeObjCARCContractPass(*PassRegistry::getPassRegistry()); |
| } |
| }; |
| } |
| |
| char ObjCARCContract::ID = 0; |
| INITIALIZE_PASS_BEGIN(ObjCARCContract, |
| "objc-arc-contract", "ObjC ARC contraction", false, false) |
| INITIALIZE_AG_DEPENDENCY(AliasAnalysis) |
| INITIALIZE_PASS_DEPENDENCY(DominatorTree) |
| INITIALIZE_PASS_END(ObjCARCContract, |
| "objc-arc-contract", "ObjC ARC contraction", false, false) |
| |
| Pass *llvm::createObjCARCContractPass() { |
| return new ObjCARCContract(); |
| } |
| |
| void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<AliasAnalysis>(); |
| AU.addRequired<DominatorTree>(); |
| AU.setPreservesCFG(); |
| } |
| |
| Constant *ObjCARCContract::getStoreStrongCallee(Module *M) { |
| if (!StoreStrongCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *I8XX = PointerType::getUnqual(I8X); |
| Type *Params[] = { I8XX, I8X }; |
| |
| Attributes::Builder BNoUnwind; |
| BNoUnwind.addAttribute(Attributes::NoUnwind); |
| Attributes::Builder BNoCapture; |
| BNoCapture.addAttribute(Attributes::NoCapture); |
| AttrListPtr Attributes = AttrListPtr() |
| .addAttr(~0u, Attributes::get(BNoUnwind)) |
| .addAttr(1, Attributes::get(BNoCapture)); |
| |
| StoreStrongCallee = |
| M->getOrInsertFunction( |
| "objc_storeStrong", |
| FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false), |
| Attributes); |
| } |
| return StoreStrongCallee; |
| } |
| |
| Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) { |
| if (!RetainAutoreleaseCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *Params[] = { I8X }; |
| FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| RetainAutoreleaseCallee = |
| M->getOrInsertFunction("objc_retainAutorelease", FTy, Attributes); |
| } |
| return RetainAutoreleaseCallee; |
| } |
| |
| Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) { |
| if (!RetainAutoreleaseRVCallee) { |
| LLVMContext &C = M->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *Params[] = { I8X }; |
| FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| Attributes::Builder B; |
| B.addAttribute(Attributes::NoUnwind); |
| AttrListPtr Attributes = AttrListPtr().addAttr(~0u, Attributes::get(B)); |
| RetainAutoreleaseRVCallee = |
| M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy, |
| Attributes); |
| } |
| return RetainAutoreleaseRVCallee; |
| } |
| |
| /// ContractAutorelease - Merge an autorelease with a retain into a fused call. |
| bool |
| ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease, |
| InstructionClass Class, |
| SmallPtrSet<Instruction *, 4> |
| &DependingInstructions, |
| SmallPtrSet<const BasicBlock *, 4> |
| &Visited) { |
| const Value *Arg = GetObjCArg(Autorelease); |
| |
| // Check that there are no instructions between the retain and the autorelease |
| // (such as an autorelease_pop) which may change the count. |
| CallInst *Retain = 0; |
| if (Class == IC_AutoreleaseRV) |
| FindDependencies(RetainAutoreleaseRVDep, Arg, |
| Autorelease->getParent(), Autorelease, |
| DependingInstructions, Visited, PA); |
| else |
| FindDependencies(RetainAutoreleaseDep, Arg, |
| Autorelease->getParent(), Autorelease, |
| DependingInstructions, Visited, PA); |
| |
| Visited.clear(); |
| if (DependingInstructions.size() != 1) { |
| DependingInstructions.clear(); |
| return false; |
| } |
| |
| Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| DependingInstructions.clear(); |
| |
| if (!Retain || |
| GetBasicInstructionClass(Retain) != IC_Retain || |
| GetObjCArg(Retain) != Arg) |
| return false; |
| |
| Changed = true; |
| ++NumPeeps; |
| |
| if (Class == IC_AutoreleaseRV) |
| Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent())); |
| else |
| Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent())); |
| |
| EraseInstruction(Autorelease); |
| return true; |
| } |
| |
| /// ContractRelease - Attempt to merge an objc_release with a store, load, and |
| /// objc_retain to form an objc_storeStrong. This can be a little tricky because |
| /// the instructions don't always appear in order, and there may be unrelated |
| /// intervening instructions. |
| void ObjCARCContract::ContractRelease(Instruction *Release, |
| inst_iterator &Iter) { |
| LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release)); |
| if (!Load || !Load->isSimple()) return; |
| |
| // For now, require everything to be in one basic block. |
| BasicBlock *BB = Release->getParent(); |
| if (Load->getParent() != BB) return; |
| |
| // Walk down to find the store and the release, which may be in either order. |
| BasicBlock::iterator I = Load, End = BB->end(); |
| ++I; |
| AliasAnalysis::Location Loc = AA->getLocation(Load); |
| StoreInst *Store = 0; |
| bool SawRelease = false; |
| for (; !Store || !SawRelease; ++I) { |
| if (I == End) |
| return; |
| |
| Instruction *Inst = I; |
| if (Inst == Release) { |
| SawRelease = true; |
| continue; |
| } |
| |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| |
| // Unrelated retains are harmless. |
| if (IsRetain(Class)) |
| continue; |
| |
| if (Store) { |
| // The store is the point where we're going to put the objc_storeStrong, |
| // so make sure there are no uses after it. |
| if (CanUse(Inst, Load, PA, Class)) |
| return; |
| } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) { |
| // We are moving the load down to the store, so check for anything |
| // else which writes to the memory between the load and the store. |
| Store = dyn_cast<StoreInst>(Inst); |
| if (!Store || !Store->isSimple()) return; |
| if (Store->getPointerOperand() != Loc.Ptr) return; |
| } |
| } |
| |
| Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand()); |
| |
| // Walk up to find the retain. |
| I = Store; |
| BasicBlock::iterator Begin = BB->begin(); |
| while (I != Begin && GetBasicInstructionClass(I) != IC_Retain) |
| --I; |
| Instruction *Retain = I; |
| if (GetBasicInstructionClass(Retain) != IC_Retain) return; |
| if (GetObjCArg(Retain) != New) return; |
| |
| Changed = true; |
| ++NumStoreStrongs; |
| |
| LLVMContext &C = Release->getContext(); |
| Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| Type *I8XX = PointerType::getUnqual(I8X); |
| |
| Value *Args[] = { Load->getPointerOperand(), New }; |
| if (Args[0]->getType() != I8XX) |
| Args[0] = new BitCastInst(Args[0], I8XX, "", Store); |
| if (Args[1]->getType() != I8X) |
| Args[1] = new BitCastInst(Args[1], I8X, "", Store); |
| CallInst *StoreStrong = |
| CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()), |
| Args, "", Store); |
| StoreStrong->setDoesNotThrow(); |
| StoreStrong->setDebugLoc(Store->getDebugLoc()); |
| |
| // We can't set the tail flag yet, because we haven't yet determined |
| // whether there are any escaping allocas. Remember this call, so that |
| // we can set the tail flag once we know it's safe. |
| StoreStrongCalls.insert(StoreStrong); |
| |
| if (&*Iter == Store) ++Iter; |
| Store->eraseFromParent(); |
| Release->eraseFromParent(); |
| EraseInstruction(Retain); |
| if (Load->use_empty()) |
| Load->eraseFromParent(); |
| } |
| |
| bool ObjCARCContract::doInitialization(Module &M) { |
| // If nothing in the Module uses ARC, don't do anything. |
| Run = ModuleHasARC(M); |
| if (!Run) |
| return false; |
| |
| // These are initialized lazily. |
| StoreStrongCallee = 0; |
| RetainAutoreleaseCallee = 0; |
| RetainAutoreleaseRVCallee = 0; |
| |
| // Initialize RetainRVMarker. |
| RetainRVMarker = 0; |
| if (NamedMDNode *NMD = |
| M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker")) |
| if (NMD->getNumOperands() == 1) { |
| const MDNode *N = NMD->getOperand(0); |
| if (N->getNumOperands() == 1) |
| if (const MDString *S = dyn_cast<MDString>(N->getOperand(0))) |
| RetainRVMarker = S; |
| } |
| |
| return false; |
| } |
| |
| bool ObjCARCContract::runOnFunction(Function &F) { |
| if (!EnableARCOpts) |
| return false; |
| |
| // If nothing in the Module uses ARC, don't do anything. |
| if (!Run) |
| return false; |
| |
| Changed = false; |
| AA = &getAnalysis<AliasAnalysis>(); |
| DT = &getAnalysis<DominatorTree>(); |
| |
| PA.setAA(&getAnalysis<AliasAnalysis>()); |
| |
| // Track whether it's ok to mark objc_storeStrong calls with the "tail" |
| // keyword. Be conservative if the function has variadic arguments. |
| // It seems that functions which "return twice" are also unsafe for the |
| // "tail" argument, because they are setjmp, which could need to |
| // return to an earlier stack state. |
| bool TailOkForStoreStrongs = !F.isVarArg() && |
| !F.callsFunctionThatReturnsTwice(); |
| |
| // For ObjC library calls which return their argument, replace uses of the |
| // argument with uses of the call return value, if it dominates the use. This |
| // reduces register pressure. |
| SmallPtrSet<Instruction *, 4> DependingInstructions; |
| SmallPtrSet<const BasicBlock *, 4> Visited; |
| for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| Instruction *Inst = &*I++; |
| |
| // Only these library routines return their argument. In particular, |
| // objc_retainBlock does not necessarily return its argument. |
| InstructionClass Class = GetBasicInstructionClass(Inst); |
| switch (Class) { |
| case IC_Retain: |
| case IC_FusedRetainAutorelease: |
| case IC_FusedRetainAutoreleaseRV: |
| break; |
| case IC_Autorelease: |
| case IC_AutoreleaseRV: |
| if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited)) |
| continue; |
| break; |
| case IC_RetainRV: { |
| // If we're compiling for a target which needs a special inline-asm |
| // marker to do the retainAutoreleasedReturnValue optimization, |
| // insert it now. |
| if (!RetainRVMarker) |
| break; |
| BasicBlock::iterator BBI = Inst; |
| BasicBlock *InstParent = Inst->getParent(); |
| |
| // Step up to see if the call immediately precedes the RetainRV call. |
| // If it's an invoke, we have to cross a block boundary. And we have |
| // to carefully dodge no-op instructions. |
| do { |
| if (&*BBI == InstParent->begin()) { |
| BasicBlock *Pred = InstParent->getSinglePredecessor(); |
| if (!Pred) |
| goto decline_rv_optimization; |
| BBI = Pred->getTerminator(); |
| break; |
| } |
| --BBI; |
| } while (isNoopInstruction(BBI)); |
| |
| if (&*BBI == GetObjCArg(Inst)) { |
| Changed = true; |
| InlineAsm *IA = |
| InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()), |
| /*isVarArg=*/false), |
| RetainRVMarker->getString(), |
| /*Constraints=*/"", /*hasSideEffects=*/true); |
| CallInst::Create(IA, "", Inst); |
| } |
| decline_rv_optimization: |
| break; |
| } |
| case IC_InitWeak: { |
| // objc_initWeak(p, null) => *p = null |
| CallInst *CI = cast<CallInst>(Inst); |
| if (isNullOrUndef(CI->getArgOperand(1))) { |
| Value *Null = |
| ConstantPointerNull::get(cast<PointerType>(CI->getType())); |
| Changed = true; |
| new StoreInst(Null, CI->getArgOperand(0), CI); |
| CI->replaceAllUsesWith(Null); |
| CI->eraseFromParent(); |
| } |
| continue; |
| } |
| case IC_Release: |
| ContractRelease(Inst, I); |
| continue; |
| case IC_User: |
| // Be conservative if the function has any alloca instructions. |
| // Technically we only care about escaping alloca instructions, |
| // but this is sufficient to handle some interesting cases. |
| if (isa<AllocaInst>(Inst)) |
| TailOkForStoreStrongs = false; |
| continue; |
| default: |
| continue; |
| } |
| |
| // Don't use GetObjCArg because we don't want to look through bitcasts |
| // and such; to do the replacement, the argument must have type i8*. |
| const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0); |
| for (;;) { |
| // If we're compiling bugpointed code, don't get in trouble. |
| if (!isa<Instruction>(Arg) && !isa<Argument>(Arg)) |
| break; |
| // Look through the uses of the pointer. |
| for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end(); |
| UI != UE; ) { |
| Use &U = UI.getUse(); |
| unsigned OperandNo = UI.getOperandNo(); |
| ++UI; // Increment UI now, because we may unlink its element. |
| |
| // If the call's return value dominates a use of the call's argument |
| // value, rewrite the use to use the return value. We check for |
| // reachability here because an unreachable call is considered to |
| // trivially dominate itself, which would lead us to rewriting its |
| // argument in terms of its return value, which would lead to |
| // infinite loops in GetObjCArg. |
| if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) { |
| Changed = true; |
| Instruction *Replacement = Inst; |
| Type *UseTy = U.get()->getType(); |
| if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) { |
| // For PHI nodes, insert the bitcast in the predecessor block. |
| unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo); |
| BasicBlock *BB = PHI->getIncomingBlock(ValNo); |
| if (Replacement->getType() != UseTy) |
| Replacement = new BitCastInst(Replacement, UseTy, "", |
| &BB->back()); |
| // While we're here, rewrite all edges for this PHI, rather |
| // than just one use at a time, to minimize the number of |
| // bitcasts we emit. |
| for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i) |
| if (PHI->getIncomingBlock(i) == BB) { |
| // Keep the UI iterator valid. |
| if (&PHI->getOperandUse( |
| PHINode::getOperandNumForIncomingValue(i)) == |
| &UI.getUse()) |
| ++UI; |
| PHI->setIncomingValue(i, Replacement); |
| } |
| } else { |
| if (Replacement->getType() != UseTy) |
| Replacement = new BitCastInst(Replacement, UseTy, "", |
| cast<Instruction>(U.getUser())); |
| U.set(Replacement); |
| } |
| } |
| } |
| |
| // If Arg is a no-op casted pointer, strip one level of casts and iterate. |
| if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg)) |
| Arg = BI->getOperand(0); |
| else if (isa<GEPOperator>(Arg) && |
| cast<GEPOperator>(Arg)->hasAllZeroIndices()) |
| Arg = cast<GEPOperator>(Arg)->getPointerOperand(); |
| else if (isa<GlobalAlias>(Arg) && |
| !cast<GlobalAlias>(Arg)->mayBeOverridden()) |
| Arg = cast<GlobalAlias>(Arg)->getAliasee(); |
| else |
| break; |
| } |
| } |
| |
| // If this function has no escaping allocas or suspicious vararg usage, |
| // objc_storeStrong calls can be marked with the "tail" keyword. |
| if (TailOkForStoreStrongs) |
| for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(), |
| E = StoreStrongCalls.end(); I != E; ++I) |
| (*I)->setTailCall(); |
| StoreStrongCalls.clear(); |
| |
| return Changed; |
| } |