MergeFunctions.cpp revision f53de86cba33b63ecd54e16dcea735939c5b0e4a
1//===- MergeFunctions.cpp - Merge identical functions ---------------------===// 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 looks for equivalent functions that are mergable and folds them. 11// 12// A hash is computed from the function, based on its type and number of 13// basic blocks. 14// 15// Once all hashes are computed, we perform an expensive equality comparison 16// on each function pair. This takes n^2/2 comparisons per bucket, so it's 17// important that the hash function be high quality. The equality comparison 18// iterates through each instruction in each basic block. 19// 20// When a match is found the functions are folded. If both functions are 21// overridable, we move the functionality into a new internal function and 22// leave two overridable thunks to it. 23// 24//===----------------------------------------------------------------------===// 25// 26// Future work: 27// 28// * virtual functions. 29// 30// Many functions have their address taken by the virtual function table for 31// the object they belong to. However, as long as it's only used for a lookup 32// and call, this is irrelevant, and we'd like to fold such functions. 33// 34// * switch from n^2 pair-wise comparisons to an n-way comparison for each 35// bucket. 36// 37// * be smarter about bitcasts. 38// 39// In order to fold functions, we will sometimes add either bitcast instructions 40// or bitcast constant expressions. Unfortunately, this can confound further 41// analysis since the two functions differ where one has a bitcast and the 42// other doesn't. We should learn to look through bitcasts. 43// 44//===----------------------------------------------------------------------===// 45 46#define DEBUG_TYPE "mergefunc" 47#include "llvm/Transforms/IPO.h" 48#include "llvm/ADT/DenseSet.h" 49#include "llvm/ADT/FoldingSet.h" 50#include "llvm/ADT/SmallSet.h" 51#include "llvm/ADT/Statistic.h" 52#include "llvm/ADT/STLExtras.h" 53#include "llvm/Constants.h" 54#include "llvm/InlineAsm.h" 55#include "llvm/Instructions.h" 56#include "llvm/LLVMContext.h" 57#include "llvm/Module.h" 58#include "llvm/Pass.h" 59#include "llvm/Support/CallSite.h" 60#include "llvm/Support/Debug.h" 61#include "llvm/Support/ErrorHandling.h" 62#include "llvm/Support/IRBuilder.h" 63#include "llvm/Support/ValueHandle.h" 64#include "llvm/Support/raw_ostream.h" 65#include "llvm/Target/TargetData.h" 66using namespace llvm; 67 68STATISTIC(NumFunctionsMerged, "Number of functions merged"); 69 70namespace { 71 /// MergeFunctions finds functions which will generate identical machine code, 72 /// by considering all pointer types to be equivalent. Once identified, 73 /// MergeFunctions will fold them by replacing a call to one to a call to a 74 /// bitcast of the other. 75 /// 76 class MergeFunctions : public ModulePass { 77 public: 78 static char ID; 79 MergeFunctions() : ModulePass(ID) {} 80 81 bool runOnModule(Module &M); 82 83 private: 84 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G 85 /// is deleted. 86 void MergeTwoFunctions(Function *F, Function *G) const; 87 88 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also 89 /// replace direct uses of G with bitcast(F). 90 void WriteThunk(Function *F, Function *G) const; 91 92 TargetData *TD; 93 }; 94} 95 96char MergeFunctions::ID = 0; 97INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false); 98 99ModulePass *llvm::createMergeFunctionsPass() { 100 return new MergeFunctions(); 101} 102 103namespace { 104/// FunctionComparator - Compares two functions to determine whether or not 105/// they will generate machine code with the same behaviour. TargetData is 106/// used if available. The comparator always fails conservatively (erring on the 107/// side of claiming that two functions are different). 108class FunctionComparator { 109public: 110 FunctionComparator(const TargetData *TD, const Function *F1, 111 const Function *F2) 112 : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {} 113 114 /// Compare - test whether the two functions have equivalent behaviour. 115 bool Compare(); 116 117private: 118 /// Compare - test whether two basic blocks have equivalent behaviour. 119 bool Compare(const BasicBlock *BB1, const BasicBlock *BB2); 120 121 /// Enumerate - Assign or look up previously assigned numbers for the two 122 /// values, and return whether the numbers are equal. Numbers are assigned in 123 /// the order visited. 124 bool Enumerate(const Value *V1, const Value *V2); 125 126 /// isEquivalentOperation - Compare two Instructions for equivalence, similar 127 /// to Instruction::isSameOperationAs but with modifications to the type 128 /// comparison. 129 bool isEquivalentOperation(const Instruction *I1, 130 const Instruction *I2) const; 131 132 /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic. 133 bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2); 134 bool isEquivalentGEP(const GetElementPtrInst *GEP1, 135 const GetElementPtrInst *GEP2) { 136 return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2)); 137 } 138 139 /// isEquivalentType - Compare two Types, treating all pointer types as equal. 140 bool isEquivalentType(const Type *Ty1, const Type *Ty2) const; 141 142 // The two functions undergoing comparison. 143 const Function *F1, *F2; 144 145 const TargetData *TD; 146 147 typedef DenseMap<const Value *, unsigned long> IDMap; 148 IDMap Map1, Map2; 149 unsigned long IDMap1Count, IDMap2Count; 150}; 151} 152 153/// isEquivalentType - any two pointers in the same address space are 154/// equivalent. Otherwise, standard type equivalence rules apply. 155bool FunctionComparator::isEquivalentType(const Type *Ty1, 156 const Type *Ty2) const { 157 if (Ty1 == Ty2) 158 return true; 159 if (Ty1->getTypeID() != Ty2->getTypeID()) 160 return false; 161 162 switch(Ty1->getTypeID()) { 163 default: 164 llvm_unreachable("Unknown type!"); 165 // Fall through in Release mode. 166 case Type::IntegerTyID: 167 case Type::OpaqueTyID: 168 // Ty1 == Ty2 would have returned true earlier. 169 return false; 170 171 case Type::VoidTyID: 172 case Type::FloatTyID: 173 case Type::DoubleTyID: 174 case Type::X86_FP80TyID: 175 case Type::FP128TyID: 176 case Type::PPC_FP128TyID: 177 case Type::LabelTyID: 178 case Type::MetadataTyID: 179 return true; 180 181 case Type::PointerTyID: { 182 const PointerType *PTy1 = cast<PointerType>(Ty1); 183 const PointerType *PTy2 = cast<PointerType>(Ty2); 184 return PTy1->getAddressSpace() == PTy2->getAddressSpace(); 185 } 186 187 case Type::StructTyID: { 188 const StructType *STy1 = cast<StructType>(Ty1); 189 const StructType *STy2 = cast<StructType>(Ty2); 190 if (STy1->getNumElements() != STy2->getNumElements()) 191 return false; 192 193 if (STy1->isPacked() != STy2->isPacked()) 194 return false; 195 196 for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) { 197 if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i))) 198 return false; 199 } 200 return true; 201 } 202 203 case Type::FunctionTyID: { 204 const FunctionType *FTy1 = cast<FunctionType>(Ty1); 205 const FunctionType *FTy2 = cast<FunctionType>(Ty2); 206 if (FTy1->getNumParams() != FTy2->getNumParams() || 207 FTy1->isVarArg() != FTy2->isVarArg()) 208 return false; 209 210 if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType())) 211 return false; 212 213 for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) { 214 if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i))) 215 return false; 216 } 217 return true; 218 } 219 220 case Type::ArrayTyID: { 221 const ArrayType *ATy1 = cast<ArrayType>(Ty1); 222 const ArrayType *ATy2 = cast<ArrayType>(Ty2); 223 return ATy1->getNumElements() == ATy2->getNumElements() && 224 isEquivalentType(ATy1->getElementType(), ATy2->getElementType()); 225 } 226 227 case Type::VectorTyID: { 228 const VectorType *VTy1 = cast<VectorType>(Ty1); 229 const VectorType *VTy2 = cast<VectorType>(Ty2); 230 return VTy1->getNumElements() == VTy2->getNumElements() && 231 isEquivalentType(VTy1->getElementType(), VTy2->getElementType()); 232 } 233 } 234} 235 236/// isEquivalentOperation - determine whether the two operations are the same 237/// except that pointer-to-A and pointer-to-B are equivalent. This should be 238/// kept in sync with Instruction::isSameOperationAs. 239bool FunctionComparator::isEquivalentOperation(const Instruction *I1, 240 const Instruction *I2) const { 241 if (I1->getOpcode() != I2->getOpcode() || 242 I1->getNumOperands() != I2->getNumOperands() || 243 !isEquivalentType(I1->getType(), I2->getType()) || 244 !I1->hasSameSubclassOptionalData(I2)) 245 return false; 246 247 // We have two instructions of identical opcode and #operands. Check to see 248 // if all operands are the same type 249 for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i) 250 if (!isEquivalentType(I1->getOperand(i)->getType(), 251 I2->getOperand(i)->getType())) 252 return false; 253 254 // Check special state that is a part of some instructions. 255 if (const LoadInst *LI = dyn_cast<LoadInst>(I1)) 256 return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() && 257 LI->getAlignment() == cast<LoadInst>(I2)->getAlignment(); 258 if (const StoreInst *SI = dyn_cast<StoreInst>(I1)) 259 return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() && 260 SI->getAlignment() == cast<StoreInst>(I2)->getAlignment(); 261 if (const CmpInst *CI = dyn_cast<CmpInst>(I1)) 262 return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate(); 263 if (const CallInst *CI = dyn_cast<CallInst>(I1)) 264 return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() && 265 CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() && 266 CI->getAttributes().getRawPointer() == 267 cast<CallInst>(I2)->getAttributes().getRawPointer(); 268 if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1)) 269 return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() && 270 CI->getAttributes().getRawPointer() == 271 cast<InvokeInst>(I2)->getAttributes().getRawPointer(); 272 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) { 273 if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices()) 274 return false; 275 for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i) 276 if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i]) 277 return false; 278 return true; 279 } 280 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) { 281 if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices()) 282 return false; 283 for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i) 284 if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i]) 285 return false; 286 return true; 287 } 288 289 return true; 290} 291 292/// isEquivalentGEP - determine whether two GEP operations perform the same 293/// underlying arithmetic. 294bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1, 295 const GEPOperator *GEP2) { 296 // When we have target data, we can reduce the GEP down to the value in bytes 297 // added to the address. 298 if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) { 299 SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end()); 300 SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end()); 301 uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(), 302 Indices1.data(), Indices1.size()); 303 uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(), 304 Indices2.data(), Indices2.size()); 305 return Offset1 == Offset2; 306 } 307 308 if (GEP1->getPointerOperand()->getType() != 309 GEP2->getPointerOperand()->getType()) 310 return false; 311 312 if (GEP1->getNumOperands() != GEP2->getNumOperands()) 313 return false; 314 315 for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) { 316 if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i))) 317 return false; 318 } 319 320 return true; 321} 322 323/// Enumerate - Compare two values used by the two functions under pair-wise 324/// comparison. If this is the first time the values are seen, they're added to 325/// the mapping so that we will detect mismatches on next use. 326bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) { 327 // Check for function @f1 referring to itself and function @f2 referring to 328 // itself, or referring to each other, or both referring to either of them. 329 // They're all equivalent if the two functions are otherwise equivalent. 330 if (V1 == F1 && V2 == F2) 331 return true; 332 if (V1 == F2 && V2 == F1) 333 return true; 334 335 // TODO: constant expressions with GEP or references to F1 or F2. 336 if (isa<Constant>(V1)) 337 return V1 == V2; 338 339 if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) { 340 const InlineAsm *IA1 = cast<InlineAsm>(V1); 341 const InlineAsm *IA2 = cast<InlineAsm>(V2); 342 return IA1->getAsmString() == IA2->getAsmString() && 343 IA1->getConstraintString() == IA2->getConstraintString(); 344 } 345 346 unsigned long &ID1 = Map1[V1]; 347 if (!ID1) 348 ID1 = ++IDMap1Count; 349 350 unsigned long &ID2 = Map2[V2]; 351 if (!ID2) 352 ID2 = ++IDMap2Count; 353 354 return ID1 == ID2; 355} 356 357/// Compare - test whether two basic blocks have equivalent behaviour. 358bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) { 359 BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end(); 360 BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end(); 361 362 do { 363 if (!Enumerate(F1I, F2I)) 364 return false; 365 366 if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) { 367 const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I); 368 if (!GEP2) 369 return false; 370 371 if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand())) 372 return false; 373 374 if (!isEquivalentGEP(GEP1, GEP2)) 375 return false; 376 } else { 377 if (!isEquivalentOperation(F1I, F2I)) 378 return false; 379 380 assert(F1I->getNumOperands() == F2I->getNumOperands()); 381 for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) { 382 Value *OpF1 = F1I->getOperand(i); 383 Value *OpF2 = F2I->getOperand(i); 384 385 if (!Enumerate(OpF1, OpF2)) 386 return false; 387 388 if (OpF1->getValueID() != OpF2->getValueID() || 389 !isEquivalentType(OpF1->getType(), OpF2->getType())) 390 return false; 391 } 392 } 393 394 ++F1I, ++F2I; 395 } while (F1I != F1E && F2I != F2E); 396 397 return F1I == F1E && F2I == F2E; 398} 399 400/// Compare - test whether the two functions have equivalent behaviour. 401bool FunctionComparator::Compare() { 402 // We need to recheck everything, but check the things that weren't included 403 // in the hash first. 404 405 if (F1->getAttributes() != F2->getAttributes()) 406 return false; 407 408 if (F1->hasGC() != F2->hasGC()) 409 return false; 410 411 if (F1->hasGC() && F1->getGC() != F2->getGC()) 412 return false; 413 414 if (F1->hasSection() != F2->hasSection()) 415 return false; 416 417 if (F1->hasSection() && F1->getSection() != F2->getSection()) 418 return false; 419 420 if (F1->isVarArg() != F2->isVarArg()) 421 return false; 422 423 // TODO: if it's internal and only used in direct calls, we could handle this 424 // case too. 425 if (F1->getCallingConv() != F2->getCallingConv()) 426 return false; 427 428 if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType())) 429 return false; 430 431 assert(F1->arg_size() == F2->arg_size() && 432 "Identical functions have a different number of args."); 433 434 // Visit the arguments so that they get enumerated in the order they're 435 // passed in. 436 for (Function::const_arg_iterator f1i = F1->arg_begin(), 437 f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) { 438 if (!Enumerate(f1i, f2i)) 439 llvm_unreachable("Arguments repeat"); 440 } 441 442 // We do a CFG-ordered walk since the actual ordering of the blocks in the 443 // linked list is immaterial. Our walk starts at the entry block for both 444 // functions, then takes each block from each terminator in order. As an 445 // artifact, this also means that unreachable blocks are ignored. 446 SmallVector<const BasicBlock *, 8> F1BBs, F2BBs; 447 SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1. 448 449 F1BBs.push_back(&F1->getEntryBlock()); 450 F2BBs.push_back(&F2->getEntryBlock()); 451 452 VisitedBBs.insert(F1BBs[0]); 453 while (!F1BBs.empty()) { 454 const BasicBlock *F1BB = F1BBs.pop_back_val(); 455 const BasicBlock *F2BB = F2BBs.pop_back_val(); 456 457 if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB)) 458 return false; 459 460 const TerminatorInst *F1TI = F1BB->getTerminator(); 461 const TerminatorInst *F2TI = F2BB->getTerminator(); 462 463 assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors()); 464 for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) { 465 if (!VisitedBBs.insert(F1TI->getSuccessor(i))) 466 continue; 467 468 F1BBs.push_back(F1TI->getSuccessor(i)); 469 F2BBs.push_back(F2TI->getSuccessor(i)); 470 } 471 } 472 return true; 473} 474 475/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace 476/// direct uses of G with bitcast(F). 477void MergeFunctions::WriteThunk(Function *F, Function *G) const { 478 if (!G->mayBeOverridden()) { 479 // Redirect direct callers of G to F. 480 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType()); 481 for (Value::use_iterator UI = G->use_begin(), UE = G->use_end(); 482 UI != UE;) { 483 Value::use_iterator TheIter = UI; 484 ++UI; 485 CallSite CS(*TheIter); 486 if (CS && CS.isCallee(TheIter)) 487 TheIter.getUse().set(BitcastF); 488 } 489 } 490 491 // If G was internal then we may have replaced all uses if G with F. If so, 492 // stop here and delete G. There's no need for a thunk. 493 if (G->hasLocalLinkage() && G->use_empty()) { 494 G->eraseFromParent(); 495 return; 496 } 497 498 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "", 499 G->getParent()); 500 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG); 501 IRBuilder<false> Builder(BB); 502 503 SmallVector<Value *, 16> Args; 504 unsigned i = 0; 505 const FunctionType *FFTy = F->getFunctionType(); 506 for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end(); 507 AI != AE; ++AI) { 508 Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i))); 509 ++i; 510 } 511 512 CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end()); 513 CI->setTailCall(); 514 CI->setCallingConv(F->getCallingConv()); 515 if (NewG->getReturnType()->isVoidTy()) { 516 Builder.CreateRetVoid(); 517 } else { 518 Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType())); 519 } 520 521 NewG->copyAttributesFrom(G); 522 NewG->takeName(G); 523 G->replaceAllUsesWith(NewG); 524 G->eraseFromParent(); 525} 526 527/// MergeTwoFunctions - Merge two equivalent functions. Upon completion, 528/// Function G is deleted. 529void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) const { 530 if (F->isWeakForLinker()) { 531 assert(G->isWeakForLinker()); 532 533 // Make them both thunks to the same internal function. 534 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "", 535 F->getParent()); 536 H->copyAttributesFrom(F); 537 H->takeName(F); 538 F->replaceAllUsesWith(H); 539 540 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment()); 541 542 WriteThunk(F, G); 543 WriteThunk(F, H); 544 545 F->setAlignment(MaxAlignment); 546 F->setLinkage(GlobalValue::InternalLinkage); 547 } else { 548 WriteThunk(F, G); 549 } 550 551 ++NumFunctionsMerged; 552} 553 554static unsigned ProfileFunction(const Function *F) { 555 const FunctionType *FTy = F->getFunctionType(); 556 557 FoldingSetNodeID ID; 558 ID.AddInteger(F->size()); 559 ID.AddInteger(F->getCallingConv()); 560 ID.AddBoolean(F->hasGC()); 561 ID.AddBoolean(FTy->isVarArg()); 562 ID.AddInteger(FTy->getReturnType()->getTypeID()); 563 for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) 564 ID.AddInteger(FTy->getParamType(i)->getTypeID()); 565 return ID.ComputeHash(); 566} 567 568class ComparableFunction { 569public: 570 ComparableFunction(Function *Func, TargetData *TD) 571 : Func(Func), Hash(ProfileFunction(Func)), TD(TD) {} 572 573 AssertingVH<Function> const Func; 574 const unsigned Hash; 575 TargetData * const TD; 576}; 577 578struct MergeFunctionsEqualityInfo { 579 static ComparableFunction *getEmptyKey() { 580 return reinterpret_cast<ComparableFunction*>(0); 581 } 582 static ComparableFunction *getTombstoneKey() { 583 return reinterpret_cast<ComparableFunction*>(-1); 584 } 585 static unsigned getHashValue(const ComparableFunction *CF) { 586 return CF->Hash; 587 } 588 static bool isEqual(const ComparableFunction *LHS, 589 const ComparableFunction *RHS) { 590 if (LHS == RHS) 591 return true; 592 if (LHS == getEmptyKey() || LHS == getTombstoneKey() || 593 RHS == getEmptyKey() || RHS == getTombstoneKey()) 594 return false; 595 assert(LHS->TD == RHS->TD && "Comparing functions for different targets"); 596 return FunctionComparator(LHS->TD, LHS->Func, RHS->Func).Compare(); 597 } 598}; 599 600bool MergeFunctions::runOnModule(Module &M) { 601 bool Changed = false; 602 603 TD = getAnalysisIfAvailable<TargetData>(); 604 605 typedef DenseSet<ComparableFunction *, MergeFunctionsEqualityInfo> FnSetType; 606 FnSetType FnSet; 607 for (Module::iterator F = M.begin(), E = M.end(); F != E;) { 608 if (F->isDeclaration() || F->hasAvailableExternallyLinkage()) { 609 ++F; 610 continue; 611 } 612 613 ComparableFunction *NewF = new ComparableFunction(F, TD); 614 ++F; 615 std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF); 616 if (!Result.second) { 617 ComparableFunction *&OldF = *Result.first; 618 assert(OldF && "Expected a hash collision"); 619 620 // NewF will be deleted in favour of OldF unless NewF is strong and OldF 621 // is weak in which case swap them to keep the strong definition. 622 623 if (OldF->Func->isWeakForLinker() && !NewF->Func->isWeakForLinker()) 624 std::swap(OldF, NewF); 625 626 DEBUG(dbgs() << " " << OldF->Func->getName() << " == " 627 << NewF->Func->getName() << '\n'); 628 629 Changed = true; 630 Function *DeleteF = NewF->Func; 631 delete NewF; 632 MergeTwoFunctions(OldF->Func, DeleteF); 633 } 634 } 635 636 DeleteContainerPointers(FnSet); 637 return Changed; 638} 639