STATISTIC(NumBacktracks, "Number of times we had to backtrack");
STATISTIC(NumCoalesce, "Number of copies coalesced");
+static cl::opt<bool>
+NewHeuristic("new-spilling-heuristic",
+ cl::desc("Use new spilling heuristic"),
+ cl::init(false), cl::Hidden);
+
static RegisterRegAlloc
linearscanRegAlloc("linearscan", " linear scan register allocator",
createLinearScanRegisterAllocator);
std::map<unsigned, const TargetRegisterClass*> OneClassForEachPhysReg;
MachineFunction* mf_;
+ MachineRegisterInfo* mri_;
const TargetMachine* tm_;
const TargetRegisterInfo* tri_;
const TargetInstrInfo* tii_;
/// is available, or spill.
void assignRegOrStackSlotAtInterval(LiveInterval* cur);
+ /// findIntervalsToSpill - Determine the intervals to spill for the
+ /// specified interval. It's passed the physical registers whose spill
+ /// weight is the lowest among all the registers whose live intervals
+ /// conflict with the interval.
+ void findIntervalsToSpill(LiveInterval *cur,
+ std::vector<std::pair<unsigned,float> > &Candidates,
+ unsigned NumCands,
+ SmallVector<LiveInterval*, 8> &SpillIntervals);
+
/// attemptTrivialCoalescing - If a simple interval is defined by a copy,
/// try allocate the definition the same register as the source register
/// if the register is not defined during live time of the interval. This
bool RALinScan::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
+ mri_ = &fn.getRegInfo();
tm_ = &fn.getTarget();
tri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
SI.MergeRangesInAsValue(RI, VNI);
}
+/// getConflictWeight - Return the number of conflicts between cur
+/// live interval and defs and uses of Reg weighted by loop depthes.
+static float getConflictWeight(LiveInterval *cur, unsigned Reg,
+ LiveIntervals *li_,
+ MachineRegisterInfo *mri_,
+ const MachineLoopInfo *loopInfo) {
+ float Conflicts = 0;
+ for (MachineRegisterInfo::reg_iterator I = mri_->reg_begin(Reg),
+ E = mri_->reg_end(); I != E; ++I) {
+ MachineInstr *MI = &*I;
+ if (cur->liveAt(li_->getInstructionIndex(MI))) {
+ unsigned loopDepth = loopInfo->getLoopDepth(MI->getParent());
+ Conflicts += powf(10.0f, (float)loopDepth);
+ }
+ }
+ return Conflicts;
+}
+
+/// findIntervalsToSpill - Determine the intervals to spill for the
+/// specified interval. It's passed the physical registers whose spill
+/// weight is the lowest among all the registers whose live intervals
+/// conflict with the interval.
+void RALinScan::findIntervalsToSpill(LiveInterval *cur,
+ std::vector<std::pair<unsigned,float> > &Candidates,
+ unsigned NumCands,
+ SmallVector<LiveInterval*, 8> &SpillIntervals) {
+ // We have figured out the *best* register to spill. But there are other
+ // registers that are pretty good as well (spill weight within 3%). Spill
+ // the one that has fewest defs and uses that conflict with cur.
+ float Conflicts[3] = { 0.0f, 0.0f, 0.0f };
+ SmallVector<LiveInterval*, 8> SLIs[3];
+
+ DOUT << "\tConsidering " << NumCands << " candidates: ";
+ DEBUG(for (unsigned i = 0; i != NumCands; ++i)
+ DOUT << tri_->getName(Candidates[i].first) << " ";
+ DOUT << "\n";);
+
+ // Calculate the number of conflicts of each candidate.
+ for (IntervalPtrs::iterator i = active_.begin(); i != active_.end(); ++i) {
+ unsigned Reg = i->first->reg;
+ unsigned PhysReg = vrm_->getPhys(Reg);
+ if (!cur->overlapsFrom(*i->first, i->second))
+ continue;
+ for (unsigned j = 0; j < NumCands; ++j) {
+ unsigned Candidate = Candidates[j].first;
+ if (tri_->regsOverlap(PhysReg, Candidate)) {
+ if (NumCands > 1)
+ Conflicts[j] += getConflictWeight(cur, Reg, li_, mri_, loopInfo);
+ SLIs[j].push_back(i->first);
+ }
+ }
+ }
+
+ for (IntervalPtrs::iterator i = inactive_.begin(); i != inactive_.end(); ++i){
+ unsigned Reg = i->first->reg;
+ unsigned PhysReg = vrm_->getPhys(Reg);
+ if (!cur->overlapsFrom(*i->first, i->second-1))
+ continue;
+ for (unsigned j = 0; j < NumCands; ++j) {
+ unsigned Candidate = Candidates[j].first;
+ if (tri_->regsOverlap(PhysReg, Candidate)) {
+ if (NumCands > 1)
+ Conflicts[j] += getConflictWeight(cur, Reg, li_, mri_, loopInfo);
+ SLIs[j].push_back(i->first);
+ }
+ }
+ }
+
+ // Which is the best candidate?
+ unsigned BestCandidate = 0;
+ float MinConflicts = Conflicts[0];
+ for (unsigned i = 1; i != NumCands; ++i) {
+ if (Conflicts[i] < MinConflicts) {
+ BestCandidate = i;
+ MinConflicts = Conflicts[i];
+ }
+ }
+
+ std::copy(SLIs[BestCandidate].begin(), SLIs[BestCandidate].end(),
+ std::back_inserter(SpillIntervals));
+}
+
+namespace {
+ struct WeightCompare {
+ typedef std::pair<unsigned, float> RegWeightPair;
+ bool operator()(const RegWeightPair &LHS, const RegWeightPair &RHS) const {
+ return LHS.second < RHS.second;
+ }
+ };
+}
+
+static bool weightsAreClose(float w1, float w2) {
+ if (!NewHeuristic)
+ return false;
+
+ float diff = w1 - w2;
+ if (diff <= 0.02f) // Within 0.02f
+ return true;
+ return (diff / w2) <= 0.05f; // Within 5%.
+}
+
/// assignRegOrStackSlotAtInterval - assign a register if one is available, or
/// spill.
void RALinScan::assignRegOrStackSlotAtInterval(LiveInterval* cur)
DOUT << "no free registers\n";
// Compile the spill weights into an array that is better for scanning.
- std::vector<float> SpillWeights(tri_->getNumRegs(), 0.0);
+ std::vector<float> SpillWeights(tri_->getNumRegs(), 0.0f);
for (std::vector<std::pair<unsigned, float> >::iterator
I = SpillWeightsToAdd.begin(), E = SpillWeightsToAdd.end(); I != E; ++I)
updateSpillWeights(SpillWeights, I->first, I->second, tri_);
// Find a register to spill.
float minWeight = HUGE_VALF;
- unsigned minReg = cur->preference; // Try the preferred register first.
-
+ unsigned minReg = 0; /*cur->preference*/; // Try the preferred register first.
+
+ bool Found = false;
+ std::vector<std::pair<unsigned,float> > RegsWeights;
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;
- }
+ float regWeight = SpillWeights[reg];
+ if (minWeight > regWeight)
+ Found = true;
+ RegsWeights.push_back(std::make_pair(reg, regWeight));
}
// If we didn't find a register that is spillable, try aliases?
- if (!minReg) {
+ if (!Found) {
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 = tri_->getAliasSet(reg); *as; ++as) {
- if (minWeight > SpillWeights[*as]) {
- minWeight = SpillWeights[*as];
- minReg = *as;
- }
- }
+ for (const unsigned* as = tri_->getAliasSet(reg); *as; ++as)
+ RegsWeights.push_back(std::make_pair(*as, SpillWeights[*as]));
}
+ }
+ // Sort all potential spill candidates by weight.
+ std::sort(RegsWeights.begin(), RegsWeights.end(), WeightCompare());
+ minReg = RegsWeights[0].first;
+ minWeight = RegsWeights[0].second;
+ if (minWeight == HUGE_VALF) {
// All registers must have inf weight. Just grab one!
- if (!minReg) {
- minReg = BestPhysReg ? BestPhysReg : *RC->allocation_order_begin(*mf_);
- if (cur->weight == HUGE_VALF || cur->getSize() == 1)
- // Spill a physical register around defs and uses.
- li_->spillPhysRegAroundRegDefsUses(*cur, minReg, *vrm_);
- }
+ minReg = BestPhysReg ? BestPhysReg : *RC->allocation_order_begin(*mf_);
+ if (cur->weight == HUGE_VALF || cur->getSize() == 1)
+ // Spill a physical register around defs and uses.
+ li_->spillPhysRegAroundRegDefsUses(*cur, minReg, *vrm_);
}
-
- DOUT << "\t\tregister with min weight: "
- << tri_->getName(minReg) << " (" << minWeight << ")\n";
+
+ // Find up to 3 registers to consider as spill candidates.
+ unsigned LastCandidate = RegsWeights.size() >= 3 ? 3 : 1;
+ while (LastCandidate > 1) {
+ if (weightsAreClose(RegsWeights[LastCandidate-1].second, minWeight))
+ break;
+ --LastCandidate;
+ }
+
+ DOUT << "\t\tregister(s) with min weight(s): ";
+ DEBUG(for (unsigned i = 0; i != LastCandidate; ++i)
+ DOUT << tri_->getName(RegsWeights[i].first)
+ << " (" << RegsWeights[i].second << ")\n");
// if the current has the minimum weight, we need to spill it and
// add any added intervals back to unhandled, and restart
// should go back right in the front of the list
unhandled_.push(cur);
- // otherwise we spill all intervals aliasing the register with
- // minimum weight, rollback to the interval with the earliest
- // start point and let the linear scan algorithm run again
- std::vector<LiveInterval*> added;
assert(TargetRegisterInfo::isPhysicalRegister(minReg) &&
"did not choose a register to spill?");
- BitVector toSpill(tri_->getNumRegs());
- // We are going to spill minReg and all its aliases.
- toSpill[minReg] = true;
- for (const unsigned* as = tri_->getAliasSet(minReg); *as; ++as)
- toSpill[*as] = true;
+ // We spill all intervals aliasing the register with
+ // minimum weight, rollback to the interval with the earliest
+ // start point and let the linear scan algorithm run again
+ SmallVector<LiveInterval*, 8> spillIs;
+
+ // Determine which intervals have to be spilled.
+ findIntervalsToSpill(cur, RegsWeights, LastCandidate, spillIs);
- // the earliest start of a spilled interval indicates up to where
+ // Set of spilled vregs (used later to rollback properly)
+ SmallSet<unsigned, 8> spilled;
+
+ // The earliest start of a Spilled interval indicates up to where
// in handled we need to roll back
unsigned earliestStart = cur->beginNumber();
- // set of spilled vregs (used later to rollback properly)
- SmallSet<unsigned, 32> spilled;
-
- // spill live intervals of virtual regs mapped to the physical register we
+ // 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 (//TargetRegisterInfo::isVirtualRegister(reg) &&
- toSpill[vrm_->getPhys(reg)] &&
- cur->overlapsFrom(*i->first, i->second)) {
- DOUT << "\t\t\tspilling(a): " << *i->first << '\n';
- earliestStart = std::min(earliestStart, i->first->beginNumber());
- float SSWeight;
- std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, loopInfo, *vrm_, SSWeight);
- addStackInterval(i->first, ls_, li_, SSWeight, *vrm_);
- 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->first->reg;
- if (//TargetRegisterInfo::isVirtualRegister(reg) &&
- toSpill[vrm_->getPhys(reg)] &&
- cur->overlapsFrom(*i->first, i->second-1)) {
- DOUT << "\t\t\tspilling(i): " << *i->first << '\n';
- earliestStart = std::min(earliestStart, i->first->beginNumber());
- float SSWeight;
- std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, loopInfo, *vrm_, SSWeight);
- addStackInterval(i->first, ls_, li_, SSWeight, *vrm_);
- std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
- spilled.insert(reg);
- }
+ std::vector<LiveInterval*> added;
+ while (!spillIs.empty()) {
+ LiveInterval *sli = spillIs.back();
+ spillIs.pop_back();
+ DOUT << "\t\t\tspilling(a): " << *sli << '\n';
+ earliestStart = std::min(earliestStart, sli->beginNumber());
+ float SSWeight;
+ std::vector<LiveInterval*> newIs =
+ li_->addIntervalsForSpills(*sli, loopInfo, *vrm_, SSWeight);
+ addStackInterval(sli, ls_, li_, SSWeight, *vrm_);
+ std::copy(newIs.begin(), newIs.end(), std::back_inserter(added));
+ spilled.insert(sli->reg);
}
DOUT << "\t\trolling back to: " << earliestStart << '\n';
projects / oota-llvm.git / commitdiff