fetch_impl.hh revision 4870:fcc39d001154 
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 <algorithm>
33#include <cstring>
34
35#include "config/use_checker.hh"
36
37#include "arch/isa_traits.hh"
38#include "arch/utility.hh"
39#include "cpu/checker/cpu.hh"
40#include "cpu/exetrace.hh"
41#include "cpu/o3/fetch.hh"
42#include "mem/packet.hh"
43#include "mem/request.hh"
44#include "sim/byteswap.hh"
45#include "sim/host.hh"
46#include "sim/core.hh"
47
48#if FULL_SYSTEM
49#include "arch/tlb.hh"
50#include "arch/vtophys.hh"
51#include "sim/system.hh"
52#endif // FULL_SYSTEM
53
54template<class Impl>
55void
56DefaultFetch<Impl>::IcachePort::setPeer(Port *port)
57{
58    Port::setPeer(port);
59
60    fetch->setIcache();
61}
62
63template<class Impl>
64Tick
65DefaultFetch<Impl>::IcachePort::recvAtomic(PacketPtr pkt)
66{
67    panic("DefaultFetch doesn't expect recvAtomic callback!");
68    return curTick;
69}
70
71template<class Impl>
72void
73DefaultFetch<Impl>::IcachePort::recvFunctional(PacketPtr pkt)
74{
75    DPRINTF(Fetch, "DefaultFetch doesn't update its state from a "
76            "functional call.");
77}
78
79template<class Impl>
80void
81DefaultFetch<Impl>::IcachePort::recvStatusChange(Status status)
82{
83    if (status == RangeChange) {
84        if (!snoopRangeSent) {
85            snoopRangeSent = true;
86            sendStatusChange(Port::RangeChange);
87        }
88        return;
89    }
90
91    panic("DefaultFetch doesn't expect recvStatusChange callback!");
92}
93
94template<class Impl>
95bool
96DefaultFetch<Impl>::IcachePort::recvTiming(PacketPtr pkt)
97{
98    DPRINTF(Fetch, "Received timing\n");
99    if (pkt->isResponse()) {
100        fetch->processCacheCompletion(pkt);
101    }
102    //else Snooped a coherence request, just return
103    return true;
104}
105
106template<class Impl>
107void
108DefaultFetch<Impl>::IcachePort::recvRetry()
109{
110    fetch->recvRetry();
111}
112
113template<class Impl>
114DefaultFetch<Impl>::DefaultFetch(O3CPU *_cpu, Params *params)
115    : cpu(_cpu),
116      branchPred(params),
117      predecoder(NULL),
118      decodeToFetchDelay(params->decodeToFetchDelay),
119      renameToFetchDelay(params->renameToFetchDelay),
120      iewToFetchDelay(params->iewToFetchDelay),
121      commitToFetchDelay(params->commitToFetchDelay),
122      fetchWidth(params->fetchWidth),
123      cacheBlocked(false),
124      retryPkt(NULL),
125      retryTid(-1),
126      numThreads(params->numberOfThreads),
127      numFetchingThreads(params->smtNumFetchingThreads),
128      interruptPending(false),
129      drainPending(false),
130      switchedOut(false)
131{
132    if (numThreads > Impl::MaxThreads)
133        fatal("numThreads is not a valid value\n");
134
135    // Set fetch stage's status to inactive.
136    _status = Inactive;
137
138    std::string policy = params->smtFetchPolicy;
139
140    // Convert string to lowercase
141    std::transform(policy.begin(), policy.end(), policy.begin(),
142                   (int(*)(int)) tolower);
143
144    // Figure out fetch policy
145    if (policy == "singlethread") {
146        fetchPolicy = SingleThread;
147        if (numThreads > 1)
148            panic("Invalid Fetch Policy for a SMT workload.");
149    } else if (policy == "roundrobin") {
150        fetchPolicy = RoundRobin;
151        DPRINTF(Fetch, "Fetch policy set to Round Robin\n");
152    } else if (policy == "branch") {
153        fetchPolicy = Branch;
154        DPRINTF(Fetch, "Fetch policy set to Branch Count\n");
155    } else if (policy == "iqcount") {
156        fetchPolicy = IQ;
157        DPRINTF(Fetch, "Fetch policy set to IQ count\n");
158    } else if (policy == "lsqcount") {
159        fetchPolicy = LSQ;
160        DPRINTF(Fetch, "Fetch policy set to LSQ count\n");
161    } else {
162        fatal("Invalid Fetch Policy. Options Are: {SingleThread,"
163              " RoundRobin,LSQcount,IQcount}\n");
164    }
165
166    // Get the size of an instruction.
167    instSize = sizeof(TheISA::MachInst);
168
169    // Name is finally available, so create the port.
170    icachePort = new IcachePort(this);
171
172    icachePort->snoopRangeSent = false;
173
174#if USE_CHECKER
175    if (cpu->checker) {
176        cpu->checker->setIcachePort(icachePort);
177    }
178#endif
179}
180
181template <class Impl>
182std::string
183DefaultFetch<Impl>::name() const
184{
185    return cpu->name() + ".fetch";
186}
187
188template <class Impl>
189void
190DefaultFetch<Impl>::regStats()
191{
192    icacheStallCycles
193        .name(name() + ".icacheStallCycles")
194        .desc("Number of cycles fetch is stalled on an Icache miss")
195        .prereq(icacheStallCycles);
196
197    fetchedInsts
198        .name(name() + ".Insts")
199        .desc("Number of instructions fetch has processed")
200        .prereq(fetchedInsts);
201
202    fetchedBranches
203        .name(name() + ".Branches")
204        .desc("Number of branches that fetch encountered")
205        .prereq(fetchedBranches);
206
207    predictedBranches
208        .name(name() + ".predictedBranches")
209        .desc("Number of branches that fetch has predicted taken")
210        .prereq(predictedBranches);
211
212    fetchCycles
213        .name(name() + ".Cycles")
214        .desc("Number of cycles fetch has run and was not squashing or"
215              " blocked")
216        .prereq(fetchCycles);
217
218    fetchSquashCycles
219        .name(name() + ".SquashCycles")
220        .desc("Number of cycles fetch has spent squashing")
221        .prereq(fetchSquashCycles);
222
223    fetchIdleCycles
224        .name(name() + ".IdleCycles")
225        .desc("Number of cycles fetch was idle")
226        .prereq(fetchIdleCycles);
227
228    fetchBlockedCycles
229        .name(name() + ".BlockedCycles")
230        .desc("Number of cycles fetch has spent blocked")
231        .prereq(fetchBlockedCycles);
232
233    fetchedCacheLines
234        .name(name() + ".CacheLines")
235        .desc("Number of cache lines fetched")
236        .prereq(fetchedCacheLines);
237
238    fetchMiscStallCycles
239        .name(name() + ".MiscStallCycles")
240        .desc("Number of cycles fetch has spent waiting on interrupts, or "
241              "bad addresses, or out of MSHRs")
242        .prereq(fetchMiscStallCycles);
243
244    fetchIcacheSquashes
245        .name(name() + ".IcacheSquashes")
246        .desc("Number of outstanding Icache misses that were squashed")
247        .prereq(fetchIcacheSquashes);
248
249    fetchNisnDist
250        .init(/* base value */ 0,
251              /* last value */ fetchWidth,
252              /* bucket size */ 1)
253        .name(name() + ".rateDist")
254        .desc("Number of instructions fetched each cycle (Total)")
255        .flags(Stats::pdf);
256
257    idleRate
258        .name(name() + ".idleRate")
259        .desc("Percent of cycles fetch was idle")
260        .prereq(idleRate);
261    idleRate = fetchIdleCycles * 100 / cpu->numCycles;
262
263    branchRate
264        .name(name() + ".branchRate")
265        .desc("Number of branch fetches per cycle")
266        .flags(Stats::total);
267    branchRate = fetchedBranches / cpu->numCycles;
268
269    fetchRate
270        .name(name() + ".rate")
271        .desc("Number of inst fetches per cycle")
272        .flags(Stats::total);
273    fetchRate = fetchedInsts / cpu->numCycles;
274
275    branchPred.regStats();
276}
277
278template<class Impl>
279void
280DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer)
281{
282    timeBuffer = time_buffer;
283
284    // Create wires to get information from proper places in time buffer.
285    fromDecode = timeBuffer->getWire(-decodeToFetchDelay);
286    fromRename = timeBuffer->getWire(-renameToFetchDelay);
287    fromIEW = timeBuffer->getWire(-iewToFetchDelay);
288    fromCommit = timeBuffer->getWire(-commitToFetchDelay);
289}
290
291template<class Impl>
292void
293DefaultFetch<Impl>::setActiveThreads(std::list<unsigned> *at_ptr)
294{
295    activeThreads = at_ptr;
296}
297
298template<class Impl>
299void
300DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr)
301{
302    fetchQueue = fq_ptr;
303
304    // Create wire to write information to proper place in fetch queue.
305    toDecode = fetchQueue->getWire(0);
306}
307
308template<class Impl>
309void
310DefaultFetch<Impl>::initStage()
311{
312    // Setup PC and nextPC with initial state.
313    for (int tid = 0; tid < numThreads; tid++) {
314        PC[tid] = cpu->readPC(tid);
315        nextPC[tid] = cpu->readNextPC(tid);
316        microPC[tid] = cpu->readMicroPC(tid);
317    }
318
319    for (int tid=0; tid < numThreads; tid++) {
320
321        fetchStatus[tid] = Running;
322
323        priorityList.push_back(tid);
324
325        memReq[tid] = NULL;
326
327        stalls[tid].decode = false;
328        stalls[tid].rename = false;
329        stalls[tid].iew = false;
330        stalls[tid].commit = false;
331    }
332
333    // Schedule fetch to get the correct PC from the CPU
334    // scheduleFetchStartupEvent(1);
335
336    // Fetch needs to start fetching instructions at the very beginning,
337    // so it must start up in active state.
338    switchToActive();
339}
340
341template<class Impl>
342void
343DefaultFetch<Impl>::setIcache()
344{
345    // Size of cache block.
346    cacheBlkSize = icachePort->peerBlockSize();
347
348    // Create mask to get rid of offset bits.
349    cacheBlkMask = (cacheBlkSize - 1);
350
351    for (int tid=0; tid < numThreads; tid++) {
352        // Create space to store a cache line.
353        cacheData[tid] = new uint8_t[cacheBlkSize];
354        cacheDataPC[tid] = 0;
355        cacheDataValid[tid] = false;
356    }
357}
358
359template<class Impl>
360void
361DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt)
362{
363    unsigned tid = pkt->req->getThreadNum();
364
365    DPRINTF(Fetch, "[tid:%u] Waking up from cache miss.\n",tid);
366
367    // Only change the status if it's still waiting on the icache access
368    // to return.
369    if (fetchStatus[tid] != IcacheWaitResponse ||
370        pkt->req != memReq[tid] ||
371        isSwitchedOut()) {
372        ++fetchIcacheSquashes;
373        delete pkt->req;
374        delete pkt;
375        return;
376    }
377
378    memcpy(cacheData[tid], pkt->getPtr<uint8_t>(), cacheBlkSize);
379    cacheDataValid[tid] = true;
380
381    if (!drainPending) {
382        // Wake up the CPU (if it went to sleep and was waiting on
383        // this completion event).
384        cpu->wakeCPU();
385
386        DPRINTF(Activity, "[tid:%u] Activating fetch due to cache completion\n",
387                tid);
388
389        switchToActive();
390    }
391
392    // Only switch to IcacheAccessComplete if we're not stalled as well.
393    if (checkStall(tid)) {
394        fetchStatus[tid] = Blocked;
395    } else {
396        fetchStatus[tid] = IcacheAccessComplete;
397    }
398
399    // Reset the mem req to NULL.
400    delete pkt->req;
401    delete pkt;
402    memReq[tid] = NULL;
403}
404
405template <class Impl>
406bool
407DefaultFetch<Impl>::drain()
408{
409    // Fetch is ready to drain at any time.
410    cpu->signalDrained();
411    drainPending = true;
412    return true;
413}
414
415template <class Impl>
416void
417DefaultFetch<Impl>::resume()
418{
419    drainPending = false;
420}
421
422template <class Impl>
423void
424DefaultFetch<Impl>::switchOut()
425{
426    switchedOut = true;
427    // Branch predictor needs to have its state cleared.
428    branchPred.switchOut();
429}
430
431template <class Impl>
432void
433DefaultFetch<Impl>::takeOverFrom()
434{
435    // Reset all state
436    for (int i = 0; i < Impl::MaxThreads; ++i) {
437        stalls[i].decode = 0;
438        stalls[i].rename = 0;
439        stalls[i].iew = 0;
440        stalls[i].commit = 0;
441        PC[i] = cpu->readPC(i);
442        nextPC[i] = cpu->readNextPC(i);
443        microPC[i] = cpu->readMicroPC(i);
444        fetchStatus[i] = Running;
445    }
446    numInst = 0;
447    wroteToTimeBuffer = false;
448    _status = Inactive;
449    switchedOut = false;
450    interruptPending = false;
451    branchPred.takeOverFrom();
452}
453
454template <class Impl>
455void
456DefaultFetch<Impl>::wakeFromQuiesce()
457{
458    DPRINTF(Fetch, "Waking up from quiesce\n");
459    // Hopefully this is safe
460    // @todo: Allow other threads to wake from quiesce.
461    fetchStatus[0] = Running;
462}
463
464template <class Impl>
465inline void
466DefaultFetch<Impl>::switchToActive()
467{
468    if (_status == Inactive) {
469        DPRINTF(Activity, "Activating stage.\n");
470
471        cpu->activateStage(O3CPU::FetchIdx);
472
473        _status = Active;
474    }
475}
476
477template <class Impl>
478inline void
479DefaultFetch<Impl>::switchToInactive()
480{
481    if (_status == Active) {
482        DPRINTF(Activity, "Deactivating stage.\n");
483
484        cpu->deactivateStage(O3CPU::FetchIdx);
485
486        _status = Inactive;
487    }
488}
489
490template <class Impl>
491bool
492DefaultFetch<Impl>::lookupAndUpdateNextPC(DynInstPtr &inst, Addr &next_PC,
493                                          Addr &next_NPC, Addr &next_MicroPC)
494{
495    // Do branch prediction check here.
496    // A bit of a misnomer...next_PC is actually the current PC until
497    // this function updates it.
498    bool predict_taken;
499
500    if (!inst->isControl()) {
501        if (inst->isMicroop() && !inst->isLastMicroop()) {
502            next_MicroPC++;
503        } else {
504            next_PC  = next_NPC;
505            next_NPC = next_NPC + instSize;
506            next_MicroPC = 0;
507        }
508        inst->setPredTarg(next_PC, next_NPC, next_MicroPC);
509        inst->setPredTaken(false);
510        return false;
511    }
512
513    //Assume for now that all control flow is to a different macroop which
514    //would reset the micro pc to 0.
515    next_MicroPC = 0;
516
517    int tid = inst->threadNumber;
518    Addr pred_PC = next_PC;
519    predict_taken = branchPred.predict(inst, pred_PC, tid);
520
521/*    if (predict_taken) {
522        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be taken to %#x.\n",
523                tid, pred_PC);
524    } else {
525        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be not taken.\n", tid);
526    }*/
527
528#if ISA_HAS_DELAY_SLOT
529    next_PC = next_NPC;
530    if (predict_taken)
531        next_NPC = pred_PC;
532    else
533        next_NPC += instSize;
534#else
535    if (predict_taken)
536        next_PC = pred_PC;
537    else
538        next_PC += instSize;
539    next_NPC = next_PC + instSize;
540#endif
541/*    DPRINTF(Fetch, "[tid:%i]: Branch predicted to go to %#x and then %#x.\n",
542            tid, next_PC, next_NPC);*/
543    inst->setPredTarg(next_PC, next_NPC, next_MicroPC);
544    inst->setPredTaken(predict_taken);
545
546    ++fetchedBranches;
547
548    if (predict_taken) {
549        ++predictedBranches;
550    }
551
552    return predict_taken;
553}
554
555template <class Impl>
556bool
557DefaultFetch<Impl>::fetchCacheLine(Addr fetch_PC, Fault &ret_fault, unsigned tid)
558{
559    Fault fault = NoFault;
560
561    //AlphaDep
562    if (cacheBlocked) {
563        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n",
564                tid);
565        return false;
566    } else if (isSwitchedOut()) {
567        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, switched out\n",
568                tid);
569        return false;
570    } else if (interruptPending && !(fetch_PC & 0x3)) {
571        // Hold off fetch from getting new instructions when:
572        // Cache is blocked, or
573        // while an interrupt is pending and we're not in PAL mode, or
574        // fetch is switched out.
575        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n",
576                tid);
577        return false;
578    }
579
580    // Align the fetch PC so it's at the start of a cache block.
581    Addr block_PC = icacheBlockAlignPC(fetch_PC);
582
583    // If we've already got the block, no need to try to fetch it again.
584    if (cacheDataValid[tid] && block_PC == cacheDataPC[tid]) {
585        return true;
586    }
587
588    // Setup the memReq to do a read of the first instruction's address.
589    // Set the appropriate read size and flags as well.
590    // Build request here.
591    RequestPtr mem_req = new Request(tid, block_PC, cacheBlkSize, 0,
592                                     fetch_PC, cpu->readCpuId(), tid);
593
594    memReq[tid] = mem_req;
595
596    // Translate the instruction request.
597    fault = cpu->translateInstReq(mem_req, cpu->thread[tid]);
598
599    // In the case of faults, the fetch stage may need to stall and wait
600    // for the ITB miss to be handled.
601
602    // If translation was successful, attempt to read the first
603    // instruction.
604    if (fault == NoFault) {
605#if 0
606        if (cpu->system->memctrl->badaddr(memReq[tid]->paddr) ||
607            memReq[tid]->isUncacheable()) {
608            DPRINTF(Fetch, "Fetch: Bad address %#x (hopefully on a "
609                    "misspeculating path)!",
610                    memReq[tid]->paddr);
611            ret_fault = TheISA::genMachineCheckFault();
612            return false;
613        }
614#endif
615
616        // Build packet here.
617        PacketPtr data_pkt = new Packet(mem_req,
618                                        MemCmd::ReadReq, Packet::Broadcast);
619        data_pkt->dataDynamicArray(new uint8_t[cacheBlkSize]);
620
621        cacheDataPC[tid] = block_PC;
622        cacheDataValid[tid] = false;
623
624        DPRINTF(Fetch, "Fetch: Doing instruction read.\n");
625
626        fetchedCacheLines++;
627
628        // Now do the timing access to see whether or not the instruction
629        // exists within the cache.
630        if (!icachePort->sendTiming(data_pkt)) {
631            assert(retryPkt == NULL);
632            assert(retryTid == -1);
633            DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid);
634            fetchStatus[tid] = IcacheWaitRetry;
635            retryPkt = data_pkt;
636            retryTid = tid;
637            cacheBlocked = true;
638            return false;
639        }
640
641        DPRINTF(Fetch, "[tid:%i]: Doing cache access.\n", tid);
642
643        lastIcacheStall[tid] = curTick;
644
645        DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache "
646                "response.\n", tid);
647
648        fetchStatus[tid] = IcacheWaitResponse;
649    } else {
650        delete mem_req;
651        memReq[tid] = NULL;
652    }
653
654    ret_fault = fault;
655    return true;
656}
657
658template <class Impl>
659inline void
660DefaultFetch<Impl>::doSquash(const Addr &new_PC,
661        const Addr &new_NPC, const Addr &new_microPC, unsigned tid)
662{
663    DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %#x, NPC to: %#x.\n",
664            tid, new_PC, new_NPC);
665
666    PC[tid] = new_PC;
667    nextPC[tid] = new_NPC;
668    microPC[tid] = new_microPC;
669
670    // Clear the icache miss if it's outstanding.
671    if (fetchStatus[tid] == IcacheWaitResponse) {
672        DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n",
673                tid);
674        memReq[tid] = NULL;
675    }
676
677    // Get rid of the retrying packet if it was from this thread.
678    if (retryTid == tid) {
679        assert(cacheBlocked);
680        if (retryPkt) {
681            delete retryPkt->req;
682            delete retryPkt;
683        }
684        retryPkt = NULL;
685        retryTid = -1;
686    }
687
688    fetchStatus[tid] = Squashing;
689
690    ++fetchSquashCycles;
691}
692
693template<class Impl>
694void
695DefaultFetch<Impl>::squashFromDecode(const Addr &new_PC, const Addr &new_NPC,
696                                     const Addr &new_MicroPC,
697                                     const InstSeqNum &seq_num, unsigned tid)
698{
699    DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n",tid);
700
701    doSquash(new_PC, new_NPC, new_MicroPC, tid);
702
703    // Tell the CPU to remove any instructions that are in flight between
704    // fetch and decode.
705    cpu->removeInstsUntil(seq_num, tid);
706}
707
708template<class Impl>
709bool
710DefaultFetch<Impl>::checkStall(unsigned tid) const
711{
712    bool ret_val = false;
713
714    if (cpu->contextSwitch) {
715        DPRINTF(Fetch,"[tid:%i]: Stalling for a context switch.\n",tid);
716        ret_val = true;
717    } else if (stalls[tid].decode) {
718        DPRINTF(Fetch,"[tid:%i]: Stall from Decode stage detected.\n",tid);
719        ret_val = true;
720    } else if (stalls[tid].rename) {
721        DPRINTF(Fetch,"[tid:%i]: Stall from Rename stage detected.\n",tid);
722        ret_val = true;
723    } else if (stalls[tid].iew) {
724        DPRINTF(Fetch,"[tid:%i]: Stall from IEW stage detected.\n",tid);
725        ret_val = true;
726    } else if (stalls[tid].commit) {
727        DPRINTF(Fetch,"[tid:%i]: Stall from Commit stage detected.\n",tid);
728        ret_val = true;
729    }
730
731    return ret_val;
732}
733
734template<class Impl>
735typename DefaultFetch<Impl>::FetchStatus
736DefaultFetch<Impl>::updateFetchStatus()
737{
738    //Check Running
739    std::list<unsigned>::iterator threads = activeThreads->begin();
740    std::list<unsigned>::iterator end = activeThreads->end();
741
742    while (threads != end) {
743        unsigned tid = *threads++;
744
745        if (fetchStatus[tid] == Running ||
746            fetchStatus[tid] == Squashing ||
747            fetchStatus[tid] == IcacheAccessComplete) {
748
749            if (_status == Inactive) {
750                DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid);
751
752                if (fetchStatus[tid] == IcacheAccessComplete) {
753                    DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache"
754                            "completion\n",tid);
755                }
756
757                cpu->activateStage(O3CPU::FetchIdx);
758            }
759
760            return Active;
761        }
762    }
763
764    // Stage is switching from active to inactive, notify CPU of it.
765    if (_status == Active) {
766        DPRINTF(Activity, "Deactivating stage.\n");
767
768        cpu->deactivateStage(O3CPU::FetchIdx);
769    }
770
771    return Inactive;
772}
773
774template <class Impl>
775void
776DefaultFetch<Impl>::squash(const Addr &new_PC, const Addr &new_NPC,
777                           const Addr &new_MicroPC,
778                           const InstSeqNum &seq_num, unsigned tid)
779{
780    DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n",tid);
781
782    doSquash(new_PC, new_NPC, new_MicroPC, tid);
783
784    // Tell the CPU to remove any instructions that are not in the ROB.
785    cpu->removeInstsNotInROB(tid);
786}
787
788template <class Impl>
789void
790DefaultFetch<Impl>::tick()
791{
792    std::list<unsigned>::iterator threads = activeThreads->begin();
793    std::list<unsigned>::iterator end = activeThreads->end();
794    bool status_change = false;
795
796    wroteToTimeBuffer = false;
797
798    while (threads != end) {
799        unsigned tid = *threads++;
800
801        // Check the signals for each thread to determine the proper status
802        // for each thread.
803        bool updated_status = checkSignalsAndUpdate(tid);
804        status_change =  status_change || updated_status;
805    }
806
807    DPRINTF(Fetch, "Running stage.\n");
808
809    // Reset the number of the instruction we're fetching.
810    numInst = 0;
811
812#if FULL_SYSTEM
813    if (fromCommit->commitInfo[0].interruptPending) {
814        interruptPending = true;
815    }
816
817    if (fromCommit->commitInfo[0].clearInterrupt) {
818        interruptPending = false;
819    }
820#endif
821
822    for (threadFetched = 0; threadFetched < numFetchingThreads;
823         threadFetched++) {
824        // Fetch each of the actively fetching threads.
825        fetch(status_change);
826    }
827
828    // Record number of instructions fetched this cycle for distribution.
829    fetchNisnDist.sample(numInst);
830
831    if (status_change) {
832        // Change the fetch stage status if there was a status change.
833        _status = updateFetchStatus();
834    }
835
836    // If there was activity this cycle, inform the CPU of it.
837    if (wroteToTimeBuffer || cpu->contextSwitch) {
838        DPRINTF(Activity, "Activity this cycle.\n");
839
840        cpu->activityThisCycle();
841    }
842}
843
844template <class Impl>
845bool
846DefaultFetch<Impl>::checkSignalsAndUpdate(unsigned tid)
847{
848    // Update the per thread stall statuses.
849    if (fromDecode->decodeBlock[tid]) {
850        stalls[tid].decode = true;
851    }
852
853    if (fromDecode->decodeUnblock[tid]) {
854        assert(stalls[tid].decode);
855        assert(!fromDecode->decodeBlock[tid]);
856        stalls[tid].decode = false;
857    }
858
859    if (fromRename->renameBlock[tid]) {
860        stalls[tid].rename = true;
861    }
862
863    if (fromRename->renameUnblock[tid]) {
864        assert(stalls[tid].rename);
865        assert(!fromRename->renameBlock[tid]);
866        stalls[tid].rename = false;
867    }
868
869    if (fromIEW->iewBlock[tid]) {
870        stalls[tid].iew = true;
871    }
872
873    if (fromIEW->iewUnblock[tid]) {
874        assert(stalls[tid].iew);
875        assert(!fromIEW->iewBlock[tid]);
876        stalls[tid].iew = false;
877    }
878
879    if (fromCommit->commitBlock[tid]) {
880        stalls[tid].commit = true;
881    }
882
883    if (fromCommit->commitUnblock[tid]) {
884        assert(stalls[tid].commit);
885        assert(!fromCommit->commitBlock[tid]);
886        stalls[tid].commit = false;
887    }
888
889    // Check squash signals from commit.
890    if (fromCommit->commitInfo[tid].squash) {
891
892        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
893                "from commit.\n",tid);
894        // In any case, squash.
895        squash(fromCommit->commitInfo[tid].nextPC,
896               fromCommit->commitInfo[tid].nextNPC,
897               fromCommit->commitInfo[tid].nextMicroPC,
898               fromCommit->commitInfo[tid].doneSeqNum,
899               tid);
900
901        // Also check if there's a mispredict that happened.
902        if (fromCommit->commitInfo[tid].branchMispredict) {
903            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
904                              fromCommit->commitInfo[tid].nextPC,
905                              fromCommit->commitInfo[tid].branchTaken,
906                              tid);
907        } else {
908            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
909                              tid);
910        }
911
912        return true;
913    } else if (fromCommit->commitInfo[tid].doneSeqNum) {
914        // Update the branch predictor if it wasn't a squashed instruction
915        // that was broadcasted.
916        branchPred.update(fromCommit->commitInfo[tid].doneSeqNum, tid);
917    }
918
919    // Check ROB squash signals from commit.
920    if (fromCommit->commitInfo[tid].robSquashing) {
921        DPRINTF(Fetch, "[tid:%u]: ROB is still squashing.\n", tid);
922
923        // Continue to squash.
924        fetchStatus[tid] = Squashing;
925
926        return true;
927    }
928
929    // Check squash signals from decode.
930    if (fromDecode->decodeInfo[tid].squash) {
931        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
932                "from decode.\n",tid);
933
934        // Update the branch predictor.
935        if (fromDecode->decodeInfo[tid].branchMispredict) {
936            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
937                              fromDecode->decodeInfo[tid].nextPC,
938                              fromDecode->decodeInfo[tid].branchTaken,
939                              tid);
940        } else {
941            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
942                              tid);
943        }
944
945        if (fetchStatus[tid] != Squashing) {
946
947            DPRINTF(Fetch, "Squashing from decode with PC = %#x, NPC = %#x\n",
948                    fromDecode->decodeInfo[tid].nextPC,
949                    fromDecode->decodeInfo[tid].nextNPC);
950            // Squash unless we're already squashing
951            squashFromDecode(fromDecode->decodeInfo[tid].nextPC,
952                             fromDecode->decodeInfo[tid].nextNPC,
953                             fromDecode->decodeInfo[tid].nextMicroPC,
954                             fromDecode->decodeInfo[tid].doneSeqNum,
955                             tid);
956
957            return true;
958        }
959    }
960
961    if (checkStall(tid) &&
962        fetchStatus[tid] != IcacheWaitResponse &&
963        fetchStatus[tid] != IcacheWaitRetry) {
964        DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid);
965
966        fetchStatus[tid] = Blocked;
967
968        return true;
969    }
970
971    if (fetchStatus[tid] == Blocked ||
972        fetchStatus[tid] == Squashing) {
973        // Switch status to running if fetch isn't being told to block or
974        // squash this cycle.
975        DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n",
976                tid);
977
978        fetchStatus[tid] = Running;
979
980        return true;
981    }
982
983    // If we've reached this point, we have not gotten any signals that
984    // cause fetch to change its status.  Fetch remains the same as before.
985    return false;
986}
987
988template<class Impl>
989void
990DefaultFetch<Impl>::fetch(bool &status_change)
991{
992    //////////////////////////////////////////
993    // Start actual fetch
994    //////////////////////////////////////////
995    int tid = getFetchingThread(fetchPolicy);
996
997    if (tid == -1 || drainPending) {
998        DPRINTF(Fetch,"There are no more threads available to fetch from.\n");
999
1000        // Breaks looping condition in tick()
1001        threadFetched = numFetchingThreads;
1002        return;
1003    }
1004
1005    DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid);
1006
1007    // The current PC.
1008    Addr fetch_PC = PC[tid];
1009    Addr fetch_NPC = nextPC[tid];
1010    Addr fetch_MicroPC = microPC[tid];
1011
1012    // Fault code for memory access.
1013    Fault fault = NoFault;
1014
1015    // If returning from the delay of a cache miss, then update the status
1016    // to running, otherwise do the cache access.  Possibly move this up
1017    // to tick() function.
1018    if (fetchStatus[tid] == IcacheAccessComplete) {
1019        DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n",
1020                tid);
1021
1022        fetchStatus[tid] = Running;
1023        status_change = true;
1024    } else if (fetchStatus[tid] == Running) {
1025        DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read "
1026                "instruction, starting at PC %08p.\n",
1027                tid, fetch_PC);
1028
1029        bool fetch_success = fetchCacheLine(fetch_PC, fault, tid);
1030        if (!fetch_success) {
1031            if (cacheBlocked) {
1032                ++icacheStallCycles;
1033            } else {
1034                ++fetchMiscStallCycles;
1035            }
1036            return;
1037        }
1038    } else {
1039        if (fetchStatus[tid] == Idle) {
1040            ++fetchIdleCycles;
1041            DPRINTF(Fetch, "[tid:%i]: Fetch is idle!\n", tid);
1042        } else if (fetchStatus[tid] == Blocked) {
1043            ++fetchBlockedCycles;
1044            DPRINTF(Fetch, "[tid:%i]: Fetch is blocked!\n", tid);
1045        } else if (fetchStatus[tid] == Squashing) {
1046            ++fetchSquashCycles;
1047            DPRINTF(Fetch, "[tid:%i]: Fetch is squashing!\n", tid);
1048        } else if (fetchStatus[tid] == IcacheWaitResponse) {
1049            ++icacheStallCycles;
1050            DPRINTF(Fetch, "[tid:%i]: Fetch is waiting cache response!\n", tid);
1051        }
1052
1053        // Status is Idle, Squashing, Blocked, or IcacheWaitResponse, so
1054        // fetch should do nothing.
1055        return;
1056    }
1057
1058    ++fetchCycles;
1059
1060    // If we had a stall due to an icache miss, then return.
1061    if (fetchStatus[tid] == IcacheWaitResponse) {
1062        ++icacheStallCycles;
1063        status_change = true;
1064        return;
1065    }
1066
1067    Addr next_PC = fetch_PC;
1068    Addr next_NPC = fetch_NPC;
1069    Addr next_MicroPC = fetch_MicroPC;
1070
1071    InstSeqNum inst_seq;
1072    MachInst inst;
1073    ExtMachInst ext_inst;
1074    // @todo: Fix this hack.
1075    unsigned offset = (fetch_PC & cacheBlkMask) & ~3;
1076
1077    StaticInstPtr staticInst = NULL;
1078    StaticInstPtr macroop = NULL;
1079
1080    if (fault == NoFault) {
1081        // If the read of the first instruction was successful, then grab the
1082        // instructions from the rest of the cache line and put them into the
1083        // queue heading to decode.
1084
1085        DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to "
1086                "decode.\n",tid);
1087
1088        // Need to keep track of whether or not a predicted branch
1089        // ended this fetch block.
1090        bool predicted_branch = false;
1091
1092        while (offset < cacheBlkSize &&
1093               numInst < fetchWidth &&
1094               !predicted_branch) {
1095
1096            // If we're branching after this instruction, quite fetching
1097            // from the same block then.
1098            predicted_branch =
1099                (fetch_PC + sizeof(TheISA::MachInst) != fetch_NPC);
1100            if (predicted_branch) {
1101                DPRINTF(Fetch, "Branch detected with PC = %#x, NPC = %#x\n",
1102                        fetch_PC, fetch_NPC);
1103            }
1104
1105            // Make sure this is a valid index.
1106            assert(offset <= cacheBlkSize - instSize);
1107
1108            if (!macroop) {
1109                // Get the instruction from the array of the cache line.
1110                inst = TheISA::gtoh(*reinterpret_cast<TheISA::MachInst *>
1111                            (&cacheData[tid][offset]));
1112
1113                predecoder.setTC(cpu->thread[tid]->getTC());
1114                predecoder.moreBytes(fetch_PC, fetch_PC, inst);
1115
1116                ext_inst = predecoder.getExtMachInst();
1117                staticInst = StaticInstPtr(ext_inst, fetch_PC);
1118                if (staticInst->isMacroop())
1119                    macroop = staticInst;
1120            }
1121            do {
1122                if (macroop) {
1123                    staticInst = macroop->fetchMicroop(fetch_MicroPC);
1124                    if (staticInst->isLastMicroop())
1125                        macroop = NULL;
1126                }
1127
1128                // Get a sequence number.
1129                inst_seq = cpu->getAndIncrementInstSeq();
1130
1131                // Create a new DynInst from the instruction fetched.
1132                DynInstPtr instruction = new DynInst(staticInst,
1133                                                     fetch_PC, fetch_NPC, fetch_MicroPC,
1134                                                     next_PC, next_NPC, next_MicroPC,
1135                                                     inst_seq, cpu);
1136                instruction->setTid(tid);
1137
1138                instruction->setASID(tid);
1139
1140                instruction->setThreadState(cpu->thread[tid]);
1141
1142                DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x created "
1143                        "[sn:%lli]\n",
1144                        tid, instruction->readPC(), inst_seq);
1145
1146                //DPRINTF(Fetch, "[tid:%i]: MachInst is %#x\n", tid, ext_inst);
1147
1148                DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n",
1149                        tid, instruction->staticInst->disassemble(fetch_PC));
1150
1151#if TRACING_ON
1152                instruction->traceData =
1153                    Trace::getInstRecord(curTick, cpu->tcBase(tid),
1154                                         instruction->staticInst,
1155                                         instruction->readPC());
1156#else
1157                instruction->traceData = NULL;
1158#endif
1159
1160                ///FIXME This needs to be more robust in dealing with delay slots
1161                predicted_branch |=
1162                    lookupAndUpdateNextPC(instruction, next_PC, next_NPC, next_MicroPC);
1163
1164                // Add instruction to the CPU's list of instructions.
1165                instruction->setInstListIt(cpu->addInst(instruction));
1166
1167                // Write the instruction to the first slot in the queue
1168                // that heads to decode.
1169                toDecode->insts[numInst] = instruction;
1170
1171                toDecode->size++;
1172
1173                // Increment stat of fetched instructions.
1174                ++fetchedInsts;
1175
1176                // Move to the next instruction, unless we have a branch.
1177                fetch_PC = next_PC;
1178                fetch_NPC = next_NPC;
1179                fetch_MicroPC = next_MicroPC;
1180
1181                if (instruction->isQuiesce()) {
1182                    DPRINTF(Fetch, "Quiesce instruction encountered, halting fetch!",
1183                            curTick);
1184                    fetchStatus[tid] = QuiescePending;
1185                    ++numInst;
1186                    status_change = true;
1187                    break;
1188                }
1189
1190                ++numInst;
1191            } while (staticInst->isMicroop() &&
1192                     !staticInst->isLastMicroop() &&
1193                     numInst < fetchWidth);
1194            offset += instSize;
1195        }
1196
1197        if (predicted_branch) {
1198            DPRINTF(Fetch, "[tid:%i]: Done fetching, predicted branch "
1199                    "instruction encountered.\n", tid);
1200        } else if (numInst >= fetchWidth) {
1201            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached fetch bandwidth "
1202                    "for this cycle.\n", tid);
1203        } else if (offset >= cacheBlkSize) {
1204            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached the end of cache "
1205                    "block.\n", tid);
1206        }
1207    }
1208
1209    if (numInst > 0) {
1210        wroteToTimeBuffer = true;
1211    }
1212
1213    // Now that fetching is completed, update the PC to signify what the next
1214    // cycle will be.
1215    if (fault == NoFault) {
1216        PC[tid] = next_PC;
1217        nextPC[tid] = next_NPC;
1218        microPC[tid] = next_MicroPC;
1219        DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n", tid, next_PC);
1220    } else {
1221        // We shouldn't be in an icache miss and also have a fault (an ITB
1222        // miss)
1223        if (fetchStatus[tid] == IcacheWaitResponse) {
1224            panic("Fetch should have exited prior to this!");
1225        }
1226
1227        // Send the fault to commit.  This thread will not do anything
1228        // until commit handles the fault.  The only other way it can
1229        // wake up is if a squash comes along and changes the PC.
1230#if FULL_SYSTEM
1231        assert(numInst < fetchWidth);
1232        // Get a sequence number.
1233        inst_seq = cpu->getAndIncrementInstSeq();
1234        // We will use a nop in order to carry the fault.
1235        ext_inst = TheISA::NoopMachInst;
1236
1237        // Create a new DynInst from the dummy nop.
1238        DynInstPtr instruction = new DynInst(ext_inst,
1239                                             fetch_PC, fetch_NPC, fetch_MicroPC,
1240                                             next_PC, next_NPC, next_MicroPC,
1241                                             inst_seq, cpu);
1242        instruction->setPredTarg(next_PC, next_NPC, 1);
1243        instruction->setTid(tid);
1244
1245        instruction->setASID(tid);
1246
1247        instruction->setThreadState(cpu->thread[tid]);
1248
1249        instruction->traceData = NULL;
1250
1251        instruction->setInstListIt(cpu->addInst(instruction));
1252
1253        instruction->fault = fault;
1254
1255        toDecode->insts[numInst] = instruction;
1256        toDecode->size++;
1257
1258        DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n",tid);
1259
1260        fetchStatus[tid] = TrapPending;
1261        status_change = true;
1262#else // !FULL_SYSTEM
1263        fetchStatus[tid] = TrapPending;
1264        status_change = true;
1265
1266#endif // FULL_SYSTEM
1267        DPRINTF(Fetch, "[tid:%i]: fault (%s) detected @ PC %08p",
1268                tid, fault->name(), PC[tid]);
1269    }
1270}
1271
1272template<class Impl>
1273void
1274DefaultFetch<Impl>::recvRetry()
1275{
1276    if (retryPkt != NULL) {
1277        assert(cacheBlocked);
1278        assert(retryTid != -1);
1279        assert(fetchStatus[retryTid] == IcacheWaitRetry);
1280
1281        if (icachePort->sendTiming(retryPkt)) {
1282            fetchStatus[retryTid] = IcacheWaitResponse;
1283            retryPkt = NULL;
1284            retryTid = -1;
1285            cacheBlocked = false;
1286        }
1287    } else {
1288        assert(retryTid == -1);
1289        // Access has been squashed since it was sent out.  Just clear
1290        // the cache being blocked.
1291        cacheBlocked = false;
1292    }
1293}
1294
1295///////////////////////////////////////
1296//                                   //
1297//  SMT FETCH POLICY MAINTAINED HERE //
1298//                                   //
1299///////////////////////////////////////
1300template<class Impl>
1301int
1302DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority)
1303{
1304    if (numThreads > 1) {
1305        switch (fetch_priority) {
1306
1307          case SingleThread:
1308            return 0;
1309
1310          case RoundRobin:
1311            return roundRobin();
1312
1313          case IQ:
1314            return iqCount();
1315
1316          case LSQ:
1317            return lsqCount();
1318
1319          case Branch:
1320            return branchCount();
1321
1322          default:
1323            return -1;
1324        }
1325    } else {
1326        std::list<unsigned>::iterator thread = activeThreads->begin();
1327        assert(thread != activeThreads->end());
1328        int tid = *thread;
1329
1330        if (fetchStatus[tid] == Running ||
1331            fetchStatus[tid] == IcacheAccessComplete ||
1332            fetchStatus[tid] == Idle) {
1333            return tid;
1334        } else {
1335            return -1;
1336        }
1337    }
1338
1339}
1340
1341
1342template<class Impl>
1343int
1344DefaultFetch<Impl>::roundRobin()
1345{
1346    std::list<unsigned>::iterator pri_iter = priorityList.begin();
1347    std::list<unsigned>::iterator end      = priorityList.end();
1348
1349    int high_pri;
1350
1351    while (pri_iter != end) {
1352        high_pri = *pri_iter;
1353
1354        assert(high_pri <= numThreads);
1355
1356        if (fetchStatus[high_pri] == Running ||
1357            fetchStatus[high_pri] == IcacheAccessComplete ||
1358            fetchStatus[high_pri] == Idle) {
1359
1360            priorityList.erase(pri_iter);
1361            priorityList.push_back(high_pri);
1362
1363            return high_pri;
1364        }
1365
1366        pri_iter++;
1367    }
1368
1369    return -1;
1370}
1371
1372template<class Impl>
1373int
1374DefaultFetch<Impl>::iqCount()
1375{
1376    std::priority_queue<unsigned> PQ;
1377
1378    std::list<unsigned>::iterator threads = activeThreads->begin();
1379    std::list<unsigned>::iterator end = activeThreads->end();
1380
1381    while (threads != end) {
1382        unsigned tid = *threads++;
1383
1384        PQ.push(fromIEW->iewInfo[tid].iqCount);
1385    }
1386
1387    while (!PQ.empty()) {
1388
1389        unsigned high_pri = PQ.top();
1390
1391        if (fetchStatus[high_pri] == Running ||
1392            fetchStatus[high_pri] == IcacheAccessComplete ||
1393            fetchStatus[high_pri] == Idle)
1394            return high_pri;
1395        else
1396            PQ.pop();
1397
1398    }
1399
1400    return -1;
1401}
1402
1403template<class Impl>
1404int
1405DefaultFetch<Impl>::lsqCount()
1406{
1407    std::priority_queue<unsigned> PQ;
1408
1409    std::list<unsigned>::iterator threads = activeThreads->begin();
1410    std::list<unsigned>::iterator end = activeThreads->end();
1411
1412    while (threads != end) {
1413        unsigned tid = *threads++;
1414
1415        PQ.push(fromIEW->iewInfo[tid].ldstqCount);
1416    }
1417
1418    while (!PQ.empty()) {
1419
1420        unsigned high_pri = PQ.top();
1421
1422        if (fetchStatus[high_pri] == Running ||
1423            fetchStatus[high_pri] == IcacheAccessComplete ||
1424            fetchStatus[high_pri] == Idle)
1425            return high_pri;
1426        else
1427            PQ.pop();
1428
1429    }
1430
1431    return -1;
1432}
1433
1434template<class Impl>
1435int
1436DefaultFetch<Impl>::branchCount()
1437{
1438    std::list<unsigned>::iterator thread = activeThreads->begin();
1439    assert(thread != activeThreads->end());
1440    unsigned tid = *thread;
1441
1442    panic("Branch Count Fetch policy unimplemented\n");
1443    return 0 * tid;
1444}
1445