John Bauman | 19bac1e | 2014-05-06 15:23:49 -0400 | [diff] [blame] | 1 | //===- ObjCARC.cpp - ObjC ARC Optimization --------------------------------===// |
| 2 | // |
| 3 | // The LLVM Compiler Infrastructure |
| 4 | // |
| 5 | // This file is distributed under the University of Illinois Open Source |
| 6 | // License. See LICENSE.TXT for details. |
| 7 | // |
| 8 | //===----------------------------------------------------------------------===// |
| 9 | // |
| 10 | // This file defines ObjC ARC optimizations. ARC stands for |
| 11 | // Automatic Reference Counting and is a system for managing reference counts |
| 12 | // for objects in Objective C. |
| 13 | // |
| 14 | // The optimizations performed include elimination of redundant, partially |
| 15 | // redundant, and inconsequential reference count operations, elimination of |
| 16 | // redundant weak pointer operations, pattern-matching and replacement of |
| 17 | // low-level operations into higher-level operations, and numerous minor |
| 18 | // simplifications. |
| 19 | // |
| 20 | // This file also defines a simple ARC-aware AliasAnalysis. |
| 21 | // |
| 22 | // WARNING: This file knows about certain library functions. It recognizes them |
| 23 | // by name, and hardwires knowedge of their semantics. |
| 24 | // |
| 25 | // WARNING: This file knows about how certain Objective-C library functions are |
| 26 | // used. Naive LLVM IR transformations which would otherwise be |
| 27 | // behavior-preserving may break these assumptions. |
| 28 | // |
| 29 | //===----------------------------------------------------------------------===// |
| 30 | |
| 31 | #define DEBUG_TYPE "objc-arc" |
| 32 | #include "llvm/Function.h" |
| 33 | #include "llvm/Intrinsics.h" |
| 34 | #include "llvm/GlobalVariable.h" |
| 35 | #include "llvm/DerivedTypes.h" |
| 36 | #include "llvm/Module.h" |
| 37 | #include "llvm/Analysis/ValueTracking.h" |
| 38 | #include "llvm/Transforms/Utils/Local.h" |
| 39 | #include "llvm/Support/CallSite.h" |
| 40 | #include "llvm/Support/CommandLine.h" |
| 41 | #include "llvm/ADT/StringSwitch.h" |
| 42 | #include "llvm/ADT/DenseMap.h" |
| 43 | #include "llvm/ADT/STLExtras.h" |
| 44 | using namespace llvm; |
| 45 | |
| 46 | // A handy option to enable/disable all optimizations in this file. |
| 47 | static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true)); |
| 48 | |
| 49 | //===----------------------------------------------------------------------===// |
| 50 | // Misc. Utilities |
| 51 | //===----------------------------------------------------------------------===// |
| 52 | |
| 53 | namespace { |
| 54 | /// MapVector - An associative container with fast insertion-order |
| 55 | /// (deterministic) iteration over its elements. Plus the special |
| 56 | /// blot operation. |
| 57 | template<class KeyT, class ValueT> |
| 58 | class MapVector { |
| 59 | /// Map - Map keys to indices in Vector. |
| 60 | typedef DenseMap<KeyT, size_t> MapTy; |
| 61 | MapTy Map; |
| 62 | |
| 63 | /// Vector - Keys and values. |
| 64 | typedef std::vector<std::pair<KeyT, ValueT> > VectorTy; |
| 65 | VectorTy Vector; |
| 66 | |
| 67 | public: |
| 68 | typedef typename VectorTy::iterator iterator; |
| 69 | typedef typename VectorTy::const_iterator const_iterator; |
| 70 | iterator begin() { return Vector.begin(); } |
| 71 | iterator end() { return Vector.end(); } |
| 72 | const_iterator begin() const { return Vector.begin(); } |
| 73 | const_iterator end() const { return Vector.end(); } |
| 74 | |
| 75 | #ifdef XDEBUG |
| 76 | ~MapVector() { |
| 77 | assert(Vector.size() >= Map.size()); // May differ due to blotting. |
| 78 | for (typename MapTy::const_iterator I = Map.begin(), E = Map.end(); |
| 79 | I != E; ++I) { |
| 80 | assert(I->second < Vector.size()); |
| 81 | assert(Vector[I->second].first == I->first); |
| 82 | } |
| 83 | for (typename VectorTy::const_iterator I = Vector.begin(), |
| 84 | E = Vector.end(); I != E; ++I) |
| 85 | assert(!I->first || |
| 86 | (Map.count(I->first) && |
| 87 | Map[I->first] == size_t(I - Vector.begin()))); |
| 88 | } |
| 89 | #endif |
| 90 | |
| 91 | ValueT &operator[](KeyT Arg) { |
| 92 | std::pair<typename MapTy::iterator, bool> Pair = |
| 93 | Map.insert(std::make_pair(Arg, size_t(0))); |
| 94 | if (Pair.second) { |
| 95 | Pair.first->second = Vector.size(); |
| 96 | Vector.push_back(std::make_pair(Arg, ValueT())); |
| 97 | return Vector.back().second; |
| 98 | } |
| 99 | return Vector[Pair.first->second].second; |
| 100 | } |
| 101 | |
| 102 | std::pair<iterator, bool> |
| 103 | insert(const std::pair<KeyT, ValueT> &InsertPair) { |
| 104 | std::pair<typename MapTy::iterator, bool> Pair = |
| 105 | Map.insert(std::make_pair(InsertPair.first, size_t(0))); |
| 106 | if (Pair.second) { |
| 107 | Pair.first->second = Vector.size(); |
| 108 | Vector.push_back(InsertPair); |
| 109 | return std::make_pair(llvm::prior(Vector.end()), true); |
| 110 | } |
| 111 | return std::make_pair(Vector.begin() + Pair.first->second, false); |
| 112 | } |
| 113 | |
| 114 | const_iterator find(KeyT Key) const { |
| 115 | typename MapTy::const_iterator It = Map.find(Key); |
| 116 | if (It == Map.end()) return Vector.end(); |
| 117 | return Vector.begin() + It->second; |
| 118 | } |
| 119 | |
| 120 | /// blot - This is similar to erase, but instead of removing the element |
| 121 | /// from the vector, it just zeros out the key in the vector. This leaves |
| 122 | /// iterators intact, but clients must be prepared for zeroed-out keys when |
| 123 | /// iterating. |
| 124 | void blot(KeyT Key) { |
| 125 | typename MapTy::iterator It = Map.find(Key); |
| 126 | if (It == Map.end()) return; |
| 127 | Vector[It->second].first = KeyT(); |
| 128 | Map.erase(It); |
| 129 | } |
| 130 | |
| 131 | void clear() { |
| 132 | Map.clear(); |
| 133 | Vector.clear(); |
| 134 | } |
| 135 | }; |
| 136 | } |
| 137 | |
| 138 | //===----------------------------------------------------------------------===// |
| 139 | // ARC Utilities. |
| 140 | //===----------------------------------------------------------------------===// |
| 141 | |
| 142 | namespace { |
| 143 | /// InstructionClass - A simple classification for instructions. |
| 144 | enum InstructionClass { |
| 145 | IC_Retain, ///< objc_retain |
| 146 | IC_RetainRV, ///< objc_retainAutoreleasedReturnValue |
| 147 | IC_RetainBlock, ///< objc_retainBlock |
| 148 | IC_Release, ///< objc_release |
| 149 | IC_Autorelease, ///< objc_autorelease |
| 150 | IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue |
| 151 | IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush |
| 152 | IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop |
| 153 | IC_NoopCast, ///< objc_retainedObject, etc. |
| 154 | IC_FusedRetainAutorelease, ///< objc_retainAutorelease |
| 155 | IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue |
| 156 | IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive) |
| 157 | IC_StoreWeak, ///< objc_storeWeak (primitive) |
| 158 | IC_InitWeak, ///< objc_initWeak (derived) |
| 159 | IC_LoadWeak, ///< objc_loadWeak (derived) |
| 160 | IC_MoveWeak, ///< objc_moveWeak (derived) |
| 161 | IC_CopyWeak, ///< objc_copyWeak (derived) |
| 162 | IC_DestroyWeak, ///< objc_destroyWeak (derived) |
| 163 | IC_CallOrUser, ///< could call objc_release and/or "use" pointers |
| 164 | IC_Call, ///< could call objc_release |
| 165 | IC_User, ///< could "use" a pointer |
| 166 | IC_None ///< anything else |
| 167 | }; |
| 168 | } |
| 169 | |
| 170 | /// IsPotentialUse - Test whether the given value is possible a |
| 171 | /// reference-counted pointer. |
| 172 | static bool IsPotentialUse(const Value *Op) { |
| 173 | // Pointers to static or stack storage are not reference-counted pointers. |
| 174 | if (isa<Constant>(Op) || isa<AllocaInst>(Op)) |
| 175 | return false; |
| 176 | // Special arguments are not reference-counted. |
| 177 | if (const Argument *Arg = dyn_cast<Argument>(Op)) |
| 178 | if (Arg->hasByValAttr() || |
| 179 | Arg->hasNestAttr() || |
| 180 | Arg->hasStructRetAttr()) |
| 181 | return false; |
| 182 | // Only consider values with pointer types, and not function pointers. |
| 183 | PointerType *Ty = dyn_cast<PointerType>(Op->getType()); |
| 184 | if (!Ty || isa<FunctionType>(Ty->getElementType())) |
| 185 | return false; |
| 186 | // Conservatively assume anything else is a potential use. |
| 187 | return true; |
| 188 | } |
| 189 | |
| 190 | /// GetCallSiteClass - Helper for GetInstructionClass. Determines what kind |
| 191 | /// of construct CS is. |
| 192 | static InstructionClass GetCallSiteClass(ImmutableCallSite CS) { |
| 193 | for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); |
| 194 | I != E; ++I) |
| 195 | if (IsPotentialUse(*I)) |
| 196 | return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser; |
| 197 | |
| 198 | return CS.onlyReadsMemory() ? IC_None : IC_Call; |
| 199 | } |
| 200 | |
| 201 | /// GetFunctionClass - Determine if F is one of the special known Functions. |
| 202 | /// If it isn't, return IC_CallOrUser. |
| 203 | static InstructionClass GetFunctionClass(const Function *F) { |
| 204 | Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end(); |
| 205 | |
| 206 | // No arguments. |
| 207 | if (AI == AE) |
| 208 | return StringSwitch<InstructionClass>(F->getName()) |
| 209 | .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush) |
| 210 | .Default(IC_CallOrUser); |
| 211 | |
| 212 | // One argument. |
| 213 | const Argument *A0 = AI++; |
| 214 | if (AI == AE) |
| 215 | // Argument is a pointer. |
| 216 | if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) { |
| 217 | Type *ETy = PTy->getElementType(); |
| 218 | // Argument is i8*. |
| 219 | if (ETy->isIntegerTy(8)) |
| 220 | return StringSwitch<InstructionClass>(F->getName()) |
| 221 | .Case("objc_retain", IC_Retain) |
| 222 | .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV) |
| 223 | .Case("objc_retainBlock", IC_RetainBlock) |
| 224 | .Case("objc_release", IC_Release) |
| 225 | .Case("objc_autorelease", IC_Autorelease) |
| 226 | .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV) |
| 227 | .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop) |
| 228 | .Case("objc_retainedObject", IC_NoopCast) |
| 229 | .Case("objc_unretainedObject", IC_NoopCast) |
| 230 | .Case("objc_unretainedPointer", IC_NoopCast) |
| 231 | .Case("objc_retain_autorelease", IC_FusedRetainAutorelease) |
| 232 | .Case("objc_retainAutorelease", IC_FusedRetainAutorelease) |
| 233 | .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV) |
| 234 | .Default(IC_CallOrUser); |
| 235 | |
| 236 | // Argument is i8** |
| 237 | if (PointerType *Pte = dyn_cast<PointerType>(ETy)) |
| 238 | if (Pte->getElementType()->isIntegerTy(8)) |
| 239 | return StringSwitch<InstructionClass>(F->getName()) |
| 240 | .Case("objc_loadWeakRetained", IC_LoadWeakRetained) |
| 241 | .Case("objc_loadWeak", IC_LoadWeak) |
| 242 | .Case("objc_destroyWeak", IC_DestroyWeak) |
| 243 | .Default(IC_CallOrUser); |
| 244 | } |
| 245 | |
| 246 | // Two arguments, first is i8**. |
| 247 | const Argument *A1 = AI++; |
| 248 | if (AI == AE) |
| 249 | if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) |
| 250 | if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType())) |
| 251 | if (Pte->getElementType()->isIntegerTy(8)) |
| 252 | if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) { |
| 253 | Type *ETy1 = PTy1->getElementType(); |
| 254 | // Second argument is i8* |
| 255 | if (ETy1->isIntegerTy(8)) |
| 256 | return StringSwitch<InstructionClass>(F->getName()) |
| 257 | .Case("objc_storeWeak", IC_StoreWeak) |
| 258 | .Case("objc_initWeak", IC_InitWeak) |
| 259 | .Default(IC_CallOrUser); |
| 260 | // Second argument is i8**. |
| 261 | if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1)) |
| 262 | if (Pte1->getElementType()->isIntegerTy(8)) |
| 263 | return StringSwitch<InstructionClass>(F->getName()) |
| 264 | .Case("objc_moveWeak", IC_MoveWeak) |
| 265 | .Case("objc_copyWeak", IC_CopyWeak) |
| 266 | .Default(IC_CallOrUser); |
| 267 | } |
| 268 | |
| 269 | // Anything else. |
| 270 | return IC_CallOrUser; |
| 271 | } |
| 272 | |
| 273 | /// GetInstructionClass - Determine what kind of construct V is. |
| 274 | static InstructionClass GetInstructionClass(const Value *V) { |
| 275 | if (const Instruction *I = dyn_cast<Instruction>(V)) { |
| 276 | // Any instruction other than bitcast and gep with a pointer operand have a |
| 277 | // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer |
| 278 | // to a subsequent use, rather than using it themselves, in this sense. |
| 279 | // As a short cut, several other opcodes are known to have no pointer |
| 280 | // operands of interest. And ret is never followed by a release, so it's |
| 281 | // not interesting to examine. |
| 282 | switch (I->getOpcode()) { |
| 283 | case Instruction::Call: { |
| 284 | const CallInst *CI = cast<CallInst>(I); |
| 285 | // Check for calls to special functions. |
| 286 | if (const Function *F = CI->getCalledFunction()) { |
| 287 | InstructionClass Class = GetFunctionClass(F); |
| 288 | if (Class != IC_CallOrUser) |
| 289 | return Class; |
| 290 | |
| 291 | // None of the intrinsic functions do objc_release. For intrinsics, the |
| 292 | // only question is whether or not they may be users. |
| 293 | switch (F->getIntrinsicID()) { |
| 294 | case 0: break; |
| 295 | case Intrinsic::bswap: case Intrinsic::ctpop: |
| 296 | case Intrinsic::ctlz: case Intrinsic::cttz: |
| 297 | case Intrinsic::returnaddress: case Intrinsic::frameaddress: |
| 298 | case Intrinsic::stacksave: case Intrinsic::stackrestore: |
| 299 | case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend: |
| 300 | // Don't let dbg info affect our results. |
| 301 | case Intrinsic::dbg_declare: case Intrinsic::dbg_value: |
| 302 | // Short cut: Some intrinsics obviously don't use ObjC pointers. |
| 303 | return IC_None; |
| 304 | default: |
| 305 | for (Function::const_arg_iterator AI = F->arg_begin(), |
| 306 | AE = F->arg_end(); AI != AE; ++AI) |
| 307 | if (IsPotentialUse(AI)) |
| 308 | return IC_User; |
| 309 | return IC_None; |
| 310 | } |
| 311 | } |
| 312 | return GetCallSiteClass(CI); |
| 313 | } |
| 314 | case Instruction::Invoke: |
| 315 | return GetCallSiteClass(cast<InvokeInst>(I)); |
| 316 | case Instruction::BitCast: |
| 317 | case Instruction::GetElementPtr: |
| 318 | case Instruction::Select: case Instruction::PHI: |
| 319 | case Instruction::Ret: case Instruction::Br: |
| 320 | case Instruction::Switch: case Instruction::IndirectBr: |
| 321 | case Instruction::Alloca: case Instruction::VAArg: |
| 322 | case Instruction::Add: case Instruction::FAdd: |
| 323 | case Instruction::Sub: case Instruction::FSub: |
| 324 | case Instruction::Mul: case Instruction::FMul: |
| 325 | case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv: |
| 326 | case Instruction::SRem: case Instruction::URem: case Instruction::FRem: |
| 327 | case Instruction::Shl: case Instruction::LShr: case Instruction::AShr: |
| 328 | case Instruction::And: case Instruction::Or: case Instruction::Xor: |
| 329 | case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc: |
| 330 | case Instruction::IntToPtr: case Instruction::FCmp: |
| 331 | case Instruction::FPTrunc: case Instruction::FPExt: |
| 332 | case Instruction::FPToUI: case Instruction::FPToSI: |
| 333 | case Instruction::UIToFP: case Instruction::SIToFP: |
| 334 | case Instruction::InsertElement: case Instruction::ExtractElement: |
| 335 | case Instruction::ShuffleVector: |
| 336 | case Instruction::ExtractValue: |
| 337 | break; |
| 338 | case Instruction::ICmp: |
| 339 | // Comparing a pointer with null, or any other constant, isn't an |
| 340 | // interesting use, because we don't care what the pointer points to, or |
| 341 | // about the values of any other dynamic reference-counted pointers. |
| 342 | if (IsPotentialUse(I->getOperand(1))) |
| 343 | return IC_User; |
| 344 | break; |
| 345 | default: |
| 346 | // For anything else, check all the operands. |
| 347 | // Note that this includes both operands of a Store: while the first |
| 348 | // operand isn't actually being dereferenced, it is being stored to |
| 349 | // memory where we can no longer track who might read it and dereference |
| 350 | // it, so we have to consider it potentially used. |
| 351 | for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end(); |
| 352 | OI != OE; ++OI) |
| 353 | if (IsPotentialUse(*OI)) |
| 354 | return IC_User; |
| 355 | } |
| 356 | } |
| 357 | |
| 358 | // Otherwise, it's totally inert for ARC purposes. |
| 359 | return IC_None; |
| 360 | } |
| 361 | |
| 362 | /// GetBasicInstructionClass - Determine what kind of construct V is. This is |
| 363 | /// similar to GetInstructionClass except that it only detects objc runtine |
| 364 | /// calls. This allows it to be faster. |
| 365 | static InstructionClass GetBasicInstructionClass(const Value *V) { |
| 366 | if (const CallInst *CI = dyn_cast<CallInst>(V)) { |
| 367 | if (const Function *F = CI->getCalledFunction()) |
| 368 | return GetFunctionClass(F); |
| 369 | // Otherwise, be conservative. |
| 370 | return IC_CallOrUser; |
| 371 | } |
| 372 | |
| 373 | // Otherwise, be conservative. |
| 374 | return IC_User; |
| 375 | } |
| 376 | |
| 377 | /// IsRetain - Test if the the given class is objc_retain or |
| 378 | /// equivalent. |
| 379 | static bool IsRetain(InstructionClass Class) { |
| 380 | return Class == IC_Retain || |
| 381 | Class == IC_RetainRV; |
| 382 | } |
| 383 | |
| 384 | /// IsAutorelease - Test if the the given class is objc_autorelease or |
| 385 | /// equivalent. |
| 386 | static bool IsAutorelease(InstructionClass Class) { |
| 387 | return Class == IC_Autorelease || |
| 388 | Class == IC_AutoreleaseRV; |
| 389 | } |
| 390 | |
| 391 | /// IsForwarding - Test if the given class represents instructions which return |
| 392 | /// their argument verbatim. |
| 393 | static bool IsForwarding(InstructionClass Class) { |
| 394 | // objc_retainBlock technically doesn't always return its argument |
| 395 | // verbatim, but it doesn't matter for our purposes here. |
| 396 | return Class == IC_Retain || |
| 397 | Class == IC_RetainRV || |
| 398 | Class == IC_Autorelease || |
| 399 | Class == IC_AutoreleaseRV || |
| 400 | Class == IC_RetainBlock || |
| 401 | Class == IC_NoopCast; |
| 402 | } |
| 403 | |
| 404 | /// IsNoopOnNull - Test if the given class represents instructions which do |
| 405 | /// nothing if passed a null pointer. |
| 406 | static bool IsNoopOnNull(InstructionClass Class) { |
| 407 | return Class == IC_Retain || |
| 408 | Class == IC_RetainRV || |
| 409 | Class == IC_Release || |
| 410 | Class == IC_Autorelease || |
| 411 | Class == IC_AutoreleaseRV || |
| 412 | Class == IC_RetainBlock; |
| 413 | } |
| 414 | |
| 415 | /// IsAlwaysTail - Test if the given class represents instructions which are |
| 416 | /// always safe to mark with the "tail" keyword. |
| 417 | static bool IsAlwaysTail(InstructionClass Class) { |
| 418 | // IC_RetainBlock may be given a stack argument. |
| 419 | return Class == IC_Retain || |
| 420 | Class == IC_RetainRV || |
| 421 | Class == IC_Autorelease || |
| 422 | Class == IC_AutoreleaseRV; |
| 423 | } |
| 424 | |
| 425 | /// IsNoThrow - Test if the given class represents instructions which are always |
| 426 | /// safe to mark with the nounwind attribute.. |
| 427 | static bool IsNoThrow(InstructionClass Class) { |
| 428 | // objc_retainBlock is not nounwind because it calls user copy constructors |
| 429 | // which could theoretically throw. |
| 430 | return Class == IC_Retain || |
| 431 | Class == IC_RetainRV || |
| 432 | Class == IC_Release || |
| 433 | Class == IC_Autorelease || |
| 434 | Class == IC_AutoreleaseRV || |
| 435 | Class == IC_AutoreleasepoolPush || |
| 436 | Class == IC_AutoreleasepoolPop; |
| 437 | } |
| 438 | |
| 439 | /// EraseInstruction - Erase the given instruction. ObjC calls return their |
| 440 | /// argument verbatim, so if it's such a call and the return value has users, |
| 441 | /// replace them with the argument value. |
| 442 | static void EraseInstruction(Instruction *CI) { |
| 443 | Value *OldArg = cast<CallInst>(CI)->getArgOperand(0); |
| 444 | |
| 445 | bool Unused = CI->use_empty(); |
| 446 | |
| 447 | if (!Unused) { |
| 448 | // Replace the return value with the argument. |
| 449 | assert(IsForwarding(GetBasicInstructionClass(CI)) && |
| 450 | "Can't delete non-forwarding instruction with users!"); |
| 451 | CI->replaceAllUsesWith(OldArg); |
| 452 | } |
| 453 | |
| 454 | CI->eraseFromParent(); |
| 455 | |
| 456 | if (Unused) |
| 457 | RecursivelyDeleteTriviallyDeadInstructions(OldArg); |
| 458 | } |
| 459 | |
| 460 | /// GetUnderlyingObjCPtr - This is a wrapper around getUnderlyingObject which |
| 461 | /// also knows how to look through objc_retain and objc_autorelease calls, which |
| 462 | /// we know to return their argument verbatim. |
| 463 | static const Value *GetUnderlyingObjCPtr(const Value *V) { |
| 464 | for (;;) { |
| 465 | V = GetUnderlyingObject(V); |
| 466 | if (!IsForwarding(GetBasicInstructionClass(V))) |
| 467 | break; |
| 468 | V = cast<CallInst>(V)->getArgOperand(0); |
| 469 | } |
| 470 | |
| 471 | return V; |
| 472 | } |
| 473 | |
| 474 | /// StripPointerCastsAndObjCCalls - This is a wrapper around |
| 475 | /// Value::stripPointerCasts which also knows how to look through objc_retain |
| 476 | /// and objc_autorelease calls, which we know to return their argument verbatim. |
| 477 | static const Value *StripPointerCastsAndObjCCalls(const Value *V) { |
| 478 | for (;;) { |
| 479 | V = V->stripPointerCasts(); |
| 480 | if (!IsForwarding(GetBasicInstructionClass(V))) |
| 481 | break; |
| 482 | V = cast<CallInst>(V)->getArgOperand(0); |
| 483 | } |
| 484 | return V; |
| 485 | } |
| 486 | |
| 487 | /// StripPointerCastsAndObjCCalls - This is a wrapper around |
| 488 | /// Value::stripPointerCasts which also knows how to look through objc_retain |
| 489 | /// and objc_autorelease calls, which we know to return their argument verbatim. |
| 490 | static Value *StripPointerCastsAndObjCCalls(Value *V) { |
| 491 | for (;;) { |
| 492 | V = V->stripPointerCasts(); |
| 493 | if (!IsForwarding(GetBasicInstructionClass(V))) |
| 494 | break; |
| 495 | V = cast<CallInst>(V)->getArgOperand(0); |
| 496 | } |
| 497 | return V; |
| 498 | } |
| 499 | |
| 500 | /// GetObjCArg - Assuming the given instruction is one of the special calls such |
| 501 | /// as objc_retain or objc_release, return the argument value, stripped of no-op |
| 502 | /// casts and forwarding calls. |
| 503 | static Value *GetObjCArg(Value *Inst) { |
| 504 | return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0)); |
| 505 | } |
| 506 | |
| 507 | /// IsObjCIdentifiedObject - This is similar to AliasAnalysis' |
| 508 | /// isObjCIdentifiedObject, except that it uses special knowledge of |
| 509 | /// ObjC conventions... |
| 510 | static bool IsObjCIdentifiedObject(const Value *V) { |
| 511 | // Assume that call results and arguments have their own "provenance". |
| 512 | // Constants (including GlobalVariables) and Allocas are never |
| 513 | // reference-counted. |
| 514 | if (isa<CallInst>(V) || isa<InvokeInst>(V) || |
| 515 | isa<Argument>(V) || isa<Constant>(V) || |
| 516 | isa<AllocaInst>(V)) |
| 517 | return true; |
| 518 | |
| 519 | if (const LoadInst *LI = dyn_cast<LoadInst>(V)) { |
| 520 | const Value *Pointer = |
| 521 | StripPointerCastsAndObjCCalls(LI->getPointerOperand()); |
| 522 | if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) { |
| 523 | // A constant pointer can't be pointing to an object on the heap. It may |
| 524 | // be reference-counted, but it won't be deleted. |
| 525 | if (GV->isConstant()) |
| 526 | return true; |
| 527 | StringRef Name = GV->getName(); |
| 528 | // These special variables are known to hold values which are not |
| 529 | // reference-counted pointers. |
| 530 | if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") || |
| 531 | Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") || |
| 532 | Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") || |
| 533 | Name.startswith("\01L_OBJC_METH_VAR_NAME_") || |
| 534 | Name.startswith("\01l_objc_msgSend_fixup_")) |
| 535 | return true; |
| 536 | } |
| 537 | } |
| 538 | |
| 539 | return false; |
| 540 | } |
| 541 | |
| 542 | /// FindSingleUseIdentifiedObject - This is similar to |
| 543 | /// StripPointerCastsAndObjCCalls but it stops as soon as it finds a value |
| 544 | /// with multiple uses. |
| 545 | static const Value *FindSingleUseIdentifiedObject(const Value *Arg) { |
| 546 | if (Arg->hasOneUse()) { |
| 547 | if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg)) |
| 548 | return FindSingleUseIdentifiedObject(BC->getOperand(0)); |
| 549 | if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg)) |
| 550 | if (GEP->hasAllZeroIndices()) |
| 551 | return FindSingleUseIdentifiedObject(GEP->getPointerOperand()); |
| 552 | if (IsForwarding(GetBasicInstructionClass(Arg))) |
| 553 | return FindSingleUseIdentifiedObject( |
| 554 | cast<CallInst>(Arg)->getArgOperand(0)); |
| 555 | if (!IsObjCIdentifiedObject(Arg)) |
| 556 | return 0; |
| 557 | return Arg; |
| 558 | } |
| 559 | |
| 560 | // If we found an identifiable object but it has multiple uses, but they |
| 561 | // are trivial uses, we can still consider this to be a single-use |
| 562 | // value. |
| 563 | if (IsObjCIdentifiedObject(Arg)) { |
| 564 | for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end(); |
| 565 | UI != UE; ++UI) { |
| 566 | const User *U = *UI; |
| 567 | if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg) |
| 568 | return 0; |
| 569 | } |
| 570 | |
| 571 | return Arg; |
| 572 | } |
| 573 | |
| 574 | return 0; |
| 575 | } |
| 576 | |
| 577 | /// ModuleHasARC - Test if the given module looks interesting to run ARC |
| 578 | /// optimization on. |
| 579 | static bool ModuleHasARC(const Module &M) { |
| 580 | return |
| 581 | M.getNamedValue("objc_retain") || |
| 582 | M.getNamedValue("objc_release") || |
| 583 | M.getNamedValue("objc_autorelease") || |
| 584 | M.getNamedValue("objc_retainAutoreleasedReturnValue") || |
| 585 | M.getNamedValue("objc_retainBlock") || |
| 586 | M.getNamedValue("objc_autoreleaseReturnValue") || |
| 587 | M.getNamedValue("objc_autoreleasePoolPush") || |
| 588 | M.getNamedValue("objc_loadWeakRetained") || |
| 589 | M.getNamedValue("objc_loadWeak") || |
| 590 | M.getNamedValue("objc_destroyWeak") || |
| 591 | M.getNamedValue("objc_storeWeak") || |
| 592 | M.getNamedValue("objc_initWeak") || |
| 593 | M.getNamedValue("objc_moveWeak") || |
| 594 | M.getNamedValue("objc_copyWeak") || |
| 595 | M.getNamedValue("objc_retainedObject") || |
| 596 | M.getNamedValue("objc_unretainedObject") || |
| 597 | M.getNamedValue("objc_unretainedPointer"); |
| 598 | } |
| 599 | |
| 600 | //===----------------------------------------------------------------------===// |
| 601 | // ARC AliasAnalysis. |
| 602 | //===----------------------------------------------------------------------===// |
| 603 | |
| 604 | #include "llvm/Pass.h" |
| 605 | #include "llvm/Analysis/AliasAnalysis.h" |
| 606 | #include "llvm/Analysis/Passes.h" |
| 607 | |
| 608 | namespace { |
| 609 | /// ObjCARCAliasAnalysis - This is a simple alias analysis |
| 610 | /// implementation that uses knowledge of ARC constructs to answer queries. |
| 611 | /// |
| 612 | /// TODO: This class could be generalized to know about other ObjC-specific |
| 613 | /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing |
| 614 | /// even though their offsets are dynamic. |
| 615 | class ObjCARCAliasAnalysis : public ImmutablePass, |
| 616 | public AliasAnalysis { |
| 617 | public: |
| 618 | static char ID; // Class identification, replacement for typeinfo |
| 619 | ObjCARCAliasAnalysis() : ImmutablePass(ID) { |
| 620 | initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry()); |
| 621 | } |
| 622 | |
| 623 | private: |
| 624 | virtual void initializePass() { |
| 625 | InitializeAliasAnalysis(this); |
| 626 | } |
| 627 | |
| 628 | /// getAdjustedAnalysisPointer - This method is used when a pass implements |
| 629 | /// an analysis interface through multiple inheritance. If needed, it |
| 630 | /// should override this to adjust the this pointer as needed for the |
| 631 | /// specified pass info. |
| 632 | virtual void *getAdjustedAnalysisPointer(const void *PI) { |
| 633 | if (PI == &AliasAnalysis::ID) |
| 634 | return (AliasAnalysis*)this; |
| 635 | return this; |
| 636 | } |
| 637 | |
| 638 | virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| 639 | virtual AliasResult alias(const Location &LocA, const Location &LocB); |
| 640 | virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal); |
| 641 | virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS); |
| 642 | virtual ModRefBehavior getModRefBehavior(const Function *F); |
| 643 | virtual ModRefResult getModRefInfo(ImmutableCallSite CS, |
| 644 | const Location &Loc); |
| 645 | virtual ModRefResult getModRefInfo(ImmutableCallSite CS1, |
| 646 | ImmutableCallSite CS2); |
| 647 | }; |
| 648 | } // End of anonymous namespace |
| 649 | |
| 650 | // Register this pass... |
| 651 | char ObjCARCAliasAnalysis::ID = 0; |
| 652 | INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa", |
| 653 | "ObjC-ARC-Based Alias Analysis", false, true, false) |
| 654 | |
| 655 | ImmutablePass *llvm::createObjCARCAliasAnalysisPass() { |
| 656 | return new ObjCARCAliasAnalysis(); |
| 657 | } |
| 658 | |
| 659 | void |
| 660 | ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const { |
| 661 | AU.setPreservesAll(); |
| 662 | AliasAnalysis::getAnalysisUsage(AU); |
| 663 | } |
| 664 | |
| 665 | AliasAnalysis::AliasResult |
| 666 | ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) { |
| 667 | if (!EnableARCOpts) |
| 668 | return AliasAnalysis::alias(LocA, LocB); |
| 669 | |
| 670 | // First, strip off no-ops, including ObjC-specific no-ops, and try making a |
| 671 | // precise alias query. |
| 672 | const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr); |
| 673 | const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr); |
| 674 | AliasResult Result = |
| 675 | AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag), |
| 676 | Location(SB, LocB.Size, LocB.TBAATag)); |
| 677 | if (Result != MayAlias) |
| 678 | return Result; |
| 679 | |
| 680 | // If that failed, climb to the underlying object, including climbing through |
| 681 | // ObjC-specific no-ops, and try making an imprecise alias query. |
| 682 | const Value *UA = GetUnderlyingObjCPtr(SA); |
| 683 | const Value *UB = GetUnderlyingObjCPtr(SB); |
| 684 | if (UA != SA || UB != SB) { |
| 685 | Result = AliasAnalysis::alias(Location(UA), Location(UB)); |
| 686 | // We can't use MustAlias or PartialAlias results here because |
| 687 | // GetUnderlyingObjCPtr may return an offsetted pointer value. |
| 688 | if (Result == NoAlias) |
| 689 | return NoAlias; |
| 690 | } |
| 691 | |
| 692 | // If that failed, fail. We don't need to chain here, since that's covered |
| 693 | // by the earlier precise query. |
| 694 | return MayAlias; |
| 695 | } |
| 696 | |
| 697 | bool |
| 698 | ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc, |
| 699 | bool OrLocal) { |
| 700 | if (!EnableARCOpts) |
| 701 | return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal); |
| 702 | |
| 703 | // First, strip off no-ops, including ObjC-specific no-ops, and try making |
| 704 | // a precise alias query. |
| 705 | const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr); |
| 706 | if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag), |
| 707 | OrLocal)) |
| 708 | return true; |
| 709 | |
| 710 | // If that failed, climb to the underlying object, including climbing through |
| 711 | // ObjC-specific no-ops, and try making an imprecise alias query. |
| 712 | const Value *U = GetUnderlyingObjCPtr(S); |
| 713 | if (U != S) |
| 714 | return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal); |
| 715 | |
| 716 | // If that failed, fail. We don't need to chain here, since that's covered |
| 717 | // by the earlier precise query. |
| 718 | return false; |
| 719 | } |
| 720 | |
| 721 | AliasAnalysis::ModRefBehavior |
| 722 | ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) { |
| 723 | // We have nothing to do. Just chain to the next AliasAnalysis. |
| 724 | return AliasAnalysis::getModRefBehavior(CS); |
| 725 | } |
| 726 | |
| 727 | AliasAnalysis::ModRefBehavior |
| 728 | ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) { |
| 729 | if (!EnableARCOpts) |
| 730 | return AliasAnalysis::getModRefBehavior(F); |
| 731 | |
| 732 | switch (GetFunctionClass(F)) { |
| 733 | case IC_NoopCast: |
| 734 | return DoesNotAccessMemory; |
| 735 | default: |
| 736 | break; |
| 737 | } |
| 738 | |
| 739 | return AliasAnalysis::getModRefBehavior(F); |
| 740 | } |
| 741 | |
| 742 | AliasAnalysis::ModRefResult |
| 743 | ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) { |
| 744 | if (!EnableARCOpts) |
| 745 | return AliasAnalysis::getModRefInfo(CS, Loc); |
| 746 | |
| 747 | switch (GetBasicInstructionClass(CS.getInstruction())) { |
| 748 | case IC_Retain: |
| 749 | case IC_RetainRV: |
| 750 | case IC_Autorelease: |
| 751 | case IC_AutoreleaseRV: |
| 752 | case IC_NoopCast: |
| 753 | case IC_AutoreleasepoolPush: |
| 754 | case IC_FusedRetainAutorelease: |
| 755 | case IC_FusedRetainAutoreleaseRV: |
| 756 | // These functions don't access any memory visible to the compiler. |
| 757 | // Note that this doesn't include objc_retainBlock, becuase it updates |
| 758 | // pointers when it copies block data. |
| 759 | return NoModRef; |
| 760 | default: |
| 761 | break; |
| 762 | } |
| 763 | |
| 764 | return AliasAnalysis::getModRefInfo(CS, Loc); |
| 765 | } |
| 766 | |
| 767 | AliasAnalysis::ModRefResult |
| 768 | ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1, |
| 769 | ImmutableCallSite CS2) { |
| 770 | // TODO: Theoretically we could check for dependencies between objc_* calls |
| 771 | // and OnlyAccessesArgumentPointees calls or other well-behaved calls. |
| 772 | return AliasAnalysis::getModRefInfo(CS1, CS2); |
| 773 | } |
| 774 | |
| 775 | //===----------------------------------------------------------------------===// |
| 776 | // ARC expansion. |
| 777 | //===----------------------------------------------------------------------===// |
| 778 | |
| 779 | #include "llvm/Support/InstIterator.h" |
| 780 | #include "llvm/Transforms/Scalar.h" |
| 781 | |
| 782 | namespace { |
| 783 | /// ObjCARCExpand - Early ARC transformations. |
| 784 | class ObjCARCExpand : public FunctionPass { |
| 785 | virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| 786 | virtual bool doInitialization(Module &M); |
| 787 | virtual bool runOnFunction(Function &F); |
| 788 | |
| 789 | /// Run - A flag indicating whether this optimization pass should run. |
| 790 | bool Run; |
| 791 | |
| 792 | public: |
| 793 | static char ID; |
| 794 | ObjCARCExpand() : FunctionPass(ID) { |
| 795 | initializeObjCARCExpandPass(*PassRegistry::getPassRegistry()); |
| 796 | } |
| 797 | }; |
| 798 | } |
| 799 | |
| 800 | char ObjCARCExpand::ID = 0; |
| 801 | INITIALIZE_PASS(ObjCARCExpand, |
| 802 | "objc-arc-expand", "ObjC ARC expansion", false, false) |
| 803 | |
| 804 | Pass *llvm::createObjCARCExpandPass() { |
| 805 | return new ObjCARCExpand(); |
| 806 | } |
| 807 | |
| 808 | void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const { |
| 809 | AU.setPreservesCFG(); |
| 810 | } |
| 811 | |
| 812 | bool ObjCARCExpand::doInitialization(Module &M) { |
| 813 | Run = ModuleHasARC(M); |
| 814 | return false; |
| 815 | } |
| 816 | |
| 817 | bool ObjCARCExpand::runOnFunction(Function &F) { |
| 818 | if (!EnableARCOpts) |
| 819 | return false; |
| 820 | |
| 821 | // If nothing in the Module uses ARC, don't do anything. |
| 822 | if (!Run) |
| 823 | return false; |
| 824 | |
| 825 | bool Changed = false; |
| 826 | |
| 827 | for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) { |
| 828 | Instruction *Inst = &*I; |
| 829 | |
| 830 | switch (GetBasicInstructionClass(Inst)) { |
| 831 | case IC_Retain: |
| 832 | case IC_RetainRV: |
| 833 | case IC_Autorelease: |
| 834 | case IC_AutoreleaseRV: |
| 835 | case IC_FusedRetainAutorelease: |
| 836 | case IC_FusedRetainAutoreleaseRV: |
| 837 | // These calls return their argument verbatim, as a low-level |
| 838 | // optimization. However, this makes high-level optimizations |
| 839 | // harder. Undo any uses of this optimization that the front-end |
| 840 | // emitted here. We'll redo them in a later pass. |
| 841 | Changed = true; |
| 842 | Inst->replaceAllUsesWith(cast<CallInst>(Inst)->getArgOperand(0)); |
| 843 | break; |
| 844 | default: |
| 845 | break; |
| 846 | } |
| 847 | } |
| 848 | |
| 849 | return Changed; |
| 850 | } |
| 851 | |
| 852 | //===----------------------------------------------------------------------===// |
| 853 | // ARC optimization. |
| 854 | //===----------------------------------------------------------------------===// |
| 855 | |
| 856 | // TODO: On code like this: |
| 857 | // |
| 858 | // objc_retain(%x) |
| 859 | // stuff_that_cannot_release() |
| 860 | // objc_autorelease(%x) |
| 861 | // stuff_that_cannot_release() |
| 862 | // objc_retain(%x) |
| 863 | // stuff_that_cannot_release() |
| 864 | // objc_autorelease(%x) |
| 865 | // |
| 866 | // The second retain and autorelease can be deleted. |
| 867 | |
| 868 | // TODO: It should be possible to delete |
| 869 | // objc_autoreleasePoolPush and objc_autoreleasePoolPop |
| 870 | // pairs if nothing is actually autoreleased between them. Also, autorelease |
| 871 | // calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code |
| 872 | // after inlining) can be turned into plain release calls. |
| 873 | |
| 874 | // TODO: Critical-edge splitting. If the optimial insertion point is |
| 875 | // a critical edge, the current algorithm has to fail, because it doesn't |
| 876 | // know how to split edges. It should be possible to make the optimizer |
| 877 | // think in terms of edges, rather than blocks, and then split critical |
| 878 | // edges on demand. |
| 879 | |
| 880 | // TODO: OptimizeSequences could generalized to be Interprocedural. |
| 881 | |
| 882 | // TODO: Recognize that a bunch of other objc runtime calls have |
| 883 | // non-escaping arguments and non-releasing arguments, and may be |
| 884 | // non-autoreleasing. |
| 885 | |
| 886 | // TODO: Sink autorelease calls as far as possible. Unfortunately we |
| 887 | // usually can't sink them past other calls, which would be the main |
| 888 | // case where it would be useful. |
| 889 | |
| 890 | // TODO: The pointer returned from objc_loadWeakRetained is retained. |
| 891 | |
| 892 | // TODO: Delete release+retain pairs (rare). |
| 893 | |
| 894 | #include "llvm/GlobalAlias.h" |
| 895 | #include "llvm/Constants.h" |
| 896 | #include "llvm/LLVMContext.h" |
| 897 | #include "llvm/Support/ErrorHandling.h" |
| 898 | #include "llvm/Support/CFG.h" |
| 899 | #include "llvm/ADT/PostOrderIterator.h" |
| 900 | #include "llvm/ADT/Statistic.h" |
| 901 | |
| 902 | STATISTIC(NumNoops, "Number of no-op objc calls eliminated"); |
| 903 | STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated"); |
| 904 | STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases"); |
| 905 | STATISTIC(NumRets, "Number of return value forwarding " |
| 906 | "retain+autoreleaes eliminated"); |
| 907 | STATISTIC(NumRRs, "Number of retain+release paths eliminated"); |
| 908 | STATISTIC(NumPeeps, "Number of calls peephole-optimized"); |
| 909 | |
| 910 | namespace { |
| 911 | /// ProvenanceAnalysis - This is similar to BasicAliasAnalysis, and it |
| 912 | /// uses many of the same techniques, except it uses special ObjC-specific |
| 913 | /// reasoning about pointer relationships. |
| 914 | class ProvenanceAnalysis { |
| 915 | AliasAnalysis *AA; |
| 916 | |
| 917 | typedef std::pair<const Value *, const Value *> ValuePairTy; |
| 918 | typedef DenseMap<ValuePairTy, bool> CachedResultsTy; |
| 919 | CachedResultsTy CachedResults; |
| 920 | |
| 921 | bool relatedCheck(const Value *A, const Value *B); |
| 922 | bool relatedSelect(const SelectInst *A, const Value *B); |
| 923 | bool relatedPHI(const PHINode *A, const Value *B); |
| 924 | |
| 925 | // Do not implement. |
| 926 | void operator=(const ProvenanceAnalysis &); |
| 927 | ProvenanceAnalysis(const ProvenanceAnalysis &); |
| 928 | |
| 929 | public: |
| 930 | ProvenanceAnalysis() {} |
| 931 | |
| 932 | void setAA(AliasAnalysis *aa) { AA = aa; } |
| 933 | |
| 934 | AliasAnalysis *getAA() const { return AA; } |
| 935 | |
| 936 | bool related(const Value *A, const Value *B); |
| 937 | |
| 938 | void clear() { |
| 939 | CachedResults.clear(); |
| 940 | } |
| 941 | }; |
| 942 | } |
| 943 | |
| 944 | bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) { |
| 945 | // If the values are Selects with the same condition, we can do a more precise |
| 946 | // check: just check for relations between the values on corresponding arms. |
| 947 | if (const SelectInst *SB = dyn_cast<SelectInst>(B)) |
| 948 | if (A->getCondition() == SB->getCondition()) { |
| 949 | if (related(A->getTrueValue(), SB->getTrueValue())) |
| 950 | return true; |
| 951 | if (related(A->getFalseValue(), SB->getFalseValue())) |
| 952 | return true; |
| 953 | return false; |
| 954 | } |
| 955 | |
| 956 | // Check both arms of the Select node individually. |
| 957 | if (related(A->getTrueValue(), B)) |
| 958 | return true; |
| 959 | if (related(A->getFalseValue(), B)) |
| 960 | return true; |
| 961 | |
| 962 | // The arms both checked out. |
| 963 | return false; |
| 964 | } |
| 965 | |
| 966 | bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) { |
| 967 | // If the values are PHIs in the same block, we can do a more precise as well |
| 968 | // as efficient check: just check for relations between the values on |
| 969 | // corresponding edges. |
| 970 | if (const PHINode *PNB = dyn_cast<PHINode>(B)) |
| 971 | if (PNB->getParent() == A->getParent()) { |
| 972 | for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) |
| 973 | if (related(A->getIncomingValue(i), |
| 974 | PNB->getIncomingValueForBlock(A->getIncomingBlock(i)))) |
| 975 | return true; |
| 976 | return false; |
| 977 | } |
| 978 | |
| 979 | // Check each unique source of the PHI node against B. |
| 980 | SmallPtrSet<const Value *, 4> UniqueSrc; |
| 981 | for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) { |
| 982 | const Value *PV1 = A->getIncomingValue(i); |
| 983 | if (UniqueSrc.insert(PV1) && related(PV1, B)) |
| 984 | return true; |
| 985 | } |
| 986 | |
| 987 | // All of the arms checked out. |
| 988 | return false; |
| 989 | } |
| 990 | |
| 991 | /// isStoredObjCPointer - Test if the value of P, or any value covered by its |
| 992 | /// provenance, is ever stored within the function (not counting callees). |
| 993 | static bool isStoredObjCPointer(const Value *P) { |
| 994 | SmallPtrSet<const Value *, 8> Visited; |
| 995 | SmallVector<const Value *, 8> Worklist; |
| 996 | Worklist.push_back(P); |
| 997 | Visited.insert(P); |
| 998 | do { |
| 999 | P = Worklist.pop_back_val(); |
| 1000 | for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end(); |
| 1001 | UI != UE; ++UI) { |
| 1002 | const User *Ur = *UI; |
| 1003 | if (isa<StoreInst>(Ur)) { |
| 1004 | if (UI.getOperandNo() == 0) |
| 1005 | // The pointer is stored. |
| 1006 | return true; |
| 1007 | // The pointed is stored through. |
| 1008 | continue; |
| 1009 | } |
| 1010 | if (isa<CallInst>(Ur)) |
| 1011 | // The pointer is passed as an argument, ignore this. |
| 1012 | continue; |
| 1013 | if (isa<PtrToIntInst>(P)) |
| 1014 | // Assume the worst. |
| 1015 | return true; |
| 1016 | if (Visited.insert(Ur)) |
| 1017 | Worklist.push_back(Ur); |
| 1018 | } |
| 1019 | } while (!Worklist.empty()); |
| 1020 | |
| 1021 | // Everything checked out. |
| 1022 | return false; |
| 1023 | } |
| 1024 | |
| 1025 | bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) { |
| 1026 | // Skip past provenance pass-throughs. |
| 1027 | A = GetUnderlyingObjCPtr(A); |
| 1028 | B = GetUnderlyingObjCPtr(B); |
| 1029 | |
| 1030 | // Quick check. |
| 1031 | if (A == B) |
| 1032 | return true; |
| 1033 | |
| 1034 | // Ask regular AliasAnalysis, for a first approximation. |
| 1035 | switch (AA->alias(A, B)) { |
| 1036 | case AliasAnalysis::NoAlias: |
| 1037 | return false; |
| 1038 | case AliasAnalysis::MustAlias: |
| 1039 | case AliasAnalysis::PartialAlias: |
| 1040 | return true; |
| 1041 | case AliasAnalysis::MayAlias: |
| 1042 | break; |
| 1043 | } |
| 1044 | |
| 1045 | bool AIsIdentified = IsObjCIdentifiedObject(A); |
| 1046 | bool BIsIdentified = IsObjCIdentifiedObject(B); |
| 1047 | |
| 1048 | // An ObjC-Identified object can't alias a load if it is never locally stored. |
| 1049 | if (AIsIdentified) { |
| 1050 | if (BIsIdentified) { |
| 1051 | // If both pointers have provenance, they can be directly compared. |
| 1052 | if (A != B) |
| 1053 | return false; |
| 1054 | } else { |
| 1055 | if (isa<LoadInst>(B)) |
| 1056 | return isStoredObjCPointer(A); |
| 1057 | } |
| 1058 | } else { |
| 1059 | if (BIsIdentified && isa<LoadInst>(A)) |
| 1060 | return isStoredObjCPointer(B); |
| 1061 | } |
| 1062 | |
| 1063 | // Special handling for PHI and Select. |
| 1064 | if (const PHINode *PN = dyn_cast<PHINode>(A)) |
| 1065 | return relatedPHI(PN, B); |
| 1066 | if (const PHINode *PN = dyn_cast<PHINode>(B)) |
| 1067 | return relatedPHI(PN, A); |
| 1068 | if (const SelectInst *S = dyn_cast<SelectInst>(A)) |
| 1069 | return relatedSelect(S, B); |
| 1070 | if (const SelectInst *S = dyn_cast<SelectInst>(B)) |
| 1071 | return relatedSelect(S, A); |
| 1072 | |
| 1073 | // Conservative. |
| 1074 | return true; |
| 1075 | } |
| 1076 | |
| 1077 | bool ProvenanceAnalysis::related(const Value *A, const Value *B) { |
| 1078 | // Begin by inserting a conservative value into the map. If the insertion |
| 1079 | // fails, we have the answer already. If it succeeds, leave it there until we |
| 1080 | // compute the real answer to guard against recursive queries. |
| 1081 | if (A > B) std::swap(A, B); |
| 1082 | std::pair<CachedResultsTy::iterator, bool> Pair = |
| 1083 | CachedResults.insert(std::make_pair(ValuePairTy(A, B), true)); |
| 1084 | if (!Pair.second) |
| 1085 | return Pair.first->second; |
| 1086 | |
| 1087 | bool Result = relatedCheck(A, B); |
| 1088 | CachedResults[ValuePairTy(A, B)] = Result; |
| 1089 | return Result; |
| 1090 | } |
| 1091 | |
| 1092 | namespace { |
| 1093 | // Sequence - A sequence of states that a pointer may go through in which an |
| 1094 | // objc_retain and objc_release are actually needed. |
| 1095 | enum Sequence { |
| 1096 | S_None, |
| 1097 | S_Retain, ///< objc_retain(x) |
| 1098 | S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement |
| 1099 | S_Use, ///< any use of x |
| 1100 | S_Stop, ///< like S_Release, but code motion is stopped |
| 1101 | S_Release, ///< objc_release(x) |
| 1102 | S_MovableRelease ///< objc_release(x), !clang.imprecise_release |
| 1103 | }; |
| 1104 | } |
| 1105 | |
| 1106 | static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) { |
| 1107 | // The easy cases. |
| 1108 | if (A == B) |
| 1109 | return A; |
| 1110 | if (A == S_None || B == S_None) |
| 1111 | return S_None; |
| 1112 | |
| 1113 | if (A > B) std::swap(A, B); |
| 1114 | if (TopDown) { |
| 1115 | // Choose the side which is further along in the sequence. |
| 1116 | if ((A == S_Retain || A == S_CanRelease) && |
| 1117 | (B == S_CanRelease || B == S_Use)) |
| 1118 | return B; |
| 1119 | } else { |
| 1120 | // Choose the side which is further along in the sequence. |
| 1121 | if ((A == S_Use || A == S_CanRelease) && |
| 1122 | (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease)) |
| 1123 | return A; |
| 1124 | // If both sides are releases, choose the more conservative one. |
| 1125 | if (A == S_Stop && (B == S_Release || B == S_MovableRelease)) |
| 1126 | return A; |
| 1127 | if (A == S_Release && B == S_MovableRelease) |
| 1128 | return A; |
| 1129 | } |
| 1130 | |
| 1131 | return S_None; |
| 1132 | } |
| 1133 | |
| 1134 | namespace { |
| 1135 | /// RRInfo - Unidirectional information about either a |
| 1136 | /// retain-decrement-use-release sequence or release-use-decrement-retain |
| 1137 | /// reverese sequence. |
| 1138 | struct RRInfo { |
| 1139 | /// KnownSafe - After an objc_retain, the reference count of the referenced |
| 1140 | /// object is known to be positive. Similarly, before an objc_release, the |
| 1141 | /// reference count of the referenced object is known to be positive. If |
| 1142 | /// there are retain-release pairs in code regions where the retain count |
| 1143 | /// is known to be positive, they can be eliminated, regardless of any side |
| 1144 | /// effects between them. |
| 1145 | /// |
| 1146 | /// Also, a retain+release pair nested within another retain+release |
| 1147 | /// pair all on the known same pointer value can be eliminated, regardless |
| 1148 | /// of any intervening side effects. |
| 1149 | /// |
| 1150 | /// KnownSafe is true when either of these conditions is satisfied. |
| 1151 | bool KnownSafe; |
| 1152 | |
| 1153 | /// IsRetainBlock - True if the Calls are objc_retainBlock calls (as |
| 1154 | /// opposed to objc_retain calls). |
| 1155 | bool IsRetainBlock; |
| 1156 | |
| 1157 | /// IsTailCallRelease - True of the objc_release calls are all marked |
| 1158 | /// with the "tail" keyword. |
| 1159 | bool IsTailCallRelease; |
| 1160 | |
| 1161 | /// ReleaseMetadata - If the Calls are objc_release calls and they all have |
| 1162 | /// a clang.imprecise_release tag, this is the metadata tag. |
| 1163 | MDNode *ReleaseMetadata; |
| 1164 | |
| 1165 | /// Calls - For a top-down sequence, the set of objc_retains or |
| 1166 | /// objc_retainBlocks. For bottom-up, the set of objc_releases. |
| 1167 | SmallPtrSet<Instruction *, 2> Calls; |
| 1168 | |
| 1169 | /// ReverseInsertPts - The set of optimal insert positions for |
| 1170 | /// moving calls in the opposite sequence. |
| 1171 | SmallPtrSet<Instruction *, 2> ReverseInsertPts; |
| 1172 | |
| 1173 | RRInfo() : |
| 1174 | KnownSafe(false), IsRetainBlock(false), IsTailCallRelease(false), |
| 1175 | ReleaseMetadata(0) {} |
| 1176 | |
| 1177 | void clear(); |
| 1178 | }; |
| 1179 | } |
| 1180 | |
| 1181 | void RRInfo::clear() { |
| 1182 | KnownSafe = false; |
| 1183 | IsRetainBlock = false; |
| 1184 | IsTailCallRelease = false; |
| 1185 | ReleaseMetadata = 0; |
| 1186 | Calls.clear(); |
| 1187 | ReverseInsertPts.clear(); |
| 1188 | } |
| 1189 | |
| 1190 | namespace { |
| 1191 | /// PtrState - This class summarizes several per-pointer runtime properties |
| 1192 | /// which are propogated through the flow graph. |
| 1193 | class PtrState { |
| 1194 | /// RefCount - The known minimum number of reference count increments. |
| 1195 | unsigned RefCount; |
| 1196 | |
| 1197 | /// NestCount - The known minimum level of retain+release nesting. |
| 1198 | unsigned NestCount; |
| 1199 | |
| 1200 | /// Seq - The current position in the sequence. |
| 1201 | Sequence Seq; |
| 1202 | |
| 1203 | public: |
| 1204 | /// RRI - Unidirectional information about the current sequence. |
| 1205 | /// TODO: Encapsulate this better. |
| 1206 | RRInfo RRI; |
| 1207 | |
| 1208 | PtrState() : RefCount(0), NestCount(0), Seq(S_None) {} |
| 1209 | |
| 1210 | void SetAtLeastOneRefCount() { |
| 1211 | if (RefCount == 0) RefCount = 1; |
| 1212 | } |
| 1213 | |
| 1214 | void IncrementRefCount() { |
| 1215 | if (RefCount != UINT_MAX) ++RefCount; |
| 1216 | } |
| 1217 | |
| 1218 | void DecrementRefCount() { |
| 1219 | if (RefCount != 0) --RefCount; |
| 1220 | } |
| 1221 | |
| 1222 | bool IsKnownIncremented() const { |
| 1223 | return RefCount > 0; |
| 1224 | } |
| 1225 | |
| 1226 | void IncrementNestCount() { |
| 1227 | if (NestCount != UINT_MAX) ++NestCount; |
| 1228 | } |
| 1229 | |
| 1230 | void DecrementNestCount() { |
| 1231 | if (NestCount != 0) --NestCount; |
| 1232 | } |
| 1233 | |
| 1234 | bool IsKnownNested() const { |
| 1235 | return NestCount > 0; |
| 1236 | } |
| 1237 | |
| 1238 | void SetSeq(Sequence NewSeq) { |
| 1239 | Seq = NewSeq; |
| 1240 | } |
| 1241 | |
| 1242 | void SetSeqToRelease(MDNode *M) { |
| 1243 | if (Seq == S_None || Seq == S_Use) { |
| 1244 | Seq = M ? S_MovableRelease : S_Release; |
| 1245 | RRI.ReleaseMetadata = M; |
| 1246 | } else if (Seq != S_MovableRelease || RRI.ReleaseMetadata != M) { |
| 1247 | Seq = S_Release; |
| 1248 | RRI.ReleaseMetadata = 0; |
| 1249 | } |
| 1250 | } |
| 1251 | |
| 1252 | Sequence GetSeq() const { |
| 1253 | return Seq; |
| 1254 | } |
| 1255 | |
| 1256 | void ClearSequenceProgress() { |
| 1257 | Seq = S_None; |
| 1258 | RRI.clear(); |
| 1259 | } |
| 1260 | |
| 1261 | void Merge(const PtrState &Other, bool TopDown); |
| 1262 | }; |
| 1263 | } |
| 1264 | |
| 1265 | void |
| 1266 | PtrState::Merge(const PtrState &Other, bool TopDown) { |
| 1267 | Seq = MergeSeqs(Seq, Other.Seq, TopDown); |
| 1268 | RefCount = std::min(RefCount, Other.RefCount); |
| 1269 | NestCount = std::min(NestCount, Other.NestCount); |
| 1270 | |
| 1271 | // We can't merge a plain objc_retain with an objc_retainBlock. |
| 1272 | if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock) |
| 1273 | Seq = S_None; |
| 1274 | |
| 1275 | if (Seq == S_None) { |
| 1276 | RRI.clear(); |
| 1277 | } else { |
| 1278 | // Conservatively merge the ReleaseMetadata information. |
| 1279 | if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata) |
| 1280 | RRI.ReleaseMetadata = 0; |
| 1281 | |
| 1282 | RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe; |
| 1283 | RRI.IsTailCallRelease = RRI.IsTailCallRelease && Other.RRI.IsTailCallRelease; |
| 1284 | RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end()); |
| 1285 | RRI.ReverseInsertPts.insert(Other.RRI.ReverseInsertPts.begin(), |
| 1286 | Other.RRI.ReverseInsertPts.end()); |
| 1287 | } |
| 1288 | } |
| 1289 | |
| 1290 | namespace { |
| 1291 | /// BBState - Per-BasicBlock state. |
| 1292 | class BBState { |
| 1293 | /// TopDownPathCount - The number of unique control paths from the entry |
| 1294 | /// which can reach this block. |
| 1295 | unsigned TopDownPathCount; |
| 1296 | |
| 1297 | /// BottomUpPathCount - The number of unique control paths to exits |
| 1298 | /// from this block. |
| 1299 | unsigned BottomUpPathCount; |
| 1300 | |
| 1301 | /// MapTy - A type for PerPtrTopDown and PerPtrBottomUp. |
| 1302 | typedef MapVector<const Value *, PtrState> MapTy; |
| 1303 | |
| 1304 | /// PerPtrTopDown - The top-down traversal uses this to record information |
| 1305 | /// known about a pointer at the bottom of each block. |
| 1306 | MapTy PerPtrTopDown; |
| 1307 | |
| 1308 | /// PerPtrBottomUp - The bottom-up traversal uses this to record information |
| 1309 | /// known about a pointer at the top of each block. |
| 1310 | MapTy PerPtrBottomUp; |
| 1311 | |
| 1312 | public: |
| 1313 | BBState() : TopDownPathCount(0), BottomUpPathCount(0) {} |
| 1314 | |
| 1315 | typedef MapTy::iterator ptr_iterator; |
| 1316 | typedef MapTy::const_iterator ptr_const_iterator; |
| 1317 | |
| 1318 | ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); } |
| 1319 | ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); } |
| 1320 | ptr_const_iterator top_down_ptr_begin() const { |
| 1321 | return PerPtrTopDown.begin(); |
| 1322 | } |
| 1323 | ptr_const_iterator top_down_ptr_end() const { |
| 1324 | return PerPtrTopDown.end(); |
| 1325 | } |
| 1326 | |
| 1327 | ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); } |
| 1328 | ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); } |
| 1329 | ptr_const_iterator bottom_up_ptr_begin() const { |
| 1330 | return PerPtrBottomUp.begin(); |
| 1331 | } |
| 1332 | ptr_const_iterator bottom_up_ptr_end() const { |
| 1333 | return PerPtrBottomUp.end(); |
| 1334 | } |
| 1335 | |
| 1336 | /// SetAsEntry - Mark this block as being an entry block, which has one |
| 1337 | /// path from the entry by definition. |
| 1338 | void SetAsEntry() { TopDownPathCount = 1; } |
| 1339 | |
| 1340 | /// SetAsExit - Mark this block as being an exit block, which has one |
| 1341 | /// path to an exit by definition. |
| 1342 | void SetAsExit() { BottomUpPathCount = 1; } |
| 1343 | |
| 1344 | PtrState &getPtrTopDownState(const Value *Arg) { |
| 1345 | return PerPtrTopDown[Arg]; |
| 1346 | } |
| 1347 | |
| 1348 | PtrState &getPtrBottomUpState(const Value *Arg) { |
| 1349 | return PerPtrBottomUp[Arg]; |
| 1350 | } |
| 1351 | |
| 1352 | void clearBottomUpPointers() { |
| 1353 | PerPtrBottomUp.clear(); |
| 1354 | } |
| 1355 | |
| 1356 | void clearTopDownPointers() { |
| 1357 | PerPtrTopDown.clear(); |
| 1358 | } |
| 1359 | |
| 1360 | void InitFromPred(const BBState &Other); |
| 1361 | void InitFromSucc(const BBState &Other); |
| 1362 | void MergePred(const BBState &Other); |
| 1363 | void MergeSucc(const BBState &Other); |
| 1364 | |
| 1365 | /// GetAllPathCount - Return the number of possible unique paths from an |
| 1366 | /// entry to an exit which pass through this block. This is only valid |
| 1367 | /// after both the top-down and bottom-up traversals are complete. |
| 1368 | unsigned GetAllPathCount() const { |
| 1369 | return TopDownPathCount * BottomUpPathCount; |
| 1370 | } |
| 1371 | |
| 1372 | /// IsVisitedTopDown - Test whether the block for this BBState has been |
| 1373 | /// visited by the top-down portion of the algorithm. |
| 1374 | bool isVisitedTopDown() const { |
| 1375 | return TopDownPathCount != 0; |
| 1376 | } |
| 1377 | }; |
| 1378 | } |
| 1379 | |
| 1380 | void BBState::InitFromPred(const BBState &Other) { |
| 1381 | PerPtrTopDown = Other.PerPtrTopDown; |
| 1382 | TopDownPathCount = Other.TopDownPathCount; |
| 1383 | } |
| 1384 | |
| 1385 | void BBState::InitFromSucc(const BBState &Other) { |
| 1386 | PerPtrBottomUp = Other.PerPtrBottomUp; |
| 1387 | BottomUpPathCount = Other.BottomUpPathCount; |
| 1388 | } |
| 1389 | |
| 1390 | /// MergePred - The top-down traversal uses this to merge information about |
| 1391 | /// predecessors to form the initial state for a new block. |
| 1392 | void BBState::MergePred(const BBState &Other) { |
| 1393 | // Other.TopDownPathCount can be 0, in which case it is either dead or a |
| 1394 | // loop backedge. Loop backedges are special. |
| 1395 | TopDownPathCount += Other.TopDownPathCount; |
| 1396 | |
| 1397 | // For each entry in the other set, if our set has an entry with the same key, |
| 1398 | // merge the entries. Otherwise, copy the entry and merge it with an empty |
| 1399 | // entry. |
| 1400 | for (ptr_const_iterator MI = Other.top_down_ptr_begin(), |
| 1401 | ME = Other.top_down_ptr_end(); MI != ME; ++MI) { |
| 1402 | std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI); |
| 1403 | Pair.first->second.Merge(Pair.second ? PtrState() : MI->second, |
| 1404 | /*TopDown=*/true); |
| 1405 | } |
| 1406 | |
| 1407 | // For each entry in our set, if the other set doesn't have an entry with the |
| 1408 | // same key, force it to merge with an empty entry. |
| 1409 | for (ptr_iterator MI = top_down_ptr_begin(), |
| 1410 | ME = top_down_ptr_end(); MI != ME; ++MI) |
| 1411 | if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end()) |
| 1412 | MI->second.Merge(PtrState(), /*TopDown=*/true); |
| 1413 | } |
| 1414 | |
| 1415 | /// MergeSucc - The bottom-up traversal uses this to merge information about |
| 1416 | /// successors to form the initial state for a new block. |
| 1417 | void BBState::MergeSucc(const BBState &Other) { |
| 1418 | // Other.BottomUpPathCount can be 0, in which case it is either dead or a |
| 1419 | // loop backedge. Loop backedges are special. |
| 1420 | BottomUpPathCount += Other.BottomUpPathCount; |
| 1421 | |
| 1422 | // For each entry in the other set, if our set has an entry with the |
| 1423 | // same key, merge the entries. Otherwise, copy the entry and merge |
| 1424 | // it with an empty entry. |
| 1425 | for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(), |
| 1426 | ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) { |
| 1427 | std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI); |
| 1428 | Pair.first->second.Merge(Pair.second ? PtrState() : MI->second, |
| 1429 | /*TopDown=*/false); |
| 1430 | } |
| 1431 | |
| 1432 | // For each entry in our set, if the other set doesn't have an entry |
| 1433 | // with the same key, force it to merge with an empty entry. |
| 1434 | for (ptr_iterator MI = bottom_up_ptr_begin(), |
| 1435 | ME = bottom_up_ptr_end(); MI != ME; ++MI) |
| 1436 | if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end()) |
| 1437 | MI->second.Merge(PtrState(), /*TopDown=*/false); |
| 1438 | } |
| 1439 | |
| 1440 | namespace { |
| 1441 | /// ObjCARCOpt - The main ARC optimization pass. |
| 1442 | class ObjCARCOpt : public FunctionPass { |
| 1443 | bool Changed; |
| 1444 | ProvenanceAnalysis PA; |
| 1445 | |
| 1446 | /// Run - A flag indicating whether this optimization pass should run. |
| 1447 | bool Run; |
| 1448 | |
| 1449 | /// RetainRVCallee, etc. - Declarations for ObjC runtime |
| 1450 | /// functions, for use in creating calls to them. These are initialized |
| 1451 | /// lazily to avoid cluttering up the Module with unused declarations. |
| 1452 | Constant *RetainRVCallee, *AutoreleaseRVCallee, *ReleaseCallee, |
| 1453 | *RetainCallee, *RetainBlockCallee, *AutoreleaseCallee; |
| 1454 | |
| 1455 | /// UsedInThisFunciton - Flags which determine whether each of the |
| 1456 | /// interesting runtine functions is in fact used in the current function. |
| 1457 | unsigned UsedInThisFunction; |
| 1458 | |
| 1459 | /// ImpreciseReleaseMDKind - The Metadata Kind for clang.imprecise_release |
| 1460 | /// metadata. |
| 1461 | unsigned ImpreciseReleaseMDKind; |
| 1462 | |
| 1463 | Constant *getRetainRVCallee(Module *M); |
| 1464 | Constant *getAutoreleaseRVCallee(Module *M); |
| 1465 | Constant *getReleaseCallee(Module *M); |
| 1466 | Constant *getRetainCallee(Module *M); |
| 1467 | Constant *getRetainBlockCallee(Module *M); |
| 1468 | Constant *getAutoreleaseCallee(Module *M); |
| 1469 | |
| 1470 | void OptimizeRetainCall(Function &F, Instruction *Retain); |
| 1471 | bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV); |
| 1472 | void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV); |
| 1473 | void OptimizeIndividualCalls(Function &F); |
| 1474 | |
| 1475 | void CheckForCFGHazards(const BasicBlock *BB, |
| 1476 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 1477 | BBState &MyStates) const; |
| 1478 | bool VisitBottomUp(BasicBlock *BB, |
| 1479 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 1480 | MapVector<Value *, RRInfo> &Retains); |
| 1481 | bool VisitTopDown(BasicBlock *BB, |
| 1482 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 1483 | DenseMap<Value *, RRInfo> &Releases); |
| 1484 | bool Visit(Function &F, |
| 1485 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 1486 | MapVector<Value *, RRInfo> &Retains, |
| 1487 | DenseMap<Value *, RRInfo> &Releases); |
| 1488 | |
| 1489 | void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove, |
| 1490 | MapVector<Value *, RRInfo> &Retains, |
| 1491 | DenseMap<Value *, RRInfo> &Releases, |
| 1492 | SmallVectorImpl<Instruction *> &DeadInsts, |
| 1493 | Module *M); |
| 1494 | |
| 1495 | bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates, |
| 1496 | MapVector<Value *, RRInfo> &Retains, |
| 1497 | DenseMap<Value *, RRInfo> &Releases, |
| 1498 | Module *M); |
| 1499 | |
| 1500 | void OptimizeWeakCalls(Function &F); |
| 1501 | |
| 1502 | bool OptimizeSequences(Function &F); |
| 1503 | |
| 1504 | void OptimizeReturns(Function &F); |
| 1505 | |
| 1506 | virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| 1507 | virtual bool doInitialization(Module &M); |
| 1508 | virtual bool runOnFunction(Function &F); |
| 1509 | virtual void releaseMemory(); |
| 1510 | |
| 1511 | public: |
| 1512 | static char ID; |
| 1513 | ObjCARCOpt() : FunctionPass(ID) { |
| 1514 | initializeObjCARCOptPass(*PassRegistry::getPassRegistry()); |
| 1515 | } |
| 1516 | }; |
| 1517 | } |
| 1518 | |
| 1519 | char ObjCARCOpt::ID = 0; |
| 1520 | INITIALIZE_PASS_BEGIN(ObjCARCOpt, |
| 1521 | "objc-arc", "ObjC ARC optimization", false, false) |
| 1522 | INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis) |
| 1523 | INITIALIZE_PASS_END(ObjCARCOpt, |
| 1524 | "objc-arc", "ObjC ARC optimization", false, false) |
| 1525 | |
| 1526 | Pass *llvm::createObjCARCOptPass() { |
| 1527 | return new ObjCARCOpt(); |
| 1528 | } |
| 1529 | |
| 1530 | void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const { |
| 1531 | AU.addRequired<ObjCARCAliasAnalysis>(); |
| 1532 | AU.addRequired<AliasAnalysis>(); |
| 1533 | // ARC optimization doesn't currently split critical edges. |
| 1534 | AU.setPreservesCFG(); |
| 1535 | } |
| 1536 | |
| 1537 | Constant *ObjCARCOpt::getRetainRVCallee(Module *M) { |
| 1538 | if (!RetainRVCallee) { |
| 1539 | LLVMContext &C = M->getContext(); |
| 1540 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 1541 | std::vector<Type *> Params; |
| 1542 | Params.push_back(I8X); |
| 1543 | FunctionType *FTy = |
| 1544 | FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| 1545 | AttrListPtr Attributes; |
| 1546 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 1547 | RetainRVCallee = |
| 1548 | M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy, |
| 1549 | Attributes); |
| 1550 | } |
| 1551 | return RetainRVCallee; |
| 1552 | } |
| 1553 | |
| 1554 | Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) { |
| 1555 | if (!AutoreleaseRVCallee) { |
| 1556 | LLVMContext &C = M->getContext(); |
| 1557 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 1558 | std::vector<Type *> Params; |
| 1559 | Params.push_back(I8X); |
| 1560 | FunctionType *FTy = |
| 1561 | FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| 1562 | AttrListPtr Attributes; |
| 1563 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 1564 | AutoreleaseRVCallee = |
| 1565 | M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy, |
| 1566 | Attributes); |
| 1567 | } |
| 1568 | return AutoreleaseRVCallee; |
| 1569 | } |
| 1570 | |
| 1571 | Constant *ObjCARCOpt::getReleaseCallee(Module *M) { |
| 1572 | if (!ReleaseCallee) { |
| 1573 | LLVMContext &C = M->getContext(); |
| 1574 | std::vector<Type *> Params; |
| 1575 | Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C))); |
| 1576 | AttrListPtr Attributes; |
| 1577 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 1578 | ReleaseCallee = |
| 1579 | M->getOrInsertFunction( |
| 1580 | "objc_release", |
| 1581 | FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false), |
| 1582 | Attributes); |
| 1583 | } |
| 1584 | return ReleaseCallee; |
| 1585 | } |
| 1586 | |
| 1587 | Constant *ObjCARCOpt::getRetainCallee(Module *M) { |
| 1588 | if (!RetainCallee) { |
| 1589 | LLVMContext &C = M->getContext(); |
| 1590 | std::vector<Type *> Params; |
| 1591 | Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C))); |
| 1592 | AttrListPtr Attributes; |
| 1593 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 1594 | RetainCallee = |
| 1595 | M->getOrInsertFunction( |
| 1596 | "objc_retain", |
| 1597 | FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| 1598 | Attributes); |
| 1599 | } |
| 1600 | return RetainCallee; |
| 1601 | } |
| 1602 | |
| 1603 | Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) { |
| 1604 | if (!RetainBlockCallee) { |
| 1605 | LLVMContext &C = M->getContext(); |
| 1606 | std::vector<Type *> Params; |
| 1607 | Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C))); |
| 1608 | AttrListPtr Attributes; |
| 1609 | // objc_retainBlock is not nounwind because it calls user copy constructors |
| 1610 | // which could theoretically throw. |
| 1611 | RetainBlockCallee = |
| 1612 | M->getOrInsertFunction( |
| 1613 | "objc_retainBlock", |
| 1614 | FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| 1615 | Attributes); |
| 1616 | } |
| 1617 | return RetainBlockCallee; |
| 1618 | } |
| 1619 | |
| 1620 | Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) { |
| 1621 | if (!AutoreleaseCallee) { |
| 1622 | LLVMContext &C = M->getContext(); |
| 1623 | std::vector<Type *> Params; |
| 1624 | Params.push_back(PointerType::getUnqual(Type::getInt8Ty(C))); |
| 1625 | AttrListPtr Attributes; |
| 1626 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 1627 | AutoreleaseCallee = |
| 1628 | M->getOrInsertFunction( |
| 1629 | "objc_autorelease", |
| 1630 | FunctionType::get(Params[0], Params, /*isVarArg=*/false), |
| 1631 | Attributes); |
| 1632 | } |
| 1633 | return AutoreleaseCallee; |
| 1634 | } |
| 1635 | |
| 1636 | /// CanAlterRefCount - Test whether the given instruction can result in a |
| 1637 | /// reference count modification (positive or negative) for the pointer's |
| 1638 | /// object. |
| 1639 | static bool |
| 1640 | CanAlterRefCount(const Instruction *Inst, const Value *Ptr, |
| 1641 | ProvenanceAnalysis &PA, InstructionClass Class) { |
| 1642 | switch (Class) { |
| 1643 | case IC_Autorelease: |
| 1644 | case IC_AutoreleaseRV: |
| 1645 | case IC_User: |
| 1646 | // These operations never directly modify a reference count. |
| 1647 | return false; |
| 1648 | default: break; |
| 1649 | } |
| 1650 | |
| 1651 | ImmutableCallSite CS = static_cast<const Value *>(Inst); |
| 1652 | assert(CS && "Only calls can alter reference counts!"); |
| 1653 | |
| 1654 | // See if AliasAnalysis can help us with the call. |
| 1655 | AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS); |
| 1656 | if (AliasAnalysis::onlyReadsMemory(MRB)) |
| 1657 | return false; |
| 1658 | if (AliasAnalysis::onlyAccessesArgPointees(MRB)) { |
| 1659 | for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); |
| 1660 | I != E; ++I) { |
| 1661 | const Value *Op = *I; |
| 1662 | if (IsPotentialUse(Op) && PA.related(Ptr, Op)) |
| 1663 | return true; |
| 1664 | } |
| 1665 | return false; |
| 1666 | } |
| 1667 | |
| 1668 | // Assume the worst. |
| 1669 | return true; |
| 1670 | } |
| 1671 | |
| 1672 | /// CanUse - Test whether the given instruction can "use" the given pointer's |
| 1673 | /// object in a way that requires the reference count to be positive. |
| 1674 | static bool |
| 1675 | CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA, |
| 1676 | InstructionClass Class) { |
| 1677 | // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers. |
| 1678 | if (Class == IC_Call) |
| 1679 | return false; |
| 1680 | |
| 1681 | // Consider various instructions which may have pointer arguments which are |
| 1682 | // not "uses". |
| 1683 | if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) { |
| 1684 | // Comparing a pointer with null, or any other constant, isn't really a use, |
| 1685 | // because we don't care what the pointer points to, or about the values |
| 1686 | // of any other dynamic reference-counted pointers. |
| 1687 | if (!IsPotentialUse(ICI->getOperand(1))) |
| 1688 | return false; |
| 1689 | } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) { |
| 1690 | // For calls, just check the arguments (and not the callee operand). |
| 1691 | for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(), |
| 1692 | OE = CS.arg_end(); OI != OE; ++OI) { |
| 1693 | const Value *Op = *OI; |
| 1694 | if (IsPotentialUse(Op) && PA.related(Ptr, Op)) |
| 1695 | return true; |
| 1696 | } |
| 1697 | return false; |
| 1698 | } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| 1699 | // Special-case stores, because we don't care about the stored value, just |
| 1700 | // the store address. |
| 1701 | const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand()); |
| 1702 | // If we can't tell what the underlying object was, assume there is a |
| 1703 | // dependence. |
| 1704 | return IsPotentialUse(Op) && PA.related(Op, Ptr); |
| 1705 | } |
| 1706 | |
| 1707 | // Check each operand for a match. |
| 1708 | for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end(); |
| 1709 | OI != OE; ++OI) { |
| 1710 | const Value *Op = *OI; |
| 1711 | if (IsPotentialUse(Op) && PA.related(Ptr, Op)) |
| 1712 | return true; |
| 1713 | } |
| 1714 | return false; |
| 1715 | } |
| 1716 | |
| 1717 | /// CanInterruptRV - Test whether the given instruction can autorelease |
| 1718 | /// any pointer or cause an autoreleasepool pop. |
| 1719 | static bool |
| 1720 | CanInterruptRV(InstructionClass Class) { |
| 1721 | switch (Class) { |
| 1722 | case IC_AutoreleasepoolPop: |
| 1723 | case IC_CallOrUser: |
| 1724 | case IC_Call: |
| 1725 | case IC_Autorelease: |
| 1726 | case IC_AutoreleaseRV: |
| 1727 | case IC_FusedRetainAutorelease: |
| 1728 | case IC_FusedRetainAutoreleaseRV: |
| 1729 | return true; |
| 1730 | default: |
| 1731 | return false; |
| 1732 | } |
| 1733 | } |
| 1734 | |
| 1735 | namespace { |
| 1736 | /// DependenceKind - There are several kinds of dependence-like concepts in |
| 1737 | /// use here. |
| 1738 | enum DependenceKind { |
| 1739 | NeedsPositiveRetainCount, |
| 1740 | CanChangeRetainCount, |
| 1741 | RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease. |
| 1742 | RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue. |
| 1743 | RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue. |
| 1744 | }; |
| 1745 | } |
| 1746 | |
| 1747 | /// Depends - Test if there can be dependencies on Inst through Arg. This |
| 1748 | /// function only tests dependencies relevant for removing pairs of calls. |
| 1749 | static bool |
| 1750 | Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg, |
| 1751 | ProvenanceAnalysis &PA) { |
| 1752 | // If we've reached the definition of Arg, stop. |
| 1753 | if (Inst == Arg) |
| 1754 | return true; |
| 1755 | |
| 1756 | switch (Flavor) { |
| 1757 | case NeedsPositiveRetainCount: { |
| 1758 | InstructionClass Class = GetInstructionClass(Inst); |
| 1759 | switch (Class) { |
| 1760 | case IC_AutoreleasepoolPop: |
| 1761 | case IC_AutoreleasepoolPush: |
| 1762 | case IC_None: |
| 1763 | return false; |
| 1764 | default: |
| 1765 | return CanUse(Inst, Arg, PA, Class); |
| 1766 | } |
| 1767 | } |
| 1768 | |
| 1769 | case CanChangeRetainCount: { |
| 1770 | InstructionClass Class = GetInstructionClass(Inst); |
| 1771 | switch (Class) { |
| 1772 | case IC_AutoreleasepoolPop: |
| 1773 | // Conservatively assume this can decrement any count. |
| 1774 | return true; |
| 1775 | case IC_AutoreleasepoolPush: |
| 1776 | case IC_None: |
| 1777 | return false; |
| 1778 | default: |
| 1779 | return CanAlterRefCount(Inst, Arg, PA, Class); |
| 1780 | } |
| 1781 | } |
| 1782 | |
| 1783 | case RetainAutoreleaseDep: |
| 1784 | switch (GetBasicInstructionClass(Inst)) { |
| 1785 | case IC_AutoreleasepoolPop: |
| 1786 | // Don't merge an objc_autorelease with an objc_retain inside a different |
| 1787 | // autoreleasepool scope. |
| 1788 | return true; |
| 1789 | case IC_Retain: |
| 1790 | case IC_RetainRV: |
| 1791 | // Check for a retain of the same pointer for merging. |
| 1792 | return GetObjCArg(Inst) == Arg; |
| 1793 | default: |
| 1794 | // Nothing else matters for objc_retainAutorelease formation. |
| 1795 | return false; |
| 1796 | } |
| 1797 | break; |
| 1798 | |
| 1799 | case RetainAutoreleaseRVDep: { |
| 1800 | InstructionClass Class = GetBasicInstructionClass(Inst); |
| 1801 | switch (Class) { |
| 1802 | case IC_Retain: |
| 1803 | case IC_RetainRV: |
| 1804 | // Check for a retain of the same pointer for merging. |
| 1805 | return GetObjCArg(Inst) == Arg; |
| 1806 | default: |
| 1807 | // Anything that can autorelease interrupts |
| 1808 | // retainAutoreleaseReturnValue formation. |
| 1809 | return CanInterruptRV(Class); |
| 1810 | } |
| 1811 | break; |
| 1812 | } |
| 1813 | |
| 1814 | case RetainRVDep: |
| 1815 | return CanInterruptRV(GetBasicInstructionClass(Inst)); |
| 1816 | } |
| 1817 | |
| 1818 | llvm_unreachable("Invalid dependence flavor"); |
| 1819 | return true; |
| 1820 | } |
| 1821 | |
| 1822 | /// FindDependencies - Walk up the CFG from StartPos (which is in StartBB) and |
| 1823 | /// find local and non-local dependencies on Arg. |
| 1824 | /// TODO: Cache results? |
| 1825 | static void |
| 1826 | FindDependencies(DependenceKind Flavor, |
| 1827 | const Value *Arg, |
| 1828 | BasicBlock *StartBB, Instruction *StartInst, |
| 1829 | SmallPtrSet<Instruction *, 4> &DependingInstructions, |
| 1830 | SmallPtrSet<const BasicBlock *, 4> &Visited, |
| 1831 | ProvenanceAnalysis &PA) { |
| 1832 | BasicBlock::iterator StartPos = StartInst; |
| 1833 | |
| 1834 | SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist; |
| 1835 | Worklist.push_back(std::make_pair(StartBB, StartPos)); |
| 1836 | do { |
| 1837 | std::pair<BasicBlock *, BasicBlock::iterator> Pair = |
| 1838 | Worklist.pop_back_val(); |
| 1839 | BasicBlock *LocalStartBB = Pair.first; |
| 1840 | BasicBlock::iterator LocalStartPos = Pair.second; |
| 1841 | BasicBlock::iterator StartBBBegin = LocalStartBB->begin(); |
| 1842 | for (;;) { |
| 1843 | if (LocalStartPos == StartBBBegin) { |
| 1844 | pred_iterator PI(LocalStartBB), PE(LocalStartBB, false); |
| 1845 | if (PI == PE) |
| 1846 | // If we've reached the function entry, produce a null dependence. |
| 1847 | DependingInstructions.insert(0); |
| 1848 | else |
| 1849 | // Add the predecessors to the worklist. |
| 1850 | do { |
| 1851 | BasicBlock *PredBB = *PI; |
| 1852 | if (Visited.insert(PredBB)) |
| 1853 | Worklist.push_back(std::make_pair(PredBB, PredBB->end())); |
| 1854 | } while (++PI != PE); |
| 1855 | break; |
| 1856 | } |
| 1857 | |
| 1858 | Instruction *Inst = --LocalStartPos; |
| 1859 | if (Depends(Flavor, Inst, Arg, PA)) { |
| 1860 | DependingInstructions.insert(Inst); |
| 1861 | break; |
| 1862 | } |
| 1863 | } |
| 1864 | } while (!Worklist.empty()); |
| 1865 | |
| 1866 | // Determine whether the original StartBB post-dominates all of the blocks we |
| 1867 | // visited. If not, insert a sentinal indicating that most optimizations are |
| 1868 | // not safe. |
| 1869 | for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(), |
| 1870 | E = Visited.end(); I != E; ++I) { |
| 1871 | const BasicBlock *BB = *I; |
| 1872 | if (BB == StartBB) |
| 1873 | continue; |
| 1874 | const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| 1875 | for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) { |
| 1876 | const BasicBlock *Succ = *SI; |
| 1877 | if (Succ != StartBB && !Visited.count(Succ)) { |
| 1878 | DependingInstructions.insert(reinterpret_cast<Instruction *>(-1)); |
| 1879 | return; |
| 1880 | } |
| 1881 | } |
| 1882 | } |
| 1883 | } |
| 1884 | |
| 1885 | static bool isNullOrUndef(const Value *V) { |
| 1886 | return isa<ConstantPointerNull>(V) || isa<UndefValue>(V); |
| 1887 | } |
| 1888 | |
| 1889 | static bool isNoopInstruction(const Instruction *I) { |
| 1890 | return isa<BitCastInst>(I) || |
| 1891 | (isa<GetElementPtrInst>(I) && |
| 1892 | cast<GetElementPtrInst>(I)->hasAllZeroIndices()); |
| 1893 | } |
| 1894 | |
| 1895 | /// OptimizeRetainCall - Turn objc_retain into |
| 1896 | /// objc_retainAutoreleasedReturnValue if the operand is a return value. |
| 1897 | void |
| 1898 | ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) { |
| 1899 | CallSite CS(GetObjCArg(Retain)); |
| 1900 | Instruction *Call = CS.getInstruction(); |
| 1901 | if (!Call) return; |
| 1902 | if (Call->getParent() != Retain->getParent()) return; |
| 1903 | |
| 1904 | // Check that the call is next to the retain. |
| 1905 | BasicBlock::iterator I = Call; |
| 1906 | ++I; |
| 1907 | while (isNoopInstruction(I)) ++I; |
| 1908 | if (&*I != Retain) |
| 1909 | return; |
| 1910 | |
| 1911 | // Turn it to an objc_retainAutoreleasedReturnValue.. |
| 1912 | Changed = true; |
| 1913 | ++NumPeeps; |
| 1914 | cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent())); |
| 1915 | } |
| 1916 | |
| 1917 | /// OptimizeRetainRVCall - Turn objc_retainAutoreleasedReturnValue into |
| 1918 | /// objc_retain if the operand is not a return value. Or, if it can be |
| 1919 | /// paired with an objc_autoreleaseReturnValue, delete the pair and |
| 1920 | /// return true. |
| 1921 | bool |
| 1922 | ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) { |
| 1923 | // Check for the argument being from an immediately preceding call. |
| 1924 | Value *Arg = GetObjCArg(RetainRV); |
| 1925 | CallSite CS(Arg); |
| 1926 | if (Instruction *Call = CS.getInstruction()) |
| 1927 | if (Call->getParent() == RetainRV->getParent()) { |
| 1928 | BasicBlock::iterator I = Call; |
| 1929 | ++I; |
| 1930 | while (isNoopInstruction(I)) ++I; |
| 1931 | if (&*I == RetainRV) |
| 1932 | return false; |
| 1933 | } |
| 1934 | |
| 1935 | // Check for being preceded by an objc_autoreleaseReturnValue on the same |
| 1936 | // pointer. In this case, we can delete the pair. |
| 1937 | BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin(); |
| 1938 | if (I != Begin) { |
| 1939 | do --I; while (I != Begin && isNoopInstruction(I)); |
| 1940 | if (GetBasicInstructionClass(I) == IC_AutoreleaseRV && |
| 1941 | GetObjCArg(I) == Arg) { |
| 1942 | Changed = true; |
| 1943 | ++NumPeeps; |
| 1944 | EraseInstruction(I); |
| 1945 | EraseInstruction(RetainRV); |
| 1946 | return true; |
| 1947 | } |
| 1948 | } |
| 1949 | |
| 1950 | // Turn it to a plain objc_retain. |
| 1951 | Changed = true; |
| 1952 | ++NumPeeps; |
| 1953 | cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent())); |
| 1954 | return false; |
| 1955 | } |
| 1956 | |
| 1957 | /// OptimizeAutoreleaseRVCall - Turn objc_autoreleaseReturnValue into |
| 1958 | /// objc_autorelease if the result is not used as a return value. |
| 1959 | void |
| 1960 | ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV) { |
| 1961 | // Check for a return of the pointer value. |
| 1962 | const Value *Ptr = GetObjCArg(AutoreleaseRV); |
| 1963 | SmallVector<const Value *, 2> Users; |
| 1964 | Users.push_back(Ptr); |
| 1965 | do { |
| 1966 | Ptr = Users.pop_back_val(); |
| 1967 | for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end(); |
| 1968 | UI != UE; ++UI) { |
| 1969 | const User *I = *UI; |
| 1970 | if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV) |
| 1971 | return; |
| 1972 | if (isa<BitCastInst>(I)) |
| 1973 | Users.push_back(I); |
| 1974 | } |
| 1975 | } while (!Users.empty()); |
| 1976 | |
| 1977 | Changed = true; |
| 1978 | ++NumPeeps; |
| 1979 | cast<CallInst>(AutoreleaseRV)-> |
| 1980 | setCalledFunction(getAutoreleaseCallee(F.getParent())); |
| 1981 | } |
| 1982 | |
| 1983 | /// OptimizeIndividualCalls - Visit each call, one at a time, and make |
| 1984 | /// simplifications without doing any additional analysis. |
| 1985 | void ObjCARCOpt::OptimizeIndividualCalls(Function &F) { |
| 1986 | // Reset all the flags in preparation for recomputing them. |
| 1987 | UsedInThisFunction = 0; |
| 1988 | |
| 1989 | // Visit all objc_* calls in F. |
| 1990 | for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| 1991 | Instruction *Inst = &*I++; |
| 1992 | InstructionClass Class = GetBasicInstructionClass(Inst); |
| 1993 | |
| 1994 | switch (Class) { |
| 1995 | default: break; |
| 1996 | |
| 1997 | // Delete no-op casts. These function calls have special semantics, but |
| 1998 | // the semantics are entirely implemented via lowering in the front-end, |
| 1999 | // so by the time they reach the optimizer, they are just no-op calls |
| 2000 | // which return their argument. |
| 2001 | // |
| 2002 | // There are gray areas here, as the ability to cast reference-counted |
| 2003 | // pointers to raw void* and back allows code to break ARC assumptions, |
| 2004 | // however these are currently considered to be unimportant. |
| 2005 | case IC_NoopCast: |
| 2006 | Changed = true; |
| 2007 | ++NumNoops; |
| 2008 | EraseInstruction(Inst); |
| 2009 | continue; |
| 2010 | |
| 2011 | // If the pointer-to-weak-pointer is null, it's undefined behavior. |
| 2012 | case IC_StoreWeak: |
| 2013 | case IC_LoadWeak: |
| 2014 | case IC_LoadWeakRetained: |
| 2015 | case IC_InitWeak: |
| 2016 | case IC_DestroyWeak: { |
| 2017 | CallInst *CI = cast<CallInst>(Inst); |
| 2018 | if (isNullOrUndef(CI->getArgOperand(0))) { |
| 2019 | Type *Ty = CI->getArgOperand(0)->getType(); |
| 2020 | new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), |
| 2021 | Constant::getNullValue(Ty), |
| 2022 | CI); |
| 2023 | CI->replaceAllUsesWith(UndefValue::get(CI->getType())); |
| 2024 | CI->eraseFromParent(); |
| 2025 | continue; |
| 2026 | } |
| 2027 | break; |
| 2028 | } |
| 2029 | case IC_CopyWeak: |
| 2030 | case IC_MoveWeak: { |
| 2031 | CallInst *CI = cast<CallInst>(Inst); |
| 2032 | if (isNullOrUndef(CI->getArgOperand(0)) || |
| 2033 | isNullOrUndef(CI->getArgOperand(1))) { |
| 2034 | Type *Ty = CI->getArgOperand(0)->getType(); |
| 2035 | new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()), |
| 2036 | Constant::getNullValue(Ty), |
| 2037 | CI); |
| 2038 | CI->replaceAllUsesWith(UndefValue::get(CI->getType())); |
| 2039 | CI->eraseFromParent(); |
| 2040 | continue; |
| 2041 | } |
| 2042 | break; |
| 2043 | } |
| 2044 | case IC_Retain: |
| 2045 | OptimizeRetainCall(F, Inst); |
| 2046 | break; |
| 2047 | case IC_RetainRV: |
| 2048 | if (OptimizeRetainRVCall(F, Inst)) |
| 2049 | continue; |
| 2050 | break; |
| 2051 | case IC_AutoreleaseRV: |
| 2052 | OptimizeAutoreleaseRVCall(F, Inst); |
| 2053 | break; |
| 2054 | } |
| 2055 | |
| 2056 | // objc_autorelease(x) -> objc_release(x) if x is otherwise unused. |
| 2057 | if (IsAutorelease(Class) && Inst->use_empty()) { |
| 2058 | CallInst *Call = cast<CallInst>(Inst); |
| 2059 | const Value *Arg = Call->getArgOperand(0); |
| 2060 | Arg = FindSingleUseIdentifiedObject(Arg); |
| 2061 | if (Arg) { |
| 2062 | Changed = true; |
| 2063 | ++NumAutoreleases; |
| 2064 | |
| 2065 | // Create the declaration lazily. |
| 2066 | LLVMContext &C = Inst->getContext(); |
| 2067 | CallInst *NewCall = |
| 2068 | CallInst::Create(getReleaseCallee(F.getParent()), |
| 2069 | Call->getArgOperand(0), "", Call); |
| 2070 | NewCall->setMetadata(ImpreciseReleaseMDKind, |
| 2071 | MDNode::get(C, ArrayRef<Value *>())); |
| 2072 | EraseInstruction(Call); |
| 2073 | Inst = NewCall; |
| 2074 | Class = IC_Release; |
| 2075 | } |
| 2076 | } |
| 2077 | |
| 2078 | // For functions which can never be passed stack arguments, add |
| 2079 | // a tail keyword. |
| 2080 | if (IsAlwaysTail(Class)) { |
| 2081 | Changed = true; |
| 2082 | cast<CallInst>(Inst)->setTailCall(); |
| 2083 | } |
| 2084 | |
| 2085 | // Set nounwind as needed. |
| 2086 | if (IsNoThrow(Class)) { |
| 2087 | Changed = true; |
| 2088 | cast<CallInst>(Inst)->setDoesNotThrow(); |
| 2089 | } |
| 2090 | |
| 2091 | if (!IsNoopOnNull(Class)) { |
| 2092 | UsedInThisFunction |= 1 << Class; |
| 2093 | continue; |
| 2094 | } |
| 2095 | |
| 2096 | const Value *Arg = GetObjCArg(Inst); |
| 2097 | |
| 2098 | // ARC calls with null are no-ops. Delete them. |
| 2099 | if (isNullOrUndef(Arg)) { |
| 2100 | Changed = true; |
| 2101 | ++NumNoops; |
| 2102 | EraseInstruction(Inst); |
| 2103 | continue; |
| 2104 | } |
| 2105 | |
| 2106 | // Keep track of which of retain, release, autorelease, and retain_block |
| 2107 | // are actually present in this function. |
| 2108 | UsedInThisFunction |= 1 << Class; |
| 2109 | |
| 2110 | // If Arg is a PHI, and one or more incoming values to the |
| 2111 | // PHI are null, and the call is control-equivalent to the PHI, and there |
| 2112 | // are no relevant side effects between the PHI and the call, the call |
| 2113 | // could be pushed up to just those paths with non-null incoming values. |
| 2114 | // For now, don't bother splitting critical edges for this. |
| 2115 | SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist; |
| 2116 | Worklist.push_back(std::make_pair(Inst, Arg)); |
| 2117 | do { |
| 2118 | std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val(); |
| 2119 | Inst = Pair.first; |
| 2120 | Arg = Pair.second; |
| 2121 | |
| 2122 | const PHINode *PN = dyn_cast<PHINode>(Arg); |
| 2123 | if (!PN) continue; |
| 2124 | |
| 2125 | // Determine if the PHI has any null operands, or any incoming |
| 2126 | // critical edges. |
| 2127 | bool HasNull = false; |
| 2128 | bool HasCriticalEdges = false; |
| 2129 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| 2130 | Value *Incoming = |
| 2131 | StripPointerCastsAndObjCCalls(PN->getIncomingValue(i)); |
| 2132 | if (isNullOrUndef(Incoming)) |
| 2133 | HasNull = true; |
| 2134 | else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back()) |
| 2135 | .getNumSuccessors() != 1) { |
| 2136 | HasCriticalEdges = true; |
| 2137 | break; |
| 2138 | } |
| 2139 | } |
| 2140 | // If we have null operands and no critical edges, optimize. |
| 2141 | if (!HasCriticalEdges && HasNull) { |
| 2142 | SmallPtrSet<Instruction *, 4> DependingInstructions; |
| 2143 | SmallPtrSet<const BasicBlock *, 4> Visited; |
| 2144 | |
| 2145 | // Check that there is nothing that cares about the reference |
| 2146 | // count between the call and the phi. |
| 2147 | FindDependencies(NeedsPositiveRetainCount, Arg, |
| 2148 | Inst->getParent(), Inst, |
| 2149 | DependingInstructions, Visited, PA); |
| 2150 | if (DependingInstructions.size() == 1 && |
| 2151 | *DependingInstructions.begin() == PN) { |
| 2152 | Changed = true; |
| 2153 | ++NumPartialNoops; |
| 2154 | // Clone the call into each predecessor that has a non-null value. |
| 2155 | CallInst *CInst = cast<CallInst>(Inst); |
| 2156 | Type *ParamTy = CInst->getArgOperand(0)->getType(); |
| 2157 | for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| 2158 | Value *Incoming = |
| 2159 | StripPointerCastsAndObjCCalls(PN->getIncomingValue(i)); |
| 2160 | if (!isNullOrUndef(Incoming)) { |
| 2161 | CallInst *Clone = cast<CallInst>(CInst->clone()); |
| 2162 | Value *Op = PN->getIncomingValue(i); |
| 2163 | Instruction *InsertPos = &PN->getIncomingBlock(i)->back(); |
| 2164 | if (Op->getType() != ParamTy) |
| 2165 | Op = new BitCastInst(Op, ParamTy, "", InsertPos); |
| 2166 | Clone->setArgOperand(0, Op); |
| 2167 | Clone->insertBefore(InsertPos); |
| 2168 | Worklist.push_back(std::make_pair(Clone, Incoming)); |
| 2169 | } |
| 2170 | } |
| 2171 | // Erase the original call. |
| 2172 | EraseInstruction(CInst); |
| 2173 | continue; |
| 2174 | } |
| 2175 | } |
| 2176 | } while (!Worklist.empty()); |
| 2177 | } |
| 2178 | } |
| 2179 | |
| 2180 | /// CheckForCFGHazards - Check for critical edges, loop boundaries, irreducible |
| 2181 | /// control flow, or other CFG structures where moving code across the edge |
| 2182 | /// would result in it being executed more. |
| 2183 | void |
| 2184 | ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB, |
| 2185 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 2186 | BBState &MyStates) const { |
| 2187 | // If any top-down local-use or possible-dec has a succ which is earlier in |
| 2188 | // the sequence, forget it. |
| 2189 | for (BBState::ptr_const_iterator I = MyStates.top_down_ptr_begin(), |
| 2190 | E = MyStates.top_down_ptr_end(); I != E; ++I) |
| 2191 | switch (I->second.GetSeq()) { |
| 2192 | default: break; |
| 2193 | case S_Use: { |
| 2194 | const Value *Arg = I->first; |
| 2195 | const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| 2196 | bool SomeSuccHasSame = false; |
| 2197 | bool AllSuccsHaveSame = true; |
| 2198 | PtrState &S = MyStates.getPtrTopDownState(Arg); |
| 2199 | for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) { |
| 2200 | PtrState &SuccS = BBStates[*SI].getPtrBottomUpState(Arg); |
| 2201 | switch (SuccS.GetSeq()) { |
| 2202 | case S_None: |
| 2203 | case S_CanRelease: { |
| 2204 | if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe) |
| 2205 | S.ClearSequenceProgress(); |
| 2206 | continue; |
| 2207 | } |
| 2208 | case S_Use: |
| 2209 | SomeSuccHasSame = true; |
| 2210 | break; |
| 2211 | case S_Stop: |
| 2212 | case S_Release: |
| 2213 | case S_MovableRelease: |
| 2214 | if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe) |
| 2215 | AllSuccsHaveSame = false; |
| 2216 | break; |
| 2217 | case S_Retain: |
| 2218 | llvm_unreachable("bottom-up pointer in retain state!"); |
| 2219 | } |
| 2220 | } |
| 2221 | // If the state at the other end of any of the successor edges |
| 2222 | // matches the current state, require all edges to match. This |
| 2223 | // guards against loops in the middle of a sequence. |
| 2224 | if (SomeSuccHasSame && !AllSuccsHaveSame) |
| 2225 | S.ClearSequenceProgress(); |
| 2226 | } |
| 2227 | case S_CanRelease: { |
| 2228 | const Value *Arg = I->first; |
| 2229 | const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| 2230 | bool SomeSuccHasSame = false; |
| 2231 | bool AllSuccsHaveSame = true; |
| 2232 | PtrState &S = MyStates.getPtrTopDownState(Arg); |
| 2233 | for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) { |
| 2234 | PtrState &SuccS = BBStates[*SI].getPtrBottomUpState(Arg); |
| 2235 | switch (SuccS.GetSeq()) { |
| 2236 | case S_None: { |
| 2237 | if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe) |
| 2238 | S.ClearSequenceProgress(); |
| 2239 | continue; |
| 2240 | } |
| 2241 | case S_CanRelease: |
| 2242 | SomeSuccHasSame = true; |
| 2243 | break; |
| 2244 | case S_Stop: |
| 2245 | case S_Release: |
| 2246 | case S_MovableRelease: |
| 2247 | case S_Use: |
| 2248 | if (!S.RRI.KnownSafe && !SuccS.RRI.KnownSafe) |
| 2249 | AllSuccsHaveSame = false; |
| 2250 | break; |
| 2251 | case S_Retain: |
| 2252 | llvm_unreachable("bottom-up pointer in retain state!"); |
| 2253 | } |
| 2254 | } |
| 2255 | // If the state at the other end of any of the successor edges |
| 2256 | // matches the current state, require all edges to match. This |
| 2257 | // guards against loops in the middle of a sequence. |
| 2258 | if (SomeSuccHasSame && !AllSuccsHaveSame) |
| 2259 | S.ClearSequenceProgress(); |
| 2260 | } |
| 2261 | } |
| 2262 | } |
| 2263 | |
| 2264 | bool |
| 2265 | ObjCARCOpt::VisitBottomUp(BasicBlock *BB, |
| 2266 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 2267 | MapVector<Value *, RRInfo> &Retains) { |
| 2268 | bool NestingDetected = false; |
| 2269 | BBState &MyStates = BBStates[BB]; |
| 2270 | |
| 2271 | // Merge the states from each successor to compute the initial state |
| 2272 | // for the current block. |
| 2273 | const TerminatorInst *TI = cast<TerminatorInst>(&BB->back()); |
| 2274 | succ_const_iterator SI(TI), SE(TI, false); |
| 2275 | if (SI == SE) |
| 2276 | MyStates.SetAsExit(); |
| 2277 | else |
| 2278 | do { |
| 2279 | const BasicBlock *Succ = *SI++; |
| 2280 | if (Succ == BB) |
| 2281 | continue; |
| 2282 | DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ); |
| 2283 | // If we haven't seen this node yet, then we've found a CFG cycle. |
| 2284 | // Be optimistic here; it's CheckForCFGHazards' job detect trouble. |
| 2285 | if (I == BBStates.end()) |
| 2286 | continue; |
| 2287 | MyStates.InitFromSucc(I->second); |
| 2288 | while (SI != SE) { |
| 2289 | Succ = *SI++; |
| 2290 | if (Succ != BB) { |
| 2291 | I = BBStates.find(Succ); |
| 2292 | if (I != BBStates.end()) |
| 2293 | MyStates.MergeSucc(I->second); |
| 2294 | } |
| 2295 | } |
| 2296 | break; |
| 2297 | } while (SI != SE); |
| 2298 | |
| 2299 | // Visit all the instructions, bottom-up. |
| 2300 | for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) { |
| 2301 | Instruction *Inst = llvm::prior(I); |
| 2302 | InstructionClass Class = GetInstructionClass(Inst); |
| 2303 | const Value *Arg = 0; |
| 2304 | |
| 2305 | switch (Class) { |
| 2306 | case IC_Release: { |
| 2307 | Arg = GetObjCArg(Inst); |
| 2308 | |
| 2309 | PtrState &S = MyStates.getPtrBottomUpState(Arg); |
| 2310 | |
| 2311 | // If we see two releases in a row on the same pointer. If so, make |
| 2312 | // a note, and we'll cicle back to revisit it after we've |
| 2313 | // hopefully eliminated the second release, which may allow us to |
| 2314 | // eliminate the first release too. |
| 2315 | // Theoretically we could implement removal of nested retain+release |
| 2316 | // pairs by making PtrState hold a stack of states, but this is |
| 2317 | // simple and avoids adding overhead for the non-nested case. |
| 2318 | if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease) |
| 2319 | NestingDetected = true; |
| 2320 | |
| 2321 | S.SetSeqToRelease(Inst->getMetadata(ImpreciseReleaseMDKind)); |
| 2322 | S.RRI.clear(); |
| 2323 | S.RRI.KnownSafe = S.IsKnownNested() || S.IsKnownIncremented(); |
| 2324 | S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall(); |
| 2325 | S.RRI.Calls.insert(Inst); |
| 2326 | |
| 2327 | S.IncrementRefCount(); |
| 2328 | S.IncrementNestCount(); |
| 2329 | break; |
| 2330 | } |
| 2331 | case IC_RetainBlock: |
| 2332 | case IC_Retain: |
| 2333 | case IC_RetainRV: { |
| 2334 | Arg = GetObjCArg(Inst); |
| 2335 | |
| 2336 | PtrState &S = MyStates.getPtrBottomUpState(Arg); |
| 2337 | S.DecrementRefCount(); |
| 2338 | S.SetAtLeastOneRefCount(); |
| 2339 | S.DecrementNestCount(); |
| 2340 | |
| 2341 | // An objc_retainBlock call with just a use still needs to be kept, |
| 2342 | // because it may be copying a block from the stack to the heap. |
| 2343 | if (Class == IC_RetainBlock && S.GetSeq() == S_Use) |
| 2344 | S.SetSeq(S_CanRelease); |
| 2345 | |
| 2346 | switch (S.GetSeq()) { |
| 2347 | case S_Stop: |
| 2348 | case S_Release: |
| 2349 | case S_MovableRelease: |
| 2350 | case S_Use: |
| 2351 | S.RRI.ReverseInsertPts.clear(); |
| 2352 | // FALL THROUGH |
| 2353 | case S_CanRelease: |
| 2354 | // Don't do retain+release tracking for IC_RetainRV, because it's |
| 2355 | // better to let it remain as the first instruction after a call. |
| 2356 | if (Class != IC_RetainRV) { |
| 2357 | S.RRI.IsRetainBlock = Class == IC_RetainBlock; |
| 2358 | Retains[Inst] = S.RRI; |
| 2359 | } |
| 2360 | S.ClearSequenceProgress(); |
| 2361 | break; |
| 2362 | case S_None: |
| 2363 | break; |
| 2364 | case S_Retain: |
| 2365 | llvm_unreachable("bottom-up pointer in retain state!"); |
| 2366 | } |
| 2367 | continue; |
| 2368 | } |
| 2369 | case IC_AutoreleasepoolPop: |
| 2370 | // Conservatively, clear MyStates for all known pointers. |
| 2371 | MyStates.clearBottomUpPointers(); |
| 2372 | continue; |
| 2373 | case IC_AutoreleasepoolPush: |
| 2374 | case IC_None: |
| 2375 | // These are irrelevant. |
| 2376 | continue; |
| 2377 | default: |
| 2378 | break; |
| 2379 | } |
| 2380 | |
| 2381 | // Consider any other possible effects of this instruction on each |
| 2382 | // pointer being tracked. |
| 2383 | for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(), |
| 2384 | ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) { |
| 2385 | const Value *Ptr = MI->first; |
| 2386 | if (Ptr == Arg) |
| 2387 | continue; // Handled above. |
| 2388 | PtrState &S = MI->second; |
| 2389 | Sequence Seq = S.GetSeq(); |
| 2390 | |
| 2391 | // Check for possible releases. |
| 2392 | if (CanAlterRefCount(Inst, Ptr, PA, Class)) { |
| 2393 | S.DecrementRefCount(); |
| 2394 | switch (Seq) { |
| 2395 | case S_Use: |
| 2396 | S.SetSeq(S_CanRelease); |
| 2397 | continue; |
| 2398 | case S_CanRelease: |
| 2399 | case S_Release: |
| 2400 | case S_MovableRelease: |
| 2401 | case S_Stop: |
| 2402 | case S_None: |
| 2403 | break; |
| 2404 | case S_Retain: |
| 2405 | llvm_unreachable("bottom-up pointer in retain state!"); |
| 2406 | } |
| 2407 | } |
| 2408 | |
| 2409 | // Check for possible direct uses. |
| 2410 | switch (Seq) { |
| 2411 | case S_Release: |
| 2412 | case S_MovableRelease: |
| 2413 | if (CanUse(Inst, Ptr, PA, Class)) { |
| 2414 | assert(S.RRI.ReverseInsertPts.empty()); |
| 2415 | S.RRI.ReverseInsertPts.insert(Inst); |
| 2416 | S.SetSeq(S_Use); |
| 2417 | } else if (Seq == S_Release && |
| 2418 | (Class == IC_User || Class == IC_CallOrUser)) { |
| 2419 | // Non-movable releases depend on any possible objc pointer use. |
| 2420 | S.SetSeq(S_Stop); |
| 2421 | assert(S.RRI.ReverseInsertPts.empty()); |
| 2422 | S.RRI.ReverseInsertPts.insert(Inst); |
| 2423 | } |
| 2424 | break; |
| 2425 | case S_Stop: |
| 2426 | if (CanUse(Inst, Ptr, PA, Class)) |
| 2427 | S.SetSeq(S_Use); |
| 2428 | break; |
| 2429 | case S_CanRelease: |
| 2430 | case S_Use: |
| 2431 | case S_None: |
| 2432 | break; |
| 2433 | case S_Retain: |
| 2434 | llvm_unreachable("bottom-up pointer in retain state!"); |
| 2435 | } |
| 2436 | } |
| 2437 | } |
| 2438 | |
| 2439 | return NestingDetected; |
| 2440 | } |
| 2441 | |
| 2442 | bool |
| 2443 | ObjCARCOpt::VisitTopDown(BasicBlock *BB, |
| 2444 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 2445 | DenseMap<Value *, RRInfo> &Releases) { |
| 2446 | bool NestingDetected = false; |
| 2447 | BBState &MyStates = BBStates[BB]; |
| 2448 | |
| 2449 | // Merge the states from each predecessor to compute the initial state |
| 2450 | // for the current block. |
| 2451 | const_pred_iterator PI(BB), PE(BB, false); |
| 2452 | if (PI == PE) |
| 2453 | MyStates.SetAsEntry(); |
| 2454 | else |
| 2455 | do { |
| 2456 | const BasicBlock *Pred = *PI++; |
| 2457 | if (Pred == BB) |
| 2458 | continue; |
| 2459 | DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred); |
| 2460 | assert(I != BBStates.end()); |
| 2461 | // If we haven't seen this node yet, then we've found a CFG cycle. |
| 2462 | // Be optimistic here; it's CheckForCFGHazards' job detect trouble. |
| 2463 | if (!I->second.isVisitedTopDown()) |
| 2464 | continue; |
| 2465 | MyStates.InitFromPred(I->second); |
| 2466 | while (PI != PE) { |
| 2467 | Pred = *PI++; |
| 2468 | if (Pred != BB) { |
| 2469 | I = BBStates.find(Pred); |
| 2470 | assert(I != BBStates.end()); |
| 2471 | if (I->second.isVisitedTopDown()) |
| 2472 | MyStates.MergePred(I->second); |
| 2473 | } |
| 2474 | } |
| 2475 | break; |
| 2476 | } while (PI != PE); |
| 2477 | |
| 2478 | // Visit all the instructions, top-down. |
| 2479 | for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { |
| 2480 | Instruction *Inst = I; |
| 2481 | InstructionClass Class = GetInstructionClass(Inst); |
| 2482 | const Value *Arg = 0; |
| 2483 | |
| 2484 | switch (Class) { |
| 2485 | case IC_RetainBlock: |
| 2486 | case IC_Retain: |
| 2487 | case IC_RetainRV: { |
| 2488 | Arg = GetObjCArg(Inst); |
| 2489 | |
| 2490 | PtrState &S = MyStates.getPtrTopDownState(Arg); |
| 2491 | |
| 2492 | // Don't do retain+release tracking for IC_RetainRV, because it's |
| 2493 | // better to let it remain as the first instruction after a call. |
| 2494 | if (Class != IC_RetainRV) { |
| 2495 | // If we see two retains in a row on the same pointer. If so, make |
| 2496 | // a note, and we'll cicle back to revisit it after we've |
| 2497 | // hopefully eliminated the second retain, which may allow us to |
| 2498 | // eliminate the first retain too. |
| 2499 | // Theoretically we could implement removal of nested retain+release |
| 2500 | // pairs by making PtrState hold a stack of states, but this is |
| 2501 | // simple and avoids adding overhead for the non-nested case. |
| 2502 | if (S.GetSeq() == S_Retain) |
| 2503 | NestingDetected = true; |
| 2504 | |
| 2505 | S.SetSeq(S_Retain); |
| 2506 | S.RRI.clear(); |
| 2507 | S.RRI.IsRetainBlock = Class == IC_RetainBlock; |
| 2508 | // Don't check S.IsKnownIncremented() here because it's not |
| 2509 | // sufficient. |
| 2510 | S.RRI.KnownSafe = S.IsKnownNested(); |
| 2511 | S.RRI.Calls.insert(Inst); |
| 2512 | } |
| 2513 | |
| 2514 | S.SetAtLeastOneRefCount(); |
| 2515 | S.IncrementRefCount(); |
| 2516 | S.IncrementNestCount(); |
| 2517 | continue; |
| 2518 | } |
| 2519 | case IC_Release: { |
| 2520 | Arg = GetObjCArg(Inst); |
| 2521 | |
| 2522 | PtrState &S = MyStates.getPtrTopDownState(Arg); |
| 2523 | S.DecrementRefCount(); |
| 2524 | S.DecrementNestCount(); |
| 2525 | |
| 2526 | switch (S.GetSeq()) { |
| 2527 | case S_Retain: |
| 2528 | case S_CanRelease: |
| 2529 | S.RRI.ReverseInsertPts.clear(); |
| 2530 | // FALL THROUGH |
| 2531 | case S_Use: |
| 2532 | S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind); |
| 2533 | S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall(); |
| 2534 | Releases[Inst] = S.RRI; |
| 2535 | S.ClearSequenceProgress(); |
| 2536 | break; |
| 2537 | case S_None: |
| 2538 | break; |
| 2539 | case S_Stop: |
| 2540 | case S_Release: |
| 2541 | case S_MovableRelease: |
| 2542 | llvm_unreachable("top-down pointer in release state!"); |
| 2543 | } |
| 2544 | break; |
| 2545 | } |
| 2546 | case IC_AutoreleasepoolPop: |
| 2547 | // Conservatively, clear MyStates for all known pointers. |
| 2548 | MyStates.clearTopDownPointers(); |
| 2549 | continue; |
| 2550 | case IC_AutoreleasepoolPush: |
| 2551 | case IC_None: |
| 2552 | // These are irrelevant. |
| 2553 | continue; |
| 2554 | default: |
| 2555 | break; |
| 2556 | } |
| 2557 | |
| 2558 | // Consider any other possible effects of this instruction on each |
| 2559 | // pointer being tracked. |
| 2560 | for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(), |
| 2561 | ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) { |
| 2562 | const Value *Ptr = MI->first; |
| 2563 | if (Ptr == Arg) |
| 2564 | continue; // Handled above. |
| 2565 | PtrState &S = MI->second; |
| 2566 | Sequence Seq = S.GetSeq(); |
| 2567 | |
| 2568 | // Check for possible releases. |
| 2569 | if (CanAlterRefCount(Inst, Ptr, PA, Class)) { |
| 2570 | S.DecrementRefCount(); |
| 2571 | switch (Seq) { |
| 2572 | case S_Retain: |
| 2573 | S.SetSeq(S_CanRelease); |
| 2574 | assert(S.RRI.ReverseInsertPts.empty()); |
| 2575 | S.RRI.ReverseInsertPts.insert(Inst); |
| 2576 | |
| 2577 | // One call can't cause a transition from S_Retain to S_CanRelease |
| 2578 | // and S_CanRelease to S_Use. If we've made the first transition, |
| 2579 | // we're done. |
| 2580 | continue; |
| 2581 | case S_Use: |
| 2582 | case S_CanRelease: |
| 2583 | case S_None: |
| 2584 | break; |
| 2585 | case S_Stop: |
| 2586 | case S_Release: |
| 2587 | case S_MovableRelease: |
| 2588 | llvm_unreachable("top-down pointer in release state!"); |
| 2589 | } |
| 2590 | } |
| 2591 | |
| 2592 | // Check for possible direct uses. |
| 2593 | switch (Seq) { |
| 2594 | case S_CanRelease: |
| 2595 | if (CanUse(Inst, Ptr, PA, Class)) |
| 2596 | S.SetSeq(S_Use); |
| 2597 | break; |
| 2598 | case S_Retain: |
| 2599 | // An objc_retainBlock call may be responsible for copying the block |
| 2600 | // data from the stack to the heap. Model this by moving it straight |
| 2601 | // from S_Retain to S_Use. |
| 2602 | if (S.RRI.IsRetainBlock && |
| 2603 | CanUse(Inst, Ptr, PA, Class)) { |
| 2604 | assert(S.RRI.ReverseInsertPts.empty()); |
| 2605 | S.RRI.ReverseInsertPts.insert(Inst); |
| 2606 | S.SetSeq(S_Use); |
| 2607 | } |
| 2608 | break; |
| 2609 | case S_Use: |
| 2610 | case S_None: |
| 2611 | break; |
| 2612 | case S_Stop: |
| 2613 | case S_Release: |
| 2614 | case S_MovableRelease: |
| 2615 | llvm_unreachable("top-down pointer in release state!"); |
| 2616 | } |
| 2617 | } |
| 2618 | } |
| 2619 | |
| 2620 | CheckForCFGHazards(BB, BBStates, MyStates); |
| 2621 | return NestingDetected; |
| 2622 | } |
| 2623 | |
| 2624 | // Visit - Visit the function both top-down and bottom-up. |
| 2625 | bool |
| 2626 | ObjCARCOpt::Visit(Function &F, |
| 2627 | DenseMap<const BasicBlock *, BBState> &BBStates, |
| 2628 | MapVector<Value *, RRInfo> &Retains, |
| 2629 | DenseMap<Value *, RRInfo> &Releases) { |
| 2630 | // Use reverse-postorder on the reverse CFG for bottom-up, because we |
| 2631 | // magically know that loops will be well behaved, i.e. they won't repeatedly |
| 2632 | // call retain on a single pointer without doing a release. We can't use |
| 2633 | // ReversePostOrderTraversal here because we want to walk up from each |
| 2634 | // function exit point. |
| 2635 | SmallPtrSet<BasicBlock *, 16> Visited; |
| 2636 | SmallVector<std::pair<BasicBlock *, pred_iterator>, 16> Stack; |
| 2637 | SmallVector<BasicBlock *, 16> Order; |
| 2638 | for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) { |
| 2639 | BasicBlock *BB = I; |
| 2640 | if (BB->getTerminator()->getNumSuccessors() == 0) |
| 2641 | Stack.push_back(std::make_pair(BB, pred_begin(BB))); |
| 2642 | } |
| 2643 | while (!Stack.empty()) { |
| 2644 | pred_iterator End = pred_end(Stack.back().first); |
| 2645 | while (Stack.back().second != End) { |
| 2646 | BasicBlock *BB = *Stack.back().second++; |
| 2647 | if (Visited.insert(BB)) |
| 2648 | Stack.push_back(std::make_pair(BB, pred_begin(BB))); |
| 2649 | } |
| 2650 | Order.push_back(Stack.pop_back_val().first); |
| 2651 | } |
| 2652 | bool BottomUpNestingDetected = false; |
| 2653 | for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I = |
| 2654 | Order.rbegin(), E = Order.rend(); I != E; ++I) { |
| 2655 | BasicBlock *BB = *I; |
| 2656 | BottomUpNestingDetected |= VisitBottomUp(BB, BBStates, Retains); |
| 2657 | } |
| 2658 | |
| 2659 | // Use regular reverse-postorder for top-down. |
| 2660 | bool TopDownNestingDetected = false; |
| 2661 | typedef ReversePostOrderTraversal<Function *> RPOTType; |
| 2662 | RPOTType RPOT(&F); |
| 2663 | for (RPOTType::rpo_iterator I = RPOT.begin(), E = RPOT.end(); I != E; ++I) { |
| 2664 | BasicBlock *BB = *I; |
| 2665 | TopDownNestingDetected |= VisitTopDown(BB, BBStates, Releases); |
| 2666 | } |
| 2667 | |
| 2668 | return TopDownNestingDetected && BottomUpNestingDetected; |
| 2669 | } |
| 2670 | |
| 2671 | /// MoveCalls - Move the calls in RetainsToMove and ReleasesToMove. |
| 2672 | void ObjCARCOpt::MoveCalls(Value *Arg, |
| 2673 | RRInfo &RetainsToMove, |
| 2674 | RRInfo &ReleasesToMove, |
| 2675 | MapVector<Value *, RRInfo> &Retains, |
| 2676 | DenseMap<Value *, RRInfo> &Releases, |
| 2677 | SmallVectorImpl<Instruction *> &DeadInsts, |
| 2678 | Module *M) { |
| 2679 | Type *ArgTy = Arg->getType(); |
| 2680 | Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext())); |
| 2681 | |
| 2682 | // Insert the new retain and release calls. |
| 2683 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2684 | PI = ReleasesToMove.ReverseInsertPts.begin(), |
| 2685 | PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) { |
| 2686 | Instruction *InsertPt = *PI; |
| 2687 | Value *MyArg = ArgTy == ParamTy ? Arg : |
| 2688 | new BitCastInst(Arg, ParamTy, "", InsertPt); |
| 2689 | CallInst *Call = |
| 2690 | CallInst::Create(RetainsToMove.IsRetainBlock ? |
| 2691 | getRetainBlockCallee(M) : getRetainCallee(M), |
| 2692 | MyArg, "", InsertPt); |
| 2693 | Call->setDoesNotThrow(); |
| 2694 | if (!RetainsToMove.IsRetainBlock) |
| 2695 | Call->setTailCall(); |
| 2696 | } |
| 2697 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2698 | PI = RetainsToMove.ReverseInsertPts.begin(), |
| 2699 | PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) { |
| 2700 | Instruction *LastUse = *PI; |
| 2701 | Instruction *InsertPts[] = { 0, 0, 0 }; |
| 2702 | if (InvokeInst *II = dyn_cast<InvokeInst>(LastUse)) { |
| 2703 | // We can't insert code immediately after an invoke instruction, so |
| 2704 | // insert code at the beginning of both successor blocks instead. |
| 2705 | // The invoke's return value isn't available in the unwind block, |
| 2706 | // but our releases will never depend on it, because they must be |
| 2707 | // paired with retains from before the invoke. |
| 2708 | InsertPts[0] = II->getNormalDest()->getFirstInsertionPt(); |
| 2709 | InsertPts[1] = II->getUnwindDest()->getFirstInsertionPt(); |
| 2710 | } else { |
| 2711 | // Insert code immediately after the last use. |
| 2712 | InsertPts[0] = llvm::next(BasicBlock::iterator(LastUse)); |
| 2713 | } |
| 2714 | |
| 2715 | for (Instruction **I = InsertPts; *I; ++I) { |
| 2716 | Instruction *InsertPt = *I; |
| 2717 | Value *MyArg = ArgTy == ParamTy ? Arg : |
| 2718 | new BitCastInst(Arg, ParamTy, "", InsertPt); |
| 2719 | CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg, |
| 2720 | "", InsertPt); |
| 2721 | // Attach a clang.imprecise_release metadata tag, if appropriate. |
| 2722 | if (MDNode *M = ReleasesToMove.ReleaseMetadata) |
| 2723 | Call->setMetadata(ImpreciseReleaseMDKind, M); |
| 2724 | Call->setDoesNotThrow(); |
| 2725 | if (ReleasesToMove.IsTailCallRelease) |
| 2726 | Call->setTailCall(); |
| 2727 | } |
| 2728 | } |
| 2729 | |
| 2730 | // Delete the original retain and release calls. |
| 2731 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2732 | AI = RetainsToMove.Calls.begin(), |
| 2733 | AE = RetainsToMove.Calls.end(); AI != AE; ++AI) { |
| 2734 | Instruction *OrigRetain = *AI; |
| 2735 | Retains.blot(OrigRetain); |
| 2736 | DeadInsts.push_back(OrigRetain); |
| 2737 | } |
| 2738 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2739 | AI = ReleasesToMove.Calls.begin(), |
| 2740 | AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) { |
| 2741 | Instruction *OrigRelease = *AI; |
| 2742 | Releases.erase(OrigRelease); |
| 2743 | DeadInsts.push_back(OrigRelease); |
| 2744 | } |
| 2745 | } |
| 2746 | |
| 2747 | bool |
| 2748 | ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState> |
| 2749 | &BBStates, |
| 2750 | MapVector<Value *, RRInfo> &Retains, |
| 2751 | DenseMap<Value *, RRInfo> &Releases, |
| 2752 | Module *M) { |
| 2753 | bool AnyPairsCompletelyEliminated = false; |
| 2754 | RRInfo RetainsToMove; |
| 2755 | RRInfo ReleasesToMove; |
| 2756 | SmallVector<Instruction *, 4> NewRetains; |
| 2757 | SmallVector<Instruction *, 4> NewReleases; |
| 2758 | SmallVector<Instruction *, 8> DeadInsts; |
| 2759 | |
| 2760 | for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(), |
| 2761 | E = Retains.end(); I != E; ++I) { |
| 2762 | Value *V = I->first; |
| 2763 | if (!V) continue; // blotted |
| 2764 | |
| 2765 | Instruction *Retain = cast<Instruction>(V); |
| 2766 | Value *Arg = GetObjCArg(Retain); |
| 2767 | |
| 2768 | // If the object being released is in static storage, we know it's |
| 2769 | // not being managed by ObjC reference counting, so we can delete pairs |
| 2770 | // regardless of what possible decrements or uses lie between them. |
| 2771 | bool KnownSafe = isa<Constant>(Arg); |
| 2772 | |
| 2773 | // Same for stack storage, unless this is an objc_retainBlock call, |
| 2774 | // which is responsible for copying the block data from the stack to |
| 2775 | // the heap. |
| 2776 | if (!I->second.IsRetainBlock && isa<AllocaInst>(Arg)) |
| 2777 | KnownSafe = true; |
| 2778 | |
| 2779 | // A constant pointer can't be pointing to an object on the heap. It may |
| 2780 | // be reference-counted, but it won't be deleted. |
| 2781 | if (const LoadInst *LI = dyn_cast<LoadInst>(Arg)) |
| 2782 | if (const GlobalVariable *GV = |
| 2783 | dyn_cast<GlobalVariable>( |
| 2784 | StripPointerCastsAndObjCCalls(LI->getPointerOperand()))) |
| 2785 | if (GV->isConstant()) |
| 2786 | KnownSafe = true; |
| 2787 | |
| 2788 | // If a pair happens in a region where it is known that the reference count |
| 2789 | // is already incremented, we can similarly ignore possible decrements. |
| 2790 | bool KnownSafeTD = true, KnownSafeBU = true; |
| 2791 | |
| 2792 | // Connect the dots between the top-down-collected RetainsToMove and |
| 2793 | // bottom-up-collected ReleasesToMove to form sets of related calls. |
| 2794 | // This is an iterative process so that we connect multiple releases |
| 2795 | // to multiple retains if needed. |
| 2796 | unsigned OldDelta = 0; |
| 2797 | unsigned NewDelta = 0; |
| 2798 | unsigned OldCount = 0; |
| 2799 | unsigned NewCount = 0; |
| 2800 | bool FirstRelease = true; |
| 2801 | bool FirstRetain = true; |
| 2802 | NewRetains.push_back(Retain); |
| 2803 | for (;;) { |
| 2804 | for (SmallVectorImpl<Instruction *>::const_iterator |
| 2805 | NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) { |
| 2806 | Instruction *NewRetain = *NI; |
| 2807 | MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain); |
| 2808 | assert(It != Retains.end()); |
| 2809 | const RRInfo &NewRetainRRI = It->second; |
| 2810 | KnownSafeTD &= NewRetainRRI.KnownSafe; |
| 2811 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2812 | LI = NewRetainRRI.Calls.begin(), |
| 2813 | LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) { |
| 2814 | Instruction *NewRetainRelease = *LI; |
| 2815 | DenseMap<Value *, RRInfo>::const_iterator Jt = |
| 2816 | Releases.find(NewRetainRelease); |
| 2817 | if (Jt == Releases.end()) |
| 2818 | goto next_retain; |
| 2819 | const RRInfo &NewRetainReleaseRRI = Jt->second; |
| 2820 | assert(NewRetainReleaseRRI.Calls.count(NewRetain)); |
| 2821 | if (ReleasesToMove.Calls.insert(NewRetainRelease)) { |
| 2822 | OldDelta -= |
| 2823 | BBStates[NewRetainRelease->getParent()].GetAllPathCount(); |
| 2824 | |
| 2825 | // Merge the ReleaseMetadata and IsTailCallRelease values. |
| 2826 | if (FirstRelease) { |
| 2827 | ReleasesToMove.ReleaseMetadata = |
| 2828 | NewRetainReleaseRRI.ReleaseMetadata; |
| 2829 | ReleasesToMove.IsTailCallRelease = |
| 2830 | NewRetainReleaseRRI.IsTailCallRelease; |
| 2831 | FirstRelease = false; |
| 2832 | } else { |
| 2833 | if (ReleasesToMove.ReleaseMetadata != |
| 2834 | NewRetainReleaseRRI.ReleaseMetadata) |
| 2835 | ReleasesToMove.ReleaseMetadata = 0; |
| 2836 | if (ReleasesToMove.IsTailCallRelease != |
| 2837 | NewRetainReleaseRRI.IsTailCallRelease) |
| 2838 | ReleasesToMove.IsTailCallRelease = false; |
| 2839 | } |
| 2840 | |
| 2841 | // Collect the optimal insertion points. |
| 2842 | if (!KnownSafe) |
| 2843 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2844 | RI = NewRetainReleaseRRI.ReverseInsertPts.begin(), |
| 2845 | RE = NewRetainReleaseRRI.ReverseInsertPts.end(); |
| 2846 | RI != RE; ++RI) { |
| 2847 | Instruction *RIP = *RI; |
| 2848 | if (ReleasesToMove.ReverseInsertPts.insert(RIP)) |
| 2849 | NewDelta -= BBStates[RIP->getParent()].GetAllPathCount(); |
| 2850 | } |
| 2851 | NewReleases.push_back(NewRetainRelease); |
| 2852 | } |
| 2853 | } |
| 2854 | } |
| 2855 | NewRetains.clear(); |
| 2856 | if (NewReleases.empty()) break; |
| 2857 | |
| 2858 | // Back the other way. |
| 2859 | for (SmallVectorImpl<Instruction *>::const_iterator |
| 2860 | NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) { |
| 2861 | Instruction *NewRelease = *NI; |
| 2862 | DenseMap<Value *, RRInfo>::const_iterator It = |
| 2863 | Releases.find(NewRelease); |
| 2864 | assert(It != Releases.end()); |
| 2865 | const RRInfo &NewReleaseRRI = It->second; |
| 2866 | KnownSafeBU &= NewReleaseRRI.KnownSafe; |
| 2867 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2868 | LI = NewReleaseRRI.Calls.begin(), |
| 2869 | LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) { |
| 2870 | Instruction *NewReleaseRetain = *LI; |
| 2871 | MapVector<Value *, RRInfo>::const_iterator Jt = |
| 2872 | Retains.find(NewReleaseRetain); |
| 2873 | if (Jt == Retains.end()) |
| 2874 | goto next_retain; |
| 2875 | const RRInfo &NewReleaseRetainRRI = Jt->second; |
| 2876 | assert(NewReleaseRetainRRI.Calls.count(NewRelease)); |
| 2877 | if (RetainsToMove.Calls.insert(NewReleaseRetain)) { |
| 2878 | unsigned PathCount = |
| 2879 | BBStates[NewReleaseRetain->getParent()].GetAllPathCount(); |
| 2880 | OldDelta += PathCount; |
| 2881 | OldCount += PathCount; |
| 2882 | |
| 2883 | // Merge the IsRetainBlock values. |
| 2884 | if (FirstRetain) { |
| 2885 | RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock; |
| 2886 | FirstRetain = false; |
| 2887 | } else if (ReleasesToMove.IsRetainBlock != |
| 2888 | NewReleaseRetainRRI.IsRetainBlock) |
| 2889 | // It's not possible to merge the sequences if one uses |
| 2890 | // objc_retain and the other uses objc_retainBlock. |
| 2891 | goto next_retain; |
| 2892 | |
| 2893 | // Collect the optimal insertion points. |
| 2894 | if (!KnownSafe) |
| 2895 | for (SmallPtrSet<Instruction *, 2>::const_iterator |
| 2896 | RI = NewReleaseRetainRRI.ReverseInsertPts.begin(), |
| 2897 | RE = NewReleaseRetainRRI.ReverseInsertPts.end(); |
| 2898 | RI != RE; ++RI) { |
| 2899 | Instruction *RIP = *RI; |
| 2900 | if (RetainsToMove.ReverseInsertPts.insert(RIP)) { |
| 2901 | PathCount = BBStates[RIP->getParent()].GetAllPathCount(); |
| 2902 | NewDelta += PathCount; |
| 2903 | NewCount += PathCount; |
| 2904 | } |
| 2905 | } |
| 2906 | NewRetains.push_back(NewReleaseRetain); |
| 2907 | } |
| 2908 | } |
| 2909 | } |
| 2910 | NewReleases.clear(); |
| 2911 | if (NewRetains.empty()) break; |
| 2912 | } |
| 2913 | |
| 2914 | // If the pointer is known incremented or nested, we can safely delete the |
| 2915 | // pair regardless of what's between them. |
| 2916 | if (KnownSafeTD || KnownSafeBU) { |
| 2917 | RetainsToMove.ReverseInsertPts.clear(); |
| 2918 | ReleasesToMove.ReverseInsertPts.clear(); |
| 2919 | NewCount = 0; |
| 2920 | } else { |
| 2921 | // Determine whether the new insertion points we computed preserve the |
| 2922 | // balance of retain and release calls through the program. |
| 2923 | // TODO: If the fully aggressive solution isn't valid, try to find a |
| 2924 | // less aggressive solution which is. |
| 2925 | if (NewDelta != 0) |
| 2926 | goto next_retain; |
| 2927 | } |
| 2928 | |
| 2929 | // Determine whether the original call points are balanced in the retain and |
| 2930 | // release calls through the program. If not, conservatively don't touch |
| 2931 | // them. |
| 2932 | // TODO: It's theoretically possible to do code motion in this case, as |
| 2933 | // long as the existing imbalances are maintained. |
| 2934 | if (OldDelta != 0) |
| 2935 | goto next_retain; |
| 2936 | |
| 2937 | // Ok, everything checks out and we're all set. Let's move some code! |
| 2938 | Changed = true; |
| 2939 | AnyPairsCompletelyEliminated = NewCount == 0; |
| 2940 | NumRRs += OldCount - NewCount; |
| 2941 | MoveCalls(Arg, RetainsToMove, ReleasesToMove, |
| 2942 | Retains, Releases, DeadInsts, M); |
| 2943 | |
| 2944 | next_retain: |
| 2945 | NewReleases.clear(); |
| 2946 | NewRetains.clear(); |
| 2947 | RetainsToMove.clear(); |
| 2948 | ReleasesToMove.clear(); |
| 2949 | } |
| 2950 | |
| 2951 | // Now that we're done moving everything, we can delete the newly dead |
| 2952 | // instructions, as we no longer need them as insert points. |
| 2953 | while (!DeadInsts.empty()) |
| 2954 | EraseInstruction(DeadInsts.pop_back_val()); |
| 2955 | |
| 2956 | return AnyPairsCompletelyEliminated; |
| 2957 | } |
| 2958 | |
| 2959 | /// OptimizeWeakCalls - Weak pointer optimizations. |
| 2960 | void ObjCARCOpt::OptimizeWeakCalls(Function &F) { |
| 2961 | // First, do memdep-style RLE and S2L optimizations. We can't use memdep |
| 2962 | // itself because it uses AliasAnalysis and we need to do provenance |
| 2963 | // queries instead. |
| 2964 | for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| 2965 | Instruction *Inst = &*I++; |
| 2966 | InstructionClass Class = GetBasicInstructionClass(Inst); |
| 2967 | if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained) |
| 2968 | continue; |
| 2969 | |
| 2970 | // Delete objc_loadWeak calls with no users. |
| 2971 | if (Class == IC_LoadWeak && Inst->use_empty()) { |
| 2972 | Inst->eraseFromParent(); |
| 2973 | continue; |
| 2974 | } |
| 2975 | |
| 2976 | // TODO: For now, just look for an earlier available version of this value |
| 2977 | // within the same block. Theoretically, we could do memdep-style non-local |
| 2978 | // analysis too, but that would want caching. A better approach would be to |
| 2979 | // use the technique that EarlyCSE uses. |
| 2980 | inst_iterator Current = llvm::prior(I); |
| 2981 | BasicBlock *CurrentBB = Current.getBasicBlockIterator(); |
| 2982 | for (BasicBlock::iterator B = CurrentBB->begin(), |
| 2983 | J = Current.getInstructionIterator(); |
| 2984 | J != B; --J) { |
| 2985 | Instruction *EarlierInst = &*llvm::prior(J); |
| 2986 | InstructionClass EarlierClass = GetInstructionClass(EarlierInst); |
| 2987 | switch (EarlierClass) { |
| 2988 | case IC_LoadWeak: |
| 2989 | case IC_LoadWeakRetained: { |
| 2990 | // If this is loading from the same pointer, replace this load's value |
| 2991 | // with that one. |
| 2992 | CallInst *Call = cast<CallInst>(Inst); |
| 2993 | CallInst *EarlierCall = cast<CallInst>(EarlierInst); |
| 2994 | Value *Arg = Call->getArgOperand(0); |
| 2995 | Value *EarlierArg = EarlierCall->getArgOperand(0); |
| 2996 | switch (PA.getAA()->alias(Arg, EarlierArg)) { |
| 2997 | case AliasAnalysis::MustAlias: |
| 2998 | Changed = true; |
| 2999 | // If the load has a builtin retain, insert a plain retain for it. |
| 3000 | if (Class == IC_LoadWeakRetained) { |
| 3001 | CallInst *CI = |
| 3002 | CallInst::Create(getRetainCallee(F.getParent()), EarlierCall, |
| 3003 | "", Call); |
| 3004 | CI->setTailCall(); |
| 3005 | } |
| 3006 | // Zap the fully redundant load. |
| 3007 | Call->replaceAllUsesWith(EarlierCall); |
| 3008 | Call->eraseFromParent(); |
| 3009 | goto clobbered; |
| 3010 | case AliasAnalysis::MayAlias: |
| 3011 | case AliasAnalysis::PartialAlias: |
| 3012 | goto clobbered; |
| 3013 | case AliasAnalysis::NoAlias: |
| 3014 | break; |
| 3015 | } |
| 3016 | break; |
| 3017 | } |
| 3018 | case IC_StoreWeak: |
| 3019 | case IC_InitWeak: { |
| 3020 | // If this is storing to the same pointer and has the same size etc. |
| 3021 | // replace this load's value with the stored value. |
| 3022 | CallInst *Call = cast<CallInst>(Inst); |
| 3023 | CallInst *EarlierCall = cast<CallInst>(EarlierInst); |
| 3024 | Value *Arg = Call->getArgOperand(0); |
| 3025 | Value *EarlierArg = EarlierCall->getArgOperand(0); |
| 3026 | switch (PA.getAA()->alias(Arg, EarlierArg)) { |
| 3027 | case AliasAnalysis::MustAlias: |
| 3028 | Changed = true; |
| 3029 | // If the load has a builtin retain, insert a plain retain for it. |
| 3030 | if (Class == IC_LoadWeakRetained) { |
| 3031 | CallInst *CI = |
| 3032 | CallInst::Create(getRetainCallee(F.getParent()), EarlierCall, |
| 3033 | "", Call); |
| 3034 | CI->setTailCall(); |
| 3035 | } |
| 3036 | // Zap the fully redundant load. |
| 3037 | Call->replaceAllUsesWith(EarlierCall->getArgOperand(1)); |
| 3038 | Call->eraseFromParent(); |
| 3039 | goto clobbered; |
| 3040 | case AliasAnalysis::MayAlias: |
| 3041 | case AliasAnalysis::PartialAlias: |
| 3042 | goto clobbered; |
| 3043 | case AliasAnalysis::NoAlias: |
| 3044 | break; |
| 3045 | } |
| 3046 | break; |
| 3047 | } |
| 3048 | case IC_MoveWeak: |
| 3049 | case IC_CopyWeak: |
| 3050 | // TOOD: Grab the copied value. |
| 3051 | goto clobbered; |
| 3052 | case IC_AutoreleasepoolPush: |
| 3053 | case IC_None: |
| 3054 | case IC_User: |
| 3055 | // Weak pointers are only modified through the weak entry points |
| 3056 | // (and arbitrary calls, which could call the weak entry points). |
| 3057 | break; |
| 3058 | default: |
| 3059 | // Anything else could modify the weak pointer. |
| 3060 | goto clobbered; |
| 3061 | } |
| 3062 | } |
| 3063 | clobbered:; |
| 3064 | } |
| 3065 | |
| 3066 | // Then, for each destroyWeak with an alloca operand, check to see if |
| 3067 | // the alloca and all its users can be zapped. |
| 3068 | for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| 3069 | Instruction *Inst = &*I++; |
| 3070 | InstructionClass Class = GetBasicInstructionClass(Inst); |
| 3071 | if (Class != IC_DestroyWeak) |
| 3072 | continue; |
| 3073 | |
| 3074 | CallInst *Call = cast<CallInst>(Inst); |
| 3075 | Value *Arg = Call->getArgOperand(0); |
| 3076 | if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) { |
| 3077 | for (Value::use_iterator UI = Alloca->use_begin(), |
| 3078 | UE = Alloca->use_end(); UI != UE; ++UI) { |
| 3079 | Instruction *UserInst = cast<Instruction>(*UI); |
| 3080 | switch (GetBasicInstructionClass(UserInst)) { |
| 3081 | case IC_InitWeak: |
| 3082 | case IC_StoreWeak: |
| 3083 | case IC_DestroyWeak: |
| 3084 | continue; |
| 3085 | default: |
| 3086 | goto done; |
| 3087 | } |
| 3088 | } |
| 3089 | Changed = true; |
| 3090 | for (Value::use_iterator UI = Alloca->use_begin(), |
| 3091 | UE = Alloca->use_end(); UI != UE; ) { |
| 3092 | CallInst *UserInst = cast<CallInst>(*UI++); |
| 3093 | if (!UserInst->use_empty()) |
| 3094 | UserInst->replaceAllUsesWith(UserInst->getOperand(1)); |
| 3095 | UserInst->eraseFromParent(); |
| 3096 | } |
| 3097 | Alloca->eraseFromParent(); |
| 3098 | done:; |
| 3099 | } |
| 3100 | } |
| 3101 | } |
| 3102 | |
| 3103 | /// OptimizeSequences - Identify program paths which execute sequences of |
| 3104 | /// retains and releases which can be eliminated. |
| 3105 | bool ObjCARCOpt::OptimizeSequences(Function &F) { |
| 3106 | /// Releases, Retains - These are used to store the results of the main flow |
| 3107 | /// analysis. These use Value* as the key instead of Instruction* so that the |
| 3108 | /// map stays valid when we get around to rewriting code and calls get |
| 3109 | /// replaced by arguments. |
| 3110 | DenseMap<Value *, RRInfo> Releases; |
| 3111 | MapVector<Value *, RRInfo> Retains; |
| 3112 | |
| 3113 | /// BBStates, This is used during the traversal of the function to track the |
| 3114 | /// states for each identified object at each block. |
| 3115 | DenseMap<const BasicBlock *, BBState> BBStates; |
| 3116 | |
| 3117 | // Analyze the CFG of the function, and all instructions. |
| 3118 | bool NestingDetected = Visit(F, BBStates, Retains, Releases); |
| 3119 | |
| 3120 | // Transform. |
| 3121 | return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) && |
| 3122 | NestingDetected; |
| 3123 | } |
| 3124 | |
| 3125 | /// OptimizeReturns - Look for this pattern: |
| 3126 | /// |
| 3127 | /// %call = call i8* @something(...) |
| 3128 | /// %2 = call i8* @objc_retain(i8* %call) |
| 3129 | /// %3 = call i8* @objc_autorelease(i8* %2) |
| 3130 | /// ret i8* %3 |
| 3131 | /// |
| 3132 | /// And delete the retain and autorelease. |
| 3133 | /// |
| 3134 | /// Otherwise if it's just this: |
| 3135 | /// |
| 3136 | /// %3 = call i8* @objc_autorelease(i8* %2) |
| 3137 | /// ret i8* %3 |
| 3138 | /// |
| 3139 | /// convert the autorelease to autoreleaseRV. |
| 3140 | void ObjCARCOpt::OptimizeReturns(Function &F) { |
| 3141 | if (!F.getReturnType()->isPointerTy()) |
| 3142 | return; |
| 3143 | |
| 3144 | SmallPtrSet<Instruction *, 4> DependingInstructions; |
| 3145 | SmallPtrSet<const BasicBlock *, 4> Visited; |
| 3146 | for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) { |
| 3147 | BasicBlock *BB = FI; |
| 3148 | ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back()); |
| 3149 | if (!Ret) continue; |
| 3150 | |
| 3151 | const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0)); |
| 3152 | FindDependencies(NeedsPositiveRetainCount, Arg, |
| 3153 | BB, Ret, DependingInstructions, Visited, PA); |
| 3154 | if (DependingInstructions.size() != 1) |
| 3155 | goto next_block; |
| 3156 | |
| 3157 | { |
| 3158 | CallInst *Autorelease = |
| 3159 | dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| 3160 | if (!Autorelease) |
| 3161 | goto next_block; |
| 3162 | InstructionClass AutoreleaseClass = |
| 3163 | GetBasicInstructionClass(Autorelease); |
| 3164 | if (!IsAutorelease(AutoreleaseClass)) |
| 3165 | goto next_block; |
| 3166 | if (GetObjCArg(Autorelease) != Arg) |
| 3167 | goto next_block; |
| 3168 | |
| 3169 | DependingInstructions.clear(); |
| 3170 | Visited.clear(); |
| 3171 | |
| 3172 | // Check that there is nothing that can affect the reference |
| 3173 | // count between the autorelease and the retain. |
| 3174 | FindDependencies(CanChangeRetainCount, Arg, |
| 3175 | BB, Autorelease, DependingInstructions, Visited, PA); |
| 3176 | if (DependingInstructions.size() != 1) |
| 3177 | goto next_block; |
| 3178 | |
| 3179 | { |
| 3180 | CallInst *Retain = |
| 3181 | dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| 3182 | |
| 3183 | // Check that we found a retain with the same argument. |
| 3184 | if (!Retain || |
| 3185 | !IsRetain(GetBasicInstructionClass(Retain)) || |
| 3186 | GetObjCArg(Retain) != Arg) |
| 3187 | goto next_block; |
| 3188 | |
| 3189 | DependingInstructions.clear(); |
| 3190 | Visited.clear(); |
| 3191 | |
| 3192 | // Convert the autorelease to an autoreleaseRV, since it's |
| 3193 | // returning the value. |
| 3194 | if (AutoreleaseClass == IC_Autorelease) { |
| 3195 | Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent())); |
| 3196 | AutoreleaseClass = IC_AutoreleaseRV; |
| 3197 | } |
| 3198 | |
| 3199 | // Check that there is nothing that can affect the reference |
| 3200 | // count between the retain and the call. |
| 3201 | // Note that Retain need not be in BB. |
| 3202 | FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain, |
| 3203 | DependingInstructions, Visited, PA); |
| 3204 | if (DependingInstructions.size() != 1) |
| 3205 | goto next_block; |
| 3206 | |
| 3207 | { |
| 3208 | CallInst *Call = |
| 3209 | dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| 3210 | |
| 3211 | // Check that the pointer is the return value of the call. |
| 3212 | if (!Call || Arg != Call) |
| 3213 | goto next_block; |
| 3214 | |
| 3215 | // Check that the call is a regular call. |
| 3216 | InstructionClass Class = GetBasicInstructionClass(Call); |
| 3217 | if (Class != IC_CallOrUser && Class != IC_Call) |
| 3218 | goto next_block; |
| 3219 | |
| 3220 | // If so, we can zap the retain and autorelease. |
| 3221 | Changed = true; |
| 3222 | ++NumRets; |
| 3223 | EraseInstruction(Retain); |
| 3224 | EraseInstruction(Autorelease); |
| 3225 | } |
| 3226 | } |
| 3227 | } |
| 3228 | |
| 3229 | next_block: |
| 3230 | DependingInstructions.clear(); |
| 3231 | Visited.clear(); |
| 3232 | } |
| 3233 | } |
| 3234 | |
| 3235 | bool ObjCARCOpt::doInitialization(Module &M) { |
| 3236 | if (!EnableARCOpts) |
| 3237 | return false; |
| 3238 | |
| 3239 | Run = ModuleHasARC(M); |
| 3240 | if (!Run) |
| 3241 | return false; |
| 3242 | |
| 3243 | // Identify the imprecise release metadata kind. |
| 3244 | ImpreciseReleaseMDKind = |
| 3245 | M.getContext().getMDKindID("clang.imprecise_release"); |
| 3246 | |
| 3247 | // Intuitively, objc_retain and others are nocapture, however in practice |
| 3248 | // they are not, because they return their argument value. And objc_release |
| 3249 | // calls finalizers. |
| 3250 | |
| 3251 | // These are initialized lazily. |
| 3252 | RetainRVCallee = 0; |
| 3253 | AutoreleaseRVCallee = 0; |
| 3254 | ReleaseCallee = 0; |
| 3255 | RetainCallee = 0; |
| 3256 | RetainBlockCallee = 0; |
| 3257 | AutoreleaseCallee = 0; |
| 3258 | |
| 3259 | return false; |
| 3260 | } |
| 3261 | |
| 3262 | bool ObjCARCOpt::runOnFunction(Function &F) { |
| 3263 | if (!EnableARCOpts) |
| 3264 | return false; |
| 3265 | |
| 3266 | // If nothing in the Module uses ARC, don't do anything. |
| 3267 | if (!Run) |
| 3268 | return false; |
| 3269 | |
| 3270 | Changed = false; |
| 3271 | |
| 3272 | PA.setAA(&getAnalysis<AliasAnalysis>()); |
| 3273 | |
| 3274 | // This pass performs several distinct transformations. As a compile-time aid |
| 3275 | // when compiling code that isn't ObjC, skip these if the relevant ObjC |
| 3276 | // library functions aren't declared. |
| 3277 | |
| 3278 | // Preliminary optimizations. This also computs UsedInThisFunction. |
| 3279 | OptimizeIndividualCalls(F); |
| 3280 | |
| 3281 | // Optimizations for weak pointers. |
| 3282 | if (UsedInThisFunction & ((1 << IC_LoadWeak) | |
| 3283 | (1 << IC_LoadWeakRetained) | |
| 3284 | (1 << IC_StoreWeak) | |
| 3285 | (1 << IC_InitWeak) | |
| 3286 | (1 << IC_CopyWeak) | |
| 3287 | (1 << IC_MoveWeak) | |
| 3288 | (1 << IC_DestroyWeak))) |
| 3289 | OptimizeWeakCalls(F); |
| 3290 | |
| 3291 | // Optimizations for retain+release pairs. |
| 3292 | if (UsedInThisFunction & ((1 << IC_Retain) | |
| 3293 | (1 << IC_RetainRV) | |
| 3294 | (1 << IC_RetainBlock))) |
| 3295 | if (UsedInThisFunction & (1 << IC_Release)) |
| 3296 | // Run OptimizeSequences until it either stops making changes or |
| 3297 | // no retain+release pair nesting is detected. |
| 3298 | while (OptimizeSequences(F)) {} |
| 3299 | |
| 3300 | // Optimizations if objc_autorelease is used. |
| 3301 | if (UsedInThisFunction & |
| 3302 | ((1 << IC_Autorelease) | (1 << IC_AutoreleaseRV))) |
| 3303 | OptimizeReturns(F); |
| 3304 | |
| 3305 | return Changed; |
| 3306 | } |
| 3307 | |
| 3308 | void ObjCARCOpt::releaseMemory() { |
| 3309 | PA.clear(); |
| 3310 | } |
| 3311 | |
| 3312 | //===----------------------------------------------------------------------===// |
| 3313 | // ARC contraction. |
| 3314 | //===----------------------------------------------------------------------===// |
| 3315 | |
| 3316 | // TODO: ObjCARCContract could insert PHI nodes when uses aren't |
| 3317 | // dominated by single calls. |
| 3318 | |
| 3319 | #include "llvm/Operator.h" |
| 3320 | #include "llvm/InlineAsm.h" |
| 3321 | #include "llvm/Analysis/Dominators.h" |
| 3322 | |
| 3323 | STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed"); |
| 3324 | |
| 3325 | namespace { |
| 3326 | /// ObjCARCContract - Late ARC optimizations. These change the IR in a way |
| 3327 | /// that makes it difficult to be analyzed by ObjCARCOpt, so it's run late. |
| 3328 | class ObjCARCContract : public FunctionPass { |
| 3329 | bool Changed; |
| 3330 | AliasAnalysis *AA; |
| 3331 | DominatorTree *DT; |
| 3332 | ProvenanceAnalysis PA; |
| 3333 | |
| 3334 | /// Run - A flag indicating whether this optimization pass should run. |
| 3335 | bool Run; |
| 3336 | |
| 3337 | /// StoreStrongCallee, etc. - Declarations for ObjC runtime |
| 3338 | /// functions, for use in creating calls to them. These are initialized |
| 3339 | /// lazily to avoid cluttering up the Module with unused declarations. |
| 3340 | Constant *StoreStrongCallee, |
| 3341 | *RetainAutoreleaseCallee, *RetainAutoreleaseRVCallee; |
| 3342 | |
| 3343 | /// RetainRVMarker - The inline asm string to insert between calls and |
| 3344 | /// RetainRV calls to make the optimization work on targets which need it. |
| 3345 | const MDString *RetainRVMarker; |
| 3346 | |
| 3347 | Constant *getStoreStrongCallee(Module *M); |
| 3348 | Constant *getRetainAutoreleaseCallee(Module *M); |
| 3349 | Constant *getRetainAutoreleaseRVCallee(Module *M); |
| 3350 | |
| 3351 | bool ContractAutorelease(Function &F, Instruction *Autorelease, |
| 3352 | InstructionClass Class, |
| 3353 | SmallPtrSet<Instruction *, 4> |
| 3354 | &DependingInstructions, |
| 3355 | SmallPtrSet<const BasicBlock *, 4> |
| 3356 | &Visited); |
| 3357 | |
| 3358 | void ContractRelease(Instruction *Release, |
| 3359 | inst_iterator &Iter); |
| 3360 | |
| 3361 | virtual void getAnalysisUsage(AnalysisUsage &AU) const; |
| 3362 | virtual bool doInitialization(Module &M); |
| 3363 | virtual bool runOnFunction(Function &F); |
| 3364 | |
| 3365 | public: |
| 3366 | static char ID; |
| 3367 | ObjCARCContract() : FunctionPass(ID) { |
| 3368 | initializeObjCARCContractPass(*PassRegistry::getPassRegistry()); |
| 3369 | } |
| 3370 | }; |
| 3371 | } |
| 3372 | |
| 3373 | char ObjCARCContract::ID = 0; |
| 3374 | INITIALIZE_PASS_BEGIN(ObjCARCContract, |
| 3375 | "objc-arc-contract", "ObjC ARC contraction", false, false) |
| 3376 | INITIALIZE_AG_DEPENDENCY(AliasAnalysis) |
| 3377 | INITIALIZE_PASS_DEPENDENCY(DominatorTree) |
| 3378 | INITIALIZE_PASS_END(ObjCARCContract, |
| 3379 | "objc-arc-contract", "ObjC ARC contraction", false, false) |
| 3380 | |
| 3381 | Pass *llvm::createObjCARCContractPass() { |
| 3382 | return new ObjCARCContract(); |
| 3383 | } |
| 3384 | |
| 3385 | void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const { |
| 3386 | AU.addRequired<AliasAnalysis>(); |
| 3387 | AU.addRequired<DominatorTree>(); |
| 3388 | AU.setPreservesCFG(); |
| 3389 | } |
| 3390 | |
| 3391 | Constant *ObjCARCContract::getStoreStrongCallee(Module *M) { |
| 3392 | if (!StoreStrongCallee) { |
| 3393 | LLVMContext &C = M->getContext(); |
| 3394 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 3395 | Type *I8XX = PointerType::getUnqual(I8X); |
| 3396 | std::vector<Type *> Params; |
| 3397 | Params.push_back(I8XX); |
| 3398 | Params.push_back(I8X); |
| 3399 | |
| 3400 | AttrListPtr Attributes; |
| 3401 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 3402 | Attributes.addAttr(1, Attribute::NoCapture); |
| 3403 | |
| 3404 | StoreStrongCallee = |
| 3405 | M->getOrInsertFunction( |
| 3406 | "objc_storeStrong", |
| 3407 | FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false), |
| 3408 | Attributes); |
| 3409 | } |
| 3410 | return StoreStrongCallee; |
| 3411 | } |
| 3412 | |
| 3413 | Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) { |
| 3414 | if (!RetainAutoreleaseCallee) { |
| 3415 | LLVMContext &C = M->getContext(); |
| 3416 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 3417 | std::vector<Type *> Params; |
| 3418 | Params.push_back(I8X); |
| 3419 | FunctionType *FTy = |
| 3420 | FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| 3421 | AttrListPtr Attributes; |
| 3422 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 3423 | RetainAutoreleaseCallee = |
| 3424 | M->getOrInsertFunction("objc_retainAutorelease", FTy, Attributes); |
| 3425 | } |
| 3426 | return RetainAutoreleaseCallee; |
| 3427 | } |
| 3428 | |
| 3429 | Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) { |
| 3430 | if (!RetainAutoreleaseRVCallee) { |
| 3431 | LLVMContext &C = M->getContext(); |
| 3432 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 3433 | std::vector<Type *> Params; |
| 3434 | Params.push_back(I8X); |
| 3435 | FunctionType *FTy = |
| 3436 | FunctionType::get(I8X, Params, /*isVarArg=*/false); |
| 3437 | AttrListPtr Attributes; |
| 3438 | Attributes.addAttr(~0u, Attribute::NoUnwind); |
| 3439 | RetainAutoreleaseRVCallee = |
| 3440 | M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy, |
| 3441 | Attributes); |
| 3442 | } |
| 3443 | return RetainAutoreleaseRVCallee; |
| 3444 | } |
| 3445 | |
| 3446 | /// ContractAutorelease - Merge an autorelease with a retain into a fused |
| 3447 | /// call. |
| 3448 | bool |
| 3449 | ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease, |
| 3450 | InstructionClass Class, |
| 3451 | SmallPtrSet<Instruction *, 4> |
| 3452 | &DependingInstructions, |
| 3453 | SmallPtrSet<const BasicBlock *, 4> |
| 3454 | &Visited) { |
| 3455 | const Value *Arg = GetObjCArg(Autorelease); |
| 3456 | |
| 3457 | // Check that there are no instructions between the retain and the autorelease |
| 3458 | // (such as an autorelease_pop) which may change the count. |
| 3459 | CallInst *Retain = 0; |
| 3460 | if (Class == IC_AutoreleaseRV) |
| 3461 | FindDependencies(RetainAutoreleaseRVDep, Arg, |
| 3462 | Autorelease->getParent(), Autorelease, |
| 3463 | DependingInstructions, Visited, PA); |
| 3464 | else |
| 3465 | FindDependencies(RetainAutoreleaseDep, Arg, |
| 3466 | Autorelease->getParent(), Autorelease, |
| 3467 | DependingInstructions, Visited, PA); |
| 3468 | |
| 3469 | Visited.clear(); |
| 3470 | if (DependingInstructions.size() != 1) { |
| 3471 | DependingInstructions.clear(); |
| 3472 | return false; |
| 3473 | } |
| 3474 | |
| 3475 | Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin()); |
| 3476 | DependingInstructions.clear(); |
| 3477 | |
| 3478 | if (!Retain || |
| 3479 | GetBasicInstructionClass(Retain) != IC_Retain || |
| 3480 | GetObjCArg(Retain) != Arg) |
| 3481 | return false; |
| 3482 | |
| 3483 | Changed = true; |
| 3484 | ++NumPeeps; |
| 3485 | |
| 3486 | if (Class == IC_AutoreleaseRV) |
| 3487 | Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent())); |
| 3488 | else |
| 3489 | Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent())); |
| 3490 | |
| 3491 | EraseInstruction(Autorelease); |
| 3492 | return true; |
| 3493 | } |
| 3494 | |
| 3495 | /// ContractRelease - Attempt to merge an objc_release with a store, load, and |
| 3496 | /// objc_retain to form an objc_storeStrong. This can be a little tricky because |
| 3497 | /// the instructions don't always appear in order, and there may be unrelated |
| 3498 | /// intervening instructions. |
| 3499 | void ObjCARCContract::ContractRelease(Instruction *Release, |
| 3500 | inst_iterator &Iter) { |
| 3501 | LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release)); |
| 3502 | if (!Load || !Load->isSimple()) return; |
| 3503 | |
| 3504 | // For now, require everything to be in one basic block. |
| 3505 | BasicBlock *BB = Release->getParent(); |
| 3506 | if (Load->getParent() != BB) return; |
| 3507 | |
| 3508 | // Walk down to find the store. |
| 3509 | BasicBlock::iterator I = Load, End = BB->end(); |
| 3510 | ++I; |
| 3511 | AliasAnalysis::Location Loc = AA->getLocation(Load); |
| 3512 | while (I != End && |
| 3513 | (&*I == Release || |
| 3514 | IsRetain(GetBasicInstructionClass(I)) || |
| 3515 | !(AA->getModRefInfo(I, Loc) & AliasAnalysis::Mod))) |
| 3516 | ++I; |
| 3517 | StoreInst *Store = dyn_cast<StoreInst>(I); |
| 3518 | if (!Store || !Store->isSimple()) return; |
| 3519 | if (Store->getPointerOperand() != Loc.Ptr) return; |
| 3520 | |
| 3521 | Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand()); |
| 3522 | |
| 3523 | // Walk up to find the retain. |
| 3524 | I = Store; |
| 3525 | BasicBlock::iterator Begin = BB->begin(); |
| 3526 | while (I != Begin && GetBasicInstructionClass(I) != IC_Retain) |
| 3527 | --I; |
| 3528 | Instruction *Retain = I; |
| 3529 | if (GetBasicInstructionClass(Retain) != IC_Retain) return; |
| 3530 | if (GetObjCArg(Retain) != New) return; |
| 3531 | |
| 3532 | Changed = true; |
| 3533 | ++NumStoreStrongs; |
| 3534 | |
| 3535 | LLVMContext &C = Release->getContext(); |
| 3536 | Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C)); |
| 3537 | Type *I8XX = PointerType::getUnqual(I8X); |
| 3538 | |
| 3539 | Value *Args[] = { Load->getPointerOperand(), New }; |
| 3540 | if (Args[0]->getType() != I8XX) |
| 3541 | Args[0] = new BitCastInst(Args[0], I8XX, "", Store); |
| 3542 | if (Args[1]->getType() != I8X) |
| 3543 | Args[1] = new BitCastInst(Args[1], I8X, "", Store); |
| 3544 | CallInst *StoreStrong = |
| 3545 | CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()), |
| 3546 | Args, "", Store); |
| 3547 | StoreStrong->setDoesNotThrow(); |
| 3548 | StoreStrong->setDebugLoc(Store->getDebugLoc()); |
| 3549 | |
| 3550 | if (&*Iter == Store) ++Iter; |
| 3551 | Store->eraseFromParent(); |
| 3552 | Release->eraseFromParent(); |
| 3553 | EraseInstruction(Retain); |
| 3554 | if (Load->use_empty()) |
| 3555 | Load->eraseFromParent(); |
| 3556 | } |
| 3557 | |
| 3558 | bool ObjCARCContract::doInitialization(Module &M) { |
| 3559 | Run = ModuleHasARC(M); |
| 3560 | if (!Run) |
| 3561 | return false; |
| 3562 | |
| 3563 | // These are initialized lazily. |
| 3564 | StoreStrongCallee = 0; |
| 3565 | RetainAutoreleaseCallee = 0; |
| 3566 | RetainAutoreleaseRVCallee = 0; |
| 3567 | |
| 3568 | // Initialize RetainRVMarker. |
| 3569 | RetainRVMarker = 0; |
| 3570 | if (NamedMDNode *NMD = |
| 3571 | M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker")) |
| 3572 | if (NMD->getNumOperands() == 1) { |
| 3573 | const MDNode *N = NMD->getOperand(0); |
| 3574 | if (N->getNumOperands() == 1) |
| 3575 | if (const MDString *S = dyn_cast<MDString>(N->getOperand(0))) |
| 3576 | RetainRVMarker = S; |
| 3577 | } |
| 3578 | |
| 3579 | return false; |
| 3580 | } |
| 3581 | |
| 3582 | bool ObjCARCContract::runOnFunction(Function &F) { |
| 3583 | if (!EnableARCOpts) |
| 3584 | return false; |
| 3585 | |
| 3586 | // If nothing in the Module uses ARC, don't do anything. |
| 3587 | if (!Run) |
| 3588 | return false; |
| 3589 | |
| 3590 | Changed = false; |
| 3591 | AA = &getAnalysis<AliasAnalysis>(); |
| 3592 | DT = &getAnalysis<DominatorTree>(); |
| 3593 | |
| 3594 | PA.setAA(&getAnalysis<AliasAnalysis>()); |
| 3595 | |
| 3596 | // For ObjC library calls which return their argument, replace uses of the |
| 3597 | // argument with uses of the call return value, if it dominates the use. This |
| 3598 | // reduces register pressure. |
| 3599 | SmallPtrSet<Instruction *, 4> DependingInstructions; |
| 3600 | SmallPtrSet<const BasicBlock *, 4> Visited; |
| 3601 | for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) { |
| 3602 | Instruction *Inst = &*I++; |
| 3603 | |
| 3604 | // Only these library routines return their argument. In particular, |
| 3605 | // objc_retainBlock does not necessarily return its argument. |
| 3606 | InstructionClass Class = GetBasicInstructionClass(Inst); |
| 3607 | switch (Class) { |
| 3608 | case IC_Retain: |
| 3609 | case IC_FusedRetainAutorelease: |
| 3610 | case IC_FusedRetainAutoreleaseRV: |
| 3611 | break; |
| 3612 | case IC_Autorelease: |
| 3613 | case IC_AutoreleaseRV: |
| 3614 | if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited)) |
| 3615 | continue; |
| 3616 | break; |
| 3617 | case IC_RetainRV: { |
| 3618 | // If we're compiling for a target which needs a special inline-asm |
| 3619 | // marker to do the retainAutoreleasedReturnValue optimization, |
| 3620 | // insert it now. |
| 3621 | if (!RetainRVMarker) |
| 3622 | break; |
| 3623 | BasicBlock::iterator BBI = Inst; |
| 3624 | --BBI; |
| 3625 | while (isNoopInstruction(BBI)) --BBI; |
| 3626 | if (&*BBI == GetObjCArg(Inst)) { |
| 3627 | InlineAsm *IA = |
| 3628 | InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()), |
| 3629 | /*isVarArg=*/false), |
| 3630 | RetainRVMarker->getString(), |
| 3631 | /*Constraints=*/"", /*hasSideEffects=*/true); |
| 3632 | CallInst::Create(IA, "", Inst); |
| 3633 | } |
| 3634 | break; |
| 3635 | } |
| 3636 | case IC_InitWeak: { |
| 3637 | // objc_initWeak(p, null) => *p = null |
| 3638 | CallInst *CI = cast<CallInst>(Inst); |
| 3639 | if (isNullOrUndef(CI->getArgOperand(1))) { |
| 3640 | Value *Null = |
| 3641 | ConstantPointerNull::get(cast<PointerType>(CI->getType())); |
| 3642 | Changed = true; |
| 3643 | new StoreInst(Null, CI->getArgOperand(0), CI); |
| 3644 | CI->replaceAllUsesWith(Null); |
| 3645 | CI->eraseFromParent(); |
| 3646 | } |
| 3647 | continue; |
| 3648 | } |
| 3649 | case IC_Release: |
| 3650 | ContractRelease(Inst, I); |
| 3651 | continue; |
| 3652 | default: |
| 3653 | continue; |
| 3654 | } |
| 3655 | |
| 3656 | // Don't use GetObjCArg because we don't want to look through bitcasts |
| 3657 | // and such; to do the replacement, the argument must have type i8*. |
| 3658 | const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0); |
| 3659 | for (;;) { |
| 3660 | // If we're compiling bugpointed code, don't get in trouble. |
| 3661 | if (!isa<Instruction>(Arg) && !isa<Argument>(Arg)) |
| 3662 | break; |
| 3663 | // Look through the uses of the pointer. |
| 3664 | for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end(); |
| 3665 | UI != UE; ) { |
| 3666 | Use &U = UI.getUse(); |
| 3667 | unsigned OperandNo = UI.getOperandNo(); |
| 3668 | ++UI; // Increment UI now, because we may unlink its element. |
| 3669 | if (Instruction *UserInst = dyn_cast<Instruction>(U.getUser())) |
| 3670 | if (Inst != UserInst && DT->dominates(Inst, UserInst)) { |
| 3671 | Changed = true; |
| 3672 | Instruction *Replacement = Inst; |
| 3673 | Type *UseTy = U.get()->getType(); |
| 3674 | if (PHINode *PHI = dyn_cast<PHINode>(UserInst)) { |
| 3675 | // For PHI nodes, insert the bitcast in the predecessor block. |
| 3676 | unsigned ValNo = |
| 3677 | PHINode::getIncomingValueNumForOperand(OperandNo); |
| 3678 | BasicBlock *BB = |
| 3679 | PHI->getIncomingBlock(ValNo); |
| 3680 | if (Replacement->getType() != UseTy) |
| 3681 | Replacement = new BitCastInst(Replacement, UseTy, "", |
| 3682 | &BB->back()); |
| 3683 | for (unsigned i = 0, e = PHI->getNumIncomingValues(); |
| 3684 | i != e; ++i) |
| 3685 | if (PHI->getIncomingBlock(i) == BB) { |
| 3686 | // Keep the UI iterator valid. |
| 3687 | if (&PHI->getOperandUse( |
| 3688 | PHINode::getOperandNumForIncomingValue(i)) == |
| 3689 | &UI.getUse()) |
| 3690 | ++UI; |
| 3691 | PHI->setIncomingValue(i, Replacement); |
| 3692 | } |
| 3693 | } else { |
| 3694 | if (Replacement->getType() != UseTy) |
| 3695 | Replacement = new BitCastInst(Replacement, UseTy, "", UserInst); |
| 3696 | U.set(Replacement); |
| 3697 | } |
| 3698 | } |
| 3699 | } |
| 3700 | |
| 3701 | // If Arg is a no-op casted pointer, strip one level of casts and |
| 3702 | // iterate. |
| 3703 | if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg)) |
| 3704 | Arg = BI->getOperand(0); |
| 3705 | else if (isa<GEPOperator>(Arg) && |
| 3706 | cast<GEPOperator>(Arg)->hasAllZeroIndices()) |
| 3707 | Arg = cast<GEPOperator>(Arg)->getPointerOperand(); |
| 3708 | else if (isa<GlobalAlias>(Arg) && |
| 3709 | !cast<GlobalAlias>(Arg)->mayBeOverridden()) |
| 3710 | Arg = cast<GlobalAlias>(Arg)->getAliasee(); |
| 3711 | else |
| 3712 | break; |
| 3713 | } |
| 3714 | } |
| 3715 | |
| 3716 | return Changed; |
| 3717 | } |