+++ /dev/null
-//===-- RegAllocIterativeScan.cpp - Iterative Scan register allocator -----===//
-//
-// 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 an iterative scan register
-// allocator. Iterative scan is a linear scan variant with the
-// following difference:
-//
-// It performs linear scan and keeps a list of the registers it cannot
-// allocate. It then spills all those registers and repeats the
-// process until allocation succeeds.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "regalloc"
-#include "llvm/Function.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstr.h"
-#include "llvm/CodeGen/Passes.h"
-#include "llvm/CodeGen/SSARegMap.h"
-#include "llvm/Target/MRegisterInfo.h"
-#include "llvm/Target/TargetMachine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/CodeGen/LiveIntervalAnalysis.h"
-#include "PhysRegTracker.h"
-#include "VirtRegMap.h"
-#include <algorithm>
-#include <cmath>
-#include <set>
-
-using namespace llvm;
-
-namespace {
-
- Statistic<double> efficiency
- ("regalloc", "Ratio of intervals processed over total intervals");
-
- static unsigned numIterations = 0;
- static unsigned numIntervals = 0;
-
- class RA : public MachineFunctionPass {
- private:
- MachineFunction* mf_;
- const TargetMachine* tm_;
- const MRegisterInfo* mri_;
- LiveIntervals* li_;
- bool *PhysRegsUsed;
- typedef std::vector<LiveInterval*> IntervalPtrs;
- IntervalPtrs unhandled_, fixed_, active_, inactive_, handled_, spilled_;
-
- std::auto_ptr<PhysRegTracker> prt_;
- std::auto_ptr<VirtRegMap> vrm_;
- std::auto_ptr<Spiller> spiller_;
-
- typedef std::vector<float> SpillWeights;
- SpillWeights spillWeights_;
-
- public:
- virtual const char* getPassName() const {
- return "Iterative Scan Register Allocator";
- }
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<LiveIntervals>();
- MachineFunctionPass::getAnalysisUsage(AU);
- }
-
- /// runOnMachineFunction - register allocate the whole function
- bool runOnMachineFunction(MachineFunction&);
-
- void releaseMemory();
-
- private:
- /// linearScan - the linear scan algorithm. Returns a boolean
- /// indicating if there were any spills
- bool linearScan();
-
- /// initIntervalSets - initializes the four interval sets:
- /// unhandled, fixed, active and inactive
- void initIntervalSets();
-
- /// processActiveIntervals - expire old intervals and move
- /// non-overlapping ones to the incative list
- void processActiveIntervals(IntervalPtrs::value_type cur);
-
- /// processInactiveIntervals - expire old intervals and move
- /// overlapping ones to the active list
- void processInactiveIntervals(IntervalPtrs::value_type cur);
-
- /// updateSpillWeights - updates the spill weights of the
- /// specifed physical register and its weight
- void updateSpillWeights(unsigned reg, SpillWeights::value_type weight);
-
- /// assignRegOrStackSlotAtInterval - assign a register if one
- /// is available, or spill.
- void assignRegOrSpillAtInterval(IntervalPtrs::value_type cur);
-
- ///
- /// register handling helpers
- ///
-
- /// getFreePhysReg - return a free physical register for this
- /// virtual register interval if we have one, otherwise return
- /// 0
- unsigned getFreePhysReg(IntervalPtrs::value_type cur);
-
- /// assignVirt2StackSlot - assigns this virtual register to a
- /// stack slot. returns the stack slot
- int assignVirt2StackSlot(unsigned virtReg);
-
- void printIntervals(const char* const str,
- RA::IntervalPtrs::const_iterator i,
- RA::IntervalPtrs::const_iterator e) const {
- if (str) std::cerr << str << " intervals:\n";
- for (; i != e; ++i) {
- std::cerr << "\t" << **i << " -> ";
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg)) {
- reg = vrm_->getPhys(reg);
- }
- std::cerr << mri_->getName(reg) << '\n';
- }
- }
- };
-}
-
-void RA::releaseMemory()
-{
- unhandled_.clear();
- fixed_.clear();
- active_.clear();
- inactive_.clear();
- handled_.clear();
- spilled_.clear();
-}
-
-bool RA::runOnMachineFunction(MachineFunction &fn) {
- mf_ = &fn;
- tm_ = &fn.getTarget();
- mri_ = tm_->getRegisterInfo();
- li_ = &getAnalysis<LiveIntervals>();
-
- PhysRegsUsed = new bool[mri_->getNumRegs()];
- std::fill(PhysRegsUsed, PhysRegsUsed+mri_->getNumRegs(), false);
- fn.setUsedPhysRegs(PhysRegsUsed);
-
- if (!prt_.get()) prt_.reset(new PhysRegTracker(*mri_));
- vrm_.reset(new VirtRegMap(*mf_));
- if (!spiller_.get()) spiller_.reset(createSpiller());
-
- initIntervalSets();
-
- numIntervals += li_->getNumIntervals();
-
- while (linearScan()) {
- // we spilled some registers, so we need to add intervals for
- // the spill code and restart the algorithm
- std::set<unsigned> spilledRegs;
- for (IntervalPtrs::iterator
- i = spilled_.begin(); i != spilled_.end(); ++i) {
- int slot = vrm_->assignVirt2StackSlot((*i)->reg);
- std::vector<LiveInterval*> added =
- li_->addIntervalsForSpills(**i, *vrm_, slot);
- std::copy(added.begin(), added.end(), std::back_inserter(handled_));
- spilledRegs.insert((*i)->reg);
- }
- spilled_.clear();
- for (IntervalPtrs::iterator
- i = handled_.begin(); i != handled_.end(); )
- if (spilledRegs.count((*i)->reg))
- i = handled_.erase(i);
- else
- ++i;
- handled_.swap(unhandled_);
- vrm_->clearAllVirt();
- }
-
- efficiency = double(numIterations) / double(numIntervals);
-
- DEBUG(std::cerr << *vrm_);
-
- spiller_->runOnMachineFunction(*mf_, *vrm_);
-
- return true;
-}
-
-bool RA::linearScan()
-{
- // linear scan algorithm
- DEBUG(std::cerr << "********** LINEAR SCAN **********\n");
- DEBUG(std::cerr << "********** Function: "
- << mf_->getFunction()->getName() << '\n');
-
-
- std::sort(unhandled_.begin(), unhandled_.end(),
- greater_ptr<LiveInterval>());
- DEBUG(printIntervals("unhandled", unhandled_.begin(), unhandled_.end()));
- DEBUG(printIntervals("fixed", fixed_.begin(), fixed_.end()));
- DEBUG(printIntervals("active", active_.begin(), active_.end()));
- DEBUG(printIntervals("inactive", inactive_.begin(), inactive_.end()));
-
- while (!unhandled_.empty()) {
- // pick the interval with the earliest start point
- IntervalPtrs::value_type cur = unhandled_.back();
- unhandled_.pop_back();
- ++numIterations;
- DEBUG(std::cerr << "\n*** CURRENT ***: " << *cur << '\n');
-
- processActiveIntervals(cur);
- processInactiveIntervals(cur);
-
- // if this register is fixed we are done
- if (MRegisterInfo::isPhysicalRegister(cur->reg)) {
- prt_->addRegUse(cur->reg);
- active_.push_back(cur);
- handled_.push_back(cur);
- }
- // otherwise we are allocating a virtual register. try to find
- // a free physical register or spill an interval in order to
- // assign it one (we could spill the current though).
- else {
- assignRegOrSpillAtInterval(cur);
- }
-
- DEBUG(printIntervals("active", active_.begin(), active_.end()));
- DEBUG(printIntervals("inactive", inactive_.begin(), inactive_.end()));
- }
-
- // expire any remaining active intervals
- for (IntervalPtrs::reverse_iterator
- i = active_.rbegin(); i != active_.rend(); ) {
- unsigned reg = (*i)->reg;
- DEBUG(std::cerr << "\tinterval " << **i << " expired\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->delRegUse(reg);
- i = IntervalPtrs::reverse_iterator(active_.erase(i.base()-1));
- }
-
- // expire any remaining inactive intervals
- for (IntervalPtrs::reverse_iterator
- i = inactive_.rbegin(); i != inactive_.rend(); ) {
- DEBUG(std::cerr << "\tinterval " << **i << " expired\n");
- i = IntervalPtrs::reverse_iterator(inactive_.erase(i.base()-1));
- }
-
- // return true if we spilled anything
- return !spilled_.empty();
-}
-
-void RA::initIntervalSets() {
- assert(unhandled_.empty() && fixed_.empty() &&
- active_.empty() && inactive_.empty() &&
- "interval sets should be empty on initialization");
-
- for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i){
- unhandled_.push_back(&i->second);
- if (MRegisterInfo::isPhysicalRegister(i->second.reg)) {
- PhysRegsUsed[i->second.reg] = true;
- fixed_.push_back(&i->second);
- }
- }
-}
-
-void RA::processActiveIntervals(IntervalPtrs::value_type cur)
-{
- DEBUG(std::cerr << "\tprocessing active intervals:\n");
- IntervalPtrs::iterator ii = active_.begin(), ie = active_.end();
- while (ii != ie) {
- LiveInterval* i = *ii;
- unsigned reg = i->reg;
-
- // remove expired intervals
- if (i->expiredAt(cur->beginNumber())) {
- DEBUG(std::cerr << "\t\tinterval " << *i << " expired\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->delRegUse(reg);
- // swap with last element and move end iterator back one position
- std::iter_swap(ii, --ie);
- }
- // move inactive intervals to inactive list
- else if (!i->liveAt(cur->beginNumber())) {
- DEBUG(std::cerr << "\t\tinterval " << *i << " inactive\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->delRegUse(reg);
- // add to inactive
- inactive_.push_back(i);
- // swap with last element and move end iterator back one postion
- std::iter_swap(ii, --ie);
- }
- else {
- ++ii;
- }
- }
- active_.erase(ie, active_.end());
-}
-
-void RA::processInactiveIntervals(IntervalPtrs::value_type cur)
-{
- DEBUG(std::cerr << "\tprocessing inactive intervals:\n");
- IntervalPtrs::iterator ii = inactive_.begin(), ie = inactive_.end();
- while (ii != ie) {
- LiveInterval* i = *ii;
- unsigned reg = i->reg;
-
- // remove expired intervals
- if (i->expiredAt(cur->beginNumber())) {
- DEBUG(std::cerr << "\t\tinterval " << *i << " expired\n");
- // swap with last element and move end iterator back one position
- std::iter_swap(ii, --ie);
- }
- // move re-activated intervals in active list
- else if (i->liveAt(cur->beginNumber())) {
- DEBUG(std::cerr << "\t\tinterval " << *i << " active\n");
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->addRegUse(reg);
- // add to active
- active_.push_back(i);
- // swap with last element and move end iterator back one position
- std::iter_swap(ii, --ie);
- }
- else {
- ++ii;
- }
- }
- inactive_.erase(ie, inactive_.end());
-}
-
-void RA::updateSpillWeights(unsigned reg, SpillWeights::value_type weight)
-{
- spillWeights_[reg] += weight;
- for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
- spillWeights_[*as] += weight;
-}
-
-void RA::assignRegOrSpillAtInterval(IntervalPtrs::value_type cur)
-{
- DEBUG(std::cerr << "\tallocating current interval: ");
-
- PhysRegTracker backupPrt = *prt_;
-
- spillWeights_.assign(mri_->getNumRegs(), 0.0);
-
- // for each interval in active update spill weights
- for (IntervalPtrs::const_iterator i = active_.begin(), e = active_.end();
- i != e; ++i) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- updateSpillWeights(reg, (*i)->weight);
- }
-
- // for every interval in inactive we overlap with, mark the
- // register as not free and update spill weights
- for (IntervalPtrs::const_iterator i = inactive_.begin(),
- e = inactive_.end(); i != e; ++i) {
- if (cur->overlaps(**i)) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- prt_->addRegUse(reg);
- updateSpillWeights(reg, (*i)->weight);
- }
- }
-
- // for every interval in fixed we overlap with,
- // mark the register as not free and update spill weights
- for (IntervalPtrs::const_iterator i = fixed_.begin(),
- e = fixed_.end(); i != e; ++i) {
- if (cur->overlaps(**i)) {
- unsigned reg = (*i)->reg;
- prt_->addRegUse(reg);
- updateSpillWeights(reg, (*i)->weight);
- }
- }
-
- unsigned physReg = getFreePhysReg(cur);
- // restore the physical register tracker
- *prt_ = backupPrt;
- // if we find a free register, we are done: assign this virtual to
- // the free physical register and add this interval to the active
- // list.
- if (physReg) {
- DEBUG(std::cerr << mri_->getName(physReg) << '\n');
- vrm_->assignVirt2Phys(cur->reg, physReg);
- prt_->addRegUse(physReg);
- active_.push_back(cur);
- handled_.push_back(cur);
- return;
- }
- DEBUG(std::cerr << "no free registers\n");
-
- DEBUG(std::cerr << "\tassigning stack slot at interval "<< *cur << ":\n");
-
- float minWeight = (float)HUGE_VAL;
- unsigned minReg = 0;
- const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
- for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_),
- e = rc->allocation_order_end(*mf_); i != e; ++i) {
- unsigned reg = *i;
- if (minWeight > spillWeights_[reg]) {
- minWeight = spillWeights_[reg];
- minReg = reg;
- }
- }
- DEBUG(std::cerr << "\t\tregister with min weight: "
- << mri_->getName(minReg) << " (" << minWeight << ")\n");
-
- // if the current has the minimum weight, we spill it and move on
- if (cur->weight <= minWeight) {
- DEBUG(std::cerr << "\t\t\tspilling(c): " << *cur << '\n');
- spilled_.push_back(cur);
- return;
- }
-
- // otherwise we spill all intervals aliasing the register with
- // minimum weight, assigned the newly cleared register to the
- // current interval and continue
- assert(MRegisterInfo::isPhysicalRegister(minReg) &&
- "did not choose a register to spill?");
- std::vector<bool> toSpill(mri_->getNumRegs(), false);
- toSpill[minReg] = true;
- for (const unsigned* as = mri_->getAliasSet(minReg); *as; ++as)
- toSpill[*as] = true;
- unsigned earliestStart = cur->beginNumber();
-
- std::set<unsigned> spilled;
-
- for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
- toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(**i)) {
- DEBUG(std::cerr << "\t\t\tspilling(a): " << **i << '\n');
- spilled_.push_back(*i);
- prt_->delRegUse(vrm_->getPhys(reg));
- vrm_->clearVirt(reg);
- i = active_.erase(i);
- }
- else
- ++i;
- }
- for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
- toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(**i)) {
- DEBUG(std::cerr << "\t\t\tspilling(i): " << **i << '\n');
- spilled_.push_back(*i);
- vrm_->clearVirt(reg);
- i = inactive_.erase(i);
- }
- else
- ++i;
- }
-
- vrm_->assignVirt2Phys(cur->reg, minReg);
- prt_->addRegUse(minReg);
- active_.push_back(cur);
- handled_.push_back(cur);
-
-}
-
-unsigned RA::getFreePhysReg(LiveInterval* cur)
-{
- std::vector<unsigned> inactiveCounts(mri_->getNumRegs(), 0);
- for (IntervalPtrs::iterator i = inactive_.begin(), e = inactive_.end();
- i != e; ++i) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg))
- reg = vrm_->getPhys(reg);
- ++inactiveCounts[reg];
- }
-
- const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
-
- unsigned freeReg = 0;
- for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_),
- e = rc->allocation_order_end(*mf_); i != e; ++i) {
- unsigned reg = *i;
- if (prt_->isRegAvail(reg) &&
- (!freeReg || inactiveCounts[freeReg] < inactiveCounts[reg]))
- freeReg = reg;
- }
- return freeReg;
-}
-
-FunctionPass* llvm::createIterativeScanRegisterAllocator() {
- return new RA();
-}
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