src/cpu/o3/lsq.hh

/*
 * Copyright (c) 2011-2012, 2014, 2018-2019 ARM Limited
 * Copyright (c) 2013 Advanced Micro Devices, Inc.
 * 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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Authors: Korey Sewell
 */

#ifndef __CPU_O3_LSQ_HH__
#define __CPU_O3_LSQ_HH__

#include <map>
#include <queue>

#include "arch/generic/tlb.hh"
#include "cpu/inst_seq.hh"
#include "cpu/o3/lsq_unit.hh"
#include "cpu/utils.hh"
#include "enums/SMTQueuePolicy.hh"
#include "mem/port.hh"
#include "sim/sim_object.hh"

struct DerivO3CPUParams;

template <class Impl>
class FullO3CPU;

template <class Impl>
class LSQ

{
  public:
    typedef typename Impl::O3CPU O3CPU;
    typedef typename Impl::DynInstPtr DynInstPtr;
    typedef typename Impl::CPUPol::IEW IEW;
    typedef typename Impl::CPUPol::LSQUnit LSQUnit;

    class LSQRequest;
    /** Derived class to hold any sender state the LSQ needs. */
    class LSQSenderState : public Packet::SenderState
    {
      protected:
        /** The senderState needs to know the LSQRequest who owns it. */
        LSQRequest* _request;

        /** Default constructor. */
        LSQSenderState(LSQRequest* request, bool isLoad_)
            : _request(request), mainPkt(nullptr), pendingPacket(nullptr),
              outstanding(0), isLoad(isLoad_), needWB(isLoad_), isSplit(false),
              pktToSend(false), deleted(false)
          { }
      public:

        /** Instruction which initiated the access to memory. */
        DynInstPtr inst;
        /** The main packet from a split load, used during writeback. */
        PacketPtr mainPkt;
        /** A second packet from a split store that needs sending. */
        PacketPtr pendingPacket;
        /** Number of outstanding packets to complete. */
        uint8_t outstanding;
        /** Whether or not it is a load. */
        bool isLoad;
        /** Whether or not the instruction will need to writeback. */
        bool needWB;
        /** Whether or not this access is split in two. */
        bool isSplit;
        /** Whether or not there is a packet that needs sending. */
        bool pktToSend;
        /** Has the request been deleted?
         * LSQ entries can be squashed before the response comes back. in that
         * case the SenderState knows.
         */
        bool deleted;
        ContextID contextId() { return inst->contextId(); }

        /** Completes a packet and returns whether the access is finished. */
        inline bool isComplete() { return outstanding == 0; }
        inline void deleteRequest() { deleted = true; }
        inline bool alive() { return !deleted; }
        LSQRequest* request() { return _request; }
        virtual void complete() = 0;
        void writebackDone() { _request->writebackDone(); }
    };

    /**
     * DcachePort class for the load/store queue.
     */
    class DcachePort : public MasterPort
    {
      protected:

        /** Pointer to LSQ. */
        LSQ<Impl> *lsq;
        FullO3CPU<Impl> *cpu;

      public:
        /** Default constructor. */
        DcachePort(LSQ<Impl> *_lsq, FullO3CPU<Impl>* _cpu)
            : MasterPort(_cpu->name() + ".dcache_port", _cpu), lsq(_lsq),
              cpu(_cpu)
        { }

      protected:

        /** Timing version of receive.  Handles writing back and
         * completing the load or store that has returned from
         * memory. */
        virtual bool recvTimingResp(PacketPtr pkt);
        virtual void recvTimingSnoopReq(PacketPtr pkt);

        virtual void recvFunctionalSnoop(PacketPtr pkt)
        {
            // @todo: Is there a need for potential invalidation here?
        }

        /** Handles doing a retry of the previous send. */
        virtual void recvReqRetry();

        /**
         * As this CPU requires snooping to maintain the load store queue
         * change the behaviour from the base CPU port.
         *
         * @return true since we have to snoop
         */
        virtual bool isSnooping() const { return true; }
    };

    /** Memory operation metadata.
     * This class holds the information about a memory operation. It lives
     * from initiateAcc to resource deallocation at commit or squash.
     * LSQRequest objects are owned by the LQ/SQ Entry in the LSQUnit that
     * holds the operation. It is also used by the LSQSenderState. In addition,
     * the LSQRequest is a TranslationState, therefore, upon squash, there must
     * be a defined ownership transferal in case the LSQ resources are
     * deallocated before the TLB is done using the TranslationState. If that
     * happens, the LSQRequest will be self-owned, and responsible to detect
     * that its services are no longer required and self-destruct.
     *
     * Lifetime of a LSQRequest:
     *                 +--------------------+
     *                 |LSQ creates and owns|
     *                 +--------------------+
     *                           |
     *                 +--------------------+
     *                 | Initate translation|
     *                 +--------------------+
     *                           |
     *                        ___^___
     *                    ___/       \___
     *             ______/   Squashed?   \
     *            |      \___         ___/
     *            |          \___ ___/
     *            |              v
     *            |              |
     *            |    +--------------------+
     *            |    |  Translation done  |
     *            |    +--------------------+
     *            |              |
     *            |    +--------------------+
     *            |    |     Send packet    |<------+
     *            |    +--------------------+       |
     *            |              |                  |
     *            |           ___^___               |
     *            |       ___/       \___           |
     *            |  ____/   Squashed?   \          |
     *            | |    \___         ___/          |
     *            | |        \___ ___/              |
     *            | |            v                  |
     *            | |            |                  |
     *            | |         ___^___               |
     *            | |     ___/       \___           |
     *            | |    /     Done?     \__________|
     *            | |    \___         ___/
     *            | |        \___ ___/
     *            | |            v
     *            | |            |
     *            | |  +--------------------+
     *            | |  |    Manage stuff    |
     *            | |  |   Free resources   |
     *            | |  +--------------------+
     *            | |
     *            | |  +--------------------+
     *            | |  |  senderState owns  |
     *            | +->|  onRecvTimingResp  |
     *            |    |   free resources   |
     *            |    +--------------------+
     *            |
     *            |   +----------------------+
     *            |   |  self owned (Trans)  |
     *            +-->| on TranslationFinish |
     *                |    free resources    |
     *                +----------------------+
     *
     *
     */
    class LSQRequest : public BaseTLB::Translation
    {
      protected:
        typedef uint32_t FlagsStorage;
        typedef ::Flags<FlagsStorage> FlagsType;

        enum Flag : FlagsStorage
        {
            IsLoad              = 0x00000001,
            /** True if this is a store/atomic that writes registers (SC). */
            WbStore             = 0x00000002,
            Delayed             = 0x00000004,
            IsSplit             = 0x00000008,
            /** True if any translation has been sent to TLB. */
            TranslationStarted  = 0x00000010,
            /** True if there are un-replied outbound translations.. */
            TranslationFinished = 0x00000020,
            Sent                = 0x00000040,
            Retry               = 0x00000080,
            Complete            = 0x00000100,
            /** Ownership tracking flags. */
            /** Translation squashed. */
            TranslationSquashed = 0x00000200,
            /** Request discarded */
            Discarded           = 0x00000400,
            /** LSQ resources freed. */
            LSQEntryFreed       = 0x00000800,
            /** Store written back. */
            WritebackScheduled  = 0x00001000,
            WritebackDone       = 0x00002000,
            /** True if this is an atomic request */
            IsAtomic            = 0x00004000
        };
        FlagsType flags;

        enum class State
        {
            NotIssued,
            Translation,
            Request,
            Fault,
            PartialFault,
        };
        State _state;
        LSQSenderState* _senderState;
        void setState(const State& newState) { _state = newState; }

        uint32_t numTranslatedFragments;
        uint32_t numInTranslationFragments;

        /** LQ/SQ entry idx. */
        uint32_t _entryIdx;

        void markDelayed() override { flags.set(Flag::Delayed); }
        bool isDelayed() { return flags.isSet(Flag::Delayed); }

      public:
        LSQUnit& _port;
        const DynInstPtr _inst;
        uint32_t _taskId;
        PacketDataPtr _data;
        std::vector<PacketPtr> _packets;
        std::vector<RequestPtr> _requests;
        std::vector<Fault> _fault;
        uint64_t* _res;
        const Addr _addr;
        const uint32_t _size;
        const Request::Flags _flags;
        std::vector<bool> _byteEnable;
        uint32_t _numOutstandingPackets;
        AtomicOpFunctorPtr _amo_op;
      protected:
        LSQUnit* lsqUnit() { return &_port; }
        LSQRequest(LSQUnit* port, const DynInstPtr& inst, bool isLoad) :
            _state(State::NotIssued), _senderState(nullptr),
            _port(*port), _inst(inst), _data(nullptr),
            _res(nullptr), _addr(0), _size(0), _flags(0),
            _numOutstandingPackets(0), _amo_op(nullptr)
        {
            flags.set(Flag::IsLoad, isLoad);
            flags.set(Flag::WbStore,
                      _inst->isStoreConditional() || _inst->isAtomic());
            flags.set(Flag::IsAtomic, _inst->isAtomic());
            install();
        }
        LSQRequest(LSQUnit* port, const DynInstPtr& inst, bool isLoad,
                   const Addr& addr, const uint32_t& size,
                   const Request::Flags& flags_,
                   PacketDataPtr data = nullptr, uint64_t* res = nullptr,
                   AtomicOpFunctorPtr amo_op = nullptr)
            : _state(State::NotIssued), _senderState(nullptr),
            numTranslatedFragments(0),
            numInTranslationFragments(0),
            _port(*port), _inst(inst), _data(data),
            _res(res), _addr(addr), _size(size),
            _flags(flags_),
            _numOutstandingPackets(0),
            _amo_op(std::move(amo_op))
        {
            flags.set(Flag::IsLoad, isLoad);
            flags.set(Flag::WbStore,
                      _inst->isStoreConditional() || _inst->isAtomic());
            flags.set(Flag::IsAtomic, _inst->isAtomic());
            install();
        }

        bool
        isLoad() const
        {
            return flags.isSet(Flag::IsLoad);
        }

        bool
        isAtomic() const
        {
            return flags.isSet(Flag::IsAtomic);
        }

        /** Install the request in the LQ/SQ. */
        void install()
        {
            if (isLoad()) {
                _port.loadQueue[_inst->lqIdx].setRequest(this);
            } else {
                // Store, StoreConditional, and Atomic requests are pushed
                // to this storeQueue
                _port.storeQueue[_inst->sqIdx].setRequest(this);
            }
        }
        virtual bool
        squashed() const override
        {
            return _inst->isSquashed();
        }

        /**
         * Test if the LSQRequest has been released, i.e. self-owned.
         * An LSQRequest manages itself when the resources on the LSQ are freed
         * but the translation is still going on and the LSQEntry was freed.
         */
        bool
        isReleased()
        {
            return flags.isSet(Flag::LSQEntryFreed) ||
                flags.isSet(Flag::Discarded);
        }

        /** Release the LSQRequest.
         * Notify the sender state that the request it points to is not valid
         * anymore. Understand if the request is orphan (self-managed) and if
         * so, mark it as freed, else destroy it, as this means
         * the end of its life cycle.
         * An LSQRequest is orphan when its resources are released
         * but there is any in-flight translation request to the TLB or access
         * request to the memory.
         */
        void release(Flag reason)
        {
            assert(reason == Flag::LSQEntryFreed || reason == Flag::Discarded);
            if (!isAnyOutstandingRequest()) {
                delete this;
            } else {
                if (_senderState) {
                    _senderState->deleteRequest();
                }
                flags.set(reason);
            }
        }

        /** Helper function used to add a (sub)request, given its address
         * `addr`, size `size` and byte-enable mask `byteEnable`.
         *
         * The request is only added if the mask is empty or if there is at
         * least an active element in it.
         */
        void
        addRequest(Addr addr, unsigned size,
                   const std::vector<bool>& byte_enable)
        {
            if (byte_enable.empty() ||
                isAnyActiveElement(byte_enable.begin(), byte_enable.end())) {
                auto request = std::make_shared<Request>(_inst->getASID(),
                        addr, size, _flags, _inst->masterId(),
                        _inst->instAddr(), _inst->contextId(),
                        std::move(_amo_op));
                if (!byte_enable.empty()) {
                    request->setByteEnable(byte_enable);
                }
                _requests.push_back(request);
            }
        }

        /** Destructor.
         * The LSQRequest owns the request. If the packet has already been
         * sent, the sender state will be deleted upon receiving the reply.
         */
        virtual ~LSQRequest()
        {
            assert(!isAnyOutstandingRequest());
            _inst->savedReq = nullptr;
            if (_senderState)
                delete _senderState;

            for (auto r: _packets)
                delete r;
        };


      public:
        /** Convenience getters/setters. */
        /** @{ */
        /** Set up Context numbers. */
        void
        setContext(const ContextID& context_id)
        {
            request()->setContext(context_id);
        }

        const DynInstPtr&
        instruction()
        {
            return _inst;
        }

        /** Set up virtual request.
         * For a previously allocated Request objects.
         */
        void
        setVirt(int asid, Addr vaddr, unsigned size, Request::Flags flags_,
                MasterID mid, Addr pc)
        {
            request()->setVirt(asid, vaddr, size, flags_, mid, pc);
        }

        void
        taskId(const uint32_t& v)
        {
            _taskId = v;
            for (auto& r: _requests)
                r->taskId(v);
        }

        uint32_t taskId() const { return _taskId; }
        RequestPtr request(int idx = 0) { return _requests.at(idx); }

        const RequestPtr
        request(int idx = 0) const
        {
            return _requests.at(idx);
        }

        Addr getVaddr(int idx = 0) const { return request(idx)->getVaddr(); }
        virtual void initiateTranslation() = 0;

        PacketPtr packet(int idx = 0) { return _packets.at(idx); }

        virtual PacketPtr
        mainPacket()
        {
            assert (_packets.size() == 1);
            return packet();
        }

        virtual RequestPtr
        mainRequest()
        {
            assert (_requests.size() == 1);
            return request();
        }

        void
        senderState(LSQSenderState* st)
        {
            _senderState = st;
            for (auto& pkt: _packets) {
                if (pkt)
                    pkt->senderState = st;
            }
        }

        const LSQSenderState*
        senderState() const
        {
            return _senderState;
        }

        /**
         * Mark senderState as discarded. This will cause to discard response
         * packets from the cache.
         */
        void
        discardSenderState()
        {
            assert(_senderState);
            _senderState->deleteRequest();
        }

        /**
         * Test if there is any in-flight translation or mem access request
         */
        bool
        isAnyOutstandingRequest()
        {
            return numInTranslationFragments > 0 ||
                _numOutstandingPackets > 0 ||
                (flags.isSet(Flag::WritebackScheduled) &&
                 !flags.isSet(Flag::WritebackDone));
        }

        bool
        isSplit() const
        {
            return flags.isSet(Flag::IsSplit);
        }
        /** @} */
        virtual bool recvTimingResp(PacketPtr pkt) = 0;
        virtual void sendPacketToCache() = 0;
        virtual void buildPackets() = 0;

        /**
         * Memory mapped IPR accesses
         */
        virtual void handleIprWrite(ThreadContext *thread, PacketPtr pkt) = 0;
        virtual Cycles handleIprRead(ThreadContext *thread, PacketPtr pkt) = 0;

        /**
         * Test if the request accesses a particular cache line.
         */
        virtual bool isCacheBlockHit(Addr blockAddr, Addr cacheBlockMask) = 0;

        /** Update the status to reflect that a packet was sent. */
        void
        packetSent()
        {
            flags.set(Flag::Sent);
        }
        /** Update the status to reflect that a packet was not sent.
         * When a packet fails to be sent, we mark the request as needing a
         * retry. Note that Retry flag is sticky.
         */
        void
        packetNotSent()
        {
            flags.set(Flag::Retry);
            flags.clear(Flag::Sent);
        }

        void sendFragmentToTranslation(int i);
        bool
        isComplete()
        {
            return flags.isSet(Flag::Complete);
        }

        bool
        isInTranslation()
        {
            return _state == State::Translation;
        }

        bool
        isTranslationComplete()
        {
            return flags.isSet(Flag::TranslationStarted) &&
                   !isInTranslation();
        }

        bool
        isTranslationBlocked()
        {
            return _state == State::Translation &&
                flags.isSet(Flag::TranslationStarted) &&
                !flags.isSet(Flag::TranslationFinished);
        }

        bool
        isSent()
        {
            return flags.isSet(Flag::Sent);
        }

        bool
        isPartialFault()
        {
            return _state == State::PartialFault;
        }

        bool
        isMemAccessRequired()
        {
            return (_state == State::Request ||
                    (isPartialFault() && isLoad()));
        }

        void
        setStateToFault()
        {
            setState(State::Fault);
        }

        /**
         * The LSQ entry is cleared
         */
        void
        freeLSQEntry()
        {
            release(Flag::LSQEntryFreed);
        }

        /**
         * The request is discarded (e.g. partial store-load forwarding)
         */
        void
        discard()
        {
            release(Flag::Discarded);
        }

        void
        packetReplied()
        {
            assert(_numOutstandingPackets > 0);
            _numOutstandingPackets--;
            if (_numOutstandingPackets == 0 && isReleased())
                delete this;
        }

        void
        writebackScheduled()
        {
            assert(!flags.isSet(Flag::WritebackScheduled));
            flags.set(Flag::WritebackScheduled);
        }

        void
        writebackDone()
        {
            flags.set(Flag::WritebackDone);
            /* If the lsq resources are already free */
            if (isReleased()) {
                delete this;
            }
        }

        void
        squashTranslation()
        {
            assert(numInTranslationFragments == 0);
            flags.set(Flag::TranslationSquashed);
            /* If we are on our own, self-destruct. */
            if (isReleased()) {
                delete this;
            }
        }

        void
        complete()
        {
            flags.set(Flag::Complete);
        }
    };

    class SingleDataRequest : public LSQRequest
    {
      protected:
        /* Given that we are inside templates, children need explicit
         * declaration of the names in the parent class. */
        using Flag = typename LSQRequest::Flag;
        using State = typename LSQRequest::State;
        using LSQRequest::_addr;
        using LSQRequest::_fault;
        using LSQRequest::_flags;
        using LSQRequest::_size;
        using LSQRequest::_byteEnable;
        using LSQRequest::_requests;
        using LSQRequest::_inst;
        using LSQRequest::_packets;
        using LSQRequest::_port;
        using LSQRequest::_res;
        using LSQRequest::_taskId;
        using LSQRequest::_senderState;
        using LSQRequest::_state;
        using LSQRequest::flags;
        using LSQRequest::isLoad;
        using LSQRequest::isTranslationComplete;
        using LSQRequest::lsqUnit;
        using LSQRequest::request;
        using LSQRequest::sendFragmentToTranslation;
        using LSQRequest::setState;
        using LSQRequest::numInTranslationFragments;
        using LSQRequest::numTranslatedFragments;
        using LSQRequest::_numOutstandingPackets;
        using LSQRequest::_amo_op;
      public:
        SingleDataRequest(LSQUnit* port, const DynInstPtr& inst, bool isLoad,
                          const Addr& addr, const uint32_t& size,
                          const Request::Flags& flags_,
                          PacketDataPtr data = nullptr,
                          uint64_t* res = nullptr,
                          AtomicOpFunctorPtr amo_op = nullptr) :
            LSQRequest(port, inst, isLoad, addr, size, flags_, data, res,
                       std::move(amo_op)) {}

        inline virtual ~SingleDataRequest() {}
        virtual void initiateTranslation();
        virtual void finish(const Fault &fault, const RequestPtr &req,
                ThreadContext* tc, BaseTLB::Mode mode);
        virtual bool recvTimingResp(PacketPtr pkt);
        virtual void sendPacketToCache();
        virtual void buildPackets();
        virtual void handleIprWrite(ThreadContext *thread, PacketPtr pkt);
        virtual Cycles handleIprRead(ThreadContext *thread, PacketPtr pkt);
        virtual bool isCacheBlockHit(Addr blockAddr, Addr cacheBlockMask);
    };

    class SplitDataRequest : public LSQRequest
    {
      protected:
        /* Given that we are inside templates, children need explicit
         * declaration of the names in the parent class. */
        using Flag = typename LSQRequest::Flag;
        using State = typename LSQRequest::State;
        using LSQRequest::_addr;
        using LSQRequest::_data;
        using LSQRequest::_fault;
        using LSQRequest::_flags;
        using LSQRequest::_inst;
        using LSQRequest::_packets;
        using LSQRequest::_port;
        using LSQRequest::_requests;
        using LSQRequest::_res;
        using LSQRequest::_byteEnable;
        using LSQRequest::_senderState;
        using LSQRequest::_size;
        using LSQRequest::_state;
        using LSQRequest::_taskId;
        using LSQRequest::flags;
        using LSQRequest::isLoad;
        using LSQRequest::isTranslationComplete;
        using LSQRequest::lsqUnit;
        using LSQRequest::numInTranslationFragments;
        using LSQRequest::numTranslatedFragments;
        using LSQRequest::request;
        using LSQRequest::sendFragmentToTranslation;
        using LSQRequest::setState;
        using LSQRequest::_numOutstandingPackets;

        uint32_t numFragments;
        uint32_t numReceivedPackets;
        RequestPtr mainReq;
        PacketPtr _mainPacket;

      public:
        SplitDataRequest(LSQUnit* port, const DynInstPtr& inst, bool isLoad,
                         const Addr& addr, const uint32_t& size,
                         const Request::Flags & flags_,
                         PacketDataPtr data = nullptr,
                         uint64_t* res = nullptr) :
            LSQRequest(port, inst, isLoad, addr, size, flags_, data, res,
                       nullptr),
            numFragments(0),
            numReceivedPackets(0),
            mainReq(nullptr),
            _mainPacket(nullptr)
        {
            flags.set(Flag::IsSplit);
        }
        virtual ~SplitDataRequest()
        {
            if (mainReq) {
                mainReq = nullptr;
            }
            if (_mainPacket) {
                delete _mainPacket;
                _mainPacket = nullptr;
            }
        }
        virtual void finish(const Fault &fault, const RequestPtr &req,
                ThreadContext* tc, BaseTLB::Mode mode);
        virtual bool recvTimingResp(PacketPtr pkt);
        virtual void initiateTranslation();
        virtual void sendPacketToCache();
        virtual void buildPackets();

        virtual void handleIprWrite(ThreadContext *thread, PacketPtr pkt);
        virtual Cycles handleIprRead(ThreadContext *thread, PacketPtr pkt);
        virtual bool isCacheBlockHit(Addr blockAddr, Addr cacheBlockMask);

        virtual RequestPtr mainRequest();
        virtual PacketPtr mainPacket();
    };

    /** Constructs an LSQ with the given parameters. */
    LSQ(O3CPU *cpu_ptr, IEW *iew_ptr, DerivO3CPUParams *params);
    ~LSQ() { }

    /** Returns the name of the LSQ. */
    std::string name() const;

    /** Registers statistics of each LSQ unit. */
    void regStats();

    /** Sets the pointer to the list of active threads. */
    void setActiveThreads(std::list<ThreadID> *at_ptr);

    /** Perform sanity checks after a drain. */
    void drainSanityCheck() const;
    /** Has the LSQ drained? */
    bool isDrained() const;
    /** Takes over execution from another CPU's thread. */
    void takeOverFrom();

    /** Number of entries needed for the given amount of threads.*/
    int entryAmount(ThreadID num_threads);

    /** Ticks the LSQ. */
    void tick();

    /** Inserts a load into the LSQ. */
    void insertLoad(const DynInstPtr &load_inst);
    /** Inserts a store into the LSQ. */
    void insertStore(const DynInstPtr &store_inst);

    /** Executes a load. */
    Fault executeLoad(const DynInstPtr &inst);

    /** Executes a store. */
    Fault executeStore(const DynInstPtr &inst);

    /**
     * Commits loads up until the given sequence number for a specific thread.
     */
    void commitLoads(InstSeqNum &youngest_inst, ThreadID tid)
    { thread.at(tid).commitLoads(youngest_inst); }

    /**
     * Commits stores up until the given sequence number for a specific thread.
     */
    void commitStores(InstSeqNum &youngest_inst, ThreadID tid)
    { thread.at(tid).commitStores(youngest_inst); }

    /**
     * Attempts to write back stores until all cache ports are used or the
     * interface becomes blocked.
     */
    void writebackStores();
    /** Same as above, but only for one thread. */
    void writebackStores(ThreadID tid);

    /**
     * Squash instructions from a thread until the specified sequence number.
     */
    void
    squash(const InstSeqNum &squashed_num, ThreadID tid)
    {
        thread.at(tid).squash(squashed_num);
    }

    /** Returns whether or not there was a memory ordering violation. */
    bool violation();
    /**
     * Returns whether or not there was a memory ordering violation for a
     * specific thread.
     */
    bool violation(ThreadID tid) { return thread.at(tid).violation(); }

    /** Gets the instruction that caused the memory ordering violation. */
    DynInstPtr
    getMemDepViolator(ThreadID tid)
    {
        return thread.at(tid).getMemDepViolator();
    }

    /** Returns the head index of the load queue for a specific thread. */
    int getLoadHead(ThreadID tid) { return thread.at(tid).getLoadHead(); }

    /** Returns the sequence number of the head of the load queue. */
    InstSeqNum
    getLoadHeadSeqNum(ThreadID tid)
    {
        return thread.at(tid).getLoadHeadSeqNum();
    }

    /** Returns the head index of the store queue. */
    int getStoreHead(ThreadID tid) { return thread.at(tid).getStoreHead(); }

    /** Returns the sequence number of the head of the store queue. */
    InstSeqNum
    getStoreHeadSeqNum(ThreadID tid)
    {
        return thread.at(tid).getStoreHeadSeqNum();
    }

    /** Returns the number of instructions in all of the queues. */
    int getCount();
    /** Returns the number of instructions in the queues of one thread. */
    int getCount(ThreadID tid) { return thread.at(tid).getCount(); }

    /** Returns the total number of loads in the load queue. */
    int numLoads();
    /** Returns the total number of loads for a single thread. */
    int numLoads(ThreadID tid) { return thread.at(tid).numLoads(); }

    /** Returns the total number of stores in the store queue. */
    int numStores();
    /** Returns the total number of stores for a single thread. */
    int numStores(ThreadID tid) { return thread.at(tid).numStores(); }

    /** Returns the number of free load entries. */
    unsigned numFreeLoadEntries();

    /** Returns the number of free store entries. */
    unsigned numFreeStoreEntries();

    /** Returns the number of free entries for a specific thread. */
    unsigned numFreeEntries(ThreadID tid);

    /** Returns the number of free entries in the LQ for a specific thread. */
    unsigned numFreeLoadEntries(ThreadID tid);

    /** Returns the number of free entries in the SQ for a specific thread. */
    unsigned numFreeStoreEntries(ThreadID tid);

    /** Returns if the LSQ is full (either LQ or SQ is full). */
    bool isFull();
    /**
     * Returns if the LSQ is full for a specific thread (either LQ or SQ is
     * full).
     */
    bool isFull(ThreadID tid);

    /** Returns if the LSQ is empty (both LQ and SQ are empty). */
    bool isEmpty() const;
    /** Returns if all of the LQs are empty. */
    bool lqEmpty() const;
    /** Returns if all of the SQs are empty. */
    bool sqEmpty() const;

    /** Returns if any of the LQs are full. */
    bool lqFull();
    /** Returns if the LQ of a given thread is full. */
    bool lqFull(ThreadID tid);

    /** Returns if any of the SQs are full. */
    bool sqFull();
    /** Returns if the SQ of a given thread is full. */
    bool sqFull(ThreadID tid);

    /**
     * Returns if the LSQ is stalled due to a memory operation that must be
     * replayed.
     */
    bool isStalled();
    /**
     * Returns if the LSQ of a specific thread is stalled due to a memory
     * operation that must be replayed.
     */
    bool isStalled(ThreadID tid);

    /** Returns whether or not there are any stores to write back to memory. */
    bool hasStoresToWB();

    /** Returns whether or not a specific thread has any stores to write back
     * to memory.
     */
    bool hasStoresToWB(ThreadID tid) { return thread.at(tid).hasStoresToWB(); }

    /** Returns the number of stores a specific thread has to write back. */
    int numStoresToWB(ThreadID tid) { return thread.at(tid).numStoresToWB(); }

    /** Returns if the LSQ will write back to memory this cycle. */
    bool willWB();
    /** Returns if the LSQ of a specific thread will write back to memory this
     * cycle.
     */
    bool willWB(ThreadID tid) { return thread.at(tid).willWB(); }

    /** Debugging function to print out all instructions. */
    void dumpInsts() const;
    /** Debugging function to print out instructions from a specific thread. */
    void dumpInsts(ThreadID tid) const { thread.at(tid).dumpInsts(); }

    /** Executes a read operation, using the load specified at the load
     * index.
     */
    Fault read(LSQRequest* req, int load_idx);

    /** Executes a store operation, using the store specified at the store
     * index.
     */
    Fault write(LSQRequest* req, uint8_t *data, int store_idx);

    /**
     * Retry the previous send that failed.
     */
    void recvReqRetry();

    void completeDataAccess(PacketPtr pkt);
    /**
     * Handles writing back and completing the load or store that has
     * returned from memory.
     *
     * @param pkt Response packet from the memory sub-system
     */
    bool recvTimingResp(PacketPtr pkt);

    void recvTimingSnoopReq(PacketPtr pkt);

    Fault pushRequest(const DynInstPtr& inst, bool isLoad, uint8_t *data,
                      unsigned int size, Addr addr, Request::Flags flags,
                      uint64_t *res, AtomicOpFunctorPtr amo_op,
                      const std::vector<bool>& byte_enable);

    /** The CPU pointer. */
    O3CPU *cpu;

    /** The IEW stage pointer. */
    IEW *iewStage;

    /** Is D-cache blocked? */
    bool cacheBlocked() const;
    /** Set D-cache blocked status */
    void cacheBlocked(bool v);
    /** Is any store port available to use? */
    bool cachePortAvailable(bool is_load) const;
    /** Another store port is in use */
    void cachePortBusy(bool is_load);

    MasterPort &getDataPort() { return dcachePort; }

  protected:
    /** D-cache is blocked */
    bool _cacheBlocked;
    /** The number of cache ports available each cycle (stores only). */
    int cacheStorePorts;
    /** The number of used cache ports in this cycle by stores. */
    int usedStorePorts;
    /** The number of cache ports available each cycle (loads only). */
    int cacheLoadPorts;
    /** The number of used cache ports in this cycle by loads. */
    int usedLoadPorts;


    /** The LSQ policy for SMT mode. */
    SMTQueuePolicy lsqPolicy;

    /** Auxiliary function to calculate per-thread max LSQ allocation limit.
     * Depending on a policy, number of entries and possibly number of threads
     * and threshold, this function calculates how many resources each thread
     * can occupy at most.
     */
    static uint32_t
    maxLSQAllocation(SMTQueuePolicy pol, uint32_t entries,
            uint32_t numThreads, uint32_t SMTThreshold)
    {
        if (pol == SMTQueuePolicy::Dynamic) {
            return entries;
        } else if (pol == SMTQueuePolicy::Partitioned) {
            //@todo:make work if part_amt doesnt divide evenly.
            return entries / numThreads;
        } else if (pol == SMTQueuePolicy::Threshold) {
            //Divide up by threshold amount
            //@todo: Should threads check the max and the total
            //amount of the LSQ
            return SMTThreshold;
        }
        return 0;
    }

    /** List of Active Threads in System. */
    std::list<ThreadID> *activeThreads;

    /** Total Size of LQ Entries. */
    unsigned LQEntries;
    /** Total Size of SQ Entries. */
    unsigned SQEntries;

    /** Max LQ Size - Used to Enforce Sharing Policies. */
    unsigned maxLQEntries;

    /** Max SQ Size - Used to Enforce Sharing Policies. */
    unsigned maxSQEntries;

    /** Data port. */
    DcachePort dcachePort;

    /** The LSQ units for individual threads. */
    std::vector<LSQUnit> thread;

    /** Number of Threads. */
    ThreadID numThreads;
};

template <class Impl>
Fault
LSQ<Impl>::read(LSQRequest* req, int load_idx)
{
    ThreadID tid = cpu->contextToThread(req->request()->contextId());

    return thread.at(tid).read(req, load_idx);
}

template <class Impl>
Fault
LSQ<Impl>::write(LSQRequest* req, uint8_t *data, int store_idx)
{
    ThreadID tid = cpu->contextToThread(req->request()->contextId());

    return thread.at(tid).write(req, data, store_idx);
}

#endif // __CPU_O3_LSQ_HH__