//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "regalloc"
-#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "PhysRegTracker.h"
#include "VirtRegMap.h"
#include "llvm/Function.h"
+#include "llvm/CodeGen/LiveIntervalAnalysis.h"
+#include "llvm/CodeGen/LiveStackAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
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_;
MachineRegisterInfo *reginfo_;
BitVector allocatableRegs_;
LiveIntervals* li_;
+ LiveStacks* ls_;
const MachineLoopInfo *loopInfo;
/// handled_ - Intervals are added to the handled_ set in the order of their
// Make sure PassManager knows which analyses to make available
// to coalescing and which analyses coalescing invalidates.
AU.addRequiredTransitive<RegisterCoalescer>();
+ AU.addRequired<LiveStacks>();
+ AU.addPreserved<LiveStacks>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreservedID(MachineDominatorsID);
/// 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
char RALinScan::ID = 0;
}
+static RegisterPass<RALinScan>
+X("linearscan-regalloc", "Linear Scan Register Allocator");
+
void RALinScan::ComputeRelatedRegClasses() {
const TargetRegisterInfo &TRI = *tri_;
bool RALinScan::runOnMachineFunction(MachineFunction &fn) {
mf_ = &fn;
+ mri_ = &fn.getRegInfo();
tm_ = &fn.getTarget();
tri_ = tm_->getRegisterInfo();
tii_ = tm_->getInstrInfo();
reginfo_ = &mf_->getRegInfo();
allocatableRegs_ = tri_->getAllocatableSet(fn);
li_ = &getAnalysis<LiveIntervals>();
+ ls_ = &getAnalysis<LiveStacks>();
loopInfo = &getAnalysis<MachineLoopInfo>();
// We don't run the coalescer here because we have no reason to
spiller_->runOnMachineFunction(*mf_, *vrm_);
vrm_.reset(); // Free the VirtRegMap
- while (!unhandled_.empty()) unhandled_.pop();
+ assert(unhandled_.empty() && "Unhandled live intervals remain!");
fixed_.clear();
active_.clear();
inactive_.clear();
++NumIters;
DOUT << "\n*** CURRENT ***: " << *cur << '\n';
- processActiveIntervals(cur->beginNumber());
- processInactiveIntervals(cur->beginNumber());
+ if (!cur->empty()) {
+ processActiveIntervals(cur->beginNumber());
+ processInactiveIntervals(cur->beginNumber());
- assert(TargetRegisterInfo::isVirtualRegister(cur->reg) &&
- "Can only allocate virtual registers!");
+ assert(TargetRegisterInfo::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
}
}
+/// addStackInterval - Create a LiveInterval for stack if the specified live
+/// interval has been spilled.
+static void addStackInterval(LiveInterval *cur, LiveStacks *ls_,
+ LiveIntervals *li_, float &Weight,
+ VirtRegMap &vrm_) {
+ int SS = vrm_.getStackSlot(cur->reg);
+ if (SS == VirtRegMap::NO_STACK_SLOT)
+ return;
+ LiveInterval &SI = ls_->getOrCreateInterval(SS);
+ SI.weight += Weight;
+
+ VNInfo *VNI;
+ if (SI.getNumValNums())
+ VNI = SI.getValNumInfo(0);
+ else
+ VNI = SI.getNextValue(~0U, 0, ls_->getVNInfoAllocator());
+
+ LiveInterval &RI = li_->getInterval(cur->reg);
+ // FIXME: This may be overly conservative.
+ 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 << "\tallocating current interval: ";
+ // This is an implicitly defined live interval, just assign any register.
+ const TargetRegisterClass *RC = reginfo_->getRegClass(cur->reg);
+ if (cur->empty()) {
+ unsigned physReg = cur->preference;
+ if (!physReg)
+ physReg = *RC->allocation_order_begin(*mf_);
+ DOUT << tri_->getName(physReg) << '\n';
+ // Note the register is not really in use.
+ vrm_->assignVirt2Phys(cur->reg, physReg);
+ return;
+ }
+
PhysRegTracker backupPrt = *prt_;
std::vector<std::pair<unsigned, float> > SpillWeightsToAdd;
unsigned StartPosition = cur->beginNumber();
- const TargetRegisterClass *RC = reginfo_->getRegClass(cur->reg);
const TargetRegisterClass *RCLeader = RelatedRegClasses.getLeaderValue(RC);
// If this live interval is defined by a move instruction and its source is
if (vni->def && vni->def != ~1U && vni->def != ~0U) {
MachineInstr *CopyMI = li_->getInstructionFromIndex(vni->def);
unsigned SrcReg, DstReg;
- if (tii_->isMoveInstr(*CopyMI, SrcReg, DstReg)) {
+ if (CopyMI && tii_->isMoveInstr(*CopyMI, SrcReg, DstReg)) {
unsigned Reg = 0;
if (TargetRegisterInfo::isPhysicalRegister(SrcReg))
Reg = SrcReg;
// 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);
+ unsigned BestPhysReg = physReg;
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
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) {
- if (active_.size() == 0) {
- // FIXME: All the registers are occupied by fixed intervals.
- cerr << "Register allocator ran out of registers!\n";
- abort();
- }
- minReg = *RC->allocation_order_begin(*mf_);
- }
+ minReg = BestPhysReg ? BestPhysReg : *RC->allocation_order_begin(*mf_);
+ if (cur->weight == HUGE_VALF ||
+ li_->getApproximateInstructionCount(*cur) == 0)
+ // 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
// linearscan.
if (cur->weight != HUGE_VALF && cur->weight <= minWeight) {
DOUT << "\t\t\tspilling(c): " << *cur << '\n';
+ float SSWeight;
std::vector<LiveInterval*> added =
- li_->addIntervalsForSpills(*cur, loopInfo, *vrm_);
+ li_->addIntervalsForSpills(*cur, loopInfo, *vrm_, SSWeight);
+ addStackInterval(cur, ls_, li_, SSWeight, *vrm_);
if (added.empty())
return; // Early exit if all spills were folded.
// 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);
+
+ // Set of spilled vregs (used later to rollback properly)
+ SmallSet<unsigned, 8> spilled;
- // the earliest start of a spilled interval indicates up to where
+ // 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());
- std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, loopInfo, *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());
- std::vector<LiveInterval*> newIs =
- li_->addIntervalsForSpills(*i->first, loopInfo, *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';
// Scan for the first available register.
TargetRegisterClass::iterator I = RC->allocation_order_begin(*mf_);
TargetRegisterClass::iterator E = RC->allocation_order_end(*mf_);
+ assert(I != E && "No allocatable register in this register class!");
for (; I != E; ++I)
if (prt_->isRegAvail(*I)) {
FreeReg = *I;
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