btb.hh

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/*
 * Copyright (c) 2004-2005 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
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 * 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
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#ifndef __CPU_PRED_BTB_HH__
#define __CPU_PRED_BTB_HH__
 
#include "arch/pcstate.hh"
#include "base/logging.hh"
#include "base/types.hh"
#include "config/the_isa.hh"
 
namespace gem5
{
 
namespace branch_prediction
{
 
class DefaultBTB
{
  private:
    struct BTBEntry
    {
        BTBEntry()
            : tag(0), target(0), valid(false)
        {}
 
        Addr tag;
 
        TheISA::PCState target;
 
        ThreadID tid;
 
        bool valid;
    };
 
  public:
    DefaultBTB(unsigned numEntries, unsigned tagBits,
               unsigned instShiftAmt, unsigned numThreads);
 
    void reset();
 
    TheISA::PCState lookup(Addr instPC, ThreadID tid);
 
    bool valid(Addr instPC, ThreadID tid);
 
    void update(Addr instPC, const TheISA::PCState &targetPC,
                ThreadID tid);
 
  private:
    inline unsigned getIndex(Addr instPC, ThreadID tid);
 
    inline Addr getTag(Addr instPC);
 
    std::vector<BTBEntry> btb;
 
    unsigned numEntries;
 
    unsigned idxMask;
 
    unsigned tagBits;
 
    unsigned tagMask;
 
    unsigned instShiftAmt;
 
    unsigned tagShiftAmt;
 
    unsigned log2NumThreads;
};
 
} // namespace branch_prediction
} // namespace gem5
 
#endif // __CPU_PRED_BTB_HH__