forked from OSchip/llvm-project
A generic code extractor: given a list of BasicBlocks, it will rip them out into
a new function, taking care of inputs and outputs. llvm-svn: 11935
This commit is contained in:
Misha Brukman
parent
be74d5f73a
commit
caa1a5abeb
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@ -0,0 +1,573 @@
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//===- CodeExtractor.cpp - Pull code region into a new function -----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the interface to tear out a code region, such as an
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// individual loop or a parallel section, into a new function, replacing it with
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// a call to the new function.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/BasicBlock.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Instructions.h"
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#include "llvm/Module.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.h"
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#include "llvm/Transforms/Utils/FunctionUtils.h"
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#include "Support/Debug.h"
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#include "Support/StringExtras.h"
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#include <algorithm>
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#include <map>
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#include <vector>
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using namespace llvm;
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namespace {
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inline bool contains(const std::vector<BasicBlock*> &V, const BasicBlock *BB){
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return std::find(V.begin(), V.end(), BB) != V.end();
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}
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/// getFunctionArg - Return a pointer to F's ARGNOth argument.
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///
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Argument *getFunctionArg(Function *F, unsigned argno) {
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Function::aiterator ai = F->abegin();
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while (argno) { ++ai; --argno; }
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return &*ai;
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}
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struct CodeExtractor {
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typedef std::vector<Value*> Values;
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typedef std::vector<std::pair<unsigned, unsigned> > PhiValChangesTy;
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typedef std::map<PHINode*, PhiValChangesTy> PhiVal2ArgTy;
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PhiVal2ArgTy PhiVal2Arg;
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public:
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Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
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private:
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void findInputsOutputs(const std::vector<BasicBlock*> &code,
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Values &inputs,
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Values &outputs,
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BasicBlock *newHeader,
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BasicBlock *newRootNode);
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void processPhiNodeInputs(PHINode *Phi,
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const std::vector<BasicBlock*> &code,
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Values &inputs,
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BasicBlock *newHeader,
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BasicBlock *newRootNode);
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void rewritePhiNodes(Function *F, BasicBlock *newFuncRoot);
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Function *constructFunction(const Values &inputs,
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const Values &outputs,
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BasicBlock *newRootNode, BasicBlock *newHeader,
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const std::vector<BasicBlock*> &code,
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Function *oldFunction, Module *M);
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void moveCodeToFunction(const std::vector<BasicBlock*> &code,
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Function *newFunction);
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void emitCallAndSwitchStatement(Function *newFunction,
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BasicBlock *newHeader,
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const std::vector<BasicBlock*> &code,
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Values &inputs,
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Values &outputs);
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};
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}
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void CodeExtractor::processPhiNodeInputs(PHINode *Phi,
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const std::vector<BasicBlock*> &code,
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Values &inputs,
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BasicBlock *codeReplacer,
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BasicBlock *newFuncRoot)
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{
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// Separate incoming values and BasicBlocks as internal/external. We ignore
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// the case where both the value and BasicBlock are internal, because we don't
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// need to do a thing.
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std::vector<unsigned> EValEBB;
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std::vector<unsigned> EValIBB;
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std::vector<unsigned> IValEBB;
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for (unsigned i = 0, e = Phi->getNumIncomingValues(); i != e; ++i) {
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Value *phiVal = Phi->getIncomingValue(i);
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if (Instruction *Inst = dyn_cast<Instruction>(phiVal)) {
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if (contains(code, Inst->getParent())) {
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if (!contains(code, Phi->getIncomingBlock(i)))
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IValEBB.push_back(i);
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} else {
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if (contains(code, Phi->getIncomingBlock(i)))
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EValIBB.push_back(i);
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else
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EValEBB.push_back(i);
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}
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} else if (Constant *Const = dyn_cast<Constant>(phiVal)) {
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// Constants are internal, but considered `external' if they are coming
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// from an external block.
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if (!contains(code, Phi->getIncomingBlock(i)))
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EValEBB.push_back(i);
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} else if (Argument *Arg = dyn_cast<Argument>(phiVal)) {
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// arguments are external
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if (contains(code, Phi->getIncomingBlock(i)))
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EValIBB.push_back(i);
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else
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EValEBB.push_back(i);
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} else {
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phiVal->dump();
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assert(0 && "Unhandled input in a Phi node");
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}
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}
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// Both value and block are external. Need to group all of
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// these, have an external phi, pass the result as an
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// argument, and have THIS phi use that result.
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if (EValEBB.size() > 0) {
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if (EValEBB.size() == 1) {
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// Now if it's coming from the newFuncRoot, it's that funky input
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unsigned phiIdx = EValEBB[0];
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if (!dyn_cast<Constant>(Phi->getIncomingValue(phiIdx)))
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{
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PhiVal2Arg[Phi].push_back(std::make_pair(phiIdx, inputs.size()));
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// We can just pass this value in as argument
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inputs.push_back(Phi->getIncomingValue(phiIdx));
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}
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Phi->setIncomingBlock(phiIdx, newFuncRoot);
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} else {
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PHINode *externalPhi = new PHINode(Phi->getType(), "extPhi");
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codeReplacer->getInstList().insert(codeReplacer->begin(), externalPhi);
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for (std::vector<unsigned>::iterator i = EValEBB.begin(),
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e = EValEBB.end(); i != e; ++i)
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{
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externalPhi->addIncoming(Phi->getIncomingValue(*i),
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Phi->getIncomingBlock(*i));
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// We make these values invalid instead of deleting them because that
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// would shift the indices of other values... The fixPhiNodes should
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// clean these phi nodes up later.
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Phi->setIncomingValue(*i, 0);
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Phi->setIncomingBlock(*i, 0);
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}
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PhiVal2Arg[Phi].push_back(std::make_pair(Phi->getNumIncomingValues(),
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inputs.size()));
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// We can just pass this value in as argument
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inputs.push_back(externalPhi);
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}
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}
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// When the value is external, but block internal...
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// just pass it in as argument, no change to phi node
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for (std::vector<unsigned>::iterator i = EValIBB.begin(),
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e = EValIBB.end(); i != e; ++i)
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{
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// rewrite the phi input node to be an argument
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PhiVal2Arg[Phi].push_back(std::make_pair(*i, inputs.size()));
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inputs.push_back(Phi->getIncomingValue(*i));
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}
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// Value internal, block external
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// this can happen if we are extracting a part of a loop
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for (std::vector<unsigned>::iterator i = IValEBB.begin(),
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e = IValEBB.end(); i != e; ++i)
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{
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assert(0 && "Cannot (YET) handle internal values via external blocks");
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}
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}
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void CodeExtractor::findInputsOutputs(const std::vector<BasicBlock*> &code,
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Values &inputs,
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Values &outputs,
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BasicBlock *newHeader,
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BasicBlock *newRootNode)
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{
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for (std::vector<BasicBlock*>::const_iterator ci = code.begin(),
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ce = code.end(); ci != ce; ++ci) {
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BasicBlock *BB = *ci;
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for (BasicBlock::iterator BBi = BB->begin(), BBe = BB->end();
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BBi != BBe; ++BBi) {
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// If a use is defined outside the region, it's an input.
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// If a def is used outside the region, it's an output.
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if (Instruction *I = dyn_cast<Instruction>(&*BBi)) {
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// If it's a phi node
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if (PHINode *Phi = dyn_cast<PHINode>(I)) {
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processPhiNodeInputs(Phi, code, inputs, newHeader, newRootNode);
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} else {
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// All other instructions go through the generic input finder
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// Loop over the operands of each instruction (inputs)
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for (User::op_iterator op = I->op_begin(), opE = I->op_end();
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op != opE; ++op) {
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if (Instruction *opI = dyn_cast<Instruction>(op->get())) {
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// Check if definition of this operand is within the loop
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if (!contains(code, opI->getParent())) {
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// add this operand to the inputs
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inputs.push_back(opI);
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}
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}
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}
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}
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// Consider uses of this instruction (outputs)
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for (Value::use_iterator use = I->use_begin(), useE = I->use_end();
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use != useE; ++use) {
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if (Instruction* inst = dyn_cast<Instruction>(*use)) {
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if (!contains(code, inst->getParent())) {
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// add this op to the outputs
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outputs.push_back(I);
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}
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}
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}
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} /* if */
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} /* for: insts */
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} /* for: basic blocks */
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}
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void CodeExtractor::rewritePhiNodes(Function *F,
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BasicBlock *newFuncRoot) {
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// Write any changes that were saved before: use function arguments as inputs
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for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
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i != e; ++i)
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{
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PHINode *phi = (*i).first;
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PhiValChangesTy &values = (*i).second;
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for (unsigned cIdx = 0, ce = values.size(); cIdx != ce; ++cIdx)
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{
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unsigned phiValueIdx = values[cIdx].first, argNum = values[cIdx].second;
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if (phiValueIdx < phi->getNumIncomingValues())
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phi->setIncomingValue(phiValueIdx, getFunctionArg(F, argNum));
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else
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phi->addIncoming(getFunctionArg(F, argNum), newFuncRoot);
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}
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}
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// Delete any invalid Phi node inputs that were marked as NULL previously
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for (PhiVal2ArgTy::iterator i = PhiVal2Arg.begin(), e = PhiVal2Arg.end();
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i != e; ++i)
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{
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PHINode *phi = (*i).first;
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for (unsigned idx = 0, end = phi->getNumIncomingValues(); idx != end; ++idx)
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{
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if (phi->getIncomingValue(idx) == 0 && phi->getIncomingBlock(idx) == 0) {
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phi->removeIncomingValue(idx);
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--idx;
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--end;
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}
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}
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}
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// We are done with the saved values
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PhiVal2Arg.clear();
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}
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/// constructFunction - make a function based on inputs and outputs, as follows:
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/// f(in0, ..., inN, out0, ..., outN)
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///
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Function *CodeExtractor::constructFunction(const Values &inputs,
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const Values &outputs,
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BasicBlock *newRootNode,
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BasicBlock *newHeader,
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const std::vector<BasicBlock*> &code,
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Function *oldFunction, Module *M) {
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DEBUG(std::cerr << "inputs: " << inputs.size() << "\n");
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DEBUG(std::cerr << "outputs: " << outputs.size() << "\n");
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BasicBlock *header = code[0];
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// This function returns unsigned, outputs will go back by reference.
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Type *retTy = Type::UShortTy;
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std::vector<const Type*> paramTy;
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// Add the types of the input values to the function's argument list
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for (Values::const_iterator i = inputs.begin(),
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e = inputs.end(); i != e; ++i) {
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const Value *value = *i;
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DEBUG(std::cerr << "value used in func: " << value << "\n");
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paramTy.push_back(value->getType());
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}
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// Add the types of the output values to the function's argument list, but
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// make them pointer types for scalars
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for (Values::const_iterator i = outputs.begin(),
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e = outputs.end(); i != e; ++i) {
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const Value *value = *i;
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DEBUG(std::cerr << "instr used in func: " << value << "\n");
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const Type *valueType = value->getType();
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// Convert scalar types into a pointer of that type
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if (valueType->isPrimitiveType()) {
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valueType = PointerType::get(valueType);
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}
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paramTy.push_back(valueType);
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}
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DEBUG(std::cerr << "Function type: " << retTy << " f(");
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for (std::vector<const Type*>::iterator i = paramTy.begin(),
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e = paramTy.end(); i != e; ++i)
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DEBUG(std::cerr << (*i) << ", ");
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DEBUG(std::cerr << ")\n");
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const FunctionType *funcType = FunctionType::get(retTy, paramTy, false);
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// Create the new function
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Function *newFunction = new Function(funcType,
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GlobalValue::InternalLinkage,
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oldFunction->getName() + "_code", M);
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newFunction->getBasicBlockList().push_back(newRootNode);
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for (unsigned i = 0, e = inputs.size(); i != e; ++i) {
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std::vector<User*> Users(inputs[i]->use_begin(), inputs[i]->use_end());
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for (std::vector<User*>::iterator use = Users.begin(), useE = Users.end();
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use != useE; ++use) {
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if (Instruction* inst = dyn_cast<Instruction>(*use)) {
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if (contains(code, inst->getParent())) {
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inst->replaceUsesOfWith(inputs[i], getFunctionArg(newFunction, i));
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}
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}
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}
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}
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// Rewrite branches to basic blocks outside of the loop to new dummy blocks
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// within the new function. This must be done before we lose track of which
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// blocks were originally in the code region.
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std::vector<User*> Users(header->use_begin(), header->use_end());
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for (std::vector<User*>::iterator i = Users.begin(), e = Users.end();
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i != e; ++i) {
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if (BranchInst *inst = dyn_cast<BranchInst>(*i)) {
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BasicBlock *BB = inst->getParent();
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if (!contains(code, BB) && BB->getParent() == oldFunction) {
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// The BasicBlock which contains the branch is not in the region
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// modify the branch target to a new block
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inst->replaceUsesOfWith(header, newHeader);
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}
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}
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}
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return newFunction;
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}
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void CodeExtractor::moveCodeToFunction(const std::vector<BasicBlock*> &code,
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Function *newFunction)
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{
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for (std::vector<BasicBlock*>::const_iterator i = code.begin(), e =code.end();
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i != e; ++i) {
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BasicBlock *BB = *i;
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Function *oldFunc = BB->getParent();
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Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
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// Delete the basic block from the old function, and the list of blocks
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oldBlocks.remove(BB);
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// Insert this basic block into the new function
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Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
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newBlocks.push_back(BB);
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}
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}
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void
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CodeExtractor::emitCallAndSwitchStatement(Function *newFunction,
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BasicBlock *codeReplacer,
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const std::vector<BasicBlock*> &code,
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Values &inputs,
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Values &outputs)
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{
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// Emit a call to the new function, passing allocated memory for outputs and
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// just plain inputs for non-scalars
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std::vector<Value*> params;
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BasicBlock *codeReplacerTail = new BasicBlock("codeReplTail",
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codeReplacer->getParent());
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for (Values::const_iterator i = inputs.begin(),
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e = inputs.end(); i != e; ++i)
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params.push_back(*i);
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for (Values::const_iterator i = outputs.begin(),
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e = outputs.end(); i != e; ++i) {
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// Create allocas for scalar outputs
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if ((*i)->getType()->isPrimitiveType()) {
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Constant *one = ConstantUInt::get(Type::UIntTy, 1);
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AllocaInst *alloca = new AllocaInst((*i)->getType(), one);
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codeReplacer->getInstList().push_back(alloca);
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params.push_back(alloca);
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LoadInst *load = new LoadInst(alloca, "alloca");
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codeReplacerTail->getInstList().push_back(load);
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std::vector<User*> Users((*i)->use_begin(), (*i)->use_end());
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for (std::vector<User*>::iterator use = Users.begin(), useE =Users.end();
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use != useE; ++use) {
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if (Instruction* inst = dyn_cast<Instruction>(*use)) {
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if (!contains(code, inst->getParent())) {
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inst->replaceUsesOfWith(*i, load);
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}
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}
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}
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} else {
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params.push_back(*i);
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}
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}
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CallInst *call = new CallInst(newFunction, params, "targetBlock");
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codeReplacer->getInstList().push_back(call);
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codeReplacer->getInstList().push_back(new BranchInst(codeReplacerTail));
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// Now we can emit a switch statement using the call as a value.
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// FIXME: perhaps instead of default being self BB, it should be a second
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// dummy block which asserts that the value is not within the range...?
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//BasicBlock *defaultBlock = new BasicBlock("defaultBlock", oldF);
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//insert abort() ?
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//defaultBlock->getInstList().push_back(new BranchInst(codeReplacer));
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SwitchInst *switchInst = new SwitchInst(call, codeReplacerTail,
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codeReplacerTail);
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// Since there may be multiple exits from the original region, make the new
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// function return an unsigned, switch on that number
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unsigned switchVal = 0;
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for (std::vector<BasicBlock*>::const_iterator i =code.begin(), e = code.end();
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i != e; ++i) {
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BasicBlock *BB = *i;
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// rewrite the terminator of the original BasicBlock
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Instruction *term = BB->getTerminator();
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if (BranchInst *brInst = dyn_cast<BranchInst>(term)) {
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// Restore values just before we exit
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// FIXME: Use a GetElementPtr to bunch the outputs in a struct
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for (unsigned outIdx = 0, outE = outputs.size(); outIdx != outE; ++outIdx)
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{
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new StoreInst(outputs[outIdx],
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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());
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue