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 = new BasicBlock("", 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 // Loop over all of the basic blocks in the function, cloning them as
87 // appropriate. Note that we save BE this way in order to handle cloning of
88 // recursive functions into themselves.
90 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
92 const BasicBlock &BB = *BI;
94 // Create a new basic block and copy instructions into it!
95 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
97 ValueMap[&BB] = CBB; // Add basic block mapping.
99 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
100 Returns.push_back(RI);
103 // Loop over all of the instructions in the function, fixing up operand
104 // references as we go. This uses ValueMap to do all the hard work.
106 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
107 BE = NewFunc->end(); BB != BE; ++BB) {
108 // Fix up the unwind destination.
109 if (BasicBlock *UnwindDest = BB->getUnwindDest())
110 BB->setUnwindDest(cast<BasicBlock>(ValueMap[UnwindDest]));
112 // Loop over all instructions, fixing each one as we find it...
113 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
114 RemapInstruction(II, ValueMap);
118 /// CloneFunction - Return a copy of the specified function, but without
119 /// embedding the function into another module. Also, any references specified
120 /// in the ValueMap are changed to refer to their mapped value instead of the
121 /// original one. If any of the arguments to the function are in the ValueMap,
122 /// the arguments are deleted from the resultant function. The ValueMap is
123 /// updated to include mappings from all of the instructions and basicblocks in
124 /// the function from their old to new values.
126 Function *llvm::CloneFunction(const Function *F,
127 DenseMap<const Value*, Value*> &ValueMap,
128 ClonedCodeInfo *CodeInfo) {
129 std::vector<const Type*> ArgTypes;
131 // The user might be deleting arguments to the function by specifying them in
132 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
134 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
136 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
137 ArgTypes.push_back(I->getType());
139 // Create a new function type...
140 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
141 ArgTypes, F->getFunctionType()->isVarArg());
143 // Create the new function...
144 Function *NewF = new Function(FTy, F->getLinkage(), F->getName());
146 // Loop over the arguments, copying the names of the mapped arguments over...
147 Function::arg_iterator DestI = NewF->arg_begin();
148 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
150 if (ValueMap.count(I) == 0) { // Is this argument preserved?
151 DestI->setName(I->getName()); // Copy the name over...
152 ValueMap[I] = DestI++; // Add mapping to ValueMap
155 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
156 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
163 /// PruningFunctionCloner - This class is a private class used to implement
164 /// the CloneAndPruneFunctionInto method.
165 struct VISIBILITY_HIDDEN PruningFunctionCloner {
167 const Function *OldFunc;
168 DenseMap<const Value*, Value*> &ValueMap;
169 std::vector<ReturnInst*> &Returns;
170 const char *NameSuffix;
171 ClonedCodeInfo *CodeInfo;
172 const TargetData *TD;
175 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
176 DenseMap<const Value*, Value*> &valueMap,
177 std::vector<ReturnInst*> &returns,
178 const char *nameSuffix,
179 ClonedCodeInfo *codeInfo,
180 const TargetData *td)
181 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
182 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
185 /// CloneBlock - The specified block is found to be reachable, clone it and
186 /// anything that it can reach.
187 void CloneBlock(const BasicBlock *BB,
188 std::vector<const BasicBlock*> &ToClone);
191 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
192 /// mapping its operands through ValueMap if they are available.
193 Constant *ConstantFoldMappedInstruction(const Instruction *I);
197 /// CloneBlock - The specified block is found to be reachable, clone it and
198 /// anything that it can reach.
199 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
200 std::vector<const BasicBlock*> &ToClone){
201 Value *&BBEntry = ValueMap[BB];
203 // Have we already cloned this block?
206 // Nope, clone it now.
208 BBEntry = NewBB = new BasicBlock();
209 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
211 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
213 // Loop over all instructions, and copy them over, DCE'ing as we go. This
214 // loop doesn't include the terminator.
215 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
217 // If this instruction constant folds, don't bother cloning the instruction,
218 // instead, just add the constant to the value map.
219 if (Constant *C = ConstantFoldMappedInstruction(II)) {
224 Instruction *NewInst = II->clone();
226 NewInst->setName(II->getName()+NameSuffix);
227 NewBB->getInstList().push_back(NewInst);
228 ValueMap[II] = NewInst; // Add instruction map to value.
230 hasCalls |= isa<CallInst>(II);
231 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
232 if (isa<ConstantInt>(AI->getArraySize()))
233 hasStaticAllocas = true;
235 hasDynamicAllocas = true;
239 // Finally, clone over the terminator.
240 const TerminatorInst *OldTI = BB->getTerminator();
241 bool TerminatorDone = false;
242 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
243 if (BI->isConditional()) {
244 // If the condition was a known constant in the callee...
245 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
246 // Or is a known constant in the caller...
248 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
250 // Constant fold to uncond branch!
252 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
253 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
254 ToClone.push_back(Dest);
255 TerminatorDone = true;
258 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
259 // If switching on a value known constant in the caller.
260 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
261 if (Cond == 0) // Or known constant after constant prop in the callee...
262 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
263 if (Cond) { // Constant fold to uncond branch!
264 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
265 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
266 ToClone.push_back(Dest);
267 TerminatorDone = true;
271 if (!TerminatorDone) {
272 Instruction *NewInst = OldTI->clone();
273 if (OldTI->hasName())
274 NewInst->setName(OldTI->getName()+NameSuffix);
275 NewBB->getInstList().push_back(NewInst);
276 ValueMap[OldTI] = NewInst; // Add instruction map to value.
278 // Recursively clone any reachable successor blocks.
279 const TerminatorInst *TI = BB->getTerminator();
280 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
281 ToClone.push_back(TI->getSuccessor(i));
285 CodeInfo->ContainsCalls |= hasCalls;
286 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
287 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
288 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
289 BB != &BB->getParent()->front();
292 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
293 Returns.push_back(RI);
296 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
297 /// mapping its operands through ValueMap if they are available.
298 Constant *PruningFunctionCloner::
299 ConstantFoldMappedInstruction(const Instruction *I) {
300 SmallVector<Constant*, 8> Ops;
301 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
302 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
306 return 0; // All operands not constant!
309 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
310 return ConstantFoldCompareInstOperands(CI->getPredicate(),
311 &Ops[0], Ops.size(), TD);
313 return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
314 &Ops[0], Ops.size(), TD);
317 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
318 /// except that it does some simple constant prop and DCE on the fly. The
319 /// effect of this is to copy significantly less code in cases where (for
320 /// example) a function call with constant arguments is inlined, and those
321 /// constant arguments cause a significant amount of code in the callee to be
322 /// dead. Since this doesn't produce an exact copy of the input, it can't be
323 /// used for things like CloneFunction or CloneModule.
324 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
325 DenseMap<const Value*, Value*> &ValueMap,
326 std::vector<ReturnInst*> &Returns,
327 const char *NameSuffix,
328 ClonedCodeInfo *CodeInfo,
329 const TargetData *TD) {
330 assert(NameSuffix && "NameSuffix cannot be null!");
333 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
334 E = OldFunc->arg_end(); II != E; ++II)
335 assert(ValueMap.count(II) && "No mapping from source argument specified!");
338 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
339 NameSuffix, CodeInfo, TD);
341 // Clone the entry block, and anything recursively reachable from it.
342 std::vector<const BasicBlock*> CloneWorklist;
343 CloneWorklist.push_back(&OldFunc->getEntryBlock());
344 while (!CloneWorklist.empty()) {
345 const BasicBlock *BB = CloneWorklist.back();
346 CloneWorklist.pop_back();
347 PFC.CloneBlock(BB, CloneWorklist);
350 // Loop over all of the basic blocks in the old function. If the block was
351 // reachable, we have cloned it and the old block is now in the value map:
352 // insert it into the new function in the right order. If not, ignore it.
354 // Defer PHI resolution until rest of function is resolved.
355 std::vector<const PHINode*> PHIToResolve;
356 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
358 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
359 if (NewBB == 0) continue; // Dead block.
361 // Add the new block to the new function.
362 NewFunc->getBasicBlockList().push_back(NewBB);
364 // Loop over all of the instructions in the block, fixing up operand
365 // references as we go. This uses ValueMap to do all the hard work.
367 BasicBlock::iterator I = NewBB->begin();
369 // Handle PHI nodes specially, as we have to remove references to dead
371 if (PHINode *PN = dyn_cast<PHINode>(I)) {
372 // Skip over all PHI nodes, remembering them for later.
373 BasicBlock::const_iterator OldI = BI->begin();
374 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
375 PHIToResolve.push_back(cast<PHINode>(OldI));
378 // Otherwise, remap the rest of the instructions normally.
379 for (; I != NewBB->end(); ++I)
380 RemapInstruction(I, ValueMap);
383 // Defer PHI resolution until rest of function is resolved, PHI resolution
384 // requires the CFG to be up-to-date.
385 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
386 const PHINode *OPN = PHIToResolve[phino];
387 unsigned NumPreds = OPN->getNumIncomingValues();
388 const BasicBlock *OldBB = OPN->getParent();
389 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
391 // Map operands for blocks that are live and remove operands for blocks
393 for (; phino != PHIToResolve.size() &&
394 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
395 OPN = PHIToResolve[phino];
396 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
397 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
398 if (BasicBlock *MappedBlock =
399 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
400 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
401 assert(InVal && "Unknown input value?");
402 PN->setIncomingValue(pred, InVal);
403 PN->setIncomingBlock(pred, MappedBlock);
405 PN->removeIncomingValue(pred, false);
406 --pred, --e; // Revisit the next entry.
411 // The loop above has removed PHI entries for those blocks that are dead
412 // and has updated others. However, if a block is live (i.e. copied over)
413 // but its terminator has been changed to not go to this block, then our
414 // phi nodes will have invalid entries. Update the PHI nodes in this
416 PHINode *PN = cast<PHINode>(NewBB->begin());
417 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
418 if (NumPreds != PN->getNumIncomingValues()) {
419 assert(NumPreds < PN->getNumIncomingValues());
420 // Count how many times each predecessor comes to this block.
421 std::map<BasicBlock*, unsigned> PredCount;
422 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
426 // Figure out how many entries to remove from each PHI.
427 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
428 ++PredCount[PN->getIncomingBlock(i)];
430 // At this point, the excess predecessor entries are positive in the
431 // map. Loop over all of the PHIs and remove excess predecessor
433 BasicBlock::iterator I = NewBB->begin();
434 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
435 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
436 E = PredCount.end(); PCI != E; ++PCI) {
437 BasicBlock *Pred = PCI->first;
438 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
439 PN->removeIncomingValue(Pred, false);
444 // If the loops above have made these phi nodes have 0 or 1 operand,
445 // replace them with undef or the input value. We must do this for
446 // correctness, because 0-operand phis are not valid.
447 PN = cast<PHINode>(NewBB->begin());
448 if (PN->getNumIncomingValues() == 0) {
449 BasicBlock::iterator I = NewBB->begin();
450 BasicBlock::const_iterator OldI = OldBB->begin();
451 while ((PN = dyn_cast<PHINode>(I++))) {
452 Value *NV = UndefValue::get(PN->getType());
453 PN->replaceAllUsesWith(NV);
454 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
456 PN->eraseFromParent();
460 // NOTE: We cannot eliminate single entry phi nodes here, because of
461 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
462 // pointing at them. Thus, deleting one would require scanning the ValueMap
463 // to update any entries in it that would require that. This would be
467 // Now that the inlined function body has been fully constructed, go through
468 // and zap unconditional fall-through branches. This happen all the time when
469 // specializing code: code specialization turns conditional branches into
470 // uncond branches, and this code folds them.
471 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
472 while (I != NewFunc->end()) {
473 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
474 if (!BI || BI->isConditional()) { ++I; continue; }
476 // Note that we can't eliminate uncond branches if the destination has
477 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
478 // require scanning the ValueMap to update any entries that point to the phi
480 BasicBlock *Dest = BI->getSuccessor(0);
481 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
485 // We know all single-entry PHI nodes in the inlined function have been
486 // removed, so we just need to splice the blocks.
487 BI->eraseFromParent();
489 // Move all the instructions in the succ to the pred.
490 I->getInstList().splice(I->end(), Dest->getInstList());
492 // Make all PHI nodes that referred to Dest now refer to I as their source.
493 Dest->replaceAllUsesWith(I);
495 // Remove the dest block.
496 Dest->eraseFromParent();
498 // Do not increment I, iteratively merge all things this block branches to.