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/ValueMapper.h"
27 #include "llvm/Analysis/ConstantFolding.h"
28 #include "llvm/Analysis/DebugInfo.h"
29 #include "llvm/ADT/SmallVector.h"
33 // CloneBasicBlock - See comments in Cloning.h
34 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
35 ValueToValueMapTy &VMap,
36 const Twine &NameSuffix, Function *F,
37 ClonedCodeInfo *CodeInfo) {
38 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
39 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
41 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
43 // Loop over all instructions, and copy them over.
44 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
46 Instruction *NewInst = II->clone();
48 NewInst->setName(II->getName()+NameSuffix);
49 NewBB->getInstList().push_back(NewInst);
50 VMap[II] = NewInst; // Add instruction map to value.
52 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
53 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
54 if (isa<ConstantInt>(AI->getArraySize()))
55 hasStaticAllocas = true;
57 hasDynamicAllocas = true;
62 CodeInfo->ContainsCalls |= hasCalls;
63 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
64 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
65 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
66 BB != &BB->getParent()->getEntryBlock();
71 // Clone OldFunc into NewFunc, transforming the old arguments into references to
74 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
75 ValueToValueMapTy &VMap,
76 SmallVectorImpl<ReturnInst*> &Returns,
77 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
78 assert(NameSuffix && "NameSuffix cannot be null!");
81 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
82 E = OldFunc->arg_end(); I != E; ++I)
83 assert(VMap.count(I) && "No mapping from source argument specified!");
86 // Clone any attributes.
87 if (NewFunc->arg_size() == OldFunc->arg_size())
88 NewFunc->copyAttributesFrom(OldFunc);
90 //Some arguments were deleted with the VMap. Copy arguments one by one
91 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
92 E = OldFunc->arg_end(); I != E; ++I)
93 if (Argument* Anew = dyn_cast<Argument>(VMap[I]))
94 Anew->addAttr( OldFunc->getAttributes()
95 .getParamAttributes(I->getArgNo() + 1));
96 NewFunc->setAttributes(NewFunc->getAttributes()
97 .addAttr(0, OldFunc->getAttributes()
98 .getRetAttributes()));
99 NewFunc->setAttributes(NewFunc->getAttributes()
100 .addAttr(~0, OldFunc->getAttributes()
101 .getFnAttributes()));
105 // Loop over all of the basic blocks in the function, cloning them as
106 // appropriate. Note that we save BE this way in order to handle cloning of
107 // recursive functions into themselves.
109 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
111 const BasicBlock &BB = *BI;
113 // Create a new basic block and copy instructions into it!
114 BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc,
116 VMap[&BB] = CBB; // Add basic block mapping.
118 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
119 Returns.push_back(RI);
122 // Loop over all of the instructions in the function, fixing up operand
123 // references as we go. This uses VMap to do all the hard work.
125 for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
126 BE = NewFunc->end(); BB != BE; ++BB)
127 // Loop over all instructions, fixing each one as we find it...
128 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
129 RemapInstruction(II, VMap);
132 /// CloneFunction - Return a copy of the specified function, but without
133 /// embedding the function into another module. Also, any references specified
134 /// in the VMap are changed to refer to their mapped value instead of the
135 /// original one. If any of the arguments to the function are in the VMap,
136 /// the arguments are deleted from the resultant function. The VMap is
137 /// updated to include mappings from all of the instructions and basicblocks in
138 /// the function from their old to new values.
140 Function *llvm::CloneFunction(const Function *F,
141 ValueToValueMapTy &VMap,
142 ClonedCodeInfo *CodeInfo) {
143 std::vector<const Type*> ArgTypes;
145 // The user might be deleting arguments to the function by specifying them in
146 // the VMap. If so, we need to not add the arguments to the arg ty vector
148 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
150 if (VMap.count(I) == 0) // Haven't mapped the argument to anything yet?
151 ArgTypes.push_back(I->getType());
153 // Create a new function type...
154 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
155 ArgTypes, F->getFunctionType()->isVarArg());
157 // Create the new function...
158 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
160 // Loop over the arguments, copying the names of the mapped arguments over...
161 Function::arg_iterator DestI = NewF->arg_begin();
162 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
164 if (VMap.count(I) == 0) { // Is this argument preserved?
165 DestI->setName(I->getName()); // Copy the name over...
166 VMap[I] = DestI++; // Add mapping to VMap
169 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
170 CloneFunctionInto(NewF, F, VMap, Returns, "", CodeInfo);
177 /// PruningFunctionCloner - This class is a private class used to implement
178 /// the CloneAndPruneFunctionInto method.
179 struct PruningFunctionCloner {
181 const Function *OldFunc;
182 ValueToValueMapTy &VMap;
183 SmallVectorImpl<ReturnInst*> &Returns;
184 const char *NameSuffix;
185 ClonedCodeInfo *CodeInfo;
186 const TargetData *TD;
188 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
189 ValueToValueMapTy &valueMap,
190 SmallVectorImpl<ReturnInst*> &returns,
191 const char *nameSuffix,
192 ClonedCodeInfo *codeInfo,
193 const TargetData *td)
194 : NewFunc(newFunc), OldFunc(oldFunc), VMap(valueMap), Returns(returns),
195 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
198 /// CloneBlock - The specified block is found to be reachable, clone it and
199 /// anything that it can reach.
200 void CloneBlock(const BasicBlock *BB,
201 std::vector<const BasicBlock*> &ToClone);
204 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
205 /// mapping its operands through VMap if they are available.
206 Constant *ConstantFoldMappedInstruction(const Instruction *I);
210 /// CloneBlock - The specified block is found to be reachable, clone it and
211 /// anything that it can reach.
212 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
213 std::vector<const BasicBlock*> &ToClone){
214 Value *&BBEntry = VMap[BB];
216 // Have we already cloned this block?
219 // Nope, clone it now.
221 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
222 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
224 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
226 // Loop over all instructions, and copy them over, DCE'ing as we go. This
227 // loop doesn't include the terminator.
228 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
230 // If this instruction constant folds, don't bother cloning the instruction,
231 // instead, just add the constant to the value map.
232 if (Constant *C = ConstantFoldMappedInstruction(II)) {
237 Instruction *NewInst = II->clone();
239 NewInst->setName(II->getName()+NameSuffix);
240 NewBB->getInstList().push_back(NewInst);
241 VMap[II] = NewInst; // Add instruction map to value.
243 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
244 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
245 if (isa<ConstantInt>(AI->getArraySize()))
246 hasStaticAllocas = true;
248 hasDynamicAllocas = true;
252 // Finally, clone over the terminator.
253 const TerminatorInst *OldTI = BB->getTerminator();
254 bool TerminatorDone = false;
255 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
256 if (BI->isConditional()) {
257 // If the condition was a known constant in the callee...
258 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
259 // Or is a known constant in the caller...
261 Cond = dyn_cast_or_null<ConstantInt>(VMap[BI->getCondition()]);
263 // Constant fold to uncond branch!
265 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
266 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
267 ToClone.push_back(Dest);
268 TerminatorDone = true;
271 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
272 // If switching on a value known constant in the caller.
273 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
274 if (Cond == 0) // Or known constant after constant prop in the callee...
275 Cond = dyn_cast_or_null<ConstantInt>(VMap[SI->getCondition()]);
276 if (Cond) { // Constant fold to uncond branch!
277 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
278 VMap[OldTI] = BranchInst::Create(Dest, NewBB);
279 ToClone.push_back(Dest);
280 TerminatorDone = true;
284 if (!TerminatorDone) {
285 Instruction *NewInst = OldTI->clone();
286 if (OldTI->hasName())
287 NewInst->setName(OldTI->getName()+NameSuffix);
288 NewBB->getInstList().push_back(NewInst);
289 VMap[OldTI] = NewInst; // Add instruction map to value.
291 // Recursively clone any reachable successor blocks.
292 const TerminatorInst *TI = BB->getTerminator();
293 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
294 ToClone.push_back(TI->getSuccessor(i));
298 CodeInfo->ContainsCalls |= hasCalls;
299 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
300 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
301 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
302 BB != &BB->getParent()->front();
305 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
306 Returns.push_back(RI);
309 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
310 /// mapping its operands through VMap if they are available.
311 Constant *PruningFunctionCloner::
312 ConstantFoldMappedInstruction(const Instruction *I) {
313 SmallVector<Constant*, 8> Ops;
314 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
315 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
319 return 0; // All operands not constant!
321 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
322 return ConstantFoldCompareInstOperands(CI->getPredicate(), Ops[0], Ops[1],
325 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
326 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
327 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
328 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
329 if (GV->isConstant() && GV->hasDefinitiveInitializer())
330 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
333 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
338 UpdateInlinedAtInfo(const DebugLoc &InsnDL, const DebugLoc &TheCallDL,
340 DebugLoc NewLoc = TheCallDL;
341 if (MDNode *IA = InsnDL.getInlinedAt(Ctx))
342 NewLoc = UpdateInlinedAtInfo(DebugLoc::getFromDILocation(IA), TheCallDL,
345 return DebugLoc::get(InsnDL.getLine(), InsnDL.getCol(),
346 InsnDL.getScope(Ctx), NewLoc.getAsMDNode(Ctx));
349 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
350 /// except that it does some simple constant prop and DCE on the fly. The
351 /// effect of this is to copy significantly less code in cases where (for
352 /// example) a function call with constant arguments is inlined, and those
353 /// constant arguments cause a significant amount of code in the callee to be
354 /// dead. Since this doesn't produce an exact copy of the input, it can't be
355 /// used for things like CloneFunction or CloneModule.
356 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
357 ValueToValueMapTy &VMap,
358 SmallVectorImpl<ReturnInst*> &Returns,
359 const char *NameSuffix,
360 ClonedCodeInfo *CodeInfo,
361 const TargetData *TD,
362 Instruction *TheCall) {
363 assert(NameSuffix && "NameSuffix cannot be null!");
366 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
367 E = OldFunc->arg_end(); II != E; ++II)
368 assert(VMap.count(II) && "No mapping from source argument specified!");
371 PruningFunctionCloner PFC(NewFunc, OldFunc, VMap, Returns,
372 NameSuffix, CodeInfo, TD);
374 // Clone the entry block, and anything recursively reachable from it.
375 std::vector<const BasicBlock*> CloneWorklist;
376 CloneWorklist.push_back(&OldFunc->getEntryBlock());
377 while (!CloneWorklist.empty()) {
378 const BasicBlock *BB = CloneWorklist.back();
379 CloneWorklist.pop_back();
380 PFC.CloneBlock(BB, CloneWorklist);
383 // Loop over all of the basic blocks in the old function. If the block was
384 // reachable, we have cloned it and the old block is now in the value map:
385 // insert it into the new function in the right order. If not, ignore it.
387 // Defer PHI resolution until rest of function is resolved.
388 SmallVector<const PHINode*, 16> PHIToResolve;
389 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
391 BasicBlock *NewBB = cast_or_null<BasicBlock>(VMap[BI]);
392 if (NewBB == 0) continue; // Dead block.
394 // Add the new block to the new function.
395 NewFunc->getBasicBlockList().push_back(NewBB);
397 // Loop over all of the instructions in the block, fixing up operand
398 // references as we go. This uses VMap to do all the hard work.
400 BasicBlock::iterator I = NewBB->begin();
404 TheCallDL = TheCall->getDebugLoc();
406 // Handle PHI nodes specially, as we have to remove references to dead
408 if (PHINode *PN = dyn_cast<PHINode>(I)) {
409 // Skip over all PHI nodes, remembering them for later.
410 BasicBlock::const_iterator OldI = BI->begin();
411 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) {
412 if (I->hasMetadata()) {
413 if (!TheCallDL.isUnknown()) {
414 DebugLoc IDL = I->getDebugLoc();
415 if (!IDL.isUnknown()) {
416 DebugLoc NewDL = UpdateInlinedAtInfo(IDL, TheCallDL,
418 I->setDebugLoc(NewDL);
421 // The cloned instruction has dbg info but the call instruction
422 // does not have dbg info. Remove dbg info from cloned instruction.
423 I->setDebugLoc(DebugLoc());
426 PHIToResolve.push_back(cast<PHINode>(OldI));
432 // FIXME: Unclone all this metadata stuff.
436 // Otherwise, remap the rest of the instructions normally.
437 for (; I != NewBB->end(); ++I) {
438 if (I->hasMetadata()) {
439 if (!TheCallDL.isUnknown()) {
440 DebugLoc IDL = I->getDebugLoc();
441 if (!IDL.isUnknown()) {
442 DebugLoc NewDL = UpdateInlinedAtInfo(IDL, TheCallDL,
444 I->setDebugLoc(NewDL);
447 // The cloned instruction has dbg info but the call instruction
448 // does not have dbg info. Remove dbg info from cloned instruction.
449 I->setDebugLoc(DebugLoc());
452 RemapInstruction(I, VMap);
456 // Defer PHI resolution until rest of function is resolved, PHI resolution
457 // requires the CFG to be up-to-date.
458 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
459 const PHINode *OPN = PHIToResolve[phino];
460 unsigned NumPreds = OPN->getNumIncomingValues();
461 const BasicBlock *OldBB = OPN->getParent();
462 BasicBlock *NewBB = cast<BasicBlock>(VMap[OldBB]);
464 // Map operands for blocks that are live and remove operands for blocks
466 for (; phino != PHIToResolve.size() &&
467 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
468 OPN = PHIToResolve[phino];
469 PHINode *PN = cast<PHINode>(VMap[OPN]);
470 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
471 if (BasicBlock *MappedBlock =
472 cast_or_null<BasicBlock>(VMap[PN->getIncomingBlock(pred)])) {
473 Value *InVal = MapValue(PN->getIncomingValue(pred),
475 assert(InVal && "Unknown input value?");
476 PN->setIncomingValue(pred, InVal);
477 PN->setIncomingBlock(pred, MappedBlock);
479 PN->removeIncomingValue(pred, false);
480 --pred, --e; // Revisit the next entry.
485 // The loop above has removed PHI entries for those blocks that are dead
486 // and has updated others. However, if a block is live (i.e. copied over)
487 // but its terminator has been changed to not go to this block, then our
488 // phi nodes will have invalid entries. Update the PHI nodes in this
490 PHINode *PN = cast<PHINode>(NewBB->begin());
491 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
492 if (NumPreds != PN->getNumIncomingValues()) {
493 assert(NumPreds < PN->getNumIncomingValues());
494 // Count how many times each predecessor comes to this block.
495 std::map<BasicBlock*, unsigned> PredCount;
496 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
500 // Figure out how many entries to remove from each PHI.
501 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
502 ++PredCount[PN->getIncomingBlock(i)];
504 // At this point, the excess predecessor entries are positive in the
505 // map. Loop over all of the PHIs and remove excess predecessor
507 BasicBlock::iterator I = NewBB->begin();
508 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
509 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
510 E = PredCount.end(); PCI != E; ++PCI) {
511 BasicBlock *Pred = PCI->first;
512 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
513 PN->removeIncomingValue(Pred, false);
518 // If the loops above have made these phi nodes have 0 or 1 operand,
519 // replace them with undef or the input value. We must do this for
520 // correctness, because 0-operand phis are not valid.
521 PN = cast<PHINode>(NewBB->begin());
522 if (PN->getNumIncomingValues() == 0) {
523 BasicBlock::iterator I = NewBB->begin();
524 BasicBlock::const_iterator OldI = OldBB->begin();
525 while ((PN = dyn_cast<PHINode>(I++))) {
526 Value *NV = UndefValue::get(PN->getType());
527 PN->replaceAllUsesWith(NV);
528 assert(VMap[OldI] == PN && "VMap mismatch");
530 PN->eraseFromParent();
534 // NOTE: We cannot eliminate single entry phi nodes here, because of
535 // VMap. Single entry phi nodes can have multiple VMap entries
536 // pointing at them. Thus, deleting one would require scanning the VMap
537 // to update any entries in it that would require that. This would be
541 // Now that the inlined function body has been fully constructed, go through
542 // and zap unconditional fall-through branches. This happen all the time when
543 // specializing code: code specialization turns conditional branches into
544 // uncond branches, and this code folds them.
545 Function::iterator I = cast<BasicBlock>(VMap[&OldFunc->getEntryBlock()]);
546 while (I != NewFunc->end()) {
547 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
548 if (!BI || BI->isConditional()) { ++I; continue; }
550 // Note that we can't eliminate uncond branches if the destination has
551 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
552 // require scanning the VMap to update any entries that point to the phi
554 BasicBlock *Dest = BI->getSuccessor(0);
555 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
559 // We know all single-entry PHI nodes in the inlined function have been
560 // removed, so we just need to splice the blocks.
561 BI->eraseFromParent();
563 // Move all the instructions in the succ to the pred.
564 I->getInstList().splice(I->end(), Dest->getInstList());
566 // Make all PHI nodes that referred to Dest now refer to I as their source.
567 Dest->replaceAllUsesWith(I);
569 // Remove the dest block.
570 Dest->eraseFromParent();
572 // Do not increment I, iteratively merge all things this block branches to.