gem5::FetchUnit Class Reference

#include <fetch_unit.hh>

Classes
class	FetchBufDesc
	fetch buffer descriptor. More...

Public Member Functions
	FetchUnit (const ComputeUnitParams &p, ComputeUnit &cu)
	~FetchUnit ()
void	init ()
void	exec ()
void	bindWaveList (std::vector< Wavefront * > *list)
void	initiateFetch (Wavefront *wavefront)
void	fetch (PacketPtr pkt, Wavefront *wavefront)
void	processFetchReturn (PacketPtr pkt)
void	flushBuf (int wfSlotId)

Static Public Attributes
static uint32_t	globalFetchUnitID

Private Attributes
bool	timingSim
ComputeUnit &	computeUnit
TheGpuISA::Decoder	decoder
Scheduler	fetchScheduler
std::vector< Wavefront * >	fetchQueue
std::vector< std::pair< Wavefront *, bool > >	fetchStatusQueue
std::vector< Wavefront * > *	waveList
std::vector< FetchBufDesc >	fetchBuf
int	fetchDepth
	number of cache lines we can fetch and buffer. More...

Detailed Description

Definition at line 54 of file fetch_unit.hh.

Constructor & Destructor Documentation

FetchUnit()

gem5::FetchUnit::FetchUnit	(	const ComputeUnitParams &	p,
		ComputeUnit &	cu
	)

Definition at line 51 of file fetch_unit.cc.

~FetchUnit()

gem5::FetchUnit::~FetchUnit

(

)

Definition at line 57 of file fetch_unit.cc.

References fetchQueue, and fetchStatusQueue.

Member Function Documentation

bindWaveList()

void gem5::FetchUnit::bindWaveList

(

std::vector< Wavefront * > *

list

)

Definition at line 316 of file fetch_unit.cc.

References waveList.

exec()

void gem5::FetchUnit::exec

(

)

now we check if any of the fetch buffers have buffered instruction data that can be decoded and sent to its wavefront's instruction buffer. then we check if any of the fetch buffer entries can be released. we only check if we can release a buffer

Definition at line 83 of file fetch_unit.cc.

References gem5::Scheduler::chooseWave(), computeUnit, fetchBuf, fetchQueue, fetchScheduler, fetchStatusQueue, gem5::Wavefront::getStatus(), initiateFetch(), gem5::ArmISA::j, gem5::Shader::n_wf, gem5::Wavefront::pendingFetch, gem5::Wavefront::S_RUNNING, gem5::Wavefront::S_WAITCNT, gem5::ComputeUnit::shader, gem5::Wavefront::stopFetch(), and gem5::Wavefront::wfSlotId.

fetch()

void gem5::FetchUnit::fetch	(	PacketPtr	pkt,
		Wavefront *	wavefront
	)

this is necessary because the GPU TLB receives packets instead of requests. when the translation is complete, all relevent fields in the request will be populated, but not in the packet. here we create the new packet so we can set the size, addr, and proper flags.

if we have not reserved an entry in the fetch buffer, stop fetching. this can happen due to a branch instruction flushing the fetch buffer while an ITLB or I-cache request is still pending, in the same cycle another instruction is trying to fetch.

we should have reserved an entry in the fetch buffer for this cache line. here we get the pointer to the entry used to buffer this request's line data.

Definition at line 220 of file fetch_unit.cc.

References gem5::Packet::cmd, computeUnit, gem5::ComputeUnit::cu_id, gem5::Packet::dataStatic(), DPRINTF, gem5::Wavefront::dropFetch, fetchBuf, gem5::Wavefront::pendingFetch, processFetchReturn(), gem5::Packet::req, gem5::ComputeUnit::SQCPort::retries, gem5::Packet::senderState, gem5::RequestPort::sendFunctional(), gem5::RequestPort::sendTimingReq(), gem5::Wavefront::simdId, gem5::ComputeUnit::sqcPort, timingSim, and gem5::Wavefront::wfSlotId.

Referenced by initiateFetch().

flushBuf()

void gem5::FetchUnit::flushBuf

(

int

wfSlotId

)

Definition at line 310 of file fetch_unit.cc.

References fetchBuf.

Referenced by gem5::Wavefront::discardFetch(), gem5::Gcn3ISA::Inst_SOPP__S_ENDPGM::execute(), and gem5::VegaISA::Inst_SOPP__S_ENDPGM::execute().

init()

void gem5::FetchUnit::init

(

)

Definition at line 64 of file fetch_unit.cc.

References gem5::Scheduler::bindList(), gem5::ComputeUnit::cacheLineSize(), computeUnit, decoder, fetchBuf, fetchDepth, fetchQueue, fetchScheduler, fetchStatusQueue, gem5::ArmISA::i, gem5::Shader::n_wf, gem5::ComputeUnit::shader, gem5::Shader::timingSim, timingSim, waveList, and gem5::Wavefront::wfSlotId.

initiateFetch()

void gem5::FetchUnit::initiateFetch

(

Wavefront *

wavefront

)

calculate the virtual address to fetch from the SQC. the fetch buffer holds a configurable number of cache lines. we start fetching at the address of the cache line immediately following the buffered line(s).

Definition at line 135 of file fetch_unit.cc.

References gem5::ComputeUnit::cacheLineSize(), computeUnit, gem5::ComputeUnit::cu_id, DPRINTF, gem5::BaseMMU::Execute, fetch(), fetchBuf, gem5::ComputeUnit::getCacheLineBits(), gem5::Shader::gpuTc, gem5::Request::INST_FETCH, gem5::ComputeUnit::ITLBPort::isStalled(), gem5::ruby::makeLineAddress(), gem5::Wavefront::pc(), gem5::MemCmd::ReadReq, gem5::ComputeUnit::requestorId(), gem5::ComputeUnit::ITLBPort::retries, gem5::Packet::senderState, gem5::RequestPort::sendFunctional(), gem5::RequestPort::sendTimingReq(), gem5::ComputeUnit::shader, gem5::Wavefront::simdId, gem5::ComputeUnit::sqcTLBPort, gem5::ComputeUnit::ITLBPort::stallPort(), timingSim, gem5::X86ISA::GpuTLB::TranslationState::tlbEntry, gem5::MipsISA::vaddr, gem5::Wavefront::wfDynId, and gem5::Wavefront::wfSlotId.

Referenced by exec().

processFetchReturn()

void gem5::FetchUnit::processFetchReturn

(

PacketPtr

pkt

)

Definition at line 284 of file fetch_unit.cc.

References computeUnit, gem5::ComputeUnit::cu_id, DPRINTF, gem5::Wavefront::dropFetch, fetchBuf, gem5::Wavefront::instructionBuffer, gem5::Wavefront::pendingFetch, gem5::Packet::req, gem5::Packet::senderState, gem5::Wavefront::simdId, gem5::ComputeUnit::SQCPort::SenderState::wavefront, and gem5::Wavefront::wfSlotId.

Referenced by fetch().

Member Data Documentation

computeUnit

ComputeUnit& gem5::FetchUnit::computeUnit

private

Definition at line 242 of file fetch_unit.hh.

Referenced by exec(), fetch(), init(), initiateFetch(), and processFetchReturn().

decoder

TheGpuISA::Decoder gem5::FetchUnit::decoder

private

Definition at line 243 of file fetch_unit.hh.

Referenced by init().

fetchBuf

std::vector<FetchBufDesc> gem5::FetchUnit::fetchBuf

private

Definition at line 263 of file fetch_unit.hh.

Referenced by exec(), fetch(), flushBuf(), init(), initiateFetch(), and processFetchReturn().

fetchDepth

int gem5::FetchUnit::fetchDepth

private

number of cache lines we can fetch and buffer.

this includes the currently fetched line (i.e., the line that corresponds to the WF's current PC), as well as any lines that may be prefetched.

Definition at line 270 of file fetch_unit.hh.

Referenced by gem5::FetchUnit::FetchBufDesc::flushBuf(), init(), and gem5::FetchUnit::FetchBufDesc::reserveBuf().

fetchQueue

std::vector<Wavefront*> gem5::FetchUnit::fetchQueue

private

Definition at line 253 of file fetch_unit.hh.

Referenced by exec(), init(), and ~FetchUnit().

fetchScheduler

Scheduler gem5::FetchUnit::fetchScheduler

private

Definition at line 249 of file fetch_unit.hh.

Referenced by exec(), and init().

fetchStatusQueue

std::vector<std::pair<Wavefront*, bool> > gem5::FetchUnit::fetchStatusQueue

private

Definition at line 258 of file fetch_unit.hh.

Referenced by exec(), init(), and ~FetchUnit().

globalFetchUnitID

uint32_t gem5::FetchUnit::globalFetchUnitID

static

Definition at line 66 of file fetch_unit.hh.

timingSim

bool gem5::FetchUnit::timingSim

private

Definition at line 241 of file fetch_unit.hh.

Referenced by fetch(), init(), and initiateFetch().

waveList

std::vector<Wavefront*>* gem5::FetchUnit::waveList

private

Definition at line 261 of file fetch_unit.hh.

Referenced by bindWaveList(), and init().

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

• gpu-compute/fetch_unit.hh
• gpu-compute/fetch_unit.cc