GlobalOpt.cpp revision afa10bfb94fb68da6cc3a895f7a4730df87064dd
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/Compiler.h" 29#include "llvm/Support/Debug.h" 30#include "llvm/Support/GetElementPtrTypeIterator.h" 31#include "llvm/ADT/SmallPtrSet.h" 32#include "llvm/ADT/SmallVector.h" 33#include "llvm/ADT/Statistic.h" 34#include "llvm/ADT/StringExtras.h" 35#include <algorithm> 36#include <set> 37using namespace llvm; 38 39STATISTIC(NumMarked , "Number of globals marked constant"); 40STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); 41STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); 42STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); 43STATISTIC(NumDeleted , "Number of globals deleted"); 44STATISTIC(NumFnDeleted , "Number of functions deleted"); 45STATISTIC(NumGlobUses , "Number of global uses devirtualized"); 46STATISTIC(NumLocalized , "Number of globals localized"); 47STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); 48STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); 49STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); 50STATISTIC(NumNestRemoved , "Number of nest attributes removed"); 51 52namespace { 53 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass { 54 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 55 AU.addRequired<TargetData>(); 56 } 57 static char ID; // Pass identification, replacement for typeid 58 GlobalOpt() : ModulePass((intptr_t)&ID) {} 59 60 bool runOnModule(Module &M); 61 62 private: 63 GlobalVariable *FindGlobalCtors(Module &M); 64 bool OptimizeFunctions(Module &M); 65 bool OptimizeGlobalVars(Module &M); 66 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); 67 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI); 68 }; 69 70 char GlobalOpt::ID = 0; 71 RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer"); 72} 73 74ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } 75 76/// GlobalStatus - As we analyze each global, keep track of some information 77/// about it. If we find out that the address of the global is taken, none of 78/// this info will be accurate. 79struct VISIBILITY_HIDDEN GlobalStatus { 80 /// isLoaded - True if the global is ever loaded. If the global isn't ever 81 /// loaded it can be deleted. 82 bool isLoaded; 83 84 /// StoredType - Keep track of what stores to the global look like. 85 /// 86 enum StoredType { 87 /// NotStored - There is no store to this global. It can thus be marked 88 /// constant. 89 NotStored, 90 91 /// isInitializerStored - This global is stored to, but the only thing 92 /// stored is the constant it was initialized with. This is only tracked 93 /// for scalar globals. 94 isInitializerStored, 95 96 /// isStoredOnce - This global is stored to, but only its initializer and 97 /// one other value is ever stored to it. If this global isStoredOnce, we 98 /// track the value stored to it in StoredOnceValue below. This is only 99 /// tracked for scalar globals. 100 isStoredOnce, 101 102 /// isStored - This global is stored to by multiple values or something else 103 /// that we cannot track. 104 isStored 105 } StoredType; 106 107 /// StoredOnceValue - If only one value (besides the initializer constant) is 108 /// ever stored to this global, keep track of what value it is. 109 Value *StoredOnceValue; 110 111 /// AccessingFunction/HasMultipleAccessingFunctions - These start out 112 /// null/false. When the first accessing function is noticed, it is recorded. 113 /// When a second different accessing function is noticed, 114 /// HasMultipleAccessingFunctions is set to true. 115 Function *AccessingFunction; 116 bool HasMultipleAccessingFunctions; 117 118 /// HasNonInstructionUser - Set to true if this global has a user that is not 119 /// an instruction (e.g. a constant expr or GV initializer). 120 bool HasNonInstructionUser; 121 122 /// HasPHIUser - Set to true if this global has a user that is a PHI node. 123 bool HasPHIUser; 124 125 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0), 126 AccessingFunction(0), HasMultipleAccessingFunctions(false), 127 HasNonInstructionUser(false), HasPHIUser(false) {} 128}; 129 130 131 132/// ConstantIsDead - Return true if the specified constant is (transitively) 133/// dead. The constant may be used by other constants (e.g. constant arrays and 134/// constant exprs) as long as they are dead, but it cannot be used by anything 135/// else. 136static bool ConstantIsDead(Constant *C) { 137 if (isa<GlobalValue>(C)) return false; 138 139 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI) 140 if (Constant *CU = dyn_cast<Constant>(*UI)) { 141 if (!ConstantIsDead(CU)) return false; 142 } else 143 return false; 144 return true; 145} 146 147 148/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus 149/// structure. If the global has its address taken, return true to indicate we 150/// can't do anything with it. 151/// 152static bool AnalyzeGlobal(Value *V, GlobalStatus &GS, 153 std::set<PHINode*> &PHIUsers) { 154 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 155 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) { 156 GS.HasNonInstructionUser = true; 157 158 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; 159 160 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) { 161 if (!GS.HasMultipleAccessingFunctions) { 162 Function *F = I->getParent()->getParent(); 163 if (GS.AccessingFunction == 0) 164 GS.AccessingFunction = F; 165 else if (GS.AccessingFunction != F) 166 GS.HasMultipleAccessingFunctions = true; 167 } 168 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 169 GS.isLoaded = true; 170 if (LI->isVolatile()) return true; // Don't hack on volatile loads. 171 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 172 // Don't allow a store OF the address, only stores TO the address. 173 if (SI->getOperand(0) == V) return true; 174 175 if (SI->isVolatile()) return true; // Don't hack on volatile stores. 176 177 // If this is a direct store to the global (i.e., the global is a scalar 178 // value, not an aggregate), keep more specific information about 179 // stores. 180 if (GS.StoredType != GlobalStatus::isStored) 181 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){ 182 Value *StoredVal = SI->getOperand(0); 183 if (StoredVal == GV->getInitializer()) { 184 if (GS.StoredType < GlobalStatus::isInitializerStored) 185 GS.StoredType = GlobalStatus::isInitializerStored; 186 } else if (isa<LoadInst>(StoredVal) && 187 cast<LoadInst>(StoredVal)->getOperand(0) == GV) { 188 // G = G 189 if (GS.StoredType < GlobalStatus::isInitializerStored) 190 GS.StoredType = GlobalStatus::isInitializerStored; 191 } else if (GS.StoredType < GlobalStatus::isStoredOnce) { 192 GS.StoredType = GlobalStatus::isStoredOnce; 193 GS.StoredOnceValue = StoredVal; 194 } else if (GS.StoredType == GlobalStatus::isStoredOnce && 195 GS.StoredOnceValue == StoredVal) { 196 // noop. 197 } else { 198 GS.StoredType = GlobalStatus::isStored; 199 } 200 } else { 201 GS.StoredType = GlobalStatus::isStored; 202 } 203 } else if (isa<GetElementPtrInst>(I)) { 204 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 205 } else if (isa<SelectInst>(I)) { 206 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 207 } else if (PHINode *PN = dyn_cast<PHINode>(I)) { 208 // PHI nodes we can check just like select or GEP instructions, but we 209 // have to be careful about infinite recursion. 210 if (PHIUsers.insert(PN).second) // Not already visited. 211 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 212 GS.HasPHIUser = true; 213 } else if (isa<CmpInst>(I)) { 214 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { 215 if (I->getOperand(1) == V) 216 GS.StoredType = GlobalStatus::isStored; 217 if (I->getOperand(2) == V) 218 GS.isLoaded = true; 219 } else if (isa<MemSetInst>(I)) { 220 assert(I->getOperand(1) == V && "Memset only takes one pointer!"); 221 GS.StoredType = GlobalStatus::isStored; 222 } else { 223 return true; // Any other non-load instruction might take address! 224 } 225 } else if (Constant *C = dyn_cast<Constant>(*UI)) { 226 GS.HasNonInstructionUser = true; 227 // We might have a dead and dangling constant hanging off of here. 228 if (!ConstantIsDead(C)) 229 return true; 230 } else { 231 GS.HasNonInstructionUser = true; 232 // Otherwise must be some other user. 233 return true; 234 } 235 236 return false; 237} 238 239static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { 240 ConstantInt *CI = dyn_cast<ConstantInt>(Idx); 241 if (!CI) return 0; 242 unsigned IdxV = CI->getZExtValue(); 243 244 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { 245 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); 246 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { 247 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); 248 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { 249 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); 250 } else if (isa<ConstantAggregateZero>(Agg)) { 251 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 252 if (IdxV < STy->getNumElements()) 253 return Constant::getNullValue(STy->getElementType(IdxV)); 254 } else if (const SequentialType *STy = 255 dyn_cast<SequentialType>(Agg->getType())) { 256 return Constant::getNullValue(STy->getElementType()); 257 } 258 } else if (isa<UndefValue>(Agg)) { 259 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 260 if (IdxV < STy->getNumElements()) 261 return UndefValue::get(STy->getElementType(IdxV)); 262 } else if (const SequentialType *STy = 263 dyn_cast<SequentialType>(Agg->getType())) { 264 return UndefValue::get(STy->getElementType()); 265 } 266 } 267 return 0; 268} 269 270 271/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 272/// users of the global, cleaning up the obvious ones. This is largely just a 273/// quick scan over the use list to clean up the easy and obvious cruft. This 274/// returns true if it made a change. 275static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) { 276 bool Changed = false; 277 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 278 User *U = *UI++; 279 280 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 281 if (Init) { 282 // Replace the load with the initializer. 283 LI->replaceAllUsesWith(Init); 284 LI->eraseFromParent(); 285 Changed = true; 286 } 287 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 288 // Store must be unreachable or storing Init into the global. 289 SI->eraseFromParent(); 290 Changed = true; 291 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 292 if (CE->getOpcode() == Instruction::GetElementPtr) { 293 Constant *SubInit = 0; 294 if (Init) 295 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 296 Changed |= CleanupConstantGlobalUsers(CE, SubInit); 297 } else if (CE->getOpcode() == Instruction::BitCast && 298 isa<PointerType>(CE->getType())) { 299 // Pointer cast, delete any stores and memsets to the global. 300 Changed |= CleanupConstantGlobalUsers(CE, 0); 301 } 302 303 if (CE->use_empty()) { 304 CE->destroyConstant(); 305 Changed = true; 306 } 307 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 308 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 309 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 310 // and will invalidate our notion of what Init is. 311 Constant *SubInit = 0; 312 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 313 ConstantExpr *CE = 314 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP)); 315 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 316 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 317 } 318 Changed |= CleanupConstantGlobalUsers(GEP, SubInit); 319 320 if (GEP->use_empty()) { 321 GEP->eraseFromParent(); 322 Changed = true; 323 } 324 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 325 if (MI->getRawDest() == V) { 326 MI->eraseFromParent(); 327 Changed = true; 328 } 329 330 } else if (Constant *C = dyn_cast<Constant>(U)) { 331 // If we have a chain of dead constantexprs or other things dangling from 332 // us, and if they are all dead, nuke them without remorse. 333 if (ConstantIsDead(C)) { 334 C->destroyConstant(); 335 // This could have invalidated UI, start over from scratch. 336 CleanupConstantGlobalUsers(V, Init); 337 return true; 338 } 339 } 340 } 341 return Changed; 342} 343 344/// isSafeSROAElementUse - Return true if the specified instruction is a safe 345/// user of a derived expression from a global that we want to SROA. 346static bool isSafeSROAElementUse(Value *V) { 347 // We might have a dead and dangling constant hanging off of here. 348 if (Constant *C = dyn_cast<Constant>(V)) 349 return ConstantIsDead(C); 350 351 Instruction *I = dyn_cast<Instruction>(V); 352 if (!I) return false; 353 354 // Loads are ok. 355 if (isa<LoadInst>(I)) return true; 356 357 // Stores *to* the pointer are ok. 358 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 359 return SI->getOperand(0) != V; 360 361 // Otherwise, it must be a GEP. 362 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 363 if (GEPI == 0) return false; 364 365 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 366 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 367 return false; 368 369 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 370 I != E; ++I) 371 if (!isSafeSROAElementUse(*I)) 372 return false; 373 return true; 374} 375 376 377/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 378/// Look at it and its uses and decide whether it is safe to SROA this global. 379/// 380static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 381 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 382 if (!isa<GetElementPtrInst>(U) && 383 (!isa<ConstantExpr>(U) || 384 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 385 return false; 386 387 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 388 // don't like < 3 operand CE's, and we don't like non-constant integer 389 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 390 // value of C. 391 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 392 !cast<Constant>(U->getOperand(1))->isNullValue() || 393 !isa<ConstantInt>(U->getOperand(2))) 394 return false; 395 396 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 397 ++GEPI; // Skip over the pointer index. 398 399 // If this is a use of an array allocation, do a bit more checking for sanity. 400 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 401 uint64_t NumElements = AT->getNumElements(); 402 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 403 404 // Check to make sure that index falls within the array. If not, 405 // something funny is going on, so we won't do the optimization. 406 // 407 if (Idx->getZExtValue() >= NumElements) 408 return false; 409 410 // We cannot scalar repl this level of the array unless any array 411 // sub-indices are in-range constants. In particular, consider: 412 // A[0][i]. We cannot know that the user isn't doing invalid things like 413 // allowing i to index an out-of-range subscript that accesses A[1]. 414 // 415 // Scalar replacing *just* the outer index of the array is probably not 416 // going to be a win anyway, so just give up. 417 for (++GEPI; // Skip array index. 418 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); 419 ++GEPI) { 420 uint64_t NumElements; 421 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 422 NumElements = SubArrayTy->getNumElements(); 423 else 424 NumElements = cast<VectorType>(*GEPI)->getNumElements(); 425 426 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 427 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 428 return false; 429 } 430 } 431 432 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 433 if (!isSafeSROAElementUse(*I)) 434 return false; 435 return true; 436} 437 438/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 439/// is safe for us to perform this transformation. 440/// 441static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 442 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 443 UI != E; ++UI) { 444 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 445 return false; 446 } 447 return true; 448} 449 450 451/// SRAGlobal - Perform scalar replacement of aggregates on the specified global 452/// variable. This opens the door for other optimizations by exposing the 453/// behavior of the program in a more fine-grained way. We have determined that 454/// this transformation is safe already. We return the first global variable we 455/// insert so that the caller can reprocess it. 456static GlobalVariable *SRAGlobal(GlobalVariable *GV) { 457 // Make sure this global only has simple uses that we can SRA. 458 if (!GlobalUsersSafeToSRA(GV)) 459 return 0; 460 461 assert(GV->hasInternalLinkage() && !GV->isConstant()); 462 Constant *Init = GV->getInitializer(); 463 const Type *Ty = Init->getType(); 464 465 std::vector<GlobalVariable*> NewGlobals; 466 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 467 468 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 469 NewGlobals.reserve(STy->getNumElements()); 470 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 471 Constant *In = getAggregateConstantElement(Init, 472 ConstantInt::get(Type::Int32Ty, i)); 473 assert(In && "Couldn't get element of initializer?"); 474 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 475 GlobalVariable::InternalLinkage, 476 In, GV->getName()+"."+utostr(i), 477 (Module *)NULL, 478 GV->isThreadLocal()); 479 Globals.insert(GV, NGV); 480 NewGlobals.push_back(NGV); 481 } 482 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 483 unsigned NumElements = 0; 484 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 485 NumElements = ATy->getNumElements(); 486 else if (const VectorType *PTy = dyn_cast<VectorType>(STy)) 487 NumElements = PTy->getNumElements(); 488 else 489 assert(0 && "Unknown aggregate sequential type!"); 490 491 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 492 return 0; // It's not worth it. 493 NewGlobals.reserve(NumElements); 494 for (unsigned i = 0, e = NumElements; i != e; ++i) { 495 Constant *In = getAggregateConstantElement(Init, 496 ConstantInt::get(Type::Int32Ty, i)); 497 assert(In && "Couldn't get element of initializer?"); 498 499 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 500 GlobalVariable::InternalLinkage, 501 In, GV->getName()+"."+utostr(i), 502 (Module *)NULL, 503 GV->isThreadLocal()); 504 Globals.insert(GV, NGV); 505 NewGlobals.push_back(NGV); 506 } 507 } 508 509 if (NewGlobals.empty()) 510 return 0; 511 512 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; 513 514 Constant *NullInt = Constant::getNullValue(Type::Int32Ty); 515 516 // Loop over all of the uses of the global, replacing the constantexpr geps, 517 // with smaller constantexpr geps or direct references. 518 while (!GV->use_empty()) { 519 User *GEP = GV->use_back(); 520 assert(((isa<ConstantExpr>(GEP) && 521 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 522 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 523 524 // Ignore the 1th operand, which has to be zero or else the program is quite 525 // broken (undefined). Get the 2nd operand, which is the structure or array 526 // index. 527 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 528 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 529 530 Value *NewPtr = NewGlobals[Val]; 531 532 // Form a shorter GEP if needed. 533 if (GEP->getNumOperands() > 3) 534 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 535 SmallVector<Constant*, 8> Idxs; 536 Idxs.push_back(NullInt); 537 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 538 Idxs.push_back(CE->getOperand(i)); 539 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), 540 &Idxs[0], Idxs.size()); 541 } else { 542 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 543 SmallVector<Value*, 8> Idxs; 544 Idxs.push_back(NullInt); 545 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 546 Idxs.push_back(GEPI->getOperand(i)); 547 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(), 548 GEPI->getName()+"."+utostr(Val), GEPI); 549 } 550 GEP->replaceAllUsesWith(NewPtr); 551 552 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 553 GEPI->eraseFromParent(); 554 else 555 cast<ConstantExpr>(GEP)->destroyConstant(); 556 } 557 558 // Delete the old global, now that it is dead. 559 Globals.erase(GV); 560 ++NumSRA; 561 562 // Loop over the new globals array deleting any globals that are obviously 563 // dead. This can arise due to scalarization of a structure or an array that 564 // has elements that are dead. 565 unsigned FirstGlobal = 0; 566 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 567 if (NewGlobals[i]->use_empty()) { 568 Globals.erase(NewGlobals[i]); 569 if (FirstGlobal == i) ++FirstGlobal; 570 } 571 572 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 573} 574 575/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 576/// value will trap if the value is dynamically null. PHIs keeps track of any 577/// phi nodes we've seen to avoid reprocessing them. 578static bool AllUsesOfValueWillTrapIfNull(Value *V, 579 SmallPtrSet<PHINode*, 8> &PHIs) { 580 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 581 if (isa<LoadInst>(*UI)) { 582 // Will trap. 583 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 584 if (SI->getOperand(0) == V) { 585 //cerr << "NONTRAPPING USE: " << **UI; 586 return false; // Storing the value. 587 } 588 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { 589 if (CI->getOperand(0) != V) { 590 //cerr << "NONTRAPPING USE: " << **UI; 591 return false; // Not calling the ptr 592 } 593 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { 594 if (II->getOperand(0) != V) { 595 //cerr << "NONTRAPPING USE: " << **UI; 596 return false; // Not calling the ptr 597 } 598 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { 599 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 600 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 601 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 602 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 603 // If we've already seen this phi node, ignore it, it has already been 604 // checked. 605 if (PHIs.insert(PN)) 606 return AllUsesOfValueWillTrapIfNull(PN, PHIs); 607 } else if (isa<ICmpInst>(*UI) && 608 isa<ConstantPointerNull>(UI->getOperand(1))) { 609 // Ignore setcc X, null 610 } else { 611 //cerr << "NONTRAPPING USE: " << **UI; 612 return false; 613 } 614 return true; 615} 616 617/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 618/// from GV will trap if the loaded value is null. Note that this also permits 619/// comparisons of the loaded value against null, as a special case. 620static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) { 621 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) 622 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 623 SmallPtrSet<PHINode*, 8> PHIs; 624 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 625 return false; 626 } else if (isa<StoreInst>(*UI)) { 627 // Ignore stores to the global. 628 } else { 629 // We don't know or understand this user, bail out. 630 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; 631 return false; 632 } 633 634 return true; 635} 636 637static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 638 bool Changed = false; 639 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 640 Instruction *I = cast<Instruction>(*UI++); 641 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 642 LI->setOperand(0, NewV); 643 Changed = true; 644 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 645 if (SI->getOperand(1) == V) { 646 SI->setOperand(1, NewV); 647 Changed = true; 648 } 649 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 650 if (I->getOperand(0) == V) { 651 // Calling through the pointer! Turn into a direct call, but be careful 652 // that the pointer is not also being passed as an argument. 653 I->setOperand(0, NewV); 654 Changed = true; 655 bool PassedAsArg = false; 656 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) 657 if (I->getOperand(i) == V) { 658 PassedAsArg = true; 659 I->setOperand(i, NewV); 660 } 661 662 if (PassedAsArg) { 663 // Being passed as an argument also. Be careful to not invalidate UI! 664 UI = V->use_begin(); 665 } 666 } 667 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 668 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 669 ConstantExpr::getCast(CI->getOpcode(), 670 NewV, CI->getType())); 671 if (CI->use_empty()) { 672 Changed = true; 673 CI->eraseFromParent(); 674 } 675 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 676 // Should handle GEP here. 677 SmallVector<Constant*, 8> Idxs; 678 Idxs.reserve(GEPI->getNumOperands()-1); 679 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 680 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i))) 681 Idxs.push_back(C); 682 else 683 break; 684 if (Idxs.size() == GEPI->getNumOperands()-1) 685 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 686 ConstantExpr::getGetElementPtr(NewV, &Idxs[0], 687 Idxs.size())); 688 if (GEPI->use_empty()) { 689 Changed = true; 690 GEPI->eraseFromParent(); 691 } 692 } 693 } 694 695 return Changed; 696} 697 698 699/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 700/// value stored into it. If there are uses of the loaded value that would trap 701/// if the loaded value is dynamically null, then we know that they cannot be 702/// reachable with a null optimize away the load. 703static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { 704 std::vector<LoadInst*> Loads; 705 bool Changed = false; 706 707 // Replace all uses of loads with uses of uses of the stored value. 708 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); 709 GUI != E; ++GUI) 710 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { 711 Loads.push_back(LI); 712 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 713 } else { 714 // If we get here we could have stores, selects, or phi nodes whose values 715 // are loaded. 716 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || 717 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && 718 "Only expect load and stores!"); 719 } 720 721 if (Changed) { 722 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; 723 ++NumGlobUses; 724 } 725 726 // Delete all of the loads we can, keeping track of whether we nuked them all! 727 bool AllLoadsGone = true; 728 while (!Loads.empty()) { 729 LoadInst *L = Loads.back(); 730 if (L->use_empty()) { 731 L->eraseFromParent(); 732 Changed = true; 733 } else { 734 AllLoadsGone = false; 735 } 736 Loads.pop_back(); 737 } 738 739 // If we nuked all of the loads, then none of the stores are needed either, 740 // nor is the global. 741 if (AllLoadsGone) { 742 DOUT << " *** GLOBAL NOW DEAD!\n"; 743 CleanupConstantGlobalUsers(GV, 0); 744 if (GV->use_empty()) { 745 GV->eraseFromParent(); 746 ++NumDeleted; 747 } 748 Changed = true; 749 } 750 return Changed; 751} 752 753/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 754/// instructions that are foldable. 755static void ConstantPropUsersOf(Value *V) { 756 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 757 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 758 if (Constant *NewC = ConstantFoldInstruction(I)) { 759 I->replaceAllUsesWith(NewC); 760 761 // Advance UI to the next non-I use to avoid invalidating it! 762 // Instructions could multiply use V. 763 while (UI != E && *UI == I) 764 ++UI; 765 I->eraseFromParent(); 766 } 767} 768 769/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 770/// variable, and transforms the program as if it always contained the result of 771/// the specified malloc. Because it is always the result of the specified 772/// malloc, there is no reason to actually DO the malloc. Instead, turn the 773/// malloc into a global, and any loads of GV as uses of the new global. 774static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 775 MallocInst *MI) { 776 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; 777 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); 778 779 if (NElements->getZExtValue() != 1) { 780 // If we have an array allocation, transform it to a single element 781 // allocation to make the code below simpler. 782 Type *NewTy = ArrayType::get(MI->getAllocatedType(), 783 NElements->getZExtValue()); 784 MallocInst *NewMI = 785 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), 786 MI->getAlignment(), MI->getName(), MI); 787 Value* Indices[2]; 788 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); 789 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2, 790 NewMI->getName()+".el0", MI); 791 MI->replaceAllUsesWith(NewGEP); 792 MI->eraseFromParent(); 793 MI = NewMI; 794 } 795 796 // Create the new global variable. The contents of the malloc'd memory is 797 // undefined, so initialize with an undef value. 798 Constant *Init = UndefValue::get(MI->getAllocatedType()); 799 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, 800 GlobalValue::InternalLinkage, Init, 801 GV->getName()+".body", 802 (Module *)NULL, 803 GV->isThreadLocal()); 804 GV->getParent()->getGlobalList().insert(GV, NewGV); 805 806 // Anything that used the malloc now uses the global directly. 807 MI->replaceAllUsesWith(NewGV); 808 809 Constant *RepValue = NewGV; 810 if (NewGV->getType() != GV->getType()->getElementType()) 811 RepValue = ConstantExpr::getBitCast(RepValue, 812 GV->getType()->getElementType()); 813 814 // If there is a comparison against null, we will insert a global bool to 815 // keep track of whether the global was initialized yet or not. 816 GlobalVariable *InitBool = 817 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage, 818 ConstantInt::getFalse(), GV->getName()+".init", 819 (Module *)NULL, GV->isThreadLocal()); 820 bool InitBoolUsed = false; 821 822 // Loop over all uses of GV, processing them in turn. 823 std::vector<StoreInst*> Stores; 824 while (!GV->use_empty()) 825 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 826 while (!LI->use_empty()) { 827 Use &LoadUse = LI->use_begin().getUse(); 828 if (!isa<ICmpInst>(LoadUse.getUser())) 829 LoadUse = RepValue; 830 else { 831 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); 832 // Replace the cmp X, 0 with a use of the bool value. 833 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); 834 InitBoolUsed = true; 835 switch (CI->getPredicate()) { 836 default: assert(0 && "Unknown ICmp Predicate!"); 837 case ICmpInst::ICMP_ULT: 838 case ICmpInst::ICMP_SLT: 839 LV = ConstantInt::getFalse(); // X < null -> always false 840 break; 841 case ICmpInst::ICMP_ULE: 842 case ICmpInst::ICMP_SLE: 843 case ICmpInst::ICMP_EQ: 844 LV = BinaryOperator::createNot(LV, "notinit", CI); 845 break; 846 case ICmpInst::ICMP_NE: 847 case ICmpInst::ICMP_UGE: 848 case ICmpInst::ICMP_SGE: 849 case ICmpInst::ICMP_UGT: 850 case ICmpInst::ICMP_SGT: 851 break; // no change. 852 } 853 CI->replaceAllUsesWith(LV); 854 CI->eraseFromParent(); 855 } 856 } 857 LI->eraseFromParent(); 858 } else { 859 StoreInst *SI = cast<StoreInst>(GV->use_back()); 860 // The global is initialized when the store to it occurs. 861 new StoreInst(ConstantInt::getTrue(), InitBool, SI); 862 SI->eraseFromParent(); 863 } 864 865 // If the initialization boolean was used, insert it, otherwise delete it. 866 if (!InitBoolUsed) { 867 while (!InitBool->use_empty()) // Delete initializations 868 cast<Instruction>(InitBool->use_back())->eraseFromParent(); 869 delete InitBool; 870 } else 871 GV->getParent()->getGlobalList().insert(GV, InitBool); 872 873 874 // Now the GV is dead, nuke it and the malloc. 875 GV->eraseFromParent(); 876 MI->eraseFromParent(); 877 878 // To further other optimizations, loop over all users of NewGV and try to 879 // constant prop them. This will promote GEP instructions with constant 880 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 881 ConstantPropUsersOf(NewGV); 882 if (RepValue != NewGV) 883 ConstantPropUsersOf(RepValue); 884 885 return NewGV; 886} 887 888/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 889/// to make sure that there are no complex uses of V. We permit simple things 890/// like dereferencing the pointer, but not storing through the address, unless 891/// it is to the specified global. 892static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V, 893 GlobalVariable *GV, 894 SmallPtrSet<PHINode*, 8> &PHIs) { 895 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 896 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) { 897 // Fine, ignore. 898 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 899 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 900 return false; // Storing the pointer itself... bad. 901 // Otherwise, storing through it, or storing into GV... fine. 902 } else if (isa<GetElementPtrInst>(*UI)) { 903 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI), 904 GV, PHIs)) 905 return false; 906 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 907 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 908 // cycles. 909 if (PHIs.insert(PN)) 910 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 911 return false; 912 } else { 913 return false; 914 } 915 return true; 916} 917 918/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 919/// somewhere. Transform all uses of the allocation into loads from the 920/// global and uses of the resultant pointer. Further, delete the store into 921/// GV. This assumes that these value pass the 922/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 923static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 924 GlobalVariable *GV) { 925 while (!Alloc->use_empty()) { 926 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 927 Instruction *InsertPt = U; 928 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 929 // If this is the store of the allocation into the global, remove it. 930 if (SI->getOperand(1) == GV) { 931 SI->eraseFromParent(); 932 continue; 933 } 934 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 935 // Insert the load in the corresponding predecessor, not right before the 936 // PHI. 937 unsigned PredNo = Alloc->use_begin().getOperandNo()/2; 938 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator(); 939 } 940 941 // Insert a load from the global, and use it instead of the malloc. 942 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 943 U->replaceUsesOfWith(Alloc, NL); 944 } 945} 946 947/// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 948/// GV are simple enough to perform HeapSRA, return true. 949static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, 950 MallocInst *MI) { 951 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; 952 ++UI) 953 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 954 // We permit two users of the load: setcc comparing against the null 955 // pointer, and a getelementptr of a specific form. 956 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E; 957 ++UI) { 958 // Comparison against null is ok. 959 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) { 960 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 961 return false; 962 continue; 963 } 964 965 // getelementptr is also ok, but only a simple form. 966 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 967 // Must index into the array and into the struct. 968 if (GEPI->getNumOperands() < 3) 969 return false; 970 971 // Otherwise the GEP is ok. 972 continue; 973 } 974 975 if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 976 // We have a phi of a load from the global. We can only handle this 977 // if the other PHI'd values are actually the same. In this case, 978 // the rewriter will just drop the phi entirely. 979 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 980 Value *IV = PN->getIncomingValue(i); 981 if (IV == LI) continue; // Trivial the same. 982 983 // If the phi'd value is from the malloc that initializes the value, 984 // we can xform it. 985 if (IV == MI) continue; 986 987 // Otherwise, we don't know what it is. 988 return false; 989 } 990 return true; 991 } 992 993 // Otherwise we don't know what this is, not ok. 994 return false; 995 } 996 } 997 return true; 998} 999 1000/// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd 1001/// value, lazily creating it on demand. 1002static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo, 1003 const std::vector<GlobalVariable*> &FieldGlobals, 1004 std::vector<Value *> &InsertedLoadsForPtr) { 1005 if (InsertedLoadsForPtr.size() <= FieldNo) 1006 InsertedLoadsForPtr.resize(FieldNo+1); 1007 if (InsertedLoadsForPtr[FieldNo] == 0) 1008 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo], 1009 Load->getName()+".f" + 1010 utostr(FieldNo), Load); 1011 return InsertedLoadsForPtr[FieldNo]; 1012} 1013 1014/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1015/// the load, rewrite the derived value to use the HeapSRoA'd load. 1016static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser, 1017 const std::vector<GlobalVariable*> &FieldGlobals, 1018 std::vector<Value *> &InsertedLoadsForPtr) { 1019 // If this is a comparison against null, handle it. 1020 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1021 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1022 // If we have a setcc of the loaded pointer, we can use a setcc of any 1023 // field. 1024 Value *NPtr; 1025 if (InsertedLoadsForPtr.empty()) { 1026 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr); 1027 } else { 1028 NPtr = InsertedLoadsForPtr.back(); 1029 } 1030 1031 Value *New = new ICmpInst(SCI->getPredicate(), NPtr, 1032 Constant::getNullValue(NPtr->getType()), 1033 SCI->getName(), SCI); 1034 SCI->replaceAllUsesWith(New); 1035 SCI->eraseFromParent(); 1036 return; 1037 } 1038 1039 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...' 1040 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1041 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1042 && "Unexpected GEPI!"); 1043 1044 // Load the pointer for this field. 1045 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1046 Value *NewPtr = GetHeapSROALoad(Load, FieldNo, 1047 FieldGlobals, InsertedLoadsForPtr); 1048 1049 // Create the new GEP idx vector. 1050 SmallVector<Value*, 8> GEPIdx; 1051 GEPIdx.push_back(GEPI->getOperand(1)); 1052 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1053 1054 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(), 1055 GEPI->getName(), GEPI); 1056 GEPI->replaceAllUsesWith(NGEPI); 1057 GEPI->eraseFromParent(); 1058 return; 1059 } 1060 1061 // Handle PHI nodes. PHI nodes must be merging in the same values, plus 1062 // potentially the original malloc. Insert phi nodes for each field, then 1063 // process uses of the PHI. 1064 PHINode *PN = cast<PHINode>(LoadUser); 1065 std::vector<Value *> PHIsForField; 1066 PHIsForField.resize(FieldGlobals.size()); 1067 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1068 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr); 1069 1070 PHINode *FieldPN = new PHINode(LoadV->getType(), 1071 PN->getName()+"."+utostr(i), PN); 1072 // Fill in the predecessor values. 1073 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) { 1074 // Each predecessor either uses the load or the original malloc. 1075 Value *InVal = PN->getIncomingValue(pred); 1076 BasicBlock *BB = PN->getIncomingBlock(pred); 1077 Value *NewVal; 1078 if (isa<MallocInst>(InVal)) { 1079 // Insert a reload from the global in the predecessor. 1080 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals, 1081 PHIsForField); 1082 } else { 1083 NewVal = InsertedLoadsForPtr[i]; 1084 } 1085 FieldPN->addIncoming(NewVal, BB); 1086 } 1087 PHIsForField[i] = FieldPN; 1088 } 1089 1090 // Since PHIsForField specifies a phi for every input value, the lazy inserter 1091 // will never insert a load. 1092 while (!PN->use_empty()) 1093 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField); 1094 PN->eraseFromParent(); 1095} 1096 1097/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1098/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1099/// use FieldGlobals instead. All uses of loaded values satisfy 1100/// GlobalLoadUsesSimpleEnoughForHeapSRA. 1101static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1102 const std::vector<GlobalVariable*> &FieldGlobals) { 1103 std::vector<Value *> InsertedLoadsForPtr; 1104 //InsertedLoadsForPtr.resize(FieldGlobals.size()); 1105 while (!Load->use_empty()) 1106 RewriteHeapSROALoadUser(Load, Load->use_back(), 1107 FieldGlobals, InsertedLoadsForPtr); 1108} 1109 1110/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break 1111/// it up into multiple allocations of arrays of the fields. 1112static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ 1113 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; 1114 const StructType *STy = cast<StructType>(MI->getAllocatedType()); 1115 1116 // There is guaranteed to be at least one use of the malloc (storing 1117 // it into GV). If there are other uses, change them to be uses of 1118 // the global to simplify later code. This also deletes the store 1119 // into GV. 1120 ReplaceUsesOfMallocWithGlobal(MI, GV); 1121 1122 // Okay, at this point, there are no users of the malloc. Insert N 1123 // new mallocs at the same place as MI, and N globals. 1124 std::vector<GlobalVariable*> FieldGlobals; 1125 std::vector<MallocInst*> FieldMallocs; 1126 1127 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1128 const Type *FieldTy = STy->getElementType(FieldNo); 1129 const Type *PFieldTy = PointerType::getUnqual(FieldTy); 1130 1131 GlobalVariable *NGV = 1132 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, 1133 Constant::getNullValue(PFieldTy), 1134 GV->getName() + ".f" + utostr(FieldNo), GV, 1135 GV->isThreadLocal()); 1136 FieldGlobals.push_back(NGV); 1137 1138 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), 1139 MI->getName() + ".f" + utostr(FieldNo),MI); 1140 FieldMallocs.push_back(NMI); 1141 new StoreInst(NMI, NGV, MI); 1142 } 1143 1144 // The tricky aspect of this transformation is handling the case when malloc 1145 // fails. In the original code, malloc failing would set the result pointer 1146 // of malloc to null. In this case, some mallocs could succeed and others 1147 // could fail. As such, we emit code that looks like this: 1148 // F0 = malloc(field0) 1149 // F1 = malloc(field1) 1150 // F2 = malloc(field2) 1151 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1152 // if (F0) { free(F0); F0 = 0; } 1153 // if (F1) { free(F1); F1 = 0; } 1154 // if (F2) { free(F2); F2 = 0; } 1155 // } 1156 Value *RunningOr = 0; 1157 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1158 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], 1159 Constant::getNullValue(FieldMallocs[i]->getType()), 1160 "isnull", MI); 1161 if (!RunningOr) 1162 RunningOr = Cond; // First seteq 1163 else 1164 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI); 1165 } 1166 1167 // Split the basic block at the old malloc. 1168 BasicBlock *OrigBB = MI->getParent(); 1169 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont"); 1170 1171 // Create the block to check the first condition. Put all these blocks at the 1172 // end of the function as they are unlikely to be executed. 1173 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null", 1174 OrigBB->getParent()); 1175 1176 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1177 // branch on RunningOr. 1178 OrigBB->getTerminator()->eraseFromParent(); 1179 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB); 1180 1181 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1182 // pointer, because some may be null while others are not. 1183 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1184 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1185 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal, 1186 Constant::getNullValue(GVVal->getType()), 1187 "tmp", NullPtrBlock); 1188 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent()); 1189 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent()); 1190 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock); 1191 1192 // Fill in FreeBlock. 1193 new FreeInst(GVVal, FreeBlock); 1194 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1195 FreeBlock); 1196 new BranchInst(NextBlock, FreeBlock); 1197 1198 NullPtrBlock = NextBlock; 1199 } 1200 1201 new BranchInst(ContBB, NullPtrBlock); 1202 1203 1204 // MI is no longer needed, remove it. 1205 MI->eraseFromParent(); 1206 1207 1208 // Okay, the malloc site is completely handled. All of the uses of GV are now 1209 // loads, and all uses of those loads are simple. Rewrite them to use loads 1210 // of the per-field globals instead. 1211 while (!GV->use_empty()) { 1212 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 1213 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals); 1214 LI->eraseFromParent(); 1215 } else { 1216 // Must be a store of null. 1217 StoreInst *SI = cast<StoreInst>(GV->use_back()); 1218 assert(isa<Constant>(SI->getOperand(0)) && 1219 cast<Constant>(SI->getOperand(0))->isNullValue() && 1220 "Unexpected heap-sra user!"); 1221 1222 // Insert a store of null into each global. 1223 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1224 Constant *Null = 1225 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType()); 1226 new StoreInst(Null, FieldGlobals[i], SI); 1227 } 1228 // Erase the original store. 1229 SI->eraseFromParent(); 1230 } 1231 } 1232 1233 // The old global is now dead, remove it. 1234 GV->eraseFromParent(); 1235 1236 ++NumHeapSRA; 1237 return FieldGlobals[0]; 1238} 1239 1240 1241// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1242// that only one value (besides its initializer) is ever stored to the global. 1243static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1244 Module::global_iterator &GVI, 1245 TargetData &TD) { 1246 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal)) 1247 StoredOnceVal = CI->getOperand(0); 1248 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){ 1249 // "getelementptr Ptr, 0, 0, 0" is really just a cast. 1250 bool IsJustACast = true; 1251 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 1252 if (!isa<Constant>(GEPI->getOperand(i)) || 1253 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) { 1254 IsJustACast = false; 1255 break; 1256 } 1257 if (IsJustACast) 1258 StoredOnceVal = GEPI->getOperand(0); 1259 } 1260 1261 // If we are dealing with a pointer global that is initialized to null and 1262 // only has one (non-null) value stored into it, then we can optimize any 1263 // users of the loaded value (often calls and loads) that would trap if the 1264 // value was null. 1265 if (isa<PointerType>(GV->getInitializer()->getType()) && 1266 GV->getInitializer()->isNullValue()) { 1267 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1268 if (GV->getInitializer()->getType() != SOVC->getType()) 1269 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1270 1271 // Optimize away any trapping uses of the loaded value. 1272 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC)) 1273 return true; 1274 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { 1275 // If this is a malloc of an abstract type, don't touch it. 1276 if (!MI->getAllocatedType()->isSized()) 1277 return false; 1278 1279 // We can't optimize this global unless all uses of it are *known* to be 1280 // of the malloc value, not of the null initializer value (consider a use 1281 // that compares the global's value against zero to see if the malloc has 1282 // been reached). To do this, we check to see if all uses of the global 1283 // would trap if the global were null: this proves that they must all 1284 // happen after the malloc. 1285 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1286 return false; 1287 1288 // We can't optimize this if the malloc itself is used in a complex way, 1289 // for example, being stored into multiple globals. This allows the 1290 // malloc to be stored into the specified global, loaded setcc'd, and 1291 // GEP'd. These are all things we could transform to using the global 1292 // for. 1293 { 1294 SmallPtrSet<PHINode*, 8> PHIs; 1295 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs)) 1296 return false; 1297 } 1298 1299 1300 // If we have a global that is only initialized with a fixed size malloc, 1301 // transform the program to use global memory instead of malloc'd memory. 1302 // This eliminates dynamic allocation, avoids an indirection accessing the 1303 // data, and exposes the resultant global to further GlobalOpt. 1304 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { 1305 // Restrict this transformation to only working on small allocations 1306 // (2048 bytes currently), as we don't want to introduce a 16M global or 1307 // something. 1308 if (NElements->getZExtValue()* 1309 TD.getABITypeSize(MI->getAllocatedType()) < 2048) { 1310 GVI = OptimizeGlobalAddressOfMalloc(GV, MI); 1311 return true; 1312 } 1313 } 1314 1315 // If the allocation is an array of structures, consider transforming this 1316 // into multiple malloc'd arrays, one for each field. This is basically 1317 // SRoA for malloc'd memory. 1318 if (const StructType *AllocTy = 1319 dyn_cast<StructType>(MI->getAllocatedType())) { 1320 // This the structure has an unreasonable number of fields, leave it 1321 // alone. 1322 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 && 1323 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { 1324 GVI = PerformHeapAllocSRoA(GV, MI); 1325 return true; 1326 } 1327 } 1328 } 1329 } 1330 1331 return false; 1332} 1333 1334/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1335/// two values ever stored into GV are its initializer and OtherVal. See if we 1336/// can shrink the global into a boolean and select between the two values 1337/// whenever it is used. This exposes the values to other scalar optimizations. 1338static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1339 const Type *GVElType = GV->getType()->getElementType(); 1340 1341 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1342 // an FP value or vector, don't do this optimization because a select between 1343 // them is very expensive and unlikely to lead to later simplification. 1344 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || 1345 isa<VectorType>(GVElType)) 1346 return false; 1347 1348 // Walk the use list of the global seeing if all the uses are load or store. 1349 // If there is anything else, bail out. 1350 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I) 1351 if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) 1352 return false; 1353 1354 DOUT << " *** SHRINKING TO BOOL: " << *GV; 1355 1356 // Create the new global, initializing it to false. 1357 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, 1358 GlobalValue::InternalLinkage, ConstantInt::getFalse(), 1359 GV->getName()+".b", 1360 (Module *)NULL, 1361 GV->isThreadLocal()); 1362 GV->getParent()->getGlobalList().insert(GV, NewGV); 1363 1364 Constant *InitVal = GV->getInitializer(); 1365 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!"); 1366 1367 // If initialized to zero and storing one into the global, we can use a cast 1368 // instead of a select to synthesize the desired value. 1369 bool IsOneZero = false; 1370 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1371 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1372 1373 while (!GV->use_empty()) { 1374 Instruction *UI = cast<Instruction>(GV->use_back()); 1375 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1376 // Change the store into a boolean store. 1377 bool StoringOther = SI->getOperand(0) == OtherVal; 1378 // Only do this if we weren't storing a loaded value. 1379 Value *StoreVal; 1380 if (StoringOther || SI->getOperand(0) == InitVal) 1381 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther); 1382 else { 1383 // Otherwise, we are storing a previously loaded copy. To do this, 1384 // change the copy from copying the original value to just copying the 1385 // bool. 1386 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1387 1388 // If we're already replaced the input, StoredVal will be a cast or 1389 // select instruction. If not, it will be a load of the original 1390 // global. 1391 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1392 assert(LI->getOperand(0) == GV && "Not a copy!"); 1393 // Insert a new load, to preserve the saved value. 1394 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI); 1395 } else { 1396 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1397 "This is not a form that we understand!"); 1398 StoreVal = StoredVal->getOperand(0); 1399 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1400 } 1401 } 1402 new StoreInst(StoreVal, NewGV, SI); 1403 } else { 1404 // Change the load into a load of bool then a select. 1405 LoadInst *LI = cast<LoadInst>(UI); 1406 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI); 1407 Value *NSI; 1408 if (IsOneZero) 1409 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1410 else 1411 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI); 1412 NSI->takeName(LI); 1413 LI->replaceAllUsesWith(NSI); 1414 } 1415 UI->eraseFromParent(); 1416 } 1417 1418 GV->eraseFromParent(); 1419 return true; 1420} 1421 1422 1423/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1424/// it if possible. If we make a change, return true. 1425bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1426 Module::global_iterator &GVI) { 1427 std::set<PHINode*> PHIUsers; 1428 GlobalStatus GS; 1429 GV->removeDeadConstantUsers(); 1430 1431 if (GV->use_empty()) { 1432 DOUT << "GLOBAL DEAD: " << *GV; 1433 GV->eraseFromParent(); 1434 ++NumDeleted; 1435 return true; 1436 } 1437 1438 if (!AnalyzeGlobal(GV, GS, PHIUsers)) { 1439#if 0 1440 cerr << "Global: " << *GV; 1441 cerr << " isLoaded = " << GS.isLoaded << "\n"; 1442 cerr << " StoredType = "; 1443 switch (GS.StoredType) { 1444 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; 1445 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; 1446 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; 1447 case GlobalStatus::isStored: cerr << "stored\n"; break; 1448 } 1449 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) 1450 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; 1451 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) 1452 cerr << " AccessingFunction = " << GS.AccessingFunction->getName() 1453 << "\n"; 1454 cerr << " HasMultipleAccessingFunctions = " 1455 << GS.HasMultipleAccessingFunctions << "\n"; 1456 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; 1457 cerr << "\n"; 1458#endif 1459 1460 // If this is a first class global and has only one accessing function 1461 // and this function is main (which we know is not recursive we can make 1462 // this global a local variable) we replace the global with a local alloca 1463 // in this function. 1464 // 1465 // NOTE: It doesn't make sense to promote non first class types since we 1466 // are just replacing static memory to stack memory. 1467 if (!GS.HasMultipleAccessingFunctions && 1468 GS.AccessingFunction && !GS.HasNonInstructionUser && 1469 GV->getType()->getElementType()->isFirstClassType() && 1470 GS.AccessingFunction->getName() == "main" && 1471 GS.AccessingFunction->hasExternalLinkage()) { 1472 DOUT << "LOCALIZING GLOBAL: " << *GV; 1473 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); 1474 const Type* ElemTy = GV->getType()->getElementType(); 1475 // FIXME: Pass Global's alignment when globals have alignment 1476 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI); 1477 if (!isa<UndefValue>(GV->getInitializer())) 1478 new StoreInst(GV->getInitializer(), Alloca, FirstI); 1479 1480 GV->replaceAllUsesWith(Alloca); 1481 GV->eraseFromParent(); 1482 ++NumLocalized; 1483 return true; 1484 } 1485 1486 // If the global is never loaded (but may be stored to), it is dead. 1487 // Delete it now. 1488 if (!GS.isLoaded) { 1489 DOUT << "GLOBAL NEVER LOADED: " << *GV; 1490 1491 // Delete any stores we can find to the global. We may not be able to 1492 // make it completely dead though. 1493 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1494 1495 // If the global is dead now, delete it. 1496 if (GV->use_empty()) { 1497 GV->eraseFromParent(); 1498 ++NumDeleted; 1499 Changed = true; 1500 } 1501 return Changed; 1502 1503 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1504 DOUT << "MARKING CONSTANT: " << *GV; 1505 GV->setConstant(true); 1506 1507 // Clean up any obviously simplifiable users now. 1508 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1509 1510 // If the global is dead now, just nuke it. 1511 if (GV->use_empty()) { 1512 DOUT << " *** Marking constant allowed us to simplify " 1513 << "all users and delete global!\n"; 1514 GV->eraseFromParent(); 1515 ++NumDeleted; 1516 } 1517 1518 ++NumMarked; 1519 return true; 1520 } else if (!GV->getInitializer()->getType()->isFirstClassType()) { 1521 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) { 1522 GVI = FirstNewGV; // Don't skip the newly produced globals! 1523 return true; 1524 } 1525 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 1526 // If the initial value for the global was an undef value, and if only 1527 // one other value was stored into it, we can just change the 1528 // initializer to be an undef value, then delete all stores to the 1529 // global. This allows us to mark it constant. 1530 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1531 if (isa<UndefValue>(GV->getInitializer())) { 1532 // Change the initial value here. 1533 GV->setInitializer(SOVConstant); 1534 1535 // Clean up any obviously simplifiable users now. 1536 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1537 1538 if (GV->use_empty()) { 1539 DOUT << " *** Substituting initializer allowed us to " 1540 << "simplify all users and delete global!\n"; 1541 GV->eraseFromParent(); 1542 ++NumDeleted; 1543 } else { 1544 GVI = GV; 1545 } 1546 ++NumSubstitute; 1547 return true; 1548 } 1549 1550 // Try to optimize globals based on the knowledge that only one value 1551 // (besides its initializer) is ever stored to the global. 1552 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, 1553 getAnalysis<TargetData>())) 1554 return true; 1555 1556 // Otherwise, if the global was not a boolean, we can shrink it to be a 1557 // boolean. 1558 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1559 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 1560 ++NumShrunkToBool; 1561 return true; 1562 } 1563 } 1564 } 1565 return false; 1566} 1567 1568/// OnlyCalledDirectly - Return true if the specified function is only called 1569/// directly. In other words, its address is never taken. 1570static bool OnlyCalledDirectly(Function *F) { 1571 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1572 Instruction *User = dyn_cast<Instruction>(*UI); 1573 if (!User) return false; 1574 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; 1575 1576 // See if the function address is passed as an argument. 1577 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i) 1578 if (User->getOperand(i) == F) return false; 1579 } 1580 return true; 1581} 1582 1583/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 1584/// function, changing them to FastCC. 1585static void ChangeCalleesToFastCall(Function *F) { 1586 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1587 Instruction *User = cast<Instruction>(*UI); 1588 if (CallInst *CI = dyn_cast<CallInst>(User)) 1589 CI->setCallingConv(CallingConv::Fast); 1590 else 1591 cast<InvokeInst>(User)->setCallingConv(CallingConv::Fast); 1592 } 1593} 1594 1595static const ParamAttrsList *StripNest(const ParamAttrsList *Attrs) { 1596 if (Attrs) { 1597 for (unsigned i = 0, e = Attrs->size(); i != e; ++i) { 1598 uint16_t A = Attrs->getParamAttrsAtIndex(i); 1599 if (A & ParamAttr::Nest) { 1600 Attrs = ParamAttrsList::excludeAttrs(Attrs, Attrs->getParamIndex(i), 1601 ParamAttr::Nest); 1602 // There can be only one. 1603 break; 1604 } 1605 } 1606 } 1607 1608 return Attrs; 1609} 1610 1611static void RemoveNestAttribute(Function *F) { 1612 F->setParamAttrs(StripNest(F->getParamAttrs())); 1613 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1614 Instruction *User = cast<Instruction>(*UI); 1615 if (CallInst *CI = dyn_cast<CallInst>(User)) { 1616 CI->setParamAttrs(StripNest(CI->getParamAttrs())); 1617 } else { 1618 InvokeInst *II = cast<InvokeInst>(User); 1619 II->setParamAttrs(StripNest(II->getParamAttrs())); 1620 } 1621 } 1622} 1623 1624bool GlobalOpt::OptimizeFunctions(Module &M) { 1625 bool Changed = false; 1626 // Optimize functions. 1627 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 1628 Function *F = FI++; 1629 F->removeDeadConstantUsers(); 1630 if (F->use_empty() && (F->hasInternalLinkage() || 1631 F->hasLinkOnceLinkage())) { 1632 M.getFunctionList().erase(F); 1633 Changed = true; 1634 ++NumFnDeleted; 1635 } else if (F->hasInternalLinkage()) { 1636 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 1637 OnlyCalledDirectly(F)) { 1638 // If this function has C calling conventions, is not a varargs 1639 // function, and is only called directly, promote it to use the Fast 1640 // calling convention. 1641 F->setCallingConv(CallingConv::Fast); 1642 ChangeCalleesToFastCall(F); 1643 ++NumFastCallFns; 1644 Changed = true; 1645 } 1646 1647 if (F->getParamAttrs() && 1648 F->getParamAttrs()->hasAttrSomewhere(ParamAttr::Nest) && 1649 OnlyCalledDirectly(F)) { 1650 // The function is not used by a trampoline intrinsic, so it is safe 1651 // to remove the 'nest' attribute. 1652 RemoveNestAttribute(F); 1653 ++NumNestRemoved; 1654 Changed = true; 1655 } 1656 } 1657 } 1658 return Changed; 1659} 1660 1661bool GlobalOpt::OptimizeGlobalVars(Module &M) { 1662 bool Changed = false; 1663 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 1664 GVI != E; ) { 1665 GlobalVariable *GV = GVI++; 1666 if (!GV->isConstant() && GV->hasInternalLinkage() && 1667 GV->hasInitializer()) 1668 Changed |= ProcessInternalGlobal(GV, GVI); 1669 } 1670 return Changed; 1671} 1672 1673/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all 1674/// initializers have an init priority of 65535. 1675GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 1676 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 1677 I != E; ++I) 1678 if (I->getName() == "llvm.global_ctors") { 1679 // Found it, verify it's an array of { int, void()* }. 1680 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); 1681 if (!ATy) return 0; 1682 const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); 1683 if (!STy || STy->getNumElements() != 2 || 1684 STy->getElementType(0) != Type::Int32Ty) return 0; 1685 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); 1686 if (!PFTy) return 0; 1687 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); 1688 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || 1689 FTy->getNumParams() != 0) 1690 return 0; 1691 1692 // Verify that the initializer is simple enough for us to handle. 1693 if (!I->hasInitializer()) return 0; 1694 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); 1695 if (!CA) return 0; 1696 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1697 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) { 1698 if (isa<ConstantPointerNull>(CS->getOperand(1))) 1699 continue; 1700 1701 // Must have a function or null ptr. 1702 if (!isa<Function>(CS->getOperand(1))) 1703 return 0; 1704 1705 // Init priority must be standard. 1706 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0)); 1707 if (!CI || CI->getZExtValue() != 65535) 1708 return 0; 1709 } else { 1710 return 0; 1711 } 1712 1713 return I; 1714 } 1715 return 0; 1716} 1717 1718/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 1719/// return a list of the functions and null terminator as a vector. 1720static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 1721 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1722 std::vector<Function*> Result; 1723 Result.reserve(CA->getNumOperands()); 1724 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) { 1725 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i)); 1726 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 1727 } 1728 return Result; 1729} 1730 1731/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 1732/// specified array, returning the new global to use. 1733static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 1734 const std::vector<Function*> &Ctors) { 1735 // If we made a change, reassemble the initializer list. 1736 std::vector<Constant*> CSVals; 1737 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); 1738 CSVals.push_back(0); 1739 1740 // Create the new init list. 1741 std::vector<Constant*> CAList; 1742 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 1743 if (Ctors[i]) { 1744 CSVals[1] = Ctors[i]; 1745 } else { 1746 const Type *FTy = FunctionType::get(Type::VoidTy, 1747 std::vector<const Type*>(), false); 1748 const PointerType *PFTy = PointerType::getUnqual(FTy); 1749 CSVals[1] = Constant::getNullValue(PFTy); 1750 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); 1751 } 1752 CAList.push_back(ConstantStruct::get(CSVals)); 1753 } 1754 1755 // Create the array initializer. 1756 const Type *StructTy = 1757 cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); 1758 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()), 1759 CAList); 1760 1761 // If we didn't change the number of elements, don't create a new GV. 1762 if (CA->getType() == GCL->getInitializer()->getType()) { 1763 GCL->setInitializer(CA); 1764 return GCL; 1765 } 1766 1767 // Create the new global and insert it next to the existing list. 1768 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 1769 GCL->getLinkage(), CA, "", 1770 (Module *)NULL, 1771 GCL->isThreadLocal()); 1772 GCL->getParent()->getGlobalList().insert(GCL, NGV); 1773 NGV->takeName(GCL); 1774 1775 // Nuke the old list, replacing any uses with the new one. 1776 if (!GCL->use_empty()) { 1777 Constant *V = NGV; 1778 if (V->getType() != GCL->getType()) 1779 V = ConstantExpr::getBitCast(V, GCL->getType()); 1780 GCL->replaceAllUsesWith(V); 1781 } 1782 GCL->eraseFromParent(); 1783 1784 if (Ctors.size()) 1785 return NGV; 1786 else 1787 return 0; 1788} 1789 1790 1791static Constant *getVal(std::map<Value*, Constant*> &ComputedValues, 1792 Value *V) { 1793 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 1794 Constant *R = ComputedValues[V]; 1795 assert(R && "Reference to an uncomputed value!"); 1796 return R; 1797} 1798 1799/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 1800/// enough for us to understand. In particular, if it is a cast of something, 1801/// we punt. We basically just support direct accesses to globals and GEP's of 1802/// globals. This should be kept up to date with CommitValueTo. 1803static bool isSimpleEnoughPointerToCommit(Constant *C) { 1804 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 1805 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1806 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1807 return !GV->isDeclaration(); // reject external globals. 1808 } 1809 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 1810 // Handle a constantexpr gep. 1811 if (CE->getOpcode() == Instruction::GetElementPtr && 1812 isa<GlobalVariable>(CE->getOperand(0))) { 1813 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1814 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1815 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1816 return GV->hasInitializer() && 1817 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1818 } 1819 return false; 1820} 1821 1822/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 1823/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 1824/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 1825static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 1826 ConstantExpr *Addr, unsigned OpNo) { 1827 // Base case of the recursion. 1828 if (OpNo == Addr->getNumOperands()) { 1829 assert(Val->getType() == Init->getType() && "Type mismatch!"); 1830 return Val; 1831 } 1832 1833 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { 1834 std::vector<Constant*> Elts; 1835 1836 // Break up the constant into its elements. 1837 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { 1838 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i) 1839 Elts.push_back(CS->getOperand(i)); 1840 } else if (isa<ConstantAggregateZero>(Init)) { 1841 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1842 Elts.push_back(Constant::getNullValue(STy->getElementType(i))); 1843 } else if (isa<UndefValue>(Init)) { 1844 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1845 Elts.push_back(UndefValue::get(STy->getElementType(i))); 1846 } else { 1847 assert(0 && "This code is out of sync with " 1848 " ConstantFoldLoadThroughGEPConstantExpr"); 1849 } 1850 1851 // Replace the element that we are supposed to. 1852 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 1853 unsigned Idx = CU->getZExtValue(); 1854 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 1855 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 1856 1857 // Return the modified struct. 1858 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked()); 1859 } else { 1860 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 1861 const ArrayType *ATy = cast<ArrayType>(Init->getType()); 1862 1863 // Break up the array into elements. 1864 std::vector<Constant*> Elts; 1865 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { 1866 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1867 Elts.push_back(CA->getOperand(i)); 1868 } else if (isa<ConstantAggregateZero>(Init)) { 1869 Constant *Elt = Constant::getNullValue(ATy->getElementType()); 1870 Elts.assign(ATy->getNumElements(), Elt); 1871 } else if (isa<UndefValue>(Init)) { 1872 Constant *Elt = UndefValue::get(ATy->getElementType()); 1873 Elts.assign(ATy->getNumElements(), Elt); 1874 } else { 1875 assert(0 && "This code is out of sync with " 1876 " ConstantFoldLoadThroughGEPConstantExpr"); 1877 } 1878 1879 assert(CI->getZExtValue() < ATy->getNumElements()); 1880 Elts[CI->getZExtValue()] = 1881 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 1882 return ConstantArray::get(ATy, Elts); 1883 } 1884} 1885 1886/// CommitValueTo - We have decided that Addr (which satisfies the predicate 1887/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 1888static void CommitValueTo(Constant *Val, Constant *Addr) { 1889 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 1890 assert(GV->hasInitializer()); 1891 GV->setInitializer(Val); 1892 return; 1893 } 1894 1895 ConstantExpr *CE = cast<ConstantExpr>(Addr); 1896 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1897 1898 Constant *Init = GV->getInitializer(); 1899 Init = EvaluateStoreInto(Init, Val, CE, 2); 1900 GV->setInitializer(Init); 1901} 1902 1903/// ComputeLoadResult - Return the value that would be computed by a load from 1904/// P after the stores reflected by 'memory' have been performed. If we can't 1905/// decide, return null. 1906static Constant *ComputeLoadResult(Constant *P, 1907 const std::map<Constant*, Constant*> &Memory) { 1908 // If this memory location has been recently stored, use the stored value: it 1909 // is the most up-to-date. 1910 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P); 1911 if (I != Memory.end()) return I->second; 1912 1913 // Access it. 1914 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 1915 if (GV->hasInitializer()) 1916 return GV->getInitializer(); 1917 return 0; 1918 } 1919 1920 // Handle a constantexpr getelementptr. 1921 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 1922 if (CE->getOpcode() == Instruction::GetElementPtr && 1923 isa<GlobalVariable>(CE->getOperand(0))) { 1924 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1925 if (GV->hasInitializer()) 1926 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1927 } 1928 1929 return 0; // don't know how to evaluate. 1930} 1931 1932/// EvaluateFunction - Evaluate a call to function F, returning true if 1933/// successful, false if we can't evaluate it. ActualArgs contains the formal 1934/// arguments for the function. 1935static bool EvaluateFunction(Function *F, Constant *&RetVal, 1936 const std::vector<Constant*> &ActualArgs, 1937 std::vector<Function*> &CallStack, 1938 std::map<Constant*, Constant*> &MutatedMemory, 1939 std::vector<GlobalVariable*> &AllocaTmps) { 1940 // Check to see if this function is already executing (recursion). If so, 1941 // bail out. TODO: we might want to accept limited recursion. 1942 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 1943 return false; 1944 1945 CallStack.push_back(F); 1946 1947 /// Values - As we compute SSA register values, we store their contents here. 1948 std::map<Value*, Constant*> Values; 1949 1950 // Initialize arguments to the incoming values specified. 1951 unsigned ArgNo = 0; 1952 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 1953 ++AI, ++ArgNo) 1954 Values[AI] = ActualArgs[ArgNo]; 1955 1956 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 1957 /// we can only evaluate any one basic block at most once. This set keeps 1958 /// track of what we have executed so we can detect recursive cases etc. 1959 std::set<BasicBlock*> ExecutedBlocks; 1960 1961 // CurInst - The current instruction we're evaluating. 1962 BasicBlock::iterator CurInst = F->begin()->begin(); 1963 1964 // This is the main evaluation loop. 1965 while (1) { 1966 Constant *InstResult = 0; 1967 1968 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 1969 if (SI->isVolatile()) return false; // no volatile accesses. 1970 Constant *Ptr = getVal(Values, SI->getOperand(1)); 1971 if (!isSimpleEnoughPointerToCommit(Ptr)) 1972 // If this is too complex for us to commit, reject it. 1973 return false; 1974 Constant *Val = getVal(Values, SI->getOperand(0)); 1975 MutatedMemory[Ptr] = Val; 1976 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 1977 InstResult = ConstantExpr::get(BO->getOpcode(), 1978 getVal(Values, BO->getOperand(0)), 1979 getVal(Values, BO->getOperand(1))); 1980 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 1981 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 1982 getVal(Values, CI->getOperand(0)), 1983 getVal(Values, CI->getOperand(1))); 1984 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 1985 InstResult = ConstantExpr::getCast(CI->getOpcode(), 1986 getVal(Values, CI->getOperand(0)), 1987 CI->getType()); 1988 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 1989 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), 1990 getVal(Values, SI->getOperand(1)), 1991 getVal(Values, SI->getOperand(2))); 1992 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 1993 Constant *P = getVal(Values, GEP->getOperand(0)); 1994 SmallVector<Constant*, 8> GEPOps; 1995 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 1996 GEPOps.push_back(getVal(Values, GEP->getOperand(i))); 1997 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); 1998 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 1999 if (LI->isVolatile()) return false; // no volatile accesses. 2000 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), 2001 MutatedMemory); 2002 if (InstResult == 0) return false; // Could not evaluate load. 2003 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 2004 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 2005 const Type *Ty = AI->getType()->getElementType(); 2006 AllocaTmps.push_back(new GlobalVariable(Ty, false, 2007 GlobalValue::InternalLinkage, 2008 UndefValue::get(Ty), 2009 AI->getName())); 2010 InstResult = AllocaTmps.back(); 2011 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { 2012 // Cannot handle inline asm. 2013 if (isa<InlineAsm>(CI->getOperand(0))) return false; 2014 2015 // Resolve function pointers. 2016 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); 2017 if (!Callee) return false; // Cannot resolve. 2018 2019 std::vector<Constant*> Formals; 2020 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i) 2021 Formals.push_back(getVal(Values, CI->getOperand(i))); 2022 2023 if (Callee->isDeclaration()) { 2024 // If this is a function we can constant fold, do it. 2025 if (Constant *C = ConstantFoldCall(Callee, &Formals[0], 2026 Formals.size())) { 2027 InstResult = C; 2028 } else { 2029 return false; 2030 } 2031 } else { 2032 if (Callee->getFunctionType()->isVarArg()) 2033 return false; 2034 2035 Constant *RetVal; 2036 2037 // Execute the call, if successful, use the return value. 2038 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, 2039 MutatedMemory, AllocaTmps)) 2040 return false; 2041 InstResult = RetVal; 2042 } 2043 } else if (isa<TerminatorInst>(CurInst)) { 2044 BasicBlock *NewBB = 0; 2045 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2046 if (BI->isUnconditional()) { 2047 NewBB = BI->getSuccessor(0); 2048 } else { 2049 ConstantInt *Cond = 2050 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); 2051 if (!Cond) return false; // Cannot determine. 2052 2053 NewBB = BI->getSuccessor(!Cond->getZExtValue()); 2054 } 2055 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2056 ConstantInt *Val = 2057 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); 2058 if (!Val) return false; // Cannot determine. 2059 NewBB = SI->getSuccessor(SI->findCaseValue(Val)); 2060 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { 2061 if (RI->getNumOperands()) 2062 RetVal = getVal(Values, RI->getOperand(0)); 2063 2064 CallStack.pop_back(); // return from fn. 2065 return true; // We succeeded at evaluating this ctor! 2066 } else { 2067 // invoke, unwind, unreachable. 2068 return false; // Cannot handle this terminator. 2069 } 2070 2071 // Okay, we succeeded in evaluating this control flow. See if we have 2072 // executed the new block before. If so, we have a looping function, 2073 // which we cannot evaluate in reasonable time. 2074 if (!ExecutedBlocks.insert(NewBB).second) 2075 return false; // looped! 2076 2077 // Okay, we have never been in this block before. Check to see if there 2078 // are any PHI nodes. If so, evaluate them with information about where 2079 // we came from. 2080 BasicBlock *OldBB = CurInst->getParent(); 2081 CurInst = NewBB->begin(); 2082 PHINode *PN; 2083 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2084 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); 2085 2086 // Do NOT increment CurInst. We know that the terminator had no value. 2087 continue; 2088 } else { 2089 // Did not know how to evaluate this! 2090 return false; 2091 } 2092 2093 if (!CurInst->use_empty()) 2094 Values[CurInst] = InstResult; 2095 2096 // Advance program counter. 2097 ++CurInst; 2098 } 2099} 2100 2101/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2102/// we can. Return true if we can, false otherwise. 2103static bool EvaluateStaticConstructor(Function *F) { 2104 /// MutatedMemory - For each store we execute, we update this map. Loads 2105 /// check this to get the most up-to-date value. If evaluation is successful, 2106 /// this state is committed to the process. 2107 std::map<Constant*, Constant*> MutatedMemory; 2108 2109 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2110 /// to represent its body. This vector is needed so we can delete the 2111 /// temporary globals when we are done. 2112 std::vector<GlobalVariable*> AllocaTmps; 2113 2114 /// CallStack - This is used to detect recursion. In pathological situations 2115 /// we could hit exponential behavior, but at least there is nothing 2116 /// unbounded. 2117 std::vector<Function*> CallStack; 2118 2119 // Call the function. 2120 Constant *RetValDummy; 2121 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), 2122 CallStack, MutatedMemory, AllocaTmps); 2123 if (EvalSuccess) { 2124 // We succeeded at evaluation: commit the result. 2125 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2126 << F->getName() << "' to " << MutatedMemory.size() 2127 << " stores.\n"; 2128 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(), 2129 E = MutatedMemory.end(); I != E; ++I) 2130 CommitValueTo(I->second, I->first); 2131 } 2132 2133 // At this point, we are done interpreting. If we created any 'alloca' 2134 // temporaries, release them now. 2135 while (!AllocaTmps.empty()) { 2136 GlobalVariable *Tmp = AllocaTmps.back(); 2137 AllocaTmps.pop_back(); 2138 2139 // If there are still users of the alloca, the program is doing something 2140 // silly, e.g. storing the address of the alloca somewhere and using it 2141 // later. Since this is undefined, we'll just make it be null. 2142 if (!Tmp->use_empty()) 2143 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2144 delete Tmp; 2145 } 2146 2147 return EvalSuccess; 2148} 2149 2150 2151 2152/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2153/// Return true if anything changed. 2154bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2155 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2156 bool MadeChange = false; 2157 if (Ctors.empty()) return false; 2158 2159 // Loop over global ctors, optimizing them when we can. 2160 for (unsigned i = 0; i != Ctors.size(); ++i) { 2161 Function *F = Ctors[i]; 2162 // Found a null terminator in the middle of the list, prune off the rest of 2163 // the list. 2164 if (F == 0) { 2165 if (i != Ctors.size()-1) { 2166 Ctors.resize(i+1); 2167 MadeChange = true; 2168 } 2169 break; 2170 } 2171 2172 // We cannot simplify external ctor functions. 2173 if (F->empty()) continue; 2174 2175 // If we can evaluate the ctor at compile time, do. 2176 if (EvaluateStaticConstructor(F)) { 2177 Ctors.erase(Ctors.begin()+i); 2178 MadeChange = true; 2179 --i; 2180 ++NumCtorsEvaluated; 2181 continue; 2182 } 2183 } 2184 2185 if (!MadeChange) return false; 2186 2187 GCL = InstallGlobalCtors(GCL, Ctors); 2188 return true; 2189} 2190 2191 2192bool GlobalOpt::runOnModule(Module &M) { 2193 bool Changed = false; 2194 2195 // Try to find the llvm.globalctors list. 2196 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 2197 2198 bool LocalChange = true; 2199 while (LocalChange) { 2200 LocalChange = false; 2201 2202 // Delete functions that are trivially dead, ccc -> fastcc 2203 LocalChange |= OptimizeFunctions(M); 2204 2205 // Optimize global_ctors list. 2206 if (GlobalCtors) 2207 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 2208 2209 // Optimize non-address-taken globals. 2210 LocalChange |= OptimizeGlobalVars(M); 2211 Changed |= LocalChange; 2212 } 2213 2214 // TODO: Move all global ctors functions to the end of the module for code 2215 // layout. 2216 2217 return Changed; 2218} 2219