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/LLVMContext.h"
24 #include "llvm/Metadata.h"
25 #include "llvm/Support/CFG.h"
26 #include "llvm/Transforms/Utils/ValueMapper.h"
27 #include "llvm/Analysis/ConstantFolding.h"
28 #include "llvm/Analysis/DebugInfo.h"
29 #include "llvm/ADT/SmallVector.h"
33 // CloneBasicBlock - See comments in Cloning.h
34 BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB,
35 DenseMap<const Value*, Value*> &ValueMap,
36 const char *NameSuffix, Function *F,
37 ClonedCodeInfo *CodeInfo) {
38 BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "", F);
39 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
41 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
43 // Loop over all instructions, and copy them over.
44 for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end();
46 Instruction *NewInst = II->clone();
48 NewInst->setName(II->getName()+NameSuffix);
49 NewBB->getInstList().push_back(NewInst);
50 ValueMap[II] = NewInst; // Add instruction map to value.
52 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
53 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
54 if (isa<ConstantInt>(AI->getArraySize()))
55 hasStaticAllocas = true;
57 hasDynamicAllocas = true;
62 CodeInfo->ContainsCalls |= hasCalls;
63 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(BB->getTerminator());
64 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
65 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
66 BB != &BB->getParent()->getEntryBlock();
71 // Clone OldFunc into NewFunc, transforming the old arguments into references to
74 void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc,
75 DenseMap<const Value*, Value*> &ValueMap,
76 SmallVectorImpl<ReturnInst*> &Returns,
77 const char *NameSuffix, ClonedCodeInfo *CodeInfo) {
78 assert(NameSuffix && "NameSuffix cannot be null!");
81 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
82 E = OldFunc->arg_end(); I != E; ++I)
83 assert(ValueMap.count(I) && "No mapping from source argument specified!");
86 // Clone any attributes.
87 if (NewFunc->arg_size() == OldFunc->arg_size())
88 NewFunc->copyAttributesFrom(OldFunc);
90 //Some arguments were deleted with the ValueMap. Copy arguments one by one
91 for (Function::const_arg_iterator I = OldFunc->arg_begin(),
92 E = OldFunc->arg_end(); I != E; ++I)
93 if (Argument* Anew = dyn_cast<Argument>(ValueMap[I]))
94 Anew->addAttr( OldFunc->getAttributes()
95 .getParamAttributes(I->getArgNo() + 1));
96 NewFunc->setAttributes(NewFunc->getAttributes()
97 .addAttr(0, OldFunc->getAttributes()
98 .getRetAttributes()));
99 NewFunc->setAttributes(NewFunc->getAttributes()
100 .addAttr(~0, OldFunc->getAttributes()
101 .getFnAttributes()));
105 // Loop over all of the basic blocks in the function, cloning them as
106 // appropriate. Note that we save BE this way in order to handle cloning of
107 // recursive functions into themselves.
109 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
111 const BasicBlock &BB = *BI;
113 // Create a new basic block and copy instructions into it!
114 BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc,
116 ValueMap[&BB] = CBB; // Add basic block mapping.
118 if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
119 Returns.push_back(RI);
122 // Loop over all of the instructions in the function, fixing up operand
123 // references as we go. This uses ValueMap to do all the hard work.
125 for (Function::iterator BB = cast<BasicBlock>(ValueMap[OldFunc->begin()]),
126 BE = NewFunc->end(); BB != BE; ++BB)
127 // Loop over all instructions, fixing each one as we find it...
128 for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
129 RemapInstruction(II, ValueMap);
132 /// CloneFunction - Return a copy of the specified function, but without
133 /// embedding the function into another module. Also, any references specified
134 /// in the ValueMap are changed to refer to their mapped value instead of the
135 /// original one. If any of the arguments to the function are in the ValueMap,
136 /// the arguments are deleted from the resultant function. The ValueMap is
137 /// updated to include mappings from all of the instructions and basicblocks in
138 /// the function from their old to new values.
140 Function *llvm::CloneFunction(const Function *F,
141 DenseMap<const Value*, Value*> &ValueMap,
142 ClonedCodeInfo *CodeInfo) {
143 std::vector<const Type*> ArgTypes;
145 // The user might be deleting arguments to the function by specifying them in
146 // the ValueMap. If so, we need to not add the arguments to the arg ty vector
148 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
150 if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet?
151 ArgTypes.push_back(I->getType());
153 // Create a new function type...
154 FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(),
155 ArgTypes, F->getFunctionType()->isVarArg());
157 // Create the new function...
158 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
160 // Loop over the arguments, copying the names of the mapped arguments over...
161 Function::arg_iterator DestI = NewF->arg_begin();
162 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
164 if (ValueMap.count(I) == 0) { // Is this argument preserved?
165 DestI->setName(I->getName()); // Copy the name over...
166 ValueMap[I] = DestI++; // Add mapping to ValueMap
169 SmallVector<ReturnInst*, 8> Returns; // Ignore returns cloned.
170 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
177 /// PruningFunctionCloner - This class is a private class used to implement
178 /// the CloneAndPruneFunctionInto method.
179 struct PruningFunctionCloner {
181 const Function *OldFunc;
182 DenseMap<const Value*, Value*> &ValueMap;
183 SmallVectorImpl<ReturnInst*> &Returns;
184 const char *NameSuffix;
185 ClonedCodeInfo *CodeInfo;
186 const TargetData *TD;
189 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
190 DenseMap<const Value*, Value*> &valueMap,
191 SmallVectorImpl<ReturnInst*> &returns,
192 const char *nameSuffix,
193 ClonedCodeInfo *codeInfo,
194 const TargetData *td)
195 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
196 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td), DbgFnStart(NULL) {
199 /// CloneBlock - The specified block is found to be reachable, clone it and
200 /// anything that it can reach.
201 void CloneBlock(const BasicBlock *BB,
202 std::vector<const BasicBlock*> &ToClone);
205 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
206 /// mapping its operands through ValueMap if they are available.
207 Constant *ConstantFoldMappedInstruction(const Instruction *I);
211 /// CloneBlock - The specified block is found to be reachable, clone it and
212 /// anything that it can reach.
213 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
214 std::vector<const BasicBlock*> &ToClone){
215 Value *&BBEntry = ValueMap[BB];
217 // Have we already cloned this block?
220 // Nope, clone it now.
222 BBEntry = NewBB = BasicBlock::Create(BB->getContext());
223 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
225 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
227 // Loop over all instructions, and copy them over, DCE'ing as we go. This
228 // loop doesn't include the terminator.
229 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
231 // If this instruction constant folds, don't bother cloning the instruction,
232 // instead, just add the constant to the value map.
233 if (Constant *C = ConstantFoldMappedInstruction(II)) {
238 // Do not clone llvm.dbg.region.end. It will be adjusted by the inliner.
239 if (const DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(II)) {
240 if (DbgFnStart == NULL) {
241 DISubprogram SP(DFSI->getSubprogram());
242 if (SP.describes(BB->getParent()))
243 DbgFnStart = DFSI->getSubprogram();
246 if (const DbgRegionEndInst *DREIS = dyn_cast<DbgRegionEndInst>(II)) {
247 if (DREIS->getContext() == DbgFnStart)
251 Instruction *NewInst = II->clone();
253 NewInst->setName(II->getName()+NameSuffix);
254 NewBB->getInstList().push_back(NewInst);
255 ValueMap[II] = NewInst; // Add instruction map to value.
257 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
258 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
259 if (isa<ConstantInt>(AI->getArraySize()))
260 hasStaticAllocas = true;
262 hasDynamicAllocas = true;
266 // Finally, clone over the terminator.
267 const TerminatorInst *OldTI = BB->getTerminator();
268 bool TerminatorDone = false;
269 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
270 if (BI->isConditional()) {
271 // If the condition was a known constant in the callee...
272 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
273 // Or is a known constant in the caller...
275 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
277 // Constant fold to uncond branch!
279 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
280 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
281 ToClone.push_back(Dest);
282 TerminatorDone = true;
285 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
286 // If switching on a value known constant in the caller.
287 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
288 if (Cond == 0) // Or known constant after constant prop in the callee...
289 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
290 if (Cond) { // Constant fold to uncond branch!
291 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
292 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
293 ToClone.push_back(Dest);
294 TerminatorDone = true;
298 if (!TerminatorDone) {
299 Instruction *NewInst = OldTI->clone();
300 if (OldTI->hasName())
301 NewInst->setName(OldTI->getName()+NameSuffix);
302 NewBB->getInstList().push_back(NewInst);
303 ValueMap[OldTI] = NewInst; // Add instruction map to value.
305 // Recursively clone any reachable successor blocks.
306 const TerminatorInst *TI = BB->getTerminator();
307 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
308 ToClone.push_back(TI->getSuccessor(i));
312 CodeInfo->ContainsCalls |= hasCalls;
313 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
314 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
315 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
316 BB != &BB->getParent()->front();
319 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
320 Returns.push_back(RI);
323 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
324 /// mapping its operands through ValueMap if they are available.
325 Constant *PruningFunctionCloner::
326 ConstantFoldMappedInstruction(const Instruction *I) {
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(), Ops[0], Ops[1],
339 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
340 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
341 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
342 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
343 if (GV->isConstant() && GV->hasDefinitiveInitializer())
344 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
347 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
351 static MDNode *UpdateInlinedAtInfo(MDNode *InsnMD, MDNode *TheCallMD) {
352 DILocation ILoc(InsnMD);
353 if (ILoc.isNull()) return InsnMD;
355 DILocation CallLoc(TheCallMD);
356 if (CallLoc.isNull()) return InsnMD;
358 DILocation OrigLocation = ILoc.getOrigLocation();
359 MDNode *NewLoc = TheCallMD;
360 if (!OrigLocation.isNull())
361 NewLoc = UpdateInlinedAtInfo(OrigLocation.getNode(), TheCallMD);
364 InsnMD->getOperand(0), // Line
365 InsnMD->getOperand(1), // Col
366 InsnMD->getOperand(2), // Scope
369 return MDNode::get(InsnMD->getContext(), MDVs, 4);
372 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
373 /// except that it does some simple constant prop and DCE on the fly. The
374 /// effect of this is to copy significantly less code in cases where (for
375 /// example) a function call with constant arguments is inlined, and those
376 /// constant arguments cause a significant amount of code in the callee to be
377 /// dead. Since this doesn't produce an exact copy of the input, it can't be
378 /// used for things like CloneFunction or CloneModule.
379 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
380 DenseMap<const Value*, Value*> &ValueMap,
381 SmallVectorImpl<ReturnInst*> &Returns,
382 const char *NameSuffix,
383 ClonedCodeInfo *CodeInfo,
384 const TargetData *TD,
385 Instruction *TheCall) {
386 assert(NameSuffix && "NameSuffix cannot be null!");
389 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
390 E = OldFunc->arg_end(); II != E; ++II)
391 assert(ValueMap.count(II) && "No mapping from source argument specified!");
394 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
395 NameSuffix, CodeInfo, TD);
397 // Clone the entry block, and anything recursively reachable from it.
398 std::vector<const BasicBlock*> CloneWorklist;
399 CloneWorklist.push_back(&OldFunc->getEntryBlock());
400 while (!CloneWorklist.empty()) {
401 const BasicBlock *BB = CloneWorklist.back();
402 CloneWorklist.pop_back();
403 PFC.CloneBlock(BB, CloneWorklist);
406 // Loop over all of the basic blocks in the old function. If the block was
407 // reachable, we have cloned it and the old block is now in the value map:
408 // insert it into the new function in the right order. If not, ignore it.
410 // Defer PHI resolution until rest of function is resolved.
411 SmallVector<const PHINode*, 16> PHIToResolve;
412 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
414 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
415 if (NewBB == 0) continue; // Dead block.
417 // Add the new block to the new function.
418 NewFunc->getBasicBlockList().push_back(NewBB);
420 // Loop over all of the instructions in the block, fixing up operand
421 // references as we go. This uses ValueMap to do all the hard work.
423 BasicBlock::iterator I = NewBB->begin();
425 unsigned DbgKind = OldFunc->getContext().getMDKindID("dbg");
426 MDNode *TheCallMD = NULL;
427 if (TheCall && TheCall->hasMetadata())
428 TheCallMD = TheCall->getMetadata(DbgKind);
430 // Handle PHI nodes specially, as we have to remove references to dead
432 if (PHINode *PN = dyn_cast<PHINode>(I)) {
433 // Skip over all PHI nodes, remembering them for later.
434 BasicBlock::const_iterator OldI = BI->begin();
435 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI) {
436 if (I->hasMetadata()) {
438 if (MDNode *IMD = I->getMetadata(DbgKind)) {
439 MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD);
440 I->setMetadata(DbgKind, NewMD);
443 // The cloned instruction has dbg info but the call instruction
444 // does not have dbg info. Remove dbg info from cloned instruction.
445 I->setMetadata(DbgKind, 0);
448 PHIToResolve.push_back(cast<PHINode>(OldI));
454 // FIXME: Unclone all this metadata stuff.
458 // Otherwise, remap the rest of the instructions normally.
459 for (; I != NewBB->end(); ++I) {
460 if (I->hasMetadata()) {
462 if (MDNode *IMD = I->getMetadata(DbgKind)) {
463 MDNode *NewMD = UpdateInlinedAtInfo(IMD, TheCallMD);
464 I->setMetadata(DbgKind, NewMD);
467 // The cloned instruction has dbg info but the call instruction
468 // does not have dbg info. Remove dbg info from cloned instruction.
469 I->setMetadata(DbgKind, 0);
472 RemapInstruction(I, ValueMap);
476 // Defer PHI resolution until rest of function is resolved, PHI resolution
477 // requires the CFG to be up-to-date.
478 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
479 const PHINode *OPN = PHIToResolve[phino];
480 unsigned NumPreds = OPN->getNumIncomingValues();
481 const BasicBlock *OldBB = OPN->getParent();
482 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
484 // Map operands for blocks that are live and remove operands for blocks
486 for (; phino != PHIToResolve.size() &&
487 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
488 OPN = PHIToResolve[phino];
489 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
490 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
491 if (BasicBlock *MappedBlock =
492 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
493 Value *InVal = MapValue(PN->getIncomingValue(pred),
495 assert(InVal && "Unknown input value?");
496 PN->setIncomingValue(pred, InVal);
497 PN->setIncomingBlock(pred, MappedBlock);
499 PN->removeIncomingValue(pred, false);
500 --pred, --e; // Revisit the next entry.
505 // The loop above has removed PHI entries for those blocks that are dead
506 // and has updated others. However, if a block is live (i.e. copied over)
507 // but its terminator has been changed to not go to this block, then our
508 // phi nodes will have invalid entries. Update the PHI nodes in this
510 PHINode *PN = cast<PHINode>(NewBB->begin());
511 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
512 if (NumPreds != PN->getNumIncomingValues()) {
513 assert(NumPreds < PN->getNumIncomingValues());
514 // Count how many times each predecessor comes to this block.
515 std::map<BasicBlock*, unsigned> PredCount;
516 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
520 // Figure out how many entries to remove from each PHI.
521 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
522 ++PredCount[PN->getIncomingBlock(i)];
524 // At this point, the excess predecessor entries are positive in the
525 // map. Loop over all of the PHIs and remove excess predecessor
527 BasicBlock::iterator I = NewBB->begin();
528 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
529 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
530 E = PredCount.end(); PCI != E; ++PCI) {
531 BasicBlock *Pred = PCI->first;
532 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
533 PN->removeIncomingValue(Pred, false);
538 // If the loops above have made these phi nodes have 0 or 1 operand,
539 // replace them with undef or the input value. We must do this for
540 // correctness, because 0-operand phis are not valid.
541 PN = cast<PHINode>(NewBB->begin());
542 if (PN->getNumIncomingValues() == 0) {
543 BasicBlock::iterator I = NewBB->begin();
544 BasicBlock::const_iterator OldI = OldBB->begin();
545 while ((PN = dyn_cast<PHINode>(I++))) {
546 Value *NV = UndefValue::get(PN->getType());
547 PN->replaceAllUsesWith(NV);
548 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
550 PN->eraseFromParent();
554 // NOTE: We cannot eliminate single entry phi nodes here, because of
555 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
556 // pointing at them. Thus, deleting one would require scanning the ValueMap
557 // to update any entries in it that would require that. This would be
561 // Now that the inlined function body has been fully constructed, go through
562 // and zap unconditional fall-through branches. This happen all the time when
563 // specializing code: code specialization turns conditional branches into
564 // uncond branches, and this code folds them.
565 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
566 while (I != NewFunc->end()) {
567 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
568 if (!BI || BI->isConditional()) { ++I; continue; }
570 // Note that we can't eliminate uncond branches if the destination has
571 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
572 // require scanning the ValueMap to update any entries that point to the phi
574 BasicBlock *Dest = BI->getSuccessor(0);
575 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
579 // We know all single-entry PHI nodes in the inlined function have been
580 // removed, so we just need to splice the blocks.
581 BI->eraseFromParent();
583 // Move all the instructions in the succ to the pred.
584 I->getInstList().splice(I->end(), Dest->getInstList());
586 // Make all PHI nodes that referred to Dest now refer to I as their source.
587 Dest->replaceAllUsesWith(I);
589 // Remove the dest block.
590 Dest->eraseFromParent();
592 // Do not increment I, iteratively merge all things this block branches to.