gem5  v21.1.0.2
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gem5::branch_prediction::MultiperspectivePerceptronTAGE Class Reference

#include <multiperspective_perceptron_tage.hh>

Inheritance diagram for gem5::branch_prediction::MultiperspectivePerceptronTAGE:
gem5::branch_prediction::MultiperspectivePerceptron gem5::branch_prediction::BPredUnit gem5::SimObject gem5::EventManager gem5::Serializable gem5::Drainable gem5::statistics::Group gem5::Named gem5::branch_prediction::MultiperspectivePerceptronTAGE64KB gem5::branch_prediction::MultiperspectivePerceptronTAGE8KB

Classes

struct  MPPTAGEBranchInfo
 Branch information data type. More...
 

Public Member Functions

 MultiperspectivePerceptronTAGE (const MultiperspectivePerceptronTAGEParams &p)
 
void init () override
 init() is called after all C++ SimObjects have been created and all ports are connected. More...
 
bool lookup (ThreadID tid, Addr instPC, void *&bp_history) override
 Looks up a given PC in the BP to see if it is taken or not taken. More...
 
void update (ThreadID tid, Addr instPC, bool taken, void *bp_history, bool squashed, const StaticInstPtr &inst, Addr corrTarget) override
 Updates the BP with taken/not taken information. More...
 
void uncondBranch (ThreadID tid, Addr pc, void *&bp_history) override
 
void squash (ThreadID tid, void *bp_history) override
 
- Public Member Functions inherited from gem5::branch_prediction::MultiperspectivePerceptron
 MultiperspectivePerceptron (const MultiperspectivePerceptronParams &params)
 
void setExtraBits (int bits)
 Sets the starting number of storage bits to compute the number of table entries. More...
 
void btbUpdate (ThreadID tid, Addr branch_addr, void *&bp_history) override
 If a branch is not taken, because the BTB address is invalid or missing, this function sets the appropriate counter in the global and local predictors to not taken. More...
 
- Public Member Functions inherited from gem5::branch_prediction::BPredUnit
 BPredUnit (const Params &p)
 
void regProbePoints () override
 Register probe points for this object. More...
 
void drainSanityCheck () const
 Perform sanity checks after a drain. More...
 
bool predict (const StaticInstPtr &inst, const InstSeqNum &seqNum, TheISA::PCState &pc, ThreadID tid)
 Predicts whether or not the instruction is a taken branch, and the target of the branch if it is taken. More...
 
void update (const InstSeqNum &done_sn, ThreadID tid)
 Tells the branch predictor to commit any updates until the given sequence number. More...
 
void squash (const InstSeqNum &squashed_sn, ThreadID tid)
 Squashes all outstanding updates until a given sequence number. More...
 
void squash (const InstSeqNum &squashed_sn, const TheISA::PCState &corr_target, bool actually_taken, ThreadID tid)
 Squashes all outstanding updates until a given sequence number, and corrects that sn's update with the proper address and taken/not taken. More...
 
bool BTBValid (Addr instPC)
 Looks up a given PC in the BTB to see if a matching entry exists. More...
 
TheISA::PCState BTBLookup (Addr instPC)
 Looks up a given PC in the BTB to get the predicted target. More...
 
void BTBUpdate (Addr instPC, const TheISA::PCState &target)
 Updates the BTB with the target of a branch. More...
 
void dump ()
 
- Public Member Functions inherited from gem5::SimObject
const Paramsparams () const
 
 SimObject (const Params &p)
 
virtual ~SimObject ()
 
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 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 gem5::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 gem5::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 gem5::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 gem5::statistics::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 (statistics::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...
 
void mergeStatGroup (Group *block)
 Merge the contents (stats & children) of a block to this block. More...
 
 Group ()=delete
 
 Group (const Group &)=delete
 
Groupoperator= (const Group &)=delete
 
- Public Member Functions inherited from gem5::Named
 Named (const std::string &name_)
 
virtual ~Named ()=default
 
virtual std::string name () const
 

Private Member Functions

unsigned int getIndex (ThreadID tid, MPPTAGEBranchInfo &bi, const HistorySpec &spec, int index) const
 
int computePartialSum (ThreadID tid, MPPTAGEBranchInfo &bi) const
 
void updatePartial (ThreadID tid, MPPTAGEBranchInfo &bi, bool taken)
 
void updateHistories (ThreadID tid, MPPTAGEBranchInfo &bi, bool taken)
 

Private Attributes

TAGEBasetage
 
LoopPredictorloopPredictor
 
StatisticalCorrectorstatisticalCorrector
 

Additional Inherited Members

- Public Types inherited from gem5::branch_prediction::BPredUnit
typedef BranchPredictorParams Params
 
- Public Types inherited from gem5::SimObject
typedef SimObjectParams Params
 
- Static Public Member Functions inherited from gem5::SimObject
static void serializeAll (const std::string &cpt_dir)
 Create a checkpoint by serializing 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 void setSimObjectResolver (SimObjectResolver *resolver)
 There is a single object name resolver, and it is only set when simulation is restoring from checkpoints. More...
 
static SimObjectResolvergetSimObjectResolver ()
 There is a single object name resolver, and it is only set when simulation is restoring from checkpoints. More...
 
- Static Public Member Functions inherited from gem5::Serializable
static const std::string & currentSection ()
 Gets the fully-qualified name of the active section. More...
 
static void generateCheckpointOut (const std::string &cpt_dir, std::ofstream &outstream)
 Generate a checkpoint file so that the serialization can be routed to it. More...
 
- Protected Member Functions inherited from gem5::branch_prediction::MultiperspectivePerceptron
void insertModhistSpec (int p1, int p2)
 Auxiliary function for MODHIST and GHISTMODPATH features. More...
 
void insertModpathSpec (int p1, int p2)
 Auxiliary function for MODPATH and GHISTMODPATH features. More...
 
int insert (std::vector< int > &v, int x)
 Auxiliary function used by insertModhistSpec and insertModpathSpec. More...
 
void computeBits (int num_filter_entries, int nlocal_histories, int local_history_length, bool ignore_path_size)
 Computes the size in bits of the structures needed to keep track of the history and the predictor tables and assigns the sizes of those tables that did not had their size specified. More...
 
virtual void createSpecs ()=0
 Creates the tables of the predictor. More...
 
unsigned int getIndex (ThreadID tid, const MPPBranchInfo &bi, const HistorySpec &spec, int index) const
 Get the position index of a predictor table. More...
 
void findBest (ThreadID tid, std::vector< int > &best_preds) const
 Finds the best subset of features to use in case of a low-confidence branch, returns the result as an ordered vector of the indices to the predictor tables. More...
 
int computeOutput (ThreadID tid, MPPBranchInfo &bi)
 Computes the output of the predictor for a given branch and the resulting best value in case the prediction has low confidence. More...
 
void train (ThreadID tid, MPPBranchInfo &bi, bool taken)
 Trains the branch predictor with the given branch and direction. More...
 
void satIncDec (bool taken, bool &sign, int &c, int max_weight) const
 Auxiliary function to increase a table counter depending on the direction of the branch. More...
 
void addSpec (HistorySpec *spec)
 Add a table spec to the prefetcher. More...
 
- Protected Member Functions inherited from gem5::branch_prediction::BPredUnit
probing::PMUUPtr pmuProbePoint (const char *name)
 Helper method to instantiate probe points belonging to this object. More...
 
- Protected Member Functions inherited from gem5::Drainable
 Drainable ()
 
virtual ~Drainable ()
 
virtual void drainResume ()
 Resume execution after a successful drain. More...
 
void signalDrainDone () const
 Signal that an object is drained. More...
 
- Protected Attributes inherited from gem5::branch_prediction::MultiperspectivePerceptron
const int blockSize
 Predictor parameters. More...
 
const int pcshift
 
const int threshold
 
const int bias0
 
const int bias1
 
const int biasmostly0
 
const int biasmostly1
 
const int nbest
 
const int tunebits
 
const int hshift
 
const unsigned long long int imli_mask1
 
const unsigned long long int imli_mask4
 
const unsigned long long int recencypos_mask
 
const double fudge
 
const int n_sign_bits
 
const int pcbit
 
const int decay
 
const unsigned int record_mask
 
const bool hash_taken
 
const bool tuneonly
 
const int extra_rounds
 
const int speed
 
const int budgetbits
 
const bool speculative_update
 
std::vector< ThreadData * > threadData
 
std::vector< HistorySpec * > specs
 Predictor tables. More...
 
std::vector< int > table_sizes
 
bool doing_local
 runtime values and data used to count the size in bits More...
 
bool doing_recency
 
int assoc
 
int ghist_length
 
int modghist_length
 
int path_length
 
int thresholdCounter
 
int theta
 
int extrabits
 
std::vector< int > imli_counter_bits
 
std::vector< int > modhist_indices
 
std::vector< int > modhist_lengths
 
std::vector< int > modpath_indices
 
std::vector< int > modpath_lengths
 
std::vector< std::vector< int > > blurrypath_bits
 
std::vector< std::vector< std::vector< bool > > > acyclic_bits
 
- Protected Attributes inherited from gem5::branch_prediction::BPredUnit
const unsigned instShiftAmt
 Number of bits to shift instructions by for predictor addresses. More...
 
probing::PMUUPtr ppBranches
 Branches seen by the branch predictor. More...
 
probing::PMUUPtr ppMisses
 Miss-predicted branches. More...
 
- Protected Attributes inherited from gem5::SimObject
const SimObjectParams & _params
 Cached copy of the object parameters. More...
 
- Protected Attributes inherited from gem5::EventManager
EventQueueeventq
 A pointer to this object's event queue. More...
 
- Static Protected Attributes inherited from gem5::branch_prediction::MultiperspectivePerceptron
static int xlat []
 Transfer function for 6-width tables. More...
 
static int xlat4 []
 Transfer function for 5-width tables. More...
 

Detailed Description

Definition at line 193 of file multiperspective_perceptron_tage.hh.

Constructor & Destructor Documentation

◆ MultiperspectivePerceptronTAGE()

gem5::branch_prediction::MultiperspectivePerceptronTAGE::MultiperspectivePerceptronTAGE ( const MultiperspectivePerceptronTAGEParams &  p)

Member Function Documentation

◆ computePartialSum()

int gem5::branch_prediction::MultiperspectivePerceptronTAGE::computePartialSum ( ThreadID  tid,
MPPTAGEBranchInfo bi 
) const
private

◆ getIndex()

unsigned int gem5::branch_prediction::MultiperspectivePerceptronTAGE::getIndex ( ThreadID  tid,
MPPTAGEBranchInfo bi,
const HistorySpec spec,
int  index 
) const
private

◆ init()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::init ( )
overridevirtual

◆ lookup()

bool gem5::branch_prediction::MultiperspectivePerceptronTAGE::lookup ( ThreadID  tid,
Addr  instPC,
void *&  bp_history 
)
overridevirtual

Looks up a given PC in the BP to see if it is taken or not taken.

Parameters
inst_PCThe PC to look up.
bp_historyPointer that will be set to an object that has the branch predictor state associated with the lookup.
Returns
Whether the branch is taken or not taken.

Reimplemented from gem5::branch_prediction::MultiperspectivePerceptron.

Definition at line 520 of file multiperspective_perceptron_tage.cc.

References gem5::PowerISA::bi, computePartialSum(), gem5::branch_prediction::TAGEBase::getPathHist(), gem5::branch_prediction::BPredUnit::instShiftAmt, gem5::branch_prediction::TAGEBase::isHighConfidence(), gem5::branch_prediction::LoopPredictor::loopPredict(), loopPredictor, gem5::branch_prediction::MultiperspectivePerceptron::pcshift, gem5::branch_prediction::StatisticalCorrector::scPredict(), statisticalCorrector, tage, and gem5::branch_prediction::TAGEBase::tagePredict().

◆ squash()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::squash ( ThreadID  tid,
void *  bp_history 
)
overridevirtual
Parameters
bp_historyPointer to the history object. The predictor will need to update any state and delete the object.

Reimplemented from gem5::branch_prediction::MultiperspectivePerceptron.

Definition at line 683 of file multiperspective_perceptron_tage.cc.

References gem5::PowerISA::bi.

◆ uncondBranch()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::uncondBranch ( ThreadID  tid,
Addr  pc,
void *&  bp_history 
)
overridevirtual

◆ update()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::update ( ThreadID  tid,
Addr  instPC,
bool  taken,
void *  bp_history,
bool  squashed,
const StaticInstPtr inst,
Addr  corrTarget 
)
overridevirtual

Updates the BP with taken/not taken information.

Parameters
inst_PCThe branch's PC that will be updated.
takenWhether the branch was taken or not taken.
bp_historyPointer to the branch predictor state that is associated with the branch lookup that is being updated.
squashedSet to true when this function is called during a squash operation.
instStatic instruction information
corrTargetThe resolved target of the branch (only needed for squashed branches)
Todo:
Make this update flexible enough to handle a global predictor.

Reimplemented from gem5::branch_prediction::MultiperspectivePerceptron.

Definition at line 593 of file multiperspective_perceptron_tage.cc.

References gem5::PowerISA::bi, gem5::branch_prediction::LoopPredictor::condBranchUpdate(), gem5::branch_prediction::StatisticalCorrector::condBranchUpdate(), gem5::branch_prediction::TAGEBase::condBranchUpdate(), gem5::branch_prediction::TAGEBase::getPathHist(), gem5::branch_prediction::BPredUnit::instShiftAmt, gem5::StaticInst::isCall(), gem5::StaticInst::isCondCtrl(), gem5::StaticInst::isDirectCtrl(), gem5::StaticInst::isReturn(), gem5::branch_prediction::TAGEBase::isSpeculativeUpdateEnabled(), loopPredictor, gem5::Random::random(), gem5::random_mt, gem5::branch_prediction::StatisticalCorrector::scHistoryUpdate(), gem5::branch_prediction::TAGEBase::squash(), gem5::branch_prediction::LoopPredictor::squashLoop(), statisticalCorrector, tage, gem5::branch_prediction::MultiperspectivePerceptron::threadData, updateHistories(), gem5::branch_prediction::TAGEBase::updateHistories(), updatePartial(), gem5::branch_prediction::LoopPredictor::updateStats(), gem5::branch_prediction::StatisticalCorrector::updateStats(), and gem5::branch_prediction::TAGEBase::updateStats().

◆ updateHistories()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::updateHistories ( ThreadID  tid,
MPPTAGEBranchInfo bi,
bool  taken 
)
private

◆ updatePartial()

void gem5::branch_prediction::MultiperspectivePerceptronTAGE::updatePartial ( ThreadID  tid,
MPPTAGEBranchInfo bi,
bool  taken 
)
private

Member Data Documentation

◆ loopPredictor

LoopPredictor* gem5::branch_prediction::MultiperspectivePerceptronTAGE::loopPredictor
private

Definition at line 196 of file multiperspective_perceptron_tage.hh.

Referenced by init(), lookup(), uncondBranch(), and update().

◆ statisticalCorrector

StatisticalCorrector* gem5::branch_prediction::MultiperspectivePerceptronTAGE::statisticalCorrector
private

Definition at line 197 of file multiperspective_perceptron_tage.hh.

Referenced by init(), lookup(), uncondBranch(), and update().

◆ tage

TAGEBase* gem5::branch_prediction::MultiperspectivePerceptronTAGE::tage
private

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

Generated on Tue Sep 21 2021 12:28:49 for gem5 by doxygen 1.8.17