//===- CloneFunction.cpp - Clone a function into another function ---------===// // // The LLVM Compiler Infrastructure // // This file was developed by the LLVM research group and is distributed under // the University of Illinois Open Source License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This file implements the CloneFunctionInto interface, which is used as the // low-level function cloner. This is used by the CloneFunction and function // inliner to do the dirty work of copying the body of a function around. // //===----------------------------------------------------------------------===// #include "llvm/Transforms/Utils/Cloning.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Instructions.h" #include "llvm/Function.h" #include "llvm/Support/CFG.h" #include "llvm/Support/Compiler.h" #include "ValueMapper.h" #include "llvm/Analysis/ConstantFolding.h" #include "llvm/ADT/SmallVector.h" #include using namespace llvm; // CloneBasicBlock - See comments in Cloning.h BasicBlock *llvm::CloneBasicBlock(const BasicBlock *BB, DenseMap &ValueMap, const char *NameSuffix, Function *F, ClonedCodeInfo *CodeInfo) { BasicBlock *NewBB = new BasicBlock("", F); if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; // Loop over all instructions, and copy them over. for (BasicBlock::const_iterator II = BB->begin(), IE = BB->end(); II != IE; ++II) { Instruction *NewInst = II->clone(); if (II->hasName()) NewInst->setName(II->getName()+NameSuffix); NewBB->getInstList().push_back(NewInst); ValueMap[II] = NewInst; // Add instruction map to value. hasCalls |= isa(II); if (const AllocaInst *AI = dyn_cast(II)) { if (isa(AI->getArraySize())) hasStaticAllocas = true; else hasDynamicAllocas = true; } } if (CodeInfo) { CodeInfo->ContainsCalls |= hasCalls; CodeInfo->ContainsUnwinds |= isa(BB->getTerminator()); CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && BB != &BB->getParent()->getEntryBlock(); } return NewBB; } // Clone OldFunc into NewFunc, transforming the old arguments into references to // ArgMap values. // void llvm::CloneFunctionInto(Function *NewFunc, const Function *OldFunc, DenseMap &ValueMap, std::vector &Returns, const char *NameSuffix, ClonedCodeInfo *CodeInfo) { assert(NameSuffix && "NameSuffix cannot be null!"); #ifndef NDEBUG for (Function::const_arg_iterator I = OldFunc->arg_begin(), E = OldFunc->arg_end(); I != E; ++I) assert(ValueMap.count(I) && "No mapping from source argument specified!"); #endif // Loop over all of the basic blocks in the function, cloning them as // appropriate. Note that we save BE this way in order to handle cloning of // recursive functions into themselves. // for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); BI != BE; ++BI) { const BasicBlock &BB = *BI; // Create a new basic block and copy instructions into it! BasicBlock *CBB = CloneBasicBlock(&BB, ValueMap, NameSuffix, NewFunc, CodeInfo); ValueMap[&BB] = CBB; // Add basic block mapping. if (ReturnInst *RI = dyn_cast(CBB->getTerminator())) Returns.push_back(RI); } // Loop over all of the instructions in the function, fixing up operand // references as we go. This uses ValueMap to do all the hard work. // for (Function::iterator BB = cast(ValueMap[OldFunc->begin()]), BE = NewFunc->end(); BB != BE; ++BB) // Loop over all instructions, fixing each one as we find it... for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) RemapInstruction(II, ValueMap); } /// CloneFunction - Return a copy of the specified function, but without /// embedding the function into another module. Also, any references specified /// in the ValueMap are changed to refer to their mapped value instead of the /// original one. If any of the arguments to the function are in the ValueMap, /// the arguments are deleted from the resultant function. The ValueMap is /// updated to include mappings from all of the instructions and basicblocks in /// the function from their old to new values. /// Function *llvm::CloneFunction(const Function *F, DenseMap &ValueMap, ClonedCodeInfo *CodeInfo) { std::vector ArgTypes; // The user might be deleting arguments to the function by specifying them in // the ValueMap. If so, we need to not add the arguments to the arg ty vector // for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I) if (ValueMap.count(I) == 0) // Haven't mapped the argument to anything yet? ArgTypes.push_back(I->getType()); // Create a new function type... FunctionType *FTy = FunctionType::get(F->getFunctionType()->getReturnType(), ArgTypes, F->getFunctionType()->isVarArg()); // Create the new function... Function *NewF = new Function(FTy, F->getLinkage(), F->getName()); // Loop over the arguments, copying the names of the mapped arguments over... Function::arg_iterator DestI = NewF->arg_begin(); for (Function::const_arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I) if (ValueMap.count(I) == 0) { // Is this argument preserved? DestI->setName(I->getName()); // Copy the name over... ValueMap[I] = DestI++; // Add mapping to ValueMap } std::vector Returns; // Ignore returns cloned... CloneFunctionInto(NewF, F, ValueMap, Returns, "", CodeInfo); return NewF; } namespace { /// PruningFunctionCloner - This class is a private class used to implement /// the CloneAndPruneFunctionInto method. struct VISIBILITY_HIDDEN PruningFunctionCloner { Function *NewFunc; const Function *OldFunc; DenseMap &ValueMap; std::vector &Returns; const char *NameSuffix; ClonedCodeInfo *CodeInfo; const TargetData *TD; public: PruningFunctionCloner(Function *newFunc, const Function *oldFunc, DenseMap &valueMap, std::vector &returns, const char *nameSuffix, ClonedCodeInfo *codeInfo, const TargetData *td) : NewFunc(newFunc), OldFunc(oldFunc), ValueMap(valueMap), Returns(returns), NameSuffix(nameSuffix), CodeInfo(codeInfo), TD(td) { } /// CloneBlock - The specified block is found to be reachable, clone it and /// anything that it can reach. void CloneBlock(const BasicBlock *BB, std::vector &ToClone); public: /// ConstantFoldMappedInstruction - Constant fold the specified instruction, /// mapping its operands through ValueMap if they are available. Constant *ConstantFoldMappedInstruction(const Instruction *I); }; } /// CloneBlock - The specified block is found to be reachable, clone it and /// anything that it can reach. void PruningFunctionCloner::CloneBlock(const BasicBlock *BB, std::vector &ToClone){ Value *&BBEntry = ValueMap[BB]; // Have we already cloned this block? if (BBEntry) return; // Nope, clone it now. BasicBlock *NewBB; BBEntry = NewBB = new BasicBlock(); if (BB->hasName()) NewBB->setName(BB->getName()+NameSuffix); bool hasCalls = false, hasDynamicAllocas = false, hasStaticAllocas = false; // Loop over all instructions, and copy them over, DCE'ing as we go. This // loop doesn't include the terminator. for (BasicBlock::const_iterator II = BB->begin(), IE = --BB->end(); II != IE; ++II) { // If this instruction constant folds, don't bother cloning the instruction, // instead, just add the constant to the value map. if (Constant *C = ConstantFoldMappedInstruction(II)) { ValueMap[II] = C; continue; } Instruction *NewInst = II->clone(); if (II->hasName()) NewInst->setName(II->getName()+NameSuffix); NewBB->getInstList().push_back(NewInst); ValueMap[II] = NewInst; // Add instruction map to value. hasCalls |= isa(II); if (const AllocaInst *AI = dyn_cast(II)) { if (isa(AI->getArraySize())) hasStaticAllocas = true; else hasDynamicAllocas = true; } } // Finally, clone over the terminator. const TerminatorInst *OldTI = BB->getTerminator(); bool TerminatorDone = false; if (const BranchInst *BI = dyn_cast(OldTI)) { if (BI->isConditional()) { // If the condition was a known constant in the callee... ConstantInt *Cond = dyn_cast(BI->getCondition()); // Or is a known constant in the caller... if (Cond == 0) Cond = dyn_cast_or_null(ValueMap[BI->getCondition()]); // Constant fold to uncond branch! if (Cond) { BasicBlock *Dest = BI->getSuccessor(!Cond->getZExtValue()); ValueMap[OldTI] = new BranchInst(Dest, NewBB); ToClone.push_back(Dest); TerminatorDone = true; } } } else if (const SwitchInst *SI = dyn_cast(OldTI)) { // If switching on a value known constant in the caller. ConstantInt *Cond = dyn_cast(SI->getCondition()); if (Cond == 0) // Or known constant after constant prop in the callee... Cond = dyn_cast_or_null(ValueMap[SI->getCondition()]); if (Cond) { // Constant fold to uncond branch! BasicBlock *Dest = SI->getSuccessor(SI->findCaseValue(Cond)); ValueMap[OldTI] = new BranchInst(Dest, NewBB); ToClone.push_back(Dest); TerminatorDone = true; } } if (!TerminatorDone) { Instruction *NewInst = OldTI->clone(); if (OldTI->hasName()) NewInst->setName(OldTI->getName()+NameSuffix); NewBB->getInstList().push_back(NewInst); ValueMap[OldTI] = NewInst; // Add instruction map to value. // Recursively clone any reachable successor blocks. const TerminatorInst *TI = BB->getTerminator(); for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) ToClone.push_back(TI->getSuccessor(i)); } if (CodeInfo) { CodeInfo->ContainsCalls |= hasCalls; CodeInfo->ContainsUnwinds |= isa(OldTI); CodeInfo->ContainsDynamicAllocas |= hasDynamicAllocas; CodeInfo->ContainsDynamicAllocas |= hasStaticAllocas && BB != &BB->getParent()->front(); } if (ReturnInst *RI = dyn_cast(NewBB->getTerminator())) Returns.push_back(RI); } /// ConstantFoldMappedInstruction - Constant fold the specified instruction, /// mapping its operands through ValueMap if they are available. Constant *PruningFunctionCloner:: ConstantFoldMappedInstruction(const Instruction *I) { SmallVector Ops; for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) if (Constant *Op = dyn_cast_or_null(MapValue(I->getOperand(i), ValueMap))) Ops.push_back(Op); else return 0; // All operands not constant! return ConstantFoldInstOperands(I, &Ops[0], Ops.size(), TD); } /// CloneAndPruneFunctionInto - This works exactly like CloneFunctionInto, /// except that it does some simple constant prop and DCE on the fly. The /// effect of this is to copy significantly less code in cases where (for /// example) a function call with constant arguments is inlined, and those /// constant arguments cause a significant amount of code in the callee to be /// dead. Since this doesn't produce an exactly copy of the input, it can't be /// used for things like CloneFunction or CloneModule. void llvm::CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc, DenseMap &ValueMap, std::vector &Returns, const char *NameSuffix, ClonedCodeInfo *CodeInfo, const TargetData *TD) { assert(NameSuffix && "NameSuffix cannot be null!"); #ifndef NDEBUG for (Function::const_arg_iterator II = OldFunc->arg_begin(), E = OldFunc->arg_end(); II != E; ++II) assert(ValueMap.count(II) && "No mapping from source argument specified!"); #endif PruningFunctionCloner PFC(NewFunc, OldFunc, ValueMap, Returns, NameSuffix, CodeInfo, TD); // Clone the entry block, and anything recursively reachable from it. std::vector CloneWorklist; CloneWorklist.push_back(&OldFunc->getEntryBlock()); while (!CloneWorklist.empty()) { const BasicBlock *BB = CloneWorklist.back(); CloneWorklist.pop_back(); PFC.CloneBlock(BB, CloneWorklist); } // Loop over all of the basic blocks in the old function. If the block was // reachable, we have cloned it and the old block is now in the value map: // insert it into the new function in the right order. If not, ignore it. // // Defer PHI resolution until rest of function is resolved. std::vector PHIToResolve; for (Function::const_iterator BI = OldFunc->begin(), BE = OldFunc->end(); BI != BE; ++BI) { BasicBlock *NewBB = cast_or_null(ValueMap[BI]); if (NewBB == 0) continue; // Dead block. // Add the new block to the new function. NewFunc->getBasicBlockList().push_back(NewBB); // Loop over all of the instructions in the block, fixing up operand // references as we go. This uses ValueMap to do all the hard work. // BasicBlock::iterator I = NewBB->begin(); // Handle PHI nodes specially, as we have to remove references to dead // blocks. if (PHINode *PN = dyn_cast(I)) { // Skip over all PHI nodes, remembering them for later. BasicBlock::const_iterator OldI = BI->begin(); for (; (PN = dyn_cast(I)); ++I, ++OldI) PHIToResolve.push_back(cast(OldI)); } // Otherwise, remap the rest of the instructions normally. for (; I != NewBB->end(); ++I) RemapInstruction(I, ValueMap); } // Defer PHI resolution until rest of function is resolved, PHI resolution // requires the CFG to be up-to-date. for (unsigned phino = 0, e = PHIToResolve.size(); phino != e; ) { const PHINode *OPN = PHIToResolve[phino]; unsigned NumPreds = OPN->getNumIncomingValues(); const BasicBlock *OldBB = OPN->getParent(); BasicBlock *NewBB = cast(ValueMap[OldBB]); // Map operands for blocks that are live and remove operands for blocks // that are dead. for (; phino != PHIToResolve.size() && PHIToResolve[phino]->getParent() == OldBB; ++phino) { OPN = PHIToResolve[phino]; PHINode *PN = cast(ValueMap[OPN]); for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) { if (BasicBlock *MappedBlock = cast_or_null(ValueMap[PN->getIncomingBlock(pred)])) { Value *InVal = MapValue(PN->getIncomingValue(pred), ValueMap); assert(InVal && "Unknown input value?"); PN->setIncomingValue(pred, InVal); PN->setIncomingBlock(pred, MappedBlock); } else { PN->removeIncomingValue(pred, false); --pred, --e; // Revisit the next entry. } } } // The loop above has removed PHI entries for those blocks that are dead // and has updated others. However, if a block is live (i.e. copied over) // but its terminator has been changed to not go to this block, then our // phi nodes will have invalid entries. Update the PHI nodes in this // case. PHINode *PN = cast(NewBB->begin()); NumPreds = std::distance(pred_begin(NewBB), pred_end(NewBB)); if (NumPreds != PN->getNumIncomingValues()) { assert(NumPreds < PN->getNumIncomingValues()); // Count how many times each predecessor comes to this block. std::map PredCount; for (pred_iterator PI = pred_begin(NewBB), E = pred_end(NewBB); PI != E; ++PI) --PredCount[*PI]; // Figure out how many entries to remove from each PHI. for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) ++PredCount[PN->getIncomingBlock(i)]; // At this point, the excess predecessor entries are positive in the // map. Loop over all of the PHIs and remove excess predecessor // entries. BasicBlock::iterator I = NewBB->begin(); for (; (PN = dyn_cast(I)); ++I) { for (std::map::iterator PCI =PredCount.begin(), E = PredCount.end(); PCI != E; ++PCI) { BasicBlock *Pred = PCI->first; for (unsigned NumToRemove = PCI->second; NumToRemove; --NumToRemove) PN->removeIncomingValue(Pred, false); } } } // If the loops above have made these phi nodes have 0 or 1 operand, // replace them with undef or the input value. We must do this for // correctness, because 0-operand phis are not valid. PN = cast(NewBB->begin()); if (PN->getNumIncomingValues() == 0) { BasicBlock::iterator I = NewBB->begin(); BasicBlock::const_iterator OldI = OldBB->begin(); while ((PN = dyn_cast(I++))) { Value *NV = UndefValue::get(PN->getType()); PN->replaceAllUsesWith(NV); assert(ValueMap[OldI] == PN && "ValueMap mismatch"); ValueMap[OldI] = NV; PN->eraseFromParent(); ++OldI; } } // NOTE: We cannot eliminate single entry phi nodes here, because of // ValueMap. Single entry phi nodes can have multiple ValueMap entries // pointing at them. Thus, deleting one would require scanning the ValueMap // to update any entries in it that would require that. This would be // really slow. } // Now that the inlined function body has been fully constructed, go through // and zap unconditional fall-through branches. This happen all the time when // specializing code: code specialization turns conditional branches into // uncond branches, and this code folds them. Function::iterator I = cast(ValueMap[&OldFunc->getEntryBlock()]); while (I != NewFunc->end()) { BranchInst *BI = dyn_cast(I->getTerminator()); if (!BI || BI->isConditional()) { ++I; continue; } // Note that we can't eliminate uncond branches if the destination has // single-entry PHI nodes. Eliminating the single-entry phi nodes would // require scanning the ValueMap to update any entries that point to the phi // node. BasicBlock *Dest = BI->getSuccessor(0); if (!Dest->getSinglePredecessor() || isa(Dest->begin())) { ++I; continue; } // We know all single-entry PHI nodes in the inlined function have been // removed, so we just need to splice the blocks. BI->eraseFromParent(); // Move all the instructions in the succ to the pred. I->getInstList().splice(I->end(), Dest->getInstList()); // Make all PHI nodes that referred to Dest now refer to I as their source. Dest->replaceAllUsesWith(I); // Remove the dest block. Dest->eraseFromParent(); // Do not increment I, iteratively merge all things this block branches to. } }