decode.hh

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 * Copyright (c) 2012 ARM Limited
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 * 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
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 * modified or unmodified, in source code or in binary form.
 *
 * Copyright (c) 2004-2006 The Regents of The University of Michigan
 * All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
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#ifndef __CPU_O3_DECODE_HH__
#define __CPU_O3_DECODE_HH__
 
#include <queue>
 
#include "base/statistics.hh"
#include "cpu/o3/comm.hh"
#include "cpu/o3/dyn_inst_ptr.hh"
#include "cpu/o3/limits.hh"
#include "cpu/timebuf.hh"
 
namespace gem5
{
 
struct BaseO3CPUParams;
 
namespace o3
{
 
class CPU;
 
class Decode
{
  public:
    enum DecodeStatus
    {
        Active,
        Inactive
    };
 
    enum ThreadStatus
    {
        Running,
        Idle,
        StartSquash,
        Squashing,
        Blocked,
        Unblocking
    };
 
  private:
    DecodeStatus _status;
 
    ThreadStatus decodeStatus[MaxThreads];
 
  public:
    Decode(CPU *_cpu, const BaseO3CPUParams &params);
 
    void startupStage();
 
    void clearStates(ThreadID tid);
 
    void resetStage();
 
    std::string name() const;
 
    void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr);
 
    void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr);
 
    void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr);
 
    void setActiveThreads(std::list<ThreadID> *at_ptr);
 
    void drainSanityCheck() const;
 
    bool isDrained() const;
 
    void takeOverFrom() { resetStage(); }
 
    void tick();
 
    void decode(bool &status_change, ThreadID tid);
 
    void decodeInsts(ThreadID tid);
 
  private:
    void skidInsert(ThreadID tid);
 
    bool skidsEmpty();
 
    void updateStatus();
 
    void sortInsts();
 
    void readStallSignals(ThreadID tid);
 
    bool checkSignalsAndUpdate(ThreadID tid);
 
    bool checkStall(ThreadID tid) const;
 
    bool fetchInstsValid();
 
    bool block(ThreadID tid);
 
    bool unblock(ThreadID tid);
 
    void squash(const DynInstPtr &inst, ThreadID tid);
 
  public:
    unsigned squash(ThreadID tid);
 
  private:
    // Interfaces to objects outside of decode.
    CPU *cpu;
 
    TimeBuffer<TimeStruct> *timeBuffer;
 
    TimeBuffer<TimeStruct>::wire fromRename;
 
    TimeBuffer<TimeStruct>::wire fromIEW;
 
    TimeBuffer<TimeStruct>::wire fromCommit;
 
    // Might not be the best name as not only fetch will read it.
    TimeBuffer<TimeStruct>::wire toFetch;
 
    TimeBuffer<DecodeStruct> *decodeQueue;
 
    TimeBuffer<DecodeStruct>::wire toRename;
 
    TimeBuffer<FetchStruct> *fetchQueue;
 
    TimeBuffer<FetchStruct>::wire fromFetch;
 
    std::queue<DynInstPtr> insts[MaxThreads];
 
    std::queue<DynInstPtr> skidBuffer[MaxThreads];
 
    bool wroteToTimeBuffer;
 
    struct Stalls
    {
        bool rename;
    };
 
    Stalls stalls[MaxThreads];
 
    Cycles renameToDecodeDelay;
 
    Cycles iewToDecodeDelay;
 
    Cycles commitToDecodeDelay;
 
    Cycles fetchToDecodeDelay;
 
    unsigned decodeWidth;
 
    unsigned toRenameIndex;
 
    ThreadID numThreads;
 
    std::list<ThreadID> *activeThreads;
 
    unsigned skidBufferMax;
 
    Addr bdelayDoneSeqNum[MaxThreads];
 
    DynInstPtr squashInst[MaxThreads];
 
    bool squashAfterDelaySlot[MaxThreads];
 
    struct DecodeStats : public statistics::Group
    {
        DecodeStats(CPU *cpu);
 
        statistics::Scalar idleCycles;
        statistics::Scalar blockedCycles;
        statistics::Scalar runCycles;
        statistics::Scalar unblockCycles;
        statistics::Scalar squashCycles;
        statistics::Scalar branchResolved;
        statistics::Scalar branchMispred;
        statistics::Scalar controlMispred;
        statistics::Scalar decodedInsts;
        statistics::Scalar squashedInsts;
    } stats;
};
 
} // namespace o3
} // namespace gem5
 
#endif // __CPU_O3_DECODE_HH__