MergeFunctions.cpp revision e8f8139429ffc41ae3a339d4a32e336a74f189c0
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" 66#include <vector> 67using namespace llvm; 68 69STATISTIC(NumFunctionsMerged, "Number of functions merged"); 70STATISTIC(NumThunksWritten, "Number of thunks generated"); 71STATISTIC(NumDoubleWeak, "Number of new functions created"); 72 73/// ProfileFunction - Creates a hash-code for the function which is the same 74/// for any two functions that will compare equal, without looking at the 75/// instructions inside the function. 76static unsigned ProfileFunction(const Function *F) { 77 const FunctionType *FTy = F->getFunctionType(); 78 79 FoldingSetNodeID ID; 80 ID.AddInteger(F->size()); 81 ID.AddInteger(F->getCallingConv()); 82 ID.AddBoolean(F->hasGC()); 83 ID.AddBoolean(FTy->isVarArg()); 84 ID.AddInteger(FTy->getReturnType()->getTypeID()); 85 for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i) 86 ID.AddInteger(FTy->getParamType(i)->getTypeID()); 87 return ID.ComputeHash(); 88} 89 90namespace { 91 92class ComparableFunction { 93public: 94 static const ComparableFunction EmptyKey; 95 static const ComparableFunction TombstoneKey; 96 97 ComparableFunction(Function *Func, TargetData *TD) 98 : Func(Func), Hash(ProfileFunction(Func)), TD(TD) {} 99 100 Function *getFunc() const { return Func; } 101 unsigned getHash() const { return Hash; } 102 TargetData *getTD() const { return TD; } 103 104 // Drops AssertingVH reference to the function. Outside of debug mode, this 105 // does nothing. 106 void release() { 107 assert(Func && 108 "Attempted to release function twice, or release empty/tombstone!"); 109 Func = NULL; 110 } 111 112 bool &getOrInsertCachedComparison(const ComparableFunction &Other, 113 bool &inserted) const { 114 typedef DenseMap<Function *, bool>::iterator iterator; 115 std::pair<iterator, bool> p = 116 CompareResultCache.insert(std::make_pair(Other.getFunc(), false)); 117 inserted = p.second; 118 return p.first->second; 119 } 120 121private: 122 explicit ComparableFunction(unsigned Hash) 123 : Func(NULL), Hash(Hash), TD(NULL) {} 124 125 // DenseMap::grow() triggers a recomparison of all keys in the map, which is 126 // wildly expensive. This cache tries to preserve known results. 127 mutable DenseMap<Function *, bool> CompareResultCache; 128 129 AssertingVH<Function> Func; 130 unsigned Hash; 131 TargetData *TD; 132}; 133 134const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0); 135const ComparableFunction ComparableFunction::TombstoneKey = 136 ComparableFunction(1); 137 138} 139 140namespace llvm { 141 template <> 142 struct DenseMapInfo<ComparableFunction> { 143 static ComparableFunction getEmptyKey() { 144 return ComparableFunction::EmptyKey; 145 } 146 static ComparableFunction getTombstoneKey() { 147 return ComparableFunction::TombstoneKey; 148 } 149 static unsigned getHashValue(const ComparableFunction &CF) { 150 return CF.getHash(); 151 } 152 static bool isEqual(const ComparableFunction &LHS, 153 const ComparableFunction &RHS); 154 }; 155} 156 157namespace { 158 159/// MergeFunctions finds functions which will generate identical machine code, 160/// by considering all pointer types to be equivalent. Once identified, 161/// MergeFunctions will fold them by replacing a call to one to a call to a 162/// bitcast of the other. 163/// 164class MergeFunctions : public ModulePass { 165public: 166 static char ID; 167 MergeFunctions() : ModulePass(ID) { 168 initializeMergeFunctionsPass(*PassRegistry::getPassRegistry()); 169 } 170 171 bool runOnModule(Module &M); 172 173private: 174 typedef DenseSet<ComparableFunction> FnSetType; 175 176 /// A work queue of functions that may have been modified and should be 177 /// analyzed again. 178 std::vector<WeakVH> Deferred; 179 180 /// Insert a ComparableFunction into the FnSet, or merge it away if it's 181 /// equal to one that's already present. 182 bool Insert(ComparableFunction &NewF); 183 184 /// Remove a Function from the FnSet and queue it up for a second sweep of 185 /// analysis. 186 void Remove(Function *F); 187 188 /// Find the functions that use this Value and remove them from FnSet and 189 /// queue the functions. 190 void RemoveUsers(Value *V); 191 192 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G 193 /// may be deleted, or may be converted into a thunk. In either case, it 194 /// should never be visited again. 195 void MergeTwoFunctions(Function *F, Function *G); 196 197 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also 198 /// replace direct uses of G with bitcast(F). Deletes G. 199 void WriteThunk(Function *F, Function *G); 200 201 /// The set of all distinct functions. Use the Insert and Remove methods to 202 /// modify it. 203 FnSetType FnSet; 204 205 /// TargetData for more accurate GEP comparisons. May be NULL. 206 TargetData *TD; 207}; 208 209} // end anonymous namespace 210 211char MergeFunctions::ID = 0; 212INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false) 213 214ModulePass *llvm::createMergeFunctionsPass() { 215 return new MergeFunctions(); 216} 217 218namespace { 219/// FunctionComparator - Compares two functions to determine whether or not 220/// they will generate machine code with the same behaviour. TargetData is 221/// used if available. The comparator always fails conservatively (erring on the 222/// side of claiming that two functions are different). 223class FunctionComparator { 224public: 225 FunctionComparator(const TargetData *TD, const Function *F1, 226 const Function *F2) 227 : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {} 228 229 /// Compare - test whether the two functions have equivalent behaviour. 230 bool Compare(); 231 232private: 233 /// Compare - test whether two basic blocks have equivalent behaviour. 234 bool Compare(const BasicBlock *BB1, const BasicBlock *BB2); 235 236 /// Enumerate - Assign or look up previously assigned numbers for the two 237 /// values, and return whether the numbers are equal. Numbers are assigned in 238 /// the order visited. 239 bool Enumerate(const Value *V1, const Value *V2); 240 241 /// isEquivalentOperation - Compare two Instructions for equivalence, similar 242 /// to Instruction::isSameOperationAs but with modifications to the type 243 /// comparison. 244 bool isEquivalentOperation(const Instruction *I1, 245 const Instruction *I2) const; 246 247 /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic. 248 bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2); 249 bool isEquivalentGEP(const GetElementPtrInst *GEP1, 250 const GetElementPtrInst *GEP2) { 251 return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2)); 252 } 253 254 /// isEquivalentType - Compare two Types, treating all pointer types as equal. 255 bool isEquivalentType(const Type *Ty1, const Type *Ty2) const; 256 257 // The two functions undergoing comparison. 258 const Function *F1, *F2; 259 260 const TargetData *TD; 261 262 typedef DenseMap<const Value *, unsigned long> IDMap; 263 IDMap Map1, Map2; 264 unsigned long IDMap1Count, IDMap2Count; 265}; 266} 267 268/// isEquivalentType - any two pointers in the same address space are 269/// equivalent. Otherwise, standard type equivalence rules apply. 270bool FunctionComparator::isEquivalentType(const Type *Ty1, 271 const Type *Ty2) const { 272 if (Ty1 == Ty2) 273 return true; 274 if (Ty1->getTypeID() != Ty2->getTypeID()) 275 return false; 276 277 switch(Ty1->getTypeID()) { 278 default: 279 llvm_unreachable("Unknown type!"); 280 // Fall through in Release mode. 281 case Type::IntegerTyID: 282 case Type::OpaqueTyID: 283 // Ty1 == Ty2 would have returned true earlier. 284 return false; 285 286 case Type::VoidTyID: 287 case Type::FloatTyID: 288 case Type::DoubleTyID: 289 case Type::X86_FP80TyID: 290 case Type::FP128TyID: 291 case Type::PPC_FP128TyID: 292 case Type::LabelTyID: 293 case Type::MetadataTyID: 294 return true; 295 296 case Type::PointerTyID: { 297 const PointerType *PTy1 = cast<PointerType>(Ty1); 298 const PointerType *PTy2 = cast<PointerType>(Ty2); 299 return PTy1->getAddressSpace() == PTy2->getAddressSpace(); 300 } 301 302 case Type::StructTyID: { 303 const StructType *STy1 = cast<StructType>(Ty1); 304 const StructType *STy2 = cast<StructType>(Ty2); 305 if (STy1->getNumElements() != STy2->getNumElements()) 306 return false; 307 308 if (STy1->isPacked() != STy2->isPacked()) 309 return false; 310 311 for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) { 312 if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i))) 313 return false; 314 } 315 return true; 316 } 317 318 case Type::FunctionTyID: { 319 const FunctionType *FTy1 = cast<FunctionType>(Ty1); 320 const FunctionType *FTy2 = cast<FunctionType>(Ty2); 321 if (FTy1->getNumParams() != FTy2->getNumParams() || 322 FTy1->isVarArg() != FTy2->isVarArg()) 323 return false; 324 325 if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType())) 326 return false; 327 328 for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) { 329 if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i))) 330 return false; 331 } 332 return true; 333 } 334 335 case Type::ArrayTyID: { 336 const ArrayType *ATy1 = cast<ArrayType>(Ty1); 337 const ArrayType *ATy2 = cast<ArrayType>(Ty2); 338 return ATy1->getNumElements() == ATy2->getNumElements() && 339 isEquivalentType(ATy1->getElementType(), ATy2->getElementType()); 340 } 341 342 case Type::VectorTyID: { 343 const VectorType *VTy1 = cast<VectorType>(Ty1); 344 const VectorType *VTy2 = cast<VectorType>(Ty2); 345 return VTy1->getNumElements() == VTy2->getNumElements() && 346 isEquivalentType(VTy1->getElementType(), VTy2->getElementType()); 347 } 348 } 349} 350 351/// isEquivalentOperation - determine whether the two operations are the same 352/// except that pointer-to-A and pointer-to-B are equivalent. This should be 353/// kept in sync with Instruction::isSameOperationAs. 354bool FunctionComparator::isEquivalentOperation(const Instruction *I1, 355 const Instruction *I2) const { 356 if (I1->getOpcode() != I2->getOpcode() || 357 I1->getNumOperands() != I2->getNumOperands() || 358 !isEquivalentType(I1->getType(), I2->getType()) || 359 !I1->hasSameSubclassOptionalData(I2)) 360 return false; 361 362 // We have two instructions of identical opcode and #operands. Check to see 363 // if all operands are the same type 364 for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i) 365 if (!isEquivalentType(I1->getOperand(i)->getType(), 366 I2->getOperand(i)->getType())) 367 return false; 368 369 // Check special state that is a part of some instructions. 370 if (const LoadInst *LI = dyn_cast<LoadInst>(I1)) 371 return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() && 372 LI->getAlignment() == cast<LoadInst>(I2)->getAlignment(); 373 if (const StoreInst *SI = dyn_cast<StoreInst>(I1)) 374 return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() && 375 SI->getAlignment() == cast<StoreInst>(I2)->getAlignment(); 376 if (const CmpInst *CI = dyn_cast<CmpInst>(I1)) 377 return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate(); 378 if (const CallInst *CI = dyn_cast<CallInst>(I1)) 379 return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() && 380 CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() && 381 CI->getAttributes().getRawPointer() == 382 cast<CallInst>(I2)->getAttributes().getRawPointer(); 383 if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1)) 384 return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() && 385 CI->getAttributes().getRawPointer() == 386 cast<InvokeInst>(I2)->getAttributes().getRawPointer(); 387 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) { 388 if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices()) 389 return false; 390 for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i) 391 if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i]) 392 return false; 393 return true; 394 } 395 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) { 396 if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices()) 397 return false; 398 for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i) 399 if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i]) 400 return false; 401 return true; 402 } 403 404 return true; 405} 406 407/// isEquivalentGEP - determine whether two GEP operations perform the same 408/// underlying arithmetic. 409bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1, 410 const GEPOperator *GEP2) { 411 // When we have target data, we can reduce the GEP down to the value in bytes 412 // added to the address. 413 if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) { 414 SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end()); 415 SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end()); 416 uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(), 417 Indices1.data(), Indices1.size()); 418 uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(), 419 Indices2.data(), Indices2.size()); 420 return Offset1 == Offset2; 421 } 422 423 if (GEP1->getPointerOperand()->getType() != 424 GEP2->getPointerOperand()->getType()) 425 return false; 426 427 if (GEP1->getNumOperands() != GEP2->getNumOperands()) 428 return false; 429 430 for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) { 431 if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i))) 432 return false; 433 } 434 435 return true; 436} 437 438/// Enumerate - Compare two values used by the two functions under pair-wise 439/// comparison. If this is the first time the values are seen, they're added to 440/// the mapping so that we will detect mismatches on next use. 441bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) { 442 // Check for function @f1 referring to itself and function @f2 referring to 443 // itself, or referring to each other, or both referring to either of them. 444 // They're all equivalent if the two functions are otherwise equivalent. 445 if (V1 == F1 && V2 == F2) 446 return true; 447 if (V1 == F2 && V2 == F1) 448 return true; 449 450 // TODO: constant expressions with GEP or references to F1 or F2. 451 if (isa<Constant>(V1)) 452 return V1 == V2; 453 454 if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) { 455 const InlineAsm *IA1 = cast<InlineAsm>(V1); 456 const InlineAsm *IA2 = cast<InlineAsm>(V2); 457 return IA1->getAsmString() == IA2->getAsmString() && 458 IA1->getConstraintString() == IA2->getConstraintString(); 459 } 460 461 unsigned long &ID1 = Map1[V1]; 462 if (!ID1) 463 ID1 = ++IDMap1Count; 464 465 unsigned long &ID2 = Map2[V2]; 466 if (!ID2) 467 ID2 = ++IDMap2Count; 468 469 return ID1 == ID2; 470} 471 472/// Compare - test whether two basic blocks have equivalent behaviour. 473bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) { 474 BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end(); 475 BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end(); 476 477 do { 478 if (!Enumerate(F1I, F2I)) 479 return false; 480 481 if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) { 482 const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I); 483 if (!GEP2) 484 return false; 485 486 if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand())) 487 return false; 488 489 if (!isEquivalentGEP(GEP1, GEP2)) 490 return false; 491 } else { 492 if (!isEquivalentOperation(F1I, F2I)) 493 return false; 494 495 assert(F1I->getNumOperands() == F2I->getNumOperands()); 496 for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) { 497 Value *OpF1 = F1I->getOperand(i); 498 Value *OpF2 = F2I->getOperand(i); 499 500 if (!Enumerate(OpF1, OpF2)) 501 return false; 502 503 if (OpF1->getValueID() != OpF2->getValueID() || 504 !isEquivalentType(OpF1->getType(), OpF2->getType())) 505 return false; 506 } 507 } 508 509 ++F1I, ++F2I; 510 } while (F1I != F1E && F2I != F2E); 511 512 return F1I == F1E && F2I == F2E; 513} 514 515/// Compare - test whether the two functions have equivalent behaviour. 516bool FunctionComparator::Compare() { 517 // We need to recheck everything, but check the things that weren't included 518 // in the hash first. 519 520 if (F1->getAttributes() != F2->getAttributes()) 521 return false; 522 523 if (F1->hasGC() != F2->hasGC()) 524 return false; 525 526 if (F1->hasGC() && F1->getGC() != F2->getGC()) 527 return false; 528 529 if (F1->hasSection() != F2->hasSection()) 530 return false; 531 532 if (F1->hasSection() && F1->getSection() != F2->getSection()) 533 return false; 534 535 if (F1->isVarArg() != F2->isVarArg()) 536 return false; 537 538 // TODO: if it's internal and only used in direct calls, we could handle this 539 // case too. 540 if (F1->getCallingConv() != F2->getCallingConv()) 541 return false; 542 543 if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType())) 544 return false; 545 546 assert(F1->arg_size() == F2->arg_size() && 547 "Identically typed functions have different numbers of args!"); 548 549 // Visit the arguments so that they get enumerated in the order they're 550 // passed in. 551 for (Function::const_arg_iterator f1i = F1->arg_begin(), 552 f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) { 553 if (!Enumerate(f1i, f2i)) 554 llvm_unreachable("Arguments repeat!"); 555 } 556 557 // We do a CFG-ordered walk since the actual ordering of the blocks in the 558 // linked list is immaterial. Our walk starts at the entry block for both 559 // functions, then takes each block from each terminator in order. As an 560 // artifact, this also means that unreachable blocks are ignored. 561 SmallVector<const BasicBlock *, 8> F1BBs, F2BBs; 562 SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1. 563 564 F1BBs.push_back(&F1->getEntryBlock()); 565 F2BBs.push_back(&F2->getEntryBlock()); 566 567 VisitedBBs.insert(F1BBs[0]); 568 while (!F1BBs.empty()) { 569 const BasicBlock *F1BB = F1BBs.pop_back_val(); 570 const BasicBlock *F2BB = F2BBs.pop_back_val(); 571 572 if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB)) 573 return false; 574 575 const TerminatorInst *F1TI = F1BB->getTerminator(); 576 const TerminatorInst *F2TI = F2BB->getTerminator(); 577 578 assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors()); 579 for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) { 580 if (!VisitedBBs.insert(F1TI->getSuccessor(i))) 581 continue; 582 583 F1BBs.push_back(F1TI->getSuccessor(i)); 584 F2BBs.push_back(F2TI->getSuccessor(i)); 585 } 586 } 587 return true; 588} 589 590/// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace 591/// direct uses of G with bitcast(F). Deletes G. 592void MergeFunctions::WriteThunk(Function *F, Function *G) { 593 if (!G->mayBeOverridden()) { 594 // Redirect direct callers of G to F. 595 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType()); 596 for (Value::use_iterator UI = G->use_begin(), UE = G->use_end(); 597 UI != UE;) { 598 Value::use_iterator TheIter = UI; 599 ++UI; 600 CallSite CS(*TheIter); 601 if (CS && CS.isCallee(TheIter)) { 602 Remove(CS.getInstruction()->getParent()->getParent()); 603 TheIter.getUse().set(BitcastF); 604 } 605 } 606 } 607 608 // If G was internal then we may have replaced all uses of G with F. If so, 609 // stop here and delete G. There's no need for a thunk. 610 if (G->hasLocalLinkage() && G->use_empty()) { 611 G->eraseFromParent(); 612 return; 613 } 614 615 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "", 616 G->getParent()); 617 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG); 618 IRBuilder<false> Builder(BB); 619 620 SmallVector<Value *, 16> Args; 621 unsigned i = 0; 622 const FunctionType *FFTy = F->getFunctionType(); 623 for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end(); 624 AI != AE; ++AI) { 625 Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i))); 626 ++i; 627 } 628 629 CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end()); 630 CI->setTailCall(); 631 CI->setCallingConv(F->getCallingConv()); 632 if (NewG->getReturnType()->isVoidTy()) { 633 Builder.CreateRetVoid(); 634 } else { 635 Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType())); 636 } 637 638 NewG->copyAttributesFrom(G); 639 NewG->takeName(G); 640 RemoveUsers(G); 641 G->replaceAllUsesWith(NewG); 642 G->eraseFromParent(); 643 644 DEBUG(dbgs() << "WriteThunk: " << NewG->getName() << '\n'); 645 ++NumThunksWritten; 646} 647 648/// MergeTwoFunctions - Merge two equivalent functions. Upon completion, 649/// Function G is deleted. 650void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) { 651 if (F->mayBeOverridden()) { 652 assert(G->mayBeOverridden()); 653 654 // Make them both thunks to the same internal function. 655 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "", 656 F->getParent()); 657 H->copyAttributesFrom(F); 658 H->takeName(F); 659 RemoveUsers(F); 660 F->replaceAllUsesWith(H); 661 662 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment()); 663 664 WriteThunk(F, G); 665 WriteThunk(F, H); 666 667 F->setAlignment(MaxAlignment); 668 F->setLinkage(GlobalValue::PrivateLinkage); 669 670 ++NumDoubleWeak; 671 } else { 672 WriteThunk(F, G); 673 } 674 675 ++NumFunctionsMerged; 676} 677 678// Insert - Insert a ComparableFunction into the FnSet, or merge it away if 679// equal to one that's already inserted. 680bool MergeFunctions::Insert(ComparableFunction &NewF) { 681 std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF); 682 if (Result.second) 683 return false; 684 685 const ComparableFunction &OldF = *Result.first; 686 687 // Never thunk a strong function to a weak function. 688 assert(!OldF.getFunc()->mayBeOverridden() || 689 NewF.getFunc()->mayBeOverridden()); 690 691 DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == " 692 << NewF.getFunc()->getName() << '\n'); 693 694 Function *DeleteF = NewF.getFunc(); 695 NewF.release(); 696 MergeTwoFunctions(OldF.getFunc(), DeleteF); 697 return true; 698} 699 700// Remove - Remove a function from FnSet. If it was already in FnSet, add it to 701// Deferred so that we'll look at it in the next round. 702void MergeFunctions::Remove(Function *F) { 703 ComparableFunction CF = ComparableFunction(F, TD); 704 if (FnSet.erase(CF)) { 705 Deferred.push_back(F); 706 } 707} 708 709// RemoveUsers - For each instruction used by the value, Remove() the function 710// that contains the instruction. This should happen right before a call to RAUW. 711void MergeFunctions::RemoveUsers(Value *V) { 712 std::vector<Value *> Worklist; 713 Worklist.push_back(V); 714 while (!Worklist.empty()) { 715 Value *V = Worklist.back(); 716 Worklist.pop_back(); 717 718 for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); 719 UI != UE; ++UI) { 720 Use &U = UI.getUse(); 721 if (Instruction *I = dyn_cast<Instruction>(U.getUser())) { 722 Remove(I->getParent()->getParent()); 723 } else if (isa<GlobalValue>(U.getUser())) { 724 // do nothing 725 } else if (Constant *C = dyn_cast<Constant>(U.getUser())) { 726 for (Value::use_iterator CUI = C->use_begin(), CUE = C->use_end(); 727 CUI != CUE; ++CUI) 728 Worklist.push_back(*CUI); 729 } 730 } 731 } 732} 733 734bool MergeFunctions::runOnModule(Module &M) { 735 bool Changed = false; 736 TD = getAnalysisIfAvailable<TargetData>(); 737 738 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) { 739 Deferred.push_back(WeakVH(I)); 740 } 741 742 do { 743 std::vector<WeakVH> Worklist; 744 Deferred.swap(Worklist); 745 746 DEBUG(dbgs() << "size of module: " << M.size() << '\n'); 747 DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n'); 748 749 // Insert only strong functions and merge them. Strong function merging 750 // always deletes one of them. 751 for (std::vector<WeakVH>::iterator I = Worklist.begin(), 752 E = Worklist.end(); I != E; ++I) { 753 if (!*I) continue; 754 Function *F = cast<Function>(*I); 755 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() && 756 !F->mayBeOverridden()) { 757 ComparableFunction CF = ComparableFunction(F, TD); 758 Changed |= Insert(CF); 759 } 760 } 761 762 // Insert only weak functions and merge them. By doing these second we 763 // create thunks to the strong function when possible. When two weak 764 // functions are identical, we create a new strong function with two weak 765 // weak thunks to it which are identical but not mergable. 766 for (std::vector<WeakVH>::iterator I = Worklist.begin(), 767 E = Worklist.end(); I != E; ++I) { 768 if (!*I) continue; 769 Function *F = cast<Function>(*I); 770 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() && 771 F->mayBeOverridden()) { 772 ComparableFunction CF = ComparableFunction(F, TD); 773 Changed |= Insert(CF); 774 } 775 } 776 DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n'); 777 } while (!Deferred.empty()); 778 779 FnSet.clear(); 780 781 return Changed; 782} 783 784bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS, 785 const ComparableFunction &RHS) { 786 if (LHS.getFunc() == RHS.getFunc() && 787 LHS.getHash() == RHS.getHash()) 788 return true; 789 if (!LHS.getFunc() || !RHS.getFunc()) 790 return false; 791 assert(LHS.getTD() == RHS.getTD() && 792 "Comparing functions for different targets"); 793 794 bool inserted; 795 bool &result1 = LHS.getOrInsertCachedComparison(RHS, inserted); 796 if (!inserted) 797 return result1; 798 bool &result2 = RHS.getOrInsertCachedComparison(LHS, inserted); 799 if (!inserted) 800 return result1 = result2; 801 802 return result1 = result2 = FunctionComparator(LHS.getTD(), LHS.getFunc(), 803 RHS.getFunc()).Compare(); 804} 805