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> 42using namespace llvm; 43 44STATISTIC(NumMarked , "Number of globals marked constant"); 45STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr"); 46STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); 47STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); 48STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); 49STATISTIC(NumDeleted , "Number of globals deleted"); 50STATISTIC(NumFnDeleted , "Number of functions deleted"); 51STATISTIC(NumGlobUses , "Number of global uses devirtualized"); 52STATISTIC(NumLocalized , "Number of globals localized"); 53STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); 54STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); 55STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); 56STATISTIC(NumNestRemoved , "Number of nest attributes removed"); 57STATISTIC(NumAliasesResolved, "Number of global aliases resolved"); 58STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated"); 59STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed"); 60 61namespace { 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 91char GlobalOpt::ID = 0; 92INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt", 93 "Global Variable Optimizer", false, false) 94INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) 95INITIALIZE_PASS_END(GlobalOpt, "globalopt", 96 "Global Variable Optimizer", false, false) 97 98ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } 99 100namespace { 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. 105struct 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/// 169static 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/// 179static 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/// 196static 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. 301static 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. 349static 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/// 379static 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. 466static 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. 544static 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/// 578static 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/// 644static 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. 659static 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. 801static 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. 847static 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 867static 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. 934static 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 isa<BitCastInst>(GlobalUser) || 967 isa<GetElementPtrInst>(GlobalUser)) && 968 "Only expect load and stores!"); 969 } 970 } 971 972 if (Changed) { 973 DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV); 974 ++NumGlobUses; 975 } 976 977 // If we nuked all of the loads, then none of the stores are needed either, 978 // nor is the global. 979 if (AllNonStoreUsesGone) { 980 if (isLeakCheckerRoot(GV)) { 981 Changed |= CleanupPointerRootUsers(GV, TLI); 982 } else { 983 Changed = true; 984 CleanupConstantGlobalUsers(GV, 0, TD, TLI); 985 } 986 if (GV->use_empty()) { 987 DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n"); 988 Changed = true; 989 GV->eraseFromParent(); 990 ++NumDeleted; 991 } 992 } 993 return Changed; 994} 995 996/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 997/// instructions that are foldable. 998static void ConstantPropUsersOf(Value *V, 999 TargetData *TD, TargetLibraryInfo *TLI) { 1000 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 1001 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 1002 if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) { 1003 I->replaceAllUsesWith(NewC); 1004 1005 // Advance UI to the next non-I use to avoid invalidating it! 1006 // Instructions could multiply use V. 1007 while (UI != E && *UI == I) 1008 ++UI; 1009 I->eraseFromParent(); 1010 } 1011} 1012 1013/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 1014/// variable, and transforms the program as if it always contained the result of 1015/// the specified malloc. Because it is always the result of the specified 1016/// malloc, there is no reason to actually DO the malloc. Instead, turn the 1017/// malloc into a global, and any loads of GV as uses of the new global. 1018static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 1019 CallInst *CI, 1020 Type *AllocTy, 1021 ConstantInt *NElements, 1022 TargetData *TD, 1023 TargetLibraryInfo *TLI) { 1024 DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n'); 1025 1026 Type *GlobalType; 1027 if (NElements->getZExtValue() == 1) 1028 GlobalType = AllocTy; 1029 else 1030 // If we have an array allocation, the global variable is of an array. 1031 GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue()); 1032 1033 // Create the new global variable. The contents of the malloc'd memory is 1034 // undefined, so initialize with an undef value. 1035 GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(), 1036 GlobalType, false, 1037 GlobalValue::InternalLinkage, 1038 UndefValue::get(GlobalType), 1039 GV->getName()+".body", 1040 GV, 1041 GV->getThreadLocalMode()); 1042 1043 // If there are bitcast users of the malloc (which is typical, usually we have 1044 // a malloc + bitcast) then replace them with uses of the new global. Update 1045 // other users to use the global as well. 1046 BitCastInst *TheBC = 0; 1047 while (!CI->use_empty()) { 1048 Instruction *User = cast<Instruction>(CI->use_back()); 1049 if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { 1050 if (BCI->getType() == NewGV->getType()) { 1051 BCI->replaceAllUsesWith(NewGV); 1052 BCI->eraseFromParent(); 1053 } else { 1054 BCI->setOperand(0, NewGV); 1055 } 1056 } else { 1057 if (TheBC == 0) 1058 TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI); 1059 User->replaceUsesOfWith(CI, TheBC); 1060 } 1061 } 1062 1063 Constant *RepValue = NewGV; 1064 if (NewGV->getType() != GV->getType()->getElementType()) 1065 RepValue = ConstantExpr::getBitCast(RepValue, 1066 GV->getType()->getElementType()); 1067 1068 // If there is a comparison against null, we will insert a global bool to 1069 // keep track of whether the global was initialized yet or not. 1070 GlobalVariable *InitBool = 1071 new GlobalVariable(Type::getInt1Ty(GV->getContext()), false, 1072 GlobalValue::InternalLinkage, 1073 ConstantInt::getFalse(GV->getContext()), 1074 GV->getName()+".init", GV->getThreadLocalMode()); 1075 bool InitBoolUsed = false; 1076 1077 // Loop over all uses of GV, processing them in turn. 1078 while (!GV->use_empty()) { 1079 if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) { 1080 // The global is initialized when the store to it occurs. 1081 new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0, 1082 SI->getOrdering(), SI->getSynchScope(), SI); 1083 SI->eraseFromParent(); 1084 continue; 1085 } 1086 1087 LoadInst *LI = cast<LoadInst>(GV->use_back()); 1088 while (!LI->use_empty()) { 1089 Use &LoadUse = LI->use_begin().getUse(); 1090 if (!isa<ICmpInst>(LoadUse.getUser())) { 1091 LoadUse = RepValue; 1092 continue; 1093 } 1094 1095 ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser()); 1096 // Replace the cmp X, 0 with a use of the bool value. 1097 // Sink the load to where the compare was, if atomic rules allow us to. 1098 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0, 1099 LI->getOrdering(), LI->getSynchScope(), 1100 LI->isUnordered() ? (Instruction*)ICI : LI); 1101 InitBoolUsed = true; 1102 switch (ICI->getPredicate()) { 1103 default: llvm_unreachable("Unknown ICmp Predicate!"); 1104 case ICmpInst::ICMP_ULT: 1105 case ICmpInst::ICMP_SLT: // X < null -> always false 1106 LV = ConstantInt::getFalse(GV->getContext()); 1107 break; 1108 case ICmpInst::ICMP_ULE: 1109 case ICmpInst::ICMP_SLE: 1110 case ICmpInst::ICMP_EQ: 1111 LV = BinaryOperator::CreateNot(LV, "notinit", ICI); 1112 break; 1113 case ICmpInst::ICMP_NE: 1114 case ICmpInst::ICMP_UGE: 1115 case ICmpInst::ICMP_SGE: 1116 case ICmpInst::ICMP_UGT: 1117 case ICmpInst::ICMP_SGT: 1118 break; // no change. 1119 } 1120 ICI->replaceAllUsesWith(LV); 1121 ICI->eraseFromParent(); 1122 } 1123 LI->eraseFromParent(); 1124 } 1125 1126 // If the initialization boolean was used, insert it, otherwise delete it. 1127 if (!InitBoolUsed) { 1128 while (!InitBool->use_empty()) // Delete initializations 1129 cast<StoreInst>(InitBool->use_back())->eraseFromParent(); 1130 delete InitBool; 1131 } else 1132 GV->getParent()->getGlobalList().insert(GV, InitBool); 1133 1134 // Now the GV is dead, nuke it and the malloc.. 1135 GV->eraseFromParent(); 1136 CI->eraseFromParent(); 1137 1138 // To further other optimizations, loop over all users of NewGV and try to 1139 // constant prop them. This will promote GEP instructions with constant 1140 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 1141 ConstantPropUsersOf(NewGV, TD, TLI); 1142 if (RepValue != NewGV) 1143 ConstantPropUsersOf(RepValue, TD, TLI); 1144 1145 return NewGV; 1146} 1147 1148/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 1149/// to make sure that there are no complex uses of V. We permit simple things 1150/// like dereferencing the pointer, but not storing through the address, unless 1151/// it is to the specified global. 1152static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V, 1153 const GlobalVariable *GV, 1154 SmallPtrSet<const PHINode*, 8> &PHIs) { 1155 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); 1156 UI != E; ++UI) { 1157 const Instruction *Inst = cast<Instruction>(*UI); 1158 1159 if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) { 1160 continue; // Fine, ignore. 1161 } 1162 1163 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { 1164 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 1165 return false; // Storing the pointer itself... bad. 1166 continue; // Otherwise, storing through it, or storing into GV... fine. 1167 } 1168 1169 // Must index into the array and into the struct. 1170 if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) { 1171 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs)) 1172 return false; 1173 continue; 1174 } 1175 1176 if (const PHINode *PN = dyn_cast<PHINode>(Inst)) { 1177 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 1178 // cycles. 1179 if (PHIs.insert(PN)) 1180 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 1181 return false; 1182 continue; 1183 } 1184 1185 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) { 1186 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs)) 1187 return false; 1188 continue; 1189 } 1190 1191 return false; 1192 } 1193 return true; 1194} 1195 1196/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 1197/// somewhere. Transform all uses of the allocation into loads from the 1198/// global and uses of the resultant pointer. Further, delete the store into 1199/// GV. This assumes that these value pass the 1200/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 1201static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 1202 GlobalVariable *GV) { 1203 while (!Alloc->use_empty()) { 1204 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 1205 Instruction *InsertPt = U; 1206 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 1207 // If this is the store of the allocation into the global, remove it. 1208 if (SI->getOperand(1) == GV) { 1209 SI->eraseFromParent(); 1210 continue; 1211 } 1212 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 1213 // Insert the load in the corresponding predecessor, not right before the 1214 // PHI. 1215 InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator(); 1216 } else if (isa<BitCastInst>(U)) { 1217 // Must be bitcast between the malloc and store to initialize the global. 1218 ReplaceUsesOfMallocWithGlobal(U, GV); 1219 U->eraseFromParent(); 1220 continue; 1221 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { 1222 // If this is a "GEP bitcast" and the user is a store to the global, then 1223 // just process it as a bitcast. 1224 if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse()) 1225 if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back())) 1226 if (SI->getOperand(1) == GV) { 1227 // Must be bitcast GEP between the malloc and store to initialize 1228 // the global. 1229 ReplaceUsesOfMallocWithGlobal(GEPI, GV); 1230 GEPI->eraseFromParent(); 1231 continue; 1232 } 1233 } 1234 1235 // Insert a load from the global, and use it instead of the malloc. 1236 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 1237 U->replaceUsesOfWith(Alloc, NL); 1238 } 1239} 1240 1241/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi 1242/// of a load) are simple enough to perform heap SRA on. This permits GEP's 1243/// that index through the array and struct field, icmps of null, and PHIs. 1244static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V, 1245 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs, 1246 SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) { 1247 // We permit two users of the load: setcc comparing against the null 1248 // pointer, and a getelementptr of a specific form. 1249 for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; 1250 ++UI) { 1251 const Instruction *User = cast<Instruction>(*UI); 1252 1253 // Comparison against null is ok. 1254 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) { 1255 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 1256 return false; 1257 continue; 1258 } 1259 1260 // getelementptr is also ok, but only a simple form. 1261 if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) { 1262 // Must index into the array and into the struct. 1263 if (GEPI->getNumOperands() < 3) 1264 return false; 1265 1266 // Otherwise the GEP is ok. 1267 continue; 1268 } 1269 1270 if (const PHINode *PN = dyn_cast<PHINode>(User)) { 1271 if (!LoadUsingPHIsPerLoad.insert(PN)) 1272 // This means some phi nodes are dependent on each other. 1273 // Avoid infinite looping! 1274 return false; 1275 if (!LoadUsingPHIs.insert(PN)) 1276 // If we have already analyzed this PHI, then it is safe. 1277 continue; 1278 1279 // Make sure all uses of the PHI are simple enough to transform. 1280 if (!LoadUsesSimpleEnoughForHeapSRA(PN, 1281 LoadUsingPHIs, LoadUsingPHIsPerLoad)) 1282 return false; 1283 1284 continue; 1285 } 1286 1287 // Otherwise we don't know what this is, not ok. 1288 return false; 1289 } 1290 1291 return true; 1292} 1293 1294 1295/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 1296/// GV are simple enough to perform HeapSRA, return true. 1297static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV, 1298 Instruction *StoredVal) { 1299 SmallPtrSet<const PHINode*, 32> LoadUsingPHIs; 1300 SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad; 1301 for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end(); 1302 UI != E; ++UI) 1303 if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 1304 if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs, 1305 LoadUsingPHIsPerLoad)) 1306 return false; 1307 LoadUsingPHIsPerLoad.clear(); 1308 } 1309 1310 // If we reach here, we know that all uses of the loads and transitive uses 1311 // (through PHI nodes) are simple enough to transform. However, we don't know 1312 // that all inputs the to the PHI nodes are in the same equivalence sets. 1313 // Check to verify that all operands of the PHIs are either PHIS that can be 1314 // transformed, loads from GV, or MI itself. 1315 for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin() 1316 , E = LoadUsingPHIs.end(); I != E; ++I) { 1317 const PHINode *PN = *I; 1318 for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) { 1319 Value *InVal = PN->getIncomingValue(op); 1320 1321 // PHI of the stored value itself is ok. 1322 if (InVal == StoredVal) continue; 1323 1324 if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) { 1325 // One of the PHIs in our set is (optimistically) ok. 1326 if (LoadUsingPHIs.count(InPN)) 1327 continue; 1328 return false; 1329 } 1330 1331 // Load from GV is ok. 1332 if (const LoadInst *LI = dyn_cast<LoadInst>(InVal)) 1333 if (LI->getOperand(0) == GV) 1334 continue; 1335 1336 // UNDEF? NULL? 1337 1338 // Anything else is rejected. 1339 return false; 1340 } 1341 } 1342 1343 return true; 1344} 1345 1346static Value *GetHeapSROAValue(Value *V, unsigned FieldNo, 1347 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1348 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1349 std::vector<Value*> &FieldVals = InsertedScalarizedValues[V]; 1350 1351 if (FieldNo >= FieldVals.size()) 1352 FieldVals.resize(FieldNo+1); 1353 1354 // If we already have this value, just reuse the previously scalarized 1355 // version. 1356 if (Value *FieldVal = FieldVals[FieldNo]) 1357 return FieldVal; 1358 1359 // Depending on what instruction this is, we have several cases. 1360 Value *Result; 1361 if (LoadInst *LI = dyn_cast<LoadInst>(V)) { 1362 // This is a scalarized version of the load from the global. Just create 1363 // a new Load of the scalarized global. 1364 Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo, 1365 InsertedScalarizedValues, 1366 PHIsToRewrite), 1367 LI->getName()+".f"+Twine(FieldNo), LI); 1368 } else if (PHINode *PN = dyn_cast<PHINode>(V)) { 1369 // PN's type is pointer to struct. Make a new PHI of pointer to struct 1370 // field. 1371 StructType *ST = 1372 cast<StructType>(cast<PointerType>(PN->getType())->getElementType()); 1373 1374 PHINode *NewPN = 1375 PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)), 1376 PN->getNumIncomingValues(), 1377 PN->getName()+".f"+Twine(FieldNo), PN); 1378 Result = NewPN; 1379 PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); 1380 } else { 1381 llvm_unreachable("Unknown usable value"); 1382 } 1383 1384 return FieldVals[FieldNo] = Result; 1385} 1386 1387/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1388/// the load, rewrite the derived value to use the HeapSRoA'd load. 1389static void RewriteHeapSROALoadUser(Instruction *LoadUser, 1390 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1391 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1392 // If this is a comparison against null, handle it. 1393 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1394 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1395 // If we have a setcc of the loaded pointer, we can use a setcc of any 1396 // field. 1397 Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0, 1398 InsertedScalarizedValues, PHIsToRewrite); 1399 1400 Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr, 1401 Constant::getNullValue(NPtr->getType()), 1402 SCI->getName()); 1403 SCI->replaceAllUsesWith(New); 1404 SCI->eraseFromParent(); 1405 return; 1406 } 1407 1408 // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...' 1409 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1410 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1411 && "Unexpected GEPI!"); 1412 1413 // Load the pointer for this field. 1414 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1415 Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo, 1416 InsertedScalarizedValues, PHIsToRewrite); 1417 1418 // Create the new GEP idx vector. 1419 SmallVector<Value*, 8> GEPIdx; 1420 GEPIdx.push_back(GEPI->getOperand(1)); 1421 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1422 1423 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx, 1424 GEPI->getName(), GEPI); 1425 GEPI->replaceAllUsesWith(NGEPI); 1426 GEPI->eraseFromParent(); 1427 return; 1428 } 1429 1430 // Recursively transform the users of PHI nodes. This will lazily create the 1431 // PHIs that are needed for individual elements. Keep track of what PHIs we 1432 // see in InsertedScalarizedValues so that we don't get infinite loops (very 1433 // antisocial). If the PHI is already in InsertedScalarizedValues, it has 1434 // already been seen first by another load, so its uses have already been 1435 // processed. 1436 PHINode *PN = cast<PHINode>(LoadUser); 1437 if (!InsertedScalarizedValues.insert(std::make_pair(PN, 1438 std::vector<Value*>())).second) 1439 return; 1440 1441 // If this is the first time we've seen this PHI, recursively process all 1442 // users. 1443 for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) { 1444 Instruction *User = cast<Instruction>(*UI++); 1445 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); 1446 } 1447} 1448 1449/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1450/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1451/// use FieldGlobals instead. All uses of loaded values satisfy 1452/// AllGlobalLoadUsesSimpleEnoughForHeapSRA. 1453static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1454 DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues, 1455 std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) { 1456 for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end(); 1457 UI != E; ) { 1458 Instruction *User = cast<Instruction>(*UI++); 1459 RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); 1460 } 1461 1462 if (Load->use_empty()) { 1463 Load->eraseFromParent(); 1464 InsertedScalarizedValues.erase(Load); 1465 } 1466} 1467 1468/// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break 1469/// it up into multiple allocations of arrays of the fields. 1470static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI, 1471 Value *NElems, TargetData *TD, 1472 const TargetLibraryInfo *TLI) { 1473 DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n'); 1474 Type *MAT = getMallocAllocatedType(CI, TLI); 1475 StructType *STy = cast<StructType>(MAT); 1476 1477 // There is guaranteed to be at least one use of the malloc (storing 1478 // it into GV). If there are other uses, change them to be uses of 1479 // the global to simplify later code. This also deletes the store 1480 // into GV. 1481 ReplaceUsesOfMallocWithGlobal(CI, GV); 1482 1483 // Okay, at this point, there are no users of the malloc. Insert N 1484 // new mallocs at the same place as CI, and N globals. 1485 std::vector<Value*> FieldGlobals; 1486 std::vector<Value*> FieldMallocs; 1487 1488 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1489 Type *FieldTy = STy->getElementType(FieldNo); 1490 PointerType *PFieldTy = PointerType::getUnqual(FieldTy); 1491 1492 GlobalVariable *NGV = 1493 new GlobalVariable(*GV->getParent(), 1494 PFieldTy, false, GlobalValue::InternalLinkage, 1495 Constant::getNullValue(PFieldTy), 1496 GV->getName() + ".f" + Twine(FieldNo), GV, 1497 GV->getThreadLocalMode()); 1498 FieldGlobals.push_back(NGV); 1499 1500 unsigned TypeSize = TD->getTypeAllocSize(FieldTy); 1501 if (StructType *ST = dyn_cast<StructType>(FieldTy)) 1502 TypeSize = TD->getStructLayout(ST)->getSizeInBytes(); 1503 Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); 1504 Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, 1505 ConstantInt::get(IntPtrTy, TypeSize), 1506 NElems, 0, 1507 CI->getName() + ".f" + Twine(FieldNo)); 1508 FieldMallocs.push_back(NMI); 1509 new StoreInst(NMI, NGV, CI); 1510 } 1511 1512 // The tricky aspect of this transformation is handling the case when malloc 1513 // fails. In the original code, malloc failing would set the result pointer 1514 // of malloc to null. In this case, some mallocs could succeed and others 1515 // could fail. As such, we emit code that looks like this: 1516 // F0 = malloc(field0) 1517 // F1 = malloc(field1) 1518 // F2 = malloc(field2) 1519 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1520 // if (F0) { free(F0); F0 = 0; } 1521 // if (F1) { free(F1); F1 = 0; } 1522 // if (F2) { free(F2); F2 = 0; } 1523 // } 1524 // The malloc can also fail if its argument is too large. 1525 Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0); 1526 Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0), 1527 ConstantZero, "isneg"); 1528 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1529 Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i], 1530 Constant::getNullValue(FieldMallocs[i]->getType()), 1531 "isnull"); 1532 RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI); 1533 } 1534 1535 // Split the basic block at the old malloc. 1536 BasicBlock *OrigBB = CI->getParent(); 1537 BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont"); 1538 1539 // Create the block to check the first condition. Put all these blocks at the 1540 // end of the function as they are unlikely to be executed. 1541 BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(), 1542 "malloc_ret_null", 1543 OrigBB->getParent()); 1544 1545 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1546 // branch on RunningOr. 1547 OrigBB->getTerminator()->eraseFromParent(); 1548 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); 1549 1550 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1551 // pointer, because some may be null while others are not. 1552 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1553 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1554 Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal, 1555 Constant::getNullValue(GVVal->getType())); 1556 BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it", 1557 OrigBB->getParent()); 1558 BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next", 1559 OrigBB->getParent()); 1560 Instruction *BI = BranchInst::Create(FreeBlock, NextBlock, 1561 Cmp, NullPtrBlock); 1562 1563 // Fill in FreeBlock. 1564 CallInst::CreateFree(GVVal, BI); 1565 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1566 FreeBlock); 1567 BranchInst::Create(NextBlock, FreeBlock); 1568 1569 NullPtrBlock = NextBlock; 1570 } 1571 1572 BranchInst::Create(ContBB, NullPtrBlock); 1573 1574 // CI is no longer needed, remove it. 1575 CI->eraseFromParent(); 1576 1577 /// InsertedScalarizedLoads - As we process loads, if we can't immediately 1578 /// update all uses of the load, keep track of what scalarized loads are 1579 /// inserted for a given load. 1580 DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues; 1581 InsertedScalarizedValues[GV] = FieldGlobals; 1582 1583 std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite; 1584 1585 // Okay, the malloc site is completely handled. All of the uses of GV are now 1586 // loads, and all uses of those loads are simple. Rewrite them to use loads 1587 // of the per-field globals instead. 1588 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) { 1589 Instruction *User = cast<Instruction>(*UI++); 1590 1591 if (LoadInst *LI = dyn_cast<LoadInst>(User)) { 1592 RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite); 1593 continue; 1594 } 1595 1596 // Must be a store of null. 1597 StoreInst *SI = cast<StoreInst>(User); 1598 assert(isa<ConstantPointerNull>(SI->getOperand(0)) && 1599 "Unexpected heap-sra user!"); 1600 1601 // Insert a store of null into each global. 1602 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1603 PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType()); 1604 Constant *Null = Constant::getNullValue(PT->getElementType()); 1605 new StoreInst(Null, FieldGlobals[i], SI); 1606 } 1607 // Erase the original store. 1608 SI->eraseFromParent(); 1609 } 1610 1611 // While we have PHIs that are interesting to rewrite, do it. 1612 while (!PHIsToRewrite.empty()) { 1613 PHINode *PN = PHIsToRewrite.back().first; 1614 unsigned FieldNo = PHIsToRewrite.back().second; 1615 PHIsToRewrite.pop_back(); 1616 PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]); 1617 assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi"); 1618 1619 // Add all the incoming values. This can materialize more phis. 1620 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1621 Value *InVal = PN->getIncomingValue(i); 1622 InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues, 1623 PHIsToRewrite); 1624 FieldPN->addIncoming(InVal, PN->getIncomingBlock(i)); 1625 } 1626 } 1627 1628 // Drop all inter-phi links and any loads that made it this far. 1629 for (DenseMap<Value*, std::vector<Value*> >::iterator 1630 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); 1631 I != E; ++I) { 1632 if (PHINode *PN = dyn_cast<PHINode>(I->first)) 1633 PN->dropAllReferences(); 1634 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) 1635 LI->dropAllReferences(); 1636 } 1637 1638 // Delete all the phis and loads now that inter-references are dead. 1639 for (DenseMap<Value*, std::vector<Value*> >::iterator 1640 I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); 1641 I != E; ++I) { 1642 if (PHINode *PN = dyn_cast<PHINode>(I->first)) 1643 PN->eraseFromParent(); 1644 else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) 1645 LI->eraseFromParent(); 1646 } 1647 1648 // The old global is now dead, remove it. 1649 GV->eraseFromParent(); 1650 1651 ++NumHeapSRA; 1652 return cast<GlobalVariable>(FieldGlobals[0]); 1653} 1654 1655/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a 1656/// pointer global variable with a single value stored it that is a malloc or 1657/// cast of malloc. 1658static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV, 1659 CallInst *CI, 1660 Type *AllocTy, 1661 AtomicOrdering Ordering, 1662 Module::global_iterator &GVI, 1663 TargetData *TD, 1664 TargetLibraryInfo *TLI) { 1665 if (!TD) 1666 return false; 1667 1668 // If this is a malloc of an abstract type, don't touch it. 1669 if (!AllocTy->isSized()) 1670 return false; 1671 1672 // We can't optimize this global unless all uses of it are *known* to be 1673 // of the malloc value, not of the null initializer value (consider a use 1674 // that compares the global's value against zero to see if the malloc has 1675 // been reached). To do this, we check to see if all uses of the global 1676 // would trap if the global were null: this proves that they must all 1677 // happen after the malloc. 1678 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1679 return false; 1680 1681 // We can't optimize this if the malloc itself is used in a complex way, 1682 // for example, being stored into multiple globals. This allows the 1683 // malloc to be stored into the specified global, loaded icmp'd, and 1684 // GEP'd. These are all things we could transform to using the global 1685 // for. 1686 SmallPtrSet<const PHINode*, 8> PHIs; 1687 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs)) 1688 return false; 1689 1690 // If we have a global that is only initialized with a fixed size malloc, 1691 // transform the program to use global memory instead of malloc'd memory. 1692 // This eliminates dynamic allocation, avoids an indirection accessing the 1693 // data, and exposes the resultant global to further GlobalOpt. 1694 // We cannot optimize the malloc if we cannot determine malloc array size. 1695 Value *NElems = getMallocArraySize(CI, TD, TLI, true); 1696 if (!NElems) 1697 return false; 1698 1699 if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) 1700 // Restrict this transformation to only working on small allocations 1701 // (2048 bytes currently), as we don't want to introduce a 16M global or 1702 // something. 1703 if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) { 1704 GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI); 1705 return true; 1706 } 1707 1708 // If the allocation is an array of structures, consider transforming this 1709 // into multiple malloc'd arrays, one for each field. This is basically 1710 // SRoA for malloc'd memory. 1711 1712 if (Ordering != NotAtomic) 1713 return false; 1714 1715 // If this is an allocation of a fixed size array of structs, analyze as a 1716 // variable size array. malloc [100 x struct],1 -> malloc struct, 100 1717 if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1)) 1718 if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy)) 1719 AllocTy = AT->getElementType(); 1720 1721 StructType *AllocSTy = dyn_cast<StructType>(AllocTy); 1722 if (!AllocSTy) 1723 return false; 1724 1725 // This the structure has an unreasonable number of fields, leave it 1726 // alone. 1727 if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 && 1728 AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) { 1729 1730 // If this is a fixed size array, transform the Malloc to be an alloc of 1731 // structs. malloc [100 x struct],1 -> malloc struct, 100 1732 if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) { 1733 Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); 1734 unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes(); 1735 Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); 1736 Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); 1737 Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, 1738 AllocSize, NumElements, 1739 0, CI->getName()); 1740 Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI); 1741 CI->replaceAllUsesWith(Cast); 1742 CI->eraseFromParent(); 1743 if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc)) 1744 CI = cast<CallInst>(BCI->getOperand(0)); 1745 else 1746 CI = cast<CallInst>(Malloc); 1747 } 1748 1749 GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true), 1750 TD, TLI); 1751 return true; 1752 } 1753 1754 return false; 1755} 1756 1757// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1758// that only one value (besides its initializer) is ever stored to the global. 1759static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1760 AtomicOrdering Ordering, 1761 Module::global_iterator &GVI, 1762 TargetData *TD, TargetLibraryInfo *TLI) { 1763 // Ignore no-op GEPs and bitcasts. 1764 StoredOnceVal = StoredOnceVal->stripPointerCasts(); 1765 1766 // If we are dealing with a pointer global that is initialized to null and 1767 // only has one (non-null) value stored into it, then we can optimize any 1768 // users of the loaded value (often calls and loads) that would trap if the 1769 // value was null. 1770 if (GV->getInitializer()->getType()->isPointerTy() && 1771 GV->getInitializer()->isNullValue()) { 1772 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1773 if (GV->getInitializer()->getType() != SOVC->getType()) 1774 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1775 1776 // Optimize away any trapping uses of the loaded value. 1777 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI)) 1778 return true; 1779 } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) { 1780 Type *MallocType = getMallocAllocatedType(CI, TLI); 1781 if (MallocType && 1782 TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI, 1783 TD, TLI)) 1784 return true; 1785 } 1786 } 1787 1788 return false; 1789} 1790 1791/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1792/// two values ever stored into GV are its initializer and OtherVal. See if we 1793/// can shrink the global into a boolean and select between the two values 1794/// whenever it is used. This exposes the values to other scalar optimizations. 1795static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1796 Type *GVElType = GV->getType()->getElementType(); 1797 1798 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1799 // an FP value, pointer or vector, don't do this optimization because a select 1800 // between them is very expensive and unlikely to lead to later 1801 // simplification. In these cases, we typically end up with "cond ? v1 : v2" 1802 // where v1 and v2 both require constant pool loads, a big loss. 1803 if (GVElType == Type::getInt1Ty(GV->getContext()) || 1804 GVElType->isFloatingPointTy() || 1805 GVElType->isPointerTy() || GVElType->isVectorTy()) 1806 return false; 1807 1808 // Walk the use list of the global seeing if all the uses are load or store. 1809 // If there is anything else, bail out. 1810 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){ 1811 User *U = *I; 1812 if (!isa<LoadInst>(U) && !isa<StoreInst>(U)) 1813 return false; 1814 } 1815 1816 DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV); 1817 1818 // Create the new global, initializing it to false. 1819 GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()), 1820 false, 1821 GlobalValue::InternalLinkage, 1822 ConstantInt::getFalse(GV->getContext()), 1823 GV->getName()+".b", 1824 GV->getThreadLocalMode()); 1825 GV->getParent()->getGlobalList().insert(GV, NewGV); 1826 1827 Constant *InitVal = GV->getInitializer(); 1828 assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && 1829 "No reason to shrink to bool!"); 1830 1831 // If initialized to zero and storing one into the global, we can use a cast 1832 // instead of a select to synthesize the desired value. 1833 bool IsOneZero = false; 1834 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1835 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1836 1837 while (!GV->use_empty()) { 1838 Instruction *UI = cast<Instruction>(GV->use_back()); 1839 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1840 // Change the store into a boolean store. 1841 bool StoringOther = SI->getOperand(0) == OtherVal; 1842 // Only do this if we weren't storing a loaded value. 1843 Value *StoreVal; 1844 if (StoringOther || SI->getOperand(0) == InitVal) 1845 StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()), 1846 StoringOther); 1847 else { 1848 // Otherwise, we are storing a previously loaded copy. To do this, 1849 // change the copy from copying the original value to just copying the 1850 // bool. 1851 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1852 1853 // If we've already replaced the input, StoredVal will be a cast or 1854 // select instruction. If not, it will be a load of the original 1855 // global. 1856 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1857 assert(LI->getOperand(0) == GV && "Not a copy!"); 1858 // Insert a new load, to preserve the saved value. 1859 StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0, 1860 LI->getOrdering(), LI->getSynchScope(), LI); 1861 } else { 1862 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1863 "This is not a form that we understand!"); 1864 StoreVal = StoredVal->getOperand(0); 1865 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1866 } 1867 } 1868 new StoreInst(StoreVal, NewGV, false, 0, 1869 SI->getOrdering(), SI->getSynchScope(), SI); 1870 } else { 1871 // Change the load into a load of bool then a select. 1872 LoadInst *LI = cast<LoadInst>(UI); 1873 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0, 1874 LI->getOrdering(), LI->getSynchScope(), LI); 1875 Value *NSI; 1876 if (IsOneZero) 1877 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1878 else 1879 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); 1880 NSI->takeName(LI); 1881 LI->replaceAllUsesWith(NSI); 1882 } 1883 UI->eraseFromParent(); 1884 } 1885 1886 GV->eraseFromParent(); 1887 return true; 1888} 1889 1890 1891/// ProcessGlobal - Analyze the specified global variable and optimize it if 1892/// possible. If we make a change, return true. 1893bool GlobalOpt::ProcessGlobal(GlobalVariable *GV, 1894 Module::global_iterator &GVI) { 1895 if (!GV->isDiscardableIfUnused()) 1896 return false; 1897 1898 // Do more involved optimizations if the global is internal. 1899 GV->removeDeadConstantUsers(); 1900 1901 if (GV->use_empty()) { 1902 DEBUG(dbgs() << "GLOBAL DEAD: " << *GV); 1903 GV->eraseFromParent(); 1904 ++NumDeleted; 1905 return true; 1906 } 1907 1908 if (!GV->hasLocalLinkage()) 1909 return false; 1910 1911 SmallPtrSet<const PHINode*, 16> PHIUsers; 1912 GlobalStatus GS; 1913 1914 if (AnalyzeGlobal(GV, GS, PHIUsers)) 1915 return false; 1916 1917 if (!GS.isCompared && !GV->hasUnnamedAddr()) { 1918 GV->setUnnamedAddr(true); 1919 NumUnnamed++; 1920 } 1921 1922 if (GV->isConstant() || !GV->hasInitializer()) 1923 return false; 1924 1925 return ProcessInternalGlobal(GV, GVI, PHIUsers, GS); 1926} 1927 1928/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1929/// it if possible. If we make a change, return true. 1930bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1931 Module::global_iterator &GVI, 1932 const SmallPtrSet<const PHINode*, 16> &PHIUsers, 1933 const GlobalStatus &GS) { 1934 // If this is a first class global and has only one accessing function 1935 // and this function is main (which we know is not recursive we can make 1936 // this global a local variable) we replace the global with a local alloca 1937 // in this function. 1938 // 1939 // NOTE: It doesn't make sense to promote non single-value types since we 1940 // are just replacing static memory to stack memory. 1941 // 1942 // If the global is in different address space, don't bring it to stack. 1943 if (!GS.HasMultipleAccessingFunctions && 1944 GS.AccessingFunction && !GS.HasNonInstructionUser && 1945 GV->getType()->getElementType()->isSingleValueType() && 1946 GS.AccessingFunction->getName() == "main" && 1947 GS.AccessingFunction->hasExternalLinkage() && 1948 GV->getType()->getAddressSpace() == 0) { 1949 DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV); 1950 Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction 1951 ->getEntryBlock().begin()); 1952 Type *ElemTy = GV->getType()->getElementType(); 1953 // FIXME: Pass Global's alignment when globals have alignment 1954 AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI); 1955 if (!isa<UndefValue>(GV->getInitializer())) 1956 new StoreInst(GV->getInitializer(), Alloca, &FirstI); 1957 1958 GV->replaceAllUsesWith(Alloca); 1959 GV->eraseFromParent(); 1960 ++NumLocalized; 1961 return true; 1962 } 1963 1964 // If the global is never loaded (but may be stored to), it is dead. 1965 // Delete it now. 1966 if (!GS.isLoaded) { 1967 DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV); 1968 1969 bool Changed; 1970 if (isLeakCheckerRoot(GV)) { 1971 // Delete any constant stores to the global. 1972 Changed = CleanupPointerRootUsers(GV, TLI); 1973 } else { 1974 // Delete any stores we can find to the global. We may not be able to 1975 // make it completely dead though. 1976 Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 1977 } 1978 1979 // If the global is dead now, delete it. 1980 if (GV->use_empty()) { 1981 GV->eraseFromParent(); 1982 ++NumDeleted; 1983 Changed = true; 1984 } 1985 return Changed; 1986 1987 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1988 DEBUG(dbgs() << "MARKING CONSTANT: " << *GV); 1989 GV->setConstant(true); 1990 1991 // Clean up any obviously simplifiable users now. 1992 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 1993 1994 // If the global is dead now, just nuke it. 1995 if (GV->use_empty()) { 1996 DEBUG(dbgs() << " *** Marking constant allowed us to simplify " 1997 << "all users and delete global!\n"); 1998 GV->eraseFromParent(); 1999 ++NumDeleted; 2000 } 2001 2002 ++NumMarked; 2003 return true; 2004 } else if (!GV->getInitializer()->getType()->isSingleValueType()) { 2005 if (TargetData *TD = getAnalysisIfAvailable<TargetData>()) 2006 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) { 2007 GVI = FirstNewGV; // Don't skip the newly produced globals! 2008 return true; 2009 } 2010 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 2011 // If the initial value for the global was an undef value, and if only 2012 // one other value was stored into it, we can just change the 2013 // initializer to be the stored value, then delete all stores to the 2014 // global. This allows us to mark it constant. 2015 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 2016 if (isa<UndefValue>(GV->getInitializer())) { 2017 // Change the initial value here. 2018 GV->setInitializer(SOVConstant); 2019 2020 // Clean up any obviously simplifiable users now. 2021 CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); 2022 2023 if (GV->use_empty()) { 2024 DEBUG(dbgs() << " *** Substituting initializer allowed us to " 2025 << "simplify all users and delete global!\n"); 2026 GV->eraseFromParent(); 2027 ++NumDeleted; 2028 } else { 2029 GVI = GV; 2030 } 2031 ++NumSubstitute; 2032 return true; 2033 } 2034 2035 // Try to optimize globals based on the knowledge that only one value 2036 // (besides its initializer) is ever stored to the global. 2037 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI, 2038 TD, TLI)) 2039 return true; 2040 2041 // Otherwise, if the global was not a boolean, we can shrink it to be a 2042 // boolean. 2043 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 2044 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 2045 ++NumShrunkToBool; 2046 return true; 2047 } 2048 } 2049 2050 return false; 2051} 2052 2053/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 2054/// function, changing them to FastCC. 2055static void ChangeCalleesToFastCall(Function *F) { 2056 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 2057 if (isa<BlockAddress>(*UI)) 2058 continue; 2059 CallSite User(cast<Instruction>(*UI)); 2060 User.setCallingConv(CallingConv::Fast); 2061 } 2062} 2063 2064static AttrListPtr StripNest(const AttrListPtr &Attrs) { 2065 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { 2066 if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0) 2067 continue; 2068 2069 // There can be only one. 2070 return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest); 2071 } 2072 2073 return Attrs; 2074} 2075 2076static void RemoveNestAttribute(Function *F) { 2077 F->setAttributes(StripNest(F->getAttributes())); 2078 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 2079 if (isa<BlockAddress>(*UI)) 2080 continue; 2081 CallSite User(cast<Instruction>(*UI)); 2082 User.setAttributes(StripNest(User.getAttributes())); 2083 } 2084} 2085 2086bool GlobalOpt::OptimizeFunctions(Module &M) { 2087 bool Changed = false; 2088 // Optimize functions. 2089 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 2090 Function *F = FI++; 2091 // Functions without names cannot be referenced outside this module. 2092 if (!F->hasName() && !F->isDeclaration()) 2093 F->setLinkage(GlobalValue::InternalLinkage); 2094 F->removeDeadConstantUsers(); 2095 if (F->isDefTriviallyDead()) { 2096 F->eraseFromParent(); 2097 Changed = true; 2098 ++NumFnDeleted; 2099 } else if (F->hasLocalLinkage()) { 2100 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 2101 !F->hasAddressTaken()) { 2102 // If this function has C calling conventions, is not a varargs 2103 // function, and is only called directly, promote it to use the Fast 2104 // calling convention. 2105 F->setCallingConv(CallingConv::Fast); 2106 ChangeCalleesToFastCall(F); 2107 ++NumFastCallFns; 2108 Changed = true; 2109 } 2110 2111 if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) && 2112 !F->hasAddressTaken()) { 2113 // The function is not used by a trampoline intrinsic, so it is safe 2114 // to remove the 'nest' attribute. 2115 RemoveNestAttribute(F); 2116 ++NumNestRemoved; 2117 Changed = true; 2118 } 2119 } 2120 } 2121 return Changed; 2122} 2123 2124bool GlobalOpt::OptimizeGlobalVars(Module &M) { 2125 bool Changed = false; 2126 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 2127 GVI != E; ) { 2128 GlobalVariable *GV = GVI++; 2129 // Global variables without names cannot be referenced outside this module. 2130 if (!GV->hasName() && !GV->isDeclaration()) 2131 GV->setLinkage(GlobalValue::InternalLinkage); 2132 // Simplify the initializer. 2133 if (GV->hasInitializer()) 2134 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) { 2135 Constant *New = ConstantFoldConstantExpression(CE, TD, TLI); 2136 if (New && New != CE) 2137 GV->setInitializer(New); 2138 } 2139 2140 Changed |= ProcessGlobal(GV, GVI); 2141 } 2142 return Changed; 2143} 2144 2145/// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all 2146/// initializers have an init priority of 65535. 2147GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 2148 GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); 2149 if (GV == 0) return 0; 2150 2151 // Verify that the initializer is simple enough for us to handle. We are 2152 // only allowed to optimize the initializer if it is unique. 2153 if (!GV->hasUniqueInitializer()) return 0; 2154 2155 if (isa<ConstantAggregateZero>(GV->getInitializer())) 2156 return GV; 2157 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 2158 2159 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { 2160 if (isa<ConstantAggregateZero>(*i)) 2161 continue; 2162 ConstantStruct *CS = cast<ConstantStruct>(*i); 2163 if (isa<ConstantPointerNull>(CS->getOperand(1))) 2164 continue; 2165 2166 // Must have a function or null ptr. 2167 if (!isa<Function>(CS->getOperand(1))) 2168 return 0; 2169 2170 // Init priority must be standard. 2171 ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0)); 2172 if (CI->getZExtValue() != 65535) 2173 return 0; 2174 } 2175 2176 return GV; 2177} 2178 2179/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 2180/// return a list of the functions and null terminator as a vector. 2181static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 2182 if (GV->getInitializer()->isNullValue()) 2183 return std::vector<Function*>(); 2184 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 2185 std::vector<Function*> Result; 2186 Result.reserve(CA->getNumOperands()); 2187 for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { 2188 ConstantStruct *CS = cast<ConstantStruct>(*i); 2189 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 2190 } 2191 return Result; 2192} 2193 2194/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 2195/// specified array, returning the new global to use. 2196static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 2197 const std::vector<Function*> &Ctors) { 2198 // If we made a change, reassemble the initializer list. 2199 Constant *CSVals[2]; 2200 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535); 2201 CSVals[1] = 0; 2202 2203 StructType *StructTy = 2204 cast <StructType>( 2205 cast<ArrayType>(GCL->getType()->getElementType())->getElementType()); 2206 2207 // Create the new init list. 2208 std::vector<Constant*> CAList; 2209 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 2210 if (Ctors[i]) { 2211 CSVals[1] = Ctors[i]; 2212 } else { 2213 Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()), 2214 false); 2215 PointerType *PFTy = PointerType::getUnqual(FTy); 2216 CSVals[1] = Constant::getNullValue(PFTy); 2217 CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 2218 0x7fffffff); 2219 } 2220 CAList.push_back(ConstantStruct::get(StructTy, CSVals)); 2221 } 2222 2223 // Create the array initializer. 2224 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, 2225 CAList.size()), CAList); 2226 2227 // If we didn't change the number of elements, don't create a new GV. 2228 if (CA->getType() == GCL->getInitializer()->getType()) { 2229 GCL->setInitializer(CA); 2230 return GCL; 2231 } 2232 2233 // Create the new global and insert it next to the existing list. 2234 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 2235 GCL->getLinkage(), CA, "", 2236 GCL->getThreadLocalMode()); 2237 GCL->getParent()->getGlobalList().insert(GCL, NGV); 2238 NGV->takeName(GCL); 2239 2240 // Nuke the old list, replacing any uses with the new one. 2241 if (!GCL->use_empty()) { 2242 Constant *V = NGV; 2243 if (V->getType() != GCL->getType()) 2244 V = ConstantExpr::getBitCast(V, GCL->getType()); 2245 GCL->replaceAllUsesWith(V); 2246 } 2247 GCL->eraseFromParent(); 2248 2249 if (Ctors.size()) 2250 return NGV; 2251 else 2252 return 0; 2253} 2254 2255 2256static inline bool 2257isSimpleEnoughValueToCommit(Constant *C, 2258 SmallPtrSet<Constant*, 8> &SimpleConstants, 2259 const TargetData *TD); 2260 2261 2262/// isSimpleEnoughValueToCommit - Return true if the specified constant can be 2263/// handled by the code generator. We don't want to generate something like: 2264/// void *X = &X/42; 2265/// because the code generator doesn't have a relocation that can handle that. 2266/// 2267/// This function should be called if C was not found (but just got inserted) 2268/// in SimpleConstants to avoid having to rescan the same constants all the 2269/// time. 2270static bool isSimpleEnoughValueToCommitHelper(Constant *C, 2271 SmallPtrSet<Constant*, 8> &SimpleConstants, 2272 const TargetData *TD) { 2273 // Simple integer, undef, constant aggregate zero, global addresses, etc are 2274 // all supported. 2275 if (C->getNumOperands() == 0 || isa<BlockAddress>(C) || 2276 isa<GlobalValue>(C)) 2277 return true; 2278 2279 // Aggregate values are safe if all their elements are. 2280 if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) || 2281 isa<ConstantVector>(C)) { 2282 for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) { 2283 Constant *Op = cast<Constant>(C->getOperand(i)); 2284 if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD)) 2285 return false; 2286 } 2287 return true; 2288 } 2289 2290 // We don't know exactly what relocations are allowed in constant expressions, 2291 // so we allow &global+constantoffset, which is safe and uniformly supported 2292 // across targets. 2293 ConstantExpr *CE = cast<ConstantExpr>(C); 2294 switch (CE->getOpcode()) { 2295 case Instruction::BitCast: 2296 // Bitcast is fine if the casted value is fine. 2297 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2298 2299 case Instruction::IntToPtr: 2300 case Instruction::PtrToInt: 2301 // int <=> ptr is fine if the int type is the same size as the 2302 // pointer type. 2303 if (!TD || TD->getTypeSizeInBits(CE->getType()) != 2304 TD->getTypeSizeInBits(CE->getOperand(0)->getType())) 2305 return false; 2306 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2307 2308 // GEP is fine if it is simple + constant offset. 2309 case Instruction::GetElementPtr: 2310 for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 2311 if (!isa<ConstantInt>(CE->getOperand(i))) 2312 return false; 2313 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2314 2315 case Instruction::Add: 2316 // We allow simple+cst. 2317 if (!isa<ConstantInt>(CE->getOperand(1))) 2318 return false; 2319 return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); 2320 } 2321 return false; 2322} 2323 2324static inline bool 2325isSimpleEnoughValueToCommit(Constant *C, 2326 SmallPtrSet<Constant*, 8> &SimpleConstants, 2327 const TargetData *TD) { 2328 // If we already checked this constant, we win. 2329 if (!SimpleConstants.insert(C)) return true; 2330 // Check the constant. 2331 return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD); 2332} 2333 2334 2335/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 2336/// enough for us to understand. In particular, if it is a cast to anything 2337/// other than from one pointer type to another pointer type, we punt. 2338/// We basically just support direct accesses to globals and GEP's of 2339/// globals. This should be kept up to date with CommitValueTo. 2340static bool isSimpleEnoughPointerToCommit(Constant *C) { 2341 // Conservatively, avoid aggregate types. This is because we don't 2342 // want to worry about them partially overlapping other stores. 2343 if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType()) 2344 return false; 2345 2346 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) 2347 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2348 // external globals. 2349 return GV->hasUniqueInitializer(); 2350 2351 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 2352 // Handle a constantexpr gep. 2353 if (CE->getOpcode() == Instruction::GetElementPtr && 2354 isa<GlobalVariable>(CE->getOperand(0)) && 2355 cast<GEPOperator>(CE)->isInBounds()) { 2356 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2357 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2358 // external globals. 2359 if (!GV->hasUniqueInitializer()) 2360 return false; 2361 2362 // The first index must be zero. 2363 ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin())); 2364 if (!CI || !CI->isZero()) return false; 2365 2366 // The remaining indices must be compile-time known integers within the 2367 // notional bounds of the corresponding static array types. 2368 if (!CE->isGEPWithNoNotionalOverIndexing()) 2369 return false; 2370 2371 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 2372 2373 // A constantexpr bitcast from a pointer to another pointer is a no-op, 2374 // and we know how to evaluate it by moving the bitcast from the pointer 2375 // operand to the value operand. 2376 } else if (CE->getOpcode() == Instruction::BitCast && 2377 isa<GlobalVariable>(CE->getOperand(0))) { 2378 // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or 2379 // external globals. 2380 return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer(); 2381 } 2382 } 2383 2384 return false; 2385} 2386 2387/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 2388/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 2389/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 2390static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 2391 ConstantExpr *Addr, unsigned OpNo) { 2392 // Base case of the recursion. 2393 if (OpNo == Addr->getNumOperands()) { 2394 assert(Val->getType() == Init->getType() && "Type mismatch!"); 2395 return Val; 2396 } 2397 2398 SmallVector<Constant*, 32> Elts; 2399 if (StructType *STy = dyn_cast<StructType>(Init->getType())) { 2400 // Break up the constant into its elements. 2401 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 2402 Elts.push_back(Init->getAggregateElement(i)); 2403 2404 // Replace the element that we are supposed to. 2405 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 2406 unsigned Idx = CU->getZExtValue(); 2407 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 2408 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 2409 2410 // Return the modified struct. 2411 return ConstantStruct::get(STy, Elts); 2412 } 2413 2414 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 2415 SequentialType *InitTy = cast<SequentialType>(Init->getType()); 2416 2417 uint64_t NumElts; 2418 if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy)) 2419 NumElts = ATy->getNumElements(); 2420 else 2421 NumElts = InitTy->getVectorNumElements(); 2422 2423 // Break up the array into elements. 2424 for (uint64_t i = 0, e = NumElts; i != e; ++i) 2425 Elts.push_back(Init->getAggregateElement(i)); 2426 2427 assert(CI->getZExtValue() < NumElts); 2428 Elts[CI->getZExtValue()] = 2429 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 2430 2431 if (Init->getType()->isArrayTy()) 2432 return ConstantArray::get(cast<ArrayType>(InitTy), Elts); 2433 return ConstantVector::get(Elts); 2434} 2435 2436/// CommitValueTo - We have decided that Addr (which satisfies the predicate 2437/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 2438static void CommitValueTo(Constant *Val, Constant *Addr) { 2439 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 2440 assert(GV->hasInitializer()); 2441 GV->setInitializer(Val); 2442 return; 2443 } 2444 2445 ConstantExpr *CE = cast<ConstantExpr>(Addr); 2446 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2447 GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2)); 2448} 2449 2450namespace { 2451 2452/// Evaluator - This class evaluates LLVM IR, producing the Constant 2453/// representing each SSA instruction. Changes to global variables are stored 2454/// in a mapping that can be iterated over after the evaluation is complete. 2455/// Once an evaluation call fails, the evaluation object should not be reused. 2456class Evaluator { 2457public: 2458 Evaluator(const TargetData *TD, const TargetLibraryInfo *TLI) 2459 : TD(TD), TLI(TLI) { 2460 ValueStack.push_back(new DenseMap<Value*, Constant*>); 2461 } 2462 2463 ~Evaluator() { 2464 DeleteContainerPointers(ValueStack); 2465 while (!AllocaTmps.empty()) { 2466 GlobalVariable *Tmp = AllocaTmps.back(); 2467 AllocaTmps.pop_back(); 2468 2469 // If there are still users of the alloca, the program is doing something 2470 // silly, e.g. storing the address of the alloca somewhere and using it 2471 // later. Since this is undefined, we'll just make it be null. 2472 if (!Tmp->use_empty()) 2473 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2474 delete Tmp; 2475 } 2476 } 2477 2478 /// EvaluateFunction - Evaluate a call to function F, returning true if 2479 /// successful, false if we can't evaluate it. ActualArgs contains the formal 2480 /// arguments for the function. 2481 bool EvaluateFunction(Function *F, Constant *&RetVal, 2482 const SmallVectorImpl<Constant*> &ActualArgs); 2483 2484 /// EvaluateBlock - Evaluate all instructions in block BB, returning true if 2485 /// successful, false if we can't evaluate it. NewBB returns the next BB that 2486 /// control flows into, or null upon return. 2487 bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB); 2488 2489 Constant *getVal(Value *V) { 2490 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 2491 Constant *R = ValueStack.back()->lookup(V); 2492 assert(R && "Reference to an uncomputed value!"); 2493 return R; 2494 } 2495 2496 void setVal(Value *V, Constant *C) { 2497 ValueStack.back()->operator[](V) = C; 2498 } 2499 2500 const DenseMap<Constant*, Constant*> &getMutatedMemory() const { 2501 return MutatedMemory; 2502 } 2503 2504 const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const { 2505 return Invariants; 2506 } 2507 2508private: 2509 Constant *ComputeLoadResult(Constant *P); 2510 2511 /// ValueStack - As we compute SSA register values, we store their contents 2512 /// here. The back of the vector contains the current function and the stack 2513 /// contains the values in the calling frames. 2514 SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack; 2515 2516 /// CallStack - This is used to detect recursion. In pathological situations 2517 /// we could hit exponential behavior, but at least there is nothing 2518 /// unbounded. 2519 SmallVector<Function*, 4> CallStack; 2520 2521 /// MutatedMemory - For each store we execute, we update this map. Loads 2522 /// check this to get the most up-to-date value. If evaluation is successful, 2523 /// this state is committed to the process. 2524 DenseMap<Constant*, Constant*> MutatedMemory; 2525 2526 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2527 /// to represent its body. This vector is needed so we can delete the 2528 /// temporary globals when we are done. 2529 SmallVector<GlobalVariable*, 32> AllocaTmps; 2530 2531 /// Invariants - These global variables have been marked invariant by the 2532 /// static constructor. 2533 SmallPtrSet<GlobalVariable*, 8> Invariants; 2534 2535 /// SimpleConstants - These are constants we have checked and know to be 2536 /// simple enough to live in a static initializer of a global. 2537 SmallPtrSet<Constant*, 8> SimpleConstants; 2538 2539 const TargetData *TD; 2540 const TargetLibraryInfo *TLI; 2541}; 2542 2543} // anonymous namespace 2544 2545/// ComputeLoadResult - Return the value that would be computed by a load from 2546/// P after the stores reflected by 'memory' have been performed. If we can't 2547/// decide, return null. 2548Constant *Evaluator::ComputeLoadResult(Constant *P) { 2549 // If this memory location has been recently stored, use the stored value: it 2550 // is the most up-to-date. 2551 DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P); 2552 if (I != MutatedMemory.end()) return I->second; 2553 2554 // Access it. 2555 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 2556 if (GV->hasDefinitiveInitializer()) 2557 return GV->getInitializer(); 2558 return 0; 2559 } 2560 2561 // Handle a constantexpr getelementptr. 2562 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 2563 if (CE->getOpcode() == Instruction::GetElementPtr && 2564 isa<GlobalVariable>(CE->getOperand(0))) { 2565 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 2566 if (GV->hasDefinitiveInitializer()) 2567 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 2568 } 2569 2570 return 0; // don't know how to evaluate. 2571} 2572 2573/// EvaluateBlock - Evaluate all instructions in block BB, returning true if 2574/// successful, false if we can't evaluate it. NewBB returns the next BB that 2575/// control flows into, or null upon return. 2576bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst, 2577 BasicBlock *&NextBB) { 2578 // This is the main evaluation loop. 2579 while (1) { 2580 Constant *InstResult = 0; 2581 2582 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 2583 if (!SI->isSimple()) return false; // no volatile/atomic accesses. 2584 Constant *Ptr = getVal(SI->getOperand(1)); 2585 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2586 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2587 if (!isSimpleEnoughPointerToCommit(Ptr)) 2588 // If this is too complex for us to commit, reject it. 2589 return false; 2590 2591 Constant *Val = getVal(SI->getOperand(0)); 2592 2593 // If this might be too difficult for the backend to handle (e.g. the addr 2594 // of one global variable divided by another) then we can't commit it. 2595 if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) 2596 return false; 2597 2598 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2599 if (CE->getOpcode() == Instruction::BitCast) { 2600 // If we're evaluating a store through a bitcast, then we need 2601 // to pull the bitcast off the pointer type and push it onto the 2602 // stored value. 2603 Ptr = CE->getOperand(0); 2604 2605 Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType(); 2606 2607 // In order to push the bitcast onto the stored value, a bitcast 2608 // from NewTy to Val's type must be legal. If it's not, we can try 2609 // introspecting NewTy to find a legal conversion. 2610 while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) { 2611 // If NewTy is a struct, we can convert the pointer to the struct 2612 // into a pointer to its first member. 2613 // FIXME: This could be extended to support arrays as well. 2614 if (StructType *STy = dyn_cast<StructType>(NewTy)) { 2615 NewTy = STy->getTypeAtIndex(0U); 2616 2617 IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32); 2618 Constant *IdxZero = ConstantInt::get(IdxTy, 0, false); 2619 Constant * const IdxList[] = {IdxZero, IdxZero}; 2620 2621 Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList); 2622 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2623 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2624 2625 // If we can't improve the situation by introspecting NewTy, 2626 // we have to give up. 2627 } else { 2628 return false; 2629 } 2630 } 2631 2632 // If we found compatible types, go ahead and push the bitcast 2633 // onto the stored value. 2634 Val = ConstantExpr::getBitCast(Val, NewTy); 2635 } 2636 2637 MutatedMemory[Ptr] = Val; 2638 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 2639 InstResult = ConstantExpr::get(BO->getOpcode(), 2640 getVal(BO->getOperand(0)), 2641 getVal(BO->getOperand(1))); 2642 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 2643 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 2644 getVal(CI->getOperand(0)), 2645 getVal(CI->getOperand(1))); 2646 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 2647 InstResult = ConstantExpr::getCast(CI->getOpcode(), 2648 getVal(CI->getOperand(0)), 2649 CI->getType()); 2650 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 2651 InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)), 2652 getVal(SI->getOperand(1)), 2653 getVal(SI->getOperand(2))); 2654 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 2655 Constant *P = getVal(GEP->getOperand(0)); 2656 SmallVector<Constant*, 8> GEPOps; 2657 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); 2658 i != e; ++i) 2659 GEPOps.push_back(getVal(*i)); 2660 InstResult = 2661 ConstantExpr::getGetElementPtr(P, GEPOps, 2662 cast<GEPOperator>(GEP)->isInBounds()); 2663 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 2664 if (!LI->isSimple()) return false; // no volatile/atomic accesses. 2665 Constant *Ptr = getVal(LI->getOperand(0)); 2666 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 2667 Ptr = ConstantFoldConstantExpression(CE, TD, TLI); 2668 InstResult = ComputeLoadResult(Ptr); 2669 if (InstResult == 0) return false; // Could not evaluate load. 2670 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 2671 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 2672 Type *Ty = AI->getType()->getElementType(); 2673 AllocaTmps.push_back(new GlobalVariable(Ty, false, 2674 GlobalValue::InternalLinkage, 2675 UndefValue::get(Ty), 2676 AI->getName())); 2677 InstResult = AllocaTmps.back(); 2678 } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) { 2679 CallSite CS(CurInst); 2680 2681 // Debug info can safely be ignored here. 2682 if (isa<DbgInfoIntrinsic>(CS.getInstruction())) { 2683 ++CurInst; 2684 continue; 2685 } 2686 2687 // Cannot handle inline asm. 2688 if (isa<InlineAsm>(CS.getCalledValue())) return false; 2689 2690 if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) { 2691 if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) { 2692 if (MSI->isVolatile()) return false; 2693 Constant *Ptr = getVal(MSI->getDest()); 2694 Constant *Val = getVal(MSI->getValue()); 2695 Constant *DestVal = ComputeLoadResult(getVal(Ptr)); 2696 if (Val->isNullValue() && DestVal && DestVal->isNullValue()) { 2697 // This memset is a no-op. 2698 ++CurInst; 2699 continue; 2700 } 2701 } 2702 2703 if (II->getIntrinsicID() == Intrinsic::lifetime_start || 2704 II->getIntrinsicID() == Intrinsic::lifetime_end) { 2705 ++CurInst; 2706 continue; 2707 } 2708 2709 if (II->getIntrinsicID() == Intrinsic::invariant_start) { 2710 // We don't insert an entry into Values, as it doesn't have a 2711 // meaningful return value. 2712 if (!II->use_empty()) 2713 return false; 2714 ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0)); 2715 Value *PtrArg = getVal(II->getArgOperand(1)); 2716 Value *Ptr = PtrArg->stripPointerCasts(); 2717 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) { 2718 Type *ElemTy = cast<PointerType>(GV->getType())->getElementType(); 2719 if (!Size->isAllOnesValue() && 2720 Size->getValue().getLimitedValue() >= 2721 TD->getTypeStoreSize(ElemTy)) 2722 Invariants.insert(GV); 2723 } 2724 // Continue even if we do nothing. 2725 ++CurInst; 2726 continue; 2727 } 2728 return false; 2729 } 2730 2731 // Resolve function pointers. 2732 Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue())); 2733 if (!Callee || Callee->mayBeOverridden()) 2734 return false; // Cannot resolve. 2735 2736 SmallVector<Constant*, 8> Formals; 2737 for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i) 2738 Formals.push_back(getVal(*i)); 2739 2740 if (Callee->isDeclaration()) { 2741 // If this is a function we can constant fold, do it. 2742 if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) { 2743 InstResult = C; 2744 } else { 2745 return false; 2746 } 2747 } else { 2748 if (Callee->getFunctionType()->isVarArg()) 2749 return false; 2750 2751 Constant *RetVal; 2752 // Execute the call, if successful, use the return value. 2753 ValueStack.push_back(new DenseMap<Value*, Constant*>); 2754 if (!EvaluateFunction(Callee, RetVal, Formals)) 2755 return false; 2756 delete ValueStack.pop_back_val(); 2757 InstResult = RetVal; 2758 } 2759 } else if (isa<TerminatorInst>(CurInst)) { 2760 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2761 if (BI->isUnconditional()) { 2762 NextBB = BI->getSuccessor(0); 2763 } else { 2764 ConstantInt *Cond = 2765 dyn_cast<ConstantInt>(getVal(BI->getCondition())); 2766 if (!Cond) return false; // Cannot determine. 2767 2768 NextBB = BI->getSuccessor(!Cond->getZExtValue()); 2769 } 2770 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2771 ConstantInt *Val = 2772 dyn_cast<ConstantInt>(getVal(SI->getCondition())); 2773 if (!Val) return false; // Cannot determine. 2774 NextBB = SI->findCaseValue(Val).getCaseSuccessor(); 2775 } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) { 2776 Value *Val = getVal(IBI->getAddress())->stripPointerCasts(); 2777 if (BlockAddress *BA = dyn_cast<BlockAddress>(Val)) 2778 NextBB = BA->getBasicBlock(); 2779 else 2780 return false; // Cannot determine. 2781 } else if (isa<ReturnInst>(CurInst)) { 2782 NextBB = 0; 2783 } else { 2784 // invoke, unwind, resume, unreachable. 2785 return false; // Cannot handle this terminator. 2786 } 2787 2788 // We succeeded at evaluating this block! 2789 return true; 2790 } else { 2791 // Did not know how to evaluate this! 2792 return false; 2793 } 2794 2795 if (!CurInst->use_empty()) { 2796 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult)) 2797 InstResult = ConstantFoldConstantExpression(CE, TD, TLI); 2798 2799 setVal(CurInst, InstResult); 2800 } 2801 2802 // If we just processed an invoke, we finished evaluating the block. 2803 if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) { 2804 NextBB = II->getNormalDest(); 2805 return true; 2806 } 2807 2808 // Advance program counter. 2809 ++CurInst; 2810 } 2811} 2812 2813/// EvaluateFunction - Evaluate a call to function F, returning true if 2814/// successful, false if we can't evaluate it. ActualArgs contains the formal 2815/// arguments for the function. 2816bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal, 2817 const SmallVectorImpl<Constant*> &ActualArgs) { 2818 // Check to see if this function is already executing (recursion). If so, 2819 // bail out. TODO: we might want to accept limited recursion. 2820 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 2821 return false; 2822 2823 CallStack.push_back(F); 2824 2825 // Initialize arguments to the incoming values specified. 2826 unsigned ArgNo = 0; 2827 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 2828 ++AI, ++ArgNo) 2829 setVal(AI, ActualArgs[ArgNo]); 2830 2831 // ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 2832 // we can only evaluate any one basic block at most once. This set keeps 2833 // track of what we have executed so we can detect recursive cases etc. 2834 SmallPtrSet<BasicBlock*, 32> ExecutedBlocks; 2835 2836 // CurBB - The current basic block we're evaluating. 2837 BasicBlock *CurBB = F->begin(); 2838 2839 BasicBlock::iterator CurInst = CurBB->begin(); 2840 2841 while (1) { 2842 BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings. 2843 if (!EvaluateBlock(CurInst, NextBB)) 2844 return false; 2845 2846 if (NextBB == 0) { 2847 // Successfully running until there's no next block means that we found 2848 // the return. Fill it the return value and pop the call stack. 2849 ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator()); 2850 if (RI->getNumOperands()) 2851 RetVal = getVal(RI->getOperand(0)); 2852 CallStack.pop_back(); 2853 return true; 2854 } 2855 2856 // Okay, we succeeded in evaluating this control flow. See if we have 2857 // executed the new block before. If so, we have a looping function, 2858 // which we cannot evaluate in reasonable time. 2859 if (!ExecutedBlocks.insert(NextBB)) 2860 return false; // looped! 2861 2862 // Okay, we have never been in this block before. Check to see if there 2863 // are any PHI nodes. If so, evaluate them with information about where 2864 // we came from. 2865 PHINode *PN = 0; 2866 for (CurInst = NextBB->begin(); 2867 (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2868 setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB))); 2869 2870 // Advance to the next block. 2871 CurBB = NextBB; 2872 } 2873} 2874 2875/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2876/// we can. Return true if we can, false otherwise. 2877static bool EvaluateStaticConstructor(Function *F, const TargetData *TD, 2878 const TargetLibraryInfo *TLI) { 2879 // Call the function. 2880 Evaluator Eval(TD, TLI); 2881 Constant *RetValDummy; 2882 bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy, 2883 SmallVector<Constant*, 0>()); 2884 2885 if (EvalSuccess) { 2886 // We succeeded at evaluation: commit the result. 2887 DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2888 << F->getName() << "' to " << Eval.getMutatedMemory().size() 2889 << " stores.\n"); 2890 for (DenseMap<Constant*, Constant*>::const_iterator I = 2891 Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end(); 2892 I != E; ++I) 2893 CommitValueTo(I->second, I->first); 2894 for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I = 2895 Eval.getInvariants().begin(), E = Eval.getInvariants().end(); 2896 I != E; ++I) 2897 (*I)->setConstant(true); 2898 } 2899 2900 return EvalSuccess; 2901} 2902 2903/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2904/// Return true if anything changed. 2905bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2906 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2907 bool MadeChange = false; 2908 if (Ctors.empty()) return false; 2909 2910 // Loop over global ctors, optimizing them when we can. 2911 for (unsigned i = 0; i != Ctors.size(); ++i) { 2912 Function *F = Ctors[i]; 2913 // Found a null terminator in the middle of the list, prune off the rest of 2914 // the list. 2915 if (F == 0) { 2916 if (i != Ctors.size()-1) { 2917 Ctors.resize(i+1); 2918 MadeChange = true; 2919 } 2920 break; 2921 } 2922 2923 // We cannot simplify external ctor functions. 2924 if (F->empty()) continue; 2925 2926 // If we can evaluate the ctor at compile time, do. 2927 if (EvaluateStaticConstructor(F, TD, TLI)) { 2928 Ctors.erase(Ctors.begin()+i); 2929 MadeChange = true; 2930 --i; 2931 ++NumCtorsEvaluated; 2932 continue; 2933 } 2934 } 2935 2936 if (!MadeChange) return false; 2937 2938 GCL = InstallGlobalCtors(GCL, Ctors); 2939 return true; 2940} 2941 2942bool GlobalOpt::OptimizeGlobalAliases(Module &M) { 2943 bool Changed = false; 2944 2945 for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); 2946 I != E;) { 2947 Module::alias_iterator J = I++; 2948 // Aliases without names cannot be referenced outside this module. 2949 if (!J->hasName() && !J->isDeclaration()) 2950 J->setLinkage(GlobalValue::InternalLinkage); 2951 // If the aliasee may change at link time, nothing can be done - bail out. 2952 if (J->mayBeOverridden()) 2953 continue; 2954 2955 Constant *Aliasee = J->getAliasee(); 2956 GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts()); 2957 Target->removeDeadConstantUsers(); 2958 bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse(); 2959 2960 // Make all users of the alias use the aliasee instead. 2961 if (!J->use_empty()) { 2962 J->replaceAllUsesWith(Aliasee); 2963 ++NumAliasesResolved; 2964 Changed = true; 2965 } 2966 2967 // If the alias is externally visible, we may still be able to simplify it. 2968 if (!J->hasLocalLinkage()) { 2969 // If the aliasee has internal linkage, give it the name and linkage 2970 // of the alias, and delete the alias. This turns: 2971 // define internal ... @f(...) 2972 // @a = alias ... @f 2973 // into: 2974 // define ... @a(...) 2975 if (!Target->hasLocalLinkage()) 2976 continue; 2977 2978 // Do not perform the transform if multiple aliases potentially target the 2979 // aliasee. This check also ensures that it is safe to replace the section 2980 // and other attributes of the aliasee with those of the alias. 2981 if (!hasOneUse) 2982 continue; 2983 2984 // Give the aliasee the name, linkage and other attributes of the alias. 2985 Target->takeName(J); 2986 Target->setLinkage(J->getLinkage()); 2987 Target->GlobalValue::copyAttributesFrom(J); 2988 } 2989 2990 // Delete the alias. 2991 M.getAliasList().erase(J); 2992 ++NumAliasesRemoved; 2993 Changed = true; 2994 } 2995 2996 return Changed; 2997} 2998 2999static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) { 3000 if (!TLI->has(LibFunc::cxa_atexit)) 3001 return 0; 3002 3003 Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit)); 3004 3005 if (!Fn) 3006 return 0; 3007 3008 FunctionType *FTy = Fn->getFunctionType(); 3009 3010 // Checking that the function has the right return type, the right number of 3011 // parameters and that they all have pointer types should be enough. 3012 if (!FTy->getReturnType()->isIntegerTy() || 3013 FTy->getNumParams() != 3 || 3014 !FTy->getParamType(0)->isPointerTy() || 3015 !FTy->getParamType(1)->isPointerTy() || 3016 !FTy->getParamType(2)->isPointerTy()) 3017 return 0; 3018 3019 return Fn; 3020} 3021 3022/// cxxDtorIsEmpty - Returns whether the given function is an empty C++ 3023/// destructor and can therefore be eliminated. 3024/// Note that we assume that other optimization passes have already simplified 3025/// the code so we only look for a function with a single basic block, where 3026/// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and 3027/// other side-effect free instructions. 3028static bool cxxDtorIsEmpty(const Function &Fn, 3029 SmallPtrSet<const Function *, 8> &CalledFunctions) { 3030 // FIXME: We could eliminate C++ destructors if they're readonly/readnone and 3031 // nounwind, but that doesn't seem worth doing. 3032 if (Fn.isDeclaration()) 3033 return false; 3034 3035 if (++Fn.begin() != Fn.end()) 3036 return false; 3037 3038 const BasicBlock &EntryBlock = Fn.getEntryBlock(); 3039 for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end(); 3040 I != E; ++I) { 3041 if (const CallInst *CI = dyn_cast<CallInst>(I)) { 3042 // Ignore debug intrinsics. 3043 if (isa<DbgInfoIntrinsic>(CI)) 3044 continue; 3045 3046 const Function *CalledFn = CI->getCalledFunction(); 3047 3048 if (!CalledFn) 3049 return false; 3050 3051 SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions); 3052 3053 // Don't treat recursive functions as empty. 3054 if (!NewCalledFunctions.insert(CalledFn)) 3055 return false; 3056 3057 if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions)) 3058 return false; 3059 } else if (isa<ReturnInst>(*I)) 3060 return true; // We're done. 3061 else if (I->mayHaveSideEffects()) 3062 return false; // Destructor with side effects, bail. 3063 } 3064 3065 return false; 3066} 3067 3068bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) { 3069 /// Itanium C++ ABI p3.3.5: 3070 /// 3071 /// After constructing a global (or local static) object, that will require 3072 /// destruction on exit, a termination function is registered as follows: 3073 /// 3074 /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d ); 3075 /// 3076 /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the 3077 /// call f(p) when DSO d is unloaded, before all such termination calls 3078 /// registered before this one. It returns zero if registration is 3079 /// successful, nonzero on failure. 3080 3081 // This pass will look for calls to __cxa_atexit where the function is trivial 3082 // and remove them. 3083 bool Changed = false; 3084 3085 for (Function::use_iterator I = CXAAtExitFn->use_begin(), 3086 E = CXAAtExitFn->use_end(); I != E;) { 3087 // We're only interested in calls. Theoretically, we could handle invoke 3088 // instructions as well, but neither llvm-gcc nor clang generate invokes 3089 // to __cxa_atexit. 3090 CallInst *CI = dyn_cast<CallInst>(*I++); 3091 if (!CI) 3092 continue; 3093 3094 Function *DtorFn = 3095 dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts()); 3096 if (!DtorFn) 3097 continue; 3098 3099 SmallPtrSet<const Function *, 8> CalledFunctions; 3100 if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions)) 3101 continue; 3102 3103 // Just remove the call. 3104 CI->replaceAllUsesWith(Constant::getNullValue(CI->getType())); 3105 CI->eraseFromParent(); 3106 3107 ++NumCXXDtorsRemoved; 3108 3109 Changed |= true; 3110 } 3111 3112 return Changed; 3113} 3114 3115bool GlobalOpt::runOnModule(Module &M) { 3116 bool Changed = false; 3117 3118 TD = getAnalysisIfAvailable<TargetData>(); 3119 TLI = &getAnalysis<TargetLibraryInfo>(); 3120 3121 // Try to find the llvm.globalctors list. 3122 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 3123 3124 Function *CXAAtExitFn = FindCXAAtExit(M, TLI); 3125 3126 bool LocalChange = true; 3127 while (LocalChange) { 3128 LocalChange = false; 3129 3130 // Delete functions that are trivially dead, ccc -> fastcc 3131 LocalChange |= OptimizeFunctions(M); 3132 3133 // Optimize global_ctors list. 3134 if (GlobalCtors) 3135 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 3136 3137 // Optimize non-address-taken globals. 3138 LocalChange |= OptimizeGlobalVars(M); 3139 3140 // Resolve aliases, when possible. 3141 LocalChange |= OptimizeGlobalAliases(M); 3142 3143 // Try to remove trivial global destructors. 3144 if (CXAAtExitFn) 3145 LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn); 3146 3147 Changed |= LocalChange; 3148 } 3149 3150 // TODO: Move all global ctors functions to the end of the module for code 3151 // layout. 3152 3153 return Changed; 3154} 3155