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;
164 /// Insert a ComparableFunction into the FnSet, or merge it away if it's
165 /// equal to one that's already present.
166 bool Insert(FnSetType &FnSet, ComparableFunction &NewF);
168 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G
169 /// may be deleted, or may be converted into a thunk. In either case, it
170 /// should never be visited again.
171 void MergeTwoFunctions(Function *F, Function *G) const;
173 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
174 /// replace direct uses of G with bitcast(F). Deletes G.
175 void WriteThunk(Function *F, Function *G) const;
180 } // end anonymous namespace
182 char MergeFunctions::ID = 0;
183 INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
185 ModulePass *llvm::createMergeFunctionsPass() {
186 return new MergeFunctions();
190 /// FunctionComparator - Compares two functions to determine whether or not
191 /// they will generate machine code with the same behaviour. TargetData is
192 /// used if available. The comparator always fails conservatively (erring on the
193 /// side of claiming that two functions are different).
194 class FunctionComparator {
196 FunctionComparator(const TargetData *TD, const Function *F1,
198 : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {}
200 /// Compare - test whether the two functions have equivalent behaviour.
204 /// Compare - test whether two basic blocks have equivalent behaviour.
205 bool Compare(const BasicBlock *BB1, const BasicBlock *BB2);
207 /// Enumerate - Assign or look up previously assigned numbers for the two
208 /// values, and return whether the numbers are equal. Numbers are assigned in
209 /// the order visited.
210 bool Enumerate(const Value *V1, const Value *V2);
212 /// isEquivalentOperation - Compare two Instructions for equivalence, similar
213 /// to Instruction::isSameOperationAs but with modifications to the type
215 bool isEquivalentOperation(const Instruction *I1,
216 const Instruction *I2) const;
218 /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic.
219 bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
220 bool isEquivalentGEP(const GetElementPtrInst *GEP1,
221 const GetElementPtrInst *GEP2) {
222 return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
225 /// isEquivalentType - Compare two Types, treating all pointer types as equal.
226 bool isEquivalentType(const Type *Ty1, const Type *Ty2) const;
228 // The two functions undergoing comparison.
229 const Function *F1, *F2;
231 const TargetData *TD;
233 typedef DenseMap<const Value *, unsigned long> IDMap;
235 unsigned long IDMap1Count, IDMap2Count;
239 /// isEquivalentType - any two pointers in the same address space are
240 /// equivalent. Otherwise, standard type equivalence rules apply.
241 bool FunctionComparator::isEquivalentType(const Type *Ty1,
242 const Type *Ty2) const {
245 if (Ty1->getTypeID() != Ty2->getTypeID())
248 switch(Ty1->getTypeID()) {
250 llvm_unreachable("Unknown type!");
251 // Fall through in Release mode.
252 case Type::IntegerTyID:
253 case Type::OpaqueTyID:
254 // Ty1 == Ty2 would have returned true earlier.
258 case Type::FloatTyID:
259 case Type::DoubleTyID:
260 case Type::X86_FP80TyID:
261 case Type::FP128TyID:
262 case Type::PPC_FP128TyID:
263 case Type::LabelTyID:
264 case Type::MetadataTyID:
267 case Type::PointerTyID: {
268 const PointerType *PTy1 = cast<PointerType>(Ty1);
269 const PointerType *PTy2 = cast<PointerType>(Ty2);
270 return PTy1->getAddressSpace() == PTy2->getAddressSpace();
273 case Type::StructTyID: {
274 const StructType *STy1 = cast<StructType>(Ty1);
275 const StructType *STy2 = cast<StructType>(Ty2);
276 if (STy1->getNumElements() != STy2->getNumElements())
279 if (STy1->isPacked() != STy2->isPacked())
282 for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) {
283 if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i)))
289 case Type::FunctionTyID: {
290 const FunctionType *FTy1 = cast<FunctionType>(Ty1);
291 const FunctionType *FTy2 = cast<FunctionType>(Ty2);
292 if (FTy1->getNumParams() != FTy2->getNumParams() ||
293 FTy1->isVarArg() != FTy2->isVarArg())
296 if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType()))
299 for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) {
300 if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i)))
306 case Type::ArrayTyID: {
307 const ArrayType *ATy1 = cast<ArrayType>(Ty1);
308 const ArrayType *ATy2 = cast<ArrayType>(Ty2);
309 return ATy1->getNumElements() == ATy2->getNumElements() &&
310 isEquivalentType(ATy1->getElementType(), ATy2->getElementType());
313 case Type::VectorTyID: {
314 const VectorType *VTy1 = cast<VectorType>(Ty1);
315 const VectorType *VTy2 = cast<VectorType>(Ty2);
316 return VTy1->getNumElements() == VTy2->getNumElements() &&
317 isEquivalentType(VTy1->getElementType(), VTy2->getElementType());
322 /// isEquivalentOperation - determine whether the two operations are the same
323 /// except that pointer-to-A and pointer-to-B are equivalent. This should be
324 /// kept in sync with Instruction::isSameOperationAs.
325 bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
326 const Instruction *I2) const {
327 if (I1->getOpcode() != I2->getOpcode() ||
328 I1->getNumOperands() != I2->getNumOperands() ||
329 !isEquivalentType(I1->getType(), I2->getType()) ||
330 !I1->hasSameSubclassOptionalData(I2))
333 // We have two instructions of identical opcode and #operands. Check to see
334 // if all operands are the same type
335 for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i)
336 if (!isEquivalentType(I1->getOperand(i)->getType(),
337 I2->getOperand(i)->getType()))
340 // Check special state that is a part of some instructions.
341 if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
342 return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
343 LI->getAlignment() == cast<LoadInst>(I2)->getAlignment();
344 if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
345 return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
346 SI->getAlignment() == cast<StoreInst>(I2)->getAlignment();
347 if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
348 return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
349 if (const CallInst *CI = dyn_cast<CallInst>(I1))
350 return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
351 CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
352 CI->getAttributes().getRawPointer() ==
353 cast<CallInst>(I2)->getAttributes().getRawPointer();
354 if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
355 return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
356 CI->getAttributes().getRawPointer() ==
357 cast<InvokeInst>(I2)->getAttributes().getRawPointer();
358 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
359 if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
361 for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
362 if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i])
366 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) {
367 if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices())
369 for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
370 if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i])
378 /// isEquivalentGEP - determine whether two GEP operations perform the same
379 /// underlying arithmetic.
380 bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
381 const GEPOperator *GEP2) {
382 // When we have target data, we can reduce the GEP down to the value in bytes
383 // added to the address.
384 if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) {
385 SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end());
386 SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end());
387 uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(),
388 Indices1.data(), Indices1.size());
389 uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(),
390 Indices2.data(), Indices2.size());
391 return Offset1 == Offset2;
394 if (GEP1->getPointerOperand()->getType() !=
395 GEP2->getPointerOperand()->getType())
398 if (GEP1->getNumOperands() != GEP2->getNumOperands())
401 for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
402 if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
409 /// Enumerate - Compare two values used by the two functions under pair-wise
410 /// comparison. If this is the first time the values are seen, they're added to
411 /// the mapping so that we will detect mismatches on next use.
412 bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) {
413 // Check for function @f1 referring to itself and function @f2 referring to
414 // itself, or referring to each other, or both referring to either of them.
415 // They're all equivalent if the two functions are otherwise equivalent.
416 if (V1 == F1 && V2 == F2)
418 if (V1 == F2 && V2 == F1)
421 // TODO: constant expressions with GEP or references to F1 or F2.
422 if (isa<Constant>(V1))
425 if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) {
426 const InlineAsm *IA1 = cast<InlineAsm>(V1);
427 const InlineAsm *IA2 = cast<InlineAsm>(V2);
428 return IA1->getAsmString() == IA2->getAsmString() &&
429 IA1->getConstraintString() == IA2->getConstraintString();
432 unsigned long &ID1 = Map1[V1];
436 unsigned long &ID2 = Map2[V2];
443 /// Compare - test whether two basic blocks have equivalent behaviour.
444 bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
445 BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
446 BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
449 if (!Enumerate(F1I, F2I))
452 if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
453 const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
457 if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
460 if (!isEquivalentGEP(GEP1, GEP2))
463 if (!isEquivalentOperation(F1I, F2I))
466 assert(F1I->getNumOperands() == F2I->getNumOperands());
467 for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
468 Value *OpF1 = F1I->getOperand(i);
469 Value *OpF2 = F2I->getOperand(i);
471 if (!Enumerate(OpF1, OpF2))
474 if (OpF1->getValueID() != OpF2->getValueID() ||
475 !isEquivalentType(OpF1->getType(), OpF2->getType()))
481 } while (F1I != F1E && F2I != F2E);
483 return F1I == F1E && F2I == F2E;
486 /// Compare - test whether the two functions have equivalent behaviour.
487 bool FunctionComparator::Compare() {
488 // We need to recheck everything, but check the things that weren't included
489 // in the hash first.
491 if (F1->getAttributes() != F2->getAttributes())
494 if (F1->hasGC() != F2->hasGC())
497 if (F1->hasGC() && F1->getGC() != F2->getGC())
500 if (F1->hasSection() != F2->hasSection())
503 if (F1->hasSection() && F1->getSection() != F2->getSection())
506 if (F1->isVarArg() != F2->isVarArg())
509 // TODO: if it's internal and only used in direct calls, we could handle this
511 if (F1->getCallingConv() != F2->getCallingConv())
514 if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
517 assert(F1->arg_size() == F2->arg_size() &&
518 "Identically typed functions have different numbers of args!");
520 // Visit the arguments so that they get enumerated in the order they're
522 for (Function::const_arg_iterator f1i = F1->arg_begin(),
523 f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) {
524 if (!Enumerate(f1i, f2i))
525 llvm_unreachable("Arguments repeat!");
528 // We do a CFG-ordered walk since the actual ordering of the blocks in the
529 // linked list is immaterial. Our walk starts at the entry block for both
530 // functions, then takes each block from each terminator in order. As an
531 // artifact, this also means that unreachable blocks are ignored.
532 SmallVector<const BasicBlock *, 8> F1BBs, F2BBs;
533 SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
535 F1BBs.push_back(&F1->getEntryBlock());
536 F2BBs.push_back(&F2->getEntryBlock());
538 VisitedBBs.insert(F1BBs[0]);
539 while (!F1BBs.empty()) {
540 const BasicBlock *F1BB = F1BBs.pop_back_val();
541 const BasicBlock *F2BB = F2BBs.pop_back_val();
543 if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB))
546 const TerminatorInst *F1TI = F1BB->getTerminator();
547 const TerminatorInst *F2TI = F2BB->getTerminator();
549 assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
550 for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
551 if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
554 F1BBs.push_back(F1TI->getSuccessor(i));
555 F2BBs.push_back(F2TI->getSuccessor(i));
561 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
562 /// direct uses of G with bitcast(F). Deletes G.
563 void MergeFunctions::WriteThunk(Function *F, Function *G) const {
564 if (!G->mayBeOverridden()) {
565 // Redirect direct callers of G to F.
566 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
567 for (Value::use_iterator UI = G->use_begin(), UE = G->use_end();
569 Value::use_iterator TheIter = UI;
571 CallSite CS(*TheIter);
572 if (CS && CS.isCallee(TheIter))
573 TheIter.getUse().set(BitcastF);
577 // If G was internal then we may have replaced all uses of G with F. If so,
578 // stop here and delete G. There's no need for a thunk.
579 if (G->hasLocalLinkage() && G->use_empty()) {
580 G->eraseFromParent();
584 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
586 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
587 IRBuilder<false> Builder(BB);
589 SmallVector<Value *, 16> Args;
591 const FunctionType *FFTy = F->getFunctionType();
592 for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
594 Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i)));
598 CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end());
600 CI->setCallingConv(F->getCallingConv());
601 if (NewG->getReturnType()->isVoidTy()) {
602 Builder.CreateRetVoid();
604 Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType()));
607 NewG->copyAttributesFrom(G);
609 G->replaceAllUsesWith(NewG);
610 G->eraseFromParent();
612 DEBUG(dbgs() << "WriteThunk: " << NewG->getName() << '\n');
616 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion,
617 /// Function G is deleted.
618 void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) const {
619 if (F->mayBeOverridden()) {
620 assert(G->mayBeOverridden());
622 // Make them both thunks to the same internal function.
623 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
625 H->copyAttributesFrom(F);
627 F->replaceAllUsesWith(H);
629 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
634 F->setAlignment(MaxAlignment);
635 F->setLinkage(GlobalValue::InternalLinkage);
642 ++NumFunctionsMerged;
645 // Insert - Insert a ComparableFunction into the FnSet, or merge it away if
646 // equal to one that's already inserted.
647 bool MergeFunctions::Insert(FnSetType &FnSet, ComparableFunction &NewF) {
648 std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
652 const ComparableFunction &OldF = *Result.first;
654 // Never thunk a strong function to a weak function.
655 assert(!OldF.getFunc()->mayBeOverridden() ||
656 NewF.getFunc()->mayBeOverridden());
658 DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
659 << NewF.getFunc()->getName() << '\n');
661 Function *DeleteF = NewF.getFunc();
663 MergeTwoFunctions(OldF.getFunc(), DeleteF);
667 // IsThunk - This method determines whether or not a given Function is a thunk\// like the ones emitted by this pass and therefore not subject to further
669 static bool IsThunk(const Function *F) {
670 // The safe direction to fail is to return true. In that case, the function
671 // will be removed from merging analysis. If we failed to including functions
672 // then we may try to merge unmergable thing (ie., identical weak functions)
673 // which will push us into an infinite loop.
675 assert(!F->isDeclaration() && "Expected a function definition.");
677 const BasicBlock *BB = &F->front();
680 // optional-reg tail call @thunkee(args...*)
681 // ret void|optional-reg
682 // where the args are in the same order as the arguments.
684 // Put this at the top since it triggers most often.
685 const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
686 if (!RI) return false;
688 // Verify that the sequence of bitcast-inst's are all casts of arguments and
689 // that there aren't any extras (ie. no repeated casts).
691 BasicBlock::const_iterator I = BB->begin();
692 while (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
693 const Argument *A = dyn_cast<Argument>(BCI->getOperand(0));
694 if (!A) return false;
695 if ((int)A->getArgNo() <= LastArgNo) return false;
696 LastArgNo = A->getArgNo();
700 // Verify that we have a direct tail call and that the calling conventions
701 // and number of arguments match.
702 const CallInst *CI = dyn_cast<CallInst>(I++);
703 if (!CI || !CI->isTailCall() || !CI->getCalledFunction() ||
704 CI->getCallingConv() != CI->getCalledFunction()->getCallingConv() ||
705 CI->getNumArgOperands() != F->arg_size())
708 // Verify that the call instruction has the same arguments as this function
709 // and that they're all either the incoming argument or a cast of the right
711 for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i) {
712 const Value *V = CI->getArgOperand(i);
713 const Argument *A = dyn_cast<Argument>(V);
715 const BitCastInst *BCI = dyn_cast<BitCastInst>(V);
716 if (!BCI) return false;
717 A = cast<Argument>(BCI->getOperand(0));
719 if (A->getArgNo() != i) return false;
722 // Verify that the terminator is a ret void (if we're void) or a ret of the
723 // call's return, or a ret of a bitcast of the call's return.
724 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
726 if (BCI->getOperand(0) != CI) return false;
728 if (RI != I) return false;
729 if (RI->getNumOperands() == 0)
730 return CI->getType()->isVoidTy();
731 return RI->getReturnValue() == CI;
734 bool MergeFunctions::runOnModule(Module &M) {
735 bool Changed = false;
736 TD = getAnalysisIfAvailable<TargetData>();
740 DEBUG(dbgs() << "size of module: " << M.size() << '\n');
741 LocalChanged = false;
744 // Insert only strong functions and merge them. Strong function merging
745 // always deletes one of them.
746 for (Module::iterator I = M.begin(), E = M.end(); I != E;) {
748 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
749 !F->mayBeOverridden() && !IsThunk(F)) {
750 ComparableFunction CF = ComparableFunction(F, TD);
751 LocalChanged |= Insert(FnSet, CF);
755 // Insert only weak functions and merge them. By doing these second we
756 // create thunks to the strong function when possible. When two weak
757 // functions are identical, we create a new strong function with two weak
758 // weak thunks to it which are identical but not mergable.
759 for (Module::iterator I = M.begin(), E = M.end(); I != E;) {
761 if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
762 F->mayBeOverridden() && !IsThunk(F)) {
763 ComparableFunction CF = ComparableFunction(F, TD);
764 LocalChanged |= Insert(FnSet, CF);
767 DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n');
768 Changed |= LocalChanged;
769 } while (LocalChanged);
774 bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS,
775 const ComparableFunction &RHS) {
776 if (LHS.getFunc() == RHS.getFunc() &&
777 LHS.getHash() == RHS.getHash())
779 if (!LHS.getFunc() || !RHS.getFunc())
781 assert(LHS.getTD() == RHS.getTD() &&
782 "Comparing functions for different targets");
783 return FunctionComparator(LHS.getTD(),
784 LHS.getFunc(), RHS.getFunc()).Compare();