1/*
2 * Copyright (c) 2011, 2014 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2004-2006 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Kevin Lim
41 * Timothy M. Jones
42 * Nilay Vaish
43 */
44
45#ifndef __CPU_PRED_TOURNAMENT_PRED_HH__
46#define __CPU_PRED_TOURNAMENT_PRED_HH__
47
48#include <vector>
49
50#include "base/types.hh"
51#include "cpu/pred/bpred_unit.hh"
52#include "cpu/pred/sat_counter.hh"
| 1/*
2 * Copyright (c) 2011, 2014 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Copyright (c) 2004-2006 The Regents of The University of Michigan
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions are
19 * met: redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer;
21 * redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution;
24 * neither the name of the copyright holders nor the names of its
25 * contributors may be used to endorse or promote products derived from
26 * this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
39 *
40 * Authors: Kevin Lim
41 * Timothy M. Jones
42 * Nilay Vaish
43 */
44
45#ifndef __CPU_PRED_TOURNAMENT_PRED_HH__
46#define __CPU_PRED_TOURNAMENT_PRED_HH__
47
48#include <vector>
49
50#include "base/types.hh"
51#include "cpu/pred/bpred_unit.hh"
52#include "cpu/pred/sat_counter.hh"
|
| 53#include "params/TournamentBP.hh"
|
53
54/**
55 * Implements a tournament branch predictor, hopefully identical to the one
56 * used in the 21264. It has a local predictor, which uses a local history
57 * table to index into a table of counters, and a global predictor, which
58 * uses a global history to index into a table of counters. A choice
59 * predictor chooses between the two. Only the global history register
60 * is speculatively updated, the rest are updated upon branches committing
61 * or misspeculating.
62 */
63class TournamentBP : public BPredUnit
64{
65 public:
66 /**
67 * Default branch predictor constructor.
68 */
| 54
55/**
56 * Implements a tournament branch predictor, hopefully identical to the one
57 * used in the 21264. It has a local predictor, which uses a local history
58 * table to index into a table of counters, and a global predictor, which
59 * uses a global history to index into a table of counters. A choice
60 * predictor chooses between the two. Only the global history register
61 * is speculatively updated, the rest are updated upon branches committing
62 * or misspeculating.
63 */
64class TournamentBP : public BPredUnit
65{
66 public:
67 /**
68 * Default branch predictor constructor.
69 */
|
69 TournamentBP(const Params *params);
| 70 TournamentBP(const TournamentBPParams *params);
|
70
71 /**
72 * Looks up the given address in the branch predictor and returns
73 * a true/false value as to whether it is taken. Also creates a
74 * BPHistory object to store any state it will need on squash/update.
75 * @param branch_addr The address of the branch to look up.
76 * @param bp_history Pointer that will be set to the BPHistory object.
77 * @return Whether or not the branch is taken.
78 */
79 bool lookup(Addr branch_addr, void * &bp_history);
80
81 /**
82 * Records that there was an unconditional branch, and modifies
83 * the bp history to point to an object that has the previous
84 * global history stored in it.
85 * @param bp_history Pointer that will be set to the BPHistory object.
86 */
| 71
72 /**
73 * Looks up the given address in the branch predictor and returns
74 * a true/false value as to whether it is taken. Also creates a
75 * BPHistory object to store any state it will need on squash/update.
76 * @param branch_addr The address of the branch to look up.
77 * @param bp_history Pointer that will be set to the BPHistory object.
78 * @return Whether or not the branch is taken.
79 */
80 bool lookup(Addr branch_addr, void * &bp_history);
81
82 /**
83 * Records that there was an unconditional branch, and modifies
84 * the bp history to point to an object that has the previous
85 * global history stored in it.
86 * @param bp_history Pointer that will be set to the BPHistory object.
87 */
|
87 void uncondBranch(void * &bp_history);
| 88 void uncondBranch(Addr pc, void * &bp_history);
|
88 /**
89 * Updates the branch predictor to Not Taken if a BTB entry is
90 * invalid or not found.
91 * @param branch_addr The address of the branch to look up.
92 * @param bp_history Pointer to any bp history state.
93 * @return Whether or not the branch is taken.
94 */
95 void btbUpdate(Addr branch_addr, void * &bp_history);
96 /**
97 * Updates the branch predictor with the actual result of a branch.
98 * @param branch_addr The address of the branch to update.
99 * @param taken Whether or not the branch was taken.
100 * @param bp_history Pointer to the BPHistory object that was created
101 * when the branch was predicted.
102 * @param squashed is set when this function is called during a squash
103 * operation.
104 */
105 void update(Addr branch_addr, bool taken, void *bp_history, bool squashed);
106
107 void retireSquashed(void *bp_history);
108
109 /**
110 * Restores the global branch history on a squash.
111 * @param bp_history Pointer to the BPHistory object that has the
112 * previous global branch history in it.
113 */
114 void squash(void *bp_history);
115
116 /** Returns the global history. */
117 inline unsigned readGlobalHist() { return globalHistory; }
118
119 private:
120 /**
121 * Returns if the branch should be taken or not, given a counter
122 * value.
123 * @param count The counter value.
124 */
125 inline bool getPrediction(uint8_t &count);
126
127 /**
128 * Returns the local history index, given a branch address.
129 * @param branch_addr The branch's PC address.
130 */
131 inline unsigned calcLocHistIdx(Addr &branch_addr);
132
133 /** Updates global history as taken. */
134 inline void updateGlobalHistTaken();
135
136 /** Updates global history as not taken. */
137 inline void updateGlobalHistNotTaken();
138
139 /**
140 * Updates local histories as taken.
141 * @param local_history_idx The local history table entry that
142 * will be updated.
143 */
144 inline void updateLocalHistTaken(unsigned local_history_idx);
145
146 /**
147 * Updates local histories as not taken.
148 * @param local_history_idx The local history table entry that
149 * will be updated.
150 */
151 inline void updateLocalHistNotTaken(unsigned local_history_idx);
152
153 /**
154 * The branch history information that is created upon predicting
155 * a branch. It will be passed back upon updating and squashing,
156 * when the BP can use this information to update/restore its
157 * state properly.
158 */
159 struct BPHistory {
160#ifdef DEBUG
161 BPHistory()
162 { newCount++; }
163 ~BPHistory()
164 { newCount--; }
165
166 static int newCount;
167#endif
168 unsigned globalHistory;
169 unsigned localHistory;
170 bool localPredTaken;
171 bool globalPredTaken;
172 bool globalUsed;
173 };
174
175 /** Flag for invalid predictor index */
176 static const int invalidPredictorIndex = -1;
177 /** Local counters. */
178 std::vector<SatCounter> localCtrs;
179
180 /** Number of counters in the local predictor. */
181 unsigned localPredictorSize;
182
183 /** Mask to truncate values stored in the local history table. */
184 unsigned localPredictorMask;
185
186 /** Number of bits of the local predictor's counters. */
187 unsigned localCtrBits;
188
189 /** Array of local history table entries. */
190 std::vector<unsigned> localHistoryTable;
191
192 /** Number of entries in the local history table. */
193 unsigned localHistoryTableSize;
194
195 /** Number of bits for each entry of the local history table. */
196 unsigned localHistoryBits;
197
198 /** Array of counters that make up the global predictor. */
199 std::vector<SatCounter> globalCtrs;
200
201 /** Number of entries in the global predictor. */
202 unsigned globalPredictorSize;
203
204 /** Number of bits of the global predictor's counters. */
205 unsigned globalCtrBits;
206
207 /** Global history register. Contains as much history as specified by
208 * globalHistoryBits. Actual number of bits used is determined by
209 * globalHistoryMask and choiceHistoryMask. */
210 unsigned globalHistory;
211
212 /** Number of bits for the global history. Determines maximum number of
213 entries in global and choice predictor tables. */
214 unsigned globalHistoryBits;
215
216 /** Mask to apply to globalHistory to access global history table.
217 * Based on globalPredictorSize.*/
218 unsigned globalHistoryMask;
219
220 /** Mask to apply to globalHistory to access choice history table.
221 * Based on choicePredictorSize.*/
222 unsigned choiceHistoryMask;
223
224 /** Mask to control how much history is stored. All of it might not be
225 * used. */
226 unsigned historyRegisterMask;
227
228 /** Array of counters that make up the choice predictor. */
229 std::vector<SatCounter> choiceCtrs;
230
231 /** Number of entries in the choice predictor. */
232 unsigned choicePredictorSize;
233
234 /** Number of bits in the choice predictor's counters. */
235 unsigned choiceCtrBits;
236
| 89 /**
90 * Updates the branch predictor to Not Taken if a BTB entry is
91 * invalid or not found.
92 * @param branch_addr The address of the branch to look up.
93 * @param bp_history Pointer to any bp history state.
94 * @return Whether or not the branch is taken.
95 */
96 void btbUpdate(Addr branch_addr, void * &bp_history);
97 /**
98 * Updates the branch predictor with the actual result of a branch.
99 * @param branch_addr The address of the branch to update.
100 * @param taken Whether or not the branch was taken.
101 * @param bp_history Pointer to the BPHistory object that was created
102 * when the branch was predicted.
103 * @param squashed is set when this function is called during a squash
104 * operation.
105 */
106 void update(Addr branch_addr, bool taken, void *bp_history, bool squashed);
107
108 void retireSquashed(void *bp_history);
109
110 /**
111 * Restores the global branch history on a squash.
112 * @param bp_history Pointer to the BPHistory object that has the
113 * previous global branch history in it.
114 */
115 void squash(void *bp_history);
116
117 /** Returns the global history. */
118 inline unsigned readGlobalHist() { return globalHistory; }
119
120 private:
121 /**
122 * Returns if the branch should be taken or not, given a counter
123 * value.
124 * @param count The counter value.
125 */
126 inline bool getPrediction(uint8_t &count);
127
128 /**
129 * Returns the local history index, given a branch address.
130 * @param branch_addr The branch's PC address.
131 */
132 inline unsigned calcLocHistIdx(Addr &branch_addr);
133
134 /** Updates global history as taken. */
135 inline void updateGlobalHistTaken();
136
137 /** Updates global history as not taken. */
138 inline void updateGlobalHistNotTaken();
139
140 /**
141 * Updates local histories as taken.
142 * @param local_history_idx The local history table entry that
143 * will be updated.
144 */
145 inline void updateLocalHistTaken(unsigned local_history_idx);
146
147 /**
148 * Updates local histories as not taken.
149 * @param local_history_idx The local history table entry that
150 * will be updated.
151 */
152 inline void updateLocalHistNotTaken(unsigned local_history_idx);
153
154 /**
155 * The branch history information that is created upon predicting
156 * a branch. It will be passed back upon updating and squashing,
157 * when the BP can use this information to update/restore its
158 * state properly.
159 */
160 struct BPHistory {
161#ifdef DEBUG
162 BPHistory()
163 { newCount++; }
164 ~BPHistory()
165 { newCount--; }
166
167 static int newCount;
168#endif
169 unsigned globalHistory;
170 unsigned localHistory;
171 bool localPredTaken;
172 bool globalPredTaken;
173 bool globalUsed;
174 };
175
176 /** Flag for invalid predictor index */
177 static const int invalidPredictorIndex = -1;
178 /** Local counters. */
179 std::vector<SatCounter> localCtrs;
180
181 /** Number of counters in the local predictor. */
182 unsigned localPredictorSize;
183
184 /** Mask to truncate values stored in the local history table. */
185 unsigned localPredictorMask;
186
187 /** Number of bits of the local predictor's counters. */
188 unsigned localCtrBits;
189
190 /** Array of local history table entries. */
191 std::vector<unsigned> localHistoryTable;
192
193 /** Number of entries in the local history table. */
194 unsigned localHistoryTableSize;
195
196 /** Number of bits for each entry of the local history table. */
197 unsigned localHistoryBits;
198
199 /** Array of counters that make up the global predictor. */
200 std::vector<SatCounter> globalCtrs;
201
202 /** Number of entries in the global predictor. */
203 unsigned globalPredictorSize;
204
205 /** Number of bits of the global predictor's counters. */
206 unsigned globalCtrBits;
207
208 /** Global history register. Contains as much history as specified by
209 * globalHistoryBits. Actual number of bits used is determined by
210 * globalHistoryMask and choiceHistoryMask. */
211 unsigned globalHistory;
212
213 /** Number of bits for the global history. Determines maximum number of
214 entries in global and choice predictor tables. */
215 unsigned globalHistoryBits;
216
217 /** Mask to apply to globalHistory to access global history table.
218 * Based on globalPredictorSize.*/
219 unsigned globalHistoryMask;
220
221 /** Mask to apply to globalHistory to access choice history table.
222 * Based on choicePredictorSize.*/
223 unsigned choiceHistoryMask;
224
225 /** Mask to control how much history is stored. All of it might not be
226 * used. */
227 unsigned historyRegisterMask;
228
229 /** Array of counters that make up the choice predictor. */
230 std::vector<SatCounter> choiceCtrs;
231
232 /** Number of entries in the choice predictor. */
233 unsigned choicePredictorSize;
234
235 /** Number of bits in the choice predictor's counters. */
236 unsigned choiceCtrBits;
237
|
237 /** Number of bits to shift the instruction over to get rid of the word
238 * offset.
239 */
240 unsigned instShiftAmt;
241
| |
242 /** Thresholds for the counter value; above the threshold is taken,
243 * equal to or below the threshold is not taken.
244 */
245 unsigned localThreshold;
246 unsigned globalThreshold;
247 unsigned choiceThreshold;
248};
249
250#endif // __CPU_PRED_TOURNAMENT_PRED_HH__
| 238 /** Thresholds for the counter value; above the threshold is taken,
239 * equal to or below the threshold is not taken.
240 */
241 unsigned localThreshold;
242 unsigned globalThreshold;
243 unsigned choiceThreshold;
244};
245
246#endif // __CPU_PRED_TOURNAMENT_PRED_HH__
|