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/Support/CFG.h"
25 #include "llvm/Support/Compiler.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("", 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 std::vector<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...
155 F->getContext()->getFunctionType(F->getFunctionType()->getReturnType(),
156 ArgTypes, F->getFunctionType()->isVarArg());
158 // Create the new function...
159 Function *NewF = Function::Create(FTy, F->getLinkage(), F->getName());
161 // Loop over the arguments, copying the names of the mapped arguments over...
162 Function::arg_iterator DestI = NewF->arg_begin();
163 for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end();
165 if (ValueMap.count(I) == 0) { // Is this argument preserved?
166 DestI->setName(I->getName()); // Copy the name over...
167 ValueMap[I] = DestI++; // Add mapping to ValueMap
170 std::vector<ReturnInst*> Returns; // Ignore returns cloned...
171 CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo);
178 /// PruningFunctionCloner - This class is a private class used to implement
179 /// the CloneAndPruneFunctionInto method.
180 struct VISIBILITY_HIDDEN PruningFunctionCloner {
182 const Function *OldFunc;
183 DenseMap<const Value*, Value*> &ValueMap;
184 std::vector<ReturnInst*> &Returns;
185 const char *NameSuffix;
186 ClonedCodeInfo *CodeInfo;
187 const TargetData *TD;
190 PruningFunctionCloner(Function *newFunc, const Function *oldFunc,
191 DenseMap<const Value*, Value*> &valueMap,
192 std::vector<ReturnInst*> &returns,
193 const char *nameSuffix,
194 ClonedCodeInfo *codeInfo,
195 const TargetData *td)
196 : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns),
197 NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td), DbgFnStart(NULL) {
200 /// CloneBlock - The specified block is found to be reachable, clone it and
201 /// anything that it can reach.
202 void CloneBlock(const BasicBlock *BB,
203 std::vector<const BasicBlock*> &ToClone);
206 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
207 /// mapping its operands through ValueMap if they are available.
208 Constant *ConstantFoldMappedInstruction(const Instruction *I);
212 /// CloneBlock - The specified block is found to be reachable, clone it and
213 /// anything that it can reach.
214 void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
215 std::vector<const BasicBlock*> &ToClone){
216 Value *&BBEntry = ValueMap[BB];
218 // Have we already cloned this block?
221 // Nope, clone it now.
223 BBEntry = NewBB = BasicBlock::Create();
224 if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix);
226 bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false;
228 // Loop over all instructions, and copy them over, DCE'ing as we go. This
229 // loop doesn't include the terminator.
230 for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end();
232 // If this instruction constant folds, don't bother cloning the instruction,
233 // instead, just add the constant to the value map.
234 if (Constant *C = ConstantFoldMappedInstruction(II)) {
239 // Do not clone llvm.dbg.region.end. It will be adjusted by the inliner.
240 if (const DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(II)) {
241 if (DbgFnStart == NULL) {
242 DISubprogram SP(cast<GlobalVariable>(DFSI->getSubprogram()));
243 if (SP.describes(BB->getParent()))
244 DbgFnStart = DFSI->getSubprogram();
247 if (const DbgRegionEndInst *DREIS = dyn_cast<DbgRegionEndInst>(II)) {
248 if (DREIS->getContext() == DbgFnStart)
252 Instruction *NewInst = II->clone();
254 NewInst->setName(II->getName()+NameSuffix);
255 NewBB->getInstList().push_back(NewInst);
256 ValueMap[II] = NewInst; // Add instruction map to value.
258 hasCalls |= (isa<CallInst>(II) && !isa<DbgInfoIntrinsic>(II));
259 if (const AllocaInst *AI = dyn_cast<AllocaInst>(II)) {
260 if (isa<ConstantInt>(AI->getArraySize()))
261 hasStaticAllocas = true;
263 hasDynamicAllocas = true;
267 // Finally, clone over the terminator.
268 const TerminatorInst *OldTI = BB->getTerminator();
269 bool TerminatorDone = false;
270 if (const BranchInst *BI = dyn_cast<BranchInst>(OldTI)) {
271 if (BI->isConditional()) {
272 // If the condition was a known constant in the callee...
273 ConstantInt *Cond = dyn_cast<ConstantInt>(BI->getCondition());
274 // Or is a known constant in the caller...
276 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[BI->getCondition()]);
278 // Constant fold to uncond branch!
280 BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue());
281 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
282 ToClone.push_back(Dest);
283 TerminatorDone = true;
286 } else if (const SwitchInst *SI = dyn_cast<SwitchInst>(OldTI)) {
287 // If switching on a value known constant in the caller.
288 ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition());
289 if (Cond == 0) // Or known constant after constant prop in the callee...
290 Cond = dyn_cast_or_null<ConstantInt>(ValueMap[SI->getCondition()]);
291 if (Cond) { // Constant fold to uncond branch!
292 BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond));
293 ValueMap[OldTI] = BranchInst::Create(Dest, NewBB);
294 ToClone.push_back(Dest);
295 TerminatorDone = true;
299 if (!TerminatorDone) {
300 Instruction *NewInst = OldTI->clone();
301 if (OldTI->hasName())
302 NewInst->setName(OldTI->getName()+NameSuffix);
303 NewBB->getInstList().push_back(NewInst);
304 ValueMap[OldTI] = NewInst; // Add instruction map to value.
306 // Recursively clone any reachable successor blocks.
307 const TerminatorInst *TI = BB->getTerminator();
308 for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
309 ToClone.push_back(TI->getSuccessor(i));
313 CodeInfo->ContainsCalls |= hasCalls;
314 CodeInfo->ContainsUnwinds |= isa<UnwindInst>(OldTI);
315 CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas;
316 CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas &&
317 BB != &BB->getParent()->front();
320 if (ReturnInst *RI = dyn_cast<ReturnInst>(NewBB->getTerminator()))
321 Returns.push_back(RI);
324 /// ConstantFoldMappedInstruction - Constant fold the specified instruction,
325 /// mapping its operands through ValueMap if they are available.
326 Constant *PruningFunctionCloner::
327 ConstantFoldMappedInstruction(const Instruction *I) {
328 LLVMContext *Context = I->getParent()->getContext();
330 SmallVector<Constant*, 8> Ops;
331 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
332 if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
337 return 0; // All operands not constant!
339 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
340 return ConstantFoldCompareInstOperands(CI->getPredicate(),
344 if (const LoadInst *LI = dyn_cast<LoadInst>(I))
345 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ops[0]))
346 if (!LI->isVolatile() && CE->getOpcode() == Instruction::GetElementPtr)
347 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(CE->getOperand(0)))
348 if (GV->isConstant() && GV->hasDefinitiveInitializer())
349 return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(),
352 return ConstantFoldInstOperands(I->getOpcode(), I->getType(), &Ops[0],
353 Ops.size(), Context, TD);
356 /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto,
357 /// except that it does some simple constant prop and DCE on the fly. The
358 /// effect of this is to copy significantly less code in cases where (for
359 /// example) a function call with constant arguments is inlined, and those
360 /// constant arguments cause a significant amount of code in the callee to be
361 /// dead. Since this doesn't produce an exact copy of the input, it can't be
362 /// used for things like CloneFunction or CloneModule.
363 void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
364 DenseMap<const Value*, Value*> &ValueMap,
365 std::vector<ReturnInst*> &Returns,
366 const char *NameSuffix,
367 ClonedCodeInfo *CodeInfo,
368 const TargetData *TD) {
369 assert(NameSuffix && "NameSuffix cannot be null!");
370 LLVMContext *Context = OldFunc->getContext();
373 for (Function::const_arg_iterator II = OldFunc->arg_begin(),
374 E = OldFunc->arg_end(); II != E; ++II)
375 assert(ValueMap.count(II) && "No mapping from source argument specified!");
378 PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns,
379 NameSuffix, CodeInfo, TD);
381 // Clone the entry block, and anything recursively reachable from it.
382 std::vector<const BasicBlock*> CloneWorklist;
383 CloneWorklist.push_back(&OldFunc->getEntryBlock());
384 while (!CloneWorklist.empty()) {
385 const BasicBlock *BB = CloneWorklist.back();
386 CloneWorklist.pop_back();
387 PFC.CloneBlock(BB, CloneWorklist);
390 // Loop over all of the basic blocks in the old function. If the block was
391 // reachable, we have cloned it and the old block is now in the value map:
392 // insert it into the new function in the right order. If not, ignore it.
394 // Defer PHI resolution until rest of function is resolved.
395 std::vector<const PHINode*> PHIToResolve;
396 for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end();
398 BasicBlock *NewBB = cast_or_null<BasicBlock>(ValueMap[BI]);
399 if (NewBB == 0) continue; // Dead block.
401 // Add the new block to the new function.
402 NewFunc->getBasicBlockList().push_back(NewBB);
404 // Loop over all of the instructions in the block, fixing up operand
405 // references as we go. This uses ValueMap to do all the hard work.
407 BasicBlock::iterator I = NewBB->begin();
409 // Handle PHI nodes specially, as we have to remove references to dead
411 if (PHINode *PN = dyn_cast<PHINode>(I)) {
412 // Skip over all PHI nodes, remembering them for later.
413 BasicBlock::const_iterator OldI = BI->begin();
414 for (; (PN = dyn_cast<PHINode>(I)); ++I, ++OldI)
415 PHIToResolve.push_back(cast<PHINode>(OldI));
418 // Otherwise, remap the rest of the instructions normally.
419 for (; I != NewBB->end(); ++I)
420 RemapInstruction(I, ValueMap);
423 // Defer PHI resolution until rest of function is resolved, PHI resolution
424 // requires the CFG to be up-to-date.
425 for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) {
426 const PHINode *OPN = PHIToResolve[phino];
427 unsigned NumPreds = OPN->getNumIncomingValues();
428 const BasicBlock *OldBB = OPN->getParent();
429 BasicBlock *NewBB = cast<BasicBlock>(ValueMap[OldBB]);
431 // Map operands for blocks that are live and remove operands for blocks
433 for (; phino != PHIToResolve.size() &&
434 PHIToResolve[phino]->getParent() == OldBB; ++phino) {
435 OPN = PHIToResolve[phino];
436 PHINode *PN = cast<PHINode>(ValueMap[OPN]);
437 for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
438 if (BasicBlock *MappedBlock =
439 cast_or_null<BasicBlock>(ValueMap[PN->getIncomingBlock(pred)])) {
440 Value *InVal = MapValue(PN->getIncomingValue(pred),
442 assert(InVal && "Unknown input value?");
443 PN->setIncomingValue(pred, InVal);
444 PN->setIncomingBlock(pred, MappedBlock);
446 PN->removeIncomingValue(pred, false);
447 --pred, --e; // Revisit the next entry.
452 // The loop above has removed PHI entries for those blocks that are dead
453 // and has updated others. However, if a block is live (i.e. copied over)
454 // but its terminator has been changed to not go to this block, then our
455 // phi nodes will have invalid entries. Update the PHI nodes in this
457 PHINode *PN = cast<PHINode>(NewBB->begin());
458 NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB));
459 if (NumPreds != PN->getNumIncomingValues()) {
460 assert(NumPreds < PN->getNumIncomingValues());
461 // Count how many times each predecessor comes to this block.
462 std::map<BasicBlock*, unsigned> PredCount;
463 for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB);
467 // Figure out how many entries to remove from each PHI.
468 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
469 ++PredCount[PN->getIncomingBlock(i)];
471 // At this point, the excess predecessor entries are positive in the
472 // map. Loop over all of the PHIs and remove excess predecessor
474 BasicBlock::iterator I = NewBB->begin();
475 for (; (PN = dyn_cast<PHINode>(I)); ++I) {
476 for (std::map<BasicBlock*, unsigned>::iterator PCI =PredCount.begin(),
477 E = PredCount.end(); PCI != E; ++PCI) {
478 BasicBlock *Pred = PCI->first;
479 for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove)
480 PN->removeIncomingValue(Pred, false);
485 // If the loops above have made these phi nodes have 0 or 1 operand,
486 // replace them with undef or the input value. We must do this for
487 // correctness, because 0-operand phis are not valid.
488 PN = cast<PHINode>(NewBB->begin());
489 if (PN->getNumIncomingValues() == 0) {
490 BasicBlock::iterator I = NewBB->begin();
491 BasicBlock::const_iterator OldI = OldBB->begin();
492 while ((PN = dyn_cast<PHINode>(I++))) {
493 Value *NV = OldFunc->getContext()->getUndef(PN->getType());
494 PN->replaceAllUsesWith(NV);
495 assert(ValueMap[OldI] == PN && "ValueMap mismatch");
497 PN->eraseFromParent();
501 // NOTE: We cannot eliminate single entry phi nodes here, because of
502 // ValueMap. Single entry phi nodes can have multiple ValueMap entries
503 // pointing at them. Thus, deleting one would require scanning the ValueMap
504 // to update any entries in it that would require that. This would be
508 // Now that the inlined function body has been fully constructed, go through
509 // and zap unconditional fall-through branches. This happen all the time when
510 // specializing code: code specialization turns conditional branches into
511 // uncond branches, and this code folds them.
512 Function::iterator I = cast<BasicBlock>(ValueMap[&OldFunc->getEntryBlock()]);
513 while (I != NewFunc->end()) {
514 BranchInst *BI = dyn_cast<BranchInst>(I->getTerminator());
515 if (!BI || BI->isConditional()) { ++I; continue; }
517 // Note that we can't eliminate uncond branches if the destination has
518 // single-entry PHI nodes. Eliminating the single-entry phi nodes would
519 // require scanning the ValueMap to update any entries that point to the phi
521 BasicBlock *Dest = BI->getSuccessor(0);
522 if (!Dest->getSinglePredecessor() || isa<PHINode>(Dest->begin())) {
526 // We know all single-entry PHI nodes in the inlined function have been
527 // removed, so we just need to splice the blocks.
528 BI->eraseFromParent();
530 // Move all the instructions in the succ to the pred.
531 I->getInstList().splice(I->end(), Dest->getInstList());
533 // Make all PHI nodes that referred to Dest now refer to I as their source.
534 Dest->replaceAllUsesWith(I);
536 // Remove the dest block.
537 Dest->eraseFromParent();
539 // Do not increment I, iteratively merge all things this block branches to.