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) {}
156 bool runOnModule(Module &M);
159 typedef DenseSet<ComparableFunction> FnSetType;
162 /// Insert a ComparableFunction into the FnSet, or merge it away if it's
163 /// equal to one that's already present.
164 bool Insert(FnSetType &FnSet, ComparableFunction &NewF);
166 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion, G
167 /// may be deleted, or may be converted into a thunk. In either case, it
168 /// should never be visited again.
169 void MergeTwoFunctions(Function *F, Function *G) const;
171 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also
172 /// replace direct uses of G with bitcast(F). Deletes G.
173 void WriteThunk(Function *F, Function *G) const;
178 } // end anonymous namespace
180 char MergeFunctions::ID = 0;
181 INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false);
183 ModulePass *llvm::createMergeFunctionsPass() {
184 return new MergeFunctions();
188 /// FunctionComparator - Compares two functions to determine whether or not
189 /// they will generate machine code with the same behaviour. TargetData is
190 /// used if available. The comparator always fails conservatively (erring on the
191 /// side of claiming that two functions are different).
192 class FunctionComparator {
194 FunctionComparator(const TargetData *TD, const Function *F1,
196 : F1(F1), F2(F2), TD(TD), IDMap1Count(0), IDMap2Count(0) {}
198 /// Compare - test whether the two functions have equivalent behaviour.
202 /// Compare - test whether two basic blocks have equivalent behaviour.
203 bool Compare(const BasicBlock *BB1, const BasicBlock *BB2);
205 /// Enumerate - Assign or look up previously assigned numbers for the two
206 /// values, and return whether the numbers are equal. Numbers are assigned in
207 /// the order visited.
208 bool Enumerate(const Value *V1, const Value *V2);
210 /// isEquivalentOperation - Compare two Instructions for equivalence, similar
211 /// to Instruction::isSameOperationAs but with modifications to the type
213 bool isEquivalentOperation(const Instruction *I1,
214 const Instruction *I2) const;
216 /// isEquivalentGEP - Compare two GEPs for equivalent pointer arithmetic.
217 bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
218 bool isEquivalentGEP(const GetElementPtrInst *GEP1,
219 const GetElementPtrInst *GEP2) {
220 return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
223 /// isEquivalentType - Compare two Types, treating all pointer types as equal.
224 bool isEquivalentType(const Type *Ty1, const Type *Ty2) const;
226 // The two functions undergoing comparison.
227 const Function *F1, *F2;
229 const TargetData *TD;
231 typedef DenseMap<const Value *, unsigned long> IDMap;
233 unsigned long IDMap1Count, IDMap2Count;
237 /// isEquivalentType - any two pointers in the same address space are
238 /// equivalent. Otherwise, standard type equivalence rules apply.
239 bool FunctionComparator::isEquivalentType(const Type *Ty1,
240 const Type *Ty2) const {
243 if (Ty1->getTypeID() != Ty2->getTypeID())
246 switch(Ty1->getTypeID()) {
248 llvm_unreachable("Unknown type!");
249 // Fall through in Release mode.
250 case Type::IntegerTyID:
251 case Type::OpaqueTyID:
252 // Ty1 == Ty2 would have returned true earlier.
256 case Type::FloatTyID:
257 case Type::DoubleTyID:
258 case Type::X86_FP80TyID:
259 case Type::FP128TyID:
260 case Type::PPC_FP128TyID:
261 case Type::LabelTyID:
262 case Type::MetadataTyID:
265 case Type::PointerTyID: {
266 const PointerType *PTy1 = cast<PointerType>(Ty1);
267 const PointerType *PTy2 = cast<PointerType>(Ty2);
268 return PTy1->getAddressSpace() == PTy2->getAddressSpace();
271 case Type::StructTyID: {
272 const StructType *STy1 = cast<StructType>(Ty1);
273 const StructType *STy2 = cast<StructType>(Ty2);
274 if (STy1->getNumElements() != STy2->getNumElements())
277 if (STy1->isPacked() != STy2->isPacked())
280 for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) {
281 if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i)))
287 case Type::FunctionTyID: {
288 const FunctionType *FTy1 = cast<FunctionType>(Ty1);
289 const FunctionType *FTy2 = cast<FunctionType>(Ty2);
290 if (FTy1->getNumParams() != FTy2->getNumParams() ||
291 FTy1->isVarArg() != FTy2->isVarArg())
294 if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType()))
297 for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) {
298 if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i)))
304 case Type::ArrayTyID: {
305 const ArrayType *ATy1 = cast<ArrayType>(Ty1);
306 const ArrayType *ATy2 = cast<ArrayType>(Ty2);
307 return ATy1->getNumElements() == ATy2->getNumElements() &&
308 isEquivalentType(ATy1->getElementType(), ATy2->getElementType());
311 case Type::VectorTyID: {
312 const VectorType *VTy1 = cast<VectorType>(Ty1);
313 const VectorType *VTy2 = cast<VectorType>(Ty2);
314 return VTy1->getNumElements() == VTy2->getNumElements() &&
315 isEquivalentType(VTy1->getElementType(), VTy2->getElementType());
320 /// isEquivalentOperation - determine whether the two operations are the same
321 /// except that pointer-to-A and pointer-to-B are equivalent. This should be
322 /// kept in sync with Instruction::isSameOperationAs.
323 bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
324 const Instruction *I2) const {
325 if (I1->getOpcode() != I2->getOpcode() ||
326 I1->getNumOperands() != I2->getNumOperands() ||
327 !isEquivalentType(I1->getType(), I2->getType()) ||
328 !I1->hasSameSubclassOptionalData(I2))
331 // We have two instructions of identical opcode and #operands. Check to see
332 // if all operands are the same type
333 for (unsigned i = 0, e = I1->getNumOperands(); i != e; ++i)
334 if (!isEquivalentType(I1->getOperand(i)->getType(),
335 I2->getOperand(i)->getType()))
338 // Check special state that is a part of some instructions.
339 if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
340 return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
341 LI->getAlignment() == cast<LoadInst>(I2)->getAlignment();
342 if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
343 return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
344 SI->getAlignment() == cast<StoreInst>(I2)->getAlignment();
345 if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
346 return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
347 if (const CallInst *CI = dyn_cast<CallInst>(I1))
348 return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
349 CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
350 CI->getAttributes().getRawPointer() ==
351 cast<CallInst>(I2)->getAttributes().getRawPointer();
352 if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
353 return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
354 CI->getAttributes().getRawPointer() ==
355 cast<InvokeInst>(I2)->getAttributes().getRawPointer();
356 if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
357 if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
359 for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
360 if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i])
364 if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) {
365 if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices())
367 for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
368 if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i])
376 /// isEquivalentGEP - determine whether two GEP operations perform the same
377 /// underlying arithmetic.
378 bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
379 const GEPOperator *GEP2) {
380 // When we have target data, we can reduce the GEP down to the value in bytes
381 // added to the address.
382 if (TD && GEP1->hasAllConstantIndices() && GEP2->hasAllConstantIndices()) {
383 SmallVector<Value *, 8> Indices1(GEP1->idx_begin(), GEP1->idx_end());
384 SmallVector<Value *, 8> Indices2(GEP2->idx_begin(), GEP2->idx_end());
385 uint64_t Offset1 = TD->getIndexedOffset(GEP1->getPointerOperandType(),
386 Indices1.data(), Indices1.size());
387 uint64_t Offset2 = TD->getIndexedOffset(GEP2->getPointerOperandType(),
388 Indices2.data(), Indices2.size());
389 return Offset1 == Offset2;
392 if (GEP1->getPointerOperand()->getType() !=
393 GEP2->getPointerOperand()->getType())
396 if (GEP1->getNumOperands() != GEP2->getNumOperands())
399 for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
400 if (!Enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
407 /// Enumerate - Compare two values used by the two functions under pair-wise
408 /// comparison. If this is the first time the values are seen, they're added to
409 /// the mapping so that we will detect mismatches on next use.
410 bool FunctionComparator::Enumerate(const Value *V1, const Value *V2) {
411 // Check for function @f1 referring to itself and function @f2 referring to
412 // itself, or referring to each other, or both referring to either of them.
413 // They're all equivalent if the two functions are otherwise equivalent.
414 if (V1 == F1 && V2 == F2)
416 if (V1 == F2 && V2 == F1)
419 // TODO: constant expressions with GEP or references to F1 or F2.
420 if (isa<Constant>(V1))
423 if (isa<InlineAsm>(V1) && isa<InlineAsm>(V2)) {
424 const InlineAsm *IA1 = cast<InlineAsm>(V1);
425 const InlineAsm *IA2 = cast<InlineAsm>(V2);
426 return IA1->getAsmString() == IA2->getAsmString() &&
427 IA1->getConstraintString() == IA2->getConstraintString();
430 unsigned long &ID1 = Map1[V1];
434 unsigned long &ID2 = Map2[V2];
441 /// Compare - test whether two basic blocks have equivalent behaviour.
442 bool FunctionComparator::Compare(const BasicBlock *BB1, const BasicBlock *BB2) {
443 BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
444 BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
447 if (!Enumerate(F1I, F2I))
450 if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
451 const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
455 if (!Enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
458 if (!isEquivalentGEP(GEP1, GEP2))
461 if (!isEquivalentOperation(F1I, F2I))
464 assert(F1I->getNumOperands() == F2I->getNumOperands());
465 for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
466 Value *OpF1 = F1I->getOperand(i);
467 Value *OpF2 = F2I->getOperand(i);
469 if (!Enumerate(OpF1, OpF2))
472 if (OpF1->getValueID() != OpF2->getValueID() ||
473 !isEquivalentType(OpF1->getType(), OpF2->getType()))
479 } while (F1I != F1E && F2I != F2E);
481 return F1I == F1E && F2I == F2E;
484 /// Compare - test whether the two functions have equivalent behaviour.
485 bool FunctionComparator::Compare() {
486 // We need to recheck everything, but check the things that weren't included
487 // in the hash first.
489 if (F1->getAttributes() != F2->getAttributes())
492 if (F1->hasGC() != F2->hasGC())
495 if (F1->hasGC() && F1->getGC() != F2->getGC())
498 if (F1->hasSection() != F2->hasSection())
501 if (F1->hasSection() && F1->getSection() != F2->getSection())
504 if (F1->isVarArg() != F2->isVarArg())
507 // TODO: if it's internal and only used in direct calls, we could handle this
509 if (F1->getCallingConv() != F2->getCallingConv())
512 if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
515 assert(F1->arg_size() == F2->arg_size() &&
516 "Identically typed functions have different numbers of args!");
518 // Visit the arguments so that they get enumerated in the order they're
520 for (Function::const_arg_iterator f1i = F1->arg_begin(),
521 f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) {
522 if (!Enumerate(f1i, f2i))
523 llvm_unreachable("Arguments repeat!");
526 // We do a CFG-ordered walk since the actual ordering of the blocks in the
527 // linked list is immaterial. Our walk starts at the entry block for both
528 // functions, then takes each block from each terminator in order. As an
529 // artifact, this also means that unreachable blocks are ignored.
530 SmallVector<const BasicBlock *, 8> F1BBs, F2BBs;
531 SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
533 F1BBs.push_back(&F1->getEntryBlock());
534 F2BBs.push_back(&F2->getEntryBlock());
536 VisitedBBs.insert(F1BBs[0]);
537 while (!F1BBs.empty()) {
538 const BasicBlock *F1BB = F1BBs.pop_back_val();
539 const BasicBlock *F2BB = F2BBs.pop_back_val();
541 if (!Enumerate(F1BB, F2BB) || !Compare(F1BB, F2BB))
544 const TerminatorInst *F1TI = F1BB->getTerminator();
545 const TerminatorInst *F2TI = F2BB->getTerminator();
547 assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
548 for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
549 if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
552 F1BBs.push_back(F1TI->getSuccessor(i));
553 F2BBs.push_back(F2TI->getSuccessor(i));
559 /// WriteThunk - Replace G with a simple tail call to bitcast(F). Also replace
560 /// direct uses of G with bitcast(F). Deletes G.
561 void MergeFunctions::WriteThunk(Function *F, Function *G) const {
562 if (!G->mayBeOverridden()) {
563 // Redirect direct callers of G to F.
564 Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
565 for (Value::use_iterator UI = G->use_begin(), UE = G->use_end();
567 Value::use_iterator TheIter = UI;
569 CallSite CS(*TheIter);
570 if (CS && CS.isCallee(TheIter))
571 TheIter.getUse().set(BitcastF);
575 // If G was internal then we may have replaced all uses of G with F. If so,
576 // stop here and delete G. There's no need for a thunk.
577 if (G->hasLocalLinkage() && G->use_empty()) {
578 G->eraseFromParent();
582 Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
584 BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
585 IRBuilder<false> Builder(BB);
587 SmallVector<Value *, 16> Args;
589 const FunctionType *FFTy = F->getFunctionType();
590 for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
592 Args.push_back(Builder.CreateBitCast(AI, FFTy->getParamType(i)));
596 CallInst *CI = Builder.CreateCall(F, Args.begin(), Args.end());
598 CI->setCallingConv(F->getCallingConv());
599 if (NewG->getReturnType()->isVoidTy()) {
600 Builder.CreateRetVoid();
602 Builder.CreateRet(Builder.CreateBitCast(CI, NewG->getReturnType()));
605 NewG->copyAttributesFrom(G);
607 G->replaceAllUsesWith(NewG);
608 G->eraseFromParent();
610 DEBUG(dbgs() << "WriteThunk: " << NewG->getName() << '\n');
614 /// MergeTwoFunctions - Merge two equivalent functions. Upon completion,
615 /// Function G is deleted.
616 void MergeFunctions::MergeTwoFunctions(Function *F, Function *G) const {
617 if (F->mayBeOverridden()) {
618 assert(G->mayBeOverridden());
620 // Make them both thunks to the same internal function.
621 Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
623 H->copyAttributesFrom(F);
625 F->replaceAllUsesWith(H);
627 unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
632 F->setAlignment(MaxAlignment);
633 F->setLinkage(GlobalValue::InternalLinkage);
640 ++NumFunctionsMerged;
643 // Insert - Insert a ComparableFunction into the FnSet, or merge it away if
644 // equal to one that's already inserted.
645 bool MergeFunctions::Insert(FnSetType &FnSet, ComparableFunction &NewF) {
646 std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
650 const ComparableFunction &OldF = *Result.first;
652 // Never thunk a strong function to a weak function.
653 assert(!OldF.getFunc()->mayBeOverridden() ||
654 NewF.getFunc()->mayBeOverridden());
656 DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
657 << NewF.getFunc()->getName() << '\n');
659 Function *DeleteF = NewF.getFunc();
661 MergeTwoFunctions(OldF.getFunc(), DeleteF);
665 // 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
667 static bool IsThunk(const Function *F) {
668 // The safe direction to fail is to return true. In that case, the function
669 // will be removed from merging analysis. If we failed to including functions
670 // then we may try to merge unmergable thing (ie., identical weak functions)
671 // which will push us into an infinite loop.
673 assert(!F->isDeclaration() && "Expected a function definition.");
675 const BasicBlock *BB = &F->front();
678 // optional-reg tail call @thunkee(args...*)
679 // ret void|optional-reg
680 // where the args are in the same order as the arguments.
682 // Put this at the top since it triggers most often.
683 const ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator());
684 if (!RI) return false;
686 // Verify that the sequence of bitcast-inst's are all casts of arguments and
687 // that there aren't any extras (ie. no repeated casts).
689 BasicBlock::const_iterator I = BB->begin();
690 while (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
691 const Argument *A = dyn_cast<Argument>(BCI->getOperand(0));
692 if (!A) return false;
693 if ((int)A->getArgNo() <= LastArgNo) return false;
694 LastArgNo = A->getArgNo();
698 // Verify that we have a direct tail call and that the calling conventions
699 // and number of arguments match.
700 const CallInst *CI = dyn_cast<CallInst>(I++);
701 if (!CI || !CI->isTailCall() || !CI->getCalledFunction() ||
702 CI->getCallingConv() != CI->getCalledFunction()->getCallingConv() ||
703 CI->getNumArgOperands() != F->arg_size())
706 // Verify that the call instruction has the same arguments as this function
707 // and that they're all either the incoming argument or a cast of the right
709 for (unsigned i = 0, e = CI->getNumArgOperands(); i != e; ++i) {
710 const Value *V = CI->getArgOperand(i);
711 const Argument *A = dyn_cast<Argument>(V);
713 const BitCastInst *BCI = dyn_cast<BitCastInst>(V);
714 if (!BCI) return false;
715 A = cast<Argument>(BCI->getOperand(0));
717 if (A->getArgNo() != i) return false;
720 // Verify that the terminator is a ret void (if we're void) or a ret of the
721 // call's return, or a ret of a bitcast of the call's return.
722 const Value *RetOp = CI;
723 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(I)) {
725 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();