Return address stack class, implements a simple RAS. More...

#include <ras.hh>

Inheritance diagram for gem5::branch_prediction::ReturnAddrStack:

Classes
class	AddrStack
	Subclass that implements the actual address stack. More...

class	RASHistory

struct	ReturnAddrStackStats

Public Types
typedef ReturnAddrStackParams	Params

Public Types inherited from gem5::SimObject
typedef SimObjectParams	Params

Public Member Functions
	ReturnAddrStack (const Params &p)

void	reset ()

void	push (ThreadID tid, const PCStateBase &pc, void *&ras_history)
	Pushes an address onto the RAS.

const PCStateBase *	pop (ThreadID tid, void *&ras_history)
	Pops the top address from the RAS.

void	squash (ThreadID tid, void *&ras_history)
	The branch (call/return) got squashed.

void	commit (ThreadID tid, bool misp, const BranchType brType, void *&ras_history)
	A branch got finally got finally commited.

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

Private Member Functions
void	makeRASHistory (void *&ras_history)

Private Attributes
std::vector< AddrStack >	addrStacks
	The RAS itself.

unsigned	numEntries
	The number of entries in the RAS.

unsigned	numThreads
	The number of threads.

gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats	stats

Additional Inherited Members
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.

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

Return address stack class, implements a simple RAS.

Definition at line 61 of file ras.hh.

Member Typedef Documentation

◆ Params

typedef ReturnAddrStackParams gem5::branch_prediction::ReturnAddrStack::Params

Definition at line 143 of file ras.hh.

Constructor & Destructor Documentation

◆ ReturnAddrStack()

gem5::branch_prediction::ReturnAddrStack::ReturnAddrStack ( const Params & p )

Definition at line 134 of file ras.cc.

References addrStacks, DPRINTF, gem5::ArmISA::i, numEntries, and numThreads.

Member Function Documentation

◆ commit()

void gem5::branch_prediction::ReturnAddrStack::commit	(	ThreadID	tid,
		bool	misp,
		const BranchType	brType,
		void *&	ras_history )

A branch got finally got finally commited.

Parameters

misp	Whether the branch was mispredicted.
brType	The type of the branch.
ras_history	The pointer to the history object.

The only case where we could have no history at this point is for a conditional call that is not taken.

Conditional calls

Conditional calls have different scenarios:

the call was predicted as non taken but was actually taken
the call was predicted taken but was actually not taken.
the call was taken but the target was incorrect.
the call was correct.

In case of mispredictions they will be handled during squashing of the BPU. It will push and pop the RAS accordingly.

Definition at line 251 of file ras.cc.

References gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats::correct, DPRINTF, gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats::incorrect, gem5::branch_prediction::ReturnAddrStack::RASHistory::poped, gem5::branch_prediction::ReturnAddrStack::RASHistory::ras_entry, stats, gem5::branch_prediction::toString(), and gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats::used.

Referenced by gem5::branch_prediction::BPredUnit::commitBranch().

◆ makeRASHistory()

void gem5::branch_prediction::ReturnAddrStack::makeRASHistory ( void *& ras_history )

private

Definition at line 157 of file ras.cc.

References gem5::branch_prediction::ReturnAddrStack::RASHistory::poped, and gem5::branch_prediction::ReturnAddrStack::RASHistory::pushed.

Referenced by pop(), and push().

◆ pop()

const PCStateBase * gem5::branch_prediction::ReturnAddrStack::pop	(	ThreadID	tid,
		void *&	ras_history )

Pops the top address from the RAS.

Parameters

ras_history Pointer that will be set to an object that has the return address state associated when an address was poped.

Returns: The address that got poped from the stack.

Definition at line 188 of file ras.cc.

References addrStacks, DPRINTF, makeRASHistory(), gem5::branch_prediction::ReturnAddrStack::RASHistory::poped, gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats::pops, gem5::branch_prediction::ReturnAddrStack::RASHistory::ras_entry, gem5::ArmISA::set, stats, and gem5::branch_prediction::ReturnAddrStack::RASHistory::tos.

Referenced by gem5::branch_prediction::BPredUnit::predict(), and gem5::branch_prediction::BPredUnit::squash().

◆ push()

void gem5::branch_prediction::ReturnAddrStack::push	(	ThreadID	tid,
		const PCStateBase &	pc,
		void *&	ras_history )

Pushes an address onto the RAS.

Parameters

PC	The current PC (should be a call).
ras_history	Pointer that will be set to an object that has the return address state associated when the address was pushed.

Definition at line 166 of file ras.cc.

References addrStacks, DPRINTF, makeRASHistory(), gem5::MipsISA::pc, gem5::branch_prediction::ReturnAddrStack::RASHistory::pushed, gem5::branch_prediction::ReturnAddrStack::ReturnAddrStackStats::pushes, and stats.

Referenced by gem5::branch_prediction::BPredUnit::predict(), and gem5::branch_prediction::BPredUnit::squash().