sat_counter.hh revision 2632:1bb2f91485ea 
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//
44class 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__
191