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//==- MachineScheduler.h - MachineInstr Scheduling Pass ----------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file provides a MachineSchedRegistry for registering alternative machine
// schedulers. A Target may provide an alternative scheduler implementation by
// implementing the following boilerplate:
//
// static ScheduleDAGInstrs *createCustomMachineSched(MachineSchedContext *C) {
// return new CustomMachineScheduler(C);
// }
// static MachineSchedRegistry
// SchedCustomRegistry("custom", "Run my target's custom scheduler",
// createCustomMachineSched);
//
// Inside <Target>PassConfig:
// enablePass(&MachineSchedulerID);
// MachineSchedRegistry::setDefault(createCustomMachineSched);
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_MACHINESCHEDULER_H
#define LLVM_CODEGEN_MACHINESCHEDULER_H
#include "llvm/CodeGen/MachinePassRegistry.h"
#include "llvm/CodeGen/RegisterPressure.h"
#include "llvm/CodeGen/ScheduleDAGInstrs.h"
namespace llvm {
extern cl::opt<bool> ForceTopDown;
extern cl::opt<bool> ForceBottomUp;
class AliasAnalysis;
class LiveIntervals;
class MachineDominatorTree;
class MachineLoopInfo;
class RegisterClassInfo;
class ScheduleDAGInstrs;
class SchedDFSResult;
/// MachineSchedContext provides enough context from the MachineScheduler pass
/// for the target to instantiate a scheduler.
struct MachineSchedContext {
MachineFunction *MF;
const MachineLoopInfo *MLI;
const MachineDominatorTree *MDT;
const TargetPassConfig *PassConfig;
AliasAnalysis *AA;
LiveIntervals *LIS;
RegisterClassInfo *RegClassInfo;
MachineSchedContext();
virtual ~MachineSchedContext();
};
/// MachineSchedRegistry provides a selection of available machine instruction
/// schedulers.
class MachineSchedRegistry : public MachinePassRegistryNode {
public:
typedef ScheduleDAGInstrs *(*ScheduleDAGCtor)(MachineSchedContext *);
// RegisterPassParser requires a (misnamed) FunctionPassCtor type.
typedef ScheduleDAGCtor FunctionPassCtor;
static MachinePassRegistry Registry;
MachineSchedRegistry(const char *N, const char *D, ScheduleDAGCtor C)
: MachinePassRegistryNode(N, D, (MachinePassCtor)C) {
Registry.Add(this);
}
~MachineSchedRegistry() { Registry.Remove(this); }
// Accessors.
//
MachineSchedRegistry *getNext() const {
return (MachineSchedRegistry *)MachinePassRegistryNode::getNext();
}
static MachineSchedRegistry *getList() {
return (MachineSchedRegistry *)Registry.getList();
}
static ScheduleDAGCtor getDefault() {
return (ScheduleDAGCtor)Registry.getDefault();
}
static void setDefault(ScheduleDAGCtor C) {
Registry.setDefault((MachinePassCtor)C);
}
static void setDefault(StringRef Name) {
Registry.setDefault(Name);
}
static void setListener(MachinePassRegistryListener *L) {
Registry.setListener(L);
}
};
class ScheduleDAGMI;
/// MachineSchedStrategy - Interface to the scheduling algorithm used by
/// ScheduleDAGMI.
class MachineSchedStrategy {
public:
virtual ~MachineSchedStrategy() {}
/// Initialize the strategy after building the DAG for a new region.
virtual void initialize(ScheduleDAGMI *DAG) = 0;
/// Notify this strategy that all roots have been released (including those
/// that depend on EntrySU or ExitSU).
virtual void registerRoots() {}
/// Pick the next node to schedule, or return NULL. Set IsTopNode to true to
/// schedule the node at the top of the unscheduled region. Otherwise it will
/// be scheduled at the bottom.
virtual SUnit *pickNode(bool &IsTopNode) = 0;
/// \brief Scheduler callback to notify that a new subtree is scheduled.
virtual void scheduleTree(unsigned SubtreeID) {}
/// Notify MachineSchedStrategy that ScheduleDAGMI has scheduled an
/// instruction and updated scheduled/remaining flags in the DAG nodes.
virtual void schedNode(SUnit *SU, bool IsTopNode) = 0;
/// When all predecessor dependencies have been resolved, free this node for
/// top-down scheduling.
virtual void releaseTopNode(SUnit *SU) = 0;
/// When all successor dependencies have been resolved, free this node for
/// bottom-up scheduling.
virtual void releaseBottomNode(SUnit *SU) = 0;
};
/// ReadyQueue encapsulates vector of "ready" SUnits with basic convenience
/// methods for pushing and removing nodes. ReadyQueue's are uniquely identified
/// by an ID. SUnit::NodeQueueId is a mask of the ReadyQueues the SUnit is in.
///
/// This is a convenience class that may be used by implementations of
/// MachineSchedStrategy.
class ReadyQueue {
unsigned ID;
std::string Name;
std::vector<SUnit*> Queue;
public:
ReadyQueue(unsigned id, const Twine &name): ID(id), Name(name.str()) {}
unsigned getID() const { return ID; }
StringRef getName() const { return Name; }
// SU is in this queue if it's NodeQueueID is a superset of this ID.
bool isInQueue(SUnit *SU) const { return (SU->NodeQueueId & ID); }
bool empty() const { return Queue.empty(); }
void clear() { Queue.clear(); }
unsigned size() const { return Queue.size(); }
typedef std::vector<SUnit*>::iterator iterator;
iterator begin() { return Queue.begin(); }
iterator end() { return Queue.end(); }
ArrayRef<SUnit*> elements() { return Queue; }
iterator find(SUnit *SU) {
return std::find(Queue.begin(), Queue.end(), SU);
}
void push(SUnit *SU) {
Queue.push_back(SU);
SU->NodeQueueId |= ID;
}
iterator remove(iterator I) {
(*I)->NodeQueueId &= ~ID;
*I = Queue.back();
unsigned idx = I - Queue.begin();
Queue.pop_back();
return Queue.begin() + idx;
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void dump();
#endif
};
/// Mutate the DAG as a postpass after normal DAG building.
class ScheduleDAGMutation {
public:
virtual ~ScheduleDAGMutation() {}
virtual void apply(ScheduleDAGMI *DAG) = 0;
};
/// ScheduleDAGMI is an implementation of ScheduleDAGInstrs that schedules
/// machine instructions while updating LiveIntervals and tracking regpressure.
class ScheduleDAGMI : public ScheduleDAGInstrs {
protected:
AliasAnalysis *AA;
RegisterClassInfo *RegClassInfo;
MachineSchedStrategy *SchedImpl;
/// Information about DAG subtrees. If DFSResult is NULL, then SchedulerTrees
/// will be empty.
SchedDFSResult *DFSResult;
BitVector ScheduledTrees;
/// Topo - A topological ordering for SUnits which permits fast IsReachable
/// and similar queries.
ScheduleDAGTopologicalSort Topo;
/// Ordered list of DAG postprocessing steps.
std::vector<ScheduleDAGMutation*> Mutations;
MachineBasicBlock::iterator LiveRegionEnd;
// Map each SU to its summary of pressure changes. This array is updated for
// liveness during bottom-up scheduling. Top-down scheduling may proceed but
// has no affect on the pressure diffs.
PressureDiffs SUPressureDiffs;
/// Register pressure in this region computed by initRegPressure.
bool ShouldTrackPressure;
IntervalPressure RegPressure;
RegPressureTracker RPTracker;
/// List of pressure sets that exceed the target's pressure limit before
/// scheduling, listed in increasing set ID order. Each pressure set is paired
/// with its max pressure in the currently scheduled regions.
std::vector<PressureChange> RegionCriticalPSets;
/// The top of the unscheduled zone.
MachineBasicBlock::iterator CurrentTop;
IntervalPressure TopPressure;
RegPressureTracker TopRPTracker;
/// The bottom of the unscheduled zone.
MachineBasicBlock::iterator CurrentBottom;
IntervalPressure BotPressure;
RegPressureTracker BotRPTracker;
/// Record the next node in a scheduled cluster.
const SUnit *NextClusterPred;
const SUnit *NextClusterSucc;
#ifndef NDEBUG
/// The number of instructions scheduled so far. Used to cut off the
/// scheduler at the point determined by misched-cutoff.
unsigned NumInstrsScheduled;
#endif
public:
ScheduleDAGMI(MachineSchedContext *C, MachineSchedStrategy *S):
ScheduleDAGInstrs(*C->MF, *C->MLI, *C->MDT, /*IsPostRA=*/false, C->LIS),
AA(C->AA), RegClassInfo(C->RegClassInfo), SchedImpl(S), DFSResult(0),
Topo(SUnits, &ExitSU), ShouldTrackPressure(false),
RPTracker(RegPressure), CurrentTop(), TopRPTracker(TopPressure),
CurrentBottom(), BotRPTracker(BotPressure),
NextClusterPred(NULL), NextClusterSucc(NULL) {
#ifndef NDEBUG
NumInstrsScheduled = 0;
#endif
}
virtual ~ScheduleDAGMI();
/// Add a postprocessing step to the DAG builder.
/// Mutations are applied in the order that they are added after normal DAG
/// building and before MachineSchedStrategy initialization.
///
/// ScheduleDAGMI takes ownership of the Mutation object.
void addMutation(ScheduleDAGMutation *Mutation) {
Mutations.push_back(Mutation);
}
/// \brief True if an edge can be added from PredSU to SuccSU without creating
/// a cycle.
bool canAddEdge(SUnit *SuccSU, SUnit *PredSU);
/// \brief Add a DAG edge to the given SU with the given predecessor
/// dependence data.
///
/// \returns true if the edge may be added without creating a cycle OR if an
/// equivalent edge already existed (false indicates failure).
bool addEdge(SUnit *SuccSU, const SDep &PredDep);
MachineBasicBlock::iterator top() const { return CurrentTop; }
MachineBasicBlock::iterator bottom() const { return CurrentBottom; }
/// Implement the ScheduleDAGInstrs interface for handling the next scheduling
/// region. This covers all instructions in a block, while schedule() may only
/// cover a subset.
void enterRegion(MachineBasicBlock *bb,
MachineBasicBlock::iterator begin,
MachineBasicBlock::iterator end,
unsigned regioninstrs) LLVM_OVERRIDE;
/// Implement ScheduleDAGInstrs interface for scheduling a sequence of
/// reorderable instructions.
virtual void schedule();
/// Change the position of an instruction within the basic block and update
/// live ranges and region boundary iterators.
void moveInstruction(MachineInstr *MI, MachineBasicBlock::iterator InsertPos);
/// Get current register pressure for the top scheduled instructions.
const IntervalPressure &getTopPressure() const { return TopPressure; }
const RegPressureTracker &getTopRPTracker() const { return TopRPTracker; }
/// Get current register pressure for the bottom scheduled instructions.
const IntervalPressure &getBotPressure() const { return BotPressure; }
const RegPressureTracker &getBotRPTracker() const { return BotRPTracker; }
/// Get register pressure for the entire scheduling region before scheduling.
const IntervalPressure &getRegPressure() const { return RegPressure; }
const std::vector<PressureChange> &getRegionCriticalPSets() const {
return RegionCriticalPSets;
}
PressureDiff &getPressureDiff(const SUnit *SU) {
return SUPressureDiffs[SU->NodeNum];
}
const SUnit *getNextClusterPred() const { return NextClusterPred; }
const SUnit *getNextClusterSucc() const { return NextClusterSucc; }
/// Compute a DFSResult after DAG building is complete, and before any
/// queue comparisons.
void computeDFSResult();
/// Return a non-null DFS result if the scheduling strategy initialized it.
const SchedDFSResult *getDFSResult() const { return DFSResult; }
BitVector &getScheduledTrees() { return ScheduledTrees; }
/// Compute the cyclic critical path through the DAG.
unsigned computeCyclicCriticalPath();
void viewGraph(const Twine &Name, const Twine &Title) LLVM_OVERRIDE;
void viewGraph() LLVM_OVERRIDE;
protected:
// Top-Level entry points for the schedule() driver...
/// Call ScheduleDAGInstrs::buildSchedGraph with register pressure tracking
/// enabled. This sets up three trackers. RPTracker will cover the entire DAG
/// region, TopTracker and BottomTracker will be initialized to the top and
/// bottom of the DAG region without covereing any unscheduled instruction.
void buildDAGWithRegPressure();
/// Apply each ScheduleDAGMutation step in order. This allows different
/// instances of ScheduleDAGMI to perform custom DAG postprocessing.
void postprocessDAG();
/// Release ExitSU predecessors and setup scheduler queues.
void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
/// Move an instruction and update register pressure.
void scheduleMI(SUnit *SU, bool IsTopNode);
/// Update scheduler DAG and queues after scheduling an instruction.
void updateQueues(SUnit *SU, bool IsTopNode);
/// Reinsert debug_values recorded in ScheduleDAGInstrs::DbgValues.
void placeDebugValues();
/// \brief dump the scheduled Sequence.
void dumpSchedule() const;
// Lesser helpers...
void initRegPressure();
void updatePressureDiffs(ArrayRef<unsigned> LiveUses);
void updateScheduledPressure(const std::vector<unsigned> &NewMaxPressure);
bool checkSchedLimit();
void findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
SmallVectorImpl<SUnit*> &BotRoots);
void releaseSucc(SUnit *SU, SDep *SuccEdge);
void releaseSuccessors(SUnit *SU);
void releasePred(SUnit *SU, SDep *PredEdge);
void releasePredecessors(SUnit *SU);
};
} // namespace llvm
#endif
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