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/Function.h"
21 #include "llvm/Support/CFG.h"
22 #include "llvm/Support/Compiler.h"
23 #include "llvm/Transforms/Utils/ValueMapper.h"
24 #include "llvm/Analysis/ConstantFolding.h"
25 #include "llvm/ADT/SmallVector.h"
29 // CloneBasicBlock - See comments in Cloning.h
30 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
31 DenseMap<const Value*, Value*> &ValueMap,
32 const char *NameSuffix, Function *F,
33 ClonedCodeInfo *CodeInfo) {
34 BasicBlock *NewBB = BasicBlock::Create("", F);
35 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
36 NewBB->setUnwindDest(const_cast<BasicBlock*>(BB->getUnwindDest()));
38 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
40 // Loop over all instructions, and copy them over.
41 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
43 Instruction *NewInst = II->clone();
45 NewInst->setName(II->getName()+NameSuffix);
46 NewBB->getInstList().push_back(NewInst);
47 ValueMap[II] = NewInst; // Add instruction map to value.
49 hasCalls |= isa<CallInst>(II);
50 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
51 if (isa<ConstantInt>(AI->getArraySize()))
52 hasStaticAllocas = true;
54 hasDynamicAllocas = true;
59 CodeInfo->ContainsCalls |= hasCalls;
60 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
61 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
62 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
63 BB != &BB->getParent()->getEntryBlock();
68 // Clone OldFunc into NewFunc, transforming the old arguments into references to
71 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
72 DenseMap<const Value*, Value*> &ValueMap,
73 std::vector<ReturnInst*> &Returns,
74 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
75 assert(NameSuffix && "NameSuffix cannot be null!");
78 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
79 E = OldFunc->arg_end(); I != E; ++I)
80 assert(ValueMap.count(I) && "No mapping from source argument specified!");
83 // Clone the parameter attributes
84 NewFunc->setParamAttrs(OldFunc->getParamAttrs());
86 // Clone the calling convention
87 NewFunc->setCallingConv(OldFunc->getCallingConv());
89 // Loop over all of the basic blocks in the function, cloning them as
90 // appropriate. Note that we save BE this way in order to handle cloning of
91 // recursive functions into themselves.
93 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
95 const BasicBlock &BB = *BI;
97 // Create a new basic block and copy instructions into it!
98 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
100 ValueMap[&BB] = CBB; // Add basic block mapping.
102 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
103 Returns.push_back(RI);
106 // Loop over all of the instructions in the function, fixing up operand
107 // references as we go. This uses ValueMap to do all the hard work.
109 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
110 BE = NewFunc->end(); BB != BE; ++BB) {
111 // Fix up the unwind destination.
112 if (BasicBlock *UnwindDest = BB->getUnwindDest())
113 BB->setUnwindDest(cast<BasicBlock>(ValueMap[UnwindDest]));
115 // Loop over all instructions, fixing each one as we find it...
116 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
117 RemapInstruction(II, ValueMap);
121 /// CloneFunction - Return a copy of the specified function, but without
122 /// embedding the function into another module. Also, any references specified
123 /// in the ValueMap are changed to refer to their mapped value instead of the
124 /// original one. If any of the arguments to the function are in the ValueMap,
125 /// the arguments are deleted from the resultant function. The ValueMap is
126 /// updated to include mappings from all of the instructions and basicblocks in
127 /// the function from their old to new values.
129 Function *llvm::CloneFunction(const Function *F,
130 DenseMap<const Value*, Value*> &ValueMap,
131 ClonedCodeInfo *CodeInfo) {
132 std::vector<const Type*> ArgTypes;
134 // The user might be deleting arguments to the function by specifying them in
135 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
137 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
139 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
140 ArgTypes.push_back(I->getType());
142 // Create a new function type...
143 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
144 ArgTypes, F->getFunctionType()->isVarArg());
146 // Create the new function...
147 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
149 // Loop over the arguments, copying the names of the mapped arguments over...
150 Function::arg_iterator DestI = NewF->arg_begin();
151 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
153 if (ValueMap.count(I) == 0) { // Is this argument preserved?
154 DestI->setName(I->getName()); // Copy the name over...
155 ValueMap[I] = DestI++; // Add mapping to ValueMap
158 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
159 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
166 /// PruningFunctionCloner - This class is a private class used to implement
167 /// the CloneAndPruneFunctionInto method.
168 struct VISIBILITY_HIDDEN PruningFunctionCloner {
170 const Function *OldFunc;
171 DenseMap<const Value*, Value*> &ValueMap;
172 std::vector<ReturnInst*> &Returns;
173 const char *NameSuffix;
174 ClonedCodeInfo *CodeInfo;
175 const TargetData *TD;
178 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
179 DenseMap<const Value*, Value*> &valueMap,
180 std::vector<ReturnInst*> &returns,
181 const char *nameSuffix,
182 ClonedCodeInfo *codeInfo,
183 const TargetData *td)
184 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
185 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
188 /// CloneBlock - The specified block is found to be reachable, clone it and
189 /// anything that it can reach.
190 void CloneBlock(const BasicBlock *BB,
191 std::vector<const BasicBlock*> &ToClone);
194 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
195 /// mapping its operands through ValueMap if they are available.
196 Constant *ConstantFoldMappedInstruction(const Instruction *I);
200 /// CloneBlock - The specified block is found to be reachable, clone it and
201 /// anything that it can reach.
202 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
203 std::vector<const BasicBlock*> &ToClone){
204 Value *&BBEntry = ValueMap[BB];
206 // Have we already cloned this block?
209 // Nope, clone it now.
211 BBEntry = NewBB = BasicBlock::Create();
212 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
214 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
216 // Loop over all instructions, and copy them over, DCE'ing as we go. This
217 // loop doesn't include the terminator.
218 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
220 // If this instruction constant folds, don't bother cloning the instruction,
221 // instead, just add the constant to the value map.
222 if (Constant *C = ConstantFoldMappedInstruction(II)) {
227 Instruction *NewInst = II->clone();
229 NewInst->setName(II->getName()+NameSuffix);
230 NewBB->getInstList().push_back(NewInst);
231 ValueMap[II] = NewInst; // Add instruction map to value.
233 hasCalls |= isa<CallInst>(II);
234 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
235 if (isa<ConstantInt>(AI->getArraySize()))
236 hasStaticAllocas = true;
238 hasDynamicAllocas = true;
242 // Finally, clone over the terminator.
243 const TerminatorInst *OldTI = BB->getTerminator();
244 bool TerminatorDone = false;
245 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
246 if (BI->isConditional()) {
247 // If the condition was a known constant in the callee...
248 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
249 // Or is a known constant in the caller...
251 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
253 // Constant fold to uncond branch!
255 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
256 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
257 ToClone.push_back(Dest);
258 TerminatorDone = true;
261 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
262 // If switching on a value known constant in the caller.
263 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
264 if (Cond == 0) // Or known constant after constant prop in the callee...
265 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
266 if (Cond) { // Constant fold to uncond branch!
267 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
268 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
269 ToClone.push_back(Dest);
270 TerminatorDone = true;
274 if (!TerminatorDone) {
275 Instruction *NewInst = OldTI->clone();
276 if (OldTI->hasName())
277 NewInst->setName(OldTI->getName()+NameSuffix);
278 NewBB->getInstList().push_back(NewInst);
279 ValueMap[OldTI] = NewInst; // Add instruction map to value.
281 // Recursively clone any reachable successor blocks.
282 const TerminatorInst *TI = BB->getTerminator();
283 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
284 ToClone.push_back(TI->getSuccessor(i));
288 CodeInfo->ContainsCalls |= hasCalls;
289 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
290 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
291 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
292 BB != &BB->getParent()->front();
295 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
296 Returns.push_back(RI);
299 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
300 /// mapping its operands through ValueMap if they are available.
301 Constant *PruningFunctionCloner::
302 ConstantFoldMappedInstruction(const Instruction *I) {
303 SmallVector<Constant*, 8> Ops;
304 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
305 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
309 return 0; // All operands not constant!
312 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
313 return ConstantFoldCompareInstOperands(CI->getPredicate(),
314 &Ops[0], Ops.size(), TD);
316 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
317 &Ops[0], Ops.size(), TD);
320 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
321 /// except that it does some simple constant prop and DCE on the fly. The
322 /// effect of this is to copy significantly less code in cases where (for
323 /// example) a function call with constant arguments is inlined, and those
324 /// constant arguments cause a significant amount of code in the callee to be
325 /// dead. Since this doesn't produce an exact copy of the input, it can't be
326 /// used for things like CloneFunction or CloneModule.
327 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
328 DenseMap<const Value*, Value*> &ValueMap,
329 std::vector<ReturnInst*> &Returns,
330 const char *NameSuffix,
331 ClonedCodeInfo *CodeInfo,
332 const TargetData *TD) {
333 assert(NameSuffix && "NameSuffix cannot be null!");
336 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
337 E = OldFunc->arg_end(); II != E; ++II)
338 assert(ValueMap.count(II) && "No mapping from source argument specified!");
341 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
342 NameSuffix, CodeInfo, TD);
344 // Clone the entry block, and anything recursively reachable from it.
345 std::vector<const BasicBlock*> CloneWorklist;
346 CloneWorklist.push_back(&OldFunc->getEntryBlock());
347 while (!CloneWorklist.empty()) {
348 const BasicBlock *BB = CloneWorklist.back();
349 CloneWorklist.pop_back();
350 PFC.CloneBlock(BB, CloneWorklist);
353 // Loop over all of the basic blocks in the old function. If the block was
354 // reachable, we have cloned it and the old block is now in the value map:
355 // insert it into the new function in the right order. If not, ignore it.
357 // Defer PHI resolution until rest of function is resolved.
358 std::vector<const PHINode*> PHIToResolve;
359 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
361 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
362 if (NewBB == 0) continue; // Dead block.
364 // Add the new block to the new function.
365 NewFunc->getBasicBlockList().push_back(NewBB);
367 // Loop over all of the instructions in the block, fixing up operand
368 // references as we go. This uses ValueMap to do all the hard work.
370 BasicBlock::iterator I = NewBB->begin();
372 // Handle PHI nodes specially, as we have to remove references to dead
374 if (PHINode *PN = dyn_cast<PHINode>(I)) {
375 // Skip over all PHI nodes, remembering them for later.
376 BasicBlock::const_iterator OldI = BI->begin();
377 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
378 PHIToResolve.push_back(cast<PHINode>(OldI));
381 // Otherwise, remap the rest of the instructions normally.
382 for (; I != NewBB->end(); ++I)
383 RemapInstruction(I, ValueMap);
386 // Defer PHI resolution until rest of function is resolved, PHI resolution
387 // requires the CFG to be up-to-date.
388 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
389 const PHINode *OPN = PHIToResolve[phino];
390 unsigned NumPreds = OPN->getNumIncomingValues();
391 const BasicBlock *OldBB = OPN->getParent();
392 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
394 // Map operands for blocks that are live and remove operands for blocks
396 for (; phino != PHIToResolve.size() &&
397 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
398 OPN = PHIToResolve[phino];
399 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
400 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
401 if (BasicBlock *MappedBlock =
402 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
403 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
404 assert(InVal && "Unknown input value?");
405 PN->setIncomingValue(pred, InVal);
406 PN->setIncomingBlock(pred, MappedBlock);
408 PN->removeIncomingValue(pred, false);
409 --pred, --e; // Revisit the next entry.
414 // The loop above has removed PHI entries for those blocks that are dead
415 // and has updated others. However, if a block is live (i.e. copied over)
416 // but its terminator has been changed to not go to this block, then our
417 // phi nodes will have invalid entries. Update the PHI nodes in this
419 PHINode *PN = cast<PHINode>(NewBB->begin());
420 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
421 if (NumPreds != PN->getNumIncomingValues()) {
422 assert(NumPreds < PN->getNumIncomingValues());
423 // Count how many times each predecessor comes to this block.
424 std::map<BasicBlock*, unsigned> PredCount;
425 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
429 // Figure out how many entries to remove from each PHI.
430 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
431 ++PredCount[PN->getIncomingBlock(i)];
433 // At this point, the excess predecessor entries are positive in the
434 // map. Loop over all of the PHIs and remove excess predecessor
436 BasicBlock::iterator I = NewBB->begin();
437 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
438 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
439 E = PredCount.end(); PCI != E; ++PCI) {
440 BasicBlock *Pred = PCI->first;
441 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
442 PN->removeIncomingValue(Pred, false);
447 // If the loops above have made these phi nodes have 0 or 1 operand,
448 // replace them with undef or the input value. We must do this for
449 // correctness, because 0-operand phis are not valid.
450 PN = cast<PHINode>(NewBB->begin());
451 if (PN->getNumIncomingValues() == 0) {
452 BasicBlock::iterator I = NewBB->begin();
453 BasicBlock::const_iterator OldI = OldBB->begin();
454 while ((PN = dyn_cast<PHINode>(I++))) {
455 Value *NV = UndefValue::get(PN->getType());
456 PN->replaceAllUsesWith(NV);
457 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
459 PN->eraseFromParent();
463 // NOTE: We cannot eliminate single entry phi nodes here, because of
464 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
465 // pointing at them. Thus, deleting one would require scanning the ValueMap
466 // to update any entries in it that would require that. This would be
470 // Now that the inlined function body has been fully constructed, go through
471 // and zap unconditional fall-through branches. This happen all the time when
472 // specializing code: code specialization turns conditional branches into
473 // uncond branches, and this code folds them.
474 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
475 while (I != NewFunc->end()) {
476 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
477 if (!BI || BI->isConditional()) { ++I; continue; }
479 // Note that we can't eliminate uncond branches if the destination has
480 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
481 // require scanning the ValueMap to update any entries that point to the phi
483 BasicBlock *Dest = BI->getSuccessor(0);
484 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
488 // We know all single-entry PHI nodes in the inlined function have been
489 // removed, so we just need to splice the blocks.
490 BI->eraseFromParent();
492 // Move all the instructions in the succ to the pred.
493 I->getInstList().splice(I->end(), Dest->getInstList());
495 // Make all PHI nodes that referred to Dest now refer to I as their source.
496 Dest->replaceAllUsesWith(I);
498 // Remove the dest block.
499 Dest->eraseFromParent();
501 // Do not increment I, iteratively merge all things this block branches to.