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/IntrinsicInst.h"
21 #include "llvm/GlobalVariable.h"
22 #include "llvm/Function.h"
23 #include "llvm/Support/CFG.h"
24 #include "llvm/Transforms/Utils/ValueMapper.h"
25 #include "llvm/Analysis/ConstantFolding.h"
26 #include "llvm/Analysis/DebugInfo.h"
27 #include "llvm/ADT/SmallVector.h"
31 // CloneBasicBlock - See comments in Cloning.h
32 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
33 DenseMap<const Value*, Value*> &ValueMap,
34 const char *NameSuffix, Function *F,
35 ClonedCodeInfo *CodeInfo) {
36 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
37 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
39 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
41 // Loop over all instructions, and copy them over.
42 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
44 Instruction *NewInst = II->clone();
46 NewInst->setName(II->getName()+NameSuffix);
47 NewBB->getInstList().push_back(NewInst);
48 ValueMap[II] = NewInst; // Add instruction map to value.
50 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
51 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
52 if (isa<ConstantInt>(AI->getArraySize()))
53 hasStaticAllocas = true;
55 hasDynamicAllocas = true;
60 CodeInfo->ContainsCalls |= hasCalls;
61 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
62 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
63 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
64 BB != &BB->getParent()->getEntryBlock();
69 // Clone OldFunc into NewFunc, transforming the old arguments into references to
72 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
73 DenseMap<const Value*, Value*> &ValueMap,
74 SmallVectorImpl<ReturnInst*> &Returns,
75 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
76 assert(NameSuffix && "NameSuffix cannot be null!");
79 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
80 E = OldFunc->arg_end(); I != E; ++I)
81 assert(ValueMap.count(I) && "No mapping from source argument specified!");
84 // Clone any attributes.
85 if (NewFunc->arg_size() == OldFunc->arg_size())
86 NewFunc->copyAttributesFrom(OldFunc);
88 //Some arguments were deleted with the ValueMap. Copy arguments one by one
89 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
90 E = OldFunc->arg_end(); I != E; ++I)
91 if (Argument* Anew = dyn_cast<Argument>(ValueMap[I]))
92 Anew->addAttr( OldFunc->getAttributes()
93 .getParamAttributes(I->getArgNo() + 1));
94 NewFunc->setAttributes(NewFunc->getAttributes()
95 .addAttr(0, OldFunc->getAttributes()
96 .getRetAttributes()));
97 NewFunc->setAttributes(NewFunc->getAttributes()
98 .addAttr(~0, OldFunc->getAttributes()
103 // Loop over all of the basic blocks in the function, cloning them as
104 // appropriate. Note that we save BE this way in order to handle cloning of
105 // recursive functions into themselves.
107 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
109 const BasicBlock &BB = *BI;
111 // Create a new basic block and copy instructions into it!
112 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
114 ValueMap[&BB] = CBB; // Add basic block mapping.
116 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
117 Returns.push_back(RI);
120 // Loop over all of the instructions in the function, fixing up operand
121 // references as we go. This uses ValueMap to do all the hard work.
123 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
124 BE = NewFunc->end(); BB != BE; ++BB)
125 // Loop over all instructions, fixing each one as we find it...
126 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
127 RemapInstruction(II, ValueMap);
130 /// CloneFunction - Return a copy of the specified function, but without
131 /// embedding the function into another module. Also, any references specified
132 /// in the ValueMap are changed to refer to their mapped value instead of the
133 /// original one. If any of the arguments to the function are in the ValueMap,
134 /// the arguments are deleted from the resultant function. The ValueMap is
135 /// updated to include mappings from all of the instructions and basicblocks in
136 /// the function from their old to new values.
138 Function *llvm::CloneFunction(const Function *F,
139 DenseMap<const Value*, Value*> &ValueMap,
140 ClonedCodeInfo *CodeInfo) {
141 std::vector<const Type*> ArgTypes;
143 // The user might be deleting arguments to the function by specifying them in
144 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
146 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
148 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
149 ArgTypes.push_back(I->getType());
151 // Create a new function type...
152 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
153 ArgTypes, F->getFunctionType()->isVarArg());
155 // Create the new function...
156 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
158 // Loop over the arguments, copying the names of the mapped arguments over...
159 Function::arg_iterator DestI = NewF->arg_begin();
160 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
162 if (ValueMap.count(I) == 0) { // Is this argument preserved?
163 DestI->setName(I->getName()); // Copy the name over...
164 ValueMap[I] = DestI++; // Add mapping to ValueMap
167 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
168 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
175 /// PruningFunctionCloner - This class is a private class used to implement
176 /// the CloneAndPruneFunctionInto method.
177 struct PruningFunctionCloner {
179 const Function *OldFunc;
180 DenseMap<const Value*, Value*> &ValueMap;
181 SmallVectorImpl<ReturnInst*> &Returns;
182 const char *NameSuffix;
183 ClonedCodeInfo *CodeInfo;
184 const TargetData *TD;
187 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
188 DenseMap<const Value*, Value*> &valueMap,
189 SmallVectorImpl<ReturnInst*> &returns,
190 const char *nameSuffix,
191 ClonedCodeInfo *codeInfo,
192 const TargetData *td)
193 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
194 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td), DbgFnStart(NULL) {
197 /// CloneBlock - The specified block is found to be reachable, clone it and
198 /// anything that it can reach.
199 void CloneBlock(const BasicBlock *BB,
200 std::vector<const BasicBlock*> &ToClone);
203 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
204 /// mapping its operands through ValueMap if they are available.
205 Constant *ConstantFoldMappedInstruction(const Instruction *I);
209 /// CloneBlock - The specified block is found to be reachable, clone it and
210 /// anything that it can reach.
211 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
212 std::vector<const BasicBlock*> &ToClone){
213 Value *&BBEntry = ValueMap[BB];
215 // Have we already cloned this block?
218 // Nope, clone it now.
220 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
221 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
223 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
225 // Loop over all instructions, and copy them over, DCE'ing as we go. This
226 // loop doesn't include the terminator.
227 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
229 // If this instruction constant folds, don't bother cloning the instruction,
230 // instead, just add the constant to the value map.
231 if (Constant *C = ConstantFoldMappedInstruction(II)) {
236 // Do not clone llvm.dbg.region.end. It will be adjusted by the inliner.
237 if (const DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(II)) {
238 if (DbgFnStart == NULL) {
239 DISubprogram SP(DFSI->getSubprogram());
240 if (SP.describes(BB->getParent()))
241 DbgFnStart = DFSI->getSubprogram();
244 if (const DbgRegionEndInst *DREIS = dyn_cast<DbgRegionEndInst>(II)) {
245 if (DREIS->getContext() == DbgFnStart)
249 Instruction *NewInst = II->clone();
251 NewInst->setName(II->getName()+NameSuffix);
252 NewBB->getInstList().push_back(NewInst);
253 ValueMap[II] = NewInst; // Add instruction map to value.
255 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
256 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
257 if (isa<ConstantInt>(AI->getArraySize()))
258 hasStaticAllocas = true;
260 hasDynamicAllocas = true;
264 // Finally, clone over the terminator.
265 const TerminatorInst *OldTI = BB->getTerminator();
266 bool TerminatorDone = false;
267 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
268 if (BI->isConditional()) {
269 // If the condition was a known constant in the callee...
270 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
271 // Or is a known constant in the caller...
273 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
275 // Constant fold to uncond branch!
277 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
278 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
279 ToClone.push_back(Dest);
280 TerminatorDone = true;
283 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
284 // If switching on a value known constant in the caller.
285 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
286 if (Cond == 0) // Or known constant after constant prop in the callee...
287 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
288 if (Cond) { // Constant fold to uncond branch!
289 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
290 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
291 ToClone.push_back(Dest);
292 TerminatorDone = true;
296 if (!TerminatorDone) {
297 Instruction *NewInst = OldTI->clone();
298 if (OldTI->hasName())
299 NewInst->setName(OldTI->getName()+NameSuffix);
300 NewBB->getInstList().push_back(NewInst);
301 ValueMap[OldTI] = NewInst; // Add instruction map to value.
303 // Recursively clone any reachable successor blocks.
304 const TerminatorInst *TI = BB->getTerminator();
305 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
306 ToClone.push_back(TI->getSuccessor(i));
310 CodeInfo->ContainsCalls |= hasCalls;
311 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
312 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
313 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
314 BB != &BB->getParent()->front();
317 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
318 Returns.push_back(RI);
321 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
322 /// mapping its operands through ValueMap if they are available.
323 Constant *PruningFunctionCloner::
324 ConstantFoldMappedInstruction(const Instruction *I) {
325 LLVMContext &Context = I->getContext();
327 SmallVector<Constant*, 8> Ops;
328 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
329 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
333 return 0; // All operands not constant!
335 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
336 return ConstantFoldCompareInstOperands(CI->getPredicate(),
340 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
341 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
342 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
343 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
344 if (GV->isConstant() && GV->hasDefinitiveInitializer())
345 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
348 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
349 Ops.size(), Context, TD);
352 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
353 /// except that it does some simple constant prop and DCE on the fly. The
354 /// effect of this is to copy significantly less code in cases where (for
355 /// example) a function call with constant arguments is inlined, and those
356 /// constant arguments cause a significant amount of code in the callee to be
357 /// dead. Since this doesn't produce an exact copy of the input, it can't be
358 /// used for things like CloneFunction or CloneModule.
359 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
360 DenseMap<const Value*, Value*> &ValueMap,
361 SmallVectorImpl<ReturnInst*> &Returns,
362 const char *NameSuffix,
363 ClonedCodeInfo *CodeInfo,
364 const TargetData *TD) {
365 assert(NameSuffix && "NameSuffix cannot be null!");
368 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
369 E = OldFunc->arg_end(); II != E; ++II)
370 assert(ValueMap.count(II) && "No mapping from source argument specified!");
373 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
374 NameSuffix, CodeInfo, TD);
376 // Clone the entry block, and anything recursively reachable from it.
377 std::vector<const BasicBlock*> CloneWorklist;
378 CloneWorklist.push_back(&OldFunc->getEntryBlock());
379 while (!CloneWorklist.empty()) {
380 const BasicBlock *BB = CloneWorklist.back();
381 CloneWorklist.pop_back();
382 PFC.CloneBlock(BB, CloneWorklist);
385 // Loop over all of the basic blocks in the old function. If the block was
386 // reachable, we have cloned it and the old block is now in the value map:
387 // insert it into the new function in the right order. If not, ignore it.
389 // Defer PHI resolution until rest of function is resolved.
390 SmallVector<const PHINode*, 16> PHIToResolve;
391 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
393 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
394 if (NewBB == 0) continue; // Dead block.
396 // Add the new block to the new function.
397 NewFunc->getBasicBlockList().push_back(NewBB);
399 // Loop over all of the instructions in the block, fixing up operand
400 // references as we go. This uses ValueMap to do all the hard work.
402 BasicBlock::iterator I = NewBB->begin();
404 // Handle PHI nodes specially, as we have to remove references to dead
406 if (PHINode *PN = dyn_cast<PHINode>(I)) {
407 // Skip over all PHI nodes, remembering them for later.
408 BasicBlock::const_iterator OldI = BI->begin();
409 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
410 PHIToResolve.push_back(cast<PHINode>(OldI));
413 // Otherwise, remap the rest of the instructions normally.
414 for (; I != NewBB->end(); ++I)
415 RemapInstruction(I, ValueMap);
418 // Defer PHI resolution until rest of function is resolved, PHI resolution
419 // requires the CFG to be up-to-date.
420 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
421 const PHINode *OPN = PHIToResolve[phino];
422 unsigned NumPreds = OPN->getNumIncomingValues();
423 const BasicBlock *OldBB = OPN->getParent();
424 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
426 // Map operands for blocks that are live and remove operands for blocks
428 for (; phino != PHIToResolve.size() &&
429 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
430 OPN = PHIToResolve[phino];
431 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
432 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
433 if (BasicBlock *MappedBlock =
434 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
435 Value *InVal = MapValue(PN->getIncomingValue(pred),
437 assert(InVal && "Unknown input value?");
438 PN->setIncomingValue(pred, InVal);
439 PN->setIncomingBlock(pred, MappedBlock);
441 PN->removeIncomingValue(pred, false);
442 --pred, --e; // Revisit the next entry.
447 // The loop above has removed PHI entries for those blocks that are dead
448 // and has updated others. However, if a block is live (i.e. copied over)
449 // but its terminator has been changed to not go to this block, then our
450 // phi nodes will have invalid entries. Update the PHI nodes in this
452 PHINode *PN = cast<PHINode>(NewBB->begin());
453 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
454 if (NumPreds != PN->getNumIncomingValues()) {
455 assert(NumPreds < PN->getNumIncomingValues());
456 // Count how many times each predecessor comes to this block.
457 std::map<BasicBlock*, unsigned> PredCount;
458 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
462 // Figure out how many entries to remove from each PHI.
463 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
464 ++PredCount[PN->getIncomingBlock(i)];
466 // At this point, the excess predecessor entries are positive in the
467 // map. Loop over all of the PHIs and remove excess predecessor
469 BasicBlock::iterator I = NewBB->begin();
470 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
471 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
472 E = PredCount.end(); PCI != E; ++PCI) {
473 BasicBlock *Pred = PCI->first;
474 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
475 PN->removeIncomingValue(Pred, false);
480 // If the loops above have made these phi nodes have 0 or 1 operand,
481 // replace them with undef or the input value. We must do this for
482 // correctness, because 0-operand phis are not valid.
483 PN = cast<PHINode>(NewBB->begin());
484 if (PN->getNumIncomingValues() == 0) {
485 BasicBlock::iterator I = NewBB->begin();
486 BasicBlock::const_iterator OldI = OldBB->begin();
487 while ((PN = dyn_cast<PHINode>(I++))) {
488 Value *NV = UndefValue::get(PN->getType());
489 PN->replaceAllUsesWith(NV);
490 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
492 PN->eraseFromParent();
496 // NOTE: We cannot eliminate single entry phi nodes here, because of
497 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
498 // pointing at them. Thus, deleting one would require scanning the ValueMap
499 // to update any entries in it that would require that. This would be
503 // Now that the inlined function body has been fully constructed, go through
504 // and zap unconditional fall-through branches. This happen all the time when
505 // specializing code: code specialization turns conditional branches into
506 // uncond branches, and this code folds them.
507 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
508 while (I != NewFunc->end()) {
509 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
510 if (!BI || BI->isConditional()) { ++I; continue; }
512 // Note that we can't eliminate uncond branches if the destination has
513 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
514 // require scanning the ValueMap to update any entries that point to the phi
516 BasicBlock *Dest = BI->getSuccessor(0);
517 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
521 // We know all single-entry PHI nodes in the inlined function have been
522 // removed, so we just need to splice the blocks.
523 BI->eraseFromParent();
525 // Move all the instructions in the succ to the pred.
526 I->getInstList().splice(I->end(), Dest->getInstList());
528 // Make all PHI nodes that referred to Dest now refer to I as their source.
529 Dest->replaceAllUsesWith(I);
531 // Remove the dest block.
532 Dest->eraseFromParent();
534 // Do not increment I, iteratively merge all things this block branches to.