GlobalOpt.cpp revision 20846274a7f535146b327141c523befa40c727de
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/Support/MathExtras.h" 32#include "llvm/ADT/SmallPtrSet.h" 33#include "llvm/ADT/SmallVector.h" 34#include "llvm/ADT/Statistic.h" 35#include "llvm/ADT/StringExtras.h" 36#include <algorithm> 37#include <map> 38#include <set> 39using namespace llvm; 40 41STATISTIC(NumMarked , "Number of globals marked constant"); 42STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); 43STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); 44STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); 45STATISTIC(NumDeleted , "Number of globals deleted"); 46STATISTIC(NumFnDeleted , "Number of functions deleted"); 47STATISTIC(NumGlobUses , "Number of global uses devirtualized"); 48STATISTIC(NumLocalized , "Number of globals localized"); 49STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); 50STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); 51STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); 52STATISTIC(NumNestRemoved , "Number of nest attributes removed"); 53 54namespace { 55 struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass { 56 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 57 AU.addRequired<TargetData>(); 58 } 59 static char ID; // Pass identification, replacement for typeid 60 GlobalOpt() : ModulePass((intptr_t)&ID) {} 61 62 bool runOnModule(Module &M); 63 64 private: 65 GlobalVariable *FindGlobalCtors(Module &M); 66 bool OptimizeFunctions(Module &M); 67 bool OptimizeGlobalVars(Module &M); 68 bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); 69 bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI); 70 }; 71 72 char GlobalOpt::ID = 0; 73 RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer"); 74} 75 76ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } 77 78/// GlobalStatus - As we analyze each global, keep track of some information 79/// about it. If we find out that the address of the global is taken, none of 80/// this info will be accurate. 81struct VISIBILITY_HIDDEN GlobalStatus { 82 /// isLoaded - True if the global is ever loaded. If the global isn't ever 83 /// loaded it can be deleted. 84 bool isLoaded; 85 86 /// StoredType - Keep track of what stores to the global look like. 87 /// 88 enum StoredType { 89 /// NotStored - There is no store to this global. It can thus be marked 90 /// constant. 91 NotStored, 92 93 /// isInitializerStored - This global is stored to, but the only thing 94 /// stored is the constant it was initialized with. This is only tracked 95 /// for scalar globals. 96 isInitializerStored, 97 98 /// isStoredOnce - This global is stored to, but only its initializer and 99 /// one other value is ever stored to it. If this global isStoredOnce, we 100 /// track the value stored to it in StoredOnceValue below. This is only 101 /// tracked for scalar globals. 102 isStoredOnce, 103 104 /// isStored - This global is stored to by multiple values or something else 105 /// that we cannot track. 106 isStored 107 } StoredType; 108 109 /// StoredOnceValue - If only one value (besides the initializer constant) is 110 /// ever stored to this global, keep track of what value it is. 111 Value *StoredOnceValue; 112 113 /// AccessingFunction/HasMultipleAccessingFunctions - These start out 114 /// null/false. When the first accessing function is noticed, it is recorded. 115 /// When a second different accessing function is noticed, 116 /// HasMultipleAccessingFunctions is set to true. 117 Function *AccessingFunction; 118 bool HasMultipleAccessingFunctions; 119 120 /// HasNonInstructionUser - Set to true if this global has a user that is not 121 /// an instruction (e.g. a constant expr or GV initializer). 122 bool HasNonInstructionUser; 123 124 /// HasPHIUser - Set to true if this global has a user that is a PHI node. 125 bool HasPHIUser; 126 127 GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0), 128 AccessingFunction(0), HasMultipleAccessingFunctions(false), 129 HasNonInstructionUser(false), HasPHIUser(false) {} 130}; 131 132 133 134/// ConstantIsDead - Return true if the specified constant is (transitively) 135/// dead. The constant may be used by other constants (e.g. constant arrays and 136/// constant exprs) as long as they are dead, but it cannot be used by anything 137/// else. 138static bool ConstantIsDead(Constant *C) { 139 if (isa<GlobalValue>(C)) return false; 140 141 for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI) 142 if (Constant *CU = dyn_cast<Constant>(*UI)) { 143 if (!ConstantIsDead(CU)) return false; 144 } else 145 return false; 146 return true; 147} 148 149 150/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus 151/// structure. If the global has its address taken, return true to indicate we 152/// can't do anything with it. 153/// 154static bool AnalyzeGlobal(Value *V, GlobalStatus &GS, 155 std::set<PHINode*> &PHIUsers) { 156 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 157 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) { 158 GS.HasNonInstructionUser = true; 159 160 if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; 161 162 } else if (Instruction *I = dyn_cast<Instruction>(*UI)) { 163 if (!GS.HasMultipleAccessingFunctions) { 164 Function *F = I->getParent()->getParent(); 165 if (GS.AccessingFunction == 0) 166 GS.AccessingFunction = F; 167 else if (GS.AccessingFunction != F) 168 GS.HasMultipleAccessingFunctions = true; 169 } 170 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 171 GS.isLoaded = true; 172 if (LI->isVolatile()) return true; // Don't hack on volatile loads. 173 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 174 // Don't allow a store OF the address, only stores TO the address. 175 if (SI->getOperand(0) == V) return true; 176 177 if (SI->isVolatile()) return true; // Don't hack on volatile stores. 178 179 // If this is a direct store to the global (i.e., the global is a scalar 180 // value, not an aggregate), keep more specific information about 181 // stores. 182 if (GS.StoredType != GlobalStatus::isStored) { 183 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){ 184 Value *StoredVal = SI->getOperand(0); 185 if (StoredVal == GV->getInitializer()) { 186 if (GS.StoredType < GlobalStatus::isInitializerStored) 187 GS.StoredType = GlobalStatus::isInitializerStored; 188 } else if (isa<LoadInst>(StoredVal) && 189 cast<LoadInst>(StoredVal)->getOperand(0) == GV) { 190 // G = G 191 if (GS.StoredType < GlobalStatus::isInitializerStored) 192 GS.StoredType = GlobalStatus::isInitializerStored; 193 } else if (GS.StoredType < GlobalStatus::isStoredOnce) { 194 GS.StoredType = GlobalStatus::isStoredOnce; 195 GS.StoredOnceValue = StoredVal; 196 } else if (GS.StoredType == GlobalStatus::isStoredOnce && 197 GS.StoredOnceValue == StoredVal) { 198 // noop. 199 } else { 200 GS.StoredType = GlobalStatus::isStored; 201 } 202 } else { 203 GS.StoredType = GlobalStatus::isStored; 204 } 205 } 206 } else if (isa<GetElementPtrInst>(I)) { 207 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 208 } else if (isa<SelectInst>(I)) { 209 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 210 } else if (PHINode *PN = dyn_cast<PHINode>(I)) { 211 // PHI nodes we can check just like select or GEP instructions, but we 212 // have to be careful about infinite recursion. 213 if (PHIUsers.insert(PN).second) // Not already visited. 214 if (AnalyzeGlobal(I, GS, PHIUsers)) return true; 215 GS.HasPHIUser = true; 216 } else if (isa<CmpInst>(I)) { 217 } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { 218 if (I->getOperand(1) == V) 219 GS.StoredType = GlobalStatus::isStored; 220 if (I->getOperand(2) == V) 221 GS.isLoaded = true; 222 } else if (isa<MemSetInst>(I)) { 223 assert(I->getOperand(1) == V && "Memset only takes one pointer!"); 224 GS.StoredType = GlobalStatus::isStored; 225 } else { 226 return true; // Any other non-load instruction might take address! 227 } 228 } else if (Constant *C = dyn_cast<Constant>(*UI)) { 229 GS.HasNonInstructionUser = true; 230 // We might have a dead and dangling constant hanging off of here. 231 if (!ConstantIsDead(C)) 232 return true; 233 } else { 234 GS.HasNonInstructionUser = true; 235 // Otherwise must be some other user. 236 return true; 237 } 238 239 return false; 240} 241 242static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { 243 ConstantInt *CI = dyn_cast<ConstantInt>(Idx); 244 if (!CI) return 0; 245 unsigned IdxV = CI->getZExtValue(); 246 247 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { 248 if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); 249 } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { 250 if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); 251 } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { 252 if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); 253 } else if (isa<ConstantAggregateZero>(Agg)) { 254 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 255 if (IdxV < STy->getNumElements()) 256 return Constant::getNullValue(STy->getElementType(IdxV)); 257 } else if (const SequentialType *STy = 258 dyn_cast<SequentialType>(Agg->getType())) { 259 return Constant::getNullValue(STy->getElementType()); 260 } 261 } else if (isa<UndefValue>(Agg)) { 262 if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { 263 if (IdxV < STy->getNumElements()) 264 return UndefValue::get(STy->getElementType(IdxV)); 265 } else if (const SequentialType *STy = 266 dyn_cast<SequentialType>(Agg->getType())) { 267 return UndefValue::get(STy->getElementType()); 268 } 269 } 270 return 0; 271} 272 273 274/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all 275/// users of the global, cleaning up the obvious ones. This is largely just a 276/// quick scan over the use list to clean up the easy and obvious cruft. This 277/// returns true if it made a change. 278static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) { 279 bool Changed = false; 280 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { 281 User *U = *UI++; 282 283 if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 284 if (Init) { 285 // Replace the load with the initializer. 286 LI->replaceAllUsesWith(Init); 287 LI->eraseFromParent(); 288 Changed = true; 289 } 290 } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 291 // Store must be unreachable or storing Init into the global. 292 SI->eraseFromParent(); 293 Changed = true; 294 } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { 295 if (CE->getOpcode() == Instruction::GetElementPtr) { 296 Constant *SubInit = 0; 297 if (Init) 298 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 299 Changed |= CleanupConstantGlobalUsers(CE, SubInit); 300 } else if (CE->getOpcode() == Instruction::BitCast && 301 isa<PointerType>(CE->getType())) { 302 // Pointer cast, delete any stores and memsets to the global. 303 Changed |= CleanupConstantGlobalUsers(CE, 0); 304 } 305 306 if (CE->use_empty()) { 307 CE->destroyConstant(); 308 Changed = true; 309 } 310 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 311 // Do not transform "gepinst (gep constexpr (GV))" here, because forming 312 // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold 313 // and will invalidate our notion of what Init is. 314 Constant *SubInit = 0; 315 if (!isa<ConstantExpr>(GEP->getOperand(0))) { 316 ConstantExpr *CE = 317 dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP)); 318 if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) 319 SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); 320 } 321 Changed |= CleanupConstantGlobalUsers(GEP, SubInit); 322 323 if (GEP->use_empty()) { 324 GEP->eraseFromParent(); 325 Changed = true; 326 } 327 } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv 328 if (MI->getRawDest() == V) { 329 MI->eraseFromParent(); 330 Changed = true; 331 } 332 333 } else if (Constant *C = dyn_cast<Constant>(U)) { 334 // If we have a chain of dead constantexprs or other things dangling from 335 // us, and if they are all dead, nuke them without remorse. 336 if (ConstantIsDead(C)) { 337 C->destroyConstant(); 338 // This could have invalidated UI, start over from scratch. 339 CleanupConstantGlobalUsers(V, Init); 340 return true; 341 } 342 } 343 } 344 return Changed; 345} 346 347/// isSafeSROAElementUse - Return true if the specified instruction is a safe 348/// user of a derived expression from a global that we want to SROA. 349static bool isSafeSROAElementUse(Value *V) { 350 // We might have a dead and dangling constant hanging off of here. 351 if (Constant *C = dyn_cast<Constant>(V)) 352 return ConstantIsDead(C); 353 354 Instruction *I = dyn_cast<Instruction>(V); 355 if (!I) return false; 356 357 // Loads are ok. 358 if (isa<LoadInst>(I)) return true; 359 360 // Stores *to* the pointer are ok. 361 if (StoreInst *SI = dyn_cast<StoreInst>(I)) 362 return SI->getOperand(0) != V; 363 364 // Otherwise, it must be a GEP. 365 GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); 366 if (GEPI == 0) return false; 367 368 if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || 369 !cast<Constant>(GEPI->getOperand(1))->isNullValue()) 370 return false; 371 372 for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); 373 I != E; ++I) 374 if (!isSafeSROAElementUse(*I)) 375 return false; 376 return true; 377} 378 379 380/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. 381/// Look at it and its uses and decide whether it is safe to SROA this global. 382/// 383static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { 384 // The user of the global must be a GEP Inst or a ConstantExpr GEP. 385 if (!isa<GetElementPtrInst>(U) && 386 (!isa<ConstantExpr>(U) || 387 cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) 388 return false; 389 390 // Check to see if this ConstantExpr GEP is SRA'able. In particular, we 391 // don't like < 3 operand CE's, and we don't like non-constant integer 392 // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some 393 // value of C. 394 if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || 395 !cast<Constant>(U->getOperand(1))->isNullValue() || 396 !isa<ConstantInt>(U->getOperand(2))) 397 return false; 398 399 gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); 400 ++GEPI; // Skip over the pointer index. 401 402 // If this is a use of an array allocation, do a bit more checking for sanity. 403 if (const ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { 404 uint64_t NumElements = AT->getNumElements(); 405 ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); 406 407 // Check to make sure that index falls within the array. If not, 408 // something funny is going on, so we won't do the optimization. 409 // 410 if (Idx->getZExtValue() >= NumElements) 411 return false; 412 413 // We cannot scalar repl this level of the array unless any array 414 // sub-indices are in-range constants. In particular, consider: 415 // A[0][i]. We cannot know that the user isn't doing invalid things like 416 // allowing i to index an out-of-range subscript that accesses A[1]. 417 // 418 // Scalar replacing *just* the outer index of the array is probably not 419 // going to be a win anyway, so just give up. 420 for (++GEPI; // Skip array index. 421 GEPI != E && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); 422 ++GEPI) { 423 uint64_t NumElements; 424 if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) 425 NumElements = SubArrayTy->getNumElements(); 426 else 427 NumElements = cast<VectorType>(*GEPI)->getNumElements(); 428 429 ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); 430 if (!IdxVal || IdxVal->getZExtValue() >= NumElements) 431 return false; 432 } 433 } 434 435 for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) 436 if (!isSafeSROAElementUse(*I)) 437 return false; 438 return true; 439} 440 441/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it 442/// is safe for us to perform this transformation. 443/// 444static bool GlobalUsersSafeToSRA(GlobalValue *GV) { 445 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); 446 UI != E; ++UI) { 447 if (!IsUserOfGlobalSafeForSRA(*UI, GV)) 448 return false; 449 } 450 return true; 451} 452 453 454/// SRAGlobal - Perform scalar replacement of aggregates on the specified global 455/// variable. This opens the door for other optimizations by exposing the 456/// behavior of the program in a more fine-grained way. We have determined that 457/// this transformation is safe already. We return the first global variable we 458/// insert so that the caller can reprocess it. 459static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) { 460 // Make sure this global only has simple uses that we can SRA. 461 if (!GlobalUsersSafeToSRA(GV)) 462 return 0; 463 464 assert(GV->hasInternalLinkage() && !GV->isConstant()); 465 Constant *Init = GV->getInitializer(); 466 const Type *Ty = Init->getType(); 467 468 std::vector<GlobalVariable*> NewGlobals; 469 Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); 470 471 // Get the alignment of the global, either explicit or target-specific. 472 unsigned StartAlignment = GV->getAlignment(); 473 if (StartAlignment == 0) 474 StartAlignment = TD.getABITypeAlignment(GV->getType()); 475 476 if (const StructType *STy = dyn_cast<StructType>(Ty)) { 477 NewGlobals.reserve(STy->getNumElements()); 478 const StructLayout &Layout = *TD.getStructLayout(STy); 479 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { 480 Constant *In = getAggregateConstantElement(Init, 481 ConstantInt::get(Type::Int32Ty, i)); 482 assert(In && "Couldn't get element of initializer?"); 483 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, 484 GlobalVariable::InternalLinkage, 485 In, GV->getName()+"."+utostr(i), 486 (Module *)NULL, 487 GV->isThreadLocal()); 488 Globals.insert(GV, NGV); 489 NewGlobals.push_back(NGV); 490 491 // Calculate the known alignment of the field. If the original aggregate 492 // had 256 byte alignment for example, something might depend on that: 493 // propagate info to each field. 494 uint64_t FieldOffset = Layout.getElementOffset(i); 495 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset); 496 if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i))) 497 NGV->setAlignment(NewAlign); 498 } 499 } else if (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { 500 unsigned NumElements = 0; 501 if (const ArrayType *ATy = dyn_cast<ArrayType>(STy)) 502 NumElements = ATy->getNumElements(); 503 else 504 NumElements = cast<VectorType>(STy)->getNumElements(); 505 506 if (NumElements > 16 && GV->hasNUsesOrMore(16)) 507 return 0; // It's not worth it. 508 NewGlobals.reserve(NumElements); 509 510 uint64_t EltSize = TD.getABITypeSize(STy->getElementType()); 511 unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType()); 512 for (unsigned i = 0, e = NumElements; i != e; ++i) { 513 Constant *In = getAggregateConstantElement(Init, 514 ConstantInt::get(Type::Int32Ty, i)); 515 assert(In && "Couldn't get element of initializer?"); 516 517 GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, 518 GlobalVariable::InternalLinkage, 519 In, GV->getName()+"."+utostr(i), 520 (Module *)NULL, 521 GV->isThreadLocal()); 522 Globals.insert(GV, NGV); 523 NewGlobals.push_back(NGV); 524 525 // Calculate the known alignment of the field. If the original aggregate 526 // had 256 byte alignment for example, something might depend on that: 527 // propagate info to each field. 528 unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i); 529 if (NewAlign > EltAlign) 530 NGV->setAlignment(NewAlign); 531 } 532 } 533 534 if (NewGlobals.empty()) 535 return 0; 536 537 DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; 538 539 Constant *NullInt = Constant::getNullValue(Type::Int32Ty); 540 541 // Loop over all of the uses of the global, replacing the constantexpr geps, 542 // with smaller constantexpr geps or direct references. 543 while (!GV->use_empty()) { 544 User *GEP = GV->use_back(); 545 assert(((isa<ConstantExpr>(GEP) && 546 cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| 547 isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); 548 549 // Ignore the 1th operand, which has to be zero or else the program is quite 550 // broken (undefined). Get the 2nd operand, which is the structure or array 551 // index. 552 unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); 553 if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. 554 555 Value *NewPtr = NewGlobals[Val]; 556 557 // Form a shorter GEP if needed. 558 if (GEP->getNumOperands() > 3) { 559 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { 560 SmallVector<Constant*, 8> Idxs; 561 Idxs.push_back(NullInt); 562 for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) 563 Idxs.push_back(CE->getOperand(i)); 564 NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), 565 &Idxs[0], Idxs.size()); 566 } else { 567 GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); 568 SmallVector<Value*, 8> Idxs; 569 Idxs.push_back(NullInt); 570 for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) 571 Idxs.push_back(GEPI->getOperand(i)); 572 NewPtr = GetElementPtrInst::Create(NewPtr, Idxs.begin(), Idxs.end(), 573 GEPI->getName()+"."+utostr(Val), GEPI); 574 } 575 } 576 GEP->replaceAllUsesWith(NewPtr); 577 578 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) 579 GEPI->eraseFromParent(); 580 else 581 cast<ConstantExpr>(GEP)->destroyConstant(); 582 } 583 584 // Delete the old global, now that it is dead. 585 Globals.erase(GV); 586 ++NumSRA; 587 588 // Loop over the new globals array deleting any globals that are obviously 589 // dead. This can arise due to scalarization of a structure or an array that 590 // has elements that are dead. 591 unsigned FirstGlobal = 0; 592 for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) 593 if (NewGlobals[i]->use_empty()) { 594 Globals.erase(NewGlobals[i]); 595 if (FirstGlobal == i) ++FirstGlobal; 596 } 597 598 return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; 599} 600 601/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified 602/// value will trap if the value is dynamically null. PHIs keeps track of any 603/// phi nodes we've seen to avoid reprocessing them. 604static bool AllUsesOfValueWillTrapIfNull(Value *V, 605 SmallPtrSet<PHINode*, 8> &PHIs) { 606 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 607 if (isa<LoadInst>(*UI)) { 608 // Will trap. 609 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 610 if (SI->getOperand(0) == V) { 611 //cerr << "NONTRAPPING USE: " << **UI; 612 return false; // Storing the value. 613 } 614 } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { 615 if (CI->getOperand(0) != V) { 616 //cerr << "NONTRAPPING USE: " << **UI; 617 return false; // Not calling the ptr 618 } 619 } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { 620 if (II->getOperand(0) != V) { 621 //cerr << "NONTRAPPING USE: " << **UI; 622 return false; // Not calling the ptr 623 } 624 } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { 625 if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; 626 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 627 if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; 628 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 629 // If we've already seen this phi node, ignore it, it has already been 630 // checked. 631 if (PHIs.insert(PN)) 632 return AllUsesOfValueWillTrapIfNull(PN, PHIs); 633 } else if (isa<ICmpInst>(*UI) && 634 isa<ConstantPointerNull>(UI->getOperand(1))) { 635 // Ignore setcc X, null 636 } else { 637 //cerr << "NONTRAPPING USE: " << **UI; 638 return false; 639 } 640 return true; 641} 642 643/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads 644/// from GV will trap if the loaded value is null. Note that this also permits 645/// comparisons of the loaded value against null, as a special case. 646static bool AllUsesOfLoadedValueWillTrapIfNull(GlobalVariable *GV) { 647 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) 648 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 649 SmallPtrSet<PHINode*, 8> PHIs; 650 if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) 651 return false; 652 } else if (isa<StoreInst>(*UI)) { 653 // Ignore stores to the global. 654 } else { 655 // We don't know or understand this user, bail out. 656 //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; 657 return false; 658 } 659 660 return true; 661} 662 663static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { 664 bool Changed = false; 665 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { 666 Instruction *I = cast<Instruction>(*UI++); 667 if (LoadInst *LI = dyn_cast<LoadInst>(I)) { 668 LI->setOperand(0, NewV); 669 Changed = true; 670 } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { 671 if (SI->getOperand(1) == V) { 672 SI->setOperand(1, NewV); 673 Changed = true; 674 } 675 } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { 676 if (I->getOperand(0) == V) { 677 // Calling through the pointer! Turn into a direct call, but be careful 678 // that the pointer is not also being passed as an argument. 679 I->setOperand(0, NewV); 680 Changed = true; 681 bool PassedAsArg = false; 682 for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) 683 if (I->getOperand(i) == V) { 684 PassedAsArg = true; 685 I->setOperand(i, NewV); 686 } 687 688 if (PassedAsArg) { 689 // Being passed as an argument also. Be careful to not invalidate UI! 690 UI = V->use_begin(); 691 } 692 } 693 } else if (CastInst *CI = dyn_cast<CastInst>(I)) { 694 Changed |= OptimizeAwayTrappingUsesOfValue(CI, 695 ConstantExpr::getCast(CI->getOpcode(), 696 NewV, CI->getType())); 697 if (CI->use_empty()) { 698 Changed = true; 699 CI->eraseFromParent(); 700 } 701 } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { 702 // Should handle GEP here. 703 SmallVector<Constant*, 8> Idxs; 704 Idxs.reserve(GEPI->getNumOperands()-1); 705 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 706 if (Constant *C = dyn_cast<Constant>(GEPI->getOperand(i))) 707 Idxs.push_back(C); 708 else 709 break; 710 if (Idxs.size() == GEPI->getNumOperands()-1) 711 Changed |= OptimizeAwayTrappingUsesOfValue(GEPI, 712 ConstantExpr::getGetElementPtr(NewV, &Idxs[0], 713 Idxs.size())); 714 if (GEPI->use_empty()) { 715 Changed = true; 716 GEPI->eraseFromParent(); 717 } 718 } 719 } 720 721 return Changed; 722} 723 724 725/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null 726/// value stored into it. If there are uses of the loaded value that would trap 727/// if the loaded value is dynamically null, then we know that they cannot be 728/// reachable with a null optimize away the load. 729static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV) { 730 std::vector<LoadInst*> Loads; 731 bool Changed = false; 732 733 // Replace all uses of loads with uses of uses of the stored value. 734 for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); 735 GUI != E; ++GUI) 736 if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { 737 Loads.push_back(LI); 738 Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); 739 } else { 740 // If we get here we could have stores, selects, or phi nodes whose values 741 // are loaded. 742 assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || 743 isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && 744 "Only expect load and stores!"); 745 } 746 747 if (Changed) { 748 DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; 749 ++NumGlobUses; 750 } 751 752 // Delete all of the loads we can, keeping track of whether we nuked them all! 753 bool AllLoadsGone = true; 754 while (!Loads.empty()) { 755 LoadInst *L = Loads.back(); 756 if (L->use_empty()) { 757 L->eraseFromParent(); 758 Changed = true; 759 } else { 760 AllLoadsGone = false; 761 } 762 Loads.pop_back(); 763 } 764 765 // If we nuked all of the loads, then none of the stores are needed either, 766 // nor is the global. 767 if (AllLoadsGone) { 768 DOUT << " *** GLOBAL NOW DEAD!\n"; 769 CleanupConstantGlobalUsers(GV, 0); 770 if (GV->use_empty()) { 771 GV->eraseFromParent(); 772 ++NumDeleted; 773 } 774 Changed = true; 775 } 776 return Changed; 777} 778 779/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the 780/// instructions that are foldable. 781static void ConstantPropUsersOf(Value *V) { 782 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) 783 if (Instruction *I = dyn_cast<Instruction>(*UI++)) 784 if (Constant *NewC = ConstantFoldInstruction(I)) { 785 I->replaceAllUsesWith(NewC); 786 787 // Advance UI to the next non-I use to avoid invalidating it! 788 // Instructions could multiply use V. 789 while (UI != E && *UI == I) 790 ++UI; 791 I->eraseFromParent(); 792 } 793} 794 795/// OptimizeGlobalAddressOfMalloc - This function takes the specified global 796/// variable, and transforms the program as if it always contained the result of 797/// the specified malloc. Because it is always the result of the specified 798/// malloc, there is no reason to actually DO the malloc. Instead, turn the 799/// malloc into a global, and any loads of GV as uses of the new global. 800static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, 801 MallocInst *MI) { 802 DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; 803 ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); 804 805 if (NElements->getZExtValue() != 1) { 806 // If we have an array allocation, transform it to a single element 807 // allocation to make the code below simpler. 808 Type *NewTy = ArrayType::get(MI->getAllocatedType(), 809 NElements->getZExtValue()); 810 MallocInst *NewMI = 811 new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), 812 MI->getAlignment(), MI->getName(), MI); 813 Value* Indices[2]; 814 Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); 815 Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2, 816 NewMI->getName()+".el0", MI); 817 MI->replaceAllUsesWith(NewGEP); 818 MI->eraseFromParent(); 819 MI = NewMI; 820 } 821 822 // Create the new global variable. The contents of the malloc'd memory is 823 // undefined, so initialize with an undef value. 824 Constant *Init = UndefValue::get(MI->getAllocatedType()); 825 GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, 826 GlobalValue::InternalLinkage, Init, 827 GV->getName()+".body", 828 (Module *)NULL, 829 GV->isThreadLocal()); 830 // FIXME: This new global should have the alignment returned by malloc. Code 831 // could depend on malloc returning large alignment (on the mac, 16 bytes) but 832 // this would only guarantee some lower alignment. 833 GV->getParent()->getGlobalList().insert(GV, NewGV); 834 835 // Anything that used the malloc now uses the global directly. 836 MI->replaceAllUsesWith(NewGV); 837 838 Constant *RepValue = NewGV; 839 if (NewGV->getType() != GV->getType()->getElementType()) 840 RepValue = ConstantExpr::getBitCast(RepValue, 841 GV->getType()->getElementType()); 842 843 // If there is a comparison against null, we will insert a global bool to 844 // keep track of whether the global was initialized yet or not. 845 GlobalVariable *InitBool = 846 new GlobalVariable(Type::Int1Ty, false, GlobalValue::InternalLinkage, 847 ConstantInt::getFalse(), GV->getName()+".init", 848 (Module *)NULL, GV->isThreadLocal()); 849 bool InitBoolUsed = false; 850 851 // Loop over all uses of GV, processing them in turn. 852 std::vector<StoreInst*> Stores; 853 while (!GV->use_empty()) 854 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 855 while (!LI->use_empty()) { 856 Use &LoadUse = LI->use_begin().getUse(); 857 if (!isa<ICmpInst>(LoadUse.getUser())) 858 LoadUse = RepValue; 859 else { 860 ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); 861 // Replace the cmp X, 0 with a use of the bool value. 862 Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); 863 InitBoolUsed = true; 864 switch (CI->getPredicate()) { 865 default: assert(0 && "Unknown ICmp Predicate!"); 866 case ICmpInst::ICMP_ULT: 867 case ICmpInst::ICMP_SLT: 868 LV = ConstantInt::getFalse(); // X < null -> always false 869 break; 870 case ICmpInst::ICMP_ULE: 871 case ICmpInst::ICMP_SLE: 872 case ICmpInst::ICMP_EQ: 873 LV = BinaryOperator::createNot(LV, "notinit", CI); 874 break; 875 case ICmpInst::ICMP_NE: 876 case ICmpInst::ICMP_UGE: 877 case ICmpInst::ICMP_SGE: 878 case ICmpInst::ICMP_UGT: 879 case ICmpInst::ICMP_SGT: 880 break; // no change. 881 } 882 CI->replaceAllUsesWith(LV); 883 CI->eraseFromParent(); 884 } 885 } 886 LI->eraseFromParent(); 887 } else { 888 StoreInst *SI = cast<StoreInst>(GV->use_back()); 889 // The global is initialized when the store to it occurs. 890 new StoreInst(ConstantInt::getTrue(), InitBool, SI); 891 SI->eraseFromParent(); 892 } 893 894 // If the initialization boolean was used, insert it, otherwise delete it. 895 if (!InitBoolUsed) { 896 while (!InitBool->use_empty()) // Delete initializations 897 cast<Instruction>(InitBool->use_back())->eraseFromParent(); 898 delete InitBool; 899 } else 900 GV->getParent()->getGlobalList().insert(GV, InitBool); 901 902 903 // Now the GV is dead, nuke it and the malloc. 904 GV->eraseFromParent(); 905 MI->eraseFromParent(); 906 907 // To further other optimizations, loop over all users of NewGV and try to 908 // constant prop them. This will promote GEP instructions with constant 909 // indices into GEP constant-exprs, which will allow global-opt to hack on it. 910 ConstantPropUsersOf(NewGV); 911 if (RepValue != NewGV) 912 ConstantPropUsersOf(RepValue); 913 914 return NewGV; 915} 916 917/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking 918/// to make sure that there are no complex uses of V. We permit simple things 919/// like dereferencing the pointer, but not storing through the address, unless 920/// it is to the specified global. 921static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Instruction *V, 922 GlobalVariable *GV, 923 SmallPtrSet<PHINode*, 8> &PHIs) { 924 for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) 925 if (isa<LoadInst>(*UI) || isa<CmpInst>(*UI)) { 926 // Fine, ignore. 927 } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { 928 if (SI->getOperand(0) == V && SI->getOperand(1) != GV) 929 return false; // Storing the pointer itself... bad. 930 // Otherwise, storing through it, or storing into GV... fine. 931 } else if (isa<GetElementPtrInst>(*UI)) { 932 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(cast<Instruction>(*UI), 933 GV, PHIs)) 934 return false; 935 } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 936 // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI 937 // cycles. 938 if (PHIs.insert(PN)) 939 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) 940 return false; 941 } else { 942 return false; 943 } 944 return true; 945} 946 947/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV 948/// somewhere. Transform all uses of the allocation into loads from the 949/// global and uses of the resultant pointer. Further, delete the store into 950/// GV. This assumes that these value pass the 951/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. 952static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, 953 GlobalVariable *GV) { 954 while (!Alloc->use_empty()) { 955 Instruction *U = cast<Instruction>(*Alloc->use_begin()); 956 Instruction *InsertPt = U; 957 if (StoreInst *SI = dyn_cast<StoreInst>(U)) { 958 // If this is the store of the allocation into the global, remove it. 959 if (SI->getOperand(1) == GV) { 960 SI->eraseFromParent(); 961 continue; 962 } 963 } else if (PHINode *PN = dyn_cast<PHINode>(U)) { 964 // Insert the load in the corresponding predecessor, not right before the 965 // PHI. 966 unsigned PredNo = Alloc->use_begin().getOperandNo()/2; 967 InsertPt = PN->getIncomingBlock(PredNo)->getTerminator(); 968 } 969 970 // Insert a load from the global, and use it instead of the malloc. 971 Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); 972 U->replaceUsesOfWith(Alloc, NL); 973 } 974} 975 976/// GlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from 977/// GV are simple enough to perform HeapSRA, return true. 978static bool GlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, 979 MallocInst *MI) { 980 for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; 981 ++UI) 982 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { 983 // We permit two users of the load: setcc comparing against the null 984 // pointer, and a getelementptr of a specific form. 985 for (Value::use_iterator UI = LI->use_begin(), E = LI->use_end(); UI != E; 986 ++UI) { 987 // Comparison against null is ok. 988 if (ICmpInst *ICI = dyn_cast<ICmpInst>(*UI)) { 989 if (!isa<ConstantPointerNull>(ICI->getOperand(1))) 990 return false; 991 continue; 992 } 993 994 // getelementptr is also ok, but only a simple form. 995 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { 996 // Must index into the array and into the struct. 997 if (GEPI->getNumOperands() < 3) 998 return false; 999 1000 // Otherwise the GEP is ok. 1001 continue; 1002 } 1003 1004 if (PHINode *PN = dyn_cast<PHINode>(*UI)) { 1005 // We have a phi of a load from the global. We can only handle this 1006 // if the other PHI'd values are actually the same. In this case, 1007 // the rewriter will just drop the phi entirely. 1008 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { 1009 Value *IV = PN->getIncomingValue(i); 1010 if (IV == LI) continue; // Trivial the same. 1011 1012 // If the phi'd value is from the malloc that initializes the value, 1013 // we can xform it. 1014 if (IV == MI) continue; 1015 1016 // Otherwise, we don't know what it is. 1017 return false; 1018 } 1019 return true; 1020 } 1021 1022 // Otherwise we don't know what this is, not ok. 1023 return false; 1024 } 1025 } 1026 return true; 1027} 1028 1029/// GetHeapSROALoad - Return the load for the specified field of the HeapSROA'd 1030/// value, lazily creating it on demand. 1031static Value *GetHeapSROALoad(Instruction *Load, unsigned FieldNo, 1032 const std::vector<GlobalVariable*> &FieldGlobals, 1033 std::vector<Value *> &InsertedLoadsForPtr) { 1034 if (InsertedLoadsForPtr.size() <= FieldNo) 1035 InsertedLoadsForPtr.resize(FieldNo+1); 1036 if (InsertedLoadsForPtr[FieldNo] == 0) 1037 InsertedLoadsForPtr[FieldNo] = new LoadInst(FieldGlobals[FieldNo], 1038 Load->getName()+".f" + 1039 utostr(FieldNo), Load); 1040 return InsertedLoadsForPtr[FieldNo]; 1041} 1042 1043/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from 1044/// the load, rewrite the derived value to use the HeapSRoA'd load. 1045static void RewriteHeapSROALoadUser(LoadInst *Load, Instruction *LoadUser, 1046 const std::vector<GlobalVariable*> &FieldGlobals, 1047 std::vector<Value *> &InsertedLoadsForPtr) { 1048 // If this is a comparison against null, handle it. 1049 if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { 1050 assert(isa<ConstantPointerNull>(SCI->getOperand(1))); 1051 // If we have a setcc of the loaded pointer, we can use a setcc of any 1052 // field. 1053 Value *NPtr; 1054 if (InsertedLoadsForPtr.empty()) { 1055 NPtr = GetHeapSROALoad(Load, 0, FieldGlobals, InsertedLoadsForPtr); 1056 } else { 1057 NPtr = InsertedLoadsForPtr.back(); 1058 } 1059 1060 Value *New = new ICmpInst(SCI->getPredicate(), NPtr, 1061 Constant::getNullValue(NPtr->getType()), 1062 SCI->getName(), SCI); 1063 SCI->replaceAllUsesWith(New); 1064 SCI->eraseFromParent(); 1065 return; 1066 } 1067 1068 // Handle 'getelementptr Ptr, Idx, uint FieldNo ...' 1069 if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { 1070 assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) 1071 && "Unexpected GEPI!"); 1072 1073 // Load the pointer for this field. 1074 unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); 1075 Value *NewPtr = GetHeapSROALoad(Load, FieldNo, 1076 FieldGlobals, InsertedLoadsForPtr); 1077 1078 // Create the new GEP idx vector. 1079 SmallVector<Value*, 8> GEPIdx; 1080 GEPIdx.push_back(GEPI->getOperand(1)); 1081 GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); 1082 1083 Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx.begin(), GEPIdx.end(), 1084 GEPI->getName(), GEPI); 1085 GEPI->replaceAllUsesWith(NGEPI); 1086 GEPI->eraseFromParent(); 1087 return; 1088 } 1089 1090 // Handle PHI nodes. PHI nodes must be merging in the same values, plus 1091 // potentially the original malloc. Insert phi nodes for each field, then 1092 // process uses of the PHI. 1093 PHINode *PN = cast<PHINode>(LoadUser); 1094 std::vector<Value *> PHIsForField; 1095 PHIsForField.resize(FieldGlobals.size()); 1096 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1097 Value *LoadV = GetHeapSROALoad(Load, i, FieldGlobals, InsertedLoadsForPtr); 1098 1099 PHINode *FieldPN = PHINode::Create(LoadV->getType(), 1100 PN->getName()+"."+utostr(i), PN); 1101 // Fill in the predecessor values. 1102 for (unsigned pred = 0, e = PN->getNumIncomingValues(); pred != e; ++pred) { 1103 // Each predecessor either uses the load or the original malloc. 1104 Value *InVal = PN->getIncomingValue(pred); 1105 BasicBlock *BB = PN->getIncomingBlock(pred); 1106 Value *NewVal; 1107 if (isa<MallocInst>(InVal)) { 1108 // Insert a reload from the global in the predecessor. 1109 NewVal = GetHeapSROALoad(BB->getTerminator(), i, FieldGlobals, 1110 PHIsForField); 1111 } else { 1112 NewVal = InsertedLoadsForPtr[i]; 1113 } 1114 FieldPN->addIncoming(NewVal, BB); 1115 } 1116 PHIsForField[i] = FieldPN; 1117 } 1118 1119 // Since PHIsForField specifies a phi for every input value, the lazy inserter 1120 // will never insert a load. 1121 while (!PN->use_empty()) 1122 RewriteHeapSROALoadUser(Load, PN->use_back(), FieldGlobals, PHIsForField); 1123 PN->eraseFromParent(); 1124} 1125 1126/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr 1127/// is a value loaded from the global. Eliminate all uses of Ptr, making them 1128/// use FieldGlobals instead. All uses of loaded values satisfy 1129/// GlobalLoadUsesSimpleEnoughForHeapSRA. 1130static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, 1131 const std::vector<GlobalVariable*> &FieldGlobals) { 1132 std::vector<Value *> InsertedLoadsForPtr; 1133 //InsertedLoadsForPtr.resize(FieldGlobals.size()); 1134 while (!Load->use_empty()) 1135 RewriteHeapSROALoadUser(Load, Load->use_back(), 1136 FieldGlobals, InsertedLoadsForPtr); 1137} 1138 1139/// PerformHeapAllocSRoA - MI is an allocation of an array of structures. Break 1140/// it up into multiple allocations of arrays of the fields. 1141static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ 1142 DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; 1143 const StructType *STy = cast<StructType>(MI->getAllocatedType()); 1144 1145 // There is guaranteed to be at least one use of the malloc (storing 1146 // it into GV). If there are other uses, change them to be uses of 1147 // the global to simplify later code. This also deletes the store 1148 // into GV. 1149 ReplaceUsesOfMallocWithGlobal(MI, GV); 1150 1151 // Okay, at this point, there are no users of the malloc. Insert N 1152 // new mallocs at the same place as MI, and N globals. 1153 std::vector<GlobalVariable*> FieldGlobals; 1154 std::vector<MallocInst*> FieldMallocs; 1155 1156 for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ 1157 const Type *FieldTy = STy->getElementType(FieldNo); 1158 const Type *PFieldTy = PointerType::getUnqual(FieldTy); 1159 1160 GlobalVariable *NGV = 1161 new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, 1162 Constant::getNullValue(PFieldTy), 1163 GV->getName() + ".f" + utostr(FieldNo), GV, 1164 GV->isThreadLocal()); 1165 FieldGlobals.push_back(NGV); 1166 1167 MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), 1168 MI->getName() + ".f" + utostr(FieldNo),MI); 1169 FieldMallocs.push_back(NMI); 1170 new StoreInst(NMI, NGV, MI); 1171 } 1172 1173 // The tricky aspect of this transformation is handling the case when malloc 1174 // fails. In the original code, malloc failing would set the result pointer 1175 // of malloc to null. In this case, some mallocs could succeed and others 1176 // could fail. As such, we emit code that looks like this: 1177 // F0 = malloc(field0) 1178 // F1 = malloc(field1) 1179 // F2 = malloc(field2) 1180 // if (F0 == 0 || F1 == 0 || F2 == 0) { 1181 // if (F0) { free(F0); F0 = 0; } 1182 // if (F1) { free(F1); F1 = 0; } 1183 // if (F2) { free(F2); F2 = 0; } 1184 // } 1185 Value *RunningOr = 0; 1186 for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { 1187 Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], 1188 Constant::getNullValue(FieldMallocs[i]->getType()), 1189 "isnull", MI); 1190 if (!RunningOr) 1191 RunningOr = Cond; // First seteq 1192 else 1193 RunningOr = BinaryOperator::createOr(RunningOr, Cond, "tmp", MI); 1194 } 1195 1196 // Split the basic block at the old malloc. 1197 BasicBlock *OrigBB = MI->getParent(); 1198 BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "malloc_cont"); 1199 1200 // Create the block to check the first condition. Put all these blocks at the 1201 // end of the function as they are unlikely to be executed. 1202 BasicBlock *NullPtrBlock = BasicBlock::Create("malloc_ret_null", 1203 OrigBB->getParent()); 1204 1205 // Remove the uncond branch from OrigBB to ContBB, turning it into a cond 1206 // branch on RunningOr. 1207 OrigBB->getTerminator()->eraseFromParent(); 1208 BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); 1209 1210 // Within the NullPtrBlock, we need to emit a comparison and branch for each 1211 // pointer, because some may be null while others are not. 1212 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1213 Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); 1214 Value *Cmp = new ICmpInst(ICmpInst::ICMP_NE, GVVal, 1215 Constant::getNullValue(GVVal->getType()), 1216 "tmp", NullPtrBlock); 1217 BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent()); 1218 BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent()); 1219 BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock); 1220 1221 // Fill in FreeBlock. 1222 new FreeInst(GVVal, FreeBlock); 1223 new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], 1224 FreeBlock); 1225 BranchInst::Create(NextBlock, FreeBlock); 1226 1227 NullPtrBlock = NextBlock; 1228 } 1229 1230 BranchInst::Create(ContBB, NullPtrBlock); 1231 1232 // MI is no longer needed, remove it. 1233 MI->eraseFromParent(); 1234 1235 1236 // Okay, the malloc site is completely handled. All of the uses of GV are now 1237 // loads, and all uses of those loads are simple. Rewrite them to use loads 1238 // of the per-field globals instead. 1239 while (!GV->use_empty()) { 1240 if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { 1241 RewriteUsesOfLoadForHeapSRoA(LI, FieldGlobals); 1242 LI->eraseFromParent(); 1243 } else { 1244 // Must be a store of null. 1245 StoreInst *SI = cast<StoreInst>(GV->use_back()); 1246 assert(isa<Constant>(SI->getOperand(0)) && 1247 cast<Constant>(SI->getOperand(0))->isNullValue() && 1248 "Unexpected heap-sra user!"); 1249 1250 // Insert a store of null into each global. 1251 for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { 1252 Constant *Null = 1253 Constant::getNullValue(FieldGlobals[i]->getType()->getElementType()); 1254 new StoreInst(Null, FieldGlobals[i], SI); 1255 } 1256 // Erase the original store. 1257 SI->eraseFromParent(); 1258 } 1259 } 1260 1261 // The old global is now dead, remove it. 1262 GV->eraseFromParent(); 1263 1264 ++NumHeapSRA; 1265 return FieldGlobals[0]; 1266} 1267 1268 1269// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge 1270// that only one value (besides its initializer) is ever stored to the global. 1271static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, 1272 Module::global_iterator &GVI, 1273 TargetData &TD) { 1274 if (CastInst *CI = dyn_cast<CastInst>(StoredOnceVal)) 1275 StoredOnceVal = CI->getOperand(0); 1276 else if (GetElementPtrInst *GEPI =dyn_cast<GetElementPtrInst>(StoredOnceVal)){ 1277 // "getelementptr Ptr, 0, 0, 0" is really just a cast. 1278 bool IsJustACast = true; 1279 for (unsigned i = 1, e = GEPI->getNumOperands(); i != e; ++i) 1280 if (!isa<Constant>(GEPI->getOperand(i)) || 1281 !cast<Constant>(GEPI->getOperand(i))->isNullValue()) { 1282 IsJustACast = false; 1283 break; 1284 } 1285 if (IsJustACast) 1286 StoredOnceVal = GEPI->getOperand(0); 1287 } 1288 1289 // If we are dealing with a pointer global that is initialized to null and 1290 // only has one (non-null) value stored into it, then we can optimize any 1291 // users of the loaded value (often calls and loads) that would trap if the 1292 // value was null. 1293 if (isa<PointerType>(GV->getInitializer()->getType()) && 1294 GV->getInitializer()->isNullValue()) { 1295 if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { 1296 if (GV->getInitializer()->getType() != SOVC->getType()) 1297 SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); 1298 1299 // Optimize away any trapping uses of the loaded value. 1300 if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC)) 1301 return true; 1302 } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { 1303 // If this is a malloc of an abstract type, don't touch it. 1304 if (!MI->getAllocatedType()->isSized()) 1305 return false; 1306 1307 // We can't optimize this global unless all uses of it are *known* to be 1308 // of the malloc value, not of the null initializer value (consider a use 1309 // that compares the global's value against zero to see if the malloc has 1310 // been reached). To do this, we check to see if all uses of the global 1311 // would trap if the global were null: this proves that they must all 1312 // happen after the malloc. 1313 if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) 1314 return false; 1315 1316 // We can't optimize this if the malloc itself is used in a complex way, 1317 // for example, being stored into multiple globals. This allows the 1318 // malloc to be stored into the specified global, loaded setcc'd, and 1319 // GEP'd. These are all things we could transform to using the global 1320 // for. 1321 { 1322 SmallPtrSet<PHINode*, 8> PHIs; 1323 if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, GV, PHIs)) 1324 return false; 1325 } 1326 1327 1328 // If we have a global that is only initialized with a fixed size malloc, 1329 // transform the program to use global memory instead of malloc'd memory. 1330 // This eliminates dynamic allocation, avoids an indirection accessing the 1331 // data, and exposes the resultant global to further GlobalOpt. 1332 if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { 1333 // Restrict this transformation to only working on small allocations 1334 // (2048 bytes currently), as we don't want to introduce a 16M global or 1335 // something. 1336 if (NElements->getZExtValue()* 1337 TD.getABITypeSize(MI->getAllocatedType()) < 2048) { 1338 GVI = OptimizeGlobalAddressOfMalloc(GV, MI); 1339 return true; 1340 } 1341 } 1342 1343 // If the allocation is an array of structures, consider transforming this 1344 // into multiple malloc'd arrays, one for each field. This is basically 1345 // SRoA for malloc'd memory. 1346 if (const StructType *AllocTy = 1347 dyn_cast<StructType>(MI->getAllocatedType())) { 1348 // This the structure has an unreasonable number of fields, leave it 1349 // alone. 1350 if (AllocTy->getNumElements() <= 16 && AllocTy->getNumElements() > 0 && 1351 GlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { 1352 GVI = PerformHeapAllocSRoA(GV, MI); 1353 return true; 1354 } 1355 } 1356 } 1357 } 1358 1359 return false; 1360} 1361 1362/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only 1363/// two values ever stored into GV are its initializer and OtherVal. See if we 1364/// can shrink the global into a boolean and select between the two values 1365/// whenever it is used. This exposes the values to other scalar optimizations. 1366static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { 1367 const Type *GVElType = GV->getType()->getElementType(); 1368 1369 // If GVElType is already i1, it is already shrunk. If the type of the GV is 1370 // an FP value or vector, don't do this optimization because a select between 1371 // them is very expensive and unlikely to lead to later simplification. 1372 if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || 1373 isa<VectorType>(GVElType)) 1374 return false; 1375 1376 // Walk the use list of the global seeing if all the uses are load or store. 1377 // If there is anything else, bail out. 1378 for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I) 1379 if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) 1380 return false; 1381 1382 DOUT << " *** SHRINKING TO BOOL: " << *GV; 1383 1384 // Create the new global, initializing it to false. 1385 GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, 1386 GlobalValue::InternalLinkage, ConstantInt::getFalse(), 1387 GV->getName()+".b", 1388 (Module *)NULL, 1389 GV->isThreadLocal()); 1390 GV->getParent()->getGlobalList().insert(GV, NewGV); 1391 1392 Constant *InitVal = GV->getInitializer(); 1393 assert(InitVal->getType() != Type::Int1Ty && "No reason to shrink to bool!"); 1394 1395 // If initialized to zero and storing one into the global, we can use a cast 1396 // instead of a select to synthesize the desired value. 1397 bool IsOneZero = false; 1398 if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) 1399 IsOneZero = InitVal->isNullValue() && CI->isOne(); 1400 1401 while (!GV->use_empty()) { 1402 Instruction *UI = cast<Instruction>(GV->use_back()); 1403 if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { 1404 // Change the store into a boolean store. 1405 bool StoringOther = SI->getOperand(0) == OtherVal; 1406 // Only do this if we weren't storing a loaded value. 1407 Value *StoreVal; 1408 if (StoringOther || SI->getOperand(0) == InitVal) 1409 StoreVal = ConstantInt::get(Type::Int1Ty, StoringOther); 1410 else { 1411 // Otherwise, we are storing a previously loaded copy. To do this, 1412 // change the copy from copying the original value to just copying the 1413 // bool. 1414 Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); 1415 1416 // If we're already replaced the input, StoredVal will be a cast or 1417 // select instruction. If not, it will be a load of the original 1418 // global. 1419 if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { 1420 assert(LI->getOperand(0) == GV && "Not a copy!"); 1421 // Insert a new load, to preserve the saved value. 1422 StoreVal = new LoadInst(NewGV, LI->getName()+".b", LI); 1423 } else { 1424 assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && 1425 "This is not a form that we understand!"); 1426 StoreVal = StoredVal->getOperand(0); 1427 assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); 1428 } 1429 } 1430 new StoreInst(StoreVal, NewGV, SI); 1431 } else { 1432 // Change the load into a load of bool then a select. 1433 LoadInst *LI = cast<LoadInst>(UI); 1434 LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", LI); 1435 Value *NSI; 1436 if (IsOneZero) 1437 NSI = new ZExtInst(NLI, LI->getType(), "", LI); 1438 else 1439 NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); 1440 NSI->takeName(LI); 1441 LI->replaceAllUsesWith(NSI); 1442 } 1443 UI->eraseFromParent(); 1444 } 1445 1446 GV->eraseFromParent(); 1447 return true; 1448} 1449 1450 1451/// ProcessInternalGlobal - Analyze the specified global variable and optimize 1452/// it if possible. If we make a change, return true. 1453bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, 1454 Module::global_iterator &GVI) { 1455 std::set<PHINode*> PHIUsers; 1456 GlobalStatus GS; 1457 GV->removeDeadConstantUsers(); 1458 1459 if (GV->use_empty()) { 1460 DOUT << "GLOBAL DEAD: " << *GV; 1461 GV->eraseFromParent(); 1462 ++NumDeleted; 1463 return true; 1464 } 1465 1466 if (!AnalyzeGlobal(GV, GS, PHIUsers)) { 1467#if 0 1468 cerr << "Global: " << *GV; 1469 cerr << " isLoaded = " << GS.isLoaded << "\n"; 1470 cerr << " StoredType = "; 1471 switch (GS.StoredType) { 1472 case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; 1473 case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; 1474 case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; 1475 case GlobalStatus::isStored: cerr << "stored\n"; break; 1476 } 1477 if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) 1478 cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; 1479 if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) 1480 cerr << " AccessingFunction = " << GS.AccessingFunction->getName() 1481 << "\n"; 1482 cerr << " HasMultipleAccessingFunctions = " 1483 << GS.HasMultipleAccessingFunctions << "\n"; 1484 cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; 1485 cerr << "\n"; 1486#endif 1487 1488 // If this is a first class global and has only one accessing function 1489 // and this function is main (which we know is not recursive we can make 1490 // this global a local variable) we replace the global with a local alloca 1491 // in this function. 1492 // 1493 // NOTE: It doesn't make sense to promote non first class types since we 1494 // are just replacing static memory to stack memory. 1495 if (!GS.HasMultipleAccessingFunctions && 1496 GS.AccessingFunction && !GS.HasNonInstructionUser && 1497 GV->getType()->getElementType()->isFirstClassType() && 1498 GS.AccessingFunction->getName() == "main" && 1499 GS.AccessingFunction->hasExternalLinkage()) { 1500 DOUT << "LOCALIZING GLOBAL: " << *GV; 1501 Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); 1502 const Type* ElemTy = GV->getType()->getElementType(); 1503 // FIXME: Pass Global's alignment when globals have alignment 1504 AllocaInst* Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), FirstI); 1505 if (!isa<UndefValue>(GV->getInitializer())) 1506 new StoreInst(GV->getInitializer(), Alloca, FirstI); 1507 1508 GV->replaceAllUsesWith(Alloca); 1509 GV->eraseFromParent(); 1510 ++NumLocalized; 1511 return true; 1512 } 1513 1514 // If the global is never loaded (but may be stored to), it is dead. 1515 // Delete it now. 1516 if (!GS.isLoaded) { 1517 DOUT << "GLOBAL NEVER LOADED: " << *GV; 1518 1519 // Delete any stores we can find to the global. We may not be able to 1520 // make it completely dead though. 1521 bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1522 1523 // If the global is dead now, delete it. 1524 if (GV->use_empty()) { 1525 GV->eraseFromParent(); 1526 ++NumDeleted; 1527 Changed = true; 1528 } 1529 return Changed; 1530 1531 } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { 1532 DOUT << "MARKING CONSTANT: " << *GV; 1533 GV->setConstant(true); 1534 1535 // Clean up any obviously simplifiable users now. 1536 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1537 1538 // If the global is dead now, just nuke it. 1539 if (GV->use_empty()) { 1540 DOUT << " *** Marking constant allowed us to simplify " 1541 << "all users and delete global!\n"; 1542 GV->eraseFromParent(); 1543 ++NumDeleted; 1544 } 1545 1546 ++NumMarked; 1547 return true; 1548 } else if (!GV->getInitializer()->getType()->isFirstClassType()) { 1549 if (GlobalVariable *FirstNewGV = SRAGlobal(GV, 1550 getAnalysis<TargetData>())) { 1551 GVI = FirstNewGV; // Don't skip the newly produced globals! 1552 return true; 1553 } 1554 } else if (GS.StoredType == GlobalStatus::isStoredOnce) { 1555 // If the initial value for the global was an undef value, and if only 1556 // one other value was stored into it, we can just change the 1557 // initializer to be an undef value, then delete all stores to the 1558 // global. This allows us to mark it constant. 1559 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1560 if (isa<UndefValue>(GV->getInitializer())) { 1561 // Change the initial value here. 1562 GV->setInitializer(SOVConstant); 1563 1564 // Clean up any obviously simplifiable users now. 1565 CleanupConstantGlobalUsers(GV, GV->getInitializer()); 1566 1567 if (GV->use_empty()) { 1568 DOUT << " *** Substituting initializer allowed us to " 1569 << "simplify all users and delete global!\n"; 1570 GV->eraseFromParent(); 1571 ++NumDeleted; 1572 } else { 1573 GVI = GV; 1574 } 1575 ++NumSubstitute; 1576 return true; 1577 } 1578 1579 // Try to optimize globals based on the knowledge that only one value 1580 // (besides its initializer) is ever stored to the global. 1581 if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, 1582 getAnalysis<TargetData>())) 1583 return true; 1584 1585 // Otherwise, if the global was not a boolean, we can shrink it to be a 1586 // boolean. 1587 if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) 1588 if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { 1589 ++NumShrunkToBool; 1590 return true; 1591 } 1592 } 1593 } 1594 return false; 1595} 1596 1597/// OnlyCalledDirectly - Return true if the specified function is only called 1598/// directly. In other words, its address is never taken. 1599static bool OnlyCalledDirectly(Function *F) { 1600 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1601 Instruction *User = dyn_cast<Instruction>(*UI); 1602 if (!User) return false; 1603 if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; 1604 1605 // See if the function address is passed as an argument. 1606 for (unsigned i = 1, e = User->getNumOperands(); i != e; ++i) 1607 if (User->getOperand(i) == F) return false; 1608 } 1609 return true; 1610} 1611 1612/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified 1613/// function, changing them to FastCC. 1614static void ChangeCalleesToFastCall(Function *F) { 1615 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1616 CallSite User(cast<Instruction>(*UI)); 1617 User.setCallingConv(CallingConv::Fast); 1618 } 1619} 1620 1621static PAListPtr StripNest(const PAListPtr &Attrs) { 1622 for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { 1623 if ((Attrs.getSlot(i).Attrs & ParamAttr::Nest) == 0) 1624 continue; 1625 1626 // There can be only one. 1627 return Attrs.removeAttr(Attrs.getSlot(i).Index, ParamAttr::Nest); 1628 } 1629 1630 return Attrs; 1631} 1632 1633static void RemoveNestAttribute(Function *F) { 1634 F->setParamAttrs(StripNest(F->getParamAttrs())); 1635 for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ 1636 CallSite User(cast<Instruction>(*UI)); 1637 User.setParamAttrs(StripNest(User.getParamAttrs())); 1638 } 1639} 1640 1641bool GlobalOpt::OptimizeFunctions(Module &M) { 1642 bool Changed = false; 1643 // Optimize functions. 1644 for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { 1645 Function *F = FI++; 1646 F->removeDeadConstantUsers(); 1647 if (F->use_empty() && (F->hasInternalLinkage() || 1648 F->hasLinkOnceLinkage())) { 1649 M.getFunctionList().erase(F); 1650 Changed = true; 1651 ++NumFnDeleted; 1652 } else if (F->hasInternalLinkage()) { 1653 if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && 1654 OnlyCalledDirectly(F)) { 1655 // If this function has C calling conventions, is not a varargs 1656 // function, and is only called directly, promote it to use the Fast 1657 // calling convention. 1658 F->setCallingConv(CallingConv::Fast); 1659 ChangeCalleesToFastCall(F); 1660 ++NumFastCallFns; 1661 Changed = true; 1662 } 1663 1664 if (F->getParamAttrs().hasAttrSomewhere(ParamAttr::Nest) && 1665 OnlyCalledDirectly(F)) { 1666 // The function is not used by a trampoline intrinsic, so it is safe 1667 // to remove the 'nest' attribute. 1668 RemoveNestAttribute(F); 1669 ++NumNestRemoved; 1670 Changed = true; 1671 } 1672 } 1673 } 1674 return Changed; 1675} 1676 1677bool GlobalOpt::OptimizeGlobalVars(Module &M) { 1678 bool Changed = false; 1679 for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); 1680 GVI != E; ) { 1681 GlobalVariable *GV = GVI++; 1682 if (!GV->isConstant() && GV->hasInternalLinkage() && 1683 GV->hasInitializer()) 1684 Changed |= ProcessInternalGlobal(GV, GVI); 1685 } 1686 return Changed; 1687} 1688 1689/// FindGlobalCtors - Find the llvm.globalctors list, verifying that all 1690/// initializers have an init priority of 65535. 1691GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { 1692 for (Module::global_iterator I = M.global_begin(), E = M.global_end(); 1693 I != E; ++I) 1694 if (I->getName() == "llvm.global_ctors") { 1695 // Found it, verify it's an array of { int, void()* }. 1696 const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); 1697 if (!ATy) return 0; 1698 const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); 1699 if (!STy || STy->getNumElements() != 2 || 1700 STy->getElementType(0) != Type::Int32Ty) return 0; 1701 const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); 1702 if (!PFTy) return 0; 1703 const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); 1704 if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || 1705 FTy->getNumParams() != 0) 1706 return 0; 1707 1708 // Verify that the initializer is simple enough for us to handle. 1709 if (!I->hasInitializer()) return 0; 1710 ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); 1711 if (!CA) return 0; 1712 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1713 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(CA->getOperand(i))) { 1714 if (isa<ConstantPointerNull>(CS->getOperand(1))) 1715 continue; 1716 1717 // Must have a function or null ptr. 1718 if (!isa<Function>(CS->getOperand(1))) 1719 return 0; 1720 1721 // Init priority must be standard. 1722 ConstantInt *CI = dyn_cast<ConstantInt>(CS->getOperand(0)); 1723 if (!CI || CI->getZExtValue() != 65535) 1724 return 0; 1725 } else { 1726 return 0; 1727 } 1728 1729 return I; 1730 } 1731 return 0; 1732} 1733 1734/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, 1735/// return a list of the functions and null terminator as a vector. 1736static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { 1737 ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); 1738 std::vector<Function*> Result; 1739 Result.reserve(CA->getNumOperands()); 1740 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) { 1741 ConstantStruct *CS = cast<ConstantStruct>(CA->getOperand(i)); 1742 Result.push_back(dyn_cast<Function>(CS->getOperand(1))); 1743 } 1744 return Result; 1745} 1746 1747/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the 1748/// specified array, returning the new global to use. 1749static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, 1750 const std::vector<Function*> &Ctors) { 1751 // If we made a change, reassemble the initializer list. 1752 std::vector<Constant*> CSVals; 1753 CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); 1754 CSVals.push_back(0); 1755 1756 // Create the new init list. 1757 std::vector<Constant*> CAList; 1758 for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { 1759 if (Ctors[i]) { 1760 CSVals[1] = Ctors[i]; 1761 } else { 1762 const Type *FTy = FunctionType::get(Type::VoidTy, 1763 std::vector<const Type*>(), false); 1764 const PointerType *PFTy = PointerType::getUnqual(FTy); 1765 CSVals[1] = Constant::getNullValue(PFTy); 1766 CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); 1767 } 1768 CAList.push_back(ConstantStruct::get(CSVals)); 1769 } 1770 1771 // Create the array initializer. 1772 const Type *StructTy = 1773 cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); 1774 Constant *CA = ConstantArray::get(ArrayType::get(StructTy, CAList.size()), 1775 CAList); 1776 1777 // If we didn't change the number of elements, don't create a new GV. 1778 if (CA->getType() == GCL->getInitializer()->getType()) { 1779 GCL->setInitializer(CA); 1780 return GCL; 1781 } 1782 1783 // Create the new global and insert it next to the existing list. 1784 GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), 1785 GCL->getLinkage(), CA, "", 1786 (Module *)NULL, 1787 GCL->isThreadLocal()); 1788 GCL->getParent()->getGlobalList().insert(GCL, NGV); 1789 NGV->takeName(GCL); 1790 1791 // Nuke the old list, replacing any uses with the new one. 1792 if (!GCL->use_empty()) { 1793 Constant *V = NGV; 1794 if (V->getType() != GCL->getType()) 1795 V = ConstantExpr::getBitCast(V, GCL->getType()); 1796 GCL->replaceAllUsesWith(V); 1797 } 1798 GCL->eraseFromParent(); 1799 1800 if (Ctors.size()) 1801 return NGV; 1802 else 1803 return 0; 1804} 1805 1806 1807static Constant *getVal(std::map<Value*, Constant*> &ComputedValues, 1808 Value *V) { 1809 if (Constant *CV = dyn_cast<Constant>(V)) return CV; 1810 Constant *R = ComputedValues[V]; 1811 assert(R && "Reference to an uncomputed value!"); 1812 return R; 1813} 1814 1815/// isSimpleEnoughPointerToCommit - Return true if this constant is simple 1816/// enough for us to understand. In particular, if it is a cast of something, 1817/// we punt. We basically just support direct accesses to globals and GEP's of 1818/// globals. This should be kept up to date with CommitValueTo. 1819static bool isSimpleEnoughPointerToCommit(Constant *C) { 1820 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { 1821 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1822 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1823 return !GV->isDeclaration(); // reject external globals. 1824 } 1825 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) 1826 // Handle a constantexpr gep. 1827 if (CE->getOpcode() == Instruction::GetElementPtr && 1828 isa<GlobalVariable>(CE->getOperand(0))) { 1829 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1830 if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) 1831 return false; // do not allow weak/linkonce/dllimport/dllexport linkage. 1832 return GV->hasInitializer() && 1833 ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1834 } 1835 return false; 1836} 1837 1838/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global 1839/// initializer. This returns 'Init' modified to reflect 'Val' stored into it. 1840/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into. 1841static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, 1842 ConstantExpr *Addr, unsigned OpNo) { 1843 // Base case of the recursion. 1844 if (OpNo == Addr->getNumOperands()) { 1845 assert(Val->getType() == Init->getType() && "Type mismatch!"); 1846 return Val; 1847 } 1848 1849 if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { 1850 std::vector<Constant*> Elts; 1851 1852 // Break up the constant into its elements. 1853 if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { 1854 for (unsigned i = 0, e = CS->getNumOperands(); i != e; ++i) 1855 Elts.push_back(CS->getOperand(i)); 1856 } else if (isa<ConstantAggregateZero>(Init)) { 1857 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1858 Elts.push_back(Constant::getNullValue(STy->getElementType(i))); 1859 } else if (isa<UndefValue>(Init)) { 1860 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1861 Elts.push_back(UndefValue::get(STy->getElementType(i))); 1862 } else { 1863 assert(0 && "This code is out of sync with " 1864 " ConstantFoldLoadThroughGEPConstantExpr"); 1865 } 1866 1867 // Replace the element that we are supposed to. 1868 ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); 1869 unsigned Idx = CU->getZExtValue(); 1870 assert(Idx < STy->getNumElements() && "Struct index out of range!"); 1871 Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); 1872 1873 // Return the modified struct. 1874 return ConstantStruct::get(&Elts[0], Elts.size(), STy->isPacked()); 1875 } else { 1876 ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); 1877 const ArrayType *ATy = cast<ArrayType>(Init->getType()); 1878 1879 // Break up the array into elements. 1880 std::vector<Constant*> Elts; 1881 if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { 1882 for (unsigned i = 0, e = CA->getNumOperands(); i != e; ++i) 1883 Elts.push_back(CA->getOperand(i)); 1884 } else if (isa<ConstantAggregateZero>(Init)) { 1885 Constant *Elt = Constant::getNullValue(ATy->getElementType()); 1886 Elts.assign(ATy->getNumElements(), Elt); 1887 } else if (isa<UndefValue>(Init)) { 1888 Constant *Elt = UndefValue::get(ATy->getElementType()); 1889 Elts.assign(ATy->getNumElements(), Elt); 1890 } else { 1891 assert(0 && "This code is out of sync with " 1892 " ConstantFoldLoadThroughGEPConstantExpr"); 1893 } 1894 1895 assert(CI->getZExtValue() < ATy->getNumElements()); 1896 Elts[CI->getZExtValue()] = 1897 EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); 1898 return ConstantArray::get(ATy, Elts); 1899 } 1900} 1901 1902/// CommitValueTo - We have decided that Addr (which satisfies the predicate 1903/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. 1904static void CommitValueTo(Constant *Val, Constant *Addr) { 1905 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { 1906 assert(GV->hasInitializer()); 1907 GV->setInitializer(Val); 1908 return; 1909 } 1910 1911 ConstantExpr *CE = cast<ConstantExpr>(Addr); 1912 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1913 1914 Constant *Init = GV->getInitializer(); 1915 Init = EvaluateStoreInto(Init, Val, CE, 2); 1916 GV->setInitializer(Init); 1917} 1918 1919/// ComputeLoadResult - Return the value that would be computed by a load from 1920/// P after the stores reflected by 'memory' have been performed. If we can't 1921/// decide, return null. 1922static Constant *ComputeLoadResult(Constant *P, 1923 const std::map<Constant*, Constant*> &Memory) { 1924 // If this memory location has been recently stored, use the stored value: it 1925 // is the most up-to-date. 1926 std::map<Constant*, Constant*>::const_iterator I = Memory.find(P); 1927 if (I != Memory.end()) return I->second; 1928 1929 // Access it. 1930 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { 1931 if (GV->hasInitializer()) 1932 return GV->getInitializer(); 1933 return 0; 1934 } 1935 1936 // Handle a constantexpr getelementptr. 1937 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) 1938 if (CE->getOpcode() == Instruction::GetElementPtr && 1939 isa<GlobalVariable>(CE->getOperand(0))) { 1940 GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); 1941 if (GV->hasInitializer()) 1942 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); 1943 } 1944 1945 return 0; // don't know how to evaluate. 1946} 1947 1948/// EvaluateFunction - Evaluate a call to function F, returning true if 1949/// successful, false if we can't evaluate it. ActualArgs contains the formal 1950/// arguments for the function. 1951static bool EvaluateFunction(Function *F, Constant *&RetVal, 1952 const std::vector<Constant*> &ActualArgs, 1953 std::vector<Function*> &CallStack, 1954 std::map<Constant*, Constant*> &MutatedMemory, 1955 std::vector<GlobalVariable*> &AllocaTmps) { 1956 // Check to see if this function is already executing (recursion). If so, 1957 // bail out. TODO: we might want to accept limited recursion. 1958 if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) 1959 return false; 1960 1961 CallStack.push_back(F); 1962 1963 /// Values - As we compute SSA register values, we store their contents here. 1964 std::map<Value*, Constant*> Values; 1965 1966 // Initialize arguments to the incoming values specified. 1967 unsigned ArgNo = 0; 1968 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; 1969 ++AI, ++ArgNo) 1970 Values[AI] = ActualArgs[ArgNo]; 1971 1972 /// ExecutedBlocks - We only handle non-looping, non-recursive code. As such, 1973 /// we can only evaluate any one basic block at most once. This set keeps 1974 /// track of what we have executed so we can detect recursive cases etc. 1975 std::set<BasicBlock*> ExecutedBlocks; 1976 1977 // CurInst - The current instruction we're evaluating. 1978 BasicBlock::iterator CurInst = F->begin()->begin(); 1979 1980 // This is the main evaluation loop. 1981 while (1) { 1982 Constant *InstResult = 0; 1983 1984 if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { 1985 if (SI->isVolatile()) return false; // no volatile accesses. 1986 Constant *Ptr = getVal(Values, SI->getOperand(1)); 1987 if (!isSimpleEnoughPointerToCommit(Ptr)) 1988 // If this is too complex for us to commit, reject it. 1989 return false; 1990 Constant *Val = getVal(Values, SI->getOperand(0)); 1991 MutatedMemory[Ptr] = Val; 1992 } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { 1993 InstResult = ConstantExpr::get(BO->getOpcode(), 1994 getVal(Values, BO->getOperand(0)), 1995 getVal(Values, BO->getOperand(1))); 1996 } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { 1997 InstResult = ConstantExpr::getCompare(CI->getPredicate(), 1998 getVal(Values, CI->getOperand(0)), 1999 getVal(Values, CI->getOperand(1))); 2000 } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { 2001 InstResult = ConstantExpr::getCast(CI->getOpcode(), 2002 getVal(Values, CI->getOperand(0)), 2003 CI->getType()); 2004 } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { 2005 InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), 2006 getVal(Values, SI->getOperand(1)), 2007 getVal(Values, SI->getOperand(2))); 2008 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { 2009 Constant *P = getVal(Values, GEP->getOperand(0)); 2010 SmallVector<Constant*, 8> GEPOps; 2011 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i) 2012 GEPOps.push_back(getVal(Values, GEP->getOperand(i))); 2013 InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); 2014 } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { 2015 if (LI->isVolatile()) return false; // no volatile accesses. 2016 InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), 2017 MutatedMemory); 2018 if (InstResult == 0) return false; // Could not evaluate load. 2019 } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { 2020 if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. 2021 const Type *Ty = AI->getType()->getElementType(); 2022 AllocaTmps.push_back(new GlobalVariable(Ty, false, 2023 GlobalValue::InternalLinkage, 2024 UndefValue::get(Ty), 2025 AI->getName())); 2026 InstResult = AllocaTmps.back(); 2027 } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { 2028 // Cannot handle inline asm. 2029 if (isa<InlineAsm>(CI->getOperand(0))) return false; 2030 2031 // Resolve function pointers. 2032 Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); 2033 if (!Callee) return false; // Cannot resolve. 2034 2035 std::vector<Constant*> Formals; 2036 for (unsigned i = 1, e = CI->getNumOperands(); i != e; ++i) 2037 Formals.push_back(getVal(Values, CI->getOperand(i))); 2038 2039 if (Callee->isDeclaration()) { 2040 // If this is a function we can constant fold, do it. 2041 if (Constant *C = ConstantFoldCall(Callee, &Formals[0], 2042 Formals.size())) { 2043 InstResult = C; 2044 } else { 2045 return false; 2046 } 2047 } else { 2048 if (Callee->getFunctionType()->isVarArg()) 2049 return false; 2050 2051 Constant *RetVal; 2052 2053 // Execute the call, if successful, use the return value. 2054 if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, 2055 MutatedMemory, AllocaTmps)) 2056 return false; 2057 InstResult = RetVal; 2058 } 2059 } else if (isa<TerminatorInst>(CurInst)) { 2060 BasicBlock *NewBB = 0; 2061 if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { 2062 if (BI->isUnconditional()) { 2063 NewBB = BI->getSuccessor(0); 2064 } else { 2065 ConstantInt *Cond = 2066 dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); 2067 if (!Cond) return false; // Cannot determine. 2068 2069 NewBB = BI->getSuccessor(!Cond->getZExtValue()); 2070 } 2071 } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { 2072 ConstantInt *Val = 2073 dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); 2074 if (!Val) return false; // Cannot determine. 2075 NewBB = SI->getSuccessor(SI->findCaseValue(Val)); 2076 } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { 2077 if (RI->getNumOperands()) 2078 RetVal = getVal(Values, RI->getOperand(0)); 2079 2080 CallStack.pop_back(); // return from fn. 2081 return true; // We succeeded at evaluating this ctor! 2082 } else { 2083 // invoke, unwind, unreachable. 2084 return false; // Cannot handle this terminator. 2085 } 2086 2087 // Okay, we succeeded in evaluating this control flow. See if we have 2088 // executed the new block before. If so, we have a looping function, 2089 // which we cannot evaluate in reasonable time. 2090 if (!ExecutedBlocks.insert(NewBB).second) 2091 return false; // looped! 2092 2093 // Okay, we have never been in this block before. Check to see if there 2094 // are any PHI nodes. If so, evaluate them with information about where 2095 // we came from. 2096 BasicBlock *OldBB = CurInst->getParent(); 2097 CurInst = NewBB->begin(); 2098 PHINode *PN; 2099 for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) 2100 Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); 2101 2102 // Do NOT increment CurInst. We know that the terminator had no value. 2103 continue; 2104 } else { 2105 // Did not know how to evaluate this! 2106 return false; 2107 } 2108 2109 if (!CurInst->use_empty()) 2110 Values[CurInst] = InstResult; 2111 2112 // Advance program counter. 2113 ++CurInst; 2114 } 2115} 2116 2117/// EvaluateStaticConstructor - Evaluate static constructors in the function, if 2118/// we can. Return true if we can, false otherwise. 2119static bool EvaluateStaticConstructor(Function *F) { 2120 /// MutatedMemory - For each store we execute, we update this map. Loads 2121 /// check this to get the most up-to-date value. If evaluation is successful, 2122 /// this state is committed to the process. 2123 std::map<Constant*, Constant*> MutatedMemory; 2124 2125 /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable 2126 /// to represent its body. This vector is needed so we can delete the 2127 /// temporary globals when we are done. 2128 std::vector<GlobalVariable*> AllocaTmps; 2129 2130 /// CallStack - This is used to detect recursion. In pathological situations 2131 /// we could hit exponential behavior, but at least there is nothing 2132 /// unbounded. 2133 std::vector<Function*> CallStack; 2134 2135 // Call the function. 2136 Constant *RetValDummy; 2137 bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), 2138 CallStack, MutatedMemory, AllocaTmps); 2139 if (EvalSuccess) { 2140 // We succeeded at evaluation: commit the result. 2141 DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" 2142 << F->getName() << "' to " << MutatedMemory.size() 2143 << " stores.\n"; 2144 for (std::map<Constant*, Constant*>::iterator I = MutatedMemory.begin(), 2145 E = MutatedMemory.end(); I != E; ++I) 2146 CommitValueTo(I->second, I->first); 2147 } 2148 2149 // At this point, we are done interpreting. If we created any 'alloca' 2150 // temporaries, release them now. 2151 while (!AllocaTmps.empty()) { 2152 GlobalVariable *Tmp = AllocaTmps.back(); 2153 AllocaTmps.pop_back(); 2154 2155 // If there are still users of the alloca, the program is doing something 2156 // silly, e.g. storing the address of the alloca somewhere and using it 2157 // later. Since this is undefined, we'll just make it be null. 2158 if (!Tmp->use_empty()) 2159 Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); 2160 delete Tmp; 2161 } 2162 2163 return EvalSuccess; 2164} 2165 2166 2167 2168/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. 2169/// Return true if anything changed. 2170bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { 2171 std::vector<Function*> Ctors = ParseGlobalCtors(GCL); 2172 bool MadeChange = false; 2173 if (Ctors.empty()) return false; 2174 2175 // Loop over global ctors, optimizing them when we can. 2176 for (unsigned i = 0; i != Ctors.size(); ++i) { 2177 Function *F = Ctors[i]; 2178 // Found a null terminator in the middle of the list, prune off the rest of 2179 // the list. 2180 if (F == 0) { 2181 if (i != Ctors.size()-1) { 2182 Ctors.resize(i+1); 2183 MadeChange = true; 2184 } 2185 break; 2186 } 2187 2188 // We cannot simplify external ctor functions. 2189 if (F->empty()) continue; 2190 2191 // If we can evaluate the ctor at compile time, do. 2192 if (EvaluateStaticConstructor(F)) { 2193 Ctors.erase(Ctors.begin()+i); 2194 MadeChange = true; 2195 --i; 2196 ++NumCtorsEvaluated; 2197 continue; 2198 } 2199 } 2200 2201 if (!MadeChange) return false; 2202 2203 GCL = InstallGlobalCtors(GCL, Ctors); 2204 return true; 2205} 2206 2207 2208bool GlobalOpt::runOnModule(Module &M) { 2209 bool Changed = false; 2210 2211 // Try to find the llvm.globalctors list. 2212 GlobalVariable *GlobalCtors = FindGlobalCtors(M); 2213 2214 bool LocalChange = true; 2215 while (LocalChange) { 2216 LocalChange = false; 2217 2218 // Delete functions that are trivially dead, ccc -> fastcc 2219 LocalChange |= OptimizeFunctions(M); 2220 2221 // Optimize global_ctors list. 2222 if (GlobalCtors) 2223 LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); 2224 2225 // Optimize non-address-taken globals. 2226 LocalChange |= OptimizeGlobalVars(M); 2227 Changed |= LocalChange; 2228 } 2229 2230 // TODO: Move all global ctors functions to the end of the module for code 2231 // layout. 2232 2233 return Changed; 2234} 2235