--- /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 a linear scan register allocator.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "regalloc"
+#include "llvm/Function.h"
+#include "llvm/CodeGen/LiveVariables.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 "Support/Debug.h"
+#include "Support/Statistic.h"
+#include "Support/STLExtras.h"
+#include "LiveIntervals.h"
+#include "PhysRegTracker.h"
+#include "VirtRegMap.h"
+#include <algorithm>
+#include <cmath>
+#include <iostream>
+#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_;
+ typedef std::list<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 "Linear Scan Register Allocator";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LiveVariables>();
+ 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(LiveIntervals::Intervals& li);
+
+ /// 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>();
+ if (!prt_.get()) prt_.reset(new PhysRegTracker(*mri_));
+ vrm_.reset(new VirtRegMap(*mf_));
+ if (!spiller_.get()) spiller_.reset(createSpiller());
+
+ initIntervalSets(li_->getIntervals());
+
+ numIntervals += li_->getIntervals().size();
+
+ 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(); ) {
+ 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);
+ i = spilled_.erase(i);
+ }
+ 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');
+
+
+ unhandled_.sort(less_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_.front();
+ unhandled_.pop_front();
+ ++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::iterator i = active_.begin(); i != active_.end(); ) {
+ unsigned reg = (*i)->reg;
+ DEBUG(std::cerr << "\tinterval " << **i << " expired\n");
+ if (MRegisterInfo::isVirtualRegister(reg))
+ reg = vrm_->getPhys(reg);
+ prt_->delRegUse(reg);
+ i = active_.erase(i);
+ }
+
+ // expire any remaining inactive intervals
+ for (IntervalPtrs::iterator
+ i = inactive_.begin(); i != inactive_.end(); ) {
+ DEBUG(std::cerr << "\tinterval " << **i << " expired\n");
+ i = inactive_.erase(i);
+ }
+
+ // return true if we spilled anything
+ return !spilled_.empty();
+}
+
+void RA::initIntervalSets(LiveIntervals::Intervals& li)
+{
+ assert(unhandled_.empty() && fixed_.empty() &&
+ active_.empty() && inactive_.empty() &&
+ "interval sets should be empty on initialization");
+
+ for (LiveIntervals::Intervals::iterator i = li.begin(), e = li.end();
+ i != e; ++i) {
+ unhandled_.push_back(&*i);
+ if (MRegisterInfo::isPhysicalRegister(i->reg))
+ fixed_.push_back(&*i);
+ }
+}
+
+void RA::processActiveIntervals(IntervalPtrs::value_type cur)
+{
+ DEBUG(std::cerr << "\tprocessing active intervals:\n");
+ for (IntervalPtrs::iterator i = active_.begin(); i != active_.end();) {
+ unsigned reg = (*i)->reg;
+ // remove expired intervals
+ if ((*i)->expiredAt(cur->start())) {
+ DEBUG(std::cerr << "\t\tinterval " << **i << " expired\n");
+ if (MRegisterInfo::isVirtualRegister(reg))
+ reg = vrm_->getPhys(reg);
+ prt_->delRegUse(reg);
+ // remove from active
+ i = active_.erase(i);
+ }
+ // move inactive intervals to inactive list
+ else if (!(*i)->liveAt(cur->start())) {
+ 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);
+ // remove from active
+ i = active_.erase(i);
+ }
+ else {
+ ++i;
+ }
+ }
+}
+
+void RA::processInactiveIntervals(IntervalPtrs::value_type cur)
+{
+ DEBUG(std::cerr << "\tprocessing inactive intervals:\n");
+ for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end();) {
+ unsigned reg = (*i)->reg;
+
+ // remove expired intervals
+ if ((*i)->expiredAt(cur->start())) {
+ DEBUG(std::cerr << "\t\tinterval " << **i << " expired\n");
+ // remove from inactive
+ i = inactive_.erase(i);
+ }
+ // move re-activated intervals in active list
+ else if ((*i)->liveAt(cur->start())) {
+ 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);
+ // remove from inactive
+ i = inactive_.erase(i);
+ }
+ else {
+ ++i;
+ }
+ }
+}
+
+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 = HUGE_VAL;
+ unsigned minReg = 0;
+ const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
+ for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
+ i != rc->allocation_order_end(*mf_); ++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
+ std::vector<LiveInterval*> added;
+ 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->start();
+
+ 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(IntervalPtrs::value_type cur)
+{
+ const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
+
+ for (TargetRegisterClass::iterator i = rc->allocation_order_begin(*mf_);
+ i != rc->allocation_order_end(*mf_); ++i) {
+ unsigned reg = *i;
+ if (prt_->isRegAvail(reg))
+ return reg;
+ }
+ return 0;
+}
+
+FunctionPass* llvm::createIterativeScanRegisterAllocator() {
+ return new RA();
+}
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