CPU: Make unaligned accesses work in the timing simple CPU.

[gem5.git] / src / cpu / simple / timing.cc

/*
 * Copyright (c) 2002-2005 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.
 *
 * Authors: Steve Reinhardt
 */

#include "arch/locked_mem.hh"
#include "arch/mmaped_ipr.hh"
#include "arch/utility.hh"
#include "base/bigint.hh"
#include "cpu/exetrace.hh"
#include "cpu/simple/timing.hh"
#include "mem/packet.hh"
#include "mem/packet_access.hh"
#include "params/TimingSimpleCPU.hh"
#include "sim/system.hh"

using namespace std;
using namespace TheISA;

Port *
TimingSimpleCPU::getPort(const std::string &if_name, int idx)
{
    if (if_name == "dcache_port")
        return &dcachePort;
    else if (if_name == "icache_port")
        return &icachePort;
    else
        panic("No Such Port\n");
}

void
TimingSimpleCPU::init()
{
    BaseCPU::init();
#if FULL_SYSTEM
    for (int i = 0; i < threadContexts.size(); ++i) {
        ThreadContext *tc = threadContexts[i];

        // initialize CPU, including PC
        TheISA::initCPU(tc, _cpuId);
    }
#endif
}

Tick
TimingSimpleCPU::CpuPort::recvAtomic(PacketPtr pkt)
{
    panic("TimingSimpleCPU doesn't expect recvAtomic callback!");
    return curTick;
}

void
TimingSimpleCPU::CpuPort::recvFunctional(PacketPtr pkt)
{
    //No internal storage to update, jusst return
    return;
}

void
TimingSimpleCPU::CpuPort::recvStatusChange(Status status)
{
    if (status == RangeChange) {
        if (!snoopRangeSent) {
            snoopRangeSent = true;
            sendStatusChange(Port::RangeChange);
        }
        return;
    }

    panic("TimingSimpleCPU doesn't expect recvStatusChange callback!");
}


void
TimingSimpleCPU::CpuPort::TickEvent::schedule(PacketPtr _pkt, Tick t)
{
    pkt = _pkt;
    cpu->schedule(this, t);
}

TimingSimpleCPU::TimingSimpleCPU(TimingSimpleCPUParams *p)
    : BaseSimpleCPU(p), icachePort(this, p->clock), dcachePort(this, p->clock), fetchEvent(this)
{
    _status = Idle;

    icachePort.snoopRangeSent = false;
    dcachePort.snoopRangeSent = false;

    ifetch_pkt = dcache_pkt = NULL;
    drainEvent = NULL;
    previousTick = 0;
    changeState(SimObject::Running);
}


TimingSimpleCPU::~TimingSimpleCPU()
{
}

void
TimingSimpleCPU::serialize(ostream &os)
{
    SimObject::State so_state = SimObject::getState();
    SERIALIZE_ENUM(so_state);
    BaseSimpleCPU::serialize(os);
}

void
TimingSimpleCPU::unserialize(Checkpoint *cp, const string &section)
{
    SimObject::State so_state;
    UNSERIALIZE_ENUM(so_state);
    BaseSimpleCPU::unserialize(cp, section);
}

unsigned int
TimingSimpleCPU::drain(Event *drain_event)
{
    // TimingSimpleCPU is ready to drain if it's not waiting for
    // an access to complete.
    if (_status == Idle || _status == Running || _status == SwitchedOut) {
        changeState(SimObject::Drained);
        return 0;
    } else {
        changeState(SimObject::Draining);
        drainEvent = drain_event;
        return 1;
    }
}

void
TimingSimpleCPU::resume()
{
    DPRINTF(SimpleCPU, "Resume\n");
    if (_status != SwitchedOut && _status != Idle) {
        assert(system->getMemoryMode() == Enums::timing);

        if (fetchEvent.scheduled())
           deschedule(fetchEvent);

        schedule(fetchEvent, nextCycle());
    }

    changeState(SimObject::Running);
}

void
TimingSimpleCPU::switchOut()
{
    assert(_status == Running || _status == Idle);
    _status = SwitchedOut;
    numCycles += tickToCycles(curTick - previousTick);

    // If we've been scheduled to resume but are then told to switch out,
    // we'll need to cancel it.
    if (fetchEvent.scheduled())
        deschedule(fetchEvent);
}


void
TimingSimpleCPU::takeOverFrom(BaseCPU *oldCPU)
{
    BaseCPU::takeOverFrom(oldCPU, &icachePort, &dcachePort);

    // if any of this CPU's ThreadContexts are active, mark the CPU as
    // running and schedule its tick event.
    for (int i = 0; i < threadContexts.size(); ++i) {
        ThreadContext *tc = threadContexts[i];
        if (tc->status() == ThreadContext::Active && _status != Running) {
            _status = Running;
            break;
        }
    }

    if (_status != Running) {
        _status = Idle;
    }
    assert(threadContexts.size() == 1);
    previousTick = curTick;
}


void
TimingSimpleCPU::activateContext(int thread_num, int delay)
{
    DPRINTF(SimpleCPU, "ActivateContext %d (%d cycles)\n", thread_num, delay);

    assert(thread_num == 0);
    assert(thread);

    assert(_status == Idle);

    notIdleFraction++;
    _status = Running;

    // kick things off by initiating the fetch of the next instruction
    schedule(fetchEvent, nextCycle(curTick + ticks(delay)));
}


void
TimingSimpleCPU::suspendContext(int thread_num)
{
    DPRINTF(SimpleCPU, "SuspendContext %d\n", thread_num);

    assert(thread_num == 0);
    assert(thread);

    assert(_status == Running);

    // just change status to Idle... if status != Running,
    // completeInst() will not initiate fetch of next instruction.

    notIdleFraction--;
    _status = Idle;
}

bool
TimingSimpleCPU::handleReadPacket(PacketPtr pkt)
{
    RequestPtr req = pkt->req;
    if (req->isMmapedIpr()) {
        Tick delay;
        delay = TheISA::handleIprRead(thread->getTC(), pkt);
        new IprEvent(pkt, this, nextCycle(curTick + delay));
        _status = DcacheWaitResponse;
        dcache_pkt = NULL;
    } else if (!dcachePort.sendTiming(pkt)) {
        _status = DcacheRetry;
        dcache_pkt = pkt;
    } else {
        _status = DcacheWaitResponse;
        // memory system takes ownership of packet
        dcache_pkt = NULL;
    }
    return dcache_pkt == NULL;
}

template <class T>
Fault
TimingSimpleCPU::read(Addr addr, T &data, unsigned flags)
{
    Fault fault;
    const int asid = 0;
    const int thread_id = 0;
    const Addr pc = thread->readPC();

    PacketPtr pkt;
    RequestPtr req;

    int block_size = dcachePort.peerBlockSize();
    int data_size = sizeof(T);

    Addr second_addr = roundDown(addr + data_size - 1, block_size);

    if (second_addr > addr) {
        Addr first_size = second_addr - addr;
        Addr second_size = data_size - first_size;
        // Make sure we'll only need two accesses.
        assert(roundDown(second_addr + second_size - 1, block_size) ==
                second_addr);

        /*
         * Do the translations. If something isn't going to work, find out
         * before we waste time setting up anything else.
         */
        req = new Request(asid, addr, first_size,
                          flags, pc, _cpuId, thread_id);
        fault = thread->translateDataReadReq(req);
        if (fault != NoFault) {
            delete req;
            return fault;
        }
        Request *second_req =
            new Request(asid, second_addr, second_size,
                        flags, pc, _cpuId, thread_id);
        fault = thread->translateDataReadReq(second_req);
        if (fault != NoFault) {
            delete req;
            delete second_req;
            return fault;
        }

        T * data_ptr = new T;

        /*
         * This is the big packet that will hold the data we've gotten so far,
         * if any, and also act as the response we actually give to the
         * instruction.
         */
        Request *orig_req =
            new Request(asid, addr, data_size, flags, pc, _cpuId, thread_id);
        orig_req->setPhys(req->getPaddr(), data_size, flags);
        PacketPtr big_pkt =
            new Packet(orig_req, MemCmd::ReadResp, Packet::Broadcast);
        big_pkt->dataDynamic<T>(data_ptr);
        SplitMainSenderState * main_send_state = new SplitMainSenderState;
        big_pkt->senderState = main_send_state;
        main_send_state->outstanding = 2;

        // This is the packet we'll process now.
        pkt = new Packet(req, MemCmd::ReadReq, Packet::Broadcast);
        pkt->dataStatic<uint8_t>((uint8_t *)data_ptr);
        pkt->senderState = new SplitFragmentSenderState(big_pkt, 0);

        // This is the second half of the access we'll deal with later.
        PacketPtr second_pkt =
            new Packet(second_req, MemCmd::ReadReq, Packet::Broadcast);
        second_pkt->dataStatic<uint8_t>((uint8_t *)data_ptr + first_size);
        second_pkt->senderState = new SplitFragmentSenderState(big_pkt, 1);
        if (!handleReadPacket(pkt)) {
            main_send_state->fragments[1] = second_pkt;
        } else {
            handleReadPacket(second_pkt);
        }
    } else {
        req = new Request(asid, addr, data_size,
                          flags, pc, _cpuId, thread_id);

        // translate to physical address
        Fault fault = thread->translateDataReadReq(req);

        if (fault != NoFault) {
            delete req;
            return fault;
        }

        pkt = new Packet(req,
                         (req->isLocked() ?
                          MemCmd::LoadLockedReq : MemCmd::ReadReq),
                          Packet::Broadcast);
        pkt->dataDynamic<T>(new T);

        handleReadPacket(pkt);
    }

    if (traceData) {
        traceData->setData(data);
        traceData->setAddr(addr);
    }

    // This will need a new way to tell if it has a dcache attached.
    if (req->isUncacheable())
        recordEvent("Uncached Read");

    return NoFault;
}

Fault
TimingSimpleCPU::translateDataReadAddr(Addr vaddr, Addr &paddr,
        int size, unsigned flags)
{
    Request *req =
        new Request(0, vaddr, size, flags, thread->readPC(), _cpuId, 0);

    if (traceData) {
        traceData->setAddr(vaddr);
    }

    Fault fault = thread->translateDataWriteReq(req);

    if (fault == NoFault)
        paddr = req->getPaddr();

    delete req;
    return fault;
}

#ifndef DOXYGEN_SHOULD_SKIP_THIS

template
Fault
TimingSimpleCPU::read(Addr addr, Twin64_t &data, unsigned flags);

template
Fault
TimingSimpleCPU::read(Addr addr, Twin32_t &data, unsigned flags);

template
Fault
TimingSimpleCPU::read(Addr addr, uint64_t &data, unsigned flags);

template
Fault
TimingSimpleCPU::read(Addr addr, uint32_t &data, unsigned flags);

template
Fault
TimingSimpleCPU::read(Addr addr, uint16_t &data, unsigned flags);

template
Fault
TimingSimpleCPU::read(Addr addr, uint8_t &data, unsigned flags);

#endif //DOXYGEN_SHOULD_SKIP_THIS

template<>
Fault
TimingSimpleCPU::read(Addr addr, double &data, unsigned flags)
{
    return read(addr, *(uint64_t*)&data, flags);
}

template<>
Fault
TimingSimpleCPU::read(Addr addr, float &data, unsigned flags)
{
    return read(addr, *(uint32_t*)&data, flags);
}


template<>
Fault
TimingSimpleCPU::read(Addr addr, int32_t &data, unsigned flags)
{
    return read(addr, (uint32_t&)data, flags);
}

bool
TimingSimpleCPU::handleWritePacket()
{
    RequestPtr req = dcache_pkt->req;
    if (req->isMmapedIpr()) {
        Tick delay;
        delay = TheISA::handleIprWrite(thread->getTC(), dcache_pkt);
        new IprEvent(dcache_pkt, this, nextCycle(curTick + delay));
        _status = DcacheWaitResponse;
        dcache_pkt = NULL;
    } else if (!dcachePort.sendTiming(dcache_pkt)) {
        _status = DcacheRetry;
    } else {
        _status = DcacheWaitResponse;
        // memory system takes ownership of packet
        dcache_pkt = NULL;
    }
    return dcache_pkt == NULL;
}

template <class T>
Fault
TimingSimpleCPU::write(T data, Addr addr, unsigned flags, uint64_t *res)
{
    const int asid = 0;
    const int thread_id = 0;
    bool do_access = true;  // flag to suppress cache access
    const Addr pc = thread->readPC();

    RequestPtr req;

    int block_size = dcachePort.peerBlockSize();
    int data_size = sizeof(T);

    Addr second_addr = roundDown(addr + data_size - 1, block_size);

    if (second_addr > addr) {
        Fault fault;
        Addr first_size = second_addr - addr;
        Addr second_size = data_size - first_size;
        // Make sure we'll only need two accesses.
        assert(roundDown(second_addr + second_size - 1, block_size) == 
                second_addr);

        req = new Request(asid, addr, first_size,
                          flags, pc, _cpuId, thread_id);
        fault = thread->translateDataWriteReq(req);
        if (fault != NoFault) {
            delete req;
            return fault;
        }
        RequestPtr second_req = new Request(asid, second_addr, second_size,
                                            flags, pc, _cpuId, thread_id);
        fault = thread->translateDataWriteReq(second_req);
        if (fault != NoFault) {
            delete req;
            delete second_req;
            return fault;
        }

        if (req->isLocked() || req->isSwap() || 
                second_req->isLocked() || second_req->isSwap()) {
            panic("LL/SCs and swaps can't be split.");
        }

        T * data_ptr = new T;

        /*
         * This is the big packet that will hold the data we've gotten so far,
         * if any, and also act as the response we actually give to the
         * instruction.
         */
        RequestPtr orig_req = 
            new Request(asid, addr, data_size, flags, pc, _cpuId, thread_id);
        orig_req->setPhys(req->getPaddr(), data_size, flags);
        PacketPtr big_pkt =
            new Packet(orig_req, MemCmd::WriteResp, Packet::Broadcast);
        big_pkt->dataDynamic<T>(data_ptr);
        big_pkt->set(data);
        SplitMainSenderState * main_send_state = new SplitMainSenderState;
        big_pkt->senderState = main_send_state;
        main_send_state->outstanding = 2;

        assert(dcache_pkt == NULL);
        // This is the packet we'll process now.
        dcache_pkt = new Packet(req, MemCmd::WriteReq, Packet::Broadcast);
        dcache_pkt->dataStatic<uint8_t>((uint8_t *)data_ptr);
        dcache_pkt->senderState = new SplitFragmentSenderState(big_pkt, 0);

        // This is the second half of the access we'll deal with later.
        PacketPtr second_pkt =
            new Packet(second_req, MemCmd::WriteReq, Packet::Broadcast);
        second_pkt->dataStatic<uint8_t>((uint8_t *)data_ptr + first_size);
        second_pkt->senderState = new SplitFragmentSenderState(big_pkt, 1);
        if (!handleWritePacket()) {
            main_send_state->fragments[1] = second_pkt;
        } else {
            dcache_pkt = second_pkt;
            handleWritePacket();
        }
    } else {
        req = new Request(asid, addr, data_size, flags, pc, _cpuId, thread_id);

        // translate to physical address
        Fault fault = thread->translateDataWriteReq(req);
        if (fault != NoFault) {
            delete req;
            return fault;
        }

        MemCmd cmd = MemCmd::WriteReq; // default

        if (req->isLocked()) {
            cmd = MemCmd::StoreCondReq;
            do_access = TheISA::handleLockedWrite(thread, req);
        } else if (req->isSwap()) {
            cmd = MemCmd::SwapReq;
            if (req->isCondSwap()) {
                assert(res);
                req->setExtraData(*res);
            }
        }

        // Note: need to allocate dcache_pkt even if do_access is
        // false, as it's used unconditionally to call completeAcc().
        assert(dcache_pkt == NULL);
        dcache_pkt = new Packet(req, cmd, Packet::Broadcast);
        dcache_pkt->allocate();
        if (req->isMmapedIpr())
            dcache_pkt->set(htog(data));
        else
            dcache_pkt->set(data);

        if (do_access)
            handleWritePacket();
    }

    if (traceData) {
        traceData->setAddr(req->getVaddr());
        traceData->setData(data);
    }

    // This will need a new way to tell if it's hooked up to a cache or not.
    if (req->isUncacheable())
        recordEvent("Uncached Write");

    // If the write needs to have a fault on the access, consider calling
    // changeStatus() and changing it to "bad addr write" or something.
    return NoFault;
}

Fault
TimingSimpleCPU::translateDataWriteAddr(Addr vaddr, Addr &paddr,
        int size, unsigned flags)
{
    Request *req =
        new Request(0, vaddr, size, flags, thread->readPC(), _cpuId, 0);

    if (traceData) {
        traceData->setAddr(vaddr);
    }

    Fault fault = thread->translateDataWriteReq(req);

    if (fault == NoFault)
        paddr = req->getPaddr();

    delete req;
    return fault;
}


#ifndef DOXYGEN_SHOULD_SKIP_THIS
template
Fault
TimingSimpleCPU::write(Twin32_t data, Addr addr,
                       unsigned flags, uint64_t *res);

template
Fault
TimingSimpleCPU::write(Twin64_t data, Addr addr,
                       unsigned flags, uint64_t *res);

template
Fault
TimingSimpleCPU::write(uint64_t data, Addr addr,
                       unsigned flags, uint64_t *res);

template
Fault
TimingSimpleCPU::write(uint32_t data, Addr addr,
                       unsigned flags, uint64_t *res);

template
Fault
TimingSimpleCPU::write(uint16_t data, Addr addr,
                       unsigned flags, uint64_t *res);

template
Fault
TimingSimpleCPU::write(uint8_t data, Addr addr,
                       unsigned flags, uint64_t *res);

#endif //DOXYGEN_SHOULD_SKIP_THIS

template<>
Fault
TimingSimpleCPU::write(double data, Addr addr, unsigned flags, uint64_t *res)
{
    return write(*(uint64_t*)&data, addr, flags, res);
}

template<>
Fault
TimingSimpleCPU::write(float data, Addr addr, unsigned flags, uint64_t *res)
{
    return write(*(uint32_t*)&data, addr, flags, res);
}


template<>
Fault
TimingSimpleCPU::write(int32_t data, Addr addr, unsigned flags, uint64_t *res)
{
    return write((uint32_t)data, addr, flags, res);
}


void
TimingSimpleCPU::fetch()
{
    DPRINTF(SimpleCPU, "Fetch\n");

    if (!curStaticInst || !curStaticInst->isDelayedCommit())
        checkForInterrupts();

    checkPcEventQueue();

    bool fromRom = isRomMicroPC(thread->readMicroPC());

    if (!fromRom) {
        Request *ifetch_req = new Request();
        ifetch_req->setThreadContext(_cpuId, /* thread ID */ 0);
        Fault fault = setupFetchRequest(ifetch_req);

        ifetch_pkt = new Packet(ifetch_req, MemCmd::ReadReq, Packet::Broadcast);
        ifetch_pkt->dataStatic(&inst);

        if (fault == NoFault) {
            if (!icachePort.sendTiming(ifetch_pkt)) {
                // Need to wait for retry
                _status = IcacheRetry;
            } else {
                // Need to wait for cache to respond
                _status = IcacheWaitResponse;
                // ownership of packet transferred to memory system
                ifetch_pkt = NULL;
            }
        } else {
            delete ifetch_req;
            delete ifetch_pkt;
            // fetch fault: advance directly to next instruction (fault handler)
            advanceInst(fault);
        }
    } else {
        _status = IcacheWaitResponse;
        completeIfetch(NULL);
    }

    numCycles += tickToCycles(curTick - previousTick);
    previousTick = curTick;
}


void
TimingSimpleCPU::advanceInst(Fault fault)
{
    if (fault != NoFault || !stayAtPC)
        advancePC(fault);

    if (_status == Running) {
        // kick off fetch of next instruction... callback from icache
        // response will cause that instruction to be executed,
        // keeping the CPU running.
        fetch();
    }
}


void
TimingSimpleCPU::completeIfetch(PacketPtr pkt)
{
    DPRINTF(SimpleCPU, "Complete ICache Fetch\n");

    // received a response from the icache: execute the received
    // instruction

    assert(!pkt || !pkt->isError());
    assert(_status == IcacheWaitResponse);

    _status = Running;

    numCycles += tickToCycles(curTick - previousTick);
    previousTick = curTick;

    if (getState() == SimObject::Draining) {
        if (pkt) {
            delete pkt->req;
            delete pkt;
        }

        completeDrain();
        return;
    }

    preExecute();
    if (curStaticInst &&
            curStaticInst->isMemRef() && !curStaticInst->isDataPrefetch()) {
        // load or store: just send to dcache
        Fault fault = curStaticInst->initiateAcc(this, traceData);
        if (_status != Running) {
            // instruction will complete in dcache response callback
            assert(_status == DcacheWaitResponse || _status == DcacheRetry);
            assert(fault == NoFault);
        } else {
            if (fault == NoFault) {
                // Note that ARM can have NULL packets if the instruction gets
                // squashed due to predication
                // early fail on store conditional: complete now
                assert(dcache_pkt != NULL || THE_ISA == ARM_ISA);

                fault = curStaticInst->completeAcc(dcache_pkt, this,
                                                   traceData);
                if (dcache_pkt != NULL)
                {
                    delete dcache_pkt->req;
                    delete dcache_pkt;
                    dcache_pkt = NULL;
                }

                // keep an instruction count
                if (fault == NoFault)
                    countInst();
            } else if (traceData) {
                // If there was a fault, we shouldn't trace this instruction.
                delete traceData;
                traceData = NULL;
            }

            postExecute();
            // @todo remove me after debugging with legion done
            if (curStaticInst && (!curStaticInst->isMicroop() ||
                        curStaticInst->isFirstMicroop()))
                instCnt++;
            advanceInst(fault);
        }
    } else if (curStaticInst) {
        // non-memory instruction: execute completely now
        Fault fault = curStaticInst->execute(this, traceData);

        // keep an instruction count
        if (fault == NoFault)
            countInst();
        else if (traceData) {
            // If there was a fault, we shouldn't trace this instruction.
            delete traceData;
            traceData = NULL;
        }

        postExecute();
        // @todo remove me after debugging with legion done
        if (curStaticInst && (!curStaticInst->isMicroop() ||
                    curStaticInst->isFirstMicroop()))
            instCnt++;
        advanceInst(fault);
    } else {
        advanceInst(NoFault);
    }

    if (pkt) {
        delete pkt->req;
        delete pkt;
    }
}

void
TimingSimpleCPU::IcachePort::ITickEvent::process()
{
    cpu->completeIfetch(pkt);
}

bool
TimingSimpleCPU::IcachePort::recvTiming(PacketPtr pkt)
{
    if (pkt->isResponse() && !pkt->wasNacked()) {
        // delay processing of returned data until next CPU clock edge
        Tick next_tick = cpu->nextCycle(curTick);

        if (next_tick == curTick)
            cpu->completeIfetch(pkt);
        else
            tickEvent.schedule(pkt, next_tick);

        return true;
    }
    else if (pkt->wasNacked()) {
        assert(cpu->_status == IcacheWaitResponse);
        pkt->reinitNacked();
        if (!sendTiming(pkt)) {
            cpu->_status = IcacheRetry;
            cpu->ifetch_pkt = pkt;
        }
    }
    //Snooping a Coherence Request, do nothing
    return true;
}

void
TimingSimpleCPU::IcachePort::recvRetry()
{
    // we shouldn't get a retry unless we have a packet that we're
    // waiting to transmit
    assert(cpu->ifetch_pkt != NULL);
    assert(cpu->_status == IcacheRetry);
    PacketPtr tmp = cpu->ifetch_pkt;
    if (sendTiming(tmp)) {
        cpu->_status = IcacheWaitResponse;
        cpu->ifetch_pkt = NULL;
    }
}

void
TimingSimpleCPU::completeDataAccess(PacketPtr pkt)
{
    // received a response from the dcache: complete the load or store
    // instruction
    assert(!pkt->isError());

    numCycles += tickToCycles(curTick - previousTick);
    previousTick = curTick;

    if (pkt->senderState) {
        SplitFragmentSenderState * send_state =
            dynamic_cast<SplitFragmentSenderState *>(pkt->senderState);
        assert(send_state);
        delete pkt->req;
        delete pkt;
        PacketPtr big_pkt = send_state->bigPkt;
        delete send_state;
        
        SplitMainSenderState * main_send_state =
            dynamic_cast<SplitMainSenderState *>(big_pkt->senderState);
        assert(main_send_state);
        // Record the fact that this packet is no longer outstanding.
        assert(main_send_state->outstanding != 0);
        main_send_state->outstanding--;

        if (main_send_state->outstanding) {
            return;
        } else {
            delete main_send_state;
            big_pkt->senderState = NULL;
            pkt = big_pkt;
        }
    }

    assert(_status == DcacheWaitResponse);
    _status = Running;

    Fault fault = curStaticInst->completeAcc(pkt, this, traceData);

    // keep an instruction count
    if (fault == NoFault)
        countInst();
    else if (traceData) {
        // If there was a fault, we shouldn't trace this instruction.
        delete traceData;
        traceData = NULL;
    }

    // the locked flag may be cleared on the response packet, so check
    // pkt->req and not pkt to see if it was a load-locked
    if (pkt->isRead() && pkt->req->isLocked()) {
        TheISA::handleLockedRead(thread, pkt->req);
    }

    delete pkt->req;
    delete pkt;

    postExecute();

    if (getState() == SimObject::Draining) {
        advancePC(fault);
        completeDrain();

        return;
    }

    advanceInst(fault);
}


void
TimingSimpleCPU::completeDrain()
{
    DPRINTF(Config, "Done draining\n");
    changeState(SimObject::Drained);
    drainEvent->process();
}

void
TimingSimpleCPU::DcachePort::setPeer(Port *port)
{
    Port::setPeer(port);

#if FULL_SYSTEM
    // Update the ThreadContext's memory ports (Functional/Virtual
    // Ports)
    cpu->tcBase()->connectMemPorts(cpu->tcBase());
#endif
}

bool
TimingSimpleCPU::DcachePort::recvTiming(PacketPtr pkt)
{
    if (pkt->isResponse() && !pkt->wasNacked()) {
        // delay processing of returned data until next CPU clock edge
        Tick next_tick = cpu->nextCycle(curTick);

        if (next_tick == curTick) {
            cpu->completeDataAccess(pkt);
        } else {
            tickEvent.schedule(pkt, next_tick);
        }

        return true;
    }
    else if (pkt->wasNacked()) {
        assert(cpu->_status == DcacheWaitResponse);
        pkt->reinitNacked();
        if (!sendTiming(pkt)) {
            cpu->_status = DcacheRetry;
            cpu->dcache_pkt = pkt;
        }
    }
    //Snooping a Coherence Request, do nothing
    return true;
}

void
TimingSimpleCPU::DcachePort::DTickEvent::process()
{
    cpu->completeDataAccess(pkt);
}

void
TimingSimpleCPU::DcachePort::recvRetry()
{
    // we shouldn't get a retry unless we have a packet that we're
    // waiting to transmit
    assert(cpu->dcache_pkt != NULL);
    assert(cpu->_status == DcacheRetry);
    PacketPtr tmp = cpu->dcache_pkt;
    if (tmp->senderState) {
        // This is a packet from a split access.
        SplitFragmentSenderState * send_state =
            dynamic_cast<SplitFragmentSenderState *>(tmp->senderState);
        assert(send_state);
        PacketPtr big_pkt = send_state->bigPkt;
        
        SplitMainSenderState * main_send_state =
            dynamic_cast<SplitMainSenderState *>(big_pkt->senderState);
        assert(main_send_state);

        if (sendTiming(tmp)) {
            // If we were able to send without retrying, record that fact
            // and try sending the other fragment.
            send_state->clearFromParent();
            int other_index = main_send_state->getPendingFragment();
            if (other_index > 0) {
                tmp = main_send_state->fragments[other_index];
                cpu->dcache_pkt = tmp;
                if ((big_pkt->isRead() && cpu->handleReadPacket(tmp)) ||
                        (big_pkt->isWrite() && cpu->handleWritePacket())) {
                    main_send_state->fragments[other_index] = NULL;
                }
            } else {
                cpu->_status = DcacheWaitResponse;
                // memory system takes ownership of packet
                cpu->dcache_pkt = NULL;
            }
        }
    } else if (sendTiming(tmp)) {
        cpu->_status = DcacheWaitResponse;
        // memory system takes ownership of packet
        cpu->dcache_pkt = NULL;
    }
}

TimingSimpleCPU::IprEvent::IprEvent(Packet *_pkt, TimingSimpleCPU *_cpu,
    Tick t)
    : pkt(_pkt), cpu(_cpu)
{
    cpu->schedule(this, t);
}

void
TimingSimpleCPU::IprEvent::process()
{
    cpu->completeDataAccess(pkt);
}

const char *
TimingSimpleCPU::IprEvent::description() const
{
    return "Timing Simple CPU Delay IPR event";
}


void
TimingSimpleCPU::printAddr(Addr a)
{
    dcachePort.printAddr(a);
}


////////////////////////////////////////////////////////////////////////
//
//  TimingSimpleCPU Simulation Object
//
TimingSimpleCPU *
TimingSimpleCPUParams::create()
{
    numThreads = 1;
#if !FULL_SYSTEM
    if (workload.size() != 1)
        panic("only one workload allowed");
#endif
    return new TimingSimpleCPU(this);
}