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  * Authors: Kevin Lim
  29  */
  30
  31 #ifndef __CPU_O3_TOURNAMENT_PRED_HH__
  32 #define __CPU_O3_TOURNAMENT_PRED_HH__
  33
  34 // For Addr type.
  35 #include "arch/isa_traits.hh"
  36 #include "cpu/o3/sat_counter.hh"
  37 #include <vector>
  38
  39 class TournamentBP
  40 {
  41   public:
  42     /**
  43      * Default branch predictor constructor.
  44      */
  45     TournamentBP(unsigned localPredictorSize,
  46                  unsigned localCtrBits,
  47                  unsigned localHistoryTableSize,
  48                  unsigned localHistoryBits,
  49                  unsigned globalPredictorSize,
  50                  unsigned globalHistoryBits,
  51                  unsigned globalCtrBits,
  52                  unsigned choicePredictorSize,
  53                  unsigned choiceCtrBits,
  54                  unsigned instShiftAmt);
  55
  56     /**
  57      * Looks up the given address in the branch predictor and returns
  58      * a true/false value as to whether it is taken.
  59      * @param branch_addr The address of the branch to look up.
  60      * @return Whether or not the branch is taken.
  61      */
  62     bool lookup(Addr &branch_addr);
  63
  64     /**
  65      * Updates the branch predictor with the actual result of a branch.
  66      * @param branch_addr The address of the branch to update.
  67      * @param taken Whether or not the branch was taken.
  68      */
  69     void update(Addr &branch_addr, unsigned global_history, bool taken);
  70
  71     inline unsigned readGlobalHist() { return globalHistory; }
  72
  73   private:
  74
  75     inline bool getPrediction(uint8_t &count);
  76
  77     inline unsigned calcLocHistIdx(Addr &branch_addr);
  78
  79     inline void updateHistoriesTaken(unsigned local_history_idx);
  80
  81     inline void updateHistoriesNotTaken(unsigned local_history_idx);
  82
  83     /** Local counters. */
  84     std::vector<SatCounter> localCtrs;
  85
  86     /** Size of the local predictor. */
  87     unsigned localPredictorSize;
  88
  89     /** Number of bits of the local predictor's counters. */
  90     unsigned localCtrBits;
  91
  92     /** Array of local history table entries. */
  93     std::vector<unsigned> localHistoryTable;
  94
  95     /** Size of the local history table. */
  96     unsigned localHistoryTableSize;
  97
  98     /** Number of bits for each entry of the local history table.
  99      *  @todo Doesn't this come from the size of the local predictor?
 100      */
 101     unsigned localHistoryBits;
 102
 103     /** Mask to get the proper local history. */
 104     unsigned localHistoryMask;
 105
 106
 107     /** Array of counters that make up the global predictor. */
 108     std::vector<SatCounter> globalCtrs;
 109
 110     /** Size of the global predictor. */
 111     unsigned globalPredictorSize;
 112
 113     /** Number of bits of the global predictor's counters. */
 114     unsigned globalCtrBits;
 115
 116     /** Global history register. */
 117     unsigned globalHistory;
 118
 119     /** Number of bits for the global history. */
 120     unsigned globalHistoryBits;
 121
 122     /** Mask to get the proper global history. */
 123     unsigned globalHistoryMask;
 124
 125
 126     /** Array of counters that make up the choice predictor. */
 127     std::vector<SatCounter> choiceCtrs;
 128
 129     /** Size of the choice predictor (identical to the global predictor). */
 130     unsigned choicePredictorSize;
 131
 132     /** Number of bits of the choice predictor's counters. */
 133     unsigned choiceCtrBits;
 134
 135     /** Number of bits to shift the instruction over to get rid of the word
 136      *  offset.
 137      */
 138     unsigned instShiftAmt;
 139
 140     /** Threshold for the counter value; above the threshold is taken,
 141      *  equal to or below the threshold is not taken.
 142      */
 143     unsigned threshold;
 144 };
 145
 146 #endif // __CPU_O3_TOURNAMENT_PRED_HH__