mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-20 11:29:24 +00:00
With this fix we now successfully extract all 149 loops from 256.bzip2 without crashing or miscompiling the program! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12493 91177308-0d34-0410-b5e6-96231b3b80d8
417 lines
17 KiB
C++
417 lines
17 KiB
C++
//===- 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/Transforms/Utils/FunctionUtils.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/Dominators.h"
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#include "llvm/Analysis/LoopInfo.h"
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#include "llvm/Analysis/Verifier.h"
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#include "llvm/Transforms/Utils/BasicBlockUtils.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 <set>
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using namespace llvm;
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namespace {
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class CodeExtractor {
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typedef std::vector<Value*> Values;
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std::set<BasicBlock*> BlocksToExtract;
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DominatorSet *DS;
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public:
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CodeExtractor(DominatorSet *ds = 0) : DS(ds) {}
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Function *ExtractCodeRegion(const std::vector<BasicBlock*> &code);
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private:
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void findInputsOutputs(Values &inputs, Values &outputs,
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BasicBlock *newHeader,
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BasicBlock *newRootNode);
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Function *constructFunction(const Values &inputs,
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const Values &outputs,
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BasicBlock *header,
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BasicBlock *newRootNode, BasicBlock *newHeader,
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Function *oldFunction, Module *M);
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void moveCodeToFunction(Function *newFunction);
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void emitCallAndSwitchStatement(Function *newFunction,
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BasicBlock *newHeader,
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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::findInputsOutputs(Values &inputs, Values &outputs,
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BasicBlock *newHeader,
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BasicBlock *newRootNode) {
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for (std::set<BasicBlock*>::const_iterator ci = BlocksToExtract.begin(),
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ce = BlocksToExtract.end(); ci != ce; ++ci) {
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BasicBlock *BB = *ci;
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
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// If a used value is defined outside the region, it's an input. If an
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// instruction is used outside the region, it's an output.
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if (PHINode *PN = dyn_cast<PHINode>(I)) {
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
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Value *V = PN->getIncomingValue(i);
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if (!BlocksToExtract.count(PN->getIncomingBlock(i)) &&
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(isa<Instruction>(V) || isa<Argument>(V)))
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inputs.push_back(V);
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else if (Instruction *opI = dyn_cast<Instruction>(V)) {
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if (!BlocksToExtract.count(opI->getParent()))
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inputs.push_back(opI);
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} else if (isa<Argument>(V))
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inputs.push_back(V);
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}
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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)) {
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// Check if definition of this operand is within the loop
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if (!BlocksToExtract.count(opI->getParent()))
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inputs.push_back(opI);
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} else if (isa<Argument>(*op)) {
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inputs.push_back(*op);
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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 UI = I->use_begin(), E = I->use_end();
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UI != E; ++UI)
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if (!BlocksToExtract.count(cast<Instruction>(*UI)->getParent())) {
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outputs.push_back(I);
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break;
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}
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} // for: insts
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} // for: basic blocks
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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 *header,
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BasicBlock *newRootNode,
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BasicBlock *newHeader,
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Function *oldFunction,
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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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// 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.
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for (Values::const_iterator I = outputs.begin(), E = outputs.end();
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I != E; ++I) {
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DEBUG(std::cerr << "instr used in func: " << *I << "\n");
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paramTy.push_back(PointerType::get((*I)->getType()));
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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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// Create an iterator to name all of the arguments we inserted.
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Function::aiterator AI = newFunction->abegin();
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// Rewrite all users of the inputs in the extracted region to use the
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// arguments instead.
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for (unsigned i = 0, e = inputs.size(); i != e; ++i, ++AI) {
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AI->setName(inputs[i]->getName());
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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 (BlocksToExtract.count(inst->getParent()))
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inst->replaceUsesOfWith(inputs[i], AI);
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}
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// Set names for all of the output arguments.
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for (unsigned i = 0, e = outputs.size(); i != e; ++i, ++AI)
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AI->setName(outputs[i]->getName()+".out");
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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 (unsigned i = 0, e = Users.size(); i != e; ++i)
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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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if (TerminatorInst *TI = dyn_cast<TerminatorInst>(Users[i]))
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if (!BlocksToExtract.count(TI->getParent()) &&
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TI->getParent()->getParent() == oldFunction)
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TI->replaceUsesOfWith(header, newHeader);
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return newFunction;
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}
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void CodeExtractor::moveCodeToFunction(Function *newFunction) {
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Function *oldFunc = (*BlocksToExtract.begin())->getParent();
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Function::BasicBlockListType &oldBlocks = oldFunc->getBasicBlockList();
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Function::BasicBlockListType &newBlocks = newFunction->getBasicBlockList();
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for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
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e = BlocksToExtract.end(); i != e; ++i) {
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// Delete the basic block from the old function, and the list of blocks
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oldBlocks.remove(*i);
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// Insert this basic block into the new function
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newBlocks.push_back(*i);
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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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Values &inputs,
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Values &outputs) {
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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(inputs);
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// Get an iterator to the first output argument.
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Function::aiterator OutputArgBegin = newFunction->abegin();
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std::advance(OutputArgBegin, inputs.size());
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for (unsigned i = 0, e = outputs.size(); i != e; ++i) {
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Value *Output = outputs[i];
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// Create allocas for scalar outputs
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AllocaInst *alloca =
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new AllocaInst(outputs[i]->getType(), 0, Output->getName()+".loc",
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codeReplacer->getParent()->begin()->begin());
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params.push_back(alloca);
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LoadInst *load = new LoadInst(alloca, Output->getName()+".reload");
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codeReplacer->getInstList().push_back(load);
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std::vector<User*> Users(outputs[i]->use_begin(), outputs[i]->use_end());
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for (unsigned u = 0, e = Users.size(); u != e; ++u) {
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Instruction *inst = cast<Instruction>(Users[u]);
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if (!BlocksToExtract.count(inst->getParent()))
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inst->replaceUsesOfWith(outputs[i], load);
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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_front(call);
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// Now we can emit a switch statement using the call as a value.
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SwitchInst *TheSwitch = new SwitchInst(call, codeReplacer, codeReplacer);
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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. This loop iterates
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// over all of the blocks in the extracted region, updating any terminator
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// instructions in the to-be-extracted region that branch to blocks that are
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// not in the region to be extracted.
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std::map<BasicBlock*, BasicBlock*> ExitBlockMap;
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unsigned switchVal = 0;
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for (std::set<BasicBlock*>::const_iterator i = BlocksToExtract.begin(),
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e = BlocksToExtract.end(); i != e; ++i) {
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TerminatorInst *TI = (*i)->getTerminator();
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for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
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if (!BlocksToExtract.count(TI->getSuccessor(i))) {
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BasicBlock *OldTarget = TI->getSuccessor(i);
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// add a new basic block which returns the appropriate value
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BasicBlock *&NewTarget = ExitBlockMap[OldTarget];
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if (!NewTarget) {
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// If we don't already have an exit stub for this non-extracted
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// destination, create one now!
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NewTarget = new BasicBlock(OldTarget->getName() + ".exitStub",
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newFunction);
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ConstantUInt *brVal = ConstantUInt::get(Type::UShortTy, switchVal++);
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ReturnInst *NTRet = new ReturnInst(brVal, NewTarget);
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// Update the switch instruction.
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TheSwitch->addCase(brVal, OldTarget);
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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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Function::aiterator OAI = OutputArgBegin;
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for (unsigned out = 0, e = outputs.size(); out != e; ++out, ++OAI)
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if (!DS ||
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DS->dominates(cast<Instruction>(outputs[out])->getParent(),
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TI->getParent()))
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new StoreInst(outputs[out], OAI, NTRet);
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}
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// rewrite the original branch instruction with this new target
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TI->setSuccessor(i, NewTarget);
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}
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}
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// Now that we've done the deed, make the default destination of the switch
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// instruction be one of the exit blocks of the region.
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if (TheSwitch->getNumSuccessors() > 1) {
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// FIXME: this is broken w.r.t. PHI nodes, but the old code was more broken.
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// This edge is not traversable.
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TheSwitch->setSuccessor(0, TheSwitch->getSuccessor(1));
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}
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}
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/// ExtractRegion - Removes a loop from a function, replaces it with a call to
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/// new function. Returns pointer to the new function.
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///
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/// algorithm:
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///
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/// find inputs and outputs for the region
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///
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/// for inputs: add to function as args, map input instr* to arg#
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/// for outputs: add allocas for scalars,
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/// add to func as args, map output instr* to arg#
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///
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/// rewrite func to use argument #s instead of instr*
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///
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/// for each scalar output in the function: at every exit, store intermediate
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/// computed result back into memory.
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///
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Function *CodeExtractor::ExtractCodeRegion(const std::vector<BasicBlock*> &code)
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{
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// 1) Find inputs, outputs
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// 2) Construct new function
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// * Add allocas for defs, pass as args by reference
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// * Pass in uses as args
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// 3) Move code region, add call instr to func
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//
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BlocksToExtract.insert(code.begin(), code.end());
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Values inputs, outputs;
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// Assumption: this is a single-entry code region, and the header is the first
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// block in the region.
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BasicBlock *header = code[0];
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for (unsigned i = 1, e = code.size(); i != e; ++i)
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for (pred_iterator PI = pred_begin(code[i]), E = pred_end(code[i]);
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PI != E; ++PI)
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assert(BlocksToExtract.count(*PI) &&
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"No blocks in this region may have entries from outside the region"
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" except for the first block!");
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Function *oldFunction = header->getParent();
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// This takes place of the original loop
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BasicBlock *codeReplacer = new BasicBlock("codeRepl", oldFunction);
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// The new function needs a root node because other nodes can branch to the
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// head of the loop, and the root cannot have predecessors
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BasicBlock *newFuncRoot = new BasicBlock("newFuncRoot");
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newFuncRoot->getInstList().push_back(new BranchInst(header));
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// Find inputs to, outputs from the code region
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//
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// If one of the inputs is coming from a different basic block and it's in a
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// phi node, we need to rewrite the phi node:
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//
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// * All the inputs which involve basic blocks OUTSIDE of this region go into
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// a NEW phi node that takes care of finding which value really came in.
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// The result of this phi is passed to the function as an argument.
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//
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// * All the other phi values stay.
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//
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// FIXME: PHI nodes' incoming blocks aren't being rewritten to accomodate for
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// blocks moving to a new function.
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// SOLUTION: move Phi nodes out of the loop header into the codeReplacer, pass
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// the values as parameters to the function
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findInputsOutputs(inputs, outputs, codeReplacer, newFuncRoot);
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// Step 2: Construct new function based on inputs/outputs,
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// Add allocas for all defs
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Function *newFunction = constructFunction(inputs, outputs, code[0],
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newFuncRoot,
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codeReplacer, oldFunction,
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oldFunction->getParent());
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emitCallAndSwitchStatement(newFunction, codeReplacer, inputs, outputs);
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moveCodeToFunction(newFunction);
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// Loop over all of the PHI nodes in the entry block (code[0]), and change any
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// references to the old incoming edge to be the new incoming edge.
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for (BasicBlock::iterator I = code[0]->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (!BlocksToExtract.count(PN->getIncomingBlock(i)))
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PN->setIncomingBlock(i, newFuncRoot);
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// Look at all successors of the codeReplacer block. If any of these blocks
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// had PHI nodes in them, we need to update the "from" block to be the code
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// replacer, not the original block in the extracted region.
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std::vector<BasicBlock*> Succs(succ_begin(codeReplacer),
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succ_end(codeReplacer));
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for (unsigned i = 0, e = Succs.size(); i != e; ++i)
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for (BasicBlock::iterator I = Succs[i]->begin();
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PHINode *PN = dyn_cast<PHINode>(I); ++I)
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for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
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if (BlocksToExtract.count(PN->getIncomingBlock(i)))
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PN->setIncomingBlock(i, codeReplacer);
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DEBUG(if (verifyFunction(*newFunction)) abort());
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return newFunction;
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}
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/// ExtractCodeRegion - slurp a sequence of basic blocks into a brand new
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/// function
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///
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Function* llvm::ExtractCodeRegion(DominatorSet &DS,
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const std::vector<BasicBlock*> &code) {
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return CodeExtractor(&DS).ExtractCodeRegion(code);
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}
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/// ExtractBasicBlock - slurp a natural loop into a brand new function
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///
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Function* llvm::ExtractLoop(DominatorSet &DS, Loop *L) {
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return CodeExtractor(&DS).ExtractCodeRegion(L->getBlocks());
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}
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/// ExtractBasicBlock - slurp a basic block into a brand new function
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///
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Function* llvm::ExtractBasicBlock(BasicBlock *BB) {
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std::vector<BasicBlock*> Blocks;
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Blocks.push_back(BB);
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return CodeExtractor().ExtractCodeRegion(Blocks);
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}
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