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/GlobalVariable.h"
21 #include "llvm/Function.h"
22 #include "llvm/Support/CFG.h"
23 #include "llvm/Support/Compiler.h"
24 #include "llvm/Transforms/Utils/ValueMapper.h"
25 #include "llvm/Analysis/ConstantFolding.h"
26 #include "llvm/ADT/SmallVector.h"
30 // CloneBasicBlock - See comments in Cloning.h
31 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
32 DenseMap<const Value*, Value*> &ValueMap,
33 const char *NameSuffix, Function *F,
34 ClonedCodeInfo *CodeInfo) {
35 BasicBlock *NewBB = BasicBlock::Create("", F);
36 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
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 any attributes.
84 if (NewFunc->arg_size() == OldFunc->arg_size())
85 NewFunc->copyAttributesFrom(OldFunc);
87 //Some arguments were deleted with the ValueMap. Copy arguments one by one
88 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
89 E = OldFunc->arg_end(); I != E; ++I)
90 if (Argument* Anew = dyn_cast<Argument>(ValueMap[I]))
91 Anew->addAttr( OldFunc->getAttributes()
92 .getParamAttributes(I->getArgNo() + 1));
93 NewFunc->setAttributes(NewFunc->getAttributes()
94 .addAttr(0, OldFunc->getAttributes()
95 .getRetAttributes()));
96 NewFunc->setAttributes(NewFunc->getAttributes()
97 .addAttr(~0, OldFunc->getAttributes()
102 // Loop over all of the basic blocks in the function, cloning them as
103 // appropriate. Note that we save BE this way in order to handle cloning of
104 // recursive functions into themselves.
106 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
108 const BasicBlock &BB = *BI;
110 // Create a new basic block and copy instructions into it!
111 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
113 ValueMap[&BB] = CBB; // Add basic block mapping.
115 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
116 Returns.push_back(RI);
119 // Loop over all of the instructions in the function, fixing up operand
120 // references as we go. This uses ValueMap to do all the hard work.
122 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
123 BE = NewFunc->end(); BB != BE; ++BB)
124 // Loop over all instructions, fixing each one as we find it...
125 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
126 RemapInstruction(II, ValueMap);
129 /// CloneFunction - Return a copy of the specified function, but without
130 /// embedding the function into another module. Also, any references specified
131 /// in the ValueMap are changed to refer to their mapped value instead of the
132 /// original one. If any of the arguments to the function are in the ValueMap,
133 /// the arguments are deleted from the resultant function. The ValueMap is
134 /// updated to include mappings from all of the instructions and basicblocks in
135 /// the function from their old to new values.
137 Function *llvm::CloneFunction(const Function *F,
138 DenseMap<const Value*, Value*> &ValueMap,
139 ClonedCodeInfo *CodeInfo) {
140 std::vector<const Type*> ArgTypes;
142 // The user might be deleting arguments to the function by specifying them in
143 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
145 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
147 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
148 ArgTypes.push_back(I->getType());
150 // Create a new function type...
151 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
152 ArgTypes, F->getFunctionType()->isVarArg());
154 // Create the new function...
155 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
157 // Loop over the arguments, copying the names of the mapped arguments over...
158 Function::arg_iterator DestI = NewF->arg_begin();
159 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
161 if (ValueMap.count(I) == 0) { // Is this argument preserved?
162 DestI->setName(I->getName()); // Copy the name over...
163 ValueMap[I] = DestI++; // Add mapping to ValueMap
166 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
167 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
174 /// PruningFunctionCloner - This class is a private class used to implement
175 /// the CloneAndPruneFunctionInto method.
176 struct VISIBILITY_HIDDEN PruningFunctionCloner {
178 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;
186 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
187 DenseMap<const Value*, Value*> &valueMap,
188 std::vector<ReturnInst*> &returns,
189 const char *nameSuffix,
190 ClonedCodeInfo *codeInfo,
191 const TargetData *td)
192 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
193 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
196 /// CloneBlock - The specified block is found to be reachable, clone it and
197 /// anything that it can reach.
198 void CloneBlock(const BasicBlock *BB,
199 std::vector<const BasicBlock*> &ToClone);
202 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
203 /// mapping its operands through ValueMap if they are available.
204 Constant *ConstantFoldMappedInstruction(const Instruction *I);
208 /// CloneBlock - The specified block is found to be reachable, clone it and
209 /// anything that it can reach.
210 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
211 std::vector<const BasicBlock*> &ToClone){
212 Value *&BBEntry = ValueMap[BB];
214 // Have we already cloned this block?
217 // Nope, clone it now.
219 BBEntry = NewBB = BasicBlock::Create();
220 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
222 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
224 // Loop over all instructions, and copy them over, DCE'ing as we go. This
225 // loop doesn't include the terminator.
226 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
228 // If this instruction constant folds, don't bother cloning the instruction,
229 // instead, just add the constant to the value map.
230 if (Constant *C = ConstantFoldMappedInstruction(II)) {
235 Instruction *NewInst = II->clone();
237 NewInst->setName(II->getName()+NameSuffix);
238 NewBB->getInstList().push_back(NewInst);
239 ValueMap[II] = NewInst; // Add instruction map to value.
241 hasCalls |= isa<CallInst>(II);
242 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
243 if (isa<ConstantInt>(AI->getArraySize()))
244 hasStaticAllocas = true;
246 hasDynamicAllocas = true;
250 // Finally, clone over the terminator.
251 const TerminatorInst *OldTI = BB->getTerminator();
252 bool TerminatorDone = false;
253 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
254 if (BI->isConditional()) {
255 // If the condition was a known constant in the callee...
256 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
257 // Or is a known constant in the caller...
259 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
261 // Constant fold to uncond branch!
263 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
264 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
265 ToClone.push_back(Dest);
266 TerminatorDone = true;
269 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
270 // If switching on a value known constant in the caller.
271 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
272 if (Cond == 0) // Or known constant after constant prop in the callee...
273 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
274 if (Cond) { // Constant fold to uncond branch!
275 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
276 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
277 ToClone.push_back(Dest);
278 TerminatorDone = true;
282 if (!TerminatorDone) {
283 Instruction *NewInst = OldTI->clone();
284 if (OldTI->hasName())
285 NewInst->setName(OldTI->getName()+NameSuffix);
286 NewBB->getInstList().push_back(NewInst);
287 ValueMap[OldTI] = NewInst; // Add instruction map to value.
289 // Recursively clone any reachable successor blocks.
290 const TerminatorInst *TI = BB->getTerminator();
291 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
292 ToClone.push_back(TI->getSuccessor(i));
296 CodeInfo->ContainsCalls |= hasCalls;
297 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
298 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
299 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
300 BB != &BB->getParent()->front();
303 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
304 Returns.push_back(RI);
307 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
308 /// mapping its operands through ValueMap if they are available.
309 Constant *PruningFunctionCloner::
310 ConstantFoldMappedInstruction(const Instruction *I) {
311 SmallVector<Constant*, 8> Ops;
312 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
313 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
317 return 0; // All operands not constant!
319 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
320 return ConstantFoldCompareInstOperands(CI->getPredicate(),
321 &Ops[0], Ops.size(), TD);
323 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
324 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
325 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
326 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
327 if (GV->isConstant() && !GV->isDeclaration())
328 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
331 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
335 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
336 /// except that it does some simple constant prop and DCE on the fly. The
337 /// effect of this is to copy significantly less code in cases where (for
338 /// example) a function call with constant arguments is inlined, and those
339 /// constant arguments cause a significant amount of code in the callee to be
340 /// dead. Since this doesn't produce an exact copy of the input, it can't be
341 /// used for things like CloneFunction or CloneModule.
342 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
343 DenseMap<const Value*, Value*> &ValueMap,
344 std::vector<ReturnInst*> &Returns,
345 const char *NameSuffix,
346 ClonedCodeInfo *CodeInfo,
347 const TargetData *TD) {
348 assert(NameSuffix && "NameSuffix cannot be null!");
351 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
352 E = OldFunc->arg_end(); II != E; ++II)
353 assert(ValueMap.count(II) && "No mapping from source argument specified!");
356 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
357 NameSuffix, CodeInfo, TD);
359 // Clone the entry block, and anything recursively reachable from it.
360 std::vector<const BasicBlock*> CloneWorklist;
361 CloneWorklist.push_back(&OldFunc->getEntryBlock());
362 while (!CloneWorklist.empty()) {
363 const BasicBlock *BB = CloneWorklist.back();
364 CloneWorklist.pop_back();
365 PFC.CloneBlock(BB, CloneWorklist);
368 // Loop over all of the basic blocks in the old function. If the block was
369 // reachable, we have cloned it and the old block is now in the value map:
370 // insert it into the new function in the right order. If not, ignore it.
372 // Defer PHI resolution until rest of function is resolved.
373 std::vector<const PHINode*> PHIToResolve;
374 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
376 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
377 if (NewBB == 0) continue; // Dead block.
379 // Add the new block to the new function.
380 NewFunc->getBasicBlockList().push_back(NewBB);
382 // Loop over all of the instructions in the block, fixing up operand
383 // references as we go. This uses ValueMap to do all the hard work.
385 BasicBlock::iterator I = NewBB->begin();
387 // Handle PHI nodes specially, as we have to remove references to dead
389 if (PHINode *PN = dyn_cast<PHINode>(I)) {
390 // Skip over all PHI nodes, remembering them for later.
391 BasicBlock::const_iterator OldI = BI->begin();
392 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
393 PHIToResolve.push_back(cast<PHINode>(OldI));
396 // Otherwise, remap the rest of the instructions normally.
397 for (; I != NewBB->end(); ++I)
398 RemapInstruction(I, ValueMap);
401 // Defer PHI resolution until rest of function is resolved, PHI resolution
402 // requires the CFG to be up-to-date.
403 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
404 const PHINode *OPN = PHIToResolve[phino];
405 unsigned NumPreds = OPN->getNumIncomingValues();
406 const BasicBlock *OldBB = OPN->getParent();
407 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
409 // Map operands for blocks that are live and remove operands for blocks
411 for (; phino != PHIToResolve.size() &&
412 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
413 OPN = PHIToResolve[phino];
414 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
415 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
416 if (BasicBlock *MappedBlock =
417 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
418 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
419 assert(InVal && "Unknown input value?");
420 PN->setIncomingValue(pred, InVal);
421 PN->setIncomingBlock(pred, MappedBlock);
423 PN->removeIncomingValue(pred, false);
424 --pred, --e; // Revisit the next entry.
429 // The loop above has removed PHI entries for those blocks that are dead
430 // and has updated others. However, if a block is live (i.e. copied over)
431 // but its terminator has been changed to not go to this block, then our
432 // phi nodes will have invalid entries. Update the PHI nodes in this
434 PHINode *PN = cast<PHINode>(NewBB->begin());
435 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
436 if (NumPreds != PN->getNumIncomingValues()) {
437 assert(NumPreds < PN->getNumIncomingValues());
438 // Count how many times each predecessor comes to this block.
439 std::map<BasicBlock*, unsigned> PredCount;
440 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
444 // Figure out how many entries to remove from each PHI.
445 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
446 ++PredCount[PN->getIncomingBlock(i)];
448 // At this point, the excess predecessor entries are positive in the
449 // map. Loop over all of the PHIs and remove excess predecessor
451 BasicBlock::iterator I = NewBB->begin();
452 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
453 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
454 E = PredCount.end(); PCI != E; ++PCI) {
455 BasicBlock *Pred = PCI->first;
456 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
457 PN->removeIncomingValue(Pred, false);
462 // If the loops above have made these phi nodes have 0 or 1 operand,
463 // replace them with undef or the input value. We must do this for
464 // correctness, because 0-operand phis are not valid.
465 PN = cast<PHINode>(NewBB->begin());
466 if (PN->getNumIncomingValues() == 0) {
467 BasicBlock::iterator I = NewBB->begin();
468 BasicBlock::const_iterator OldI = OldBB->begin();
469 while ((PN = dyn_cast<PHINode>(I++))) {
470 Value *NV = UndefValue::get(PN->getType());
471 PN->replaceAllUsesWith(NV);
472 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
474 PN->eraseFromParent();
478 // NOTE: We cannot eliminate single entry phi nodes here, because of
479 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
480 // pointing at them. Thus, deleting one would require scanning the ValueMap
481 // to update any entries in it that would require that. This would be
485 // Now that the inlined function body has been fully constructed, go through
486 // and zap unconditional fall-through branches. This happen all the time when
487 // specializing code: code specialization turns conditional branches into
488 // uncond branches, and this code folds them.
489 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
490 while (I != NewFunc->end()) {
491 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
492 if (!BI || BI->isConditional()) { ++I; continue; }
494 // Note that we can't eliminate uncond branches if the destination has
495 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
496 // require scanning the ValueMap to update any entries that point to the phi
498 BasicBlock *Dest = BI->getSuccessor(0);
499 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
503 // We know all single-entry PHI nodes in the inlined function have been
504 // removed, so we just need to splice the blocks.
505 BI->eraseFromParent();
507 // Move all the instructions in the succ to the pred.
508 I->getInstList().splice(I->end(), Dest->getInstList());
510 // Make all PHI nodes that referred to Dest now refer to I as their source.
511 Dest->replaceAllUsesWith(I);
513 // Remove the dest block.
514 Dest->eraseFromParent();
516 // Do not increment I, iteratively merge all things this block branches to.