TAGEBase Class Reference

#include <tage_base.hh>

Inheritance diagram for 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 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. More...
virtual BranchInfo *	makeBranchInfo ()
virtual int	bindex (Addr pc_in) const
	Computes the index used to access the bimodal table. More...
virtual int	gindex (ThreadID tid, Addr pc, int bank) const
	Computes the index used to access a partially tagged table. More...
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. More...
virtual uint16_t	gtag (ThreadID tid, Addr pc, int bank) const
	Computes the partial tag of a tagged table. More...
virtual bool	getBimodePred (Addr pc, BranchInfo *bi) const
	Get a branch prediction from the bimodal predictor. More...
void	baseUpdate (Addr pc, bool taken, BranchInfo *bi)
	Updates the bimodal predictor. More...
void	updateGHist (uint8_t *&h, bool dir, uint8_t *tab, int &PT)
	(Speculatively) updates the global branch history. More...
void	update (ThreadID tid, Addr branch_pc, bool taken, BranchInfo *bi)
	Update TAGE. More...
virtual void	updateHistories (ThreadID tid, Addr branch_pc, bool taken, BranchInfo *b, bool speculative, const StaticInstPtr &inst=StaticInst::nullStaticInstPtr, Addr target=MaxAddr)
	(Speculatively) updates global histories (path and direction). More...
virtual void	squash (ThreadID tid, bool taken, BranchInfo *bi, Addr target)
	Restores speculatively updated path and direction histories. More...
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. More...
bool	tagePredict (ThreadID tid, Addr branch_pc, bool cond_branch, BranchInfo *bi)
	TAGE prediction called from TAGE::predict. More...
virtual void	updateStats (bool taken, BranchInfo *bi)
	Update the stats. More...
virtual void	buildTageTables ()
	Instantiates the TAGE table entries. More...
virtual void	calculateParameters ()
	Calculates the history lengths and some other paramters in derived classes. More...
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. More...
virtual unsigned	getUseAltIdx (BranchInfo *bi, Addr branch_pc)
	Calculation of the index for useAltPredForNewlyAllocated On this base TAGE implementation it is always 0. More...
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. More...
virtual void	handleAllocAndUReset (bool alloc, bool taken, BranchInfo *bi, int nrand)
	Handles Allocation and U bits reset on an update. More...
virtual void	handleUReset ()
	Handles the U bits reset. More...
virtual void	handleTAGEUpdate (Addr branch_pc, bool taken, BranchInfo *bi)
	Handles the update of the TAGE entries. More...
virtual void	resetUctr (uint8_t &u)
	Algorithm for resetting a single U counter. More...
virtual void	extraAltCalc (BranchInfo *bi)
	Extra steps for calculating altTaken For this base TAGE class it does nothing. More...
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 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 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. More...
static void	unsignedCtrUpdate (uint8_t &ctr, bool up, unsigned nbits)
	Updates an unsigned counter based on up/down parameter. More...
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
virtual void	initFoldedHistories (ThreadHistory &history)
	Initialization of the folded histories. More...
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...

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
TAGEBase::TAGEBaseStats	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...

Detailed Description

Definition at line 58 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 111 of file tage_base.hh.

Constructor & Destructor Documentation

TAGEBase()

TAGEBase::TAGEBase

(

const TAGEBaseParams *

p

)

Definition at line 45 of file tage_base.cc.

References nHistoryTables, and noSkip.

Member Function Documentation

adjustAlloc()

void 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 TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 432 of file tage_base.cc.

Referenced by condBranchUpdate().

baseUpdate()

void 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 296 of file tage_base.cc.

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

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

bindex()

int 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 TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 201 of file tage_base.cc.

References instShiftAmt, logTagTableSizes, and ULL.

Referenced by tagePredict().

btbUpdate()

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

Definition at line 182 of file tage_base.cc.

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

Referenced by TAGE::btbUpdate().

buildTageTables()

void TAGEBase::buildTageTables ( )

virtual

Instantiates the TAGE table entries.

Reimplemented in TAGE_SC_L_TAGE.

Definition at line 160 of file tage_base.cc.

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

Referenced by init().

calculateIndicesAndTags()

void 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 TAGE_SC_L_TAGE.

Definition at line 334 of file tage_base.cc.

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

Referenced by tagePredict().

calculateParameters()

void TAGEBase::calculateParameters ( )

virtual

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

Reimplemented in TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 168 of file tage_base.cc.

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

Referenced by init().

condBranchUpdate()

void 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 508 of file tage_base.cc.

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

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

ctrUpdate()

template<typename T >

template void 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 255 of file tage_base.cc.

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

extraAltCalc()

void TAGEBase::extraAltCalc ( BranchInfo *  bi )

virtual

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

Reimplemented in TAGE_SC_L_TAGE.

Definition at line 649 of file tage_base.cc.

Referenced by tagePredict().

F()

int 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 TAGE_SC_L_TAGE.

Definition at line 207 of file tage_base.cc.

References logTagTableSizes, and ULL.

Referenced by gindex().

getBimodePred()

bool 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 TAGE_SC_L_TAGE.

Definition at line 287 of file tage_base.cc.

References PowerISA::bi, and btablePrediction.

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

getCtr()

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

Definition at line 754 of file tage_base.cc.

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

Referenced by TAGE_SC_L::predict().

getGHR()

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

Definition at line 705 of file tage_base.cc.

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

getPathHist()

int TAGEBase::getPathHist

(

ThreadID

tid

)

const

Definition at line 766 of file tage_base.cc.

References threadHistory.

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

getSizeInBits()

size_t TAGEBase::getSizeInBits

(

)

const

Definition at line 778 of file tage_base.cc.

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

Referenced by MultiperspectivePerceptronTAGE::init().

getTageCtrBits()

unsigned TAGEBase::getTageCtrBits

(

)

const

Definition at line 760 of file tage_base.cc.

References tagTableCounterBits.

Referenced by TAGE_SC_L::predict().

getUseAltIdx()

unsigned 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 TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 347 of file tage_base.cc.

Referenced by condBranchUpdate(), and tagePredict().

gindex()

int 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 TAGE_SC_L_TAGE.

Definition at line 224 of file tage_base.cc.

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

Referenced by calculateIndicesAndTags().

gtag()

uint16_t 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 TAGE_SC_L_TAGE, TAGE_SC_L_TAGE_64KB, and TAGE_SC_L_TAGE_8KB.

Definition at line 242 of file tage_base.cc.

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

Referenced by calculateIndicesAndTags().

handleAllocAndUReset()

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

virtual

Handles Allocation and U bits reset on an update.

Reimplemented in TAGE_SC_L_TAGE, MPP_TAGE, TAGE_SC_L_TAGE_64KB, and TAGE_SC_L_TAGE_8KB.

Definition at line 438 of file tage_base.cc.

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

Referenced by condBranchUpdate().

handleTAGEUpdate()

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

virtual

Handles the update of the TAGE entries.

Reimplemented in TAGE_SC_L_TAGE, MPP_TAGE, TAGE_SC_L_TAGE_64KB, and TAGE_SC_L_TAGE_8KB.

Definition at line 549 of file tage_base.cc.

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

Referenced by condBranchUpdate().

handleUReset()

void TAGEBase::handleUReset ( )

virtual

Handles the U bits reset.

Reimplemented in TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 487 of file tage_base.cc.

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

Referenced by handleAllocAndUReset().

init()

void 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 SimObject.

Definition at line 81 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, ULL, and useAltPredForNewlyAllocated.

Referenced by MultiperspectivePerceptronTAGE::init().

initFoldedHistories()

void TAGEBase::initFoldedHistories ( ThreadHistory &  history )

protectedvirtual

Initialization of the folded histories.

Reimplemented in TAGE_SC_L_TAGE_8KB.

Definition at line 145 of file tage_base.cc.

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

Referenced by init().

isHighConfidence()

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

inlinevirtual

Reimplemented in MPP_TAGE.

Definition at line 402 of file tage_base.hh.

Referenced by MultiperspectivePerceptronTAGE::lookup().

isSpeculativeUpdateEnabled()

bool TAGEBase::isSpeculativeUpdateEnabled

(

)

const

Definition at line 772 of file tage_base.cc.

References speculativeHistUpdate.

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

makeBranchInfo()

TAGEBase::BranchInfo * TAGEBase::makeBranchInfo ( )

virtual

Reimplemented in TAGE_SC_L_TAGE.

Definition at line 76 of file tage_base.cc.

resetUctr()

void TAGEBase::resetUctr ( uint8_t &  u )

virtual

Algorithm for resetting a single U counter.

Reimplemented in MPP_TAGE, and TAGE_SC_L_TAGE_8KB.

Definition at line 502 of file tage_base.cc.

References ArmISA::u.

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

squash()

void 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 TAGE_SC_L_TAGE.

Definition at line 623 of file tage_base.cc.

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

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

tagePredict()

bool 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 354 of file tage_base.cc.

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

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

unsignedCtrUpdate()

void 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 273 of file tage_base.cc.

References ArmISA::up.

Referenced by handleTAGEUpdate().

update()

void 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 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 316 of file tage_base.cc.

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

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

updateHistories()

void TAGEBase::updateHistories ( ThreadID  tid, Addr  branch_pc, bool  taken, BranchInfo *  b, bool  speculative, const StaticInstPtr &  inst = StaticInst::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 TAGE_SC_L_TAGE, and MPP_TAGE.

Definition at line 582 of file tage_base.cc.

References PowerISA::bi, TAGEBase::FoldedHistory::comp, TAGEBase::ThreadHistory::computeIndices, TAGEBase::ThreadHistory::computeTags, DPRINTF, TAGEBase::ThreadHistory::gHist, TAGEBase::ThreadHistory::globalHistory, ArmISA::i, instShiftAmt, nHistoryTables, TAGEBase::ThreadHistory::pathHist, pathHistBits, TAGEBase::ThreadHistory::ptGhist, speculativeHistUpdate, threadHistory, ULL, TAGEBase::FoldedHistory::update(), and updateGHist().

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

updateStats()

void 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 656 of file tage_base.cc.

References TAGEBase::TAGEBaseStats::altMatchProvider, TAGEBase::TAGEBaseStats::altMatchProviderCorrect, TAGEBase::TAGEBaseStats::altMatchProviderWouldHaveHit, TAGEBase::TAGEBaseStats::altMatchProviderWrong, PowerISA::bi, BIMODAL_ALT_MATCH, BIMODAL_ONLY, TAGEBase::TAGEBaseStats::bimodalAltMatchProviderCorrect, TAGEBase::TAGEBaseStats::bimodalAltMatchProviderWrong, TAGEBase::TAGEBaseStats::bimodalProviderCorrect, TAGEBase::TAGEBaseStats::bimodalProviderWrong, TAGEBase::TAGEBaseStats::longestMatchProvider, TAGEBase::TAGEBaseStats::longestMatchProviderCorrect, TAGEBase::TAGEBaseStats::longestMatchProviderWouldHaveHit, TAGEBase::TAGEBaseStats::longestMatchProviderWrong, stats, TAGE_ALT_MATCH, and TAGE_LONGEST_MATCH.

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

Member Data Documentation

btableHysteresis

std::vector<bool> TAGEBase::btableHysteresis

protected

Definition at line 429 of file tage_base.hh.

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

btablePrediction

std::vector<bool> TAGEBase::btablePrediction

protected

Definition at line 428 of file tage_base.hh.

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

gtable

TageEntry** TAGEBase::gtable

protected

Definition at line 430 of file tage_base.hh.

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

histBufferSize

const unsigned TAGEBase::histBufferSize

protected

Definition at line 420 of file tage_base.hh.

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

histLengths

int* TAGEBase::histLengths

protected

Definition at line 462 of file tage_base.hh.

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

initialized

bool TAGEBase::initialized

protected

Definition at line 483 of file tage_base.hh.

Referenced by init().

initialTCounterValue

const int64_t TAGEBase::initialTCounterValue

protected

Definition at line 469 of file tage_base.hh.

Referenced by init().

instShiftAmt

const unsigned TAGEBase::instShiftAmt

protected

Definition at line 481 of file tage_base.hh.

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

logRatioBiModalHystEntries

const unsigned TAGEBase::logRatioBiModalHystEntries

protected

Definition at line 416 of file tage_base.hh.

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

logTagTableSizes

std::vector<int> TAGEBase::logTagTableSizes

protected

Definition at line 426 of file tage_base.hh.

Referenced by MPP_TAGE::bindex(), TAGE_SC_L_TAGE::bindex(), bindex(), buildTageTables(), TAGE_SC_L_TAGE::calculateIndicesAndTags(), TAGE_SC_L_TAGE::calculateParameters(), TAGE_SC_L_TAGE::F(), F(), getSizeInBits(), TAGE_SC_L_TAGE::gindex(), gindex(), TAGE_SC_L_TAGE_8KB::gindex_ext(), MPP_TAGE::handleUReset(), handleUReset(), init(), TAGE_SC_L_TAGE_8KB::initFoldedHistories(), and initFoldedHistories().

logUResetPeriod

uint64_t TAGEBase::logUResetPeriod

protected

Definition at line 468 of file tage_base.hh.

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

maxHist

const unsigned TAGEBase::maxHist

protected

Definition at line 422 of file tage_base.hh.

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

maxNumAlloc

unsigned TAGEBase::maxNumAlloc

protected

Definition at line 472 of file tage_base.hh.

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

minHist

const unsigned TAGEBase::minHist

protected

Definition at line 421 of file tage_base.hh.

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

nHistoryTables

const unsigned TAGEBase::nHistoryTables

protected

Definition at line 417 of file tage_base.hh.

Referenced by TAGEBase::BranchInfo::BranchInfo(), btbUpdate(), TAGE_SC_L_TAGE::buildTageTables(), buildTageTables(), TAGE_SC_L_TAGE::calculateIndicesAndTags(), calculateIndicesAndTags(), MPP_TAGE::calculateParameters(), TAGE_SC_L_TAGE::calculateParameters(), calculateParameters(), condBranchUpdate(), getSizeInBits(), MPP_TAGE::getUseAltIdx(), TAGE_SC_L_TAGE_8KB::handleAllocAndUReset(), TAGE_SC_L_TAGE_64KB::handleAllocAndUReset(), MPP_TAGE::handleAllocAndUReset(), handleAllocAndUReset(), MPP_TAGE::handleUReset(), handleUReset(), init(), TAGE_SC_L_TAGE_8KB::initFoldedHistories(), initFoldedHistories(), squash(), TAGEBase(), TAGEBase::TAGEBaseStats::TAGEBaseStats(), tagePredict(), updateHistories(), MPP_TAGE::updatePathAndGlobalHistory(), and TAGE_SC_L_TAGE::updatePathAndGlobalHistory().

noSkip

std::vector<bool> TAGEBase::noSkip

protected

Definition at line 477 of file tage_base.hh.

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

numUseAltOnNa

unsigned TAGEBase::numUseAltOnNa

protected

Definition at line 470 of file tage_base.hh.

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

pathHistBits

const unsigned TAGEBase::pathHistBits

protected

Definition at line 423 of file tage_base.hh.

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

speculativeHistUpdate

const bool TAGEBase::speculativeHistUpdate

protected

Definition at line 479 of file tage_base.hh.

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

stats

TAGEBase::TAGEBaseStats TAGEBase::stats

protected

Referenced by updateStats().

tableIndices

int* TAGEBase::tableIndices

protected

Definition at line 463 of file tage_base.hh.

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

tableTags

int* TAGEBase::tableTags

protected

Definition at line 464 of file tage_base.hh.

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

tagTableCounterBits

const unsigned TAGEBase::tagTableCounterBits

protected

Definition at line 418 of file tage_base.hh.

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

tagTableTagWidths

std::vector<unsigned> TAGEBase::tagTableTagWidths

protected

Definition at line 425 of file tage_base.hh.

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

tagTableUBits

const unsigned TAGEBase::tagTableUBits

protected

Definition at line 419 of file tage_base.hh.

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

tCounter

int64_t TAGEBase::tCounter

protected

Definition at line 467 of file tage_base.hh.

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

threadHistory

std::vector<ThreadHistory> TAGEBase::threadHistory

protected

Definition at line 455 of file tage_base.hh.

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

useAltOnNaBits

unsigned TAGEBase::useAltOnNaBits

protected

Definition at line 471 of file tage_base.hh.

Referenced by condBranchUpdate(), and getSizeInBits().

useAltPredForNewlyAllocated

std::vector<int8_t> TAGEBase::useAltPredForNewlyAllocated

protected

Definition at line 466 of file tage_base.hh.

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

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

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