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,
179 std::vector<const BasicBlock*> &ToClone);
182 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
183 /// mapping its operands through ValueMap if they are available.
184 Constant *ConstantFoldMappedInstruction(const Instruction *I);
188 /// CloneBlock - The specified block is found to be reachable, clone it and
189 /// anything that it can reach.
190 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
191 std::vector<const BasicBlock*> &ToClone){
192 Value *&BBEntry = ValueMap[BB];
194 // Have we already cloned this block?
197 // Nope, clone it now.
199 BBEntry = NewBB = new BasicBlock();
200 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
202 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
204 // Loop over all instructions, and copy them over, DCE'ing as we go. This
205 // loop doesn't include the terminator.
206 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
208 // If this instruction constant folds, don't bother cloning the instruction,
209 // instead, just add the constant to the value map.
210 if (Constant *C = ConstantFoldMappedInstruction(II)) {
215 Instruction *NewInst = II->clone();
217 NewInst->setName(II->getName()+NameSuffix);
218 NewBB->getInstList().push_back(NewInst);
219 ValueMap[II] = NewInst; // Add instruction map to value.
221 hasCalls |= isa<CallInst>(II);
222 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
223 if (isa<ConstantInt>(AI->getArraySize()))
224 hasStaticAllocas = true;
226 hasDynamicAllocas = true;
230 // Finally, clone over the terminator.
231 const TerminatorInst *OldTI = BB->getTerminator();
232 bool TerminatorDone = false;
233 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
234 if (BI->isConditional()) {
235 // If the condition was a known constant in the callee...
236 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
237 // Or is a known constant in the caller...
239 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
241 // Constant fold to uncond branch!
243 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
244 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
245 ToClone.push_back(Dest);
246 TerminatorDone = true;
249 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
250 // If switching on a value known constant in the caller.
251 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
252 if (Cond == 0) // Or known constant after constant prop in the callee...
253 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
254 if (Cond) { // Constant fold to uncond branch!
255 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
256 ValueMap[OldTI] = new BranchInst(Dest, NewBB);
257 ToClone.push_back(Dest);
258 TerminatorDone = true;
262 if (!TerminatorDone) {
263 Instruction *NewInst = OldTI->clone();
264 if (OldTI->hasName())
265 NewInst->setName(OldTI->getName()+NameSuffix);
266 NewBB->getInstList().push_back(NewInst);
267 ValueMap[OldTI] = NewInst; // Add instruction map to value.
269 // Recursively clone any reachable successor blocks.
270 const TerminatorInst *TI = BB->getTerminator();
271 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
272 ToClone.push_back(TI->getSuccessor(i));
276 CodeInfo->ContainsCalls |= hasCalls;
277 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
278 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
279 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
280 BB != &BB->getParent()->front();
283 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
284 Returns.push_back(RI);
287 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
288 /// mapping its operands through ValueMap if they are available.
289 Constant *PruningFunctionCloner::
290 ConstantFoldMappedInstruction(const Instruction *I) {
291 SmallVector<Constant*, 8> Ops;
292 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
293 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
297 return 0; // All operands not constant!
299 return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD);
302 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
303 /// except that it does some simple constant prop and DCE on the fly. The
304 /// effect of this is to copy significantly less code in cases where (for
305 /// example) a function call with constant arguments is inlined, and those
306 /// constant arguments cause a significant amount of code in the callee to be
307 /// dead. Since this doesn't produce an exactly copy of the input, it can't be
308 /// used for things like CloneFunction or CloneModule.
309 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
310 DenseMap<const Value*, Value*> &ValueMap,
311 std::vector<ReturnInst*> &Returns,
312 const char *NameSuffix,
313 ClonedCodeInfo *CodeInfo,
314 const TargetData *TD) {
315 assert(NameSuffix && "NameSuffix cannot be null!");
318 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
319 E = OldFunc->arg_end(); II != E; ++II)
320 assert(ValueMap.count(II) && "No mapping from source argument specified!");
323 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
324 NameSuffix, CodeInfo, TD);
326 // Clone the entry block, and anything recursively reachable from it.
327 std::vector<const BasicBlock*> CloneWorklist;
328 CloneWorklist.push_back(&OldFunc->getEntryBlock());
329 while (!CloneWorklist.empty()) {
330 const BasicBlock *BB = CloneWorklist.back();
331 CloneWorklist.pop_back();
332 PFC.CloneBlock(BB, CloneWorklist);
335 // Loop over all of the basic blocks in the old function. If the block was
336 // reachable, we have cloned it and the old block is now in the value map:
337 // insert it into the new function in the right order. If not, ignore it.
339 // Defer PHI resolution until rest of function is resolved.
340 std::vector<const PHINode*> PHIToResolve;
341 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
343 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
344 if (NewBB == 0) continue; // Dead block.
346 // Add the new block to the new function.
347 NewFunc->getBasicBlockList().push_back(NewBB);
349 // Loop over all of the instructions in the block, fixing up operand
350 // references as we go. This uses ValueMap to do all the hard work.
352 BasicBlock::iterator I = NewBB->begin();
354 // Handle PHI nodes specially, as we have to remove references to dead
356 if (PHINode *PN = dyn_cast<PHINode>(I)) {
357 // Skip over all PHI nodes, remembering them for later.
358 BasicBlock::const_iterator OldI = BI->begin();
359 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
360 PHIToResolve.push_back(cast<PHINode>(OldI));
363 // Otherwise, remap the rest of the instructions normally.
364 for (; I != NewBB->end(); ++I)
365 RemapInstruction(I, ValueMap);
368 // Defer PHI resolution until rest of function is resolved, PHI resolution
369 // requires the CFG to be up-to-date.
370 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
371 const PHINode *OPN = PHIToResolve[phino];
372 unsigned NumPreds = OPN->getNumIncomingValues();
373 const BasicBlock *OldBB = OPN->getParent();
374 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
376 // Map operands for blocks that are live and remove operands for blocks
378 for (; phino != PHIToResolve.size() &&
379 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
380 OPN = PHIToResolve[phino];
381 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
382 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
383 if (BasicBlock *MappedBlock =
384 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
385 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
386 assert(InVal && "Unknown input value?");
387 PN->setIncomingValue(pred, InVal);
388 PN->setIncomingBlock(pred, MappedBlock);
390 PN->removeIncomingValue(pred, false);
391 --pred, --e; // Revisit the next entry.
396 // The loop above has removed PHI entries for those blocks that are dead
397 // and has updated others. However, if a block is live (i.e. copied over)
398 // but its terminator has been changed to not go to this block, then our
399 // phi nodes will have invalid entries. Update the PHI nodes in this
401 PHINode *PN = cast<PHINode>(NewBB->begin());
402 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
403 if (NumPreds != PN->getNumIncomingValues()) {
404 assert(NumPreds < PN->getNumIncomingValues());
405 // Count how many times each predecessor comes to this block.
406 std::map<BasicBlock*, unsigned> PredCount;
407 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
411 // Figure out how many entries to remove from each PHI.
412 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
413 ++PredCount[PN->getIncomingBlock(i)];
415 // At this point, the excess predecessor entries are positive in the
416 // map. Loop over all of the PHIs and remove excess predecessor
418 BasicBlock::iterator I = NewBB->begin();
419 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
420 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
421 E = PredCount.end(); PCI != E; ++PCI) {
422 BasicBlock *Pred = PCI->first;
423 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
424 PN->removeIncomingValue(Pred, false);
429 // If the loops above have made these phi nodes have 0 or 1 operand,
430 // replace them with undef or the input value. We must do this for
431 // correctness, because 0-operand phis are not valid.
432 PN = cast<PHINode>(NewBB->begin());
433 if (PN->getNumIncomingValues() == 0) {
434 BasicBlock::iterator I = NewBB->begin();
435 BasicBlock::const_iterator OldI = OldBB->begin();
436 while ((PN = dyn_cast<PHINode>(I++))) {
437 Value *NV = UndefValue::get(PN->getType());
438 PN->replaceAllUsesWith(NV);
439 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
441 PN->eraseFromParent();
445 // NOTE: We cannot eliminate single entry phi nodes here, because of
446 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
447 // pointing at them. Thus, deleting one would require scanning the ValueMap
448 // to update any entries in it that would require that. This would be
452 // Now that the inlined function body has been fully constructed, go through
453 // and zap unconditional fall-through branches. This happen all the time when
454 // specializing code: code specialization turns conditional branches into
455 // uncond branches, and this code folds them.
456 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
457 while (I != NewFunc->end()) {
458 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
459 if (!BI || BI->isConditional()) { ++I; continue; }
461 // Note that we can't eliminate uncond branches if the destination has
462 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
463 // require scanning the ValueMap to update any entries that point to the phi
465 BasicBlock *Dest = BI->getSuccessor(0);
466 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
470 // We know all single-entry PHI nodes in the inlined function have been
471 // removed, so we just need to splice the blocks.
472 BI->eraseFromParent();
474 // Move all the instructions in the succ to the pred.
475 I->getInstList().splice(I->end(), Dest->getInstList());
477 // Make all PHI nodes that referred to Dest now refer to I as their source.
478 Dest->replaceAllUsesWith(I);
480 // Remove the dest block.
481 Dest->eraseFromParent();
483 // Do not increment I, iteratively merge all things this block branches to.