#include <simple_indirect.hh>

Inheritance diagram for gem5::branch_prediction::SimpleIndirectPredictor:

Classes
struct	HistoryEntry

struct	IndirectHistory
	Indirect branch history information Used for prediction, update and recovery. More...

struct	IndirectStats

struct	IPredEntry

struct	ThreadInfo
	Per thread path and global history registers. More...

Public Member Functions
	SimpleIndirectPredictor (const SimpleIndirectPredictorParams &params)

void	reset () override
	Indirect predictor interface.

const PCStateBase *	lookup (ThreadID tid, InstSeqNum sn, Addr pc, void *&iHistory) override
	Predicts the indirect target of an indirect branch.

void	update (ThreadID tid, InstSeqNum sn, Addr pc, bool squash, bool taken, const PCStateBase &target, BranchType br_type, void *&iHistory) override
	Updates the indirect predictor with history information of a branch.

void	squash (ThreadID tid, InstSeqNum sn, void *&iHistory) override
	Squashes a branch.

void	commit (ThreadID tid, InstSeqNum sn, void *&iHistory) override
	A branch gets finally commited.

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

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

	SimObject (const Params &p)

virtual	~SimObject ()

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

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

Protected Attributes
gem5::branch_prediction::SimpleIndirectPredictor::IndirectStats	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.

Private Member Functions
bool	lookup (ThreadID tid, Addr br_addr, PCStateBase &target, IndirectHistory &history)

void	recordTarget (ThreadID tid, InstSeqNum sn, const PCStateBase &target, IndirectHistory *&history)

void	genIndirectInfo (ThreadID tid, void *&iHistory)

void	updateDirectionInfo (ThreadID tid, bool taken, Addr pc, Addr target)

Addr	getSetIndex (Addr br_addr, ThreadID tid)

Addr	getTag (Addr br_addr)

bool	isIndirectNoReturn (BranchType type)

Private Attributes
const bool	hashGHR

const bool	hashTargets

const unsigned	numSets

const unsigned	numWays

const unsigned	tagBits

const unsigned	pathLength

const unsigned	speculativePathLength

const unsigned	instShift

const unsigned	ghrNumBits

const unsigned	ghrMask

std::vector< std::vector< IPredEntry > >	targetCache

std::vector< ThreadInfo >	threadInfo

Additional Inherited Members
Public Types inherited from gem5::branch_prediction::IndirectPredictor
typedef IndirectPredictorParams	Params

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Static Public Member Functions inherited from gem5::SimObject
static void	serializeAll (const std::string &cpt_dir)
	Create a checkpoint by serializing all SimObjects in the system.

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

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

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

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

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

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

virtual	~Drainable ()

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

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

Detailed Description

Definition at line 55 of file simple_indirect.hh.

Constructor & Destructor Documentation

◆ SimpleIndirectPredictor()

gem5::branch_prediction::SimpleIndirectPredictor::SimpleIndirectPredictor ( const SimpleIndirectPredictorParams & params )

Definition at line 50 of file simple_indirect.cc.

References fatal_if, gem5::branch_prediction::SimpleIndirectPredictor::ThreadInfo::ghr, ghrNumBits, gem5::ArmISA::i, gem5::isPowerOf2(), numSets, numWays, panic, gem5::SimObject::params(), targetCache, and threadInfo.

Member Function Documentation

◆ commit()

void gem5::branch_prediction::SimpleIndirectPredictor::commit	(	ThreadID	tid,
		InstSeqNum	sn,
		void *&	i_history )

overridevirtual

A branch gets finally commited.

Updates the internal state of the indirect predictor (counter and target information).

Parameters

tid	Thread ID
sn	The sequence number of the branch.
i_history	The pointer to the history object.

Delete histories if the history grows to much

Implements gem5::branch_prediction::IndirectPredictor.

Definition at line 176 of file simple_indirect.cc.

References DPRINTF, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::ghr, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pathHist, pathLength, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pcAddr, speculativePathLength, and threadInfo.

◆ genIndirectInfo()

void gem5::branch_prediction::SimpleIndirectPredictor::genIndirectInfo	(	ThreadID	tid,
		void *&	iHistory )

private

Definition at line 99 of file simple_indirect.cc.

References gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::ghr, and threadInfo.

Referenced by lookup(), and update().

◆ getSetIndex()

Addr gem5::branch_prediction::SimpleIndirectPredictor::getSetIndex	(	Addr	br_addr,
		ThreadID	tid )

inlineprivate

Definition at line 354 of file simple_indirect.cc.

References gem5::floorLog2(), hashGHR, hashTargets, gem5::ArmISA::i, instShift, numSets, gem5::MipsISA::p, pathLength, and threadInfo.

Referenced by lookup(), and update().

◆ getTag()

Addr gem5::branch_prediction::SimpleIndirectPredictor::getTag ( Addr br_addr )

inlineprivate

Definition at line 372 of file simple_indirect.cc.

References instShift, and tagBits.

Referenced by lookup(), and update().

◆ isIndirectNoReturn()

bool gem5::branch_prediction::SimpleIndirectPredictor::isIndirectNoReturn ( BranchType type )

inlineprivate

Definition at line 161 of file simple_indirect.hh.

References gem5::X86ISA::type.

Referenced by update().

◆ lookup() [1/2]

bool gem5::branch_prediction::SimpleIndirectPredictor::lookup	(	ThreadID	tid,
		Addr	br_addr,
		PCStateBase *&	target,
		IndirectHistory *&	history )

private

Definition at line 141 of file simple_indirect.cc.

◆ lookup() [2/2]

const PCStateBase * gem5::branch_prediction::SimpleIndirectPredictor::lookup	(	ThreadID	tid,
		InstSeqNum	sn,
		Addr	pc,
		void *&	i_history )

overridevirtual

Predicts the indirect target of an indirect branch.

Parameters

tid	Thread ID of the branch.
sn	The sequence number of the branch.
pc	The branch PC address.
i_history	The pointer to the history object.

Returns: For a hit the predictor returns a pointer to the target PCState otherwise a nullptr is returned.

Do the prediction for indirect branches (no returns)

Implements gem5::branch_prediction::IndirectPredictor.

Definition at line 123 of file simple_indirect.cc.

References genIndirectInfo(), gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::hit, lookup(), gem5::MipsISA::pc, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pcAddr, and gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::was_indirect.

Referenced by lookup().

◆ recordTarget()

void gem5::branch_prediction::SimpleIndirectPredictor::recordTarget	(	ThreadID	tid,
		InstSeqNum	sn,
		const PCStateBase &	target,
		IndirectHistory *&	history )

private

Definition at line 307 of file simple_indirect.cc.

References DPRINTF, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::ghr, gem5::PCStateBase::instAddr(), numSets, numWays, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pcAddr, gem5::ArmISA::set, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::set_index, stats, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::tag, targetCache, gem5::branch_prediction::SimpleIndirectPredictor::IndirectStats::targetRecords, threadInfo, and gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::was_indirect.

Referenced by update().

◆ reset()

void gem5::branch_prediction::SimpleIndirectPredictor::reset ( )

overridevirtual

Indirect predictor interface.

Reimplemented from gem5::branch_prediction::IndirectPredictor.

Definition at line 81 of file simple_indirect.cc.

References DPRINTF, gem5::ArmISA::i, numSets, numWays, targetCache, threadInfo, and gem5::MipsISA::ti.

◆ squash()

void gem5::branch_prediction::SimpleIndirectPredictor::squash	(	ThreadID	tid,
		InstSeqNum	sn,
		void *&	i_history )

overridevirtual

Squashes a branch.

If the branch modified the history reverts the modification.

Parameters

tid	Thread ID
sn	The sequence number of the branch.
i_history	The pointer to the history object.

Implements gem5::branch_prediction::IndirectPredictor.

Definition at line 263 of file simple_indirect.cc.

References DPRINTF, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::ghr, pathLength, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pcAddr, gem5::branch_prediction::SimpleIndirectPredictor::IndirectStats::speculativeOverflows, stats, threadInfo, and gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::was_indirect.

Referenced by update().

◆ update()

void gem5::branch_prediction::SimpleIndirectPredictor::update	(	ThreadID	tid,
		InstSeqNum	sn,
		Addr	pc,
		bool	squash,
		bool	taken,
		const PCStateBase &	target,
		BranchType	br_type,
		void *&	i_history )

overridevirtual

Updates the indirect predictor with history information of a branch.

Is called right after the prediction which updates the state speculatively. In case the branch was mispredicted the function is called again with the corrected information. The function is called for ALL branches as some predictors incooperate all branches in their history.

Parameters

tid	Thread ID
sn	The sequence number of the branch.
pc	The branch PC address.
squash	Whether the update is called at a misprediction
taken	Whether a conditional branch was taken
target	The target address if this branch.
br_type	The branch instruction type.
i_history	The pointer to the history object.

If update was called during squash we need to fix the indirect path history and the global path history. We restore the state before this branch incorrectly updated it and perform the update afterwards again.

restore global history

For indirect branches recalculate index and tag

Implements gem5::branch_prediction::IndirectPredictor.

Definition at line 198 of file simple_indirect.cc.

References DPRINTF, genIndirectInfo(), getSetIndex(), getTag(), gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::ghr, gem5::branch_prediction::SimpleIndirectPredictor::IndirectStats::indirectRecords, gem5::PCStateBase::instAddr(), isIndirectNoReturn(), gem5::MipsISA::pc, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::pcAddr, recordTarget(), gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::set_index, squash(), stats, gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::tag, threadInfo, updateDirectionInfo(), and gem5::branch_prediction::SimpleIndirectPredictor::IndirectHistory::was_indirect.

◆ updateDirectionInfo()

void gem5::branch_prediction::SimpleIndirectPredictor::updateDirectionInfo	(	ThreadID	tid,
		bool	taken,
		Addr	pc,
		Addr	target )

private

Definition at line 110 of file simple_indirect.cc.

References ghrMask, and threadInfo.

Referenced by update().

Member Data Documentation

◆ ghrMask

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::ghrMask

private

Definition at line 87 of file simple_indirect.hh.

Referenced by updateDirectionInfo().

◆ ghrNumBits

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::ghrNumBits

private

Definition at line 86 of file simple_indirect.hh.

Referenced by SimpleIndirectPredictor().

◆ hashGHR

const bool gem5::branch_prediction::SimpleIndirectPredictor::hashGHR

private

The actual predictor

Definition at line 78 of file simple_indirect.hh.

Referenced by getSetIndex().

◆ hashTargets

const bool gem5::branch_prediction::SimpleIndirectPredictor::hashTargets

private

Definition at line 79 of file simple_indirect.hh.

Referenced by getSetIndex().

◆ instShift

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::instShift

private

Definition at line 85 of file simple_indirect.hh.

Referenced by getSetIndex(), and getTag().

◆ numSets

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::numSets

private

Definition at line 80 of file simple_indirect.hh.

Referenced by getSetIndex(), lookup(), recordTarget(), reset(), and SimpleIndirectPredictor().

◆ numWays

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::numWays

private

Definition at line 81 of file simple_indirect.hh.

Referenced by recordTarget(), reset(), and SimpleIndirectPredictor().

◆ pathLength

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::pathLength

private

Definition at line 83 of file simple_indirect.hh.

Referenced by commit(), getSetIndex(), and squash().

◆ speculativePathLength

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::speculativePathLength

private

Definition at line 84 of file simple_indirect.hh.

Referenced by commit().

◆ stats

gem5::branch_prediction::SimpleIndirectPredictor::IndirectStats gem5::branch_prediction::SimpleIndirectPredictor::stats

protected

Referenced by lookup(), recordTarget(), squash(), and update().

◆ tagBits

const unsigned gem5::branch_prediction::SimpleIndirectPredictor::tagBits

private

Definition at line 82 of file simple_indirect.hh.

Referenced by getTag().

◆ targetCache

std::vector<std::vector<IPredEntry> > gem5::branch_prediction::SimpleIndirectPredictor::targetCache

private

Definition at line 95 of file simple_indirect.hh.

Referenced by lookup(), recordTarget(), reset(), and SimpleIndirectPredictor().

◆ threadInfo

std::vector<ThreadInfo> gem5::branch_prediction::SimpleIndirectPredictor::threadInfo

private

Definition at line 143 of file simple_indirect.hh.

Referenced by commit(), genIndirectInfo(), getSetIndex(), lookup(), recordTarget(), reset(), SimpleIndirectPredictor(), squash(), update(), and updateDirectionInfo().

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

cpu/pred/simple_indirect.hh
cpu/pred/simple_indirect.cc

Classes

Public Member Functions

Protected Attributes

Private Member Functions

Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

◆ SimpleIndirectPredictor()

Member Function Documentation

◆ commit()

◆ genIndirectInfo()

◆ getSetIndex()

◆ getTag()

◆ isIndirectNoReturn()

◆ lookup() [1/2]

◆ lookup() [2/2]

◆ recordTarget()

◆ reset()

◆ squash()

◆ update()

◆ updateDirectionInfo()

Member Data Documentation

◆ ghrMask

◆ ghrNumBits

◆ hashGHR

The actual predictor

◆ hashTargets

◆ instShift

◆ numSets

◆ numWays

◆ pathLength

◆ speculativePathLength

◆ stats

◆ tagBits

◆ targetCache

◆ threadInfo