base/sat_counter.hh

   1 /*
   2  * Copyright (c) 2001-2005 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 __SAT_COUNTER_HH__
  30 #define __SAT_COUNTER_HH__
  31
  32 #include <string>
  33
  34 #include "base/predictor.hh"
  35
  36 #include "base/statistics.hh"
  37 #include "sim/stats.hh"
  38
  39 //
  40 //
  41 //  A simple saturating counter predictor
  42 //
  43 //
  44 class SaturatingCounterPred : public GenericPredictor
  45 {
  46   private:
  47     std::string   pred_name;
  48     std::string   zero_name;
  49     std::string   one_name;
  50
  51     unsigned index_bits;
  52     unsigned counter_bits;
  53     unsigned zero_change;
  54     unsigned one_change;
  55     unsigned thresh;
  56     unsigned init_value;
  57
  58     unsigned max_value;       // maximum counter value
  59
  60     unsigned long max_index;  // also the index mask value
  61     unsigned *table;
  62
  63     //  Statistics
  64     Stats::Scalar<> predicted_one;      // Total predictions of one, preds_one
  65     Stats::Scalar<> predicted_zero;     // Total predictions of zero, preds_zero
  66     Stats::Scalar<> correct_pred_one;   // Total correct predictions of one, correct_one
  67     Stats::Scalar<> correct_pred_zero;  // Total correct predictions of zero, correct_zero
  68
  69     Stats::Scalar<> record_zero;        //updates_zero
  70     Stats::Scalar<> record_one;         //updates_one
  71
  72     Stats::Formula preds_total;
  73     Stats::Formula pred_frac_zero;
  74     Stats::Formula pred_frac_one;
  75     Stats::Formula correct_total;
  76     Stats::Formula updates_total;
  77     Stats::Formula pred_rate;
  78     Stats::Formula frac_correct_zero;
  79     Stats::Formula frac_correct_one;
  80     Stats::Formula coverage_zero;
  81     Stats::Formula coverage_one;
  82
  83   private:
  84     bool pred_one(unsigned &counter)  { return counter >  thresh; }
  85     bool pred_zero(unsigned &counter) { return counter <= thresh; }
  86
  87     void update_one(unsigned &counter) {
  88
  89         if (one_change)
  90             counter += one_change;
  91         else
  92             counter = 0;
  93
  94         // check for wrap
  95         if (counter > max_value)
  96             counter = max_value;
  97     }
  98
  99     void update_zero(unsigned &counter) {
 100         if (zero_change) {
 101             // check for wrap
 102             if (counter < zero_change)
 103                 counter = 0;
 104             else
 105                 counter -= zero_change;
 106         } else
 107             counter = 0;
 108     }
 109
 110
 111   public:
 112
 113     SaturatingCounterPred(std::string p_name,
 114                           std::string z_name, std::string o_name,
 115                           unsigned _index_bits, unsigned _counter_bits = 2,
 116                           unsigned _zero_change = 1, unsigned _one_change = 1,
 117                           unsigned _thresh = 1, unsigned _init_value = 0);
 118
 119     void clear() {
 120         for (int i = 0; i <= max_index; ++i)
 121             table[i] = init_value;
 122     }
 123
 124     //  Record the ACTUAL result... and indicate whether the prediction
 125     //  corresponding to this event was correct
 126     void record(unsigned long _index, unsigned _val, unsigned _predicted,
 127                 unsigned _pdata)
 128     {
 129         record(_index, _val, _predicted);
 130     }
 131
 132     void record(unsigned long _index, unsigned _val, unsigned _predicted) {
 133         unsigned long index = _index & max_index;
 134
 135         if (_val) {
 136             update_one(table[index]);
 137             ++record_one;
 138
 139             if (_predicted)
 140                 ++correct_pred_one;
 141         } else {
 142             update_zero(table[index]);
 143             ++record_zero;
 144
 145             if (!_predicted)
 146                 ++correct_pred_zero;
 147         }
 148     }
 149
 150     unsigned value(unsigned long _index) {
 151         unsigned long index = _index & max_index;
 152
 153         return table[index];
 154     }
 155
 156
 157     unsigned predict(unsigned long _index, unsigned &pdata) {
 158         return predict(_index);
 159     }
 160
 161     unsigned predict(unsigned long _index) {
 162         unsigned long index = _index & max_index;
 163
 164         if (pred_one(table[index])) {
 165             ++predicted_one;
 166             return 1;
 167         }
 168
 169         ++predicted_zero;
 170         return 0;
 171     }
 172
 173     //  No internal state is changed here
 174     unsigned peek(unsigned long _index) {
 175         unsigned long index = _index & max_index;
 176
 177         if (pred_one(table[index]))
 178             return 1;
 179
 180         return 0;
 181     }
 182
 183
 184     //=======================================================
 185     void regStats();
 186     void regFormulas();
 187 };
 188
 189
 190 #endif // __SAT_COUNTER_HH__