Implements a store set predictor for determining if memory instructions are dependent upon each other. More...

#include <store_set.hh>

Public Types
typedef unsigned	SSID

Public Member Functions
	StoreSet ()
	Default constructor.

	StoreSet (uint64_t clear_period, int SSIT_size, int LFST_size)
	Creates store set predictor with given table sizes.

	~StoreSet ()
	Default destructor.

void	init (uint64_t clear_period, int SSIT_size, int LFST_size)
	Initializes the store set predictor with the given table sizes.

void	violation (Addr store_PC, Addr load_PC)
	Records a memory ordering violation between the younger load and the older store.

void	checkClear ()
	Clears the store set predictor every so often so that all the entries aren't used and stores are constantly predicted as conflicting.

void	insertLoad (Addr load_PC, InstSeqNum load_seq_num)
	Inserts a load into the store set predictor.

void	insertStore (Addr store_PC, InstSeqNum store_seq_num, ThreadID tid)
	Inserts a store into the store set predictor.

InstSeqNum	checkInst (Addr PC)
	Checks if the instruction with the given PC is dependent upon any store.

void	issued (Addr issued_PC, InstSeqNum issued_seq_num, bool is_store)
	Records this PC/sequence number as issued.

void	squash (InstSeqNum squashed_num, ThreadID tid)
	Squashes for a specific thread until the given sequence number.

void	clear ()
	Resets all tables.

void	dump ()
	Debug function to dump the contents of the store list.

Private Types
typedef std::map< InstSeqNum, int, ltseqnum >::iterator	SeqNumMapIt

Private Member Functions
int	calcIndex (Addr PC)
	Calculates the index into the SSIT based on the PC.

SSID	calcSSID (Addr PC)
	Calculates a Store Set ID based on the PC.

Private Attributes
std::vector< SSID >	SSIT
	The Store Set ID Table.

std::vector< bool >	validSSIT
	Bit vector to tell if the SSIT has a valid entry.

std::vector< InstSeqNum >	LFST
	Last Fetched Store Table.

std::vector< bool >	validLFST
	Bit vector to tell if the LFST has a valid entry.

std::map< InstSeqNum, int, ltseqnum >	storeList
	Map of stores that have been inserted into the store set, but not yet issued or squashed.

uint64_t	clearPeriod
	Number of loads/stores to process before wiping predictor so all entries don't get saturated.

int	SSITSize
	Store Set ID Table size, in entries.

int	LFSTSize
	Last Fetched Store Table size, in entries.

int	indexMask
	Mask to obtain the index.

int	offsetBits

int	memOpsPred
	Number of memory operations predicted since last clear of predictor.

Detailed Description

Implements a store set predictor for determining if memory instructions are dependent upon each other.

See paper "Memory Dependence Prediction using Store Sets" by Chrysos and Emer. SSID stands for Store Set ID, SSIT stands for Store Set ID Table, and LFST is Last Fetched Store Table.

Definition at line 62 of file store_set.hh.

Member Typedef Documentation

◆ SeqNumMapIt

typedef std::map<InstSeqNum,int,ltseqnum>::iterator gem5::o3::StoreSet::SeqNumMapIt

private

Definition at line 143 of file store_set.hh.

◆ SSID

typedef unsigned gem5::o3::StoreSet::SSID

Definition at line 65 of file store_set.hh.

Constructor & Destructor Documentation

◆ StoreSet() [1/2]

gem5::o3::StoreSet::StoreSet ( )

inline

Default constructor.

init() must be called prior to use.

Definition at line 69 of file store_set.hh.

◆ StoreSet() [2/2]

gem5::o3::StoreSet::StoreSet	(	uint64_t	clear_period,
		int	SSIT_size,
		int	LFST_size )

Creates store set predictor with given table sizes.

Definition at line 42 of file store_set.cc.

References DPRINTF, fatal, gem5::ArmISA::i, indexMask, gem5::isPowerOf2(), LFST, LFSTSize, memOpsPred, offsetBits, SSIT, SSITSize, validLFST, and validSSIT.

◆ ~StoreSet()

gem5::o3::StoreSet::~StoreSet ( )

Default destructor.

Definition at line 80 of file store_set.cc.

Member Function Documentation

◆ calcIndex()

int gem5::o3::StoreSet::calcIndex ( Addr PC )

inlineprivate

Calculates the index into the SSIT based on the PC.

Definition at line 119 of file store_set.hh.

References indexMask, and offsetBits.

Referenced by checkInst(), insertStore(), issued(), and violation().

◆ calcSSID()

SSID gem5::o3::StoreSet::calcSSID ( Addr PC )

inlineprivate

Calculates a Store Set ID based on the PC.

Definition at line 123 of file store_set.hh.

References LFSTSize.

Referenced by violation().

◆ checkClear()

void gem5::o3::StoreSet::checkClear ( )

Clears the store set predictor every so often so that all the entries aren't used and stores are constantly predicted as conflicting.

Definition at line 193 of file store_set.cc.

References clear(), clearPeriod, DPRINTF, and memOpsPred.

Referenced by insertLoad(), and insertStore().

◆ checkInst()

InstSeqNum gem5::o3::StoreSet::checkInst ( Addr PC )

Checks if the instruction with the given PC is dependent upon any store.

Returns: Returns the sequence number of the store instruction this PC is dependent upon. Returns 0 if none.

Definition at line 243 of file store_set.cc.

References calcIndex(), DPRINTF, gem5::MipsISA::index, LFST, LFSTSize, SSIT, SSITSize, validLFST, and validSSIT.

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

◆ clear()

void gem5::o3::StoreSet::clear ( )

Resets all tables.

Definition at line 345 of file store_set.cc.

References gem5::ArmISA::i, LFSTSize, SSITSize, storeList, validLFST, and validSSIT.

Referenced by checkClear(), and gem5::o3::MemDepUnit::takeOverFrom().

◆ dump()

void gem5::o3::StoreSet::dump ( )

Debug function to dump the contents of the store list.

Definition at line 359 of file store_set.cc.

References gem5::cprintf(), and storeList.

◆ init()

void gem5::o3::StoreSet::init	(	uint64_t	clear_period,
		int	SSIT_size,
		int	LFST_size )

Initializes the store set predictor with the given table sizes.

Definition at line 85 of file store_set.cc.

References clearPeriod, DPRINTF, gem5::ArmISA::i, indexMask, LFST, LFSTSize, memOpsPred, offsetBits, SSIT, SSITSize, validLFST, and validSSIT.

Referenced by gem5::o3::MemDepUnit::init().

◆ insertLoad()

void gem5::o3::StoreSet::insertLoad	(	Addr	load_PC,
		InstSeqNum	load_seq_num )

Inserts a load into the store set predictor.

This does nothing but is included in case other predictors require a similar function.

Definition at line 205 of file store_set.cc.

References checkClear().

◆ insertStore()

void gem5::o3::StoreSet::insertStore	(	Addr	store_PC,
		InstSeqNum	store_seq_num,
		ThreadID	tid )

Inserts a store into the store set predictor.

Updates the LFST if the store has a valid SSID.

Definition at line 213 of file store_set.cc.

References calcIndex(), checkClear(), DPRINTF, gem5::MipsISA::index, LFST, LFSTSize, SSIT, SSITSize, storeList, validLFST, and validSSIT.

Referenced by gem5::o3::MemDepUnit::insert(), and gem5::o3::MemDepUnit::insertNonSpec().

◆ issued()

void gem5::o3::StoreSet::issued	(	Addr	issued_PC,
		InstSeqNum	issued_seq_num,
		bool	is_store )

Records this PC/sequence number as issued.

Definition at line 278 of file store_set.cc.

References calcIndex(), DPRINTF, gem5::MipsISA::index, LFST, LFSTSize, SSIT, SSITSize, storeList, validLFST, and validSSIT.

Referenced by gem5::o3::MemDepUnit::issue().

◆ squash()

void gem5::o3::StoreSet::squash	(	InstSeqNum	squashed_num,
		ThreadID	tid )

Squashes for a specific thread until the given sequence number.

Definition at line 315 of file store_set.cc.

References DPRINTF, LFST, storeList, and validLFST.

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

◆ violation()

void gem5::o3::StoreSet::violation	(	Addr	store_PC,
		Addr	load_PC )

Records a memory ordering violation between the younger load and the older store.

Definition at line 120 of file store_set.cc.

References calcIndex(), calcSSID(), DPRINTF, LFSTSize, SSIT, SSITSize, and validSSIT.

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

Member Data Documentation

◆ clearPeriod

uint64_t gem5::o3::StoreSet::clearPeriod

private

Number of loads/stores to process before wiping predictor so all entries don't get saturated.

Definition at line 148 of file store_set.hh.

Referenced by checkClear(), and init().

◆ indexMask

int gem5::o3::StoreSet::indexMask

private

Mask to obtain the index.

Definition at line 157 of file store_set.hh.

Referenced by calcIndex(), init(), and StoreSet().

◆ LFST

std::vector<InstSeqNum> gem5::o3::StoreSet::LFST

private

Last Fetched Store Table.

Definition at line 133 of file store_set.hh.

Referenced by checkInst(), init(), insertStore(), issued(), squash(), and StoreSet().

◆ LFSTSize

int gem5::o3::StoreSet::LFSTSize

private

Last Fetched Store Table size, in entries.

Definition at line 154 of file store_set.hh.

Referenced by calcSSID(), checkInst(), clear(), init(), insertStore(), issued(), StoreSet(), and violation().

◆ memOpsPred

int gem5::o3::StoreSet::memOpsPred

private

Number of memory operations predicted since last clear of predictor.

Definition at line 163 of file store_set.hh.

Referenced by checkClear(), init(), and StoreSet().

◆ offsetBits

int gem5::o3::StoreSet::offsetBits

private

Definition at line 160 of file store_set.hh.

Referenced by calcIndex(), init(), and StoreSet().

◆ SSIT

std::vector<SSID> gem5::o3::StoreSet::SSIT

private

The Store Set ID Table.

Definition at line 127 of file store_set.hh.

Referenced by checkInst(), init(), insertStore(), issued(), StoreSet(), and violation().

◆ SSITSize

int gem5::o3::StoreSet::SSITSize

private

Store Set ID Table size, in entries.

Definition at line 151 of file store_set.hh.

Referenced by checkInst(), clear(), init(), insertStore(), issued(), StoreSet(), and violation().

◆ storeList

std::map<InstSeqNum, int, ltseqnum> gem5::o3::StoreSet::storeList

private

Map of stores that have been inserted into the store set, but not yet issued or squashed.

Definition at line 141 of file store_set.hh.

Referenced by clear(), dump(), insertStore(), issued(), and squash().

◆ validLFST

std::vector<bool> gem5::o3::StoreSet::validLFST

private

Bit vector to tell if the LFST has a valid entry.

Definition at line 136 of file store_set.hh.

Referenced by checkInst(), clear(), init(), insertStore(), issued(), squash(), and StoreSet().

◆ validSSIT

std::vector<bool> gem5::o3::StoreSet::validSSIT

private

Bit vector to tell if the SSIT has a valid entry.

Definition at line 130 of file store_set.hh.

Referenced by checkInst(), clear(), init(), insertStore(), issued(), StoreSet(), and violation().

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

cpu/o3/store_set.hh
cpu/o3/store_set.cc

Public Types

Public Member Functions

Private Types

Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

◆ SeqNumMapIt

◆ SSID

Constructor & Destructor Documentation

◆ StoreSet() [1/2]

◆ StoreSet() [2/2]

◆ ~StoreSet()

Member Function Documentation

◆ calcIndex()

◆ calcSSID()

◆ checkClear()

◆ checkInst()

◆ clear()

◆ dump()

◆ init()

◆ insertLoad()

◆ insertStore()

◆ issued()

◆ squash()

◆ violation()

Member Data Documentation

◆ clearPeriod

◆ indexMask

◆ LFST

◆ LFSTSize

◆ memOpsPred

◆ offsetBits

◆ SSIT

◆ SSITSize

◆ storeList

◆ validLFST

◆ validSSIT