GlobalOpt.cpp revision 1c8733e1fd69e634daaa7fefd0d1436b846a8eb3
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 <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 } 204 } else if (isa<GetElementPtrInst>(I)) { 205 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 206 } else if (isa<SelectInst>(I)) { 207 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 208 } else if (PHINode *PN = dyn_cast<PHINode>(I)) { 209 // PHI nodes we can check just like select or GEP instructions, but we 210 // have to be careful about infinite recursion. 211 if (PHIUsers.insert(PN).second) // Not already visited. 212 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 213 GS.HasPHIUser = true; 214 } else if (isa<CmpInst>(I)) { 215 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { 216 if (I->getOperand(1) == V) 217 GS.StoredType = GlobalStatus::isStored; 218 if (I->getOperand(2) == V) 219 GS.isLoaded = true; 220 } else if (isa<MemSetInst>(I)) { 221 assert(I->getOperand(1) == V && "Memset only takes one pointer!"); 222 GS.StoredType = GlobalStatus::isStored; 223 } else { 224 return true; // Any other non-load instruction might take address! 225 } 226 } else if (Constant *C = dyn_cast<Constant>(*UI)) { 227 GS.HasNonInstructionUser = true; 228 // We might have a dead and dangling constant hanging off of here. 229 if (!ConstantIsDead(C)) 230 return true; 231 } else { 232 GS.HasNonInstructionUser = true; 233 // Otherwise must be some other user. 234 return true; 235 } 236 237 return false; 238} 239 240static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { 241 ConstantInt *CI = dyn_cast<ConstantInt>(Idx); 242 if (!CI) return 0; 243 unsigned IdxV = CI->getZExtValue(); 244 245 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { 246 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); 247 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { 248 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); 249 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { 250 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); 251 } else if (isa<ConstantAggregateZero>(Agg)) { 252 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 253 if (IdxV < STy->getNumElements()) 254 return Constant::getNullValue(STy->getElementType(IdxV)); 255 } else if (const SequentialType *STy = 256 dyn_cast<SequentialType>(Agg->getType())) { 257 return Constant::getNullValue(STy->getElementType()); 258 } 259 } else if (isa<UndefValue>(Agg)) { 260 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 261 if (IdxV < STy->getNumElements()) 262 return UndefValue::get(STy->getElementType(IdxV)); 263 } else if (const SequentialType *STy = 264 dyn_cast<SequentialType>(Agg->getType())) { 265 return UndefValue::get(STy->getElementType()); 266 } 267 } 268 return 0; 269} 270 271 272/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 273/// users of the global, cleaning up the obvious ones. This is largely just a 274/// quick scan over the use list to clean up the easy and obvious cruft. This 275/// returns true if it made a change. 276static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) { 277 bool Changed = false; 278 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 279 User *U = *UI++; 280 281 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 282 if (Init) { 283 // Replace the load with the initializer. 284 LI->replaceAllUsesWith(Init); 285 LI->eraseFromParent(); 286 Changed = true; 287 } 288 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 289 // Store must be unreachable or storing Init into the global. 290 SI->eraseFromParent(); 291 Changed = true; 292 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 293 if (CE->getOpcode() == Instruction::GetElementPtr) { 294 Constant *SubInit = 0; 295 if (Init) 296 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 297 Changed |= CleanupConstantGlobalUsers(CE, SubInit); 298 } else if (CE->getOpcode() == Instruction::BitCast && 299 isa<PointerType>(CE->getType())) { 300 // Pointer cast, delete any stores and memsets to the global. 301 Changed |= CleanupConstantGlobalUsers(CE, 0); 302 } 303 304 if (CE->use_empty()) { 305 CE->destroyConstant(); 306 Changed = true; 307 } 308 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 309 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 310 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 311 // and will invalidate our notion of what Init is. 312 Constant *SubInit = 0; 313 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 314 ConstantExpr *CE = 315 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP)); 316 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 317 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 318 } 319 Changed |= CleanupConstantGlobalUsers(GEP, SubInit); 320 321 if (GEP->use_empty()) { 322 GEP->eraseFromParent(); 323 Changed = true; 324 } 325 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 326 if (MI->getRawDest() == V) { 327 MI->eraseFromParent(); 328 Changed = true; 329 } 330 331 } else if (Constant *C = dyn_cast<Constant>(U)) { 332 // If we have a chain of dead constantexprs or other things dangling from 333 // us, and if they are all dead, nuke them without remorse. 334 if (ConstantIsDead(C)) { 335 C->destroyConstant(); 336 // This could have invalidated UI, start over from scratch. 337 CleanupConstantGlobalUsers(V, Init); 338 return true; 339 } 340 } 341 } 342 return Changed; 343} 344 345/// isSafeSROAElementUse - Return true if the specified instruction is a safe 346/// user of a derived expression from a global that we want to SROA. 347static bool isSafeSROAElementUse(Value *V) { 348 // We might have a dead and dangling constant hanging off of here. 349 if (Constant *C = dyn_cast<Constant>(V)) 350 return ConstantIsDead(C); 351 352 Instruction *I = dyn_cast<Instruction>(V); 353 if (!I) return false; 354 355 // Loads are ok. 356 if (isa<LoadInst>(I)) return true; 357 358 // Stores *to* the pointer are ok. 359 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 360 return SI->getOperand(0) != V; 361 362 // Otherwise, it must be a GEP. 363 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 364 if (GEPI == 0) return false; 365 366 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 367 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 368 return false; 369 370 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 371 I != E; ++I) 372 if (!isSafeSROAElementUse(*I)) 373 return false; 374 return true; 375} 376 377 378/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 379/// Look at it and its uses and decide whether it is safe to SROA this global. 380/// 381static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 382 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 383 if (!isa<GetElementPtrInst>(U) && 384 (!isa<ConstantExpr>(U) || 385 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 386 return false; 387 388 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 389 // don't like < 3 operand CE's, and we don't like non-constant integer 390 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 391 // value of C. 392 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 393 !cast<Constant>(U->getOperand(1))->isNullValue() || 394 !isa<ConstantInt>(U->getOperand(2))) 395 return false; 396 397 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 398 ++GEPI; // Skip over the pointer index. 399 400 // If this is a use of an array allocation, do a bit more checking for sanity. 401 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 402 uint64_t NumElements = AT->getNumElements(); 403 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 404 405 // Check to make sure that index falls within the array. If not, 406 // something funny is going on, so we won't do the optimization. 407 // 408 if (Idx->getZExtValue() >= NumElements) 409 return false; 410 411 // We cannot scalar repl this level of the array unless any array 412 // sub-indices are in-range constants. In particular, consider: 413 // A[0][i]. We cannot know that the user isn't doing invalid things like 414 // allowing i to index an out-of-range subscript that accesses A[1]. 415 // 416 // Scalar replacing *just* the outer index of the array is probably not 417 // going to be a win anyway, so just give up. 418 for (++GEPI; // Skip array index. 419 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); 420 ++GEPI) { 421 uint64_t NumElements; 422 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 423 NumElements = SubArrayTy->getNumElements(); 424 else 425 NumElements = cast<VectorType>(*GEPI)->getNumElements(); 426 427 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 428 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 429 return false; 430 } 431 } 432 433 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 434 if (!isSafeSROAElementUse(*I)) 435 return false; 436 return true; 437} 438 439/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 440/// is safe for us to perform this transformation. 441/// 442static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 443 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 444 UI != E; ++UI) { 445 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 446 return false; 447 } 448 return true; 449} 450 451 452/// SRAGlobal - Perform scalar replacement of aggregates on the specified global 453/// variable. This opens the door for other optimizations by exposing the 454/// behavior of the program in a more fine-grained way. We have determined that 455/// this transformation is safe already. We return the first global variable we 456/// insert so that the caller can reprocess it. 457static GlobalVariable *SRAGlobal(GlobalVariable *GV) { 458 // Make sure this global only has simple uses that we can SRA. 459 if (!GlobalUsersSafeToSRA(GV)) 460 return 0; 461 462 assert(GV->hasInternalLinkage() && !GV->isConstant()); 463 Constant *Init = GV->getInitializer(); 464 const Type *Ty = Init->getType(); 465 466 std::vector<GlobalVariable*> NewGlobals; 467 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 468 469 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 470 NewGlobals.reserve(STy->getNumElements()); 471 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 472 Constant *In = getAggregateConstantElement(Init, 473 ConstantInt::get(Type::Int32Ty, i)); 474 assert(In && "Couldn't get element of initializer?"); 475 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 476 GlobalVariable::InternalLinkage, 477 In, GV->getName()+"."+utostr(i), 478 (Module *)NULL, 479 GV->isThreadLocal()); 480 Globals.insert(GV, NGV); 481 NewGlobals.push_back(NGV); 482 } 483 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 484 unsigned NumElements = 0; 485 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 486 NumElements = ATy->getNumElements(); 487 else if (const VectorType *PTy = dyn_cast<VectorType>(STy)) 488 NumElements = PTy->getNumElements(); 489 else 490 assert(0 && "Unknown aggregate sequential type!"); 491 492 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 493 return 0; // It's not worth it. 494 NewGlobals.reserve(NumElements); 495 for (unsigned i = 0, e = NumElements; i != e; ++i) { 496 Constant *In = getAggregateConstantElement(Init, 497 ConstantInt::get(Type::Int32Ty, i)); 498 assert(In && "Couldn't get element of initializer?"); 499 500 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 501 GlobalVariable::InternalLinkage, 502 In, GV->getName()+"."+utostr(i), 503 (Module *)NULL, 504 GV->isThreadLocal()); 505 Globals.insert(GV, NGV); 506 NewGlobals.push_back(NGV); 507 } 508 } 509 510 if (NewGlobals.empty()) 511 return 0; 512 513 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; 514 515 Constant *NullInt = Constant::getNullValue(Type::Int32Ty); 516 517 // Loop over all of the uses of the global, replacing the constantexpr geps, 518 // with smaller constantexpr geps or direct references. 519 while (!GV->use_empty()) { 520 User *GEP = GV->use_back(); 521 assert(((isa<ConstantExpr>(GEP) && 522 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 523 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 524 525 // Ignore the 1th operand, which has to be zero or else the program is quite 526 // broken (undefined). Get the 2nd operand, which is the structure or array 527 // index. 528 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 529 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 530 531 Value *NewPtr = NewGlobals[Val]; 532 533 // Form a shorter GEP if needed. 534 if (GEP->getNumOperands() > 3) { 535 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 536 SmallVector<Constant*, 8> Idxs; 537 Idxs.push_back(NullInt); 538 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 539 Idxs.push_back(CE->getOperand(i)); 540 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), 541 &Idxs[0], Idxs.size()); 542 } else { 543 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 544 SmallVector<Value*, 8> Idxs; 545 Idxs.push_back(NullInt); 546 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 547 Idxs.push_back(GEPI->getOperand(i)); 548 NewPtr = new GetElementPtrInst(NewPtr, Idxs.begin(), Idxs.end(), 549 GEPI->getName()+"."+utostr(Val), GEPI); 550 } 551 } 552 GEP->replaceAllUsesWith(NewPtr); 553 554 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 555 GEPI->eraseFromParent(); 556 else 557 cast<ConstantExpr>(GEP)->destroyConstant(); 558 } 559 560 // Delete the old global, now that it is dead. 561 Globals.erase(GV); 562 ++NumSRA; 563 564 // Loop over the new globals array deleting any globals that are obviously 565 // dead. This can arise due to scalarization of a structure or an array that 566 // has elements that are dead. 567 unsigned FirstGlobal = 0; 568 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 569 if (NewGlobals[i]->use_empty()) { 570 Globals.erase(NewGlobals[i]); 571 if (FirstGlobal == i) ++FirstGlobal; 572 } 573 574 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 575} 576 577/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 578/// value will trap if the value is dynamically null. PHIs keeps track of any 579/// phi nodes we've seen to avoid reprocessing them. 580static bool AllUsesOfValueWillTrapIfNull(Value *V, 581 SmallPtrSet<PHINode*, 8> &PHIs) { 582 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 583 if (isa<LoadInst>(*UI)) { 584 // Will trap. 585 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 586 if (SI->getOperand(0) == V) { 587 //cerr << "NONTRAPPING USE: " << **UI; 588 return false; // Storing the value. 589 } 590 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { 591 if (CI->getOperand(0) != V) { 592 //cerr << "NONTRAPPING USE: " << **UI; 593 return false; // Not calling the ptr 594 } 595 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { 596 if (II->getOperand(0) != V) { 597 //cerr << "NONTRAPPING USE: " << **UI; 598 return false; // Not calling the ptr 599 } 600 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { 601 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 602 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 603 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 604 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 605 // If we've already seen this phi node, ignore it, it has already been 606 // checked. 607 if (PHIs.insert(PN)) 608 return AllUsesOfValueWillTrapIfNull(PN, PHIs); 609 } else if (isa<ICmpInst>(*UI) && 610 isa<ConstantPointerNull>(UI->getOperand(1))) { 611 // Ignore setcc X, null 612 } else { 613 //cerr << "NONTRAPPING USE: " << **UI; 614 return false; 615 } 616 return true; 617} 618 619/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 620/// from GV will trap if the loaded value is null. Note that this also permits 621/// comparisons of the loaded value against null, as a special case. 622static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) { 623 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) 624 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 625 SmallPtrSet<PHINode*, 8> PHIs; 626 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 627 return false; 628 } else if (isa<StoreInst>(*UI)) { 629 // Ignore stores to the global. 630 } else { 631 // We don't know or understand this user, bail out. 632 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; 633 return false; 634 } 635 636 return true; 637} 638 639static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 640 bool Changed = false; 641 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 642 Instruction *I = cast<Instruction>(*UI++); 643 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 644 LI->setOperand(0, NewV); 645 Changed = true; 646 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 647 if (SI->getOperand(1) == V) { 648 SI->setOperand(1, NewV); 649 Changed = true; 650 } 651 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 652 if (I->getOperand(0) == V) { 653 // Calling through the pointer! Turn into a direct call, but be careful 654 // that the pointer is not also being passed as an argument. 655 I->setOperand(0, NewV); 656 Changed = true; 657 bool PassedAsArg = false; 658 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) 659 if (I->getOperand(i) == V) { 660 PassedAsArg = true; 661 I->setOperand(i, NewV); 662 } 663 664 if (PassedAsArg) { 665 // Being passed as an argument also. Be careful to not invalidate UI! 666 UI = V->use_begin(); 667 } 668 } 669 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 670 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 671 ConstantExpr::getCast(CI->getOpcode(), 672 NewV, CI->getType())); 673 if (CI->use_empty()) { 674 Changed = true; 675 CI->eraseFromParent(); 676 } 677 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 678 // Should handle GEP here. 679 SmallVector<Constant*, 8> Idxs; 680 Idxs.reserve(GEPI->getNumOperands()-1); 681 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 682 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i))) 683 Idxs.push_back(C); 684 else 685 break; 686 if (Idxs.size() == GEPI->getNumOperands()-1) 687 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 688 ConstantExpr::getGetElementPtr(NewV, &Idxs[0], 689 Idxs.size())); 690 if (GEPI->use_empty()) { 691 Changed = true; 692 GEPI->eraseFromParent(); 693 } 694 } 695 } 696 697 return Changed; 698} 699 700 701/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 702/// value stored into it. If there are uses of the loaded value that would trap 703/// if the loaded value is dynamically null, then we know that they cannot be 704/// reachable with a null optimize away the load. 705static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { 706 std::vector<LoadInst*> Loads; 707 bool Changed = false; 708 709 // Replace all uses of loads with uses of uses of the stored value. 710 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); 711 GUI != E; ++GUI) 712 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { 713 Loads.push_back(LI); 714 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 715 } else { 716 // If we get here we could have stores, selects, or phi nodes whose values 717 // are loaded. 718 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || 719 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && 720 "Only expect load and stores!"); 721 } 722 723 if (Changed) { 724 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; 725 ++NumGlobUses; 726 } 727 728 // Delete all of the loads we can, keeping track of whether we nuked them all! 729 bool AllLoadsGone = true; 730 while (!Loads.empty()) { 731 LoadInst *L = Loads.back(); 732 if (L->use_empty()) { 733 L->eraseFromParent(); 734 Changed = true; 735 } else { 736 AllLoadsGone = false; 737 } 738 Loads.pop_back(); 739 } 740 741 // If we nuked all of the loads, then none of the stores are needed either, 742 // nor is the global. 743 if (AllLoadsGone) { 744 DOUT << " *** GLOBAL NOW DEAD!\n"; 745 CleanupConstantGlobalUsers(GV, 0); 746 if (GV->use_empty()) { 747 GV->eraseFromParent(); 748 ++NumDeleted; 749 } 750 Changed = true; 751 } 752 return Changed; 753} 754 755/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 756/// instructions that are foldable. 757static void ConstantPropUsersOf(Value *V) { 758 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 759 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 760 if (Constant *NewC = ConstantFoldInstruction(I)) { 761 I->replaceAllUsesWith(NewC); 762 763 // Advance UI to the next non-I use to avoid invalidating it! 764 // Instructions could multiply use V. 765 while (UI != E && *UI == I) 766 ++UI; 767 I->eraseFromParent(); 768 } 769} 770 771/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 772/// variable, and transforms the program as if it always contained the result of 773/// the specified malloc. Because it is always the result of the specified 774/// malloc, there is no reason to actually DO the malloc. Instead, turn the 775/// malloc into a global, and any loads of GV as uses of the new global. 776static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 777 MallocInst *MI) { 778 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; 779 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); 780 781 if (NElements->getZExtValue() != 1) { 782 // If we have an array allocation, transform it to a single element 783 // allocation to make the code below simpler. 784 Type *NewTy = ArrayType::get(MI->getAllocatedType(), 785 NElements->getZExtValue()); 786 MallocInst *NewMI = 787 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), 788 MI->getAlignment(), MI->getName(), MI); 789 Value* Indices[2]; 790 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); 791 Value *NewGEP = new GetElementPtrInst(NewMI, Indices, Indices + 2, 792 NewMI->getName()+".el0", MI); 793 MI->replaceAllUsesWith(NewGEP); 794 MI->eraseFromParent(); 795 MI = NewMI; 796 } 797 798 // Create the new global variable. The contents of the malloc'd memory is 799 // undefined, so initialize with an undef value. 800 Constant *Init = UndefValue::get(MI->getAllocatedType()); 801 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, 802 GlobalValue::InternalLinkage, Init, 803 GV->getName()+".body", 804 (Module *)NULL, 805 GV->isThreadLocal()); 806 GV->getParent()->getGlobalList().insert(GV, NewGV); 807 808 // Anything that used the malloc now uses the global directly. 809 MI->replaceAllUsesWith(NewGV); 810 811 Constant *RepValue = NewGV; 812 if (NewGV->getType() != GV->getType()->getElementType()) 813 RepValue = ConstantExpr::getBitCast(RepValue, 814 GV->getType()->getElementType()); 815 816 // If there is a comparison against null, we will insert a global bool to 817 // keep track of whether the global was initialized yet or not. 818 GlobalVariable *InitBool = 819 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage, 820 ConstantInt::getFalse(), GV->getName()+".init", 821 (Module *)NULL, GV->isThreadLocal()); 822 bool InitBoolUsed = false; 823 824 // Loop over all uses of GV, processing them in turn. 825 std::vector<StoreInst*> Stores; 826 while (!GV->use_empty()) 827 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 828 while (!LI->use_empty()) { 829 Use &LoadUse = LI->use_begin().getUse(); 830 if (!isa<ICmpInst>(LoadUse.getUser())) 831 LoadUse = RepValue; 832 else { 833 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); 834 // Replace the cmp X, 0 with a use of the bool value. 835 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); 836 InitBoolUsed = true; 837 switch (CI->getPredicate()) { 838 default: assert(0 && "Unknown ICmp Predicate!"); 839 case ICmpInst::ICMP_ULT: 840 case ICmpInst::ICMP_SLT: 841 LV = ConstantInt::getFalse(); // X < null -> always false 842 break; 843 case ICmpInst::ICMP_ULE: 844 case ICmpInst::ICMP_SLE: 845 case ICmpInst::ICMP_EQ: 846 LV = BinaryOperator::createNot(LV, "notinit", CI); 847 break; 848 case ICmpInst::ICMP_NE: 849 case ICmpInst::ICMP_UGE: 850 case ICmpInst::ICMP_SGE: 851 case ICmpInst::ICMP_UGT: 852 case ICmpInst::ICMP_SGT: 853 break; // no change. 854 } 855 CI->replaceAllUsesWith(LV); 856 CI->eraseFromParent(); 857 } 858 } 859 LI->eraseFromParent(); 860 } else { 861 StoreInst *SI = cast<StoreInst>(GV->use_back()); 862 // The global is initialized when the store to it occurs. 863 new StoreInst(ConstantInt::getTrue(), InitBool, SI); 864 SI->eraseFromParent(); 865 } 866 867 // If the initialization boolean was used, insert it, otherwise delete it. 868 if (!InitBoolUsed) { 869 while (!InitBool->use_empty()) // Delete initializations 870 cast<Instruction>(InitBool->use_back())->eraseFromParent(); 871 delete InitBool; 872 } else 873 GV->getParent()->getGlobalList().insert(GV, InitBool); 874 875 876 // Now the GV is dead, nuke it and the malloc. 877 GV->eraseFromParent(); 878 MI->eraseFromParent(); 879 880 // To further other optimizations, loop over all users of NewGV and try to 881 // constant prop them. This will promote GEP instructions with constant 882 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 883 ConstantPropUsersOf(NewGV); 884 if (RepValue != NewGV) 885 ConstantPropUsersOf(RepValue); 886 887 return NewGV; 888} 889 890/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 891/// to make sure that there are no complex uses of V. We permit simple things 892/// like dereferencing the pointer, but not storing through the address, unless 893/// it is to the specified global. 894static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V, 895 GlobalVariable *GV, 896 SmallPtrSet<PHINode*, 8> &PHIs) { 897 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 898 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) { 899 // Fine, ignore. 900 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 901 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 902 return false; // Storing the pointer itself... bad. 903 // Otherwise, storing through it, or storing into GV... fine. 904 } else if (isa<GetElementPtrInst>(*UI)) { 905 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI), 906 GV, PHIs)) 907 return false; 908 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 909 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 910 // cycles. 911 if (PHIs.insert(PN)) 912 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 913 return false; 914 } else { 915 return false; 916 } 917 return true; 918} 919 920/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 921/// somewhere. Transform all uses of the allocation into loads from the 922/// global and uses of the resultant pointer. Further, delete the store into 923/// GV. This assumes that these value pass the 924/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 925static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 926 GlobalVariable *GV) { 927 while (!Alloc->use_empty()) { 928 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 929 Instruction *InsertPt = U; 930 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 931 // If this is the store of the allocation into the global, remove it. 932 if (SI->getOperand(1) == GV) { 933 SI->eraseFromParent(); 934 continue; 935 } 936 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 937 // Insert the load in the corresponding predecessor, not right before the 938 // PHI. 939 unsigned PredNo = Alloc->use_begin().getOperandNo()/2; 940 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator(); 941 } 942 943 // Insert a load from the global, and use it instead of the malloc. 944 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 945 U->replaceUsesOfWith(Alloc, NL); 946 } 947} 948 949/// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 950/// GV are simple enough to perform HeapSRA, return true. 951static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, 952 MallocInst *MI) { 953 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; 954 ++UI) 955 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 956 // We permit two users of the load: setcc comparing against the null 957 // pointer, and a getelementptr of a specific form. 958 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E; 959 ++UI) { 960 // Comparison against null is ok. 961 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) { 962 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 963 return false; 964 continue; 965 } 966 967 // getelementptr is also ok, but only a simple form. 968 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 969 // Must index into the array and into the struct. 970 if (GEPI->getNumOperands() < 3) 971 return false; 972 973 // Otherwise the GEP is ok. 974 continue; 975 } 976 977 if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 978 // We have a phi of a load from the global. We can only handle this 979 // if the other PHI'd values are actually the same. In this case, 980 // the rewriter will just drop the phi entirely. 981 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 982 Value *IV = PN->getIncomingValue(i); 983 if (IV == LI) continue; // Trivial the same. 984 985 // If the phi'd value is from the malloc that initializes the value, 986 // we can xform it. 987 if (IV == MI) continue; 988 989 // Otherwise, we don't know what it is. 990 return false; 991 } 992 return true; 993 } 994 995 // Otherwise we don't know what this is, not ok. 996 return false; 997 } 998 } 999 return true; 1000} 1001 1002/// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd 1003/// value, lazily creating it on demand. 1004static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo, 1005 const std::vector<GlobalVariable*> &FieldGlobals, 1006 std::vector<Value *> &InsertedLoadsForPtr) { 1007 if (InsertedLoadsForPtr.size() <= FieldNo) 1008 InsertedLoadsForPtr.resize(FieldNo+1); 1009 if (InsertedLoadsForPtr[FieldNo] == 0) 1010 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo], 1011 Load->getName()+".f" + 1012 utostr(FieldNo), Load); 1013 return InsertedLoadsForPtr[FieldNo]; 1014} 1015 1016/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1017/// the load, rewrite the derived value to use the HeapSRoA'd load. 1018static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser, 1019 const std::vector<GlobalVariable*> &FieldGlobals, 1020 std::vector<Value *> &InsertedLoadsForPtr) { 1021 // If this is a comparison against null, handle it. 1022 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1023 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1024 // If we have a setcc of the loaded pointer, we can use a setcc of any 1025 // field. 1026 Value *NPtr; 1027 if (InsertedLoadsForPtr.empty()) { 1028 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr); 1029 } else { 1030 NPtr = InsertedLoadsForPtr.back(); 1031 } 1032 1033 Value *New = new ICmpInst(SCI->getPredicate(), NPtr, 1034 Constant::getNullValue(NPtr->getType()), 1035 SCI->getName(), SCI); 1036 SCI->replaceAllUsesWith(New); 1037 SCI->eraseFromParent(); 1038 return; 1039 } 1040 1041 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...' 1042 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1043 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1044 && "Unexpected GEPI!"); 1045 1046 // Load the pointer for this field. 1047 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1048 Value *NewPtr = GetHeapSROALoad(Load, FieldNo, 1049 FieldGlobals, InsertedLoadsForPtr); 1050 1051 // Create the new GEP idx vector. 1052 SmallVector<Value*, 8> GEPIdx; 1053 GEPIdx.push_back(GEPI->getOperand(1)); 1054 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1055 1056 Value *NGEPI = new GetElementPtrInst(NewPtr, GEPIdx.begin(), GEPIdx.end(), 1057 GEPI->getName(), GEPI); 1058 GEPI->replaceAllUsesWith(NGEPI); 1059 GEPI->eraseFromParent(); 1060 return; 1061 } 1062 1063 // Handle PHI nodes. PHI nodes must be merging in the same values, plus 1064 // potentially the original malloc. Insert phi nodes for each field, then 1065 // process uses of the PHI. 1066 PHINode *PN = cast<PHINode>(LoadUser); 1067 std::vector<Value *> PHIsForField; 1068 PHIsForField.resize(FieldGlobals.size()); 1069 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1070 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr); 1071 1072 PHINode *FieldPN = new PHINode(LoadV->getType(), 1073 PN->getName()+"."+utostr(i), PN); 1074 // Fill in the predecessor values. 1075 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) { 1076 // Each predecessor either uses the load or the original malloc. 1077 Value *InVal = PN->getIncomingValue(pred); 1078 BasicBlock *BB = PN->getIncomingBlock(pred); 1079 Value *NewVal; 1080 if (isa<MallocInst>(InVal)) { 1081 // Insert a reload from the global in the predecessor. 1082 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals, 1083 PHIsForField); 1084 } else { 1085 NewVal = InsertedLoadsForPtr[i]; 1086 } 1087 FieldPN->addIncoming(NewVal, BB); 1088 } 1089 PHIsForField[i] = FieldPN; 1090 } 1091 1092 // Since PHIsForField specifies a phi for every input value, the lazy inserter 1093 // will never insert a load. 1094 while (!PN->use_empty()) 1095 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField); 1096 PN->eraseFromParent(); 1097} 1098 1099/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1100/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1101/// use FieldGlobals instead. All uses of loaded values satisfy 1102/// GlobalLoadUsesSimpleEnoughForHeapSRA. 1103static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1104 const std::vector<GlobalVariable*> &FieldGlobals) { 1105 std::vector<Value *> InsertedLoadsForPtr; 1106 //InsertedLoadsForPtr.resize(FieldGlobals.size()); 1107 while (!Load->use_empty()) 1108 RewriteHeapSROALoadUser(Load, Load->use_back(), 1109 FieldGlobals, InsertedLoadsForPtr); 1110} 1111 1112/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break 1113/// it up into multiple allocations of arrays of the fields. 1114static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ 1115 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; 1116 const StructType *STy = cast<StructType>(MI->getAllocatedType()); 1117 1118 // There is guaranteed to be at least one use of the malloc (storing 1119 // it into GV). If there are other uses, change them to be uses of 1120 // the global to simplify later code. This also deletes the store 1121 // into GV. 1122 ReplaceUsesOfMallocWithGlobal(MI, GV); 1123 1124 // Okay, at this point, there are no users of the malloc. Insert N 1125 // new mallocs at the same place as MI, and N globals. 1126 std::vector<GlobalVariable*> FieldGlobals; 1127 std::vector<MallocInst*> FieldMallocs; 1128 1129 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1130 const Type *FieldTy = STy->getElementType(FieldNo); 1131 const Type *PFieldTy = PointerType::getUnqual(FieldTy); 1132 1133 GlobalVariable *NGV = 1134 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, 1135 Constant::getNullValue(PFieldTy), 1136 GV->getName() + ".f" + utostr(FieldNo), GV, 1137 GV->isThreadLocal()); 1138 FieldGlobals.push_back(NGV); 1139 1140 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), 1141 MI->getName() + ".f" + utostr(FieldNo),MI); 1142 FieldMallocs.push_back(NMI); 1143 new StoreInst(NMI, NGV, MI); 1144 } 1145 1146 // The tricky aspect of this transformation is handling the case when malloc 1147 // fails. In the original code, malloc failing would set the result pointer 1148 // of malloc to null. In this case, some mallocs could succeed and others 1149 // could fail. As such, we emit code that looks like this: 1150 // F0 = malloc(field0) 1151 // F1 = malloc(field1) 1152 // F2 = malloc(field2) 1153 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1154 // if (F0) { free(F0); F0 = 0; } 1155 // if (F1) { free(F1); F1 = 0; } 1156 // if (F2) { free(F2); F2 = 0; } 1157 // } 1158 Value *RunningOr = 0; 1159 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1160 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], 1161 Constant::getNullValue(FieldMallocs[i]->getType()), 1162 "isnull", MI); 1163 if (!RunningOr) 1164 RunningOr = Cond; // First seteq 1165 else 1166 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI); 1167 } 1168 1169 // Split the basic block at the old malloc. 1170 BasicBlock *OrigBB = MI->getParent(); 1171 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont"); 1172 1173 // Create the block to check the first condition. Put all these blocks at the 1174 // end of the function as they are unlikely to be executed. 1175 BasicBlock *NullPtrBlock = new BasicBlock("malloc_ret_null", 1176 OrigBB->getParent()); 1177 1178 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1179 // branch on RunningOr. 1180 OrigBB->getTerminator()->eraseFromParent(); 1181 new BranchInst(NullPtrBlock, ContBB, RunningOr, OrigBB); 1182 1183 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1184 // pointer, because some may be null while others are not. 1185 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1186 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1187 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal, 1188 Constant::getNullValue(GVVal->getType()), 1189 "tmp", NullPtrBlock); 1190 BasicBlock *FreeBlock = new BasicBlock("free_it", OrigBB->getParent()); 1191 BasicBlock *NextBlock = new BasicBlock("next", OrigBB->getParent()); 1192 new BranchInst(FreeBlock, NextBlock, Cmp, NullPtrBlock); 1193 1194 // Fill in FreeBlock. 1195 new FreeInst(GVVal, FreeBlock); 1196 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1197 FreeBlock); 1198 new BranchInst(NextBlock, FreeBlock); 1199 1200 NullPtrBlock = NextBlock; 1201 } 1202 1203 new BranchInst(ContBB, NullPtrBlock); 1204 1205 1206 // MI is no longer needed, remove it. 1207 MI->eraseFromParent(); 1208 1209 1210 // Okay, the malloc site is completely handled. All of the uses of GV are now 1211 // loads, and all uses of those loads are simple. Rewrite them to use loads 1212 // of the per-field globals instead. 1213 while (!GV->use_empty()) { 1214 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 1215 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals); 1216 LI->eraseFromParent(); 1217 } else { 1218 // Must be a store of null. 1219 StoreInst *SI = cast<StoreInst>(GV->use_back()); 1220 assert(isa<Constant>(SI->getOperand(0)) && 1221 cast<Constant>(SI->getOperand(0))->isNullValue() && 1222 "Unexpected heap-sra user!"); 1223 1224 // Insert a store of null into each global. 1225 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1226 Constant *Null = 1227 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType()); 1228 new StoreInst(Null, FieldGlobals[i], SI); 1229 } 1230 // Erase the original store. 1231 SI->eraseFromParent(); 1232 } 1233 } 1234 1235 // The old global is now dead, remove it. 1236 GV->eraseFromParent(); 1237 1238 ++NumHeapSRA; 1239 return FieldGlobals[0]; 1240} 1241 1242 1243// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1244// that only one value (besides its initializer) is ever stored to the global. 1245static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1246 Module::global_iterator &GVI, 1247 TargetData &TD) { 1248 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal)) 1249 StoredOnceVal = CI->getOperand(0); 1250 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){ 1251 // "getelementptr Ptr, 0, 0, 0" is really just a cast. 1252 bool IsJustACast = true; 1253 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 1254 if (!isa<Constant>(GEPI->getOperand(i)) || 1255 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) { 1256 IsJustACast = false; 1257 break; 1258 } 1259 if (IsJustACast) 1260 StoredOnceVal = GEPI->getOperand(0); 1261 } 1262 1263 // If we are dealing with a pointer global that is initialized to null and 1264 // only has one (non-null) value stored into it, then we can optimize any 1265 // users of the loaded value (often calls and loads) that would trap if the 1266 // value was null. 1267 if (isa<PointerType>(GV->getInitializer()->getType()) && 1268 GV->getInitializer()->isNullValue()) { 1269 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1270 if (GV->getInitializer()->getType() != SOVC->getType()) 1271 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1272 1273 // Optimize away any trapping uses of the loaded value. 1274 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC)) 1275 return true; 1276 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { 1277 // If this is a malloc of an abstract type, don't touch it. 1278 if (!MI->getAllocatedType()->isSized()) 1279 return false; 1280 1281 // We can't optimize this global unless all uses of it are *known* to be 1282 // of the malloc value, not of the null initializer value (consider a use 1283 // that compares the global's value against zero to see if the malloc has 1284 // been reached). To do this, we check to see if all uses of the global 1285 // would trap if the global were null: this proves that they must all 1286 // happen after the malloc. 1287 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1288 return false; 1289 1290 // We can't optimize this if the malloc itself is used in a complex way, 1291 // for example, being stored into multiple globals. This allows the 1292 // malloc to be stored into the specified global, loaded setcc'd, and 1293 // GEP'd. These are all things we could transform to using the global 1294 // for. 1295 { 1296 SmallPtrSet<PHINode*, 8> PHIs; 1297 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs)) 1298 return false; 1299 } 1300 1301 1302 // If we have a global that is only initialized with a fixed size malloc, 1303 // transform the program to use global memory instead of malloc'd memory. 1304 // This eliminates dynamic allocation, avoids an indirection accessing the 1305 // data, and exposes the resultant global to further GlobalOpt. 1306 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { 1307 // Restrict this transformation to only working on small allocations 1308 // (2048 bytes currently), as we don't want to introduce a 16M global or 1309 // something. 1310 if (NElements->getZExtValue()* 1311 TD.getABITypeSize(MI->getAllocatedType()) < 2048) { 1312 GVI = OptimizeGlobalAddressOfMalloc(GV, MI); 1313 return true; 1314 } 1315 } 1316 1317 // If the allocation is an array of structures, consider transforming this 1318 // into multiple malloc'd arrays, one for each field. This is basically 1319 // SRoA for malloc'd memory. 1320 if (const StructType *AllocTy = 1321 dyn_cast<StructType>(MI->getAllocatedType())) { 1322 // This the structure has an unreasonable number of fields, leave it 1323 // alone. 1324 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 && 1325 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { 1326 GVI = PerformHeapAllocSRoA(GV, MI); 1327 return true; 1328 } 1329 } 1330 } 1331 } 1332 1333 return false; 1334} 1335 1336/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1337/// two values ever stored into GV are its initializer and OtherVal. See if we 1338/// can shrink the global into a boolean and select between the two values 1339/// whenever it is used. This exposes the values to other scalar optimizations. 1340static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1341 const Type *GVElType = GV->getType()->getElementType(); 1342 1343 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1344 // an FP value or vector, don't do this optimization because a select between 1345 // them is very expensive and unlikely to lead to later simplification. 1346 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || 1347 isa<VectorType>(GVElType)) 1348 return false; 1349 1350 // Walk the use list of the global seeing if all the uses are load or store. 1351 // If there is anything else, bail out. 1352 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I) 1353 if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) 1354 return false; 1355 1356 DOUT << " *** SHRINKING TO BOOL: " << *GV; 1357 1358 // Create the new global, initializing it to false. 1359 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, 1360 GlobalValue::InternalLinkage, ConstantInt::getFalse(), 1361 GV->getName()+".b", 1362 (Module *)NULL, 1363 GV->isThreadLocal()); 1364 GV->getParent()->getGlobalList().insert(GV, NewGV); 1365 1366 Constant *InitVal = GV->getInitializer(); 1367 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!"); 1368 1369 // If initialized to zero and storing one into the global, we can use a cast 1370 // instead of a select to synthesize the desired value. 1371 bool IsOneZero = false; 1372 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1373 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1374 1375 while (!GV->use_empty()) { 1376 Instruction *UI = cast<Instruction>(GV->use_back()); 1377 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1378 // Change the store into a boolean store. 1379 bool StoringOther = SI->getOperand(0) == OtherVal; 1380 // Only do this if we weren't storing a loaded value. 1381 Value *StoreVal; 1382 if (StoringOther || SI->getOperand(0) == InitVal) 1383 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther); 1384 else { 1385 // Otherwise, we are storing a previously loaded copy. To do this, 1386 // change the copy from copying the original value to just copying the 1387 // bool. 1388 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1389 1390 // If we're already replaced the input, StoredVal will be a cast or 1391 // select instruction. If not, it will be a load of the original 1392 // global. 1393 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1394 assert(LI->getOperand(0) == GV && "Not a copy!"); 1395 // Insert a new load, to preserve the saved value. 1396 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI); 1397 } else { 1398 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1399 "This is not a form that we understand!"); 1400 StoreVal = StoredVal->getOperand(0); 1401 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1402 } 1403 } 1404 new StoreInst(StoreVal, NewGV, SI); 1405 } else { 1406 // Change the load into a load of bool then a select. 1407 LoadInst *LI = cast<LoadInst>(UI); 1408 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI); 1409 Value *NSI; 1410 if (IsOneZero) 1411 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1412 else 1413 NSI = new SelectInst(NLI, OtherVal, InitVal, "", LI); 1414 NSI->takeName(LI); 1415 LI->replaceAllUsesWith(NSI); 1416 } 1417 UI->eraseFromParent(); 1418 } 1419 1420 GV->eraseFromParent(); 1421 return true; 1422} 1423 1424 1425/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1426/// it if possible. If we make a change, return true. 1427bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1428 Module::global_iterator &GVI) { 1429 std::set<PHINode*> PHIUsers; 1430 GlobalStatus GS; 1431 GV->removeDeadConstantUsers(); 1432 1433 if (GV->use_empty()) { 1434 DOUT << "GLOBAL DEAD: " << *GV; 1435 GV->eraseFromParent(); 1436 ++NumDeleted; 1437 return true; 1438 } 1439 1440 if (!AnalyzeGlobal(GV, GS, PHIUsers)) { 1441#if 0 1442 cerr << "Global: " << *GV; 1443 cerr << " isLoaded = " << GS.isLoaded << "\n"; 1444 cerr << " StoredType = "; 1445 switch (GS.StoredType) { 1446 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; 1447 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; 1448 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; 1449 case GlobalStatus::isStored: cerr << "stored\n"; break; 1450 } 1451 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) 1452 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; 1453 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) 1454 cerr << " AccessingFunction = " << GS.AccessingFunction->getName() 1455 << "\n"; 1456 cerr << " HasMultipleAccessingFunctions = " 1457 << GS.HasMultipleAccessingFunctions << "\n"; 1458 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; 1459 cerr << "\n"; 1460#endif 1461 1462 // If this is a first class global and has only one accessing function 1463 // and this function is main (which we know is not recursive we can make 1464 // this global a local variable) we replace the global with a local alloca 1465 // in this function. 1466 // 1467 // NOTE: It doesn't make sense to promote non first class types since we 1468 // are just replacing static memory to stack memory. 1469 if (!GS.HasMultipleAccessingFunctions && 1470 GS.AccessingFunction && !GS.HasNonInstructionUser && 1471 GV->getType()->getElementType()->isFirstClassType() && 1472 GS.AccessingFunction->getName() == "main" && 1473 GS.AccessingFunction->hasExternalLinkage()) { 1474 DOUT << "LOCALIZING GLOBAL: " << *GV; 1475 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); 1476 const Type* ElemTy = GV->getType()->getElementType(); 1477 // FIXME: Pass Global's alignment when globals have alignment 1478 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI); 1479 if (!isa<UndefValue>(GV->getInitializer())) 1480 new StoreInst(GV->getInitializer(), Alloca, FirstI); 1481 1482 GV->replaceAllUsesWith(Alloca); 1483 GV->eraseFromParent(); 1484 ++NumLocalized; 1485 return true; 1486 } 1487 1488 // If the global is never loaded (but may be stored to), it is dead. 1489 // Delete it now. 1490 if (!GS.isLoaded) { 1491 DOUT << "GLOBAL NEVER LOADED: " << *GV; 1492 1493 // Delete any stores we can find to the global. We may not be able to 1494 // make it completely dead though. 1495 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1496 1497 // If the global is dead now, delete it. 1498 if (GV->use_empty()) { 1499 GV->eraseFromParent(); 1500 ++NumDeleted; 1501 Changed = true; 1502 } 1503 return Changed; 1504 1505 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1506 DOUT << "MARKING CONSTANT: " << *GV; 1507 GV->setConstant(true); 1508 1509 // Clean up any obviously simplifiable users now. 1510 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1511 1512 // If the global is dead now, just nuke it. 1513 if (GV->use_empty()) { 1514 DOUT << " *** Marking constant allowed us to simplify " 1515 << "all users and delete global!\n"; 1516 GV->eraseFromParent(); 1517 ++NumDeleted; 1518 } 1519 1520 ++NumMarked; 1521 return true; 1522 } else if (!GV->getInitializer()->getType()->isFirstClassType()) { 1523 if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) { 1524 GVI = FirstNewGV; // Don't skip the newly produced globals! 1525 return true; 1526 } 1527 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 1528 // If the initial value for the global was an undef value, and if only 1529 // one other value was stored into it, we can just change the 1530 // initializer to be an undef value, then delete all stores to the 1531 // global. This allows us to mark it constant. 1532 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1533 if (isa<UndefValue>(GV->getInitializer())) { 1534 // Change the initial value here. 1535 GV->setInitializer(SOVConstant); 1536 1537 // Clean up any obviously simplifiable users now. 1538 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1539 1540 if (GV->use_empty()) { 1541 DOUT << " *** Substituting initializer allowed us to " 1542 << "simplify all users and delete global!\n"; 1543 GV->eraseFromParent(); 1544 ++NumDeleted; 1545 } else { 1546 GVI = GV; 1547 } 1548 ++NumSubstitute; 1549 return true; 1550 } 1551 1552 // Try to optimize globals based on the knowledge that only one value 1553 // (besides its initializer) is ever stored to the global. 1554 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, 1555 getAnalysis<TargetData>())) 1556 return true; 1557 1558 // Otherwise, if the global was not a boolean, we can shrink it to be a 1559 // boolean. 1560 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1561 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 1562 ++NumShrunkToBool; 1563 return true; 1564 } 1565 } 1566 } 1567 return false; 1568} 1569 1570/// OnlyCalledDirectly - Return true if the specified function is only called 1571/// directly. In other words, its address is never taken. 1572static bool OnlyCalledDirectly(Function *F) { 1573 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1574 Instruction *User = dyn_cast<Instruction>(*UI); 1575 if (!User) return false; 1576 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; 1577 1578 // See if the function address is passed as an argument. 1579 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i) 1580 if (User->getOperand(i) == F) return false; 1581 } 1582 return true; 1583} 1584 1585/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 1586/// function, changing them to FastCC. 1587static void ChangeCalleesToFastCall(Function *F) { 1588 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1589 CallSite User(cast<Instruction>(*UI)); 1590 User.setCallingConv(CallingConv::Fast); 1591 } 1592} 1593 1594static PAListPtr StripNest(const PAListPtr &Attrs) { 1595 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { 1596 if ((Attrs.getSlot(i).Attrs & ParamAttr::Nest) == 0) 1597 continue; 1598 1599 // There can be only one. 1600 return Attrs.removeAttr(Attrs.getSlot(i).Index, ParamAttr::Nest); 1601 } 1602 1603 return Attrs; 1604} 1605 1606static void RemoveNestAttribute(Function *F) { 1607 F->setParamAttrs(StripNest(F->getParamAttrs())); 1608 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1609 CallSite User(cast<Instruction>(*UI)); 1610 User.setParamAttrs(StripNest(User.getParamAttrs())); 1611 } 1612} 1613 1614bool GlobalOpt::OptimizeFunctions(Module &M) { 1615 bool Changed = false; 1616 // Optimize functions. 1617 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 1618 Function *F = FI++; 1619 F->removeDeadConstantUsers(); 1620 if (F->use_empty() && (F->hasInternalLinkage() || 1621 F->hasLinkOnceLinkage())) { 1622 M.getFunctionList().erase(F); 1623 Changed = true; 1624 ++NumFnDeleted; 1625 } else if (F->hasInternalLinkage()) { 1626 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 1627 OnlyCalledDirectly(F)) { 1628 // If this function has C calling conventions, is not a varargs 1629 // function, and is only called directly, promote it to use the Fast 1630 // calling convention. 1631 F->setCallingConv(CallingConv::Fast); 1632 ChangeCalleesToFastCall(F); 1633 ++NumFastCallFns; 1634 Changed = true; 1635 } 1636 1637 if (F->getParamAttrs().hasAttrSomewhere(ParamAttr::Nest) && 1638 OnlyCalledDirectly(F)) { 1639 // The function is not used by a trampoline intrinsic, so it is safe 1640 // to remove the 'nest' attribute. 1641 RemoveNestAttribute(F); 1642 ++NumNestRemoved; 1643 Changed = true; 1644 } 1645 } 1646 } 1647 return Changed; 1648} 1649 1650bool GlobalOpt::OptimizeGlobalVars(Module &M) { 1651 bool Changed = false; 1652 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 1653 GVI != E; ) { 1654 GlobalVariable *GV = GVI++; 1655 if (!GV->isConstant() && GV->hasInternalLinkage() && 1656 GV->hasInitializer()) 1657 Changed |= ProcessInternalGlobal(GV, GVI); 1658 } 1659 return Changed; 1660} 1661 1662/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all 1663/// initializers have an init priority of 65535. 1664GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 1665 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 1666 I != E; ++I) 1667 if (I->getName() == "llvm.global_ctors") { 1668 // Found it, verify it's an array of { int, void()* }. 1669 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); 1670 if (!ATy) return 0; 1671 const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); 1672 if (!STy || STy->getNumElements() != 2 || 1673 STy->getElementType(0) != Type::Int32Ty) return 0; 1674 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); 1675 if (!PFTy) return 0; 1676 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); 1677 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || 1678 FTy->getNumParams() != 0) 1679 return 0; 1680 1681 // Verify that the initializer is simple enough for us to handle. 1682 if (!I->hasInitializer()) return 0; 1683 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); 1684 if (!CA) return 0; 1685 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1686 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) { 1687 if (isa<ConstantPointerNull>(CS->getOperand(1))) 1688 continue; 1689 1690 // Must have a function or null ptr. 1691 if (!isa<Function>(CS->getOperand(1))) 1692 return 0; 1693 1694 // Init priority must be standard. 1695 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0)); 1696 if (!CI || CI->getZExtValue() != 65535) 1697 return 0; 1698 } else { 1699 return 0; 1700 } 1701 1702 return I; 1703 } 1704 return 0; 1705} 1706 1707/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 1708/// return a list of the functions and null terminator as a vector. 1709static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 1710 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1711 std::vector<Function*> Result; 1712 Result.reserve(CA->getNumOperands()); 1713 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) { 1714 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i)); 1715 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 1716 } 1717 return Result; 1718} 1719 1720/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 1721/// specified array, returning the new global to use. 1722static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 1723 const std::vector<Function*> &Ctors) { 1724 // If we made a change, reassemble the initializer list. 1725 std::vector<Constant*> CSVals; 1726 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); 1727 CSVals.push_back(0); 1728 1729 // Create the new init list. 1730 std::vector<Constant*> CAList; 1731 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 1732 if (Ctors[i]) { 1733 CSVals[1] = Ctors[i]; 1734 } else { 1735 const Type *FTy = FunctionType::get(Type::VoidTy, 1736 std::vector<const Type*>(), false); 1737 const PointerType *PFTy = PointerType::getUnqual(FTy); 1738 CSVals[1] = Constant::getNullValue(PFTy); 1739 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); 1740 } 1741 CAList.push_back(ConstantStruct::get(CSVals)); 1742 } 1743 1744 // Create the array initializer. 1745 const Type *StructTy = 1746 cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); 1747 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()), 1748 CAList); 1749 1750 // If we didn't change the number of elements, don't create a new GV. 1751 if (CA->getType() == GCL->getInitializer()->getType()) { 1752 GCL->setInitializer(CA); 1753 return GCL; 1754 } 1755 1756 // Create the new global and insert it next to the existing list. 1757 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 1758 GCL->getLinkage(), CA, "", 1759 (Module *)NULL, 1760 GCL->isThreadLocal()); 1761 GCL->getParent()->getGlobalList().insert(GCL, NGV); 1762 NGV->takeName(GCL); 1763 1764 // Nuke the old list, replacing any uses with the new one. 1765 if (!GCL->use_empty()) { 1766 Constant *V = NGV; 1767 if (V->getType() != GCL->getType()) 1768 V = ConstantExpr::getBitCast(V, GCL->getType()); 1769 GCL->replaceAllUsesWith(V); 1770 } 1771 GCL->eraseFromParent(); 1772 1773 if (Ctors.size()) 1774 return NGV; 1775 else 1776 return 0; 1777} 1778 1779 1780static Constant *getVal(std::map<Value*, Constant*> &ComputedValues, 1781 Value *V) { 1782 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 1783 Constant *R = ComputedValues[V]; 1784 assert(R && "Reference to an uncomputed value!"); 1785 return R; 1786} 1787 1788/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 1789/// enough for us to understand. In particular, if it is a cast of something, 1790/// we punt. We basically just support direct accesses to globals and GEP's of 1791/// globals. This should be kept up to date with CommitValueTo. 1792static bool isSimpleEnoughPointerToCommit(Constant *C) { 1793 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 1794 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1795 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1796 return !GV->isDeclaration(); // reject external globals. 1797 } 1798 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 1799 // Handle a constantexpr gep. 1800 if (CE->getOpcode() == Instruction::GetElementPtr && 1801 isa<GlobalVariable>(CE->getOperand(0))) { 1802 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1803 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1804 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1805 return GV->hasInitializer() && 1806 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1807 } 1808 return false; 1809} 1810 1811/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 1812/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 1813/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 1814static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 1815 ConstantExpr *Addr, unsigned OpNo) { 1816 // Base case of the recursion. 1817 if (OpNo == Addr->getNumOperands()) { 1818 assert(Val->getType() == Init->getType() && "Type mismatch!"); 1819 return Val; 1820 } 1821 1822 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { 1823 std::vector<Constant*> Elts; 1824 1825 // Break up the constant into its elements. 1826 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { 1827 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i) 1828 Elts.push_back(CS->getOperand(i)); 1829 } else if (isa<ConstantAggregateZero>(Init)) { 1830 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1831 Elts.push_back(Constant::getNullValue(STy->getElementType(i))); 1832 } else if (isa<UndefValue>(Init)) { 1833 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1834 Elts.push_back(UndefValue::get(STy->getElementType(i))); 1835 } else { 1836 assert(0 && "This code is out of sync with " 1837 " ConstantFoldLoadThroughGEPConstantExpr"); 1838 } 1839 1840 // Replace the element that we are supposed to. 1841 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 1842 unsigned Idx = CU->getZExtValue(); 1843 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 1844 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 1845 1846 // Return the modified struct. 1847 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked()); 1848 } else { 1849 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 1850 const ArrayType *ATy = cast<ArrayType>(Init->getType()); 1851 1852 // Break up the array into elements. 1853 std::vector<Constant*> Elts; 1854 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { 1855 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1856 Elts.push_back(CA->getOperand(i)); 1857 } else if (isa<ConstantAggregateZero>(Init)) { 1858 Constant *Elt = Constant::getNullValue(ATy->getElementType()); 1859 Elts.assign(ATy->getNumElements(), Elt); 1860 } else if (isa<UndefValue>(Init)) { 1861 Constant *Elt = UndefValue::get(ATy->getElementType()); 1862 Elts.assign(ATy->getNumElements(), Elt); 1863 } else { 1864 assert(0 && "This code is out of sync with " 1865 " ConstantFoldLoadThroughGEPConstantExpr"); 1866 } 1867 1868 assert(CI->getZExtValue() < ATy->getNumElements()); 1869 Elts[CI->getZExtValue()] = 1870 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 1871 return ConstantArray::get(ATy, Elts); 1872 } 1873} 1874 1875/// CommitValueTo - We have decided that Addr (which satisfies the predicate 1876/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 1877static void CommitValueTo(Constant *Val, Constant *Addr) { 1878 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 1879 assert(GV->hasInitializer()); 1880 GV->setInitializer(Val); 1881 return; 1882 } 1883 1884 ConstantExpr *CE = cast<ConstantExpr>(Addr); 1885 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1886 1887 Constant *Init = GV->getInitializer(); 1888 Init = EvaluateStoreInto(Init, Val, CE, 2); 1889 GV->setInitializer(Init); 1890} 1891 1892/// ComputeLoadResult - Return the value that would be computed by a load from 1893/// P after the stores reflected by 'memory' have been performed. If we can't 1894/// decide, return null. 1895static Constant *ComputeLoadResult(Constant *P, 1896 const std::map<Constant*, Constant*> &Memory) { 1897 // If this memory location has been recently stored, use the stored value: it 1898 // is the most up-to-date. 1899 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P); 1900 if (I != Memory.end()) return I->second; 1901 1902 // Access it. 1903 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 1904 if (GV->hasInitializer()) 1905 return GV->getInitializer(); 1906 return 0; 1907 } 1908 1909 // Handle a constantexpr getelementptr. 1910 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 1911 if (CE->getOpcode() == Instruction::GetElementPtr && 1912 isa<GlobalVariable>(CE->getOperand(0))) { 1913 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1914 if (GV->hasInitializer()) 1915 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1916 } 1917 1918 return 0; // don't know how to evaluate. 1919} 1920 1921/// EvaluateFunction - Evaluate a call to function F, returning true if 1922/// successful, false if we can't evaluate it. ActualArgs contains the formal 1923/// arguments for the function. 1924static bool EvaluateFunction(Function *F, Constant *&RetVal, 1925 const std::vector<Constant*> &ActualArgs, 1926 std::vector<Function*> &CallStack, 1927 std::map<Constant*, Constant*> &MutatedMemory, 1928 std::vector<GlobalVariable*> &AllocaTmps) { 1929 // Check to see if this function is already executing (recursion). If so, 1930 // bail out. TODO: we might want to accept limited recursion. 1931 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 1932 return false; 1933 1934 CallStack.push_back(F); 1935 1936 /// Values - As we compute SSA register values, we store their contents here. 1937 std::map<Value*, Constant*> Values; 1938 1939 // Initialize arguments to the incoming values specified. 1940 unsigned ArgNo = 0; 1941 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 1942 ++AI, ++ArgNo) 1943 Values[AI] = ActualArgs[ArgNo]; 1944 1945 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 1946 /// we can only evaluate any one basic block at most once. This set keeps 1947 /// track of what we have executed so we can detect recursive cases etc. 1948 std::set<BasicBlock*> ExecutedBlocks; 1949 1950 // CurInst - The current instruction we're evaluating. 1951 BasicBlock::iterator CurInst = F->begin()->begin(); 1952 1953 // This is the main evaluation loop. 1954 while (1) { 1955 Constant *InstResult = 0; 1956 1957 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 1958 if (SI->isVolatile()) return false; // no volatile accesses. 1959 Constant *Ptr = getVal(Values, SI->getOperand(1)); 1960 if (!isSimpleEnoughPointerToCommit(Ptr)) 1961 // If this is too complex for us to commit, reject it. 1962 return false; 1963 Constant *Val = getVal(Values, SI->getOperand(0)); 1964 MutatedMemory[Ptr] = Val; 1965 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 1966 InstResult = ConstantExpr::get(BO->getOpcode(), 1967 getVal(Values, BO->getOperand(0)), 1968 getVal(Values, BO->getOperand(1))); 1969 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 1970 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 1971 getVal(Values, CI->getOperand(0)), 1972 getVal(Values, CI->getOperand(1))); 1973 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 1974 InstResult = ConstantExpr::getCast(CI->getOpcode(), 1975 getVal(Values, CI->getOperand(0)), 1976 CI->getType()); 1977 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 1978 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), 1979 getVal(Values, SI->getOperand(1)), 1980 getVal(Values, SI->getOperand(2))); 1981 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 1982 Constant *P = getVal(Values, GEP->getOperand(0)); 1983 SmallVector<Constant*, 8> GEPOps; 1984 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 1985 GEPOps.push_back(getVal(Values, GEP->getOperand(i))); 1986 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); 1987 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 1988 if (LI->isVolatile()) return false; // no volatile accesses. 1989 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), 1990 MutatedMemory); 1991 if (InstResult == 0) return false; // Could not evaluate load. 1992 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 1993 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 1994 const Type *Ty = AI->getType()->getElementType(); 1995 AllocaTmps.push_back(new GlobalVariable(Ty, false, 1996 GlobalValue::InternalLinkage, 1997 UndefValue::get(Ty), 1998 AI->getName())); 1999 InstResult = AllocaTmps.back(); 2000 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { 2001 // Cannot handle inline asm. 2002 if (isa<InlineAsm>(CI->getOperand(0))) return false; 2003 2004 // Resolve function pointers. 2005 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); 2006 if (!Callee) return false; // Cannot resolve. 2007 2008 std::vector<Constant*> Formals; 2009 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i) 2010 Formals.push_back(getVal(Values, CI->getOperand(i))); 2011 2012 if (Callee->isDeclaration()) { 2013 // If this is a function we can constant fold, do it. 2014 if (Constant *C = ConstantFoldCall(Callee, &Formals[0], 2015 Formals.size())) { 2016 InstResult = C; 2017 } else { 2018 return false; 2019 } 2020 } else { 2021 if (Callee->getFunctionType()->isVarArg()) 2022 return false; 2023 2024 Constant *RetVal; 2025 2026 // Execute the call, if successful, use the return value. 2027 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, 2028 MutatedMemory, AllocaTmps)) 2029 return false; 2030 InstResult = RetVal; 2031 } 2032 } else if (isa<TerminatorInst>(CurInst)) { 2033 BasicBlock *NewBB = 0; 2034 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2035 if (BI->isUnconditional()) { 2036 NewBB = BI->getSuccessor(0); 2037 } else { 2038 ConstantInt *Cond = 2039 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); 2040 if (!Cond) return false; // Cannot determine. 2041 2042 NewBB = BI->getSuccessor(!Cond->getZExtValue()); 2043 } 2044 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2045 ConstantInt *Val = 2046 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); 2047 if (!Val) return false; // Cannot determine. 2048 NewBB = SI->getSuccessor(SI->findCaseValue(Val)); 2049 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { 2050 if (RI->getNumOperands()) 2051 RetVal = getVal(Values, RI->getOperand(0)); 2052 2053 CallStack.pop_back(); // return from fn. 2054 return true; // We succeeded at evaluating this ctor! 2055 } else { 2056 // invoke, unwind, unreachable. 2057 return false; // Cannot handle this terminator. 2058 } 2059 2060 // Okay, we succeeded in evaluating this control flow. See if we have 2061 // executed the new block before. If so, we have a looping function, 2062 // which we cannot evaluate in reasonable time. 2063 if (!ExecutedBlocks.insert(NewBB).second) 2064 return false; // looped! 2065 2066 // Okay, we have never been in this block before. Check to see if there 2067 // are any PHI nodes. If so, evaluate them with information about where 2068 // we came from. 2069 BasicBlock *OldBB = CurInst->getParent(); 2070 CurInst = NewBB->begin(); 2071 PHINode *PN; 2072 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2073 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); 2074 2075 // Do NOT increment CurInst. We know that the terminator had no value. 2076 continue; 2077 } else { 2078 // Did not know how to evaluate this! 2079 return false; 2080 } 2081 2082 if (!CurInst->use_empty()) 2083 Values[CurInst] = InstResult; 2084 2085 // Advance program counter. 2086 ++CurInst; 2087 } 2088} 2089 2090/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2091/// we can. Return true if we can, false otherwise. 2092static bool EvaluateStaticConstructor(Function *F) { 2093 /// MutatedMemory - For each store we execute, we update this map. Loads 2094 /// check this to get the most up-to-date value. If evaluation is successful, 2095 /// this state is committed to the process. 2096 std::map<Constant*, Constant*> MutatedMemory; 2097 2098 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2099 /// to represent its body. This vector is needed so we can delete the 2100 /// temporary globals when we are done. 2101 std::vector<GlobalVariable*> AllocaTmps; 2102 2103 /// CallStack - This is used to detect recursion. In pathological situations 2104 /// we could hit exponential behavior, but at least there is nothing 2105 /// unbounded. 2106 std::vector<Function*> CallStack; 2107 2108 // Call the function. 2109 Constant *RetValDummy; 2110 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), 2111 CallStack, MutatedMemory, AllocaTmps); 2112 if (EvalSuccess) { 2113 // We succeeded at evaluation: commit the result. 2114 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2115 << F->getName() << "' to " << MutatedMemory.size() 2116 << " stores.\n"; 2117 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(), 2118 E = MutatedMemory.end(); I != E; ++I) 2119 CommitValueTo(I->second, I->first); 2120 } 2121 2122 // At this point, we are done interpreting. If we created any 'alloca' 2123 // temporaries, release them now. 2124 while (!AllocaTmps.empty()) { 2125 GlobalVariable *Tmp = AllocaTmps.back(); 2126 AllocaTmps.pop_back(); 2127 2128 // If there are still users of the alloca, the program is doing something 2129 // silly, e.g. storing the address of the alloca somewhere and using it 2130 // later. Since this is undefined, we'll just make it be null. 2131 if (!Tmp->use_empty()) 2132 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2133 delete Tmp; 2134 } 2135 2136 return EvalSuccess; 2137} 2138 2139 2140 2141/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2142/// Return true if anything changed. 2143bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2144 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2145 bool MadeChange = false; 2146 if (Ctors.empty()) return false; 2147 2148 // Loop over global ctors, optimizing them when we can. 2149 for (unsigned i = 0; i != Ctors.size(); ++i) { 2150 Function *F = Ctors[i]; 2151 // Found a null terminator in the middle of the list, prune off the rest of 2152 // the list. 2153 if (F == 0) { 2154 if (i != Ctors.size()-1) { 2155 Ctors.resize(i+1); 2156 MadeChange = true; 2157 } 2158 break; 2159 } 2160 2161 // We cannot simplify external ctor functions. 2162 if (F->empty()) continue; 2163 2164 // If we can evaluate the ctor at compile time, do. 2165 if (EvaluateStaticConstructor(F)) { 2166 Ctors.erase(Ctors.begin()+i); 2167 MadeChange = true; 2168 --i; 2169 ++NumCtorsEvaluated; 2170 continue; 2171 } 2172 } 2173 2174 if (!MadeChange) return false; 2175 2176 GCL = InstallGlobalCtors(GCL, Ctors); 2177 return true; 2178} 2179 2180 2181bool GlobalOpt::runOnModule(Module &M) { 2182 bool Changed = false; 2183 2184 // Try to find the llvm.globalctors list. 2185 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 2186 2187 bool LocalChange = true; 2188 while (LocalChange) { 2189 LocalChange = false; 2190 2191 // Delete functions that are trivially dead, ccc -> fastcc 2192 LocalChange |= OptimizeFunctions(M); 2193 2194 // Optimize global_ctors list. 2195 if (GlobalCtors) 2196 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 2197 2198 // Optimize non-address-taken globals. 2199 LocalChange |= OptimizeGlobalVars(M); 2200 Changed |= LocalChange; 2201 } 2202 2203 // TODO: Move all global ctors functions to the end of the module for code 2204 // layout. 2205 2206 return Changed; 2207} 2208