LLVM  8.0.0svn
Public Member Functions | Protected Member Functions | Protected Attributes | List of all members
llvm::GenericScheduler Class Reference

GenericScheduler shrinks the unscheduled zone using heuristics to balance the schedule. More...

#include "llvm/CodeGen/MachineScheduler.h"

Inheritance diagram for llvm::GenericScheduler:
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Public Member Functions

 GenericScheduler (const MachineSchedContext *C)
 
void initPolicy (MachineBasicBlock::iterator Begin, MachineBasicBlock::iterator End, unsigned NumRegionInstrs) override
 Initialize the per-region scheduling policy. More...
 
void dumpPolicy () const override
 
bool shouldTrackPressure () const override
 Check if pressure tracking is needed before building the DAG and initializing this strategy. More...
 
bool shouldTrackLaneMasks () const override
 Returns true if lanemasks should be tracked. More...
 
void initialize (ScheduleDAGMI *dag) override
 Initialize the strategy after building the DAG for a new region. More...
 
SUnitpickNode (bool &IsTopNode) override
 Pick the best node to balance the schedule. Implements MachineSchedStrategy. More...
 
void schedNode (SUnit *SU, bool IsTopNode) override
 Update the scheduler's state after scheduling a node. More...
 
void releaseTopNode (SUnit *SU) override
 When all predecessor dependencies have been resolved, free this node for top-down scheduling. More...
 
void releaseBottomNode (SUnit *SU) override
 When all successor dependencies have been resolved, free this node for bottom-up scheduling. More...
 
void registerRoots () override
 Notify this strategy that all roots have been released (including those that depend on EntrySU or ExitSU). More...
 
- Public Member Functions inherited from llvm::MachineSchedStrategy
virtual ~MachineSchedStrategy ()=default
 
virtual bool doMBBSchedRegionsTopDown () const
 
virtual void enterMBB (MachineBasicBlock *MBB)
 Tell the strategy that MBB is about to be processed. More...
 
virtual void leaveMBB ()
 Tell the strategy that current MBB is done. More...
 
virtual void scheduleTree (unsigned SubtreeID)
 Scheduler callback to notify that a new subtree is scheduled. More...
 

Protected Member Functions

void checkAcyclicLatency ()
 Set IsAcyclicLatencyLimited if the acyclic path is longer than the cyclic critical path by more cycles than it takes to drain the instruction buffer. More...
 
void initCandidate (SchedCandidate &Cand, SUnit *SU, bool AtTop, const RegPressureTracker &RPTracker, RegPressureTracker &TempTracker)
 
virtual void tryCandidate (SchedCandidate &Cand, SchedCandidate &TryCand, SchedBoundary *Zone) const
 Apply a set of heuristics to a new candidate. More...
 
SUnitpickNodeBidirectional (bool &IsTopNode)
 Pick the best candidate node from either the top or bottom queue. More...
 
void pickNodeFromQueue (SchedBoundary &Zone, const CandPolicy &ZonePolicy, const RegPressureTracker &RPTracker, SchedCandidate &Candidate)
 Pick the best candidate from the queue. More...
 
void reschedulePhysRegCopies (SUnit *SU, bool isTop)
 
- Protected Member Functions inherited from llvm::GenericSchedulerBase
 GenericSchedulerBase (const MachineSchedContext *C)
 
void setPolicy (CandPolicy &Policy, bool IsPostRA, SchedBoundary &CurrZone, SchedBoundary *OtherZone)
 Set the CandPolicy given a scheduling zone given the current resources and latencies inside and outside the zone. More...
 
void traceCandidate (const SchedCandidate &Cand)
 

Protected Attributes

ScheduleDAGMILiveDAG = nullptr
 
MachineSchedPolicy RegionPolicy
 
SchedBoundary Top
 
SchedBoundary Bot
 
SchedCandidate TopCand
 Candidate last picked from Top boundary. More...
 
SchedCandidate BotCand
 Candidate last picked from Bot boundary. More...
 
- Protected Attributes inherited from llvm::GenericSchedulerBase
const MachineSchedContextContext
 
const TargetSchedModelSchedModel = nullptr
 
const TargetRegisterInfoTRI = nullptr
 
SchedRemainder Rem
 

Additional Inherited Members

- Public Types inherited from llvm::GenericSchedulerBase
enum  CandReason : uint8_t {
  NoCand, Only1, PhysRegCopy, RegExcess,
  RegCritical, Stall, Cluster, Weak,
  RegMax, ResourceReduce, ResourceDemand, BotHeightReduce,
  BotPathReduce, TopDepthReduce, TopPathReduce, NextDefUse,
  NodeOrder
}
 Represent the type of SchedCandidate found within a single queue. More...
 
- Static Public Member Functions inherited from llvm::GenericSchedulerBase
static const chargetReasonStr (GenericSchedulerBase::CandReason Reason)
 

Detailed Description

GenericScheduler shrinks the unscheduled zone using heuristics to balance the schedule.

Definition at line 928 of file MachineScheduler.h.

Constructor & Destructor Documentation

◆ GenericScheduler()

llvm::GenericScheduler::GenericScheduler ( const MachineSchedContext C)
inline

Definition at line 930 of file MachineScheduler.h.

Member Function Documentation

◆ checkAcyclicLatency()

void GenericScheduler::checkAcyclicLatency ( )
protected

Set IsAcyclicLatencyLimited if the acyclic path is longer than the cyclic critical path by more cycles than it takes to drain the instruction buffer.

We estimate an upper bounds on in-flight instructions as:

CyclesPerIteration = max( CyclicPath, Loop-Resource-Height ) InFlightIterations = AcyclicPath / CyclesPerIteration InFlightResources = InFlightIterations * LoopResources

TODO: Check execution resources in addition to IssueCount.

Definition at line 2746 of file MachineScheduler.cpp.

References llvm::dbgs(), LLVM_DEBUG, and llvm::max().

◆ dumpPolicy()

void GenericScheduler::dumpPolicy ( ) const
overridevirtual

Reimplemented from llvm::MachineSchedStrategy.

Definition at line 2726 of file MachineScheduler.cpp.

References llvm::dbgs().

◆ initCandidate()

void GenericScheduler::initCandidate ( SchedCandidate Cand,
SUnit SU,
bool  AtTop,
const RegPressureTracker RPTracker,
RegPressureTracker TempTracker 
)
protected

◆ initialize()

void GenericScheduler::initialize ( ScheduleDAGMI DAG)
overridevirtual

Initialize the strategy after building the DAG for a new region.

Implements llvm::MachineSchedStrategy.

Reimplemented in llvm::GCNMaxOccupancySchedStrategy.

Definition at line 2649 of file MachineScheduler.cpp.

References assert(), llvm::ScheduleDAGInstrs::getSchedModel(), llvm::ScheduleDAGMI::hasVRegLiveness(), and TRI.

Referenced by llvm::GCNMaxOccupancySchedStrategy::initialize().

◆ initPolicy()

void GenericScheduler::initPolicy ( MachineBasicBlock::iterator  Begin,
MachineBasicBlock::iterator  End,
unsigned  NumRegionInstrs 
)
overridevirtual

Initialize the per-region scheduling policy.

Reimplemented from llvm::MachineSchedStrategy.

Definition at line 2680 of file MachineScheduler.cpp.

◆ pickNode()

SUnit * GenericScheduler::pickNode ( bool IsTopNode)
overridevirtual

◆ pickNodeBidirectional()

SUnit * GenericScheduler::pickNodeBidirectional ( bool IsTopNode)
protected

◆ pickNodeFromQueue()

void GenericScheduler::pickNodeFromQueue ( SchedBoundary Zone,
const CandPolicy ZonePolicy,
const RegPressureTracker RPTracker,
SchedCandidate Cand 
)
protected

Pick the best candidate from the queue.

TODO: getMaxPressureDelta results can be mostly cached for each SUnit during DAG building. To adjust for the current scheduling location we need to maintain the number of vreg uses remaining to be top-scheduled.

Definition at line 3021 of file MachineScheduler.cpp.

References llvm::GenericSchedulerBase::SchedCandidate::AtTop, llvm::SchedBoundary::Available, llvm::GenericSchedulerBase::SchedCandidate::initResourceDelta(), llvm::SchedBoundary::isTop(), LLVM_DEBUG, llvm::NoCand, llvm::GenericSchedulerBase::SchedCandidate::Reason, llvm::GenericSchedulerBase::SchedCandidate::ResDelta, and llvm::GenericSchedulerBase::SchedCandidate::setBest().

◆ registerRoots()

void GenericScheduler::registerRoots ( )
overridevirtual

Notify this strategy that all roots have been released (including those that depend on EntrySU or ExitSU).

Reimplemented from llvm::MachineSchedStrategy.

Definition at line 2774 of file MachineScheduler.cpp.

References llvm::ScheduleDAGMILive::computeCyclicCriticalPath(), llvm::dbgs(), llvm::DumpCriticalPathLength, llvm::errs(), llvm::ScheduleDAG::ExitSU, llvm::SUnit::getDepth(), and LLVM_DEBUG.

◆ releaseBottomNode()

void llvm::GenericScheduler::releaseBottomNode ( SUnit SU)
inlineoverridevirtual

When all successor dependencies have been resolved, free this node for bottom-up scheduling.

Implements llvm::MachineSchedStrategy.

Definition at line 962 of file MachineScheduler.h.

References llvm::SUnit::BotReadyCycle, and llvm::SUnit::isScheduled.

◆ releaseTopNode()

void llvm::GenericScheduler::releaseTopNode ( SUnit SU)
inlineoverridevirtual

When all predecessor dependencies have been resolved, free this node for top-down scheduling.

Implements llvm::MachineSchedStrategy.

Definition at line 954 of file MachineScheduler.h.

References llvm::SUnit::isScheduled, and llvm::SUnit::TopReadyCycle.

◆ reschedulePhysRegCopies()

void GenericScheduler::reschedulePhysRegCopies ( SUnit SU,
bool  isTop 
)
protected

◆ schedNode()

void GenericScheduler::schedNode ( SUnit SU,
bool  IsTopNode 
)
overridevirtual

Update the scheduler's state after scheduling a node.

This is the same node that was just returned by pickNode(). However, ScheduleDAGMILive needs to update it's state based on the current cycle before MachineSchedStrategy does.

FIXME: Eventually, we may bundle physreg copies rather than rescheduling them here. See comments in biasPhysRegCopy.

Implements llvm::MachineSchedStrategy.

Definition at line 3201 of file MachineScheduler.cpp.

References llvm::SUnit::BotReadyCycle, llvm::SUnit::hasPhysRegDefs, llvm::SUnit::hasPhysRegUses, llvm::max(), and llvm::SUnit::TopReadyCycle.

◆ shouldTrackLaneMasks()

bool llvm::GenericScheduler::shouldTrackLaneMasks ( ) const
inlineoverridevirtual

Returns true if lanemasks should be tracked.

LaneMask tracking is necessary to reorder independent subregister defs for the same vreg. This has to be enabled in combination with shouldTrackPressure().

Reimplemented from llvm::MachineSchedStrategy.

Definition at line 944 of file MachineScheduler.h.

References initialize().

◆ shouldTrackPressure()

bool llvm::GenericScheduler::shouldTrackPressure ( ) const
inlineoverridevirtual

Check if pressure tracking is needed before building the DAG and initializing this strategy.

Called after initPolicy.

Reimplemented from llvm::MachineSchedStrategy.

Definition at line 940 of file MachineScheduler.h.

◆ tryCandidate()

void GenericScheduler::tryCandidate ( SchedCandidate Cand,
SchedCandidate TryCand,
SchedBoundary Zone 
) const
protectedvirtual

Apply a set of heuristics to a new candidate.

Heuristics are currently hierarchical. This may be more efficient than a graduated cost model because we don't need to evaluate all aspects of the model for each node in the queue. But it's really done to make the heuristics easier to debug and statistically analyze.

Parameters
Candprovides the policy and current best candidate.
TryCandrefers to the next SUnit candidate, otherwise uninitialized.
Zonedescribes the scheduled zone that we are extending, or nullptr

Definition at line 2913 of file MachineScheduler.cpp.

References llvm::GenericSchedulerBase::SchedCandidate::AtTop, llvm::biasPhysRegCopy(), llvm::RegPressureDelta::CriticalMax, llvm::GenericSchedulerBase::SchedResourceDelta::CritResources, llvm::RegPressureDelta::CurrentMax, llvm::GenericSchedulerBase::SchedResourceDelta::DemandedResources, llvm::RegPressureDelta::Excess, llvm::SchedBoundary::getCurrMOps(), llvm::SchedBoundary::getLatencyStallCycles(), llvm::ScheduleDAGMI::getNextClusterPred(), llvm::ScheduleDAGMI::getNextClusterSucc(), llvm::getWeakLeft(), llvm::GenericSchedulerBase::SchedCandidate::initResourceDelta(), llvm::SchedBoundary::isTop(), llvm::ScheduleDAGMILive::isTrackingPressure(), llvm::GenericSchedulerBase::SchedCandidate::isValid(), llvm::ScheduleDAG::MF, llvm::SUnit::NodeNum, llvm::NodeOrder, llvm::GenericSchedulerBase::SchedCandidate::Policy, llvm::GenericSchedulerBase::SchedCandidate::Reason, llvm::GenericSchedulerBase::CandPolicy::ReduceLatency, llvm::GenericSchedulerBase::SchedCandidate::ResDelta, llvm::GenericSchedulerBase::SchedCandidate::RPDelta, llvm::GenericSchedulerBase::SchedCandidate::SU, TRI, llvm::tryGreater(), llvm::tryLatency(), llvm::tryLess(), and llvm::tryPressure().

Referenced by llvm::GCNMaxOccupancySchedStrategy::initialize().

Member Data Documentation

◆ Bot

SchedBoundary llvm::GenericScheduler::Bot
protected

◆ BotCand

SchedCandidate llvm::GenericScheduler::BotCand
protected

Candidate last picked from Bot boundary.

Definition at line 984 of file MachineScheduler.h.

Referenced by llvm::GCNMaxOccupancySchedStrategy::initialize(), and llvm::GCNMaxOccupancySchedStrategy::pickNode().

◆ DAG

ScheduleDAGMILive* llvm::GenericScheduler::DAG = nullptr
protected

◆ RegionPolicy

MachineSchedPolicy llvm::GenericScheduler::RegionPolicy
protected

Definition at line 975 of file MachineScheduler.h.

Referenced by llvm::GCNMaxOccupancySchedStrategy::pickNode().

◆ Top

SchedBoundary llvm::GenericScheduler::Top
protected

◆ TopCand

SchedCandidate llvm::GenericScheduler::TopCand
protected

Candidate last picked from Top boundary.

Definition at line 982 of file MachineScheduler.h.

Referenced by llvm::GCNMaxOccupancySchedStrategy::initialize(), and llvm::GCNMaxOccupancySchedStrategy::pickNode().


The documentation for this class was generated from the following files: