GlobalOpt.cpp revision 249ddbfb29dfc2335f98984878c52b2c77703417
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/Pass.h" 25#include "llvm/Analysis/ConstantFolding.h" 26#include "llvm/Target/TargetData.h" 27#include "llvm/Support/CallSite.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 <map> 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 } 205 } else if (isa<GetElementPtrInst>(I)) { 206 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 207 } else if (isa<SelectInst>(I)) { 208 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 209 } else if (PHINode *PN = dyn_cast<PHINode>(I)) { 210 // PHI nodes we can check just like select or GEP instructions, but we 211 // have to be careful about infinite recursion. 212 if (PHIUsers.insert(PN).second) // Not already visited. 213 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 214 GS.HasPHIUser = true; 215 } else if (isa<CmpInst>(I)) { 216 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { 217 if (I->getOperand(1) == V) 218 GS.StoredType = GlobalStatus::isStored; 219 if (I->getOperand(2) == V) 220 GS.isLoaded = true; 221 } else if (isa<MemSetInst>(I)) { 222 assert(I->getOperand(1) == V && "Memset only takes one pointer!"); 223 GS.StoredType = GlobalStatus::isStored; 224 } else { 225 return true; // Any other non-load instruction might take address! 226 } 227 } else if (Constant *C = dyn_cast<Constant>(*UI)) { 228 GS.HasNonInstructionUser = true; 229 // We might have a dead and dangling constant hanging off of here. 230 if (!ConstantIsDead(C)) 231 return true; 232 } else { 233 GS.HasNonInstructionUser = true; 234 // Otherwise must be some other user. 235 return true; 236 } 237 238 return false; 239} 240 241static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { 242 ConstantInt *CI = dyn_cast<ConstantInt>(Idx); 243 if (!CI) return 0; 244 unsigned IdxV = CI->getZExtValue(); 245 246 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { 247 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); 248 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { 249 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); 250 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { 251 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); 252 } else if (isa<ConstantAggregateZero>(Agg)) { 253 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 254 if (IdxV < STy->getNumElements()) 255 return Constant::getNullValue(STy->getElementType(IdxV)); 256 } else if (const SequentialType *STy = 257 dyn_cast<SequentialType>(Agg->getType())) { 258 return Constant::getNullValue(STy->getElementType()); 259 } 260 } else if (isa<UndefValue>(Agg)) { 261 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 262 if (IdxV < STy->getNumElements()) 263 return UndefValue::get(STy->getElementType(IdxV)); 264 } else if (const SequentialType *STy = 265 dyn_cast<SequentialType>(Agg->getType())) { 266 return UndefValue::get(STy->getElementType()); 267 } 268 } 269 return 0; 270} 271 272 273/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 274/// users of the global, cleaning up the obvious ones. This is largely just a 275/// quick scan over the use list to clean up the easy and obvious cruft. This 276/// returns true if it made a change. 277static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) { 278 bool Changed = false; 279 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 280 User *U = *UI++; 281 282 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 283 if (Init) { 284 // Replace the load with the initializer. 285 LI->replaceAllUsesWith(Init); 286 LI->eraseFromParent(); 287 Changed = true; 288 } 289 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 290 // Store must be unreachable or storing Init into the global. 291 SI->eraseFromParent(); 292 Changed = true; 293 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 294 if (CE->getOpcode() == Instruction::GetElementPtr) { 295 Constant *SubInit = 0; 296 if (Init) 297 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 298 Changed |= CleanupConstantGlobalUsers(CE, SubInit); 299 } else if (CE->getOpcode() == Instruction::BitCast && 300 isa<PointerType>(CE->getType())) { 301 // Pointer cast, delete any stores and memsets to the global. 302 Changed |= CleanupConstantGlobalUsers(CE, 0); 303 } 304 305 if (CE->use_empty()) { 306 CE->destroyConstant(); 307 Changed = true; 308 } 309 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 310 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 311 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 312 // and will invalidate our notion of what Init is. 313 Constant *SubInit = 0; 314 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 315 ConstantExpr *CE = 316 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP)); 317 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 318 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 319 } 320 Changed |= CleanupConstantGlobalUsers(GEP, SubInit); 321 322 if (GEP->use_empty()) { 323 GEP->eraseFromParent(); 324 Changed = true; 325 } 326 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 327 if (MI->getRawDest() == V) { 328 MI->eraseFromParent(); 329 Changed = true; 330 } 331 332 } else if (Constant *C = dyn_cast<Constant>(U)) { 333 // If we have a chain of dead constantexprs or other things dangling from 334 // us, and if they are all dead, nuke them without remorse. 335 if (ConstantIsDead(C)) { 336 C->destroyConstant(); 337 // This could have invalidated UI, start over from scratch. 338 CleanupConstantGlobalUsers(V, Init); 339 return true; 340 } 341 } 342 } 343 return Changed; 344} 345 346/// isSafeSROAElementUse - Return true if the specified instruction is a safe 347/// user of a derived expression from a global that we want to SROA. 348static bool isSafeSROAElementUse(Value *V) { 349 // We might have a dead and dangling constant hanging off of here. 350 if (Constant *C = dyn_cast<Constant>(V)) 351 return ConstantIsDead(C); 352 353 Instruction *I = dyn_cast<Instruction>(V); 354 if (!I) return false; 355 356 // Loads are ok. 357 if (isa<LoadInst>(I)) return true; 358 359 // Stores *to* the pointer are ok. 360 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 361 return SI->getOperand(0) != V; 362 363 // Otherwise, it must be a GEP. 364 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 365 if (GEPI == 0) return false; 366 367 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 368 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 369 return false; 370 371 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 372 I != E; ++I) 373 if (!isSafeSROAElementUse(*I)) 374 return false; 375 return true; 376} 377 378 379/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 380/// Look at it and its uses and decide whether it is safe to SROA this global. 381/// 382static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 383 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 384 if (!isa<GetElementPtrInst>(U) && 385 (!isa<ConstantExpr>(U) || 386 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 387 return false; 388 389 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 390 // don't like < 3 operand CE's, and we don't like non-constant integer 391 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 392 // value of C. 393 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 394 !cast<Constant>(U->getOperand(1))->isNullValue() || 395 !isa<ConstantInt>(U->getOperand(2))) 396 return false; 397 398 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 399 ++GEPI; // Skip over the pointer index. 400 401 // If this is a use of an array allocation, do a bit more checking for sanity. 402 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 403 uint64_t NumElements = AT->getNumElements(); 404 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 405 406 // Check to make sure that index falls within the array. If not, 407 // something funny is going on, so we won't do the optimization. 408 // 409 if (Idx->getZExtValue() >= NumElements) 410 return false; 411 412 // We cannot scalar repl this level of the array unless any array 413 // sub-indices are in-range constants. In particular, consider: 414 // A[0][i]. We cannot know that the user isn't doing invalid things like 415 // allowing i to index an out-of-range subscript that accesses A[1]. 416 // 417 // Scalar replacing *just* the outer index of the array is probably not 418 // going to be a win anyway, so just give up. 419 for (++GEPI; // Skip array index. 420 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); 421 ++GEPI) { 422 uint64_t NumElements; 423 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 424 NumElements = SubArrayTy->getNumElements(); 425 else 426 NumElements = cast<VectorType>(*GEPI)->getNumElements(); 427 428 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 429 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 430 return false; 431 } 432 } 433 434 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 435 if (!isSafeSROAElementUse(*I)) 436 return false; 437 return true; 438} 439 440/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 441/// is safe for us to perform this transformation. 442/// 443static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 444 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 445 UI != E; ++UI) { 446 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 447 return false; 448 } 449 return true; 450} 451 452 453/// SRAGlobal - Perform scalar replacement of aggregates on the specified global 454/// variable. This opens the door for other optimizations by exposing the 455/// behavior of the program in a more fine-grained way. We have determined that 456/// this transformation is safe already. We return the first global variable we 457/// insert so that the caller can reprocess it. 458static GlobalVariable *SRAGlobal(GlobalVariable *GV) { 459 // Make sure this global only has simple uses that we can SRA. 460 if (!GlobalUsersSafeToSRA(GV)) 461 return 0; 462 463 assert(GV->hasInternalLinkage() && !GV->isConstant()); 464 Constant *Init = GV->getInitializer(); 465 const Type *Ty = Init->getType(); 466 467 std::vector<GlobalVariable*> NewGlobals; 468 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 469 470 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 471 NewGlobals.reserve(STy->getNumElements()); 472 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 473 Constant *In = getAggregateConstantElement(Init, 474 ConstantInt::get(Type::Int32Ty, i)); 475 assert(In && "Couldn't get element of initializer?"); 476 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 477 GlobalVariable::InternalLinkage, 478 In, GV->getName()+"."+utostr(i), 479 (Module *)NULL, 480 GV->isThreadLocal()); 481 Globals.insert(GV, NGV); 482 NewGlobals.push_back(NGV); 483 } 484 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 485 unsigned NumElements = 0; 486 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 487 NumElements = ATy->getNumElements(); 488 else if (const VectorType *PTy = dyn_cast<VectorType>(STy)) 489 NumElements = PTy->getNumElements(); 490 else 491 assert(0 && "Unknown aggregate sequential type!"); 492 493 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 494 return 0; // It's not worth it. 495 NewGlobals.reserve(NumElements); 496 for (unsigned i = 0, e = NumElements; i != e; ++i) { 497 Constant *In = getAggregateConstantElement(Init, 498 ConstantInt::get(Type::Int32Ty, i)); 499 assert(In && "Couldn't get element of initializer?"); 500 501 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 502 GlobalVariable::InternalLinkage, 503 In, GV->getName()+"."+utostr(i), 504 (Module *)NULL, 505 GV->isThreadLocal()); 506 Globals.insert(GV, NGV); 507 NewGlobals.push_back(NGV); 508 } 509 } 510 511 if (NewGlobals.empty()) 512 return 0; 513 514 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; 515 516 Constant *NullInt = Constant::getNullValue(Type::Int32Ty); 517 518 // Loop over all of the uses of the global, replacing the constantexpr geps, 519 // with smaller constantexpr geps or direct references. 520 while (!GV->use_empty()) { 521 User *GEP = GV->use_back(); 522 assert(((isa<ConstantExpr>(GEP) && 523 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 524 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 525 526 // Ignore the 1th operand, which has to be zero or else the program is quite 527 // broken (undefined). Get the 2nd operand, which is the structure or array 528 // index. 529 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 530 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 531 532 Value *NewPtr = NewGlobals[Val]; 533 534 // Form a shorter GEP if needed. 535 if (GEP->getNumOperands() > 3) { 536 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 537 SmallVector<Constant*, 8> Idxs; 538 Idxs.push_back(NullInt); 539 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 540 Idxs.push_back(CE->getOperand(i)); 541 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), 542 &Idxs[0], Idxs.size()); 543 } else { 544 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 545 SmallVector<Value*, 8> Idxs; 546 Idxs.push_back(NullInt); 547 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 548 Idxs.push_back(GEPI->getOperand(i)); 549 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(), 550 GEPI->getName()+"."+utostr(Val), GEPI); 551 } 552 } 553 GEP->replaceAllUsesWith(NewPtr); 554 555 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 556 GEPI->eraseFromParent(); 557 else 558 cast<ConstantExpr>(GEP)->destroyConstant(); 559 } 560 561 // Delete the old global, now that it is dead. 562 Globals.erase(GV); 563 ++NumSRA; 564 565 // Loop over the new globals array deleting any globals that are obviously 566 // dead. This can arise due to scalarization of a structure or an array that 567 // has elements that are dead. 568 unsigned FirstGlobal = 0; 569 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 570 if (NewGlobals[i]->use_empty()) { 571 Globals.erase(NewGlobals[i]); 572 if (FirstGlobal == i) ++FirstGlobal; 573 } 574 575 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 576} 577 578/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 579/// value will trap if the value is dynamically null. PHIs keeps track of any 580/// phi nodes we've seen to avoid reprocessing them. 581static bool AllUsesOfValueWillTrapIfNull(Value *V, 582 SmallPtrSet<PHINode*, 8> &PHIs) { 583 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 584 if (isa<LoadInst>(*UI)) { 585 // Will trap. 586 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 587 if (SI->getOperand(0) == V) { 588 //cerr << "NONTRAPPING USE: " << **UI; 589 return false; // Storing the value. 590 } 591 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { 592 if (CI->getOperand(0) != V) { 593 //cerr << "NONTRAPPING USE: " << **UI; 594 return false; // Not calling the ptr 595 } 596 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { 597 if (II->getOperand(0) != V) { 598 //cerr << "NONTRAPPING USE: " << **UI; 599 return false; // Not calling the ptr 600 } 601 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { 602 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 603 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 604 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 605 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 606 // If we've already seen this phi node, ignore it, it has already been 607 // checked. 608 if (PHIs.insert(PN)) 609 return AllUsesOfValueWillTrapIfNull(PN, PHIs); 610 } else if (isa<ICmpInst>(*UI) && 611 isa<ConstantPointerNull>(UI->getOperand(1))) { 612 // Ignore setcc X, null 613 } else { 614 //cerr << "NONTRAPPING USE: " << **UI; 615 return false; 616 } 617 return true; 618} 619 620/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 621/// from GV will trap if the loaded value is null. Note that this also permits 622/// comparisons of the loaded value against null, as a special case. 623static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) { 624 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) 625 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 626 SmallPtrSet<PHINode*, 8> PHIs; 627 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 628 return false; 629 } else if (isa<StoreInst>(*UI)) { 630 // Ignore stores to the global. 631 } else { 632 // We don't know or understand this user, bail out. 633 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; 634 return false; 635 } 636 637 return true; 638} 639 640static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 641 bool Changed = false; 642 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 643 Instruction *I = cast<Instruction>(*UI++); 644 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 645 LI->setOperand(0, NewV); 646 Changed = true; 647 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 648 if (SI->getOperand(1) == V) { 649 SI->setOperand(1, NewV); 650 Changed = true; 651 } 652 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 653 if (I->getOperand(0) == V) { 654 // Calling through the pointer! Turn into a direct call, but be careful 655 // that the pointer is not also being passed as an argument. 656 I->setOperand(0, NewV); 657 Changed = true; 658 bool PassedAsArg = false; 659 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) 660 if (I->getOperand(i) == V) { 661 PassedAsArg = true; 662 I->setOperand(i, NewV); 663 } 664 665 if (PassedAsArg) { 666 // Being passed as an argument also. Be careful to not invalidate UI! 667 UI = V->use_begin(); 668 } 669 } 670 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 671 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 672 ConstantExpr::getCast(CI->getOpcode(), 673 NewV, CI->getType())); 674 if (CI->use_empty()) { 675 Changed = true; 676 CI->eraseFromParent(); 677 } 678 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 679 // Should handle GEP here. 680 SmallVector<Constant*, 8> Idxs; 681 Idxs.reserve(GEPI->getNumOperands()-1); 682 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 683 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i))) 684 Idxs.push_back(C); 685 else 686 break; 687 if (Idxs.size() == GEPI->getNumOperands()-1) 688 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 689 ConstantExpr::getGetElementPtr(NewV, &Idxs[0], 690 Idxs.size())); 691 if (GEPI->use_empty()) { 692 Changed = true; 693 GEPI->eraseFromParent(); 694 } 695 } 696 } 697 698 return Changed; 699} 700 701 702/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 703/// value stored into it. If there are uses of the loaded value that would trap 704/// if the loaded value is dynamically null, then we know that they cannot be 705/// reachable with a null optimize away the load. 706static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { 707 std::vector<LoadInst*> Loads; 708 bool Changed = false; 709 710 // Replace all uses of loads with uses of uses of the stored value. 711 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); 712 GUI != E; ++GUI) 713 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { 714 Loads.push_back(LI); 715 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 716 } else { 717 // If we get here we could have stores, selects, or phi nodes whose values 718 // are loaded. 719 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || 720 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && 721 "Only expect load and stores!"); 722 } 723 724 if (Changed) { 725 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; 726 ++NumGlobUses; 727 } 728 729 // Delete all of the loads we can, keeping track of whether we nuked them all! 730 bool AllLoadsGone = true; 731 while (!Loads.empty()) { 732 LoadInst *L = Loads.back(); 733 if (L->use_empty()) { 734 L->eraseFromParent(); 735 Changed = true; 736 } else { 737 AllLoadsGone = false; 738 } 739 Loads.pop_back(); 740 } 741 742 // If we nuked all of the loads, then none of the stores are needed either, 743 // nor is the global. 744 if (AllLoadsGone) { 745 DOUT << " *** GLOBAL NOW DEAD!\n"; 746 CleanupConstantGlobalUsers(GV, 0); 747 if (GV->use_empty()) { 748 GV->eraseFromParent(); 749 ++NumDeleted; 750 } 751 Changed = true; 752 } 753 return Changed; 754} 755 756/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 757/// instructions that are foldable. 758static void ConstantPropUsersOf(Value *V) { 759 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 760 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 761 if (Constant *NewC = ConstantFoldInstruction(I)) { 762 I->replaceAllUsesWith(NewC); 763 764 // Advance UI to the next non-I use to avoid invalidating it! 765 // Instructions could multiply use V. 766 while (UI != E && *UI == I) 767 ++UI; 768 I->eraseFromParent(); 769 } 770} 771 772/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 773/// variable, and transforms the program as if it always contained the result of 774/// the specified malloc. Because it is always the result of the specified 775/// malloc, there is no reason to actually DO the malloc. Instead, turn the 776/// malloc into a global, and any loads of GV as uses of the new global. 777static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 778 MallocInst *MI) { 779 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; 780 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); 781 782 if (NElements->getZExtValue() != 1) { 783 // If we have an array allocation, transform it to a single element 784 // allocation to make the code below simpler. 785 Type *NewTy = ArrayType::get(MI->getAllocatedType(), 786 NElements->getZExtValue()); 787 MallocInst *NewMI = 788 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), 789 MI->getAlignment(), MI->getName(), MI); 790 Value* Indices[2]; 791 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); 792 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2, 793 NewMI->getName()+".el0", MI); 794 MI->replaceAllUsesWith(NewGEP); 795 MI->eraseFromParent(); 796 MI = NewMI; 797 } 798 799 // Create the new global variable. The contents of the malloc'd memory is 800 // undefined, so initialize with an undef value. 801 Constant *Init = UndefValue::get(MI->getAllocatedType()); 802 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, 803 GlobalValue::InternalLinkage, Init, 804 GV->getName()+".body", 805 (Module *)NULL, 806 GV->isThreadLocal()); 807 GV->getParent()->getGlobalList().insert(GV, NewGV); 808 809 // Anything that used the malloc now uses the global directly. 810 MI->replaceAllUsesWith(NewGV); 811 812 Constant *RepValue = NewGV; 813 if (NewGV->getType() != GV->getType()->getElementType()) 814 RepValue = ConstantExpr::getBitCast(RepValue, 815 GV->getType()->getElementType()); 816 817 // If there is a comparison against null, we will insert a global bool to 818 // keep track of whether the global was initialized yet or not. 819 GlobalVariable *InitBool = 820 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage, 821 ConstantInt::getFalse(), GV->getName()+".init", 822 (Module *)NULL, GV->isThreadLocal()); 823 bool InitBoolUsed = false; 824 825 // Loop over all uses of GV, processing them in turn. 826 std::vector<StoreInst*> Stores; 827 while (!GV->use_empty()) 828 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 829 while (!LI->use_empty()) { 830 Use &LoadUse = LI->use_begin().getUse(); 831 if (!isa<ICmpInst>(LoadUse.getUser())) 832 LoadUse = RepValue; 833 else { 834 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); 835 // Replace the cmp X, 0 with a use of the bool value. 836 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); 837 InitBoolUsed = true; 838 switch (CI->getPredicate()) { 839 default: assert(0 && "Unknown ICmp Predicate!"); 840 case ICmpInst::ICMP_ULT: 841 case ICmpInst::ICMP_SLT: 842 LV = ConstantInt::getFalse(); // X < null -> always false 843 break; 844 case ICmpInst::ICMP_ULE: 845 case ICmpInst::ICMP_SLE: 846 case ICmpInst::ICMP_EQ: 847 LV = BinaryOperator::createNot(LV, "notinit", CI); 848 break; 849 case ICmpInst::ICMP_NE: 850 case ICmpInst::ICMP_UGE: 851 case ICmpInst::ICMP_SGE: 852 case ICmpInst::ICMP_UGT: 853 case ICmpInst::ICMP_SGT: 854 break; // no change. 855 } 856 CI->replaceAllUsesWith(LV); 857 CI->eraseFromParent(); 858 } 859 } 860 LI->eraseFromParent(); 861 } else { 862 StoreInst *SI = cast<StoreInst>(GV->use_back()); 863 // The global is initialized when the store to it occurs. 864 new StoreInst(ConstantInt::getTrue(), InitBool, SI); 865 SI->eraseFromParent(); 866 } 867 868 // If the initialization boolean was used, insert it, otherwise delete it. 869 if (!InitBoolUsed) { 870 while (!InitBool->use_empty()) // Delete initializations 871 cast<Instruction>(InitBool->use_back())->eraseFromParent(); 872 delete InitBool; 873 } else 874 GV->getParent()->getGlobalList().insert(GV, InitBool); 875 876 877 // Now the GV is dead, nuke it and the malloc. 878 GV->eraseFromParent(); 879 MI->eraseFromParent(); 880 881 // To further other optimizations, loop over all users of NewGV and try to 882 // constant prop them. This will promote GEP instructions with constant 883 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 884 ConstantPropUsersOf(NewGV); 885 if (RepValue != NewGV) 886 ConstantPropUsersOf(RepValue); 887 888 return NewGV; 889} 890 891/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 892/// to make sure that there are no complex uses of V. We permit simple things 893/// like dereferencing the pointer, but not storing through the address, unless 894/// it is to the specified global. 895static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V, 896 GlobalVariable *GV, 897 SmallPtrSet<PHINode*, 8> &PHIs) { 898 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 899 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) { 900 // Fine, ignore. 901 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 902 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 903 return false; // Storing the pointer itself... bad. 904 // Otherwise, storing through it, or storing into GV... fine. 905 } else if (isa<GetElementPtrInst>(*UI)) { 906 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI), 907 GV, PHIs)) 908 return false; 909 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 910 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 911 // cycles. 912 if (PHIs.insert(PN)) 913 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 914 return false; 915 } else { 916 return false; 917 } 918 return true; 919} 920 921/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 922/// somewhere. Transform all uses of the allocation into loads from the 923/// global and uses of the resultant pointer. Further, delete the store into 924/// GV. This assumes that these value pass the 925/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 926static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 927 GlobalVariable *GV) { 928 while (!Alloc->use_empty()) { 929 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 930 Instruction *InsertPt = U; 931 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 932 // If this is the store of the allocation into the global, remove it. 933 if (SI->getOperand(1) == GV) { 934 SI->eraseFromParent(); 935 continue; 936 } 937 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 938 // Insert the load in the corresponding predecessor, not right before the 939 // PHI. 940 unsigned PredNo = Alloc->use_begin().getOperandNo()/2; 941 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator(); 942 } 943 944 // Insert a load from the global, and use it instead of the malloc. 945 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 946 U->replaceUsesOfWith(Alloc, NL); 947 } 948} 949 950/// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 951/// GV are simple enough to perform HeapSRA, return true. 952static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, 953 MallocInst *MI) { 954 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; 955 ++UI) 956 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 957 // We permit two users of the load: setcc comparing against the null 958 // pointer, and a getelementptr of a specific form. 959 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E; 960 ++UI) { 961 // Comparison against null is ok. 962 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) { 963 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 964 return false; 965 continue; 966 } 967 968 // getelementptr is also ok, but only a simple form. 969 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 970 // Must index into the array and into the struct. 971 if (GEPI->getNumOperands() < 3) 972 return false; 973 974 // Otherwise the GEP is ok. 975 continue; 976 } 977 978 if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 979 // We have a phi of a load from the global. We can only handle this 980 // if the other PHI'd values are actually the same. In this case, 981 // the rewriter will just drop the phi entirely. 982 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 983 Value *IV = PN->getIncomingValue(i); 984 if (IV == LI) continue; // Trivial the same. 985 986 // If the phi'd value is from the malloc that initializes the value, 987 // we can xform it. 988 if (IV == MI) continue; 989 990 // Otherwise, we don't know what it is. 991 return false; 992 } 993 return true; 994 } 995 996 // Otherwise we don't know what this is, not ok. 997 return false; 998 } 999 } 1000 return true; 1001} 1002 1003/// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd 1004/// value, lazily creating it on demand. 1005static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo, 1006 const std::vector<GlobalVariable*> &FieldGlobals, 1007 std::vector<Value *> &InsertedLoadsForPtr) { 1008 if (InsertedLoadsForPtr.size() <= FieldNo) 1009 InsertedLoadsForPtr.resize(FieldNo+1); 1010 if (InsertedLoadsForPtr[FieldNo] == 0) 1011 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo], 1012 Load->getName()+".f" + 1013 utostr(FieldNo), Load); 1014 return InsertedLoadsForPtr[FieldNo]; 1015} 1016 1017/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1018/// the load, rewrite the derived value to use the HeapSRoA'd load. 1019static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser, 1020 const std::vector<GlobalVariable*> &FieldGlobals, 1021 std::vector<Value *> &InsertedLoadsForPtr) { 1022 // If this is a comparison against null, handle it. 1023 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1024 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1025 // If we have a setcc of the loaded pointer, we can use a setcc of any 1026 // field. 1027 Value *NPtr; 1028 if (InsertedLoadsForPtr.empty()) { 1029 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr); 1030 } else { 1031 NPtr = InsertedLoadsForPtr.back(); 1032 } 1033 1034 Value *New = new ICmpInst(SCI->getPredicate(), NPtr, 1035 Constant::getNullValue(NPtr->getType()), 1036 SCI->getName(), SCI); 1037 SCI->replaceAllUsesWith(New); 1038 SCI->eraseFromParent(); 1039 return; 1040 } 1041 1042 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...' 1043 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1044 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1045 && "Unexpected GEPI!"); 1046 1047 // Load the pointer for this field. 1048 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1049 Value *NewPtr = GetHeapSROALoad(Load, FieldNo, 1050 FieldGlobals, InsertedLoadsForPtr); 1051 1052 // Create the new GEP idx vector. 1053 SmallVector<Value*, 8> GEPIdx; 1054 GEPIdx.push_back(GEPI->getOperand(1)); 1055 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1056 1057 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(), 1058 GEPI->getName(), GEPI); 1059 GEPI->replaceAllUsesWith(NGEPI); 1060 GEPI->eraseFromParent(); 1061 return; 1062 } 1063 1064 // Handle PHI nodes. PHI nodes must be merging in the same values, plus 1065 // potentially the original malloc. Insert phi nodes for each field, then 1066 // process uses of the PHI. 1067 PHINode *PN = cast<PHINode>(LoadUser); 1068 std::vector<Value *> PHIsForField; 1069 PHIsForField.resize(FieldGlobals.size()); 1070 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1071 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr); 1072 1073 PHINode *FieldPN = new PHINode(LoadV->getType(), 1074 PN->getName()+"."+utostr(i), PN); 1075 // Fill in the predecessor values. 1076 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) { 1077 // Each predecessor either uses the load or the original malloc. 1078 Value *InVal = PN->getIncomingValue(pred); 1079 BasicBlock *BB = PN->getIncomingBlock(pred); 1080 Value *NewVal; 1081 if (isa<MallocInst>(InVal)) { 1082 // Insert a reload from the global in the predecessor. 1083 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals, 1084 PHIsForField); 1085 } else { 1086 NewVal = InsertedLoadsForPtr[i]; 1087 } 1088 FieldPN->addIncoming(NewVal, BB); 1089 } 1090 PHIsForField[i] = FieldPN; 1091 } 1092 1093 // Since PHIsForField specifies a phi for every input value, the lazy inserter 1094 // will never insert a load. 1095 while (!PN->use_empty()) 1096 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField); 1097 PN->eraseFromParent(); 1098} 1099 1100/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1101/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1102/// use FieldGlobals instead. All uses of loaded values satisfy 1103/// GlobalLoadUsesSimpleEnoughForHeapSRA. 1104static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1105 const std::vector<GlobalVariable*> &FieldGlobals) { 1106 std::vector<Value *> InsertedLoadsForPtr; 1107 //InsertedLoadsForPtr.resize(FieldGlobals.size()); 1108 while (!Load->use_empty()) 1109 RewriteHeapSROALoadUser(Load, Load->use_back(), 1110 FieldGlobals, InsertedLoadsForPtr); 1111} 1112 1113/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break 1114/// it up into multiple allocations of arrays of the fields. 1115static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ 1116 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; 1117 const StructType *STy = cast<StructType>(MI->getAllocatedType()); 1118 1119 // There is guaranteed to be at least one use of the malloc (storing 1120 // it into GV). If there are other uses, change them to be uses of 1121 // the global to simplify later code. This also deletes the store 1122 // into GV. 1123 ReplaceUsesOfMallocWithGlobal(MI, GV); 1124 1125 // Okay, at this point, there are no users of the malloc. Insert N 1126 // new mallocs at the same place as MI, and N globals. 1127 std::vector<GlobalVariable*> FieldGlobals; 1128 std::vector<MallocInst*> FieldMallocs; 1129 1130 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1131 const Type *FieldTy = STy->getElementType(FieldNo); 1132 const Type *PFieldTy = PointerType::getUnqual(FieldTy); 1133 1134 GlobalVariable *NGV = 1135 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, 1136 Constant::getNullValue(PFieldTy), 1137 GV->getName() + ".f" + utostr(FieldNo), GV, 1138 GV->isThreadLocal()); 1139 FieldGlobals.push_back(NGV); 1140 1141 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), 1142 MI->getName() + ".f" + utostr(FieldNo),MI); 1143 FieldMallocs.push_back(NMI); 1144 new StoreInst(NMI, NGV, MI); 1145 } 1146 1147 // The tricky aspect of this transformation is handling the case when malloc 1148 // fails. In the original code, malloc failing would set the result pointer 1149 // of malloc to null. In this case, some mallocs could succeed and others 1150 // could fail. As such, we emit code that looks like this: 1151 // F0 = malloc(field0) 1152 // F1 = malloc(field1) 1153 // F2 = malloc(field2) 1154 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1155 // if (F0) { free(F0); F0 = 0; } 1156 // if (F1) { free(F1); F1 = 0; } 1157 // if (F2) { free(F2); F2 = 0; } 1158 // } 1159 Value *RunningOr = 0; 1160 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1161 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], 1162 Constant::getNullValue(FieldMallocs[i]->getType()), 1163 "isnull", MI); 1164 if (!RunningOr) 1165 RunningOr = Cond; // First seteq 1166 else 1167 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI); 1168 } 1169 1170 // Split the basic block at the old malloc. 1171 BasicBlock *OrigBB = MI->getParent(); 1172 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont"); 1173 1174 // Create the block to check the first condition. Put all these blocks at the 1175 // end of the function as they are unlikely to be executed. 1176 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null", 1177 OrigBB->getParent()); 1178 1179 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1180 // branch on RunningOr. 1181 OrigBB->getTerminator()->eraseFromParent(); 1182 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB); 1183 1184 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1185 // pointer, because some may be null while others are not. 1186 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1187 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1188 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal, 1189 Constant::getNullValue(GVVal->getType()), 1190 "tmp", NullPtrBlock); 1191 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent()); 1192 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent()); 1193 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock); 1194 1195 // Fill in FreeBlock. 1196 new FreeInst(GVVal, FreeBlock); 1197 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1198 FreeBlock); 1199 new BranchInst(NextBlock, FreeBlock); 1200 1201 NullPtrBlock = NextBlock; 1202 } 1203 1204 new BranchInst(ContBB, NullPtrBlock); 1205 1206 1207 // MI is no longer needed, remove it. 1208 MI->eraseFromParent(); 1209 1210 1211 // Okay, the malloc site is completely handled. All of the uses of GV are now 1212 // loads, and all uses of those loads are simple. Rewrite them to use loads 1213 // of the per-field globals instead. 1214 while (!GV->use_empty()) { 1215 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 1216 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals); 1217 LI->eraseFromParent(); 1218 } else { 1219 // Must be a store of null. 1220 StoreInst *SI = cast<StoreInst>(GV->use_back()); 1221 assert(isa<Constant>(SI->getOperand(0)) && 1222 cast<Constant>(SI->getOperand(0))->isNullValue() && 1223 "Unexpected heap-sra user!"); 1224 1225 // Insert a store of null into each global. 1226 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1227 Constant *Null = 1228 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType()); 1229 new StoreInst(Null, FieldGlobals[i], SI); 1230 } 1231 // Erase the original store. 1232 SI->eraseFromParent(); 1233 } 1234 } 1235 1236 // The old global is now dead, remove it. 1237 GV->eraseFromParent(); 1238 1239 ++NumHeapSRA; 1240 return FieldGlobals[0]; 1241} 1242 1243 1244// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1245// that only one value (besides its initializer) is ever stored to the global. 1246static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1247 Module::global_iterator &GVI, 1248 TargetData &TD) { 1249 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal)) 1250 StoredOnceVal = CI->getOperand(0); 1251 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){ 1252 // "getelementptr Ptr, 0, 0, 0" is really just a cast. 1253 bool IsJustACast = true; 1254 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 1255 if (!isa<Constant>(GEPI->getOperand(i)) || 1256 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) { 1257 IsJustACast = false; 1258 break; 1259 } 1260 if (IsJustACast) 1261 StoredOnceVal = GEPI->getOperand(0); 1262 } 1263 1264 // If we are dealing with a pointer global that is initialized to null and 1265 // only has one (non-null) value stored into it, then we can optimize any 1266 // users of the loaded value (often calls and loads) that would trap if the 1267 // value was null. 1268 if (isa<PointerType>(GV->getInitializer()->getType()) && 1269 GV->getInitializer()->isNullValue()) { 1270 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1271 if (GV->getInitializer()->getType() != SOVC->getType()) 1272 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1273 1274 // Optimize away any trapping uses of the loaded value. 1275 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC)) 1276 return true; 1277 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { 1278 // If this is a malloc of an abstract type, don't touch it. 1279 if (!MI->getAllocatedType()->isSized()) 1280 return false; 1281 1282 // We can't optimize this global unless all uses of it are *known* to be 1283 // of the malloc value, not of the null initializer value (consider a use 1284 // that compares the global's value against zero to see if the malloc has 1285 // been reached). To do this, we check to see if all uses of the global 1286 // would trap if the global were null: this proves that they must all 1287 // happen after the malloc. 1288 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1289 return false; 1290 1291 // We can't optimize this if the malloc itself is used in a complex way, 1292 // for example, being stored into multiple globals. This allows the 1293 // malloc to be stored into the specified global, loaded setcc'd, and 1294 // GEP'd. These are all things we could transform to using the global 1295 // for. 1296 { 1297 SmallPtrSet<PHINode*, 8> PHIs; 1298 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs)) 1299 return false; 1300 } 1301 1302 1303 // If we have a global that is only initialized with a fixed size malloc, 1304 // transform the program to use global memory instead of malloc'd memory. 1305 // This eliminates dynamic allocation, avoids an indirection accessing the 1306 // data, and exposes the resultant global to further GlobalOpt. 1307 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { 1308 // Restrict this transformation to only working on small allocations 1309 // (2048 bytes currently), as we don't want to introduce a 16M global or 1310 // something. 1311 if (NElements->getZExtValue()* 1312 TD.getABITypeSize(MI->getAllocatedType()) < 2048) { 1313 GVI = OptimizeGlobalAddressOfMalloc(GV, MI); 1314 return true; 1315 } 1316 } 1317 1318 // If the allocation is an array of structures, consider transforming this 1319 // into multiple malloc'd arrays, one for each field. This is basically 1320 // SRoA for malloc'd memory. 1321 if (const StructType *AllocTy = 1322 dyn_cast<StructType>(MI->getAllocatedType())) { 1323 // This the structure has an unreasonable number of fields, leave it 1324 // alone. 1325 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 && 1326 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { 1327 GVI = PerformHeapAllocSRoA(GV, MI); 1328 return true; 1329 } 1330 } 1331 } 1332 } 1333 1334 return false; 1335} 1336 1337/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1338/// two values ever stored into GV are its initializer and OtherVal. See if we 1339/// can shrink the global into a boolean and select between the two values 1340/// whenever it is used. This exposes the values to other scalar optimizations. 1341static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1342 const Type *GVElType = GV->getType()->getElementType(); 1343 1344 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1345 // an FP value or vector, don't do this optimization because a select between 1346 // them is very expensive and unlikely to lead to later simplification. 1347 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || 1348 isa<VectorType>(GVElType)) 1349 return false; 1350 1351 // Walk the use list of the global seeing if all the uses are load or store. 1352 // If there is anything else, bail out. 1353 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I) 1354 if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) 1355 return false; 1356 1357 DOUT << " *** SHRINKING TO BOOL: " << *GV; 1358 1359 // Create the new global, initializing it to false. 1360 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, 1361 GlobalValue::InternalLinkage, ConstantInt::getFalse(), 1362 GV->getName()+".b", 1363 (Module *)NULL, 1364 GV->isThreadLocal()); 1365 GV->getParent()->getGlobalList().insert(GV, NewGV); 1366 1367 Constant *InitVal = GV->getInitializer(); 1368 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!"); 1369 1370 // If initialized to zero and storing one into the global, we can use a cast 1371 // instead of a select to synthesize the desired value. 1372 bool IsOneZero = false; 1373 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1374 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1375 1376 while (!GV->use_empty()) { 1377 Instruction *UI = cast<Instruction>(GV->use_back()); 1378 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1379 // Change the store into a boolean store. 1380 bool StoringOther = SI->getOperand(0) == OtherVal; 1381 // Only do this if we weren't storing a loaded value. 1382 Value *StoreVal; 1383 if (StoringOther || SI->getOperand(0) == InitVal) 1384 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther); 1385 else { 1386 // Otherwise, we are storing a previously loaded copy. To do this, 1387 // change the copy from copying the original value to just copying the 1388 // bool. 1389 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1390 1391 // If we're already replaced the input, StoredVal will be a cast or 1392 // select instruction. If not, it will be a load of the original 1393 // global. 1394 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1395 assert(LI->getOperand(0) == GV && "Not a copy!"); 1396 // Insert a new load, to preserve the saved value. 1397 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI); 1398 } else { 1399 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1400 "This is not a form that we understand!"); 1401 StoreVal = StoredVal->getOperand(0); 1402 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1403 } 1404 } 1405 new StoreInst(StoreVal, NewGV, SI); 1406 } else { 1407 // Change the load into a load of bool then a select. 1408 LoadInst *LI = cast<LoadInst>(UI); 1409 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI); 1410 Value *NSI; 1411 if (IsOneZero) 1412 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1413 else 1414 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI); 1415 NSI->takeName(LI); 1416 LI->replaceAllUsesWith(NSI); 1417 } 1418 UI->eraseFromParent(); 1419 } 1420 1421 GV->eraseFromParent(); 1422 return true; 1423} 1424 1425 1426/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1427/// it if possible. If we make a change, return true. 1428bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1429 Module::global_iterator &GVI) { 1430 std::set<PHINode*> PHIUsers; 1431 GlobalStatus GS; 1432 GV->removeDeadConstantUsers(); 1433 1434 if (GV->use_empty()) { 1435 DOUT << "GLOBAL DEAD: " << *GV; 1436 GV->eraseFromParent(); 1437 ++NumDeleted; 1438 return true; 1439 } 1440 1441 if (!AnalyzeGlobal(GV, GS, PHIUsers)) { 1442#if 0 1443 cerr << "Global: " << *GV; 1444 cerr << " isLoaded = " << GS.isLoaded << "\n"; 1445 cerr << " StoredType = "; 1446 switch (GS.StoredType) { 1447 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; 1448 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; 1449 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; 1450 case GlobalStatus::isStored: cerr << "stored\n"; break; 1451 } 1452 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) 1453 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; 1454 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) 1455 cerr << " AccessingFunction = " << GS.AccessingFunction->getName() 1456 << "\n"; 1457 cerr << " HasMultipleAccessingFunctions = " 1458 << GS.HasMultipleAccessingFunctions << "\n"; 1459 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; 1460 cerr << "\n"; 1461#endif 1462 1463 // If this is a first class global and has only one accessing function 1464 // and this function is main (which we know is not recursive we can make 1465 // this global a local variable) we replace the global with a local alloca 1466 // in this function. 1467 // 1468 // NOTE: It doesn't make sense to promote non first class types since we 1469 // are just replacing static memory to stack memory. 1470 if (!GS.HasMultipleAccessingFunctions && 1471 GS.AccessingFunction && !GS.HasNonInstructionUser && 1472 GV->getType()->getElementType()->isFirstClassType() && 1473 GS.AccessingFunction->getName() == "main" && 1474 GS.AccessingFunction->hasExternalLinkage()) { 1475 DOUT << "LOCALIZING GLOBAL: " << *GV; 1476 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); 1477 const Type* ElemTy = GV->getType()->getElementType(); 1478 // FIXME: Pass Global's alignment when globals have alignment 1479 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI); 1480 if (!isa<UndefValue>(GV->getInitializer())) 1481 new StoreInst(GV->getInitializer(), Alloca, FirstI); 1482 1483 GV->replaceAllUsesWith(Alloca); 1484 GV->eraseFromParent(); 1485 ++NumLocalized; 1486 return true; 1487 } 1488 1489 // If the global is never loaded (but may be stored to), it is dead. 1490 // Delete it now. 1491 if (!GS.isLoaded) { 1492 DOUT << "GLOBAL NEVER LOADED: " << *GV; 1493 1494 // Delete any stores we can find to the global. We may not be able to 1495 // make it completely dead though. 1496 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1497 1498 // If the global is dead now, delete it. 1499 if (GV->use_empty()) { 1500 GV->eraseFromParent(); 1501 ++NumDeleted; 1502 Changed = true; 1503 } 1504 return Changed; 1505 1506 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1507 DOUT << "MARKING CONSTANT: " << *GV; 1508 GV->setConstant(true); 1509 1510 // Clean up any obviously simplifiable users now. 1511 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1512 1513 // If the global is dead now, just nuke it. 1514 if (GV->use_empty()) { 1515 DOUT << " *** Marking constant allowed us to simplify " 1516 << "all users and delete global!\n"; 1517 GV->eraseFromParent(); 1518 ++NumDeleted; 1519 } 1520 1521 ++NumMarked; 1522 return true; 1523 } else if (!GV->getInitializer()->getType()->isFirstClassType()) { 1524 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) { 1525 GVI = FirstNewGV; // Don't skip the newly produced globals! 1526 return true; 1527 } 1528 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 1529 // If the initial value for the global was an undef value, and if only 1530 // one other value was stored into it, we can just change the 1531 // initializer to be an undef value, then delete all stores to the 1532 // global. This allows us to mark it constant. 1533 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1534 if (isa<UndefValue>(GV->getInitializer())) { 1535 // Change the initial value here. 1536 GV->setInitializer(SOVConstant); 1537 1538 // Clean up any obviously simplifiable users now. 1539 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1540 1541 if (GV->use_empty()) { 1542 DOUT << " *** Substituting initializer allowed us to " 1543 << "simplify all users and delete global!\n"; 1544 GV->eraseFromParent(); 1545 ++NumDeleted; 1546 } else { 1547 GVI = GV; 1548 } 1549 ++NumSubstitute; 1550 return true; 1551 } 1552 1553 // Try to optimize globals based on the knowledge that only one value 1554 // (besides its initializer) is ever stored to the global. 1555 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, 1556 getAnalysis<TargetData>())) 1557 return true; 1558 1559 // Otherwise, if the global was not a boolean, we can shrink it to be a 1560 // boolean. 1561 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1562 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 1563 ++NumShrunkToBool; 1564 return true; 1565 } 1566 } 1567 } 1568 return false; 1569} 1570 1571/// OnlyCalledDirectly - Return true if the specified function is only called 1572/// directly. In other words, its address is never taken. 1573static bool OnlyCalledDirectly(Function *F) { 1574 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1575 Instruction *User = dyn_cast<Instruction>(*UI); 1576 if (!User) return false; 1577 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; 1578 1579 // See if the function address is passed as an argument. 1580 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i) 1581 if (User->getOperand(i) == F) return false; 1582 } 1583 return true; 1584} 1585 1586/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 1587/// function, changing them to FastCC. 1588static void ChangeCalleesToFastCall(Function *F) { 1589 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1590 CallSite User(cast<Instruction>(*UI)); 1591 User.setCallingConv(CallingConv::Fast); 1592 } 1593} 1594 1595static PAListPtr StripNest(const PAListPtr &Attrs) { 1596 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { 1597 if ((Attrs.getSlot(i).Attrs & ParamAttr::Nest) == 0) 1598 continue; 1599 1600 // There can be only one. 1601 return Attrs.removeAttr(Attrs.getSlot(i).Index, ParamAttr::Nest); 1602 } 1603 1604 return Attrs; 1605} 1606 1607static void RemoveNestAttribute(Function *F) { 1608 F->setParamAttrs(StripNest(F->getParamAttrs())); 1609 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1610 CallSite User(cast<Instruction>(*UI)); 1611 User.setParamAttrs(StripNest(User.getParamAttrs())); 1612 } 1613} 1614 1615bool GlobalOpt::OptimizeFunctions(Module &M) { 1616 bool Changed = false; 1617 // Optimize functions. 1618 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 1619 Function *F = FI++; 1620 F->removeDeadConstantUsers(); 1621 if (F->use_empty() && (F->hasInternalLinkage() || 1622 F->hasLinkOnceLinkage())) { 1623 M.getFunctionList().erase(F); 1624 Changed = true; 1625 ++NumFnDeleted; 1626 } else if (F->hasInternalLinkage()) { 1627 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 1628 OnlyCalledDirectly(F)) { 1629 // If this function has C calling conventions, is not a varargs 1630 // function, and is only called directly, promote it to use the Fast 1631 // calling convention. 1632 F->setCallingConv(CallingConv::Fast); 1633 ChangeCalleesToFastCall(F); 1634 ++NumFastCallFns; 1635 Changed = true; 1636 } 1637 1638 if (F->getParamAttrs().hasAttrSomewhere(ParamAttr::Nest) && 1639 OnlyCalledDirectly(F)) { 1640 // The function is not used by a trampoline intrinsic, so it is safe 1641 // to remove the 'nest' attribute. 1642 RemoveNestAttribute(F); 1643 ++NumNestRemoved; 1644 Changed = true; 1645 } 1646 } 1647 } 1648 return Changed; 1649} 1650 1651bool GlobalOpt::OptimizeGlobalVars(Module &M) { 1652 bool Changed = false; 1653 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 1654 GVI != E; ) { 1655 GlobalVariable *GV = GVI++; 1656 if (!GV->isConstant() && GV->hasInternalLinkage() && 1657 GV->hasInitializer()) 1658 Changed |= ProcessInternalGlobal(GV, GVI); 1659 } 1660 return Changed; 1661} 1662 1663/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all 1664/// initializers have an init priority of 65535. 1665GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 1666 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 1667 I != E; ++I) 1668 if (I->getName() == "llvm.global_ctors") { 1669 // Found it, verify it's an array of { int, void()* }. 1670 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); 1671 if (!ATy) return 0; 1672 const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); 1673 if (!STy || STy->getNumElements() != 2 || 1674 STy->getElementType(0) != Type::Int32Ty) return 0; 1675 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); 1676 if (!PFTy) return 0; 1677 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); 1678 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || 1679 FTy->getNumParams() != 0) 1680 return 0; 1681 1682 // Verify that the initializer is simple enough for us to handle. 1683 if (!I->hasInitializer()) return 0; 1684 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); 1685 if (!CA) return 0; 1686 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1687 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) { 1688 if (isa<ConstantPointerNull>(CS->getOperand(1))) 1689 continue; 1690 1691 // Must have a function or null ptr. 1692 if (!isa<Function>(CS->getOperand(1))) 1693 return 0; 1694 1695 // Init priority must be standard. 1696 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0)); 1697 if (!CI || CI->getZExtValue() != 65535) 1698 return 0; 1699 } else { 1700 return 0; 1701 } 1702 1703 return I; 1704 } 1705 return 0; 1706} 1707 1708/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 1709/// return a list of the functions and null terminator as a vector. 1710static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 1711 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1712 std::vector<Function*> Result; 1713 Result.reserve(CA->getNumOperands()); 1714 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) { 1715 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i)); 1716 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 1717 } 1718 return Result; 1719} 1720 1721/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 1722/// specified array, returning the new global to use. 1723static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 1724 const std::vector<Function*> &Ctors) { 1725 // If we made a change, reassemble the initializer list. 1726 std::vector<Constant*> CSVals; 1727 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); 1728 CSVals.push_back(0); 1729 1730 // Create the new init list. 1731 std::vector<Constant*> CAList; 1732 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 1733 if (Ctors[i]) { 1734 CSVals[1] = Ctors[i]; 1735 } else { 1736 const Type *FTy = FunctionType::get(Type::VoidTy, 1737 std::vector<const Type*>(), false); 1738 const PointerType *PFTy = PointerType::getUnqual(FTy); 1739 CSVals[1] = Constant::getNullValue(PFTy); 1740 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); 1741 } 1742 CAList.push_back(ConstantStruct::get(CSVals)); 1743 } 1744 1745 // Create the array initializer. 1746 const Type *StructTy = 1747 cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); 1748 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()), 1749 CAList); 1750 1751 // If we didn't change the number of elements, don't create a new GV. 1752 if (CA->getType() == GCL->getInitializer()->getType()) { 1753 GCL->setInitializer(CA); 1754 return GCL; 1755 } 1756 1757 // Create the new global and insert it next to the existing list. 1758 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 1759 GCL->getLinkage(), CA, "", 1760 (Module *)NULL, 1761 GCL->isThreadLocal()); 1762 GCL->getParent()->getGlobalList().insert(GCL, NGV); 1763 NGV->takeName(GCL); 1764 1765 // Nuke the old list, replacing any uses with the new one. 1766 if (!GCL->use_empty()) { 1767 Constant *V = NGV; 1768 if (V->getType() != GCL->getType()) 1769 V = ConstantExpr::getBitCast(V, GCL->getType()); 1770 GCL->replaceAllUsesWith(V); 1771 } 1772 GCL->eraseFromParent(); 1773 1774 if (Ctors.size()) 1775 return NGV; 1776 else 1777 return 0; 1778} 1779 1780 1781static Constant *getVal(std::map<Value*, Constant*> &ComputedValues, 1782 Value *V) { 1783 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 1784 Constant *R = ComputedValues[V]; 1785 assert(R && "Reference to an uncomputed value!"); 1786 return R; 1787} 1788 1789/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 1790/// enough for us to understand. In particular, if it is a cast of something, 1791/// we punt. We basically just support direct accesses to globals and GEP's of 1792/// globals. This should be kept up to date with CommitValueTo. 1793static bool isSimpleEnoughPointerToCommit(Constant *C) { 1794 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 1795 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1796 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1797 return !GV->isDeclaration(); // reject external globals. 1798 } 1799 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 1800 // Handle a constantexpr gep. 1801 if (CE->getOpcode() == Instruction::GetElementPtr && 1802 isa<GlobalVariable>(CE->getOperand(0))) { 1803 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1804 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1805 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1806 return GV->hasInitializer() && 1807 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1808 } 1809 return false; 1810} 1811 1812/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 1813/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 1814/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 1815static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 1816 ConstantExpr *Addr, unsigned OpNo) { 1817 // Base case of the recursion. 1818 if (OpNo == Addr->getNumOperands()) { 1819 assert(Val->getType() == Init->getType() && "Type mismatch!"); 1820 return Val; 1821 } 1822 1823 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { 1824 std::vector<Constant*> Elts; 1825 1826 // Break up the constant into its elements. 1827 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { 1828 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i) 1829 Elts.push_back(CS->getOperand(i)); 1830 } else if (isa<ConstantAggregateZero>(Init)) { 1831 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1832 Elts.push_back(Constant::getNullValue(STy->getElementType(i))); 1833 } else if (isa<UndefValue>(Init)) { 1834 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1835 Elts.push_back(UndefValue::get(STy->getElementType(i))); 1836 } else { 1837 assert(0 && "This code is out of sync with " 1838 " ConstantFoldLoadThroughGEPConstantExpr"); 1839 } 1840 1841 // Replace the element that we are supposed to. 1842 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 1843 unsigned Idx = CU->getZExtValue(); 1844 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 1845 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 1846 1847 // Return the modified struct. 1848 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked()); 1849 } else { 1850 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 1851 const ArrayType *ATy = cast<ArrayType>(Init->getType()); 1852 1853 // Break up the array into elements. 1854 std::vector<Constant*> Elts; 1855 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { 1856 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1857 Elts.push_back(CA->getOperand(i)); 1858 } else if (isa<ConstantAggregateZero>(Init)) { 1859 Constant *Elt = Constant::getNullValue(ATy->getElementType()); 1860 Elts.assign(ATy->getNumElements(), Elt); 1861 } else if (isa<UndefValue>(Init)) { 1862 Constant *Elt = UndefValue::get(ATy->getElementType()); 1863 Elts.assign(ATy->getNumElements(), Elt); 1864 } else { 1865 assert(0 && "This code is out of sync with " 1866 " ConstantFoldLoadThroughGEPConstantExpr"); 1867 } 1868 1869 assert(CI->getZExtValue() < ATy->getNumElements()); 1870 Elts[CI->getZExtValue()] = 1871 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 1872 return ConstantArray::get(ATy, Elts); 1873 } 1874} 1875 1876/// CommitValueTo - We have decided that Addr (which satisfies the predicate 1877/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 1878static void CommitValueTo(Constant *Val, Constant *Addr) { 1879 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 1880 assert(GV->hasInitializer()); 1881 GV->setInitializer(Val); 1882 return; 1883 } 1884 1885 ConstantExpr *CE = cast<ConstantExpr>(Addr); 1886 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1887 1888 Constant *Init = GV->getInitializer(); 1889 Init = EvaluateStoreInto(Init, Val, CE, 2); 1890 GV->setInitializer(Init); 1891} 1892 1893/// ComputeLoadResult - Return the value that would be computed by a load from 1894/// P after the stores reflected by 'memory' have been performed. If we can't 1895/// decide, return null. 1896static Constant *ComputeLoadResult(Constant *P, 1897 const std::map<Constant*, Constant*> &Memory) { 1898 // If this memory location has been recently stored, use the stored value: it 1899 // is the most up-to-date. 1900 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P); 1901 if (I != Memory.end()) return I->second; 1902 1903 // Access it. 1904 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 1905 if (GV->hasInitializer()) 1906 return GV->getInitializer(); 1907 return 0; 1908 } 1909 1910 // Handle a constantexpr getelementptr. 1911 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 1912 if (CE->getOpcode() == Instruction::GetElementPtr && 1913 isa<GlobalVariable>(CE->getOperand(0))) { 1914 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1915 if (GV->hasInitializer()) 1916 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1917 } 1918 1919 return 0; // don't know how to evaluate. 1920} 1921 1922/// EvaluateFunction - Evaluate a call to function F, returning true if 1923/// successful, false if we can't evaluate it. ActualArgs contains the formal 1924/// arguments for the function. 1925static bool EvaluateFunction(Function *F, Constant *&RetVal, 1926 const std::vector<Constant*> &ActualArgs, 1927 std::vector<Function*> &CallStack, 1928 std::map<Constant*, Constant*> &MutatedMemory, 1929 std::vector<GlobalVariable*> &AllocaTmps) { 1930 // Check to see if this function is already executing (recursion). If so, 1931 // bail out. TODO: we might want to accept limited recursion. 1932 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 1933 return false; 1934 1935 CallStack.push_back(F); 1936 1937 /// Values - As we compute SSA register values, we store their contents here. 1938 std::map<Value*, Constant*> Values; 1939 1940 // Initialize arguments to the incoming values specified. 1941 unsigned ArgNo = 0; 1942 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 1943 ++AI, ++ArgNo) 1944 Values[AI] = ActualArgs[ArgNo]; 1945 1946 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 1947 /// we can only evaluate any one basic block at most once. This set keeps 1948 /// track of what we have executed so we can detect recursive cases etc. 1949 std::set<BasicBlock*> ExecutedBlocks; 1950 1951 // CurInst - The current instruction we're evaluating. 1952 BasicBlock::iterator CurInst = F->begin()->begin(); 1953 1954 // This is the main evaluation loop. 1955 while (1) { 1956 Constant *InstResult = 0; 1957 1958 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 1959 if (SI->isVolatile()) return false; // no volatile accesses. 1960 Constant *Ptr = getVal(Values, SI->getOperand(1)); 1961 if (!isSimpleEnoughPointerToCommit(Ptr)) 1962 // If this is too complex for us to commit, reject it. 1963 return false; 1964 Constant *Val = getVal(Values, SI->getOperand(0)); 1965 MutatedMemory[Ptr] = Val; 1966 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 1967 InstResult = ConstantExpr::get(BO->getOpcode(), 1968 getVal(Values, BO->getOperand(0)), 1969 getVal(Values, BO->getOperand(1))); 1970 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 1971 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 1972 getVal(Values, CI->getOperand(0)), 1973 getVal(Values, CI->getOperand(1))); 1974 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 1975 InstResult = ConstantExpr::getCast(CI->getOpcode(), 1976 getVal(Values, CI->getOperand(0)), 1977 CI->getType()); 1978 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 1979 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), 1980 getVal(Values, SI->getOperand(1)), 1981 getVal(Values, SI->getOperand(2))); 1982 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 1983 Constant *P = getVal(Values, GEP->getOperand(0)); 1984 SmallVector<Constant*, 8> GEPOps; 1985 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 1986 GEPOps.push_back(getVal(Values, GEP->getOperand(i))); 1987 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); 1988 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 1989 if (LI->isVolatile()) return false; // no volatile accesses. 1990 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), 1991 MutatedMemory); 1992 if (InstResult == 0) return false; // Could not evaluate load. 1993 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 1994 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 1995 const Type *Ty = AI->getType()->getElementType(); 1996 AllocaTmps.push_back(new GlobalVariable(Ty, false, 1997 GlobalValue::InternalLinkage, 1998 UndefValue::get(Ty), 1999 AI->getName())); 2000 InstResult = AllocaTmps.back(); 2001 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { 2002 // Cannot handle inline asm. 2003 if (isa<InlineAsm>(CI->getOperand(0))) return false; 2004 2005 // Resolve function pointers. 2006 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); 2007 if (!Callee) return false; // Cannot resolve. 2008 2009 std::vector<Constant*> Formals; 2010 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i) 2011 Formals.push_back(getVal(Values, CI->getOperand(i))); 2012 2013 if (Callee->isDeclaration()) { 2014 // If this is a function we can constant fold, do it. 2015 if (Constant *C = ConstantFoldCall(Callee, &Formals[0], 2016 Formals.size())) { 2017 InstResult = C; 2018 } else { 2019 return false; 2020 } 2021 } else { 2022 if (Callee->getFunctionType()->isVarArg()) 2023 return false; 2024 2025 Constant *RetVal; 2026 2027 // Execute the call, if successful, use the return value. 2028 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, 2029 MutatedMemory, AllocaTmps)) 2030 return false; 2031 InstResult = RetVal; 2032 } 2033 } else if (isa<TerminatorInst>(CurInst)) { 2034 BasicBlock *NewBB = 0; 2035 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2036 if (BI->isUnconditional()) { 2037 NewBB = BI->getSuccessor(0); 2038 } else { 2039 ConstantInt *Cond = 2040 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); 2041 if (!Cond) return false; // Cannot determine. 2042 2043 NewBB = BI->getSuccessor(!Cond->getZExtValue()); 2044 } 2045 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2046 ConstantInt *Val = 2047 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); 2048 if (!Val) return false; // Cannot determine. 2049 NewBB = SI->getSuccessor(SI->findCaseValue(Val)); 2050 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { 2051 if (RI->getNumOperands()) 2052 RetVal = getVal(Values, RI->getOperand(0)); 2053 2054 CallStack.pop_back(); // return from fn. 2055 return true; // We succeeded at evaluating this ctor! 2056 } else { 2057 // invoke, unwind, unreachable. 2058 return false; // Cannot handle this terminator. 2059 } 2060 2061 // Okay, we succeeded in evaluating this control flow. See if we have 2062 // executed the new block before. If so, we have a looping function, 2063 // which we cannot evaluate in reasonable time. 2064 if (!ExecutedBlocks.insert(NewBB).second) 2065 return false; // looped! 2066 2067 // Okay, we have never been in this block before. Check to see if there 2068 // are any PHI nodes. If so, evaluate them with information about where 2069 // we came from. 2070 BasicBlock *OldBB = CurInst->getParent(); 2071 CurInst = NewBB->begin(); 2072 PHINode *PN; 2073 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2074 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); 2075 2076 // Do NOT increment CurInst. We know that the terminator had no value. 2077 continue; 2078 } else { 2079 // Did not know how to evaluate this! 2080 return false; 2081 } 2082 2083 if (!CurInst->use_empty()) 2084 Values[CurInst] = InstResult; 2085 2086 // Advance program counter. 2087 ++CurInst; 2088 } 2089} 2090 2091/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2092/// we can. Return true if we can, false otherwise. 2093static bool EvaluateStaticConstructor(Function *F) { 2094 /// MutatedMemory - For each store we execute, we update this map. Loads 2095 /// check this to get the most up-to-date value. If evaluation is successful, 2096 /// this state is committed to the process. 2097 std::map<Constant*, Constant*> MutatedMemory; 2098 2099 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2100 /// to represent its body. This vector is needed so we can delete the 2101 /// temporary globals when we are done. 2102 std::vector<GlobalVariable*> AllocaTmps; 2103 2104 /// CallStack - This is used to detect recursion. In pathological situations 2105 /// we could hit exponential behavior, but at least there is nothing 2106 /// unbounded. 2107 std::vector<Function*> CallStack; 2108 2109 // Call the function. 2110 Constant *RetValDummy; 2111 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), 2112 CallStack, MutatedMemory, AllocaTmps); 2113 if (EvalSuccess) { 2114 // We succeeded at evaluation: commit the result. 2115 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2116 << F->getName() << "' to " << MutatedMemory.size() 2117 << " stores.\n"; 2118 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(), 2119 E = MutatedMemory.end(); I != E; ++I) 2120 CommitValueTo(I->second, I->first); 2121 } 2122 2123 // At this point, we are done interpreting. If we created any 'alloca' 2124 // temporaries, release them now. 2125 while (!AllocaTmps.empty()) { 2126 GlobalVariable *Tmp = AllocaTmps.back(); 2127 AllocaTmps.pop_back(); 2128 2129 // If there are still users of the alloca, the program is doing something 2130 // silly, e.g. storing the address of the alloca somewhere and using it 2131 // later. Since this is undefined, we'll just make it be null. 2132 if (!Tmp->use_empty()) 2133 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2134 delete Tmp; 2135 } 2136 2137 return EvalSuccess; 2138} 2139 2140 2141 2142/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2143/// Return true if anything changed. 2144bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2145 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2146 bool MadeChange = false; 2147 if (Ctors.empty()) return false; 2148 2149 // Loop over global ctors, optimizing them when we can. 2150 for (unsigned i = 0; i != Ctors.size(); ++i) { 2151 Function *F = Ctors[i]; 2152 // Found a null terminator in the middle of the list, prune off the rest of 2153 // the list. 2154 if (F == 0) { 2155 if (i != Ctors.size()-1) { 2156 Ctors.resize(i+1); 2157 MadeChange = true; 2158 } 2159 break; 2160 } 2161 2162 // We cannot simplify external ctor functions. 2163 if (F->empty()) continue; 2164 2165 // If we can evaluate the ctor at compile time, do. 2166 if (EvaluateStaticConstructor(F)) { 2167 Ctors.erase(Ctors.begin()+i); 2168 MadeChange = true; 2169 --i; 2170 ++NumCtorsEvaluated; 2171 continue; 2172 } 2173 } 2174 2175 if (!MadeChange) return false; 2176 2177 GCL = InstallGlobalCtors(GCL, Ctors); 2178 return true; 2179} 2180 2181 2182bool GlobalOpt::runOnModule(Module &M) { 2183 bool Changed = false; 2184 2185 // Try to find the llvm.globalctors list. 2186 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 2187 2188 bool LocalChange = true; 2189 while (LocalChange) { 2190 LocalChange = false; 2191 2192 // Delete functions that are trivially dead, ccc -> fastcc 2193 LocalChange |= OptimizeFunctions(M); 2194 2195 // Optimize global_ctors list. 2196 if (GlobalCtors) 2197 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 2198 2199 // Optimize non-address-taken globals. 2200 LocalChange |= OptimizeGlobalVars(M); 2201 Changed |= LocalChange; 2202 } 2203 2204 // TODO: Move all global ctors functions to the end of the module for code 2205 // layout. 2206 2207 return Changed; 2208} 2209