src/cpu/o3/tournament_pred.hh

   1 /*
   2  * Copyright (c) 2004-2005 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __CPU_O3_TOURNAMENT_PRED_HH__
  30 #define __CPU_O3_TOURNAMENT_PRED_HH__
  31
  32 // For Addr type.
  33 #include "arch/isa_traits.hh"
  34 #include "cpu/o3/sat_counter.hh"
  35 #include <vector>
  36
  37 class TournamentBP
  38 {
  39   public:
  40     /**
  41      * Default branch predictor constructor.
  42      */
  43     TournamentBP(unsigned localPredictorSize,
  44                  unsigned localCtrBits,
  45                  unsigned localHistoryTableSize,
  46                  unsigned localHistoryBits,
  47                  unsigned globalPredictorSize,
  48                  unsigned globalHistoryBits,
  49                  unsigned globalCtrBits,
  50                  unsigned choicePredictorSize,
  51                  unsigned choiceCtrBits,
  52                  unsigned instShiftAmt);
  53
  54     /**
  55      * Looks up the given address in the branch predictor and returns
  56      * a true/false value as to whether it is taken.
  57      * @param branch_addr The address of the branch to look up.
  58      * @return Whether or not the branch is taken.
  59      */
  60     bool lookup(Addr &branch_addr);
  61
  62     /**
  63      * Updates the branch predictor with the actual result of a branch.
  64      * @param branch_addr The address of the branch to update.
  65      * @param taken Whether or not the branch was taken.
  66      */
  67     void update(Addr &branch_addr, unsigned global_history, bool taken);
  68
  69     inline unsigned readGlobalHist() { return globalHistory; }
  70
  71   private:
  72
  73     inline bool getPrediction(uint8_t &count);
  74
  75     inline unsigned calcLocHistIdx(Addr &branch_addr);
  76
  77     inline void updateHistoriesTaken(unsigned local_history_idx);
  78
  79     inline void updateHistoriesNotTaken(unsigned local_history_idx);
  80
  81     /** Local counters. */
  82     std::vector<SatCounter> localCtrs;
  83
  84     /** Size of the local predictor. */
  85     unsigned localPredictorSize;
  86
  87     /** Number of bits of the local predictor's counters. */
  88     unsigned localCtrBits;
  89
  90     /** Array of local history table entries. */
  91     std::vector<unsigned> localHistoryTable;
  92
  93     /** Size of the local history table. */
  94     unsigned localHistoryTableSize;
  95
  96     /** Number of bits for each entry of the local history table.
  97      *  @todo Doesn't this come from the size of the local predictor?
  98      */
  99     unsigned localHistoryBits;
 100
 101     /** Mask to get the proper local history. */
 102     unsigned localHistoryMask;
 103
 104
 105     /** Array of counters that make up the global predictor. */
 106     std::vector<SatCounter> globalCtrs;
 107
 108     /** Size of the global predictor. */
 109     unsigned globalPredictorSize;
 110
 111     /** Number of bits of the global predictor's counters. */
 112     unsigned globalCtrBits;
 113
 114     /** Global history register. */
 115     unsigned globalHistory;
 116
 117     /** Number of bits for the global history. */
 118     unsigned globalHistoryBits;
 119
 120     /** Mask to get the proper global history. */
 121     unsigned globalHistoryMask;
 122
 123
 124     /** Array of counters that make up the choice predictor. */
 125     std::vector<SatCounter> choiceCtrs;
 126
 127     /** Size of the choice predictor (identical to the global predictor). */
 128     unsigned choicePredictorSize;
 129
 130     /** Number of bits of the choice predictor's counters. */
 131     unsigned choiceCtrBits;
 132
 133     /** Number of bits to shift the instruction over to get rid of the word
 134      *  offset.
 135      */
 136     unsigned instShiftAmt;
 137
 138     /** Threshold for the counter value; above the threshold is taken,
 139      *  equal to or below the threshold is not taken.
 140      */
 141     unsigned threshold;
 142 };
 143
 144 #endif // __CPU_O3_TOURNAMENT_PRED_HH__