#include <loop_predictor.hh>

Inheritance diagram for LoopPredictor:

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 BranchInfo *	makeBranchInfo ()

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 Params *	params () 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...

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

virtual Port &	getPort (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
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. 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 Info *	resolveStat (std::string name) const
	Resolve a stat by its name within this group. More...

	Group ()=delete

	Group (const Group &)=delete

Group &	operator= (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

LoopEntry *	ltable

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
EventQueue *	eventq
	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 SimObject *	find (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

Reimplemented in TAGE_SC_L_LoopPredictor, and MPP_LoopPredictor.

Definition at line 150 of file loop_predictor.cc.

References LoopPredictor::LoopEntry::confidence, confidenceThreshold, MipsISA::index, and ltable.

Referenced by MPP_LoopPredictor::calcConf(), TAGE_SC_L_LoopPredictor::calcConf(), and getLoop().

◆ 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_pc	The unshifted branch PC.
taken	Actual branch outcome.
tage_pred	Prediction from TAGE
bi	Pointer to information on the prediction recorded at prediction time.
instShiftAmt	Number 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

index	Result of lindex function
lowPcBits	PC bits masked with set size
way	Way 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

pc	The unshifted branch PC.
bi	Pointer to information on the prediction.
speculative	Use speculative number of iterations
instShiftAmt	Shift 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

Definition at line 358 of file loop_predictor.cc.

References logSizeLoopPred, loopTableAgeBits, loopTableConfidenceBits, loopTableIterBits, loopTableTagBits, ULL, useDirectionBit, and useSpeculation.

Referenced by MultiperspectivePerceptronTAGE::init().

◆ 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_in	The unshifted branch PC.
instShiftAmt	Shift 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

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	Reference to wrapping pointer to allow storing derived class prediction information in the base class.
prev_pred_taken	Result of the TAGE prediction
instShiftAmt	Shift the pc by as many bits
instShiftAmt	Shift 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
	)

Updates the loop predictor.

Parameters

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

Definition at line 176 of file loop_predictor.cc.

References LoopPredictor::LoopEntry::age, PowerISA::bi, LoopPredictor::LoopEntry::confidence, LoopPredictor::LoopEntry::currentIter, LoopPredictor::LoopEntry::dir, DPRINTF, finallindex(), ArmISA::i, initialLoopAge, initialLoopIter, logLoopTableAssoc, loopNumIterMask, loopTableAgeBits, loopTableConfidenceBits, ltable, LoopPredictor::LoopEntry::numIter, optionalAgeInc(), optionalAgeReset, MipsISA::pc, Random::random(), random_mt, restrictAllocation, LoopPredictor::LoopEntry::tag, unsignedCtrUpdate(), and useDirectionBit.

Referenced by condBranchUpdate().

◆ 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

taken	The predicted branch outcome.
bi	Pointer 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
	)

Definition at line 293 of file loop_predictor.cc.

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

Referenced by LTAGE::squash().

◆ squashLoop()

void LoopPredictor::squashLoop ( BranchInfo * bi )

Definition at line 304 of file loop_predictor.cc.

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

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

◆ unsignedCtrUpdate()

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

inlinestaticprotected

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 99 of file loop_predictor.hh.

References ArmISA::up.

Referenced by loopUpdate().

◆ updateStats()

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

Update the stats.

Parameters

taken	Actual branch outcome
bi	Pointer 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

Definition at line 73 of file loop_predictor.hh.

Referenced by MPP_LoopPredictor::calcConf(), TAGE_SC_L_LoopPredictor::calcConf(), calcConf(), getLoop(), init(), loopUpdate(), specLoopUpdate(), squash(), and squashLoop().

◆ 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:

cpu/pred/loop_predictor.hh
cpu/pred/loop_predictor.cc

Classes

Public Member Functions

Static Protected Member Functions

Protected Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ LoopPredictor()

Member Function Documentation

◆ calcConf()

◆ condBranchUpdate()

◆ finallindex()

◆ getLoop()

◆ getLoopUseCounter()

◆ getSizeInBits()

◆ init()

◆ lindex()

◆ loopPredict()

◆ loopUpdate()

◆ makeBranchInfo()

◆ optionalAgeInc()

◆ signedCtrUpdate()

◆ specLoopUpdate()

◆ squash()

◆ squashLoop()

◆ unsignedCtrUpdate()

◆ updateStats()

Member Data Documentation

◆ confidenceThreshold

◆ initialLoopAge

◆ initialLoopIter

◆ logLoopTableAssoc

◆ logSizeLoopPred

◆ loopNumIterMask

◆ loopSetMask

◆ loopTableAgeBits

◆ loopTableConfidenceBits

◆ loopTableIterBits

◆ loopTableTagBits

◆ loopTagMask

◆ loopUseCounter

◆ ltable

◆ optionalAgeReset

◆ restrictAllocation

◆ stats

◆ useDirectionBit

◆ useHashing

◆ useSpeculation

◆ withLoopBits