[llvm-commits] CVS: llvm/lib/Transforms/Utils/CodeExtractor.cpp
Misha Brukman
brukman at cs.uiuc.edu
Fri Feb 27 21:27:00 PST 2004
Changes in directory llvm/lib/Transforms/Utils:
CodeExtractor.cpp added (r1.1)
---
Log message:
A generic code extractor: given a list of BasicBlocks, it will rip them out into
a new function, taking care of inputs and outputs.
---
Diffs of the changes: (+573 -0)
Index: llvm/lib/Transforms/Utils/CodeExtractor.cpp
diff -c /dev/null llvm/lib/Transforms/Utils/CodeExtractor.cpp:1.1
*** /dev/null Fri Feb 27 21:26:30 2004
--- llvm/lib/Transforms/Utils/CodeExtractor.cpp Fri Feb 27 21:26:20 2004
***************
*** 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());
+ }
+
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