sim/sat_counter.hh

   1 /*
   2  * Copyright (c) 2003 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 __SAT_COUNTER_HH__
  30 #define __SAT_COUNTER_HH__
  31
  32 #include <string>
  33
  34 #include "predictor.hh"
  35
  36 #include "statistics.hh"
  37 #include "sim_stats.hh"
  38
  39 struct stat_sdb_t;
  40
  41 //
  42 //
  43 //  A simple saturating counter predictor
  44 //
  45 //
  46 class SaturatingCounterPred : public GenericPredictor
  47 {
  48   private:
  49     std::string   pred_name;
  50     std::string   zero_name;
  51     std::string   one_name;
  52
  53     unsigned index_bits;
  54     unsigned counter_bits;
  55     unsigned zero_change;
  56     unsigned one_change;
  57     unsigned thresh;
  58     unsigned init_value;
  59
  60     unsigned max_value;       // maximum counter value
  61
  62     unsigned long max_index;  // also the index mask value
  63     unsigned *table;
  64
  65     //  Statistics
  66     Statistics::Scalar<> predicted_one;      // Total predictions of one, preds_one
  67     Statistics::Scalar<> predicted_zero;     // Total predictions of zero, preds_zero
  68     Statistics::Scalar<> correct_pred_one;   // Total correct predictions of one, correct_one
  69     Statistics::Scalar<> correct_pred_zero;  // Total correct predictions of zero, correct_zero
  70
  71     Statistics::Scalar<> record_zero;        //updates_zero
  72     Statistics::Scalar<> record_one;         //updates_one
  73
  74     Statistics::Formula preds_total;
  75     Statistics::Formula pred_frac_zero;
  76     Statistics::Formula pred_frac_one;
  77     Statistics::Formula correct_total;
  78     Statistics::Formula updates_total;
  79     Statistics::Formula pred_rate;
  80     Statistics::Formula frac_correct_zero;
  81     Statistics::Formula frac_correct_one;
  82     Statistics::Formula coverage_zero;
  83     Statistics::Formula coverage_one;
  84
  85   private:
  86     bool pred_one(unsigned &counter)  { return counter >  thresh; }
  87     bool pred_zero(unsigned &counter) { return counter <= thresh; }
  88
  89     void update_one(unsigned &counter) {
  90
  91         if (one_change)
  92             counter += one_change;
  93         else
  94             counter = 0;
  95
  96         // check for wrap
  97         if (counter > max_value)
  98             counter = max_value;
  99     }
 100
 101     void update_zero(unsigned &counter) {
 102         if (zero_change) {
 103             // check for wrap
 104             if (counter < zero_change)
 105                 counter = 0;
 106             else
 107                 counter -= zero_change;
 108         } else
 109             counter = 0;
 110     }
 111
 112
 113   public:
 114
 115     SaturatingCounterPred(std::string p_name,
 116                           std::string z_name, std::string o_name,
 117                           unsigned _index_bits, unsigned _counter_bits = 2,
 118                           unsigned _zero_change = 1, unsigned _one_change = 1,
 119                           unsigned _thresh = 1, unsigned _init_value = 0);
 120
 121     void clear() {
 122         for (int i = 0; i <= max_index; ++i)
 123             table[i] = init_value;
 124     }
 125
 126     //  Record the ACTUAL result... and indicate whether the prediction
 127     //  corresponding to this event was correct
 128     void record(unsigned long _index, unsigned _val, unsigned _predicted,
 129                 unsigned _pdata)
 130     {
 131         record(_index, _val, _predicted);
 132     }
 133
 134     void record(unsigned long _index, unsigned _val, unsigned _predicted) {
 135         unsigned long index = _index & max_index;
 136
 137         if (_val) {
 138             update_one(table[index]);
 139             ++record_one;
 140
 141             if (_predicted)
 142                 ++correct_pred_one;
 143         } else {
 144             update_zero(table[index]);
 145             ++record_zero;
 146
 147             if (!_predicted)
 148                 ++correct_pred_zero;
 149         }
 150     }
 151
 152     unsigned value(unsigned long _index) {
 153         unsigned long index = _index & max_index;
 154
 155         return table[index];
 156     }
 157
 158
 159     unsigned predict(unsigned long _index, unsigned &pdata) {
 160         return predict(_index);
 161     }
 162
 163     unsigned predict(unsigned long _index) {
 164         unsigned long index = _index & max_index;
 165
 166         if (pred_one(table[index])) {
 167             ++predicted_one;
 168             return 1;
 169         }
 170
 171         ++predicted_zero;
 172         return 0;
 173     }
 174
 175     //  No internal state is changed here
 176     unsigned peek(unsigned long _index) {
 177         unsigned long index = _index & max_index;
 178
 179         if (pred_one(table[index]))
 180             return 1;
 181
 182         return 0;
 183     }
 184
 185
 186     //=======================================================
 187     void regStats();
 188     void regFormulas();
 189 };
 190
 191
 192 #endif // __SAT_COUNTER_HH__