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/SetVector.h"
18 #include "llvm/ADT/SmallVector.h"
19 #include "llvm/Analysis/ConstantFolding.h"
20 #include "llvm/Analysis/InstructionSimplify.h"
21 #include "llvm/Analysis/LoopInfo.h"
22 #include "llvm/IR/CFG.h"
23 #include "llvm/IR/Constants.h"
24 #include "llvm/IR/DebugInfo.h"
25 #include "llvm/IR/DerivedTypes.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/GlobalVariable.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/IntrinsicInst.h"
30 #include "llvm/IR/LLVMContext.h"
31 #include "llvm/IR/Metadata.h"
32 #include "llvm/IR/Module.h"
33 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
34 #include "llvm/Transforms/Utils/Local.h"
35 #include "llvm/Transforms/Utils/ValueMapper.h"
39 /// See comments in Cloning.h.
40 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
41 ValueToValueMapTy &VMap,
42 const Twine &NameSuffix, Function *F,
43 ClonedCodeInfo *CodeInfo) {
44 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
45 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
47 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
49 // Loop over all instructions, and copy them over.
50 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
52 Instruction *NewInst = II->clone();
54 NewInst->setName(II->getName()+NameSuffix);
55 NewBB->getInstList().push_back(NewInst);
56 VMap[&*II] = NewInst; // Add instruction map to value.
58 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
59 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
60 if (isa<ConstantInt>(AI->getArraySize()))
61 hasStaticAllocas = true;
63 hasDynamicAllocas = true;
68 CodeInfo->ContainsCalls |= hasCalls;
69 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
70 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
71 BB != &BB->getParent()->getEntryBlock();
76 // Clone OldFunc into NewFunc, transforming the old arguments into references to
79 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
80 ValueToValueMapTy &VMap,
81 bool ModuleLevelChanges,
82 SmallVectorImpl<ReturnInst*> &Returns,
83 const char *NameSuffix, ClonedCodeInfo *CodeInfo,
84 ValueMapTypeRemapper *TypeMapper,
85 ValueMaterializer *Materializer) {
86 assert(NameSuffix && "NameSuffix cannot be null!");
89 for (const Argument &I : OldFunc->args())
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 // Fix up the personality function that got copied over.
100 if (OldFunc->hasPersonalityFn())
101 NewFunc->setPersonalityFn(
102 MapValue(OldFunc->getPersonalityFn(), VMap,
103 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
104 TypeMapper, Materializer));
106 AttributeSet OldAttrs = OldFunc->getAttributes();
107 // Clone any argument attributes that are present in the VMap.
108 for (const Argument &OldArg : OldFunc->args())
109 if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
111 OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
112 if (attrs.getNumSlots() > 0)
113 NewArg->addAttr(attrs);
116 NewFunc->setAttributes(
117 NewFunc->getAttributes()
118 .addAttributes(NewFunc->getContext(), AttributeSet::ReturnIndex,
119 OldAttrs.getRetAttributes())
120 .addAttributes(NewFunc->getContext(), AttributeSet::FunctionIndex,
121 OldAttrs.getFnAttributes()));
123 SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
124 OldFunc->getAllMetadata(MDs);
126 NewFunc->addMetadata(
128 *MapMetadata(MD.second, VMap,
129 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
130 TypeMapper, Materializer));
132 // Loop over all of the basic blocks in the function, cloning them as
133 // appropriate. Note that we save BE this way in order to handle cloning of
134 // recursive functions into themselves.
136 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
138 const BasicBlock &BB = *BI;
140 // Create a new basic block and copy instructions into it!
141 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
143 // Add basic block mapping.
146 // It is only legal to clone a function if a block address within that
147 // function is never referenced outside of the function. Given that, we
148 // want to map block addresses from the old function to block addresses in
149 // the clone. (This is different from the generic ValueMapper
150 // implementation, which generates an invalid blockaddress when
151 // cloning a function.)
152 if (BB.hasAddressTaken()) {
153 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
154 const_cast<BasicBlock*>(&BB));
155 VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
158 // Note return instructions for the caller.
159 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
160 Returns.push_back(RI);
163 // Loop over all of the instructions in the function, fixing up operand
164 // references as we go. This uses VMap to do all the hard work.
165 for (Function::iterator BB =
166 cast<BasicBlock>(VMap[&OldFunc->front()])->getIterator(),
169 // Loop over all instructions, fixing each one as we find it...
170 for (Instruction &II : *BB)
171 RemapInstruction(&II, VMap,
172 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
173 TypeMapper, Materializer);
176 /// Return a copy of the specified function and add it to that function's
177 /// module. Also, any references specified in the VMap are changed to refer to
178 /// their mapped value instead of the original one. If any of the arguments to
179 /// the function are in the VMap, the arguments are deleted from the resultant
180 /// function. The VMap is updated to include mappings from all of the
181 /// instructions and basicblocks in the function from their old to new values.
183 Function *llvm::CloneFunction(Function *F, ValueToValueMapTy &VMap,
184 ClonedCodeInfo *CodeInfo) {
185 std::vector<Type*> ArgTypes;
187 // The user might be deleting arguments to the function by specifying them in
188 // the VMap. If so, we need to not add the arguments to the arg ty vector
190 for (const Argument &I : F->args())
191 if (VMap.count(&I) == 0) // Haven't mapped the argument to anything yet?
192 ArgTypes.push_back(I.getType());
194 // Create a new function type...
195 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
196 ArgTypes, F->getFunctionType()->isVarArg());
198 // Create the new function...
200 Function::Create(FTy, F->getLinkage(), F->getName(), F->getParent());
202 // Loop over the arguments, copying the names of the mapped arguments over...
203 Function::arg_iterator DestI = NewF->arg_begin();
204 for (const Argument & I : F->args())
205 if (VMap.count(&I) == 0) { // Is this argument preserved?
206 DestI->setName(I.getName()); // Copy the name over...
207 VMap[&I] = &*DestI++; // Add mapping to VMap
210 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
211 CloneFunctionInto(NewF, F, VMap, /*ModuleLevelChanges=*/false, Returns, "",
220 /// This is a private class used to implement CloneAndPruneFunctionInto.
221 struct PruningFunctionCloner {
223 const Function *OldFunc;
224 ValueToValueMapTy &VMap;
225 bool ModuleLevelChanges;
226 const char *NameSuffix;
227 ClonedCodeInfo *CodeInfo;
230 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
231 ValueToValueMapTy &valueMap, bool moduleLevelChanges,
232 const char *nameSuffix, ClonedCodeInfo *codeInfo)
233 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap),
234 ModuleLevelChanges(moduleLevelChanges), NameSuffix(nameSuffix),
235 CodeInfo(codeInfo) {}
237 /// The specified block is found to be reachable, clone it and
238 /// anything that it can reach.
239 void CloneBlock(const BasicBlock *BB,
240 BasicBlock::const_iterator StartingInst,
241 std::vector<const BasicBlock*> &ToClone);
245 /// The specified block is found to be reachable, clone it and
246 /// anything that it can reach.
247 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
248 BasicBlock::const_iterator StartingInst,
249 std::vector<const BasicBlock*> &ToClone){
250 WeakVH &BBEntry = VMap[BB];
252 // Have we already cloned this block?
255 // Nope, clone it now.
257 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
258 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
260 // It is only legal to clone a function if a block address within that
261 // function is never referenced outside of the function. Given that, we
262 // want to map block addresses from the old function to block addresses in
263 // the clone. (This is different from the generic ValueMapper
264 // implementation, which generates an invalid blockaddress when
265 // cloning a function.)
267 // Note that we don't need to fix the mapping for unreachable blocks;
268 // the default mapping there is safe.
269 if (BB->hasAddressTaken()) {
270 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
271 const_cast<BasicBlock*>(BB));
272 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
275 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
277 // Loop over all instructions, and copy them over, DCE'ing as we go. This
278 // loop doesn't include the terminator.
279 for (BasicBlock::const_iterator II = StartingInst, IE = --BB->end();
282 Instruction *NewInst = II->clone();
284 // Eagerly remap operands to the newly cloned instruction, except for PHI
285 // nodes for which we defer processing until we update the CFG.
286 if (!isa<PHINode>(NewInst)) {
287 RemapInstruction(NewInst, VMap,
288 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
290 // If we can simplify this instruction to some other value, simply add
291 // a mapping to that value rather than inserting a new instruction into
294 SimplifyInstruction(NewInst, BB->getModule()->getDataLayout())) {
295 // On the off-chance that this simplifies to an instruction in the old
296 // function, map it back into the new function.
297 if (Value *MappedV = VMap.lookup(V))
300 if (!NewInst->mayHaveSideEffects()) {
309 NewInst->setName(II->getName()+NameSuffix);
310 VMap[&*II] = NewInst; // Add instruction map to value.
311 NewBB->getInstList().push_back(NewInst);
312 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
315 if (auto CS = ImmutableCallSite(&*II))
316 if (CS.hasOperandBundles())
317 CodeInfo->OperandBundleCallSites.push_back(NewInst);
319 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
320 if (isa<ConstantInt>(AI->getArraySize()))
321 hasStaticAllocas = true;
323 hasDynamicAllocas = true;
327 // Finally, clone over the terminator.
328 const TerminatorInst *OldTI = BB->getTerminator();
329 bool TerminatorDone = false;
330 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
331 if (BI->isConditional()) {
332 // If the condition was a known constant in the callee...
333 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
334 // Or is a known constant in the caller...
336 Value *V = VMap.lookup(BI->getCondition());
337 Cond = dyn_cast_or_null<ConstantInt>(V);
340 // Constant fold to uncond branch!
342 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
343 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
344 ToClone.push_back(Dest);
345 TerminatorDone = true;
348 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
349 // If switching on a value known constant in the caller.
350 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
351 if (!Cond) { // Or known constant after constant prop in the callee...
352 Value *V = VMap.lookup(SI->getCondition());
353 Cond = dyn_cast_or_null<ConstantInt>(V);
355 if (Cond) { // Constant fold to uncond branch!
356 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
357 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
358 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
359 ToClone.push_back(Dest);
360 TerminatorDone = true;
364 if (!TerminatorDone) {
365 Instruction *NewInst = OldTI->clone();
366 if (OldTI->hasName())
367 NewInst->setName(OldTI->getName()+NameSuffix);
368 NewBB->getInstList().push_back(NewInst);
369 VMap[OldTI] = NewInst; // Add instruction map to value.
372 if (auto CS = ImmutableCallSite(OldTI))
373 if (CS.hasOperandBundles())
374 CodeInfo->OperandBundleCallSites.push_back(NewInst);
376 // Recursively clone any reachable successor blocks.
377 const TerminatorInst *TI = BB->getTerminator();
378 for (const BasicBlock *Succ : TI->successors())
379 ToClone.push_back(Succ);
383 CodeInfo->ContainsCalls |= hasCalls;
384 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
385 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
386 BB != &BB->getParent()->front();
390 /// This works like CloneAndPruneFunctionInto, except that it does not clone the
391 /// entire function. Instead it starts at an instruction provided by the caller
392 /// and copies (and prunes) only the code reachable from that instruction.
393 void llvm::CloneAndPruneIntoFromInst(Function *NewFunc, const Function *OldFunc,
394 const Instruction *StartingInst,
395 ValueToValueMapTy &VMap,
396 bool ModuleLevelChanges,
397 SmallVectorImpl<ReturnInst *> &Returns,
398 const char *NameSuffix,
399 ClonedCodeInfo *CodeInfo) {
400 assert(NameSuffix && "NameSuffix cannot be null!");
402 ValueMapTypeRemapper *TypeMapper = nullptr;
403 ValueMaterializer *Materializer = nullptr;
406 // If the cloning starts at the beginning of the function, verify that
407 // the function arguments are mapped.
409 for (const Argument &II : OldFunc->args())
410 assert(VMap.count(&II) && "No mapping from source argument specified!");
413 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
414 NameSuffix, CodeInfo);
415 const BasicBlock *StartingBB;
417 StartingBB = StartingInst->getParent();
419 StartingBB = &OldFunc->getEntryBlock();
420 StartingInst = &StartingBB->front();
423 // Clone the entry block, and anything recursively reachable from it.
424 std::vector<const BasicBlock*> CloneWorklist;
425 PFC.CloneBlock(StartingBB, StartingInst->getIterator(), CloneWorklist);
426 while (!CloneWorklist.empty()) {
427 const BasicBlock *BB = CloneWorklist.back();
428 CloneWorklist.pop_back();
429 PFC.CloneBlock(BB, BB->begin(), CloneWorklist);
432 // Loop over all of the basic blocks in the old function. If the block was
433 // reachable, we have cloned it and the old block is now in the value map:
434 // insert it into the new function in the right order. If not, ignore it.
436 // Defer PHI resolution until rest of function is resolved.
437 SmallVector<const PHINode*, 16> PHIToResolve;
438 for (const BasicBlock &BI : *OldFunc) {
439 Value *V = VMap.lookup(&BI);
440 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
441 if (!NewBB) continue; // Dead block.
443 // Add the new block to the new function.
444 NewFunc->getBasicBlockList().push_back(NewBB);
446 // Handle PHI nodes specially, as we have to remove references to dead
448 for (BasicBlock::const_iterator I = BI.begin(), E = BI.end(); I != E; ++I) {
449 // PHI nodes may have been remapped to non-PHI nodes by the caller or
450 // during the cloning process.
451 if (const PHINode *PN = dyn_cast<PHINode>(I)) {
452 if (isa<PHINode>(VMap[PN]))
453 PHIToResolve.push_back(PN);
461 // Finally, remap the terminator instructions, as those can't be remapped
462 // until all BBs are mapped.
463 RemapInstruction(NewBB->getTerminator(), VMap,
464 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
465 TypeMapper, Materializer);
468 // Defer PHI resolution until rest of function is resolved, PHI resolution
469 // requires the CFG to be up-to-date.
470 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
471 const PHINode *OPN = PHIToResolve[phino];
472 unsigned NumPreds = OPN->getNumIncomingValues();
473 const BasicBlock *OldBB = OPN->getParent();
474 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
476 // Map operands for blocks that are live and remove operands for blocks
478 for (; phino != PHIToResolve.size() &&
479 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
480 OPN = PHIToResolve[phino];
481 PHINode *PN = cast<PHINode>(VMap[OPN]);
482 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
483 Value *V = VMap.lookup(PN->getIncomingBlock(pred));
484 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
485 Value *InVal = MapValue(PN->getIncomingValue(pred),
487 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
488 assert(InVal && "Unknown input value?");
489 PN->setIncomingValue(pred, InVal);
490 PN->setIncomingBlock(pred, MappedBlock);
492 PN->removeIncomingValue(pred, false);
493 --pred; // Revisit the next entry.
499 // The loop above has removed PHI entries for those blocks that are dead
500 // and has updated others. However, if a block is live (i.e. copied over)
501 // but its terminator has been changed to not go to this block, then our
502 // phi nodes will have invalid entries. Update the PHI nodes in this
504 PHINode *PN = cast<PHINode>(NewBB->begin());
505 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
506 if (NumPreds != PN->getNumIncomingValues()) {
507 assert(NumPreds < PN->getNumIncomingValues());
508 // Count how many times each predecessor comes to this block.
509 std::map<BasicBlock*, unsigned> PredCount;
510 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
514 // Figure out how many entries to remove from each PHI.
515 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
516 ++PredCount[PN->getIncomingBlock(i)];
518 // At this point, the excess predecessor entries are positive in the
519 // map. Loop over all of the PHIs and remove excess predecessor
521 BasicBlock::iterator I = NewBB->begin();
522 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
523 for (const auto &PCI : PredCount) {
524 BasicBlock *Pred = PCI.first;
525 for (unsigned NumToRemove = PCI.second; NumToRemove; --NumToRemove)
526 PN->removeIncomingValue(Pred, false);
531 // If the loops above have made these phi nodes have 0 or 1 operand,
532 // replace them with undef or the input value. We must do this for
533 // correctness, because 0-operand phis are not valid.
534 PN = cast<PHINode>(NewBB->begin());
535 if (PN->getNumIncomingValues() == 0) {
536 BasicBlock::iterator I = NewBB->begin();
537 BasicBlock::const_iterator OldI = OldBB->begin();
538 while ((PN = dyn_cast<PHINode>(I++))) {
539 Value *NV = UndefValue::get(PN->getType());
540 PN->replaceAllUsesWith(NV);
541 assert(VMap[&*OldI] == PN && "VMap mismatch");
543 PN->eraseFromParent();
549 // Make a second pass over the PHINodes now that all of them have been
550 // remapped into the new function, simplifying the PHINode and performing any
551 // recursive simplifications exposed. This will transparently update the
552 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
553 // two PHINodes, the iteration over the old PHIs remains valid, and the
554 // mapping will just map us to the new node (which may not even be a PHI
556 const DataLayout &DL = NewFunc->getParent()->getDataLayout();
557 SmallSetVector<const Value *, 8> Worklist;
558 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
559 if (isa<PHINode>(VMap[PHIToResolve[Idx]]))
560 Worklist.insert(PHIToResolve[Idx]);
562 // Note that we must test the size on each iteration, the worklist can grow.
563 for (unsigned Idx = 0; Idx != Worklist.size(); ++Idx) {
564 const Value *OrigV = Worklist[Idx];
565 auto *I = dyn_cast_or_null<Instruction>(VMap.lookup(OrigV));
569 // Skip over non-intrinsic callsites, we don't want to remove any nodes from
571 CallSite CS = CallSite(I);
572 if (CS && CS.getCalledFunction() && !CS.getCalledFunction()->isIntrinsic())
575 // See if this instruction simplifies.
576 Value *SimpleV = SimplifyInstruction(I, DL);
580 // Stash away all the uses of the old instruction so we can check them for
581 // recursive simplifications after a RAUW. This is cheaper than checking all
582 // uses of To on the recursive step in most cases.
583 for (const User *U : OrigV->users())
584 Worklist.insert(cast<Instruction>(U));
586 // Replace the instruction with its simplified value.
587 I->replaceAllUsesWith(SimpleV);
589 // If the original instruction had no side effects, remove it.
590 if (isInstructionTriviallyDead(I))
591 I->eraseFromParent();
596 // Now that the inlined function body has been fully constructed, go through
597 // and zap unconditional fall-through branches. This happens all the time when
598 // specializing code: code specialization turns conditional branches into
599 // uncond branches, and this code folds them.
600 Function::iterator Begin = cast<BasicBlock>(VMap[StartingBB])->getIterator();
601 Function::iterator I = Begin;
602 while (I != NewFunc->end()) {
603 // Check if this block has become dead during inlining or other
604 // simplifications. Note that the first block will appear dead, as it has
605 // not yet been wired up properly.
606 if (I != Begin && (pred_begin(&*I) == pred_end(&*I) ||
607 I->getSinglePredecessor() == &*I)) {
608 BasicBlock *DeadBB = &*I++;
609 DeleteDeadBlock(DeadBB);
613 // We need to simplify conditional branches and switches with a constant
614 // operand. We try to prune these out when cloning, but if the
615 // simplification required looking through PHI nodes, those are only
616 // available after forming the full basic block. That may leave some here,
617 // and we still want to prune the dead code as early as possible.
618 ConstantFoldTerminator(&*I);
620 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
621 if (!BI || BI->isConditional()) { ++I; continue; }
623 BasicBlock *Dest = BI->getSuccessor(0);
624 if (!Dest->getSinglePredecessor()) {
628 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
629 // above should have zapped all of them..
630 assert(!isa<PHINode>(Dest->begin()));
632 // We know all single-entry PHI nodes in the inlined function have been
633 // removed, so we just need to splice the blocks.
634 BI->eraseFromParent();
636 // Make all PHI nodes that referred to Dest now refer to I as their source.
637 Dest->replaceAllUsesWith(&*I);
639 // Move all the instructions in the succ to the pred.
640 I->getInstList().splice(I->end(), Dest->getInstList());
642 // Remove the dest block.
643 Dest->eraseFromParent();
645 // Do not increment I, iteratively merge all things this block branches to.
648 // Make a final pass over the basic blocks from the old function to gather
649 // any return instructions which survived folding. We have to do this here
650 // because we can iteratively remove and merge returns above.
651 for (Function::iterator I = cast<BasicBlock>(VMap[StartingBB])->getIterator(),
654 if (ReturnInst *RI = dyn_cast<ReturnInst>(I->getTerminator()))
655 Returns.push_back(RI);
659 /// This works exactly like CloneFunctionInto,
660 /// except that it does some simple constant prop and DCE on the fly. The
661 /// effect of this is to copy significantly less code in cases where (for
662 /// example) a function call with constant arguments is inlined, and those
663 /// constant arguments cause a significant amount of code in the callee to be
664 /// dead. Since this doesn't produce an exact copy of the input, it can't be
665 /// used for things like CloneFunction or CloneModule.
666 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
667 ValueToValueMapTy &VMap,
668 bool ModuleLevelChanges,
669 SmallVectorImpl<ReturnInst*> &Returns,
670 const char *NameSuffix,
671 ClonedCodeInfo *CodeInfo,
672 Instruction *TheCall) {
673 CloneAndPruneIntoFromInst(NewFunc, OldFunc, &OldFunc->front().front(), VMap,
674 ModuleLevelChanges, Returns, NameSuffix, CodeInfo);
677 /// \brief Remaps instructions in \p Blocks using the mapping in \p VMap.
678 void llvm::remapInstructionsInBlocks(
679 const SmallVectorImpl<BasicBlock *> &Blocks, ValueToValueMapTy &VMap) {
680 // Rewrite the code to refer to itself.
681 for (auto *BB : Blocks)
682 for (auto &Inst : *BB)
683 RemapInstruction(&Inst, VMap,
684 RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
687 /// \brief Clones a loop \p OrigLoop. Returns the loop and the blocks in \p
690 /// Updates LoopInfo and DominatorTree assuming the loop is dominated by block
691 /// \p LoopDomBB. Insert the new blocks before block specified in \p Before.
692 Loop *llvm::cloneLoopWithPreheader(BasicBlock *Before, BasicBlock *LoopDomBB,
693 Loop *OrigLoop, ValueToValueMapTy &VMap,
694 const Twine &NameSuffix, LoopInfo *LI,
696 SmallVectorImpl<BasicBlock *> &Blocks) {
697 assert(OrigLoop->getSubLoops().empty() &&
698 "Loop to be cloned cannot have inner loop");
699 Function *F = OrigLoop->getHeader()->getParent();
700 Loop *ParentLoop = OrigLoop->getParentLoop();
702 Loop *NewLoop = new Loop();
704 ParentLoop->addChildLoop(NewLoop);
706 LI->addTopLevelLoop(NewLoop);
708 BasicBlock *OrigPH = OrigLoop->getLoopPreheader();
709 assert(OrigPH && "No preheader");
710 BasicBlock *NewPH = CloneBasicBlock(OrigPH, VMap, NameSuffix, F);
711 // To rename the loop PHIs.
712 VMap[OrigPH] = NewPH;
713 Blocks.push_back(NewPH);
717 ParentLoop->addBasicBlockToLoop(NewPH, *LI);
719 // Update DominatorTree.
720 DT->addNewBlock(NewPH, LoopDomBB);
722 for (BasicBlock *BB : OrigLoop->getBlocks()) {
723 BasicBlock *NewBB = CloneBasicBlock(BB, VMap, NameSuffix, F);
727 NewLoop->addBasicBlockToLoop(NewBB, *LI);
729 // Add DominatorTree node. After seeing all blocks, update to correct IDom.
730 DT->addNewBlock(NewBB, NewPH);
732 Blocks.push_back(NewBB);
735 for (BasicBlock *BB : OrigLoop->getBlocks()) {
736 // Update DominatorTree.
737 BasicBlock *IDomBB = DT->getNode(BB)->getIDom()->getBlock();
738 DT->changeImmediateDominator(cast<BasicBlock>(VMap[BB]),
739 cast<BasicBlock>(VMap[IDomBB]));
742 // Move them physically from the end of the block list.
743 F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
745 F->getBasicBlockList().splice(Before->getIterator(), F->getBasicBlockList(),
746 NewLoop->getHeader()->getIterator(), F->end());