#include "SpillPlacement.h"
#include "SplitKit.h"
#include "VirtRegMap.h"
-#include "VirtRegRewriter.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Function.h"
#include "llvm/PassAnalysisSupport.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Timer.h"
+#include <queue>
+
using namespace llvm;
+STATISTIC(NumGlobalSplits, "Number of split global live ranges");
+STATISTIC(NumLocalSplits, "Number of split local live ranges");
+STATISTIC(NumEvicted, "Number of interferences evicted");
+
static RegisterRegAlloc greedyRegAlloc("greedy", "greedy register allocator",
createGreedyRegisterAllocator);
namespace {
-class RAGreedy : public MachineFunctionPass, public RegAllocBase {
+class RAGreedy : public MachineFunctionPass,
+ public RegAllocBase,
+ private LiveRangeEdit::Delegate {
+
// context
MachineFunction *MF;
BitVector ReservedRegs;
// state
std::auto_ptr<Spiller> SpillerInstance;
- std::auto_ptr<SplitAnalysis> SA;
+ std::priority_queue<std::pair<unsigned, unsigned> > Queue;
+
+ // Live ranges pass through a number of stages as we try to allocate them.
+ // Some of the stages may also create new live ranges:
+ //
+ // - Region splitting.
+ // - Per-block splitting.
+ // - Local splitting.
+ // - Spilling.
+ //
+ // Ranges produced by one of the stages skip the previous stages when they are
+ // dequeued. This improves performance because we can skip interference checks
+ // that are unlikely to give any results. It also guarantees that the live
+ // range splitting algorithm terminates, something that is otherwise hard to
+ // ensure.
+ enum LiveRangeStage {
+ RS_Original, ///< Never seen before, never split.
+ RS_Second, ///< Second time in the queue.
+ RS_Region, ///< Produced by region splitting.
+ RS_Block, ///< Produced by per-block splitting.
+ RS_Local, ///< Produced by local splitting.
+ RS_Spill ///< Produced by spilling.
+ };
+
+ IndexedMap<unsigned char, VirtReg2IndexFunctor> LRStage;
+
+ LiveRangeStage getStage(const LiveInterval &VirtReg) const {
+ return LiveRangeStage(LRStage[VirtReg.reg]);
+ }
+
+ template<typename Iterator>
+ void setStage(Iterator Begin, Iterator End, LiveRangeStage NewStage) {
+ LRStage.resize(MRI->getNumVirtRegs());
+ for (;Begin != End; ++Begin)
+ LRStage[(*Begin)->reg] = NewStage;
+ }
// splitting state.
+ std::auto_ptr<SplitAnalysis> SA;
+ std::auto_ptr<SplitEditor> SE;
/// All basic blocks where the current register is live.
- SmallVector<SpillPlacement::BlockConstraint, 8> SpillConstraints;
+ SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints;
+
+ typedef std::pair<SlotIndex, SlotIndex> IndexPair;
+
+ /// Global live range splitting candidate info.
+ struct GlobalSplitCandidate {
+ unsigned PhysReg;
+ SmallVector<IndexPair, 8> Interference;
+ BitVector LiveBundles;
+ };
+
+ /// Candidate info for for each PhysReg in AllocationOrder.
+ /// This vector never shrinks, but grows to the size of the largest register
+ /// class.
+ SmallVector<GlobalSplitCandidate, 32> GlobalCand;
+
+ /// For every instruction in SA->UseSlots, store the previous non-copy
+ /// instruction.
+ SmallVector<SlotIndex, 8> PrevSlot;
public:
RAGreedy();
/// RAGreedy analysis usage.
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
-
virtual void releaseMemory();
-
virtual Spiller &spiller() { return *SpillerInstance; }
-
- virtual float getPriority(LiveInterval *LI);
-
+ virtual void enqueue(LiveInterval *LI);
+ virtual LiveInterval *dequeue();
virtual unsigned selectOrSplit(LiveInterval&,
SmallVectorImpl<LiveInterval*>&);
static char ID;
private:
- bool checkUncachedInterference(LiveInterval&, unsigned);
- LiveInterval *getSingleInterference(LiveInterval&, unsigned);
- bool reassignVReg(LiveInterval &InterferingVReg, unsigned OldPhysReg);
- float calcInterferenceWeight(LiveInterval&, unsigned);
- float calcInterferenceInfo(LiveInterval&, unsigned);
+ void LRE_WillEraseInstruction(MachineInstr*);
+ bool LRE_CanEraseVirtReg(unsigned);
+ void LRE_WillShrinkVirtReg(unsigned);
+
+ void mapGlobalInterference(unsigned, SmallVectorImpl<IndexPair>&);
+ float calcSplitConstraints(const SmallVectorImpl<IndexPair>&);
+
float calcGlobalSplitCost(const BitVector&);
void splitAroundRegion(LiveInterval&, unsigned, const BitVector&,
SmallVectorImpl<LiveInterval*>&);
+ void calcGapWeights(unsigned, SmallVectorImpl<float>&);
+ SlotIndex getPrevMappedIndex(const MachineInstr*);
+ void calcPrevSlots();
+ unsigned nextSplitPoint(unsigned);
+ bool canEvictInterference(LiveInterval&, unsigned, float&);
- unsigned tryReassignOrEvict(LiveInterval&, AllocationOrder&,
- SmallVectorImpl<LiveInterval*>&);
+ unsigned tryEvict(LiveInterval&, AllocationOrder&,
+ SmallVectorImpl<LiveInterval*>&);
unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
+ unsigned tryLocalSplit(LiveInterval&, AllocationOrder&,
+ SmallVectorImpl<LiveInterval*>&);
unsigned trySplit(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
- unsigned trySpillInterferences(LiveInterval&, AllocationOrder&,
- SmallVectorImpl<LiveInterval*>&);
};
} // end anonymous namespace
return new RAGreedy();
}
-RAGreedy::RAGreedy(): MachineFunctionPass(ID) {
+RAGreedy::RAGreedy(): MachineFunctionPass(ID), LRStage(RS_Original) {
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
MachineFunctionPass::getAnalysisUsage(AU);
}
-void RAGreedy::releaseMemory() {
- SpillerInstance.reset(0);
- RegAllocBase::releaseMemory();
-}
-float RAGreedy::getPriority(LiveInterval *LI) {
- float Priority = LI->weight;
+//===----------------------------------------------------------------------===//
+// LiveRangeEdit delegate methods
+//===----------------------------------------------------------------------===//
- // Prioritize hinted registers so they are allocated first.
- std::pair<unsigned, unsigned> Hint;
- if (Hint.first || Hint.second) {
- // The hint can be target specific, a virtual register, or a physreg.
- Priority *= 2;
+void RAGreedy::LRE_WillEraseInstruction(MachineInstr *MI) {
+ // LRE itself will remove from SlotIndexes and parent basic block.
+ VRM->RemoveMachineInstrFromMaps(MI);
+}
- // Prefer physreg hints above anything else.
- if (Hint.first == 0 && TargetRegisterInfo::isPhysicalRegister(Hint.second))
- Priority *= 2;
+bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) {
+ if (unsigned PhysReg = VRM->getPhys(VirtReg)) {
+ unassign(LIS->getInterval(VirtReg), PhysReg);
+ return true;
}
- return Priority;
+ // Unassigned virtreg is probably in the priority queue.
+ // RegAllocBase will erase it after dequeueing.
+ return false;
}
+void RAGreedy::LRE_WillShrinkVirtReg(unsigned VirtReg) {
+ unsigned PhysReg = VRM->getPhys(VirtReg);
+ if (!PhysReg)
+ return;
-//===----------------------------------------------------------------------===//
-// Register Reassignment
-//===----------------------------------------------------------------------===//
+ // Register is assigned, put it back on the queue for reassignment.
+ LiveInterval &LI = LIS->getInterval(VirtReg);
+ unassign(LI, PhysReg);
+ enqueue(&LI);
+}
-// Check interference without using the cache.
-bool RAGreedy::checkUncachedInterference(LiveInterval &VirtReg,
- unsigned PhysReg) {
- for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
- LiveIntervalUnion::Query subQ(&VirtReg, &PhysReg2LiveUnion[*AliasI]);
- if (subQ.checkInterference())
- return true;
- }
- return false;
+void RAGreedy::releaseMemory() {
+ SpillerInstance.reset(0);
+ LRStage.clear();
+ RegAllocBase::releaseMemory();
}
-/// getSingleInterference - Return the single interfering virtual register
-/// assigned to PhysReg. Return 0 if more than one virtual register is
-/// interfering.
-LiveInterval *RAGreedy::getSingleInterference(LiveInterval &VirtReg,
- unsigned PhysReg) {
- // Check physreg and aliases.
- LiveInterval *Interference = 0;
- for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
- LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
- if (Q.checkInterference()) {
- if (Interference)
- return 0;
- Q.collectInterferingVRegs(1);
- if (!Q.seenAllInterferences())
- return 0;
- Interference = Q.interferingVRegs().front();
- }
+void RAGreedy::enqueue(LiveInterval *LI) {
+ // Prioritize live ranges by size, assigning larger ranges first.
+ // The queue holds (size, reg) pairs.
+ const unsigned Size = LI->getSize();
+ const unsigned Reg = LI->reg;
+ assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
+ "Can only enqueue virtual registers");
+ unsigned Prio;
+
+ LRStage.grow(Reg);
+ if (LRStage[Reg] == RS_Second)
+ // Unsplit ranges that couldn't be allocated immediately are deferred until
+ // everything else has been allocated. Long ranges are allocated last so
+ // they are split against realistic interference.
+ Prio = (1u << 31) - Size;
+ else {
+ // Everything else is allocated in long->short order. Long ranges that don't
+ // fit should be spilled ASAP so they don't create interference.
+ Prio = (1u << 31) + Size;
+
+ // Boost ranges that have a physical register hint.
+ if (TargetRegisterInfo::isPhysicalRegister(VRM->getRegAllocPref(Reg)))
+ Prio |= (1u << 30);
}
- return Interference;
+
+ Queue.push(std::make_pair(Prio, Reg));
}
-// Attempt to reassign this virtual register to a different physical register.
-//
-// FIXME: we are not yet caching these "second-level" interferences discovered
-// in the sub-queries. These interferences can change with each call to
-// selectOrSplit. However, we could implement a "may-interfere" cache that
-// could be conservatively dirtied when we reassign or split.
-//
-// FIXME: This may result in a lot of alias queries. We could summarize alias
-// live intervals in their parent register's live union, but it's messy.
-bool RAGreedy::reassignVReg(LiveInterval &InterferingVReg,
- unsigned WantedPhysReg) {
- assert(TargetRegisterInfo::isVirtualRegister(InterferingVReg.reg) &&
- "Can only reassign virtual registers");
- assert(TRI->regsOverlap(WantedPhysReg, VRM->getPhys(InterferingVReg.reg)) &&
- "inconsistent phys reg assigment");
-
- AllocationOrder Order(InterferingVReg.reg, *VRM, ReservedRegs);
- while (unsigned PhysReg = Order.next()) {
- // Don't reassign to a WantedPhysReg alias.
- if (TRI->regsOverlap(PhysReg, WantedPhysReg))
- continue;
+LiveInterval *RAGreedy::dequeue() {
+ if (Queue.empty())
+ return 0;
+ LiveInterval *LI = &LIS->getInterval(Queue.top().second);
+ Queue.pop();
+ return LI;
+}
- if (checkUncachedInterference(InterferingVReg, PhysReg))
- continue;
+//===----------------------------------------------------------------------===//
+// Interference eviction
+//===----------------------------------------------------------------------===//
- // Reassign the interfering virtual reg to this physical reg.
- unsigned OldAssign = VRM->getPhys(InterferingVReg.reg);
- DEBUG(dbgs() << "reassigning: " << InterferingVReg << " from " <<
- TRI->getName(OldAssign) << " to " << TRI->getName(PhysReg) << '\n');
- unassign(InterferingVReg, OldAssign);
- assign(InterferingVReg, PhysReg);
- return true;
+/// canEvict - Return true if all interferences between VirtReg and PhysReg can
+/// be evicted. Set maxWeight to the maximal spill weight of an interference.
+bool RAGreedy::canEvictInterference(LiveInterval &VirtReg, unsigned PhysReg,
+ float &MaxWeight) {
+ float Weight = 0;
+ for (const unsigned *AliasI = TRI->getOverlaps(PhysReg); *AliasI; ++AliasI) {
+ LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
+ // If there is 10 or more interferences, chances are one is smaller.
+ if (Q.collectInterferingVRegs(10) >= 10)
+ return false;
+
+ // Check if any interfering live range is heavier than VirtReg.
+ for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
+ LiveInterval *Intf = Q.interferingVRegs()[i];
+ if (TargetRegisterInfo::isPhysicalRegister(Intf->reg))
+ return false;
+ if (Intf->weight >= VirtReg.weight)
+ return false;
+ Weight = std::max(Weight, Intf->weight);
+ }
}
- return false;
+ MaxWeight = Weight;
+ return true;
}
-/// tryReassignOrEvict - Try to reassign a single interferences to a different
-/// physreg, or evict a single interference with a lower spill weight.
+/// tryEvict - Try to evict all interferences for a physreg.
/// @param VirtReg Currently unassigned virtual register.
/// @param Order Physregs to try.
/// @return Physreg to assign VirtReg, or 0.
-unsigned RAGreedy::tryReassignOrEvict(LiveInterval &VirtReg,
- AllocationOrder &Order,
- SmallVectorImpl<LiveInterval*> &NewVRegs){
- NamedRegionTimer T("Reassign", TimerGroupName, TimePassesIsEnabled);
+unsigned RAGreedy::tryEvict(LiveInterval &VirtReg,
+ AllocationOrder &Order,
+ SmallVectorImpl<LiveInterval*> &NewVRegs){
+ NamedRegionTimer T("Evict", TimerGroupName, TimePassesIsEnabled);
// Keep track of the lightest single interference seen so far.
- float BestWeight = VirtReg.weight;
- LiveInterval *BestVirt = 0;
+ float BestWeight = 0;
unsigned BestPhys = 0;
Order.rewind();
while (unsigned PhysReg = Order.next()) {
- LiveInterval *InterferingVReg = getSingleInterference(VirtReg, PhysReg);
- if (!InterferingVReg)
+ float Weight = 0;
+ if (!canEvictInterference(VirtReg, PhysReg, Weight))
continue;
- if (TargetRegisterInfo::isPhysicalRegister(InterferingVReg->reg))
+
+ // This is an eviction candidate.
+ DEBUG(dbgs() << "max " << PrintReg(PhysReg, TRI) << " interference = "
+ << Weight << '\n');
+ if (BestPhys && Weight >= BestWeight)
continue;
- if (reassignVReg(*InterferingVReg, PhysReg))
- return PhysReg;
- // Cannot reassign, is this an eviction candidate?
- if (InterferingVReg->weight < BestWeight) {
- BestVirt = InterferingVReg;
- BestPhys = PhysReg;
- BestWeight = InterferingVReg->weight;
- }
+ // Best so far.
+ BestPhys = PhysReg;
+ BestWeight = Weight;
+ // Stop if the hint can be used.
+ if (Order.isHint(PhysReg))
+ break;
}
- // Nothing reassigned, can we evict a lighter single interference?
- if (BestVirt) {
- DEBUG(dbgs() << "evicting lighter " << *BestVirt << '\n');
- unassign(*BestVirt, VRM->getPhys(BestVirt->reg));
- NewVRegs.push_back(BestVirt);
- return BestPhys;
- }
+ if (!BestPhys)
+ return 0;
- return 0;
+ DEBUG(dbgs() << "evicting " << PrintReg(BestPhys, TRI) << " interference\n");
+ for (const unsigned *AliasI = TRI->getOverlaps(BestPhys); *AliasI; ++AliasI) {
+ LiveIntervalUnion::Query &Q = query(VirtReg, *AliasI);
+ assert(Q.seenAllInterferences() && "Didn't check all interfererences.");
+ for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
+ LiveInterval *Intf = Q.interferingVRegs()[i];
+ unassign(*Intf, VRM->getPhys(Intf->reg));
+ ++NumEvicted;
+ NewVRegs.push_back(Intf);
+ }
+ }
+ return BestPhys;
}
// Region Splitting
//===----------------------------------------------------------------------===//
-/// calcInterferenceInfo - Compute per-block outgoing and ingoing constraints
-/// when considering interference from PhysReg. Also compute an optimistic local
-/// cost of this interference pattern.
-///
-/// The final cost of a split is the local cost + global cost of preferences
-/// broken by SpillPlacement.
-///
-float RAGreedy::calcInterferenceInfo(LiveInterval &VirtReg, unsigned PhysReg) {
- // Reset interference dependent info.
- SpillConstraints.resize(SA->LiveBlocks.size());
- for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
- SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
- SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
- BC.Number = BI.MBB->getNumber();
- BC.Entry = (BI.Uses && BI.LiveIn) ?
- SpillPlacement::PrefReg : SpillPlacement::DontCare;
- BC.Exit = (BI.Uses && BI.LiveOut) ?
- SpillPlacement::PrefReg : SpillPlacement::DontCare;
- BI.OverlapEntry = BI.OverlapExit = false;
- }
-
- // Add interference info from each PhysReg alias.
+/// mapGlobalInterference - Compute a map of the interference from PhysReg and
+/// its aliases in each block in SA->LiveBlocks.
+/// If LiveBlocks[i] is live-in, Ranges[i].first is the first interference.
+/// If LiveBlocks[i] is live-out, Ranges[i].second is the last interference.
+void RAGreedy::mapGlobalInterference(unsigned PhysReg,
+ SmallVectorImpl<IndexPair> &Ranges) {
+ Ranges.assign(SA->LiveBlocks.size(), IndexPair());
+ LiveInterval &VirtReg = const_cast<LiveInterval&>(SA->getParent());
for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
if (!query(VirtReg, *AI).checkInterference())
continue;
PhysReg2LiveUnion[*AI].find(VirtReg.beginIndex());
if (!IntI.valid())
continue;
-
- // Determine which blocks have interference live in or after the last split
- // point.
for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
- SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
- SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
+ const SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
+ IndexPair &IP = Ranges[i];
// Skip interference-free blocks.
- if (IntI.start() >= Stop)
+ if (IntI.start() >= BI.Stop)
continue;
- // Is the interference live-in?
+ // First interference in block.
if (BI.LiveIn) {
- IntI.advanceTo(Start);
+ IntI.advanceTo(BI.Start);
if (!IntI.valid())
break;
- if (IntI.start() <= Start)
- BC.Entry = SpillPlacement::MustSpill;
+ if (IntI.start() >= BI.Stop)
+ continue;
+ if (!IP.first.isValid() || IntI.start() < IP.first)
+ IP.first = IntI.start();
}
- // Is the interference overlapping the last split point?
+ // Last interference in block.
if (BI.LiveOut) {
- if (IntI.stop() < BI.LastSplitPoint)
- IntI.advanceTo(BI.LastSplitPoint.getPrevSlot());
- if (!IntI.valid())
- break;
- if (IntI.start() < Stop)
- BC.Exit = SpillPlacement::MustSpill;
- }
- }
-
- // Rewind iterator and check other interferences.
- IntI.find(VirtReg.beginIndex());
- for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
- SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
- SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
-
- // Skip interference-free blocks.
- if (IntI.start() >= Stop)
- continue;
-
- // Handle transparent blocks with interference separately.
- // Transparent blocks never incur any fixed cost.
- if (BI.LiveThrough && !BI.Uses) {
- IntI.advanceTo(Start);
- if (!IntI.valid())
- break;
- if (IntI.start() >= Stop)
+ IntI.advanceTo(BI.Stop);
+ if (!IntI.valid() || IntI.start() >= BI.Stop)
+ --IntI;
+ if (IntI.stop() <= BI.Start)
continue;
-
- if (BC.Entry != SpillPlacement::MustSpill)
- BC.Entry = SpillPlacement::PrefSpill;
- if (BC.Exit != SpillPlacement::MustSpill)
- BC.Exit = SpillPlacement::PrefSpill;
- continue;
- }
-
- // Now we only have blocks with uses left.
- // Check if the interference overlaps the uses.
- assert(BI.Uses && "Non-transparent block without any uses");
-
- // Check interference on entry.
- if (BI.LiveIn && BC.Entry != SpillPlacement::MustSpill) {
- IntI.advanceTo(Start);
- if (!IntI.valid())
- break;
- // Not live in, but before the first use.
- if (IntI.start() < BI.FirstUse)
- BC.Entry = SpillPlacement::PrefSpill;
- }
-
- // Does interference overlap the uses in the entry segment
- // [FirstUse;Kill)?
- if (BI.LiveIn && !BI.OverlapEntry) {
- IntI.advanceTo(BI.FirstUse);
- if (!IntI.valid())
- break;
- // A live-through interval has no kill.
- // Check [FirstUse;LastUse) instead.
- if (IntI.start() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
- BI.OverlapEntry = true;
- }
-
- // Does interference overlap the uses in the exit segment [Def;LastUse)?
- if (BI.LiveOut && !BI.LiveThrough && !BI.OverlapExit) {
- IntI.advanceTo(BI.Def);
- if (!IntI.valid())
- break;
- if (IntI.start() < BI.LastUse)
- BI.OverlapExit = true;
- }
-
- // Check interference on exit.
- if (BI.LiveOut && BC.Exit != SpillPlacement::MustSpill) {
- // Check interference between LastUse and Stop.
- if (BC.Exit != SpillPlacement::PrefSpill) {
- IntI.advanceTo(BI.LastUse);
- if (!IntI.valid())
- break;
- if (IntI.start() < Stop)
- BC.Exit = SpillPlacement::PrefSpill;
- }
+ if (!IP.second.isValid() || IntI.stop() > IP.second)
+ IP.second = IntI.stop();
}
}
}
+}
- // Accumulate a local cost of this interference pattern.
- float LocalCost = 0;
+/// calcSplitConstraints - Fill out the SplitConstraints vector based on the
+/// interference pattern in Intf. Return the static cost of this split,
+/// assuming that all preferences in SplitConstraints are met.
+float RAGreedy::calcSplitConstraints(const SmallVectorImpl<IndexPair> &Intf) {
+ // Reset interference dependent info.
+ SplitConstraints.resize(SA->LiveBlocks.size());
+ float StaticCost = 0;
for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
- if (!BI.Uses)
- continue;
- SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
- unsigned Inserts = 0;
+ SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
+ IndexPair IP = Intf[i];
- // Do we need spill code for the entry segment?
- if (BI.LiveIn)
- Inserts += BI.OverlapEntry || BC.Entry != SpillPlacement::PrefReg;
+ BC.Number = BI.MBB->getNumber();
+ BC.Entry = (BI.Uses && BI.LiveIn) ?
+ SpillPlacement::PrefReg : SpillPlacement::DontCare;
+ BC.Exit = (BI.Uses && BI.LiveOut) ?
+ SpillPlacement::PrefReg : SpillPlacement::DontCare;
+
+ // Number of spill code instructions to insert.
+ unsigned Ins = 0;
+
+ // Interference for the live-in value.
+ if (IP.first.isValid()) {
+ if (IP.first <= BI.Start)
+ BC.Entry = SpillPlacement::MustSpill, Ins += BI.Uses;
+ else if (!BI.Uses)
+ BC.Entry = SpillPlacement::PrefSpill;
+ else if (IP.first < BI.FirstUse)
+ BC.Entry = SpillPlacement::PrefSpill, ++Ins;
+ else if (IP.first < (BI.LiveThrough ? BI.LastUse : BI.Kill))
+ ++Ins;
+ }
- // For the exit segment?
- if (BI.LiveOut)
- Inserts += BI.OverlapExit || BC.Exit != SpillPlacement::PrefReg;
+ // Interference for the live-out value.
+ if (IP.second.isValid()) {
+ if (IP.second >= BI.LastSplitPoint)
+ BC.Exit = SpillPlacement::MustSpill, Ins += BI.Uses;
+ else if (!BI.Uses)
+ BC.Exit = SpillPlacement::PrefSpill;
+ else if (IP.second > BI.LastUse)
+ BC.Exit = SpillPlacement::PrefSpill, ++Ins;
+ else if (IP.second > (BI.LiveThrough ? BI.FirstUse : BI.Def))
+ ++Ins;
+ }
- // The local cost of spill code in this block is the block frequency times
- // the number of spill instructions inserted.
- if (Inserts)
- LocalCost += Inserts * SpillPlacer->getBlockFrequency(BI.MBB);
+ // Accumulate the total frequency of inserted spill code.
+ if (Ins)
+ StaticCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
}
- DEBUG(dbgs() << "Local cost of " << PrintReg(PhysReg, TRI) << " = "
- << LocalCost << '\n');
- return LocalCost;
+ return StaticCost;
}
+
/// calcGlobalSplitCost - Return the global split cost of following the split
/// pattern in LiveBundles. This cost should be added to the local cost of the
-/// interference pattern in SpillConstraints.
+/// interference pattern in SplitConstraints.
///
float RAGreedy::calcGlobalSplitCost(const BitVector &LiveBundles) {
float GlobalCost = 0;
- for (unsigned i = 0, e = SpillConstraints.size(); i != e; ++i) {
- SpillPlacement::BlockConstraint &BC = SpillConstraints[i];
- unsigned Inserts = 0;
- // Broken entry preference?
- Inserts += LiveBundles[Bundles->getBundle(BC.Number, 0)] !=
- (BC.Entry == SpillPlacement::PrefReg);
- // Broken exit preference?
- Inserts += LiveBundles[Bundles->getBundle(BC.Number, 1)] !=
- (BC.Exit == SpillPlacement::PrefReg);
- if (Inserts)
- GlobalCost +=
- Inserts * SpillPlacer->getBlockFrequency(SA->LiveBlocks[i].MBB);
+ for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
+ SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
+ SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
+ bool RegIn = LiveBundles[Bundles->getBundle(BC.Number, 0)];
+ bool RegOut = LiveBundles[Bundles->getBundle(BC.Number, 1)];
+ unsigned Ins = 0;
+
+ if (!BI.Uses)
+ Ins += RegIn != RegOut;
+ else {
+ if (BI.LiveIn)
+ Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
+ if (BI.LiveOut)
+ Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
+ }
+ if (Ins)
+ GlobalCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
}
- DEBUG(dbgs() << "Global cost = " << GlobalCost << '\n');
return GlobalCost;
}
});
// First compute interference ranges in the live blocks.
- typedef std::pair<SlotIndex, SlotIndex> IndexPair;
SmallVector<IndexPair, 8> InterferenceRanges;
- InterferenceRanges.resize(SA->LiveBlocks.size());
- for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
- if (!query(VirtReg, *AI).checkInterference())
- continue;
- LiveIntervalUnion::SegmentIter IntI =
- PhysReg2LiveUnion[*AI].find(VirtReg.beginIndex());
- if (!IntI.valid())
- continue;
- for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
- const SplitAnalysis::BlockInfo &BI = SA->LiveBlocks[i];
- IndexPair &IP = InterferenceRanges[i];
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
- // Skip interference-free blocks.
- if (IntI.start() >= Stop)
- continue;
-
- // First interference in block.
- if (BI.LiveIn) {
- IntI.advanceTo(Start);
- if (!IntI.valid())
- break;
- if (IntI.start() >= Stop)
- continue;
- if (!IP.first.isValid() || IntI.start() < IP.first)
- IP.first = IntI.start();
- }
-
- // Last interference in block.
- if (BI.LiveOut) {
- IntI.advanceTo(Stop);
- if (!IntI.valid() || IntI.start() >= Stop)
- --IntI;
- if (IntI.stop() <= Start)
- continue;
- if (!IP.second.isValid() || IntI.stop() > IP.second)
- IP.second = IntI.stop();
- }
- }
- }
+ mapGlobalInterference(PhysReg, InterferenceRanges);
- SmallVector<LiveInterval*, 4> SpillRegs;
- LiveRangeEdit LREdit(VirtReg, NewVRegs, SpillRegs);
- SplitEditor SE(*SA, *LIS, *VRM, *DomTree, LREdit);
+ LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
+ SE->reset(LREdit);
// Create the main cross-block interval.
- SE.openIntv();
+ SE->openIntv();
// First add all defs that are live out of a block.
for (unsigned i = 0, e = SA->LiveBlocks.size(); i != e; ++i) {
continue;
IndexPair &IP = InterferenceRanges[i];
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
-
DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
<< Bundles->getBundle(BI.MBB->getNumber(), 1)
- << " intf [" << IP.first << ';' << IP.second << ')');
+ << " [" << BI.Start << ';' << BI.LastSplitPoint << '-'
+ << BI.Stop << ") intf [" << IP.first << ';' << IP.second
+ << ')');
// The interference interval should either be invalid or overlap MBB.
- assert((!IP.first.isValid() || IP.first < Stop) && "Bad interference");
- assert((!IP.second.isValid() || IP.second > Start) && "Bad interference");
+ assert((!IP.first.isValid() || IP.first < BI.Stop) && "Bad interference");
+ assert((!IP.second.isValid() || IP.second > BI.Start)
+ && "Bad interference");
// Check interference leaving the block.
if (!IP.second.isValid()) {
DEBUG(dbgs() << ", no uses"
<< (RegIn ? ", live-through.\n" : ", stack in.\n"));
if (!RegIn)
- SE.enterIntvAtEnd(*BI.MBB);
+ SE->enterIntvAtEnd(*BI.MBB);
continue;
}
if (!BI.LiveThrough) {
DEBUG(dbgs() << ", not live-through.\n");
- SE.useIntv(SE.enterIntvBefore(BI.Def), Stop);
+ SE->useIntv(SE->enterIntvBefore(BI.Def), BI.Stop);
continue;
}
if (!RegIn) {
// Block is live-through, but entry bundle is on the stack.
// Reload just before the first use.
DEBUG(dbgs() << ", not live-in, enter before first use.\n");
- SE.useIntv(SE.enterIntvBefore(BI.FirstUse), Stop);
+ SE->useIntv(SE->enterIntvBefore(BI.FirstUse), BI.Stop);
continue;
}
DEBUG(dbgs() << ", live-through.\n");
if (!BI.LiveThrough && IP.second <= BI.Def) {
// The interference doesn't reach the outgoing segment.
DEBUG(dbgs() << " doesn't affect def from " << BI.Def << '\n');
- SE.useIntv(BI.Def, Stop);
+ SE->useIntv(BI.Def, BI.Stop);
continue;
}
if (!BI.Uses) {
// No uses in block, avoid interference by reloading as late as possible.
DEBUG(dbgs() << ", no uses.\n");
- SlotIndex SegStart = SE.enterIntvAtEnd(*BI.MBB);
+ SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
assert(SegStart >= IP.second && "Couldn't avoid interference");
continue;
}
// Only attempt a split befroe the last split point.
if (Use.getBaseIndex() <= BI.LastSplitPoint) {
DEBUG(dbgs() << ", free use at " << Use << ".\n");
- SlotIndex SegStart = SE.enterIntvBefore(Use);
+ SlotIndex SegStart = SE->enterIntvBefore(Use);
assert(SegStart >= IP.second && "Couldn't avoid interference");
assert(SegStart < BI.LastSplitPoint && "Impossible split point");
- SE.useIntv(SegStart, Stop);
+ SE->useIntv(SegStart, BI.Stop);
continue;
}
}
// Interference is after the last use.
DEBUG(dbgs() << " after last use.\n");
- SlotIndex SegStart = SE.enterIntvAtEnd(*BI.MBB);
+ SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
assert(SegStart >= IP.second && "Couldn't avoid interference");
}
// We have an incoming register. Check for interference.
IndexPair &IP = InterferenceRanges[i];
- SlotIndex Start, Stop;
- tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
- << " -> BB#" << BI.MBB->getNumber());
+ << " -> BB#" << BI.MBB->getNumber() << " [" << BI.Start << ';'
+ << BI.LastSplitPoint << '-' << BI.Stop << ')');
// Check interference entering the block.
if (!IP.first.isValid()) {
// Block is live-through without interference.
if (RegOut) {
DEBUG(dbgs() << ", no uses, live-through.\n");
- SE.useIntv(Start, Stop);
+ SE->useIntv(BI.Start, BI.Stop);
} else {
DEBUG(dbgs() << ", no uses, stack-out.\n");
- SE.leaveIntvAtTop(*BI.MBB);
+ SE->leaveIntvAtTop(*BI.MBB);
}
continue;
}
if (!BI.LiveThrough) {
DEBUG(dbgs() << ", killed in block.\n");
- SE.useIntv(Start, SE.leaveIntvAfter(BI.Kill));
+ SE->useIntv(BI.Start, SE->leaveIntvAfter(BI.Kill));
continue;
}
if (!RegOut) {
// Spill immediately after the last use.
if (BI.LastUse < BI.LastSplitPoint) {
DEBUG(dbgs() << ", uses, stack-out.\n");
- SE.useIntv(Start, SE.leaveIntvAfter(BI.LastUse));
+ SE->useIntv(BI.Start, SE->leaveIntvAfter(BI.LastUse));
continue;
}
// The last use is after the last split point, it is probably an
// indirect jump.
DEBUG(dbgs() << ", uses at " << BI.LastUse << " after split point "
<< BI.LastSplitPoint << ", stack-out.\n");
- SlotIndex SegEnd;
- // Find the last real instruction before the split point.
- MachineBasicBlock::iterator SplitI =
- LIS->getInstructionFromIndex(BI.LastSplitPoint);
- MachineBasicBlock::iterator I = SplitI, B = BI.MBB->begin();
- while (I != B && (--I)->isDebugValue())
- ;
- if (I == SplitI)
- SegEnd = SE.leaveIntvAtTop(*BI.MBB);
- else {
- SegEnd = SE.leaveIntvAfter(LIS->getInstructionIndex(I));
- SE.useIntv(Start, SegEnd);
- }
+ SlotIndex SegEnd = SE->leaveIntvBefore(BI.LastSplitPoint);
+ SE->useIntv(BI.Start, SegEnd);
// Run a double interval from the split to the last use.
// This makes it possible to spill the complement without affecting the
// indirect branch.
- SE.overlapIntv(SegEnd, BI.LastUse);
+ SE->overlapIntv(SegEnd, BI.LastUse);
continue;
}
// Register is live-through.
DEBUG(dbgs() << ", uses, live-through.\n");
- SE.useIntv(Start, Stop);
+ SE->useIntv(BI.Start, BI.Stop);
continue;
}
if (!BI.LiveThrough && IP.first >= BI.Kill) {
// The interference doesn't reach the outgoing segment.
DEBUG(dbgs() << " doesn't affect kill at " << BI.Kill << '\n');
- SE.useIntv(Start, BI.Kill);
+ SE->useIntv(BI.Start, BI.Kill);
continue;
}
if (!BI.Uses) {
// No uses in block, avoid interference by spilling as soon as possible.
DEBUG(dbgs() << ", no uses.\n");
- SlotIndex SegEnd = SE.leaveIntvAtTop(*BI.MBB);
+ SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
assert(SegEnd <= IP.first && "Couldn't avoid interference");
continue;
}
assert(UI != SA->UseSlots.begin() && "Couldn't find first use");
SlotIndex Use = (--UI)->getBoundaryIndex();
DEBUG(dbgs() << ", free use at " << *UI << ".\n");
- SlotIndex SegEnd = SE.leaveIntvAfter(Use);
+ SlotIndex SegEnd = SE->leaveIntvAfter(Use);
assert(SegEnd <= IP.first && "Couldn't avoid interference");
- SE.useIntv(Start, SegEnd);
+ SE->useIntv(BI.Start, SegEnd);
continue;
}
// Interference is before the first use.
DEBUG(dbgs() << " before first use.\n");
- SlotIndex SegEnd = SE.leaveIntvAtTop(*BI.MBB);
+ SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
assert(SegEnd <= IP.first && "Couldn't avoid interference");
}
- SE.closeIntv();
+ SE->closeIntv();
// FIXME: Should we be more aggressive about splitting the stack region into
// per-block segments? The current approach allows the stack region to
// separate into connected components. Some components may be allocatable.
- SE.finish();
+ SE->finish();
+ ++NumGlobalSplits;
- if (VerifyEnabled) {
+ if (VerifyEnabled)
MF->verify(this, "After splitting live range around region");
-
-#ifndef NDEBUG
- // Make sure that at least one of the new intervals can allocate to PhysReg.
- // That was the whole point of splitting the live range.
- bool found = false;
- for (LiveRangeEdit::iterator I = LREdit.begin(), E = LREdit.end(); I != E;
- ++I)
- if (!checkUncachedInterference(**I, PhysReg)) {
- found = true;
- break;
- }
- assert(found && "No allocatable intervals after pointless splitting");
-#endif
- }
}
unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
BitVector LiveBundles, BestBundles;
float BestCost = 0;
unsigned BestReg = 0;
+
Order.rewind();
- while (unsigned PhysReg = Order.next()) {
- float Cost = calcInterferenceInfo(VirtReg, PhysReg);
- if (BestReg && Cost >= BestCost)
+ for (unsigned Cand = 0; unsigned PhysReg = Order.next(); ++Cand) {
+ if (GlobalCand.size() <= Cand)
+ GlobalCand.resize(Cand+1);
+ GlobalCand[Cand].PhysReg = PhysReg;
+
+ mapGlobalInterference(PhysReg, GlobalCand[Cand].Interference);
+ float Cost = calcSplitConstraints(GlobalCand[Cand].Interference);
+ DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tstatic = " << Cost);
+ if (BestReg && Cost >= BestCost) {
+ DEBUG(dbgs() << " higher.\n");
continue;
+ }
- SpillPlacer->placeSpills(SpillConstraints, LiveBundles);
+ SpillPlacer->placeSpills(SplitConstraints, LiveBundles);
// No live bundles, defer to splitSingleBlocks().
- if (!LiveBundles.any())
+ if (!LiveBundles.any()) {
+ DEBUG(dbgs() << " no bundles.\n");
continue;
+ }
Cost += calcGlobalSplitCost(LiveBundles);
+ DEBUG({
+ dbgs() << ", total = " << Cost << " with bundles";
+ for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
+ dbgs() << " EB#" << i;
+ dbgs() << ".\n";
+ });
if (!BestReg || Cost < BestCost) {
BestReg = PhysReg;
- BestCost = Cost;
+ BestCost = 0.98f * Cost; // Prevent rounding effects.
BestBundles.swap(LiveBundles);
}
}
return 0;
splitAroundRegion(VirtReg, BestReg, BestBundles, NewVRegs);
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Region);
return 0;
}
//===----------------------------------------------------------------------===//
-// Live Range Splitting
+// Local Splitting
//===----------------------------------------------------------------------===//
-/// trySplit - Try to split VirtReg or one of its interferences, making it
-/// assignable.
-/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
-unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
- SmallVectorImpl<LiveInterval*>&NewVRegs) {
- NamedRegionTimer T("Splitter", TimerGroupName, TimePassesIsEnabled);
- SA->analyze(&VirtReg);
- // Don't attempt splitting on local intervals for now. TBD.
- if (LIS->intervalIsInOneMBB(VirtReg))
- return 0;
+/// calcGapWeights - Compute the maximum spill weight that needs to be evicted
+/// in order to use PhysReg between two entries in SA->UseSlots.
+///
+/// GapWeight[i] represents the gap between UseSlots[i] and UseSlots[i+1].
+///
+void RAGreedy::calcGapWeights(unsigned PhysReg,
+ SmallVectorImpl<float> &GapWeight) {
+ assert(SA->LiveBlocks.size() == 1 && "Not a local interval");
+ const SplitAnalysis::BlockInfo &BI = SA->LiveBlocks.front();
+ const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
+ const unsigned NumGaps = Uses.size()-1;
- // First try to split around a region spanning multiple blocks.
- unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
- if (PhysReg || !NewVRegs.empty())
- return PhysReg;
+ // Start and end points for the interference check.
+ SlotIndex StartIdx = BI.LiveIn ? BI.FirstUse.getBaseIndex() : BI.FirstUse;
+ SlotIndex StopIdx = BI.LiveOut ? BI.LastUse.getBoundaryIndex() : BI.LastUse;
- // Then isolate blocks with multiple uses.
- SplitAnalysis::BlockPtrSet Blocks;
- if (SA->getMultiUseBlocks(Blocks)) {
- SmallVector<LiveInterval*, 4> SpillRegs;
- LiveRangeEdit LREdit(VirtReg, NewVRegs, SpillRegs);
- SplitEditor(*SA, *LIS, *VRM, *DomTree, LREdit).splitSingleBlocks(Blocks);
- if (VerifyEnabled)
- MF->verify(this, "After splitting live range around basic blocks");
- }
+ GapWeight.assign(NumGaps, 0.0f);
- // Don't assign any physregs.
- return 0;
-}
+ // Add interference from each overlapping register.
+ for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
+ if (!query(const_cast<LiveInterval&>(SA->getParent()), *AI)
+ .checkInterference())
+ continue;
+ // We know that VirtReg is a continuous interval from FirstUse to LastUse,
+ // so we don't need InterferenceQuery.
+ //
+ // Interference that overlaps an instruction is counted in both gaps
+ // surrounding the instruction. The exception is interference before
+ // StartIdx and after StopIdx.
+ //
+ LiveIntervalUnion::SegmentIter IntI = PhysReg2LiveUnion[*AI].find(StartIdx);
+ for (unsigned Gap = 0; IntI.valid() && IntI.start() < StopIdx; ++IntI) {
+ // Skip the gaps before IntI.
+ while (Uses[Gap+1].getBoundaryIndex() < IntI.start())
+ if (++Gap == NumGaps)
+ break;
+ if (Gap == NumGaps)
+ break;
-//===----------------------------------------------------------------------===//
-// Spilling
-//===----------------------------------------------------------------------===//
+ // Update the gaps covered by IntI.
+ const float weight = IntI.value()->weight;
+ for (; Gap != NumGaps; ++Gap) {
+ GapWeight[Gap] = std::max(GapWeight[Gap], weight);
+ if (Uses[Gap+1].getBaseIndex() >= IntI.stop())
+ break;
+ }
+ if (Gap == NumGaps)
+ break;
+ }
+ }
+}
-/// calcInterferenceWeight - Calculate the combined spill weight of
-/// interferences when assigning VirtReg to PhysReg.
-float RAGreedy::calcInterferenceWeight(LiveInterval &VirtReg, unsigned PhysReg){
- float Sum = 0;
- for (const unsigned *AI = TRI->getOverlaps(PhysReg); *AI; ++AI) {
- LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
- Q.collectInterferingVRegs();
- if (Q.seenUnspillableVReg())
- return HUGE_VALF;
- for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i)
- Sum += Q.interferingVRegs()[i]->weight;
+/// getPrevMappedIndex - Return the slot index of the last non-copy instruction
+/// before MI that has a slot index. If MI is the first mapped instruction in
+/// its block, return the block start index instead.
+///
+SlotIndex RAGreedy::getPrevMappedIndex(const MachineInstr *MI) {
+ assert(MI && "Missing MachineInstr");
+ const MachineBasicBlock *MBB = MI->getParent();
+ MachineBasicBlock::const_iterator B = MBB->begin(), I = MI;
+ while (I != B)
+ if (!(--I)->isDebugValue() && !I->isCopy())
+ return Indexes->getInstructionIndex(I);
+ return Indexes->getMBBStartIdx(MBB);
+}
+
+/// calcPrevSlots - Fill in the PrevSlot array with the index of the previous
+/// real non-copy instruction for each instruction in SA->UseSlots.
+///
+void RAGreedy::calcPrevSlots() {
+ const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
+ PrevSlot.clear();
+ PrevSlot.reserve(Uses.size());
+ for (unsigned i = 0, e = Uses.size(); i != e; ++i) {
+ const MachineInstr *MI = Indexes->getInstructionFromIndex(Uses[i]);
+ PrevSlot.push_back(getPrevMappedIndex(MI).getDefIndex());
}
- return Sum;
}
-/// trySpillInterferences - Try to spill interfering registers instead of the
-/// current one. Only do it if the accumulated spill weight is smaller than the
-/// current spill weight.
-unsigned RAGreedy::trySpillInterferences(LiveInterval &VirtReg,
- AllocationOrder &Order,
- SmallVectorImpl<LiveInterval*> &NewVRegs) {
- NamedRegionTimer T("Spill Interference", TimerGroupName, TimePassesIsEnabled);
- unsigned BestPhys = 0;
- float BestWeight = 0;
+/// nextSplitPoint - Find the next index into SA->UseSlots > i such that it may
+/// be beneficial to split before UseSlots[i].
+///
+/// 0 is always a valid split point
+unsigned RAGreedy::nextSplitPoint(unsigned i) {
+ const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
+ const unsigned Size = Uses.size();
+ assert(i != Size && "No split points after the end");
+ // Allow split before i when Uses[i] is not adjacent to the previous use.
+ while (++i != Size && PrevSlot[i].getBaseIndex() <= Uses[i-1].getBaseIndex())
+ ;
+ return i;
+}
+
+/// tryLocalSplit - Try to split VirtReg into smaller intervals inside its only
+/// basic block.
+///
+unsigned RAGreedy::tryLocalSplit(LiveInterval &VirtReg, AllocationOrder &Order,
+ SmallVectorImpl<LiveInterval*> &NewVRegs) {
+ assert(SA->LiveBlocks.size() == 1 && "Not a local interval");
+ const SplitAnalysis::BlockInfo &BI = SA->LiveBlocks.front();
+
+ // Note that it is possible to have an interval that is live-in or live-out
+ // while only covering a single block - A phi-def can use undef values from
+ // predecessors, and the block could be a single-block loop.
+ // We don't bother doing anything clever about such a case, we simply assume
+ // that the interval is continuous from FirstUse to LastUse. We should make
+ // sure that we don't do anything illegal to such an interval, though.
+
+ const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
+ if (Uses.size() <= 2)
+ return 0;
+ const unsigned NumGaps = Uses.size()-1;
+
+ DEBUG({
+ dbgs() << "tryLocalSplit: ";
+ for (unsigned i = 0, e = Uses.size(); i != e; ++i)
+ dbgs() << ' ' << SA->UseSlots[i];
+ dbgs() << '\n';
+ });
+
+ // For every use, find the previous mapped non-copy instruction.
+ // We use this to detect valid split points, and to estimate new interval
+ // sizes.
+ calcPrevSlots();
+
+ unsigned BestBefore = NumGaps;
+ unsigned BestAfter = 0;
+ float BestDiff = 0;
+
+ const float blockFreq = SpillPlacer->getBlockFrequency(BI.MBB->getNumber());
+ SmallVector<float, 8> GapWeight;
Order.rewind();
while (unsigned PhysReg = Order.next()) {
- float Weight = calcInterferenceWeight(VirtReg, PhysReg);
- if (Weight == HUGE_VALF || Weight >= VirtReg.weight)
- continue;
- if (!BestPhys || Weight < BestWeight)
- BestPhys = PhysReg, BestWeight = Weight;
+ // Keep track of the largest spill weight that would need to be evicted in
+ // order to make use of PhysReg between UseSlots[i] and UseSlots[i+1].
+ calcGapWeights(PhysReg, GapWeight);
+
+ // Try to find the best sequence of gaps to close.
+ // The new spill weight must be larger than any gap interference.
+
+ // We will split before Uses[SplitBefore] and after Uses[SplitAfter].
+ unsigned SplitBefore = 0, SplitAfter = nextSplitPoint(1) - 1;
+
+ // MaxGap should always be max(GapWeight[SplitBefore..SplitAfter-1]).
+ // It is the spill weight that needs to be evicted.
+ float MaxGap = GapWeight[0];
+ for (unsigned i = 1; i != SplitAfter; ++i)
+ MaxGap = std::max(MaxGap, GapWeight[i]);
+
+ for (;;) {
+ // Live before/after split?
+ const bool LiveBefore = SplitBefore != 0 || BI.LiveIn;
+ const bool LiveAfter = SplitAfter != NumGaps || BI.LiveOut;
+
+ DEBUG(dbgs() << PrintReg(PhysReg, TRI) << ' '
+ << Uses[SplitBefore] << '-' << Uses[SplitAfter]
+ << " i=" << MaxGap);
+
+ // Stop before the interval gets so big we wouldn't be making progress.
+ if (!LiveBefore && !LiveAfter) {
+ DEBUG(dbgs() << " all\n");
+ break;
+ }
+ // Should the interval be extended or shrunk?
+ bool Shrink = true;
+ if (MaxGap < HUGE_VALF) {
+ // Estimate the new spill weight.
+ //
+ // Each instruction reads and writes the register, except the first
+ // instr doesn't read when !FirstLive, and the last instr doesn't write
+ // when !LastLive.
+ //
+ // We will be inserting copies before and after, so the total number of
+ // reads and writes is 2 * EstUses.
+ //
+ const unsigned EstUses = 2*(SplitAfter - SplitBefore) +
+ 2*(LiveBefore + LiveAfter);
+
+ // Try to guess the size of the new interval. This should be trivial,
+ // but the slot index of an inserted copy can be a lot smaller than the
+ // instruction it is inserted before if there are many dead indexes
+ // between them.
+ //
+ // We measure the distance from the instruction before SplitBefore to
+ // get a conservative estimate.
+ //
+ // The final distance can still be different if inserting copies
+ // triggers a slot index renumbering.
+ //
+ const float EstWeight = normalizeSpillWeight(blockFreq * EstUses,
+ PrevSlot[SplitBefore].distance(Uses[SplitAfter]));
+ // Would this split be possible to allocate?
+ // Never allocate all gaps, we wouldn't be making progress.
+ float Diff = EstWeight - MaxGap;
+ DEBUG(dbgs() << " w=" << EstWeight << " d=" << Diff);
+ if (Diff > 0) {
+ Shrink = false;
+ if (Diff > BestDiff) {
+ DEBUG(dbgs() << " (best)");
+ BestDiff = Diff;
+ BestBefore = SplitBefore;
+ BestAfter = SplitAfter;
+ }
+ }
+ }
+
+ // Try to shrink.
+ if (Shrink) {
+ SplitBefore = nextSplitPoint(SplitBefore);
+ if (SplitBefore < SplitAfter) {
+ DEBUG(dbgs() << " shrink\n");
+ // Recompute the max when necessary.
+ if (GapWeight[SplitBefore - 1] >= MaxGap) {
+ MaxGap = GapWeight[SplitBefore];
+ for (unsigned i = SplitBefore + 1; i != SplitAfter; ++i)
+ MaxGap = std::max(MaxGap, GapWeight[i]);
+ }
+ continue;
+ }
+ MaxGap = 0;
+ }
+
+ // Try to extend the interval.
+ if (SplitAfter >= NumGaps) {
+ DEBUG(dbgs() << " end\n");
+ break;
+ }
+
+ DEBUG(dbgs() << " extend\n");
+ for (unsigned e = nextSplitPoint(SplitAfter + 1) - 1;
+ SplitAfter != e; ++SplitAfter)
+ MaxGap = std::max(MaxGap, GapWeight[SplitAfter]);
+ continue;
+ }
}
- // No candidates found.
- if (!BestPhys)
+ // Didn't find any candidates?
+ if (BestBefore == NumGaps)
return 0;
- // Collect all interfering registers.
- SmallVector<LiveInterval*, 8> Spills;
- for (const unsigned *AI = TRI->getOverlaps(BestPhys); *AI; ++AI) {
- LiveIntervalUnion::Query &Q = query(VirtReg, *AI);
- Spills.append(Q.interferingVRegs().begin(), Q.interferingVRegs().end());
- for (unsigned i = 0, e = Q.interferingVRegs().size(); i != e; ++i) {
- LiveInterval *VReg = Q.interferingVRegs()[i];
- unassign(*VReg, *AI);
+ DEBUG(dbgs() << "Best local split range: " << Uses[BestBefore]
+ << '-' << Uses[BestAfter] << ", " << BestDiff
+ << ", " << (BestAfter - BestBefore + 1) << " instrs\n");
+
+ LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
+ SE->reset(LREdit);
+
+ SE->openIntv();
+ SlotIndex SegStart = SE->enterIntvBefore(Uses[BestBefore]);
+ SlotIndex SegStop = SE->leaveIntvAfter(Uses[BestAfter]);
+ SE->useIntv(SegStart, SegStop);
+ SE->closeIntv();
+ SE->finish();
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Local);
+ ++NumLocalSplits;
+
+ return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Live Range Splitting
+//===----------------------------------------------------------------------===//
+
+/// trySplit - Try to split VirtReg or one of its interferences, making it
+/// assignable.
+/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
+unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
+ SmallVectorImpl<LiveInterval*>&NewVRegs) {
+ // Local intervals are handled separately.
+ if (LIS->intervalIsInOneMBB(VirtReg)) {
+ NamedRegionTimer T("Local Splitting", TimerGroupName, TimePassesIsEnabled);
+ SA->analyze(&VirtReg);
+ return tryLocalSplit(VirtReg, Order, NewVRegs);
+ }
+
+ NamedRegionTimer T("Global Splitting", TimerGroupName, TimePassesIsEnabled);
+
+ // Don't iterate global splitting.
+ // Move straight to spilling if this range was produced by a global split.
+ LiveRangeStage Stage = getStage(VirtReg);
+ if (Stage >= RS_Block)
+ return 0;
+
+ SA->analyze(&VirtReg);
+
+ // First try to split around a region spanning multiple blocks.
+ if (Stage < RS_Region) {
+ unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
+ if (PhysReg || !NewVRegs.empty())
+ return PhysReg;
+ }
+
+ // Then isolate blocks with multiple uses.
+ if (Stage < RS_Block) {
+ SplitAnalysis::BlockPtrSet Blocks;
+ if (SA->getMultiUseBlocks(Blocks)) {
+ LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
+ SE->reset(LREdit);
+ SE->splitSingleBlocks(Blocks);
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Block);
+ if (VerifyEnabled)
+ MF->verify(this, "After splitting live range around basic blocks");
}
}
- // Spill them all.
- DEBUG(dbgs() << "spilling " << Spills.size() << " interferences with weight "
- << BestWeight << '\n');
- for (unsigned i = 0, e = Spills.size(); i != e; ++i)
- spiller().spill(Spills[i], NewVRegs, Spills);
- return BestPhys;
+ // Don't assign any physregs.
+ return 0;
}
return PhysReg;
}
- // Try to reassign interferences.
- if (unsigned PhysReg = tryReassignOrEvict(VirtReg, Order, NewVRegs))
+ if (unsigned PhysReg = tryEvict(VirtReg, Order, NewVRegs))
return PhysReg;
assert(NewVRegs.empty() && "Cannot append to existing NewVRegs");
+ // The first time we see a live range, don't try to split or spill.
+ // Wait until the second time, when all smaller ranges have been allocated.
+ // This gives a better picture of the interference to split around.
+ LiveRangeStage Stage = getStage(VirtReg);
+ if (Stage == RS_Original) {
+ LRStage[VirtReg.reg] = RS_Second;
+ DEBUG(dbgs() << "wait for second round\n");
+ NewVRegs.push_back(&VirtReg);
+ return 0;
+ }
+
+ assert(Stage < RS_Spill && "Cannot allocate after spilling");
+
// Try splitting VirtReg or interferences.
unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs);
if (PhysReg || !NewVRegs.empty())
return PhysReg;
- // Try to spill another interfering reg with less spill weight.
- PhysReg = trySpillInterferences(VirtReg, Order, NewVRegs);
- if (PhysReg)
- return PhysReg;
-
// Finally spill VirtReg itself.
NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
- SmallVector<LiveInterval*, 1> pendingSpills;
- spiller().spill(&VirtReg, NewVRegs, pendingSpills);
+ LiveRangeEdit LRE(VirtReg, NewVRegs, this);
+ spiller().spill(LRE);
+
+ if (VerifyEnabled)
+ MF->verify(this, "After spilling");
// The live virtual register requesting allocation was spilled, so tell
// the caller not to allocate anything during this round.
Bundles = &getAnalysis<EdgeBundles>();
SpillPlacer = &getAnalysis<SpillPlacement>();
- SA.reset(new SplitAnalysis(*MF, *LIS, *Loops));
+ SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
+ SE.reset(new SplitEditor(*SA, *LIS, *VRM, *DomTree));
+ LRStage.clear();
+ LRStage.resize(MRI->getNumVirtRegs());
allocatePhysRegs();
addMBBLiveIns(MF);
// Run rewriter
{
NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
- std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
- rewriter->runOnMachineFunction(*MF, *VRM, LIS);
+ VRM->rewrite(Indexes);
}
// The pass output is in VirtRegMap. Release all the transient data.
projects / oota-llvm.git / blobdiff