fetch_impl.hh revision 4032:8b987a6a2afc 
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 "config/use_checker.hh"
33
34#include "arch/isa_traits.hh"
35#include "arch/utility.hh"
36#include "cpu/checker/cpu.hh"
37#include "cpu/exetrace.hh"
38#include "cpu/o3/fetch.hh"
39#include "mem/packet.hh"
40#include "mem/request.hh"
41#include "sim/byteswap.hh"
42#include "sim/host.hh"
43#include "sim/root.hh"
44
45#if FULL_SYSTEM
46#include "arch/tlb.hh"
47#include "arch/vtophys.hh"
48#include "sim/system.hh"
49#endif // FULL_SYSTEM
50
51#include <algorithm>
52
53template<class Impl>
54Tick
55DefaultFetch<Impl>::IcachePort::recvAtomic(PacketPtr pkt)
56{
57    panic("DefaultFetch doesn't expect recvAtomic callback!");
58    return curTick;
59}
60
61template<class Impl>
62void
63DefaultFetch<Impl>::IcachePort::recvFunctional(PacketPtr pkt)
64{
65    DPRINTF(Fetch, "DefaultFetch doesn't update its state from a "
66            "functional call.");
67}
68
69template<class Impl>
70void
71DefaultFetch<Impl>::IcachePort::recvStatusChange(Status status)
72{
73    if (status == RangeChange) {
74        if (!snoopRangeSent) {
75            snoopRangeSent = true;
76            sendStatusChange(Port::RangeChange);
77        }
78        return;
79    }
80
81    panic("DefaultFetch doesn't expect recvStatusChange callback!");
82}
83
84template<class Impl>
85bool
86DefaultFetch<Impl>::IcachePort::recvTiming(PacketPtr pkt)
87{
88    DPRINTF(Fetch, "Received timing\n");
89    if (pkt->isResponse()) {
90        fetch->processCacheCompletion(pkt);
91    }
92    //else Snooped a coherence request, just return
93    return true;
94}
95
96template<class Impl>
97void
98DefaultFetch<Impl>::IcachePort::recvRetry()
99{
100    fetch->recvRetry();
101}
102
103template<class Impl>
104DefaultFetch<Impl>::DefaultFetch(Params *params)
105    : branchPred(params),
106      decodeToFetchDelay(params->decodeToFetchDelay),
107      renameToFetchDelay(params->renameToFetchDelay),
108      iewToFetchDelay(params->iewToFetchDelay),
109      commitToFetchDelay(params->commitToFetchDelay),
110      fetchWidth(params->fetchWidth),
111      cacheBlocked(false),
112      retryPkt(NULL),
113      retryTid(-1),
114      numThreads(params->numberOfThreads),
115      numFetchingThreads(params->smtNumFetchingThreads),
116      interruptPending(false),
117      drainPending(false),
118      switchedOut(false)
119{
120    if (numThreads > Impl::MaxThreads)
121        fatal("numThreads is not a valid value\n");
122
123    // Set fetch stage's status to inactive.
124    _status = Inactive;
125
126    std::string policy = params->smtFetchPolicy;
127
128    // Convert string to lowercase
129    std::transform(policy.begin(), policy.end(), policy.begin(),
130                   (int(*)(int)) tolower);
131
132    // Figure out fetch policy
133    if (policy == "singlethread") {
134        fetchPolicy = SingleThread;
135        if (numThreads > 1)
136            panic("Invalid Fetch Policy for a SMT workload.");
137    } else if (policy == "roundrobin") {
138        fetchPolicy = RoundRobin;
139        DPRINTF(Fetch, "Fetch policy set to Round Robin\n");
140    } else if (policy == "branch") {
141        fetchPolicy = Branch;
142        DPRINTF(Fetch, "Fetch policy set to Branch Count\n");
143    } else if (policy == "iqcount") {
144        fetchPolicy = IQ;
145        DPRINTF(Fetch, "Fetch policy set to IQ count\n");
146    } else if (policy == "lsqcount") {
147        fetchPolicy = LSQ;
148        DPRINTF(Fetch, "Fetch policy set to LSQ count\n");
149    } else {
150        fatal("Invalid Fetch Policy. Options Are: {SingleThread,"
151              " RoundRobin,LSQcount,IQcount}\n");
152    }
153
154    // Get the size of an instruction.
155    instSize = sizeof(TheISA::MachInst);
156}
157
158template <class Impl>
159std::string
160DefaultFetch<Impl>::name() const
161{
162    return cpu->name() + ".fetch";
163}
164
165template <class Impl>
166void
167DefaultFetch<Impl>::regStats()
168{
169    icacheStallCycles
170        .name(name() + ".icacheStallCycles")
171        .desc("Number of cycles fetch is stalled on an Icache miss")
172        .prereq(icacheStallCycles);
173
174    fetchedInsts
175        .name(name() + ".Insts")
176        .desc("Number of instructions fetch has processed")
177        .prereq(fetchedInsts);
178
179    fetchedBranches
180        .name(name() + ".Branches")
181        .desc("Number of branches that fetch encountered")
182        .prereq(fetchedBranches);
183
184    predictedBranches
185        .name(name() + ".predictedBranches")
186        .desc("Number of branches that fetch has predicted taken")
187        .prereq(predictedBranches);
188
189    fetchCycles
190        .name(name() + ".Cycles")
191        .desc("Number of cycles fetch has run and was not squashing or"
192              " blocked")
193        .prereq(fetchCycles);
194
195    fetchSquashCycles
196        .name(name() + ".SquashCycles")
197        .desc("Number of cycles fetch has spent squashing")
198        .prereq(fetchSquashCycles);
199
200    fetchIdleCycles
201        .name(name() + ".IdleCycles")
202        .desc("Number of cycles fetch was idle")
203        .prereq(fetchIdleCycles);
204
205    fetchBlockedCycles
206        .name(name() + ".BlockedCycles")
207        .desc("Number of cycles fetch has spent blocked")
208        .prereq(fetchBlockedCycles);
209
210    fetchedCacheLines
211        .name(name() + ".CacheLines")
212        .desc("Number of cache lines fetched")
213        .prereq(fetchedCacheLines);
214
215    fetchMiscStallCycles
216        .name(name() + ".MiscStallCycles")
217        .desc("Number of cycles fetch has spent waiting on interrupts, or "
218              "bad addresses, or out of MSHRs")
219        .prereq(fetchMiscStallCycles);
220
221    fetchIcacheSquashes
222        .name(name() + ".IcacheSquashes")
223        .desc("Number of outstanding Icache misses that were squashed")
224        .prereq(fetchIcacheSquashes);
225
226    fetchNisnDist
227        .init(/* base value */ 0,
228              /* last value */ fetchWidth,
229              /* bucket size */ 1)
230        .name(name() + ".rateDist")
231        .desc("Number of instructions fetched each cycle (Total)")
232        .flags(Stats::pdf);
233
234    idleRate
235        .name(name() + ".idleRate")
236        .desc("Percent of cycles fetch was idle")
237        .prereq(idleRate);
238    idleRate = fetchIdleCycles * 100 / cpu->numCycles;
239
240    branchRate
241        .name(name() + ".branchRate")
242        .desc("Number of branch fetches per cycle")
243        .flags(Stats::total);
244    branchRate = fetchedBranches / cpu->numCycles;
245
246    fetchRate
247        .name(name() + ".rate")
248        .desc("Number of inst fetches per cycle")
249        .flags(Stats::total);
250    fetchRate = fetchedInsts / cpu->numCycles;
251
252    branchPred.regStats();
253}
254
255template<class Impl>
256void
257DefaultFetch<Impl>::setCPU(O3CPU *cpu_ptr)
258{
259    DPRINTF(Fetch, "Setting the CPU pointer.\n");
260    cpu = cpu_ptr;
261
262    // Name is finally available, so create the port.
263    icachePort = new IcachePort(this);
264
265    icachePort->snoopRangeSent = false;
266
267#if USE_CHECKER
268    if (cpu->checker) {
269        cpu->checker->setIcachePort(icachePort);
270    }
271#endif
272
273    // Schedule fetch to get the correct PC from the CPU
274    // scheduleFetchStartupEvent(1);
275
276    // Fetch needs to start fetching instructions at the very beginning,
277    // so it must start up in active state.
278    switchToActive();
279}
280
281template<class Impl>
282void
283DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer)
284{
285    DPRINTF(Fetch, "Setting the time buffer pointer.\n");
286    timeBuffer = time_buffer;
287
288    // Create wires to get information from proper places in time buffer.
289    fromDecode = timeBuffer->getWire(-decodeToFetchDelay);
290    fromRename = timeBuffer->getWire(-renameToFetchDelay);
291    fromIEW = timeBuffer->getWire(-iewToFetchDelay);
292    fromCommit = timeBuffer->getWire(-commitToFetchDelay);
293}
294
295template<class Impl>
296void
297DefaultFetch<Impl>::setActiveThreads(std::list<unsigned> *at_ptr)
298{
299    DPRINTF(Fetch, "Setting active threads list pointer.\n");
300    activeThreads = at_ptr;
301}
302
303template<class Impl>
304void
305DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr)
306{
307    DPRINTF(Fetch, "Setting the fetch queue pointer.\n");
308    fetchQueue = fq_ptr;
309
310    // Create wire to write information to proper place in fetch queue.
311    toDecode = fetchQueue->getWire(0);
312}
313
314template<class Impl>
315void
316DefaultFetch<Impl>::initStage()
317{
318    // Setup PC and nextPC with initial state.
319    for (int tid = 0; tid < numThreads; tid++) {
320        PC[tid] = cpu->readPC(tid);
321        nextPC[tid] = cpu->readNextPC(tid);
322        nextNPC[tid] = cpu->readNextNPC(tid);
323    }
324
325    // Size of cache block.
326    cacheBlkSize = icachePort->peerBlockSize();
327
328    // Create mask to get rid of offset bits.
329    cacheBlkMask = (cacheBlkSize - 1);
330
331    for (int tid=0; tid < numThreads; tid++) {
332
333        fetchStatus[tid] = Running;
334
335        priorityList.push_back(tid);
336
337        memReq[tid] = NULL;
338
339        // Create space to store a cache line.
340        cacheData[tid] = new uint8_t[cacheBlkSize];
341        cacheDataPC[tid] = 0;
342        cacheDataValid[tid] = false;
343
344        stalls[tid].decode = false;
345        stalls[tid].rename = false;
346        stalls[tid].iew = false;
347        stalls[tid].commit = false;
348    }
349}
350
351template<class Impl>
352void
353DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt)
354{
355    unsigned tid = pkt->req->getThreadNum();
356
357    DPRINTF(Fetch, "[tid:%u] Waking up from cache miss.\n",tid);
358
359    // Only change the status if it's still waiting on the icache access
360    // to return.
361    if (fetchStatus[tid] != IcacheWaitResponse ||
362        pkt->req != memReq[tid] ||
363        isSwitchedOut()) {
364        ++fetchIcacheSquashes;
365        delete pkt->req;
366        delete pkt;
367        return;
368    }
369
370    memcpy(cacheData[tid], pkt->getPtr<uint8_t *>(), cacheBlkSize);
371    cacheDataValid[tid] = true;
372
373    if (!drainPending) {
374        // Wake up the CPU (if it went to sleep and was waiting on
375        // this completion event).
376        cpu->wakeCPU();
377
378        DPRINTF(Activity, "[tid:%u] Activating fetch due to cache completion\n",
379                tid);
380
381        switchToActive();
382    }
383
384    // Only switch to IcacheAccessComplete if we're not stalled as well.
385    if (checkStall(tid)) {
386        fetchStatus[tid] = Blocked;
387    } else {
388        fetchStatus[tid] = IcacheAccessComplete;
389    }
390
391    // Reset the mem req to NULL.
392    delete pkt->req;
393    delete pkt;
394    memReq[tid] = NULL;
395}
396
397template <class Impl>
398bool
399DefaultFetch<Impl>::drain()
400{
401    // Fetch is ready to drain at any time.
402    cpu->signalDrained();
403    drainPending = true;
404    return true;
405}
406
407template <class Impl>
408void
409DefaultFetch<Impl>::resume()
410{
411    drainPending = false;
412}
413
414template <class Impl>
415void
416DefaultFetch<Impl>::switchOut()
417{
418    switchedOut = true;
419    // Branch predictor needs to have its state cleared.
420    branchPred.switchOut();
421}
422
423template <class Impl>
424void
425DefaultFetch<Impl>::takeOverFrom()
426{
427    // Reset all state
428    for (int i = 0; i < Impl::MaxThreads; ++i) {
429        stalls[i].decode = 0;
430        stalls[i].rename = 0;
431        stalls[i].iew = 0;
432        stalls[i].commit = 0;
433        PC[i] = cpu->readPC(i);
434        nextPC[i] = cpu->readNextPC(i);
435#if ISA_HAS_DELAY_SLOT
436        nextNPC[i] = cpu->readNextNPC(i);
437#else
438        nextNPC[i] = nextPC[i] + sizeof(TheISA::MachInst);
439#endif
440        fetchStatus[i] = Running;
441    }
442    numInst = 0;
443    wroteToTimeBuffer = false;
444    _status = Inactive;
445    switchedOut = false;
446    interruptPending = false;
447    branchPred.takeOverFrom();
448}
449
450template <class Impl>
451void
452DefaultFetch<Impl>::wakeFromQuiesce()
453{
454    DPRINTF(Fetch, "Waking up from quiesce\n");
455    // Hopefully this is safe
456    // @todo: Allow other threads to wake from quiesce.
457    fetchStatus[0] = Running;
458}
459
460template <class Impl>
461inline void
462DefaultFetch<Impl>::switchToActive()
463{
464    if (_status == Inactive) {
465        DPRINTF(Activity, "Activating stage.\n");
466
467        cpu->activateStage(O3CPU::FetchIdx);
468
469        _status = Active;
470    }
471}
472
473template <class Impl>
474inline void
475DefaultFetch<Impl>::switchToInactive()
476{
477    if (_status == Active) {
478        DPRINTF(Activity, "Deactivating stage.\n");
479
480        cpu->deactivateStage(O3CPU::FetchIdx);
481
482        _status = Inactive;
483    }
484}
485
486template <class Impl>
487bool
488DefaultFetch<Impl>::lookupAndUpdateNextPC(DynInstPtr &inst, Addr &next_PC,
489                                          Addr &next_NPC)
490{
491    // Do branch prediction check here.
492    // A bit of a misnomer...next_PC is actually the current PC until
493    // this function updates it.
494    bool predict_taken;
495
496    if (!inst->isControl()) {
497        next_PC  = next_NPC;
498        next_NPC = next_NPC + instSize;
499        inst->setPredTarg(next_PC, next_NPC);
500        inst->setPredTaken(false);
501        return false;
502    }
503
504    int tid = inst->threadNumber;
505    Addr pred_PC = next_PC;
506    predict_taken = branchPred.predict(inst, pred_PC, tid);
507
508/*    if (predict_taken) {
509        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be taken to %#x.\n",
510                tid, pred_PC);
511    } else {
512        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be not taken.\n", tid);
513    }*/
514
515#if ISA_HAS_DELAY_SLOT
516    next_PC = next_NPC;
517    if (predict_taken)
518        next_NPC = pred_PC;
519    else
520        next_NPC += instSize;
521#else
522    if (predict_taken)
523        next_PC = pred_PC;
524    else
525        next_PC += instSize;
526    next_NPC = next_PC + instSize;
527#endif
528/*    DPRINTF(Fetch, "[tid:%i]: Branch predicted to go to %#x and then %#x.\n",
529            tid, next_PC, next_NPC);*/
530    inst->setPredTarg(next_PC, next_NPC);
531    inst->setPredTaken(predict_taken);
532
533    ++fetchedBranches;
534
535    if (predict_taken) {
536        ++predictedBranches;
537    }
538
539    return predict_taken;
540}
541
542template <class Impl>
543bool
544DefaultFetch<Impl>::fetchCacheLine(Addr fetch_PC, Fault &ret_fault, unsigned tid)
545{
546    Fault fault = NoFault;
547
548    //AlphaDep
549    if (cacheBlocked) {
550        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n",
551                tid);
552        return false;
553    } else if (isSwitchedOut()) {
554        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, switched out\n",
555                tid);
556        return false;
557    } else if (interruptPending && !(fetch_PC & 0x3)) {
558        // Hold off fetch from getting new instructions when:
559        // Cache is blocked, or
560        // while an interrupt is pending and we're not in PAL mode, or
561        // fetch is switched out.
562        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n",
563                tid);
564        return false;
565    }
566
567    // Align the fetch PC so it's at the start of a cache block.
568    Addr block_PC = icacheBlockAlignPC(fetch_PC);
569
570    // If we've already got the block, no need to try to fetch it again.
571    if (cacheDataValid[tid] && block_PC == cacheDataPC[tid]) {
572        return true;
573    }
574
575    // Setup the memReq to do a read of the first instruction's address.
576    // Set the appropriate read size and flags as well.
577    // Build request here.
578    RequestPtr mem_req = new Request(tid, block_PC, cacheBlkSize, 0,
579                                     fetch_PC, cpu->readCpuId(), tid);
580
581    memReq[tid] = mem_req;
582
583    // Translate the instruction request.
584    fault = cpu->translateInstReq(mem_req, cpu->thread[tid]);
585
586    // In the case of faults, the fetch stage may need to stall and wait
587    // for the ITB miss to be handled.
588
589    // If translation was successful, attempt to read the first
590    // instruction.
591    if (fault == NoFault) {
592#if 0
593        if (cpu->system->memctrl->badaddr(memReq[tid]->paddr) ||
594            memReq[tid]->isUncacheable()) {
595            DPRINTF(Fetch, "Fetch: Bad address %#x (hopefully on a "
596                    "misspeculating path)!",
597                    memReq[tid]->paddr);
598            ret_fault = TheISA::genMachineCheckFault();
599            return false;
600        }
601#endif
602
603        // Build packet here.
604        PacketPtr data_pkt = new Packet(mem_req,
605                                        Packet::ReadReq, Packet::Broadcast);
606        data_pkt->dataDynamicArray(new uint8_t[cacheBlkSize]);
607
608        cacheDataPC[tid] = block_PC;
609        cacheDataValid[tid] = false;
610
611        DPRINTF(Fetch, "Fetch: Doing instruction read.\n");
612
613        fetchedCacheLines++;
614
615        // Now do the timing access to see whether or not the instruction
616        // exists within the cache.
617        if (!icachePort->sendTiming(data_pkt)) {
618            if (data_pkt->result == Packet::BadAddress) {
619                fault = TheISA::genMachineCheckFault();
620                delete mem_req;
621                memReq[tid] = NULL;
622                warn("Bad address!\n");
623            }
624            assert(retryPkt == NULL);
625            assert(retryTid == -1);
626            DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid);
627            fetchStatus[tid] = IcacheWaitRetry;
628            retryPkt = data_pkt;
629            retryTid = tid;
630            cacheBlocked = true;
631            return false;
632        }
633
634        DPRINTF(Fetch, "[tid:%i]: Doing cache access.\n", tid);
635
636        lastIcacheStall[tid] = curTick;
637
638        DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache "
639                "response.\n", tid);
640
641        fetchStatus[tid] = IcacheWaitResponse;
642    } else {
643        delete mem_req;
644        memReq[tid] = NULL;
645    }
646
647    ret_fault = fault;
648    return true;
649}
650
651template <class Impl>
652inline void
653DefaultFetch<Impl>::doSquash(const Addr &new_PC,
654        const Addr &new_NPC, unsigned tid)
655{
656    DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %#x, NPC to: %#x.\n",
657            tid, new_PC, new_NPC);
658
659    PC[tid] = new_PC;
660    nextPC[tid] = new_NPC;
661    nextNPC[tid] = new_NPC + instSize;
662
663    // Clear the icache miss if it's outstanding.
664    if (fetchStatus[tid] == IcacheWaitResponse) {
665        DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n",
666                tid);
667        memReq[tid] = NULL;
668    }
669
670    // Get rid of the retrying packet if it was from this thread.
671    if (retryTid == tid) {
672        assert(cacheBlocked);
673        if (retryPkt) {
674            delete retryPkt->req;
675            delete retryPkt;
676        }
677        retryPkt = NULL;
678        retryTid = -1;
679    }
680
681    fetchStatus[tid] = Squashing;
682
683    ++fetchSquashCycles;
684}
685
686template<class Impl>
687void
688DefaultFetch<Impl>::squashFromDecode(const Addr &new_PC, const Addr &new_NPC,
689                                     const InstSeqNum &seq_num,
690                                     unsigned tid)
691{
692    DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n",tid);
693
694    doSquash(new_PC, new_NPC, tid);
695
696    // Tell the CPU to remove any instructions that are in flight between
697    // fetch and decode.
698    cpu->removeInstsUntil(seq_num, tid);
699}
700
701template<class Impl>
702bool
703DefaultFetch<Impl>::checkStall(unsigned tid) const
704{
705    bool ret_val = false;
706
707    if (cpu->contextSwitch) {
708        DPRINTF(Fetch,"[tid:%i]: Stalling for a context switch.\n",tid);
709        ret_val = true;
710    } else if (stalls[tid].decode) {
711        DPRINTF(Fetch,"[tid:%i]: Stall from Decode stage detected.\n",tid);
712        ret_val = true;
713    } else if (stalls[tid].rename) {
714        DPRINTF(Fetch,"[tid:%i]: Stall from Rename stage detected.\n",tid);
715        ret_val = true;
716    } else if (stalls[tid].iew) {
717        DPRINTF(Fetch,"[tid:%i]: Stall from IEW stage detected.\n",tid);
718        ret_val = true;
719    } else if (stalls[tid].commit) {
720        DPRINTF(Fetch,"[tid:%i]: Stall from Commit stage detected.\n",tid);
721        ret_val = true;
722    }
723
724    return ret_val;
725}
726
727template<class Impl>
728typename DefaultFetch<Impl>::FetchStatus
729DefaultFetch<Impl>::updateFetchStatus()
730{
731    //Check Running
732    std::list<unsigned>::iterator threads = activeThreads->begin();
733    std::list<unsigned>::iterator end = activeThreads->end();
734
735    while (threads != end) {
736        unsigned tid = *threads++;
737
738        if (fetchStatus[tid] == Running ||
739            fetchStatus[tid] == Squashing ||
740            fetchStatus[tid] == IcacheAccessComplete) {
741
742            if (_status == Inactive) {
743                DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid);
744
745                if (fetchStatus[tid] == IcacheAccessComplete) {
746                    DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache"
747                            "completion\n",tid);
748                }
749
750                cpu->activateStage(O3CPU::FetchIdx);
751            }
752
753            return Active;
754        }
755    }
756
757    // Stage is switching from active to inactive, notify CPU of it.
758    if (_status == Active) {
759        DPRINTF(Activity, "Deactivating stage.\n");
760
761        cpu->deactivateStage(O3CPU::FetchIdx);
762    }
763
764    return Inactive;
765}
766
767template <class Impl>
768void
769DefaultFetch<Impl>::squash(const Addr &new_PC, const Addr &new_NPC,
770                           const InstSeqNum &seq_num,
771                           bool squash_delay_slot, unsigned tid)
772{
773    DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n",tid);
774
775    doSquash(new_PC, new_NPC, tid);
776
777#if ISA_HAS_DELAY_SLOT
778    // Tell the CPU to remove any instructions that are not in the ROB.
779    cpu->removeInstsNotInROB(tid, squash_delay_slot, seq_num);
780#else
781    // Tell the CPU to remove any instructions that are not in the ROB.
782    cpu->removeInstsNotInROB(tid, true, 0);
783#endif
784}
785
786template <class Impl>
787void
788DefaultFetch<Impl>::tick()
789{
790    std::list<unsigned>::iterator threads = activeThreads->begin();
791    std::list<unsigned>::iterator end = activeThreads->end();
792    bool status_change = false;
793
794    wroteToTimeBuffer = false;
795
796    while (threads != end) {
797        unsigned tid = *threads++;
798
799        // Check the signals for each thread to determine the proper status
800        // for each thread.
801        bool updated_status = checkSignalsAndUpdate(tid);
802        status_change =  status_change || updated_status;
803    }
804
805    DPRINTF(Fetch, "Running stage.\n");
806
807    // Reset the number of the instruction we're fetching.
808    numInst = 0;
809
810#if FULL_SYSTEM
811    if (fromCommit->commitInfo[0].interruptPending) {
812        interruptPending = true;
813    }
814
815    if (fromCommit->commitInfo[0].clearInterrupt) {
816        interruptPending = false;
817    }
818#endif
819
820    for (threadFetched = 0; threadFetched < numFetchingThreads;
821         threadFetched++) {
822        // Fetch each of the actively fetching threads.
823        fetch(status_change);
824    }
825
826    // Record number of instructions fetched this cycle for distribution.
827    fetchNisnDist.sample(numInst);
828
829    if (status_change) {
830        // Change the fetch stage status if there was a status change.
831        _status = updateFetchStatus();
832    }
833
834    // If there was activity this cycle, inform the CPU of it.
835    if (wroteToTimeBuffer || cpu->contextSwitch) {
836        DPRINTF(Activity, "Activity this cycle.\n");
837
838        cpu->activityThisCycle();
839    }
840}
841
842template <class Impl>
843bool
844DefaultFetch<Impl>::checkSignalsAndUpdate(unsigned tid)
845{
846    // Update the per thread stall statuses.
847    if (fromDecode->decodeBlock[tid]) {
848        stalls[tid].decode = true;
849    }
850
851    if (fromDecode->decodeUnblock[tid]) {
852        assert(stalls[tid].decode);
853        assert(!fromDecode->decodeBlock[tid]);
854        stalls[tid].decode = false;
855    }
856
857    if (fromRename->renameBlock[tid]) {
858        stalls[tid].rename = true;
859    }
860
861    if (fromRename->renameUnblock[tid]) {
862        assert(stalls[tid].rename);
863        assert(!fromRename->renameBlock[tid]);
864        stalls[tid].rename = false;
865    }
866
867    if (fromIEW->iewBlock[tid]) {
868        stalls[tid].iew = true;
869    }
870
871    if (fromIEW->iewUnblock[tid]) {
872        assert(stalls[tid].iew);
873        assert(!fromIEW->iewBlock[tid]);
874        stalls[tid].iew = false;
875    }
876
877    if (fromCommit->commitBlock[tid]) {
878        stalls[tid].commit = true;
879    }
880
881    if (fromCommit->commitUnblock[tid]) {
882        assert(stalls[tid].commit);
883        assert(!fromCommit->commitBlock[tid]);
884        stalls[tid].commit = false;
885    }
886
887    // Check squash signals from commit.
888    if (fromCommit->commitInfo[tid].squash) {
889
890        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
891                "from commit.\n",tid);
892
893#if ISA_HAS_DELAY_SLOT
894    InstSeqNum doneSeqNum = fromCommit->commitInfo[tid].bdelayDoneSeqNum;
895#else
896    InstSeqNum doneSeqNum = fromCommit->commitInfo[tid].doneSeqNum;
897#endif
898        // In any case, squash.
899        squash(fromCommit->commitInfo[tid].nextPC,
900               fromCommit->commitInfo[tid].nextNPC,
901               doneSeqNum,
902               fromCommit->commitInfo[tid].squashDelaySlot,
903               tid);
904
905        // Also check if there's a mispredict that happened.
906        if (fromCommit->commitInfo[tid].branchMispredict) {
907            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
908                              fromCommit->commitInfo[tid].nextPC,
909                              fromCommit->commitInfo[tid].branchTaken,
910                              tid);
911        } else {
912            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
913                              tid);
914        }
915
916        return true;
917    } else if (fromCommit->commitInfo[tid].doneSeqNum) {
918        // Update the branch predictor if it wasn't a squashed instruction
919        // that was broadcasted.
920        branchPred.update(fromCommit->commitInfo[tid].doneSeqNum, tid);
921    }
922
923    // Check ROB squash signals from commit.
924    if (fromCommit->commitInfo[tid].robSquashing) {
925        DPRINTF(Fetch, "[tid:%u]: ROB is still squashing.\n", tid);
926
927        // Continue to squash.
928        fetchStatus[tid] = Squashing;
929
930        return true;
931    }
932
933    // Check squash signals from decode.
934    if (fromDecode->decodeInfo[tid].squash) {
935        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
936                "from decode.\n",tid);
937
938        // Update the branch predictor.
939        if (fromDecode->decodeInfo[tid].branchMispredict) {
940            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
941                              fromDecode->decodeInfo[tid].nextPC,
942                              fromDecode->decodeInfo[tid].branchTaken,
943                              tid);
944        } else {
945            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
946                              tid);
947        }
948
949        if (fetchStatus[tid] != Squashing) {
950
951#if ISA_HAS_DELAY_SLOT
952            InstSeqNum doneSeqNum = fromDecode->decodeInfo[tid].bdelayDoneSeqNum;
953#else
954            InstSeqNum doneSeqNum = fromDecode->decodeInfo[tid].doneSeqNum;
955#endif
956            DPRINTF(Fetch, "Squashing from decode with PC = %#x, NPC = %#x\n",
957                    fromDecode->decodeInfo[tid].nextPC,
958                    fromDecode->decodeInfo[tid].nextNPC);
959            // Squash unless we're already squashing
960            squashFromDecode(fromDecode->decodeInfo[tid].nextPC,
961                             fromDecode->decodeInfo[tid].nextNPC,
962                             doneSeqNum,
963                             tid);
964
965            return true;
966        }
967    }
968
969    if (checkStall(tid) &&
970        fetchStatus[tid] != IcacheWaitResponse &&
971        fetchStatus[tid] != IcacheWaitRetry) {
972        DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid);
973
974        fetchStatus[tid] = Blocked;
975
976        return true;
977    }
978
979    if (fetchStatus[tid] == Blocked ||
980        fetchStatus[tid] == Squashing) {
981        // Switch status to running if fetch isn't being told to block or
982        // squash this cycle.
983        DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n",
984                tid);
985
986        fetchStatus[tid] = Running;
987
988        return true;
989    }
990
991    // If we've reached this point, we have not gotten any signals that
992    // cause fetch to change its status.  Fetch remains the same as before.
993    return false;
994}
995
996template<class Impl>
997void
998DefaultFetch<Impl>::fetch(bool &status_change)
999{
1000    //////////////////////////////////////////
1001    // Start actual fetch
1002    //////////////////////////////////////////
1003    int tid = getFetchingThread(fetchPolicy);
1004
1005    if (tid == -1 || drainPending) {
1006        DPRINTF(Fetch,"There are no more threads available to fetch from.\n");
1007
1008        // Breaks looping condition in tick()
1009        threadFetched = numFetchingThreads;
1010        return;
1011    }
1012
1013    DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid);
1014
1015    // The current PC.
1016    Addr &fetch_PC = PC[tid];
1017
1018    Addr &fetch_NPC = nextPC[tid];
1019
1020    // Fault code for memory access.
1021    Fault fault = NoFault;
1022
1023    // If returning from the delay of a cache miss, then update the status
1024    // to running, otherwise do the cache access.  Possibly move this up
1025    // to tick() function.
1026    if (fetchStatus[tid] == IcacheAccessComplete) {
1027        DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n",
1028                tid);
1029
1030        fetchStatus[tid] = Running;
1031        status_change = true;
1032    } else if (fetchStatus[tid] == Running) {
1033        DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read "
1034                "instruction, starting at PC %08p.\n",
1035                tid, fetch_PC);
1036
1037        bool fetch_success = fetchCacheLine(fetch_PC, fault, tid);
1038        if (!fetch_success) {
1039            if (cacheBlocked) {
1040                ++icacheStallCycles;
1041            } else {
1042                ++fetchMiscStallCycles;
1043            }
1044            return;
1045        }
1046    } else {
1047        if (fetchStatus[tid] == Idle) {
1048            ++fetchIdleCycles;
1049            DPRINTF(Fetch, "[tid:%i]: Fetch is idle!\n", tid);
1050        } else if (fetchStatus[tid] == Blocked) {
1051            ++fetchBlockedCycles;
1052            DPRINTF(Fetch, "[tid:%i]: Fetch is blocked!\n", tid);
1053        } else if (fetchStatus[tid] == Squashing) {
1054            ++fetchSquashCycles;
1055            DPRINTF(Fetch, "[tid:%i]: Fetch is squashing!\n", tid);
1056        } else if (fetchStatus[tid] == IcacheWaitResponse) {
1057            ++icacheStallCycles;
1058            DPRINTF(Fetch, "[tid:%i]: Fetch is waiting cache response!\n", tid);
1059        }
1060
1061        // Status is Idle, Squashing, Blocked, or IcacheWaitResponse, so
1062        // fetch should do nothing.
1063        return;
1064    }
1065
1066    ++fetchCycles;
1067
1068    // If we had a stall due to an icache miss, then return.
1069    if (fetchStatus[tid] == IcacheWaitResponse) {
1070        ++icacheStallCycles;
1071        status_change = true;
1072        return;
1073    }
1074
1075    Addr next_PC = fetch_PC;
1076    Addr next_NPC = fetch_NPC;
1077
1078    InstSeqNum inst_seq;
1079    MachInst inst;
1080    ExtMachInst ext_inst;
1081    // @todo: Fix this hack.
1082    unsigned offset = (fetch_PC & cacheBlkMask) & ~3;
1083
1084    if (fault == NoFault) {
1085        // If the read of the first instruction was successful, then grab the
1086        // instructions from the rest of the cache line and put them into the
1087        // queue heading to decode.
1088
1089        DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to "
1090                "decode.\n",tid);
1091
1092        // Need to keep track of whether or not a predicted branch
1093        // ended this fetch block.
1094        bool predicted_branch = false;
1095
1096        for (;
1097             offset < cacheBlkSize &&
1098                 numInst < fetchWidth &&
1099                 !predicted_branch;
1100             ++numInst) {
1101
1102            // If we're branching after this instruction, quite fetching
1103            // from the same block then.
1104            predicted_branch =
1105                (fetch_PC + sizeof(TheISA::MachInst) != fetch_NPC);
1106            if (predicted_branch) {
1107                DPRINTF(Fetch, "Branch detected with PC = %#x, NPC = %#x\n",
1108                        fetch_PC, fetch_NPC);
1109            }
1110
1111
1112            // Get a sequence number.
1113            inst_seq = cpu->getAndIncrementInstSeq();
1114
1115            // Make sure this is a valid index.
1116            assert(offset <= cacheBlkSize - instSize);
1117
1118            // Get the instruction from the array of the cache line.
1119            inst = TheISA::gtoh(*reinterpret_cast<TheISA::MachInst *>
1120                        (&cacheData[tid][offset]));
1121
1122#if THE_ISA == ALPHA_ISA
1123            ext_inst = TheISA::makeExtMI(inst, fetch_PC);
1124#elif THE_ISA == SPARC_ISA
1125            ext_inst = TheISA::makeExtMI(inst, cpu->thread[tid]->getTC());
1126#elif THE_ISA == MIPS_ISA
1127            ext_inst = TheISA::makeExtMI(inst, cpu->thread[tid]->getTC());
1128#endif
1129
1130            // Create a new DynInst from the instruction fetched.
1131            DynInstPtr instruction = new DynInst(ext_inst,
1132                                                 fetch_PC, fetch_NPC,
1133                                                 next_PC, next_NPC,
1134                                                 inst_seq, cpu);
1135            instruction->setTid(tid);
1136
1137            instruction->setASID(tid);
1138
1139            instruction->setThreadState(cpu->thread[tid]);
1140
1141            DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x created "
1142                    "[sn:%lli]\n",
1143                    tid, instruction->readPC(), inst_seq);
1144
1145            //DPRINTF(Fetch, "[tid:%i]: MachInst is %#x\n", tid, ext_inst);
1146
1147            DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n",
1148                    tid, instruction->staticInst->disassemble(fetch_PC));
1149
1150            instruction->traceData =
1151                Trace::getInstRecord(curTick, cpu->tcBase(tid),
1152                                     instruction->staticInst,
1153                                     instruction->readPC());
1154
1155            ///FIXME This needs to be more robust in dealing with delay slots
1156#if !ISA_HAS_DELAY_SLOT
1157//	    predicted_branch |=
1158#endif
1159            lookupAndUpdateNextPC(instruction, next_PC, next_NPC);
1160            predicted_branch |= (next_PC != fetch_NPC);
1161
1162            // Add instruction to the CPU's list of instructions.
1163            instruction->setInstListIt(cpu->addInst(instruction));
1164
1165            // Write the instruction to the first slot in the queue
1166            // that heads to decode.
1167            toDecode->insts[numInst] = instruction;
1168
1169            toDecode->size++;
1170
1171            // Increment stat of fetched instructions.
1172            ++fetchedInsts;
1173
1174            // Move to the next instruction, unless we have a branch.
1175            fetch_PC = next_PC;
1176            fetch_NPC = next_NPC;
1177
1178            if (instruction->isQuiesce()) {
1179                DPRINTF(Fetch, "Quiesce instruction encountered, halting fetch!",
1180                        curTick);
1181                fetchStatus[tid] = QuiescePending;
1182                ++numInst;
1183                status_change = true;
1184                break;
1185            }
1186
1187            offset += instSize;
1188        }
1189
1190        if (offset >= cacheBlkSize) {
1191            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached the end of cache "
1192                    "block.\n", tid);
1193        } else if (numInst >= fetchWidth) {
1194            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached fetch bandwidth "
1195                    "for this cycle.\n", tid);
1196        } else if (predicted_branch) {
1197            DPRINTF(Fetch, "[tid:%i]: Done fetching, predicted branch "
1198                    "instruction encountered.\n", tid);
1199        }
1200    }
1201
1202    if (numInst > 0) {
1203        wroteToTimeBuffer = true;
1204    }
1205
1206    // Now that fetching is completed, update the PC to signify what the next
1207    // cycle will be.
1208    if (fault == NoFault) {
1209        PC[tid] = next_PC;
1210        nextPC[tid] = next_NPC;
1211        nextNPC[tid] = next_NPC + instSize;
1212#if ISA_HAS_DELAY_SLOT
1213        DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n", tid, PC[tid]);
1214#else
1215        DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n", tid, next_PC);
1216#endif
1217    } else {
1218        // We shouldn't be in an icache miss and also have a fault (an ITB
1219        // miss)
1220        if (fetchStatus[tid] == IcacheWaitResponse) {
1221            panic("Fetch should have exited prior to this!");
1222        }
1223
1224        // Send the fault to commit.  This thread will not do anything
1225        // until commit handles the fault.  The only other way it can
1226        // wake up is if a squash comes along and changes the PC.
1227#if FULL_SYSTEM
1228        assert(numInst < fetchWidth);
1229        // Get a sequence number.
1230        inst_seq = cpu->getAndIncrementInstSeq();
1231        // We will use a nop in order to carry the fault.
1232        ext_inst = TheISA::NoopMachInst;
1233
1234        // Create a new DynInst from the dummy nop.
1235        DynInstPtr instruction = new DynInst(ext_inst,
1236                                             fetch_PC, fetch_NPC,
1237                                             next_PC, next_NPC,
1238                                             inst_seq, cpu);
1239        instruction->setPredTarg(next_PC, next_NPC);
1240        instruction->setTid(tid);
1241
1242        instruction->setASID(tid);
1243
1244        instruction->setThreadState(cpu->thread[tid]);
1245
1246        instruction->traceData = NULL;
1247
1248        instruction->setInstListIt(cpu->addInst(instruction));
1249
1250        instruction->fault = fault;
1251
1252        toDecode->insts[numInst] = instruction;
1253        toDecode->size++;
1254
1255        DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n",tid);
1256
1257        fetchStatus[tid] = TrapPending;
1258        status_change = true;
1259#else // !FULL_SYSTEM
1260        fetchStatus[tid] = TrapPending;
1261        status_change = true;
1262
1263#endif // FULL_SYSTEM
1264        DPRINTF(Fetch, "[tid:%i]: fault (%s) detected @ PC %08p",
1265                tid, fault->name(), PC[tid]);
1266    }
1267}
1268
1269template<class Impl>
1270void
1271DefaultFetch<Impl>::recvRetry()
1272{
1273    if (retryPkt != NULL) {
1274        assert(cacheBlocked);
1275        assert(retryTid != -1);
1276        assert(fetchStatus[retryTid] == IcacheWaitRetry);
1277
1278        if (icachePort->sendTiming(retryPkt)) {
1279            fetchStatus[retryTid] = IcacheWaitResponse;
1280            retryPkt = NULL;
1281            retryTid = -1;
1282            cacheBlocked = false;
1283        }
1284    } else {
1285        assert(retryTid == -1);
1286        // Access has been squashed since it was sent out.  Just clear
1287        // the cache being blocked.
1288        cacheBlocked = false;
1289    }
1290}
1291
1292///////////////////////////////////////
1293//                                   //
1294//  SMT FETCH POLICY MAINTAINED HERE //
1295//                                   //
1296///////////////////////////////////////
1297template<class Impl>
1298int
1299DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority)
1300{
1301    if (numThreads > 1) {
1302        switch (fetch_priority) {
1303
1304          case SingleThread:
1305            return 0;
1306
1307          case RoundRobin:
1308            return roundRobin();
1309
1310          case IQ:
1311            return iqCount();
1312
1313          case LSQ:
1314            return lsqCount();
1315
1316          case Branch:
1317            return branchCount();
1318
1319          default:
1320            return -1;
1321        }
1322    } else {
1323        std::list<unsigned>::iterator thread = activeThreads->begin();
1324        assert(thread != activeThreads->end());
1325        int tid = *thread;
1326
1327        if (fetchStatus[tid] == Running ||
1328            fetchStatus[tid] == IcacheAccessComplete ||
1329            fetchStatus[tid] == Idle) {
1330            return tid;
1331        } else {
1332            return -1;
1333        }
1334    }
1335
1336}
1337
1338
1339template<class Impl>
1340int
1341DefaultFetch<Impl>::roundRobin()
1342{
1343    std::list<unsigned>::iterator pri_iter = priorityList.begin();
1344    std::list<unsigned>::iterator end      = priorityList.end();
1345
1346    int high_pri;
1347
1348    while (pri_iter != end) {
1349        high_pri = *pri_iter;
1350
1351        assert(high_pri <= numThreads);
1352
1353        if (fetchStatus[high_pri] == Running ||
1354            fetchStatus[high_pri] == IcacheAccessComplete ||
1355            fetchStatus[high_pri] == Idle) {
1356
1357            priorityList.erase(pri_iter);
1358            priorityList.push_back(high_pri);
1359
1360            return high_pri;
1361        }
1362
1363        pri_iter++;
1364    }
1365
1366    return -1;
1367}
1368
1369template<class Impl>
1370int
1371DefaultFetch<Impl>::iqCount()
1372{
1373    std::priority_queue<unsigned> PQ;
1374
1375    std::list<unsigned>::iterator threads = activeThreads->begin();
1376    std::list<unsigned>::iterator end = activeThreads->end();
1377
1378    while (threads != end) {
1379        unsigned tid = *threads++;
1380
1381        PQ.push(fromIEW->iewInfo[tid].iqCount);
1382    }
1383
1384    while (!PQ.empty()) {
1385
1386        unsigned high_pri = PQ.top();
1387
1388        if (fetchStatus[high_pri] == Running ||
1389            fetchStatus[high_pri] == IcacheAccessComplete ||
1390            fetchStatus[high_pri] == Idle)
1391            return high_pri;
1392        else
1393            PQ.pop();
1394
1395    }
1396
1397    return -1;
1398}
1399
1400template<class Impl>
1401int
1402DefaultFetch<Impl>::lsqCount()
1403{
1404    std::priority_queue<unsigned> PQ;
1405
1406    std::list<unsigned>::iterator threads = activeThreads->begin();
1407    std::list<unsigned>::iterator end = activeThreads->end();
1408
1409    while (threads != end) {
1410        unsigned tid = *threads++;
1411
1412        PQ.push(fromIEW->iewInfo[tid].ldstqCount);
1413    }
1414
1415    while (!PQ.empty()) {
1416
1417        unsigned high_pri = PQ.top();
1418
1419        if (fetchStatus[high_pri] == Running ||
1420            fetchStatus[high_pri] == IcacheAccessComplete ||
1421            fetchStatus[high_pri] == Idle)
1422            return high_pri;
1423        else
1424            PQ.pop();
1425
1426    }
1427
1428    return -1;
1429}
1430
1431template<class Impl>
1432int
1433DefaultFetch<Impl>::branchCount()
1434{
1435    std::list<unsigned>::iterator thread = activeThreads->begin();
1436    assert(thread != activeThreads->end());
1437    unsigned tid = *thread;
1438
1439    panic("Branch Count Fetch policy unimplemented\n");
1440    return 0 * tid;
1441}
1442