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 NewFunc->copyAttributesFrom(OldFunc);
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 // Loop over all instructions, fixing each one as we find it...
109 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
110 RemapInstruction(II, ValueMap);
113 /// CloneFunction - Return a copy of the specified function, but without
114 /// embedding the function into another module. Also, any references specified
115 /// in the ValueMap are changed to refer to their mapped value instead of the
116 /// original one. If any of the arguments to the function are in the ValueMap,
117 /// the arguments are deleted from the resultant function. The ValueMap is
118 /// updated to include mappings from all of the instructions and basicblocks in
119 /// the function from their old to new values.
121 Function *llvm::CloneFunction(const Function *F,
122 DenseMap<const Value*, Value*> &ValueMap,
123 ClonedCodeInfo *CodeInfo) {
124 std::vector<const Type*> ArgTypes;
126 // The user might be deleting arguments to the function by specifying them in
127 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
129 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
131 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
132 ArgTypes.push_back(I->getType());
134 // Create a new function type...
135 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
136 ArgTypes, F->getFunctionType()->isVarArg());
138 // Create the new function...
139 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
141 // Loop over the arguments, copying the names of the mapped arguments over...
142 Function::arg_iterator DestI = NewF->arg_begin();
143 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
145 if (ValueMap.count(I) == 0) { // Is this argument preserved?
146 DestI->setName(I->getName()); // Copy the name over...
147 ValueMap[I] = DestI++; // Add mapping to ValueMap
150 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
151 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
158 /// PruningFunctionCloner - This class is a private class used to implement
159 /// the CloneAndPruneFunctionInto method.
160 struct VISIBILITY_HIDDEN PruningFunctionCloner {
162 const Function *OldFunc;
163 DenseMap<const Value*, Value*> &ValueMap;
164 std::vector<ReturnInst*> &Returns;
165 const char *NameSuffix;
166 ClonedCodeInfo *CodeInfo;
167 const TargetData *TD;
170 PruningFunctionCloner(Function *newFunc, 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)
176 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
177 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
180 /// CloneBlock - The specified block is found to be reachable, clone it and
181 /// anything that it can reach.
182 void CloneBlock(const BasicBlock *BB,
183 std::vector<const BasicBlock*> &ToClone);
186 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
187 /// mapping its operands through ValueMap if they are available.
188 Constant *ConstantFoldMappedInstruction(const Instruction *I);
192 /// CloneBlock - The specified block is found to be reachable, clone it and
193 /// anything that it can reach.
194 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
195 std::vector<const BasicBlock*> &ToClone){
196 Value *&BBEntry = ValueMap[BB];
198 // Have we already cloned this block?
201 // Nope, clone it now.
203 BBEntry = NewBB = BasicBlock::Create();
204 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
206 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
208 // Loop over all instructions, and copy them over, DCE'ing as we go. This
209 // loop doesn't include the terminator.
210 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
212 // If this instruction constant folds, don't bother cloning the instruction,
213 // instead, just add the constant to the value map.
214 if (Constant *C = ConstantFoldMappedInstruction(II)) {
219 Instruction *NewInst = II->clone();
221 NewInst->setName(II->getName()+NameSuffix);
222 NewBB->getInstList().push_back(NewInst);
223 ValueMap[II] = NewInst; // Add instruction map to value.
225 hasCalls |= isa<CallInst>(II);
226 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
227 if (isa<ConstantInt>(AI->getArraySize()))
228 hasStaticAllocas = true;
230 hasDynamicAllocas = true;
234 // Finally, clone over the terminator.
235 const TerminatorInst *OldTI = BB->getTerminator();
236 bool TerminatorDone = false;
237 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
238 if (BI->isConditional()) {
239 // If the condition was a known constant in the callee...
240 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
241 // Or is a known constant in the caller...
243 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
245 // Constant fold to uncond branch!
247 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
248 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
249 ToClone.push_back(Dest);
250 TerminatorDone = true;
253 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
254 // If switching on a value known constant in the caller.
255 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
256 if (Cond == 0) // Or known constant after constant prop in the callee...
257 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
258 if (Cond) { // Constant fold to uncond branch!
259 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
260 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
261 ToClone.push_back(Dest);
262 TerminatorDone = true;
266 if (!TerminatorDone) {
267 Instruction *NewInst = OldTI->clone();
268 if (OldTI->hasName())
269 NewInst->setName(OldTI->getName()+NameSuffix);
270 NewBB->getInstList().push_back(NewInst);
271 ValueMap[OldTI] = NewInst; // Add instruction map to value.
273 // Recursively clone any reachable successor blocks.
274 const TerminatorInst *TI = BB->getTerminator();
275 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
276 ToClone.push_back(TI->getSuccessor(i));
280 CodeInfo->ContainsCalls |= hasCalls;
281 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
282 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
283 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
284 BB != &BB->getParent()->front();
287 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
288 Returns.push_back(RI);
291 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
292 /// mapping its operands through ValueMap if they are available.
293 Constant *PruningFunctionCloner::
294 ConstantFoldMappedInstruction(const Instruction *I) {
295 SmallVector<Constant*, 8> Ops;
296 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
297 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
301 return 0; // All operands not constant!
303 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
304 return ConstantFoldCompareInstOperands(CI->getPredicate(),
305 &Ops[0], Ops.size(), TD);
307 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
308 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
309 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
310 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
311 if (GV->isConstant() && !GV->isDeclaration())
312 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
315 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
319 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
320 /// except that it does some simple constant prop and DCE on the fly. The
321 /// effect of this is to copy significantly less code in cases where (for
322 /// example) a function call with constant arguments is inlined, and those
323 /// constant arguments cause a significant amount of code in the callee to be
324 /// dead. Since this doesn't produce an exact copy of the input, it can't be
325 /// used for things like CloneFunction or CloneModule.
326 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
327 DenseMap<const Value*, Value*> &ValueMap,
328 std::vector<ReturnInst*> &Returns,
329 const char *NameSuffix,
330 ClonedCodeInfo *CodeInfo,
331 const TargetData *TD) {
332 assert(NameSuffix && "NameSuffix cannot be null!");
335 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
336 E = OldFunc->arg_end(); II != E; ++II)
337 assert(ValueMap.count(II) && "No mapping from source argument specified!");
340 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
341 NameSuffix, CodeInfo, TD);
343 // Clone the entry block, and anything recursively reachable from it.
344 std::vector<const BasicBlock*> CloneWorklist;
345 CloneWorklist.push_back(&OldFunc->getEntryBlock());
346 while (!CloneWorklist.empty()) {
347 const BasicBlock *BB = CloneWorklist.back();
348 CloneWorklist.pop_back();
349 PFC.CloneBlock(BB, CloneWorklist);
352 // Loop over all of the basic blocks in the old function. If the block was
353 // reachable, we have cloned it and the old block is now in the value map:
354 // insert it into the new function in the right order. If not, ignore it.
356 // Defer PHI resolution until rest of function is resolved.
357 std::vector<const PHINode*> PHIToResolve;
358 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
360 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
361 if (NewBB == 0) continue; // Dead block.
363 // Add the new block to the new function.
364 NewFunc->getBasicBlockList().push_back(NewBB);
366 // Loop over all of the instructions in the block, fixing up operand
367 // references as we go. This uses ValueMap to do all the hard work.
369 BasicBlock::iterator I = NewBB->begin();
371 // Handle PHI nodes specially, as we have to remove references to dead
373 if (PHINode *PN = dyn_cast<PHINode>(I)) {
374 // Skip over all PHI nodes, remembering them for later.
375 BasicBlock::const_iterator OldI = BI->begin();
376 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
377 PHIToResolve.push_back(cast<PHINode>(OldI));
380 // Otherwise, remap the rest of the instructions normally.
381 for (; I != NewBB->end(); ++I)
382 RemapInstruction(I, ValueMap);
385 // Defer PHI resolution until rest of function is resolved, PHI resolution
386 // requires the CFG to be up-to-date.
387 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
388 const PHINode *OPN = PHIToResolve[phino];
389 unsigned NumPreds = OPN->getNumIncomingValues();
390 const BasicBlock *OldBB = OPN->getParent();
391 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
393 // Map operands for blocks that are live and remove operands for blocks
395 for (; phino != PHIToResolve.size() &&
396 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
397 OPN = PHIToResolve[phino];
398 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
399 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
400 if (BasicBlock *MappedBlock =
401 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
402 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
403 assert(InVal && "Unknown input value?");
404 PN->setIncomingValue(pred, InVal);
405 PN->setIncomingBlock(pred, MappedBlock);
407 PN->removeIncomingValue(pred, false);
408 --pred, --e; // Revisit the next entry.
413 // The loop above has removed PHI entries for those blocks that are dead
414 // and has updated others. However, if a block is live (i.e. copied over)
415 // but its terminator has been changed to not go to this block, then our
416 // phi nodes will have invalid entries. Update the PHI nodes in this
418 PHINode *PN = cast<PHINode>(NewBB->begin());
419 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
420 if (NumPreds != PN->getNumIncomingValues()) {
421 assert(NumPreds < PN->getNumIncomingValues());
422 // Count how many times each predecessor comes to this block.
423 std::map<BasicBlock*, unsigned> PredCount;
424 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
428 // Figure out how many entries to remove from each PHI.
429 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
430 ++PredCount[PN->getIncomingBlock(i)];
432 // At this point, the excess predecessor entries are positive in the
433 // map. Loop over all of the PHIs and remove excess predecessor
435 BasicBlock::iterator I = NewBB->begin();
436 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
437 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
438 E = PredCount.end(); PCI != E; ++PCI) {
439 BasicBlock *Pred = PCI->first;
440 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
441 PN->removeIncomingValue(Pred, false);
446 // If the loops above have made these phi nodes have 0 or 1 operand,
447 // replace them with undef or the input value. We must do this for
448 // correctness, because 0-operand phis are not valid.
449 PN = cast<PHINode>(NewBB->begin());
450 if (PN->getNumIncomingValues() == 0) {
451 BasicBlock::iterator I = NewBB->begin();
452 BasicBlock::const_iterator OldI = OldBB->begin();
453 while ((PN = dyn_cast<PHINode>(I++))) {
454 Value *NV = UndefValue::get(PN->getType());
455 PN->replaceAllUsesWith(NV);
456 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
458 PN->eraseFromParent();
462 // NOTE: We cannot eliminate single entry phi nodes here, because of
463 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
464 // pointing at them. Thus, deleting one would require scanning the ValueMap
465 // to update any entries in it that would require that. This would be
469 // Now that the inlined function body has been fully constructed, go through
470 // and zap unconditional fall-through branches. This happen all the time when
471 // specializing code: code specialization turns conditional branches into
472 // uncond branches, and this code folds them.
473 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
474 while (I != NewFunc->end()) {
475 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
476 if (!BI || BI->isConditional()) { ++I; continue; }
478 // Note that we can't eliminate uncond branches if the destination has
479 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
480 // require scanning the ValueMap to update any entries that point to the phi
482 BasicBlock *Dest = BI->getSuccessor(0);
483 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
487 // We know all single-entry PHI nodes in the inlined function have been
488 // removed, so we just need to splice the blocks.
489 BI->eraseFromParent();
491 // Move all the instructions in the succ to the pred.
492 I->getInstList().splice(I->end(), Dest->getInstList());
494 // Make all PHI nodes that referred to Dest now refer to I as their source.
495 Dest->replaceAllUsesWith(I);
497 // Remove the dest block.
498 Dest->eraseFromParent();
500 // Do not increment I, iteratively merge all things this block branches to.