Memory dependency unit class. More...

#include <mem_dep_unit.hh>

Classes
class	MemDepEntry
	Memory dependence entries that track memory operations, marking when the instruction is ready to execute and what instructions depend upon it. More...

struct	MemDepUnitStats

Public Member Functions
	MemDepUnit ()
	Empty constructor.

	MemDepUnit (const BaseO3CPUParams &params)
	Constructs a MemDepUnit with given parameters.

	~MemDepUnit ()
	Frees up any memory allocated.

std::string	name () const
	Returns the name of the memory dependence unit.

void	init (const BaseO3CPUParams &params, ThreadID tid, CPU *cpu)
	Initializes the unit with parameters and a thread id.

bool	isDrained () const
	Determine if we are drained.

void	drainSanityCheck () const
	Perform sanity checks after a drain.

void	takeOverFrom ()
	Takes over from another CPU's thread.

void	setIQ (InstructionQueue *iq_ptr)
	Sets the pointer to the IQ.

void	insert (const DynInstPtr &inst)
	Inserts a memory instruction.

void	insertNonSpec (const DynInstPtr &inst)
	Inserts a non-speculative memory instruction.

void	insertBarrier (const DynInstPtr &barr_inst)
	Inserts a barrier instruction.

void	regsReady (const DynInstPtr &inst)
	Indicate that an instruction has its registers ready.

void	nonSpecInstReady (const DynInstPtr &inst)
	Indicate that a non-speculative instruction is ready.

void	reschedule (const DynInstPtr &inst)
	Reschedules an instruction to be re-executed.

void	replay ()
	Replays all instructions that have been rescheduled by moving them to the ready list.

void	completeInst (const DynInstPtr &inst)
	Notifies completion of an instruction.

void	squash (const InstSeqNum &squashed_num, ThreadID tid)
	Squashes all instructions up until a given sequence number for a specific thread.

void	violation (const DynInstPtr &store_inst, const DynInstPtr &violating_load)
	Indicates an ordering violation between a store and a younger load.

void	issue (const DynInstPtr &inst)
	Issues the given instruction.

void	dumpLists ()
	Debugging function to dump the lists of instructions.

Protected Attributes
std::string	_name

Private Types
typedef std::list< DynInstPtr >::iterator	ListIt

typedef std::shared_ptr< MemDepEntry >	MemDepEntryPtr

typedef std::unordered_map< InstSeqNum, MemDepEntryPtr, SNHash >	MemDepHash

typedef MemDepHash::iterator	MemDepHashIt

Private Member Functions
void	completed (const DynInstPtr &inst)
	Completes a memory instruction.

void	wakeDependents (const DynInstPtr &inst)
	Wakes any dependents of a memory instruction.

MemDepEntryPtr &	findInHash (const DynInstConstPtr &inst)
	Finds the memory dependence entry in the hash map.

void	moveToReady (MemDepEntryPtr &ready_inst_entry)
	Moves an entry to the ready list.

bool	hasLoadBarrier () const
	Is there an outstanding load barrier that loads must wait on.

bool	hasStoreBarrier () const
	Is there an outstanding store barrier that loads must wait on.

void	insertBarrierSN (const DynInstPtr &barr_inst)
	Inserts the SN of a barrier inst.

Private Attributes
MemDepHash	memDepHash
	A hash map of all memory dependence entries.

std::list< DynInstPtr >	instList [MaxThreads]
	A list of all instructions in the memory dependence unit.

std::list< DynInstPtr >	instsToReplay
	A list of all instructions that are going to be replayed.

StoreSet	depPred
	The memory dependence predictor.

std::unordered_set< InstSeqNum >	loadBarrierSNs
	Sequence numbers of outstanding load barriers.

std::unordered_set< InstSeqNum >	storeBarrierSNs
	Sequence numbers of outstanding store barriers.

InstructionQueue *	iqPtr
	Pointer to the IQ.

int	id
	The thread id of this memory dependence unit.

gem5::o3::MemDepUnit::MemDepUnitStats	stats

Detailed Description

Memory dependency unit class.

This holds the memory dependence predictor. As memory operations are issued to the IQ, they are also issued to this unit, which then looks up the prediction as to what they are dependent upon. This unit must be checked prior to a memory operation being able to issue. Although this is templated, it's somewhat hard to make a generic memory dependence unit. This one is mostly for store sets; it will be quite limited in what other memory dependence predictions it can also utilize. Thus this class should be most likely be rewritten for other dependence prediction schemes.

Definition at line 90 of file mem_dep_unit.hh.

Member Typedef Documentation

◆ ListIt

typedef std::list<DynInstPtr>::iterator gem5::o3::MemDepUnit::ListIt

private

Definition at line 172 of file mem_dep_unit.hh.

◆ MemDepEntryPtr

typedef std::shared_ptr<MemDepEntry> gem5::o3::MemDepUnit::MemDepEntryPtr

private

Definition at line 176 of file mem_dep_unit.hh.

◆ MemDepHash

typedef std::unordered_map<InstSeqNum, MemDepEntryPtr, SNHash> gem5::o3::MemDepUnit::MemDepHash

private

Definition at line 226 of file mem_dep_unit.hh.

◆ MemDepHashIt

typedef MemDepHash::iterator gem5::o3::MemDepUnit::MemDepHashIt

private

Definition at line 228 of file mem_dep_unit.hh.

Constructor & Destructor Documentation

◆ MemDepUnit() [1/2]

gem5::o3::MemDepUnit::MemDepUnit ( )

Empty constructor.

Must call init() prior to using in this case.

Definition at line 55 of file mem_dep_unit.cc.

◆ MemDepUnit() [2/2]

gem5::o3::MemDepUnit::MemDepUnit ( const BaseO3CPUParams & params )

Constructs a MemDepUnit with given parameters.

Definition at line 57 of file mem_dep_unit.cc.

References DPRINTF.

◆ ~MemDepUnit()

gem5::o3::MemDepUnit::~MemDepUnit ( )

Frees up any memory allocated.

Definition at line 67 of file mem_dep_unit.cc.

References instList, gem5::o3::MaxThreads, and memDepHash.

Member Function Documentation

◆ completed()

void gem5::o3::MemDepUnit::completed ( const DynInstPtr & inst )

private

Completes a memory instruction.

Definition at line 405 of file mem_dep_unit.cc.

References DPRINTF, instList, and memDepHash.

Referenced by completeInst().

◆ completeInst()

void gem5::o3::MemDepUnit::completeInst ( const DynInstPtr & inst )

Notifies completion of an instruction.

Definition at line 428 of file mem_dep_unit.cc.

References completed(), DPRINTF, hasLoadBarrier(), hasStoreBarrier(), loadBarrierSNs, storeBarrierSNs, and wakeDependents().

Referenced by gem5::o3::InstructionQueue::wakeDependents().

◆ drainSanityCheck()

void gem5::o3::MemDepUnit::drainSanityCheck ( ) const

Perform sanity checks after a drain.

Definition at line 132 of file mem_dep_unit.cc.

References gem5::ArmISA::i, instList, instsToReplay, gem5::o3::MaxThreads, and memDepHash.

◆ dumpLists()

void gem5::o3::MemDepUnit::dumpLists ( )

Debugging function to dump the lists of instructions.

Definition at line 614 of file mem_dep_unit.cc.

References gem5::cprintf(), instList, gem5::o3::MaxThreads, and memDepHash.

◆ findInHash()

MemDepUnit::MemDepEntryPtr & gem5::o3::MemDepUnit::findInHash ( const DynInstConstPtr & inst )

private

Finds the memory dependence entry in the hash map.

Definition at line 592 of file mem_dep_unit.cc.

References memDepHash.

Referenced by nonSpecInstReady(), regsReady(), replay(), and wakeDependents().

◆ hasLoadBarrier()

bool gem5::o3::MemDepUnit::hasLoadBarrier ( ) const

inlineprivate

Is there an outstanding load barrier that loads must wait on.

Definition at line 253 of file mem_dep_unit.hh.

References loadBarrierSNs.

Referenced by completeInst(), and insert().

◆ hasStoreBarrier()

bool gem5::o3::MemDepUnit::hasStoreBarrier ( ) const

inlineprivate

Is there an outstanding store barrier that loads must wait on.

Definition at line 256 of file mem_dep_unit.hh.

References storeBarrierSNs.

Referenced by completeInst(), and insert().

◆ init()

void gem5::o3::MemDepUnit::init	(	const BaseO3CPUParams &	params,
		ThreadID	tid,
		CPU *	cpu )

Initializes the unit with parameters and a thread id.

Definition at line 92 of file mem_dep_unit.cc.

References _name, gem5::statistics::Group::addStatGroup(), gem5::csprintf(), depPred, DPRINTF, gem5::o3::StoreSet::init(), and stats.

Referenced by gem5::o3::InstructionQueue::InstructionQueue().

◆ insert()

void gem5::o3::MemDepUnit::insert ( const DynInstPtr & inst )

Inserts a memory instruction.

Definition at line 190 of file mem_dep_unit.cc.

References gem5::o3::StoreSet::checkInst(), gem5::o3::MemDepUnit::MemDepUnitStats::conflictingLoads, gem5::o3::MemDepUnit::MemDepUnitStats::conflictingStores, depPred, DPRINTF, hasLoadBarrier(), hasStoreBarrier(), insertBarrierSN(), gem5::o3::MemDepUnit::MemDepUnitStats::insertedLoads, gem5::o3::MemDepUnit::MemDepUnitStats::insertedStores, gem5::o3::StoreSet::insertStore(), instList, loadBarrierSNs, memDepHash, moveToReady(), panic, stats, and storeBarrierSNs.

Referenced by gem5::o3::InstructionQueue::insert().

◆ insertBarrier()

void gem5::o3::MemDepUnit::insertBarrier ( const DynInstPtr & barr_inst )

Inserts a barrier instruction.

Definition at line 323 of file mem_dep_unit.cc.

References insertBarrierSN(), instList, and memDepHash.

Referenced by gem5::o3::InstructionQueue::insertBarrier(), and insertNonSpec().

◆ insertBarrierSN()

void gem5::o3::MemDepUnit::insertBarrierSN ( const DynInstPtr & barr_inst )

private

Inserts the SN of a barrier inst.

to the list of tracked barriers

Definition at line 158 of file mem_dep_unit.cc.

References DPRINTF, loadBarrierSNs, and storeBarrierSNs.

Referenced by insert(), and insertBarrier().

◆ insertNonSpec()

void gem5::o3::MemDepUnit::insertNonSpec ( const DynInstPtr & inst )

Inserts a non-speculative memory instruction.

Definition at line 301 of file mem_dep_unit.cc.

References depPred, DPRINTF, insertBarrier(), gem5::o3::MemDepUnit::MemDepUnitStats::insertedLoads, gem5::o3::MemDepUnit::MemDepUnitStats::insertedStores, gem5::o3::StoreSet::insertStore(), panic, and stats.

Referenced by gem5::o3::InstructionQueue::insertNonSpec().

◆ isDrained()

bool gem5::o3::MemDepUnit::isDrained ( ) const

Determine if we are drained.

Definition at line 120 of file mem_dep_unit.cc.

References gem5::ArmISA::i, instList, instsToReplay, gem5::o3::MaxThreads, and memDepHash.

◆ issue()

void gem5::o3::MemDepUnit::issue ( const DynInstPtr & inst )

Issues the given instruction.

Definition at line 583 of file mem_dep_unit.cc.

References depPred, DPRINTF, and gem5::o3::StoreSet::issued().

Referenced by gem5::o3::InstructionQueue::scheduleReadyInsts().

◆ moveToReady()

void gem5::o3::MemDepUnit::moveToReady ( MemDepEntryPtr & ready_inst_entry )

private

Moves an entry to the ready list.

Definition at line 602 of file mem_dep_unit.cc.

References gem5::o3::InstructionQueue::addReadyMemInst(), DPRINTF, and iqPtr.

Referenced by insert(), nonSpecInstReady(), regsReady(), replay(), and wakeDependents().

◆ name()

std::string gem5::o3::MemDepUnit::name ( ) const

inline

Returns the name of the memory dependence unit.

Definition at line 106 of file mem_dep_unit.hh.

References _name.

◆ nonSpecInstReady()

void gem5::o3::MemDepUnit::nonSpecInstReady ( const DynInstPtr & inst )

Indicate that a non-speculative instruction is ready.

Definition at line 367 of file mem_dep_unit.cc.

References DPRINTF, findInHash(), and moveToReady().

Referenced by gem5::o3::InstructionQueue::scheduleNonSpec().

◆ regsReady()

void gem5::o3::MemDepUnit::regsReady ( const DynInstPtr & inst )

Indicate that an instruction has its registers ready.

Definition at line 345 of file mem_dep_unit.cc.

References DPRINTF, findInHash(), and moveToReady().

Referenced by gem5::o3::InstructionQueue::addIfReady().

◆ replay()

void gem5::o3::MemDepUnit::replay ( )

Replays all instructions that have been rescheduled by moving them to the ready list.

Definition at line 385 of file mem_dep_unit.cc.

References DPRINTF, findInHash(), instsToReplay, and moveToReady().

Referenced by gem5::o3::InstructionQueue::replayMemInst().

◆ reschedule()

void gem5::o3::MemDepUnit::reschedule ( const DynInstPtr & inst )

Reschedules an instruction to be re-executed.

Definition at line 379 of file mem_dep_unit.cc.

References instsToReplay.

Referenced by gem5::o3::InstructionQueue::rescheduleMemInst().

◆ setIQ()

void gem5::o3::MemDepUnit::setIQ ( InstructionQueue * iq_ptr )

Sets the pointer to the IQ.

Definition at line 152 of file mem_dep_unit.cc.

References iqPtr.

Referenced by gem5::o3::InstructionQueue::InstructionQueue().

◆ squash()

void gem5::o3::MemDepUnit::squash	(	const InstSeqNum &	squashed_num,
		ThreadID	tid )

Squashes all instructions up until a given sequence number for a specific thread.

Definition at line 521 of file mem_dep_unit.cc.

References depPred, DPRINTF, instList, instsToReplay, loadBarrierSNs, memDepHash, gem5::o3::StoreSet::squash(), and storeBarrierSNs.

Referenced by gem5::o3::InstructionQueue::squash().

◆ takeOverFrom()

void gem5::o3::MemDepUnit::takeOverFrom ( )

Takes over from another CPU's thread.

Definition at line 143 of file mem_dep_unit.cc.

References gem5::o3::StoreSet::clear(), depPred, loadBarrierSNs, and storeBarrierSNs.

◆ violation()

void gem5::o3::MemDepUnit::violation	(	const DynInstPtr &	store_inst,
		const DynInstPtr &	violating_load )

Indicates an ordering violation between a store and a younger load.

Definition at line 571 of file mem_dep_unit.cc.

References depPred, DPRINTF, and gem5::o3::StoreSet::violation().

Referenced by gem5::o3::InstructionQueue::violation().

◆ wakeDependents()

void gem5::o3::MemDepUnit::wakeDependents ( const DynInstPtr & inst )

private

Wakes any dependents of a memory instruction.

Definition at line 459 of file mem_dep_unit.cc.

References DPRINTF, findInHash(), gem5::ArmISA::i, and moveToReady().

Referenced by completeInst().

Member Data Documentation

◆ _name

std::string gem5::o3::MemDepUnit::_name

protected

Definition at line 93 of file mem_dep_unit.hh.

Referenced by init(), and name().

◆ depPred

StoreSet gem5::o3::MemDepUnit::depPred

private

The memory dependence predictor.

It is accessed upon new instructions being added to the IQ, and responds by telling this unit what instruction the newly added instruction is dependent upon.

Definition at line 244 of file mem_dep_unit.hh.

Referenced by init(), insert(), insertNonSpec(), issue(), squash(), takeOverFrom(), and violation().

◆ id

int gem5::o3::MemDepUnit::id

private

The thread id of this memory dependence unit.

Definition at line 265 of file mem_dep_unit.hh.

◆ instList

std::list<DynInstPtr> gem5::o3::MemDepUnit::instList[MaxThreads]

private

A list of all instructions in the memory dependence unit.

Definition at line 234 of file mem_dep_unit.hh.

Referenced by completed(), drainSanityCheck(), dumpLists(), insert(), insertBarrier(), isDrained(), squash(), and ~MemDepUnit().

◆ instsToReplay

std::list<DynInstPtr> gem5::o3::MemDepUnit::instsToReplay

private

A list of all instructions that are going to be replayed.

Definition at line 237 of file mem_dep_unit.hh.

Referenced by drainSanityCheck(), isDrained(), replay(), reschedule(), and squash().

◆ iqPtr

InstructionQueue* gem5::o3::MemDepUnit::iqPtr

private

Pointer to the IQ.

Definition at line 262 of file mem_dep_unit.hh.

Referenced by moveToReady(), and setIQ().

◆ loadBarrierSNs

std::unordered_set<InstSeqNum> gem5::o3::MemDepUnit::loadBarrierSNs

private

Sequence numbers of outstanding load barriers.

Definition at line 247 of file mem_dep_unit.hh.

Referenced by completeInst(), hasLoadBarrier(), insert(), insertBarrierSN(), squash(), and takeOverFrom().

◆ memDepHash

MemDepHash gem5::o3::MemDepUnit::memDepHash

private

A hash map of all memory dependence entries.

Definition at line 231 of file mem_dep_unit.hh.

Referenced by completed(), drainSanityCheck(), dumpLists(), findInHash(), insert(), insertBarrier(), isDrained(), squash(), and ~MemDepUnit().

◆ stats

gem5::o3::MemDepUnit::MemDepUnitStats gem5::o3::MemDepUnit::stats

private

Referenced by init(), insert(), and insertNonSpec().

◆ storeBarrierSNs

std::unordered_set<InstSeqNum> gem5::o3::MemDepUnit::storeBarrierSNs

private

Sequence numbers of outstanding store barriers.

Definition at line 250 of file mem_dep_unit.hh.

Referenced by completeInst(), hasStoreBarrier(), insert(), insertBarrierSN(), squash(), and takeOverFrom().

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

cpu/o3/mem_dep_unit.hh
cpu/o3/mem_dep_unit.cc

Classes

Public Member Functions

Protected Attributes

Private Types

Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

◆ ListIt

◆ MemDepEntryPtr

◆ MemDepHash

◆ MemDepHashIt

Constructor & Destructor Documentation

◆ MemDepUnit() [1/2]

◆ MemDepUnit() [2/2]

◆ ~MemDepUnit()

Member Function Documentation

◆ completed()

◆ completeInst()

◆ drainSanityCheck()

◆ dumpLists()

◆ findInHash()

◆ hasLoadBarrier()

◆ hasStoreBarrier()

◆ init()

◆ insert()

◆ insertBarrier()

◆ insertBarrierSN()

◆ insertNonSpec()

◆ isDrained()

◆ issue()

◆ moveToReady()

◆ name()

◆ nonSpecInstReady()

◆ regsReady()

◆ replay()

◆ reschedule()

◆ setIQ()

◆ squash()

◆ takeOverFrom()

◆ violation()

◆ wakeDependents()

Member Data Documentation

◆ _name

◆ depPred

◆ id

◆ instList

◆ instsToReplay

◆ iqPtr

◆ loadBarrierSNs

◆ memDepHash

◆ stats

◆ storeBarrierSNs