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Diffstat (limited to 'lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp | 635 |
1 files changed, 635 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp b/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp new file mode 100644 index 000000000000..af73b28fae93 --- /dev/null +++ b/lib/CodeGen/SelectionDAG/ScheduleDAGFast.cpp @@ -0,0 +1,635 @@ +//===----- ScheduleDAGFast.cpp - Fast poor list scheduler -----------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This implements a fast scheduler. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "pre-RA-sched" +#include "ScheduleDAGSDNodes.h" +#include "llvm/CodeGen/SchedulerRegistry.h" +#include "llvm/CodeGen/SelectionDAGISel.h" +#include "llvm/Target/TargetRegisterInfo.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/Compiler.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/Support/CommandLine.h" +using namespace llvm; + +STATISTIC(NumUnfolds, "Number of nodes unfolded"); +STATISTIC(NumDups, "Number of duplicated nodes"); +STATISTIC(NumPRCopies, "Number of physical copies"); + +static RegisterScheduler + fastDAGScheduler("fast", "Fast suboptimal list scheduling", + createFastDAGScheduler); + +namespace { + /// FastPriorityQueue - A degenerate priority queue that considers + /// all nodes to have the same priority. + /// + struct VISIBILITY_HIDDEN FastPriorityQueue { + SmallVector<SUnit *, 16> Queue; + + bool empty() const { return Queue.empty(); } + + void push(SUnit *U) { + Queue.push_back(U); + } + + SUnit *pop() { + if (empty()) return NULL; + SUnit *V = Queue.back(); + Queue.pop_back(); + return V; + } + }; + +//===----------------------------------------------------------------------===// +/// ScheduleDAGFast - The actual "fast" list scheduler implementation. +/// +class VISIBILITY_HIDDEN ScheduleDAGFast : public ScheduleDAGSDNodes { +private: + /// AvailableQueue - The priority queue to use for the available SUnits. + FastPriorityQueue AvailableQueue; + + /// LiveRegDefs - A set of physical registers and their definition + /// that are "live". These nodes must be scheduled before any other nodes that + /// modifies the registers can be scheduled. + unsigned NumLiveRegs; + std::vector<SUnit*> LiveRegDefs; + std::vector<unsigned> LiveRegCycles; + +public: + ScheduleDAGFast(MachineFunction &mf) + : ScheduleDAGSDNodes(mf) {} + + void Schedule(); + + /// AddPred - adds a predecessor edge to SUnit SU. + /// This returns true if this is a new predecessor. + void AddPred(SUnit *SU, const SDep &D) { + SU->addPred(D); + } + + /// RemovePred - removes a predecessor edge from SUnit SU. + /// This returns true if an edge was removed. + void RemovePred(SUnit *SU, const SDep &D) { + SU->removePred(D); + } + +private: + void ReleasePred(SUnit *SU, SDep *PredEdge); + void ReleasePredecessors(SUnit *SU, unsigned CurCycle); + void ScheduleNodeBottomUp(SUnit*, unsigned); + SUnit *CopyAndMoveSuccessors(SUnit*); + void InsertCopiesAndMoveSuccs(SUnit*, unsigned, + const TargetRegisterClass*, + const TargetRegisterClass*, + SmallVector<SUnit*, 2>&); + bool DelayForLiveRegsBottomUp(SUnit*, SmallVector<unsigned, 4>&); + void ListScheduleBottomUp(); + + /// ForceUnitLatencies - The fast scheduler doesn't care about real latencies. + bool ForceUnitLatencies() const { return true; } +}; +} // end anonymous namespace + + +/// Schedule - Schedule the DAG using list scheduling. +void ScheduleDAGFast::Schedule() { + DOUT << "********** List Scheduling **********\n"; + + NumLiveRegs = 0; + LiveRegDefs.resize(TRI->getNumRegs(), NULL); + LiveRegCycles.resize(TRI->getNumRegs(), 0); + + // Build the scheduling graph. + BuildSchedGraph(); + + DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su) + SUnits[su].dumpAll(this)); + + // Execute the actual scheduling loop. + ListScheduleBottomUp(); +} + +//===----------------------------------------------------------------------===// +// Bottom-Up Scheduling +//===----------------------------------------------------------------------===// + +/// ReleasePred - Decrement the NumSuccsLeft count of a predecessor. Add it to +/// the AvailableQueue if the count reaches zero. Also update its cycle bound. +void ScheduleDAGFast::ReleasePred(SUnit *SU, SDep *PredEdge) { + SUnit *PredSU = PredEdge->getSUnit(); + --PredSU->NumSuccsLeft; + +#ifndef NDEBUG + if (PredSU->NumSuccsLeft < 0) { + cerr << "*** Scheduling failed! ***\n"; + PredSU->dump(this); + cerr << " has been released too many times!\n"; + assert(0); + } +#endif + + // If all the node's successors are scheduled, this node is ready + // to be scheduled. Ignore the special EntrySU node. + if (PredSU->NumSuccsLeft == 0 && PredSU != &EntrySU) { + PredSU->isAvailable = true; + AvailableQueue.push(PredSU); + } +} + +void ScheduleDAGFast::ReleasePredecessors(SUnit *SU, unsigned CurCycle) { + // Bottom up: release predecessors + for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); + I != E; ++I) { + ReleasePred(SU, &*I); + if (I->isAssignedRegDep()) { + // This is a physical register dependency and it's impossible or + // expensive to copy the register. Make sure nothing that can + // clobber the register is scheduled between the predecessor and + // this node. + if (!LiveRegDefs[I->getReg()]) { + ++NumLiveRegs; + LiveRegDefs[I->getReg()] = I->getSUnit(); + LiveRegCycles[I->getReg()] = CurCycle; + } + } + } +} + +/// ScheduleNodeBottomUp - Add the node to the schedule. Decrement the pending +/// count of its predecessors. If a predecessor pending count is zero, add it to +/// the Available queue. +void ScheduleDAGFast::ScheduleNodeBottomUp(SUnit *SU, unsigned CurCycle) { + DOUT << "*** Scheduling [" << CurCycle << "]: "; + DEBUG(SU->dump(this)); + + assert(CurCycle >= SU->getHeight() && "Node scheduled below its height!"); + SU->setHeightToAtLeast(CurCycle); + Sequence.push_back(SU); + + ReleasePredecessors(SU, CurCycle); + + // Release all the implicit physical register defs that are live. + for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); + I != E; ++I) { + if (I->isAssignedRegDep()) { + if (LiveRegCycles[I->getReg()] == I->getSUnit()->getHeight()) { + assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!"); + assert(LiveRegDefs[I->getReg()] == SU && + "Physical register dependency violated?"); + --NumLiveRegs; + LiveRegDefs[I->getReg()] = NULL; + LiveRegCycles[I->getReg()] = 0; + } + } + } + + SU->isScheduled = true; +} + +/// CopyAndMoveSuccessors - Clone the specified node and move its scheduled +/// successors to the newly created node. +SUnit *ScheduleDAGFast::CopyAndMoveSuccessors(SUnit *SU) { + if (SU->getNode()->getFlaggedNode()) + return NULL; + + SDNode *N = SU->getNode(); + if (!N) + return NULL; + + SUnit *NewSU; + bool TryUnfold = false; + for (unsigned i = 0, e = N->getNumValues(); i != e; ++i) { + MVT VT = N->getValueType(i); + if (VT == MVT::Flag) + return NULL; + else if (VT == MVT::Other) + TryUnfold = true; + } + for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i) { + const SDValue &Op = N->getOperand(i); + MVT VT = Op.getNode()->getValueType(Op.getResNo()); + if (VT == MVT::Flag) + return NULL; + } + + if (TryUnfold) { + SmallVector<SDNode*, 2> NewNodes; + if (!TII->unfoldMemoryOperand(*DAG, N, NewNodes)) + return NULL; + + DOUT << "Unfolding SU # " << SU->NodeNum << "\n"; + assert(NewNodes.size() == 2 && "Expected a load folding node!"); + + N = NewNodes[1]; + SDNode *LoadNode = NewNodes[0]; + unsigned NumVals = N->getNumValues(); + unsigned OldNumVals = SU->getNode()->getNumValues(); + for (unsigned i = 0; i != NumVals; ++i) + DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), i), SDValue(N, i)); + DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), OldNumVals-1), + SDValue(LoadNode, 1)); + + SUnit *NewSU = NewSUnit(N); + assert(N->getNodeId() == -1 && "Node already inserted!"); + N->setNodeId(NewSU->NodeNum); + + const TargetInstrDesc &TID = TII->get(N->getMachineOpcode()); + for (unsigned i = 0; i != TID.getNumOperands(); ++i) { + if (TID.getOperandConstraint(i, TOI::TIED_TO) != -1) { + NewSU->isTwoAddress = true; + break; + } + } + if (TID.isCommutable()) + NewSU->isCommutable = true; + + // LoadNode may already exist. This can happen when there is another + // load from the same location and producing the same type of value + // but it has different alignment or volatileness. + bool isNewLoad = true; + SUnit *LoadSU; + if (LoadNode->getNodeId() != -1) { + LoadSU = &SUnits[LoadNode->getNodeId()]; + isNewLoad = false; + } else { + LoadSU = NewSUnit(LoadNode); + LoadNode->setNodeId(LoadSU->NodeNum); + } + + SDep ChainPred; + SmallVector<SDep, 4> ChainSuccs; + SmallVector<SDep, 4> LoadPreds; + SmallVector<SDep, 4> NodePreds; + SmallVector<SDep, 4> NodeSuccs; + for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); + I != E; ++I) { + if (I->isCtrl()) + ChainPred = *I; + else if (I->getSUnit()->getNode() && + I->getSUnit()->getNode()->isOperandOf(LoadNode)) + LoadPreds.push_back(*I); + else + NodePreds.push_back(*I); + } + for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); + I != E; ++I) { + if (I->isCtrl()) + ChainSuccs.push_back(*I); + else + NodeSuccs.push_back(*I); + } + + if (ChainPred.getSUnit()) { + RemovePred(SU, ChainPred); + if (isNewLoad) + AddPred(LoadSU, ChainPred); + } + for (unsigned i = 0, e = LoadPreds.size(); i != e; ++i) { + const SDep &Pred = LoadPreds[i]; + RemovePred(SU, Pred); + if (isNewLoad) { + AddPred(LoadSU, Pred); + } + } + for (unsigned i = 0, e = NodePreds.size(); i != e; ++i) { + const SDep &Pred = NodePreds[i]; + RemovePred(SU, Pred); + AddPred(NewSU, Pred); + } + for (unsigned i = 0, e = NodeSuccs.size(); i != e; ++i) { + SDep D = NodeSuccs[i]; + SUnit *SuccDep = D.getSUnit(); + D.setSUnit(SU); + RemovePred(SuccDep, D); + D.setSUnit(NewSU); + AddPred(SuccDep, D); + } + for (unsigned i = 0, e = ChainSuccs.size(); i != e; ++i) { + SDep D = ChainSuccs[i]; + SUnit *SuccDep = D.getSUnit(); + D.setSUnit(SU); + RemovePred(SuccDep, D); + if (isNewLoad) { + D.setSUnit(LoadSU); + AddPred(SuccDep, D); + } + } + if (isNewLoad) { + AddPred(NewSU, SDep(LoadSU, SDep::Order, LoadSU->Latency)); + } + + ++NumUnfolds; + + if (NewSU->NumSuccsLeft == 0) { + NewSU->isAvailable = true; + return NewSU; + } + SU = NewSU; + } + + DOUT << "Duplicating SU # " << SU->NodeNum << "\n"; + NewSU = Clone(SU); + + // New SUnit has the exact same predecessors. + for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); + I != E; ++I) + if (!I->isArtificial()) + AddPred(NewSU, *I); + + // Only copy scheduled successors. Cut them from old node's successor + // list and move them over. + SmallVector<std::pair<SUnit *, SDep>, 4> DelDeps; + for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); + I != E; ++I) { + if (I->isArtificial()) + continue; + SUnit *SuccSU = I->getSUnit(); + if (SuccSU->isScheduled) { + SDep D = *I; + D.setSUnit(NewSU); + AddPred(SuccSU, D); + D.setSUnit(SU); + DelDeps.push_back(std::make_pair(SuccSU, D)); + } + } + for (unsigned i = 0, e = DelDeps.size(); i != e; ++i) + RemovePred(DelDeps[i].first, DelDeps[i].second); + + ++NumDups; + return NewSU; +} + +/// InsertCopiesAndMoveSuccs - Insert register copies and move all +/// scheduled successors of the given SUnit to the last copy. +void ScheduleDAGFast::InsertCopiesAndMoveSuccs(SUnit *SU, unsigned Reg, + const TargetRegisterClass *DestRC, + const TargetRegisterClass *SrcRC, + SmallVector<SUnit*, 2> &Copies) { + SUnit *CopyFromSU = NewSUnit(static_cast<SDNode *>(NULL)); + CopyFromSU->CopySrcRC = SrcRC; + CopyFromSU->CopyDstRC = DestRC; + + SUnit *CopyToSU = NewSUnit(static_cast<SDNode *>(NULL)); + CopyToSU->CopySrcRC = DestRC; + CopyToSU->CopyDstRC = SrcRC; + + // Only copy scheduled successors. Cut them from old node's successor + // list and move them over. + SmallVector<std::pair<SUnit *, SDep>, 4> DelDeps; + for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end(); + I != E; ++I) { + if (I->isArtificial()) + continue; + SUnit *SuccSU = I->getSUnit(); + if (SuccSU->isScheduled) { + SDep D = *I; + D.setSUnit(CopyToSU); + AddPred(SuccSU, D); + DelDeps.push_back(std::make_pair(SuccSU, *I)); + } + } + for (unsigned i = 0, e = DelDeps.size(); i != e; ++i) { + RemovePred(DelDeps[i].first, DelDeps[i].second); + } + + AddPred(CopyFromSU, SDep(SU, SDep::Data, SU->Latency, Reg)); + AddPred(CopyToSU, SDep(CopyFromSU, SDep::Data, CopyFromSU->Latency, 0)); + + Copies.push_back(CopyFromSU); + Copies.push_back(CopyToSU); + + ++NumPRCopies; +} + +/// getPhysicalRegisterVT - Returns the ValueType of the physical register +/// definition of the specified node. +/// FIXME: Move to SelectionDAG? +static MVT getPhysicalRegisterVT(SDNode *N, unsigned Reg, + const TargetInstrInfo *TII) { + const TargetInstrDesc &TID = TII->get(N->getMachineOpcode()); + assert(TID.ImplicitDefs && "Physical reg def must be in implicit def list!"); + unsigned NumRes = TID.getNumDefs(); + for (const unsigned *ImpDef = TID.getImplicitDefs(); *ImpDef; ++ImpDef) { + if (Reg == *ImpDef) + break; + ++NumRes; + } + return N->getValueType(NumRes); +} + +/// DelayForLiveRegsBottomUp - Returns true if it is necessary to delay +/// scheduling of the given node to satisfy live physical register dependencies. +/// If the specific node is the last one that's available to schedule, do +/// whatever is necessary (i.e. backtracking or cloning) to make it possible. +bool ScheduleDAGFast::DelayForLiveRegsBottomUp(SUnit *SU, + SmallVector<unsigned, 4> &LRegs){ + if (NumLiveRegs == 0) + return false; + + SmallSet<unsigned, 4> RegAdded; + // If this node would clobber any "live" register, then it's not ready. + for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end(); + I != E; ++I) { + if (I->isAssignedRegDep()) { + unsigned Reg = I->getReg(); + if (LiveRegDefs[Reg] && LiveRegDefs[Reg] != I->getSUnit()) { + if (RegAdded.insert(Reg)) + LRegs.push_back(Reg); + } + for (const unsigned *Alias = TRI->getAliasSet(Reg); + *Alias; ++Alias) + if (LiveRegDefs[*Alias] && LiveRegDefs[*Alias] != I->getSUnit()) { + if (RegAdded.insert(*Alias)) + LRegs.push_back(*Alias); + } + } + } + + for (SDNode *Node = SU->getNode(); Node; Node = Node->getFlaggedNode()) { + if (!Node->isMachineOpcode()) + continue; + const TargetInstrDesc &TID = TII->get(Node->getMachineOpcode()); + if (!TID.ImplicitDefs) + continue; + for (const unsigned *Reg = TID.ImplicitDefs; *Reg; ++Reg) { + if (LiveRegDefs[*Reg] && LiveRegDefs[*Reg] != SU) { + if (RegAdded.insert(*Reg)) + LRegs.push_back(*Reg); + } + for (const unsigned *Alias = TRI->getAliasSet(*Reg); + *Alias; ++Alias) + if (LiveRegDefs[*Alias] && LiveRegDefs[*Alias] != SU) { + if (RegAdded.insert(*Alias)) + LRegs.push_back(*Alias); + } + } + } + return !LRegs.empty(); +} + + +/// ListScheduleBottomUp - The main loop of list scheduling for bottom-up +/// schedulers. +void ScheduleDAGFast::ListScheduleBottomUp() { + unsigned CurCycle = 0; + + // Release any predecessors of the special Exit node. + ReleasePredecessors(&ExitSU, CurCycle); + + // Add root to Available queue. + if (!SUnits.empty()) { + SUnit *RootSU = &SUnits[DAG->getRoot().getNode()->getNodeId()]; + assert(RootSU->Succs.empty() && "Graph root shouldn't have successors!"); + RootSU->isAvailable = true; + AvailableQueue.push(RootSU); + } + + // While Available queue is not empty, grab the node with the highest + // priority. If it is not ready put it back. Schedule the node. + SmallVector<SUnit*, 4> NotReady; + DenseMap<SUnit*, SmallVector<unsigned, 4> > LRegsMap; + Sequence.reserve(SUnits.size()); + while (!AvailableQueue.empty()) { + bool Delayed = false; + LRegsMap.clear(); + SUnit *CurSU = AvailableQueue.pop(); + while (CurSU) { + SmallVector<unsigned, 4> LRegs; + if (!DelayForLiveRegsBottomUp(CurSU, LRegs)) + break; + Delayed = true; + LRegsMap.insert(std::make_pair(CurSU, LRegs)); + + CurSU->isPending = true; // This SU is not in AvailableQueue right now. + NotReady.push_back(CurSU); + CurSU = AvailableQueue.pop(); + } + + // All candidates are delayed due to live physical reg dependencies. + // Try code duplication or inserting cross class copies + // to resolve it. + if (Delayed && !CurSU) { + if (!CurSU) { + // Try duplicating the nodes that produces these + // "expensive to copy" values to break the dependency. In case even + // that doesn't work, insert cross class copies. + SUnit *TrySU = NotReady[0]; + SmallVector<unsigned, 4> &LRegs = LRegsMap[TrySU]; + assert(LRegs.size() == 1 && "Can't handle this yet!"); + unsigned Reg = LRegs[0]; + SUnit *LRDef = LiveRegDefs[Reg]; + MVT VT = getPhysicalRegisterVT(LRDef->getNode(), Reg, TII); + const TargetRegisterClass *RC = + TRI->getPhysicalRegisterRegClass(Reg, VT); + const TargetRegisterClass *DestRC = TRI->getCrossCopyRegClass(RC); + + // If cross copy register class is null, then it must be possible copy + // the value directly. Do not try duplicate the def. + SUnit *NewDef = 0; + if (DestRC) + NewDef = CopyAndMoveSuccessors(LRDef); + else + DestRC = RC; + if (!NewDef) { + // Issue copies, these can be expensive cross register class copies. + SmallVector<SUnit*, 2> Copies; + InsertCopiesAndMoveSuccs(LRDef, Reg, DestRC, RC, Copies); + DOUT << "Adding an edge from SU # " << TrySU->NodeNum + << " to SU #" << Copies.front()->NodeNum << "\n"; + AddPred(TrySU, SDep(Copies.front(), SDep::Order, /*Latency=*/1, + /*Reg=*/0, /*isNormalMemory=*/false, + /*isMustAlias=*/false, /*isArtificial=*/true)); + NewDef = Copies.back(); + } + + DOUT << "Adding an edge from SU # " << NewDef->NodeNum + << " to SU #" << TrySU->NodeNum << "\n"; + LiveRegDefs[Reg] = NewDef; + AddPred(NewDef, SDep(TrySU, SDep::Order, /*Latency=*/1, + /*Reg=*/0, /*isNormalMemory=*/false, + /*isMustAlias=*/false, /*isArtificial=*/true)); + TrySU->isAvailable = false; + CurSU = NewDef; + } + + if (!CurSU) { + assert(false && "Unable to resolve live physical register dependencies!"); + abort(); + } + } + + // Add the nodes that aren't ready back onto the available list. + for (unsigned i = 0, e = NotReady.size(); i != e; ++i) { + NotReady[i]->isPending = false; + // May no longer be available due to backtracking. + if (NotReady[i]->isAvailable) + AvailableQueue.push(NotReady[i]); + } + NotReady.clear(); + + if (CurSU) + ScheduleNodeBottomUp(CurSU, CurCycle); + ++CurCycle; + } + + // Reverse the order if it is bottom up. + std::reverse(Sequence.begin(), Sequence.end()); + + +#ifndef NDEBUG + // Verify that all SUnits were scheduled. + bool AnyNotSched = false; + unsigned DeadNodes = 0; + unsigned Noops = 0; + for (unsigned i = 0, e = SUnits.size(); i != e; ++i) { + if (!SUnits[i].isScheduled) { + if (SUnits[i].NumPreds == 0 && SUnits[i].NumSuccs == 0) { + ++DeadNodes; + continue; + } + if (!AnyNotSched) + cerr << "*** List scheduling failed! ***\n"; + SUnits[i].dump(this); + cerr << "has not been scheduled!\n"; + AnyNotSched = true; + } + if (SUnits[i].NumSuccsLeft != 0) { + if (!AnyNotSched) + cerr << "*** List scheduling failed! ***\n"; + SUnits[i].dump(this); + cerr << "has successors left!\n"; + AnyNotSched = true; + } + } + for (unsigned i = 0, e = Sequence.size(); i != e; ++i) + if (!Sequence[i]) + ++Noops; + assert(!AnyNotSched); + assert(Sequence.size() + DeadNodes - Noops == SUnits.size() && + "The number of nodes scheduled doesn't match the expected number!"); +#endif +} + +//===----------------------------------------------------------------------===// +// Public Constructor Functions +//===----------------------------------------------------------------------===// + +llvm::ScheduleDAGSDNodes * +llvm::createFastDAGScheduler(SelectionDAGISel *IS, CodeGenOpt::Level) { + return new ScheduleDAGFast(*IS->MF); +} |