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_CPU_TOURNAMENT_PRED_HH__
  30 #define __CPU_O3_CPU_TOURNAMENT_PRED_HH__
  31
  32 // For Addr type.
  33 #include "arch/isa_traits.hh"
  34 #include "cpu/o3/sat_counter.hh"
  35
  36 class TournamentBP
  37 {
  38   public:
  39     /**
  40      * Default branch predictor constructor.
  41      */
  42     TournamentBP(unsigned local_predictor_size,
  43                  unsigned local_ctr_bits,
  44                  unsigned local_history_table_size,
  45                  unsigned local_history_bits,
  46                  unsigned global_predictor_size,
  47                  unsigned global_history_bits,
  48                  unsigned global_ctr_bits,
  49                  unsigned choice_predictor_size,
  50                  unsigned choice_ctr_bits,
  51                  unsigned instShiftAmt);
  52
  53     /**
  54      * Looks up the given address in the branch predictor and returns
  55      * a true/false value as to whether it is taken.
  56      * @param branch_addr The address of the branch to look up.
  57      * @return Whether or not the branch is taken.
  58      */
  59     bool lookup(Addr &branch_addr);
  60
  61     /**
  62      * Updates the branch predictor with the actual result of a branch.
  63      * @param branch_addr The address of the branch to update.
  64      * @param taken Whether or not the branch was taken.
  65      */
  66     void update(Addr &branch_addr, unsigned global_history, bool taken);
  67
  68     inline unsigned readGlobalHist() { return globalHistory; }
  69
  70   private:
  71
  72     inline bool getPrediction(uint8_t &count);
  73
  74     inline unsigned calcLocHistIdx(Addr &branch_addr);
  75
  76     inline void updateHistoriesTaken(unsigned local_history_idx);
  77
  78     inline void updateHistoriesNotTaken(unsigned local_history_idx);
  79
  80     /** Local counters. */
  81     SatCounter *localCtrs;
  82
  83     /** Size of the local predictor. */
  84     unsigned localPredictorSize;
  85
  86     /** Number of bits of the local predictor's counters. */
  87     unsigned localCtrBits;
  88
  89     /** Array of local history table entries. */
  90     unsigned *localHistoryTable;
  91
  92     /** Size of the local history table. */
  93     unsigned localHistoryTableSize;
  94
  95     /** Number of bits for each entry of the local history table.
  96      *  @todo Doesn't this come from the size of the local predictor?
  97      */
  98     unsigned localHistoryBits;
  99
 100     /** Mask to get the proper local history. */
 101     unsigned localHistoryMask;
 102
 103
 104     /** Array of counters that make up the global predictor. */
 105     SatCounter *globalCtrs;
 106
 107     /** Size of the global predictor. */
 108     unsigned globalPredictorSize;
 109
 110     /** Number of bits of the global predictor's counters. */
 111     unsigned globalCtrBits;
 112
 113     /** Global history register. */
 114     unsigned globalHistory;
 115
 116     /** Number of bits for the global history. */
 117     unsigned globalHistoryBits;
 118
 119     /** Mask to get the proper global history. */
 120     unsigned globalHistoryMask;
 121
 122
 123     /** Array of counters that make up the choice predictor. */
 124     SatCounter *choiceCtrs;
 125
 126     /** Size of the choice predictor (identical to the global predictor). */
 127     unsigned choicePredictorSize;
 128
 129     /** Number of bits of the choice predictor's counters. */
 130     unsigned choiceCtrBits;
 131
 132     /** Number of bits to shift the instruction over to get rid of the word
 133      *  offset.
 134      */
 135     unsigned instShiftAmt;
 136
 137     /** Threshold for the counter value; above the threshold is taken,
 138      *  equal to or below the threshold is not taken.
 139      */
 140     unsigned threshold;
 141 };
 142
 143 #endif // __CPU_O3_CPU_TOURNAMENT_PRED_HH__