1 //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===// 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 pass transforms simple global variables that never have their address 11 // taken. If obviously true, it marks read/write globals as constant, deletes 12 // variables only stored to, etc. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #define DEBUG_TYPE "globalopt" 17 #include "llvm/Transforms/IPO.h" 18 #include "llvm/CallingConv.h" 19 #include "llvm/Constants.h" 20 #include "llvm/DerivedTypes.h" 21 #include "llvm/Instructions.h" 22 #include "llvm/IntrinsicInst.h" 23 #include "llvm/Module.h" 24 #include "llvm/Operator.h" 25 #include "llvm/Pass.h" 26 #include "llvm/Analysis/ConstantFolding.h" 27 #include "llvm/Analysis/MemoryBuiltins.h" 28 #include "llvm/Target/TargetData.h" 29 #include "llvm/Target/TargetLibraryInfo.h" 30 #include "llvm/Support/CallSite.h" 31 #include "llvm/Support/Debug.h" 32 #include "llvm/Support/ErrorHandling.h" 33 #include "llvm/Support/GetElementPtrTypeIterator.h" 34 #include "llvm/Support/MathExtras.h" 35 #include "llvm/Support/raw_ostream.h" 36 #include "llvm/ADT/DenseMap.h" 37 #include "llvm/ADT/SmallPtrSet.h" 38 #include "llvm/ADT/SmallVector.h" 39 #include "llvm/ADT/Statistic.h" 40 #include "llvm/ADT/STLExtras.h" 41 #include <algorithm> 42 using namespace llvm; 43 44 STATISTIC(NumMarked , "Number of globals marked constant"); 45 STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr"); 46 STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); 47 STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); 48 STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); 49 STATISTIC(NumDeleted , "Number of globals deleted"); 50 STATISTIC(NumFnDeleted , "Number of functions deleted"); 51 STATISTIC(NumGlobUses , "Number of global uses devirtualized"); 52 STATISTIC(NumLocalized , "Number of globals localized"); 53 STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); 54 STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); 55 STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); 56 STATISTIC(NumNestRemoved , "Number of nest attributes removed"); 57 STATISTIC(NumAliasesResolved, "Number of global aliases resolved"); 58 STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated"); 59 STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed"); 60 61 namespace { 62 struct GlobalStatus; 63 struct GlobalOpt : public ModulePass { 64 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 65 AU.addRequired<TargetLibraryInfo>(); 66 } 67 static char ID; // Pass identification, replacement for typeid 68 GlobalOpt() : ModulePass(ID) { 69 initializeGlobalOptPass(*PassRegistry::getPassRegistry()); 70 } 71 72 bool runOnModule(Module &M); 73 74 private: 75 GlobalVariable *FindGlobalCtors(Module &M); 76 bool OptimizeFunctions(Module &M); 77 bool OptimizeGlobalVars(Module &M); 78 bool OptimizeGlobalAliases(Module &M); 79 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); 80 bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI); 81 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI, 82 const SmallPtrSet<const PHINode*, 16> &PHIUsers, 83 const GlobalStatus &GS); 84 bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn); 85 86 TargetData *TD; 87 TargetLibraryInfo *TLI; 88 }; 89 } 90 91 char GlobalOpt::ID = 0; 92 INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt", 93 "Global Variable Optimizer", false, false) 94 INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 95 INITIALIZE_PASS_END(GlobalOpt, "globalopt", 96 "Global Variable Optimizer", false, false) 97 98 ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } 99 100 namespace { 101 102 /// GlobalStatus - As we analyze each global, keep track of some information 103 /// about it. If we find out that the address of the global is taken, none of 104 /// this info will be accurate. 105 struct GlobalStatus { 106 /// isCompared - True if the global's address is used in a comparison. 107 bool isCompared; 108 109 /// isLoaded - True if the global is ever loaded. If the global isn't ever 110 /// loaded it can be deleted. 111 bool isLoaded; 112 113 /// StoredType - Keep track of what stores to the global look like. 114 /// 115 enum StoredType { 116 /// NotStored - There is no store to this global. It can thus be marked 117 /// constant. 118 NotStored, 119 120 /// isInitializerStored - This global is stored to, but the only thing 121 /// stored is the constant it was initialized with. This is only tracked 122 /// for scalar globals. 123 isInitializerStored, 124 125 /// isStoredOnce - This global is stored to, but only its initializer and 126 /// one other value is ever stored to it. If this global isStoredOnce, we 127 /// track the value stored to it in StoredOnceValue below. This is only 128 /// tracked for scalar globals. 129 isStoredOnce, 130 131 /// isStored - This global is stored to by multiple values or something else 132 /// that we cannot track. 133 isStored 134 } StoredType; 135 136 /// StoredOnceValue - If only one value (besides the initializer constant) is 137 /// ever stored to this global, keep track of what value it is. 138 Value *StoredOnceValue; 139 140 /// AccessingFunction/HasMultipleAccessingFunctions - These start out 141 /// null/false. When the first accessing function is noticed, it is recorded. 142 /// When a second different accessing function is noticed, 143 /// HasMultipleAccessingFunctions is set to true. 144 const Function *AccessingFunction; 145 bool HasMultipleAccessingFunctions; 146 147 /// HasNonInstructionUser - Set to true if this global has a user that is not 148 /// an instruction (e.g. a constant expr or GV initializer). 149 bool HasNonInstructionUser; 150 151 /// HasPHIUser - Set to true if this global has a user that is a PHI node. 152 bool HasPHIUser; 153 154 /// AtomicOrdering - Set to the strongest atomic ordering requirement. 155 AtomicOrdering Ordering; 156 157 GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored), 158 StoredOnceValue(0), AccessingFunction(0), 159 HasMultipleAccessingFunctions(false), 160 HasNonInstructionUser(false), HasPHIUser(false), 161 Ordering(NotAtomic) {} 162 }; 163 164 } 165 166 /// StrongerOrdering - Return the stronger of the two ordering. If the two 167 /// orderings are acquire and release, then return AcquireRelease. 168 /// 169 static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) { 170 if (X == Acquire && Y == Release) return AcquireRelease; 171 if (Y == Acquire && X == Release) return AcquireRelease; 172 return (AtomicOrdering)std::max(X, Y); 173 } 174 175 /// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used 176 /// by constants itself. Note that constants cannot be cyclic, so this test is 177 /// pretty easy to implement recursively. 178 /// 179 static bool SafeToDestroyConstant(const Constant *C) { 180 if (isa<GlobalValue>(C)) return false; 181 182 for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; 183 ++UI) 184 if (const Constant *CU = dyn_cast<Constant>(*UI)) { 185 if (!SafeToDestroyConstant(CU)) return false; 186 } else 187 return false; 188 return true; 189 } 190 191 192 /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus 193 /// structure. If the global has its address taken, return true to indicate we 194 /// can't do anything with it. 195 /// 196 static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS, 197 SmallPtrSet<const PHINode*, 16> &PHIUsers) { 198 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; 199 ++UI) { 200 const User *U = *UI; 201 if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 202 GS.HasNonInstructionUser = true; 203 204 // If the result of the constantexpr isn't pointer type, then we won't 205 // know to expect it in various places. Just reject early. 206 if (!isa<PointerType>(CE->getType())) return true; 207 208 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; 209 } else if (const Instruction *I = dyn_cast<Instruction>(U)) { 210 if (!GS.HasMultipleAccessingFunctions) { 211 const Function *F = I->getParent()->getParent(); 212 if (GS.AccessingFunction == 0) 213 GS.AccessingFunction = F; 214 else if (GS.AccessingFunction != F) 215 GS.HasMultipleAccessingFunctions = true; 216 } 217 if (const LoadInst *LI = dyn_cast<LoadInst>(I)) { 218 GS.isLoaded = true; 219 // Don't hack on volatile loads. 220 if (LI->isVolatile()) return true; 221 GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering()); 222 } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) { 223 // Don't allow a store OF the address, only stores TO the address. 224 if (SI->getOperand(0) == V) return true; 225 226 // Don't hack on volatile stores. 227 if (SI->isVolatile()) return true; 228 GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering()); 229 230 // If this is a direct store to the global (i.e., the global is a scalar 231 // value, not an aggregate), keep more specific information about 232 // stores. 233 if (GS.StoredType != GlobalStatus::isStored) { 234 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>( 235 SI->getOperand(1))) { 236 Value *StoredVal = SI->getOperand(0); 237 if (StoredVal == GV->getInitializer()) { 238 if (GS.StoredType < GlobalStatus::isInitializerStored) 239 GS.StoredType = GlobalStatus::isInitializerStored; 240 } else if (isa<LoadInst>(StoredVal) && 241 cast<LoadInst>(StoredVal)->getOperand(0) == GV) { 242 if (GS.StoredType < GlobalStatus::isInitializerStored) 243 GS.StoredType = GlobalStatus::isInitializerStored; 244 } else if (GS.StoredType < GlobalStatus::isStoredOnce) { 245 GS.StoredType = GlobalStatus::isStoredOnce; 246 GS.StoredOnceValue = StoredVal; 247 } else if (GS.StoredType == GlobalStatus::isStoredOnce && 248 GS.StoredOnceValue == StoredVal) { 249 // noop. 250 } else { 251 GS.StoredType = GlobalStatus::isStored; 252 } 253 } else { 254 GS.StoredType = GlobalStatus::isStored; 255 } 256 } 257 } else if (isa<BitCastInst>(I)) { 258 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 259 } else if (isa<GetElementPtrInst>(I)) { 260 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 261 } else if (isa<SelectInst>(I)) { 262 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 263 } else if (const PHINode *PN = dyn_cast<PHINode>(I)) { 264 // PHI nodes we can check just like select or GEP instructions, but we 265 // have to be careful about infinite recursion. 266 if (PHIUsers.insert(PN)) // Not already visited. 267 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 268 GS.HasPHIUser = true; 269 } else if (isa<CmpInst>(I)) { 270 GS.isCompared = true; 271 } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) { 272 if (MTI->isVolatile()) return true; 273 if (MTI->getArgOperand(0) == V) 274 GS.StoredType = GlobalStatus::isStored; 275 if (MTI->getArgOperand(1) == V) 276 GS.isLoaded = true; 277 } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) { 278 assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!"); 279 if (MSI->isVolatile()) return true; 280 GS.StoredType = GlobalStatus::isStored; 281 } else { 282 return true; // Any other non-load instruction might take address! 283 } 284 } else if (const Constant *C = dyn_cast<Constant>(U)) { 285 GS.HasNonInstructionUser = true; 286 // We might have a dead and dangling constant hanging off of here. 287 if (!SafeToDestroyConstant(C)) 288 return true; 289 } else { 290 GS.HasNonInstructionUser = true; 291 // Otherwise must be some other user. 292 return true; 293 } 294 } 295 296 return false; 297 } 298 299 /// isLeakCheckerRoot - Is this global variable possibly used by a leak checker 300 /// as a root? If so, we might not really want to eliminate the stores to it. 301 static bool isLeakCheckerRoot(GlobalVariable *GV) { 302 // A global variable is a root if it is a pointer, or could plausibly contain 303 // a pointer. There are two challenges; one is that we could have a struct 304 // the has an inner member which is a pointer. We recurse through the type to 305 // detect these (up to a point). The other is that we may actually be a union 306 // of a pointer and another type, and so our LLVM type is an integer which 307 // gets converted into a pointer, or our type is an [i8 x #] with a pointer 308 // potentially contained here. 309 310 if (GV->hasPrivateLinkage()) 311 return false; 312 313 SmallVector<Type *, 4> Types; 314 Types.push_back(cast<PointerType>(GV->getType())->getElementType()); 315 316 unsigned Limit = 20; 317 do { 318 Type *Ty = Types.pop_back_val(); 319 switch (Ty->getTypeID()) { 320 default: break; 321 case Type::PointerTyID: return true; 322 case Type::ArrayTyID: 323 case Type::VectorTyID: { 324 SequentialType *STy = cast<SequentialType>(Ty); 325 Types.push_back(STy->getElementType()); 326 break; 327 } 328 case Type::StructTyID: { 329 StructType *STy = cast<StructType>(Ty); 330 if (STy->isOpaque()) return true; 331 for (StructType::element_iterator I = STy->element_begin(), 332 E = STy->element_end(); I != E; ++I) { 333 Type *InnerTy = *I; 334 if (isa<PointerType>(InnerTy)) return true; 335 if (isa<CompositeType>(InnerTy)) 336 Types.push_back(InnerTy); 337 } 338 break; 339 } 340 } 341 if (--Limit == 0) return true; 342 } while (!Types.empty()); 343 return false; 344 } 345 346 /// Given a value that is stored to a global but never read, determine whether 347 /// it's safe to remove the store and the chain of computation that feeds the 348 /// store. 349 static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) { 350 do { 351 if (isa<Constant>(V)) 352 return true; 353 if (!V->hasOneUse()) 354 return false; 355 if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) || 356 isa<GlobalValue>(V)) 357 return false; 358 if (isAllocationFn(V, TLI)) 359 return true; 360 361 Instruction *I = cast<Instruction>(V); 362 if (I->mayHaveSideEffects()) 363 return false; 364 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { 365 if (!GEP->hasAllConstantIndices()) 366 return false; 367 } else if (I->getNumOperands() != 1) { 368 return false; 369 } 370 371 V = I->getOperand(0); 372 } while (1); 373 } 374 375 /// CleanupPointerRootUsers - This GV is a pointer root. Loop over all users 376 /// of the global and clean up any that obviously don't assign the global a 377 /// value that isn't dynamically allocated. 378 /// 379 static bool CleanupPointerRootUsers(GlobalVariable *GV, 380 const TargetLibraryInfo *TLI) { 381 // A brief explanation of leak checkers. The goal is to find bugs where 382 // pointers are forgotten, causing an accumulating growth in memory 383 // usage over time. The common strategy for leak checkers is to whitelist the 384 // memory pointed to by globals at exit. This is popular because it also 385 // solves another problem where the main thread of a C++ program may shut down 386 // before other threads that are still expecting to use those globals. To 387 // handle that case, we expect the program may create a singleton and never 388 // destroy it. 389 390 bool Changed = false; 391 392 // If Dead[n].first is the only use of a malloc result, we can delete its 393 // chain of computation and the store to the global in Dead[n].second. 394 SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead; 395 396 // Constants can't be pointers to dynamically allocated memory. 397 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 398 UI != E;) { 399 User *U = *UI++; 400 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 401 Value *V = SI->getValueOperand(); 402 if (isa<Constant>(V)) { 403 Changed = true; 404 SI->eraseFromParent(); 405 } else if (Instruction *I = dyn_cast<Instruction>(V)) { 406 if (I->hasOneUse()) 407 Dead.push_back(std::make_pair(I, SI)); 408 } 409 } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) { 410 if (isa<Constant>(MSI->getValue())) { 411 Changed = true; 412 MSI->eraseFromParent(); 413 } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) { 414 if (I->hasOneUse()) 415 Dead.push_back(std::make_pair(I, MSI)); 416 } 417 } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) { 418 GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource()); 419 if (MemSrc && MemSrc->isConstant()) { 420 Changed = true; 421 MTI->eraseFromParent(); 422 } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) { 423 if (I->hasOneUse()) 424 Dead.push_back(std::make_pair(I, MTI)); 425 } 426 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 427 if (CE->use_empty()) { 428 CE->destroyConstant(); 429 Changed = true; 430 } 431 } else if (Constant *C = dyn_cast<Constant>(U)) { 432 if (SafeToDestroyConstant(C)) { 433 C->destroyConstant(); 434 // This could have invalidated UI, start over from scratch. 435 Dead.clear(); 436 CleanupPointerRootUsers(GV, TLI); 437 return true; 438 } 439 } 440 } 441 442 for (int i = 0, e = Dead.size(); i != e; ++i) { 443 if (IsSafeComputationToRemove(Dead[i].first, TLI)) { 444 Dead[i].second->eraseFromParent(); 445 Instruction *I = Dead[i].first; 446 do { 447 if (isAllocationFn(I, TLI)) 448 break; 449 Instruction *J = dyn_cast<Instruction>(I->getOperand(0)); 450 if (!J) 451 break; 452 I->eraseFromParent(); 453 I = J; 454 } while (1); 455 I->eraseFromParent(); 456 } 457 } 458 459 return Changed; 460 } 461 462 /// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 463 /// users of the global, cleaning up the obvious ones. This is largely just a 464 /// quick scan over the use list to clean up the easy and obvious cruft. This 465 /// returns true if it made a change. 466 static bool CleanupConstantGlobalUsers(Value *V, Constant *Init, 467 TargetData *TD, TargetLibraryInfo *TLI) { 468 bool Changed = false; 469 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 470 User *U = *UI++; 471 472 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 473 if (Init) { 474 // Replace the load with the initializer. 475 LI->replaceAllUsesWith(Init); 476 LI->eraseFromParent(); 477 Changed = true; 478 } 479 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 480 // Store must be unreachable or storing Init into the global. 481 SI->eraseFromParent(); 482 Changed = true; 483 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 484 if (CE->getOpcode() == Instruction::GetElementPtr) { 485 Constant *SubInit = 0; 486 if (Init) 487 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 488 Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI); 489 } else if (CE->getOpcode() == Instruction::BitCast && 490 CE->getType()->isPointerTy()) { 491 // Pointer cast, delete any stores and memsets to the global. 492 Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI); 493 } 494 495 if (CE->use_empty()) { 496 CE->destroyConstant(); 497 Changed = true; 498 } 499 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 500 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 501 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 502 // and will invalidate our notion of what Init is. 503 Constant *SubInit = 0; 504 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 505 ConstantExpr *CE = 506 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI)); 507 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 508 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 509 510 // If the initializer is an all-null value and we have an inbounds GEP, 511 // we already know what the result of any load from that GEP is. 512 // TODO: Handle splats. 513 if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds()) 514 SubInit = Constant::getNullValue(GEP->getType()->getElementType()); 515 } 516 Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI); 517 518 if (GEP->use_empty()) { 519 GEP->eraseFromParent(); 520 Changed = true; 521 } 522 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 523 if (MI->getRawDest() == V) { 524 MI->eraseFromParent(); 525 Changed = true; 526 } 527 528 } else if (Constant *C = dyn_cast<Constant>(U)) { 529 // If we have a chain of dead constantexprs or other things dangling from 530 // us, and if they are all dead, nuke them without remorse. 531 if (SafeToDestroyConstant(C)) { 532 C->destroyConstant(); 533 // This could have invalidated UI, start over from scratch. 534 CleanupConstantGlobalUsers(V, Init, TD, TLI); 535 return true; 536 } 537 } 538 } 539 return Changed; 540 } 541 542 /// isSafeSROAElementUse - Return true if the specified instruction is a safe 543 /// user of a derived expression from a global that we want to SROA. 544 static bool isSafeSROAElementUse(Value *V) { 545 // We might have a dead and dangling constant hanging off of here. 546 if (Constant *C = dyn_cast<Constant>(V)) 547 return SafeToDestroyConstant(C); 548 549 Instruction *I = dyn_cast<Instruction>(V); 550 if (!I) return false; 551 552 // Loads are ok. 553 if (isa<LoadInst>(I)) return true; 554 555 // Stores *to* the pointer are ok. 556 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 557 return SI->getOperand(0) != V; 558 559 // Otherwise, it must be a GEP. 560 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 561 if (GEPI == 0) return false; 562 563 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 564 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 565 return false; 566 567 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 568 I != E; ++I) 569 if (!isSafeSROAElementUse(*I)) 570 return false; 571 return true; 572 } 573 574 575 /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 576 /// Look at it and its uses and decide whether it is safe to SROA this global. 577 /// 578 static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 579 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 580 if (!isa<GetElementPtrInst>(U) && 581 (!isa<ConstantExpr>(U) || 582 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 583 return false; 584 585 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 586 // don't like < 3 operand CE's, and we don't like non-constant integer 587 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 588 // value of C. 589 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 590 !cast<Constant>(U->getOperand(1))->isNullValue() || 591 !isa<ConstantInt>(U->getOperand(2))) 592 return false; 593 594 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 595 ++GEPI; // Skip over the pointer index. 596 597 // If this is a use of an array allocation, do a bit more checking for sanity. 598 if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 599 uint64_t NumElements = AT->getNumElements(); 600 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 601 602 // Check to make sure that index falls within the array. If not, 603 // something funny is going on, so we won't do the optimization. 604 // 605 if (Idx->getZExtValue() >= NumElements) 606 return false; 607 608 // We cannot scalar repl this level of the array unless any array 609 // sub-indices are in-range constants. In particular, consider: 610 // A[0][i]. We cannot know that the user isn't doing invalid things like 611 // allowing i to index an out-of-range subscript that accesses A[1]. 612 // 613 // Scalar replacing *just* the outer index of the array is probably not 614 // going to be a win anyway, so just give up. 615 for (++GEPI; // Skip array index. 616 GEPI != E; 617 ++GEPI) { 618 uint64_t NumElements; 619 if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 620 NumElements = SubArrayTy->getNumElements(); 621 else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI)) 622 NumElements = SubVectorTy->getNumElements(); 623 else { 624 assert((*GEPI)->isStructTy() && 625 "Indexed GEP type is not array, vector, or struct!"); 626 continue; 627 } 628 629 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 630 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 631 return false; 632 } 633 } 634 635 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 636 if (!isSafeSROAElementUse(*I)) 637 return false; 638 return true; 639 } 640 641 /// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 642 /// is safe for us to perform this transformation. 643 /// 644 static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 645 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 646 UI != E; ++UI) { 647 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 648 return false; 649 } 650 return true; 651 } 652 653 654 /// SRAGlobal - Perform scalar replacement of aggregates on the specified global 655 /// variable. This opens the door for other optimizations by exposing the 656 /// behavior of the program in a more fine-grained way. We have determined that 657 /// this transformation is safe already. We return the first global variable we 658 /// insert so that the caller can reprocess it. 659 static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) { 660 // Make sure this global only has simple uses that we can SRA. 661 if (!GlobalUsersSafeToSRA(GV)) 662 return 0; 663 664 assert(GV->hasLocalLinkage() && !GV->isConstant()); 665 Constant *Init = GV->getInitializer(); 666 Type *Ty = Init->getType(); 667 668 std::vector<GlobalVariable*> NewGlobals; 669 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 670 671 // Get the alignment of the global, either explicit or target-specific. 672 unsigned StartAlignment = GV->getAlignment(); 673 if (StartAlignment == 0) 674 StartAlignment = TD.getABITypeAlignment(GV->getType()); 675 676 if (StructType *STy = dyn_cast<StructType>(Ty)) { 677 NewGlobals.reserve(STy->getNumElements()); 678 const StructLayout &Layout = *TD.getStructLayout(STy); 679 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 680 Constant *In = Init->getAggregateElement(i); 681 assert(In && "Couldn't get element of initializer?"); 682 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 683 GlobalVariable::InternalLinkage, 684 In, GV->getName()+"."+Twine(i), 685 GV->getThreadLocalMode(), 686 GV->getType()->getAddressSpace()); 687 Globals.insert(GV, NGV); 688 NewGlobals.push_back(NGV); 689 690 // Calculate the known alignment of the field. If the original aggregate 691 // had 256 byte alignment for example, something might depend on that: 692 // propagate info to each field. 693 uint64_t FieldOffset = Layout.getElementOffset(i); 694 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset); 695 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i))) 696 NGV->setAlignment(NewAlign); 697 } 698 } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 699 unsigned NumElements = 0; 700 if (ArrayType *ATy = dyn_cast<ArrayType>(STy)) 701 NumElements = ATy->getNumElements(); 702 else 703 NumElements = cast<VectorType>(STy)->getNumElements(); 704 705 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 706 return 0; // It's not worth it. 707 NewGlobals.reserve(NumElements); 708 709 uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType()); 710 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType()); 711 for (unsigned i = 0, e = NumElements; i != e; ++i) { 712 Constant *In = Init->getAggregateElement(i); 713 assert(In && "Couldn't get element of initializer?"); 714 715 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 716 GlobalVariable::InternalLinkage, 717 In, GV->getName()+"."+Twine(i), 718 GV->getThreadLocalMode(), 719 GV->getType()->getAddressSpace()); 720 Globals.insert(GV, NGV); 721 NewGlobals.push_back(NGV); 722 723 // Calculate the known alignment of the field. If the original aggregate 724 // had 256 byte alignment for example, something might depend on that: 725 // propagate info to each field. 726 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i); 727 if (NewAlign > EltAlign) 728 NGV->setAlignment(NewAlign); 729 } 730 } 731 732 if (NewGlobals.empty()) 733 return 0; 734 735 DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV); 736 737 Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext())); 738 739 // Loop over all of the uses of the global, replacing the constantexpr geps, 740 // with smaller constantexpr geps or direct references. 741 while (!GV->use_empty()) { 742 User *GEP = GV->use_back(); 743 assert(((isa<ConstantExpr>(GEP) && 744 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 745 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 746 747 // Ignore the 1th operand, which has to be zero or else the program is quite 748 // broken (undefined). Get the 2nd operand, which is the structure or array 749 // index. 750 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 751 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 752 753 Value *NewPtr = NewGlobals[Val]; 754 755 // Form a shorter GEP if needed. 756 if (GEP->getNumOperands() > 3) { 757 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 758 SmallVector<Constant*, 8> Idxs; 759 Idxs.push_back(NullInt); 760 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 761 Idxs.push_back(CE->getOperand(i)); 762 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs); 763 } else { 764 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 765 SmallVector<Value*, 8> Idxs; 766 Idxs.push_back(NullInt); 767 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 768 Idxs.push_back(GEPI->getOperand(i)); 769 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs, 770 GEPI->getName()+"."+Twine(Val),GEPI); 771 } 772 } 773 GEP->replaceAllUsesWith(NewPtr); 774 775 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 776 GEPI->eraseFromParent(); 777 else 778 cast<ConstantExpr>(GEP)->destroyConstant(); 779 } 780 781 // Delete the old global, now that it is dead. 782 Globals.erase(GV); 783 ++NumSRA; 784 785 // Loop over the new globals array deleting any globals that are obviously 786 // dead. This can arise due to scalarization of a structure or an array that 787 // has elements that are dead. 788 unsigned FirstGlobal = 0; 789 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 790 if (NewGlobals[i]->use_empty()) { 791 Globals.erase(NewGlobals[i]); 792 if (FirstGlobal == i) ++FirstGlobal; 793 } 794 795 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 796 } 797 798 /// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 799 /// value will trap if the value is dynamically null. PHIs keeps track of any 800 /// phi nodes we've seen to avoid reprocessing them. 801 static bool AllUsesOfValueWillTrapIfNull(const Value *V, 802 SmallPtrSet<const PHINode*, 8> &PHIs) { 803 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; 804 ++UI) { 805 const User *U = *UI; 806 807 if (isa<LoadInst>(U)) { 808 // Will trap. 809 } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) { 810 if (SI->getOperand(0) == V) { 811 //cerr << "NONTRAPPING USE: " << *U; 812 return false; // Storing the value. 813 } 814 } else if (const CallInst *CI = dyn_cast<CallInst>(U)) { 815 if (CI->getCalledValue() != V) { 816 //cerr << "NONTRAPPING USE: " << *U; 817 return false; // Not calling the ptr 818 } 819 } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) { 820 if (II->getCalledValue() != V) { 821 //cerr << "NONTRAPPING USE: " << *U; 822 return false; // Not calling the ptr 823 } 824 } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) { 825 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 826 } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { 827 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 828 } else if (const PHINode *PN = dyn_cast<PHINode>(U)) { 829 // If we've already seen this phi node, ignore it, it has already been 830 // checked. 831 if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs)) 832 return false; 833 } else if (isa<ICmpInst>(U) && 834 isa<ConstantPointerNull>(UI->getOperand(1))) { 835 // Ignore icmp X, null 836 } else { 837 //cerr << "NONTRAPPING USE: " << *U; 838 return false; 839 } 840 } 841 return true; 842 } 843 844 /// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 845 /// from GV will trap if the loaded value is null. Note that this also permits 846 /// comparisons of the loaded value against null, as a special case. 847 static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) { 848 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end(); 849 UI != E; ++UI) { 850 const User *U = *UI; 851 852 if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { 853 SmallPtrSet<const PHINode*, 8> PHIs; 854 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 855 return false; 856 } else if (isa<StoreInst>(U)) { 857 // Ignore stores to the global. 858 } else { 859 // We don't know or understand this user, bail out. 860 //cerr << "UNKNOWN USER OF GLOBAL!: " << *U; 861 return false; 862 } 863 } 864 return true; 865 } 866 867 static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 868 bool Changed = false; 869 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 870 Instruction *I = cast<Instruction>(*UI++); 871 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 872 LI->setOperand(0, NewV); 873 Changed = true; 874 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 875 if (SI->getOperand(1) == V) { 876 SI->setOperand(1, NewV); 877 Changed = true; 878 } 879 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 880 CallSite CS(I); 881 if (CS.getCalledValue() == V) { 882 // Calling through the pointer! Turn into a direct call, but be careful 883 // that the pointer is not also being passed as an argument. 884 CS.setCalledFunction(NewV); 885 Changed = true; 886 bool PassedAsArg = false; 887 for (unsigned i = 0, e = CS.arg_size(); i != e; ++i) 888 if (CS.getArgument(i) == V) { 889 PassedAsArg = true; 890 CS.setArgument(i, NewV); 891 } 892 893 if (PassedAsArg) { 894 // Being passed as an argument also. Be careful to not invalidate UI! 895 UI = V->use_begin(); 896 } 897 } 898 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 899 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 900 ConstantExpr::getCast(CI->getOpcode(), 901 NewV, CI->getType())); 902 if (CI->use_empty()) { 903 Changed = true; 904 CI->eraseFromParent(); 905 } 906 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 907 // Should handle GEP here. 908 SmallVector<Constant*, 8> Idxs; 909 Idxs.reserve(GEPI->getNumOperands()-1); 910 for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end(); 911 i != e; ++i) 912 if (Constant *C = dyn_cast<Constant>(*i)) 913 Idxs.push_back(C); 914 else 915 break; 916 if (Idxs.size() == GEPI->getNumOperands()-1) 917 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 918 ConstantExpr::getGetElementPtr(NewV, Idxs)); 919 if (GEPI->use_empty()) { 920 Changed = true; 921 GEPI->eraseFromParent(); 922 } 923 } 924 } 925 926 return Changed; 927 } 928 929 930 /// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 931 /// value stored into it. If there are uses of the loaded value that would trap 932 /// if the loaded value is dynamically null, then we know that they cannot be 933 /// reachable with a null optimize away the load. 934 static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV, 935 TargetData *TD, 936 TargetLibraryInfo *TLI) { 937 bool Changed = false; 938 939 // Keep track of whether we are able to remove all the uses of the global 940 // other than the store that defines it. 941 bool AllNonStoreUsesGone = true; 942 943 // Replace all uses of loads with uses of uses of the stored value. 944 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){ 945 User *GlobalUser = *GUI++; 946 if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) { 947 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 948 // If we were able to delete all uses of the loads 949 if (LI->use_empty()) { 950 LI->eraseFromParent(); 951 Changed = true; 952 } else { 953 AllNonStoreUsesGone = false; 954 } 955 } else if (isa<StoreInst>(GlobalUser)) { 956 // Ignore the store that stores "LV" to the global. 957 assert(GlobalUser->getOperand(1) == GV && 958 "Must be storing *to* the global"); 959 } else { 960 AllNonStoreUsesGone = false; 961 962 // If we get here we could have other crazy uses that are transitively 963 // loaded. 964 assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) || 965 isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser)) && 966 "Only expect load and stores!"); 967 } 968 } 969 970 if (Changed) { 971 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV); 972 ++NumGlobUses; 973 } 974 975 // If we nuked all of the loads, then none of the stores are needed either, 976 // nor is the global. 977 if (AllNonStoreUsesGone) { 978 if (isLeakCheckerRoot(GV)) { 979 Changed |= CleanupPointerRootUsers(GV, TLI); 980 } else { 981 Changed = true; 982 CleanupConstantGlobalUsers(GV, 0, TD, TLI); 983 } 984 if (GV->use_empty()) { 985 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n"); 986 Changed = true; 987 GV->eraseFromParent(); 988 ++NumDeleted; 989 } 990 } 991 return Changed; 992 } 993 994 /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 995 /// instructions that are foldable. 996 static void ConstantPropUsersOf(Value *V, 997 TargetData *TD, TargetLibraryInfo *TLI) { 998 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 999 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 1000 if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) { 1001 I->replaceAllUsesWith(NewC); 1002 1003 // Advance UI to the next non-I use to avoid invalidating it! 1004 // Instructions could multiply use V. 1005 while (UI != E && *UI == I) 1006 ++UI; 1007 I->eraseFromParent(); 1008 } 1009 } 1010 1011 /// OptimizeGlobalAddressOfMalloc - This function takes the specified global 1012 /// variable, and transforms the program as if it always contained the result of 1013 /// the specified malloc. Because it is always the result of the specified 1014 /// malloc, there is no reason to actually DO the malloc. Instead, turn the 1015 /// malloc into a global, and any loads of GV as uses of the new global. 1016 static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 1017 CallInst *CI, 1018 Type *AllocTy, 1019 ConstantInt *NElements, 1020 TargetData *TD, 1021 TargetLibraryInfo *TLI) { 1022 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n'); 1023 1024 Type *GlobalType; 1025 if (NElements->getZExtValue() == 1) 1026 GlobalType = AllocTy; 1027 else 1028 // If we have an array allocation, the global variable is of an array. 1029 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue()); 1030 1031 // Create the new global variable. The contents of the malloc'd memory is 1032 // undefined, so initialize with an undef value. 1033 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(), 1034 GlobalType, false, 1035 GlobalValue::InternalLinkage, 1036 UndefValue::get(GlobalType), 1037 GV->getName()+".body", 1038 GV, 1039 GV->getThreadLocalMode()); 1040 1041 // If there are bitcast users of the malloc (which is typical, usually we have 1042 // a malloc + bitcast) then replace them with uses of the new global. Update 1043 // other users to use the global as well. 1044 BitCastInst *TheBC = 0; 1045 while (!CI->use_empty()) { 1046 Instruction *User = cast<Instruction>(CI->use_back()); 1047 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1048 if (BCI->getType() == NewGV->getType()) { 1049 BCI->replaceAllUsesWith(NewGV); 1050 BCI->eraseFromParent(); 1051 } else { 1052 BCI->setOperand(0, NewGV); 1053 } 1054 } else { 1055 if (TheBC == 0) 1056 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI); 1057 User->replaceUsesOfWith(CI, TheBC); 1058 } 1059 } 1060 1061 Constant *RepValue = NewGV; 1062 if (NewGV->getType() != GV->getType()->getElementType()) 1063 RepValue = ConstantExpr::getBitCast(RepValue, 1064 GV->getType()->getElementType()); 1065 1066 // If there is a comparison against null, we will insert a global bool to 1067 // keep track of whether the global was initialized yet or not. 1068 GlobalVariable *InitBool = 1069 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false, 1070 GlobalValue::InternalLinkage, 1071 ConstantInt::getFalse(GV->getContext()), 1072 GV->getName()+".init", GV->getThreadLocalMode()); 1073 bool InitBoolUsed = false; 1074 1075 // Loop over all uses of GV, processing them in turn. 1076 while (!GV->use_empty()) { 1077 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) { 1078 // The global is initialized when the store to it occurs. 1079 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0, 1080 SI->getOrdering(), SI->getSynchScope(), SI); 1081 SI->eraseFromParent(); 1082 continue; 1083 } 1084 1085 LoadInst *LI = cast<LoadInst>(GV->use_back()); 1086 while (!LI->use_empty()) { 1087 Use &LoadUse = LI->use_begin().getUse(); 1088 if (!isa<ICmpInst>(LoadUse.getUser())) { 1089 LoadUse = RepValue; 1090 continue; 1091 } 1092 1093 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser()); 1094 // Replace the cmp X, 0 with a use of the bool value. 1095 // Sink the load to where the compare was, if atomic rules allow us to. 1096 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0, 1097 LI->getOrdering(), LI->getSynchScope(), 1098 LI->isUnordered() ? (Instruction*)ICI : LI); 1099 InitBoolUsed = true; 1100 switch (ICI->getPredicate()) { 1101 default: llvm_unreachable("Unknown ICmp Predicate!"); 1102 case ICmpInst::ICMP_ULT: 1103 case ICmpInst::ICMP_SLT: // X < null -> always false 1104 LV = ConstantInt::getFalse(GV->getContext()); 1105 break; 1106 case ICmpInst::ICMP_ULE: 1107 case ICmpInst::ICMP_SLE: 1108 case ICmpInst::ICMP_EQ: 1109 LV = BinaryOperator::CreateNot(LV, "notinit", ICI); 1110 break; 1111 case ICmpInst::ICMP_NE: 1112 case ICmpInst::ICMP_UGE: 1113 case ICmpInst::ICMP_SGE: 1114 case ICmpInst::ICMP_UGT: 1115 case ICmpInst::ICMP_SGT: 1116 break; // no change. 1117 } 1118 ICI->replaceAllUsesWith(LV); 1119 ICI->eraseFromParent(); 1120 } 1121 LI->eraseFromParent(); 1122 } 1123 1124 // If the initialization boolean was used, insert it, otherwise delete it. 1125 if (!InitBoolUsed) { 1126 while (!InitBool->use_empty()) // Delete initializations 1127 cast<StoreInst>(InitBool->use_back())->eraseFromParent(); 1128 delete InitBool; 1129 } else 1130 GV->getParent()->getGlobalList().insert(GV, InitBool); 1131 1132 // Now the GV is dead, nuke it and the malloc.. 1133 GV->eraseFromParent(); 1134 CI->eraseFromParent(); 1135 1136 // To further other optimizations, loop over all users of NewGV and try to 1137 // constant prop them. This will promote GEP instructions with constant 1138 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 1139 ConstantPropUsersOf(NewGV, TD, TLI); 1140 if (RepValue != NewGV) 1141 ConstantPropUsersOf(RepValue, TD, TLI); 1142 1143 return NewGV; 1144 } 1145 1146 /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 1147 /// to make sure that there are no complex uses of V. We permit simple things 1148 /// like dereferencing the pointer, but not storing through the address, unless 1149 /// it is to the specified global. 1150 static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V, 1151 const GlobalVariable *GV, 1152 SmallPtrSet<const PHINode*, 8> &PHIs) { 1153 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); 1154 UI != E; ++UI) { 1155 const Instruction *Inst = cast<Instruction>(*UI); 1156 1157 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) { 1158 continue; // Fine, ignore. 1159 } 1160 1161 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 1162 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 1163 return false; // Storing the pointer itself... bad. 1164 continue; // Otherwise, storing through it, or storing into GV... fine. 1165 } 1166 1167 // Must index into the array and into the struct. 1168 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) { 1169 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs)) 1170 return false; 1171 continue; 1172 } 1173 1174 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) { 1175 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 1176 // cycles. 1177 if (PHIs.insert(PN)) 1178 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 1179 return false; 1180 continue; 1181 } 1182 1183 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) { 1184 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs)) 1185 return false; 1186 continue; 1187 } 1188 1189 return false; 1190 } 1191 return true; 1192 } 1193 1194 /// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 1195 /// somewhere. Transform all uses of the allocation into loads from the 1196 /// global and uses of the resultant pointer. Further, delete the store into 1197 /// GV. This assumes that these value pass the 1198 /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 1199 static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 1200 GlobalVariable *GV) { 1201 while (!Alloc->use_empty()) { 1202 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 1203 Instruction *InsertPt = U; 1204 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1205 // If this is the store of the allocation into the global, remove it. 1206 if (SI->getOperand(1) == GV) { 1207 SI->eraseFromParent(); 1208 continue; 1209 } 1210 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 1211 // Insert the load in the corresponding predecessor, not right before the 1212 // PHI. 1213 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator(); 1214 } else if (isa<BitCastInst>(U)) { 1215 // Must be bitcast between the malloc and store to initialize the global. 1216 ReplaceUsesOfMallocWithGlobal(U, GV); 1217 U->eraseFromParent(); 1218 continue; 1219 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { 1220 // If this is a "GEP bitcast" and the user is a store to the global, then 1221 // just process it as a bitcast. 1222 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse()) 1223 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back())) 1224 if (SI->getOperand(1) == GV) { 1225 // Must be bitcast GEP between the malloc and store to initialize 1226 // the global. 1227 ReplaceUsesOfMallocWithGlobal(GEPI, GV); 1228 GEPI->eraseFromParent(); 1229 continue; 1230 } 1231 } 1232 1233 // Insert a load from the global, and use it instead of the malloc. 1234 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 1235 U->replaceUsesOfWith(Alloc, NL); 1236 } 1237 } 1238 1239 /// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi 1240 /// of a load) are simple enough to perform heap SRA on. This permits GEP's 1241 /// that index through the array and struct field, icmps of null, and PHIs. 1242 static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V, 1243 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs, 1244 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) { 1245 // We permit two users of the load: setcc comparing against the null 1246 // pointer, and a getelementptr of a specific form. 1247 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; 1248 ++UI) { 1249 const Instruction *User = cast<Instruction>(*UI); 1250 1251 // Comparison against null is ok. 1252 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) { 1253 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 1254 return false; 1255 continue; 1256 } 1257 1258 // getelementptr is also ok, but only a simple form. 1259 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1260 // Must index into the array and into the struct. 1261 if (GEPI->getNumOperands() < 3) 1262 return false; 1263 1264 // Otherwise the GEP is ok. 1265 continue; 1266 } 1267 1268 if (const PHINode *PN = dyn_cast<PHINode>(User)) { 1269 if (!LoadUsingPHIsPerLoad.insert(PN)) 1270 // This means some phi nodes are dependent on each other. 1271 // Avoid infinite looping! 1272 return false; 1273 if (!LoadUsingPHIs.insert(PN)) 1274 // If we have already analyzed this PHI, then it is safe. 1275 continue; 1276 1277 // Make sure all uses of the PHI are simple enough to transform. 1278 if (!LoadUsesSimpleEnoughForHeapSRA(PN, 1279 LoadUsingPHIs, LoadUsingPHIsPerLoad)) 1280 return false; 1281 1282 continue; 1283 } 1284 1285 // Otherwise we don't know what this is, not ok. 1286 return false; 1287 } 1288 1289 return true; 1290 } 1291 1292 1293 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 1294 /// GV are simple enough to perform HeapSRA, return true. 1295 static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV, 1296 Instruction *StoredVal) { 1297 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs; 1298 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad; 1299 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end(); 1300 UI != E; ++UI) 1301 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 1302 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs, 1303 LoadUsingPHIsPerLoad)) 1304 return false; 1305 LoadUsingPHIsPerLoad.clear(); 1306 } 1307 1308 // If we reach here, we know that all uses of the loads and transitive uses 1309 // (through PHI nodes) are simple enough to transform. However, we don't know 1310 // that all inputs the to the PHI nodes are in the same equivalence sets. 1311 // Check to verify that all operands of the PHIs are either PHIS that can be 1312 // transformed, loads from GV, or MI itself. 1313 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin() 1314 , E = LoadUsingPHIs.end(); I != E; ++I) { 1315 const PHINode *PN = *I; 1316 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) { 1317 Value *InVal = PN->getIncomingValue(op); 1318 1319 // PHI of the stored value itself is ok. 1320 if (InVal == StoredVal) continue; 1321 1322 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) { 1323 // One of the PHIs in our set is (optimistically) ok. 1324 if (LoadUsingPHIs.count(InPN)) 1325 continue; 1326 return false; 1327 } 1328 1329 // Load from GV is ok. 1330 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal)) 1331 if (LI->getOperand(0) == GV) 1332 continue; 1333 1334 // UNDEF? NULL? 1335 1336 // Anything else is rejected. 1337 return false; 1338 } 1339 } 1340 1341 return true; 1342 } 1343 1344 static Value *GetHeapSROAValue(Value *V, unsigned FieldNo, 1345 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1346 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1347 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V]; 1348 1349 if (FieldNo >= FieldVals.size()) 1350 FieldVals.resize(FieldNo+1); 1351 1352 // If we already have this value, just reuse the previously scalarized 1353 // version. 1354 if (Value *FieldVal = FieldVals[FieldNo]) 1355 return FieldVal; 1356 1357 // Depending on what instruction this is, we have several cases. 1358 Value *Result; 1359 if (LoadInst *LI = dyn_cast<LoadInst>(V)) { 1360 // This is a scalarized version of the load from the global. Just create 1361 // a new Load of the scalarized global. 1362 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo, 1363 InsertedScalarizedValues, 1364 PHIsToRewrite), 1365 LI->getName()+".f"+Twine(FieldNo), LI); 1366 } else if (PHINode *PN = dyn_cast<PHINode>(V)) { 1367 // PN's type is pointer to struct. Make a new PHI of pointer to struct 1368 // field. 1369 StructType *ST = 1370 cast<StructType>(cast<PointerType>(PN->getType())->getElementType()); 1371 1372 PHINode *NewPN = 1373 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)), 1374 PN->getNumIncomingValues(), 1375 PN->getName()+".f"+Twine(FieldNo), PN); 1376 Result = NewPN; 1377 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); 1378 } else { 1379 llvm_unreachable("Unknown usable value"); 1380 } 1381 1382 return FieldVals[FieldNo] = Result; 1383 } 1384 1385 /// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1386 /// the load, rewrite the derived value to use the HeapSRoA'd load. 1387 static void RewriteHeapSROALoadUser(Instruction *LoadUser, 1388 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1389 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1390 // If this is a comparison against null, handle it. 1391 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1392 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1393 // If we have a setcc of the loaded pointer, we can use a setcc of any 1394 // field. 1395 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0, 1396 InsertedScalarizedValues, PHIsToRewrite); 1397 1398 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr, 1399 Constant::getNullValue(NPtr->getType()), 1400 SCI->getName()); 1401 SCI->replaceAllUsesWith(New); 1402 SCI->eraseFromParent(); 1403 return; 1404 } 1405 1406 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...' 1407 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1408 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1409 && "Unexpected GEPI!"); 1410 1411 // Load the pointer for this field. 1412 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1413 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo, 1414 InsertedScalarizedValues, PHIsToRewrite); 1415 1416 // Create the new GEP idx vector. 1417 SmallVector<Value*, 8> GEPIdx; 1418 GEPIdx.push_back(GEPI->getOperand(1)); 1419 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1420 1421 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx, 1422 GEPI->getName(), GEPI); 1423 GEPI->replaceAllUsesWith(NGEPI); 1424 GEPI->eraseFromParent(); 1425 return; 1426 } 1427 1428 // Recursively transform the users of PHI nodes. This will lazily create the 1429 // PHIs that are needed for individual elements. Keep track of what PHIs we 1430 // see in InsertedScalarizedValues so that we don't get infinite loops (very 1431 // antisocial). If the PHI is already in InsertedScalarizedValues, it has 1432 // already been seen first by another load, so its uses have already been 1433 // processed. 1434 PHINode *PN = cast<PHINode>(LoadUser); 1435 if (!InsertedScalarizedValues.insert(std::make_pair(PN, 1436 std::vector<Value*>())).second) 1437 return; 1438 1439 // If this is the first time we've seen this PHI, recursively process all 1440 // users. 1441 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) { 1442 Instruction *User = cast<Instruction>(*UI++); 1443 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); 1444 } 1445 } 1446 1447 /// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1448 /// is a value loaded from the global. Eliminate all uses of Ptr, making them 1449 /// use FieldGlobals instead. All uses of loaded values satisfy 1450 /// AllGlobalLoadUsesSimpleEnoughForHeapSRA. 1451 static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1452 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1453 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1454 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end(); 1455 UI != E; ) { 1456 Instruction *User = cast<Instruction>(*UI++); 1457 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); 1458 } 1459 1460 if (Load->use_empty()) { 1461 Load->eraseFromParent(); 1462 InsertedScalarizedValues.erase(Load); 1463 } 1464 } 1465 1466 /// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break 1467 /// it up into multiple allocations of arrays of the fields. 1468 static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI, 1469 Value *NElems, TargetData *TD, 1470 const TargetLibraryInfo *TLI) { 1471 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n'); 1472 Type *MAT = getMallocAllocatedType(CI, TLI); 1473 StructType *STy = cast<StructType>(MAT); 1474 1475 // There is guaranteed to be at least one use of the malloc (storing 1476 // it into GV). If there are other uses, change them to be uses of 1477 // the global to simplify later code. This also deletes the store 1478 // into GV. 1479 ReplaceUsesOfMallocWithGlobal(CI, GV); 1480 1481 // Okay, at this point, there are no users of the malloc. Insert N 1482 // new mallocs at the same place as CI, and N globals. 1483 std::vector<Value*> FieldGlobals; 1484 std::vector<Value*> FieldMallocs; 1485 1486 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1487 Type *FieldTy = STy->getElementType(FieldNo); 1488 PointerType *PFieldTy = PointerType::getUnqual(FieldTy); 1489 1490 GlobalVariable *NGV = 1491 new GlobalVariable(*GV->getParent(), 1492 PFieldTy, false, GlobalValue::InternalLinkage, 1493 Constant::getNullValue(PFieldTy), 1494 GV->getName() + ".f" + Twine(FieldNo), GV, 1495 GV->getThreadLocalMode()); 1496 FieldGlobals.push_back(NGV); 1497 1498 unsigned TypeSize = TD->getTypeAllocSize(FieldTy); 1499 if (StructType *ST = dyn_cast<StructType>(FieldTy)) 1500 TypeSize = TD->getStructLayout(ST)->getSizeInBytes(); 1501 Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); 1502 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, 1503 ConstantInt::get(IntPtrTy, TypeSize), 1504 NElems, 0, 1505 CI->getName() + ".f" + Twine(FieldNo)); 1506 FieldMallocs.push_back(NMI); 1507 new StoreInst(NMI, NGV, CI); 1508 } 1509 1510 // The tricky aspect of this transformation is handling the case when malloc 1511 // fails. In the original code, malloc failing would set the result pointer 1512 // of malloc to null. In this case, some mallocs could succeed and others 1513 // could fail. As such, we emit code that looks like this: 1514 // F0 = malloc(field0) 1515 // F1 = malloc(field1) 1516 // F2 = malloc(field2) 1517 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1518 // if (F0) { free(F0); F0 = 0; } 1519 // if (F1) { free(F1); F1 = 0; } 1520 // if (F2) { free(F2); F2 = 0; } 1521 // } 1522 // The malloc can also fail if its argument is too large. 1523 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0); 1524 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0), 1525 ConstantZero, "isneg"); 1526 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1527 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i], 1528 Constant::getNullValue(FieldMallocs[i]->getType()), 1529 "isnull"); 1530 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI); 1531 } 1532 1533 // Split the basic block at the old malloc. 1534 BasicBlock *OrigBB = CI->getParent(); 1535 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont"); 1536 1537 // Create the block to check the first condition. Put all these blocks at the 1538 // end of the function as they are unlikely to be executed. 1539 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(), 1540 "malloc_ret_null", 1541 OrigBB->getParent()); 1542 1543 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1544 // branch on RunningOr. 1545 OrigBB->getTerminator()->eraseFromParent(); 1546 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); 1547 1548 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1549 // pointer, because some may be null while others are not. 1550 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1551 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1552 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal, 1553 Constant::getNullValue(GVVal->getType())); 1554 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it", 1555 OrigBB->getParent()); 1556 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next", 1557 OrigBB->getParent()); 1558 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock, 1559 Cmp, NullPtrBlock); 1560 1561 // Fill in FreeBlock. 1562 CallInst::CreateFree(GVVal, BI); 1563 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1564 FreeBlock); 1565 BranchInst::Create(NextBlock, FreeBlock); 1566 1567 NullPtrBlock = NextBlock; 1568 } 1569 1570 BranchInst::Create(ContBB, NullPtrBlock); 1571 1572 // CI is no longer needed, remove it. 1573 CI->eraseFromParent(); 1574 1575 /// InsertedScalarizedLoads - As we process loads, if we can't immediately 1576 /// update all uses of the load, keep track of what scalarized loads are 1577 /// inserted for a given load. 1578 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues; 1579 InsertedScalarizedValues[GV] = FieldGlobals; 1580 1581 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite; 1582 1583 // Okay, the malloc site is completely handled. All of the uses of GV are now 1584 // loads, and all uses of those loads are simple. Rewrite them to use loads 1585 // of the per-field globals instead. 1586 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) { 1587 Instruction *User = cast<Instruction>(*UI++); 1588 1589 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1590 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite); 1591 continue; 1592 } 1593 1594 // Must be a store of null. 1595 StoreInst *SI = cast<StoreInst>(User); 1596 assert(isa<ConstantPointerNull>(SI->getOperand(0)) && 1597 "Unexpected heap-sra user!"); 1598 1599 // Insert a store of null into each global. 1600 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1601 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType()); 1602 Constant *Null = Constant::getNullValue(PT->getElementType()); 1603 new StoreInst(Null, FieldGlobals[i], SI); 1604 } 1605 // Erase the original store. 1606 SI->eraseFromParent(); 1607 } 1608 1609 // While we have PHIs that are interesting to rewrite, do it. 1610 while (!PHIsToRewrite.empty()) { 1611 PHINode *PN = PHIsToRewrite.back().first; 1612 unsigned FieldNo = PHIsToRewrite.back().second; 1613 PHIsToRewrite.pop_back(); 1614 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]); 1615 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi"); 1616 1617 // Add all the incoming values. This can materialize more phis. 1618 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1619 Value *InVal = PN->getIncomingValue(i); 1620 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues, 1621 PHIsToRewrite); 1622 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i)); 1623 } 1624 } 1625 1626 // Drop all inter-phi links and any loads that made it this far. 1627 for (DenseMap<Value*, std::vector<Value*> >::iterator 1628 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); 1629 I != E; ++I) { 1630 if (PHINode *PN = dyn_cast<PHINode>(I->first)) 1631 PN->dropAllReferences(); 1632 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) 1633 LI->dropAllReferences(); 1634 } 1635 1636 // Delete all the phis and loads now that inter-references are dead. 1637 for (DenseMap<Value*, std::vector<Value*> >::iterator 1638 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); 1639 I != E; ++I) { 1640 if (PHINode *PN = dyn_cast<PHINode>(I->first)) 1641 PN->eraseFromParent(); 1642 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) 1643 LI->eraseFromParent(); 1644 } 1645 1646 // The old global is now dead, remove it. 1647 GV->eraseFromParent(); 1648 1649 ++NumHeapSRA; 1650 return cast<GlobalVariable>(FieldGlobals[0]); 1651 } 1652 1653 /// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a 1654 /// pointer global variable with a single value stored it that is a malloc or 1655 /// cast of malloc. 1656 static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV, 1657 CallInst *CI, 1658 Type *AllocTy, 1659 AtomicOrdering Ordering, 1660 Module::global_iterator &GVI, 1661 TargetData *TD, 1662 TargetLibraryInfo *TLI) { 1663 if (!TD) 1664 return false; 1665 1666 // If this is a malloc of an abstract type, don't touch it. 1667 if (!AllocTy->isSized()) 1668 return false; 1669 1670 // We can't optimize this global unless all uses of it are *known* to be 1671 // of the malloc value, not of the null initializer value (consider a use 1672 // that compares the global's value against zero to see if the malloc has 1673 // been reached). To do this, we check to see if all uses of the global 1674 // would trap if the global were null: this proves that they must all 1675 // happen after the malloc. 1676 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1677 return false; 1678 1679 // We can't optimize this if the malloc itself is used in a complex way, 1680 // for example, being stored into multiple globals. This allows the 1681 // malloc to be stored into the specified global, loaded icmp'd, and 1682 // GEP'd. These are all things we could transform to using the global 1683 // for. 1684 SmallPtrSet<const PHINode*, 8> PHIs; 1685 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs)) 1686 return false; 1687 1688 // If we have a global that is only initialized with a fixed size malloc, 1689 // transform the program to use global memory instead of malloc'd memory. 1690 // This eliminates dynamic allocation, avoids an indirection accessing the 1691 // data, and exposes the resultant global to further GlobalOpt. 1692 // We cannot optimize the malloc if we cannot determine malloc array size. 1693 Value *NElems = getMallocArraySize(CI, TD, TLI, true); 1694 if (!NElems) 1695 return false; 1696 1697 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) 1698 // Restrict this transformation to only working on small allocations 1699 // (2048 bytes currently), as we don't want to introduce a 16M global or 1700 // something. 1701 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) { 1702 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI); 1703 return true; 1704 } 1705 1706 // If the allocation is an array of structures, consider transforming this 1707 // into multiple malloc'd arrays, one for each field. This is basically 1708 // SRoA for malloc'd memory. 1709 1710 if (Ordering != NotAtomic) 1711 return false; 1712 1713 // If this is an allocation of a fixed size array of structs, analyze as a 1714 // variable size array. malloc [100 x struct],1 -> malloc struct, 100 1715 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1)) 1716 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy)) 1717 AllocTy = AT->getElementType(); 1718 1719 StructType *AllocSTy = dyn_cast<StructType>(AllocTy); 1720 if (!AllocSTy) 1721 return false; 1722 1723 // This the structure has an unreasonable number of fields, leave it 1724 // alone. 1725 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 && 1726 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) { 1727 1728 // If this is a fixed size array, transform the Malloc to be an alloc of 1729 // structs. malloc [100 x struct],1 -> malloc struct, 100 1730 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) { 1731 Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); 1732 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes(); 1733 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); 1734 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); 1735 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, 1736 AllocSize, NumElements, 1737 0, CI->getName()); 1738 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI); 1739 CI->replaceAllUsesWith(Cast); 1740 CI->eraseFromParent(); 1741 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc)) 1742 CI = cast<CallInst>(BCI->getOperand(0)); 1743 else 1744 CI = cast<CallInst>(Malloc); 1745 } 1746 1747 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true), 1748 TD, TLI); 1749 return true; 1750 } 1751 1752 return false; 1753 } 1754 1755 // OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1756 // that only one value (besides its initializer) is ever stored to the global. 1757 static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1758 AtomicOrdering Ordering, 1759 Module::global_iterator &GVI, 1760 TargetData *TD, TargetLibraryInfo *TLI) { 1761 // Ignore no-op GEPs and bitcasts. 1762 StoredOnceVal = StoredOnceVal->stripPointerCasts(); 1763 1764 // If we are dealing with a pointer global that is initialized to null and 1765 // only has one (non-null) value stored into it, then we can optimize any 1766 // users of the loaded value (often calls and loads) that would trap if the 1767 // value was null. 1768 if (GV->getInitializer()->getType()->isPointerTy() && 1769 GV->getInitializer()->isNullValue()) { 1770 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1771 if (GV->getInitializer()->getType() != SOVC->getType()) 1772 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1773 1774 // Optimize away any trapping uses of the loaded value. 1775 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI)) 1776 return true; 1777 } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) { 1778 Type *MallocType = getMallocAllocatedType(CI, TLI); 1779 if (MallocType && 1780 TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI, 1781 TD, TLI)) 1782 return true; 1783 } 1784 } 1785 1786 return false; 1787 } 1788 1789 /// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1790 /// two values ever stored into GV are its initializer and OtherVal. See if we 1791 /// can shrink the global into a boolean and select between the two values 1792 /// whenever it is used. This exposes the values to other scalar optimizations. 1793 static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1794 Type *GVElType = GV->getType()->getElementType(); 1795 1796 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1797 // an FP value, pointer or vector, don't do this optimization because a select 1798 // between them is very expensive and unlikely to lead to later 1799 // simplification. In these cases, we typically end up with "cond ? v1 : v2" 1800 // where v1 and v2 both require constant pool loads, a big loss. 1801 if (GVElType == Type::getInt1Ty(GV->getContext()) || 1802 GVElType->isFloatingPointTy() || 1803 GVElType->isPointerTy() || GVElType->isVectorTy()) 1804 return false; 1805 1806 // Walk the use list of the global seeing if all the uses are load or store. 1807 // If there is anything else, bail out. 1808 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){ 1809 User *U = *I; 1810 if (!isa<LoadInst>(U) && !isa<StoreInst>(U)) 1811 return false; 1812 } 1813 1814 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV); 1815 1816 // Create the new global, initializing it to false. 1817 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()), 1818 false, 1819 GlobalValue::InternalLinkage, 1820 ConstantInt::getFalse(GV->getContext()), 1821 GV->getName()+".b", 1822 GV->getThreadLocalMode()); 1823 GV->getParent()->getGlobalList().insert(GV, NewGV); 1824 1825 Constant *InitVal = GV->getInitializer(); 1826 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && 1827 "No reason to shrink to bool!"); 1828 1829 // If initialized to zero and storing one into the global, we can use a cast 1830 // instead of a select to synthesize the desired value. 1831 bool IsOneZero = false; 1832 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1833 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1834 1835 while (!GV->use_empty()) { 1836 Instruction *UI = cast<Instruction>(GV->use_back()); 1837 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1838 // Change the store into a boolean store. 1839 bool StoringOther = SI->getOperand(0) == OtherVal; 1840 // Only do this if we weren't storing a loaded value. 1841 Value *StoreVal; 1842 if (StoringOther || SI->getOperand(0) == InitVal) 1843 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()), 1844 StoringOther); 1845 else { 1846 // Otherwise, we are storing a previously loaded copy. To do this, 1847 // change the copy from copying the original value to just copying the 1848 // bool. 1849 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1850 1851 // If we've already replaced the input, StoredVal will be a cast or 1852 // select instruction. If not, it will be a load of the original 1853 // global. 1854 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1855 assert(LI->getOperand(0) == GV && "Not a copy!"); 1856 // Insert a new load, to preserve the saved value. 1857 StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0, 1858 LI->getOrdering(), LI->getSynchScope(), LI); 1859 } else { 1860 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1861 "This is not a form that we understand!"); 1862 StoreVal = StoredVal->getOperand(0); 1863 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1864 } 1865 } 1866 new StoreInst(StoreVal, NewGV, false, 0, 1867 SI->getOrdering(), SI->getSynchScope(), SI); 1868 } else { 1869 // Change the load into a load of bool then a select. 1870 LoadInst *LI = cast<LoadInst>(UI); 1871 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0, 1872 LI->getOrdering(), LI->getSynchScope(), LI); 1873 Value *NSI; 1874 if (IsOneZero) 1875 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1876 else 1877 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); 1878 NSI->takeName(LI); 1879 LI->replaceAllUsesWith(NSI); 1880 } 1881 UI->eraseFromParent(); 1882 } 1883 1884 GV->eraseFromParent(); 1885 return true; 1886 } 1887 1888 1889 /// ProcessGlobal - Analyze the specified global variable and optimize it if 1890 /// possible. If we make a change, return true. 1891 bool GlobalOpt::ProcessGlobal(GlobalVariable *GV, 1892 Module::global_iterator &GVI) { 1893 if (!GV->isDiscardableIfUnused()) 1894 return false; 1895 1896 // Do more involved optimizations if the global is internal. 1897 GV->removeDeadConstantUsers(); 1898 1899 if (GV->use_empty()) { 1900 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV); 1901 GV->eraseFromParent(); 1902 ++NumDeleted; 1903 return true; 1904 } 1905 1906 if (!GV->hasLocalLinkage()) 1907 return false; 1908 1909 SmallPtrSet<const PHINode*, 16> PHIUsers; 1910 GlobalStatus GS; 1911 1912 if (AnalyzeGlobal(GV, GS, PHIUsers)) 1913 return false; 1914 1915 if (!GS.isCompared && !GV->hasUnnamedAddr()) { 1916 GV->setUnnamedAddr(true); 1917 NumUnnamed++; 1918 } 1919 1920 if (GV->isConstant() || !GV->hasInitializer()) 1921 return false; 1922 1923 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS); 1924 } 1925 1926 /// ProcessInternalGlobal - Analyze the specified global variable and optimize 1927 /// it if possible. If we make a change, return true. 1928 bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1929 Module::global_iterator &GVI, 1930 const SmallPtrSet<const PHINode*, 16> &PHIUsers, 1931 const GlobalStatus &GS) { 1932 // If this is a first class global and has only one accessing function 1933 // and this function is main (which we know is not recursive we can make 1934 // this global a local variable) we replace the global with a local alloca 1935 // in this function. 1936 // 1937 // NOTE: It doesn't make sense to promote non single-value types since we 1938 // are just replacing static memory to stack memory. 1939 // 1940 // If the global is in different address space, don't bring it to stack. 1941 if (!GS.HasMultipleAccessingFunctions && 1942 GS.AccessingFunction && !GS.HasNonInstructionUser && 1943 GV->getType()->getElementType()->isSingleValueType() && 1944 GS.AccessingFunction->getName() == "main" && 1945 GS.AccessingFunction->hasExternalLinkage() && 1946 GV->getType()->getAddressSpace() == 0) { 1947 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV); 1948 Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction 1949 ->getEntryBlock().begin()); 1950 Type *ElemTy = GV->getType()->getElementType(); 1951 // FIXME: Pass Global's alignment when globals have alignment 1952 AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI); 1953 if (!isa<UndefValue>(GV->getInitializer())) 1954 new StoreInst(GV->getInitializer(), Alloca, &FirstI); 1955 1956 GV->replaceAllUsesWith(Alloca); 1957 GV->eraseFromParent(); 1958 ++NumLocalized; 1959 return true; 1960 } 1961 1962 // If the global is never loaded (but may be stored to), it is dead. 1963 // Delete it now. 1964 if (!GS.isLoaded) { 1965 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV); 1966 1967 bool Changed; 1968 if (isLeakCheckerRoot(GV)) { 1969 // Delete any constant stores to the global. 1970 Changed = CleanupPointerRootUsers(GV, TLI); 1971 } else { 1972 // Delete any stores we can find to the global. We may not be able to 1973 // make it completely dead though. 1974 Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 1975 } 1976 1977 // If the global is dead now, delete it. 1978 if (GV->use_empty()) { 1979 GV->eraseFromParent(); 1980 ++NumDeleted; 1981 Changed = true; 1982 } 1983 return Changed; 1984 1985 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1986 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV); 1987 GV->setConstant(true); 1988 1989 // Clean up any obviously simplifiable users now. 1990 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 1991 1992 // If the global is dead now, just nuke it. 1993 if (GV->use_empty()) { 1994 DEBUG(dbgs() << " *** Marking constant allowed us to simplify " 1995 << "all users and delete global!\n"); 1996 GV->eraseFromParent(); 1997 ++NumDeleted; 1998 } 1999 2000 ++NumMarked; 2001 return true; 2002 } else if (!GV->getInitializer()->getType()->isSingleValueType()) { 2003 if (TargetData *TD = getAnalysisIfAvailable<TargetData>()) 2004 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) { 2005 GVI = FirstNewGV; // Don't skip the newly produced globals! 2006 return true; 2007 } 2008 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 2009 // If the initial value for the global was an undef value, and if only 2010 // one other value was stored into it, we can just change the 2011 // initializer to be the stored value, then delete all stores to the 2012 // global. This allows us to mark it constant. 2013 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 2014 if (isa<UndefValue>(GV->getInitializer())) { 2015 // Change the initial value here. 2016 GV->setInitializer(SOVConstant); 2017 2018 // Clean up any obviously simplifiable users now. 2019 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 2020 2021 if (GV->use_empty()) { 2022 DEBUG(dbgs() << " *** Substituting initializer allowed us to " 2023 << "simplify all users and delete global!\n"); 2024 GV->eraseFromParent(); 2025 ++NumDeleted; 2026 } else { 2027 GVI = GV; 2028 } 2029 ++NumSubstitute; 2030 return true; 2031 } 2032 2033 // Try to optimize globals based on the knowledge that only one value 2034 // (besides its initializer) is ever stored to the global. 2035 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI, 2036 TD, TLI)) 2037 return true; 2038 2039 // Otherwise, if the global was not a boolean, we can shrink it to be a 2040 // boolean. 2041 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 2042 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 2043 ++NumShrunkToBool; 2044 return true; 2045 } 2046 } 2047 2048 return false; 2049 } 2050 2051 /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 2052 /// function, changing them to FastCC. 2053 static void ChangeCalleesToFastCall(Function *F) { 2054 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 2055 if (isa<BlockAddress>(*UI)) 2056 continue; 2057 CallSite User(cast<Instruction>(*UI)); 2058 User.setCallingConv(CallingConv::Fast); 2059 } 2060 } 2061 2062 static AttrListPtr StripNest(const AttrListPtr &Attrs) { 2063 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { 2064 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0) 2065 continue; 2066 2067 // There can be only one. 2068 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest); 2069 } 2070 2071 return Attrs; 2072 } 2073 2074 static void RemoveNestAttribute(Function *F) { 2075 F->setAttributes(StripNest(F->getAttributes())); 2076 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 2077 if (isa<BlockAddress>(*UI)) 2078 continue; 2079 CallSite User(cast<Instruction>(*UI)); 2080 User.setAttributes(StripNest(User.getAttributes())); 2081 } 2082 } 2083 2084 bool GlobalOpt::OptimizeFunctions(Module &M) { 2085 bool Changed = false; 2086 // Optimize functions. 2087 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 2088 Function *F = FI++; 2089 // Functions without names cannot be referenced outside this module. 2090 if (!F->hasName() && !F->isDeclaration()) 2091 F->setLinkage(GlobalValue::InternalLinkage); 2092 F->removeDeadConstantUsers(); 2093 if (F->isDefTriviallyDead()) { 2094 F->eraseFromParent(); 2095 Changed = true; 2096 ++NumFnDeleted; 2097 } else if (F->hasLocalLinkage()) { 2098 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 2099 !F->hasAddressTaken()) { 2100 // If this function has C calling conventions, is not a varargs 2101 // function, and is only called directly, promote it to use the Fast 2102 // calling convention. 2103 F->setCallingConv(CallingConv::Fast); 2104 ChangeCalleesToFastCall(F); 2105 ++NumFastCallFns; 2106 Changed = true; 2107 } 2108 2109 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) && 2110 !F->hasAddressTaken()) { 2111 // The function is not used by a trampoline intrinsic, so it is safe 2112 // to remove the 'nest' attribute. 2113 RemoveNestAttribute(F); 2114 ++NumNestRemoved; 2115 Changed = true; 2116 } 2117 } 2118 } 2119 return Changed; 2120 } 2121 2122 bool GlobalOpt::OptimizeGlobalVars(Module &M) { 2123 bool Changed = false; 2124 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 2125 GVI != E; ) { 2126 GlobalVariable *GV = GVI++; 2127 // Global variables without names cannot be referenced outside this module. 2128 if (!GV->hasName() && !GV->isDeclaration()) 2129 GV->setLinkage(GlobalValue::InternalLinkage); 2130 // Simplify the initializer. 2131 if (GV->hasInitializer()) 2132 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) { 2133 Constant *New = ConstantFoldConstantExpression(CE, TD, TLI); 2134 if (New && New != CE) 2135 GV->setInitializer(New); 2136 } 2137 2138 Changed |= ProcessGlobal(GV, GVI); 2139 } 2140 return Changed; 2141 } 2142 2143 /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all 2144 /// initializers have an init priority of 65535. 2145 GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 2146 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); 2147 if (GV == 0) return 0; 2148 2149 // Verify that the initializer is simple enough for us to handle. We are 2150 // only allowed to optimize the initializer if it is unique. 2151 if (!GV->hasUniqueInitializer()) return 0; 2152 2153 if (isa<ConstantAggregateZero>(GV->getInitializer())) 2154 return GV; 2155 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 2156 2157 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { 2158 if (isa<ConstantAggregateZero>(*i)) 2159 continue; 2160 ConstantStruct *CS = cast<ConstantStruct>(*i); 2161 if (isa<ConstantPointerNull>(CS->getOperand(1))) 2162 continue; 2163 2164 // Must have a function or null ptr. 2165 if (!isa<Function>(CS->getOperand(1))) 2166 return 0; 2167 2168 // Init priority must be standard. 2169 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0)); 2170 if (CI->getZExtValue() != 65535) 2171 return 0; 2172 } 2173 2174 return GV; 2175 } 2176 2177 /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 2178 /// return a list of the functions and null terminator as a vector. 2179 static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 2180 if (GV->getInitializer()->isNullValue()) 2181 return std::vector<Function*>(); 2182 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 2183 std::vector<Function*> Result; 2184 Result.reserve(CA->getNumOperands()); 2185 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { 2186 ConstantStruct *CS = cast<ConstantStruct>(*i); 2187 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 2188 } 2189 return Result; 2190 } 2191 2192 /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 2193 /// specified array, returning the new global to use. 2194 static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 2195 const std::vector<Function*> &Ctors) { 2196 // If we made a change, reassemble the initializer list. 2197 Constant *CSVals[2]; 2198 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535); 2199 CSVals[1] = 0; 2200 2201 StructType *StructTy = 2202 cast <StructType>( 2203 cast<ArrayType>(GCL->getType()->getElementType())->getElementType()); 2204 2205 // Create the new init list. 2206 std::vector<Constant*> CAList; 2207 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 2208 if (Ctors[i]) { 2209 CSVals[1] = Ctors[i]; 2210 } else { 2211 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()), 2212 false); 2213 PointerType *PFTy = PointerType::getUnqual(FTy); 2214 CSVals[1] = Constant::getNullValue(PFTy); 2215 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 2216 0x7fffffff); 2217 } 2218 CAList.push_back(ConstantStruct::get(StructTy, CSVals)); 2219 } 2220 2221 // Create the array initializer. 2222 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, 2223 CAList.size()), CAList); 2224 2225 // If we didn't change the number of elements, don't create a new GV. 2226 if (CA->getType() == GCL->getInitializer()->getType()) { 2227 GCL->setInitializer(CA); 2228 return GCL; 2229 } 2230 2231 // Create the new global and insert it next to the existing list. 2232 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 2233 GCL->getLinkage(), CA, "", 2234 GCL->getThreadLocalMode()); 2235 GCL->getParent()->getGlobalList().insert(GCL, NGV); 2236 NGV->takeName(GCL); 2237 2238 // Nuke the old list, replacing any uses with the new one. 2239 if (!GCL->use_empty()) { 2240 Constant *V = NGV; 2241 if (V->getType() != GCL->getType()) 2242 V = ConstantExpr::getBitCast(V, GCL->getType()); 2243 GCL->replaceAllUsesWith(V); 2244 } 2245 GCL->eraseFromParent(); 2246 2247 if (Ctors.size()) 2248 return NGV; 2249 else 2250 return 0; 2251 } 2252 2253 2254 static inline bool 2255 isSimpleEnoughValueToCommit(Constant *C, 2256 SmallPtrSet<Constant*, 8> &SimpleConstants, 2257 const TargetData *TD); 2258 2259 2260 /// isSimpleEnoughValueToCommit - Return true if the specified constant can be 2261 /// handled by the code generator. We don't want to generate something like: 2262 /// void *X = &X/42; 2263 /// because the code generator doesn't have a relocation that can handle that. 2264 /// 2265 /// This function should be called if C was not found (but just got inserted) 2266 /// in SimpleConstants to avoid having to rescan the same constants all the 2267 /// time. 2268 static bool isSimpleEnoughValueToCommitHelper(Constant *C, 2269 SmallPtrSet<Constant*, 8> &SimpleConstants, 2270 const TargetData *TD) { 2271 // Simple integer, undef, constant aggregate zero, global addresses, etc are 2272 // all supported. 2273 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) || 2274 isa<GlobalValue>(C)) 2275 return true; 2276 2277 // Aggregate values are safe if all their elements are. 2278 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) || 2279 isa<ConstantVector>(C)) { 2280 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) { 2281 Constant *Op = cast<Constant>(C->getOperand(i)); 2282 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD)) 2283 return false; 2284 } 2285 return true; 2286 } 2287 2288 // We don't know exactly what relocations are allowed in constant expressions, 2289 // so we allow &global+constantoffset, which is safe and uniformly supported 2290 // across targets. 2291 ConstantExpr *CE = cast<ConstantExpr>(C); 2292 switch (CE->getOpcode()) { 2293 case Instruction::BitCast: 2294 // Bitcast is fine if the casted value is fine. 2295 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2296 2297 case Instruction::IntToPtr: 2298 case Instruction::PtrToInt: 2299 // int <=> ptr is fine if the int type is the same size as the 2300 // pointer type. 2301 if (!TD || TD->getTypeSizeInBits(CE->getType()) != 2302 TD->getTypeSizeInBits(CE->getOperand(0)->getType())) 2303 return false; 2304 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2305 2306 // GEP is fine if it is simple + constant offset. 2307 case Instruction::GetElementPtr: 2308 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 2309 if (!isa<ConstantInt>(CE->getOperand(i))) 2310 return false; 2311 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2312 2313 case Instruction::Add: 2314 // We allow simple+cst. 2315 if (!isa<ConstantInt>(CE->getOperand(1))) 2316 return false; 2317 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2318 } 2319 return false; 2320 } 2321 2322 static inline bool 2323 isSimpleEnoughValueToCommit(Constant *C, 2324 SmallPtrSet<Constant*, 8> &SimpleConstants, 2325 const TargetData *TD) { 2326 // If we already checked this constant, we win. 2327 if (!SimpleConstants.insert(C)) return true; 2328 // Check the constant. 2329 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD); 2330 } 2331 2332 2333 /// isSimpleEnoughPointerToCommit - Return true if this constant is simple 2334 /// enough for us to understand. In particular, if it is a cast to anything 2335 /// other than from one pointer type to another pointer type, we punt. 2336 /// We basically just support direct accesses to globals and GEP's of 2337 /// globals. This should be kept up to date with CommitValueTo. 2338 static bool isSimpleEnoughPointerToCommit(Constant *C) { 2339 // Conservatively, avoid aggregate types. This is because we don't 2340 // want to worry about them partially overlapping other stores. 2341 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType()) 2342 return false; 2343 2344 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 2345 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2346 // external globals. 2347 return GV->hasUniqueInitializer(); 2348 2349 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 2350 // Handle a constantexpr gep. 2351 if (CE->getOpcode() == Instruction::GetElementPtr && 2352 isa<GlobalVariable>(CE->getOperand(0)) && 2353 cast<GEPOperator>(CE)->isInBounds()) { 2354 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2355 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2356 // external globals. 2357 if (!GV->hasUniqueInitializer()) 2358 return false; 2359 2360 // The first index must be zero. 2361 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin())); 2362 if (!CI || !CI->isZero()) return false; 2363 2364 // The remaining indices must be compile-time known integers within the 2365 // notional bounds of the corresponding static array types. 2366 if (!CE->isGEPWithNoNotionalOverIndexing()) 2367 return false; 2368 2369 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 2370 2371 // A constantexpr bitcast from a pointer to another pointer is a no-op, 2372 // and we know how to evaluate it by moving the bitcast from the pointer 2373 // operand to the value operand. 2374 } else if (CE->getOpcode() == Instruction::BitCast && 2375 isa<GlobalVariable>(CE->getOperand(0))) { 2376 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2377 // external globals. 2378 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer(); 2379 } 2380 } 2381 2382 return false; 2383 } 2384 2385 /// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 2386 /// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 2387 /// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 2388 static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 2389 ConstantExpr *Addr, unsigned OpNo) { 2390 // Base case of the recursion. 2391 if (OpNo == Addr->getNumOperands()) { 2392 assert(Val->getType() == Init->getType() && "Type mismatch!"); 2393 return Val; 2394 } 2395 2396 SmallVector<Constant*, 32> Elts; 2397 if (StructType *STy = dyn_cast<StructType>(Init->getType())) { 2398 // Break up the constant into its elements. 2399 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 2400 Elts.push_back(Init->getAggregateElement(i)); 2401 2402 // Replace the element that we are supposed to. 2403 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 2404 unsigned Idx = CU->getZExtValue(); 2405 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 2406 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 2407 2408 // Return the modified struct. 2409 return ConstantStruct::get(STy, Elts); 2410 } 2411 2412 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 2413 SequentialType *InitTy = cast<SequentialType>(Init->getType()); 2414 2415 uint64_t NumElts; 2416 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy)) 2417 NumElts = ATy->getNumElements(); 2418 else 2419 NumElts = InitTy->getVectorNumElements(); 2420 2421 // Break up the array into elements. 2422 for (uint64_t i = 0, e = NumElts; i != e; ++i) 2423 Elts.push_back(Init->getAggregateElement(i)); 2424 2425 assert(CI->getZExtValue() < NumElts); 2426 Elts[CI->getZExtValue()] = 2427 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 2428 2429 if (Init->getType()->isArrayTy()) 2430 return ConstantArray::get(cast<ArrayType>(InitTy), Elts); 2431 return ConstantVector::get(Elts); 2432 } 2433 2434 /// CommitValueTo - We have decided that Addr (which satisfies the predicate 2435 /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 2436 static void CommitValueTo(Constant *Val, Constant *Addr) { 2437 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 2438 assert(GV->hasInitializer()); 2439 GV->setInitializer(Val); 2440 return; 2441 } 2442 2443 ConstantExpr *CE = cast<ConstantExpr>(Addr); 2444 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2445 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2)); 2446 } 2447 2448 namespace { 2449 2450 /// Evaluator - This class evaluates LLVM IR, producing the Constant 2451 /// representing each SSA instruction. Changes to global variables are stored 2452 /// in a mapping that can be iterated over after the evaluation is complete. 2453 /// Once an evaluation call fails, the evaluation object should not be reused. 2454 class Evaluator { 2455 public: 2456 Evaluator(const TargetData *TD, const TargetLibraryInfo *TLI) 2457 : TD(TD), TLI(TLI) { 2458 ValueStack.push_back(new DenseMap<Value*, Constant*>); 2459 } 2460 2461 ~Evaluator() { 2462 DeleteContainerPointers(ValueStack); 2463 while (!AllocaTmps.empty()) { 2464 GlobalVariable *Tmp = AllocaTmps.back(); 2465 AllocaTmps.pop_back(); 2466 2467 // If there are still users of the alloca, the program is doing something 2468 // silly, e.g. storing the address of the alloca somewhere and using it 2469 // later. Since this is undefined, we'll just make it be null. 2470 if (!Tmp->use_empty()) 2471 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2472 delete Tmp; 2473 } 2474 } 2475 2476 /// EvaluateFunction - Evaluate a call to function F, returning true if 2477 /// successful, false if we can't evaluate it. ActualArgs contains the formal 2478 /// arguments for the function. 2479 bool EvaluateFunction(Function *F, Constant *&RetVal, 2480 const SmallVectorImpl<Constant*> &ActualArgs); 2481 2482 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if 2483 /// successful, false if we can't evaluate it. NewBB returns the next BB that 2484 /// control flows into, or null upon return. 2485 bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB); 2486 2487 Constant *getVal(Value *V) { 2488 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 2489 Constant *R = ValueStack.back()->lookup(V); 2490 assert(R && "Reference to an uncomputed value!"); 2491 return R; 2492 } 2493 2494 void setVal(Value *V, Constant *C) { 2495 ValueStack.back()->operator[](V) = C; 2496 } 2497 2498 const DenseMap<Constant*, Constant*> &getMutatedMemory() const { 2499 return MutatedMemory; 2500 } 2501 2502 const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const { 2503 return Invariants; 2504 } 2505 2506 private: 2507 Constant *ComputeLoadResult(Constant *P); 2508 2509 /// ValueStack - As we compute SSA register values, we store their contents 2510 /// here. The back of the vector contains the current function and the stack 2511 /// contains the values in the calling frames. 2512 SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack; 2513 2514 /// CallStack - This is used to detect recursion. In pathological situations 2515 /// we could hit exponential behavior, but at least there is nothing 2516 /// unbounded. 2517 SmallVector<Function*, 4> CallStack; 2518 2519 /// MutatedMemory - For each store we execute, we update this map. Loads 2520 /// check this to get the most up-to-date value. If evaluation is successful, 2521 /// this state is committed to the process. 2522 DenseMap<Constant*, Constant*> MutatedMemory; 2523 2524 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2525 /// to represent its body. This vector is needed so we can delete the 2526 /// temporary globals when we are done. 2527 SmallVector<GlobalVariable*, 32> AllocaTmps; 2528 2529 /// Invariants - These global variables have been marked invariant by the 2530 /// static constructor. 2531 SmallPtrSet<GlobalVariable*, 8> Invariants; 2532 2533 /// SimpleConstants - These are constants we have checked and know to be 2534 /// simple enough to live in a static initializer of a global. 2535 SmallPtrSet<Constant*, 8> SimpleConstants; 2536 2537 const TargetData *TD; 2538 const TargetLibraryInfo *TLI; 2539 }; 2540 2541 } // anonymous namespace 2542 2543 /// ComputeLoadResult - Return the value that would be computed by a load from 2544 /// P after the stores reflected by 'memory' have been performed. If we can't 2545 /// decide, return null. 2546 Constant *Evaluator::ComputeLoadResult(Constant *P) { 2547 // If this memory location has been recently stored, use the stored value: it 2548 // is the most up-to-date. 2549 DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P); 2550 if (I != MutatedMemory.end()) return I->second; 2551 2552 // Access it. 2553 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 2554 if (GV->hasDefinitiveInitializer()) 2555 return GV->getInitializer(); 2556 return 0; 2557 } 2558 2559 // Handle a constantexpr getelementptr. 2560 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 2561 if (CE->getOpcode() == Instruction::GetElementPtr && 2562 isa<GlobalVariable>(CE->getOperand(0))) { 2563 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2564 if (GV->hasDefinitiveInitializer()) 2565 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 2566 } 2567 2568 return 0; // don't know how to evaluate. 2569 } 2570 2571 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if 2572 /// successful, false if we can't evaluate it. NewBB returns the next BB that 2573 /// control flows into, or null upon return. 2574 bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst, 2575 BasicBlock *&NextBB) { 2576 // This is the main evaluation loop. 2577 while (1) { 2578 Constant *InstResult = 0; 2579 2580 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 2581 if (!SI->isSimple()) return false; // no volatile/atomic accesses. 2582 Constant *Ptr = getVal(SI->getOperand(1)); 2583 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2584 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2585 if (!isSimpleEnoughPointerToCommit(Ptr)) 2586 // If this is too complex for us to commit, reject it. 2587 return false; 2588 2589 Constant *Val = getVal(SI->getOperand(0)); 2590 2591 // If this might be too difficult for the backend to handle (e.g. the addr 2592 // of one global variable divided by another) then we can't commit it. 2593 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) 2594 return false; 2595 2596 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2597 if (CE->getOpcode() == Instruction::BitCast) { 2598 // If we're evaluating a store through a bitcast, then we need 2599 // to pull the bitcast off the pointer type and push it onto the 2600 // stored value. 2601 Ptr = CE->getOperand(0); 2602 2603 Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType(); 2604 2605 // In order to push the bitcast onto the stored value, a bitcast 2606 // from NewTy to Val's type must be legal. If it's not, we can try 2607 // introspecting NewTy to find a legal conversion. 2608 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) { 2609 // If NewTy is a struct, we can convert the pointer to the struct 2610 // into a pointer to its first member. 2611 // FIXME: This could be extended to support arrays as well. 2612 if (StructType *STy = dyn_cast<StructType>(NewTy)) { 2613 NewTy = STy->getTypeAtIndex(0U); 2614 2615 IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32); 2616 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false); 2617 Constant * const IdxList[] = {IdxZero, IdxZero}; 2618 2619 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList); 2620 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2621 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2622 2623 // If we can't improve the situation by introspecting NewTy, 2624 // we have to give up. 2625 } else { 2626 return false; 2627 } 2628 } 2629 2630 // If we found compatible types, go ahead and push the bitcast 2631 // onto the stored value. 2632 Val = ConstantExpr::getBitCast(Val, NewTy); 2633 } 2634 2635 MutatedMemory[Ptr] = Val; 2636 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 2637 InstResult = ConstantExpr::get(BO->getOpcode(), 2638 getVal(BO->getOperand(0)), 2639 getVal(BO->getOperand(1))); 2640 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 2641 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 2642 getVal(CI->getOperand(0)), 2643 getVal(CI->getOperand(1))); 2644 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 2645 InstResult = ConstantExpr::getCast(CI->getOpcode(), 2646 getVal(CI->getOperand(0)), 2647 CI->getType()); 2648 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 2649 InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)), 2650 getVal(SI->getOperand(1)), 2651 getVal(SI->getOperand(2))); 2652 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 2653 Constant *P = getVal(GEP->getOperand(0)); 2654 SmallVector<Constant*, 8> GEPOps; 2655 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); 2656 i != e; ++i) 2657 GEPOps.push_back(getVal(*i)); 2658 InstResult = 2659 ConstantExpr::getGetElementPtr(P, GEPOps, 2660 cast<GEPOperator>(GEP)->isInBounds()); 2661 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 2662 if (!LI->isSimple()) return false; // no volatile/atomic accesses. 2663 Constant *Ptr = getVal(LI->getOperand(0)); 2664 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2665 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2666 InstResult = ComputeLoadResult(Ptr); 2667 if (InstResult == 0) return false; // Could not evaluate load. 2668 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 2669 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 2670 Type *Ty = AI->getType()->getElementType(); 2671 AllocaTmps.push_back(new GlobalVariable(Ty, false, 2672 GlobalValue::InternalLinkage, 2673 UndefValue::get(Ty), 2674 AI->getName())); 2675 InstResult = AllocaTmps.back(); 2676 } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) { 2677 CallSite CS(CurInst); 2678 2679 // Debug info can safely be ignored here. 2680 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) { 2681 ++CurInst; 2682 continue; 2683 } 2684 2685 // Cannot handle inline asm. 2686 if (isa<InlineAsm>(CS.getCalledValue())) return false; 2687 2688 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) { 2689 if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) { 2690 if (MSI->isVolatile()) return false; 2691 Constant *Ptr = getVal(MSI->getDest()); 2692 Constant *Val = getVal(MSI->getValue()); 2693 Constant *DestVal = ComputeLoadResult(getVal(Ptr)); 2694 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) { 2695 // This memset is a no-op. 2696 ++CurInst; 2697 continue; 2698 } 2699 } 2700 2701 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 2702 II->getIntrinsicID() == Intrinsic::lifetime_end) { 2703 ++CurInst; 2704 continue; 2705 } 2706 2707 if (II->getIntrinsicID() == Intrinsic::invariant_start) { 2708 // We don't insert an entry into Values, as it doesn't have a 2709 // meaningful return value. 2710 if (!II->use_empty()) 2711 return false; 2712 ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0)); 2713 Value *PtrArg = getVal(II->getArgOperand(1)); 2714 Value *Ptr = PtrArg->stripPointerCasts(); 2715 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) { 2716 Type *ElemTy = cast<PointerType>(GV->getType())->getElementType(); 2717 if (!Size->isAllOnesValue() && 2718 Size->getValue().getLimitedValue() >= 2719 TD->getTypeStoreSize(ElemTy)) 2720 Invariants.insert(GV); 2721 } 2722 // Continue even if we do nothing. 2723 ++CurInst; 2724 continue; 2725 } 2726 return false; 2727 } 2728 2729 // Resolve function pointers. 2730 Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue())); 2731 if (!Callee || Callee->mayBeOverridden()) 2732 return false; // Cannot resolve. 2733 2734 SmallVector<Constant*, 8> Formals; 2735 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i) 2736 Formals.push_back(getVal(*i)); 2737 2738 if (Callee->isDeclaration()) { 2739 // If this is a function we can constant fold, do it. 2740 if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) { 2741 InstResult = C; 2742 } else { 2743 return false; 2744 } 2745 } else { 2746 if (Callee->getFunctionType()->isVarArg()) 2747 return false; 2748 2749 Constant *RetVal; 2750 // Execute the call, if successful, use the return value. 2751 ValueStack.push_back(new DenseMap<Value*, Constant*>); 2752 if (!EvaluateFunction(Callee, RetVal, Formals)) 2753 return false; 2754 delete ValueStack.pop_back_val(); 2755 InstResult = RetVal; 2756 } 2757 } else if (isa<TerminatorInst>(CurInst)) { 2758 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2759 if (BI->isUnconditional()) { 2760 NextBB = BI->getSuccessor(0); 2761 } else { 2762 ConstantInt *Cond = 2763 dyn_cast<ConstantInt>(getVal(BI->getCondition())); 2764 if (!Cond) return false; // Cannot determine. 2765 2766 NextBB = BI->getSuccessor(!Cond->getZExtValue()); 2767 } 2768 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2769 ConstantInt *Val = 2770 dyn_cast<ConstantInt>(getVal(SI->getCondition())); 2771 if (!Val) return false; // Cannot determine. 2772 NextBB = SI->findCaseValue(Val).getCaseSuccessor(); 2773 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) { 2774 Value *Val = getVal(IBI->getAddress())->stripPointerCasts(); 2775 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val)) 2776 NextBB = BA->getBasicBlock(); 2777 else 2778 return false; // Cannot determine. 2779 } else if (isa<ReturnInst>(CurInst)) { 2780 NextBB = 0; 2781 } else { 2782 // invoke, unwind, resume, unreachable. 2783 return false; // Cannot handle this terminator. 2784 } 2785 2786 // We succeeded at evaluating this block! 2787 return true; 2788 } else { 2789 // Did not know how to evaluate this! 2790 return false; 2791 } 2792 2793 if (!CurInst->use_empty()) { 2794 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult)) 2795 InstResult = ConstantFoldConstantExpression(CE, TD, TLI); 2796 2797 setVal(CurInst, InstResult); 2798 } 2799 2800 // If we just processed an invoke, we finished evaluating the block. 2801 if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) { 2802 NextBB = II->getNormalDest(); 2803 return true; 2804 } 2805 2806 // Advance program counter. 2807 ++CurInst; 2808 } 2809 } 2810 2811 /// EvaluateFunction - Evaluate a call to function F, returning true if 2812 /// successful, false if we can't evaluate it. ActualArgs contains the formal 2813 /// arguments for the function. 2814 bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal, 2815 const SmallVectorImpl<Constant*> &ActualArgs) { 2816 // Check to see if this function is already executing (recursion). If so, 2817 // bail out. TODO: we might want to accept limited recursion. 2818 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 2819 return false; 2820 2821 CallStack.push_back(F); 2822 2823 // Initialize arguments to the incoming values specified. 2824 unsigned ArgNo = 0; 2825 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 2826 ++AI, ++ArgNo) 2827 setVal(AI, ActualArgs[ArgNo]); 2828 2829 // ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 2830 // we can only evaluate any one basic block at most once. This set keeps 2831 // track of what we have executed so we can detect recursive cases etc. 2832 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks; 2833 2834 // CurBB - The current basic block we're evaluating. 2835 BasicBlock *CurBB = F->begin(); 2836 2837 BasicBlock::iterator CurInst = CurBB->begin(); 2838 2839 while (1) { 2840 BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings. 2841 if (!EvaluateBlock(CurInst, NextBB)) 2842 return false; 2843 2844 if (NextBB == 0) { 2845 // Successfully running until there's no next block means that we found 2846 // the return. Fill it the return value and pop the call stack. 2847 ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator()); 2848 if (RI->getNumOperands()) 2849 RetVal = getVal(RI->getOperand(0)); 2850 CallStack.pop_back(); 2851 return true; 2852 } 2853 2854 // Okay, we succeeded in evaluating this control flow. See if we have 2855 // executed the new block before. If so, we have a looping function, 2856 // which we cannot evaluate in reasonable time. 2857 if (!ExecutedBlocks.insert(NextBB)) 2858 return false; // looped! 2859 2860 // Okay, we have never been in this block before. Check to see if there 2861 // are any PHI nodes. If so, evaluate them with information about where 2862 // we came from. 2863 PHINode *PN = 0; 2864 for (CurInst = NextBB->begin(); 2865 (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2866 setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB))); 2867 2868 // Advance to the next block. 2869 CurBB = NextBB; 2870 } 2871 } 2872 2873 /// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2874 /// we can. Return true if we can, false otherwise. 2875 static bool EvaluateStaticConstructor(Function *F, const TargetData *TD, 2876 const TargetLibraryInfo *TLI) { 2877 // Call the function. 2878 Evaluator Eval(TD, TLI); 2879 Constant *RetValDummy; 2880 bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy, 2881 SmallVector<Constant*, 0>()); 2882 2883 if (EvalSuccess) { 2884 // We succeeded at evaluation: commit the result. 2885 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2886 << F->getName() << "' to " << Eval.getMutatedMemory().size() 2887 << " stores.\n"); 2888 for (DenseMap<Constant*, Constant*>::const_iterator I = 2889 Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end(); 2890 I != E; ++I) 2891 CommitValueTo(I->second, I->first); 2892 for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I = 2893 Eval.getInvariants().begin(), E = Eval.getInvariants().end(); 2894 I != E; ++I) 2895 (*I)->setConstant(true); 2896 } 2897 2898 return EvalSuccess; 2899 } 2900 2901 /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2902 /// Return true if anything changed. 2903 bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2904 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2905 bool MadeChange = false; 2906 if (Ctors.empty()) return false; 2907 2908 // Loop over global ctors, optimizing them when we can. 2909 for (unsigned i = 0; i != Ctors.size(); ++i) { 2910 Function *F = Ctors[i]; 2911 // Found a null terminator in the middle of the list, prune off the rest of 2912 // the list. 2913 if (F == 0) { 2914 if (i != Ctors.size()-1) { 2915 Ctors.resize(i+1); 2916 MadeChange = true; 2917 } 2918 break; 2919 } 2920 2921 // We cannot simplify external ctor functions. 2922 if (F->empty()) continue; 2923 2924 // If we can evaluate the ctor at compile time, do. 2925 if (EvaluateStaticConstructor(F, TD, TLI)) { 2926 Ctors.erase(Ctors.begin()+i); 2927 MadeChange = true; 2928 --i; 2929 ++NumCtorsEvaluated; 2930 continue; 2931 } 2932 } 2933 2934 if (!MadeChange) return false; 2935 2936 GCL = InstallGlobalCtors(GCL, Ctors); 2937 return true; 2938 } 2939 2940 bool GlobalOpt::OptimizeGlobalAliases(Module &M) { 2941 bool Changed = false; 2942 2943 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); 2944 I != E;) { 2945 Module::alias_iterator J = I++; 2946 // Aliases without names cannot be referenced outside this module. 2947 if (!J->hasName() && !J->isDeclaration()) 2948 J->setLinkage(GlobalValue::InternalLinkage); 2949 // If the aliasee may change at link time, nothing can be done - bail out. 2950 if (J->mayBeOverridden()) 2951 continue; 2952 2953 Constant *Aliasee = J->getAliasee(); 2954 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts()); 2955 Target->removeDeadConstantUsers(); 2956 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse(); 2957 2958 // Make all users of the alias use the aliasee instead. 2959 if (!J->use_empty()) { 2960 J->replaceAllUsesWith(Aliasee); 2961 ++NumAliasesResolved; 2962 Changed = true; 2963 } 2964 2965 // If the alias is externally visible, we may still be able to simplify it. 2966 if (!J->hasLocalLinkage()) { 2967 // If the aliasee has internal linkage, give it the name and linkage 2968 // of the alias, and delete the alias. This turns: 2969 // define internal ... @f(...) 2970 // @a = alias ... @f 2971 // into: 2972 // define ... @a(...) 2973 if (!Target->hasLocalLinkage()) 2974 continue; 2975 2976 // Do not perform the transform if multiple aliases potentially target the 2977 // aliasee. This check also ensures that it is safe to replace the section 2978 // and other attributes of the aliasee with those of the alias. 2979 if (!hasOneUse) 2980 continue; 2981 2982 // Give the aliasee the name, linkage and other attributes of the alias. 2983 Target->takeName(J); 2984 Target->setLinkage(J->getLinkage()); 2985 Target->GlobalValue::copyAttributesFrom(J); 2986 } 2987 2988 // Delete the alias. 2989 M.getAliasList().erase(J); 2990 ++NumAliasesRemoved; 2991 Changed = true; 2992 } 2993 2994 return Changed; 2995 } 2996 2997 static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) { 2998 if (!TLI->has(LibFunc::cxa_atexit)) 2999 return 0; 3000 3001 Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit)); 3002 3003 if (!Fn) 3004 return 0; 3005 3006 FunctionType *FTy = Fn->getFunctionType(); 3007 3008 // Checking that the function has the right return type, the right number of 3009 // parameters and that they all have pointer types should be enough. 3010 if (!FTy->getReturnType()->isIntegerTy() || 3011 FTy->getNumParams() != 3 || 3012 !FTy->getParamType(0)->isPointerTy() || 3013 !FTy->getParamType(1)->isPointerTy() || 3014 !FTy->getParamType(2)->isPointerTy()) 3015 return 0; 3016 3017 return Fn; 3018 } 3019 3020 /// cxxDtorIsEmpty - Returns whether the given function is an empty C++ 3021 /// destructor and can therefore be eliminated. 3022 /// Note that we assume that other optimization passes have already simplified 3023 /// the code so we only look for a function with a single basic block, where 3024 /// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and 3025 /// other side-effect free instructions. 3026 static bool cxxDtorIsEmpty(const Function &Fn, 3027 SmallPtrSet<const Function *, 8> &CalledFunctions) { 3028 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and 3029 // nounwind, but that doesn't seem worth doing. 3030 if (Fn.isDeclaration()) 3031 return false; 3032 3033 if (++Fn.begin() != Fn.end()) 3034 return false; 3035 3036 const BasicBlock &EntryBlock = Fn.getEntryBlock(); 3037 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end(); 3038 I != E; ++I) { 3039 if (const CallInst *CI = dyn_cast<CallInst>(I)) { 3040 // Ignore debug intrinsics. 3041 if (isa<DbgInfoIntrinsic>(CI)) 3042 continue; 3043 3044 const Function *CalledFn = CI->getCalledFunction(); 3045 3046 if (!CalledFn) 3047 return false; 3048 3049 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions); 3050 3051 // Don't treat recursive functions as empty. 3052 if (!NewCalledFunctions.insert(CalledFn)) 3053 return false; 3054 3055 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions)) 3056 return false; 3057 } else if (isa<ReturnInst>(*I)) 3058 return true; // We're done. 3059 else if (I->mayHaveSideEffects()) 3060 return false; // Destructor with side effects, bail. 3061 } 3062 3063 return false; 3064 } 3065 3066 bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) { 3067 /// Itanium C++ ABI p3.3.5: 3068 /// 3069 /// After constructing a global (or local static) object, that will require 3070 /// destruction on exit, a termination function is registered as follows: 3071 /// 3072 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d ); 3073 /// 3074 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the 3075 /// call f(p) when DSO d is unloaded, before all such termination calls 3076 /// registered before this one. It returns zero if registration is 3077 /// successful, nonzero on failure. 3078 3079 // This pass will look for calls to __cxa_atexit where the function is trivial 3080 // and remove them. 3081 bool Changed = false; 3082 3083 for (Function::use_iterator I = CXAAtExitFn->use_begin(), 3084 E = CXAAtExitFn->use_end(); I != E;) { 3085 // We're only interested in calls. Theoretically, we could handle invoke 3086 // instructions as well, but neither llvm-gcc nor clang generate invokes 3087 // to __cxa_atexit. 3088 CallInst *CI = dyn_cast<CallInst>(*I++); 3089 if (!CI) 3090 continue; 3091 3092 Function *DtorFn = 3093 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts()); 3094 if (!DtorFn) 3095 continue; 3096 3097 SmallPtrSet<const Function *, 8> CalledFunctions; 3098 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions)) 3099 continue; 3100 3101 // Just remove the call. 3102 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType())); 3103 CI->eraseFromParent(); 3104 3105 ++NumCXXDtorsRemoved; 3106 3107 Changed |= true; 3108 } 3109 3110 return Changed; 3111 } 3112 3113 bool GlobalOpt::runOnModule(Module &M) { 3114 bool Changed = false; 3115 3116 TD = getAnalysisIfAvailable<TargetData>(); 3117 TLI = &getAnalysis<TargetLibraryInfo>(); 3118 3119 // Try to find the llvm.globalctors list. 3120 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 3121 3122 Function *CXAAtExitFn = FindCXAAtExit(M, TLI); 3123 3124 bool LocalChange = true; 3125 while (LocalChange) { 3126 LocalChange = false; 3127 3128 // Delete functions that are trivially dead, ccc -> fastcc 3129 LocalChange |= OptimizeFunctions(M); 3130 3131 // Optimize global_ctors list. 3132 if (GlobalCtors) 3133 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 3134 3135 // Optimize non-address-taken globals. 3136 LocalChange |= OptimizeGlobalVars(M); 3137 3138 // Resolve aliases, when possible. 3139 LocalChange |= OptimizeGlobalAliases(M); 3140 3141 // Try to remove trivial global destructors. 3142 if (CXAAtExitFn) 3143 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn); 3144 3145 Changed |= LocalChange; 3146 } 3147 3148 // TODO: Move all global ctors functions to the end of the module for code 3149 // layout. 3150 3151 return Changed; 3152 } 3153