GlobalOpt.cpp revision 551ec909057f58b1103f57a9dee45e4d7cf5e061
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/ParameterAttributes.h" 25#include "llvm/Pass.h" 26#include "llvm/Analysis/ConstantFolding.h" 27#include "llvm/Target/TargetData.h" 28#include "llvm/Support/CallSite.h" 29#include "llvm/Support/Compiler.h" 30#include "llvm/Support/Debug.h" 31#include "llvm/Support/GetElementPtrTypeIterator.h" 32#include "llvm/ADT/SmallPtrSet.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/ADT/Statistic.h" 35#include "llvm/ADT/StringExtras.h" 36#include <algorithm> 37#include <set> 38using namespace llvm; 39 40STATISTIC(NumMarked , "Number of globals marked constant"); 41STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); 42STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); 43STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); 44STATISTIC(NumDeleted , "Number of globals deleted"); 45STATISTIC(NumFnDeleted , "Number of functions deleted"); 46STATISTIC(NumGlobUses , "Number of global uses devirtualized"); 47STATISTIC(NumLocalized , "Number of globals localized"); 48STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); 49STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); 50STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); 51STATISTIC(NumNestRemoved , "Number of nest attributes removed"); 52 53namespace { 54 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass { 55 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 56 AU.addRequired<TargetData>(); 57 } 58 static char ID; // Pass identification, replacement for typeid 59 GlobalOpt() : ModulePass((intptr_t)&ID) {} 60 61 bool runOnModule(Module &M); 62 63 private: 64 GlobalVariable *FindGlobalCtors(Module &M); 65 bool OptimizeFunctions(Module &M); 66 bool OptimizeGlobalVars(Module &M); 67 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); 68 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI); 69 }; 70 71 char GlobalOpt::ID = 0; 72 RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer"); 73} 74 75ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } 76 77/// GlobalStatus - As we analyze each global, keep track of some information 78/// about it. If we find out that the address of the global is taken, none of 79/// this info will be accurate. 80struct VISIBILITY_HIDDEN GlobalStatus { 81 /// isLoaded - True if the global is ever loaded. If the global isn't ever 82 /// loaded it can be deleted. 83 bool isLoaded; 84 85 /// StoredType - Keep track of what stores to the global look like. 86 /// 87 enum StoredType { 88 /// NotStored - There is no store to this global. It can thus be marked 89 /// constant. 90 NotStored, 91 92 /// isInitializerStored - This global is stored to, but the only thing 93 /// stored is the constant it was initialized with. This is only tracked 94 /// for scalar globals. 95 isInitializerStored, 96 97 /// isStoredOnce - This global is stored to, but only its initializer and 98 /// one other value is ever stored to it. If this global isStoredOnce, we 99 /// track the value stored to it in StoredOnceValue below. This is only 100 /// tracked for scalar globals. 101 isStoredOnce, 102 103 /// isStored - This global is stored to by multiple values or something else 104 /// that we cannot track. 105 isStored 106 } StoredType; 107 108 /// StoredOnceValue - If only one value (besides the initializer constant) is 109 /// ever stored to this global, keep track of what value it is. 110 Value *StoredOnceValue; 111 112 /// AccessingFunction/HasMultipleAccessingFunctions - These start out 113 /// null/false. When the first accessing function is noticed, it is recorded. 114 /// When a second different accessing function is noticed, 115 /// HasMultipleAccessingFunctions is set to true. 116 Function *AccessingFunction; 117 bool HasMultipleAccessingFunctions; 118 119 /// HasNonInstructionUser - Set to true if this global has a user that is not 120 /// an instruction (e.g. a constant expr or GV initializer). 121 bool HasNonInstructionUser; 122 123 /// HasPHIUser - Set to true if this global has a user that is a PHI node. 124 bool HasPHIUser; 125 126 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0), 127 AccessingFunction(0), HasMultipleAccessingFunctions(false), 128 HasNonInstructionUser(false), HasPHIUser(false) {} 129}; 130 131 132 133/// ConstantIsDead - Return true if the specified constant is (transitively) 134/// dead. The constant may be used by other constants (e.g. constant arrays and 135/// constant exprs) as long as they are dead, but it cannot be used by anything 136/// else. 137static bool ConstantIsDead(Constant *C) { 138 if (isa<GlobalValue>(C)) return false; 139 140 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI) 141 if (Constant *CU = dyn_cast<Constant>(*UI)) { 142 if (!ConstantIsDead(CU)) return false; 143 } else 144 return false; 145 return true; 146} 147 148 149/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus 150/// structure. If the global has its address taken, return true to indicate we 151/// can't do anything with it. 152/// 153static bool AnalyzeGlobal(Value *V, GlobalStatus &GS, 154 std::set<PHINode*> &PHIUsers) { 155 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 156 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) { 157 GS.HasNonInstructionUser = true; 158 159 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; 160 161 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) { 162 if (!GS.HasMultipleAccessingFunctions) { 163 Function *F = I->getParent()->getParent(); 164 if (GS.AccessingFunction == 0) 165 GS.AccessingFunction = F; 166 else if (GS.AccessingFunction != F) 167 GS.HasMultipleAccessingFunctions = true; 168 } 169 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 170 GS.isLoaded = true; 171 if (LI->isVolatile()) return true; // Don't hack on volatile loads. 172 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 173 // Don't allow a store OF the address, only stores TO the address. 174 if (SI->getOperand(0) == V) return true; 175 176 if (SI->isVolatile()) return true; // Don't hack on volatile stores. 177 178 // If this is a direct store to the global (i.e., the global is a scalar 179 // value, not an aggregate), keep more specific information about 180 // stores. 181 if (GS.StoredType != GlobalStatus::isStored) 182 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){ 183 Value *StoredVal = SI->getOperand(0); 184 if (StoredVal == GV->getInitializer()) { 185 if (GS.StoredType < GlobalStatus::isInitializerStored) 186 GS.StoredType = GlobalStatus::isInitializerStored; 187 } else if (isa<LoadInst>(StoredVal) && 188 cast<LoadInst>(StoredVal)->getOperand(0) == GV) { 189 // G = G 190 if (GS.StoredType < GlobalStatus::isInitializerStored) 191 GS.StoredType = GlobalStatus::isInitializerStored; 192 } else if (GS.StoredType < GlobalStatus::isStoredOnce) { 193 GS.StoredType = GlobalStatus::isStoredOnce; 194 GS.StoredOnceValue = StoredVal; 195 } else if (GS.StoredType == GlobalStatus::isStoredOnce && 196 GS.StoredOnceValue == StoredVal) { 197 // noop. 198 } else { 199 GS.StoredType = GlobalStatus::isStored; 200 } 201 } else { 202 GS.StoredType = GlobalStatus::isStored; 203 } 204 } else if (isa<GetElementPtrInst>(I)) { 205 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 206 } else if (isa<SelectInst>(I)) { 207 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 208 } else if (PHINode *PN = dyn_cast<PHINode>(I)) { 209 // PHI nodes we can check just like select or GEP instructions, but we 210 // have to be careful about infinite recursion. 211 if (PHIUsers.insert(PN).second) // Not already visited. 212 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 213 GS.HasPHIUser = true; 214 } else if (isa<CmpInst>(I)) { 215 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { 216 if (I->getOperand(1) == V) 217 GS.StoredType = GlobalStatus::isStored; 218 if (I->getOperand(2) == V) 219 GS.isLoaded = true; 220 } else if (isa<MemSetInst>(I)) { 221 assert(I->getOperand(1) == V && "Memset only takes one pointer!"); 222 GS.StoredType = GlobalStatus::isStored; 223 } else { 224 return true; // Any other non-load instruction might take address! 225 } 226 } else if (Constant *C = dyn_cast<Constant>(*UI)) { 227 GS.HasNonInstructionUser = true; 228 // We might have a dead and dangling constant hanging off of here. 229 if (!ConstantIsDead(C)) 230 return true; 231 } else { 232 GS.HasNonInstructionUser = true; 233 // Otherwise must be some other user. 234 return true; 235 } 236 237 return false; 238} 239 240static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { 241 ConstantInt *CI = dyn_cast<ConstantInt>(Idx); 242 if (!CI) return 0; 243 unsigned IdxV = CI->getZExtValue(); 244 245 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { 246 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); 247 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { 248 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); 249 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { 250 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); 251 } else if (isa<ConstantAggregateZero>(Agg)) { 252 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 253 if (IdxV < STy->getNumElements()) 254 return Constant::getNullValue(STy->getElementType(IdxV)); 255 } else if (const SequentialType *STy = 256 dyn_cast<SequentialType>(Agg->getType())) { 257 return Constant::getNullValue(STy->getElementType()); 258 } 259 } else if (isa<UndefValue>(Agg)) { 260 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 261 if (IdxV < STy->getNumElements()) 262 return UndefValue::get(STy->getElementType(IdxV)); 263 } else if (const SequentialType *STy = 264 dyn_cast<SequentialType>(Agg->getType())) { 265 return UndefValue::get(STy->getElementType()); 266 } 267 } 268 return 0; 269} 270 271 272/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 273/// users of the global, cleaning up the obvious ones. This is largely just a 274/// quick scan over the use list to clean up the easy and obvious cruft. This 275/// returns true if it made a change. 276static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) { 277 bool Changed = false; 278 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 279 User *U = *UI++; 280 281 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 282 if (Init) { 283 // Replace the load with the initializer. 284 LI->replaceAllUsesWith(Init); 285 LI->eraseFromParent(); 286 Changed = true; 287 } 288 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 289 // Store must be unreachable or storing Init into the global. 290 SI->eraseFromParent(); 291 Changed = true; 292 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 293 if (CE->getOpcode() == Instruction::GetElementPtr) { 294 Constant *SubInit = 0; 295 if (Init) 296 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 297 Changed |= CleanupConstantGlobalUsers(CE, SubInit); 298 } else if (CE->getOpcode() == Instruction::BitCast && 299 isa<PointerType>(CE->getType())) { 300 // Pointer cast, delete any stores and memsets to the global. 301 Changed |= CleanupConstantGlobalUsers(CE, 0); 302 } 303 304 if (CE->use_empty()) { 305 CE->destroyConstant(); 306 Changed = true; 307 } 308 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 309 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 310 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 311 // and will invalidate our notion of what Init is. 312 Constant *SubInit = 0; 313 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 314 ConstantExpr *CE = 315 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP)); 316 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 317 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 318 } 319 Changed |= CleanupConstantGlobalUsers(GEP, SubInit); 320 321 if (GEP->use_empty()) { 322 GEP->eraseFromParent(); 323 Changed = true; 324 } 325 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 326 if (MI->getRawDest() == V) { 327 MI->eraseFromParent(); 328 Changed = true; 329 } 330 331 } else if (Constant *C = dyn_cast<Constant>(U)) { 332 // If we have a chain of dead constantexprs or other things dangling from 333 // us, and if they are all dead, nuke them without remorse. 334 if (ConstantIsDead(C)) { 335 C->destroyConstant(); 336 // This could have invalidated UI, start over from scratch. 337 CleanupConstantGlobalUsers(V, Init); 338 return true; 339 } 340 } 341 } 342 return Changed; 343} 344 345/// isSafeSROAElementUse - Return true if the specified instruction is a safe 346/// user of a derived expression from a global that we want to SROA. 347static bool isSafeSROAElementUse(Value *V) { 348 // We might have a dead and dangling constant hanging off of here. 349 if (Constant *C = dyn_cast<Constant>(V)) 350 return ConstantIsDead(C); 351 352 Instruction *I = dyn_cast<Instruction>(V); 353 if (!I) return false; 354 355 // Loads are ok. 356 if (isa<LoadInst>(I)) return true; 357 358 // Stores *to* the pointer are ok. 359 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 360 return SI->getOperand(0) != V; 361 362 // Otherwise, it must be a GEP. 363 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 364 if (GEPI == 0) return false; 365 366 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 367 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 368 return false; 369 370 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 371 I != E; ++I) 372 if (!isSafeSROAElementUse(*I)) 373 return false; 374 return true; 375} 376 377 378/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 379/// Look at it and its uses and decide whether it is safe to SROA this global. 380/// 381static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 382 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 383 if (!isa<GetElementPtrInst>(U) && 384 (!isa<ConstantExpr>(U) || 385 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 386 return false; 387 388 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 389 // don't like < 3 operand CE's, and we don't like non-constant integer 390 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 391 // value of C. 392 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 393 !cast<Constant>(U->getOperand(1))->isNullValue() || 394 !isa<ConstantInt>(U->getOperand(2))) 395 return false; 396 397 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 398 ++GEPI; // Skip over the pointer index. 399 400 // If this is a use of an array allocation, do a bit more checking for sanity. 401 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 402 uint64_t NumElements = AT->getNumElements(); 403 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 404 405 // Check to make sure that index falls within the array. If not, 406 // something funny is going on, so we won't do the optimization. 407 // 408 if (Idx->getZExtValue() >= NumElements) 409 return false; 410 411 // We cannot scalar repl this level of the array unless any array 412 // sub-indices are in-range constants. In particular, consider: 413 // A[0][i]. We cannot know that the user isn't doing invalid things like 414 // allowing i to index an out-of-range subscript that accesses A[1]. 415 // 416 // Scalar replacing *just* the outer index of the array is probably not 417 // going to be a win anyway, so just give up. 418 for (++GEPI; // Skip array index. 419 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); 420 ++GEPI) { 421 uint64_t NumElements; 422 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 423 NumElements = SubArrayTy->getNumElements(); 424 else 425 NumElements = cast<VectorType>(*GEPI)->getNumElements(); 426 427 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 428 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 429 return false; 430 } 431 } 432 433 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 434 if (!isSafeSROAElementUse(*I)) 435 return false; 436 return true; 437} 438 439/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 440/// is safe for us to perform this transformation. 441/// 442static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 443 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 444 UI != E; ++UI) { 445 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 446 return false; 447 } 448 return true; 449} 450 451 452/// SRAGlobal - Perform scalar replacement of aggregates on the specified global 453/// variable. This opens the door for other optimizations by exposing the 454/// behavior of the program in a more fine-grained way. We have determined that 455/// this transformation is safe already. We return the first global variable we 456/// insert so that the caller can reprocess it. 457static GlobalVariable *SRAGlobal(GlobalVariable *GV) { 458 // Make sure this global only has simple uses that we can SRA. 459 if (!GlobalUsersSafeToSRA(GV)) 460 return 0; 461 462 assert(GV->hasInternalLinkage() && !GV->isConstant()); 463 Constant *Init = GV->getInitializer(); 464 const Type *Ty = Init->getType(); 465 466 std::vector<GlobalVariable*> NewGlobals; 467 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 468 469 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 470 NewGlobals.reserve(STy->getNumElements()); 471 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 472 Constant *In = getAggregateConstantElement(Init, 473 ConstantInt::get(Type::Int32Ty, i)); 474 assert(In && "Couldn't get element of initializer?"); 475 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 476 GlobalVariable::InternalLinkage, 477 In, GV->getName()+"."+utostr(i), 478 (Module *)NULL, 479 GV->isThreadLocal()); 480 Globals.insert(GV, NGV); 481 NewGlobals.push_back(NGV); 482 } 483 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 484 unsigned NumElements = 0; 485 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 486 NumElements = ATy->getNumElements(); 487 else if (const VectorType *PTy = dyn_cast<VectorType>(STy)) 488 NumElements = PTy->getNumElements(); 489 else 490 assert(0 && "Unknown aggregate sequential type!"); 491 492 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 493 return 0; // It's not worth it. 494 NewGlobals.reserve(NumElements); 495 for (unsigned i = 0, e = NumElements; i != e; ++i) { 496 Constant *In = getAggregateConstantElement(Init, 497 ConstantInt::get(Type::Int32Ty, i)); 498 assert(In && "Couldn't get element of initializer?"); 499 500 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 501 GlobalVariable::InternalLinkage, 502 In, GV->getName()+"."+utostr(i), 503 (Module *)NULL, 504 GV->isThreadLocal()); 505 Globals.insert(GV, NGV); 506 NewGlobals.push_back(NGV); 507 } 508 } 509 510 if (NewGlobals.empty()) 511 return 0; 512 513 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; 514 515 Constant *NullInt = Constant::getNullValue(Type::Int32Ty); 516 517 // Loop over all of the uses of the global, replacing the constantexpr geps, 518 // with smaller constantexpr geps or direct references. 519 while (!GV->use_empty()) { 520 User *GEP = GV->use_back(); 521 assert(((isa<ConstantExpr>(GEP) && 522 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 523 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 524 525 // Ignore the 1th operand, which has to be zero or else the program is quite 526 // broken (undefined). Get the 2nd operand, which is the structure or array 527 // index. 528 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 529 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 530 531 Value *NewPtr = NewGlobals[Val]; 532 533 // Form a shorter GEP if needed. 534 if (GEP->getNumOperands() > 3) 535 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 536 SmallVector<Constant*, 8> Idxs; 537 Idxs.push_back(NullInt); 538 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 539 Idxs.push_back(CE->getOperand(i)); 540 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), 541 &Idxs[0], Idxs.size()); 542 } else { 543 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 544 SmallVector<Value*, 8> Idxs; 545 Idxs.push_back(NullInt); 546 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 547 Idxs.push_back(GEPI->getOperand(i)); 548 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(), 549 GEPI->getName()+"."+utostr(Val), GEPI); 550 } 551 GEP->replaceAllUsesWith(NewPtr); 552 553 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 554 GEPI->eraseFromParent(); 555 else 556 cast<ConstantExpr>(GEP)->destroyConstant(); 557 } 558 559 // Delete the old global, now that it is dead. 560 Globals.erase(GV); 561 ++NumSRA; 562 563 // Loop over the new globals array deleting any globals that are obviously 564 // dead. This can arise due to scalarization of a structure or an array that 565 // has elements that are dead. 566 unsigned FirstGlobal = 0; 567 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 568 if (NewGlobals[i]->use_empty()) { 569 Globals.erase(NewGlobals[i]); 570 if (FirstGlobal == i) ++FirstGlobal; 571 } 572 573 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 574} 575 576/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 577/// value will trap if the value is dynamically null. PHIs keeps track of any 578/// phi nodes we've seen to avoid reprocessing them. 579static bool AllUsesOfValueWillTrapIfNull(Value *V, 580 SmallPtrSet<PHINode*, 8> &PHIs) { 581 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 582 if (isa<LoadInst>(*UI)) { 583 // Will trap. 584 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 585 if (SI->getOperand(0) == V) { 586 //cerr << "NONTRAPPING USE: " << **UI; 587 return false; // Storing the value. 588 } 589 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { 590 if (CI->getOperand(0) != V) { 591 //cerr << "NONTRAPPING USE: " << **UI; 592 return false; // Not calling the ptr 593 } 594 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { 595 if (II->getOperand(0) != V) { 596 //cerr << "NONTRAPPING USE: " << **UI; 597 return false; // Not calling the ptr 598 } 599 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { 600 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 601 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 602 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 603 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 604 // If we've already seen this phi node, ignore it, it has already been 605 // checked. 606 if (PHIs.insert(PN)) 607 return AllUsesOfValueWillTrapIfNull(PN, PHIs); 608 } else if (isa<ICmpInst>(*UI) && 609 isa<ConstantPointerNull>(UI->getOperand(1))) { 610 // Ignore setcc X, null 611 } else { 612 //cerr << "NONTRAPPING USE: " << **UI; 613 return false; 614 } 615 return true; 616} 617 618/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 619/// from GV will trap if the loaded value is null. Note that this also permits 620/// comparisons of the loaded value against null, as a special case. 621static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) { 622 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) 623 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 624 SmallPtrSet<PHINode*, 8> PHIs; 625 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 626 return false; 627 } else if (isa<StoreInst>(*UI)) { 628 // Ignore stores to the global. 629 } else { 630 // We don't know or understand this user, bail out. 631 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; 632 return false; 633 } 634 635 return true; 636} 637 638static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 639 bool Changed = false; 640 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 641 Instruction *I = cast<Instruction>(*UI++); 642 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 643 LI->setOperand(0, NewV); 644 Changed = true; 645 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 646 if (SI->getOperand(1) == V) { 647 SI->setOperand(1, NewV); 648 Changed = true; 649 } 650 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 651 if (I->getOperand(0) == V) { 652 // Calling through the pointer! Turn into a direct call, but be careful 653 // that the pointer is not also being passed as an argument. 654 I->setOperand(0, NewV); 655 Changed = true; 656 bool PassedAsArg = false; 657 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) 658 if (I->getOperand(i) == V) { 659 PassedAsArg = true; 660 I->setOperand(i, NewV); 661 } 662 663 if (PassedAsArg) { 664 // Being passed as an argument also. Be careful to not invalidate UI! 665 UI = V->use_begin(); 666 } 667 } 668 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 669 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 670 ConstantExpr::getCast(CI->getOpcode(), 671 NewV, CI->getType())); 672 if (CI->use_empty()) { 673 Changed = true; 674 CI->eraseFromParent(); 675 } 676 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 677 // Should handle GEP here. 678 SmallVector<Constant*, 8> Idxs; 679 Idxs.reserve(GEPI->getNumOperands()-1); 680 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 681 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i))) 682 Idxs.push_back(C); 683 else 684 break; 685 if (Idxs.size() == GEPI->getNumOperands()-1) 686 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 687 ConstantExpr::getGetElementPtr(NewV, &Idxs[0], 688 Idxs.size())); 689 if (GEPI->use_empty()) { 690 Changed = true; 691 GEPI->eraseFromParent(); 692 } 693 } 694 } 695 696 return Changed; 697} 698 699 700/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 701/// value stored into it. If there are uses of the loaded value that would trap 702/// if the loaded value is dynamically null, then we know that they cannot be 703/// reachable with a null optimize away the load. 704static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { 705 std::vector<LoadInst*> Loads; 706 bool Changed = false; 707 708 // Replace all uses of loads with uses of uses of the stored value. 709 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); 710 GUI != E; ++GUI) 711 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { 712 Loads.push_back(LI); 713 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 714 } else { 715 // If we get here we could have stores, selects, or phi nodes whose values 716 // are loaded. 717 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || 718 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && 719 "Only expect load and stores!"); 720 } 721 722 if (Changed) { 723 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; 724 ++NumGlobUses; 725 } 726 727 // Delete all of the loads we can, keeping track of whether we nuked them all! 728 bool AllLoadsGone = true; 729 while (!Loads.empty()) { 730 LoadInst *L = Loads.back(); 731 if (L->use_empty()) { 732 L->eraseFromParent(); 733 Changed = true; 734 } else { 735 AllLoadsGone = false; 736 } 737 Loads.pop_back(); 738 } 739 740 // If we nuked all of the loads, then none of the stores are needed either, 741 // nor is the global. 742 if (AllLoadsGone) { 743 DOUT << " *** GLOBAL NOW DEAD!\n"; 744 CleanupConstantGlobalUsers(GV, 0); 745 if (GV->use_empty()) { 746 GV->eraseFromParent(); 747 ++NumDeleted; 748 } 749 Changed = true; 750 } 751 return Changed; 752} 753 754/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 755/// instructions that are foldable. 756static void ConstantPropUsersOf(Value *V) { 757 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 758 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 759 if (Constant *NewC = ConstantFoldInstruction(I)) { 760 I->replaceAllUsesWith(NewC); 761 762 // Advance UI to the next non-I use to avoid invalidating it! 763 // Instructions could multiply use V. 764 while (UI != E && *UI == I) 765 ++UI; 766 I->eraseFromParent(); 767 } 768} 769 770/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 771/// variable, and transforms the program as if it always contained the result of 772/// the specified malloc. Because it is always the result of the specified 773/// malloc, there is no reason to actually DO the malloc. Instead, turn the 774/// malloc into a global, and any loads of GV as uses of the new global. 775static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 776 MallocInst *MI) { 777 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; 778 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); 779 780 if (NElements->getZExtValue() != 1) { 781 // If we have an array allocation, transform it to a single element 782 // allocation to make the code below simpler. 783 Type *NewTy = ArrayType::get(MI->getAllocatedType(), 784 NElements->getZExtValue()); 785 MallocInst *NewMI = 786 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), 787 MI->getAlignment(), MI->getName(), MI); 788 Value* Indices[2]; 789 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); 790 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2, 791 NewMI->getName()+".el0", MI); 792 MI->replaceAllUsesWith(NewGEP); 793 MI->eraseFromParent(); 794 MI = NewMI; 795 } 796 797 // Create the new global variable. The contents of the malloc'd memory is 798 // undefined, so initialize with an undef value. 799 Constant *Init = UndefValue::get(MI->getAllocatedType()); 800 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, 801 GlobalValue::InternalLinkage, Init, 802 GV->getName()+".body", 803 (Module *)NULL, 804 GV->isThreadLocal()); 805 GV->getParent()->getGlobalList().insert(GV, NewGV); 806 807 // Anything that used the malloc now uses the global directly. 808 MI->replaceAllUsesWith(NewGV); 809 810 Constant *RepValue = NewGV; 811 if (NewGV->getType() != GV->getType()->getElementType()) 812 RepValue = ConstantExpr::getBitCast(RepValue, 813 GV->getType()->getElementType()); 814 815 // If there is a comparison against null, we will insert a global bool to 816 // keep track of whether the global was initialized yet or not. 817 GlobalVariable *InitBool = 818 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage, 819 ConstantInt::getFalse(), GV->getName()+".init", 820 (Module *)NULL, GV->isThreadLocal()); 821 bool InitBoolUsed = false; 822 823 // Loop over all uses of GV, processing them in turn. 824 std::vector<StoreInst*> Stores; 825 while (!GV->use_empty()) 826 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 827 while (!LI->use_empty()) { 828 Use &LoadUse = LI->use_begin().getUse(); 829 if (!isa<ICmpInst>(LoadUse.getUser())) 830 LoadUse = RepValue; 831 else { 832 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); 833 // Replace the cmp X, 0 with a use of the bool value. 834 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); 835 InitBoolUsed = true; 836 switch (CI->getPredicate()) { 837 default: assert(0 && "Unknown ICmp Predicate!"); 838 case ICmpInst::ICMP_ULT: 839 case ICmpInst::ICMP_SLT: 840 LV = ConstantInt::getFalse(); // X < null -> always false 841 break; 842 case ICmpInst::ICMP_ULE: 843 case ICmpInst::ICMP_SLE: 844 case ICmpInst::ICMP_EQ: 845 LV = BinaryOperator::createNot(LV, "notinit", CI); 846 break; 847 case ICmpInst::ICMP_NE: 848 case ICmpInst::ICMP_UGE: 849 case ICmpInst::ICMP_SGE: 850 case ICmpInst::ICMP_UGT: 851 case ICmpInst::ICMP_SGT: 852 break; // no change. 853 } 854 CI->replaceAllUsesWith(LV); 855 CI->eraseFromParent(); 856 } 857 } 858 LI->eraseFromParent(); 859 } else { 860 StoreInst *SI = cast<StoreInst>(GV->use_back()); 861 // The global is initialized when the store to it occurs. 862 new StoreInst(ConstantInt::getTrue(), InitBool, SI); 863 SI->eraseFromParent(); 864 } 865 866 // If the initialization boolean was used, insert it, otherwise delete it. 867 if (!InitBoolUsed) { 868 while (!InitBool->use_empty()) // Delete initializations 869 cast<Instruction>(InitBool->use_back())->eraseFromParent(); 870 delete InitBool; 871 } else 872 GV->getParent()->getGlobalList().insert(GV, InitBool); 873 874 875 // Now the GV is dead, nuke it and the malloc. 876 GV->eraseFromParent(); 877 MI->eraseFromParent(); 878 879 // To further other optimizations, loop over all users of NewGV and try to 880 // constant prop them. This will promote GEP instructions with constant 881 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 882 ConstantPropUsersOf(NewGV); 883 if (RepValue != NewGV) 884 ConstantPropUsersOf(RepValue); 885 886 return NewGV; 887} 888 889/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 890/// to make sure that there are no complex uses of V. We permit simple things 891/// like dereferencing the pointer, but not storing through the address, unless 892/// it is to the specified global. 893static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V, 894 GlobalVariable *GV, 895 SmallPtrSet<PHINode*, 8> &PHIs) { 896 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 897 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) { 898 // Fine, ignore. 899 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 900 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 901 return false; // Storing the pointer itself... bad. 902 // Otherwise, storing through it, or storing into GV... fine. 903 } else if (isa<GetElementPtrInst>(*UI)) { 904 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI), 905 GV, PHIs)) 906 return false; 907 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 908 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 909 // cycles. 910 if (PHIs.insert(PN)) 911 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 912 return false; 913 } else { 914 return false; 915 } 916 return true; 917} 918 919/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 920/// somewhere. Transform all uses of the allocation into loads from the 921/// global and uses of the resultant pointer. Further, delete the store into 922/// GV. This assumes that these value pass the 923/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 924static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 925 GlobalVariable *GV) { 926 while (!Alloc->use_empty()) { 927 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 928 Instruction *InsertPt = U; 929 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 930 // If this is the store of the allocation into the global, remove it. 931 if (SI->getOperand(1) == GV) { 932 SI->eraseFromParent(); 933 continue; 934 } 935 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 936 // Insert the load in the corresponding predecessor, not right before the 937 // PHI. 938 unsigned PredNo = Alloc->use_begin().getOperandNo()/2; 939 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator(); 940 } 941 942 // Insert a load from the global, and use it instead of the malloc. 943 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 944 U->replaceUsesOfWith(Alloc, NL); 945 } 946} 947 948/// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 949/// GV are simple enough to perform HeapSRA, return true. 950static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, 951 MallocInst *MI) { 952 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; 953 ++UI) 954 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 955 // We permit two users of the load: setcc comparing against the null 956 // pointer, and a getelementptr of a specific form. 957 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E; 958 ++UI) { 959 // Comparison against null is ok. 960 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) { 961 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 962 return false; 963 continue; 964 } 965 966 // getelementptr is also ok, but only a simple form. 967 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 968 // Must index into the array and into the struct. 969 if (GEPI->getNumOperands() < 3) 970 return false; 971 972 // Otherwise the GEP is ok. 973 continue; 974 } 975 976 if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 977 // We have a phi of a load from the global. We can only handle this 978 // if the other PHI'd values are actually the same. In this case, 979 // the rewriter will just drop the phi entirely. 980 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 981 Value *IV = PN->getIncomingValue(i); 982 if (IV == LI) continue; // Trivial the same. 983 984 // If the phi'd value is from the malloc that initializes the value, 985 // we can xform it. 986 if (IV == MI) continue; 987 988 // Otherwise, we don't know what it is. 989 return false; 990 } 991 return true; 992 } 993 994 // Otherwise we don't know what this is, not ok. 995 return false; 996 } 997 } 998 return true; 999} 1000 1001/// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd 1002/// value, lazily creating it on demand. 1003static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo, 1004 const std::vector<GlobalVariable*> &FieldGlobals, 1005 std::vector<Value *> &InsertedLoadsForPtr) { 1006 if (InsertedLoadsForPtr.size() <= FieldNo) 1007 InsertedLoadsForPtr.resize(FieldNo+1); 1008 if (InsertedLoadsForPtr[FieldNo] == 0) 1009 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo], 1010 Load->getName()+".f" + 1011 utostr(FieldNo), Load); 1012 return InsertedLoadsForPtr[FieldNo]; 1013} 1014 1015/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1016/// the load, rewrite the derived value to use the HeapSRoA'd load. 1017static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser, 1018 const std::vector<GlobalVariable*> &FieldGlobals, 1019 std::vector<Value *> &InsertedLoadsForPtr) { 1020 // If this is a comparison against null, handle it. 1021 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1022 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1023 // If we have a setcc of the loaded pointer, we can use a setcc of any 1024 // field. 1025 Value *NPtr; 1026 if (InsertedLoadsForPtr.empty()) { 1027 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr); 1028 } else { 1029 NPtr = InsertedLoadsForPtr.back(); 1030 } 1031 1032 Value *New = new ICmpInst(SCI->getPredicate(), NPtr, 1033 Constant::getNullValue(NPtr->getType()), 1034 SCI->getName(), SCI); 1035 SCI->replaceAllUsesWith(New); 1036 SCI->eraseFromParent(); 1037 return; 1038 } 1039 1040 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...' 1041 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1042 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1043 && "Unexpected GEPI!"); 1044 1045 // Load the pointer for this field. 1046 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1047 Value *NewPtr = GetHeapSROALoad(Load, FieldNo, 1048 FieldGlobals, InsertedLoadsForPtr); 1049 1050 // Create the new GEP idx vector. 1051 SmallVector<Value*, 8> GEPIdx; 1052 GEPIdx.push_back(GEPI->getOperand(1)); 1053 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1054 1055 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(), 1056 GEPI->getName(), GEPI); 1057 GEPI->replaceAllUsesWith(NGEPI); 1058 GEPI->eraseFromParent(); 1059 return; 1060 } 1061 1062 // Handle PHI nodes. PHI nodes must be merging in the same values, plus 1063 // potentially the original malloc. Insert phi nodes for each field, then 1064 // process uses of the PHI. 1065 PHINode *PN = cast<PHINode>(LoadUser); 1066 std::vector<Value *> PHIsForField; 1067 PHIsForField.resize(FieldGlobals.size()); 1068 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1069 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr); 1070 1071 PHINode *FieldPN = new PHINode(LoadV->getType(), 1072 PN->getName()+"."+utostr(i), PN); 1073 // Fill in the predecessor values. 1074 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) { 1075 // Each predecessor either uses the load or the original malloc. 1076 Value *InVal = PN->getIncomingValue(pred); 1077 BasicBlock *BB = PN->getIncomingBlock(pred); 1078 Value *NewVal; 1079 if (isa<MallocInst>(InVal)) { 1080 // Insert a reload from the global in the predecessor. 1081 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals, 1082 PHIsForField); 1083 } else { 1084 NewVal = InsertedLoadsForPtr[i]; 1085 } 1086 FieldPN->addIncoming(NewVal, BB); 1087 } 1088 PHIsForField[i] = FieldPN; 1089 } 1090 1091 // Since PHIsForField specifies a phi for every input value, the lazy inserter 1092 // will never insert a load. 1093 while (!PN->use_empty()) 1094 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField); 1095 PN->eraseFromParent(); 1096} 1097 1098/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1099/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1100/// use FieldGlobals instead. All uses of loaded values satisfy 1101/// GlobalLoadUsesSimpleEnoughForHeapSRA. 1102static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1103 const std::vector<GlobalVariable*> &FieldGlobals) { 1104 std::vector<Value *> InsertedLoadsForPtr; 1105 //InsertedLoadsForPtr.resize(FieldGlobals.size()); 1106 while (!Load->use_empty()) 1107 RewriteHeapSROALoadUser(Load, Load->use_back(), 1108 FieldGlobals, InsertedLoadsForPtr); 1109} 1110 1111/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break 1112/// it up into multiple allocations of arrays of the fields. 1113static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ 1114 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; 1115 const StructType *STy = cast<StructType>(MI->getAllocatedType()); 1116 1117 // There is guaranteed to be at least one use of the malloc (storing 1118 // it into GV). If there are other uses, change them to be uses of 1119 // the global to simplify later code. This also deletes the store 1120 // into GV. 1121 ReplaceUsesOfMallocWithGlobal(MI, GV); 1122 1123 // Okay, at this point, there are no users of the malloc. Insert N 1124 // new mallocs at the same place as MI, and N globals. 1125 std::vector<GlobalVariable*> FieldGlobals; 1126 std::vector<MallocInst*> FieldMallocs; 1127 1128 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1129 const Type *FieldTy = STy->getElementType(FieldNo); 1130 const Type *PFieldTy = PointerType::getUnqual(FieldTy); 1131 1132 GlobalVariable *NGV = 1133 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, 1134 Constant::getNullValue(PFieldTy), 1135 GV->getName() + ".f" + utostr(FieldNo), GV, 1136 GV->isThreadLocal()); 1137 FieldGlobals.push_back(NGV); 1138 1139 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), 1140 MI->getName() + ".f" + utostr(FieldNo),MI); 1141 FieldMallocs.push_back(NMI); 1142 new StoreInst(NMI, NGV, MI); 1143 } 1144 1145 // The tricky aspect of this transformation is handling the case when malloc 1146 // fails. In the original code, malloc failing would set the result pointer 1147 // of malloc to null. In this case, some mallocs could succeed and others 1148 // could fail. As such, we emit code that looks like this: 1149 // F0 = malloc(field0) 1150 // F1 = malloc(field1) 1151 // F2 = malloc(field2) 1152 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1153 // if (F0) { free(F0); F0 = 0; } 1154 // if (F1) { free(F1); F1 = 0; } 1155 // if (F2) { free(F2); F2 = 0; } 1156 // } 1157 Value *RunningOr = 0; 1158 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1159 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], 1160 Constant::getNullValue(FieldMallocs[i]->getType()), 1161 "isnull", MI); 1162 if (!RunningOr) 1163 RunningOr = Cond; // First seteq 1164 else 1165 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI); 1166 } 1167 1168 // Split the basic block at the old malloc. 1169 BasicBlock *OrigBB = MI->getParent(); 1170 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont"); 1171 1172 // Create the block to check the first condition. Put all these blocks at the 1173 // end of the function as they are unlikely to be executed. 1174 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null", 1175 OrigBB->getParent()); 1176 1177 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1178 // branch on RunningOr. 1179 OrigBB->getTerminator()->eraseFromParent(); 1180 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB); 1181 1182 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1183 // pointer, because some may be null while others are not. 1184 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1185 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1186 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal, 1187 Constant::getNullValue(GVVal->getType()), 1188 "tmp", NullPtrBlock); 1189 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent()); 1190 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent()); 1191 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock); 1192 1193 // Fill in FreeBlock. 1194 new FreeInst(GVVal, FreeBlock); 1195 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1196 FreeBlock); 1197 new BranchInst(NextBlock, FreeBlock); 1198 1199 NullPtrBlock = NextBlock; 1200 } 1201 1202 new BranchInst(ContBB, NullPtrBlock); 1203 1204 1205 // MI is no longer needed, remove it. 1206 MI->eraseFromParent(); 1207 1208 1209 // Okay, the malloc site is completely handled. All of the uses of GV are now 1210 // loads, and all uses of those loads are simple. Rewrite them to use loads 1211 // of the per-field globals instead. 1212 while (!GV->use_empty()) { 1213 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 1214 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals); 1215 LI->eraseFromParent(); 1216 } else { 1217 // Must be a store of null. 1218 StoreInst *SI = cast<StoreInst>(GV->use_back()); 1219 assert(isa<Constant>(SI->getOperand(0)) && 1220 cast<Constant>(SI->getOperand(0))->isNullValue() && 1221 "Unexpected heap-sra user!"); 1222 1223 // Insert a store of null into each global. 1224 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1225 Constant *Null = 1226 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType()); 1227 new StoreInst(Null, FieldGlobals[i], SI); 1228 } 1229 // Erase the original store. 1230 SI->eraseFromParent(); 1231 } 1232 } 1233 1234 // The old global is now dead, remove it. 1235 GV->eraseFromParent(); 1236 1237 ++NumHeapSRA; 1238 return FieldGlobals[0]; 1239} 1240 1241 1242// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1243// that only one value (besides its initializer) is ever stored to the global. 1244static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1245 Module::global_iterator &GVI, 1246 TargetData &TD) { 1247 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal)) 1248 StoredOnceVal = CI->getOperand(0); 1249 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){ 1250 // "getelementptr Ptr, 0, 0, 0" is really just a cast. 1251 bool IsJustACast = true; 1252 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 1253 if (!isa<Constant>(GEPI->getOperand(i)) || 1254 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) { 1255 IsJustACast = false; 1256 break; 1257 } 1258 if (IsJustACast) 1259 StoredOnceVal = GEPI->getOperand(0); 1260 } 1261 1262 // If we are dealing with a pointer global that is initialized to null and 1263 // only has one (non-null) value stored into it, then we can optimize any 1264 // users of the loaded value (often calls and loads) that would trap if the 1265 // value was null. 1266 if (isa<PointerType>(GV->getInitializer()->getType()) && 1267 GV->getInitializer()->isNullValue()) { 1268 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1269 if (GV->getInitializer()->getType() != SOVC->getType()) 1270 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1271 1272 // Optimize away any trapping uses of the loaded value. 1273 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC)) 1274 return true; 1275 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { 1276 // If this is a malloc of an abstract type, don't touch it. 1277 if (!MI->getAllocatedType()->isSized()) 1278 return false; 1279 1280 // We can't optimize this global unless all uses of it are *known* to be 1281 // of the malloc value, not of the null initializer value (consider a use 1282 // that compares the global's value against zero to see if the malloc has 1283 // been reached). To do this, we check to see if all uses of the global 1284 // would trap if the global were null: this proves that they must all 1285 // happen after the malloc. 1286 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1287 return false; 1288 1289 // We can't optimize this if the malloc itself is used in a complex way, 1290 // for example, being stored into multiple globals. This allows the 1291 // malloc to be stored into the specified global, loaded setcc'd, and 1292 // GEP'd. These are all things we could transform to using the global 1293 // for. 1294 { 1295 SmallPtrSet<PHINode*, 8> PHIs; 1296 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs)) 1297 return false; 1298 } 1299 1300 1301 // If we have a global that is only initialized with a fixed size malloc, 1302 // transform the program to use global memory instead of malloc'd memory. 1303 // This eliminates dynamic allocation, avoids an indirection accessing the 1304 // data, and exposes the resultant global to further GlobalOpt. 1305 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { 1306 // Restrict this transformation to only working on small allocations 1307 // (2048 bytes currently), as we don't want to introduce a 16M global or 1308 // something. 1309 if (NElements->getZExtValue()* 1310 TD.getABITypeSize(MI->getAllocatedType()) < 2048) { 1311 GVI = OptimizeGlobalAddressOfMalloc(GV, MI); 1312 return true; 1313 } 1314 } 1315 1316 // If the allocation is an array of structures, consider transforming this 1317 // into multiple malloc'd arrays, one for each field. This is basically 1318 // SRoA for malloc'd memory. 1319 if (const StructType *AllocTy = 1320 dyn_cast<StructType>(MI->getAllocatedType())) { 1321 // This the structure has an unreasonable number of fields, leave it 1322 // alone. 1323 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 && 1324 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { 1325 GVI = PerformHeapAllocSRoA(GV, MI); 1326 return true; 1327 } 1328 } 1329 } 1330 } 1331 1332 return false; 1333} 1334 1335/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1336/// two values ever stored into GV are its initializer and OtherVal. See if we 1337/// can shrink the global into a boolean and select between the two values 1338/// whenever it is used. This exposes the values to other scalar optimizations. 1339static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1340 const Type *GVElType = GV->getType()->getElementType(); 1341 1342 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1343 // an FP value or vector, don't do this optimization because a select between 1344 // them is very expensive and unlikely to lead to later simplification. 1345 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || 1346 isa<VectorType>(GVElType)) 1347 return false; 1348 1349 // Walk the use list of the global seeing if all the uses are load or store. 1350 // If there is anything else, bail out. 1351 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I) 1352 if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) 1353 return false; 1354 1355 DOUT << " *** SHRINKING TO BOOL: " << *GV; 1356 1357 // Create the new global, initializing it to false. 1358 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, 1359 GlobalValue::InternalLinkage, ConstantInt::getFalse(), 1360 GV->getName()+".b", 1361 (Module *)NULL, 1362 GV->isThreadLocal()); 1363 GV->getParent()->getGlobalList().insert(GV, NewGV); 1364 1365 Constant *InitVal = GV->getInitializer(); 1366 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!"); 1367 1368 // If initialized to zero and storing one into the global, we can use a cast 1369 // instead of a select to synthesize the desired value. 1370 bool IsOneZero = false; 1371 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1372 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1373 1374 while (!GV->use_empty()) { 1375 Instruction *UI = cast<Instruction>(GV->use_back()); 1376 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1377 // Change the store into a boolean store. 1378 bool StoringOther = SI->getOperand(0) == OtherVal; 1379 // Only do this if we weren't storing a loaded value. 1380 Value *StoreVal; 1381 if (StoringOther || SI->getOperand(0) == InitVal) 1382 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther); 1383 else { 1384 // Otherwise, we are storing a previously loaded copy. To do this, 1385 // change the copy from copying the original value to just copying the 1386 // bool. 1387 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1388 1389 // If we're already replaced the input, StoredVal will be a cast or 1390 // select instruction. If not, it will be a load of the original 1391 // global. 1392 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1393 assert(LI->getOperand(0) == GV && "Not a copy!"); 1394 // Insert a new load, to preserve the saved value. 1395 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI); 1396 } else { 1397 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1398 "This is not a form that we understand!"); 1399 StoreVal = StoredVal->getOperand(0); 1400 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1401 } 1402 } 1403 new StoreInst(StoreVal, NewGV, SI); 1404 } else { 1405 // Change the load into a load of bool then a select. 1406 LoadInst *LI = cast<LoadInst>(UI); 1407 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI); 1408 Value *NSI; 1409 if (IsOneZero) 1410 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1411 else 1412 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI); 1413 NSI->takeName(LI); 1414 LI->replaceAllUsesWith(NSI); 1415 } 1416 UI->eraseFromParent(); 1417 } 1418 1419 GV->eraseFromParent(); 1420 return true; 1421} 1422 1423 1424/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1425/// it if possible. If we make a change, return true. 1426bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1427 Module::global_iterator &GVI) { 1428 std::set<PHINode*> PHIUsers; 1429 GlobalStatus GS; 1430 GV->removeDeadConstantUsers(); 1431 1432 if (GV->use_empty()) { 1433 DOUT << "GLOBAL DEAD: " << *GV; 1434 GV->eraseFromParent(); 1435 ++NumDeleted; 1436 return true; 1437 } 1438 1439 if (!AnalyzeGlobal(GV, GS, PHIUsers)) { 1440#if 0 1441 cerr << "Global: " << *GV; 1442 cerr << " isLoaded = " << GS.isLoaded << "\n"; 1443 cerr << " StoredType = "; 1444 switch (GS.StoredType) { 1445 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; 1446 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; 1447 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; 1448 case GlobalStatus::isStored: cerr << "stored\n"; break; 1449 } 1450 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) 1451 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; 1452 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) 1453 cerr << " AccessingFunction = " << GS.AccessingFunction->getName() 1454 << "\n"; 1455 cerr << " HasMultipleAccessingFunctions = " 1456 << GS.HasMultipleAccessingFunctions << "\n"; 1457 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; 1458 cerr << "\n"; 1459#endif 1460 1461 // If this is a first class global and has only one accessing function 1462 // and this function is main (which we know is not recursive we can make 1463 // this global a local variable) we replace the global with a local alloca 1464 // in this function. 1465 // 1466 // NOTE: It doesn't make sense to promote non first class types since we 1467 // are just replacing static memory to stack memory. 1468 if (!GS.HasMultipleAccessingFunctions && 1469 GS.AccessingFunction && !GS.HasNonInstructionUser && 1470 GV->getType()->getElementType()->isFirstClassType() && 1471 GS.AccessingFunction->getName() == "main" && 1472 GS.AccessingFunction->hasExternalLinkage()) { 1473 DOUT << "LOCALIZING GLOBAL: " << *GV; 1474 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); 1475 const Type* ElemTy = GV->getType()->getElementType(); 1476 // FIXME: Pass Global's alignment when globals have alignment 1477 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI); 1478 if (!isa<UndefValue>(GV->getInitializer())) 1479 new StoreInst(GV->getInitializer(), Alloca, FirstI); 1480 1481 GV->replaceAllUsesWith(Alloca); 1482 GV->eraseFromParent(); 1483 ++NumLocalized; 1484 return true; 1485 } 1486 1487 // If the global is never loaded (but may be stored to), it is dead. 1488 // Delete it now. 1489 if (!GS.isLoaded) { 1490 DOUT << "GLOBAL NEVER LOADED: " << *GV; 1491 1492 // Delete any stores we can find to the global. We may not be able to 1493 // make it completely dead though. 1494 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1495 1496 // If the global is dead now, delete it. 1497 if (GV->use_empty()) { 1498 GV->eraseFromParent(); 1499 ++NumDeleted; 1500 Changed = true; 1501 } 1502 return Changed; 1503 1504 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1505 DOUT << "MARKING CONSTANT: " << *GV; 1506 GV->setConstant(true); 1507 1508 // Clean up any obviously simplifiable users now. 1509 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1510 1511 // If the global is dead now, just nuke it. 1512 if (GV->use_empty()) { 1513 DOUT << " *** Marking constant allowed us to simplify " 1514 << "all users and delete global!\n"; 1515 GV->eraseFromParent(); 1516 ++NumDeleted; 1517 } 1518 1519 ++NumMarked; 1520 return true; 1521 } else if (!GV->getInitializer()->getType()->isFirstClassType()) { 1522 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) { 1523 GVI = FirstNewGV; // Don't skip the newly produced globals! 1524 return true; 1525 } 1526 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 1527 // If the initial value for the global was an undef value, and if only 1528 // one other value was stored into it, we can just change the 1529 // initializer to be an undef value, then delete all stores to the 1530 // global. This allows us to mark it constant. 1531 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1532 if (isa<UndefValue>(GV->getInitializer())) { 1533 // Change the initial value here. 1534 GV->setInitializer(SOVConstant); 1535 1536 // Clean up any obviously simplifiable users now. 1537 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1538 1539 if (GV->use_empty()) { 1540 DOUT << " *** Substituting initializer allowed us to " 1541 << "simplify all users and delete global!\n"; 1542 GV->eraseFromParent(); 1543 ++NumDeleted; 1544 } else { 1545 GVI = GV; 1546 } 1547 ++NumSubstitute; 1548 return true; 1549 } 1550 1551 // Try to optimize globals based on the knowledge that only one value 1552 // (besides its initializer) is ever stored to the global. 1553 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, 1554 getAnalysis<TargetData>())) 1555 return true; 1556 1557 // Otherwise, if the global was not a boolean, we can shrink it to be a 1558 // boolean. 1559 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1560 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 1561 ++NumShrunkToBool; 1562 return true; 1563 } 1564 } 1565 } 1566 return false; 1567} 1568 1569/// OnlyCalledDirectly - Return true if the specified function is only called 1570/// directly. In other words, its address is never taken. 1571static bool OnlyCalledDirectly(Function *F) { 1572 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1573 Instruction *User = dyn_cast<Instruction>(*UI); 1574 if (!User) return false; 1575 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; 1576 1577 // See if the function address is passed as an argument. 1578 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i) 1579 if (User->getOperand(i) == F) return false; 1580 } 1581 return true; 1582} 1583 1584/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 1585/// function, changing them to FastCC. 1586static void ChangeCalleesToFastCall(Function *F) { 1587 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1588 CallSite User(cast<Instruction>(*UI)); 1589 User.setCallingConv(CallingConv::Fast); 1590 } 1591} 1592 1593static const ParamAttrsList *StripNest(const ParamAttrsList *Attrs) { 1594 if (!Attrs) 1595 return NULL; 1596 1597 for (unsigned i = 0, e = Attrs->size(); i != e; ++i) { 1598 if ((Attrs->getParamAttrsAtIndex(i) & ParamAttr::Nest) == 0) 1599 continue; 1600 1601 Attrs = ParamAttrsList::excludeAttrs(Attrs, Attrs->getParamIndex(i), 1602 ParamAttr::Nest); 1603 // There can be only one. 1604 break; 1605 } 1606 1607 return Attrs; 1608} 1609 1610static void RemoveNestAttribute(Function *F) { 1611 F->setParamAttrs(StripNest(F->getParamAttrs())); 1612 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1613 CallSite User(cast<Instruction>(*UI)); 1614 User.setParamAttrs(StripNest(User.getParamAttrs())); 1615 } 1616} 1617 1618bool GlobalOpt::OptimizeFunctions(Module &M) { 1619 bool Changed = false; 1620 // Optimize functions. 1621 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 1622 Function *F = FI++; 1623 F->removeDeadConstantUsers(); 1624 if (F->use_empty() && (F->hasInternalLinkage() || 1625 F->hasLinkOnceLinkage())) { 1626 M.getFunctionList().erase(F); 1627 Changed = true; 1628 ++NumFnDeleted; 1629 } else if (F->hasInternalLinkage()) { 1630 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 1631 OnlyCalledDirectly(F)) { 1632 // If this function has C calling conventions, is not a varargs 1633 // function, and is only called directly, promote it to use the Fast 1634 // calling convention. 1635 F->setCallingConv(CallingConv::Fast); 1636 ChangeCalleesToFastCall(F); 1637 ++NumFastCallFns; 1638 Changed = true; 1639 } 1640 1641 if (F->getParamAttrs() && 1642 F->getParamAttrs()->hasAttrSomewhere(ParamAttr::Nest) && 1643 OnlyCalledDirectly(F)) { 1644 // The function is not used by a trampoline intrinsic, so it is safe 1645 // to remove the 'nest' attribute. 1646 RemoveNestAttribute(F); 1647 ++NumNestRemoved; 1648 Changed = true; 1649 } 1650 } 1651 } 1652 return Changed; 1653} 1654 1655bool GlobalOpt::OptimizeGlobalVars(Module &M) { 1656 bool Changed = false; 1657 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 1658 GVI != E; ) { 1659 GlobalVariable *GV = GVI++; 1660 if (!GV->isConstant() && GV->hasInternalLinkage() && 1661 GV->hasInitializer()) 1662 Changed |= ProcessInternalGlobal(GV, GVI); 1663 } 1664 return Changed; 1665} 1666 1667/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all 1668/// initializers have an init priority of 65535. 1669GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 1670 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 1671 I != E; ++I) 1672 if (I->getName() == "llvm.global_ctors") { 1673 // Found it, verify it's an array of { int, void()* }. 1674 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); 1675 if (!ATy) return 0; 1676 const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); 1677 if (!STy || STy->getNumElements() != 2 || 1678 STy->getElementType(0) != Type::Int32Ty) return 0; 1679 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); 1680 if (!PFTy) return 0; 1681 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); 1682 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || 1683 FTy->getNumParams() != 0) 1684 return 0; 1685 1686 // Verify that the initializer is simple enough for us to handle. 1687 if (!I->hasInitializer()) return 0; 1688 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); 1689 if (!CA) return 0; 1690 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1691 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) { 1692 if (isa<ConstantPointerNull>(CS->getOperand(1))) 1693 continue; 1694 1695 // Must have a function or null ptr. 1696 if (!isa<Function>(CS->getOperand(1))) 1697 return 0; 1698 1699 // Init priority must be standard. 1700 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0)); 1701 if (!CI || CI->getZExtValue() != 65535) 1702 return 0; 1703 } else { 1704 return 0; 1705 } 1706 1707 return I; 1708 } 1709 return 0; 1710} 1711 1712/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 1713/// return a list of the functions and null terminator as a vector. 1714static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 1715 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1716 std::vector<Function*> Result; 1717 Result.reserve(CA->getNumOperands()); 1718 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) { 1719 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i)); 1720 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 1721 } 1722 return Result; 1723} 1724 1725/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 1726/// specified array, returning the new global to use. 1727static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 1728 const std::vector<Function*> &Ctors) { 1729 // If we made a change, reassemble the initializer list. 1730 std::vector<Constant*> CSVals; 1731 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); 1732 CSVals.push_back(0); 1733 1734 // Create the new init list. 1735 std::vector<Constant*> CAList; 1736 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 1737 if (Ctors[i]) { 1738 CSVals[1] = Ctors[i]; 1739 } else { 1740 const Type *FTy = FunctionType::get(Type::VoidTy, 1741 std::vector<const Type*>(), false); 1742 const PointerType *PFTy = PointerType::getUnqual(FTy); 1743 CSVals[1] = Constant::getNullValue(PFTy); 1744 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); 1745 } 1746 CAList.push_back(ConstantStruct::get(CSVals)); 1747 } 1748 1749 // Create the array initializer. 1750 const Type *StructTy = 1751 cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); 1752 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()), 1753 CAList); 1754 1755 // If we didn't change the number of elements, don't create a new GV. 1756 if (CA->getType() == GCL->getInitializer()->getType()) { 1757 GCL->setInitializer(CA); 1758 return GCL; 1759 } 1760 1761 // Create the new global and insert it next to the existing list. 1762 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 1763 GCL->getLinkage(), CA, "", 1764 (Module *)NULL, 1765 GCL->isThreadLocal()); 1766 GCL->getParent()->getGlobalList().insert(GCL, NGV); 1767 NGV->takeName(GCL); 1768 1769 // Nuke the old list, replacing any uses with the new one. 1770 if (!GCL->use_empty()) { 1771 Constant *V = NGV; 1772 if (V->getType() != GCL->getType()) 1773 V = ConstantExpr::getBitCast(V, GCL->getType()); 1774 GCL->replaceAllUsesWith(V); 1775 } 1776 GCL->eraseFromParent(); 1777 1778 if (Ctors.size()) 1779 return NGV; 1780 else 1781 return 0; 1782} 1783 1784 1785static Constant *getVal(std::map<Value*, Constant*> &ComputedValues, 1786 Value *V) { 1787 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 1788 Constant *R = ComputedValues[V]; 1789 assert(R && "Reference to an uncomputed value!"); 1790 return R; 1791} 1792 1793/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 1794/// enough for us to understand. In particular, if it is a cast of something, 1795/// we punt. We basically just support direct accesses to globals and GEP's of 1796/// globals. This should be kept up to date with CommitValueTo. 1797static bool isSimpleEnoughPointerToCommit(Constant *C) { 1798 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 1799 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1800 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1801 return !GV->isDeclaration(); // reject external globals. 1802 } 1803 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 1804 // Handle a constantexpr gep. 1805 if (CE->getOpcode() == Instruction::GetElementPtr && 1806 isa<GlobalVariable>(CE->getOperand(0))) { 1807 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1808 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1809 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1810 return GV->hasInitializer() && 1811 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1812 } 1813 return false; 1814} 1815 1816/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 1817/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 1818/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 1819static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 1820 ConstantExpr *Addr, unsigned OpNo) { 1821 // Base case of the recursion. 1822 if (OpNo == Addr->getNumOperands()) { 1823 assert(Val->getType() == Init->getType() && "Type mismatch!"); 1824 return Val; 1825 } 1826 1827 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { 1828 std::vector<Constant*> Elts; 1829 1830 // Break up the constant into its elements. 1831 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { 1832 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i) 1833 Elts.push_back(CS->getOperand(i)); 1834 } else if (isa<ConstantAggregateZero>(Init)) { 1835 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1836 Elts.push_back(Constant::getNullValue(STy->getElementType(i))); 1837 } else if (isa<UndefValue>(Init)) { 1838 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1839 Elts.push_back(UndefValue::get(STy->getElementType(i))); 1840 } else { 1841 assert(0 && "This code is out of sync with " 1842 " ConstantFoldLoadThroughGEPConstantExpr"); 1843 } 1844 1845 // Replace the element that we are supposed to. 1846 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 1847 unsigned Idx = CU->getZExtValue(); 1848 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 1849 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 1850 1851 // Return the modified struct. 1852 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked()); 1853 } else { 1854 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 1855 const ArrayType *ATy = cast<ArrayType>(Init->getType()); 1856 1857 // Break up the array into elements. 1858 std::vector<Constant*> Elts; 1859 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { 1860 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1861 Elts.push_back(CA->getOperand(i)); 1862 } else if (isa<ConstantAggregateZero>(Init)) { 1863 Constant *Elt = Constant::getNullValue(ATy->getElementType()); 1864 Elts.assign(ATy->getNumElements(), Elt); 1865 } else if (isa<UndefValue>(Init)) { 1866 Constant *Elt = UndefValue::get(ATy->getElementType()); 1867 Elts.assign(ATy->getNumElements(), Elt); 1868 } else { 1869 assert(0 && "This code is out of sync with " 1870 " ConstantFoldLoadThroughGEPConstantExpr"); 1871 } 1872 1873 assert(CI->getZExtValue() < ATy->getNumElements()); 1874 Elts[CI->getZExtValue()] = 1875 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 1876 return ConstantArray::get(ATy, Elts); 1877 } 1878} 1879 1880/// CommitValueTo - We have decided that Addr (which satisfies the predicate 1881/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 1882static void CommitValueTo(Constant *Val, Constant *Addr) { 1883 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 1884 assert(GV->hasInitializer()); 1885 GV->setInitializer(Val); 1886 return; 1887 } 1888 1889 ConstantExpr *CE = cast<ConstantExpr>(Addr); 1890 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1891 1892 Constant *Init = GV->getInitializer(); 1893 Init = EvaluateStoreInto(Init, Val, CE, 2); 1894 GV->setInitializer(Init); 1895} 1896 1897/// ComputeLoadResult - Return the value that would be computed by a load from 1898/// P after the stores reflected by 'memory' have been performed. If we can't 1899/// decide, return null. 1900static Constant *ComputeLoadResult(Constant *P, 1901 const std::map<Constant*, Constant*> &Memory) { 1902 // If this memory location has been recently stored, use the stored value: it 1903 // is the most up-to-date. 1904 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P); 1905 if (I != Memory.end()) return I->second; 1906 1907 // Access it. 1908 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 1909 if (GV->hasInitializer()) 1910 return GV->getInitializer(); 1911 return 0; 1912 } 1913 1914 // Handle a constantexpr getelementptr. 1915 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 1916 if (CE->getOpcode() == Instruction::GetElementPtr && 1917 isa<GlobalVariable>(CE->getOperand(0))) { 1918 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1919 if (GV->hasInitializer()) 1920 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1921 } 1922 1923 return 0; // don't know how to evaluate. 1924} 1925 1926/// EvaluateFunction - Evaluate a call to function F, returning true if 1927/// successful, false if we can't evaluate it. ActualArgs contains the formal 1928/// arguments for the function. 1929static bool EvaluateFunction(Function *F, Constant *&RetVal, 1930 const std::vector<Constant*> &ActualArgs, 1931 std::vector<Function*> &CallStack, 1932 std::map<Constant*, Constant*> &MutatedMemory, 1933 std::vector<GlobalVariable*> &AllocaTmps) { 1934 // Check to see if this function is already executing (recursion). If so, 1935 // bail out. TODO: we might want to accept limited recursion. 1936 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 1937 return false; 1938 1939 CallStack.push_back(F); 1940 1941 /// Values - As we compute SSA register values, we store their contents here. 1942 std::map<Value*, Constant*> Values; 1943 1944 // Initialize arguments to the incoming values specified. 1945 unsigned ArgNo = 0; 1946 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 1947 ++AI, ++ArgNo) 1948 Values[AI] = ActualArgs[ArgNo]; 1949 1950 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 1951 /// we can only evaluate any one basic block at most once. This set keeps 1952 /// track of what we have executed so we can detect recursive cases etc. 1953 std::set<BasicBlock*> ExecutedBlocks; 1954 1955 // CurInst - The current instruction we're evaluating. 1956 BasicBlock::iterator CurInst = F->begin()->begin(); 1957 1958 // This is the main evaluation loop. 1959 while (1) { 1960 Constant *InstResult = 0; 1961 1962 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 1963 if (SI->isVolatile()) return false; // no volatile accesses. 1964 Constant *Ptr = getVal(Values, SI->getOperand(1)); 1965 if (!isSimpleEnoughPointerToCommit(Ptr)) 1966 // If this is too complex for us to commit, reject it. 1967 return false; 1968 Constant *Val = getVal(Values, SI->getOperand(0)); 1969 MutatedMemory[Ptr] = Val; 1970 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 1971 InstResult = ConstantExpr::get(BO->getOpcode(), 1972 getVal(Values, BO->getOperand(0)), 1973 getVal(Values, BO->getOperand(1))); 1974 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 1975 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 1976 getVal(Values, CI->getOperand(0)), 1977 getVal(Values, CI->getOperand(1))); 1978 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 1979 InstResult = ConstantExpr::getCast(CI->getOpcode(), 1980 getVal(Values, CI->getOperand(0)), 1981 CI->getType()); 1982 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 1983 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), 1984 getVal(Values, SI->getOperand(1)), 1985 getVal(Values, SI->getOperand(2))); 1986 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 1987 Constant *P = getVal(Values, GEP->getOperand(0)); 1988 SmallVector<Constant*, 8> GEPOps; 1989 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 1990 GEPOps.push_back(getVal(Values, GEP->getOperand(i))); 1991 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); 1992 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 1993 if (LI->isVolatile()) return false; // no volatile accesses. 1994 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), 1995 MutatedMemory); 1996 if (InstResult == 0) return false; // Could not evaluate load. 1997 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 1998 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 1999 const Type *Ty = AI->getType()->getElementType(); 2000 AllocaTmps.push_back(new GlobalVariable(Ty, false, 2001 GlobalValue::InternalLinkage, 2002 UndefValue::get(Ty), 2003 AI->getName())); 2004 InstResult = AllocaTmps.back(); 2005 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { 2006 // Cannot handle inline asm. 2007 if (isa<InlineAsm>(CI->getOperand(0))) return false; 2008 2009 // Resolve function pointers. 2010 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); 2011 if (!Callee) return false; // Cannot resolve. 2012 2013 std::vector<Constant*> Formals; 2014 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i) 2015 Formals.push_back(getVal(Values, CI->getOperand(i))); 2016 2017 if (Callee->isDeclaration()) { 2018 // If this is a function we can constant fold, do it. 2019 if (Constant *C = ConstantFoldCall(Callee, &Formals[0], 2020 Formals.size())) { 2021 InstResult = C; 2022 } else { 2023 return false; 2024 } 2025 } else { 2026 if (Callee->getFunctionType()->isVarArg()) 2027 return false; 2028 2029 Constant *RetVal; 2030 2031 // Execute the call, if successful, use the return value. 2032 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, 2033 MutatedMemory, AllocaTmps)) 2034 return false; 2035 InstResult = RetVal; 2036 } 2037 } else if (isa<TerminatorInst>(CurInst)) { 2038 BasicBlock *NewBB = 0; 2039 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2040 if (BI->isUnconditional()) { 2041 NewBB = BI->getSuccessor(0); 2042 } else { 2043 ConstantInt *Cond = 2044 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); 2045 if (!Cond) return false; // Cannot determine. 2046 2047 NewBB = BI->getSuccessor(!Cond->getZExtValue()); 2048 } 2049 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2050 ConstantInt *Val = 2051 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); 2052 if (!Val) return false; // Cannot determine. 2053 NewBB = SI->getSuccessor(SI->findCaseValue(Val)); 2054 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { 2055 if (RI->getNumOperands()) 2056 RetVal = getVal(Values, RI->getOperand(0)); 2057 2058 CallStack.pop_back(); // return from fn. 2059 return true; // We succeeded at evaluating this ctor! 2060 } else { 2061 // invoke, unwind, unreachable. 2062 return false; // Cannot handle this terminator. 2063 } 2064 2065 // Okay, we succeeded in evaluating this control flow. See if we have 2066 // executed the new block before. If so, we have a looping function, 2067 // which we cannot evaluate in reasonable time. 2068 if (!ExecutedBlocks.insert(NewBB).second) 2069 return false; // looped! 2070 2071 // Okay, we have never been in this block before. Check to see if there 2072 // are any PHI nodes. If so, evaluate them with information about where 2073 // we came from. 2074 BasicBlock *OldBB = CurInst->getParent(); 2075 CurInst = NewBB->begin(); 2076 PHINode *PN; 2077 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2078 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); 2079 2080 // Do NOT increment CurInst. We know that the terminator had no value. 2081 continue; 2082 } else { 2083 // Did not know how to evaluate this! 2084 return false; 2085 } 2086 2087 if (!CurInst->use_empty()) 2088 Values[CurInst] = InstResult; 2089 2090 // Advance program counter. 2091 ++CurInst; 2092 } 2093} 2094 2095/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2096/// we can. Return true if we can, false otherwise. 2097static bool EvaluateStaticConstructor(Function *F) { 2098 /// MutatedMemory - For each store we execute, we update this map. Loads 2099 /// check this to get the most up-to-date value. If evaluation is successful, 2100 /// this state is committed to the process. 2101 std::map<Constant*, Constant*> MutatedMemory; 2102 2103 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2104 /// to represent its body. This vector is needed so we can delete the 2105 /// temporary globals when we are done. 2106 std::vector<GlobalVariable*> AllocaTmps; 2107 2108 /// CallStack - This is used to detect recursion. In pathological situations 2109 /// we could hit exponential behavior, but at least there is nothing 2110 /// unbounded. 2111 std::vector<Function*> CallStack; 2112 2113 // Call the function. 2114 Constant *RetValDummy; 2115 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), 2116 CallStack, MutatedMemory, AllocaTmps); 2117 if (EvalSuccess) { 2118 // We succeeded at evaluation: commit the result. 2119 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2120 << F->getName() << "' to " << MutatedMemory.size() 2121 << " stores.\n"; 2122 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(), 2123 E = MutatedMemory.end(); I != E; ++I) 2124 CommitValueTo(I->second, I->first); 2125 } 2126 2127 // At this point, we are done interpreting. If we created any 'alloca' 2128 // temporaries, release them now. 2129 while (!AllocaTmps.empty()) { 2130 GlobalVariable *Tmp = AllocaTmps.back(); 2131 AllocaTmps.pop_back(); 2132 2133 // If there are still users of the alloca, the program is doing something 2134 // silly, e.g. storing the address of the alloca somewhere and using it 2135 // later. Since this is undefined, we'll just make it be null. 2136 if (!Tmp->use_empty()) 2137 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2138 delete Tmp; 2139 } 2140 2141 return EvalSuccess; 2142} 2143 2144 2145 2146/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2147/// Return true if anything changed. 2148bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2149 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2150 bool MadeChange = false; 2151 if (Ctors.empty()) return false; 2152 2153 // Loop over global ctors, optimizing them when we can. 2154 for (unsigned i = 0; i != Ctors.size(); ++i) { 2155 Function *F = Ctors[i]; 2156 // Found a null terminator in the middle of the list, prune off the rest of 2157 // the list. 2158 if (F == 0) { 2159 if (i != Ctors.size()-1) { 2160 Ctors.resize(i+1); 2161 MadeChange = true; 2162 } 2163 break; 2164 } 2165 2166 // We cannot simplify external ctor functions. 2167 if (F->empty()) continue; 2168 2169 // If we can evaluate the ctor at compile time, do. 2170 if (EvaluateStaticConstructor(F)) { 2171 Ctors.erase(Ctors.begin()+i); 2172 MadeChange = true; 2173 --i; 2174 ++NumCtorsEvaluated; 2175 continue; 2176 } 2177 } 2178 2179 if (!MadeChange) return false; 2180 2181 GCL = InstallGlobalCtors(GCL, Ctors); 2182 return true; 2183} 2184 2185 2186bool GlobalOpt::runOnModule(Module &M) { 2187 bool Changed = false; 2188 2189 // Try to find the llvm.globalctors list. 2190 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 2191 2192 bool LocalChange = true; 2193 while (LocalChange) { 2194 LocalChange = false; 2195 2196 // Delete functions that are trivially dead, ccc -> fastcc 2197 LocalChange |= OptimizeFunctions(M); 2198 2199 // Optimize global_ctors list. 2200 if (GlobalCtors) 2201 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 2202 2203 // Optimize non-address-taken globals. 2204 LocalChange |= OptimizeGlobalVars(M); 2205 Changed |= LocalChange; 2206 } 2207 2208 // TODO: Move all global ctors functions to the end of the module for code 2209 // layout. 2210 2211 return Changed; 2212} 2213