//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "PhysRegTracker.h"
+#include "VirtRegMap.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/RegAllocRegistry.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 "LiveIntervalAnalysis.h"
-#include "PhysRegTracker.h"
-#include "VirtRegMap.h"
+#include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Compiler.h"
#include <algorithm>
-#include <cmath>
#include <set>
#include <queue>
-
+#include <memory>
+#include <cmath>
using namespace llvm;
-namespace {
+STATISTIC(NumIters , "Number of iterations performed");
+STATISTIC(NumBacktracks, "Number of times we had to backtrack");
- Statistic<double> efficiency
- ("regalloc", "Ratio of intervals processed over total intervals");
+static RegisterRegAlloc
+linearscanRegAlloc("linearscan", " linear scan register allocator",
+ createLinearScanRegisterAllocator);
+namespace {
static unsigned numIterations = 0;
static unsigned numIntervals = 0;
- class RA : public MachineFunctionPass {
+ struct VISIBILITY_HIDDEN RA : public MachineFunctionPass {
+ typedef std::pair<LiveInterval*, LiveInterval::iterator> IntervalPtr;
+ typedef std::vector<IntervalPtr> IntervalPtrs;
private:
+ /// RelatedRegClasses - This structure is built the first time a function is
+ /// compiled, and keeps track of which register classes have registers that
+ /// belong to multiple classes or have aliases that are in other classes.
+ EquivalenceClasses<const TargetRegisterClass*> RelatedRegClasses;
+ std::map<unsigned, const TargetRegisterClass*> OneClassForEachPhysReg;
+
MachineFunction* mf_;
const TargetMachine* tm_;
const MRegisterInfo* mri_;
LiveIntervals* li_;
- typedef std::vector<LiveInterval*> IntervalPtrs;
- IntervalPtrs handled_, fixed_, active_, inactive_;
+
+ /// handled_ - Intervals are added to the handled_ set in the order of their
+ /// start value. This is uses for backtracking.
+ std::vector<LiveInterval*> handled_;
+
+ /// fixed_ - Intervals that correspond to machine registers.
+ ///
+ IntervalPtrs fixed_;
+
+ /// active_ - Intervals that are currently being processed, and which have a
+ /// live range active for the current point.
+ IntervalPtrs active_;
+
+ /// inactive_ - Intervals that are currently being processed, but which have
+ /// a hold at the current point.
+ IntervalPtrs inactive_;
+
typedef std::priority_queue<LiveInterval*,
- IntervalPtrs,
+ std::vector<LiveInterval*>,
greater_ptr<LiveInterval> > IntervalHeap;
IntervalHeap unhandled_;
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";
/// runOnMachineFunction - register allocate the whole function
bool runOnMachineFunction(MachineFunction&);
- void releaseMemory();
-
private:
/// linearScan - the linear scan algorithm
void linearScan();
- /// initIntervalSets - initializa the four interval sets:
- /// unhandled, fixed, active and inactive
+ /// initIntervalSets - initialize the interval sets.
+ ///
void initIntervalSets();
- /// processActiveIntervals - expire old intervals and move
- /// non-overlapping ones to the incative list
- void processActiveIntervals(LiveInterval* cur);
-
- /// processInactiveIntervals - expire old intervals and move
- /// overlapping ones to the active list
- void processInactiveIntervals(LiveInterval* cur);
+ /// processActiveIntervals - expire old intervals and move non-overlapping
+ /// ones to the inactive list.
+ void processActiveIntervals(unsigned CurPoint);
- /// updateSpillWeights - updates the spill weights of the
- /// specifed physical register and its weight
- void updateSpillWeights(unsigned reg, SpillWeights::value_type weight);
+ /// processInactiveIntervals - expire old intervals and move overlapping
+ /// ones to the active list.
+ void processInactiveIntervals(unsigned CurPoint);
/// assignRegOrStackSlotAtInterval - assign a register if one
/// is available, or spill.
/// register handling helpers
///
- /// getFreePhysReg - return a free physical register for this
- /// virtual register interval if we have one, otherwise return
- /// 0
+ /// getFreePhysReg - return a free physical register for this virtual
+ /// register interval if we have one, otherwise return 0.
unsigned getFreePhysReg(LiveInterval* cur);
/// assignVirt2StackSlot - assigns this virtual register to a
/// stack slot. returns the stack slot
int assignVirt2StackSlot(unsigned virtReg);
+ void ComputeRelatedRegClasses();
+
template <typename ItTy>
void printIntervals(const char* const str, ItTy i, ItTy e) const {
- if (str) std::cerr << str << " intervals:\n";
+ if (str) DOUT << str << " intervals:\n";
for (; i != e; ++i) {
- std::cerr << "\t" << **i << " -> ";
- unsigned reg = (*i)->reg;
+ DOUT << "\t" << *i->first << " -> ";
+ unsigned reg = i->first->reg;
if (MRegisterInfo::isVirtualRegister(reg)) {
reg = vrm_->getPhys(reg);
}
- std::cerr << mri_->getName(reg) << '\n';
+ DOUT << mri_->getName(reg) << '\n';
}
}
};
}
-void RA::releaseMemory()
-{
- while (!unhandled_.empty()) unhandled_.pop();
- fixed_.clear();
- active_.clear();
- inactive_.clear();
- handled_.clear();
+void RA::ComputeRelatedRegClasses() {
+ const MRegisterInfo &MRI = *mri_;
+
+ // First pass, add all reg classes to the union, and determine at least one
+ // reg class that each register is in.
+ bool HasAliases = false;
+ for (MRegisterInfo::regclass_iterator RCI = MRI.regclass_begin(),
+ E = MRI.regclass_end(); RCI != E; ++RCI) {
+ RelatedRegClasses.insert(*RCI);
+ for (TargetRegisterClass::iterator I = (*RCI)->begin(), E = (*RCI)->end();
+ I != E; ++I) {
+ HasAliases = HasAliases || *MRI.getAliasSet(*I) != 0;
+
+ const TargetRegisterClass *&PRC = OneClassForEachPhysReg[*I];
+ if (PRC) {
+ // Already processed this register. Just make sure we know that
+ // multiple register classes share a register.
+ RelatedRegClasses.unionSets(PRC, *RCI);
+ } else {
+ PRC = *RCI;
+ }
+ }
+ }
+
+ // Second pass, now that we know conservatively what register classes each reg
+ // belongs to, add info about aliases. We don't need to do this for targets
+ // without register aliases.
+ if (HasAliases)
+ for (std::map<unsigned, const TargetRegisterClass*>::iterator
+ I = OneClassForEachPhysReg.begin(), E = OneClassForEachPhysReg.end();
+ I != E; ++I)
+ for (const unsigned *AS = MRI.getAliasSet(I->first); *AS; ++AS)
+ RelatedRegClasses.unionSets(I->second, OneClassForEachPhysReg[*AS]);
}
bool RA::runOnMachineFunction(MachineFunction &fn) {
tm_ = &fn.getTarget();
mri_ = tm_->getRegisterInfo();
li_ = &getAnalysis<LiveIntervals>();
+
+ // If this is the first function compiled, compute the related reg classes.
+ if (RelatedRegClasses.empty())
+ ComputeRelatedRegClasses();
+
if (!prt_.get()) prt_.reset(new PhysRegTracker(*mri_));
vrm_.reset(new VirtRegMap(*mf_));
if (!spiller_.get()) spiller_.reset(createSpiller());
linearScan();
+ // Rewrite spill code and update the PhysRegsUsed set.
spiller_->runOnMachineFunction(*mf_, *vrm_);
+ vrm_.reset(); // Free the VirtRegMap
+
+
+ while (!unhandled_.empty()) unhandled_.pop();
+ fixed_.clear();
+ active_.clear();
+ inactive_.clear();
+ handled_.clear();
+
return true;
}
+/// initIntervalSets - initialize the interval sets.
+///
+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) {
+ if (MRegisterInfo::isPhysicalRegister(i->second.reg)) {
+ mf_->setPhysRegUsed(i->second.reg);
+ fixed_.push_back(std::make_pair(&i->second, i->second.begin()));
+ } else
+ unhandled_.push(&i->second);
+ }
+}
+
void RA::linearScan()
{
// linear scan algorithm
- DEBUG(std::cerr << "********** LINEAR SCAN **********\n");
- DEBUG(std::cerr << "********** Function: "
- << mf_->getFunction()->getName() << '\n');
+ DOUT << "********** LINEAR SCAN **********\n";
+ DOUT << "********** Function: " << mf_->getFunction()->getName() << '\n';
// DEBUG(printIntervals("unhandled", unhandled_.begin(), unhandled_.end()));
DEBUG(printIntervals("fixed", fixed_.begin(), fixed_.end()));
LiveInterval* cur = unhandled_.top();
unhandled_.pop();
++numIterations;
- DEBUG(std::cerr << "\n*** CURRENT ***: " << *cur << '\n');
+ DOUT << "\n*** CURRENT ***: " << *cur << '\n';
- processActiveIntervals(cur);
- processInactiveIntervals(cur);
+ processActiveIntervals(cur->beginNumber());
+ processInactiveIntervals(cur->beginNumber());
- // 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 {
- assignRegOrStackSlotAtInterval(cur);
- }
+ assert(MRegisterInfo::isVirtualRegister(cur->reg) &&
+ "Can only allocate virtual registers!");
+
+ // Allocating a virtual register. try to find a free
+ // physical register or spill an interval (possibly this one) in order to
+ // assign it one.
+ assignRegOrStackSlotAtInterval(cur);
DEBUG(printIntervals("active", active_.begin(), active_.end()));
DEBUG(printIntervals("inactive", inactive_.begin(), inactive_.end()));
}
numIntervals += li_->getNumIntervals();
- efficiency = double(numIterations) / double(numIntervals);
+ NumIters += numIterations;
// 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);
+ unsigned reg = i->first->reg;
+ DOUT << "\tinterval " << *i->first << " expired\n";
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ 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");
+ DOUT << "\tinterval " << *i->first << " expired\n";
i = IntervalPtrs::reverse_iterator(inactive_.erase(i.base()-1));
}
- DEBUG(std::cerr << *vrm_);
+ // A brute force way of adding live-ins to every BB.
+ MachineFunction::iterator MBB = mf_->begin();
+ ++MBB; // Skip entry MBB.
+ for (MachineFunction::iterator E = mf_->end(); MBB != E; ++MBB) {
+ unsigned StartIdx = li_->getMBBStartIdx(MBB->getNumber());
+ for (IntervalPtrs::iterator i = fixed_.begin(), e = fixed_.end();
+ i != e; ++i)
+ if (i->first->liveAt(StartIdx))
+ MBB->addLiveIn(i->first->reg);
+
+ for (unsigned i = 0, e = handled_.size(); i != e; ++i) {
+ LiveInterval *HI = handled_[i];
+ unsigned Reg = HI->reg;
+ if (!vrm_->hasStackSlot(Reg) && HI->liveAt(StartIdx)) {
+ assert(MRegisterInfo::isVirtualRegister(Reg));
+ Reg = vrm_->getPhys(Reg);
+ MBB->addLiveIn(Reg);
+ }
+ }
+ }
+
+ DOUT << *vrm_;
}
-void RA::initIntervalSets()
+/// processActiveIntervals - expire old intervals and move non-overlapping ones
+/// to the inactive list.
+void RA::processActiveIntervals(unsigned CurPoint)
{
- assert(unhandled_.empty() && fixed_.empty() &&
- active_.empty() && inactive_.empty() &&
- "interval sets should be empty on initialization");
+ DOUT << "\tprocessing active intervals:\n";
- for (LiveIntervals::iterator i = li_->begin(), e = li_->end(); i != e; ++i){
- unhandled_.push(&i->second);
- if (MRegisterInfo::isPhysicalRegister(i->second.reg))
- fixed_.push_back(&i->second);
- }
-}
+ for (unsigned i = 0, e = active_.size(); i != e; ++i) {
+ LiveInterval *Interval = active_[i].first;
+ LiveInterval::iterator IntervalPos = active_[i].second;
+ unsigned reg = Interval->reg;
-void RA::processActiveIntervals(IntervalPtrs::value_type cur)
-{
- DEBUG(std::cerr << "\tprocessing active intervals:\n");
- for (IntervalPtrs::reverse_iterator
- i = active_.rbegin(); i != active_.rend();) {
- 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);
+ IntervalPos = Interval->advanceTo(IntervalPos, CurPoint);
+
+ if (IntervalPos == Interval->end()) { // Remove expired intervals.
+ DOUT << "\t\tinterval " << *Interval << " expired\n";
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->delRegUse(reg);
- // remove from active
- i = IntervalPtrs::reverse_iterator(active_.erase(i.base()-1));
- }
- // 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);
+
+ // Pop off the end of the list.
+ active_[i] = active_.back();
+ active_.pop_back();
+ --i; --e;
+
+ } else if (IntervalPos->start > CurPoint) {
+ // Move inactive intervals to inactive list.
+ DOUT << "\t\tinterval " << *Interval << " inactive\n";
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->delRegUse(reg);
- // add to inactive
- inactive_.push_back(*i);
- // remove from active
- i = IntervalPtrs::reverse_iterator(active_.erase(i.base()-1));
- }
- else {
- ++i;
+ // add to inactive.
+ inactive_.push_back(std::make_pair(Interval, IntervalPos));
+
+ // Pop off the end of the list.
+ active_[i] = active_.back();
+ active_.pop_back();
+ --i; --e;
+ } else {
+ // Otherwise, just update the iterator position.
+ active_[i].second = IntervalPos;
}
}
}
-void RA::processInactiveIntervals(IntervalPtrs::value_type cur)
+/// processInactiveIntervals - expire old intervals and move overlapping
+/// ones to the active list.
+void RA::processInactiveIntervals(unsigned CurPoint)
{
- DEBUG(std::cerr << "\tprocessing inactive intervals:\n");
- for (IntervalPtrs::reverse_iterator
- i = inactive_.rbegin(); i != inactive_.rend();) {
- unsigned reg = (*i)->reg;
-
- // remove expired intervals
- if ((*i)->expiredAt(cur->start())) {
- DEBUG(std::cerr << "\t\tinterval " << **i << " expired\n");
- // remove from inactive
- i = IntervalPtrs::reverse_iterator(inactive_.erase(i.base()-1));
- }
- // 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);
+ DOUT << "\tprocessing inactive intervals:\n";
+
+ for (unsigned i = 0, e = inactive_.size(); i != e; ++i) {
+ LiveInterval *Interval = inactive_[i].first;
+ LiveInterval::iterator IntervalPos = inactive_[i].second;
+ unsigned reg = Interval->reg;
+
+ IntervalPos = Interval->advanceTo(IntervalPos, CurPoint);
+
+ if (IntervalPos == Interval->end()) { // remove expired intervals.
+ DOUT << "\t\tinterval " << *Interval << " expired\n";
+
+ // Pop off the end of the list.
+ inactive_[i] = inactive_.back();
+ inactive_.pop_back();
+ --i; --e;
+ } else if (IntervalPos->start <= CurPoint) {
+ // move re-activated intervals in active list
+ DOUT << "\t\tinterval " << *Interval << " active\n";
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
prt_->addRegUse(reg);
// add to active
- active_.push_back(*i);
- // remove from inactive
- i = IntervalPtrs::reverse_iterator(inactive_.erase(i.base()-1));
- }
- else {
- ++i;
+ active_.push_back(std::make_pair(Interval, IntervalPos));
+
+ // Pop off the end of the list.
+ inactive_[i] = inactive_.back();
+ inactive_.pop_back();
+ --i; --e;
+ } else {
+ // Otherwise, just update the iterator position.
+ inactive_[i].second = IntervalPos;
}
}
}
-void RA::updateSpillWeights(unsigned reg, SpillWeights::value_type weight)
-{
- spillWeights_[reg] += weight;
- for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as)
- spillWeights_[*as] += weight;
+/// updateSpillWeights - updates the spill weights of the specifed physical
+/// register and its weight.
+static void updateSpillWeights(std::vector<float> &Weights,
+ unsigned reg, float weight,
+ const MRegisterInfo *MRI) {
+ Weights[reg] += weight;
+ for (const unsigned* as = MRI->getAliasSet(reg); *as; ++as)
+ Weights[*as] += weight;
+}
+
+static RA::IntervalPtrs::iterator FindIntervalInVector(RA::IntervalPtrs &IP,
+ LiveInterval *LI) {
+ for (RA::IntervalPtrs::iterator I = IP.begin(), E = IP.end(); I != E; ++I)
+ if (I->first == LI) return I;
+ return IP.end();
}
+static void RevertVectorIteratorsTo(RA::IntervalPtrs &V, unsigned Point) {
+ for (unsigned i = 0, e = V.size(); i != e; ++i) {
+ RA::IntervalPtr &IP = V[i];
+ LiveInterval::iterator I = std::upper_bound(IP.first->begin(),
+ IP.second, Point);
+ if (I != IP.first->begin()) --I;
+ IP.second = I;
+ }
+}
+
+/// assignRegOrStackSlotAtInterval - assign a register if one is available, or
+/// spill.
void RA::assignRegOrStackSlotAtInterval(LiveInterval* cur)
{
- DEBUG(std::cerr << "\tallocating current interval: ");
+ DOUT << "\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);
- }
-
+ std::vector<std::pair<unsigned, float> > SpillWeightsToAdd;
+ unsigned StartPosition = cur->beginNumber();
+ const TargetRegisterClass *RC = mf_->getSSARegMap()->getRegClass(cur->reg);
+ const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
+
// for every interval in inactive we overlap with, mark the
- // register as not free and update spill weights
+ // 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);
+ unsigned Reg = i->first->reg;
+ assert(MRegisterInfo::isVirtualRegister(Reg) &&
+ "Can only allocate virtual registers!");
+ const TargetRegisterClass *RegRC = mf_->getSSARegMap()->getRegClass(Reg);
+ // If this is not in a related reg class to the register we're allocating,
+ // don't check it.
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader &&
+ cur->overlapsFrom(*i->first, i->second-1)) {
+ Reg = vrm_->getPhys(Reg);
+ prt_->addRegUse(Reg);
+ SpillWeightsToAdd.push_back(std::make_pair(Reg, i->first->weight));
}
}
+
+ // Speculatively check to see if we can get a register right now. If not,
+ // we know we won't be able to by adding more constraints. If so, we can
+ // check to see if it is valid. Doing an exhaustive search of the fixed_ list
+ // is very bad (it contains all callee clobbered registers for any functions
+ // with a call), so we want to avoid doing that if possible.
+ unsigned physReg = getFreePhysReg(cur);
+ if (physReg) {
+ // We got a register. However, if it's in the fixed_ list, we might
+ // conflict with it. Check to see if we conflict with it or any of its
+ // aliases.
+ std::set<unsigned> RegAliases;
+ for (const unsigned *AS = mri_->getAliasSet(physReg); *AS; ++AS)
+ RegAliases.insert(*AS);
+
+ bool ConflictsWithFixed = false;
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ if (physReg == IP.first->reg || RegAliases.count(IP.first->reg)) {
+ // Okay, this reg is on the fixed list. Check to see if we actually
+ // conflict.
+ LiveInterval *I = IP.first;
+ if (I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ ConflictsWithFixed = true;
+ break;
+ }
+ }
+ }
+ }
+
+ // Okay, the register picked by our speculative getFreePhysReg call turned
+ // out to be in use. Actually add all of the conflicting fixed registers to
+ // prt so we can do an accurate query.
+ if (ConflictsWithFixed) {
+ // For every interval in fixed we overlap with, mark the register as not
+ // free and update spill weights.
+ for (unsigned i = 0, e = fixed_.size(); i != e; ++i) {
+ IntervalPtr &IP = fixed_[i];
+ LiveInterval *I = IP.first;
+
+ const TargetRegisterClass *RegRC = OneClassForEachPhysReg[I->reg];
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader &&
+ I->endNumber() > StartPosition) {
+ LiveInterval::iterator II = I->advanceTo(IP.second, StartPosition);
+ IP.second = II;
+ if (II != I->begin() && II->start > StartPosition)
+ --II;
+ if (cur->overlapsFrom(*I, II)) {
+ unsigned reg = I->reg;
+ prt_->addRegUse(reg);
+ SpillWeightsToAdd.push_back(std::make_pair(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);
+ // Using the newly updated prt_ object, which includes conflicts in the
+ // future, see if there are any registers available.
+ physReg = getFreePhysReg(cur);
}
}
-
- unsigned physReg = getFreePhysReg(cur);
- // restore the physical register tracker
+
+ // Restore the physical register tracker, removing information about the
+ // future.
*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');
+ DOUT << mri_->getName(physReg) << '\n';
vrm_->assignVirt2Phys(cur->reg, physReg);
prt_->addRegUse(physReg);
- active_.push_back(cur);
+ active_.push_back(std::make_pair(cur, cur->begin()));
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;
+ DOUT << "no free registers\n";
+
+ // Compile the spill weights into an array that is better for scanning.
+ std::vector<float> SpillWeights(mri_->getNumRegs(), 0.0);
+ for (std::vector<std::pair<unsigned, float> >::iterator
+ I = SpillWeightsToAdd.begin(), E = SpillWeightsToAdd.end(); I != E; ++I)
+ updateSpillWeights(SpillWeights, I->first, I->second, mri_);
+
+ // for each interval in active, update spill weights.
+ for (IntervalPtrs::const_iterator i = active_.begin(), e = active_.end();
+ i != e; ++i) {
+ unsigned reg = i->first->reg;
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+ reg = vrm_->getPhys(reg);
+ updateSpillWeights(SpillWeights, reg, i->first->weight, mri_);
+ }
+
+ DOUT << "\tassigning stack slot at interval "<< *cur << ":\n";
+
+ // Find a register to spill.
+ float minWeight = HUGE_VALF;
+ unsigned minReg = cur->preference; // Try the preferred register first.
+
+ if (!minReg || SpillWeights[minReg] == HUGE_VALF)
+ 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;
+ }
+ }
+
+ // If we didn't find a register that is spillable, try aliases?
+ if (!minReg) {
+ for (TargetRegisterClass::iterator i = RC->allocation_order_begin(*mf_),
+ e = RC->allocation_order_end(*mf_); i != e; ++i) {
+ unsigned reg = *i;
+ // No need to worry about if the alias register size < regsize of RC.
+ // We are going to spill all registers that alias it anyway.
+ for (const unsigned* as = mri_->getAliasSet(reg); *as; ++as) {
+ if (minWeight > SpillWeights[*as]) {
+ minWeight = SpillWeights[*as];
+ minReg = *as;
+ }
+ }
}
+
+ // All registers must have inf weight. Just grab one!
+ if (!minReg)
+ minReg = *RC->allocation_order_begin(*mf_);
}
- DEBUG(std::cerr << "\t\tregister with min weight: "
- << mri_->getName(minReg) << " (" << minWeight << ")\n");
+
+ DOUT << "\t\tregister with min weight: "
+ << mri_->getName(minReg) << " (" << minWeight << ")\n";
// if the current has the minimum weight, we need to spill it and
// add any added intervals back to unhandled, and restart
// linearscan.
- if (cur->weight <= minWeight) {
- DEBUG(std::cerr << "\t\t\tspilling(c): " << *cur << '\n';);
- int slot = vrm_->assignVirt2StackSlot(cur->reg);
+ if (cur->weight != HUGE_VALF && cur->weight <= minWeight) {
+ DOUT << "\t\t\tspilling(c): " << *cur << '\n';
+ // if the current interval is re-materializable, remember so and don't
+ // assign it a spill slot.
+ if (cur->remat)
+ vrm_->setVirtIsReMaterialized(cur->reg, cur->remat);
+ int slot = cur->remat ? vrm_->assignVirtReMatId(cur->reg)
+ : vrm_->assignVirt2StackSlot(cur->reg);
std::vector<LiveInterval*> added =
li_->addIntervalsForSpills(*cur, *vrm_, slot);
if (added.empty())
return;
}
+ ++NumBacktracks;
+
// push the current interval back to unhandled since we are going
// to re-run at least this iteration. Since we didn't modify it it
// should go back right in the front of the list
std::vector<LiveInterval*> added;
assert(MRegisterInfo::isPhysicalRegister(minReg) &&
"did not choose a register to spill?");
- std::vector<bool> toSpill(mri_->getNumRegs(), false);
- // we are going to spill minReg and all its aliases
+ BitVector toSpill(mri_->getNumRegs());
+
+ // We are going to spill minReg and all its aliases.
toSpill[minReg] = true;
for (const unsigned* as = mri_->getAliasSet(minReg); *as; ++as)
toSpill[*as] = true;
// the earliest start of a spilled interval indicates up to where
// in handled we need to roll back
- unsigned earliestStart = cur->start();
+ unsigned earliestStart = cur->beginNumber();
// set of spilled vregs (used later to rollback properly)
std::set<unsigned> spilled;
- // spill live intervals of virtual regs mapped to the physical
- // register we want to clear (and its aliases). we only spill
- // those that overlap with the current interval as the rest do not
- // affect its allocation. we also keep track of the earliest start
- // of all spilled live intervals since this will mark our rollback
- // point
- for (IntervalPtrs::iterator
- i = active_.begin(); i != active_.end(); ++i) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
+ // spill live intervals of virtual regs mapped to the physical register we
+ // want to clear (and its aliases). We only spill those that overlap with the
+ // current interval as the rest do not affect its allocation. we also keep
+ // track of the earliest start of all spilled live intervals since this will
+ // mark our rollback point.
+ for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) {
+ unsigned reg = i->first->reg;
+ if (//MRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(**i)) {
- DEBUG(std::cerr << "\t\t\tspilling(a): " << **i << '\n');
- earliestStart = std::min(earliestStart, (*i)->start());
- int slot = vrm_->assignVirt2StackSlot((*i)->reg);
+ cur->overlapsFrom(*i->first, i->second)) {
+ DOUT << "\t\t\tspilling(a): " << *i->first << '\n';
+ earliestStart = std::min(earliestStart, i->first->beginNumber());
+ if (i->first->remat)
+ vrm_->setVirtIsReMaterialized(reg, i->first->remat);
+ int slot = i->first->remat ? vrm_->assignVirtReMatId(reg)
+ : vrm_->assignVirt2StackSlot(reg);
std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(**i, *vrm_, slot);
+ li_->addIntervalsForSpills(*i->first, *vrm_, slot);
std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
spilled.insert(reg);
}
}
- for (IntervalPtrs::iterator
- i = inactive_.begin(); i != inactive_.end(); ++i) {
- unsigned reg = (*i)->reg;
- if (MRegisterInfo::isVirtualRegister(reg) &&
+ for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ++i){
+ unsigned reg = i->first->reg;
+ if (//MRegisterInfo::isVirtualRegister(reg) &&
toSpill[vrm_->getPhys(reg)] &&
- cur->overlaps(**i)) {
- DEBUG(std::cerr << "\t\t\tspilling(i): " << **i << '\n');
- earliestStart = std::min(earliestStart, (*i)->start());
- int slot = vrm_->assignVirt2StackSlot((*i)->reg);
+ cur->overlapsFrom(*i->first, i->second-1)) {
+ DOUT << "\t\t\tspilling(i): " << *i->first << '\n';
+ earliestStart = std::min(earliestStart, i->first->beginNumber());
+ if (i->first->remat)
+ vrm_->setVirtIsReMaterialized(reg, i->first->remat);
+ int slot = i->first->remat ? vrm_->assignVirtReMatId(reg)
+ : vrm_->assignVirt2StackSlot(reg);
std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(**i, *vrm_, slot);
+ li_->addIntervalsForSpills(*i->first, *vrm_, slot);
std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
spilled.insert(reg);
}
}
- DEBUG(std::cerr << "\t\trolling back to: " << earliestStart << '\n');
- // scan handled in reverse order up to the earliaset start of a
+ DOUT << "\t\trolling back to: " << earliestStart << '\n';
+
+ // Scan handled in reverse order up to the earliest start of a
// spilled live interval and undo each one, restoring the state of
- // unhandled
+ // unhandled.
while (!handled_.empty()) {
LiveInterval* i = handled_.back();
- // if this interval starts before t we are done
- if (i->start() < earliestStart)
+ // If this interval starts before t we are done.
+ if (i->beginNumber() < earliestStart)
break;
- DEBUG(std::cerr << "\t\t\tundo changes for: " << *i << '\n');
+ DOUT << "\t\t\tundo changes for: " << *i << '\n';
handled_.pop_back();
- // when undoing a live interval allocation we must know if it
- // is active or inactive to properly update the PhysRegTracker
- // and the VirtRegMap
+
+ // When undoing a live interval allocation we must know if it is active or
+ // inactive to properly update the PhysRegTracker and the VirtRegMap.
IntervalPtrs::iterator it;
- if ((it = find(active_.begin(), active_.end(), i)) != active_.end()) {
+ if ((it = FindIntervalInVector(active_, i)) != active_.end()) {
active_.erase(it);
- if (MRegisterInfo::isPhysicalRegister(i->reg)) {
- prt_->delRegUse(i->reg);
+ assert(!MRegisterInfo::isPhysicalRegister(i->reg));
+ if (!spilled.count(i->reg))
unhandled_.push(i);
- }
- else {
- if (!spilled.count(i->reg))
- unhandled_.push(i);
- prt_->delRegUse(vrm_->getPhys(i->reg));
- vrm_->clearVirt(i->reg);
- }
- }
- else if ((it = find(inactive_.begin(), inactive_.end(), i)) != inactive_.end()) {
+ prt_->delRegUse(vrm_->getPhys(i->reg));
+ vrm_->clearVirt(i->reg);
+ } else if ((it = FindIntervalInVector(inactive_, i)) != inactive_.end()) {
inactive_.erase(it);
- if (MRegisterInfo::isPhysicalRegister(i->reg))
+ assert(!MRegisterInfo::isPhysicalRegister(i->reg));
+ if (!spilled.count(i->reg))
unhandled_.push(i);
- else {
- if (!spilled.count(i->reg))
- unhandled_.push(i);
- vrm_->clearVirt(i->reg);
- }
- }
- else {
- if (MRegisterInfo::isVirtualRegister(i->reg))
- vrm_->clearVirt(i->reg);
+ vrm_->clearVirt(i->reg);
+ } else {
+ assert(MRegisterInfo::isVirtualRegister(i->reg) &&
+ "Can only allocate virtual registers!");
+ vrm_->clearVirt(i->reg);
unhandled_.push(i);
}
}
+ // Rewind the iterators in the active, inactive, and fixed lists back to the
+ // point we reverted to.
+ RevertVectorIteratorsTo(active_, earliestStart);
+ RevertVectorIteratorsTo(inactive_, earliestStart);
+ RevertVectorIteratorsTo(fixed_, earliestStart);
+
// scan the rest and undo each interval that expired after t and
// insert it in active (the next iteration of the algorithm will
// put it in inactive if required)
- IntervalPtrs::iterator i = handled_.begin(), e = handled_.end();
- for (; i != e; ++i) {
- if (!(*i)->expiredAt(earliestStart) && (*i)->expiredAt(cur->start())) {
- DEBUG(std::cerr << "\t\t\tundo changes for: " << **i << '\n');
- active_.push_back(*i);
- if (MRegisterInfo::isPhysicalRegister((*i)->reg))
- prt_->addRegUse((*i)->reg);
- else
- prt_->addRegUse(vrm_->getPhys((*i)->reg));
+ for (unsigned i = 0, e = handled_.size(); i != e; ++i) {
+ LiveInterval *HI = handled_[i];
+ if (!HI->expiredAt(earliestStart) &&
+ HI->expiredAt(cur->beginNumber())) {
+ DOUT << "\t\t\tundo changes for: " << *HI << '\n';
+ active_.push_back(std::make_pair(HI, HI->begin()));
+ assert(!MRegisterInfo::isPhysicalRegister(HI->reg));
+ prt_->addRegUse(vrm_->getPhys(HI->reg));
}
}
- std::sort(added.begin(), added.end(), less_ptr<LiveInterval>());
// merge added with unhandled
for (unsigned i = 0, e = added.size(); i != e; ++i)
unhandled_.push(added[i]);
}
-unsigned RA::getFreePhysReg(LiveInterval* cur)
-{
- const TargetRegisterClass* rc = mf_->getSSARegMap()->getRegClass(cur->reg);
+/// getFreePhysReg - return a free physical register for this virtual register
+/// interval if we have one, otherwise return 0.
+unsigned RA::getFreePhysReg(LiveInterval *cur) {
+ std::vector<unsigned> inactiveCounts(mri_->getNumRegs(), 0);
+ unsigned MaxInactiveCount = 0;
+
+ const TargetRegisterClass *RC = mf_->getSSARegMap()->getRegClass(cur->reg);
+ const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
+
+ for (IntervalPtrs::iterator i = inactive_.begin(), e = inactive_.end();
+ i != e; ++i) {
+ unsigned reg = i->first->reg;
+ assert(MRegisterInfo::isVirtualRegister(reg) &&
+ "Can only allocate virtual registers!");
+
+ // If this is not in a related reg class to the register we're allocating,
+ // don't check it.
+ const TargetRegisterClass *RegRC = mf_->getSSARegMap()->getRegClass(reg);
+ if (RelatedRegClasses.getLeaderValue(RegRC) == RCLeader) {
+ reg = vrm_->getPhys(reg);
+ ++inactiveCounts[reg];
+ MaxInactiveCount = std::max(MaxInactiveCount, inactiveCounts[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;
+ unsigned FreeReg = 0;
+ unsigned FreeRegInactiveCount = 0;
+
+ // If copy coalescer has assigned a "preferred" register, check if it's
+ // available first.
+ if (cur->preference)
+ if (prt_->isRegAvail(cur->preference)) {
+ DOUT << "\t\tassigned the preferred register: "
+ << mri_->getName(cur->preference) << "\n";
+ return cur->preference;
+ } else
+ DOUT << "\t\tunable to assign the preferred register: "
+ << mri_->getName(cur->preference) << "\n";
+
+ // Scan for the first available register.
+ TargetRegisterClass::iterator I = RC->allocation_order_begin(*mf_);
+ TargetRegisterClass::iterator E = RC->allocation_order_end(*mf_);
+ for (; I != E; ++I)
+ if (prt_->isRegAvail(*I)) {
+ FreeReg = *I;
+ FreeRegInactiveCount = inactiveCounts[FreeReg];
+ break;
+ }
+
+ // If there are no free regs, or if this reg has the max inactive count,
+ // return this register.
+ if (FreeReg == 0 || FreeRegInactiveCount == MaxInactiveCount) return FreeReg;
+
+ // Continue scanning the registers, looking for the one with the highest
+ // inactive count. Alkis found that this reduced register pressure very
+ // slightly on X86 (in rev 1.94 of this file), though this should probably be
+ // reevaluated now.
+ for (; I != E; ++I) {
+ unsigned Reg = *I;
+ if (prt_->isRegAvail(Reg) && FreeRegInactiveCount < inactiveCounts[Reg]) {
+ FreeReg = Reg;
+ FreeRegInactiveCount = inactiveCounts[Reg];
+ if (FreeRegInactiveCount == MaxInactiveCount)
+ break; // We found the one with the max inactive count.
+ }
}
- return 0;
+
+ return FreeReg;
}
FunctionPass* llvm::createLinearScanRegisterAllocator() {
projects / oota-llvm.git / blobdiff