#include <tage_base.hh>

Inheritance diagram for gem5::branch_prediction::TAGEBase:

Classes
struct	BranchInfo

struct	FoldedHistory

struct	TAGEBaseStats

struct	TageEntry

struct	ThreadHistory

Public Types
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

Public Member Functions
	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 ()

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

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 (uint8_t &h, bool dir, uint8_t tab, int &PT)
	(Speculatively) updates the global branch history.

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

virtual void	updateHistories (ThreadID tid, Addr branch_pc, bool taken, BranchInfo *b, bool speculative, const StaticInstPtr &inst=nullStaticInstPtr, Addr target=MaxAddr)
	(Speculatively) updates global histories (path and direction).

virtual void	squash (ThreadID tid, bool taken, BranchInfo *bi, Addr target)
	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	calculateParameters ()
	Calculates the history lengths and some other paramters in derived classes.

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

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

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

virtual void	handleUReset ()
	Handles the U bits reset.

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

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

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

virtual bool	isHighConfidence (BranchInfo *bi) const

void	btbUpdate (ThreadID tid, Addr branch_addr, BranchInfo *&bi)

unsigned	getGHR (ThreadID tid, BranchInfo *bi) const

int8_t	getCtr (int hitBank, int hitBankIndex) const

unsigned	getTageCtrBits () const

int	getPathHist (ThreadID tid) 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 (const std::string &name_)

virtual	~Named ()=default

virtual std::string	name () const

Static Public Member Functions
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
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
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 65 of file tage_base.hh.

Member Enumeration Documentation

◆ anonymous enum

anonymous enum

Enumerator
BIMODAL_ONLY
TAGE_LONGEST_MATCH
BIMODAL_ALT_MATCH
TAGE_ALT_MATCH
LAST_TAGE_PROVIDER_TYPE

Definition at line 118 of file tage_base.hh.

Constructor & Destructor Documentation

◆ TAGEBase()

gem5::branch_prediction::TAGEBase::TAGEBase ( const TAGEBaseParams & p )

Definition at line 51 of file tage_base.cc.

References nHistoryTables, and noSkip.

Member Function Documentation

◆ adjustAlloc()

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

virtual

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

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 438 of file tage_base.cc.

Referenced by condBranchUpdate().

◆ baseUpdate()

void gem5::branch_prediction::TAGEBase::baseUpdate	(	Addr	pc,
		bool	taken,
		BranchInfo *	bi )

Updates the bimodal predictor.

Parameters

pc	The unshifted branch PC.
taken	The actual branch outcome.
bi	Pointer to information on the prediction recorded at prediction time.

Definition at line 302 of file tage_base.cc.

References gem5::PowerISA::bi, btableHysteresis, btablePrediction, DPRINTF, logRatioBiModalHystEntries, gem5::MipsISA::pc, and gem5::RiscvISA::pred.

Referenced by gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleTAGEUpdate(), and handleTAGEUpdate().

◆ bindex()

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

virtual

Computes the index used to access the bimodal table.

Parameters

pc_in The unshifted branch PC.

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 207 of file tage_base.cc.

References instShiftAmt, and logTagTableSizes.

Referenced by tagePredict().

◆ btbUpdate()

void gem5::branch_prediction::TAGEBase::btbUpdate	(	ThreadID	tid,
		Addr	branch_addr,
		BranchInfo *&	bi )

Definition at line 188 of file tage_base.cc.

References gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::FoldedHistory::comp, gem5::branch_prediction::TAGEBase::ThreadHistory::computeIndices, gem5::branch_prediction::TAGEBase::ThreadHistory::computeTags, DPRINTF, gem5::branch_prediction::TAGEBase::ThreadHistory::gHist, gem5::branch_prediction::TAGEBase::ThreadHistory::globalHistory, gem5::ArmISA::i, nHistoryTables, gem5::branch_prediction::TAGEBase::ThreadHistory::ptGhist, speculativeHistUpdate, threadHistory, and gem5::branch_prediction::TAGEBase::FoldedHistory::update().

◆ buildTageTables()

void gem5::branch_prediction::TAGEBase::buildTageTables ( )

virtual

Instantiates the TAGE table entries.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 166 of file tage_base.cc.

References gtable, gem5::ArmISA::i, logTagTableSizes, and nHistoryTables.

Referenced by init().

◆ calculateIndicesAndTags()

void gem5::branch_prediction::TAGEBase::calculateIndicesAndTags	(	ThreadID	tid,
		Addr	branch_pc,
		BranchInfo *	bi )

virtual

On a prediction, calculates the TAGE indices and tags for all the different history lengths.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 340 of file tage_base.cc.

References gem5::PowerISA::bi, gindex(), gtag(), gem5::ArmISA::i, nHistoryTables, tableIndices, and tableTags.

Referenced by tagePredict().

◆ calculateParameters()

void gem5::branch_prediction::TAGEBase::calculateParameters ( )

virtual

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

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 174 of file tage_base.cc.

References histLengths, gem5::ArmISA::i, maxHist, minHist, and nHistoryTables.

Referenced by init().

◆ condBranchUpdate()

void gem5::branch_prediction::TAGEBase::condBranchUpdate	(	ThreadID	tid,
		Addr	branch_pc,
		bool	taken,
		BranchInfo *	bi,
		int	nrand,
		Addr	corrTarget,
		bool	pred,
		bool	preAdjustAlloc = false )

virtual

Update TAGE for conditional branches.

Parameters

branch_pc	The unshifted branch PC.
taken	Actual branch outcome.
bi	Pointer to information on the prediction recorded at prediction time. @nrand Random int number from 0 to 3
corrTarget	The correct branch target
pred	Final prediction for this branch
preAdjustAlloc	call adjustAlloc before checking pseudo newly allocated entries

Definition at line 514 of file tage_base.cc.

References adjustAlloc(), gem5::PowerISA::bi, ctrUpdate(), getUseAltIdx(), handleAllocAndUReset(), handleTAGEUpdate(), nHistoryTables, gem5::RiscvISA::pred, useAltOnNaBits, and useAltPredForNewlyAllocated.

Referenced by gem5::branch_prediction::LTAGE::update(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), gem5::branch_prediction::TAGE::update(), and gem5::branch_prediction::TAGE_SC_L::update().

◆ ctrUpdate()

template<typename T >

template void gem5::branch_prediction::TAGEBase::ctrUpdate	(	T &	ctr,
		bool	taken,
		int	nbits )

static

Updates a direction counter based on the actual branch outcome.

Parameters

ctr	Reference to counter to update.
taken	Actual branch outcome.
nbits	Counter width.

Definition at line 261 of file tage_base.cc.

Referenced by condBranchUpdate(), gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleTAGEUpdate(), and handleTAGEUpdate().

◆ extraAltCalc()

void gem5::branch_prediction::TAGEBase::extraAltCalc ( BranchInfo * bi )

virtual

Extra steps for calculating altTaken For this base TAGE class it does nothing.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 655 of file tage_base.cc.

Referenced by tagePredict().

◆ F()

int gem5::branch_prediction::TAGEBase::F	(	int	phist,
		int	size,
		int	bank ) const

virtual

Utility function to shuffle the path history depending on which tagged table we are accessing.

Parameters

phist	The path history.
size	Number of path history bits to use.
bank	The partially tagged table to access.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 213 of file tage_base.cc.

References logTagTableSizes.

Referenced by gindex().

◆ getBimodePred()

bool gem5::branch_prediction::TAGEBase::getBimodePred	(	Addr	pc,
		BranchInfo *	bi ) const

virtual

Get a branch prediction from the bimodal predictor.

Parameters

pc	The unshifted branch PC.
bi	Pointer to information on the prediction.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 293 of file tage_base.cc.

References gem5::PowerISA::bi, and btablePrediction.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::getBimodePred(), and tagePredict().

◆ getCtr()

int8_t gem5::branch_prediction::TAGEBase::getCtr	(	int	hitBank,
		int	hitBankIndex ) const

Definition at line 768 of file tage_base.cc.

References gem5::branch_prediction::TAGEBase::TageEntry::ctr, and gtable.

Referenced by gem5::branch_prediction::TAGE_SC_L::predict().

◆ getGHR()

unsigned gem5::branch_prediction::TAGEBase::getGHR	(	ThreadID	tid,
		BranchInfo *	bi ) const

Definition at line 711 of file tage_base.cc.

References gem5::PowerISA::bi, histBufferSize, gem5::ArmISA::i, threadHistory, and gem5::X86ISA::val.

◆ getPathHist()

int gem5::branch_prediction::TAGEBase::getPathHist ( ThreadID tid ) const

Definition at line 780 of file tage_base.cc.

References threadHistory.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::lookup(), gem5::branch_prediction::TAGE_SC_L::predict(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), and gem5::branch_prediction::TAGE_SC_L::update().

◆ getSizeInBits()

size_t gem5::branch_prediction::TAGEBase::getSizeInBits ( ) const

Definition at line 792 of file tage_base.cc.

References gem5::bits(), histLengths, gem5::ArmISA::i, logRatioBiModalHystEntries, logTagTableSizes, logUResetPeriod, nHistoryTables, numUseAltOnNa, pathHistBits, tagTableCounterBits, tagTableTagWidths, tagTableUBits, and useAltOnNaBits.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::init().

◆ getTageCtrBits()

unsigned gem5::branch_prediction::TAGEBase::getTageCtrBits ( ) const

Definition at line 774 of file tage_base.cc.

References tagTableCounterBits.

Referenced by gem5::branch_prediction::TAGE_SC_L::predict().

◆ getUseAltIdx()

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

virtual

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

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 353 of file tage_base.cc.

Referenced by condBranchUpdate(), and tagePredict().

◆ gindex()

int gem5::branch_prediction::TAGEBase::gindex	(	ThreadID	tid,
		Addr	pc,
		int	bank ) const

virtual

Computes the index used to access a partially tagged table.

Parameters

tid	The thread ID used to select the global histories to use.
pc	The unshifted branch PC.
bank	The partially tagged table to access.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 230 of file tage_base.cc.

References F(), histLengths, gem5::MipsISA::index, instShiftAmt, logTagTableSizes, pathHistBits, gem5::MipsISA::pc, and threadHistory.

Referenced by calculateIndicesAndTags().

◆ gtag()

uint16_t gem5::branch_prediction::TAGEBase::gtag	(	ThreadID	tid,
		Addr	pc,
		int	bank ) const

virtual

Computes the partial tag of a tagged table.

Parameters

tid	the thread ID used to select the global histories to use.
pc	The unshifted branch PC.
bank	The partially tagged table to access.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE, gem5::branch_prediction::TAGE_SC_L_TAGE_64KB, and gem5::branch_prediction::TAGE_SC_L_TAGE_8KB.

Definition at line 248 of file tage_base.cc.

References instShiftAmt, gem5::MipsISA::pc, tagTableTagWidths, and threadHistory.

Referenced by calculateIndicesAndTags().

◆ handleAllocAndUReset()

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

virtual

Handles Allocation and U bits reset on an update.

Reimplemented in gem5::branch_prediction::MPP_TAGE, gem5::branch_prediction::TAGE_SC_L_TAGE, gem5::branch_prediction::TAGE_SC_L_TAGE_64KB, and gem5::branch_prediction::TAGE_SC_L_TAGE_8KB.

Definition at line 444 of file tage_base.cc.

References gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::TageEntry::ctr, gtable, handleUReset(), gem5::ArmISA::i, maxNumAlloc, nHistoryTables, gem5::branch_prediction::TAGEBase::TageEntry::tag, tCounter, gem5::branch_prediction::TAGEBase::TageEntry::u, and gem5::X86ISA::X.

Referenced by condBranchUpdate().

◆ handleTAGEUpdate()

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

virtual

Handles the update of the TAGE entries.

Reimplemented in gem5::branch_prediction::MPP_TAGE, gem5::branch_prediction::TAGE_SC_L_TAGE, gem5::branch_prediction::TAGE_SC_L_TAGE_64KB, and gem5::branch_prediction::TAGE_SC_L_TAGE_8KB.

Definition at line 555 of file tage_base.cc.

References baseUpdate(), gem5::PowerISA::bi, gem5::branch_prediction::TAGEBase::TageEntry::ctr, ctrUpdate(), DPRINTF, gtable, tagTableCounterBits, tagTableUBits, gem5::branch_prediction::TAGEBase::TageEntry::u, and unsignedCtrUpdate().

Referenced by condBranchUpdate().

◆ handleUReset()

void gem5::branch_prediction::TAGEBase::handleUReset ( )

virtual

Handles the U bits reset.

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 493 of file tage_base.cc.

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

Referenced by handleAllocAndUReset().

◆ init()

void gem5::branch_prediction::TAGEBase::init ( )

overridevirtual

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

Initializations that are independent of unserialization but rely on a fully instantiated and connected SimObject graph should be done here.

Reimplemented from gem5::SimObject.

Definition at line 87 of file tage_base.cc.

References btableHysteresis, btablePrediction, buildTageTables(), calculateParameters(), gtable, histBufferSize, histLengths, initFoldedHistories(), initialized, initialTCounterValue, logRatioBiModalHystEntries, logTagTableSizes, logUResetPeriod, maxHist, nHistoryTables, numUseAltOnNa, pathHistBits, tableIndices, tableTags, tagTableTagWidths, tagTableUBits, tCounter, threadHistory, and useAltPredForNewlyAllocated.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::init().

◆ initFoldedHistories()

void gem5::branch_prediction::TAGEBase::initFoldedHistories ( ThreadHistory & history )

protectedvirtual

Initialization of the folded histories.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE_8KB.

Definition at line 151 of file tage_base.cc.

References gem5::branch_prediction::TAGEBase::ThreadHistory::computeIndices, gem5::branch_prediction::TAGEBase::ThreadHistory::computeTags, DPRINTF, histLengths, gem5::ArmISA::i, gem5::branch_prediction::TAGEBase::FoldedHistory::init(), logTagTableSizes, nHistoryTables, gem5::branch_prediction::TAGEBase::FoldedHistory::origLength, and tagTableTagWidths.

Referenced by init().

◆ isHighConfidence()

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

inlinevirtual

Reimplemented in gem5::branch_prediction::MPP_TAGE.

Definition at line 410 of file tage_base.hh.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::lookup().

◆ isSpeculativeUpdateEnabled()

bool gem5::branch_prediction::TAGEBase::isSpeculativeUpdateEnabled ( ) const

Definition at line 786 of file tage_base.cc.

References speculativeHistUpdate.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::MultiperspectivePerceptronTAGE(), gem5::branch_prediction::LTAGE::update(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), and gem5::branch_prediction::TAGE_SC_L::update().

◆ makeBranchInfo()

TAGEBase::BranchInfo * gem5::branch_prediction::TAGEBase::makeBranchInfo ( )

virtual

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 82 of file tage_base.cc.

◆ resetUctr()

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

virtual

Algorithm for resetting a single U counter.

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE_8KB.

Definition at line 508 of file tage_base.cc.

References gem5::ArmISA::u.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::handleUReset(), and handleUReset().

◆ squash()

void gem5::branch_prediction::TAGEBase::squash	(	ThreadID	tid,
		bool	taken,
		TAGEBase::BranchInfo *	bi,
		Addr	target )

virtual

Restores speculatively updated path and direction histories.

Also recomputes compressed (folded) histories based on the correct branch outcome. This version of squash() is called once on a branch misprediction.

Parameters

tid	The Thread ID to select the histories to rollback.
taken	The correct branch outcome.
bp_history	Wrapping pointer to BranchInfo (to allow storing derived class prediction information in the base class).
target	The correct branch target

Postcondition: bp_history points to valid memory.

Reimplemented in gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 629 of file tage_base.cc.

Referenced by gem5::branch_prediction::LTAGE::update(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), gem5::branch_prediction::TAGE::update(), and gem5::branch_prediction::TAGE_SC_L::update().

◆ tagePredict()

bool gem5::branch_prediction::TAGEBase::tagePredict	(	ThreadID	tid,
		Addr	branch_pc,
		bool	cond_branch,
		BranchInfo *	bi )

TAGE prediction called from TAGE::predict.

Parameters

tid	The thread ID to select the global histories to use.
branch_pc	The unshifted branch PC.
cond_branch	True if the branch is conditional.
bi	Pointer to the BranchInfo

Definition at line 360 of file tage_base.cc.

References gem5::PowerISA::bi, BIMODAL_ALT_MATCH, BIMODAL_ONLY, bindex(), calculateIndicesAndTags(), gem5::branch_prediction::TAGEBase::TageEntry::ctr, DPRINTF, extraAltCalc(), getBimodePred(), getUseAltIdx(), gtable, gem5::ArmISA::i, nHistoryTables, noSkip, gem5::MipsISA::pc, tableIndices, tableTags, TAGE_ALT_MATCH, TAGE_LONGEST_MATCH, and useAltPredForNewlyAllocated.

Referenced by gem5::branch_prediction::MultiperspectivePerceptronTAGE::lookup(), gem5::branch_prediction::LTAGE::predict(), gem5::branch_prediction::TAGE::predict(), and gem5::branch_prediction::TAGE_SC_L::predict().

◆ unsignedCtrUpdate()

void gem5::branch_prediction::TAGEBase::unsignedCtrUpdate	(	uint8_t &	ctr,
		bool	up,
		unsigned	nbits )

static

Updates an unsigned counter based on up/down parameter.

Parameters

ctr	Reference to counter to update.
up	Boolean indicating if the counter is incremented/decremented If true it is incremented, if false it is decremented
nbits	Counter width.

Definition at line 279 of file tage_base.cc.

References gem5::ArmISA::up.

Referenced by handleTAGEUpdate().

◆ update()

void gem5::branch_prediction::TAGEBase::update	(	ThreadID	tid,
		Addr	branch_pc,
		bool	taken,
		BranchInfo *	bi )

Update TAGE.

Called at execute to repair histories on a misprediction and at commit to update the tables.

Parameters

tid	The thread ID to select the global histories to use.
branch_pc	The unshifted branch PC.
taken	Actual branch outcome.
bi	Pointer to information on the prediction recorded at prediction time.

◆ updateGHist()

void gem5::branch_prediction::TAGEBase::updateGHist	(	uint8_t *&	h,
		bool	dir,
		uint8_t *	tab,
		int &	PT )

(Speculatively) updates the global branch history.

Parameters

h	Reference to pointer to global branch history.
dir	(Predicted) outcome to update the histories with.
tab
PT	Reference to path history.

Definition at line 322 of file tage_base.cc.

References DPRINTF, histBufferSize, gem5::ArmISA::i, maxHist, and gem5::pt.

Referenced by updateHistories(), gem5::branch_prediction::MPP_TAGE::updatePathAndGlobalHistory(), and gem5::branch_prediction::TAGE_SC_L_TAGE::updatePathAndGlobalHistory().

◆ updateHistories()

void gem5::branch_prediction::TAGEBase::updateHistories	(	ThreadID	tid,
		Addr	branch_pc,
		bool	taken,
		BranchInfo *	b,
		bool	speculative,
		const StaticInstPtr &	inst = nullStaticInstPtr,
		Addr	target = MaxAddr )

virtual

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

Also recomputes compressed (folded) histories based on the branch direction.

Parameters

tid	The thread ID to select the histories to update.
branch_pc	The unshifted branch PC.
taken	(Predicted) branch direction.
b	Wrapping pointer to BranchInfo (to allow storing derived class prediction information in the base class).

Reimplemented in gem5::branch_prediction::MPP_TAGE, and gem5::branch_prediction::TAGE_SC_L_TAGE.

Definition at line 588 of file tage_base.cc.

Referenced by gem5::branch_prediction::LTAGE::update(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), gem5::branch_prediction::TAGE::update(), gem5::branch_prediction::TAGE_SC_L::update(), and gem5::branch_prediction::TAGE::updateHistories().

◆ updateStats()

void gem5::branch_prediction::TAGEBase::updateStats	(	bool	taken,
		BranchInfo *	bi )

virtual

Update the stats.

Parameters

taken	Actual branch outcome
bi	Pointer to information on the prediction recorded at prediction time.

Definition at line 662 of file tage_base.cc.

Referenced by gem5::branch_prediction::LTAGE::update(), gem5::branch_prediction::MultiperspectivePerceptronTAGE::update(), gem5::branch_prediction::TAGE::update(), and gem5::branch_prediction::TAGE_SC_L::update().

Member Data Documentation

◆ btableHysteresis

std::vector<bool> gem5::branch_prediction::TAGEBase::btableHysteresis

protected

Definition at line 437 of file tage_base.hh.

Referenced by baseUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE::getBimodePred(), init(), and gem5::branch_prediction::MPP_TAGE::isHighConfidence().

◆ btablePrediction

std::vector<bool> gem5::branch_prediction::TAGEBase::btablePrediction

protected

Definition at line 436 of file tage_base.hh.

Referenced by baseUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE::getBimodePred(), getBimodePred(), init(), and gem5::branch_prediction::MPP_TAGE::isHighConfidence().

◆ gtable

TageEntry** gem5::branch_prediction::TAGEBase::gtable

protected

Definition at line 438 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::buildTageTables(), buildTageTables(), gem5::branch_prediction::TAGE_SC_L_TAGE::extraAltCalc(), getCtr(), gem5::branch_prediction::MPP_TAGE::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleAllocAndUReset(), handleAllocAndUReset(), gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleTAGEUpdate(), handleTAGEUpdate(), gem5::branch_prediction::MPP_TAGE::handleUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE::handleUReset(), handleUReset(), init(), gem5::branch_prediction::MPP_TAGE::isHighConfidence(), and tagePredict().

◆ histBufferSize

const unsigned gem5::branch_prediction::TAGEBase::histBufferSize

protected

Definition at line 428 of file tage_base.hh.

Referenced by getGHR(), init(), and updateGHist().

◆ histLengths

int* gem5::branch_prediction::TAGEBase::histLengths

protected

Definition at line 471 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateIndicesAndTags(), gem5::branch_prediction::MPP_TAGE::calculateParameters(), gem5::branch_prediction::TAGE_SC_L_TAGE::calculateParameters(), calculateParameters(), getSizeInBits(), gem5::branch_prediction::TAGE_SC_L_TAGE::gindex(), gindex(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::gtag(), init(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::initFoldedHistories(), and initFoldedHistories().

◆ initialized

bool gem5::branch_prediction::TAGEBase::initialized

protected

Definition at line 492 of file tage_base.hh.

Referenced by init().

◆ initialTCounterValue

const int64_t gem5::branch_prediction::TAGEBase::initialTCounterValue

protected

Definition at line 478 of file tage_base.hh.

Referenced by init().

◆ instShiftAmt

const unsigned gem5::branch_prediction::TAGEBase::instShiftAmt

protected

Definition at line 490 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::bindex(), bindex(), gindex(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::gtag(), gtag(), updateHistories(), and gem5::branch_prediction::TAGE_SC_L_TAGE::updatePathAndGlobalHistory().

◆ logRatioBiModalHystEntries

const unsigned gem5::branch_prediction::TAGEBase::logRatioBiModalHystEntries

protected

Definition at line 424 of file tage_base.hh.

Referenced by baseUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE::getBimodePred(), getSizeInBits(), init(), and gem5::branch_prediction::MPP_TAGE::isHighConfidence().

◆ logTagTableSizes

std::vector<int> gem5::branch_prediction::TAGEBase::logTagTableSizes

protected

Definition at line 434 of file tage_base.hh.

◆ logUResetPeriod

uint64_t gem5::branch_prediction::TAGEBase::logUResetPeriod

protected

Definition at line 477 of file tage_base.hh.

Referenced by getSizeInBits(), gem5::branch_prediction::MPP_TAGE::handleUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE::handleUReset(), handleUReset(), and init().

◆ maxHist

const unsigned gem5::branch_prediction::TAGEBase::maxHist

protected

Definition at line 430 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateParameters(), calculateParameters(), init(), and updateGHist().

◆ maxNumAlloc

unsigned gem5::branch_prediction::TAGEBase::maxNumAlloc

protected

Definition at line 481 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleAllocAndUReset(), and handleAllocAndUReset().

◆ minHist

const unsigned gem5::branch_prediction::TAGEBase::minHist

protected

Definition at line 429 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateParameters(), and calculateParameters().

◆ nHistoryTables

const unsigned gem5::branch_prediction::TAGEBase::nHistoryTables

protected

Definition at line 425 of file tage_base.hh.

◆ noSkip

std::vector<bool> gem5::branch_prediction::TAGEBase::noSkip

protected

Definition at line 486 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateIndicesAndTags(), gem5::branch_prediction::MPP_TAGE::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleAllocAndUReset(), TAGEBase(), and tagePredict().

◆ numUseAltOnNa

unsigned gem5::branch_prediction::TAGEBase::numUseAltOnNa

protected

Definition at line 479 of file tage_base.hh.

Referenced by getSizeInBits(), gem5::branch_prediction::MPP_TAGE::getUseAltIdx(), gem5::branch_prediction::TAGE_SC_L_TAGE::getUseAltIdx(), and init().

◆ pathHistBits

const unsigned gem5::branch_prediction::TAGEBase::pathHistBits

protected

Definition at line 431 of file tage_base.hh.

Referenced by getSizeInBits(), gem5::branch_prediction::TAGE_SC_L_TAGE::gindex(), gindex(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::gtag(), init(), updateHistories(), and gem5::branch_prediction::TAGE_SC_L_TAGE::updatePathAndGlobalHistory().

◆ speculativeHistUpdate

const bool gem5::branch_prediction::TAGEBase::speculativeHistUpdate

protected

Definition at line 488 of file tage_base.hh.

Referenced by btbUpdate(), isSpeculativeUpdateEnabled(), squash(), gem5::branch_prediction::MPP_TAGE::updateHistories(), gem5::branch_prediction::TAGE_SC_L_TAGE::updateHistories(), and updateHistories().

◆ stats

gem5::branch_prediction::TAGEBase::TAGEBaseStats gem5::branch_prediction::TAGEBase::stats

protected

Referenced by updateStats().

◆ tableIndices

int* gem5::branch_prediction::TAGEBase::tableIndices

protected

Definition at line 472 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateIndicesAndTags(), calculateIndicesAndTags(), init(), and tagePredict().

◆ tableTags

int* gem5::branch_prediction::TAGEBase::tableTags

protected

Definition at line 473 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateIndicesAndTags(), calculateIndicesAndTags(), init(), and tagePredict().

◆ tagTableCounterBits

const unsigned gem5::branch_prediction::TAGEBase::tagTableCounterBits

protected

Definition at line 426 of file tage_base.hh.

Referenced by getSizeInBits(), getTageCtrBits(), gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleTAGEUpdate(), handleTAGEUpdate(), and gem5::branch_prediction::MPP_TAGE::isHighConfidence().

◆ tagTableTagWidths

std::vector<unsigned> gem5::branch_prediction::TAGEBase::tagTableTagWidths

protected

Definition at line 433 of file tage_base.hh.

Referenced by gem5::branch_prediction::TAGE_SC_L_TAGE::calculateParameters(), getSizeInBits(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::gtag(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::gtag(), gtag(), init(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::initFoldedHistories(), and initFoldedHistories().

◆ tagTableUBits

const unsigned gem5::branch_prediction::TAGEBase::tagTableUBits

protected

Definition at line 427 of file tage_base.hh.

Referenced by getSizeInBits(), gem5::branch_prediction::MPP_TAGE::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleTAGEUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleTAGEUpdate(), handleTAGEUpdate(), and init().

◆ tCounter

int64_t gem5::branch_prediction::TAGEBase::tCounter

protected

Definition at line 476 of file tage_base.hh.

Referenced by gem5::branch_prediction::MPP_TAGE::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::handleAllocAndUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::handleAllocAndUReset(), handleAllocAndUReset(), gem5::branch_prediction::MPP_TAGE::handleUReset(), gem5::branch_prediction::TAGE_SC_L_TAGE::handleUReset(), handleUReset(), and init().

◆ threadHistory

std::vector<ThreadHistory> gem5::branch_prediction::TAGEBase::threadHistory

protected

Definition at line 464 of file tage_base.hh.

Referenced by btbUpdate(), gem5::branch_prediction::TAGE_SC_L_TAGE::calculateIndicesAndTags(), getGHR(), getPathHist(), gem5::branch_prediction::TAGE_SC_L_TAGE::gindex(), gindex(), gem5::branch_prediction::TAGE_SC_L_TAGE_64KB::gtag(), gem5::branch_prediction::TAGE_SC_L_TAGE_8KB::gtag(), gtag(), init(), squash(), gem5::branch_prediction::MPP_TAGE::updateHistories(), gem5::branch_prediction::TAGE_SC_L_TAGE::updateHistories(), and updateHistories().

◆ useAltOnNaBits

unsigned gem5::branch_prediction::TAGEBase::useAltOnNaBits

protected

Definition at line 480 of file tage_base.hh.

Referenced by condBranchUpdate(), and getSizeInBits().

◆ useAltPredForNewlyAllocated

std::vector<int8_t> gem5::branch_prediction::TAGEBase::useAltPredForNewlyAllocated

protected

Definition at line 475 of file tage_base.hh.

Referenced by condBranchUpdate(), init(), and tagePredict().

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

cpu/pred/tage_base.hh
cpu/pred/tage_base.cc

Classes

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Member Enumeration Documentation

◆ anonymous enum

Constructor & Destructor Documentation

◆ TAGEBase()

Member Function Documentation

◆ adjustAlloc()

◆ baseUpdate()

◆ bindex()

◆ btbUpdate()

◆ buildTageTables()

◆ calculateIndicesAndTags()

◆ calculateParameters()

◆ condBranchUpdate()

◆ ctrUpdate()

◆ extraAltCalc()

◆ F()

◆ getBimodePred()

◆ getCtr()

◆ getGHR()

◆ getPathHist()

◆ getSizeInBits()

◆ getTageCtrBits()

◆ getUseAltIdx()

◆ gindex()

◆ gtag()

◆ handleAllocAndUReset()

◆ handleTAGEUpdate()

◆ handleUReset()

◆ init()

◆ initFoldedHistories()

◆ isHighConfidence()

◆ isSpeculativeUpdateEnabled()

◆ makeBranchInfo()

◆ resetUctr()

◆ squash()

◆ tagePredict()

◆ unsignedCtrUpdate()

◆ update()

◆ updateGHist()

◆ updateHistories()

◆ updateStats()

Member Data Documentation

◆ btableHysteresis

◆ btablePrediction

◆ gtable

◆ histBufferSize

◆ histLengths

◆ initialized

◆ initialTCounterValue

◆ instShiftAmt

◆ logRatioBiModalHystEntries

◆ logTagTableSizes

◆ logUResetPeriod

◆ maxHist

◆ maxNumAlloc

◆ minHist

◆ nHistoryTables

◆ noSkip

◆ numUseAltOnNa

◆ pathHistBits

◆ speculativeHistUpdate

◆ stats

◆ tableIndices

◆ tableTags

◆ tagTableCounterBits

◆ tagTableTagWidths

◆ tagTableUBits

◆ tCounter

◆ threadHistory

◆ useAltOnNaBits

◆ useAltPredForNewlyAllocated