tournament.hh

Go to the documentation of this file.

/*
 * Copyright (c) 2011, 2014 ARM Limited
 * Copyright (c) 2022-2023 The University of Edinburgh
 * 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
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#ifndef __CPU_PRED_TOURNAMENT_PRED_HH__
#define __CPU_PRED_TOURNAMENT_PRED_HH__
 
#include <vector>
 
#include "base/sat_counter.hh"
#include "base/types.hh"
#include "cpu/pred/bpred_unit.hh"
#include "params/TournamentBP.hh"
 
namespace gem5
{
 
namespace branch_prediction
{
 
class TournamentBP : public BPredUnit
{
  public:
    TournamentBP(const TournamentBPParams &params);
 
    // Base class methods.
    bool lookup(ThreadID tid, Addr pc, void* &bp_history) override;
    void updateHistories(ThreadID tid, Addr pc, bool uncond, bool taken,
                         Addr target,  void * &bp_history) override;
    void update(ThreadID tid, Addr pc, bool taken,
                void * &bp_history, bool squashed,
                const StaticInstPtr & inst, Addr target) override;
    void squash(ThreadID tid, void * &bp_history) override;
 
  private:
    inline bool getPrediction(uint8_t &count);
 
    inline unsigned calcLocHistIdx(Addr &branch_addr);
 
    inline void updateGlobalHist(ThreadID tid, bool taken);
 
    inline void updateLocalHist(unsigned local_history_idx, bool taken);
 
    struct BPHistory
    {
#ifdef GEM5_DEBUG
        BPHistory()
        { newCount++; }
        ~BPHistory()
        { newCount--; }
 
        static int newCount;
#endif
        unsigned globalHistory;
        unsigned localHistoryIdx;
        unsigned localHistory;
        bool localPredTaken;
        bool globalPredTaken;
        bool globalUsed;
    };
 
    static const int invalidPredictorIndex = -1;
    unsigned localPredictorSize;
 
    unsigned localPredictorMask;
 
    unsigned localCtrBits;
 
    std::vector<SatCounter8> localCtrs;
 
    std::vector<unsigned> localHistoryTable;
 
    unsigned localHistoryTableSize;
 
    unsigned localHistoryBits;
 
    unsigned globalPredictorSize;
 
    unsigned globalCtrBits;
 
    std::vector<SatCounter8> globalCtrs;
 
    std::vector<unsigned> globalHistory;
 
    unsigned globalHistoryBits;
 
    unsigned globalHistoryMask;
 
    unsigned choiceHistoryMask;
 
    unsigned historyRegisterMask;
 
    unsigned choicePredictorSize;
 
    unsigned choiceCtrBits;
 
    std::vector<SatCounter8> choiceCtrs;
 
    unsigned localThreshold;
    unsigned globalThreshold;
    unsigned choiceThreshold;
};
 
} // namespace branch_prediction
} // namespace gem5
 
#endif // __CPU_PRED_TOURNAMENT_PRED_HH__