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2cb09e4042a55240cc086378347b000eedb76b11
gem5/src/cpu/o3/fetch_impl.hh
Gabe Black 2cb09e4042 arch,cpu: Collapse away TheISA::advancePC. 
In most ISAs except MIPS and Power, this was implemented as
inst->advancePC(). It works just fine to call this function all the
time, but the idea had originally been that for ISAs which could simply
advance the PC using the PC itself, they could save the virtual function
call. Since the only ISAs which could skip the call were MIPS and Power,
and neither is at the point where that level of performance tuning
matters, this function can be collapsed with little downside.

If this turns out to be a performance bottleneck in the future, the way
the PC is managed could be revisited to see if we can factor out this
trip to the instruction object in the first place.

Change-Id: I533d1ad316e5c936466c529b7f1238a9ab87bd1c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39335
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Alex Dutu <alexandru.dutu@amd.com>
2021-03-22 21:01:07 +00:00

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/*
* Copyright (c) 2010-2014 ARM Limited
* Copyright (c) 2012-2013 AMD
* All rights reserved.
*
* The license below extends only to copyright in the software and shall
* not be construed as granting a license to any other intellectual
* property including but not limited to intellectual property relating
* to a hardware implementation of the functionality of the software
* licensed hereunder. You may use the software subject to the license
* terms below provided that you ensure that this notice is replicated
* unmodified and in its entirety in all distributions of the software,
* modified or unmodified, in source code or in binary form.
*
* Copyright (c) 2004-2006 The Regents of The University of Michigan
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __CPU_O3_FETCH_IMPL_HH__
#define __CPU_O3_FETCH_IMPL_HH__
#include <algorithm>
#include <cstring>
#include <list>
#include <map>
#include <queue>
#include "arch/generic/tlb.hh"
#include "arch/utility.hh"
#include "base/random.hh"
#include "base/types.hh"
#include "config/the_isa.hh"
#include "cpu/base.hh"
#include "cpu/o3/cpu.hh"
#include "cpu/o3/fetch.hh"
#include "cpu/exetrace.hh"
#include "debug/Activity.hh"
#include "debug/Drain.hh"
#include "debug/Fetch.hh"
#include "debug/O3CPU.hh"
#include "debug/O3PipeView.hh"
#include "mem/packet.hh"
#include "params/DerivO3CPU.hh"
#include "sim/byteswap.hh"
#include "sim/core.hh"
#include "sim/eventq.hh"
#include "sim/full_system.hh"
#include "sim/system.hh"
#include "cpu/o3/isa_specific.hh"
template<class Impl>
DefaultFetch<Impl>::DefaultFetch(O3CPU *_cpu, const DerivO3CPUParams &params)
: fetchPolicy(params.smtFetchPolicy),
cpu(_cpu),
branchPred(nullptr),
decodeToFetchDelay(params.decodeToFetchDelay),
renameToFetchDelay(params.renameToFetchDelay),
iewToFetchDelay(params.iewToFetchDelay),
commitToFetchDelay(params.commitToFetchDelay),
fetchWidth(params.fetchWidth),
decodeWidth(params.decodeWidth),
retryPkt(NULL),
retryTid(InvalidThreadID),
cacheBlkSize(cpu->cacheLineSize()),
fetchBufferSize(params.fetchBufferSize),
fetchBufferMask(fetchBufferSize - 1),
fetchQueueSize(params.fetchQueueSize),
numThreads(params.numThreads),
numFetchingThreads(params.smtNumFetchingThreads),
icachePort(this, _cpu),
finishTranslationEvent(this), fetchStats(_cpu, this)
{
if (numThreads > Impl::MaxThreads)
fatal("numThreads (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxThreads in src/cpu/o3/impl.hh\n",
numThreads, static_cast<int>(Impl::MaxThreads));
if (fetchWidth > Impl::MaxWidth)
fatal("fetchWidth (%d) is larger than compiled limit (%d),\n"
"\tincrease MaxWidth in src/cpu/o3/impl.hh\n",
fetchWidth, static_cast<int>(Impl::MaxWidth));
if (fetchBufferSize > cacheBlkSize)
fatal("fetch buffer size (%u bytes) is greater than the cache "
"block size (%u bytes)\n", fetchBufferSize, cacheBlkSize);
if (cacheBlkSize % fetchBufferSize)
fatal("cache block (%u bytes) is not a multiple of the "
"fetch buffer (%u bytes)\n", cacheBlkSize, fetchBufferSize);
// Get the size of an instruction.
instSize = sizeof(TheISA::MachInst);
for (int i = 0; i < Impl::MaxThreads; i++) {
fetchStatus[i] = Idle;
decoder[i] = nullptr;
pc[i] = 0;
fetchOffset[i] = 0;
macroop[i] = nullptr;
delayedCommit[i] = false;
memReq[i] = nullptr;
stalls[i] = {false, false};
fetchBuffer[i] = NULL;
fetchBufferPC[i] = 0;
fetchBufferValid[i] = false;
lastIcacheStall[i] = 0;
issuePipelinedIfetch[i] = false;
}
branchPred = params.branchPred;
for (ThreadID tid = 0; tid < numThreads; tid++) {
decoder[tid] = new TheISA::Decoder(
dynamic_cast<TheISA::ISA *>(params.isa[tid]));
// Create space to buffer the cache line data,
// which may not hold the entire cache line.
fetchBuffer[tid] = new uint8_t[fetchBufferSize];
}
}
template <class Impl>
std::string
DefaultFetch<Impl>::name() const
{
return cpu->name() + ".fetch";
}
template <class Impl>
void
DefaultFetch<Impl>::regProbePoints()
{
ppFetch = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Fetch");
ppFetchRequestSent = new ProbePointArg<RequestPtr>(cpu->getProbeManager(),
"FetchRequest");
}
template <class Impl>
DefaultFetch<Impl>::
FetchStatGroup::FetchStatGroup(O3CPU *cpu, DefaultFetch *fetch)
: Stats::Group(cpu, "fetch"),
ADD_STAT(icacheStallCycles, UNIT_CYCLE,
"Number of cycles fetch is stalled on an Icache miss"),
ADD_STAT(insts, UNIT_COUNT, "Number of instructions fetch has processed"),
ADD_STAT(branches, UNIT_COUNT,
"Number of branches that fetch encountered"),
ADD_STAT(predictedBranches, UNIT_COUNT,
"Number of branches that fetch has predicted taken"),
ADD_STAT(cycles, UNIT_CYCLE,
"Number of cycles fetch has run and was not squashing or "
"blocked"),
ADD_STAT(squashCycles, UNIT_CYCLE,
"Number of cycles fetch has spent squashing"),
ADD_STAT(tlbCycles, UNIT_CYCLE,
"Number of cycles fetch has spent waiting for tlb"),
ADD_STAT(idleCycles, UNIT_CYCLE, "Number of cycles fetch was idle"),
ADD_STAT(blockedCycles, UNIT_CYCLE,
"Number of cycles fetch has spent blocked"),
ADD_STAT(miscStallCycles, UNIT_CYCLE,
"Number of cycles fetch has spent waiting on interrupts, or bad "
"addresses, or out of MSHRs"),
ADD_STAT(pendingDrainCycles, UNIT_CYCLE,
"Number of cycles fetch has spent waiting on pipes to drain"),
ADD_STAT(noActiveThreadStallCycles, UNIT_CYCLE,
"Number of stall cycles due to no active thread to fetch from"),
ADD_STAT(pendingTrapStallCycles, UNIT_CYCLE,
"Number of stall cycles due to pending traps"),
ADD_STAT(pendingQuiesceStallCycles, UNIT_CYCLE,
"Number of stall cycles due to pending quiesce instructions"),
ADD_STAT(icacheWaitRetryStallCycles, UNIT_CYCLE,
"Number of stall cycles due to full MSHR"),
ADD_STAT(cacheLines, UNIT_COUNT, "Number of cache lines fetched"),
ADD_STAT(icacheSquashes, UNIT_COUNT,
"Number of outstanding Icache misses that were squashed"),
ADD_STAT(tlbSquashes, UNIT_COUNT,
"Number of outstanding ITLB misses that were squashed"),
ADD_STAT(nisnDist, UNIT_COUNT,
"Number of instructions fetched each cycle (Total)"),
ADD_STAT(idleRate, UNIT_RATIO, "Ratio of cycles fetch was idle",
idleCycles / cpu->baseStats.numCycles),
ADD_STAT(branchRate, UNIT_RATIO, "Number of branch fetches per cycle",
branches / cpu->baseStats.numCycles),
ADD_STAT(rate, UNIT_RATE(Stats::Units::Count, Stats::Units::Cycle),
"Number of inst fetches per cycle",
insts / cpu->baseStats.numCycles)
{
icacheStallCycles
.prereq(icacheStallCycles);
insts
.prereq(insts);
branches
.prereq(branches);
predictedBranches
.prereq(predictedBranches);
cycles
.prereq(cycles);
squashCycles
.prereq(squashCycles);
tlbCycles
.prereq(tlbCycles);
idleCycles
.prereq(idleCycles);
blockedCycles
.prereq(blockedCycles);
cacheLines
.prereq(cacheLines);
miscStallCycles
.prereq(miscStallCycles);
pendingDrainCycles
.prereq(pendingDrainCycles);
noActiveThreadStallCycles
.prereq(noActiveThreadStallCycles);
pendingTrapStallCycles
.prereq(pendingTrapStallCycles);
pendingQuiesceStallCycles
.prereq(pendingQuiesceStallCycles);
icacheWaitRetryStallCycles
.prereq(icacheWaitRetryStallCycles);
icacheSquashes
.prereq(icacheSquashes);
tlbSquashes
.prereq(tlbSquashes);
nisnDist
.init(/* base value */ 0,
/* last value */ fetch->fetchWidth,
/* bucket size */ 1)
.flags(Stats::pdf);
idleRate
.prereq(idleRate);
branchRate
.flags(Stats::total);
rate
.flags(Stats::total);
}
template<class Impl>
void
DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer)
{
timeBuffer = time_buffer;
// Create wires to get information from proper places in time buffer.
fromDecode = timeBuffer->getWire(-decodeToFetchDelay);
fromRename = timeBuffer->getWire(-renameToFetchDelay);
fromIEW = timeBuffer->getWire(-iewToFetchDelay);
fromCommit = timeBuffer->getWire(-commitToFetchDelay);
}
template<class Impl>
void
DefaultFetch<Impl>::setActiveThreads(std::list<ThreadID> *at_ptr)
{
activeThreads = at_ptr;
}
template<class Impl>
void
DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *ftb_ptr)
{
// Create wire to write information to proper place in fetch time buf.
toDecode = ftb_ptr->getWire(0);
}
template<class Impl>
void
DefaultFetch<Impl>::startupStage()
{
assert(priorityList.empty());
resetStage();
// Fetch needs to start fetching instructions at the very beginning,
// so it must start up in active state.
switchToActive();
}
template<class Impl>
void
DefaultFetch<Impl>::clearStates(ThreadID tid)
{
fetchStatus[tid] = Running;
pc[tid] = cpu->pcState(tid);
fetchOffset[tid] = 0;
macroop[tid] = NULL;
delayedCommit[tid] = false;
memReq[tid] = NULL;
stalls[tid].decode = false;
stalls[tid].drain = false;
fetchBufferPC[tid] = 0;
fetchBufferValid[tid] = false;
fetchQueue[tid].clear();
// TODO not sure what to do with priorityList for now
// priorityList.push_back(tid);
}
template<class Impl>
void
DefaultFetch<Impl>::resetStage()
{
numInst = 0;
interruptPending = false;
cacheBlocked = false;
priorityList.clear();
// Setup PC and nextPC with initial state.
for (ThreadID tid = 0; tid < numThreads; ++tid) {
fetchStatus[tid] = Running;
pc[tid] = cpu->pcState(tid);
fetchOffset[tid] = 0;
macroop[tid] = NULL;
delayedCommit[tid] = false;
memReq[tid] = NULL;
stalls[tid].decode = false;
stalls[tid].drain = false;
fetchBufferPC[tid] = 0;
fetchBufferValid[tid] = false;
fetchQueue[tid].clear();
priorityList.push_back(tid);
}
wroteToTimeBuffer = false;
_status = Inactive;
}
template<class Impl>
void
DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt)
{
ThreadID tid = cpu->contextToThread(pkt->req->contextId());
DPRINTF(Fetch, "[tid:%i] Waking up from cache miss.\n", tid);
assert(!cpu->switchedOut());
// Only change the status if it's still waiting on the icache access
// to return.
if (fetchStatus[tid] != IcacheWaitResponse ||
pkt->req != memReq[tid]) {
++fetchStats.icacheSquashes;
delete pkt;
return;
}
memcpy(fetchBuffer[tid], pkt->getConstPtr<uint8_t>(), fetchBufferSize);
fetchBufferValid[tid] = true;
// Wake up the CPU (if it went to sleep and was waiting on
// this completion event).
cpu->wakeCPU();
DPRINTF(Activity, "[tid:%i] Activating fetch due to cache completion\n",
tid);
switchToActive();
// Only switch to IcacheAccessComplete if we're not stalled as well.
if (checkStall(tid)) {
fetchStatus[tid] = Blocked;
} else {
fetchStatus[tid] = IcacheAccessComplete;
}
pkt->req->setAccessLatency();
cpu->ppInstAccessComplete->notify(pkt);
// Reset the mem req to NULL.
delete pkt;
memReq[tid] = NULL;
}
template <class Impl>
void
DefaultFetch<Impl>::drainResume()
{
for (ThreadID i = 0; i < numThreads; ++i) {
stalls[i].decode = false;
stalls[i].drain = false;
}
}
template <class Impl>
void
DefaultFetch<Impl>::drainSanityCheck() const
{
assert(isDrained());
assert(retryPkt == NULL);
assert(retryTid == InvalidThreadID);
assert(!cacheBlocked);
assert(!interruptPending);
for (ThreadID i = 0; i < numThreads; ++i) {
assert(!memReq[i]);
assert(fetchStatus[i] == Idle || stalls[i].drain);
}
branchPred->drainSanityCheck();
}
template <class Impl>
bool
DefaultFetch<Impl>::isDrained() const
{
/* Make sure that threads are either idle of that the commit stage
* has signaled that draining has completed by setting the drain
* stall flag. This effectively forces the pipeline to be disabled
* until the whole system is drained (simulation may continue to
* drain other components).
*/
for (ThreadID i = 0; i < numThreads; ++i) {
// Verify fetch queues are drained
if (!fetchQueue[i].empty())
return false;
// Return false if not idle or drain stalled
if (fetchStatus[i] != Idle) {
if (fetchStatus[i] == Blocked && stalls[i].drain)
continue;
else
return false;
}
}
/* The pipeline might start up again in the middle of the drain
* cycle if the finish translation event is scheduled, so make
* sure that's not the case.
*/
return !finishTranslationEvent.scheduled();
}
template <class Impl>
void
DefaultFetch<Impl>::takeOverFrom()
{
assert(cpu->getInstPort().isConnected());
resetStage();
}
template <class Impl>
void
DefaultFetch<Impl>::drainStall(ThreadID tid)
{
assert(cpu->isDraining());
assert(!stalls[tid].drain);
DPRINTF(Drain, "%i: Thread drained.\n", tid);
stalls[tid].drain = true;
}
template <class Impl>
void
DefaultFetch<Impl>::wakeFromQuiesce()
{
DPRINTF(Fetch, "Waking up from quiesce\n");
// Hopefully this is safe
// @todo: Allow other threads to wake from quiesce.
fetchStatus[0] = Running;
}
template <class Impl>
inline void
DefaultFetch<Impl>::switchToActive()
{
if (_status == Inactive) {
DPRINTF(Activity, "Activating stage.\n");
cpu->activateStage(O3CPU::FetchIdx);
_status = Active;
}
}
template <class Impl>
inline void
DefaultFetch<Impl>::switchToInactive()
{
if (_status == Active) {
DPRINTF(Activity, "Deactivating stage.\n");
cpu->deactivateStage(O3CPU::FetchIdx);
_status = Inactive;
}
}
template <class Impl>
void
DefaultFetch<Impl>::deactivateThread(ThreadID tid)
{
// Update priority list
auto thread_it = std::find(priorityList.begin(), priorityList.end(), tid);
if (thread_it != priorityList.end()) {
priorityList.erase(thread_it);
}
}
template <class Impl>
bool
DefaultFetch<Impl>::lookupAndUpdateNextPC(
const DynInstPtr &inst, TheISA::PCState &nextPC)
{
// Do branch prediction check here.
// A bit of a misnomer...next_PC is actually the current PC until
// this function updates it.
bool predict_taken;
if (!inst->isControl()) {
inst->staticInst->advancePC(nextPC);
inst->setPredTarg(nextPC);
inst->setPredTaken(false);
return false;
}
ThreadID tid = inst->threadNumber;
predict_taken = branchPred->predict(inst->staticInst, inst->seqNum,
nextPC, tid);
if (predict_taken) {
DPRINTF(Fetch, "[tid:%i] [sn:%llu] Branch at PC %#x "
"predicted to be taken to %s\n",
tid, inst->seqNum, inst->pcState().instAddr(), nextPC);
} else {
DPRINTF(Fetch, "[tid:%i] [sn:%llu] Branch at PC %#x "
"predicted to be not taken\n",
tid, inst->seqNum, inst->pcState().instAddr());
}
DPRINTF(Fetch, "[tid:%i] [sn:%llu] Branch at PC %#x "
"predicted to go to %s\n",
tid, inst->seqNum, inst->pcState().instAddr(), nextPC);
inst->setPredTarg(nextPC);
inst->setPredTaken(predict_taken);
++fetchStats.branches;
if (predict_taken) {
++fetchStats.predictedBranches;
}
return predict_taken;
}
template <class Impl>
bool
DefaultFetch<Impl>::fetchCacheLine(Addr vaddr, ThreadID tid, Addr pc)
{
Fault fault = NoFault;
assert(!cpu->switchedOut());
// @todo: not sure if these should block translation.
//AlphaDep
if (cacheBlocked) {
DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n",
tid);
return false;
} else if (checkInterrupt(pc) && !delayedCommit[tid]) {
// Hold off fetch from getting new instructions when:
// Cache is blocked, or
// while an interrupt is pending and we're not in PAL mode, or
// fetch is switched out.
DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n",
tid);
return false;
}
// Align the fetch address to the start of a fetch buffer segment.
Addr fetchBufferBlockPC = fetchBufferAlignPC(vaddr);
DPRINTF(Fetch, "[tid:%i] Fetching cache line %#x for addr %#x\n",
tid, fetchBufferBlockPC, vaddr);
// Setup the memReq to do a read of the first instruction's address.
// Set the appropriate read size and flags as well.
// Build request here.
RequestPtr mem_req = std::make_shared<Request>(
fetchBufferBlockPC, fetchBufferSize,
Request::INST_FETCH, cpu->instRequestorId(), pc,
cpu->thread[tid]->contextId());
mem_req->taskId(cpu->taskId());
memReq[tid] = mem_req;
// Initiate translation of the icache block
fetchStatus[tid] = ItlbWait;
FetchTranslation *trans = new FetchTranslation(this);
cpu->mmu->translateTiming(mem_req, cpu->thread[tid]->getTC(),
trans, BaseTLB::Execute);
return true;
}
template <class Impl>
void
DefaultFetch<Impl>::finishTranslation(const Fault &fault,
const RequestPtr &mem_req)
{
ThreadID tid = cpu->contextToThread(mem_req->contextId());
Addr fetchBufferBlockPC = mem_req->getVaddr();
assert(!cpu->switchedOut());
// Wake up CPU if it was idle
cpu->wakeCPU();
if (fetchStatus[tid] != ItlbWait || mem_req != memReq[tid] ||
mem_req->getVaddr() != memReq[tid]->getVaddr()) {
DPRINTF(Fetch, "[tid:%i] Ignoring itlb completed after squash\n",
tid);
++fetchStats.tlbSquashes;
return;
}
// If translation was successful, attempt to read the icache block.
if (fault == NoFault) {
// Check that we're not going off into random memory
// If we have, just wait around for commit to squash something and put
// us on the right track
if (!cpu->system->isMemAddr(mem_req->getPaddr())) {
warn("Address %#x is outside of physical memory, stopping fetch\n",
mem_req->getPaddr());
fetchStatus[tid] = NoGoodAddr;
memReq[tid] = NULL;
return;
}
// Build packet here.
PacketPtr data_pkt = new Packet(mem_req, MemCmd::ReadReq);
data_pkt->dataDynamic(new uint8_t[fetchBufferSize]);
fetchBufferPC[tid] = fetchBufferBlockPC;
fetchBufferValid[tid] = false;
DPRINTF(Fetch, "Fetch: Doing instruction read.\n");
fetchStats.cacheLines++;
// Access the cache.
if (!icachePort.sendTimingReq(data_pkt)) {
assert(retryPkt == NULL);
assert(retryTid == InvalidThreadID);
DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid);
fetchStatus[tid] = IcacheWaitRetry;
retryPkt = data_pkt;
retryTid = tid;
cacheBlocked = true;
} else {
DPRINTF(Fetch, "[tid:%i] Doing Icache access.\n", tid);
DPRINTF(Activity, "[tid:%i] Activity: Waiting on I-cache "
"response.\n", tid);
lastIcacheStall[tid] = curTick();
fetchStatus[tid] = IcacheWaitResponse;
// Notify Fetch Request probe when a packet containing a fetch
// request is successfully sent
ppFetchRequestSent->notify(mem_req);
}
} else {
// Don't send an instruction to decode if we can't handle it.
if (!(numInst < fetchWidth) || !(fetchQueue[tid].size() < fetchQueueSize)) {
assert(!finishTranslationEvent.scheduled());
finishTranslationEvent.setFault(fault);
finishTranslationEvent.setReq(mem_req);
cpu->schedule(finishTranslationEvent,
cpu->clockEdge(Cycles(1)));
return;
}
DPRINTF(Fetch, "[tid:%i] Got back req with addr %#x but expected %#x\n",
tid, mem_req->getVaddr(), memReq[tid]->getVaddr());
// Translation faulted, icache request won't be sent.
memReq[tid] = NULL;
// Send the fault to commit. This thread will not do anything
// until commit handles the fault. The only other way it can
// wake up is if a squash comes along and changes the PC.
TheISA::PCState fetchPC = pc[tid];
DPRINTF(Fetch, "[tid:%i] Translation faulted, building noop.\n", tid);
// We will use a nop in ordier to carry the fault.
DynInstPtr instruction = buildInst(tid, StaticInst::nopStaticInstPtr,
NULL, fetchPC, fetchPC, false);
instruction->setNotAnInst();
instruction->setPredTarg(fetchPC);
instruction->fault = fault;
wroteToTimeBuffer = true;
DPRINTF(Activity, "Activity this cycle.\n");
cpu->activityThisCycle();
fetchStatus[tid] = TrapPending;
DPRINTF(Fetch, "[tid:%i] Blocked, need to handle the trap.\n", tid);
DPRINTF(Fetch, "[tid:%i] fault (%s) detected @ PC %s.\n",
tid, fault->name(), pc[tid]);
}
_status = updateFetchStatus();
}
template <class Impl>
inline void
DefaultFetch<Impl>::doSquash(const TheISA::PCState &newPC,
const DynInstPtr squashInst, ThreadID tid)
{
DPRINTF(Fetch, "[tid:%i] Squashing, setting PC to: %s.\n",
tid, newPC);
pc[tid] = newPC;
fetchOffset[tid] = 0;
if (squashInst && squashInst->pcState().instAddr() == newPC.instAddr())
macroop[tid] = squashInst->macroop;
else
macroop[tid] = NULL;
decoder[tid]->reset();
// Clear the icache miss if it's outstanding.
if (fetchStatus[tid] == IcacheWaitResponse) {
DPRINTF(Fetch, "[tid:%i] Squashing outstanding Icache miss.\n",
tid);
memReq[tid] = NULL;
} else if (fetchStatus[tid] == ItlbWait) {
DPRINTF(Fetch, "[tid:%i] Squashing outstanding ITLB miss.\n",
tid);
memReq[tid] = NULL;
}
// Get rid of the retrying packet if it was from this thread.
if (retryTid == tid) {
assert(cacheBlocked);
if (retryPkt) {
delete retryPkt;
}
retryPkt = NULL;
retryTid = InvalidThreadID;
}
fetchStatus[tid] = Squashing;
// Empty fetch queue
fetchQueue[tid].clear();
// microops are being squashed, it is not known wheather the
// youngest non-squashed microop was marked delayed commit
// or not. Setting the flag to true ensures that the
// interrupts are not handled when they cannot be, though
// some opportunities to handle interrupts may be missed.
delayedCommit[tid] = true;
++fetchStats.squashCycles;
}
template<class Impl>
void
DefaultFetch<Impl>::squashFromDecode(const TheISA::PCState &newPC,
const DynInstPtr squashInst,
const InstSeqNum seq_num, ThreadID tid)
{
DPRINTF(Fetch, "[tid:%i] Squashing from decode.\n", tid);
doSquash(newPC, squashInst, tid);
// Tell the CPU to remove any instructions that are in flight between
// fetch and decode.
cpu->removeInstsUntil(seq_num, tid);
}
template<class Impl>
bool
DefaultFetch<Impl>::checkStall(ThreadID tid) const
{
bool ret_val = false;
if (stalls[tid].drain) {
assert(cpu->isDraining());
DPRINTF(Fetch,"[tid:%i] Drain stall detected.\n",tid);
ret_val = true;
}
return ret_val;
}
template<class Impl>
typename DefaultFetch<Impl>::FetchStatus
DefaultFetch<Impl>::updateFetchStatus()
{
//Check Running
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
if (fetchStatus[tid] == Running ||
fetchStatus[tid] == Squashing ||
fetchStatus[tid] == IcacheAccessComplete) {
if (_status == Inactive) {
DPRINTF(Activity, "[tid:%i] Activating stage.\n",tid);
if (fetchStatus[tid] == IcacheAccessComplete) {
DPRINTF(Activity, "[tid:%i] Activating fetch due to cache"
"completion\n",tid);
}
cpu->activateStage(O3CPU::FetchIdx);
}
return Active;
}
}
// Stage is switching from active to inactive, notify CPU of it.
if (_status == Active) {
DPRINTF(Activity, "Deactivating stage.\n");
cpu->deactivateStage(O3CPU::FetchIdx);
}
return Inactive;
}
template <class Impl>
void
DefaultFetch<Impl>::squash(const TheISA::PCState &newPC,
const InstSeqNum seq_num, DynInstPtr squashInst,
ThreadID tid)
{
DPRINTF(Fetch, "[tid:%i] Squash from commit.\n", tid);
doSquash(newPC, squashInst, tid);
// Tell the CPU to remove any instructions that are not in the ROB.
cpu->removeInstsNotInROB(tid);
}
template <class Impl>
void
DefaultFetch<Impl>::tick()
{
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::list<ThreadID>::iterator end = activeThreads->end();
bool status_change = false;
wroteToTimeBuffer = false;
for (ThreadID i = 0; i < numThreads; ++i) {
issuePipelinedIfetch[i] = false;
}
while (threads != end) {
ThreadID tid = *threads++;
// Check the signals for each thread to determine the proper status
// for each thread.
bool updated_status = checkSignalsAndUpdate(tid);
status_change = status_change || updated_status;
}
DPRINTF(Fetch, "Running stage.\n");
if (FullSystem) {
if (fromCommit->commitInfo[0].interruptPending) {
interruptPending = true;
}
if (fromCommit->commitInfo[0].clearInterrupt) {
interruptPending = false;
}
}
for (threadFetched = 0; threadFetched < numFetchingThreads;
threadFetched++) {
// Fetch each of the actively fetching threads.
fetch(status_change);
}
// Record number of instructions fetched this cycle for distribution.
fetchStats.nisnDist.sample(numInst);
if (status_change) {
// Change the fetch stage status if there was a status change.
_status = updateFetchStatus();
}
// Issue the next I-cache request if possible.
for (ThreadID i = 0; i < numThreads; ++i) {
if (issuePipelinedIfetch[i]) {
pipelineIcacheAccesses(i);
}
}
// Send instructions enqueued into the fetch queue to decode.
// Limit rate by fetchWidth. Stall if decode is stalled.
unsigned insts_to_decode = 0;
unsigned available_insts = 0;
for (auto tid : *activeThreads) {
if (!stalls[tid].decode) {
available_insts += fetchQueue[tid].size();
}
}
// Pick a random thread to start trying to grab instructions from
auto tid_itr = activeThreads->begin();
std::advance(tid_itr, random_mt.random<uint8_t>(0, activeThreads->size() - 1));
while (available_insts != 0 && insts_to_decode < decodeWidth) {
ThreadID tid = *tid_itr;
if (!stalls[tid].decode && !fetchQueue[tid].empty()) {
const auto& inst = fetchQueue[tid].front();
toDecode->insts[toDecode->size++] = inst;
DPRINTF(Fetch, "[tid:%i] [sn:%llu] Sending instruction to decode "
"from fetch queue. Fetch queue size: %i.\n",
tid, inst->seqNum, fetchQueue[tid].size());
wroteToTimeBuffer = true;
fetchQueue[tid].pop_front();
insts_to_decode++;
available_insts--;
}
tid_itr++;
// Wrap around if at end of active threads list
if (tid_itr == activeThreads->end())
tid_itr = activeThreads->begin();
}
// If there was activity this cycle, inform the CPU of it.
if (wroteToTimeBuffer) {
DPRINTF(Activity, "Activity this cycle.\n");
cpu->activityThisCycle();
}
// Reset the number of the instruction we've fetched.
numInst = 0;
}
template <class Impl>
bool
DefaultFetch<Impl>::checkSignalsAndUpdate(ThreadID tid)
{
// Update the per thread stall statuses.
if (fromDecode->decodeBlock[tid]) {
stalls[tid].decode = true;
}
if (fromDecode->decodeUnblock[tid]) {
assert(stalls[tid].decode);
assert(!fromDecode->decodeBlock[tid]);
stalls[tid].decode = false;
}
// Check squash signals from commit.
if (fromCommit->commitInfo[tid].squash) {
DPRINTF(Fetch, "[tid:%i] Squashing instructions due to squash "
"from commit.\n",tid);
// In any case, squash.
squash(fromCommit->commitInfo[tid].pc,
fromCommit->commitInfo[tid].doneSeqNum,
fromCommit->commitInfo[tid].squashInst, tid);
// If it was a branch mispredict on a control instruction, update the
// branch predictor with that instruction, otherwise just kill the
// invalid state we generated in after sequence number
if (fromCommit->commitInfo[tid].mispredictInst &&
fromCommit->commitInfo[tid].mispredictInst->isControl()) {
branchPred->squash(fromCommit->commitInfo[tid].doneSeqNum,
fromCommit->commitInfo[tid].pc,
fromCommit->commitInfo[tid].branchTaken,
tid);
} else {
branchPred->squash(fromCommit->commitInfo[tid].doneSeqNum,
tid);
}
return true;
} else if (fromCommit->commitInfo[tid].doneSeqNum) {
// Update the branch predictor if it wasn't a squashed instruction
// that was broadcasted.
branchPred->update(fromCommit->commitInfo[tid].doneSeqNum, tid);
}
// Check squash signals from decode.
if (fromDecode->decodeInfo[tid].squash) {
DPRINTF(Fetch, "[tid:%i] Squashing instructions due to squash "
"from decode.\n",tid);
// Update the branch predictor.
if (fromDecode->decodeInfo[tid].branchMispredict) {
branchPred->squash(fromDecode->decodeInfo[tid].doneSeqNum,
fromDecode->decodeInfo[tid].nextPC,
fromDecode->decodeInfo[tid].branchTaken,
tid);
} else {
branchPred->squash(fromDecode->decodeInfo[tid].doneSeqNum,
tid);
}
if (fetchStatus[tid] != Squashing) {
DPRINTF(Fetch, "Squashing from decode with PC = %s\n",
fromDecode->decodeInfo[tid].nextPC);
// Squash unless we're already squashing
squashFromDecode(fromDecode->decodeInfo[tid].nextPC,
fromDecode->decodeInfo[tid].squashInst,
fromDecode->decodeInfo[tid].doneSeqNum,
tid);
return true;
}
}
if (checkStall(tid) &&
fetchStatus[tid] != IcacheWaitResponse &&
fetchStatus[tid] != IcacheWaitRetry &&
fetchStatus[tid] != ItlbWait &&
fetchStatus[tid] != QuiescePending) {
DPRINTF(Fetch, "[tid:%i] Setting to blocked\n",tid);
fetchStatus[tid] = Blocked;
return true;
}
if (fetchStatus[tid] == Blocked ||
fetchStatus[tid] == Squashing) {
// Switch status to running if fetch isn't being told to block or
// squash this cycle.
DPRINTF(Fetch, "[tid:%i] Done squashing, switching to running.\n",
tid);
fetchStatus[tid] = Running;
return true;
}
// If we've reached this point, we have not gotten any signals that
// cause fetch to change its status. Fetch remains the same as before.
return false;
}
template<class Impl>
typename Impl::DynInstPtr
DefaultFetch<Impl>::buildInst(ThreadID tid, StaticInstPtr staticInst,
StaticInstPtr curMacroop, TheISA::PCState thisPC,
TheISA::PCState nextPC, bool trace)
{
// Get a sequence number.
InstSeqNum seq = cpu->getAndIncrementInstSeq();
// Create a new DynInst from the instruction fetched.
DynInstPtr instruction =
new DynInst(staticInst, curMacroop, thisPC, nextPC, seq, cpu);
instruction->setTid(tid);
instruction->setThreadState(cpu->thread[tid]);
DPRINTF(Fetch, "[tid:%i] Instruction PC %#x (%d) created "
"[sn:%lli].\n", tid, thisPC.instAddr(),
thisPC.microPC(), seq);
DPRINTF(Fetch, "[tid:%i] Instruction is: %s\n", tid,
instruction->staticInst->
disassemble(thisPC.instAddr()));
#if TRACING_ON
if (trace) {
instruction->traceData =
cpu->getTracer()->getInstRecord(curTick(), cpu->tcBase(tid),
instruction->staticInst, thisPC, curMacroop);
}
#else
instruction->traceData = NULL;
#endif
// Add instruction to the CPU's list of instructions.
instruction->setInstListIt(cpu->addInst(instruction));
// Write the instruction to the first slot in the queue
// that heads to decode.
assert(numInst < fetchWidth);
fetchQueue[tid].push_back(instruction);
assert(fetchQueue[tid].size() <= fetchQueueSize);
DPRINTF(Fetch, "[tid:%i] Fetch queue entry created (%i/%i).\n",
tid, fetchQueue[tid].size(), fetchQueueSize);
//toDecode->insts[toDecode->size++] = instruction;
// Keep track of if we can take an interrupt at this boundary
delayedCommit[tid] = instruction->isDelayedCommit();
return instruction;
}
template<class Impl>
void
DefaultFetch<Impl>::fetch(bool &status_change)
{
//////////////////////////////////////////
// Start actual fetch
//////////////////////////////////////////
ThreadID tid = getFetchingThread();
assert(!cpu->switchedOut());
if (tid == InvalidThreadID) {
// Breaks looping condition in tick()
threadFetched = numFetchingThreads;
if (numThreads == 1) { // @todo Per-thread stats
profileStall(0);
}
return;
}
DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid);
// The current PC.
TheISA::PCState thisPC = pc[tid];
Addr pcOffset = fetchOffset[tid];
Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask;
bool inRom = isRomMicroPC(thisPC.microPC());
// If returning from the delay of a cache miss, then update the status
// to running, otherwise do the cache access. Possibly move this up
// to tick() function.
if (fetchStatus[tid] == IcacheAccessComplete) {
DPRINTF(Fetch, "[tid:%i] Icache miss is complete.\n", tid);
fetchStatus[tid] = Running;
status_change = true;
} else if (fetchStatus[tid] == Running) {
// Align the fetch PC so its at the start of a fetch buffer segment.
Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr);
// If buffer is no longer valid or fetchAddr has moved to point
// to the next cache block, AND we have no remaining ucode
// from a macro-op, then start fetch from icache.
if (!(fetchBufferValid[tid] && fetchBufferBlockPC == fetchBufferPC[tid])
&& !inRom && !macroop[tid]) {
DPRINTF(Fetch, "[tid:%i] Attempting to translate and read "
"instruction, starting at PC %s.\n", tid, thisPC);
fetchCacheLine(fetchAddr, tid, thisPC.instAddr());
if (fetchStatus[tid] == IcacheWaitResponse)
++fetchStats.icacheStallCycles;
else if (fetchStatus[tid] == ItlbWait)
++fetchStats.tlbCycles;
else
++fetchStats.miscStallCycles;
return;
} else if ((checkInterrupt(thisPC.instAddr()) && !delayedCommit[tid])) {
// Stall CPU if an interrupt is posted and we're not issuing
// an delayed commit micro-op currently (delayed commit instructions
// are not interruptable by interrupts, only faults)
++fetchStats.miscStallCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is stalled!\n", tid);
return;
}
} else {
if (fetchStatus[tid] == Idle) {
++fetchStats.idleCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is idle!\n", tid);
}
// Status is Idle, so fetch should do nothing.
return;
}
++fetchStats.cycles;
TheISA::PCState nextPC = thisPC;
StaticInstPtr staticInst = NULL;
StaticInstPtr curMacroop = macroop[tid];
// If the read of the first instruction was successful, then grab the
// instructions from the rest of the cache line and put them into the
// queue heading to decode.
DPRINTF(Fetch, "[tid:%i] Adding instructions to queue to "
"decode.\n", tid);
// Need to keep track of whether or not a predicted branch
// ended this fetch block.
bool predictedBranch = false;
// Need to halt fetch if quiesce instruction detected
bool quiesce = false;
TheISA::MachInst *cacheInsts =
reinterpret_cast<TheISA::MachInst *>(fetchBuffer[tid]);
const unsigned numInsts = fetchBufferSize / instSize;
unsigned blkOffset = (fetchAddr - fetchBufferPC[tid]) / instSize;
// Loop through instruction memory from the cache.
// Keep issuing while fetchWidth is available and branch is not
// predicted taken
while (numInst < fetchWidth && fetchQueue[tid].size() < fetchQueueSize
&& !predictedBranch && !quiesce) {
// We need to process more memory if we aren't going to get a
// StaticInst from the rom, the current macroop, or what's already
// in the decoder.
bool needMem = !inRom && !curMacroop &&
!decoder[tid]->instReady();
fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask;
Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr);
if (needMem) {
// If buffer is no longer valid or fetchAddr has moved to point
// to the next cache block then start fetch from icache.
if (!fetchBufferValid[tid] ||
fetchBufferBlockPC != fetchBufferPC[tid])
break;
if (blkOffset >= numInsts) {
// We need to process more memory, but we've run out of the
// current block.
break;
}
decoder[tid]->moreBytes(thisPC, fetchAddr, cacheInsts[blkOffset]);
if (decoder[tid]->needMoreBytes()) {
blkOffset++;
fetchAddr += instSize;
pcOffset += instSize;
}
}
// Extract as many instructions and/or microops as we can from
// the memory we've processed so far.
do {
if (!(curMacroop || inRom)) {
if (decoder[tid]->instReady()) {
staticInst = decoder[tid]->decode(thisPC);
// Increment stat of fetched instructions.
++fetchStats.insts;
if (staticInst->isMacroop()) {
curMacroop = staticInst;
} else {
pcOffset = 0;
}
} else {
// We need more bytes for this instruction so blkOffset and
// pcOffset will be updated
break;
}
}
// Whether we're moving to a new macroop because we're at the
// end of the current one, or the branch predictor incorrectly
// thinks we are...
bool newMacro = false;
if (curMacroop || inRom) {
if (inRom) {
staticInst = decoder[tid]->fetchRomMicroop(
thisPC.microPC(), curMacroop);
} else {
staticInst = curMacroop->fetchMicroop(thisPC.microPC());
}
newMacro |= staticInst->isLastMicroop();
}
DynInstPtr instruction =
buildInst(tid, staticInst, curMacroop,
thisPC, nextPC, true);
ppFetch->notify(instruction);
numInst++;
#if TRACING_ON
if (DTRACE(O3PipeView)) {
instruction->fetchTick = curTick();
}
#endif
nextPC = thisPC;
// If we're branching after this instruction, quit fetching
// from the same block.
predictedBranch |= thisPC.branching();
predictedBranch |=
lookupAndUpdateNextPC(instruction, nextPC);
if (predictedBranch) {
DPRINTF(Fetch, "Branch detected with PC = %s\n", thisPC);
}
newMacro |= thisPC.instAddr() != nextPC.instAddr();
// Move to the next instruction, unless we have a branch.
thisPC = nextPC;
inRom = isRomMicroPC(thisPC.microPC());
if (newMacro) {
fetchAddr = thisPC.instAddr() & BaseCPU::PCMask;
blkOffset = (fetchAddr - fetchBufferPC[tid]) / instSize;
pcOffset = 0;
curMacroop = NULL;
}
if (instruction->isQuiesce()) {
DPRINTF(Fetch,
"Quiesce instruction encountered, halting fetch!\n");
fetchStatus[tid] = QuiescePending;
status_change = true;
quiesce = true;
break;
}
} while ((curMacroop || decoder[tid]->instReady()) &&
numInst < fetchWidth &&
fetchQueue[tid].size() < fetchQueueSize);
// Re-evaluate whether the next instruction to fetch is in micro-op ROM
// or not.
inRom = isRomMicroPC(thisPC.microPC());
}
if (predictedBranch) {
DPRINTF(Fetch, "[tid:%i] Done fetching, predicted branch "
"instruction encountered.\n", tid);
} else if (numInst >= fetchWidth) {
DPRINTF(Fetch, "[tid:%i] Done fetching, reached fetch bandwidth "
"for this cycle.\n", tid);
} else if (blkOffset >= fetchBufferSize) {
DPRINTF(Fetch, "[tid:%i] Done fetching, reached the end of the"
"fetch buffer.\n", tid);
}
macroop[tid] = curMacroop;
fetchOffset[tid] = pcOffset;
if (numInst > 0) {
wroteToTimeBuffer = true;
}
pc[tid] = thisPC;
// pipeline a fetch if we're crossing a fetch buffer boundary and not in
// a state that would preclude fetching
fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask;
Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr);
issuePipelinedIfetch[tid] = fetchBufferBlockPC != fetchBufferPC[tid] &&
fetchStatus[tid] != IcacheWaitResponse &&
fetchStatus[tid] != ItlbWait &&
fetchStatus[tid] != IcacheWaitRetry &&
fetchStatus[tid] != QuiescePending &&
!curMacroop;
}
template<class Impl>
void
DefaultFetch<Impl>::recvReqRetry()
{
if (retryPkt != NULL) {
assert(cacheBlocked);
assert(retryTid != InvalidThreadID);
assert(fetchStatus[retryTid] == IcacheWaitRetry);
if (icachePort.sendTimingReq(retryPkt)) {
fetchStatus[retryTid] = IcacheWaitResponse;
// Notify Fetch Request probe when a retryPkt is successfully sent.
// Note that notify must be called before retryPkt is set to NULL.
ppFetchRequestSent->notify(retryPkt->req);
retryPkt = NULL;
retryTid = InvalidThreadID;
cacheBlocked = false;
}
} else {
assert(retryTid == InvalidThreadID);
// Access has been squashed since it was sent out. Just clear
// the cache being blocked.
cacheBlocked = false;
}
}
///////////////////////////////////////
// //
// SMT FETCH POLICY MAINTAINED HERE //
// //
///////////////////////////////////////
template<class Impl>
ThreadID
DefaultFetch<Impl>::getFetchingThread()
{
if (numThreads > 1) {
switch (fetchPolicy) {
case SMTFetchPolicy::RoundRobin:
return roundRobin();
case SMTFetchPolicy::IQCount:
return iqCount();
case SMTFetchPolicy::LSQCount:
return lsqCount();
case SMTFetchPolicy::Branch:
return branchCount();
default:
return InvalidThreadID;
}
} else {
std::list<ThreadID>::iterator thread = activeThreads->begin();
if (thread == activeThreads->end()) {
return InvalidThreadID;
}
ThreadID tid = *thread;
if (fetchStatus[tid] == Running ||
fetchStatus[tid] == IcacheAccessComplete ||
fetchStatus[tid] == Idle) {
return tid;
} else {
return InvalidThreadID;
}
}
}
template<class Impl>
ThreadID
DefaultFetch<Impl>::roundRobin()
{
std::list<ThreadID>::iterator pri_iter = priorityList.begin();
std::list<ThreadID>::iterator end = priorityList.end();
ThreadID high_pri;
while (pri_iter != end) {
high_pri = *pri_iter;
assert(high_pri <= numThreads);
if (fetchStatus[high_pri] == Running ||
fetchStatus[high_pri] == IcacheAccessComplete ||
fetchStatus[high_pri] == Idle) {
priorityList.erase(pri_iter);
priorityList.push_back(high_pri);
return high_pri;
}
pri_iter++;
}
return InvalidThreadID;
}
template<class Impl>
ThreadID
DefaultFetch<Impl>::iqCount()
{
//sorted from lowest->highest
std::priority_queue<unsigned, std::vector<unsigned>,
std::greater<unsigned> > PQ;
std::map<unsigned, ThreadID> threadMap;
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
unsigned iqCount = fromIEW->iewInfo[tid].iqCount;
//we can potentially get tid collisions if two threads
//have the same iqCount, but this should be rare.
PQ.push(iqCount);
threadMap[iqCount] = tid;
}
while (!PQ.empty()) {
ThreadID high_pri = threadMap[PQ.top()];
if (fetchStatus[high_pri] == Running ||
fetchStatus[high_pri] == IcacheAccessComplete ||
fetchStatus[high_pri] == Idle)
return high_pri;
else
PQ.pop();
}
return InvalidThreadID;
}
template<class Impl>
ThreadID
DefaultFetch<Impl>::lsqCount()
{
//sorted from lowest->highest
std::priority_queue<unsigned, std::vector<unsigned>,
std::greater<unsigned> > PQ;
std::map<unsigned, ThreadID> threadMap;
std::list<ThreadID>::iterator threads = activeThreads->begin();
std::list<ThreadID>::iterator end = activeThreads->end();
while (threads != end) {
ThreadID tid = *threads++;
unsigned ldstqCount = fromIEW->iewInfo[tid].ldstqCount;
//we can potentially get tid collisions if two threads
//have the same iqCount, but this should be rare.
PQ.push(ldstqCount);
threadMap[ldstqCount] = tid;
}
while (!PQ.empty()) {
ThreadID high_pri = threadMap[PQ.top()];
if (fetchStatus[high_pri] == Running ||
fetchStatus[high_pri] == IcacheAccessComplete ||
fetchStatus[high_pri] == Idle)
return high_pri;
else
PQ.pop();
}
return InvalidThreadID;
}
template<class Impl>
ThreadID
DefaultFetch<Impl>::branchCount()
{
panic("Branch Count Fetch policy unimplemented\n");
return InvalidThreadID;
}
template<class Impl>
void
DefaultFetch<Impl>::pipelineIcacheAccesses(ThreadID tid)
{
if (!issuePipelinedIfetch[tid]) {
return;
}
// The next PC to access.
TheISA::PCState thisPC = pc[tid];
if (isRomMicroPC(thisPC.microPC())) {
return;
}
Addr pcOffset = fetchOffset[tid];
Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask;
// Align the fetch PC so its at the start of a fetch buffer segment.
Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr);
// Unless buffer already got the block, fetch it from icache.
if (!(fetchBufferValid[tid] && fetchBufferBlockPC == fetchBufferPC[tid])) {
DPRINTF(Fetch, "[tid:%i] Issuing a pipelined I-cache access, "
"starting at PC %s.\n", tid, thisPC);
fetchCacheLine(fetchAddr, tid, thisPC.instAddr());
}
}
template<class Impl>
void
DefaultFetch<Impl>::profileStall(ThreadID tid) {
DPRINTF(Fetch,"There are no more threads available to fetch from.\n");
// @todo Per-thread stats
if (stalls[tid].drain) {
++fetchStats.pendingDrainCycles;
DPRINTF(Fetch, "Fetch is waiting for a drain!\n");
} else if (activeThreads->empty()) {
++fetchStats.noActiveThreadStallCycles;
DPRINTF(Fetch, "Fetch has no active thread!\n");
} else if (fetchStatus[tid] == Blocked) {
++fetchStats.blockedCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is blocked!\n", tid);
} else if (fetchStatus[tid] == Squashing) {
++fetchStats.squashCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is squashing!\n", tid);
} else if (fetchStatus[tid] == IcacheWaitResponse) {
++fetchStats.icacheStallCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is waiting cache response!\n",
tid);
} else if (fetchStatus[tid] == ItlbWait) {
++fetchStats.tlbCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is waiting ITLB walk to "
"finish!\n", tid);
} else if (fetchStatus[tid] == TrapPending) {
++fetchStats.pendingTrapStallCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is waiting for a pending trap!\n",
tid);
} else if (fetchStatus[tid] == QuiescePending) {
++fetchStats.pendingQuiesceStallCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is waiting for a pending quiesce "
"instruction!\n", tid);
} else if (fetchStatus[tid] == IcacheWaitRetry) {
++fetchStats.icacheWaitRetryStallCycles;
DPRINTF(Fetch, "[tid:%i] Fetch is waiting for an I-cache retry!\n",
tid);
} else if (fetchStatus[tid] == NoGoodAddr) {
DPRINTF(Fetch, "[tid:%i] Fetch predicted non-executable address\n",
tid);
} else {
DPRINTF(Fetch, "[tid:%i] Unexpected fetch stall reason "
"(Status: %i)\n",
tid, fetchStatus[tid]);
}
}
template<class Impl>
bool
DefaultFetch<Impl>::IcachePort::recvTimingResp(PacketPtr pkt)
{
DPRINTF(O3CPU, "Fetch unit received timing\n");
// We shouldn't ever get a cacheable block in Modified state
assert(pkt->req->isUncacheable() ||
!(pkt->cacheResponding() && !pkt->hasSharers()));
fetch->processCacheCompletion(pkt);
return true;
}
template<class Impl>
void
DefaultFetch<Impl>::IcachePort::recvReqRetry()
{
fetch->recvReqRetry();
}
#endif//__CPU_O3_FETCH_IMPL_HH__
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