rob_impl.hh revision 7720:65d338a8dba4 
1/*
2 * Copyright (c) 2004-2006 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: Kevin Lim
29 *          Korey Sewell
30 */
31
32#include <list>
33
34#include "config/full_system.hh"
35#include "cpu/o3/rob.hh"
36
37using namespace std;
38
39template <class Impl>
40ROB<Impl>::ROB(O3CPU *_cpu, unsigned _numEntries, unsigned _squashWidth,
41               std::string _smtROBPolicy, unsigned _smtROBThreshold,
42               ThreadID _numThreads)
43    : cpu(_cpu),
44      numEntries(_numEntries),
45      squashWidth(_squashWidth),
46      numInstsInROB(0),
47      numThreads(_numThreads)
48{
49    for (ThreadID tid = 0; tid  < numThreads; tid++) {
50        squashedSeqNum[tid] = 0;
51        doneSquashing[tid] = true;
52        threadEntries[tid] = 0;
53    }
54
55    std::string policy = _smtROBPolicy;
56
57    //Convert string to lowercase
58    std::transform(policy.begin(), policy.end(), policy.begin(),
59                   (int(*)(int)) tolower);
60
61    //Figure out rob policy
62    if (policy == "dynamic") {
63        robPolicy = Dynamic;
64
65        //Set Max Entries to Total ROB Capacity
66        for (ThreadID tid = 0; tid < numThreads; tid++) {
67            maxEntries[tid] = numEntries;
68        }
69
70    } else if (policy == "partitioned") {
71        robPolicy = Partitioned;
72        DPRINTF(Fetch, "ROB sharing policy set to Partitioned\n");
73
74        //@todo:make work if part_amt doesnt divide evenly.
75        int part_amt = numEntries / numThreads;
76
77        //Divide ROB up evenly
78        for (ThreadID tid = 0; tid < numThreads; tid++) {
79            maxEntries[tid] = part_amt;
80        }
81
82    } else if (policy == "threshold") {
83        robPolicy = Threshold;
84        DPRINTF(Fetch, "ROB sharing policy set to Threshold\n");
85
86        int threshold =  _smtROBThreshold;;
87
88        //Divide up by threshold amount
89        for (ThreadID tid = 0; tid < numThreads; tid++) {
90            maxEntries[tid] = threshold;
91        }
92    } else {
93        assert(0 && "Invalid ROB Sharing Policy.Options Are:{Dynamic,"
94                    "Partitioned, Threshold}");
95    }
96
97    // Set the per-thread iterators to the end of the instruction list.
98    for (ThreadID tid = 0; tid < numThreads; tid++) {
99        squashIt[tid] = instList[tid].end();
100    }
101
102    // Initialize the "universal" ROB head & tail point to invalid
103    // pointers
104    head = instList[0].end();
105    tail = instList[0].end();
106}
107
108template <class Impl>
109std::string
110ROB<Impl>::name() const
111{
112    return cpu->name() + ".rob";
113}
114
115template <class Impl>
116void
117ROB<Impl>::setActiveThreads(list<ThreadID> *at_ptr)
118{
119    DPRINTF(ROB, "Setting active threads list pointer.\n");
120    activeThreads = at_ptr;
121}
122
123template <class Impl>
124void
125ROB<Impl>::switchOut()
126{
127    for (ThreadID tid = 0; tid < numThreads; tid++) {
128        instList[tid].clear();
129    }
130}
131
132template <class Impl>
133void
134ROB<Impl>::takeOverFrom()
135{
136    for (ThreadID tid = 0; tid  < numThreads; tid++) {
137        doneSquashing[tid] = true;
138        threadEntries[tid] = 0;
139        squashIt[tid] = instList[tid].end();
140    }
141    numInstsInROB = 0;
142
143    // Initialize the "universal" ROB head & tail point to invalid
144    // pointers
145    head = instList[0].end();
146    tail = instList[0].end();
147}
148
149template <class Impl>
150void
151ROB<Impl>::resetEntries()
152{
153    if (robPolicy != Dynamic || numThreads > 1) {
154        int active_threads = activeThreads->size();
155
156        list<ThreadID>::iterator threads = activeThreads->begin();
157        list<ThreadID>::iterator end = activeThreads->end();
158
159        while (threads != end) {
160            ThreadID tid = *threads++;
161
162            if (robPolicy == Partitioned) {
163                maxEntries[tid] = numEntries / active_threads;
164            } else if (robPolicy == Threshold && active_threads == 1) {
165                maxEntries[tid] = numEntries;
166            }
167        }
168    }
169}
170
171template <class Impl>
172int
173ROB<Impl>::entryAmount(ThreadID num_threads)
174{
175    if (robPolicy == Partitioned) {
176        return numEntries / num_threads;
177    } else {
178        return 0;
179    }
180}
181
182template <class Impl>
183int
184ROB<Impl>::countInsts()
185{
186    int total = 0;
187
188    for (ThreadID tid = 0; tid < numThreads; tid++)
189        total += countInsts(tid);
190
191    return total;
192}
193
194template <class Impl>
195int
196ROB<Impl>::countInsts(ThreadID tid)
197{
198    return instList[tid].size();
199}
200
201template <class Impl>
202void
203ROB<Impl>::insertInst(DynInstPtr &inst)
204{
205    assert(inst);
206
207    DPRINTF(ROB, "Adding inst PC %s to the ROB.\n", inst->pcState());
208
209    assert(numInstsInROB != numEntries);
210
211    ThreadID tid = inst->threadNumber;
212
213    instList[tid].push_back(inst);
214
215    //Set Up head iterator if this is the 1st instruction in the ROB
216    if (numInstsInROB == 0) {
217        head = instList[tid].begin();
218        assert((*head) == inst);
219    }
220
221    //Must Decrement for iterator to actually be valid  since __.end()
222    //actually points to 1 after the last inst
223    tail = instList[tid].end();
224    tail--;
225
226    inst->setInROB();
227
228    ++numInstsInROB;
229    ++threadEntries[tid];
230
231    assert((*tail) == inst);
232
233    DPRINTF(ROB, "[tid:%i] Now has %d instructions.\n", tid, threadEntries[tid]);
234}
235
236template <class Impl>
237void
238ROB<Impl>::retireHead(ThreadID tid)
239{
240    assert(numInstsInROB > 0);
241
242    // Get the head ROB instruction.
243    InstIt head_it = instList[tid].begin();
244
245    DynInstPtr head_inst = (*head_it);
246
247    assert(head_inst->readyToCommit());
248
249    DPRINTF(ROB, "[tid:%u]: Retiring head instruction, "
250            "instruction PC %s, [sn:%lli]\n", tid, head_inst->pcState(),
251            head_inst->seqNum);
252
253    --numInstsInROB;
254    --threadEntries[tid];
255
256    head_inst->clearInROB();
257    head_inst->setCommitted();
258
259    instList[tid].erase(head_it);
260
261    //Update "Global" Head of ROB
262    updateHead();
263
264    // @todo: A special case is needed if the instruction being
265    // retired is the only instruction in the ROB; otherwise the tail
266    // iterator will become invalidated.
267    cpu->removeFrontInst(head_inst);
268}
269
270template <class Impl>
271bool
272ROB<Impl>::isHeadReady(ThreadID tid)
273{
274    if (threadEntries[tid] != 0) {
275        return instList[tid].front()->readyToCommit();
276    }
277
278    return false;
279}
280
281template <class Impl>
282bool
283ROB<Impl>::canCommit()
284{
285    //@todo: set ActiveThreads through ROB or CPU
286    list<ThreadID>::iterator threads = activeThreads->begin();
287    list<ThreadID>::iterator end = activeThreads->end();
288
289    while (threads != end) {
290        ThreadID tid = *threads++;
291
292        if (isHeadReady(tid)) {
293            return true;
294        }
295    }
296
297    return false;
298}
299
300template <class Impl>
301unsigned
302ROB<Impl>::numFreeEntries()
303{
304    return numEntries - numInstsInROB;
305}
306
307template <class Impl>
308unsigned
309ROB<Impl>::numFreeEntries(ThreadID tid)
310{
311    return maxEntries[tid] - threadEntries[tid];
312}
313
314template <class Impl>
315void
316ROB<Impl>::doSquash(ThreadID tid)
317{
318    DPRINTF(ROB, "[tid:%u]: Squashing instructions until [sn:%i].\n",
319            tid, squashedSeqNum[tid]);
320
321    assert(squashIt[tid] != instList[tid].end());
322
323    if ((*squashIt[tid])->seqNum < squashedSeqNum[tid]) {
324        DPRINTF(ROB, "[tid:%u]: Done squashing instructions.\n",
325                tid);
326
327        squashIt[tid] = instList[tid].end();
328
329        doneSquashing[tid] = true;
330        return;
331    }
332
333    bool robTailUpdate = false;
334
335    for (int numSquashed = 0;
336         numSquashed < squashWidth &&
337         squashIt[tid] != instList[tid].end() &&
338         (*squashIt[tid])->seqNum > squashedSeqNum[tid];
339         ++numSquashed)
340    {
341        DPRINTF(ROB, "[tid:%u]: Squashing instruction PC %s, seq num %i.\n",
342                (*squashIt[tid])->threadNumber,
343                (*squashIt[tid])->pcState(),
344                (*squashIt[tid])->seqNum);
345
346        // Mark the instruction as squashed, and ready to commit so that
347        // it can drain out of the pipeline.
348        (*squashIt[tid])->setSquashed();
349
350        (*squashIt[tid])->setCanCommit();
351
352
353        if (squashIt[tid] == instList[tid].begin()) {
354            DPRINTF(ROB, "Reached head of instruction list while "
355                    "squashing.\n");
356
357            squashIt[tid] = instList[tid].end();
358
359            doneSquashing[tid] = true;
360
361            return;
362        }
363
364        InstIt tail_thread = instList[tid].end();
365        tail_thread--;
366
367        if ((*squashIt[tid]) == (*tail_thread))
368            robTailUpdate = true;
369
370        squashIt[tid]--;
371    }
372
373
374    // Check if ROB is done squashing.
375    if ((*squashIt[tid])->seqNum <= squashedSeqNum[tid]) {
376        DPRINTF(ROB, "[tid:%u]: Done squashing instructions.\n",
377                tid);
378
379        squashIt[tid] = instList[tid].end();
380
381        doneSquashing[tid] = true;
382    }
383
384    if (robTailUpdate) {
385        updateTail();
386    }
387}
388
389
390template <class Impl>
391void
392ROB<Impl>::updateHead()
393{
394    DynInstPtr head_inst;
395    InstSeqNum lowest_num = 0;
396    bool first_valid = true;
397
398    // @todo: set ActiveThreads through ROB or CPU
399    list<ThreadID>::iterator threads = activeThreads->begin();
400    list<ThreadID>::iterator end = activeThreads->end();
401
402    while (threads != end) {
403        ThreadID tid = *threads++;
404
405        if (instList[tid].empty())
406            continue;
407
408        if (first_valid) {
409            head = instList[tid].begin();
410            lowest_num = (*head)->seqNum;
411            first_valid = false;
412            continue;
413        }
414
415        InstIt head_thread = instList[tid].begin();
416
417        DynInstPtr head_inst = (*head_thread);
418
419        assert(head_inst != 0);
420
421        if (head_inst->seqNum < lowest_num) {
422            head = head_thread;
423            lowest_num = head_inst->seqNum;
424        }
425    }
426
427    if (first_valid) {
428        head = instList[0].end();
429    }
430
431}
432
433template <class Impl>
434void
435ROB<Impl>::updateTail()
436{
437    tail = instList[0].end();
438    bool first_valid = true;
439
440    list<ThreadID>::iterator threads = activeThreads->begin();
441    list<ThreadID>::iterator end = activeThreads->end();
442
443    while (threads != end) {
444        ThreadID tid = *threads++;
445
446        if (instList[tid].empty()) {
447            continue;
448        }
449
450        // If this is the first valid then assign w/out
451        // comparison
452        if (first_valid) {
453            tail = instList[tid].end();
454            tail--;
455            first_valid = false;
456            continue;
457        }
458
459        // Assign new tail if this thread's tail is younger
460        // than our current "tail high"
461        InstIt tail_thread = instList[tid].end();
462        tail_thread--;
463
464        if ((*tail_thread)->seqNum > (*tail)->seqNum) {
465            tail = tail_thread;
466        }
467    }
468}
469
470
471template <class Impl>
472void
473ROB<Impl>::squash(InstSeqNum squash_num, ThreadID tid)
474{
475    if (isEmpty()) {
476        DPRINTF(ROB, "Does not need to squash due to being empty "
477                "[sn:%i]\n",
478                squash_num);
479
480        return;
481    }
482
483    DPRINTF(ROB, "Starting to squash within the ROB.\n");
484
485    robStatus[tid] = ROBSquashing;
486
487    doneSquashing[tid] = false;
488
489    squashedSeqNum[tid] = squash_num;
490
491    if (!instList[tid].empty()) {
492        InstIt tail_thread = instList[tid].end();
493        tail_thread--;
494
495        squashIt[tid] = tail_thread;
496
497        doSquash(tid);
498    }
499}
500
501template <class Impl>
502typename Impl::DynInstPtr
503ROB<Impl>::readHeadInst(ThreadID tid)
504{
505    if (threadEntries[tid] != 0) {
506        InstIt head_thread = instList[tid].begin();
507
508        assert((*head_thread)->isInROB()==true);
509
510        return *head_thread;
511    } else {
512        return dummyInst;
513    }
514}
515
516template <class Impl>
517typename Impl::DynInstPtr
518ROB<Impl>::readTailInst(ThreadID tid)
519{
520    InstIt tail_thread = instList[tid].end();
521    tail_thread--;
522
523    return *tail_thread;
524}
525
526