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Diffstat (limited to 'lib/Transforms/Utils/CodeExtractor.cpp')
| -rw-r--r-- | lib/Transforms/Utils/CodeExtractor.cpp | 795 |
1 files changed, 795 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/CodeExtractor.cpp b/lib/Transforms/Utils/CodeExtractor.cpp new file mode 100644 index 0000000..b208494 --- /dev/null +++ b/lib/Transforms/Utils/CodeExtractor.cpp @@ -0,0 +1,795 @@ +//===- CodeExtractor.cpp - Pull code region into a new function -----------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file implements the interface to tear out a code region, such as an +// individual loop or a parallel section, into a new function, replacing it with +// a call to the new function. +// +//===----------------------------------------------------------------------===// + +#include "llvm/Transforms/Utils/FunctionUtils.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/Instructions.h" +#include "llvm/Intrinsics.h" +#include "llvm/LLVMContext.h" +#include "llvm/Module.h" +#include "llvm/Pass.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/Verifier.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/StringExtras.h" +#include <algorithm> +#include <set> +using namespace llvm; + +// Provide a command-line option to aggregate function arguments into a struct +// for functions produced by the code extractor. This is useful when converting +// extracted functions to pthread-based code, as only one argument (void*) can +// be passed in to pthread_create(). +static cl::opt<bool> +AggregateArgsOpt("aggregate-extracted-args", cl::Hidden, + cl::desc("Aggregate arguments to code-extracted functions")); + +namespace { + class CodeExtractor { + typedef SetVector<Value*> Values; + SetVector<BasicBlock*> BlocksToExtract; + DominatorTree* DT; + bool AggregateArgs; + unsigned NumExitBlocks; + const Type *RetTy; + public: + CodeExtractor(DominatorTree* dt = 0, bool AggArgs = false) + : DT(dt), AggregateArgs(AggArgs||AggregateArgsOpt), NumExitBlocks(~0U) {} + + Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code); + + bool isEligible(const std::vector<BasicBlock*> &code); + + private: + /// definedInRegion - Return true if the specified value is defined in the + /// extracted region. + bool definedInRegion(Value *V) const { + if (Instruction *I = dyn_cast<Instruction>(V)) + if (BlocksToExtract.count(I->getParent())) + return true; + return false; + } + + /// definedInCaller - Return true if the specified value is defined in the + /// function being code extracted, but not in the region being extracted. + /// These values must be passed in as live-ins to the function. + bool definedInCaller(Value *V) const { + if (isa<Argument>(V)) return true; + if (Instruction *I = dyn_cast<Instruction>(V)) + if (!BlocksToExtract.count(I->getParent())) + return true; + return false; + } + + void severSplitPHINodes(BasicBlock *&Header); + void splitReturnBlocks(); + void findInputsOutputs(Values &inputs, Values &outputs); + + Function *constructFunction(const Values &inputs, + const Values &outputs, + BasicBlock *header, + BasicBlock *newRootNode, BasicBlock *newHeader, + Function *oldFunction, Module *M); + + void moveCodeToFunction(Function *newFunction); + + void emitCallAndSwitchStatement(Function *newFunction, + BasicBlock *newHeader, + Values &inputs, + Values &outputs); + + }; +} + +/// severSplitPHINodes - If a PHI node has multiple inputs from outside of the +/// region, we need to split the entry block of the region so that the PHI node +/// is easier to deal with. +void CodeExtractor::severSplitPHINodes(BasicBlock *&Header) { + bool HasPredsFromRegion = false; + unsigned NumPredsOutsideRegion = 0; + + if (Header != &Header->getParent()->getEntryBlock()) { + PHINode *PN = dyn_cast<PHINode>(Header->begin()); + if (!PN) return; // No PHI nodes. + + // If the header node contains any PHI nodes, check to see if there is more + // than one entry from outside the region. If so, we need to sever the + // header block into two. + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (BlocksToExtract.count(PN->getIncomingBlock(i))) + HasPredsFromRegion = true; + else + ++NumPredsOutsideRegion; + + // If there is one (or fewer) predecessor from outside the region, we don't + // need to do anything special. + if (NumPredsOutsideRegion <= 1) return; + } + + // Otherwise, we need to split the header block into two pieces: one + // containing PHI nodes merging values from outside of the region, and a + // second that contains all of the code for the block and merges back any + // incoming values from inside of the region. + BasicBlock::iterator AfterPHIs = Header->getFirstNonPHI(); + BasicBlock *NewBB = Header->splitBasicBlock(AfterPHIs, + Header->getName()+".ce"); + + // We only want to code extract the second block now, and it becomes the new + // header of the region. + BasicBlock *OldPred = Header; + BlocksToExtract.remove(OldPred); + BlocksToExtract.insert(NewBB); + Header = NewBB; + + // Okay, update dominator sets. The blocks that dominate the new one are the + // blocks that dominate TIBB plus the new block itself. + if (DT) + DT->splitBlock(NewBB); + + // Okay, now we need to adjust the PHI nodes and any branches from within the + // region to go to the new header block instead of the old header block. + if (HasPredsFromRegion) { + PHINode *PN = cast<PHINode>(OldPred->begin()); + // Loop over all of the predecessors of OldPred that are in the region, + // changing them to branch to NewBB instead. + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (BlocksToExtract.count(PN->getIncomingBlock(i))) { + TerminatorInst *TI = PN->getIncomingBlock(i)->getTerminator(); + TI->replaceUsesOfWith(OldPred, NewBB); + } + + // Okay, everthing within the region is now branching to the right block, we + // just have to update the PHI nodes now, inserting PHI nodes into NewBB. + for (AfterPHIs = OldPred->begin(); isa<PHINode>(AfterPHIs); ++AfterPHIs) { + PHINode *PN = cast<PHINode>(AfterPHIs); + // Create a new PHI node in the new region, which has an incoming value + // from OldPred of PN. + PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".ce", + NewBB->begin()); + NewPN->addIncoming(PN, OldPred); + + // Loop over all of the incoming value in PN, moving them to NewPN if they + // are from the extracted region. + for (unsigned i = 0; i != PN->getNumIncomingValues(); ++i) { + if (BlocksToExtract.count(PN->getIncomingBlock(i))) { + NewPN->addIncoming(PN->getIncomingValue(i), PN->getIncomingBlock(i)); + PN->removeIncomingValue(i); + --i; + } + } + } + } +} + +void CodeExtractor::splitReturnBlocks() { + for (SetVector<BasicBlock*>::iterator I = BlocksToExtract.begin(), + E = BlocksToExtract.end(); I != E; ++I) + if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) { + BasicBlock *New = (*I)->splitBasicBlock(RI, (*I)->getName()+".ret"); + if (DT) { + // Old dominates New. New node domiantes all other nodes dominated + //by Old. + DomTreeNode *OldNode = DT->getNode(*I); + SmallVector<DomTreeNode*, 8> Children; + for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end(); + DI != DE; ++DI) + Children.push_back(*DI); + + DomTreeNode *NewNode = DT->addNewBlock(New, *I); + + for (SmallVector<DomTreeNode*, 8>::iterator I = Children.begin(), + E = Children.end(); I != E; ++I) + DT->changeImmediateDominator(*I, NewNode); + } + } +} + +// findInputsOutputs - Find inputs to, outputs from the code region. +// +void CodeExtractor::findInputsOutputs(Values &inputs, Values &outputs) { + std::set<BasicBlock*> ExitBlocks; + for (SetVector<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(), + ce = BlocksToExtract.end(); ci != ce; ++ci) { + BasicBlock *BB = *ci; + + for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { + // If a used value is defined outside the region, it's an input. If an + // instruction is used outside the region, it's an output. + for (User::op_iterator O = I->op_begin(), E = I->op_end(); O != E; ++O) + if (definedInCaller(*O)) + inputs.insert(*O); + + // Consider uses of this instruction (outputs). + for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); + UI != E; ++UI) + if (!definedInRegion(*UI)) { + outputs.insert(I); + break; + } + } // for: insts + + // Keep track of the exit blocks from the region. + TerminatorInst *TI = BB->getTerminator(); + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + if (!BlocksToExtract.count(TI->getSuccessor(i))) + ExitBlocks.insert(TI->getSuccessor(i)); + } // for: basic blocks + + NumExitBlocks = ExitBlocks.size(); +} + +/// constructFunction - make a function based on inputs and outputs, as follows: +/// f(in0, ..., inN, out0, ..., outN) +/// +Function *CodeExtractor::constructFunction(const Values &inputs, + const Values &outputs, + BasicBlock *header, + BasicBlock *newRootNode, + BasicBlock *newHeader, + Function *oldFunction, + Module *M) { + DEBUG(dbgs() << "inputs: " << inputs.size() << "\n"); + DEBUG(dbgs() << "outputs: " << outputs.size() << "\n"); + + // This function returns unsigned, outputs will go back by reference. + switch (NumExitBlocks) { + case 0: + case 1: RetTy = Type::getVoidTy(header->getContext()); break; + case 2: RetTy = Type::getInt1Ty(header->getContext()); break; + default: RetTy = Type::getInt16Ty(header->getContext()); break; + } + + std::vector<const Type*> paramTy; + + // Add the types of the input values to the function's argument list + for (Values::const_iterator i = inputs.begin(), + e = inputs.end(); i != e; ++i) { + const Value *value = *i; + DEBUG(dbgs() << "value used in func: " << *value << "\n"); + paramTy.push_back(value->getType()); + } + + // Add the types of the output values to the function's argument list. + for (Values::const_iterator I = outputs.begin(), E = outputs.end(); + I != E; ++I) { + DEBUG(dbgs() << "instr used in func: " << **I << "\n"); + if (AggregateArgs) + paramTy.push_back((*I)->getType()); + else + paramTy.push_back(PointerType::getUnqual((*I)->getType())); + } + + DEBUG(dbgs() << "Function type: " << *RetTy << " f("); + for (std::vector<const Type*>::iterator i = paramTy.begin(), + e = paramTy.end(); i != e; ++i) + DEBUG(dbgs() << **i << ", "); + DEBUG(dbgs() << ")\n"); + + if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { + PointerType *StructPtr = + PointerType::getUnqual(StructType::get(M->getContext(), paramTy)); + paramTy.clear(); + paramTy.push_back(StructPtr); + } + const FunctionType *funcType = + FunctionType::get(RetTy, paramTy, false); + + // Create the new function + Function *newFunction = Function::Create(funcType, + GlobalValue::InternalLinkage, + oldFunction->getName() + "_" + + header->getName(), M); + // If the old function is no-throw, so is the new one. + if (oldFunction->doesNotThrow()) + newFunction->setDoesNotThrow(true); + + newFunction->getBasicBlockList().push_back(newRootNode); + + // Create an iterator to name all of the arguments we inserted. + Function::arg_iterator AI = newFunction->arg_begin(); + + // Rewrite all users of the inputs in the extracted region to use the + // arguments (or appropriate addressing into struct) instead. + for (unsigned i = 0, e = inputs.size(); i != e; ++i) { + Value *RewriteVal; + if (AggregateArgs) { + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(header->getContext())); + Idx[1] = ConstantInt::get(Type::getInt32Ty(header->getContext()), i); + TerminatorInst *TI = newFunction->begin()->getTerminator(); + GetElementPtrInst *GEP = + GetElementPtrInst::Create(AI, Idx, Idx+2, + "gep_" + inputs[i]->getName(), TI); + RewriteVal = new LoadInst(GEP, "loadgep_" + inputs[i]->getName(), TI); + } else + RewriteVal = AI++; + + std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end()); + for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end(); + use != useE; ++use) + if (Instruction* inst = dyn_cast<Instruction>(*use)) + if (BlocksToExtract.count(inst->getParent())) + inst->replaceUsesOfWith(inputs[i], RewriteVal); + } + + // Set names for input and output arguments. + if (!AggregateArgs) { + AI = newFunction->arg_begin(); + for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI) + AI->setName(inputs[i]->getName()); + for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI) + AI->setName(outputs[i]->getName()+".out"); + } + + // Rewrite branches to basic blocks outside of the loop to new dummy blocks + // within the new function. This must be done before we lose track of which + // blocks were originally in the code region. + std::vector<User*> Users(header->use_begin(), header->use_end()); + for (unsigned i = 0, e = Users.size(); i != e; ++i) + // The BasicBlock which contains the branch is not in the region + // modify the branch target to a new block + if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i])) + if (!BlocksToExtract.count(TI->getParent()) && + TI->getParent()->getParent() == oldFunction) + TI->replaceUsesOfWith(header, newHeader); + + return newFunction; +} + +/// FindPhiPredForUseInBlock - Given a value and a basic block, find a PHI +/// that uses the value within the basic block, and return the predecessor +/// block associated with that use, or return 0 if none is found. +static BasicBlock* FindPhiPredForUseInBlock(Value* Used, BasicBlock* BB) { + for (Value::use_iterator UI = Used->use_begin(), + UE = Used->use_end(); UI != UE; ++UI) { + PHINode *P = dyn_cast<PHINode>(*UI); + if (P && P->getParent() == BB) + return P->getIncomingBlock(UI); + } + + return 0; +} + +/// emitCallAndSwitchStatement - This method sets up the caller side by adding +/// the call instruction, splitting any PHI nodes in the header block as +/// necessary. +void CodeExtractor:: +emitCallAndSwitchStatement(Function *newFunction, BasicBlock *codeReplacer, + Values &inputs, Values &outputs) { + // Emit a call to the new function, passing in: *pointer to struct (if + // aggregating parameters), or plan inputs and allocated memory for outputs + std::vector<Value*> params, StructValues, ReloadOutputs, Reloads; + + LLVMContext &Context = newFunction->getContext(); + + // Add inputs as params, or to be filled into the struct + for (Values::iterator i = inputs.begin(), e = inputs.end(); i != e; ++i) + if (AggregateArgs) + StructValues.push_back(*i); + else + params.push_back(*i); + + // Create allocas for the outputs + for (Values::iterator i = outputs.begin(), e = outputs.end(); i != e; ++i) { + if (AggregateArgs) { + StructValues.push_back(*i); + } else { + AllocaInst *alloca = + new AllocaInst((*i)->getType(), 0, (*i)->getName()+".loc", + codeReplacer->getParent()->begin()->begin()); + ReloadOutputs.push_back(alloca); + params.push_back(alloca); + } + } + + AllocaInst *Struct = 0; + if (AggregateArgs && (inputs.size() + outputs.size() > 0)) { + std::vector<const Type*> ArgTypes; + for (Values::iterator v = StructValues.begin(), + ve = StructValues.end(); v != ve; ++v) + ArgTypes.push_back((*v)->getType()); + + // Allocate a struct at the beginning of this function + Type *StructArgTy = StructType::get(newFunction->getContext(), ArgTypes); + Struct = + new AllocaInst(StructArgTy, 0, "structArg", + codeReplacer->getParent()->begin()->begin()); + params.push_back(Struct); + + for (unsigned i = 0, e = inputs.size(); i != e; ++i) { + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); + Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), i); + GetElementPtrInst *GEP = + GetElementPtrInst::Create(Struct, Idx, Idx + 2, + "gep_" + StructValues[i]->getName()); + codeReplacer->getInstList().push_back(GEP); + StoreInst *SI = new StoreInst(StructValues[i], GEP); + codeReplacer->getInstList().push_back(SI); + } + } + + // Emit the call to the function + CallInst *call = CallInst::Create(newFunction, params.begin(), params.end(), + NumExitBlocks > 1 ? "targetBlock" : ""); + codeReplacer->getInstList().push_back(call); + + Function::arg_iterator OutputArgBegin = newFunction->arg_begin(); + unsigned FirstOut = inputs.size(); + if (!AggregateArgs) + std::advance(OutputArgBegin, inputs.size()); + + // Reload the outputs passed in by reference + for (unsigned i = 0, e = outputs.size(); i != e; ++i) { + Value *Output = 0; + if (AggregateArgs) { + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); + Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), FirstOut + i); + GetElementPtrInst *GEP + = GetElementPtrInst::Create(Struct, Idx, Idx + 2, + "gep_reload_" + outputs[i]->getName()); + codeReplacer->getInstList().push_back(GEP); + Output = GEP; + } else { + Output = ReloadOutputs[i]; + } + LoadInst *load = new LoadInst(Output, outputs[i]->getName()+".reload"); + Reloads.push_back(load); + codeReplacer->getInstList().push_back(load); + std::vector<User*> Users(outputs[i]->use_begin(), outputs[i]->use_end()); + for (unsigned u = 0, e = Users.size(); u != e; ++u) { + Instruction *inst = cast<Instruction>(Users[u]); + if (!BlocksToExtract.count(inst->getParent())) + inst->replaceUsesOfWith(outputs[i], load); + } + } + + // Now we can emit a switch statement using the call as a value. + SwitchInst *TheSwitch = + SwitchInst::Create(Constant::getNullValue(Type::getInt16Ty(Context)), + codeReplacer, 0, codeReplacer); + + // Since there may be multiple exits from the original region, make the new + // function return an unsigned, switch on that number. This loop iterates + // over all of the blocks in the extracted region, updating any terminator + // instructions in the to-be-extracted region that branch to blocks that are + // not in the region to be extracted. + std::map<BasicBlock*, BasicBlock*> ExitBlockMap; + + unsigned switchVal = 0; + for (SetVector<BasicBlock*>::const_iterator i = BlocksToExtract.begin(), + e = BlocksToExtract.end(); i != e; ++i) { + TerminatorInst *TI = (*i)->getTerminator(); + for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i) + if (!BlocksToExtract.count(TI->getSuccessor(i))) { + BasicBlock *OldTarget = TI->getSuccessor(i); + // add a new basic block which returns the appropriate value + BasicBlock *&NewTarget = ExitBlockMap[OldTarget]; + if (!NewTarget) { + // If we don't already have an exit stub for this non-extracted + // destination, create one now! + NewTarget = BasicBlock::Create(Context, + OldTarget->getName() + ".exitStub", + newFunction); + unsigned SuccNum = switchVal++; + + Value *brVal = 0; + switch (NumExitBlocks) { + case 0: + case 1: break; // No value needed. + case 2: // Conditional branch, return a bool + brVal = ConstantInt::get(Type::getInt1Ty(Context), !SuccNum); + break; + default: + brVal = ConstantInt::get(Type::getInt16Ty(Context), SuccNum); + break; + } + + ReturnInst *NTRet = ReturnInst::Create(Context, brVal, NewTarget); + + // Update the switch instruction. + TheSwitch->addCase(ConstantInt::get(Type::getInt16Ty(Context), + SuccNum), + OldTarget); + + // Restore values just before we exit + Function::arg_iterator OAI = OutputArgBegin; + for (unsigned out = 0, e = outputs.size(); out != e; ++out) { + // For an invoke, the normal destination is the only one that is + // dominated by the result of the invocation + BasicBlock *DefBlock = cast<Instruction>(outputs[out])->getParent(); + + bool DominatesDef = true; + + if (InvokeInst *Invoke = dyn_cast<InvokeInst>(outputs[out])) { + DefBlock = Invoke->getNormalDest(); + + // Make sure we are looking at the original successor block, not + // at a newly inserted exit block, which won't be in the dominator + // info. + for (std::map<BasicBlock*, BasicBlock*>::iterator I = + ExitBlockMap.begin(), E = ExitBlockMap.end(); I != E; ++I) + if (DefBlock == I->second) { + DefBlock = I->first; + break; + } + + // In the extract block case, if the block we are extracting ends + // with an invoke instruction, make sure that we don't emit a + // store of the invoke value for the unwind block. + if (!DT && DefBlock != OldTarget) + DominatesDef = false; + } + + if (DT) { + DominatesDef = DT->dominates(DefBlock, OldTarget); + + // If the output value is used by a phi in the target block, + // then we need to test for dominance of the phi's predecessor + // instead. Unfortunately, this a little complicated since we + // have already rewritten uses of the value to uses of the reload. + BasicBlock* pred = FindPhiPredForUseInBlock(Reloads[out], + OldTarget); + if (pred && DT && DT->dominates(DefBlock, pred)) + DominatesDef = true; + } + + if (DominatesDef) { + if (AggregateArgs) { + Value *Idx[2]; + Idx[0] = Constant::getNullValue(Type::getInt32Ty(Context)); + Idx[1] = ConstantInt::get(Type::getInt32Ty(Context), + FirstOut+out); + GetElementPtrInst *GEP = + GetElementPtrInst::Create(OAI, Idx, Idx + 2, + "gep_" + outputs[out]->getName(), + NTRet); + new StoreInst(outputs[out], GEP, NTRet); + } else { + new StoreInst(outputs[out], OAI, NTRet); + } + } + // Advance output iterator even if we don't emit a store + if (!AggregateArgs) ++OAI; + } + } + + // rewrite the original branch instruction with this new target + TI->setSuccessor(i, NewTarget); + } + } + + // Now that we've done the deed, simplify the switch instruction. + const Type *OldFnRetTy = TheSwitch->getParent()->getParent()->getReturnType(); + switch (NumExitBlocks) { + case 0: + // There are no successors (the block containing the switch itself), which + // means that previously this was the last part of the function, and hence + // this should be rewritten as a `ret' + + // Check if the function should return a value + if (OldFnRetTy->isVoidTy()) { + ReturnInst::Create(Context, 0, TheSwitch); // Return void + } else if (OldFnRetTy == TheSwitch->getCondition()->getType()) { + // return what we have + ReturnInst::Create(Context, TheSwitch->getCondition(), TheSwitch); + } else { + // Otherwise we must have code extracted an unwind or something, just + // return whatever we want. + ReturnInst::Create(Context, + Constant::getNullValue(OldFnRetTy), TheSwitch); + } + + TheSwitch->eraseFromParent(); + break; + case 1: + // Only a single destination, change the switch into an unconditional + // branch. + BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch); + TheSwitch->eraseFromParent(); + break; + case 2: + BranchInst::Create(TheSwitch->getSuccessor(1), TheSwitch->getSuccessor(2), + call, TheSwitch); + TheSwitch->eraseFromParent(); + break; + default: + // Otherwise, make the default destination of the switch instruction be one + // of the other successors. + TheSwitch->setOperand(0, call); + TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(NumExitBlocks)); + TheSwitch->removeCase(NumExitBlocks); // Remove redundant case + break; + } +} + +void CodeExtractor::moveCodeToFunction(Function *newFunction) { + Function *oldFunc = (*BlocksToExtract.begin())->getParent(); + Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList(); + Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList(); + + for (SetVector<BasicBlock*>::const_iterator i = BlocksToExtract.begin(), + e = BlocksToExtract.end(); i != e; ++i) { + // Delete the basic block from the old function, and the list of blocks + oldBlocks.remove(*i); + + // Insert this basic block into the new function + newBlocks.push_back(*i); + } +} + +/// ExtractRegion - Removes a loop from a function, replaces it with a call to +/// new function. Returns pointer to the new function. +/// +/// algorithm: +/// +/// find inputs and outputs for the region +/// +/// for inputs: add to function as args, map input instr* to arg# +/// for outputs: add allocas for scalars, +/// add to func as args, map output instr* to arg# +/// +/// rewrite func to use argument #s instead of instr* +/// +/// for each scalar output in the function: at every exit, store intermediate +/// computed result back into memory. +/// +Function *CodeExtractor:: +ExtractCodeRegion(const std::vector<BasicBlock*> &code) { + if (!isEligible(code)) + return 0; + + // 1) Find inputs, outputs + // 2) Construct new function + // * Add allocas for defs, pass as args by reference + // * Pass in uses as args + // 3) Move code region, add call instr to func + // + BlocksToExtract.insert(code.begin(), code.end()); + + Values inputs, outputs; + + // Assumption: this is a single-entry code region, and the header is the first + // block in the region. + BasicBlock *header = code[0]; + + for (unsigned i = 1, e = code.size(); i != e; ++i) + for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]); + PI != E; ++PI) + assert(BlocksToExtract.count(*PI) && + "No blocks in this region may have entries from outside the region" + " except for the first block!"); + + // If we have to split PHI nodes or the entry block, do so now. + severSplitPHINodes(header); + + // If we have any return instructions in the region, split those blocks so + // that the return is not in the region. + splitReturnBlocks(); + + Function *oldFunction = header->getParent(); + + // This takes place of the original loop + BasicBlock *codeReplacer = BasicBlock::Create(header->getContext(), + "codeRepl", oldFunction, + header); + + // The new function needs a root node because other nodes can branch to the + // head of the region, but the entry node of a function cannot have preds. + BasicBlock *newFuncRoot = BasicBlock::Create(header->getContext(), + "newFuncRoot"); + newFuncRoot->getInstList().push_back(BranchInst::Create(header)); + + // Find inputs to, outputs from the code region. + findInputsOutputs(inputs, outputs); + + // Construct new function based on inputs/outputs & add allocas for all defs. + Function *newFunction = constructFunction(inputs, outputs, header, + newFuncRoot, + codeReplacer, oldFunction, + oldFunction->getParent()); + + emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs); + + moveCodeToFunction(newFunction); + + // Loop over all of the PHI nodes in the header block, and change any + // references to the old incoming edge to be the new incoming edge. + for (BasicBlock::iterator I = header->begin(); isa<PHINode>(I); ++I) { + PHINode *PN = cast<PHINode>(I); + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (!BlocksToExtract.count(PN->getIncomingBlock(i))) + PN->setIncomingBlock(i, newFuncRoot); + } + + // Look at all successors of the codeReplacer block. If any of these blocks + // had PHI nodes in them, we need to update the "from" block to be the code + // replacer, not the original block in the extracted region. + std::vector<BasicBlock*> Succs(succ_begin(codeReplacer), + succ_end(codeReplacer)); + for (unsigned i = 0, e = Succs.size(); i != e; ++i) + for (BasicBlock::iterator I = Succs[i]->begin(); isa<PHINode>(I); ++I) { + PHINode *PN = cast<PHINode>(I); + std::set<BasicBlock*> ProcessedPreds; + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (BlocksToExtract.count(PN->getIncomingBlock(i))) { + if (ProcessedPreds.insert(PN->getIncomingBlock(i)).second) + PN->setIncomingBlock(i, codeReplacer); + else { + // There were multiple entries in the PHI for this block, now there + // is only one, so remove the duplicated entries. + PN->removeIncomingValue(i, false); + --i; --e; + } + } + } + + //cerr << "NEW FUNCTION: " << *newFunction; + // verifyFunction(*newFunction); + + // cerr << "OLD FUNCTION: " << *oldFunction; + // verifyFunction(*oldFunction); + + DEBUG(if (verifyFunction(*newFunction)) + llvm_report_error("verifyFunction failed!")); + return newFunction; +} + +bool CodeExtractor::isEligible(const std::vector<BasicBlock*> &code) { + // Deny code region if it contains allocas or vastarts. + for (std::vector<BasicBlock*>::const_iterator BB = code.begin(), e=code.end(); + BB != e; ++BB) + for (BasicBlock::const_iterator I = (*BB)->begin(), Ie = (*BB)->end(); + I != Ie; ++I) + if (isa<AllocaInst>(*I)) + return false; + else if (const CallInst *CI = dyn_cast<CallInst>(I)) + if (const Function *F = CI->getCalledFunction()) + if (F->getIntrinsicID() == Intrinsic::vastart) + return false; + return true; +} + + +/// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new +/// function +/// +Function* llvm::ExtractCodeRegion(DominatorTree &DT, + const std::vector<BasicBlock*> &code, + bool AggregateArgs) { + return CodeExtractor(&DT, AggregateArgs).ExtractCodeRegion(code); +} + +/// ExtractBasicBlock - slurp a natural loop into a brand new function +/// +Function* llvm::ExtractLoop(DominatorTree &DT, Loop *L, bool AggregateArgs) { + return CodeExtractor(&DT, AggregateArgs).ExtractCodeRegion(L->getBlocks()); +} + +/// ExtractBasicBlock - slurp a basic block into a brand new function +/// +Function* llvm::ExtractBasicBlock(BasicBlock *BB, bool AggregateArgs) { + std::vector<BasicBlock*> Blocks; + Blocks.push_back(BB); + return CodeExtractor(0, AggregateArgs).ExtractCodeRegion(Blocks); +} |