1 //===- CloneFunction.cpp - Clone a function into another function ---------===//
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 file implements the CloneFunctionInto interface, which is used as the
11 // low-level function cloner. This is used by the CloneFunction and function
12 // inliner to do the dirty work of copying the body of a function around.
14 //===----------------------------------------------------------------------===//
16 #include "llvm/Transforms/Utils/Cloning.h"
17 #include "llvm/ADT/SmallVector.h"
18 #include "llvm/Analysis/ConstantFolding.h"
19 #include "llvm/Analysis/InstructionSimplify.h"
20 #include "llvm/IR/CFG.h"
21 #include "llvm/IR/Constants.h"
22 #include "llvm/IR/DebugInfo.h"
23 #include "llvm/IR/DerivedTypes.h"
24 #include "llvm/IR/Function.h"
25 #include "llvm/IR/GlobalVariable.h"
26 #include "llvm/IR/Instructions.h"
27 #include "llvm/IR/IntrinsicInst.h"
28 #include "llvm/IR/LLVMContext.h"
29 #include "llvm/IR/Metadata.h"
30 #include "llvm/IR/Module.h"
31 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
32 #include "llvm/Transforms/Utils/Local.h"
33 #include "llvm/Transforms/Utils/ValueMapper.h"
37 /// See comments in Cloning.h.
38 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
39 ValueToValueMapTy &VMap,
40 const Twine &NameSuffix, Function *F,
41 ClonedCodeInfo *CodeInfo) {
42 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
43 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
45 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
47 // Loop over all instructions, and copy them over.
48 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
50 Instruction *NewInst = II->clone();
52 NewInst->setName(II->getName()+NameSuffix);
53 NewBB->getInstList().push_back(NewInst);
54 VMap[II] = NewInst; // Add instruction map to value.
56 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
57 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
58 if (isa<ConstantInt>(AI->getArraySize()))
59 hasStaticAllocas = true;
61 hasDynamicAllocas = true;
66 CodeInfo->ContainsCalls |= hasCalls;
67 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
68 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
69 BB != &BB->getParent()->getEntryBlock();
74 // Clone OldFunc into NewFunc, transforming the old arguments into references to
77 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
78 ValueToValueMapTy &VMap,
79 bool ModuleLevelChanges,
80 SmallVectorImpl<ReturnInst*> &Returns,
81 const char *NameSuffix, ClonedCodeInfo *CodeInfo,
82 ValueMapTypeRemapper *TypeMapper,
83 ValueMaterializer *Materializer) {
84 assert(NameSuffix && "NameSuffix cannot be null!");
87 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
88 E = OldFunc->arg_end(); I != E; ++I)
89 assert(VMap.count(I) && "No mapping from source argument specified!");
92 // Copy all attributes other than those stored in the AttributeSet. We need
93 // to remap the parameter indices of the AttributeSet.
94 AttributeSet NewAttrs = NewFunc->getAttributes();
95 NewFunc->copyAttributesFrom(OldFunc);
96 NewFunc->setAttributes(NewAttrs);
98 AttributeSet OldAttrs = OldFunc->getAttributes();
99 // Clone any argument attributes that are present in the VMap.
100 for (const Argument &OldArg : OldFunc->args())
101 if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
103 OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
104 if (attrs.getNumSlots() > 0)
105 NewArg->addAttr(attrs);
108 NewFunc->setAttributes(
109 NewFunc->getAttributes()
110 .addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
111 OldAttrs.getRetAttributes())
112 .addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
113 OldAttrs.getFnAttributes()));
115 // Loop over all of the basic blocks in the function, cloning them as
116 // appropriate. Note that we save BE this way in order to handle cloning of
117 // recursive functions into themselves.
119 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
121 const BasicBlock &BB = *BI;
123 // Create a new basic block and copy instructions into it!
124 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
126 // Add basic block mapping.
129 // It is only legal to clone a function if a block address within that
130 // function is never referenced outside of the function. Given that, we
131 // want to map block addresses from the old function to block addresses in
132 // the clone. (This is different from the generic ValueMapper
133 // implementation, which generates an invalid blockaddress when
134 // cloning a function.)
135 if (BB.hasAddressTaken()) {
136 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
137 const_cast<BasicBlock*>(&BB));
138 VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
141 // Note return instructions for the caller.
142 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
143 Returns.push_back(RI);
146 // Loop over all of the instructions in the function, fixing up operand
147 // references as we go. This uses VMap to do all the hard work.
148 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
149 BE = NewFunc->end(); BB != BE; ++BB)
150 // Loop over all instructions, fixing each one as we find it...
151 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
152 RemapInstruction(II, VMap,
153 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
154 TypeMapper, Materializer);
157 // Find the MDNode which corresponds to the DISubprogram data that described F.
158 static MDNode* FindSubprogram(const Function *F, DebugInfoFinder &Finder) {
159 for (DISubprogram Subprogram : Finder.subprograms()) {
160 if (Subprogram->describes(F))
166 // Add an operand to an existing MDNode. The new operand will be added at the
167 // back of the operand list.
168 static void AddOperand(DICompileUnit CU, MDSubprogramArray SPs, Metadata *NewSP) {
169 SmallVector<Metadata *, 16> NewSPs;
170 NewSPs.reserve(SPs.size() + 1);
172 NewSPs.push_back(SP);
173 NewSPs.push_back(NewSP);
174 CU.replaceSubprograms(MDTuple::get(CU->getContext(), NewSPs));
177 // Clone the module-level debug info associated with OldFunc. The cloned data
178 // will point to NewFunc instead.
179 static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
180 ValueToValueMapTy &VMap) {
181 DebugInfoFinder Finder;
182 Finder.processModule(*OldFunc->getParent());
184 const MDNode *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
185 if (!OldSubprogramMDNode) return;
187 // Ensure that OldFunc appears in the map.
188 // (if it's already there it must point to NewFunc anyway)
189 VMap[OldFunc] = NewFunc;
190 DISubprogram NewSubprogram =
191 cast<MDSubprogram>(MapMetadata(OldSubprogramMDNode, VMap));
193 for (DICompileUnit CU : Finder.compile_units()) {
194 auto Subprograms = CU->getSubprograms();
195 // If the compile unit's function list contains the old function, it should
196 // also contain the new one.
197 for (auto *SP : Subprograms) {
198 if (SP == OldSubprogramMDNode) {
199 AddOperand(CU, Subprograms, NewSubprogram);
206 /// Return a copy of the specified function, but without
207 /// embedding the function into another module. Also, any references specified
208 /// in the VMap are changed to refer to their mapped value instead of the
209 /// original one. If any of the arguments to the function are in the VMap,
210 /// the arguments are deleted from the resultant function. The VMap is
211 /// updated to include mappings from all of the instructions and basicblocks in
212 /// the function from their old to new values.
214 Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
215 bool ModuleLevelChanges,
216 ClonedCodeInfo *CodeInfo) {
217 std::vector<Type*> ArgTypes;
219 // The user might be deleting arguments to the function by specifying them in
220 // the VMap. If so, we need to not add the arguments to the arg ty vector
222 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
224 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
225 ArgTypes.push_back(I->getType());
227 // Create a new function type...
228 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
229 ArgTypes, F->getFunctionType()->isVarArg());
231 // Create the new function...
232 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
234 // Loop over the arguments, copying the names of the mapped arguments over...
235 Function::arg_iterator DestI = NewF->arg_begin();
236 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
238 if (VMap.count(I) == 0) { // Is this argument preserved?
239 DestI->setName(I->getName()); // Copy the name over...
240 VMap[I] = DestI++; // Add mapping to VMap
243 if (ModuleLevelChanges)
244 CloneDebugInfoMetadata(NewF, F, VMap);
246 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
247 CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
254 /// This is a private class used to implement CloneAndPruneFunctionInto.
255 struct PruningFunctionCloner {
257 const Function *OldFunc;
258 ValueToValueMapTy &VMap;
259 bool ModuleLevelChanges;
260 const char *NameSuffix;
261 ClonedCodeInfo *CodeInfo;
262 CloningDirector *Director;
263 ValueMapTypeRemapper *TypeMapper;
264 ValueMaterializer *Materializer;
267 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
268 ValueToValueMapTy &valueMap, bool moduleLevelChanges,
269 const char *nameSuffix, ClonedCodeInfo *codeInfo,
270 CloningDirector *Director)
271 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
272 ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
273 CodeInfo(codeInfo), Director(Director) {
274 // These are optional components. The Director may return null.
276 TypeMapper = Director->getTypeRemapper();
277 Materializer = Director->getValueMaterializer();
279 TypeMapper = nullptr;
280 Materializer = nullptr;
284 /// The specified block is found to be reachable, clone it and
285 /// anything that it can reach.
286 void CloneBlock(const BasicBlock *BB,
287 BasicBlock::const_iterator StartingInst,
288 std::vector<const BasicBlock*> &ToClone);
292 /// The specified block is found to be reachable, clone it and
293 /// anything that it can reach.
294 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
295 BasicBlock::const_iterator StartingInst,
296 std::vector<const BasicBlock*> &ToClone){
297 WeakVH &BBEntry = VMap[BB];
299 // Have we already cloned this block?
302 // Nope, clone it now.
304 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
305 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
307 // It is only legal to clone a function if a block address within that
308 // function is never referenced outside of the function. Given that, we
309 // want to map block addresses from the old function to block addresses in
310 // the clone. (This is different from the generic ValueMapper
311 // implementation, which generates an invalid blockaddress when
312 // cloning a function.)
314 // Note that we don't need to fix the mapping for unreachable blocks;
315 // the default mapping there is safe.
316 if (BB->hasAddressTaken()) {
317 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
318 const_cast<BasicBlock*>(BB));
319 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
322 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
324 // Loop over all instructions, and copy them over, DCE'ing as we go. This
325 // loop doesn't include the terminator.
326 for (BasicBlock::const_iterator II = StartingInst, IE = --BB->end();
328 // If the "Director" remaps the instruction, don't clone it.
330 CloningDirector::CloningAction Action
331 = Director->handleInstruction(VMap, II, NewBB);
332 // If the cloning director says stop, we want to stop everything, not
333 // just break out of the loop (which would cause the terminator to be
334 // cloned). The cloning director is responsible for inserting a proper
335 // terminator into the new basic block in this case.
336 if (Action == CloningDirector::StopCloningBB)
338 // If the cloning director says skip, continue to the next instruction.
339 // In this case, the cloning director is responsible for mapping the
340 // skipped instruction to some value that is defined in the new
342 if (Action == CloningDirector::SkipInstruction)
346 Instruction *NewInst = II->clone();
348 // Eagerly remap operands to the newly cloned instruction, except for PHI
349 // nodes for which we defer processing until we update the CFG.
350 if (!isa<PHINode>(NewInst)) {
351 RemapInstruction(NewInst, VMap,
352 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
353 TypeMapper, Materializer);
355 // If we can simplify this instruction to some other value, simply add
356 // a mapping to that value rather than inserting a new instruction into
359 SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
360 // On the off-chance that this simplifies to an instruction in the old
361 // function, map it back into the new function.
362 if (Value *MappedV = VMap.lookup(V))
372 NewInst->setName(II->getName()+NameSuffix);
373 VMap[II] = NewInst; // Add instruction map to value.
374 NewBB->getInstList().push_back(NewInst);
375 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
376 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
377 if (isa<ConstantInt>(AI->getArraySize()))
378 hasStaticAllocas = true;
380 hasDynamicAllocas = true;
384 // Finally, clone over the terminator.
385 const TerminatorInst *OldTI = BB->getTerminator();
386 bool TerminatorDone = false;
388 CloningDirector::CloningAction Action
389 = Director->handleInstruction(VMap, OldTI, NewBB);
390 // If the cloning director says stop, we want to stop everything, not
391 // just break out of the loop (which would cause the terminator to be
392 // cloned). The cloning director is responsible for inserting a proper
393 // terminator into the new basic block in this case.
394 if (Action == CloningDirector::StopCloningBB)
396 if (Action == CloningDirector::CloneSuccessors) {
397 // If the director says to skip with a terminate instruction, we still
398 // need to clone this block's successors.
399 const TerminatorInst *TI = NewBB->getTerminator();
400 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
401 ToClone.push_back(TI->getSuccessor(i));
404 assert(Action != CloningDirector::SkipInstruction &&
405 "SkipInstruction is not valid for terminators.");
407 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
408 if (BI->isConditional()) {
409 // If the condition was a known constant in the callee...
410 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
411 // Or is a known constant in the caller...
413 Value *V = VMap[BI->getCondition()];
414 Cond = dyn_cast_or_null<ConstantInt>(V);
417 // Constant fold to uncond branch!
419 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
420 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
421 ToClone.push_back(Dest);
422 TerminatorDone = true;
425 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
426 // If switching on a value known constant in the caller.
427 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
428 if (!Cond) { // Or known constant after constant prop in the callee...
429 Value *V = VMap[SI->getCondition()];
430 Cond = dyn_cast_or_null<ConstantInt>(V);
432 if (Cond) { // Constant fold to uncond branch!
433 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
434 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
435 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
436 ToClone.push_back(Dest);
437 TerminatorDone = true;
441 if (!TerminatorDone) {
442 Instruction *NewInst = OldTI->clone();
443 if (OldTI->hasName())
444 NewInst->setName(OldTI->getName()+NameSuffix);
445 NewBB->getInstList().push_back(NewInst);
446 VMap[OldTI] = NewInst; // Add instruction map to value.
448 // Recursively clone any reachable successor blocks.
449 const TerminatorInst *TI = BB->getTerminator();
450 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
451 ToClone.push_back(TI->getSuccessor(i));
455 CodeInfo->ContainsCalls |= hasCalls;
456 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
457 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
458 BB != &BB->getParent()->front();
462 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
463 /// entire function. Instead it starts at an instruction provided by the caller
464 /// and copies (and prunes) only the code reachable from that instruction.
465 void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
466 const Instruction *StartingInst,
467 ValueToValueMapTy &VMap,
468 bool ModuleLevelChanges,
469 SmallVectorImpl<ReturnInst *> &Returns,
470 const char *NameSuffix,
471 ClonedCodeInfo *CodeInfo,
472 CloningDirector *Director) {
473 assert(NameSuffix && "NameSuffix cannot be null!");
475 ValueMapTypeRemapper *TypeMapper = nullptr;
476 ValueMaterializer *Materializer = nullptr;
479 TypeMapper = Director->getTypeRemapper();
480 Materializer = Director->getValueMaterializer();
484 // If the cloning starts at the begining of the function, verify that
485 // the function arguments are mapped.
487 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
488 E = OldFunc->arg_end(); II != E; ++II)
489 assert(VMap.count(II) && "No mapping from source argument specified!");
492 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
493 NameSuffix, CodeInfo, Director);
494 const BasicBlock *StartingBB;
496 StartingBB = StartingInst->getParent();
498 StartingBB = &OldFunc->getEntryBlock();
499 StartingInst = StartingBB->begin();
502 // Clone the entry block, and anything recursively reachable from it.
503 std::vector<const BasicBlock*> CloneWorklist;
504 PFC.CloneBlock(StartingBB, StartingInst, CloneWorklist);
505 while (!CloneWorklist.empty()) {
506 const BasicBlock *BB = CloneWorklist.back();
507 CloneWorklist.pop_back();
508 PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
511 // Loop over all of the basic blocks in the old function. If the block was
512 // reachable, we have cloned it and the old block is now in the value map:
513 // insert it into the new function in the right order. If not, ignore it.
515 // Defer PHI resolution until rest of function is resolved.
516 SmallVector<const PHINode*, 16> PHIToResolve;
517 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
520 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
521 if (!NewBB) continue; // Dead block.
523 // Add the new block to the new function.
524 NewFunc->getBasicBlockList().push_back(NewBB);
526 // Handle PHI nodes specially, as we have to remove references to dead
528 for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I) {
529 // PHI nodes may have been remapped to non-PHI nodes by the caller or
530 // during the cloning process.
531 if (const PHINode *PN = dyn_cast<PHINode>(I)) {
532 if (isa<PHINode>(VMap[PN]))
533 PHIToResolve.push_back(PN);
541 // Finally, remap the terminator instructions, as those can't be remapped
542 // until all BBs are mapped.
543 RemapInstruction(NewBB->getTerminator(), VMap,
544 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
545 TypeMapper, Materializer);
548 // Defer PHI resolution until rest of function is resolved, PHI resolution
549 // requires the CFG to be up-to-date.
550 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
551 const PHINode *OPN = PHIToResolve[phino];
552 unsigned NumPreds = OPN->getNumIncomingValues();
553 const BasicBlock *OldBB = OPN->getParent();
554 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
556 // Map operands for blocks that are live and remove operands for blocks
558 for (; phino != PHIToResolve.size() &&
559 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
560 OPN = PHIToResolve[phino];
561 PHINode *PN = cast<PHINode>(VMap[OPN]);
562 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
563 Value *V = VMap[PN->getIncomingBlock(pred)];
564 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
565 Value *InVal = MapValue(PN->getIncomingValue(pred),
567 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
568 assert(InVal && "Unknown input value?");
569 PN->setIncomingValue(pred, InVal);
570 PN->setIncomingBlock(pred, MappedBlock);
572 PN->removeIncomingValue(pred, false);
573 --pred, --e; // Revisit the next entry.
578 // The loop above has removed PHI entries for those blocks that are dead
579 // and has updated others. However, if a block is live (i.e. copied over)
580 // but its terminator has been changed to not go to this block, then our
581 // phi nodes will have invalid entries. Update the PHI nodes in this
583 PHINode *PN = cast<PHINode>(NewBB->begin());
584 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
585 if (NumPreds != PN->getNumIncomingValues()) {
586 assert(NumPreds < PN->getNumIncomingValues());
587 // Count how many times each predecessor comes to this block.
588 std::map<BasicBlock*, unsigned> PredCount;
589 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
593 // Figure out how many entries to remove from each PHI.
594 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
595 ++PredCount[PN->getIncomingBlock(i)];
597 // At this point, the excess predecessor entries are positive in the
598 // map. Loop over all of the PHIs and remove excess predecessor
600 BasicBlock::iterator I = NewBB->begin();
601 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
602 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
603 E = PredCount.end(); PCI != E; ++PCI) {
604 BasicBlock *Pred = PCI->first;
605 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
606 PN->removeIncomingValue(Pred, false);
611 // If the loops above have made these phi nodes have 0 or 1 operand,
612 // replace them with undef or the input value. We must do this for
613 // correctness, because 0-operand phis are not valid.
614 PN = cast<PHINode>(NewBB->begin());
615 if (PN->getNumIncomingValues() == 0) {
616 BasicBlock::iterator I = NewBB->begin();
617 BasicBlock::const_iterator OldI = OldBB->begin();
618 while ((PN = dyn_cast<PHINode>(I++))) {
619 Value *NV = UndefValue::get(PN->getType());
620 PN->replaceAllUsesWith(NV);
621 assert(VMap[OldI] == PN && "VMap mismatch");
623 PN->eraseFromParent();
629 // Make a second pass over the PHINodes now that all of them have been
630 // remapped into the new function, simplifying the PHINode and performing any
631 // recursive simplifications exposed. This will transparently update the
632 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
633 // two PHINodes, the iteration over the old PHIs remains valid, and the
634 // mapping will just map us to the new node (which may not even be a PHI
636 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
637 if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
638 recursivelySimplifyInstruction(PN);
640 // Now that the inlined function body has been fully constructed, go through
641 // and zap unconditional fall-through branches. This happens all the time when
642 // specializing code: code specialization turns conditional branches into
643 // uncond branches, and this code folds them.
644 Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB]);
645 Function::iterator I = Begin;
646 while (I != NewFunc->end()) {
647 // Check if this block has become dead during inlining or other
648 // simplifications. Note that the first block will appear dead, as it has
649 // not yet been wired up properly.
650 if (I != Begin && (pred_begin(I) == pred_end(I) ||
651 I->getSinglePredecessor() == I)) {
652 BasicBlock *DeadBB = I++;
653 DeleteDeadBlock(DeadBB);
657 // We need to simplify conditional branches and switches with a constant
658 // operand. We try to prune these out when cloning, but if the
659 // simplification required looking through PHI nodes, those are only
660 // available after forming the full basic block. That may leave some here,
661 // and we still want to prune the dead code as early as possible.
662 ConstantFoldTerminator(I);
664 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
665 if (!BI || BI->isConditional()) { ++I; continue; }
667 BasicBlock *Dest = BI->getSuccessor(0);
668 if (!Dest->getSinglePredecessor()) {
672 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
673 // above should have zapped all of them..
674 assert(!isa<PHINode>(Dest->begin()));
676 // We know all single-entry PHI nodes in the inlined function have been
677 // removed, so we just need to splice the blocks.
678 BI->eraseFromParent();
680 // Make all PHI nodes that referred to Dest now refer to I as their source.
681 Dest->replaceAllUsesWith(I);
683 // Move all the instructions in the succ to the pred.
684 I->getInstList().splice(I->end(), Dest->getInstList());
686 // Remove the dest block.
687 Dest->eraseFromParent();
689 // Do not increment I, iteratively merge all things this block branches to.
692 // Make a final pass over the basic blocks from the old function to gather
693 // any return instructions which survived folding. We have to do this here
694 // because we can iteratively remove and merge returns above.
695 for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB]),
698 if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
699 Returns.push_back(RI);
703 /// This works exactly like CloneFunctionInto,
704 /// except that it does some simple constant prop and DCE on the fly. The
705 /// effect of this is to copy significantly less code in cases where (for
706 /// example) a function call with constant arguments is inlined, and those
707 /// constant arguments cause a significant amount of code in the callee to be
708 /// dead. Since this doesn't produce an exact copy of the input, it can't be
709 /// used for things like CloneFunction or CloneModule.
710 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
711 ValueToValueMapTy &VMap,
712 bool ModuleLevelChanges,
713 SmallVectorImpl<ReturnInst*> &Returns,
714 const char *NameSuffix,
715 ClonedCodeInfo *CodeInfo,
716 Instruction *TheCall) {
717 CloneAndPruneIntoFromInst(NewFunc, OldFunc, OldFunc->front().begin(), VMap,
718 ModuleLevelChanges, Returns, NameSuffix, CodeInfo,