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)) return Subprogram;
165 // Add an operand to an existing MDNode. The new operand will be added at the
166 // back of the operand list.
167 static void AddOperand(DICompileUnit CU, MDSubprogramArray SPs, Metadata *NewSP) {
168 SmallVector<Metadata *, 16> NewSPs;
169 NewSPs.reserve(SPs.size() + 1);
171 NewSPs.push_back(SP);
172 NewSPs.push_back(NewSP);
173 CU.replaceSubprograms(DIArray(MDNode::get(CU->getContext(), NewSPs)));
176 // Clone the module-level debug info associated with OldFunc. The cloned data
177 // will point to NewFunc instead.
178 static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
179 ValueToValueMapTy &VMap) {
180 DebugInfoFinder Finder;
181 Finder.processModule(*OldFunc->getParent());
183 const MDNode *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
184 if (!OldSubprogramMDNode) return;
186 // Ensure that OldFunc appears in the map.
187 // (if it's already there it must point to NewFunc anyway)
188 VMap[OldFunc] = NewFunc;
189 DISubprogram NewSubprogram =
190 cast<MDSubprogram>(MapMetadata(OldSubprogramMDNode, VMap));
192 for (DICompileUnit CU : Finder.compile_units()) {
193 auto Subprograms = CU->getSubprograms();
194 // If the compile unit's function list contains the old function, it should
195 // also contain the new one.
196 for (auto *SP : Subprograms) {
197 if (SP == OldSubprogramMDNode) {
198 AddOperand(CU, Subprograms, NewSubprogram);
205 /// Return a copy of the specified function, but without
206 /// embedding the function into another module. Also, any references specified
207 /// in the VMap are changed to refer to their mapped value instead of the
208 /// original one. If any of the arguments to the function are in the VMap,
209 /// the arguments are deleted from the resultant function. The VMap is
210 /// updated to include mappings from all of the instructions and basicblocks in
211 /// the function from their old to new values.
213 Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
214 bool ModuleLevelChanges,
215 ClonedCodeInfo *CodeInfo) {
216 std::vector<Type*> ArgTypes;
218 // The user might be deleting arguments to the function by specifying them in
219 // the VMap. If so, we need to not add the arguments to the arg ty vector
221 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
223 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
224 ArgTypes.push_back(I->getType());
226 // Create a new function type...
227 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
228 ArgTypes, F->getFunctionType()->isVarArg());
230 // Create the new function...
231 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
233 // Loop over the arguments, copying the names of the mapped arguments over...
234 Function::arg_iterator DestI = NewF->arg_begin();
235 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
237 if (VMap.count(I) == 0) { // Is this argument preserved?
238 DestI->setName(I->getName()); // Copy the name over...
239 VMap[I] = DestI++; // Add mapping to VMap
242 if (ModuleLevelChanges)
243 CloneDebugInfoMetadata(NewF, F, VMap);
245 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
246 CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
253 /// This is a private class used to implement CloneAndPruneFunctionInto.
254 struct PruningFunctionCloner {
256 const Function *OldFunc;
257 ValueToValueMapTy &VMap;
258 bool ModuleLevelChanges;
259 const char *NameSuffix;
260 ClonedCodeInfo *CodeInfo;
261 CloningDirector *Director;
262 ValueMapTypeRemapper *TypeMapper;
263 ValueMaterializer *Materializer;
266 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
267 ValueToValueMapTy &valueMap, bool moduleLevelChanges,
268 const char *nameSuffix, ClonedCodeInfo *codeInfo,
269 CloningDirector *Director)
270 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
271 ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
272 CodeInfo(codeInfo), Director(Director) {
273 // These are optional components. The Director may return null.
275 TypeMapper = Director->getTypeRemapper();
276 Materializer = Director->getValueMaterializer();
278 TypeMapper = nullptr;
279 Materializer = nullptr;
283 /// The specified block is found to be reachable, clone it and
284 /// anything that it can reach.
285 void CloneBlock(const BasicBlock *BB,
286 BasicBlock::const_iterator StartingInst,
287 std::vector<const BasicBlock*> &ToClone);
291 /// The specified block is found to be reachable, clone it and
292 /// anything that it can reach.
293 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
294 BasicBlock::const_iterator StartingInst,
295 std::vector<const BasicBlock*> &ToClone){
296 WeakVH &BBEntry = VMap[BB];
298 // Have we already cloned this block?
301 // Nope, clone it now.
303 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
304 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
306 // It is only legal to clone a function if a block address within that
307 // function is never referenced outside of the function. Given that, we
308 // want to map block addresses from the old function to block addresses in
309 // the clone. (This is different from the generic ValueMapper
310 // implementation, which generates an invalid blockaddress when
311 // cloning a function.)
313 // Note that we don't need to fix the mapping for unreachable blocks;
314 // the default mapping there is safe.
315 if (BB->hasAddressTaken()) {
316 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
317 const_cast<BasicBlock*>(BB));
318 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
321 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
323 // Loop over all instructions, and copy them over, DCE'ing as we go. This
324 // loop doesn't include the terminator.
325 for (BasicBlock::const_iterator II = StartingInst, IE = --BB->end();
327 // If the "Director" remaps the instruction, don't clone it.
329 CloningDirector::CloningAction Action
330 = Director->handleInstruction(VMap, II, NewBB);
331 // If the cloning director says stop, we want to stop everything, not
332 // just break out of the loop (which would cause the terminator to be
333 // cloned). The cloning director is responsible for inserting a proper
334 // terminator into the new basic block in this case.
335 if (Action == CloningDirector::StopCloningBB)
337 // If the cloning director says skip, continue to the next instruction.
338 // In this case, the cloning director is responsible for mapping the
339 // skipped instruction to some value that is defined in the new
341 if (Action == CloningDirector::SkipInstruction)
345 Instruction *NewInst = II->clone();
347 // Eagerly remap operands to the newly cloned instruction, except for PHI
348 // nodes for which we defer processing until we update the CFG.
349 if (!isa<PHINode>(NewInst)) {
350 RemapInstruction(NewInst, VMap,
351 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
352 TypeMapper, Materializer);
354 // If we can simplify this instruction to some other value, simply add
355 // a mapping to that value rather than inserting a new instruction into
358 SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
359 // On the off-chance that this simplifies to an instruction in the old
360 // function, map it back into the new function.
361 if (Value *MappedV = VMap.lookup(V))
371 NewInst->setName(II->getName()+NameSuffix);
372 VMap[II] = NewInst; // Add instruction map to value.
373 NewBB->getInstList().push_back(NewInst);
374 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
375 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
376 if (isa<ConstantInt>(AI->getArraySize()))
377 hasStaticAllocas = true;
379 hasDynamicAllocas = true;
383 // Finally, clone over the terminator.
384 const TerminatorInst *OldTI = BB->getTerminator();
385 bool TerminatorDone = false;
387 CloningDirector::CloningAction Action
388 = Director->handleInstruction(VMap, OldTI, NewBB);
389 // If the cloning director says stop, we want to stop everything, not
390 // just break out of the loop (which would cause the terminator to be
391 // cloned). The cloning director is responsible for inserting a proper
392 // terminator into the new basic block in this case.
393 if (Action == CloningDirector::StopCloningBB)
395 if (Action == CloningDirector::CloneSuccessors) {
396 // If the director says to skip with a terminate instruction, we still
397 // need to clone this block's successors.
398 const TerminatorInst *TI = NewBB->getTerminator();
399 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
400 ToClone.push_back(TI->getSuccessor(i));
403 assert(Action != CloningDirector::SkipInstruction &&
404 "SkipInstruction is not valid for terminators.");
406 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
407 if (BI->isConditional()) {
408 // If the condition was a known constant in the callee...
409 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
410 // Or is a known constant in the caller...
412 Value *V = VMap[BI->getCondition()];
413 Cond = dyn_cast_or_null<ConstantInt>(V);
416 // Constant fold to uncond branch!
418 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
419 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
420 ToClone.push_back(Dest);
421 TerminatorDone = true;
424 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
425 // If switching on a value known constant in the caller.
426 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
427 if (!Cond) { // Or known constant after constant prop in the callee...
428 Value *V = VMap[SI->getCondition()];
429 Cond = dyn_cast_or_null<ConstantInt>(V);
431 if (Cond) { // Constant fold to uncond branch!
432 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
433 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
434 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
435 ToClone.push_back(Dest);
436 TerminatorDone = true;
440 if (!TerminatorDone) {
441 Instruction *NewInst = OldTI->clone();
442 if (OldTI->hasName())
443 NewInst->setName(OldTI->getName()+NameSuffix);
444 NewBB->getInstList().push_back(NewInst);
445 VMap[OldTI] = NewInst; // Add instruction map to value.
447 // Recursively clone any reachable successor blocks.
448 const TerminatorInst *TI = BB->getTerminator();
449 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
450 ToClone.push_back(TI->getSuccessor(i));
454 CodeInfo->ContainsCalls |= hasCalls;
455 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
456 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
457 BB != &BB->getParent()->front();
461 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
462 /// entire function. Instead it starts at an instruction provided by the caller
463 /// and copies (and prunes) only the code reachable from that instruction.
464 void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
465 const Instruction *StartingInst,
466 ValueToValueMapTy &VMap,
467 bool ModuleLevelChanges,
468 SmallVectorImpl<ReturnInst *> &Returns,
469 const char *NameSuffix,
470 ClonedCodeInfo *CodeInfo,
471 CloningDirector *Director) {
472 assert(NameSuffix && "NameSuffix cannot be null!");
474 ValueMapTypeRemapper *TypeMapper = nullptr;
475 ValueMaterializer *Materializer = nullptr;
478 TypeMapper = Director->getTypeRemapper();
479 Materializer = Director->getValueMaterializer();
483 // If the cloning starts at the begining of the function, verify that
484 // the function arguments are mapped.
486 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
487 E = OldFunc->arg_end(); II != E; ++II)
488 assert(VMap.count(II) && "No mapping from source argument specified!");
491 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
492 NameSuffix, CodeInfo, Director);
493 const BasicBlock *StartingBB;
495 StartingBB = StartingInst->getParent();
497 StartingBB = &OldFunc->getEntryBlock();
498 StartingInst = StartingBB->begin();
501 // Clone the entry block, and anything recursively reachable from it.
502 std::vector<const BasicBlock*> CloneWorklist;
503 PFC.CloneBlock(StartingBB, StartingInst, CloneWorklist);
504 while (!CloneWorklist.empty()) {
505 const BasicBlock *BB = CloneWorklist.back();
506 CloneWorklist.pop_back();
507 PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
510 // Loop over all of the basic blocks in the old function. If the block was
511 // reachable, we have cloned it and the old block is now in the value map:
512 // insert it into the new function in the right order. If not, ignore it.
514 // Defer PHI resolution until rest of function is resolved.
515 SmallVector<const PHINode*, 16> PHIToResolve;
516 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
519 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
520 if (!NewBB) continue; // Dead block.
522 // Add the new block to the new function.
523 NewFunc->getBasicBlockList().push_back(NewBB);
525 // Handle PHI nodes specially, as we have to remove references to dead
527 for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I) {
528 // PHI nodes may have been remapped to non-PHI nodes by the caller or
529 // during the cloning process.
530 if (const PHINode *PN = dyn_cast<PHINode>(I)) {
531 if (isa<PHINode>(VMap[PN]))
532 PHIToResolve.push_back(PN);
540 // Finally, remap the terminator instructions, as those can't be remapped
541 // until all BBs are mapped.
542 RemapInstruction(NewBB->getTerminator(), VMap,
543 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
544 TypeMapper, Materializer);
547 // Defer PHI resolution until rest of function is resolved, PHI resolution
548 // requires the CFG to be up-to-date.
549 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
550 const PHINode *OPN = PHIToResolve[phino];
551 unsigned NumPreds = OPN->getNumIncomingValues();
552 const BasicBlock *OldBB = OPN->getParent();
553 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
555 // Map operands for blocks that are live and remove operands for blocks
557 for (; phino != PHIToResolve.size() &&
558 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
559 OPN = PHIToResolve[phino];
560 PHINode *PN = cast<PHINode>(VMap[OPN]);
561 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
562 Value *V = VMap[PN->getIncomingBlock(pred)];
563 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
564 Value *InVal = MapValue(PN->getIncomingValue(pred),
566 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
567 assert(InVal && "Unknown input value?");
568 PN->setIncomingValue(pred, InVal);
569 PN->setIncomingBlock(pred, MappedBlock);
571 PN->removeIncomingValue(pred, false);
572 --pred, --e; // Revisit the next entry.
577 // The loop above has removed PHI entries for those blocks that are dead
578 // and has updated others. However, if a block is live (i.e. copied over)
579 // but its terminator has been changed to not go to this block, then our
580 // phi nodes will have invalid entries. Update the PHI nodes in this
582 PHINode *PN = cast<PHINode>(NewBB->begin());
583 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
584 if (NumPreds != PN->getNumIncomingValues()) {
585 assert(NumPreds < PN->getNumIncomingValues());
586 // Count how many times each predecessor comes to this block.
587 std::map<BasicBlock*, unsigned> PredCount;
588 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
592 // Figure out how many entries to remove from each PHI.
593 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
594 ++PredCount[PN->getIncomingBlock(i)];
596 // At this point, the excess predecessor entries are positive in the
597 // map. Loop over all of the PHIs and remove excess predecessor
599 BasicBlock::iterator I = NewBB->begin();
600 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
601 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
602 E = PredCount.end(); PCI != E; ++PCI) {
603 BasicBlock *Pred = PCI->first;
604 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
605 PN->removeIncomingValue(Pred, false);
610 // If the loops above have made these phi nodes have 0 or 1 operand,
611 // replace them with undef or the input value. We must do this for
612 // correctness, because 0-operand phis are not valid.
613 PN = cast<PHINode>(NewBB->begin());
614 if (PN->getNumIncomingValues() == 0) {
615 BasicBlock::iterator I = NewBB->begin();
616 BasicBlock::const_iterator OldI = OldBB->begin();
617 while ((PN = dyn_cast<PHINode>(I++))) {
618 Value *NV = UndefValue::get(PN->getType());
619 PN->replaceAllUsesWith(NV);
620 assert(VMap[OldI] == PN && "VMap mismatch");
622 PN->eraseFromParent();
628 // Make a second pass over the PHINodes now that all of them have been
629 // remapped into the new function, simplifying the PHINode and performing any
630 // recursive simplifications exposed. This will transparently update the
631 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
632 // two PHINodes, the iteration over the old PHIs remains valid, and the
633 // mapping will just map us to the new node (which may not even be a PHI
635 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
636 if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
637 recursivelySimplifyInstruction(PN);
639 // Now that the inlined function body has been fully constructed, go through
640 // and zap unconditional fall-through branches. This happens all the time when
641 // specializing code: code specialization turns conditional branches into
642 // uncond branches, and this code folds them.
643 Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB]);
644 Function::iterator I = Begin;
645 while (I != NewFunc->end()) {
646 // Check if this block has become dead during inlining or other
647 // simplifications. Note that the first block will appear dead, as it has
648 // not yet been wired up properly.
649 if (I != Begin && (pred_begin(I) == pred_end(I) ||
650 I->getSinglePredecessor() == I)) {
651 BasicBlock *DeadBB = I++;
652 DeleteDeadBlock(DeadBB);
656 // We need to simplify conditional branches and switches with a constant
657 // operand. We try to prune these out when cloning, but if the
658 // simplification required looking through PHI nodes, those are only
659 // available after forming the full basic block. That may leave some here,
660 // and we still want to prune the dead code as early as possible.
661 ConstantFoldTerminator(I);
663 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
664 if (!BI || BI->isConditional()) { ++I; continue; }
666 BasicBlock *Dest = BI->getSuccessor(0);
667 if (!Dest->getSinglePredecessor()) {
671 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
672 // above should have zapped all of them..
673 assert(!isa<PHINode>(Dest->begin()));
675 // We know all single-entry PHI nodes in the inlined function have been
676 // removed, so we just need to splice the blocks.
677 BI->eraseFromParent();
679 // Make all PHI nodes that referred to Dest now refer to I as their source.
680 Dest->replaceAllUsesWith(I);
682 // Move all the instructions in the succ to the pred.
683 I->getInstList().splice(I->end(), Dest->getInstList());
685 // Remove the dest block.
686 Dest->eraseFromParent();
688 // Do not increment I, iteratively merge all things this block branches to.
691 // Make a final pass over the basic blocks from the old function to gather
692 // any return instructions which survived folding. We have to do this here
693 // because we can iteratively remove and merge returns above.
694 for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB]),
697 if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
698 Returns.push_back(RI);
702 /// This works exactly like CloneFunctionInto,
703 /// except that it does some simple constant prop and DCE on the fly. The
704 /// effect of this is to copy significantly less code in cases where (for
705 /// example) a function call with constant arguments is inlined, and those
706 /// constant arguments cause a significant amount of code in the callee to be
707 /// dead. Since this doesn't produce an exact copy of the input, it can't be
708 /// used for things like CloneFunction or CloneModule.
709 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
710 ValueToValueMapTy &VMap,
711 bool ModuleLevelChanges,
712 SmallVectorImpl<ReturnInst*> &Returns,
713 const char *NameSuffix,
714 ClonedCodeInfo *CodeInfo,
715 Instruction *TheCall) {
716 CloneAndPruneIntoFromInst(NewFunc, OldFunc, OldFunc->front().begin(), VMap,
717 ModuleLevelChanges, Returns, NameSuffix, CodeInfo,