#include <multiperspective_perceptron_tage.hh>

Inheritance diagram for gem5::branch_prediction::MPP_TAGE:

Classes
struct	BranchInfo

Public Member Functions
	MPP_TAGE (const MPP_TAGEParams &p)

void	calculateParameters () override
	Calculates the history lengths and some other paramters in derived classes.

void	handleTAGEUpdate (Addr branch_pc, bool taken, TAGEBase::BranchInfo *bi) override
	Handles the update of the TAGE entries.

void	handleAllocAndUReset (bool alloc, bool taken, TAGEBase::BranchInfo *bi, int nrand) override
	Handles Allocation and U bits reset on an update.

void	handleUReset () override
	Handles the U bits reset.

void	resetUctr (uint8_t &u) override
	Algorithm for resetting a single U counter.

int	bindex (Addr pc_in) const override
	Computes the index used to access the bimodal table.

bool	isHighConfidence (TAGEBase::BranchInfo *bi) const override

unsigned	getUseAltIdx (TAGEBase::BranchInfo *bi, Addr branch_pc) override
	Calculation of the index for useAltPredForNewlyAllocated On this base TAGE implementation it is always 0.

void	adjustAlloc (bool &alloc, bool taken, bool pred_taken) override
	Extra calculation to tell whether TAGE allocaitons may happen or not on an update For this base TAGE implementation it does nothing.

void	updateHistories (ThreadID tid, Addr branch_pc, bool speculative, bool taken, Addr target, const StaticInstPtr &inst, TAGEBase::BranchInfo *bi) override
	(Speculatively) updates global histories (path and direction).

Public Member Functions inherited from gem5::branch_prediction::TAGEBase
	TAGEBase (const TAGEBaseParams &p)

void	init () override
	init() is called after all C++ SimObjects have been created and all ports are connected.

virtual BranchInfo *	makeBranchInfo (Addr pc, bool conditional)

virtual int	gindex (ThreadID tid, Addr pc, int bank) const
	Computes the index used to access a partially tagged table.

virtual int	F (int phist, int size, int bank) const
	Utility function to shuffle the path history depending on which tagged table we are accessing.

virtual uint16_t	gtag (ThreadID tid, Addr pc, int bank) const
	Computes the partial tag of a tagged table.

virtual bool	getBimodePred (Addr pc, BranchInfo *bi) const
	Get a branch prediction from the bimodal predictor.

void	baseUpdate (Addr pc, bool taken, BranchInfo *bi)
	Updates the bimodal predictor.

void	updateGHist (ThreadID tid, uint64_t bv, uint8_t n)
	Internal history update function.

void	update (ThreadID tid, Addr branch_pc, bool taken, BranchInfo *bi)
	Update TAGE.

void	recordHistState (ThreadID tid, BranchInfo *bi)
	Records the current state of the histories to be able to restore it in case of a mispredicted speculative update.

void	restoreHistState (ThreadID tid, BranchInfo *bi)
	Restore the state of the histories in case of detecting a mispredicted speculative update.

virtual void	updatePathAndGlobalHistory (ThreadID tid, int brtype, bool taken, Addr branch_pc, Addr target, BranchInfo *bi)
	Does the actual update of path and global history.

virtual int	branchTypeExtra (const StaticInstPtr &inst)
	This function acts as a hook for other TAGE implementations to adjust the branch type.

virtual void	squash (ThreadID tid, bool taken, Addr target, const StaticInstPtr &inst, BranchInfo *bi)
	Restores speculatively updated path and direction histories.

virtual void	condBranchUpdate (ThreadID tid, Addr branch_pc, bool taken, BranchInfo *bi, int nrand, Addr corrTarget, bool pred, bool preAdjustAlloc=false)
	Update TAGE for conditional branches.

bool	tagePredict (ThreadID tid, Addr branch_pc, bool cond_branch, BranchInfo *bi)
	TAGE prediction called from TAGE::predict.

virtual void	updateStats (bool taken, BranchInfo *bi)
	Update the stats.

virtual void	buildTageTables ()
	Instantiates the TAGE table entries.

virtual void	calculateIndicesAndTags (ThreadID tid, Addr branch_pc, BranchInfo *bi)
	On a prediction, calculates the TAGE indices and tags for all the different history lengths.

virtual void	extraAltCalc (BranchInfo *bi)
	Extra steps for calculating altTaken For this base TAGE class it does nothing.

unsigned	getGHR (ThreadID tid) const

int8_t	getCtr (int hitBank, int hitBankIndex) const

unsigned	getTageCtrBits () const

int	getPathHist (ThreadID tid, bool speculative=true) const

int	calcNewPathHist (ThreadID tid, Addr pc, int cur_phist) const

bool	isSpeculativeUpdateEnabled () const

size_t	getSizeInBits () const

Public Member Functions inherited from gem5::SimObject
const Params &	params () const

	SimObject (const Params &p)

virtual	~SimObject ()

virtual void	loadState (CheckpointIn &cp)
	loadState() is called on each SimObject when restoring from a checkpoint.

virtual void	initState ()
	initState() is called on each SimObject when not restoring from a checkpoint.

virtual void	regProbePoints ()
	Register probe points for this object.

virtual void	regProbeListeners ()
	Register probe listeners for this object.

ProbeManager *	getProbeManager ()
	Get the probe manager for this object.

virtual Port &	getPort (const std::string &if_name, PortID idx=InvalidPortID)
	Get a port with a given name and index.

virtual void	startup ()
	startup() is the final initialization call before simulation.

DrainState	drain () override
	Provide a default implementation of the drain interface for objects that don't need draining.

virtual void	memWriteback ()
	Write back dirty buffers to memory using functional writes.

virtual void	memInvalidate ()
	Invalidate the contents of memory buffers.

void	serialize (CheckpointOut &cp) const override
	Serialize an object.

void	unserialize (CheckpointIn &cp) override
	Unserialize an object.

Public Member Functions inherited from gem5::EventManager
EventQueue *	eventQueue () 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.

void	setCurTick (Tick newVal)

	EventManager (EventManager &em)
	Event manger manages events in the event queue.

	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.

void	serializeSection (CheckpointOut &cp, const std::string &name) const

void	unserializeSection (CheckpointIn &cp, const char *name)
	Unserialize an a child object.

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.

virtual void	notifyFork ()
	Notify a child process of a fork.

Public Member Functions inherited from gem5::statistics::Group
	Group (Group parent, const char name=nullptr)
	Construct a new statistics group.

virtual	~Group ()

virtual void	regStats ()
	Callback to set stat parameters.

virtual void	resetStats ()
	Callback to reset stats.

virtual void	preDumpStats ()
	Callback before stats are dumped.

void	addStat (statistics::Info *info)
	Register a stat with this group.

const std::map< std::string, Group * > &	getStatGroups () const
	Get all child groups associated with this object.

const std::vector< Info * > &	getStats () const
	Get all stats associated with this object.

void	addStatGroup (const char name, Group block)
	Add a stat block as a child of this block.

const Info *	resolveStat (std::string name) const
	Resolve a stat by its name within this group.

void	mergeStatGroup (Group *block)
	Merge the contents (stats & children) of a block to this block.

	Group ()=delete

	Group (const Group &)=delete

Group &	operator= (const Group &)=delete

Public Member Functions inherited from gem5::Named
	Named (std::string_view name_)

virtual	~Named ()=default

virtual std::string	name () const

Private Attributes
std::vector< unsigned int >	tunedHistoryLengths

Random::RandomPtr	rng = Random::genRandom()

Additional Inherited Members
Public Types inherited from gem5::branch_prediction::TAGEBase
enum	{ BIMODAL_ONLY = 0 , TAGE_LONGEST_MATCH , BIMODAL_ALT_MATCH , TAGE_ALT_MATCH , LAST_TAGE_PROVIDER_TYPE = TAGE_ALT_MATCH }

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Static Public Member Functions inherited from gem5::branch_prediction::TAGEBase
template<typename T>
static void	ctrUpdate (T &ctr, bool taken, int nbits)
	Updates a direction counter based on the actual branch outcome.

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

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.

static SimObject *	find (const char *name)
	Find the SimObject with the given name and return a pointer to it.

static void	setSimObjectResolver (SimObjectResolver *resolver)
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

static SimObjectResolver *	getSimObjectResolver ()
	There is a single object name resolver, and it is only set when simulation is restoring from checkpoints.

Static Public Member Functions inherited from gem5::Serializable
static const std::string &	currentSection ()
	Gets the fully-qualified name of the active section.

static void	generateCheckpointOut (const std::string &cpt_dir, std::ofstream &outstream)
	Generate a checkpoint file so that the serialization can be routed to it.

Protected Member Functions inherited from gem5::branch_prediction::TAGEBase
virtual void	initFoldedHistories (ThreadHistory &history)
	Initialization of the folded histories.

Protected Member Functions inherited from gem5::Drainable
	Drainable ()

virtual	~Drainable ()

virtual void	drainResume ()
	Resume execution after a successful drain.

void	signalDrainDone () const
	Signal that an object is drained.

Protected Attributes inherited from gem5::branch_prediction::TAGEBase
const unsigned	logRatioBiModalHystEntries

const unsigned	nHistoryTables

const unsigned	tagTableCounterBits

const unsigned	tagTableUBits

const unsigned	histBufferSize

const unsigned	minHist

const unsigned	maxHist

const unsigned	pathHistBits

std::vector< unsigned >	tagTableTagWidths

std::vector< int >	logTagTableSizes

std::vector< bool >	btablePrediction

std::vector< bool >	btableHysteresis

TageEntry **	gtable

std::vector< ThreadHistory >	threadHistory

int *	histLengths

int *	tableIndices

int *	tableTags

std::vector< int8_t >	useAltPredForNewlyAllocated

int64_t	tCounter

uint64_t	logUResetPeriod

const int64_t	initialTCounterValue

unsigned	numUseAltOnNa

unsigned	useAltOnNaBits

unsigned	maxNumAlloc

std::vector< bool >	noSkip

const bool	speculativeHistUpdate

const unsigned	instShiftAmt

bool	initialized

gem5::branch_prediction::TAGEBase::TAGEBaseStats	stats

Protected Attributes inherited from gem5::SimObject
const SimObjectParams &	_params
	Cached copy of the object parameters.

Protected Attributes inherited from gem5::EventManager
EventQueue *	eventq
	A pointer to this object's event queue.

Detailed Description

Definition at line 70 of file multiperspective_perceptron_tage.hh.

Constructor & Destructor Documentation

◆ MPP_TAGE()

gem5::branch_prediction::MPP_TAGE::MPP_TAGE ( const MPP_TAGEParams & p )

inline

Definition at line 86 of file multiperspective_perceptron_tage.hh.

References gem5::MipsISA::p, gem5::branch_prediction::TAGEBase::TAGEBase(), and tunedHistoryLengths.

Referenced by gem5::branch_prediction::MPP_TAGE_8KB::MPP_TAGE_8KB().

Member Function Documentation

◆ adjustAlloc()

void gem5::branch_prediction::MPP_TAGE::adjustAlloc	(	bool &	alloc,
		bool	taken,
		bool	pred_taken )

overridevirtual

Extra calculation to tell whether TAGE allocaitons may happen or not on an update For this base TAGE implementation it does nothing.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 195 of file multiperspective_perceptron_tage.cc.

References rng.

◆ bindex()

int gem5::branch_prediction::MPP_TAGE::bindex ( Addr pc_in ) const

overridevirtual

Computes the index used to access the bimodal table.

Parameters

pc_in The unshifted branch PC.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 179 of file multiperspective_perceptron_tage.cc.

References gem5::branch_prediction::TAGEBase::logTagTableSizes, and gem5::MipsISA::pc.

◆ calculateParameters()

void gem5::branch_prediction::MPP_TAGE::calculateParameters ( )

overridevirtual

Calculates the history lengths and some other paramters in derived classes.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 62 of file multiperspective_perceptron_tage.cc.

References gem5::branch_prediction::TAGEBase::histLengths, gem5::ArmISA::i, gem5::branch_prediction::TAGEBase::nHistoryTables, and tunedHistoryLengths.

◆ getUseAltIdx()

unsigned gem5::branch_prediction::MPP_TAGE::getUseAltIdx	(	TAGEBase::BranchInfo *	bi,
		Addr	branch_pc )

overridevirtual

Calculation of the index for useAltPredForNewlyAllocated On this base TAGE implementation it is always 0.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 186 of file multiperspective_perceptron_tage.cc.

References gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::nHistoryTables, and gem5::branch_prediction::TAGEBase::numUseAltOnNa.

◆ handleAllocAndUReset()

void gem5::branch_prediction::MPP_TAGE::handleAllocAndUReset	(	bool	alloc,
		bool	taken,
		TAGEBase::BranchInfo *	bi,
		int	nrand )

overridevirtual

Handles Allocation and U bits reset on an update.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 107 of file multiperspective_perceptron_tage.cc.

References gem5::ArmISA::a, gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::gtable, handleUReset(), gem5::ArmISA::i, gem5::branch_prediction::TAGEBase::nHistoryTables, gem5::branch_prediction::TAGEBase::noSkip, rng, and gem5::branch_prediction::TAGEBase::tCounter.

◆ handleTAGEUpdate()

void gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate	(	Addr	branch_pc,
		bool	taken,
		TAGEBase::BranchInfo *	bi )

overridevirtual

Handles the update of the TAGE entries.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 71 of file multiperspective_perceptron_tage.cc.

References gem5::branch_prediction::TAGEBase::baseUpdate(), gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::ctrUpdate(), gem5::branch_prediction::TAGEBase::gtable, gem5::branch_prediction::TAGEBase::tagTableCounterBits, and gem5::branch_prediction::TAGEBase::tagTableUBits.

◆ handleUReset()

void gem5::branch_prediction::MPP_TAGE::handleUReset ( )

overridevirtual

Handles the U bits reset.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 148 of file multiperspective_perceptron_tage.cc.

References gem5::branch_prediction::TAGEBase::gtable, gem5::ArmISA::i, gem5::branch_prediction::TAGEBase::logTagTableSizes, gem5::branch_prediction::TAGEBase::logUResetPeriod, gem5::branch_prediction::TAGEBase::nHistoryTables, resetUctr(), gem5::branch_prediction::TAGEBase::tCounter, and gem5::ArmISA::u.

Referenced by handleAllocAndUReset().

◆ isHighConfidence()

bool gem5::branch_prediction::MPP_TAGE::isHighConfidence ( TAGEBase::BranchInfo * bi ) const

overridevirtual

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 238 of file multiperspective_perceptron_tage.cc.

References gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::btableHysteresis, gem5::branch_prediction::TAGEBase::btablePrediction, gem5::branch_prediction::TAGEBase::gtable, gem5::branch_prediction::TAGEBase::logRatioBiModalHystEntries, and gem5::branch_prediction::TAGEBase::tagTableCounterBits.

◆ resetUctr()

void gem5::branch_prediction::MPP_TAGE::resetUctr ( uint8_t & u )

overridevirtual

Algorithm for resetting a single U counter.

Reimplemented from gem5::branch_prediction::TAGEBase.

Definition at line 169 of file multiperspective_perceptron_tage.cc.

References gem5::ArmISA::u.

Referenced by handleUReset().

◆ updateHistories()

void gem5::branch_prediction::MPP_TAGE::updateHistories	(	ThreadID	tid,
		Addr	branch_pc,
		bool	speculative,
		bool	taken,
		Addr	target,
		const StaticInstPtr &	inst,
		TAGEBase::BranchInfo *	bi )

overridevirtual

(Speculatively) updates global histories (path and direction).

It manages squashing of histories in case of a mispredicted. In that case it also recomputes compressed (folded) histories based on the squashed state

Parameters

tid	The thread ID to select the histories to update.
branch_pc	The unshifted branch PC.
speculative	Whether the update is speculative or not
taken	(Predicted) branch direction.
target	(Predicted) branch target.
inst	The branch instruction. Some predictors do different things depending on the branch type.
bi	Pointer to information on the prediction recorded at prediction time.