gem5  v20.1.0.0
Classes | Public Member Functions | Static Protected Member Functions | Protected Attributes | List of all members
LoopPredictor Class Reference

#include <loop_predictor.hh>

Inheritance diagram for LoopPredictor:
SimObject EventManager Serializable Drainable Stats::Group MPP_LoopPredictor TAGE_SC_L_LoopPredictor MPP_LoopPredictor_8KB

Classes

struct  BranchInfo
 
struct  LoopEntry
 
struct  LoopPredictorStats
 

Public Member Functions

int lindex (Addr pc_in, unsigned instShiftAmt) const
 Computes the index used to access the loop predictor. More...
 
int finallindex (int lindex, int lowPcBits, int way) const
 Computes the index used to access the ltable structures. More...
 
bool getLoop (Addr pc, BranchInfo *bi, bool speculative, unsigned instShiftAmt) const
 Get a branch prediction from the loop predictor. More...
 
void loopUpdate (Addr pc, bool Taken, BranchInfo *bi, bool tage_pred)
 Updates the loop predictor. More...
 
void specLoopUpdate (bool taken, BranchInfo *bi)
 Speculatively updates the loop predictor iteration count (only for useSpeculation). More...
 
void condBranchUpdate (ThreadID tid, Addr branch_pc, bool taken, bool tage_pred, BranchInfo *bi, unsigned instShiftAmt)
 Update LTAGE for conditional branches. More...
 
bool loopPredict (ThreadID tid, Addr branch_pc, bool cond_branch, BranchInfo *bi, bool prev_pred_taken, unsigned instShiftAmt)
 Get the loop prediction. More...
 
void updateStats (bool taken, BranchInfo *bi)
 Update the stats. More...
 
void squashLoop (BranchInfo *bi)
 
void squash (ThreadID tid, BranchInfo *bi)
 
virtual bool calcConf (int index) const
 
virtual bool optionalAgeInc () const
 
virtual BranchInfomakeBranchInfo ()
 
int8_t getLoopUseCounter () const
 Gets the value of the loop use counter. More...
 
void init () override
 Initialize the loop predictor. More...
 
 LoopPredictor (LoopPredictorParams *p)
 
size_t getSizeInBits () const
 
- Public Member Functions inherited from SimObject
const Paramsparams () const
 
 SimObject (const Params *_params)
 
virtual ~SimObject ()
 
virtual const std::string name () const
 
virtual void loadState (CheckpointIn &cp)
 loadState() is called on each SimObject when restoring from a checkpoint. More...
 
virtual void initState ()
 initState() is called on each SimObject when not restoring from a checkpoint. More...
 
virtual void regProbePoints ()
 Register probe points for this object. More...
 
virtual void regProbeListeners ()
 Register probe listeners for this object. More...
 
ProbeManagergetProbeManager ()
 Get the probe manager for this object. More...
 
virtual PortgetPort (const std::string &if_name, PortID idx=InvalidPortID)
 Get a port with a given name and index. More...
 
virtual void startup ()
 startup() is the final initialization call before simulation. More...
 
DrainState drain () override
 Provide a default implementation of the drain interface for objects that don't need draining. More...
 
virtual void memWriteback ()
 Write back dirty buffers to memory using functional writes. More...
 
virtual void memInvalidate ()
 Invalidate the contents of memory buffers. More...
 
void serialize (CheckpointOut &cp) const override
 Serialize an object. More...
 
void unserialize (CheckpointIn &cp) override
 Unserialize an object. More...
 
- Public Member Functions inherited from EventManager
EventQueueeventQueue () const
 
void schedule (Event &event, Tick when)
 
void deschedule (Event &event)
 
void reschedule (Event &event, Tick when, bool always=false)
 
void schedule (Event *event, Tick when)
 
void deschedule (Event *event)
 
void reschedule (Event *event, Tick when, bool always=false)
 
void wakeupEventQueue (Tick when=(Tick) -1)
 This function is not needed by the usual gem5 event loop but may be necessary in derived EventQueues which host gem5 on other schedulers. More...
 
void setCurTick (Tick newVal)
 
 EventManager (EventManager &em)
 Event manger manages events in the event queue. More...
 
 EventManager (EventManager *em)
 
 EventManager (EventQueue *eq)
 
- Public Member Functions inherited from Serializable
 Serializable ()
 
virtual ~Serializable ()
 
void serializeSection (CheckpointOut &cp, const char *name) const
 Serialize an object into a new section. More...
 
void serializeSection (CheckpointOut &cp, const std::string &name) const
 
void unserializeSection (CheckpointIn &cp, const char *name)
 Unserialize an a child object. More...
 
void unserializeSection (CheckpointIn &cp, const std::string &name)
 
- Public Member Functions inherited from Drainable
DrainState drainState () const
 Return the current drain state of an object. More...
 
virtual void notifyFork ()
 Notify a child process of a fork. More...
 
- Public Member Functions inherited from Stats::Group
 Group (Group *parent, const char *name=nullptr)
 Construct a new statistics group. More...
 
virtual ~Group ()
 
virtual void regStats ()
 Callback to set stat parameters. More...
 
virtual void resetStats ()
 Callback to reset stats. More...
 
virtual void preDumpStats ()
 Callback before stats are dumped. More...
 
void addStat (Stats::Info *info)
 Register a stat with this group. More...
 
const std::map< std::string, Group * > & getStatGroups () const
 Get all child groups associated with this object. More...
 
const std::vector< Info * > & getStats () const
 Get all stats associated with this object. More...
 
void addStatGroup (const char *name, Group *block)
 Add a stat block as a child of this block. More...
 
const InforesolveStat (std::string name) const
 Resolve a stat by its name within this group. More...
 
 Group ()=delete
 
 Group (const Group &)=delete
 
Groupoperator= (const Group &)=delete
 

Static Protected Member Functions

static void unsignedCtrUpdate (uint8_t &ctr, bool up, unsigned nbits)
 Updates an unsigned counter based on up/down parameter. More...
 
static void signedCtrUpdate (int8_t &ctr, bool up, unsigned nbits)
 

Protected Attributes

const unsigned logSizeLoopPred
 
const unsigned loopTableAgeBits
 
const unsigned loopTableConfidenceBits
 
const unsigned loopTableTagBits
 
const unsigned loopTableIterBits
 
const unsigned logLoopTableAssoc
 
const uint8_t confidenceThreshold
 
const uint16_t loopTagMask
 
const uint16_t loopNumIterMask
 
const int loopSetMask
 
LoopEntryltable
 
int8_t loopUseCounter
 
unsigned withLoopBits
 
const bool useDirectionBit
 
const bool useSpeculation
 
const bool useHashing
 
const bool restrictAllocation
 
const unsigned initialLoopIter
 
const unsigned initialLoopAge
 
const bool optionalAgeReset
 
LoopPredictor::LoopPredictorStats stats
 
- Protected Attributes inherited from SimObject
const SimObjectParams * _params
 Cached copy of the object parameters. More...
 
- Protected Attributes inherited from EventManager
EventQueueeventq
 A pointer to this object's event queue. More...
 

Additional Inherited Members

- Public Types inherited from SimObject
typedef SimObjectParams Params
 
- Static Public Member Functions inherited from SimObject
static void serializeAll (CheckpointOut &cp)
 Serialize all SimObjects in the system. More...
 
static SimObjectfind (const char *name)
 Find the SimObject with the given name and return a pointer to it. More...
 
- Static Public Member Functions inherited from Serializable
static const std::string & currentSection ()
 Gets the fully-qualified name of the active section. More...
 
static void serializeAll (const std::string &cpt_dir)
 Serializes all the SimObjects. More...
 
static void unserializeGlobals (CheckpointIn &cp)
 
- Protected Member Functions inherited from Drainable
 Drainable ()
 
virtual ~Drainable ()
 
virtual void drainResume ()
 Resume execution after a successful drain. More...
 
void signalDrainDone () const
 Signal that an object is drained. More...
 

Detailed Description

Definition at line 43 of file loop_predictor.hh.

Constructor & Destructor Documentation

◆ LoopPredictor()

LoopPredictor::LoopPredictor ( LoopPredictorParams *  p)

Definition at line 41 of file loop_predictor.cc.

References initialLoopAge, and loopTableAgeBits.

Member Function Documentation

◆ calcConf()

bool LoopPredictor::calcConf ( int  index) const
virtual

◆ condBranchUpdate()

void LoopPredictor::condBranchUpdate ( ThreadID  tid,
Addr  branch_pc,
bool  taken,
bool  tage_pred,
BranchInfo bi,
unsigned  instShiftAmt 
)

Update LTAGE for conditional branches.

Parameters
branch_pcThe unshifted branch PC.
takenActual branch outcome.
tage_predPrediction from TAGE
biPointer to information on the prediction recorded at prediction time.
instShiftAmtNumber of bits to shift instructions

Definition at line 325 of file loop_predictor.cc.

References PowerISA::bi, getLoop(), loopUpdate(), loopUseCounter, signedCtrUpdate(), useSpeculation, and withLoopBits.

Referenced by LTAGE::update(), TAGE_SC_L::update(), and MultiperspectivePerceptronTAGE::update().

◆ finallindex()

int LoopPredictor::finallindex ( int  lindex,
int  lowPcBits,
int  way 
) const

Computes the index used to access the ltable structures.

It may take hashing into account

Parameters
indexResult of lindex function
lowPcBitsPC bits masked with set size
wayWay to be used

Definition at line 103 of file loop_predictor.cc.

References MipsISA::index, logLoopTableAssoc, and useHashing.

Referenced by getLoop(), loopUpdate(), specLoopUpdate(), squash(), and squashLoop().

◆ getLoop()

bool LoopPredictor::getLoop ( Addr  pc,
BranchInfo bi,
bool  speculative,
unsigned  instShiftAmt 
) const

Get a branch prediction from the loop predictor.

Parameters
pcThe unshifted branch PC.
biPointer to information on the prediction.
speculativeUse speculative number of iterations
instShiftAmtShift the pc by as many bits (if hashing is not used)
Returns
the result of the prediction, if it could be predicted

Definition at line 112 of file loop_predictor.cc.

References PowerISA::bi, calcConf(), LoopPredictor::LoopEntry::currentIter, LoopPredictor::LoopEntry::currentIterSpec, LoopPredictor::LoopEntry::dir, finallindex(), ArmISA::i, lindex(), logLoopTableAssoc, logSizeLoopPred, loopSetMask, loopTableTagBits, loopTagMask, ltable, MipsISA::pc, useDirectionBit, and useHashing.

Referenced by condBranchUpdate(), and loopPredict().

◆ getLoopUseCounter()

int8_t LoopPredictor::getLoopUseCounter ( ) const
inline

Gets the value of the loop use counter.

Returns
the loop use counter value

Definition at line 245 of file loop_predictor.hh.

References loopUseCounter.

Referenced by LTAGE::predict().

◆ getSizeInBits()

size_t LoopPredictor::getSizeInBits ( ) const

◆ init()

void LoopPredictor::init ( )
overridevirtual

Initialize the loop predictor.

Reimplemented from SimObject.

Definition at line 67 of file loop_predictor.cc.

References logLoopTableAssoc, logSizeLoopPred, loopTableIterBits, loopTableTagBits, ltable, and ULL.

◆ lindex()

int LoopPredictor::lindex ( Addr  pc_in,
unsigned  instShiftAmt 
) const

Computes the index used to access the loop predictor.

Parameters
pc_inThe unshifted branch PC.
instShiftAmtShift the pc by as many bits

Definition at line 86 of file loop_predictor.cc.

References logLoopTableAssoc, loopSetMask, MipsISA::pc, and useHashing.

Referenced by getLoop().

◆ loopPredict()

bool LoopPredictor::loopPredict ( ThreadID  tid,
Addr  branch_pc,
bool  cond_branch,
BranchInfo bi,
bool  prev_pred_taken,
unsigned  instShiftAmt 
)

Get the loop prediction.

Parameters
tidThe thread ID to select the global histories to use.
branch_pcThe unshifted branch PC.
cond_branchTrue if the branch is conditional.
biReference to wrapping pointer to allow storing derived class prediction information in the base class.
prev_pred_takenResult of the TAGE prediction
instShiftAmtShift the pc by as many bits
instShiftAmtShift the pc by as many bits
Returns
the prediction, true if taken

Definition at line 271 of file loop_predictor.cc.

References PowerISA::bi, getLoop(), loopUseCounter, specLoopUpdate(), and useSpeculation.

Referenced by MultiperspectivePerceptronTAGE::lookup(), LTAGE::predict(), and TAGE_SC_L::predict().

◆ loopUpdate()

void LoopPredictor::loopUpdate ( Addr  pc,
bool  Taken,
BranchInfo bi,
bool  tage_pred 
)

◆ makeBranchInfo()

LoopPredictor::BranchInfo * LoopPredictor::makeBranchInfo ( )
virtual

Definition at line 80 of file loop_predictor.cc.

◆ optionalAgeInc()

bool LoopPredictor::optionalAgeInc ( ) const
virtual

Reimplemented in TAGE_SC_L_LoopPredictor, and MPP_LoopPredictor.

Definition at line 170 of file loop_predictor.cc.

Referenced by loopUpdate().

◆ signedCtrUpdate()

static void LoopPredictor::signedCtrUpdate ( int8_t &  ctr,
bool  up,
unsigned  nbits 
)
inlinestaticprotected

Definition at line 110 of file loop_predictor.hh.

References ArmISA::up.

Referenced by condBranchUpdate().

◆ specLoopUpdate()

void LoopPredictor::specLoopUpdate ( bool  taken,
BranchInfo bi 
)

Speculatively updates the loop predictor iteration count (only for useSpeculation).

Parameters
takenThe predicted branch outcome.
biPointer to information on the prediction recorded at prediction time.

Definition at line 156 of file loop_predictor.cc.

References PowerISA::bi, LoopPredictor::LoopEntry::currentIterSpec, finallindex(), MipsISA::index, loopNumIterMask, and ltable.

Referenced by loopPredict().

◆ squash()

void LoopPredictor::squash ( ThreadID  tid,
BranchInfo bi 
)

◆ squashLoop()

void LoopPredictor::squashLoop ( BranchInfo bi)

◆ unsignedCtrUpdate()

static void LoopPredictor::unsignedCtrUpdate ( uint8_t &  ctr,
bool  up,
unsigned  nbits 
)
inlinestaticprotected

Updates an unsigned counter based on up/down parameter.

Parameters
ctrReference to counter to update.
upBoolean indicating if the counter is incremented/decremented If true it is incremented, if false it is decremented
nbitsCounter width.

Definition at line 99 of file loop_predictor.hh.

References ArmISA::up.

Referenced by loopUpdate().

◆ updateStats()

void LoopPredictor::updateStats ( bool  taken,
BranchInfo bi 
)

Update the stats.

Parameters
takenActual branch outcome
biPointer to information on the prediction recorded at prediction time.

Definition at line 315 of file loop_predictor.cc.

References PowerISA::bi, LoopPredictor::LoopPredictorStats::correct, stats, and LoopPredictor::LoopPredictorStats::wrong.

Referenced by LTAGE::update(), TAGE_SC_L::update(), and MultiperspectivePerceptronTAGE::update().

Member Data Documentation

◆ confidenceThreshold

const uint8_t LoopPredictor::confidenceThreshold
protected

Definition at line 52 of file loop_predictor.hh.

Referenced by calcConf().

◆ initialLoopAge

const unsigned LoopPredictor::initialLoopAge
protected

Definition at line 83 of file loop_predictor.hh.

Referenced by LoopPredictor(), and loopUpdate().

◆ initialLoopIter

const unsigned LoopPredictor::initialLoopIter
protected

Definition at line 82 of file loop_predictor.hh.

Referenced by loopUpdate().

◆ logLoopTableAssoc

const unsigned LoopPredictor::logLoopTableAssoc
protected

Definition at line 51 of file loop_predictor.hh.

Referenced by finallindex(), getLoop(), init(), lindex(), and loopUpdate().

◆ logSizeLoopPred

const unsigned LoopPredictor::logSizeLoopPred
protected

Definition at line 46 of file loop_predictor.hh.

Referenced by getLoop(), getSizeInBits(), and init().

◆ loopNumIterMask

const uint16_t LoopPredictor::loopNumIterMask
protected

Definition at line 54 of file loop_predictor.hh.

Referenced by loopUpdate(), and specLoopUpdate().

◆ loopSetMask

const int LoopPredictor::loopSetMask
protected

Definition at line 55 of file loop_predictor.hh.

Referenced by getLoop(), and lindex().

◆ loopTableAgeBits

const unsigned LoopPredictor::loopTableAgeBits
protected

Definition at line 47 of file loop_predictor.hh.

Referenced by getSizeInBits(), LoopPredictor(), and loopUpdate().

◆ loopTableConfidenceBits

const unsigned LoopPredictor::loopTableConfidenceBits
protected

Definition at line 48 of file loop_predictor.hh.

Referenced by getSizeInBits(), and loopUpdate().

◆ loopTableIterBits

const unsigned LoopPredictor::loopTableIterBits
protected

Definition at line 50 of file loop_predictor.hh.

Referenced by getSizeInBits(), and init().

◆ loopTableTagBits

const unsigned LoopPredictor::loopTableTagBits
protected

Definition at line 49 of file loop_predictor.hh.

Referenced by getLoop(), getSizeInBits(), and init().

◆ loopTagMask

const uint16_t LoopPredictor::loopTagMask
protected

Definition at line 53 of file loop_predictor.hh.

Referenced by getLoop().

◆ loopUseCounter

int8_t LoopPredictor::loopUseCounter
protected

Definition at line 75 of file loop_predictor.hh.

Referenced by condBranchUpdate(), getLoopUseCounter(), and loopPredict().

◆ ltable

LoopEntry* LoopPredictor::ltable
protected

◆ optionalAgeReset

const bool LoopPredictor::optionalAgeReset
protected

Definition at line 84 of file loop_predictor.hh.

Referenced by loopUpdate().

◆ restrictAllocation

const bool LoopPredictor::restrictAllocation
protected

Definition at line 81 of file loop_predictor.hh.

Referenced by loopUpdate().

◆ stats

LoopPredictor::LoopPredictorStats LoopPredictor::stats
protected

Referenced by updateStats().

◆ useDirectionBit

const bool LoopPredictor::useDirectionBit
protected

Definition at line 78 of file loop_predictor.hh.

Referenced by getLoop(), getSizeInBits(), and loopUpdate().

◆ useHashing

const bool LoopPredictor::useHashing
protected

Definition at line 80 of file loop_predictor.hh.

Referenced by finallindex(), getLoop(), and lindex().

◆ useSpeculation

const bool LoopPredictor::useSpeculation
protected

Definition at line 79 of file loop_predictor.hh.

Referenced by condBranchUpdate(), getSizeInBits(), and loopPredict().

◆ withLoopBits

unsigned LoopPredictor::withLoopBits
protected

Definition at line 76 of file loop_predictor.hh.

Referenced by condBranchUpdate().


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

Generated on Wed Sep 30 2020 14:02:27 for gem5 by doxygen 1.8.17