1 //===- MergeFunctions.cpp - Merge identical functions ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass looks for equivalent functions that are mergable and folds them.
12 // A hash is computed from the function, based on its type and number of
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.
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.
24 //===----------------------------------------------------------------------===//
28 // * virtual functions.
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.
34 // * switch from n^2 pair-wise comparisons to an n-way comparison for each
37 // * be smarter about bitcasts.
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.
44 //===----------------------------------------------------------------------===//
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"
69 STATISTIC(NumFunctionsMerged, "Number of functions merged");
70 STATISTIC(NumThunksWritten, "Number of thunks generated");
71 STATISTIC(NumDoubleWeak, "Number of new functions created");
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.
76 static unsigned ProfileFunction(const Function *F) {
77 const FunctionType *FTy = F->getFunctionType();
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();
92 class ComparableFunction {
94 static const ComparableFunction EmptyKey;
95 static const ComparableFunction TombstoneKey;
97 ComparableFunction(Function *Func, TargetData *TD)
98 : Func(Func), Hash(ProfileFunction(Func)), TD(TD) {}
100 Function *getFunc() const { return Func; }
101 unsigned getHash() const { return Hash; }
102 TargetData *getTD() const { return TD; }
104 // Drops AssertingVH reference to the function. Outside of debug mode, this
108 "Attempted to release function twice, or release empty/tombstone!");
113 explicit ComparableFunction(unsigned Hash)
114 : Func(NULL), Hash(Hash), TD(NULL) {}
116 AssertingVH<Function> Func;
121 const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0);
122 const ComparableFunction ComparableFunction::TombstoneKey =
123 ComparableFunction(1);
129 struct DenseMapInfo<ComparableFunction> {
130 static ComparableFunction getEmptyKey() {
131 return ComparableFunction::EmptyKey;
133 static ComparableFunction getTombstoneKey() {
134 return ComparableFunction::TombstoneKey;
136 static unsigned getHashValue(const ComparableFunction &CF) {
139 static bool isEqual(const ComparableFunction &LHS,
140 const ComparableFunction &RHS);
146 /// MergeFunctions finds functions which will generate identical machine code,
147 /// by considering all pointer types to be equivalent. Once identified,
148 /// MergeFunctions will fold them by replacing a call to one to a call to a
149 /// bitcast of the other.
151 class MergeFunctions : public ModulePass {
154 MergeFunctions() : ModulePass(ID) {
155 initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
158 bool runOnModule(Module &M);
161 typedef DenseSet<ComparableFunction> FnSetType;
163 /// A work queue of functions that may have been modified and should be
165 std::vector<WeakVH> Deferred;
167 /// Insert a ComparableFunction into the FnSet, or merge it away if it's
168 /// equal to one that's already present.
169 bool Insert(ComparableFunction &NewF);
171 /// Remove a Function from the FnSet and queue it up for a second sweep of
173 void Remove(Function *F);
175 /// Find the functions that use this Value and remove them from FnSet and
176 /// queue the functions.
177 void RemoveUsers(Value *V);
179 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G
180 /// may be deleted, or may be converted into a thunk. In either case, it
181 /// should never be visited again.
182 void MergeTwoFunctions(Function *F, Function *G);
184 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
185 /// replace direct uses of G with bitcast(F). Deletes G.
186 void WriteThunk(Function *F, Function *G);
188 /// The set of all distinct functions. Use the Insert and Remove methods to
192 /// TargetData for more accurate GEP comparisons. May be NULL.
196 } // end anonymous namespace
198 char MergeFunctions::ID = 0;
199 INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
201 ModulePass *llvm::createMergeFunctionsPass() {
202 return new MergeFunctions();
206 /// FunctionComparator - Compares two functions to determine whether or not
207 /// they will generate machine code with the same behaviour. TargetData is
208 /// used if available. The comparator always fails conservatively (erring on the
209 /// side of claiming that two functions are different).
210 class FunctionComparator {
212 FunctionComparator(const TargetData *TD, const Function *F1,
214 : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {}
216 /// Compare - test whether the two functions have equivalent behaviour.
220 /// Compare - test whether two basic blocks have equivalent behaviour.
221 bool Compare(const BasicBlock *BB1, const BasicBlock *BB2);
223 /// Enumerate - Assign or look up previously assigned numbers for the two
224 /// values, and return whether the numbers are equal. Numbers are assigned in
225 /// the order visited.
226 bool Enumerate(const Value *V1, const Value *V2);
228 /// isEquivalentOperation - Compare two Instructions for equivalence, similar
229 /// to Instruction::isSameOperationAs but with modifications to the type
231 bool isEquivalentOperation(const Instruction *I1,
232 const Instruction *I2) const;
234 /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic.
235 bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
236 bool isEquivalentGEP(const GetElementPtrInst *GEP1,
237 const GetElementPtrInst *GEP2) {
238 return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
241 /// isEquivalentType - Compare two Types, treating all pointer types as equal.
242 bool isEquivalentType(const Type *Ty1, const Type *Ty2) const;
244 // The two functions undergoing comparison.
245 const Function *F1, *F2;
247 const TargetData *TD;
249 typedef DenseMap<const Value *, unsigned long> IDMap;
251 unsigned long IDMap1Count, IDMap2Count;
255 /// isEquivalentType - any two pointers in the same address space are
256 /// equivalent. Otherwise, standard type equivalence rules apply.
257 bool FunctionComparator::isEquivalentType(const Type *Ty1,
258 const Type *Ty2) const {
261 if (Ty1->getTypeID() != Ty2->getTypeID())
264 switch(Ty1->getTypeID()) {
266 llvm_unreachable("Unknown type!");
267 // Fall through in Release mode.
268 case Type::IntegerTyID:
269 case Type::OpaqueTyID:
270 // Ty1 == Ty2 would have returned true earlier.
274 case Type::FloatTyID:
275 case Type::DoubleTyID:
276 case Type::X86_FP80TyID:
277 case Type::FP128TyID:
278 case Type::PPC_FP128TyID:
279 case Type::LabelTyID:
280 case Type::MetadataTyID:
283 case Type::PointerTyID: {
284 const PointerType *PTy1 = cast<PointerType>(Ty1);
285 const PointerType *PTy2 = cast<PointerType>(Ty2);
286 return PTy1->getAddressSpace() == PTy2->getAddressSpace();
289 case Type::StructTyID: {
290 const StructType *STy1 = cast<StructType>(Ty1);
291 const StructType *STy2 = cast<StructType>(Ty2);
292 if (STy1->getNumElements() != STy2->getNumElements())
295 if (STy1->isPacked() != STy2->isPacked())
298 for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) {
299 if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i)))
305 case Type::FunctionTyID: {
306 const FunctionType *FTy1 = cast<FunctionType>(Ty1);
307 const FunctionType *FTy2 = cast<FunctionType>(Ty2);
308 if (FTy1->getNumParams() != FTy2->getNumParams() ||
309 FTy1->isVarArg() != FTy2->isVarArg())
312 if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType()))
315 for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) {
316 if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i)))
322 case Type::ArrayTyID: {
323 const ArrayType *ATy1 = cast<ArrayType>(Ty1);
324 const ArrayType *ATy2 = cast<ArrayType>(Ty2);
325 return ATy1->getNumElements() == ATy2->getNumElements() &&
326 isEquivalentType(ATy1->getElementType(), ATy2->getElementType());
329 case Type::VectorTyID: {
330 const VectorType *VTy1 = cast<VectorType>(Ty1);
331 const VectorType *VTy2 = cast<VectorType>(Ty2);
332 return VTy1->getNumElements() == VTy2->getNumElements() &&
333 isEquivalentType(VTy1->getElementType(), VTy2->getElementType());
338 /// isEquivalentOperation - determine whether the two operations are the same
339 /// except that pointer-to-A and pointer-to-B are equivalent. This should be
340 /// kept in sync with Instruction::isSameOperationAs.
341 bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
342 const Instruction *I2) const {
343 if (I1->getOpcode() != I2->getOpcode() ||
344 I1->getNumOperands() != I2->getNumOperands() ||
345 !isEquivalentType(I1->getType(), I2->getType()) ||
346 !I1->hasSameSubclassOptionalData(I2))
349 // We have two instructions of identical opcode and #operands. Check to see
350 // if all operands are the same type
351 for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i)
352 if (!isEquivalentType(I1->getOperand(i)->getType(),
353 I2->getOperand(i)->getType()))
356 // Check special state that is a part of some instructions.
357 if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
358 return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
359 LI->getAlignment() == cast<LoadInst>(I2)->getAlignment();
360 if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
361 return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
362 SI->getAlignment() == cast<StoreInst>(I2)->getAlignment();
363 if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
364 return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
365 if (const CallInst *CI = dyn_cast<CallInst>(I1))
366 return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
367 CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
368 CI->getAttributes().getRawPointer() ==
369 cast<CallInst>(I2)->getAttributes().getRawPointer();
370 if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
371 return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
372 CI->getAttributes().getRawPointer() ==
373 cast<InvokeInst>(I2)->getAttributes().getRawPointer();
374 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
375 if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
377 for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
378 if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i])
382 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) {
383 if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices())
385 for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
386 if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i])
394 /// isEquivalentGEP - determine whether two GEP operations perform the same
395 /// underlying arithmetic.
396 bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
397 const GEPOperator *GEP2) {
398 // When we have target data, we can reduce the GEP down to the value in bytes
399 // added to the address.
400 if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) {
401 SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end());
402 SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end());
403 uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(),
404 Indices1.data(), Indices1.size());
405 uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(),
406 Indices2.data(), Indices2.size());
407 return Offset1 == Offset2;
410 if (GEP1->getPointerOperand()->getType() !=
411 GEP2->getPointerOperand()->getType())
414 if (GEP1->getNumOperands() != GEP2->getNumOperands())
417 for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
418 if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
425 /// Enumerate - Compare two values used by the two functions under pair-wise
426 /// comparison. If this is the first time the values are seen, they're added to
427 /// the mapping so that we will detect mismatches on next use.
428 bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) {
429 // Check for function @f1 referring to itself and function @f2 referring to
430 // itself, or referring to each other, or both referring to either of them.
431 // They're all equivalent if the two functions are otherwise equivalent.
432 if (V1 == F1 && V2 == F2)
434 if (V1 == F2 && V2 == F1)
437 // TODO: constant expressions with GEP or references to F1 or F2.
438 if (isa<Constant>(V1))
441 if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) {
442 const InlineAsm *IA1 = cast<InlineAsm>(V1);
443 const InlineAsm *IA2 = cast<InlineAsm>(V2);
444 return IA1->getAsmString() == IA2->getAsmString() &&
445 IA1->getConstraintString() == IA2->getConstraintString();
448 unsigned long &ID1 = Map1[V1];
452 unsigned long &ID2 = Map2[V2];
459 /// Compare - test whether two basic blocks have equivalent behaviour.
460 bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
461 BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
462 BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
465 if (!Enumerate(F1I, F2I))
468 if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
469 const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
473 if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
476 if (!isEquivalentGEP(GEP1, GEP2))
479 if (!isEquivalentOperation(F1I, F2I))
482 assert(F1I->getNumOperands() == F2I->getNumOperands());
483 for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
484 Value *OpF1 = F1I->getOperand(i);
485 Value *OpF2 = F2I->getOperand(i);
487 if (!Enumerate(OpF1, OpF2))
490 if (OpF1->getValueID() != OpF2->getValueID() ||
491 !isEquivalentType(OpF1->getType(), OpF2->getType()))
497 } while (F1I != F1E && F2I != F2E);
499 return F1I == F1E && F2I == F2E;
502 /// Compare - test whether the two functions have equivalent behaviour.
503 bool FunctionComparator::Compare() {
504 // We need to recheck everything, but check the things that weren't included
505 // in the hash first.
507 if (F1->getAttributes() != F2->getAttributes())
510 if (F1->hasGC() != F2->hasGC())
513 if (F1->hasGC() && F1->getGC() != F2->getGC())
516 if (F1->hasSection() != F2->hasSection())
519 if (F1->hasSection() && F1->getSection() != F2->getSection())
522 if (F1->isVarArg() != F2->isVarArg())
525 // TODO: if it's internal and only used in direct calls, we could handle this
527 if (F1->getCallingConv() != F2->getCallingConv())
530 if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
533 assert(F1->arg_size() == F2->arg_size() &&
534 "Identically typed functions have different numbers of args!");
536 // Visit the arguments so that they get enumerated in the order they're
538 for (Function::const_arg_iterator f1i = F1->arg_begin(),
539 f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) {
540 if (!Enumerate(f1i, f2i))
541 llvm_unreachable("Arguments repeat!");
544 // We do a CFG-ordered walk since the actual ordering of the blocks in the
545 // linked list is immaterial. Our walk starts at the entry block for both
546 // functions, then takes each block from each terminator in order. As an
547 // artifact, this also means that unreachable blocks are ignored.
548 SmallVector<const BasicBlock *, 8> F1BBs, F2BBs;
549 SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
551 F1BBs.push_back(&F1->getEntryBlock());
552 F2BBs.push_back(&F2->getEntryBlock());
554 VisitedBBs.insert(F1BBs[0]);
555 while (!F1BBs.empty()) {
556 const BasicBlock *F1BB = F1BBs.pop_back_val();
557 const BasicBlock *F2BB = F2BBs.pop_back_val();
559 if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB))
562 const TerminatorInst *F1TI = F1BB->getTerminator();
563 const TerminatorInst *F2TI = F2BB->getTerminator();
565 assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
566 for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
567 if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
570 F1BBs.push_back(F1TI->getSuccessor(i));
571 F2BBs.push_back(F2TI->getSuccessor(i));
577 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
578 /// direct uses of G with bitcast(F). Deletes G.
579 void MergeFunctions::WriteThunk(Function *F, Function *G) {
580 if (!G->mayBeOverridden()) {
581 // Redirect direct callers of G to F.
582 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
583 for (Value::use_iterator UI = G->use_begin(), UE = G->use_end();
585 Value::use_iterator TheIter = UI;
587 CallSite CS(*TheIter);
588 if (CS && CS.isCallee(TheIter)) {
589 Remove(CS.getInstruction()->getParent()->getParent());
590 TheIter.getUse().set(BitcastF);
595 // If G was internal then we may have replaced all uses of G with F. If so,
596 // stop here and delete G. There's no need for a thunk.
597 if (G->hasLocalLinkage() && G->use_empty()) {
598 G->eraseFromParent();
602 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
604 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
605 IRBuilder<false> Builder(BB);
607 SmallVector<Value *, 16> Args;
609 const FunctionType *FFTy = F->getFunctionType();
610 for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
612 Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i)));
616 CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end());
618 CI->setCallingConv(F->getCallingConv());
619 if (NewG->getReturnType()->isVoidTy()) {
620 Builder.CreateRetVoid();
622 Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType()));
625 NewG->copyAttributesFrom(G);
628 G->replaceAllUsesWith(NewG);
629 G->eraseFromParent();
631 DEBUG(dbgs() << "WriteThunk: " << NewG->getName() << '\n');
635 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion,
636 /// Function G is deleted.
637 void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) {
638 if (F->mayBeOverridden()) {
639 assert(G->mayBeOverridden());
641 // Make them both thunks to the same internal function.
642 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
644 H->copyAttributesFrom(F);
647 F->replaceAllUsesWith(H);
649 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
654 F->setAlignment(MaxAlignment);
655 F->setLinkage(GlobalValue::PrivateLinkage);
662 ++NumFunctionsMerged;
665 // Insert - Insert a ComparableFunction into the FnSet, or merge it away if
666 // equal to one that's already inserted.
667 bool MergeFunctions::Insert(ComparableFunction &NewF) {
668 std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
672 const ComparableFunction &OldF = *Result.first;
674 // Never thunk a strong function to a weak function.
675 assert(!OldF.getFunc()->mayBeOverridden() ||
676 NewF.getFunc()->mayBeOverridden());
678 DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
679 << NewF.getFunc()->getName() << '\n');
681 Function *DeleteF = NewF.getFunc();
683 MergeTwoFunctions(OldF.getFunc(), DeleteF);
687 // Remove - Remove a function from FnSet. If it was already in FnSet, add it to
688 // Deferred so that we'll look at it in the next round.
689 void MergeFunctions::Remove(Function *F) {
690 ComparableFunction CF = ComparableFunction(F, TD);
691 if (FnSet.erase(CF)) {
692 Deferred.push_back(F);
696 // RemoveUsers - For each instruction used by the value, Remove() the function
697 // that contains the instruction. This should happen right before a call to RAUW.
698 void MergeFunctions::RemoveUsers(Value *V) {
699 for (Value::use_iterator UI = V->use_begin(), UE = V->use_end();
701 Use &U = UI.getUse();
702 if (Instruction *I = dyn_cast<Instruction>(U.getUser())) {
703 Remove(I->getParent()->getParent());
708 bool MergeFunctions::runOnModule(Module &M) {
709 bool Changed = false;
710 TD = getAnalysisIfAvailable<TargetData>();
712 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
713 Deferred.push_back(WeakVH(I));
717 std::vector<WeakVH> Worklist;
718 Deferred.swap(Worklist);
720 DEBUG(dbgs() << "size of module: " << M.size() << '\n');
721 DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
723 // Insert only strong functions and merge them. Strong function merging
724 // always deletes one of them.
725 for (std::vector<WeakVH>::iterator I = Worklist.begin(),
726 E = Worklist.end(); I != E; ++I) {
728 Function *F = cast<Function>(*I);
729 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
730 !F->mayBeOverridden()) {
731 ComparableFunction CF = ComparableFunction(F, TD);
732 Changed |= Insert(CF);
736 // Insert only weak functions and merge them. By doing these second we
737 // create thunks to the strong function when possible. When two weak
738 // functions are identical, we create a new strong function with two weak
739 // weak thunks to it which are identical but not mergable.
740 for (std::vector<WeakVH>::iterator I = Worklist.begin(),
741 E = Worklist.end(); I != E; ++I) {
743 Function *F = cast<Function>(*I);
744 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
745 F->mayBeOverridden()) {
746 ComparableFunction CF = ComparableFunction(F, TD);
747 Changed |= Insert(CF);
750 DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n');
751 } while (!Deferred.empty());
758 bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS,
759 const ComparableFunction &RHS) {
760 if (LHS.getFunc() == RHS.getFunc() &&
761 LHS.getHash() == RHS.getHash())
763 if (!LHS.getFunc() || !RHS.getFunc())
765 assert(LHS.getTD() == RHS.getTD() &&
766 "Comparing functions for different targets");
767 return FunctionComparator(LHS.getTD(),
768 LHS.getFunc(), RHS.getFunc()).Compare();