sat_counter.hh revision 2665:a124942bacb8 
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 * Authors: Steve Raasch
29 *          Steve Reinhardt
30 */
31
32#ifndef __SAT_COUNTER_HH__
33#define __SAT_COUNTER_HH__
34
35#include <string>
36
37#include "base/predictor.hh"
38
39#include "base/statistics.hh"
40#include "sim/stats.hh"
41
42//
43//
44//  A simple saturating counter predictor
45//
46//
47class SaturatingCounterPred : public GenericPredictor
48{
49  private:
50    std::string   pred_name;
51    std::string   zero_name;
52    std::string   one_name;
53
54    unsigned index_bits;
55    unsigned counter_bits;
56    unsigned zero_change;
57    unsigned one_change;
58    unsigned thresh;
59    unsigned init_value;
60
61    unsigned max_value;       // maximum counter value
62
63    unsigned long max_index;  // also the index mask value
64    unsigned *table;
65
66    //  Statistics
67    Stats::Scalar<> predicted_one;      // Total predictions of one, preds_one
68    Stats::Scalar<> predicted_zero;     // Total predictions of zero, preds_zero
69    Stats::Scalar<> correct_pred_one;   // Total correct predictions of one, correct_one
70    Stats::Scalar<> correct_pred_zero;  // Total correct predictions of zero, correct_zero
71
72    Stats::Scalar<> record_zero;        //updates_zero
73    Stats::Scalar<> record_one;         //updates_one
74
75    Stats::Formula preds_total;
76    Stats::Formula pred_frac_zero;
77    Stats::Formula pred_frac_one;
78    Stats::Formula correct_total;
79    Stats::Formula updates_total;
80    Stats::Formula pred_rate;
81    Stats::Formula frac_correct_zero;
82    Stats::Formula frac_correct_one;
83    Stats::Formula coverage_zero;
84    Stats::Formula coverage_one;
85
86  private:
87    bool pred_one(unsigned &counter)  { return counter >  thresh; }
88    bool pred_zero(unsigned &counter) { return counter <= thresh; }
89
90    void update_one(unsigned &counter) {
91
92        if (one_change)
93            counter += one_change;
94        else
95            counter = 0;
96
97        // check for wrap
98        if (counter > max_value)
99            counter = max_value;
100    }
101
102    void update_zero(unsigned &counter) {
103        if (zero_change) {
104            // check for wrap
105            if (counter < zero_change)
106                counter = 0;
107            else
108                counter -= zero_change;
109        } else
110            counter = 0;
111    }
112
113
114  public:
115
116    SaturatingCounterPred(std::string p_name,
117                          std::string z_name, std::string o_name,
118                          unsigned _index_bits, unsigned _counter_bits = 2,
119                          unsigned _zero_change = 1, unsigned _one_change = 1,
120                          unsigned _thresh = 1, unsigned _init_value = 0);
121
122    void clear() {
123        for (int i = 0; i <= max_index; ++i)
124            table[i] = init_value;
125    }
126
127    //  Record the ACTUAL result... and indicate whether the prediction
128    //  corresponding to this event was correct
129    void record(unsigned long _index, unsigned _val, unsigned _predicted,
130                unsigned _pdata)
131    {
132        record(_index, _val, _predicted);
133    }
134
135    void record(unsigned long _index, unsigned _val, unsigned _predicted) {
136        unsigned long index = _index & max_index;
137
138        if (_val) {
139            update_one(table[index]);
140            ++record_one;
141
142            if (_predicted)
143                ++correct_pred_one;
144        } else {
145            update_zero(table[index]);
146            ++record_zero;
147
148            if (!_predicted)
149                ++correct_pred_zero;
150        }
151    }
152
153    unsigned value(unsigned long _index) {
154        unsigned long index = _index & max_index;
155
156        return table[index];
157    }
158
159
160    unsigned predict(unsigned long _index, unsigned &pdata) {
161        return predict(_index);
162    }
163
164    unsigned predict(unsigned long _index) {
165        unsigned long index = _index & max_index;
166
167        if (pred_one(table[index])) {
168            ++predicted_one;
169            return 1;
170        }
171
172        ++predicted_zero;
173        return 0;
174    }
175
176    //  No internal state is changed here
177    unsigned peek(unsigned long _index) {
178        unsigned long index = _index & max_index;
179
180        if (pred_one(table[index]))
181            return 1;
182
183        return 0;
184    }
185
186
187    //=======================================================
188    void regStats();
189    void regFormulas();
190};
191
192
193#endif // __SAT_COUNTER_HH__
194