#define DEBUG_TYPE "regalloc"
#include "AllocationOrder.h"
-#include "LiveIntervalUnion.h"
+#include "InterferenceCache.h"
+#include "LiveDebugVariables.h"
+#include "LiveRangeEdit.h"
#include "RegAllocBase.h"
#include "Spiller.h"
+#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/CodeGen/CalcSpillWeights.h"
+#include "llvm/CodeGen/EdgeBundles.h"
#include "llvm/CodeGen/LiveIntervalAnalysis.h"
#include "llvm/CodeGen/LiveStackAnalysis.h"
+#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/MachineLoopRanges.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/RegAllocRegistry.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;
// analyses
+ SlotIndexes *Indexes;
LiveStacks *LS;
+ MachineDominatorTree *DomTree;
+ MachineLoopInfo *Loops;
+ MachineLoopRanges *LoopRanges;
+ EdgeBundles *Bundles;
+ SpillPlacement *SpillPlacer;
// state
std::auto_ptr<Spiller> SpillerInstance;
+ 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_New, ///< Never seen before.
+ RS_First, ///< First time in the queue.
+ RS_Second, ///< Second time in the queue.
+ RS_Global, ///< Produced by global 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) {
+ unsigned Reg = (*Begin)->reg;
+ if (LRStage[Reg] == RS_New)
+ LRStage[Reg] = NewStage;
+ }
+ }
+
+ // splitting state.
+ std::auto_ptr<SplitAnalysis> SA;
+ std::auto_ptr<SplitEditor> SE;
+
+ /// Cached per-block interference maps
+ InterferenceCache IntfCache;
+
+ /// All basic blocks where the current register has uses.
+ SmallVector<SpillPlacement::BlockConstraint, 8> SplitConstraints;
+
+ /// Global live range splitting candidate info.
+ struct GlobalSplitCandidate {
+ unsigned PhysReg;
+ BitVector LiveBundles;
+ SmallVector<unsigned, 8> ActiveBlocks;
+
+ void reset(unsigned Reg) {
+ PhysReg = Reg;
+ LiveBundles.clear();
+ ActiveBlocks.clear();
+ }
+ };
+
+ /// 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 unsigned selectOrSplit(LiveInterval &VirtReg,
- SmallVectorImpl<LiveInterval*> &SplitVRegs);
+ virtual void enqueue(LiveInterval *LI);
+ virtual LiveInterval *dequeue();
+ virtual unsigned selectOrSplit(LiveInterval&,
+ SmallVectorImpl<LiveInterval*>&);
/// Perform register allocation.
virtual bool runOnMachineFunction(MachineFunction &mf);
static char ID;
private:
- bool checkUncachedInterference(LiveInterval&, unsigned);
- LiveInterval *getSingleInterference(LiveInterval&, unsigned);
- bool reassignVReg(LiveInterval &InterferingVReg, unsigned OldPhysReg);
- bool reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg);
+ void LRE_WillEraseInstruction(MachineInstr*);
+ bool LRE_CanEraseVirtReg(unsigned);
+ void LRE_WillShrinkVirtReg(unsigned);
+ void LRE_DidCloneVirtReg(unsigned, unsigned);
- unsigned tryReassign(LiveInterval&, AllocationOrder&);
+ bool addSplitConstraints(InterferenceCache::Cursor, float&);
+ void addThroughConstraints(InterferenceCache::Cursor, ArrayRef<unsigned>);
+ void growRegion(GlobalSplitCandidate &Cand, InterferenceCache::Cursor);
+ float calcGlobalSplitCost(GlobalSplitCandidate&, InterferenceCache::Cursor);
+ void splitAroundRegion(LiveInterval&, GlobalSplitCandidate&,
+ SmallVectorImpl<LiveInterval*>&);
+ void calcGapWeights(unsigned, SmallVectorImpl<float>&);
+ SlotIndex getPrevMappedIndex(const MachineInstr*);
+ void calcPrevSlots();
+ unsigned nextSplitPoint(unsigned);
+ bool canEvictInterference(LiveInterval&, unsigned, float&);
+
+ unsigned tryEvict(LiveInterval&, AllocationOrder&,
+ SmallVectorImpl<LiveInterval*>&);
+ unsigned tryRegionSplit(LiveInterval&, AllocationOrder&,
+ SmallVectorImpl<LiveInterval*>&);
+ unsigned tryLocalSplit(LiveInterval&, AllocationOrder&,
+ SmallVectorImpl<LiveInterval*>&);
unsigned trySplit(LiveInterval&, AllocationOrder&,
SmallVectorImpl<LiveInterval*>&);
};
return new RAGreedy();
}
-RAGreedy::RAGreedy(): MachineFunctionPass(ID) {
+RAGreedy::RAGreedy(): MachineFunctionPass(ID), LRStage(RS_New) {
+ initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
+ initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeLiveIntervalsPass(*PassRegistry::getPassRegistry());
initializeSlotIndexesPass(*PassRegistry::getPassRegistry());
initializeStrongPHIEliminationPass(*PassRegistry::getPassRegistry());
initializeLiveStacksPass(*PassRegistry::getPassRegistry());
initializeMachineDominatorTreePass(*PassRegistry::getPassRegistry());
initializeMachineLoopInfoPass(*PassRegistry::getPassRegistry());
+ initializeMachineLoopRangesPass(*PassRegistry::getPassRegistry());
initializeVirtRegMapPass(*PassRegistry::getPassRegistry());
+ initializeEdgeBundlesPass(*PassRegistry::getPassRegistry());
+ initializeSpillPlacementPass(*PassRegistry::getPassRegistry());
}
void RAGreedy::getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<AliasAnalysis>();
AU.addPreserved<AliasAnalysis>();
AU.addRequired<LiveIntervals>();
+ AU.addRequired<SlotIndexes>();
AU.addPreserved<SlotIndexes>();
+ AU.addRequired<LiveDebugVariables>();
+ AU.addPreserved<LiveDebugVariables>();
if (StrongPHIElim)
AU.addRequiredID(StrongPHIEliminationID);
AU.addRequiredTransitive<RegisterCoalescer>();
AU.addRequired<CalculateSpillWeights>();
AU.addRequired<LiveStacks>();
AU.addPreserved<LiveStacks>();
- AU.addRequiredID(MachineDominatorsID);
- AU.addPreservedID(MachineDominatorsID);
+ AU.addRequired<MachineDominatorTree>();
+ AU.addPreserved<MachineDominatorTree>();
AU.addRequired<MachineLoopInfo>();
AU.addPreserved<MachineLoopInfo>();
+ AU.addRequired<MachineLoopRanges>();
+ AU.addPreserved<MachineLoopRanges>();
AU.addRequired<VirtRegMap>();
AU.addPreserved<VirtRegMap>();
+ AU.addRequired<EdgeBundles>();
+ AU.addRequired<SpillPlacement>();
MachineFunctionPass::getAnalysisUsage(AU);
}
+
+//===----------------------------------------------------------------------===//
+// LiveRangeEdit delegate methods
+//===----------------------------------------------------------------------===//
+
+void RAGreedy::LRE_WillEraseInstruction(MachineInstr *MI) {
+ // LRE itself will remove from SlotIndexes and parent basic block.
+ VRM->RemoveMachineInstrFromMaps(MI);
+}
+
+bool RAGreedy::LRE_CanEraseVirtReg(unsigned VirtReg) {
+ if (unsigned PhysReg = VRM->getPhys(VirtReg)) {
+ unassign(LIS->getInterval(VirtReg), PhysReg);
+ return true;
+ }
+ // 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 is assigned, put it back on the queue for reassignment.
+ LiveInterval &LI = LIS->getInterval(VirtReg);
+ unassign(LI, PhysReg);
+ enqueue(&LI);
+}
+
+void RAGreedy::LRE_DidCloneVirtReg(unsigned New, unsigned Old) {
+ // LRE may clone a virtual register because dead code elimination causes it to
+ // be split into connected components. Ensure that the new register gets the
+ // same stage as the parent.
+ LRStage.grow(New);
+ LRStage[New] = LRStage[Old];
+}
+
void RAGreedy::releaseMemory() {
SpillerInstance.reset(0);
+ LRStage.clear();
+ GlobalCand.clear();
RegAllocBase::releaseMemory();
}
-float RAGreedy::getPriority(LiveInterval *LI) {
- float Priority = LI->weight;
+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_New)
+ LRStage[Reg] = RS_First;
- // 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;
+ 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;
- // Prefer physreg hints above anything else.
- if (Hint.first == 0 && TargetRegisterInfo::isPhysicalRegister(Hint.second))
- Priority *= 2;
+ // Boost ranges that have a physical register hint.
+ if (TargetRegisterInfo::isPhysicalRegister(VRM->getRegAllocPref(Reg)))
+ Prio |= (1u << 30);
}
- return Priority;
+
+ Queue.push(std::make_pair(Prio, Reg));
+}
+
+LiveInterval *RAGreedy::dequeue() {
+ if (Queue.empty())
+ return 0;
+ LiveInterval *LI = &LIS->getInterval(Queue.top().second);
+ Queue.pop();
+ return LI;
}
-// Check interference without using the cache.
-bool RAGreedy::checkUncachedInterference(LiveInterval &VirtReg,
- unsigned PhysReg) {
- LiveIntervalUnion::Query subQ(&VirtReg, &PhysReg2LiveUnion[PhysReg]);
- if (subQ.checkInterference())
- return true;
- for (const unsigned *AliasI = TRI->getAliasSet(PhysReg); *AliasI; ++AliasI) {
- subQ.init(&VirtReg, &PhysReg2LiveUnion[*AliasI]);
- if (subQ.checkInterference())
- return true;
+//===----------------------------------------------------------------------===//
+// Interference eviction
+//===----------------------------------------------------------------------===//
+
+/// canEvict - Return true if all interferences between VirtReg and PhysReg can
+/// be evicted.
+/// Return false if any interference is heavier than MaxWeight.
+/// On return, 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 heavier.
+ if (Q.collectInterferingVRegs(10, MaxWeight) >= 10)
+ return false;
+
+ // Check if any interfering live range is heavier than MaxWeight.
+ for (unsigned i = Q.interferingVRegs().size(); i; --i) {
+ LiveInterval *Intf = Q.interferingVRegs()[i - 1];
+ if (TargetRegisterInfo::isPhysicalRegister(Intf->reg))
+ return false;
+ if (Intf->weight >= MaxWeight)
+ return false;
+ Weight = std::max(Weight, Intf->weight);
+ }
}
- return false;
+ MaxWeight = Weight;
+ return true;
}
-/// 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) {
- LiveInterval *Interference = 0;
-
- // Check direct interferences.
- LiveIntervalUnion::Query &Q = query(VirtReg, PhysReg);
- if (Q.checkInterference()) {
- Q.collectInterferingVRegs(1);
- if (!Q.seenAllInterferences())
- return 0;
- Interference = Q.interferingVRegs().front();
+/// 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::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;
+ unsigned BestPhys = 0;
+
+ Order.rewind();
+ while (unsigned PhysReg = Order.next()) {
+ float Weight = BestWeight;
+ if (!canEvictInterference(VirtReg, PhysReg, Weight))
+ continue;
+
+ // This is an eviction candidate.
+ DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " interference = "
+ << Weight << '\n');
+ if (BestPhys && Weight >= BestWeight)
+ continue;
+
+ // Best so far.
+ BestPhys = PhysReg;
+ BestWeight = Weight;
+ // Stop if the hint can be used.
+ if (Order.isHint(PhysReg))
+ break;
}
- // Check aliases.
- for (const unsigned *AliasI = TRI->getAliasSet(PhysReg); *AliasI; ++AliasI) {
+ if (!BestPhys)
+ 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);
- if (Q.checkInterference()) {
- if (Interference)
- return 0;
- Q.collectInterferingVRegs(1);
- if (!Q.seenAllInterferences())
- return 0;
- Interference = Q.interferingVRegs().front();
+ 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 Interference;
+ return BestPhys;
}
-// 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))
+
+//===----------------------------------------------------------------------===//
+// Region Splitting
+//===----------------------------------------------------------------------===//
+
+/// addSplitConstraints - Fill out the SplitConstraints vector based on the
+/// interference pattern in Physreg and its aliases. Add the constraints to
+/// SpillPlacement and return the static cost of this split in Cost, assuming
+/// that all preferences in SplitConstraints are met.
+/// Return false if there are no bundles with positive bias.
+bool RAGreedy::addSplitConstraints(InterferenceCache::Cursor Intf,
+ float &Cost) {
+ ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
+
+ // Reset interference dependent info.
+ SplitConstraints.resize(UseBlocks.size());
+ float StaticCost = 0;
+ for (unsigned i = 0; i != UseBlocks.size(); ++i) {
+ const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
+ SpillPlacement::BlockConstraint &BC = SplitConstraints[i];
+
+ BC.Number = BI.MBB->getNumber();
+ Intf.moveToBlock(BC.Number);
+ BC.Entry = BI.LiveIn ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
+ BC.Exit = BI.LiveOut ? SpillPlacement::PrefReg : SpillPlacement::DontCare;
+
+ if (!Intf.hasInterference())
continue;
- if (checkUncachedInterference(InterferingVReg, PhysReg))
+ // Number of spill code instructions to insert.
+ unsigned Ins = 0;
+
+ // Interference for the live-in value.
+ if (BI.LiveIn) {
+ if (Intf.first() <= Indexes->getMBBStartIdx(BC.Number))
+ BC.Entry = SpillPlacement::MustSpill, ++Ins;
+ else if (Intf.first() < BI.FirstUse)
+ BC.Entry = SpillPlacement::PrefSpill, ++Ins;
+ else if (Intf.first() < (BI.LiveThrough ? BI.LastUse : BI.Kill))
+ ++Ins;
+ }
+
+ // Interference for the live-out value.
+ if (BI.LiveOut) {
+ if (Intf.last() >= SA->getLastSplitPoint(BC.Number))
+ BC.Exit = SpillPlacement::MustSpill, ++Ins;
+ else if (Intf.last() > BI.LastUse)
+ BC.Exit = SpillPlacement::PrefSpill, ++Ins;
+ else if (Intf.last() > (BI.LiveThrough ? BI.FirstUse : BI.Def))
+ ++Ins;
+ }
+
+ // Accumulate the total frequency of inserted spill code.
+ if (Ins)
+ StaticCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
+ }
+ Cost = StaticCost;
+
+ // Add constraints for use-blocks. Note that these are the only constraints
+ // that may add a positive bias, it is downhill from here.
+ SpillPlacer->addConstraints(SplitConstraints);
+ return SpillPlacer->scanActiveBundles();
+}
+
+
+/// addThroughConstraints - Add constraints and links to SpillPlacer from the
+/// live-through blocks in Blocks.
+void RAGreedy::addThroughConstraints(InterferenceCache::Cursor Intf,
+ ArrayRef<unsigned> Blocks) {
+ const unsigned GroupSize = 8;
+ SpillPlacement::BlockConstraint BCS[GroupSize];
+ unsigned TBS[GroupSize];
+ unsigned B = 0, T = 0;
+
+ for (unsigned i = 0; i != Blocks.size(); ++i) {
+ unsigned Number = Blocks[i];
+ Intf.moveToBlock(Number);
+
+ if (!Intf.hasInterference()) {
+ assert(T < GroupSize && "Array overflow");
+ TBS[T] = Number;
+ if (++T == GroupSize) {
+ SpillPlacer->addLinks(ArrayRef<unsigned>(TBS, T));
+ T = 0;
+ }
continue;
+ }
- // 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');
- PhysReg2LiveUnion[OldAssign].extract(InterferingVReg);
- VRM->clearVirt(InterferingVReg.reg);
- VRM->assignVirt2Phys(InterferingVReg.reg, PhysReg);
- PhysReg2LiveUnion[PhysReg].unify(InterferingVReg);
+ assert(B < GroupSize && "Array overflow");
+ BCS[B].Number = Number;
- return true;
+ // Interference for the live-in value.
+ if (Intf.first() <= Indexes->getMBBStartIdx(Number))
+ BCS[B].Entry = SpillPlacement::MustSpill;
+ else
+ BCS[B].Entry = SpillPlacement::PrefSpill;
+
+ // Interference for the live-out value.
+ if (Intf.last() >= SA->getLastSplitPoint(Number))
+ BCS[B].Exit = SpillPlacement::MustSpill;
+ else
+ BCS[B].Exit = SpillPlacement::PrefSpill;
+
+ if (++B == GroupSize) {
+ ArrayRef<SpillPlacement::BlockConstraint> Array(BCS, B);
+ SpillPlacer->addConstraints(Array);
+ B = 0;
+ }
}
- return false;
+
+ ArrayRef<SpillPlacement::BlockConstraint> Array(BCS, B);
+ SpillPlacer->addConstraints(Array);
+ SpillPlacer->addLinks(ArrayRef<unsigned>(TBS, T));
}
-/// reassignInterferences - Reassign all interferences to different physical
-/// registers such that Virtreg can be assigned to PhysReg.
-/// Currently this only works with a single interference.
-/// @param VirtReg Currently unassigned virtual register.
-/// @param PhysReg Physical register to be cleared.
-/// @return True on success, false if nothing was changed.
-bool RAGreedy::reassignInterferences(LiveInterval &VirtReg, unsigned PhysReg) {
- LiveInterval *InterferingVReg = getSingleInterference(VirtReg, PhysReg);
- if (!InterferingVReg)
- return false;
- if (TargetRegisterInfo::isPhysicalRegister(InterferingVReg->reg))
- return false;
- return reassignVReg(*InterferingVReg, PhysReg);
+void RAGreedy::growRegion(GlobalSplitCandidate &Cand,
+ InterferenceCache::Cursor Intf) {
+ // Keep track of through blocks that have not been added to SpillPlacer.
+ BitVector Todo = SA->getThroughBlocks();
+ SmallVectorImpl<unsigned> &ActiveBlocks = Cand.ActiveBlocks;
+ unsigned AddedTo = 0;
+#ifndef NDEBUG
+ unsigned Visited = 0;
+#endif
+
+ for (;;) {
+ ArrayRef<unsigned> NewBundles = SpillPlacer->getRecentPositive();
+ if (NewBundles.empty())
+ break;
+ // Find new through blocks in the periphery of PrefRegBundles.
+ for (int i = 0, e = NewBundles.size(); i != e; ++i) {
+ unsigned Bundle = NewBundles[i];
+ // Look at all blocks connected to Bundle in the full graph.
+ ArrayRef<unsigned> Blocks = Bundles->getBlocks(Bundle);
+ for (ArrayRef<unsigned>::iterator I = Blocks.begin(), E = Blocks.end();
+ I != E; ++I) {
+ unsigned Block = *I;
+ if (!Todo.test(Block))
+ continue;
+ Todo.reset(Block);
+ // This is a new through block. Add it to SpillPlacer later.
+ ActiveBlocks.push_back(Block);
+#ifndef NDEBUG
+ ++Visited;
+#endif
+ }
+ }
+ // Any new blocks to add?
+ if (ActiveBlocks.size() > AddedTo) {
+ ArrayRef<unsigned> Add(&ActiveBlocks[AddedTo],
+ ActiveBlocks.size() - AddedTo);
+ addThroughConstraints(Intf, Add);
+ AddedTo = ActiveBlocks.size();
+ }
+ // Perhaps iterating can enable more bundles?
+ SpillPlacer->iterate();
+ }
+ DEBUG(dbgs() << ", v=" << Visited);
}
-/// tryReassign - Try to reassign interferences to different physregs.
-/// @param VirtReg Currently unassigned virtual register.
-/// @param Order Physregs to try.
-/// @return Physreg to assign VirtReg, or 0.
-unsigned RAGreedy::tryReassign(LiveInterval &VirtReg, AllocationOrder &Order) {
- NamedRegionTimer T("Reassign", TimerGroupName, TimePassesIsEnabled);
+/// 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 SplitConstraints.
+///
+float RAGreedy::calcGlobalSplitCost(GlobalSplitCandidate &Cand,
+ InterferenceCache::Cursor Intf) {
+ float GlobalCost = 0;
+ const BitVector &LiveBundles = Cand.LiveBundles;
+ ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
+ for (unsigned i = 0; i != UseBlocks.size(); ++i) {
+ const SplitAnalysis::BlockInfo &BI = UseBlocks[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.LiveIn)
+ Ins += RegIn != (BC.Entry == SpillPlacement::PrefReg);
+ if (BI.LiveOut)
+ Ins += RegOut != (BC.Exit == SpillPlacement::PrefReg);
+ if (Ins)
+ GlobalCost += Ins * SpillPlacer->getBlockFrequency(BC.Number);
+ }
+
+ for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) {
+ unsigned Number = Cand.ActiveBlocks[i];
+ bool RegIn = LiveBundles[Bundles->getBundle(Number, 0)];
+ bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
+ if (!RegIn && !RegOut)
+ continue;
+ if (RegIn && RegOut) {
+ // We need double spill code if this block has interference.
+ Intf.moveToBlock(Number);
+ if (Intf.hasInterference())
+ GlobalCost += 2*SpillPlacer->getBlockFrequency(Number);
+ continue;
+ }
+ // live-in / stack-out or stack-in live-out.
+ GlobalCost += SpillPlacer->getBlockFrequency(Number);
+ }
+ return GlobalCost;
+}
+
+/// splitAroundRegion - Split VirtReg around the region determined by
+/// LiveBundles. Make an effort to avoid interference from PhysReg.
+///
+/// The 'register' interval is going to contain as many uses as possible while
+/// avoiding interference. The 'stack' interval is the complement constructed by
+/// SplitEditor. It will contain the rest.
+///
+void RAGreedy::splitAroundRegion(LiveInterval &VirtReg,
+ GlobalSplitCandidate &Cand,
+ SmallVectorImpl<LiveInterval*> &NewVRegs) {
+ const BitVector &LiveBundles = Cand.LiveBundles;
+
+ DEBUG({
+ dbgs() << "Splitting around region for " << PrintReg(Cand.PhysReg, TRI)
+ << " with bundles";
+ for (int i = LiveBundles.find_first(); i>=0; i = LiveBundles.find_next(i))
+ dbgs() << " EB#" << i;
+ dbgs() << ".\n";
+ });
+
+ InterferenceCache::Cursor Intf(IntfCache, Cand.PhysReg);
+ LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
+ SE->reset(LREdit);
+
+ // Create the main cross-block interval.
+ const unsigned MainIntv = SE->openIntv();
+
+ // First add all defs that are live out of a block.
+ ArrayRef<SplitAnalysis::BlockInfo> UseBlocks = SA->getUseBlocks();
+ for (unsigned i = 0; i != UseBlocks.size(); ++i) {
+ const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
+ bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
+ bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
+
+ // Create separate intervals for isolated blocks with multiple uses.
+ if (!RegIn && !RegOut && BI.FirstUse != BI.LastUse) {
+ DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " isolated.\n");
+ SE->splitSingleBlock(BI);
+ SE->selectIntv(MainIntv);
+ continue;
+ }
+
+ // Should the register be live out?
+ if (!BI.LiveOut || !RegOut)
+ continue;
+
+ SlotIndex Start, Stop;
+ tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
+ Intf.moveToBlock(BI.MBB->getNumber());
+ DEBUG(dbgs() << "BB#" << BI.MBB->getNumber() << " -> EB#"
+ << Bundles->getBundle(BI.MBB->getNumber(), 1)
+ << " [" << Start << ';'
+ << SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
+ << ") intf [" << Intf.first() << ';' << Intf.last() << ')');
+
+ // The interference interval should either be invalid or overlap MBB.
+ assert((!Intf.hasInterference() || Intf.first() < Stop)
+ && "Bad interference");
+ assert((!Intf.hasInterference() || Intf.last() > Start)
+ && "Bad interference");
+
+ // Check interference leaving the block.
+ if (!Intf.hasInterference()) {
+ // Block is interference-free.
+ DEBUG(dbgs() << ", no interference");
+ if (!BI.LiveThrough) {
+ DEBUG(dbgs() << ", not live-through.\n");
+ SE->useIntv(SE->enterIntvBefore(BI.Def), 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);
+ continue;
+ }
+ DEBUG(dbgs() << ", live-through.\n");
+ continue;
+ }
+
+ // Block has interference.
+ DEBUG(dbgs() << ", interference to " << Intf.last());
+
+ if (!BI.LiveThrough && Intf.last() <= 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);
+ continue;
+ }
+
+ SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
+ if (Intf.last().getBoundaryIndex() < BI.LastUse) {
+ // There are interference-free uses at the end of the block.
+ // Find the first use that can get the live-out register.
+ SmallVectorImpl<SlotIndex>::const_iterator UI =
+ std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
+ Intf.last().getBoundaryIndex());
+ assert(UI != SA->UseSlots.end() && "Couldn't find last use");
+ SlotIndex Use = *UI;
+ assert(Use <= BI.LastUse && "Couldn't find last use");
+ // Only attempt a split befroe the last split point.
+ if (Use.getBaseIndex() <= LastSplitPoint) {
+ DEBUG(dbgs() << ", free use at " << Use << ".\n");
+ SlotIndex SegStart = SE->enterIntvBefore(Use);
+ assert(SegStart >= Intf.last() && "Couldn't avoid interference");
+ assert(SegStart < LastSplitPoint && "Impossible split point");
+ SE->useIntv(SegStart, Stop);
+ continue;
+ }
+ }
+
+ // Interference is after the last use.
+ DEBUG(dbgs() << " after last use.\n");
+ SlotIndex SegStart = SE->enterIntvAtEnd(*BI.MBB);
+ assert(SegStart >= Intf.last() && "Couldn't avoid interference");
+ }
+
+ // Now all defs leading to live bundles are handled, do everything else.
+ for (unsigned i = 0; i != UseBlocks.size(); ++i) {
+ const SplitAnalysis::BlockInfo &BI = UseBlocks[i];
+ bool RegIn = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 0)];
+ bool RegOut = LiveBundles[Bundles->getBundle(BI.MBB->getNumber(), 1)];
+
+ // Is the register live-in?
+ if (!BI.LiveIn || !RegIn)
+ continue;
+
+ // We have an incoming register. Check for interference.
+ SlotIndex Start, Stop;
+ tie(Start, Stop) = Indexes->getMBBRange(BI.MBB);
+ Intf.moveToBlock(BI.MBB->getNumber());
+ DEBUG(dbgs() << "EB#" << Bundles->getBundle(BI.MBB->getNumber(), 0)
+ << " -> BB#" << BI.MBB->getNumber() << " [" << Start << ';'
+ << SA->getLastSplitPoint(BI.MBB->getNumber()) << '-' << Stop
+ << ')');
+
+ // Check interference entering the block.
+ if (!Intf.hasInterference()) {
+ // Block is interference-free.
+ DEBUG(dbgs() << ", no interference");
+ if (!BI.LiveThrough) {
+ DEBUG(dbgs() << ", killed in block.\n");
+ SE->useIntv(Start, SE->leaveIntvAfter(BI.Kill));
+ continue;
+ }
+ if (!RegOut) {
+ SlotIndex LastSplitPoint = SA->getLastSplitPoint(BI.MBB->getNumber());
+ // Block is live-through, but exit bundle is on the stack.
+ // Spill immediately after the last use.
+ if (BI.LastUse < LastSplitPoint) {
+ DEBUG(dbgs() << ", uses, stack-out.\n");
+ SE->useIntv(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 "
+ << LastSplitPoint << ", stack-out.\n");
+ SlotIndex SegEnd = SE->leaveIntvBefore(LastSplitPoint);
+ SE->useIntv(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);
+ continue;
+ }
+ // Register is live-through.
+ DEBUG(dbgs() << ", uses, live-through.\n");
+ SE->useIntv(Start, Stop);
+ continue;
+ }
+
+ // Block has interference.
+ DEBUG(dbgs() << ", interference from " << Intf.first());
+
+ if (!BI.LiveThrough && Intf.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);
+ continue;
+ }
+
+ if (Intf.first().getBaseIndex() > BI.FirstUse) {
+ // There are interference-free uses at the beginning of the block.
+ // Find the last use that can get the register.
+ SmallVectorImpl<SlotIndex>::const_iterator UI =
+ std::lower_bound(SA->UseSlots.begin(), SA->UseSlots.end(),
+ Intf.first().getBaseIndex());
+ 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);
+ assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
+ SE->useIntv(Start, SegEnd);
+ continue;
+ }
+
+ // Interference is before the first use.
+ DEBUG(dbgs() << " before first use.\n");
+ SlotIndex SegEnd = SE->leaveIntvAtTop(*BI.MBB);
+ assert(SegEnd <= Intf.first() && "Couldn't avoid interference");
+ }
+
+ // Handle live-through blocks.
+ for (unsigned i = 0, e = Cand.ActiveBlocks.size(); i != e; ++i) {
+ unsigned Number = Cand.ActiveBlocks[i];
+ bool RegIn = LiveBundles[Bundles->getBundle(Number, 0)];
+ bool RegOut = LiveBundles[Bundles->getBundle(Number, 1)];
+ DEBUG(dbgs() << "Live through BB#" << Number << '\n');
+ if (RegIn && RegOut) {
+ Intf.moveToBlock(Number);
+ if (!Intf.hasInterference()) {
+ SE->useIntv(Indexes->getMBBStartIdx(Number),
+ Indexes->getMBBEndIdx(Number));
+ continue;
+ }
+ }
+ MachineBasicBlock *MBB = MF->getBlockNumbered(Number);
+ if (RegIn)
+ SE->leaveIntvAtTop(*MBB);
+ if (RegOut)
+ SE->enterIntvAtEnd(*MBB);
+ }
+
+ 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();
+ ++NumGlobalSplits;
+
+ if (VerifyEnabled)
+ MF->verify(this, "After splitting live range around region");
+}
+
+unsigned RAGreedy::tryRegionSplit(LiveInterval &VirtReg, AllocationOrder &Order,
+ SmallVectorImpl<LiveInterval*> &NewVRegs) {
+ float BestCost = 0;
+ const unsigned NoCand = ~0u;
+ unsigned BestCand = NoCand;
+
Order.rewind();
- while (unsigned PhysReg = Order.next())
- if (reassignInterferences(VirtReg, PhysReg))
- return PhysReg;
+ for (unsigned Cand = 0; unsigned PhysReg = Order.next(); ++Cand) {
+ if (GlobalCand.size() <= Cand)
+ GlobalCand.resize(Cand+1);
+ GlobalCand[Cand].reset(PhysReg);
+
+ SpillPlacer->prepare(GlobalCand[Cand].LiveBundles);
+ float Cost;
+ InterferenceCache::Cursor Intf(IntfCache, PhysReg);
+ if (!addSplitConstraints(Intf, Cost)) {
+ DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tno positive bundles\n");
+ continue;
+ }
+ DEBUG(dbgs() << PrintReg(PhysReg, TRI) << "\tstatic = " << Cost);
+ if (BestCand != NoCand && Cost >= BestCost) {
+ DEBUG(dbgs() << " worse than "
+ << PrintReg(GlobalCand[BestCand].PhysReg, TRI) << '\n');
+ continue;
+ }
+ growRegion(GlobalCand[Cand], Intf);
+
+ SpillPlacer->finish();
+
+ // No live bundles, defer to splitSingleBlocks().
+ if (!GlobalCand[Cand].LiveBundles.any()) {
+ DEBUG(dbgs() << " no bundles.\n");
+ continue;
+ }
+
+ Cost += calcGlobalSplitCost(GlobalCand[Cand], Intf);
+ DEBUG({
+ dbgs() << ", total = " << Cost << " with bundles";
+ for (int i = GlobalCand[Cand].LiveBundles.find_first(); i>=0;
+ i = GlobalCand[Cand].LiveBundles.find_next(i))
+ dbgs() << " EB#" << i;
+ dbgs() << ".\n";
+ });
+ if (BestCand == NoCand || Cost < BestCost) {
+ BestCand = Cand;
+ BestCost = 0.98f * Cost; // Prevent rounding effects.
+ }
+ }
+
+ if (BestCand == NoCand)
+ return 0;
+
+ splitAroundRegion(VirtReg, GlobalCand[BestCand], NewVRegs);
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Global);
+ return 0;
+}
+
+
+//===----------------------------------------------------------------------===//
+// Local Splitting
+//===----------------------------------------------------------------------===//
+
+
+/// 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->getUseBlocks().size() == 1 && "Not a local interval");
+ const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().front();
+ const SmallVectorImpl<SlotIndex> &Uses = SA->UseSlots;
+ const unsigned NumGaps = Uses.size()-1;
+
+ // 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;
+
+ GapWeight.assign(NumGaps, 0.0f);
+
+ // 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;
+
+ // 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;
+ }
+ }
+}
+
+/// 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());
+ }
+}
+
+/// 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->getUseBlocks().size() == 1 && "Not a local interval");
+ const SplitAnalysis::BlockInfo &BI = SA->getUseBlocks().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()) {
+ // 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;
+ }
+ }
+
+ // Didn't find any candidates?
+ if (BestBefore == NumGaps)
+ return 0;
+
+ 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 SplitVRegs.
+/// @return Physreg when VirtReg may be assigned and/or new NewVRegs.
unsigned RAGreedy::trySplit(LiveInterval &VirtReg, AllocationOrder &Order,
- SmallVectorImpl<LiveInterval*>&SplitVRegs) {
- NamedRegionTimer T("Splitter", TimerGroupName, TimePassesIsEnabled);
+ 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.
+ if (getStage(VirtReg) >= RS_Global)
+ return 0;
+
+ SA->analyze(&VirtReg);
+
+ // First try to split around a region spanning multiple blocks.
+ unsigned PhysReg = tryRegionSplit(VirtReg, Order, NewVRegs);
+ if (PhysReg || !NewVRegs.empty())
+ return PhysReg;
+
+ // Then isolate blocks with multiple uses.
+ SplitAnalysis::BlockPtrSet Blocks;
+ if (SA->getMultiUseBlocks(Blocks)) {
+ LiveRangeEdit LREdit(VirtReg, NewVRegs, this);
+ SE->reset(LREdit);
+ SE->splitSingleBlocks(Blocks);
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Global);
+ if (VerifyEnabled)
+ MF->verify(this, "After splitting live range around basic blocks");
+ }
+
+ // Don't assign any physregs.
return 0;
}
-unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
- SmallVectorImpl<LiveInterval*> &SplitVRegs) {
- // Populate a list of physical register spill candidates.
- SmallVector<unsigned, 8> PhysRegSpillCands;
- // Check for an available register in this class.
+//===----------------------------------------------------------------------===//
+// Main Entry Point
+//===----------------------------------------------------------------------===//
+
+unsigned RAGreedy::selectOrSplit(LiveInterval &VirtReg,
+ SmallVectorImpl<LiveInterval*> &NewVRegs) {
+ // First try assigning a free register.
AllocationOrder Order(VirtReg.reg, *VRM, ReservedRegs);
while (unsigned PhysReg = Order.next()) {
- // Check interference and as a side effect, intialize queries for this
- // VirtReg and its aliases.
- unsigned InterfReg = checkPhysRegInterference(VirtReg, PhysReg);
- if (InterfReg == 0) {
- // Found an available register.
+ if (!checkPhysRegInterference(VirtReg, PhysReg))
return PhysReg;
- }
- assert(!VirtReg.empty() && "Empty VirtReg has interference");
- LiveInterval *InterferingVirtReg =
- Queries[InterfReg].firstInterference().liveUnionPos().value();
-
- // The current VirtReg must either be spillable, or one of its interferences
- // must have less spill weight.
- if (InterferingVirtReg->weight < VirtReg.weight )
- PhysRegSpillCands.push_back(PhysReg);
}
- // Try to reassign interferences.
- if (unsigned PhysReg = tryReassign(VirtReg, Order))
+ 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_First) {
+ 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, SplitVRegs);
- if (PhysReg || !SplitVRegs.empty())
+ unsigned PhysReg = trySplit(VirtReg, Order, NewVRegs);
+ if (PhysReg || !NewVRegs.empty())
return PhysReg;
- // Try to spill another interfering reg with less spill weight.
+ // Finally spill VirtReg itself.
NamedRegionTimer T("Spiller", TimerGroupName, TimePassesIsEnabled);
- //
- // FIXME: do this in two steps: (1) check for unspillable interferences while
- // accumulating spill weight; (2) spill the interferences with lowest
- // aggregate spill weight.
- for (SmallVectorImpl<unsigned>::iterator PhysRegI = PhysRegSpillCands.begin(),
- PhysRegE = PhysRegSpillCands.end(); PhysRegI != PhysRegE; ++PhysRegI) {
-
- if (!spillInterferences(VirtReg, *PhysRegI, SplitVRegs)) continue;
-
- assert(checkPhysRegInterference(VirtReg, *PhysRegI) == 0 &&
- "Interference after spill.");
- // Tell the caller to allocate to this newly freed physical register.
- return *PhysRegI;
- }
+ LiveRangeEdit LRE(VirtReg, NewVRegs, this);
+ spiller().spill(LRE);
+ setStage(NewVRegs.begin(), NewVRegs.end(), RS_Spill);
- // No other spill candidates were found, so spill the current VirtReg.
- DEBUG(dbgs() << "spilling: " << VirtReg << '\n');
- SmallVector<LiveInterval*, 1> pendingSpills;
-
- spiller().spill(&VirtReg, SplitVRegs, pendingSpills);
+ 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.
<< ((Value*)mf.getFunction())->getName() << '\n');
MF = &mf;
- RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
+ if (VerifyEnabled)
+ MF->verify(this, "Before greedy register allocator");
+ RegAllocBase::init(getAnalysis<VirtRegMap>(), getAnalysis<LiveIntervals>());
+ Indexes = &getAnalysis<SlotIndexes>();
+ DomTree = &getAnalysis<MachineDominatorTree>();
ReservedRegs = TRI->getReservedRegs(*MF);
SpillerInstance.reset(createInlineSpiller(*this, *MF, *VRM));
+ Loops = &getAnalysis<MachineLoopInfo>();
+ LoopRanges = &getAnalysis<MachineLoopRanges>();
+ Bundles = &getAnalysis<EdgeBundles>();
+ SpillPlacer = &getAnalysis<SpillPlacement>();
+
+ SA.reset(new SplitAnalysis(*VRM, *LIS, *Loops));
+ SE.reset(new SplitEditor(*SA, *LIS, *VRM, *DomTree));
+ LRStage.clear();
+ LRStage.resize(MRI->getNumVirtRegs());
+ IntfCache.init(MF, &PhysReg2LiveUnion[0], Indexes, TRI);
+
allocatePhysRegs();
addMBBLiveIns(MF);
+ LIS->addKillFlags();
// Run rewriter
{
NamedRegionTimer T("Rewriter", TimerGroupName, TimePassesIsEnabled);
- std::auto_ptr<VirtRegRewriter> rewriter(createVirtRegRewriter());
- rewriter->runOnMachineFunction(*MF, *VRM, LIS);
+ VRM->rewrite(Indexes);
}
+ // Write out new DBG_VALUE instructions.
+ getAnalysis<LiveDebugVariables>().emitDebugValues(VRM);
+
// The pass output is in VirtRegMap. Release all the transient data.
releaseMemory();
projects / oota-llvm.git / blobdiff