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/Constants.h"
18 #include "llvm/DerivedTypes.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/IntrinsicInst.h"
21 #include "llvm/GlobalVariable.h"
22 #include "llvm/Function.h"
23 #include "llvm/LLVMContext.h"
24 #include "llvm/Metadata.h"
25 #include "llvm/Support/CFG.h"
26 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
27 #include "llvm/Transforms/Utils/Local.h"
28 #include "llvm/Transforms/Utils/ValueMapper.h"
29 #include "llvm/Analysis/ConstantFolding.h"
30 #include "llvm/Analysis/InstructionSimplify.h"
31 #include "llvm/Analysis/DebugInfo.h"
32 #include "llvm/ADT/SmallVector.h"
36 // CloneBasicBlock - See comments in Cloning.h
37 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
38 ValueToValueMapTy &VMap,
39 const Twine &NameSuffix, Function *F,
40 ClonedCodeInfo *CodeInfo) {
41 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
42 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
44 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
46 // Loop over all instructions, and copy them over.
47 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
49 Instruction *NewInst = II->clone();
51 NewInst->setName(II->getName()+NameSuffix);
52 NewBB->getInstList().push_back(NewInst);
53 VMap[II] = NewInst; // Add instruction map to value.
55 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
56 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
57 if (isa<ConstantInt>(AI->getArraySize()))
58 hasStaticAllocas = true;
60 hasDynamicAllocas = true;
65 CodeInfo->ContainsCalls |= hasCalls;
66 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
67 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
68 BB != &BB->getParent()->getEntryBlock();
73 // Clone OldFunc into NewFunc, transforming the old arguments into references to
76 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
77 ValueToValueMapTy &VMap,
78 bool ModuleLevelChanges,
79 SmallVectorImpl<ReturnInst*> &Returns,
80 const char *NameSuffix, ClonedCodeInfo *CodeInfo,
81 ValueMapTypeRemapper *TypeMapper) {
82 assert(NameSuffix && "NameSuffix cannot be null!");
85 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
86 E = OldFunc->arg_end(); I != E; ++I)
87 assert(VMap.count(I) && "No mapping from source argument specified!");
90 // Clone any attributes.
91 if (NewFunc->arg_size() == OldFunc->arg_size())
92 NewFunc->copyAttributesFrom(OldFunc);
94 //Some arguments were deleted with the VMap. Copy arguments one by one
95 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
96 E = OldFunc->arg_end(); I != E; ++I)
97 if (Argument* Anew = dyn_cast<Argument>(VMap[I]))
98 Anew->addAttr( OldFunc->getAttributes()
99 .getParamAttributes(I->getArgNo() + 1));
100 NewFunc->setAttributes(NewFunc->getAttributes()
101 .addAttr(0, OldFunc->getAttributes()
102 .getRetAttributes()));
103 NewFunc->setAttributes(NewFunc->getAttributes()
104 .addAttr(~0, OldFunc->getAttributes()
105 .getFnAttributes()));
109 // Loop over all of the basic blocks in the function, cloning them as
110 // appropriate. Note that we save BE this way in order to handle cloning of
111 // recursive functions into themselves.
113 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
115 const BasicBlock &BB = *BI;
117 // Create a new basic block and copy instructions into it!
118 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
120 // Add basic block mapping.
123 // It is only legal to clone a function if a block address within that
124 // function is never referenced outside of the function. Given that, we
125 // want to map block addresses from the old function to block addresses in
126 // the clone. (This is different from the generic ValueMapper
127 // implementation, which generates an invalid blockaddress when
128 // cloning a function.)
129 if (BB.hasAddressTaken()) {
130 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
131 const_cast<BasicBlock*>(&BB));
132 VMap[OldBBAddr] = BlockAddress::get(NewFunc, CBB);
135 // Note return instructions for the caller.
136 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
137 Returns.push_back(RI);
140 // Loop over all of the instructions in the function, fixing up operand
141 // references as we go. This uses VMap to do all the hard work.
142 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
143 BE = NewFunc->end(); BB != BE; ++BB)
144 // Loop over all instructions, fixing each one as we find it...
145 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
146 RemapInstruction(II, VMap,
147 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
151 /// CloneFunction - Return a copy of the specified function, but without
152 /// embedding the function into another module. Also, any references specified
153 /// in the VMap are changed to refer to their mapped value instead of the
154 /// original one. If any of the arguments to the function are in the VMap,
155 /// the arguments are deleted from the resultant function. The VMap is
156 /// updated to include mappings from all of the instructions and basicblocks in
157 /// the function from their old to new values.
159 Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
160 bool ModuleLevelChanges,
161 ClonedCodeInfo *CodeInfo) {
162 std::vector<Type*> ArgTypes;
164 // The user might be deleting arguments to the function by specifying them in
165 // the VMap. If so, we need to not add the arguments to the arg ty vector
167 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
169 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
170 ArgTypes.push_back(I->getType());
172 // Create a new function type...
173 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
174 ArgTypes, F->getFunctionType()->isVarArg());
176 // Create the new function...
177 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
179 // Loop over the arguments, copying the names of the mapped arguments over...
180 Function::arg_iterator DestI = NewF->arg_begin();
181 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
183 if (VMap.count(I) == 0) { // Is this argument preserved?
184 DestI->setName(I->getName()); // Copy the name over...
185 VMap[I] = DestI++; // Add mapping to VMap
188 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
189 CloneFunctionInto(NewF, F, VMap, ModuleLevelChanges, Returns, "", CodeInfo);
196 /// PruningFunctionCloner - This class is a private class used to implement
197 /// the CloneAndPruneFunctionInto method.
198 struct PruningFunctionCloner {
200 const Function *OldFunc;
201 ValueToValueMapTy &VMap;
202 bool ModuleLevelChanges;
203 SmallVectorImpl<ReturnInst*> &Returns;
204 const char *NameSuffix;
205 ClonedCodeInfo *CodeInfo;
206 const TargetData *TD;
208 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
209 ValueToValueMapTy &valueMap,
210 bool moduleLevelChanges,
211 SmallVectorImpl<ReturnInst*> &returns,
212 const char *nameSuffix,
213 ClonedCodeInfo *codeInfo,
214 const TargetData *td)
215 : NewFunc(newFunc), OldFunc(oldFunc),
216 VMap(valueMap), ModuleLevelChanges(moduleLevelChanges),
217 Returns(returns), NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
220 /// CloneBlock - The specified block is found to be reachable, clone it and
221 /// anything that it can reach.
222 void CloneBlock(const BasicBlock *BB,
223 std::vector<const BasicBlock*> &ToClone);
227 /// CloneBlock - The specified block is found to be reachable, clone it and
228 /// anything that it can reach.
229 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
230 std::vector<const BasicBlock*> &ToClone){
231 WeakVH &BBEntry = VMap[BB];
233 // Have we already cloned this block?
236 // Nope, clone it now.
238 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
239 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
241 // It is only legal to clone a function if a block address within that
242 // function is never referenced outside of the function. Given that, we
243 // want to map block addresses from the old function to block addresses in
244 // the clone. (This is different from the generic ValueMapper
245 // implementation, which generates an invalid blockaddress when
246 // cloning a function.)
248 // Note that we don't need to fix the mapping for unreachable blocks;
249 // the default mapping there is safe.
250 if (BB->hasAddressTaken()) {
251 Constant *OldBBAddr = BlockAddress::get(const_cast<Function*>(OldFunc),
252 const_cast<BasicBlock*>(BB));
253 VMap[OldBBAddr] = BlockAddress::get(NewFunc, NewBB);
257 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
259 // Loop over all instructions, and copy them over, DCE'ing as we go. This
260 // loop doesn't include the terminator.
261 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
263 Instruction *NewInst = II->clone();
265 // Eagerly remap operands to the newly cloned instruction, except for PHI
266 // nodes for which we defer processing until we update the CFG.
267 if (!isa<PHINode>(NewInst)) {
268 RemapInstruction(NewInst, VMap,
269 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
271 // If we can simplify this instruction to some other value, simply add
272 // a mapping to that value rather than inserting a new instruction into
274 if (Value *V = SimplifyInstruction(NewInst, TD)) {
275 // On the off-chance that this simplifies to an instruction in the old
276 // function, map it back into the new function.
277 if (Value *MappedV = VMap.lookup(V))
287 NewInst->setName(II->getName()+NameSuffix);
288 VMap[II] = NewInst; // Add instruction map to value.
289 NewBB->getInstList().push_back(NewInst);
290 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
291 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
292 if (isa<ConstantInt>(AI->getArraySize()))
293 hasStaticAllocas = true;
295 hasDynamicAllocas = true;
299 // Finally, clone over the terminator.
300 const TerminatorInst *OldTI = BB->getTerminator();
301 bool TerminatorDone = false;
302 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
303 if (BI->isConditional()) {
304 // If the condition was a known constant in the callee...
305 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
306 // Or is a known constant in the caller...
308 Value *V = VMap[BI->getCondition()];
309 Cond = dyn_cast_or_null<ConstantInt>(V);
312 // Constant fold to uncond branch!
314 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
315 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
316 ToClone.push_back(Dest);
317 TerminatorDone = true;
320 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
321 // If switching on a value known constant in the caller.
322 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
323 if (Cond == 0) { // Or known constant after constant prop in the callee...
324 Value *V = VMap[SI->getCondition()];
325 Cond = dyn_cast_or_null<ConstantInt>(V);
327 if (Cond) { // Constant fold to uncond branch!
328 SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
329 BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
330 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
331 ToClone.push_back(Dest);
332 TerminatorDone = true;
336 if (!TerminatorDone) {
337 Instruction *NewInst = OldTI->clone();
338 if (OldTI->hasName())
339 NewInst->setName(OldTI->getName()+NameSuffix);
340 NewBB->getInstList().push_back(NewInst);
341 VMap[OldTI] = NewInst; // Add instruction map to value.
343 // Recursively clone any reachable successor blocks.
344 const TerminatorInst *TI = BB->getTerminator();
345 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
346 ToClone.push_back(TI->getSuccessor(i));
350 CodeInfo->ContainsCalls |= hasCalls;
351 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
352 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
353 BB != &BB->getParent()->front();
356 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
357 Returns.push_back(RI);
360 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
361 /// except that it does some simple constant prop and DCE on the fly. The
362 /// effect of this is to copy significantly less code in cases where (for
363 /// example) a function call with constant arguments is inlined, and those
364 /// constant arguments cause a significant amount of code in the callee to be
365 /// dead. Since this doesn't produce an exact copy of the input, it can't be
366 /// used for things like CloneFunction or CloneModule.
367 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
368 ValueToValueMapTy &VMap,
369 bool ModuleLevelChanges,
370 SmallVectorImpl<ReturnInst*> &Returns,
371 const char *NameSuffix,
372 ClonedCodeInfo *CodeInfo,
373 const TargetData *TD,
374 Instruction *TheCall) {
375 assert(NameSuffix && "NameSuffix cannot be null!");
378 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
379 E = OldFunc->arg_end(); II != E; ++II)
380 assert(VMap.count(II) && "No mapping from source argument specified!");
383 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, ModuleLevelChanges,
384 Returns, NameSuffix, CodeInfo, TD);
386 // Clone the entry block, and anything recursively reachable from it.
387 std::vector<const BasicBlock*> CloneWorklist;
388 CloneWorklist.push_back(&OldFunc->getEntryBlock());
389 while (!CloneWorklist.empty()) {
390 const BasicBlock *BB = CloneWorklist.back();
391 CloneWorklist.pop_back();
392 PFC.CloneBlock(BB, CloneWorklist);
395 // Loop over all of the basic blocks in the old function. If the block was
396 // reachable, we have cloned it and the old block is now in the value map:
397 // insert it into the new function in the right order. If not, ignore it.
399 // Defer PHI resolution until rest of function is resolved.
400 SmallVector<const PHINode*, 16> PHIToResolve;
401 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
404 BasicBlock *NewBB = cast_or_null<BasicBlock>(V);
405 if (NewBB == 0) continue; // Dead block.
407 // Add the new block to the new function.
408 NewFunc->getBasicBlockList().push_back(NewBB);
410 // Handle PHI nodes specially, as we have to remove references to dead
412 for (BasicBlock::const_iterator I = BI->begin(), E = BI->end(); I != E; ++I)
413 if (const PHINode *PN = dyn_cast<PHINode>(I))
414 PHIToResolve.push_back(PN);
418 // Finally, remap the terminator instructions, as those can't be remapped
419 // until all BBs are mapped.
420 RemapInstruction(NewBB->getTerminator(), VMap,
421 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
424 // Defer PHI resolution until rest of function is resolved, PHI resolution
425 // requires the CFG to be up-to-date.
426 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
427 const PHINode *OPN = PHIToResolve[phino];
428 unsigned NumPreds = OPN->getNumIncomingValues();
429 const BasicBlock *OldBB = OPN->getParent();
430 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
432 // Map operands for blocks that are live and remove operands for blocks
434 for (; phino != PHIToResolve.size() &&
435 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
436 OPN = PHIToResolve[phino];
437 PHINode *PN = cast<PHINode>(VMap[OPN]);
438 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
439 Value *V = VMap[PN->getIncomingBlock(pred)];
440 if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
441 Value *InVal = MapValue(PN->getIncomingValue(pred),
443 ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
444 assert(InVal && "Unknown input value?");
445 PN->setIncomingValue(pred, InVal);
446 PN->setIncomingBlock(pred, MappedBlock);
448 PN->removeIncomingValue(pred, false);
449 --pred, --e; // Revisit the next entry.
454 // The loop above has removed PHI entries for those blocks that are dead
455 // and has updated others. However, if a block is live (i.e. copied over)
456 // but its terminator has been changed to not go to this block, then our
457 // phi nodes will have invalid entries. Update the PHI nodes in this
459 PHINode *PN = cast<PHINode>(NewBB->begin());
460 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
461 if (NumPreds != PN->getNumIncomingValues()) {
462 assert(NumPreds < PN->getNumIncomingValues());
463 // Count how many times each predecessor comes to this block.
464 std::map<BasicBlock*, unsigned> PredCount;
465 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
469 // Figure out how many entries to remove from each PHI.
470 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
471 ++PredCount[PN->getIncomingBlock(i)];
473 // At this point, the excess predecessor entries are positive in the
474 // map. Loop over all of the PHIs and remove excess predecessor
476 BasicBlock::iterator I = NewBB->begin();
477 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
478 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
479 E = PredCount.end(); PCI != E; ++PCI) {
480 BasicBlock *Pred = PCI->first;
481 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
482 PN->removeIncomingValue(Pred, false);
487 // If the loops above have made these phi nodes have 0 or 1 operand,
488 // replace them with undef or the input value. We must do this for
489 // correctness, because 0-operand phis are not valid.
490 PN = cast<PHINode>(NewBB->begin());
491 if (PN->getNumIncomingValues() == 0) {
492 BasicBlock::iterator I = NewBB->begin();
493 BasicBlock::const_iterator OldI = OldBB->begin();
494 while ((PN = dyn_cast<PHINode>(I++))) {
495 Value *NV = UndefValue::get(PN->getType());
496 PN->replaceAllUsesWith(NV);
497 assert(VMap[OldI] == PN && "VMap mismatch");
499 PN->eraseFromParent();
505 // Make a second pass over the PHINodes now that all of them have been
506 // remapped into the new function, simplifying the PHINode and performing any
507 // recursive simplifications exposed. This will transparently update the
508 // WeakVH in the VMap. Notably, we rely on that so that if we coalesce
509 // two PHINodes, the iteration over the old PHIs remains valid, and the
510 // mapping will just map us to the new node (which may not even be a PHI
512 for (unsigned Idx = 0, Size = PHIToResolve.size(); Idx != Size; ++Idx)
513 if (PHINode *PN = dyn_cast<PHINode>(VMap[PHIToResolve[Idx]]))
514 recursivelySimplifyInstruction(PN, TD);
516 // Now that the inlined function body has been fully constructed, go through
517 // and zap unconditional fall-through branches. This happen all the time when
518 // specializing code: code specialization turns conditional branches into
519 // uncond branches, and this code folds them.
520 Function::iterator Begin = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]);
521 Function::iterator I = Begin;
522 while (I != NewFunc->end()) {
523 // Check if this block has become dead during inlining or other
524 // simplifications. Note that the first block will appear dead, as it has
525 // not yet been wired up properly.
526 if (I != Begin && (pred_begin(I) == pred_end(I) ||
527 I->getSinglePredecessor() == I)) {
528 BasicBlock *DeadBB = I++;
529 DeleteDeadBlock(DeadBB);
533 // We need to simplify conditional branches and switches with a constant
534 // operand. We try to prune these out when cloning, but if the
535 // simplification required looking through PHI nodes, those are only
536 // available after forming the full basic block. That may leave some here,
537 // and we still want to prune the dead code as early as possible.
538 ConstantFoldTerminator(I);
540 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
541 if (!BI || BI->isConditional()) { ++I; continue; }
543 BasicBlock *Dest = BI->getSuccessor(0);
544 if (!Dest->getSinglePredecessor()) {
548 // We shouldn't be able to get single-entry PHI nodes here, as instsimplify
549 // above should have zapped all of them..
550 assert(!isa<PHINode>(Dest->begin()));
552 // We know all single-entry PHI nodes in the inlined function have been
553 // removed, so we just need to splice the blocks.
554 BI->eraseFromParent();
556 // Make all PHI nodes that referred to Dest now refer to I as their source.
557 Dest->replaceAllUsesWith(I);
559 // Move all the instructions in the succ to the pred.
560 I->getInstList().splice(I->end(), Dest->getInstList());
562 // Remove the dest block.
563 Dest->eraseFromParent();
565 // Do not increment I, iteratively merge all things this block branches to.