decoder.hh

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/*
 * Copyright 2020 Google, Inc.
 *
 * 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
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 * 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
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#ifndef __ARCH_GENERIC_DECODER_HH__
#define __ARCH_GENERIC_DECODER_HH__
 
#include "arch/generic/pcstate.hh"
#include "base/bitfield.hh"
#include "base/intmath.hh"
#include "base/types.hh"
#include "cpu/static_inst_fwd.hh"
#include "params/InstDecoder.hh"
#include "sim/sim_object.hh"
 
namespace gem5
{
 
class InstDecoder : public SimObject
{
  protected:
    void *_moreBytesPtr;
    size_t _moreBytesSize;
    Addr _pcMask;
 
    bool instDone = false;
    bool outOfBytes = true;
 
  public:
    template <typename MoreBytesType>
    InstDecoder(const InstDecoderParams &params, MoreBytesType *mb_buf) :
        SimObject(params), _moreBytesPtr(mb_buf),
        _moreBytesSize(sizeof(MoreBytesType)),
        _pcMask(~mask(floorLog2(_moreBytesSize)))
    {}
 
    virtual StaticInstPtr fetchRomMicroop(
            MicroPC micropc, StaticInstPtr curMacroop);
    virtual void
    reset()
    {
        instDone = false;
        outOfBytes = true;
    }
 
    template <class Type>
    Type &
    as()
    {
        return *static_cast<Type *>(this);
    }
 
    template <class Type>
    const Type &
    as() const
    {
        return *static_cast<const Type *>(this);
    }
 
    virtual void
    takeOverFrom(InstDecoder *old)
    {
        instDone = old->instDone;
        outOfBytes = old->outOfBytes;
    }
 
    void *moreBytesPtr() const { return _moreBytesPtr; }
    size_t moreBytesSize() const { return _moreBytesSize; }
    Addr pcMask() const { return _pcMask; }
 
    bool instReady() const { return instDone; }
 
    bool needMoreBytes() const { return outOfBytes; }
 
    virtual void moreBytes(const PCStateBase &pc, Addr fetchPC) = 0;
 
    virtual StaticInstPtr decode(PCStateBase &pc) = 0;
};
 
} // namespace gem5
 
#endif // __ARCH_DECODER_GENERIC_HH__