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 */
42
43#include "base/bitfield.hh"
44#include "base/intmath.hh"
45#include "cpu/pred/tournament.hh"
46
47TournamentBP::TournamentBP(const TournamentBPParams *params)
48 : BPredUnit(params),
49 localPredictorSize(params->localPredictorSize),
50 localCtrBits(params->localCtrBits),
51 localHistoryTableSize(params->localHistoryTableSize),
52 localHistoryBits(ceilLog2(params->localPredictorSize)),
53 globalPredictorSize(params->globalPredictorSize),
54 globalCtrBits(params->globalCtrBits),
55 globalHistoryBits(
56 ceilLog2(params->globalPredictorSize) >
57 ceilLog2(params->choicePredictorSize) ?
58 ceilLog2(params->globalPredictorSize) :
59 ceilLog2(params->choicePredictorSize)),
60 choicePredictorSize(params->choicePredictorSize),
61 choiceCtrBits(params->choiceCtrBits)
62{
63 if (!isPowerOf2(localPredictorSize)) {
64 fatal("Invalid local predictor size!\n");
65 }
66
67 if (!isPowerOf2(globalPredictorSize)) {
68 fatal("Invalid global predictor size!\n");
69 }
70
71 //Set up the array of counters for the local predictor
72 localCtrs.resize(localPredictorSize);
73
74 for (int i = 0; i < localPredictorSize; ++i)
75 localCtrs[i].setBits(localCtrBits);
76
77 localPredictorMask = mask(localHistoryBits);
78
79 if (!isPowerOf2(localHistoryTableSize)) {
80 fatal("Invalid local history table size!\n");
81 }
82
83 //Setup the history table for the local table
84 localHistoryTable.resize(localHistoryTableSize);
85
86 for (int i = 0; i < localHistoryTableSize; ++i)
87 localHistoryTable[i] = 0;
88
89 //Setup the array of counters for the global predictor
90 globalCtrs.resize(globalPredictorSize);
91
92 for (int i = 0; i < globalPredictorSize; ++i)
93 globalCtrs[i].setBits(globalCtrBits);
94
95 //Clear the global history
96 globalHistory = 0;
97 // Set up the global history mask
98 // this is equivalent to mask(log2(globalPredictorSize)
99 globalHistoryMask = globalPredictorSize - 1;
100
101 if (!isPowerOf2(choicePredictorSize)) {
102 fatal("Invalid choice predictor size!\n");
103 }
104
105 // Set up choiceHistoryMask
106 // this is equivalent to mask(log2(choicePredictorSize)
107 choiceHistoryMask = choicePredictorSize - 1;
108
109 //Setup the array of counters for the choice predictor
110 choiceCtrs.resize(choicePredictorSize);
111
112 for (int i = 0; i < choicePredictorSize; ++i)
113 choiceCtrs[i].setBits(choiceCtrBits);
114
115 //Set up historyRegisterMask
116 historyRegisterMask = mask(globalHistoryBits);
117
118 //Check that predictors don't use more bits than they have available
119 if (globalHistoryMask > historyRegisterMask) {
120 fatal("Global predictor too large for global history bits!\n");
121 }
122 if (choiceHistoryMask > historyRegisterMask) {
123 fatal("Choice predictor too large for global history bits!\n");
124 }
125
126 if (globalHistoryMask < historyRegisterMask &&
127 choiceHistoryMask < historyRegisterMask) {
128 inform("More global history bits than required by predictors\n");
129 }
130
131 // Set thresholds for the three predictors' counters
132 // This is equivalent to (2^(Ctr))/2 - 1
133 localThreshold = (ULL(1) << (localCtrBits - 1)) - 1;
134 globalThreshold = (ULL(1) << (globalCtrBits - 1)) - 1;
135 choiceThreshold = (ULL(1) << (choiceCtrBits - 1)) - 1;
136}
137
138inline
139unsigned
140TournamentBP::calcLocHistIdx(Addr &branch_addr)
141{
142 // Get low order bits after removing instruction offset.
143 return (branch_addr >> instShiftAmt) & (localHistoryTableSize - 1);
144}
145
146inline
147void
148TournamentBP::updateGlobalHistTaken()
149{
150 globalHistory = (globalHistory << 1) | 1;
151 globalHistory = globalHistory & historyRegisterMask;
152}
153
154inline
155void
156TournamentBP::updateGlobalHistNotTaken()
157{
158 globalHistory = (globalHistory << 1);
159 globalHistory = globalHistory & historyRegisterMask;
160}
161
162inline
163void
164TournamentBP::updateLocalHistTaken(unsigned local_history_idx)
165{
166 localHistoryTable[local_history_idx] =
167 (localHistoryTable[local_history_idx] << 1) | 1;
168}
169
170inline
171void
172TournamentBP::updateLocalHistNotTaken(unsigned local_history_idx)
173{
174 localHistoryTable[local_history_idx] =
175 (localHistoryTable[local_history_idx] << 1);
176}
177
178
179void
180TournamentBP::btbUpdate(Addr branch_addr, void * &bp_history)
181{
182 unsigned local_history_idx = calcLocHistIdx(branch_addr);
183 //Update Global History to Not Taken (clear LSB)
184 globalHistory &= (historyRegisterMask & ~ULL(1));
185 //Update Local History to Not Taken
186 localHistoryTable[local_history_idx] =
187 localHistoryTable[local_history_idx] & (localPredictorMask & ~ULL(1));
188}
189
190bool
191TournamentBP::lookup(Addr branch_addr, void * &bp_history)
192{
193 bool local_prediction;
194 unsigned local_history_idx;
195 unsigned local_predictor_idx;
196
197 bool global_prediction;
198 bool choice_prediction;
199
200 //Lookup in the local predictor to get its branch prediction
201 local_history_idx = calcLocHistIdx(branch_addr);
202 local_predictor_idx = localHistoryTable[local_history_idx]
203 & localPredictorMask;
204 local_prediction = localCtrs[local_predictor_idx].read() > localThreshold;
205
206 //Lookup in the global predictor to get its branch prediction
207 global_prediction =
208 globalCtrs[globalHistory & globalHistoryMask].read() > globalThreshold;
209
210 //Lookup in the choice predictor to see which one to use
211 choice_prediction =
212 choiceCtrs[globalHistory & choiceHistoryMask].read() > choiceThreshold;
213
214 // Create BPHistory and pass it back to be recorded.
215 BPHistory *history = new BPHistory;
216 history->globalHistory = globalHistory;
217 history->localPredTaken = local_prediction;
218 history->globalPredTaken = global_prediction;
219 history->globalUsed = choice_prediction;
220 history->localHistoryIdx = local_history_idx;
221 history->localHistory = local_predictor_idx;
222 bp_history = (void *)history;
223
224 assert(local_history_idx < localHistoryTableSize);
225
226 // Commented code is for doing speculative update of counters and
227 // all histories.
228 if (choice_prediction) {
229 if (global_prediction) {
230 updateGlobalHistTaken();
231 updateLocalHistTaken(local_history_idx);
232 return true;
233 } else {
234 updateGlobalHistNotTaken();
235 updateLocalHistNotTaken(local_history_idx);
236 return false;
237 }
238 } else {
239 if (local_prediction) {
240 updateGlobalHistTaken();
241 updateLocalHistTaken(local_history_idx);
242 return true;
243 } else {
244 updateGlobalHistNotTaken();
245 updateLocalHistNotTaken(local_history_idx);
246 return false;
247 }
248 }
249}
250
251void
252TournamentBP::uncondBranch(Addr pc, void * &bp_history)
253{
254 // Create BPHistory and pass it back to be recorded.
255 BPHistory *history = new BPHistory;
256 history->globalHistory = globalHistory;
257 history->localPredTaken = true;
258 history->globalPredTaken = true;
259 history->globalUsed = true;
260 history->localHistoryIdx = invalidPredictorIndex;
261 history->localHistory = invalidPredictorIndex;
262 bp_history = static_cast<void *>(history);
263
264 updateGlobalHistTaken();
265}
266
267void
268TournamentBP::update(Addr branch_addr, bool taken, void *bp_history,
269 bool squashed)
270{
271 unsigned local_history_idx;
272 unsigned local_predictor_idx M5_VAR_USED;
273 unsigned local_predictor_hist;
274
275 // Get the local predictor's current prediction
276 local_history_idx = calcLocHistIdx(branch_addr);
277 local_predictor_hist = localHistoryTable[local_history_idx];
278 local_predictor_idx = local_predictor_hist & localPredictorMask;
279
280 if (bp_history) {
281 BPHistory *history = static_cast<BPHistory *>(bp_history);
282 // Update may also be called if the Branch target is incorrect even if
283 // the prediction is correct. In that case do not update the counters.
284 bool historyPred = false;
285 unsigned old_local_pred_index = history->localHistory &
286 localPredictorMask;
287
288 bool old_local_pred_valid = history->localHistory !=
289 invalidPredictorIndex;
290
291 assert(old_local_pred_index < localPredictorSize);
292
293 if (history->globalUsed) {
294 historyPred = history->globalPredTaken;
295 } else {
296 historyPred = history->localPredTaken;
297 }
298 if (historyPred != taken || !squashed) {
299 // Update the choice predictor to tell it which one was correct if
300 // there was a prediction.
301 if (history->localPredTaken != history->globalPredTaken) {
302 // If the local prediction matches the actual outcome,
303 // decerement the counter. Otherwise increment the
304 // counter.
305 unsigned choice_predictor_idx =
306 history->globalHistory & choiceHistoryMask;
307 if (history->localPredTaken == taken) {
308 choiceCtrs[choice_predictor_idx].decrement();
309 } else if (history->globalPredTaken == taken) {
310 choiceCtrs[choice_predictor_idx].increment();
311 }
312
313 }
314
315 // Update the counters and local history with the proper
316 // resolution of the branch. Global history is updated
317 // speculatively and restored upon squash() calls, so it does not
318 // need to be updated.
319 unsigned global_predictor_idx =
320 history->globalHistory & globalHistoryMask;
321 if (taken) {
322 globalCtrs[global_predictor_idx].increment();
323 if (old_local_pred_valid) {
324 localCtrs[old_local_pred_index].increment();
325 }
326 } else {
327 globalCtrs[global_predictor_idx].decrement();
328 if (old_local_pred_valid) {
329 localCtrs[old_local_pred_index].decrement();
330 }
331 }
332 }
333 if (squashed) {
334 if (taken) {
335 globalHistory = (history->globalHistory << 1) | 1;
336 globalHistory = globalHistory & historyRegisterMask;
337 if (old_local_pred_valid) {
338 localHistoryTable[local_history_idx] =
339 (history->localHistory << 1) | 1;
340 }
341 } else {
342 globalHistory = (history->globalHistory << 1);
343 globalHistory = globalHistory & historyRegisterMask;
344 if (old_local_pred_valid) {
345 localHistoryTable[local_history_idx] =
346 history->localHistory << 1;
347 }
348 }
349
350 } else {
351 // We're done with this history, now delete it.
352 delete history;
353 }
354 }
355
356 assert(local_history_idx < localHistoryTableSize);
357
358
359}
360
361void
362TournamentBP::retireSquashed(void *bp_history)
363{
364 BPHistory *history = static_cast<BPHistory *>(bp_history);
365 delete history;
366}
367
368void
369TournamentBP::squash(void *bp_history)
370{
371 BPHistory *history = static_cast<BPHistory *>(bp_history);
372
373 // Restore global history to state prior to this branch.
374 globalHistory = history->globalHistory;
375
376 // Restore local history
377 if (history->localHistoryIdx != invalidPredictorIndex) {
378 localHistoryTable[history->localHistoryIdx] = history->localHistory;
379 }
380
381 // Delete this BPHistory now that we're done with it.
382 delete history;
383}
384
385TournamentBP*
386TournamentBPParams::create()
387{
388 return new TournamentBP(this);
389}
390
| 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 */
42
43#include "base/bitfield.hh"
44#include "base/intmath.hh"
45#include "cpu/pred/tournament.hh"
46
47TournamentBP::TournamentBP(const TournamentBPParams *params)
48 : BPredUnit(params),
49 localPredictorSize(params->localPredictorSize),
50 localCtrBits(params->localCtrBits),
51 localHistoryTableSize(params->localHistoryTableSize),
52 localHistoryBits(ceilLog2(params->localPredictorSize)),
53 globalPredictorSize(params->globalPredictorSize),
54 globalCtrBits(params->globalCtrBits),
55 globalHistoryBits(
56 ceilLog2(params->globalPredictorSize) >
57 ceilLog2(params->choicePredictorSize) ?
58 ceilLog2(params->globalPredictorSize) :
59 ceilLog2(params->choicePredictorSize)),
60 choicePredictorSize(params->choicePredictorSize),
61 choiceCtrBits(params->choiceCtrBits)
62{
63 if (!isPowerOf2(localPredictorSize)) {
64 fatal("Invalid local predictor size!\n");
65 }
66
67 if (!isPowerOf2(globalPredictorSize)) {
68 fatal("Invalid global predictor size!\n");
69 }
70
71 //Set up the array of counters for the local predictor
72 localCtrs.resize(localPredictorSize);
73
74 for (int i = 0; i < localPredictorSize; ++i)
75 localCtrs[i].setBits(localCtrBits);
76
77 localPredictorMask = mask(localHistoryBits);
78
79 if (!isPowerOf2(localHistoryTableSize)) {
80 fatal("Invalid local history table size!\n");
81 }
82
83 //Setup the history table for the local table
84 localHistoryTable.resize(localHistoryTableSize);
85
86 for (int i = 0; i < localHistoryTableSize; ++i)
87 localHistoryTable[i] = 0;
88
89 //Setup the array of counters for the global predictor
90 globalCtrs.resize(globalPredictorSize);
91
92 for (int i = 0; i < globalPredictorSize; ++i)
93 globalCtrs[i].setBits(globalCtrBits);
94
95 //Clear the global history
96 globalHistory = 0;
97 // Set up the global history mask
98 // this is equivalent to mask(log2(globalPredictorSize)
99 globalHistoryMask = globalPredictorSize - 1;
100
101 if (!isPowerOf2(choicePredictorSize)) {
102 fatal("Invalid choice predictor size!\n");
103 }
104
105 // Set up choiceHistoryMask
106 // this is equivalent to mask(log2(choicePredictorSize)
107 choiceHistoryMask = choicePredictorSize - 1;
108
109 //Setup the array of counters for the choice predictor
110 choiceCtrs.resize(choicePredictorSize);
111
112 for (int i = 0; i < choicePredictorSize; ++i)
113 choiceCtrs[i].setBits(choiceCtrBits);
114
115 //Set up historyRegisterMask
116 historyRegisterMask = mask(globalHistoryBits);
117
118 //Check that predictors don't use more bits than they have available
119 if (globalHistoryMask > historyRegisterMask) {
120 fatal("Global predictor too large for global history bits!\n");
121 }
122 if (choiceHistoryMask > historyRegisterMask) {
123 fatal("Choice predictor too large for global history bits!\n");
124 }
125
126 if (globalHistoryMask < historyRegisterMask &&
127 choiceHistoryMask < historyRegisterMask) {
128 inform("More global history bits than required by predictors\n");
129 }
130
131 // Set thresholds for the three predictors' counters
132 // This is equivalent to (2^(Ctr))/2 - 1
133 localThreshold = (ULL(1) << (localCtrBits - 1)) - 1;
134 globalThreshold = (ULL(1) << (globalCtrBits - 1)) - 1;
135 choiceThreshold = (ULL(1) << (choiceCtrBits - 1)) - 1;
136}
137
138inline
139unsigned
140TournamentBP::calcLocHistIdx(Addr &branch_addr)
141{
142 // Get low order bits after removing instruction offset.
143 return (branch_addr >> instShiftAmt) & (localHistoryTableSize - 1);
144}
145
146inline
147void
148TournamentBP::updateGlobalHistTaken()
149{
150 globalHistory = (globalHistory << 1) | 1;
151 globalHistory = globalHistory & historyRegisterMask;
152}
153
154inline
155void
156TournamentBP::updateGlobalHistNotTaken()
157{
158 globalHistory = (globalHistory << 1);
159 globalHistory = globalHistory & historyRegisterMask;
160}
161
162inline
163void
164TournamentBP::updateLocalHistTaken(unsigned local_history_idx)
165{
166 localHistoryTable[local_history_idx] =
167 (localHistoryTable[local_history_idx] << 1) | 1;
168}
169
170inline
171void
172TournamentBP::updateLocalHistNotTaken(unsigned local_history_idx)
173{
174 localHistoryTable[local_history_idx] =
175 (localHistoryTable[local_history_idx] << 1);
176}
177
178
179void
180TournamentBP::btbUpdate(Addr branch_addr, void * &bp_history)
181{
182 unsigned local_history_idx = calcLocHistIdx(branch_addr);
183 //Update Global History to Not Taken (clear LSB)
184 globalHistory &= (historyRegisterMask & ~ULL(1));
185 //Update Local History to Not Taken
186 localHistoryTable[local_history_idx] =
187 localHistoryTable[local_history_idx] & (localPredictorMask & ~ULL(1));
188}
189
190bool
191TournamentBP::lookup(Addr branch_addr, void * &bp_history)
192{
193 bool local_prediction;
194 unsigned local_history_idx;
195 unsigned local_predictor_idx;
196
197 bool global_prediction;
198 bool choice_prediction;
199
200 //Lookup in the local predictor to get its branch prediction
201 local_history_idx = calcLocHistIdx(branch_addr);
202 local_predictor_idx = localHistoryTable[local_history_idx]
203 & localPredictorMask;
204 local_prediction = localCtrs[local_predictor_idx].read() > localThreshold;
205
206 //Lookup in the global predictor to get its branch prediction
207 global_prediction =
208 globalCtrs[globalHistory & globalHistoryMask].read() > globalThreshold;
209
210 //Lookup in the choice predictor to see which one to use
211 choice_prediction =
212 choiceCtrs[globalHistory & choiceHistoryMask].read() > choiceThreshold;
213
214 // Create BPHistory and pass it back to be recorded.
215 BPHistory *history = new BPHistory;
216 history->globalHistory = globalHistory;
217 history->localPredTaken = local_prediction;
218 history->globalPredTaken = global_prediction;
219 history->globalUsed = choice_prediction;
220 history->localHistoryIdx = local_history_idx;
221 history->localHistory = local_predictor_idx;
222 bp_history = (void *)history;
223
224 assert(local_history_idx < localHistoryTableSize);
225
226 // Commented code is for doing speculative update of counters and
227 // all histories.
228 if (choice_prediction) {
229 if (global_prediction) {
230 updateGlobalHistTaken();
231 updateLocalHistTaken(local_history_idx);
232 return true;
233 } else {
234 updateGlobalHistNotTaken();
235 updateLocalHistNotTaken(local_history_idx);
236 return false;
237 }
238 } else {
239 if (local_prediction) {
240 updateGlobalHistTaken();
241 updateLocalHistTaken(local_history_idx);
242 return true;
243 } else {
244 updateGlobalHistNotTaken();
245 updateLocalHistNotTaken(local_history_idx);
246 return false;
247 }
248 }
249}
250
251void
252TournamentBP::uncondBranch(Addr pc, void * &bp_history)
253{
254 // Create BPHistory and pass it back to be recorded.
255 BPHistory *history = new BPHistory;
256 history->globalHistory = globalHistory;
257 history->localPredTaken = true;
258 history->globalPredTaken = true;
259 history->globalUsed = true;
260 history->localHistoryIdx = invalidPredictorIndex;
261 history->localHistory = invalidPredictorIndex;
262 bp_history = static_cast<void *>(history);
263
264 updateGlobalHistTaken();
265}
266
267void
268TournamentBP::update(Addr branch_addr, bool taken, void *bp_history,
269 bool squashed)
270{
271 unsigned local_history_idx;
272 unsigned local_predictor_idx M5_VAR_USED;
273 unsigned local_predictor_hist;
274
275 // Get the local predictor's current prediction
276 local_history_idx = calcLocHistIdx(branch_addr);
277 local_predictor_hist = localHistoryTable[local_history_idx];
278 local_predictor_idx = local_predictor_hist & localPredictorMask;
279
280 if (bp_history) {
281 BPHistory *history = static_cast<BPHistory *>(bp_history);
282 // Update may also be called if the Branch target is incorrect even if
283 // the prediction is correct. In that case do not update the counters.
284 bool historyPred = false;
285 unsigned old_local_pred_index = history->localHistory &
286 localPredictorMask;
287
288 bool old_local_pred_valid = history->localHistory !=
289 invalidPredictorIndex;
290
291 assert(old_local_pred_index < localPredictorSize);
292
293 if (history->globalUsed) {
294 historyPred = history->globalPredTaken;
295 } else {
296 historyPred = history->localPredTaken;
297 }
298 if (historyPred != taken || !squashed) {
299 // Update the choice predictor to tell it which one was correct if
300 // there was a prediction.
301 if (history->localPredTaken != history->globalPredTaken) {
302 // If the local prediction matches the actual outcome,
303 // decerement the counter. Otherwise increment the
304 // counter.
305 unsigned choice_predictor_idx =
306 history->globalHistory & choiceHistoryMask;
307 if (history->localPredTaken == taken) {
308 choiceCtrs[choice_predictor_idx].decrement();
309 } else if (history->globalPredTaken == taken) {
310 choiceCtrs[choice_predictor_idx].increment();
311 }
312
313 }
314
315 // Update the counters and local history with the proper
316 // resolution of the branch. Global history is updated
317 // speculatively and restored upon squash() calls, so it does not
318 // need to be updated.
319 unsigned global_predictor_idx =
320 history->globalHistory & globalHistoryMask;
321 if (taken) {
322 globalCtrs[global_predictor_idx].increment();
323 if (old_local_pred_valid) {
324 localCtrs[old_local_pred_index].increment();
325 }
326 } else {
327 globalCtrs[global_predictor_idx].decrement();
328 if (old_local_pred_valid) {
329 localCtrs[old_local_pred_index].decrement();
330 }
331 }
332 }
333 if (squashed) {
334 if (taken) {
335 globalHistory = (history->globalHistory << 1) | 1;
336 globalHistory = globalHistory & historyRegisterMask;
337 if (old_local_pred_valid) {
338 localHistoryTable[local_history_idx] =
339 (history->localHistory << 1) | 1;
340 }
341 } else {
342 globalHistory = (history->globalHistory << 1);
343 globalHistory = globalHistory & historyRegisterMask;
344 if (old_local_pred_valid) {
345 localHistoryTable[local_history_idx] =
346 history->localHistory << 1;
347 }
348 }
349
350 } else {
351 // We're done with this history, now delete it.
352 delete history;
353 }
354 }
355
356 assert(local_history_idx < localHistoryTableSize);
357
358
359}
360
361void
362TournamentBP::retireSquashed(void *bp_history)
363{
364 BPHistory *history = static_cast<BPHistory *>(bp_history);
365 delete history;
366}
367
368void
369TournamentBP::squash(void *bp_history)
370{
371 BPHistory *history = static_cast<BPHistory *>(bp_history);
372
373 // Restore global history to state prior to this branch.
374 globalHistory = history->globalHistory;
375
376 // Restore local history
377 if (history->localHistoryIdx != invalidPredictorIndex) {
378 localHistoryTable[history->localHistoryIdx] = history->localHistory;
379 }
380
381 // Delete this BPHistory now that we're done with it.
382 delete history;
383}
384
385TournamentBP*
386TournamentBPParams::create()
387{
388 return new TournamentBP(this);
389}
390
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