1 //===- CloneFunction.cpp - Clone a function into another function ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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 "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 = new BasicBlock("", F);
35 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
37 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
39 // Loop over all instructions, and copy them over.
40 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
42 Instruction *NewInst = II->clone();
44 NewInst->setName(II->getName()+NameSuffix);
45 NewBB->getInstList().push_back(NewInst);
46 ValueMap[II] = NewInst; // Add instruction map to value.
48 hasCalls |= isa<CallInst>(II);
49 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
50 if (isa<ConstantInt>(AI->getArraySize()))
51 hasStaticAllocas = true;
53 hasDynamicAllocas = true;
58 CodeInfo->ContainsCalls |= hasCalls;
59 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
60 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
61 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
62 BB != &BB->getParent()->front();
67 // Clone OldFunc into NewFunc, transforming the old arguments into references to
70 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
71 DenseMap<const Value*, Value*> &ValueMap,
72 std::vector<ReturnInst*> &Returns,
73 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
74 assert(NameSuffix && "NameSuffix cannot be null!");
77 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
78 E = OldFunc->arg_end(); I != E; ++I)
79 assert(ValueMap.count(I) && "No mapping from source argument specified!");
82 // Loop over all of the basic blocks in the function, cloning them as
83 // appropriate. Note that we save BE this way in order to handle cloning of
84 // recursive functions into themselves.
86 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
88 const BasicBlock &BB = *BI;
90 // Create a new basic block and copy instructions into it!
91 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
93 ValueMap[&BB] = CBB; // Add basic block mapping.
95 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
96 Returns.push_back(RI);
99 // Loop over all of the instructions in the function, fixing up operand
100 // references as we go. This uses ValueMap to do all the hard work.
102 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
103 BE = NewFunc->end(); BB != BE; ++BB)
104 // Loop over all instructions, fixing each one as we find it...
105 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
106 RemapInstruction(II, ValueMap);
109 /// CloneFunction - Return a copy of the specified function, but without
110 /// embedding the function into another module. Also, any references specified
111 /// in the ValueMap are changed to refer to their mapped value instead of the
112 /// original one. If any of the arguments to the function are in the ValueMap,
113 /// the arguments are deleted from the resultant function. The ValueMap is
114 /// updated to include mappings from all of the instructions and basicblocks in
115 /// the function from their old to new values.
117 Function *llvm::CloneFunction(const Function *F,
118 DenseMap<const Value*, Value*> &ValueMap,
119 ClonedCodeInfo *CodeInfo) {
120 std::vector<const Type*> ArgTypes;
122 // The user might be deleting arguments to the function by specifying them in
123 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
125 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
127 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
128 ArgTypes.push_back(I->getType());
130 // Create a new function type...
131 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
132 ArgTypes, F->getFunctionType()->isVarArg());
134 // Create the new function...
135 Function *NewF = new Function(FTy, F->getLinkage(), F->getName());
137 // Loop over the arguments, copying the names of the mapped arguments over...
138 Function::arg_iterator DestI = NewF->arg_begin();
139 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
141 if (ValueMap.count(I) == 0) { // Is this argument preserved?
142 DestI->setName(I->getName()); // Copy the name over...
143 ValueMap[I] = DestI++; // Add mapping to ValueMap
146 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
147 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
154 /// PruningFunctionCloner - This class is a private class used to implement
155 /// the CloneAndPruneFunctionInto method.
156 struct VISIBILITY_HIDDEN PruningFunctionCloner {
158 const Function *OldFunc;
159 DenseMap<const Value*, Value*> &ValueMap;
160 std::vector<ReturnInst*> &Returns;
161 const char *NameSuffix;
162 ClonedCodeInfo *CodeInfo;
163 const TargetData *TD;
166 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
167 DenseMap<const Value*, Value*> &valueMap,
168 std::vector<ReturnInst*> &returns,
169 const char *nameSuffix,
170 ClonedCodeInfo *codeInfo,
171 const TargetData *td)
172 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
173 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
176 /// CloneBlock - The specified block is found to be reachable, clone it and
177 /// anything that it can reach.
178 void CloneBlock(const BasicBlock *BB);
181 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
182 /// mapping its operands through ValueMap if they are available.
183 Constant *ConstantFoldMappedInstruction(const Instruction *I);
187 /// CloneBlock - The specified block is found to be reachable, clone it and
188 /// anything that it can reach.
189 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB) {
190 Value *&BBEntry = ValueMap[BB];
192 // Have we already cloned this block?
195 // Nope, clone it now.
197 BBEntry = NewBB = new BasicBlock();
198 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
200 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
202 // Loop over all instructions, and copy them over, DCE'ing as we go. This
203 // loop doesn't include the terminator.
204 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
206 // If this instruction constant folds, don't bother cloning the instruction,
207 // instead, just add the constant to the value map.
208 if (Constant *C = ConstantFoldMappedInstruction(II)) {
213 Instruction *NewInst = II->clone();
215 NewInst->setName(II->getName()+NameSuffix);
216 NewBB->getInstList().push_back(NewInst);
217 ValueMap[II] = NewInst; // Add instruction map to value.
219 hasCalls |= isa<CallInst>(II);
220 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
221 if (isa<ConstantInt>(AI->getArraySize()))
222 hasStaticAllocas = true;
224 hasDynamicAllocas = true;
228 // Finally, clone over the terminator.
229 const TerminatorInst *OldTI = BB->getTerminator();
230 bool TerminatorDone = false;
231 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
232 if (BI->isConditional()) {
233 // If the condition was a known constant in the callee...
234 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
235 // Or is a known constant in the caller...
237 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
239 // Constant fold to uncond branch!
241 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
242 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
244 TerminatorDone = true;
247 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
248 // If switching on a value known constant in the caller.
249 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
250 if (Cond == 0) // Or known constant after constant prop in the callee...
251 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
252 if (Cond) { // Constant fold to uncond branch!
253 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
254 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
256 TerminatorDone = true;
260 if (!TerminatorDone) {
261 Instruction *NewInst = OldTI->clone();
262 if (OldTI->hasName())
263 NewInst->setName(OldTI->getName()+NameSuffix);
264 NewBB->getInstList().push_back(NewInst);
265 ValueMap[OldTI] = NewInst; // Add instruction map to value.
267 // Recursively clone any reachable successor blocks.
268 const TerminatorInst *TI = BB->getTerminator();
269 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
270 CloneBlock(TI->getSuccessor(i));
274 CodeInfo->ContainsCalls |= hasCalls;
275 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
276 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
277 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
278 BB != &BB->getParent()->front();
281 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
282 Returns.push_back(RI);
285 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
286 /// mapping its operands through ValueMap if they are available.
287 Constant *PruningFunctionCloner::
288 ConstantFoldMappedInstruction(const Instruction *I) {
289 SmallVector<Constant*, 8> Ops;
290 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
291 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
295 return 0; // All operands not constant!
297 return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD);
300 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
301 /// except that it does some simple constant prop and DCE on the fly. The
302 /// effect of this is to copy significantly less code in cases where (for
303 /// example) a function call with constant arguments is inlined, and those
304 /// constant arguments cause a significant amount of code in the callee to be
305 /// dead. Since this doesn't produce an exactly copy of the input, it can't be
306 /// used for things like CloneFunction or CloneModule.
307 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
308 DenseMap<const Value*, Value*> &ValueMap,
309 std::vector<ReturnInst*> &Returns,
310 const char *NameSuffix,
311 ClonedCodeInfo *CodeInfo,
312 const TargetData *TD) {
313 assert(NameSuffix && "NameSuffix cannot be null!");
316 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
317 E = OldFunc->arg_end(); II != E; ++II)
318 assert(ValueMap.count(II) && "No mapping from source argument specified!");
321 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
322 NameSuffix, CodeInfo, TD);
324 // Clone the entry block, and anything recursively reachable from it.
325 PFC.CloneBlock(&OldFunc->getEntryBlock());
327 // Loop over all of the basic blocks in the old function. If the block was
328 // reachable, we have cloned it and the old block is now in the value map:
329 // insert it into the new function in the right order. If not, ignore it.
331 // Defer PHI resolution until rest of function is resolved.
332 std::vector<const PHINode*> PHIToResolve;
333 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
335 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
336 if (NewBB == 0) continue; // Dead block.
338 // Add the new block to the new function.
339 NewFunc->getBasicBlockList().push_back(NewBB);
341 // Loop over all of the instructions in the block, fixing up operand
342 // references as we go. This uses ValueMap to do all the hard work.
344 BasicBlock::iterator I = NewBB->begin();
346 // Handle PHI nodes specially, as we have to remove references to dead
348 if (PHINode *PN = dyn_cast<PHINode>(I)) {
349 // Skip over all PHI nodes, remembering them for later.
350 BasicBlock::const_iterator OldI = BI->begin();
351 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
352 PHIToResolve.push_back(cast<PHINode>(OldI));
355 // Otherwise, remap the rest of the instructions normally.
356 for (; I != NewBB->end(); ++I)
357 RemapInstruction(I, ValueMap);
360 // Defer PHI resolution until rest of function is resolved, PHI resolution
361 // requires the CFG to be up-to-date.
362 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
363 const PHINode *OPN = PHIToResolve[phino];
364 unsigned NumPreds = OPN->getNumIncomingValues();
365 const BasicBlock *OldBB = OPN->getParent();
366 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
368 // Map operands for blocks that are live and remove operands for blocks
370 for (; phino != PHIToResolve.size() &&
371 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
372 OPN = PHIToResolve[phino];
373 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
374 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
375 if (BasicBlock *MappedBlock =
376 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
377 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
378 assert(InVal && "Unknown input value?");
379 PN->setIncomingValue(pred, InVal);
380 PN->setIncomingBlock(pred, MappedBlock);
382 PN->removeIncomingValue(pred, false);
383 --pred, --e; // Revisit the next entry.
388 // The loop above has removed PHI entries for those blocks that are dead
389 // and has updated others. However, if a block is live (i.e. copied over)
390 // but its terminator has been changed to not go to this block, then our
391 // phi nodes will have invalid entries. Update the PHI nodes in this
393 PHINode *PN = cast<PHINode>(NewBB->begin());
394 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
395 if (NumPreds != PN->getNumIncomingValues()) {
396 assert(NumPreds < PN->getNumIncomingValues());
397 // Count how many times each predecessor comes to this block.
398 std::map<BasicBlock*, unsigned> PredCount;
399 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
403 // Figure out how many entries to remove from each PHI.
404 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
405 ++PredCount[PN->getIncomingBlock(i)];
407 // At this point, the excess predecessor entries are positive in the
408 // map. Loop over all of the PHIs and remove excess predecessor
410 BasicBlock::iterator I = NewBB->begin();
411 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
412 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
413 E = PredCount.end(); PCI != E; ++PCI) {
414 BasicBlock *Pred = PCI->first;
415 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
416 PN->removeIncomingValue(Pred, false);
421 // If the loops above have made these phi nodes have 0 or 1 operand,
422 // replace them with undef or the input value. We must do this for
423 // correctness, because 0-operand phis are not valid.
424 PN = cast<PHINode>(NewBB->begin());
425 if (PN->getNumIncomingValues() == 0) {
426 BasicBlock::iterator I = NewBB->begin();
427 BasicBlock::const_iterator OldI = OldBB->begin();
428 while ((PN = dyn_cast<PHINode>(I++))) {
429 Value *NV = UndefValue::get(PN->getType());
430 PN->replaceAllUsesWith(NV);
431 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
433 PN->eraseFromParent();
437 // NOTE: We cannot eliminate single entry phi nodes here, because of
438 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
439 // pointing at them. Thus, deleting one would require scanning the ValueMap
440 // to update any entries in it that would require that. This would be
444 // Now that the inlined function body has been fully constructed, go through
445 // and zap unconditional fall-through branches. This happen all the time when
446 // specializing code: code specialization turns conditional branches into
447 // uncond branches, and this code folds them.
448 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
449 while (I != NewFunc->end()) {
450 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
451 if (!BI || BI->isConditional()) { ++I; continue; }
453 // Note that we can't eliminate uncond branches if the destination has
454 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
455 // require scanning the ValueMap to update any entries that point to the phi
457 BasicBlock *Dest = BI->getSuccessor(0);
458 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
462 // We know all single-entry PHI nodes in the inlined function have been
463 // removed, so we just need to splice the blocks.
464 BI->eraseFromParent();
466 // Move all the instructions in the succ to the pred.
467 I->getInstList().splice(I->end(), Dest->getInstList());
469 // Make all PHI nodes that referred to Dest now refer to I as their source.
470 Dest->replaceAllUsesWith(I);
472 // Remove the dest block.
473 Dest->eraseFromParent();
475 // Do not increment I, iteratively merge all things this block branches to.