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/Analysis/LoopInfo.h"
21 #include "llvm/IR/CFG.h"
22 #include "llvm/IR/Constants.h"
23 #include "llvm/IR/DebugInfo.h"
24 #include "llvm/IR/DerivedTypes.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/IR/GlobalVariable.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/IR/IntrinsicInst.h"
29 #include "llvm/IR/LLVMContext.h"
30 #include "llvm/IR/Metadata.h"
31 #include "llvm/IR/Module.h"
32 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
33 #include "llvm/Transforms/Utils/Local.h"
34 #include "llvm/Transforms/Utils/ValueMapper.h"
38 /// See comments in Cloning.h.
39 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
40 ValueToValueMapTy &VMap,
41 const Twine &NameSuffix, Function *F,
42 ClonedCodeInfo *CodeInfo) {
43 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
44 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
46 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
48 // Loop over all instructions, and copy them over.
49 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
51 Instruction *NewInst = II->clone();
53 NewInst->setName(II->getName()+NameSuffix);
54 NewBB->getInstList().push_back(NewInst);
55 VMap[II] = NewInst; // Add instruction map to value.
57 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
58 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
59 if (isa<ConstantInt>(AI->getArraySize()))
60 hasStaticAllocas = true;
62 hasDynamicAllocas = true;
67 CodeInfo->ContainsCalls |= hasCalls;
68 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
69 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
70 BB != &BB->getParent()->getEntryBlock();
75 // Clone OldFunc into NewFunc, transforming the old arguments into references to
78 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
79 ValueToValueMapTy &VMap,
80 bool ModuleLevelChanges,
81 SmallVectorImpl<ReturnInst*> &Returns,
82 const char *NameSuffix, ClonedCodeInfo *CodeInfo,
83 ValueMapTypeRemapper *TypeMapper,
84 ValueMaterializer *Materializer) {
85 assert(NameSuffix && "NameSuffix cannot be null!");
88 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
89 E = OldFunc->arg_end(); I != E; ++I)
90 assert(VMap.count(I) && "No mapping from source argument specified!");
93 // Copy all attributes other than those stored in the AttributeSet. We need
94 // to remap the parameter indices of the AttributeSet.
95 AttributeSet NewAttrs = NewFunc->getAttributes();
96 NewFunc->copyAttributesFrom(OldFunc);
97 NewFunc->setAttributes(NewAttrs);
99 AttributeSet OldAttrs = OldFunc->getAttributes();
100 // Clone any argument attributes that are present in the VMap.
101 for (const Argument &OldArg : OldFunc->args())
102 if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
104 OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
105 if (attrs.getNumSlots() > 0)
106 NewArg->addAttr(attrs);
109 NewFunc->setAttributes(
110 NewFunc->getAttributes()
111 .addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
112 OldAttrs.getRetAttributes())
113 .addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
114 OldAttrs.getFnAttributes()));
116 // Loop over all of the basic blocks in the function, cloning them as
117 // appropriate. Note that we save BE this way in order to handle cloning of
118 // recursive functions into themselves.
120 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
122 const BasicBlock &BB = *BI;
124 // Create a new basic block and copy instructions into it!
125 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
127 // Add basic block mapping.
130 // It is only legal to clone a function if a block address within that
131 // function is never referenced outside of the function. Given that, we
132 // want to map block addresses from the old function to block addresses in
133 // the clone. (This is different from the generic ValueMapper
134 // implementation, which generates an invalid blockaddress when
135 // cloning a function.)
136 if (BB.hasAddressTaken()) {
137 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
138 const_cast<BasicBlock*>(&BB));
139 VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
142 // Note return instructions for the caller.
143 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
144 Returns.push_back(RI);
147 // Loop over all of the instructions in the function, fixing up operand
148 // references as we go. This uses VMap to do all the hard work.
149 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
150 BE = NewFunc->end(); BB != BE; ++BB)
151 // Loop over all instructions, fixing each one as we find it...
152 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
153 RemapInstruction(II, VMap,
154 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
155 TypeMapper, Materializer);
158 // Find the MDNode which corresponds to the subprogram data that described F.
159 static DISubprogram *FindSubprogram(const Function *F,
160 DebugInfoFinder &Finder) {
161 for (DISubprogram *Subprogram : Finder.subprograms()) {
162 if (Subprogram->describes(F))
168 // Add an operand to an existing MDNode. The new operand will be added at the
169 // back of the operand list.
170 static void AddOperand(DICompileUnit *CU, DISubprogramArray SPs,
172 SmallVector<Metadata *, 16> NewSPs;
173 NewSPs.reserve(SPs.size() + 1);
175 NewSPs.push_back(SP);
176 NewSPs.push_back(NewSP);
177 CU->replaceSubprograms(MDTuple::get(CU->getContext(), NewSPs));
180 // Clone the module-level debug info associated with OldFunc. The cloned data
181 // will point to NewFunc instead.
182 static void CloneDebugInfoMetadata(Function *NewFunc, const Function *OldFunc,
183 ValueToValueMapTy &VMap) {
184 DebugInfoFinder Finder;
185 Finder.processModule(*OldFunc->getParent());
187 const DISubprogram *OldSubprogramMDNode = FindSubprogram(OldFunc, Finder);
188 if (!OldSubprogramMDNode) return;
190 // Ensure that OldFunc appears in the map.
191 // (if it's already there it must point to NewFunc anyway)
192 VMap[OldFunc] = NewFunc;
193 auto *NewSubprogram =
194 cast<DISubprogram>(MapMetadata(OldSubprogramMDNode, VMap));
196 for (auto *CU : Finder.compile_units()) {
197 auto Subprograms = CU->getSubprograms();
198 // If the compile unit's function list contains the old function, it should
199 // also contain the new one.
200 for (auto *SP : Subprograms) {
201 if (SP == OldSubprogramMDNode) {
202 AddOperand(CU, Subprograms, NewSubprogram);
209 /// Return a copy of the specified function, but without
210 /// embedding the function into another module. Also, any references specified
211 /// in the VMap are changed to refer to their mapped value instead of the
212 /// original one. If any of the arguments to the function are in the VMap,
213 /// the arguments are deleted from the resultant function. The VMap is
214 /// updated to include mappings from all of the instructions and basicblocks in
215 /// the function from their old to new values.
217 Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
218 bool ModuleLevelChanges,
219 ClonedCodeInfo *CodeInfo) {
220 std::vector<Type*> ArgTypes;
222 // The user might be deleting arguments to the function by specifying them in
223 // the VMap. If so, we need to not add the arguments to the arg ty vector
225 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
227 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
228 ArgTypes.push_back(I->getType());
230 // Create a new function type...
231 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
232 ArgTypes, F->getFunctionType()->isVarArg());
234 // Create the new function...
235 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
237 // Loop over the arguments, copying the names of the mapped arguments over...
238 Function::arg_iterator DestI = NewF->arg_begin();
239 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
241 if (VMap.count(I) == 0) { // Is this argument preserved?
242 DestI->setName(I->getName()); // Copy the name over...
243 VMap[I] = DestI++; // Add mapping to VMap
246 if (ModuleLevelChanges)
247 CloneDebugInfoMetadata(NewF, F, VMap);
249 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
250 CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
257 /// This is a private class used to implement CloneAndPruneFunctionInto.
258 struct PruningFunctionCloner {
260 const Function *OldFunc;
261 ValueToValueMapTy &VMap;
262 bool ModuleLevelChanges;
263 const char *NameSuffix;
264 ClonedCodeInfo *CodeInfo;
265 CloningDirector *Director;
266 ValueMapTypeRemapper *TypeMapper;
267 ValueMaterializer *Materializer;
270 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
271 ValueToValueMapTy &valueMap, bool moduleLevelChanges,
272 const char *nameSuffix, ClonedCodeInfo *codeInfo,
273 CloningDirector *Director)
274 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
275 ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
276 CodeInfo(codeInfo), Director(Director) {
277 // These are optional components. The Director may return null.
279 TypeMapper = Director->getTypeRemapper();
280 Materializer = Director->getValueMaterializer();
282 TypeMapper = nullptr;
283 Materializer = nullptr;
287 /// The specified block is found to be reachable, clone it and
288 /// anything that it can reach.
289 void CloneBlock(const BasicBlock *BB,
290 BasicBlock::const_iterator StartingInst,
291 std::vector<const BasicBlock*> &ToClone);
295 /// The specified block is found to be reachable, clone it and
296 /// anything that it can reach.
297 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
298 BasicBlock::const_iterator StartingInst,
299 std::vector<const BasicBlock*> &ToClone){
300 WeakVH &BBEntry = VMap[BB];
302 // Have we already cloned this block?
305 // Nope, clone it now.
307 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
308 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
310 // It is only legal to clone a function if a block address within that
311 // function is never referenced outside of the function. Given that, we
312 // want to map block addresses from the old function to block addresses in
313 // the clone. (This is different from the generic ValueMapper
314 // implementation, which generates an invalid blockaddress when
315 // cloning a function.)
317 // Note that we don't need to fix the mapping for unreachable blocks;
318 // the default mapping there is safe.
319 if (BB->hasAddressTaken()) {
320 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
321 const_cast<BasicBlock*>(BB));
322 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
325 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
327 // Loop over all instructions, and copy them over, DCE'ing as we go. This
328 // loop doesn't include the terminator.
329 for (BasicBlock::const_iterator II = StartingInst, IE = --BB->end();
331 // If the "Director" remaps the instruction, don't clone it.
333 CloningDirector::CloningAction Action
334 = Director->handleInstruction(VMap, II, NewBB);
335 // If the cloning director says stop, we want to stop everything, not
336 // just break out of the loop (which would cause the terminator to be
337 // cloned). The cloning director is responsible for inserting a proper
338 // terminator into the new basic block in this case.
339 if (Action == CloningDirector::StopCloningBB)
341 // If the cloning director says skip, continue to the next instruction.
342 // In this case, the cloning director is responsible for mapping the
343 // skipped instruction to some value that is defined in the new
345 if (Action == CloningDirector::SkipInstruction)
349 Instruction *NewInst = II->clone();
351 // Eagerly remap operands to the newly cloned instruction, except for PHI
352 // nodes for which we defer processing until we update the CFG.
353 if (!isa<PHINode>(NewInst)) {
354 RemapInstruction(NewInst, VMap,
355 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
356 TypeMapper, Materializer);
358 // If we can simplify this instruction to some other value, simply add
359 // a mapping to that value rather than inserting a new instruction into
362 SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
363 // On the off-chance that this simplifies to an instruction in the old
364 // function, map it back into the new function.
365 if (Value *MappedV = VMap.lookup(V))
375 NewInst->setName(II->getName()+NameSuffix);
376 VMap[II] = NewInst; // Add instruction map to value.
377 NewBB->getInstList().push_back(NewInst);
378 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
379 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
380 if (isa<ConstantInt>(AI->getArraySize()))
381 hasStaticAllocas = true;
383 hasDynamicAllocas = true;
387 // Finally, clone over the terminator.
388 const TerminatorInst *OldTI = BB->getTerminator();
389 bool TerminatorDone = false;
391 CloningDirector::CloningAction Action
392 = Director->handleInstruction(VMap, OldTI, NewBB);
393 // If the cloning director says stop, we want to stop everything, not
394 // just break out of the loop (which would cause the terminator to be
395 // cloned). The cloning director is responsible for inserting a proper
396 // terminator into the new basic block in this case.
397 if (Action == CloningDirector::StopCloningBB)
399 if (Action == CloningDirector::CloneSuccessors) {
400 // If the director says to skip with a terminate instruction, we still
401 // need to clone this block's successors.
402 const TerminatorInst *TI = NewBB->getTerminator();
403 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
404 ToClone.push_back(TI->getSuccessor(i));
407 assert(Action != CloningDirector::SkipInstruction &&
408 "SkipInstruction is not valid for terminators.");
410 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
411 if (BI->isConditional()) {
412 // If the condition was a known constant in the callee...
413 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
414 // Or is a known constant in the caller...
416 Value *V = VMap[BI->getCondition()];
417 Cond = dyn_cast_or_null<ConstantInt>(V);
420 // Constant fold to uncond branch!
422 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
423 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
424 ToClone.push_back(Dest);
425 TerminatorDone = true;
428 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
429 // If switching on a value known constant in the caller.
430 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
431 if (!Cond) { // Or known constant after constant prop in the callee...
432 Value *V = VMap[SI->getCondition()];
433 Cond = dyn_cast_or_null<ConstantInt>(V);
435 if (Cond) { // Constant fold to uncond branch!
436 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
437 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
438 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
439 ToClone.push_back(Dest);
440 TerminatorDone = true;
444 if (!TerminatorDone) {
445 Instruction *NewInst = OldTI->clone();
446 if (OldTI->hasName())
447 NewInst->setName(OldTI->getName()+NameSuffix);
448 NewBB->getInstList().push_back(NewInst);
449 VMap[OldTI] = NewInst; // Add instruction map to value.
451 // Recursively clone any reachable successor blocks.
452 const TerminatorInst *TI = BB->getTerminator();
453 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
454 ToClone.push_back(TI->getSuccessor(i));
458 CodeInfo->ContainsCalls |= hasCalls;
459 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
460 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
461 BB != &BB->getParent()->front();
465 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
466 /// entire function. Instead it starts at an instruction provided by the caller
467 /// and copies (and prunes) only the code reachable from that instruction.
468 void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
469 const Instruction *StartingInst,
470 ValueToValueMapTy &VMap,
471 bool ModuleLevelChanges,
472 SmallVectorImpl<ReturnInst *> &Returns,
473 const char *NameSuffix,
474 ClonedCodeInfo *CodeInfo,
475 CloningDirector *Director) {
476 assert(NameSuffix && "NameSuffix cannot be null!");
478 ValueMapTypeRemapper *TypeMapper = nullptr;
479 ValueMaterializer *Materializer = nullptr;
482 TypeMapper = Director->getTypeRemapper();
483 Materializer = Director->getValueMaterializer();
487 // If the cloning starts at the begining of the function, verify that
488 // the function arguments are mapped.
490 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
491 E = OldFunc->arg_end(); II != E; ++II)
492 assert(VMap.count(II) && "No mapping from source argument specified!");
495 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
496 NameSuffix, CodeInfo, Director);
497 const BasicBlock *StartingBB;
499 StartingBB = StartingInst->getParent();
501 StartingBB = &OldFunc->getEntryBlock();
502 StartingInst = StartingBB->begin();
505 // Clone the entry block, and anything recursively reachable from it.
506 std::vector<const BasicBlock*> CloneWorklist;
507 PFC.CloneBlock(StartingBB, StartingInst, CloneWorklist);
508 while (!CloneWorklist.empty()) {
509 const BasicBlock *BB = CloneWorklist.back();
510 CloneWorklist.pop_back();
511 PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
514 // Loop over all of the basic blocks in the old function. If the block was
515 // reachable, we have cloned it and the old block is now in the value map:
516 // insert it into the new function in the right order. If not, ignore it.
518 // Defer PHI resolution until rest of function is resolved.
519 SmallVector<const PHINode*, 16> PHIToResolve;
520 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
523 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
524 if (!NewBB) continue; // Dead block.
526 // Add the new block to the new function.
527 NewFunc->getBasicBlockList().push_back(NewBB);
529 // Handle PHI nodes specially, as we have to remove references to dead
531 for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I) {
532 // PHI nodes may have been remapped to non-PHI nodes by the caller or
533 // during the cloning process.
534 if (const PHINode *PN = dyn_cast<PHINode>(I)) {
535 if (isa<PHINode>(VMap[PN]))
536 PHIToResolve.push_back(PN);
544 // Finally, remap the terminator instructions, as those can't be remapped
545 // until all BBs are mapped.
546 RemapInstruction(NewBB->getTerminator(), VMap,
547 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
548 TypeMapper, Materializer);
551 // Defer PHI resolution until rest of function is resolved, PHI resolution
552 // requires the CFG to be up-to-date.
553 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
554 const PHINode *OPN = PHIToResolve[phino];
555 unsigned NumPreds = OPN->getNumIncomingValues();
556 const BasicBlock *OldBB = OPN->getParent();
557 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
559 // Map operands for blocks that are live and remove operands for blocks
561 for (; phino != PHIToResolve.size() &&
562 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
563 OPN = PHIToResolve[phino];
564 PHINode *PN = cast<PHINode>(VMap[OPN]);
565 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
566 Value *V = VMap[PN->getIncomingBlock(pred)];
567 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
568 Value *InVal = MapValue(PN->getIncomingValue(pred),
570 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
571 assert(InVal && "Unknown input value?");
572 PN->setIncomingValue(pred, InVal);
573 PN->setIncomingBlock(pred, MappedBlock);
575 PN->removeIncomingValue(pred, false);
576 --pred, --e; // Revisit the next entry.
581 // The loop above has removed PHI entries for those blocks that are dead
582 // and has updated others. However, if a block is live (i.e. copied over)
583 // but its terminator has been changed to not go to this block, then our
584 // phi nodes will have invalid entries. Update the PHI nodes in this
586 PHINode *PN = cast<PHINode>(NewBB->begin());
587 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
588 if (NumPreds != PN->getNumIncomingValues()) {
589 assert(NumPreds < PN->getNumIncomingValues());
590 // Count how many times each predecessor comes to this block.
591 std::map<BasicBlock*, unsigned> PredCount;
592 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
596 // Figure out how many entries to remove from each PHI.
597 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
598 ++PredCount[PN->getIncomingBlock(i)];
600 // At this point, the excess predecessor entries are positive in the
601 // map. Loop over all of the PHIs and remove excess predecessor
603 BasicBlock::iterator I = NewBB->begin();
604 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
605 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
606 E = PredCount.end(); PCI != E; ++PCI) {
607 BasicBlock *Pred = PCI->first;
608 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
609 PN->removeIncomingValue(Pred, false);
614 // If the loops above have made these phi nodes have 0 or 1 operand,
615 // replace them with undef or the input value. We must do this for
616 // correctness, because 0-operand phis are not valid.
617 PN = cast<PHINode>(NewBB->begin());
618 if (PN->getNumIncomingValues() == 0) {
619 BasicBlock::iterator I = NewBB->begin();
620 BasicBlock::const_iterator OldI = OldBB->begin();
621 while ((PN = dyn_cast<PHINode>(I++))) {
622 Value *NV = UndefValue::get(PN->getType());
623 PN->replaceAllUsesWith(NV);
624 assert(VMap[OldI] == PN && "VMap mismatch");
626 PN->eraseFromParent();
632 // Make a second pass over the PHINodes now that all of them have been
633 // remapped into the new function, simplifying the PHINode and performing any
634 // recursive simplifications exposed. This will transparently update the
635 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
636 // two PHINodes, the iteration over the old PHIs remains valid, and the
637 // mapping will just map us to the new node (which may not even be a PHI
639 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
640 if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
641 recursivelySimplifyInstruction(PN);
643 // Now that the inlined function body has been fully constructed, go through
644 // and zap unconditional fall-through branches. This happens all the time when
645 // specializing code: code specialization turns conditional branches into
646 // uncond branches, and this code folds them.
647 Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB]);
648 Function::iterator I = Begin;
649 while (I != NewFunc->end()) {
650 // Check if this block has become dead during inlining or other
651 // simplifications. Note that the first block will appear dead, as it has
652 // not yet been wired up properly.
653 if (I != Begin && (pred_begin(I) == pred_end(I) ||
654 I->getSinglePredecessor() == I)) {
655 BasicBlock *DeadBB = I++;
656 DeleteDeadBlock(DeadBB);
660 // We need to simplify conditional branches and switches with a constant
661 // operand. We try to prune these out when cloning, but if the
662 // simplification required looking through PHI nodes, those are only
663 // available after forming the full basic block. That may leave some here,
664 // and we still want to prune the dead code as early as possible.
665 ConstantFoldTerminator(I);
667 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
668 if (!BI || BI->isConditional()) { ++I; continue; }
670 BasicBlock *Dest = BI->getSuccessor(0);
671 if (!Dest->getSinglePredecessor()) {
675 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
676 // above should have zapped all of them..
677 assert(!isa<PHINode>(Dest->begin()));
679 // We know all single-entry PHI nodes in the inlined function have been
680 // removed, so we just need to splice the blocks.
681 BI->eraseFromParent();
683 // Make all PHI nodes that referred to Dest now refer to I as their source.
684 Dest->replaceAllUsesWith(I);
686 // Move all the instructions in the succ to the pred.
687 I->getInstList().splice(I->end(), Dest->getInstList());
689 // Remove the dest block.
690 Dest->eraseFromParent();
692 // Do not increment I, iteratively merge all things this block branches to.
695 // Make a final pass over the basic blocks from the old function to gather
696 // any return instructions which survived folding. We have to do this here
697 // because we can iteratively remove and merge returns above.
698 for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB]),
701 if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
702 Returns.push_back(RI);
706 /// This works exactly like CloneFunctionInto,
707 /// except that it does some simple constant prop and DCE on the fly. The
708 /// effect of this is to copy significantly less code in cases where (for
709 /// example) a function call with constant arguments is inlined, and those
710 /// constant arguments cause a significant amount of code in the callee to be
711 /// dead. Since this doesn't produce an exact copy of the input, it can't be
712 /// used for things like CloneFunction or CloneModule.
713 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
714 ValueToValueMapTy &VMap,
715 bool ModuleLevelChanges,
716 SmallVectorImpl<ReturnInst*> &Returns,
717 const char *NameSuffix,
718 ClonedCodeInfo *CodeInfo,
719 Instruction *TheCall) {
720 CloneAndPruneIntoFromInst(NewFunc, OldFunc, OldFunc->front().begin(), VMap,
721 ModuleLevelChanges, Returns, NameSuffix, CodeInfo,
725 /// \brief Remaps instructions in \p Blocks using the mapping in \p VMap.
726 void llvm::remapInstructionsInBlocks(
727 const SmallVectorImpl<BasicBlock *> &Blocks, ValueToValueMapTy &VMap) {
728 // Rewrite the code to refer to itself.
729 for (auto *BB : Blocks)
730 for (auto &Inst : *BB)
731 RemapInstruction(&Inst, VMap,
732 RF_NoModuleLevelChanges | RF_IgnoreMissingEntries);
735 /// \brief Clones a loop \p OrigLoop. Returns the loop and the blocks in \p
738 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
739 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before.
740 Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
741 Loop *OrigLoop, ValueToValueMapTy &VMap,
742 const Twine &NameSuffix, LoopInfo *LI,
744 SmallVectorImpl<BasicBlock *> &Blocks) {
745 Function *F = OrigLoop->getHeader()->getParent();
746 Loop *ParentLoop = OrigLoop->getParentLoop();
748 Loop *NewLoop = new Loop();
750 ParentLoop->addChildLoop(NewLoop);
752 LI->addTopLevelLoop(NewLoop);
754 BasicBlock *OrigPH = OrigLoop->getLoopPreheader();
755 assert(OrigPH && "No preheader");
756 BasicBlock *NewPH = CloneBasicBlock(OrigPH, VMap, NameSuffix, F);
757 // To rename the loop PHIs.
758 VMap[OrigPH] = NewPH;
759 Blocks.push_back(NewPH);
763 ParentLoop->addBasicBlockToLoop(NewPH, *LI);
765 // Update DominatorTree.
766 DT->addNewBlock(NewPH, LoopDomBB);
768 for (BasicBlock *BB : OrigLoop->getBlocks()) {
769 BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
773 NewLoop->addBasicBlockToLoop(NewBB, *LI);
775 // Update DominatorTree.
776 BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
777 DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
779 Blocks.push_back(NewBB);
782 // Move them physically from the end of the block list.
783 F->getBasicBlockList().splice(Before, F->getBasicBlockList(), NewPH);
784 F->getBasicBlockList().splice(Before, F->getBasicBlockList(),
785 NewLoop->getHeader(), F->end());