decoder.hh

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/*
 * Copyright (c) 2012 Google
 * 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
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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
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#ifndef __ARCH_MIPS_DECODER_HH__
#define __ARCH_MIPS_DECODER_HH__
 
#include "arch/generic/decode_cache.hh"
#include "arch/generic/decoder.hh"
#include "arch/mips/types.hh"
#include "base/logging.hh"
#include "base/types.hh"
#include "cpu/static_inst.hh"
#include "debug/Decode.hh"
 
namespace MipsISA
{
 
class ISA;
class Decoder : public InstDecoder
{
  protected:
    //The extended machine instruction being generated
    ExtMachInst emi;
    bool instDone;
 
  public:
    Decoder(ISA* isa = nullptr) : instDone(false)
    {}
 
    void
    process()
    {
    }
 
    void
    reset()
    {
        instDone = false;
    }
 
    //Use this to give data to the decoder. This should be used
    //when there is control flow.
    void
    moreBytes(const PCState &pc, Addr fetchPC, MachInst inst)
    {
        emi = letoh(inst);
        instDone = true;
    }
 
    bool
    needMoreBytes()
    {
        return true;
    }
 
    bool
    instReady()
    {
        return instDone;
    }
 
    void takeOverFrom(Decoder *old) {}
 
  protected:
    static GenericISA::BasicDecodeCache<Decoder, ExtMachInst> defaultCache;
 
  public:
    StaticInstPtr decodeInst(ExtMachInst mach_inst);
 
    StaticInstPtr
    decode(ExtMachInst mach_inst, Addr addr)
    {
        StaticInstPtr si = defaultCache.decode(this, mach_inst, addr);
        DPRINTF(Decode, "Decode: Decoded %s instruction: %#x\n",
                si->getName(), mach_inst);
        return si;
    }
 
    StaticInstPtr
    decode(MipsISA::PCState &nextPC)
    {
        if (!instDone)
            return NULL;
        instDone = false;
        return decode(emi, nextPC.instAddr());
    }
};
 
} // namespace MipsISA
 
#endif // __ARCH_MIPS_DECODER_HH__