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llvm-mirror/lib/CodeGen/RegAllocPBQP.cpp
Owen Anderson 46990c17f7 Get rid of static constructors for pass registration. Instead, every pass exposes an initializeMyPassFunction(), which 
must be called in the pass's constructor.  This function uses static dependency declarations to recursively initialize
the pass's dependencies.

Clients that only create passes through the createFooPass() APIs will require no changes.  Clients that want to use the
CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h
before parsing commandline arguments.

I have tested this with all standard configurations of clang and llvm-gcc on Darwin.  It is possible that there are problems
with the static dependencies that will only be visible with non-standard options.  If you encounter any crash in pass
registration/creation, please send the testcase to me directly.

llvm-svn: 116820
2010-10-19 17:21:58 +00:00

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//===------ RegAllocPBQP.cpp ---- PBQP Register Allocator -------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains a Partitioned Boolean Quadratic Programming (PBQP) based
// register allocator for LLVM. This allocator works by constructing a PBQP
// problem representing the register allocation problem under consideration,
// solving this using a PBQP solver, and mapping the solution back to a
// register assignment. If any variables are selected for spilling then spill
// code is inserted and the process repeated.
//
// The PBQP solver (pbqp.c) provided for this allocator uses a heuristic tuned
// for register allocation. For more information on PBQP for register
// allocation, see the following papers:
//
// (1) Hames, L. and Scholz, B. 2006. Nearly optimal register allocation with
// PBQP. In Proceedings of the 7th Joint Modular Languages Conference
// (JMLC'06). LNCS, vol. 4228. Springer, New York, NY, USA. 346-361.
//
// (2) Scholz, B., Eckstein, E. 2002. Register allocation for irregular
// architectures. In Proceedings of the Joint Conference on Languages,
// Compilers and Tools for Embedded Systems (LCTES'02), ACM Press, New York,
// NY, USA, 139-148.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
#include "RenderMachineFunction.h"
#include "Splitter.h"
#include "VirtRegMap.h"
#include "VirtRegRewriter.h"
#include "llvm/CodeGen/CalcSpillWeights.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/RegAllocPBQP.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/PBQP/HeuristicSolver.h"
#include "llvm/CodeGen/PBQP/Graph.h"
#include "llvm/CodeGen/PBQP/Heuristics/Briggs.h"
#include "llvm/CodeGen/RegAllocRegistry.h"
#include "llvm/CodeGen/RegisterCoalescer.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
#include <limits>
#include <memory>
#include <set>
#include <vector>
using namespace llvm;
static RegisterRegAlloc
registerPBQPRepAlloc("pbqp", "PBQP register allocator",
createDefaultPBQPRegisterAllocator);
static cl::opt<bool>
pbqpCoalescing("pbqp-coalescing",
cl::desc("Attempt coalescing during PBQP register allocation."),
cl::init(false), cl::Hidden);
static cl::opt<bool>
pbqpPreSplitting("pbqp-pre-splitting",
cl::desc("Pre-split before PBQP register allocation."),
cl::init(false), cl::Hidden);
namespace {
///
/// PBQP based allocators solve the register allocation problem by mapping
/// register allocation problems to Partitioned Boolean Quadratic
/// Programming problems.
class RegAllocPBQP : public MachineFunctionPass {
public:
static char ID;
/// Construct a PBQP register allocator.
RegAllocPBQP(std::auto_ptr<PBQPBuilder> b)
: MachineFunctionPass(ID), builder(b) {
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
initializeRegisterCoalescerAnalysisGroup(*PassRegistry::getPassRegistry());
initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
initializeLiveStacksPass(*PassRegistry::getPassRegistry());
initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
initializeLoopSplitterPass(*PassRegistry::getPassRegistry());
initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
initializeRenderMachineFunctionPass(*PassRegistry::getPassRegistry());
}
/// Return the pass name.
virtual const char* getPassName() const {
return "PBQP Register Allocator";
}
/// PBQP analysis usage.
virtual void getAnalysisUsage(AnalysisUsage &au) const;
/// Perform register allocation
virtual bool runOnMachineFunction(MachineFunction &MF);
private:
typedef std::map<const LiveInterval*, unsigned> LI2NodeMap;
typedef std::vector<const LiveInterval*> Node2LIMap;
typedef std::vector<unsigned> AllowedSet;
typedef std::vector<AllowedSet> AllowedSetMap;
typedef std::pair<unsigned, unsigned> RegPair;
typedef std::map<RegPair, PBQP::PBQPNum> CoalesceMap;
typedef std::vector<PBQP::Graph::NodeItr> NodeVector;
typedef std::set<unsigned> RegSet;
std::auto_ptr<PBQPBuilder> builder;
MachineFunction *mf;
const TargetMachine *tm;
const TargetRegisterInfo *tri;
const TargetInstrInfo *tii;
const MachineLoopInfo *loopInfo;
MachineRegisterInfo *mri;
RenderMachineFunction *rmf;
LiveIntervals *lis;
LiveStacks *lss;
VirtRegMap *vrm;
RegSet vregsToAlloc, emptyIntervalVRegs;
/// \brief Finds the initial set of vreg intervals to allocate.
void findVRegIntervalsToAlloc();
/// \brief Adds a stack interval if the given live interval has been
/// spilled. Used to support stack slot coloring.
void addStackInterval(const LiveInterval *spilled,MachineRegisterInfo* mri);
/// \brief Given a solved PBQP problem maps this solution back to a register
/// assignment.
bool mapPBQPToRegAlloc(const PBQPRAProblem &problem,
const PBQP::Solution &solution);
/// \brief Postprocessing before final spilling. Sets basic block "live in"
/// variables.
void finalizeAlloc() const;
};
char RegAllocPBQP::ID = 0;
} // End anonymous namespace.
unsigned PBQPRAProblem::getVRegForNode(PBQP::Graph::ConstNodeItr node) const {
Node2VReg::const_iterator vregItr = node2VReg.find(node);
assert(vregItr != node2VReg.end() && "No vreg for node.");
return vregItr->second;
}
PBQP::Graph::NodeItr PBQPRAProblem::getNodeForVReg(unsigned vreg) const {
VReg2Node::const_iterator nodeItr = vreg2Node.find(vreg);
assert(nodeItr != vreg2Node.end() && "No node for vreg.");
return nodeItr->second;
}
const PBQPRAProblem::AllowedSet&
PBQPRAProblem::getAllowedSet(unsigned vreg) const {
AllowedSetMap::const_iterator allowedSetItr = allowedSets.find(vreg);
assert(allowedSetItr != allowedSets.end() && "No pregs for vreg.");
const AllowedSet &allowedSet = allowedSetItr->second;
return allowedSet;
}
unsigned PBQPRAProblem::getPRegForOption(unsigned vreg, unsigned option) const {
assert(isPRegOption(vreg, option) && "Not a preg option.");
const AllowedSet& allowedSet = getAllowedSet(vreg);
assert(option <= allowedSet.size() && "Option outside allowed set.");
return allowedSet[option - 1];
}
std::auto_ptr<PBQPRAProblem> PBQPBuilder::build(MachineFunction *mf,
const LiveIntervals *lis,
const MachineLoopInfo *loopInfo,
const RegSet &vregs) {
typedef std::vector<const LiveInterval*> LIVector;
MachineRegisterInfo *mri = &mf->getRegInfo();
const TargetRegisterInfo *tri = mf->getTarget().getRegisterInfo();
std::auto_ptr<PBQPRAProblem> p(new PBQPRAProblem());
PBQP::Graph &g = p->getGraph();
RegSet pregs;
// Collect the set of preg intervals, record that they're used in the MF.
for (LiveIntervals::const_iterator itr = lis->begin(), end = lis->end();
itr != end; ++itr) {
if (TargetRegisterInfo::isPhysicalRegister(itr->first)) {
pregs.insert(itr->first);
mri->setPhysRegUsed(itr->first);
}
}
BitVector reservedRegs = tri->getReservedRegs(*mf);
// Iterate over vregs.
for (RegSet::const_iterator vregItr = vregs.begin(), vregEnd = vregs.end();
vregItr != vregEnd; ++vregItr) {
unsigned vreg = *vregItr;
const TargetRegisterClass *trc = mri->getRegClass(vreg);
const LiveInterval *vregLI = &lis->getInterval(vreg);
// Compute an initial allowed set for the current vreg.
typedef std::vector<unsigned> VRAllowed;
VRAllowed vrAllowed;
for (TargetRegisterClass::iterator aoItr = trc->allocation_order_begin(*mf),
aoEnd = trc->allocation_order_end(*mf);
aoItr != aoEnd; ++aoItr) {
unsigned preg = *aoItr;
if (!reservedRegs.test(preg)) {
vrAllowed.push_back(preg);
}
}
// Remove any physical registers which overlap.
for (RegSet::const_iterator pregItr = pregs.begin(),
pregEnd = pregs.end();
pregItr != pregEnd; ++pregItr) {
unsigned preg = *pregItr;
const LiveInterval *pregLI = &lis->getInterval(preg);
if (pregLI->empty())
continue;
if (!vregLI->overlaps(*pregLI))
continue;
// Remove the register from the allowed set.
VRAllowed::iterator eraseItr =
std::find(vrAllowed.begin(), vrAllowed.end(), preg);
if (eraseItr != vrAllowed.end()) {
vrAllowed.erase(eraseItr);
}
// Also remove any aliases.
const unsigned *aliasItr = tri->getAliasSet(preg);
if (aliasItr != 0) {
for (; *aliasItr != 0; ++aliasItr) {
VRAllowed::iterator eraseItr =
std::find(vrAllowed.begin(), vrAllowed.end(), *aliasItr);
if (eraseItr != vrAllowed.end()) {
vrAllowed.erase(eraseItr);
}
}
}
}
// Construct the node.
PBQP::Graph::NodeItr node =
g.addNode(PBQP::Vector(vrAllowed.size() + 1, 0));
// Record the mapping and allowed set in the problem.
p->recordVReg(vreg, node, vrAllowed.begin(), vrAllowed.end());
PBQP::PBQPNum spillCost = (vregLI->weight != 0.0) ?
vregLI->weight : std::numeric_limits<PBQP::PBQPNum>::min();
addSpillCosts(g.getNodeCosts(node), spillCost);
}
for (RegSet::const_iterator vr1Itr = vregs.begin(), vrEnd = vregs.end();
vr1Itr != vrEnd; ++vr1Itr) {
unsigned vr1 = *vr1Itr;
const LiveInterval &l1 = lis->getInterval(vr1);
const PBQPRAProblem::AllowedSet &vr1Allowed = p->getAllowedSet(vr1);
for (RegSet::const_iterator vr2Itr = llvm::next(vr1Itr);
vr2Itr != vrEnd; ++vr2Itr) {
unsigned vr2 = *vr2Itr;
const LiveInterval &l2 = lis->getInterval(vr2);
const PBQPRAProblem::AllowedSet &vr2Allowed = p->getAllowedSet(vr2);
assert(!l2.empty() && "Empty interval in vreg set?");
if (l1.overlaps(l2)) {
PBQP::Graph::EdgeItr edge =
g.addEdge(p->getNodeForVReg(vr1), p->getNodeForVReg(vr2),
PBQP::Matrix(vr1Allowed.size()+1, vr2Allowed.size()+1, 0));
addInterferenceCosts(g.getEdgeCosts(edge), vr1Allowed, vr2Allowed, tri);
}
}
}
return p;
}
void PBQPBuilder::addSpillCosts(PBQP::Vector &costVec,
PBQP::PBQPNum spillCost) {
costVec[0] = spillCost;
}
void PBQPBuilder::addInterferenceCosts(
PBQP::Matrix &costMat,
const PBQPRAProblem::AllowedSet &vr1Allowed,
const PBQPRAProblem::AllowedSet &vr2Allowed,
const TargetRegisterInfo *tri) {
assert(costMat.getRows() == vr1Allowed.size() + 1 && "Matrix height mismatch.");
assert(costMat.getCols() == vr2Allowed.size() + 1 && "Matrix width mismatch.");
for (unsigned i = 0; i < vr1Allowed.size(); ++i) {
unsigned preg1 = vr1Allowed[i];
for (unsigned j = 0; j < vr2Allowed.size(); ++j) {
unsigned preg2 = vr2Allowed[j];
if (tri->regsOverlap(preg1, preg2)) {
costMat[i + 1][j + 1] = std::numeric_limits<PBQP::PBQPNum>::infinity();
}
}
}
}
std::auto_ptr<PBQPRAProblem> PBQPBuilderWithCoalescing::build(
MachineFunction *mf,
const LiveIntervals *lis,
const MachineLoopInfo *loopInfo,
const RegSet &vregs) {
std::auto_ptr<PBQPRAProblem> p = PBQPBuilder::build(mf, lis, loopInfo, vregs);
PBQP::Graph &g = p->getGraph();
const TargetMachine &tm = mf->getTarget();
CoalescerPair cp(*tm.getInstrInfo(), *tm.getRegisterInfo());
// Scan the machine function and add a coalescing cost whenever CoalescerPair
// gives the Ok.
for (MachineFunction::const_iterator mbbItr = mf->begin(),
mbbEnd = mf->end();
mbbItr != mbbEnd; ++mbbItr) {
const MachineBasicBlock *mbb = &*mbbItr;
for (MachineBasicBlock::const_iterator miItr = mbb->begin(),
miEnd = mbb->end();
miItr != miEnd; ++miItr) {
const MachineInstr *mi = &*miItr;
if (!cp.setRegisters(mi))
continue; // Not coalescable.
if (cp.getSrcReg() == cp.getDstReg())
continue; // Already coalesced.
unsigned dst = cp.getDstReg(),
src = cp.getSrcReg();
const float copyFactor = 0.5; // Cost of copy relative to load. Current
// value plucked randomly out of the air.
PBQP::PBQPNum cBenefit =
copyFactor * LiveIntervals::getSpillWeight(false, true,
loopInfo->getLoopDepth(mbb));
if (cp.isPhys()) {
if (!lis->isAllocatable(dst))
continue;
const PBQPRAProblem::AllowedSet &allowed = p->getAllowedSet(src);
unsigned pregOpt = 0;
while (pregOpt < allowed.size() && allowed[pregOpt] != dst)
++pregOpt;
if (pregOpt < allowed.size()) {
++pregOpt; // +1 to account for spill option.
PBQP::Graph::NodeItr node = p->getNodeForVReg(src);
addPhysRegCoalesce(g.getNodeCosts(node), pregOpt, cBenefit);
}
} else {
const PBQPRAProblem::AllowedSet *allowed1 = &p->getAllowedSet(dst);
const PBQPRAProblem::AllowedSet *allowed2 = &p->getAllowedSet(src);
PBQP::Graph::NodeItr node1 = p->getNodeForVReg(dst);
PBQP::Graph::NodeItr node2 = p->getNodeForVReg(src);
PBQP::Graph::EdgeItr edge = g.findEdge(node1, node2);
if (edge == g.edgesEnd()) {
edge = g.addEdge(node1, node2, PBQP::Matrix(allowed1->size() + 1,
allowed2->size() + 1,
0));
} else {
if (g.getEdgeNode1(edge) == node2) {
std::swap(node1, node2);
std::swap(allowed1, allowed2);
}
}
addVirtRegCoalesce(g.getEdgeCosts(edge), *allowed1, *allowed2,
cBenefit);
}
}
}
return p;
}
void PBQPBuilderWithCoalescing::addPhysRegCoalesce(PBQP::Vector &costVec,
unsigned pregOption,
PBQP::PBQPNum benefit) {
costVec[pregOption] += -benefit;
}
void PBQPBuilderWithCoalescing::addVirtRegCoalesce(
PBQP::Matrix &costMat,
const PBQPRAProblem::AllowedSet &vr1Allowed,
const PBQPRAProblem::AllowedSet &vr2Allowed,
PBQP::PBQPNum benefit) {
assert(costMat.getRows() == vr1Allowed.size() + 1 && "Size mismatch.");
assert(costMat.getCols() == vr2Allowed.size() + 1 && "Size mismatch.");
for (unsigned i = 0; i < vr1Allowed.size(); ++i) {
unsigned preg1 = vr1Allowed[i];
for (unsigned j = 0; j < vr2Allowed.size(); ++j) {
unsigned preg2 = vr2Allowed[j];
if (preg1 == preg2) {
costMat[i + 1][j + 1] += -benefit;
}
}
}
}
void RegAllocPBQP::getAnalysisUsage(AnalysisUsage &au) const {
au.addRequired<SlotIndexes>();
au.addPreserved<SlotIndexes>();
au.addRequired<LiveIntervals>();
//au.addRequiredID(SplitCriticalEdgesID);
au.addRequired<RegisterCoalescer>();
au.addRequired<CalculateSpillWeights>();
au.addRequired<LiveStacks>();
au.addPreserved<LiveStacks>();
au.addRequired<MachineLoopInfo>();
au.addPreserved<MachineLoopInfo>();
if (pbqpPreSplitting)
au.addRequired<LoopSplitter>();
au.addRequired<VirtRegMap>();
au.addRequired<RenderMachineFunction>();
MachineFunctionPass::getAnalysisUsage(au);
}
void RegAllocPBQP::findVRegIntervalsToAlloc() {
// Iterate over all live ranges.
for (LiveIntervals::iterator itr = lis->begin(), end = lis->end();
itr != end; ++itr) {
// Ignore physical ones.
if (TargetRegisterInfo::isPhysicalRegister(itr->first))
continue;
LiveInterval *li = itr->second;
// If this live interval is non-empty we will use pbqp to allocate it.
// Empty intervals we allocate in a simple post-processing stage in
// finalizeAlloc.
if (!li->empty()) {
vregsToAlloc.insert(li->reg);
}
else {
emptyIntervalVRegs.insert(li->reg);
}
}
}
void RegAllocPBQP::addStackInterval(const LiveInterval *spilled,
MachineRegisterInfo* mri) {
int stackSlot = vrm->getStackSlot(spilled->reg);
if (stackSlot == VirtRegMap::NO_STACK_SLOT)
return;
const TargetRegisterClass *RC = mri->getRegClass(spilled->reg);
LiveInterval &stackInterval = lss->getOrCreateInterval(stackSlot, RC);
VNInfo *vni;
if (stackInterval.getNumValNums() != 0)
vni = stackInterval.getValNumInfo(0);
else
vni = stackInterval.getNextValue(
SlotIndex(), 0, lss->getVNInfoAllocator());
LiveInterval &rhsInterval = lis->getInterval(spilled->reg);
stackInterval.MergeRangesInAsValue(rhsInterval, vni);
}
bool RegAllocPBQP::mapPBQPToRegAlloc(const PBQPRAProblem &problem,
const PBQP::Solution &solution) {
// Set to true if we have any spills
bool anotherRoundNeeded = false;
// Clear the existing allocation.
vrm->clearAllVirt();
const PBQP::Graph &g = problem.getGraph();
// Iterate over the nodes mapping the PBQP solution to a register
// assignment.
for (PBQP::Graph::ConstNodeItr node = g.nodesBegin(),
nodeEnd = g.nodesEnd();
node != nodeEnd; ++node) {
unsigned vreg = problem.getVRegForNode(node);
unsigned alloc = solution.getSelection(node);
if (problem.isPRegOption(vreg, alloc)) {
unsigned preg = problem.getPRegForOption(vreg, alloc);
DEBUG(dbgs() << "VREG " << vreg << " -> " << tri->getName(preg) << "\n");
assert(preg != 0 && "Invalid preg selected.");
vrm->assignVirt2Phys(vreg, preg);
} else if (problem.isSpillOption(vreg, alloc)) {
vregsToAlloc.erase(vreg);
const LiveInterval* spillInterval = &lis->getInterval(vreg);
double oldWeight = spillInterval->weight;
SmallVector<LiveInterval*, 8> spillIs;
rmf->rememberUseDefs(spillInterval);
std::vector<LiveInterval*> newSpills =
lis->addIntervalsForSpills(*spillInterval, spillIs, loopInfo, *vrm);
addStackInterval(spillInterval, mri);
rmf->rememberSpills(spillInterval, newSpills);
(void) oldWeight;
DEBUG(dbgs() << "VREG " << vreg << " -> SPILLED (Cost: "
<< oldWeight << ", New vregs: ");
// Copy any newly inserted live intervals into the list of regs to
// allocate.
for (std::vector<LiveInterval*>::const_iterator
itr = newSpills.begin(), end = newSpills.end();
itr != end; ++itr) {
assert(!(*itr)->empty() && "Empty spill range.");
DEBUG(dbgs() << (*itr)->reg << " ");
vregsToAlloc.insert((*itr)->reg);
}
DEBUG(dbgs() << ")\n");
// We need another round if spill intervals were added.
anotherRoundNeeded |= !newSpills.empty();
} else {
assert(false && "Unknown allocation option.");
}
}
return !anotherRoundNeeded;
}
void RegAllocPBQP::finalizeAlloc() const {
typedef LiveIntervals::iterator LIIterator;
typedef LiveInterval::Ranges::const_iterator LRIterator;
// First allocate registers for the empty intervals.
for (RegSet::const_iterator
itr = emptyIntervalVRegs.begin(), end = emptyIntervalVRegs.end();
itr != end; ++itr) {
LiveInterval *li = &lis->getInterval(*itr);
unsigned physReg = vrm->getRegAllocPref(li->reg);
if (physReg == 0) {
const TargetRegisterClass *liRC = mri->getRegClass(li->reg);
physReg = *liRC->allocation_order_begin(*mf);
}
vrm->assignVirt2Phys(li->reg, physReg);
}
// Finally iterate over the basic blocks to compute and set the live-in sets.
SmallVector<MachineBasicBlock*, 8> liveInMBBs;
MachineBasicBlock *entryMBB = &*mf->begin();
for (LIIterator liItr = lis->begin(), liEnd = lis->end();
liItr != liEnd; ++liItr) {
const LiveInterval *li = liItr->second;
unsigned reg = 0;
// Get the physical register for this interval
if (TargetRegisterInfo::isPhysicalRegister(li->reg)) {
reg = li->reg;
}
else if (vrm->isAssignedReg(li->reg)) {
reg = vrm->getPhys(li->reg);
}
else {
// Ranges which are assigned a stack slot only are ignored.
continue;
}
if (reg == 0) {
// Filter out zero regs - they're for intervals that were spilled.
continue;
}
// Iterate over the ranges of the current interval...
for (LRIterator lrItr = li->begin(), lrEnd = li->end();
lrItr != lrEnd; ++lrItr) {
// Find the set of basic blocks which this range is live into...
if (lis->findLiveInMBBs(lrItr->start, lrItr->end, liveInMBBs)) {
// And add the physreg for this interval to their live-in sets.
for (unsigned i = 0; i < liveInMBBs.size(); ++i) {
if (liveInMBBs[i] != entryMBB) {
if (!liveInMBBs[i]->isLiveIn(reg)) {
liveInMBBs[i]->addLiveIn(reg);
}
}
}
liveInMBBs.clear();
}
}
}
}
bool RegAllocPBQP::runOnMachineFunction(MachineFunction &MF) {
mf = &MF;
tm = &mf->getTarget();
tri = tm->getRegisterInfo();
tii = tm->getInstrInfo();
mri = &mf->getRegInfo();
lis = &getAnalysis<LiveIntervals>();
lss = &getAnalysis<LiveStacks>();
loopInfo = &getAnalysis<MachineLoopInfo>();
rmf = &getAnalysis<RenderMachineFunction>();
vrm = &getAnalysis<VirtRegMap>();
DEBUG(dbgs() << "PBQP Register Allocating for " << mf->getFunction()->getName() << "\n");
// Allocator main loop:
//
// * Map current regalloc problem to a PBQP problem
// * Solve the PBQP problem
// * Map the solution back to a register allocation
// * Spill if necessary
//
// This process is continued till no more spills are generated.
// Find the vreg intervals in need of allocation.
findVRegIntervalsToAlloc();
// If there are non-empty intervals allocate them using pbqp.
if (!vregsToAlloc.empty()) {
bool pbqpAllocComplete = false;
unsigned round = 0;
while (!pbqpAllocComplete) {
DEBUG(dbgs() << " PBQP Regalloc round " << round << ":\n");
std::auto_ptr<PBQPRAProblem> problem =
builder->build(mf, lis, loopInfo, vregsToAlloc);
PBQP::Solution solution =
PBQP::HeuristicSolver<PBQP::Heuristics::Briggs>::solve(
problem->getGraph());
pbqpAllocComplete = mapPBQPToRegAlloc(*problem, solution);
++round;
}
}
// Finalise allocation, allocate empty ranges.
finalizeAlloc();
rmf->renderMachineFunction("After PBQP register allocation.", vrm);
vregsToAlloc.clear();
emptyIntervalVRegs.clear();
DEBUG(dbgs() << "Post alloc VirtRegMap:\n" << *vrm << "\n");
// Run rewriter
std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
rewriter->runOnMachineFunction(*mf, *vrm, lis);
return true;
}
FunctionPass* llvm::createPBQPRegisterAllocator(
std::auto_ptr<PBQPBuilder> builder) {
return new RegAllocPBQP(builder);
}
FunctionPass* llvm::createDefaultPBQPRegisterAllocator() {
if (pbqpCoalescing) {
return createPBQPRegisterAllocator(
std::auto_ptr<PBQPBuilder>(new PBQPBuilderWithCoalescing()));
} // else
return createPBQPRegisterAllocator(
std::auto_ptr<PBQPBuilder>(new PBQPBuilder()));
}
#undef DEBUG_TYPE
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