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/Support/Compiler.h"
25 #include "llvm/Transforms/Utils/ValueMapper.h"
26 #include "llvm/Analysis/ConstantFolding.h"
27 #include "llvm/Analysis/DebugInfo.h"
28 #include "llvm/ADT/SmallVector.h"
32 // CloneBasicBlock - See comments in Cloning.h
33 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
34 DenseMap<const Value*, Value*> &ValueMap,
35 const char *NameSuffix, Function *F,
36 ClonedCodeInfo *CodeInfo) {
37 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
38 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
40 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
42 // Loop over all instructions, and copy them over.
43 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
45 Instruction *NewInst = II->clone();
47 NewInst->setName(II->getName()+NameSuffix);
48 NewBB->getInstList().push_back(NewInst);
49 ValueMap[II] = NewInst; // Add instruction map to value.
51 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
52 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
53 if (isa<ConstantInt>(AI->getArraySize()))
54 hasStaticAllocas = true;
56 hasDynamicAllocas = true;
61 CodeInfo->ContainsCalls |= hasCalls;
62 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
63 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
64 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
65 BB != &BB->getParent()->getEntryBlock();
70 // Clone OldFunc into NewFunc, transforming the old arguments into references to
73 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
74 DenseMap<const Value*, Value*> &ValueMap,
75 SmallVectorImpl<ReturnInst*> &Returns,
76 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
77 assert(NameSuffix && "NameSuffix cannot be null!");
80 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
81 E = OldFunc->arg_end(); I != E; ++I)
82 assert(ValueMap.count(I) && "No mapping from source argument specified!");
85 // Clone any attributes.
86 if (NewFunc->arg_size() == OldFunc->arg_size())
87 NewFunc->copyAttributesFrom(OldFunc);
89 //Some arguments were deleted with the ValueMap. Copy arguments one by one
90 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
91 E = OldFunc->arg_end(); I != E; ++I)
92 if (Argument* Anew = dyn_cast<Argument>(ValueMap[I]))
93 Anew->addAttr( OldFunc->getAttributes()
94 .getParamAttributes(I->getArgNo() + 1));
95 NewFunc->setAttributes(NewFunc->getAttributes()
96 .addAttr(0, OldFunc->getAttributes()
97 .getRetAttributes()));
98 NewFunc->setAttributes(NewFunc->getAttributes()
99 .addAttr(~0, OldFunc->getAttributes()
100 .getFnAttributes()));
104 // Loop over all of the basic blocks in the function, cloning them as
105 // appropriate. Note that we save BE this way in order to handle cloning of
106 // recursive functions into themselves.
108 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
110 const BasicBlock &BB = *BI;
112 // Create a new basic block and copy instructions into it!
113 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
115 ValueMap[&BB] = CBB; // Add basic block mapping.
117 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
118 Returns.push_back(RI);
121 // Loop over all of the instructions in the function, fixing up operand
122 // references as we go. This uses ValueMap to do all the hard work.
124 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
125 BE = NewFunc->end(); BB != BE; ++BB)
126 // Loop over all instructions, fixing each one as we find it...
127 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
128 RemapInstruction(II, ValueMap);
131 /// CloneFunction - Return a copy of the specified function, but without
132 /// embedding the function into another module. Also, any references specified
133 /// in the ValueMap are changed to refer to their mapped value instead of the
134 /// original one. If any of the arguments to the function are in the ValueMap,
135 /// the arguments are deleted from the resultant function. The ValueMap is
136 /// updated to include mappings from all of the instructions and basicblocks in
137 /// the function from their old to new values.
139 Function *llvm::CloneFunction(const Function *F,
140 DenseMap<const Value*, Value*> &ValueMap,
141 ClonedCodeInfo *CodeInfo) {
142 std::vector<const Type*> ArgTypes;
144 // The user might be deleting arguments to the function by specifying them in
145 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
147 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
149 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
150 ArgTypes.push_back(I->getType());
152 // Create a new function type...
153 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
154 ArgTypes, F->getFunctionType()->isVarArg());
156 // Create the new function...
157 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
159 // Loop over the arguments, copying the names of the mapped arguments over...
160 Function::arg_iterator DestI = NewF->arg_begin();
161 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
163 if (ValueMap.count(I) == 0) { // Is this argument preserved?
164 DestI->setName(I->getName()); // Copy the name over...
165 ValueMap[I] = DestI++; // Add mapping to ValueMap
168 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
169 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
176 /// PruningFunctionCloner - This class is a private class used to implement
177 /// the CloneAndPruneFunctionInto method.
178 struct VISIBILITY_HIDDEN PruningFunctionCloner {
180 const Function *OldFunc;
181 DenseMap<const Value*, Value*> &ValueMap;
182 SmallVectorImpl<ReturnInst*> &Returns;
183 const char *NameSuffix;
184 ClonedCodeInfo *CodeInfo;
185 const TargetData *TD;
188 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
189 DenseMap<const Value*, Value*> &valueMap,
190 SmallVectorImpl<ReturnInst*> &returns,
191 const char *nameSuffix,
192 ClonedCodeInfo *codeInfo,
193 const TargetData *td)
194 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
195 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td), DbgFnStart(NULL) {
198 /// CloneBlock - The specified block is found to be reachable, clone it and
199 /// anything that it can reach.
200 void CloneBlock(const BasicBlock *BB,
201 std::vector<const BasicBlock*> &ToClone);
204 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
205 /// mapping its operands through ValueMap if they are available.
206 Constant *ConstantFoldMappedInstruction(const Instruction *I);
210 /// CloneBlock - The specified block is found to be reachable, clone it and
211 /// anything that it can reach.
212 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
213 std::vector<const BasicBlock*> &ToClone){
214 Value *&BBEntry = ValueMap[BB];
216 // Have we already cloned this block?
219 // Nope, clone it now.
221 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
222 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
224 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
226 // Loop over all instructions, and copy them over, DCE'ing as we go. This
227 // loop doesn't include the terminator.
228 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
230 // If this instruction constant folds, don't bother cloning the instruction,
231 // instead, just add the constant to the value map.
232 if (Constant *C = ConstantFoldMappedInstruction(II)) {
237 // Do not clone llvm.dbg.region.end. It will be adjusted by the inliner.
238 if (const DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(II)) {
239 if (DbgFnStart == NULL) {
240 DISubprogram SP(DFSI->getSubprogram());
241 if (SP.describes(BB->getParent()))
242 DbgFnStart = DFSI->getSubprogram();
245 if (const DbgRegionEndInst *DREIS = dyn_cast<DbgRegionEndInst>(II)) {
246 if (DREIS->getContext() == DbgFnStart)
250 Instruction *NewInst = II->clone();
252 NewInst->setName(II->getName()+NameSuffix);
253 NewBB->getInstList().push_back(NewInst);
254 ValueMap[II] = NewInst; // Add instruction map to value.
256 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
257 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
258 if (isa<ConstantInt>(AI->getArraySize()))
259 hasStaticAllocas = true;
261 hasDynamicAllocas = true;
265 // Finally, clone over the terminator.
266 const TerminatorInst *OldTI = BB->getTerminator();
267 bool TerminatorDone = false;
268 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
269 if (BI->isConditional()) {
270 // If the condition was a known constant in the callee...
271 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
272 // Or is a known constant in the caller...
274 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
276 // Constant fold to uncond branch!
278 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
279 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
280 ToClone.push_back(Dest);
281 TerminatorDone = true;
284 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
285 // If switching on a value known constant in the caller.
286 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
287 if (Cond == 0) // Or known constant after constant prop in the callee...
288 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
289 if (Cond) { // Constant fold to uncond branch!
290 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
291 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
292 ToClone.push_back(Dest);
293 TerminatorDone = true;
297 if (!TerminatorDone) {
298 Instruction *NewInst = OldTI->clone();
299 if (OldTI->hasName())
300 NewInst->setName(OldTI->getName()+NameSuffix);
301 NewBB->getInstList().push_back(NewInst);
302 ValueMap[OldTI] = NewInst; // Add instruction map to value.
304 // Recursively clone any reachable successor blocks.
305 const TerminatorInst *TI = BB->getTerminator();
306 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
307 ToClone.push_back(TI->getSuccessor(i));
311 CodeInfo->ContainsCalls |= hasCalls;
312 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
313 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
314 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
315 BB != &BB->getParent()->front();
318 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
319 Returns.push_back(RI);
322 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
323 /// mapping its operands through ValueMap if they are available.
324 Constant *PruningFunctionCloner::
325 ConstantFoldMappedInstruction(const Instruction *I) {
326 LLVMContext &Context = I->getContext();
328 SmallVector<Constant*, 8> Ops;
329 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
330 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
334 return 0; // All operands not constant!
336 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
337 return ConstantFoldCompareInstOperands(CI->getPredicate(),
341 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
342 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
343 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
344 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
345 if (GV->isConstant() && GV->hasDefinitiveInitializer())
346 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
349 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
350 Ops.size(), Context, TD);
353 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
354 /// except that it does some simple constant prop and DCE on the fly. The
355 /// effect of this is to copy significantly less code in cases where (for
356 /// example) a function call with constant arguments is inlined, and those
357 /// constant arguments cause a significant amount of code in the callee to be
358 /// dead. Since this doesn't produce an exact copy of the input, it can't be
359 /// used for things like CloneFunction or CloneModule.
360 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
361 DenseMap<const Value*, Value*> &ValueMap,
362 SmallVectorImpl<ReturnInst*> &Returns,
363 const char *NameSuffix,
364 ClonedCodeInfo *CodeInfo,
365 const TargetData *TD) {
366 assert(NameSuffix && "NameSuffix cannot be null!");
369 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
370 E = OldFunc->arg_end(); II != E; ++II)
371 assert(ValueMap.count(II) && "No mapping from source argument specified!");
374 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
375 NameSuffix, CodeInfo, TD);
377 // Clone the entry block, and anything recursively reachable from it.
378 std::vector<const BasicBlock*> CloneWorklist;
379 CloneWorklist.push_back(&OldFunc->getEntryBlock());
380 while (!CloneWorklist.empty()) {
381 const BasicBlock *BB = CloneWorklist.back();
382 CloneWorklist.pop_back();
383 PFC.CloneBlock(BB, CloneWorklist);
386 // Loop over all of the basic blocks in the old function. If the block was
387 // reachable, we have cloned it and the old block is now in the value map:
388 // insert it into the new function in the right order. If not, ignore it.
390 // Defer PHI resolution until rest of function is resolved.
391 SmallVector<const PHINode*, 16> PHIToResolve;
392 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
394 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
395 if (NewBB == 0) continue; // Dead block.
397 // Add the new block to the new function.
398 NewFunc->getBasicBlockList().push_back(NewBB);
400 // Loop over all of the instructions in the block, fixing up operand
401 // references as we go. This uses ValueMap to do all the hard work.
403 BasicBlock::iterator I = NewBB->begin();
405 // Handle PHI nodes specially, as we have to remove references to dead
407 if (PHINode *PN = dyn_cast<PHINode>(I)) {
408 // Skip over all PHI nodes, remembering them for later.
409 BasicBlock::const_iterator OldI = BI->begin();
410 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
411 PHIToResolve.push_back(cast<PHINode>(OldI));
414 // Otherwise, remap the rest of the instructions normally.
415 for (; I != NewBB->end(); ++I)
416 RemapInstruction(I, ValueMap);
419 // Defer PHI resolution until rest of function is resolved, PHI resolution
420 // requires the CFG to be up-to-date.
421 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
422 const PHINode *OPN = PHIToResolve[phino];
423 unsigned NumPreds = OPN->getNumIncomingValues();
424 const BasicBlock *OldBB = OPN->getParent();
425 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
427 // Map operands for blocks that are live and remove operands for blocks
429 for (; phino != PHIToResolve.size() &&
430 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
431 OPN = PHIToResolve[phino];
432 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
433 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
434 if (BasicBlock *MappedBlock =
435 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
436 Value *InVal = MapValue(PN->getIncomingValue(pred),
438 assert(InVal && "Unknown input value?");
439 PN->setIncomingValue(pred, InVal);
440 PN->setIncomingBlock(pred, MappedBlock);
442 PN->removeIncomingValue(pred, false);
443 --pred, --e; // Revisit the next entry.
448 // The loop above has removed PHI entries for those blocks that are dead
449 // and has updated others. However, if a block is live (i.e. copied over)
450 // but its terminator has been changed to not go to this block, then our
451 // phi nodes will have invalid entries. Update the PHI nodes in this
453 PHINode *PN = cast<PHINode>(NewBB->begin());
454 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
455 if (NumPreds != PN->getNumIncomingValues()) {
456 assert(NumPreds < PN->getNumIncomingValues());
457 // Count how many times each predecessor comes to this block.
458 std::map<BasicBlock*, unsigned> PredCount;
459 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
463 // Figure out how many entries to remove from each PHI.
464 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
465 ++PredCount[PN->getIncomingBlock(i)];
467 // At this point, the excess predecessor entries are positive in the
468 // map. Loop over all of the PHIs and remove excess predecessor
470 BasicBlock::iterator I = NewBB->begin();
471 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
472 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
473 E = PredCount.end(); PCI != E; ++PCI) {
474 BasicBlock *Pred = PCI->first;
475 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
476 PN->removeIncomingValue(Pred, false);
481 // If the loops above have made these phi nodes have 0 or 1 operand,
482 // replace them with undef or the input value. We must do this for
483 // correctness, because 0-operand phis are not valid.
484 PN = cast<PHINode>(NewBB->begin());
485 if (PN->getNumIncomingValues() == 0) {
486 BasicBlock::iterator I = NewBB->begin();
487 BasicBlock::const_iterator OldI = OldBB->begin();
488 while ((PN = dyn_cast<PHINode>(I++))) {
489 Value *NV = UndefValue::get(PN->getType());
490 PN->replaceAllUsesWith(NV);
491 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
493 PN->eraseFromParent();
497 // NOTE: We cannot eliminate single entry phi nodes here, because of
498 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
499 // pointing at them. Thus, deleting one would require scanning the ValueMap
500 // to update any entries in it that would require that. This would be
504 // Now that the inlined function body has been fully constructed, go through
505 // and zap unconditional fall-through branches. This happen all the time when
506 // specializing code: code specialization turns conditional branches into
507 // uncond branches, and this code folds them.
508 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
509 while (I != NewFunc->end()) {
510 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
511 if (!BI || BI->isConditional()) { ++I; continue; }
513 // Note that we can't eliminate uncond branches if the destination has
514 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
515 // require scanning the ValueMap to update any entries that point to the phi
517 BasicBlock *Dest = BI->getSuccessor(0);
518 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
522 // We know all single-entry PHI nodes in the inlined function have been
523 // removed, so we just need to splice the blocks.
524 BI->eraseFromParent();
526 // Move all the instructions in the succ to the pred.
527 I->getInstList().splice(I->end(), Dest->getInstList());
529 // Make all PHI nodes that referred to Dest now refer to I as their source.
530 Dest->replaceAllUsesWith(I);
532 // Remove the dest block.
533 Dest->eraseFromParent();
535 // Do not increment I, iteratively merge all things this block branches to.