diff options
author | Misha Brukman <brukman+llvm@gmail.com> | 2004-02-28 03:26:20 +0000 |
---|---|---|
committer | Misha Brukman <brukman+llvm@gmail.com> | 2004-02-28 03:26:20 +0000 |
commit | e6336031b8b85a438e2fcaa9e56e7392afbbb7dc (patch) | |
tree | 778954b5c30d2a38e774c6a3c2a3cc9daffb456f | |
parent | 870e587d5d8b5f9005e0e42e19120fe6f21c1c35 (diff) | |
download | external_llvm-e6336031b8b85a438e2fcaa9e56e7392afbbb7dc.zip external_llvm-e6336031b8b85a438e2fcaa9e56e7392afbbb7dc.tar.gz external_llvm-e6336031b8b85a438e2fcaa9e56e7392afbbb7dc.tar.bz2 |
A generic code extractor: given a list of BasicBlocks, it will rip them out into
a new function, taking care of inputs and outputs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11935 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r-- | lib/Transforms/Utils/CodeExtractor.cpp | 573 |
1 files changed, 573 insertions, 0 deletions
diff --git a/lib/Transforms/Utils/CodeExtractor.cpp b/lib/Transforms/Utils/CodeExtractor.cpp new file mode 100644 index 0000000..38f3c8a --- /dev/null +++ b/lib/Transforms/Utils/CodeExtractor.cpp @@ -0,0 +1,573 @@ +//===- CodeExtractor.cpp - Pull code region into a new 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 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/BasicBlock.h" +#include "llvm/Constants.h" +#include "llvm/DerivedTypes.h" +#include "llvm/Instructions.h" +#include "llvm/Module.h" +#include "llvm/Pass.h" +#include "llvm/Analysis/LoopInfo.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/FunctionUtils.h" +#include "Support/Debug.h" +#include "Support/StringExtras.h" +#include <algorithm> +#include <map> +#include <vector> +using namespace llvm; + +namespace { + + inline bool contains(const std::vector<BasicBlock*> &V, const BasicBlock *BB){ + return std::find(V.begin(), V.end(), BB) != V.end(); + } + + /// getFunctionArg - Return a pointer to F's ARGNOth argument. + /// + Argument *getFunctionArg(Function *F, unsigned argno) { + Function::aiterator ai = F->abegin(); + while (argno) { ++ai; --argno; } + return &*ai; + } + + struct CodeExtractor { + typedef std::vector<Value*> Values; + typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy; + typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy; + PhiVal2ArgTy PhiVal2Arg; + + public: + Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code); + + private: + void findInputsOutputs(const std::vector<BasicBlock*> &code, + Values &inputs, + Values &outputs, + BasicBlock *newHeader, + BasicBlock *newRootNode); + + void processPhiNodeInputs(PHINode *Phi, + const std::vector<BasicBlock*> &code, + Values &inputs, + BasicBlock *newHeader, + BasicBlock *newRootNode); + + void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot); + + Function *constructFunction(const Values &inputs, + const Values &outputs, + BasicBlock *newRootNode, BasicBlock *newHeader, + const std::vector<BasicBlock*> &code, + Function *oldFunction, Module *M); + + void moveCodeToFunction(const std::vector<BasicBlock*> &code, + Function *newFunction); + + void emitCallAndSwitchStatement(Function *newFunction, + BasicBlock *newHeader, + const std::vector<BasicBlock*> &code, + Values &inputs, + Values &outputs); + + }; +} + +void CodeExtractor::processPhiNodeInputs(PHINode *Phi, + const std::vector<BasicBlock*> &code, + Values &inputs, + BasicBlock *codeReplacer, + BasicBlock *newFuncRoot) +{ + // Separate incoming values and BasicBlocks as internal/external. We ignore + // the case where both the value and BasicBlock are internal, because we don't + // need to do a thing. + std::vector<unsigned> EValEBB; + std::vector<unsigned> EValIBB; + std::vector<unsigned> IValEBB; + + for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) { + Value *phiVal = Phi->getIncomingValue(i); + if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) { + if (contains(code, Inst->getParent())) { + if (!contains(code, Phi->getIncomingBlock(i))) + IValEBB.push_back(i); + } else { + if (contains(code, Phi->getIncomingBlock(i))) + EValIBB.push_back(i); + else + EValEBB.push_back(i); + } + } else if (Constant *Const = dyn_cast<Constant>(phiVal)) { + // Constants are internal, but considered `external' if they are coming + // from an external block. + if (!contains(code, Phi->getIncomingBlock(i))) + EValEBB.push_back(i); + } else if (Argument *Arg = dyn_cast<Argument>(phiVal)) { + // arguments are external + if (contains(code, Phi->getIncomingBlock(i))) + EValIBB.push_back(i); + else + EValEBB.push_back(i); + } else { + phiVal->dump(); + assert(0 && "Unhandled input in a Phi node"); + } + } + + // Both value and block are external. Need to group all of + // these, have an external phi, pass the result as an + // argument, and have THIS phi use that result. + if (EValEBB.size() > 0) { + if (EValEBB.size() == 1) { + // Now if it's coming from the newFuncRoot, it's that funky input + unsigned phiIdx = EValEBB[0]; + if (!dyn_cast<Constant>(Phi->getIncomingValue(phiIdx))) + { + PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size())); + // We can just pass this value in as argument + inputs.push_back(Phi->getIncomingValue(phiIdx)); + } + Phi->setIncomingBlock(phiIdx, newFuncRoot); + } else { + PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi"); + codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi); + for (std::vector<unsigned>::iterator i = EValEBB.begin(), + e = EValEBB.end(); i != e; ++i) + { + externalPhi->addIncoming(Phi->getIncomingValue(*i), + Phi->getIncomingBlock(*i)); + + // We make these values invalid instead of deleting them because that + // would shift the indices of other values... The fixPhiNodes should + // clean these phi nodes up later. + Phi->setIncomingValue(*i, 0); + Phi->setIncomingBlock(*i, 0); + } + PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(), + inputs.size())); + // We can just pass this value in as argument + inputs.push_back(externalPhi); + } + } + + // When the value is external, but block internal... + // just pass it in as argument, no change to phi node + for (std::vector<unsigned>::iterator i = EValIBB.begin(), + e = EValIBB.end(); i != e; ++i) + { + // rewrite the phi input node to be an argument + PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size())); + inputs.push_back(Phi->getIncomingValue(*i)); + } + + // Value internal, block external + // this can happen if we are extracting a part of a loop + for (std::vector<unsigned>::iterator i = IValEBB.begin(), + e = IValEBB.end(); i != e; ++i) + { + assert(0 && "Cannot (YET) handle internal values via external blocks"); + } +} + + +void CodeExtractor::findInputsOutputs(const std::vector<BasicBlock*> &code, + Values &inputs, + Values &outputs, + BasicBlock *newHeader, + BasicBlock *newRootNode) +{ + for (std::vector<BasicBlock*>::const_iterator ci = code.begin(), + ce = code.end(); ci != ce; ++ci) { + BasicBlock *BB = *ci; + for (BasicBlock::iterator BBi = BB->begin(), BBe = BB->end(); + BBi != BBe; ++BBi) { + // If a use is defined outside the region, it's an input. + // If a def is used outside the region, it's an output. + if (Instruction *I = dyn_cast<Instruction>(&*BBi)) { + // If it's a phi node + if (PHINode *Phi = dyn_cast<PHINode>(I)) { + processPhiNodeInputs(Phi, code, inputs, newHeader, newRootNode); + } else { + // All other instructions go through the generic input finder + // Loop over the operands of each instruction (inputs) + for (User::op_iterator op = I->op_begin(), opE = I->op_end(); + op != opE; ++op) { + if (Instruction *opI = dyn_cast<Instruction>(op->get())) { + // Check if definition of this operand is within the loop + if (!contains(code, opI->getParent())) { + // add this operand to the inputs + inputs.push_back(opI); + } + } + } + } + + // Consider uses of this instruction (outputs) + for (Value::use_iterator use = I->use_begin(), useE = I->use_end(); + use != useE; ++use) { + if (Instruction* inst = dyn_cast<Instruction>(*use)) { + if (!contains(code, inst->getParent())) { + // add this op to the outputs + outputs.push_back(I); + } + } + } + } /* if */ + } /* for: insts */ + } /* for: basic blocks */ +} + +void CodeExtractor::rewritePhiNodes(Function *F, + BasicBlock *newFuncRoot) { + // Write any changes that were saved before: use function arguments as inputs + for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end(); + i != e; ++i) + { + PHINode *phi = (*i).first; + PhiValChangesTy &values = (*i).second; + for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx) + { + unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second; + if (phiValueIdx < phi->getNumIncomingValues()) + phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum)); + else + phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot); + } + } + + // Delete any invalid Phi node inputs that were marked as NULL previously + for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end(); + i != e; ++i) + { + PHINode *phi = (*i).first; + for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx) + { + if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) { + phi->removeIncomingValue(idx); + --idx; + --end; + } + } + } + + // We are done with the saved values + PhiVal2Arg.clear(); +} + + +/// 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 *newRootNode, + BasicBlock *newHeader, + const std::vector<BasicBlock*> &code, + Function *oldFunction, Module *M) { + DEBUG(std::cerr << "inputs: " << inputs.size() << "\n"); + DEBUG(std::cerr << "outputs: " << outputs.size() << "\n"); + BasicBlock *header = code[0]; + + // This function returns unsigned, outputs will go back by reference. + Type *retTy = Type::UShortTy; + 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(std::cerr << "value used in func: " << value << "\n"); + paramTy.push_back(value->getType()); + } + + // Add the types of the output values to the function's argument list, but + // make them pointer types for scalars + for (Values::const_iterator i = outputs.begin(), + e = outputs.end(); i != e; ++i) { + const Value *value = *i; + DEBUG(std::cerr << "instr used in func: " << value << "\n"); + const Type *valueType = value->getType(); + // Convert scalar types into a pointer of that type + if (valueType->isPrimitiveType()) { + valueType = PointerType::get(valueType); + } + paramTy.push_back(valueType); + } + + DEBUG(std::cerr << "Function type: " << retTy << " f("); + for (std::vector<const Type*>::iterator i = paramTy.begin(), + e = paramTy.end(); i != e; ++i) + DEBUG(std::cerr << (*i) << ", "); + DEBUG(std::cerr << ")\n"); + + const FunctionType *funcType = FunctionType::get(retTy, paramTy, false); + + // Create the new function + Function *newFunction = new Function(funcType, + GlobalValue::InternalLinkage, + oldFunction->getName() + "_code", M); + newFunction->getBasicBlockList().push_back(newRootNode); + + for (unsigned i = 0, e = inputs.size(); i != e; ++i) { + 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 (contains(code, inst->getParent())) { + inst->replaceUsesOfWith(inputs[i], getFunctionArg(newFunction, i)); + } + } + } + } + + // 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 (std::vector<User*>::iterator i = Users.begin(), e = Users.end(); + i != e; ++i) { + if (BranchInst *inst = dyn_cast<BranchInst>(*i)) { + BasicBlock *BB = inst->getParent(); + if (!contains(code, BB) && BB->getParent() == oldFunction) { + // The BasicBlock which contains the branch is not in the region + // modify the branch target to a new block + inst->replaceUsesOfWith(header, newHeader); + } + } + } + + return newFunction; +} + +void CodeExtractor::moveCodeToFunction(const std::vector<BasicBlock*> &code, + Function *newFunction) +{ + for (std::vector<BasicBlock*>::const_iterator i = code.begin(), e =code.end(); + i != e; ++i) { + BasicBlock *BB = *i; + Function *oldFunc = BB->getParent(); + Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList(); + + // Delete the basic block from the old function, and the list of blocks + oldBlocks.remove(BB); + + // Insert this basic block into the new function + Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList(); + newBlocks.push_back(BB); + } +} + +void +CodeExtractor::emitCallAndSwitchStatement(Function *newFunction, + BasicBlock *codeReplacer, + const std::vector<BasicBlock*> &code, + Values &inputs, + Values &outputs) +{ + // Emit a call to the new function, passing allocated memory for outputs and + // just plain inputs for non-scalars + std::vector<Value*> params; + BasicBlock *codeReplacerTail = new BasicBlock("codeReplTail", + codeReplacer->getParent()); + for (Values::const_iterator i = inputs.begin(), + e = inputs.end(); i != e; ++i) + params.push_back(*i); + for (Values::const_iterator i = outputs.begin(), + e = outputs.end(); i != e; ++i) { + // Create allocas for scalar outputs + if ((*i)->getType()->isPrimitiveType()) { + Constant *one = ConstantUInt::get(Type::UIntTy, 1); + AllocaInst *alloca = new AllocaInst((*i)->getType(), one); + codeReplacer->getInstList().push_back(alloca); + params.push_back(alloca); + + LoadInst *load = new LoadInst(alloca, "alloca"); + codeReplacerTail->getInstList().push_back(load); + std::vector<User*> Users((*i)->use_begin(), (*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 (!contains(code, inst->getParent())) { + inst->replaceUsesOfWith(*i, load); + } + } + } + } else { + params.push_back(*i); + } + } + CallInst *call = new CallInst(newFunction, params, "targetBlock"); + codeReplacer->getInstList().push_back(call); + codeReplacer->getInstList().push_back(new BranchInst(codeReplacerTail)); + + // Now we can emit a switch statement using the call as a value. + // FIXME: perhaps instead of default being self BB, it should be a second + // dummy block which asserts that the value is not within the range...? + //BasicBlock *defaultBlock = new BasicBlock("defaultBlock", oldF); + //insert abort() ? + //defaultBlock->getInstList().push_back(new BranchInst(codeReplacer)); + + SwitchInst *switchInst = new SwitchInst(call, codeReplacerTail, + codeReplacerTail); + + // Since there may be multiple exits from the original region, make the new + // function return an unsigned, switch on that number + unsigned switchVal = 0; + for (std::vector<BasicBlock*>::const_iterator i =code.begin(), e = code.end(); + i != e; ++i) { + BasicBlock *BB = *i; + + // rewrite the terminator of the original BasicBlock + Instruction *term = BB->getTerminator(); + if (BranchInst *brInst = dyn_cast<BranchInst>(term)) { + + // Restore values just before we exit + // FIXME: Use a GetElementPtr to bunch the outputs in a struct + for (unsigned outIdx = 0, outE = outputs.size(); outIdx != outE; ++outIdx) + { + new StoreInst(outputs[outIdx], + getFunctionArg(newFunction, outIdx), + brInst); + } + + // Rewrite branches into exists which return a value based on which + // exit we take from this function + if (brInst->isUnconditional()) { + if (!contains(code, brInst->getSuccessor(0))) { + ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal); + ReturnInst *newRet = new ReturnInst(brVal); + // add a new target to the switch + switchInst->addCase(brVal, brInst->getSuccessor(0)); + ++switchVal; + // rewrite the branch with a return + BasicBlock::iterator ii(brInst); + ReplaceInstWithInst(BB->getInstList(), ii, newRet); + delete brInst; + } + } else { + // Replace the conditional branch to branch + // to two new blocks, each of which returns a different code. + for (unsigned idx = 0; idx < 2; ++idx) { + BasicBlock *oldTarget = brInst->getSuccessor(idx); + if (!contains(code, oldTarget)) { + // add a new basic block which returns the appropriate value + BasicBlock *newTarget = new BasicBlock("newTarget", newFunction); + ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal); + ReturnInst *newRet = new ReturnInst(brVal); + newTarget->getInstList().push_back(newRet); + // rewrite the original branch instruction with this new target + brInst->setSuccessor(idx, newTarget); + // the switch statement knows what to do with this value + switchInst->addCase(brVal, oldTarget); + ++switchVal; + } + } + } + } else if (ReturnInst *retTerm = dyn_cast<ReturnInst>(term)) { + assert(0 && "Cannot handle return instructions just yet."); + // FIXME: what if the terminator is a return!??! + // Need to rewrite: add new basic block, move the return there + // treat the original as an unconditional branch to that basicblock + } else if (SwitchInst *swTerm = dyn_cast<SwitchInst>(term)) { + assert(0 && "Cannot handle switch instructions just yet."); + } else if (InvokeInst *invInst = dyn_cast<InvokeInst>(term)) { + assert(0 && "Cannot handle invoke instructions just yet."); + } else { + assert(0 && "Unrecognized terminator, or badly-formed BasicBlock."); + } + } +} + + +/// 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) +{ + // 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 + // + + Values inputs, outputs; + + // Assumption: this is a single-entry code region, and the header is the first + // block in the region. FIXME: is this true for a list of blocks from a + // natural function? + BasicBlock *header = code[0]; + Function *oldFunction = header->getParent(); + Module *module = oldFunction->getParent(); + + // This takes place of the original loop + BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction); + + // The new function needs a root node because other nodes can branch to the + // head of the loop, and the root cannot have predecessors + BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot"); + newFuncRoot->getInstList().push_back(new BranchInst(header)); + + // Find inputs to, outputs from the code region + // + // If one of the inputs is coming from a different basic block and it's in a + // phi node, we need to rewrite the phi node: + // + // * All the inputs which involve basic blocks OUTSIDE of this region go into + // a NEW phi node that takes care of finding which value really came in. + // The result of this phi is passed to the function as an argument. + // + // * All the other phi values stay. + // + // FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for + // blocks moving to a new function. + // SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass + // the values as parameters to the function + findInputsOutputs(code, inputs, outputs, codeReplacer, newFuncRoot); + + // Step 2: Construct new function based on inputs/outputs, + // Add allocas for all defs + Function *newFunction = constructFunction(inputs, outputs, newFuncRoot, + codeReplacer, code, + oldFunction, module); + + rewritePhiNodes(newFunction, newFuncRoot); + + emitCallAndSwitchStatement(newFunction, codeReplacer, code, inputs, outputs); + + moveCodeToFunction(code, newFunction); + + return newFunction; +} + +Function* llvm::ExtractLoop(Loop *L) { + CodeExtractor CE; + return CE.ExtractCodeRegion(L->getBlocks()); +} + |