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);
37 NewBB->setUnwindDest(const_cast<BasicBlock*>(BB->getUnwindDest()));
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);
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 std::vector<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 the parameter attributes
85 NewFunc->setParamAttrs(OldFunc->getParamAttrs());
87 // Clone the calling convention
88 NewFunc->setCallingConv(OldFunc->getCallingConv());
90 // Loop over all of the basic blocks in the function, cloning them as
91 // appropriate. Note that we save BE this way in order to handle cloning of
92 // recursive functions into themselves.
94 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
96 const BasicBlock &BB = *BI;
98 // Create a new basic block and copy instructions into it!
99 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
101 ValueMap[&BB] = CBB; // Add basic block mapping.
103 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
104 Returns.push_back(RI);
107 // Loop over all of the instructions in the function, fixing up operand
108 // references as we go. This uses ValueMap to do all the hard work.
110 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
111 BE = NewFunc->end(); BB != BE; ++BB) {
112 // Fix up the unwind destination.
113 if (BasicBlock *UnwindDest = BB->getUnwindDest())
114 BB->setUnwindDest(cast<BasicBlock>(ValueMap[UnwindDest]));
116 // Loop over all instructions, fixing each one as we find it...
117 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
118 RemapInstruction(II, ValueMap);
122 /// CloneFunction - Return a copy of the specified function, but without
123 /// embedding the function into another module. Also, any references specified
124 /// in the ValueMap are changed to refer to their mapped value instead of the
125 /// original one. If any of the arguments to the function are in the ValueMap,
126 /// the arguments are deleted from the resultant function. The ValueMap is
127 /// updated to include mappings from all of the instructions and basicblocks in
128 /// the function from their old to new values.
130 Function *llvm::CloneFunction(const Function *F,
131 DenseMap<const Value*, Value*> &ValueMap,
132 ClonedCodeInfo *CodeInfo) {
133 std::vector<const Type*> ArgTypes;
135 // The user might be deleting arguments to the function by specifying them in
136 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
138 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
140 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
141 ArgTypes.push_back(I->getType());
143 // Create a new function type...
144 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
145 ArgTypes, F->getFunctionType()->isVarArg());
147 // Create the new function...
148 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
150 // Loop over the arguments, copying the names of the mapped arguments over...
151 Function::arg_iterator DestI = NewF->arg_begin();
152 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
154 if (ValueMap.count(I) == 0) { // Is this argument preserved?
155 DestI->setName(I->getName()); // Copy the name over...
156 ValueMap[I] = DestI++; // Add mapping to ValueMap
159 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
160 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
167 /// PruningFunctionCloner - This class is a private class used to implement
168 /// the CloneAndPruneFunctionInto method.
169 struct VISIBILITY_HIDDEN PruningFunctionCloner {
171 const Function *OldFunc;
172 DenseMap<const Value*, Value*> &ValueMap;
173 std::vector<ReturnInst*> &Returns;
174 const char *NameSuffix;
175 ClonedCodeInfo *CodeInfo;
176 const TargetData *TD;
179 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
180 DenseMap<const Value*, Value*> &valueMap,
181 std::vector<ReturnInst*> &returns,
182 const char *nameSuffix,
183 ClonedCodeInfo *codeInfo,
184 const TargetData *td)
185 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
186 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) {
189 /// CloneBlock - The specified block is found to be reachable, clone it and
190 /// anything that it can reach.
191 void CloneBlock(const BasicBlock *BB,
192 std::vector<const BasicBlock*> &ToClone);
195 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
196 /// mapping its operands through ValueMap if they are available.
197 Constant *ConstantFoldMappedInstruction(const Instruction *I);
201 /// CloneBlock - The specified block is found to be reachable, clone it and
202 /// anything that it can reach.
203 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
204 std::vector<const BasicBlock*> &ToClone){
205 Value *&BBEntry = ValueMap[BB];
207 // Have we already cloned this block?
210 // Nope, clone it now.
212 BBEntry = NewBB = BasicBlock::Create();
213 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
215 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
217 // Loop over all instructions, and copy them over, DCE'ing as we go. This
218 // loop doesn't include the terminator.
219 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
221 // If this instruction constant folds, don't bother cloning the instruction,
222 // instead, just add the constant to the value map.
223 if (Constant *C = ConstantFoldMappedInstruction(II)) {
228 Instruction *NewInst = II->clone();
230 NewInst->setName(II->getName()+NameSuffix);
231 NewBB->getInstList().push_back(NewInst);
232 ValueMap[II] = NewInst; // Add instruction map to value.
234 hasCalls |= isa<CallInst>(II);
235 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
236 if (isa<ConstantInt>(AI->getArraySize()))
237 hasStaticAllocas = true;
239 hasDynamicAllocas = true;
243 // Finally, clone over the terminator.
244 const TerminatorInst *OldTI = BB->getTerminator();
245 bool TerminatorDone = false;
246 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
247 if (BI->isConditional()) {
248 // If the condition was a known constant in the callee...
249 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
250 // Or is a known constant in the caller...
252 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
254 // Constant fold to uncond branch!
256 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
257 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
258 ToClone.push_back(Dest);
259 TerminatorDone = true;
262 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
263 // If switching on a value known constant in the caller.
264 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
265 if (Cond == 0) // Or known constant after constant prop in the callee...
266 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
267 if (Cond) { // Constant fold to uncond branch!
268 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
269 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
270 ToClone.push_back(Dest);
271 TerminatorDone = true;
275 if (!TerminatorDone) {
276 Instruction *NewInst = OldTI->clone();
277 if (OldTI->hasName())
278 NewInst->setName(OldTI->getName()+NameSuffix);
279 NewBB->getInstList().push_back(NewInst);
280 ValueMap[OldTI] = NewInst; // Add instruction map to value.
282 // Recursively clone any reachable successor blocks.
283 const TerminatorInst *TI = BB->getTerminator();
284 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
285 ToClone.push_back(TI->getSuccessor(i));
289 CodeInfo->ContainsCalls |= hasCalls;
290 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
291 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
292 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
293 BB != &BB->getParent()->front();
296 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
297 Returns.push_back(RI);
300 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
301 /// mapping its operands through ValueMap if they are available.
302 Constant *PruningFunctionCloner::
303 ConstantFoldMappedInstruction(const Instruction *I) {
304 SmallVector<Constant*, 8> Ops;
305 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
306 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
310 return 0; // All operands not constant!
312 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
313 return ConstantFoldCompareInstOperands(CI->getPredicate(),
314 &Ops[0], Ops.size(), TD);
316 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
317 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
318 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
319 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
320 if (GV->isConstant() && !GV->isDeclaration())
321 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
324 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
328 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
329 /// except that it does some simple constant prop and DCE on the fly. The
330 /// effect of this is to copy significantly less code in cases where (for
331 /// example) a function call with constant arguments is inlined, and those
332 /// constant arguments cause a significant amount of code in the callee to be
333 /// dead. Since this doesn't produce an exact copy of the input, it can't be
334 /// used for things like CloneFunction or CloneModule.
335 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
336 DenseMap<const Value*, Value*> &ValueMap,
337 std::vector<ReturnInst*> &Returns,
338 const char *NameSuffix,
339 ClonedCodeInfo *CodeInfo,
340 const TargetData *TD) {
341 assert(NameSuffix && "NameSuffix cannot be null!");
344 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
345 E = OldFunc->arg_end(); II != E; ++II)
346 assert(ValueMap.count(II) && "No mapping from source argument specified!");
349 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
350 NameSuffix, CodeInfo, TD);
352 // Clone the entry block, and anything recursively reachable from it.
353 std::vector<const BasicBlock*> CloneWorklist;
354 CloneWorklist.push_back(&OldFunc->getEntryBlock());
355 while (!CloneWorklist.empty()) {
356 const BasicBlock *BB = CloneWorklist.back();
357 CloneWorklist.pop_back();
358 PFC.CloneBlock(BB, CloneWorklist);
361 // Loop over all of the basic blocks in the old function. If the block was
362 // reachable, we have cloned it and the old block is now in the value map:
363 // insert it into the new function in the right order. If not, ignore it.
365 // Defer PHI resolution until rest of function is resolved.
366 std::vector<const PHINode*> PHIToResolve;
367 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
369 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
370 if (NewBB == 0) continue; // Dead block.
372 // Add the new block to the new function.
373 NewFunc->getBasicBlockList().push_back(NewBB);
375 // Loop over all of the instructions in the block, fixing up operand
376 // references as we go. This uses ValueMap to do all the hard work.
378 BasicBlock::iterator I = NewBB->begin();
380 // Handle PHI nodes specially, as we have to remove references to dead
382 if (PHINode *PN = dyn_cast<PHINode>(I)) {
383 // Skip over all PHI nodes, remembering them for later.
384 BasicBlock::const_iterator OldI = BI->begin();
385 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
386 PHIToResolve.push_back(cast<PHINode>(OldI));
389 // Otherwise, remap the rest of the instructions normally.
390 for (; I != NewBB->end(); ++I)
391 RemapInstruction(I, ValueMap);
394 // Defer PHI resolution until rest of function is resolved, PHI resolution
395 // requires the CFG to be up-to-date.
396 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
397 const PHINode *OPN = PHIToResolve[phino];
398 unsigned NumPreds = OPN->getNumIncomingValues();
399 const BasicBlock *OldBB = OPN->getParent();
400 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
402 // Map operands for blocks that are live and remove operands for blocks
404 for (; phino != PHIToResolve.size() &&
405 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
406 OPN = PHIToResolve[phino];
407 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
408 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
409 if (BasicBlock *MappedBlock =
410 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
411 Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap);
412 assert(InVal && "Unknown input value?");
413 PN->setIncomingValue(pred, InVal);
414 PN->setIncomingBlock(pred, MappedBlock);
416 PN->removeIncomingValue(pred, false);
417 --pred, --e; // Revisit the next entry.
422 // The loop above has removed PHI entries for those blocks that are dead
423 // and has updated others. However, if a block is live (i.e. copied over)
424 // but its terminator has been changed to not go to this block, then our
425 // phi nodes will have invalid entries. Update the PHI nodes in this
427 PHINode *PN = cast<PHINode>(NewBB->begin());
428 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
429 if (NumPreds != PN->getNumIncomingValues()) {
430 assert(NumPreds < PN->getNumIncomingValues());
431 // Count how many times each predecessor comes to this block.
432 std::map<BasicBlock*, unsigned> PredCount;
433 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
437 // Figure out how many entries to remove from each PHI.
438 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
439 ++PredCount[PN->getIncomingBlock(i)];
441 // At this point, the excess predecessor entries are positive in the
442 // map. Loop over all of the PHIs and remove excess predecessor
444 BasicBlock::iterator I = NewBB->begin();
445 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
446 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
447 E = PredCount.end(); PCI != E; ++PCI) {
448 BasicBlock *Pred = PCI->first;
449 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
450 PN->removeIncomingValue(Pred, false);
455 // If the loops above have made these phi nodes have 0 or 1 operand,
456 // replace them with undef or the input value. We must do this for
457 // correctness, because 0-operand phis are not valid.
458 PN = cast<PHINode>(NewBB->begin());
459 if (PN->getNumIncomingValues() == 0) {
460 BasicBlock::iterator I = NewBB->begin();
461 BasicBlock::const_iterator OldI = OldBB->begin();
462 while ((PN = dyn_cast<PHINode>(I++))) {
463 Value *NV = UndefValue::get(PN->getType());
464 PN->replaceAllUsesWith(NV);
465 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
467 PN->eraseFromParent();
471 // NOTE: We cannot eliminate single entry phi nodes here, because of
472 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
473 // pointing at them. Thus, deleting one would require scanning the ValueMap
474 // to update any entries in it that would require that. This would be
478 // Now that the inlined function body has been fully constructed, go through
479 // and zap unconditional fall-through branches. This happen all the time when
480 // specializing code: code specialization turns conditional branches into
481 // uncond branches, and this code folds them.
482 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
483 while (I != NewFunc->end()) {
484 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
485 if (!BI || BI->isConditional()) { ++I; continue; }
487 // Note that we can't eliminate uncond branches if the destination has
488 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
489 // require scanning the ValueMap to update any entries that point to the phi
491 BasicBlock *Dest = BI->getSuccessor(0);
492 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
496 // We know all single-entry PHI nodes in the inlined function have been
497 // removed, so we just need to splice the blocks.
498 BI->eraseFromParent();
500 // Move all the instructions in the succ to the pred.
501 I->getInstList().splice(I->end(), Dest->getInstList());
503 // Make all PHI nodes that referred to Dest now refer to I as their source.
504 Dest->replaceAllUsesWith(I);
506 // Remove the dest block.
507 Dest->eraseFromParent();
509 // Do not increment I, iteratively merge all things this block branches to.