fetch_impl.hh revision 3635:8f3b67d2accd 
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        return;
75
76    panic("DefaultFetch doesn't expect recvStatusChange callback!");
77}
78
79template<class Impl>
80bool
81DefaultFetch<Impl>::IcachePort::recvTiming(PacketPtr pkt)
82{
83    DPRINTF(Fetch, "Received timing\n");
84    if (pkt->isResponse()) {
85        fetch->processCacheCompletion(pkt);
86    }
87    //else Snooped a coherence request, just return
88    return true;
89}
90
91template<class Impl>
92void
93DefaultFetch<Impl>::IcachePort::recvRetry()
94{
95    fetch->recvRetry();
96}
97
98template<class Impl>
99DefaultFetch<Impl>::DefaultFetch(Params *params)
100    : branchPred(params),
101      decodeToFetchDelay(params->decodeToFetchDelay),
102      renameToFetchDelay(params->renameToFetchDelay),
103      iewToFetchDelay(params->iewToFetchDelay),
104      commitToFetchDelay(params->commitToFetchDelay),
105      fetchWidth(params->fetchWidth),
106      cacheBlocked(false),
107      retryPkt(NULL),
108      retryTid(-1),
109      numThreads(params->numberOfThreads),
110      numFetchingThreads(params->smtNumFetchingThreads),
111      interruptPending(false),
112      drainPending(false),
113      switchedOut(false)
114{
115    if (numThreads > Impl::MaxThreads)
116        fatal("numThreads is not a valid value\n");
117
118    // Set fetch stage's status to inactive.
119    _status = Inactive;
120
121    std::string policy = params->smtFetchPolicy;
122
123    // Convert string to lowercase
124    std::transform(policy.begin(), policy.end(), policy.begin(),
125                   (int(*)(int)) tolower);
126
127    // Figure out fetch policy
128    if (policy == "singlethread") {
129        fetchPolicy = SingleThread;
130        if (numThreads > 1)
131            panic("Invalid Fetch Policy for a SMT workload.");
132    } else if (policy == "roundrobin") {
133        fetchPolicy = RoundRobin;
134        DPRINTF(Fetch, "Fetch policy set to Round Robin\n");
135    } else if (policy == "branch") {
136        fetchPolicy = Branch;
137        DPRINTF(Fetch, "Fetch policy set to Branch Count\n");
138    } else if (policy == "iqcount") {
139        fetchPolicy = IQ;
140        DPRINTF(Fetch, "Fetch policy set to IQ count\n");
141    } else if (policy == "lsqcount") {
142        fetchPolicy = LSQ;
143        DPRINTF(Fetch, "Fetch policy set to LSQ count\n");
144    } else {
145        fatal("Invalid Fetch Policy. Options Are: {SingleThread,"
146              " RoundRobin,LSQcount,IQcount}\n");
147    }
148
149    // Size of cache block.
150    cacheBlkSize = 64;
151
152    // Create mask to get rid of offset bits.
153    cacheBlkMask = (cacheBlkSize - 1);
154
155    for (int tid=0; tid < numThreads; tid++) {
156
157        fetchStatus[tid] = Running;
158
159        priorityList.push_back(tid);
160
161        memReq[tid] = NULL;
162
163        // Create space to store a cache line.
164        cacheData[tid] = new uint8_t[cacheBlkSize];
165        cacheDataPC[tid] = 0;
166        cacheDataValid[tid] = false;
167
168        delaySlotInfo[tid].branchSeqNum = -1;
169        delaySlotInfo[tid].numInsts = 0;
170        delaySlotInfo[tid].targetAddr = 0;
171        delaySlotInfo[tid].targetReady = false;
172
173        stalls[tid].decode = false;
174        stalls[tid].rename = false;
175        stalls[tid].iew = false;
176        stalls[tid].commit = false;
177    }
178
179    // Get the size of an instruction.
180    instSize = sizeof(TheISA::MachInst);
181}
182
183template <class Impl>
184std::string
185DefaultFetch<Impl>::name() const
186{
187    return cpu->name() + ".fetch";
188}
189
190template <class Impl>
191void
192DefaultFetch<Impl>::regStats()
193{
194    icacheStallCycles
195        .name(name() + ".icacheStallCycles")
196        .desc("Number of cycles fetch is stalled on an Icache miss")
197        .prereq(icacheStallCycles);
198
199    fetchedInsts
200        .name(name() + ".Insts")
201        .desc("Number of instructions fetch has processed")
202        .prereq(fetchedInsts);
203
204    fetchedBranches
205        .name(name() + ".Branches")
206        .desc("Number of branches that fetch encountered")
207        .prereq(fetchedBranches);
208
209    predictedBranches
210        .name(name() + ".predictedBranches")
211        .desc("Number of branches that fetch has predicted taken")
212        .prereq(predictedBranches);
213
214    fetchCycles
215        .name(name() + ".Cycles")
216        .desc("Number of cycles fetch has run and was not squashing or"
217              " blocked")
218        .prereq(fetchCycles);
219
220    fetchSquashCycles
221        .name(name() + ".SquashCycles")
222        .desc("Number of cycles fetch has spent squashing")
223        .prereq(fetchSquashCycles);
224
225    fetchIdleCycles
226        .name(name() + ".IdleCycles")
227        .desc("Number of cycles fetch was idle")
228        .prereq(fetchIdleCycles);
229
230    fetchBlockedCycles
231        .name(name() + ".BlockedCycles")
232        .desc("Number of cycles fetch has spent blocked")
233        .prereq(fetchBlockedCycles);
234
235    fetchedCacheLines
236        .name(name() + ".CacheLines")
237        .desc("Number of cache lines fetched")
238        .prereq(fetchedCacheLines);
239
240    fetchMiscStallCycles
241        .name(name() + ".MiscStallCycles")
242        .desc("Number of cycles fetch has spent waiting on interrupts, or "
243              "bad addresses, or out of MSHRs")
244        .prereq(fetchMiscStallCycles);
245
246    fetchIcacheSquashes
247        .name(name() + ".IcacheSquashes")
248        .desc("Number of outstanding Icache misses that were squashed")
249        .prereq(fetchIcacheSquashes);
250
251    fetchNisnDist
252        .init(/* base value */ 0,
253              /* last value */ fetchWidth,
254              /* bucket size */ 1)
255        .name(name() + ".rateDist")
256        .desc("Number of instructions fetched each cycle (Total)")
257        .flags(Stats::pdf);
258
259    idleRate
260        .name(name() + ".idleRate")
261        .desc("Percent of cycles fetch was idle")
262        .prereq(idleRate);
263    idleRate = fetchIdleCycles * 100 / cpu->numCycles;
264
265    branchRate
266        .name(name() + ".branchRate")
267        .desc("Number of branch fetches per cycle")
268        .flags(Stats::total);
269    branchRate = fetchedBranches / cpu->numCycles;
270
271    fetchRate
272        .name(name() + ".rate")
273        .desc("Number of inst fetches per cycle")
274        .flags(Stats::total);
275    fetchRate = fetchedInsts / cpu->numCycles;
276
277    branchPred.regStats();
278}
279
280template<class Impl>
281void
282DefaultFetch<Impl>::setCPU(O3CPU *cpu_ptr)
283{
284    DPRINTF(Fetch, "Setting the CPU pointer.\n");
285    cpu = cpu_ptr;
286
287    // Name is finally available, so create the port.
288    icachePort = new IcachePort(this);
289
290#if USE_CHECKER
291    if (cpu->checker) {
292        cpu->checker->setIcachePort(icachePort);
293    }
294#endif
295
296    // Schedule fetch to get the correct PC from the CPU
297    // scheduleFetchStartupEvent(1);
298
299    // Fetch needs to start fetching instructions at the very beginning,
300    // so it must start up in active state.
301    switchToActive();
302}
303
304template<class Impl>
305void
306DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer)
307{
308    DPRINTF(Fetch, "Setting the time buffer pointer.\n");
309    timeBuffer = time_buffer;
310
311    // Create wires to get information from proper places in time buffer.
312    fromDecode = timeBuffer->getWire(-decodeToFetchDelay);
313    fromRename = timeBuffer->getWire(-renameToFetchDelay);
314    fromIEW = timeBuffer->getWire(-iewToFetchDelay);
315    fromCommit = timeBuffer->getWire(-commitToFetchDelay);
316}
317
318template<class Impl>
319void
320DefaultFetch<Impl>::setActiveThreads(std::list<unsigned> *at_ptr)
321{
322    DPRINTF(Fetch, "Setting active threads list pointer.\n");
323    activeThreads = at_ptr;
324}
325
326template<class Impl>
327void
328DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr)
329{
330    DPRINTF(Fetch, "Setting the fetch queue pointer.\n");
331    fetchQueue = fq_ptr;
332
333    // Create wire to write information to proper place in fetch queue.
334    toDecode = fetchQueue->getWire(0);
335}
336
337template<class Impl>
338void
339DefaultFetch<Impl>::initStage()
340{
341    // Setup PC and nextPC with initial state.
342    for (int tid = 0; tid < numThreads; tid++) {
343        PC[tid] = cpu->readPC(tid);
344        nextPC[tid] = cpu->readNextPC(tid);
345#if ISA_HAS_DELAY_SLOT
346        nextNPC[tid] = cpu->readNextNPC(tid);
347#endif
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        delaySlotInfo[i].branchSeqNum = -1;
438        delaySlotInfo[i].numInsts = 0;
439        delaySlotInfo[i].targetAddr = 0;
440        delaySlotInfo[i].targetReady = false;
441#endif
442        fetchStatus[i] = Running;
443    }
444    numInst = 0;
445    wroteToTimeBuffer = false;
446    _status = Inactive;
447    switchedOut = false;
448    interruptPending = false;
449    branchPred.takeOverFrom();
450}
451
452template <class Impl>
453void
454DefaultFetch<Impl>::wakeFromQuiesce()
455{
456    DPRINTF(Fetch, "Waking up from quiesce\n");
457    // Hopefully this is safe
458    // @todo: Allow other threads to wake from quiesce.
459    fetchStatus[0] = Running;
460}
461
462template <class Impl>
463inline void
464DefaultFetch<Impl>::switchToActive()
465{
466    if (_status == Inactive) {
467        DPRINTF(Activity, "Activating stage.\n");
468
469        cpu->activateStage(O3CPU::FetchIdx);
470
471        _status = Active;
472    }
473}
474
475template <class Impl>
476inline void
477DefaultFetch<Impl>::switchToInactive()
478{
479    if (_status == Active) {
480        DPRINTF(Activity, "Deactivating stage.\n");
481
482        cpu->deactivateStage(O3CPU::FetchIdx);
483
484        _status = Inactive;
485    }
486}
487
488template <class Impl>
489bool
490DefaultFetch<Impl>::lookupAndUpdateNextPC(DynInstPtr &inst, Addr &next_PC,
491                                          Addr &next_NPC)
492{
493    // Do branch prediction check here.
494    // A bit of a misnomer...next_PC is actually the current PC until
495    // this function updates it.
496    bool predict_taken;
497
498    if (!inst->isControl()) {
499#if ISA_HAS_DELAY_SLOT
500        Addr cur_PC = next_PC;
501        next_PC  = cur_PC + instSize;      //next_NPC;
502        next_NPC = cur_PC + (2 * instSize);//next_NPC + instSize;
503        inst->setPredTarg(next_NPC);
504#else
505        next_PC = next_PC + instSize;
506        inst->setPredTarg(next_PC);
507#endif
508        return false;
509    }
510
511    int tid = inst->threadNumber;
512#if ISA_HAS_DELAY_SLOT
513    Addr pred_PC = next_PC;
514    predict_taken = branchPred.predict(inst, pred_PC, tid);
515
516    if (predict_taken) {
517        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be true.\n", tid);
518    } else {
519        DPRINTF(Fetch, "[tid:%i]: Branch predicted to be false.\n", tid);
520    }
521
522    if (predict_taken) {
523        next_PC = next_NPC;
524        next_NPC = pred_PC;
525
526        // Update delay slot info
527        ++delaySlotInfo[tid].numInsts;
528        delaySlotInfo[tid].targetAddr = pred_PC;
529        DPRINTF(Fetch, "[tid:%i]: %i delay slot inst(s) to process.\n", tid,
530                delaySlotInfo[tid].numInsts);
531    } else { // !predict_taken
532        if (inst->isCondDelaySlot()) {
533            next_PC = pred_PC;
534            // The delay slot is skipped here if there is on
535            // prediction
536        } else {
537            next_PC = next_NPC;
538            // No need to declare a delay slot here since
539            // there is no for the pred. target to jump
540        }
541
542        next_NPC = next_NPC + instSize;
543    }
544#else
545    predict_taken = branchPred.predict(inst, next_PC, tid);
546#endif
547
548    ++fetchedBranches;
549
550    if (predict_taken) {
551        ++predictedBranches;
552    }
553
554    return predict_taken;
555}
556
557template <class Impl>
558bool
559DefaultFetch<Impl>::fetchCacheLine(Addr fetch_PC, Fault &ret_fault, unsigned tid)
560{
561    Fault fault = NoFault;
562
563    //AlphaDep
564    if (cacheBlocked) {
565        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n",
566                tid);
567        return false;
568    } else if (isSwitchedOut()) {
569        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, switched out\n",
570                tid);
571        return false;
572    } else if (interruptPending && !(fetch_PC & 0x3)) {
573        // Hold off fetch from getting new instructions when:
574        // Cache is blocked, or
575        // while an interrupt is pending and we're not in PAL mode, or
576        // fetch is switched out.
577        DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n",
578                tid);
579        return false;
580    }
581
582    // Align the fetch PC so it's at the start of a cache block.
583    Addr block_PC = icacheBlockAlignPC(fetch_PC);
584
585    // If we've already got the block, no need to try to fetch it again.
586    if (cacheDataValid[tid] && block_PC == cacheDataPC[tid]) {
587        return true;
588    }
589
590    // Setup the memReq to do a read of the first instruction's address.
591    // Set the appropriate read size and flags as well.
592    // Build request here.
593    RequestPtr mem_req = new Request(tid, block_PC, cacheBlkSize, 0,
594                                     fetch_PC, cpu->readCpuId(), tid);
595
596    memReq[tid] = mem_req;
597
598    // Translate the instruction request.
599    fault = cpu->translateInstReq(mem_req, cpu->thread[tid]);
600
601    // In the case of faults, the fetch stage may need to stall and wait
602    // for the ITB miss to be handled.
603
604    // If translation was successful, attempt to read the first
605    // instruction.
606    if (fault == NoFault) {
607#if 0
608        if (cpu->system->memctrl->badaddr(memReq[tid]->paddr) ||
609            memReq[tid]->isUncacheable()) {
610            DPRINTF(Fetch, "Fetch: Bad address %#x (hopefully on a "
611                    "misspeculating path)!",
612                    memReq[tid]->paddr);
613            ret_fault = TheISA::genMachineCheckFault();
614            return false;
615        }
616#endif
617
618        // Build packet here.
619        PacketPtr data_pkt = new Packet(mem_req,
620                                        Packet::ReadReq, Packet::Broadcast);
621        data_pkt->dataDynamicArray(new uint8_t[cacheBlkSize]);
622
623        cacheDataPC[tid] = block_PC;
624        cacheDataValid[tid] = false;
625
626        DPRINTF(Fetch, "Fetch: Doing instruction read.\n");
627
628        fetchedCacheLines++;
629
630        // Now do the timing access to see whether or not the instruction
631        // exists within the cache.
632        if (!icachePort->sendTiming(data_pkt)) {
633            if (data_pkt->result == Packet::BadAddress) {
634                fault = TheISA::genMachineCheckFault();
635                delete mem_req;
636                memReq[tid] = NULL;
637            }
638            assert(retryPkt == NULL);
639            assert(retryTid == -1);
640            DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid);
641            fetchStatus[tid] = IcacheWaitRetry;
642            retryPkt = data_pkt;
643            retryTid = tid;
644            cacheBlocked = true;
645            return false;
646        }
647
648        DPRINTF(Fetch, "[tid:%i]: Doing cache access.\n", tid);
649
650        lastIcacheStall[tid] = curTick;
651
652        DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache "
653                "response.\n", tid);
654
655        fetchStatus[tid] = IcacheWaitResponse;
656    } else {
657        delete mem_req;
658        memReq[tid] = NULL;
659    }
660
661    ret_fault = fault;
662    return true;
663}
664
665template <class Impl>
666inline void
667DefaultFetch<Impl>::doSquash(const Addr &new_PC, unsigned tid)
668{
669    DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %#x.\n",
670            tid, new_PC);
671
672    PC[tid] = new_PC;
673    nextPC[tid] = new_PC + instSize;
674    nextNPC[tid] = new_PC + (2 * instSize);
675
676    // Clear the icache miss if it's outstanding.
677    if (fetchStatus[tid] == IcacheWaitResponse) {
678        DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n",
679                tid);
680        memReq[tid] = NULL;
681    }
682
683    // Get rid of the retrying packet if it was from this thread.
684    if (retryTid == tid) {
685        assert(cacheBlocked);
686        cacheBlocked = false;
687        retryTid = -1;
688        delete retryPkt->req;
689        delete retryPkt;
690        retryPkt = NULL;
691    }
692
693    fetchStatus[tid] = Squashing;
694
695    ++fetchSquashCycles;
696}
697
698template<class Impl>
699void
700DefaultFetch<Impl>::squashFromDecode(const Addr &new_PC,
701                                     const InstSeqNum &seq_num,
702                                     unsigned tid)
703{
704    DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n",tid);
705
706    doSquash(new_PC, tid);
707
708#if ISA_HAS_DELAY_SLOT
709    if (seq_num <=  delaySlotInfo[tid].branchSeqNum) {
710        delaySlotInfo[tid].numInsts = 0;
711        delaySlotInfo[tid].targetAddr = 0;
712        delaySlotInfo[tid].targetReady = false;
713    }
714#endif
715
716    // Tell the CPU to remove any instructions that are in flight between
717    // fetch and decode.
718    cpu->removeInstsUntil(seq_num, tid);
719}
720
721template<class Impl>
722bool
723DefaultFetch<Impl>::checkStall(unsigned tid) const
724{
725    bool ret_val = false;
726
727    if (cpu->contextSwitch) {
728        DPRINTF(Fetch,"[tid:%i]: Stalling for a context switch.\n",tid);
729        ret_val = true;
730    } else if (stalls[tid].decode) {
731        DPRINTF(Fetch,"[tid:%i]: Stall from Decode stage detected.\n",tid);
732        ret_val = true;
733    } else if (stalls[tid].rename) {
734        DPRINTF(Fetch,"[tid:%i]: Stall from Rename stage detected.\n",tid);
735        ret_val = true;
736    } else if (stalls[tid].iew) {
737        DPRINTF(Fetch,"[tid:%i]: Stall from IEW stage detected.\n",tid);
738        ret_val = true;
739    } else if (stalls[tid].commit) {
740        DPRINTF(Fetch,"[tid:%i]: Stall from Commit stage detected.\n",tid);
741        ret_val = true;
742    }
743
744    return ret_val;
745}
746
747template<class Impl>
748typename DefaultFetch<Impl>::FetchStatus
749DefaultFetch<Impl>::updateFetchStatus()
750{
751    //Check Running
752    std::list<unsigned>::iterator threads = (*activeThreads).begin();
753
754    while (threads != (*activeThreads).end()) {
755
756        unsigned tid = *threads++;
757
758        if (fetchStatus[tid] == Running ||
759            fetchStatus[tid] == Squashing ||
760            fetchStatus[tid] == IcacheAccessComplete) {
761
762            if (_status == Inactive) {
763                DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid);
764
765                if (fetchStatus[tid] == IcacheAccessComplete) {
766                    DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache"
767                            "completion\n",tid);
768                }
769
770                cpu->activateStage(O3CPU::FetchIdx);
771            }
772
773            return Active;
774        }
775    }
776
777    // Stage is switching from active to inactive, notify CPU of it.
778    if (_status == Active) {
779        DPRINTF(Activity, "Deactivating stage.\n");
780
781        cpu->deactivateStage(O3CPU::FetchIdx);
782    }
783
784    return Inactive;
785}
786
787template <class Impl>
788void
789DefaultFetch<Impl>::squash(const Addr &new_PC, const InstSeqNum &seq_num,
790                           bool squash_delay_slot, unsigned tid)
791{
792    DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n",tid);
793
794    doSquash(new_PC, tid);
795
796#if ISA_HAS_DELAY_SLOT
797    if (seq_num <=  delaySlotInfo[tid].branchSeqNum) {
798        delaySlotInfo[tid].numInsts = 0;
799        delaySlotInfo[tid].targetAddr = 0;
800        delaySlotInfo[tid].targetReady = false;
801    }
802
803    // Tell the CPU to remove any instructions that are not in the ROB.
804    cpu->removeInstsNotInROB(tid, squash_delay_slot, seq_num);
805#else
806    // Tell the CPU to remove any instructions that are not in the ROB.
807    cpu->removeInstsNotInROB(tid, true, 0);
808#endif
809}
810
811template <class Impl>
812void
813DefaultFetch<Impl>::tick()
814{
815    std::list<unsigned>::iterator threads = (*activeThreads).begin();
816    bool status_change = false;
817
818    wroteToTimeBuffer = false;
819
820    while (threads != (*activeThreads).end()) {
821        unsigned tid = *threads++;
822
823        // Check the signals for each thread to determine the proper status
824        // for each thread.
825        bool updated_status = checkSignalsAndUpdate(tid);
826        status_change =  status_change || updated_status;
827    }
828
829    DPRINTF(Fetch, "Running stage.\n");
830
831    // Reset the number of the instruction we're fetching.
832    numInst = 0;
833
834#if FULL_SYSTEM
835    if (fromCommit->commitInfo[0].interruptPending) {
836        interruptPending = true;
837    }
838
839    if (fromCommit->commitInfo[0].clearInterrupt) {
840        interruptPending = false;
841    }
842#endif
843
844    for (threadFetched = 0; threadFetched < numFetchingThreads;
845         threadFetched++) {
846        // Fetch each of the actively fetching threads.
847        fetch(status_change);
848    }
849
850    // Record number of instructions fetched this cycle for distribution.
851    fetchNisnDist.sample(numInst);
852
853    if (status_change) {
854        // Change the fetch stage status if there was a status change.
855        _status = updateFetchStatus();
856    }
857
858    // If there was activity this cycle, inform the CPU of it.
859    if (wroteToTimeBuffer || cpu->contextSwitch) {
860        DPRINTF(Activity, "Activity this cycle.\n");
861
862        cpu->activityThisCycle();
863    }
864}
865
866template <class Impl>
867bool
868DefaultFetch<Impl>::checkSignalsAndUpdate(unsigned tid)
869{
870    // Update the per thread stall statuses.
871    if (fromDecode->decodeBlock[tid]) {
872        stalls[tid].decode = true;
873    }
874
875    if (fromDecode->decodeUnblock[tid]) {
876        assert(stalls[tid].decode);
877        assert(!fromDecode->decodeBlock[tid]);
878        stalls[tid].decode = false;
879    }
880
881    if (fromRename->renameBlock[tid]) {
882        stalls[tid].rename = true;
883    }
884
885    if (fromRename->renameUnblock[tid]) {
886        assert(stalls[tid].rename);
887        assert(!fromRename->renameBlock[tid]);
888        stalls[tid].rename = false;
889    }
890
891    if (fromIEW->iewBlock[tid]) {
892        stalls[tid].iew = true;
893    }
894
895    if (fromIEW->iewUnblock[tid]) {
896        assert(stalls[tid].iew);
897        assert(!fromIEW->iewBlock[tid]);
898        stalls[tid].iew = false;
899    }
900
901    if (fromCommit->commitBlock[tid]) {
902        stalls[tid].commit = true;
903    }
904
905    if (fromCommit->commitUnblock[tid]) {
906        assert(stalls[tid].commit);
907        assert(!fromCommit->commitBlock[tid]);
908        stalls[tid].commit = false;
909    }
910
911    // Check squash signals from commit.
912    if (fromCommit->commitInfo[tid].squash) {
913
914        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
915                "from commit.\n",tid);
916
917#if ISA_HAS_DELAY_SLOT
918    InstSeqNum doneSeqNum = fromCommit->commitInfo[tid].bdelayDoneSeqNum;
919#else
920    InstSeqNum doneSeqNum = fromCommit->commitInfo[tid].doneSeqNum;
921#endif
922        // In any case, squash.
923        squash(fromCommit->commitInfo[tid].nextPC,
924               doneSeqNum,
925               fromCommit->commitInfo[tid].squashDelaySlot,
926               tid);
927
928        // Also check if there's a mispredict that happened.
929        if (fromCommit->commitInfo[tid].branchMispredict) {
930            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
931                              fromCommit->commitInfo[tid].nextPC,
932                              fromCommit->commitInfo[tid].branchTaken,
933                              tid);
934        } else {
935            branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum,
936                              tid);
937        }
938
939        return true;
940    } else if (fromCommit->commitInfo[tid].doneSeqNum) {
941        // Update the branch predictor if it wasn't a squashed instruction
942        // that was broadcasted.
943        branchPred.update(fromCommit->commitInfo[tid].doneSeqNum, tid);
944    }
945
946    // Check ROB squash signals from commit.
947    if (fromCommit->commitInfo[tid].robSquashing) {
948        DPRINTF(Fetch, "[tid:%u]: ROB is still squashing.\n", tid);
949
950        // Continue to squash.
951        fetchStatus[tid] = Squashing;
952
953        return true;
954    }
955
956    // Check squash signals from decode.
957    if (fromDecode->decodeInfo[tid].squash) {
958        DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash "
959                "from decode.\n",tid);
960
961        // Update the branch predictor.
962        if (fromDecode->decodeInfo[tid].branchMispredict) {
963            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
964                              fromDecode->decodeInfo[tid].nextPC,
965                              fromDecode->decodeInfo[tid].branchTaken,
966                              tid);
967        } else {
968            branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum,
969                              tid);
970        }
971
972        if (fetchStatus[tid] != Squashing) {
973
974#if ISA_HAS_DELAY_SLOT
975            InstSeqNum doneSeqNum = fromDecode->decodeInfo[tid].bdelayDoneSeqNum;
976#else
977            InstSeqNum doneSeqNum = fromDecode->decodeInfo[tid].doneSeqNum;
978#endif
979            // Squash unless we're already squashing
980            squashFromDecode(fromDecode->decodeInfo[tid].nextPC,
981                             doneSeqNum,
982                             tid);
983
984            return true;
985        }
986    }
987
988    if (checkStall(tid) && fetchStatus[tid] != IcacheWaitResponse) {
989        DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid);
990
991        fetchStatus[tid] = Blocked;
992
993        return true;
994    }
995
996    if (fetchStatus[tid] == Blocked ||
997        fetchStatus[tid] == Squashing) {
998        // Switch status to running if fetch isn't being told to block or
999        // squash this cycle.
1000        DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n",
1001                tid);
1002
1003        fetchStatus[tid] = Running;
1004
1005        return true;
1006    }
1007
1008    // If we've reached this point, we have not gotten any signals that
1009    // cause fetch to change its status.  Fetch remains the same as before.
1010    return false;
1011}
1012
1013template<class Impl>
1014void
1015DefaultFetch<Impl>::fetch(bool &status_change)
1016{
1017    //////////////////////////////////////////
1018    // Start actual fetch
1019    //////////////////////////////////////////
1020    int tid = getFetchingThread(fetchPolicy);
1021
1022    if (tid == -1 || drainPending) {
1023        DPRINTF(Fetch,"There are no more threads available to fetch from.\n");
1024
1025        // Breaks looping condition in tick()
1026        threadFetched = numFetchingThreads;
1027        return;
1028    }
1029
1030    DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid);
1031
1032    // The current PC.
1033    Addr &fetch_PC = PC[tid];
1034
1035    // Fault code for memory access.
1036    Fault fault = NoFault;
1037
1038    // If returning from the delay of a cache miss, then update the status
1039    // to running, otherwise do the cache access.  Possibly move this up
1040    // to tick() function.
1041    if (fetchStatus[tid] == IcacheAccessComplete) {
1042        DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n",
1043                tid);
1044
1045        fetchStatus[tid] = Running;
1046        status_change = true;
1047    } else if (fetchStatus[tid] == Running) {
1048        DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read "
1049                "instruction, starting at PC %08p.\n",
1050                tid, fetch_PC);
1051
1052        bool fetch_success = fetchCacheLine(fetch_PC, fault, tid);
1053        if (!fetch_success) {
1054            if (cacheBlocked) {
1055                ++icacheStallCycles;
1056            } else {
1057                ++fetchMiscStallCycles;
1058            }
1059            return;
1060        }
1061    } else {
1062        if (fetchStatus[tid] == Idle) {
1063            ++fetchIdleCycles;
1064            DPRINTF(Fetch, "[tid:%i]: Fetch is idle!\n", tid);
1065        } else if (fetchStatus[tid] == Blocked) {
1066            ++fetchBlockedCycles;
1067            DPRINTF(Fetch, "[tid:%i]: Fetch is blocked!\n", tid);
1068        } else if (fetchStatus[tid] == Squashing) {
1069            ++fetchSquashCycles;
1070            DPRINTF(Fetch, "[tid:%i]: Fetch is squashing!\n", tid);
1071        } else if (fetchStatus[tid] == IcacheWaitResponse) {
1072            ++icacheStallCycles;
1073            DPRINTF(Fetch, "[tid:%i]: Fetch is waiting cache response!\n", tid);
1074        }
1075
1076        // Status is Idle, Squashing, Blocked, or IcacheWaitResponse, so
1077        // fetch should do nothing.
1078        return;
1079    }
1080
1081    ++fetchCycles;
1082
1083    // If we had a stall due to an icache miss, then return.
1084    if (fetchStatus[tid] == IcacheWaitResponse) {
1085        ++icacheStallCycles;
1086        status_change = true;
1087        return;
1088    }
1089
1090    Addr next_PC = fetch_PC;
1091    Addr next_NPC = next_PC + instSize;
1092    InstSeqNum inst_seq;
1093    MachInst inst;
1094    ExtMachInst ext_inst;
1095    // @todo: Fix this hack.
1096    unsigned offset = (fetch_PC & cacheBlkMask) & ~3;
1097
1098    if (fault == NoFault) {
1099        // If the read of the first instruction was successful, then grab the
1100        // instructions from the rest of the cache line and put them into the
1101        // queue heading to decode.
1102
1103        DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to "
1104                "decode.\n",tid);
1105
1106        // Need to keep track of whether or not a predicted branch
1107        // ended this fetch block.
1108        bool predicted_branch = false;
1109
1110        // Need to keep track of whether or not a delay slot
1111        // instruction has been fetched
1112
1113        for (;
1114             offset < cacheBlkSize &&
1115                 numInst < fetchWidth &&
1116                 (!predicted_branch || delaySlotInfo[tid].numInsts > 0);
1117             ++numInst) {
1118
1119            // Get a sequence number.
1120            inst_seq = cpu->getAndIncrementInstSeq();
1121
1122            // Make sure this is a valid index.
1123            assert(offset <= cacheBlkSize - instSize);
1124
1125            // Get the instruction from the array of the cache line.
1126            inst = TheISA::gtoh(*reinterpret_cast<TheISA::MachInst *>
1127                        (&cacheData[tid][offset]));
1128
1129#if THE_ISA == ALPHA_ISA
1130            ext_inst = TheISA::makeExtMI(inst, fetch_PC);
1131#elif THE_ISA == SPARC_ISA
1132            ext_inst = TheISA::makeExtMI(inst, cpu->thread[tid]->getTC());
1133#endif
1134
1135            // Create a new DynInst from the instruction fetched.
1136            DynInstPtr instruction = new DynInst(ext_inst, fetch_PC,
1137                                                 next_PC,
1138                                                 inst_seq, cpu);
1139            instruction->setTid(tid);
1140
1141            instruction->setASID(tid);
1142
1143            instruction->setThreadState(cpu->thread[tid]);
1144
1145            DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x created "
1146                    "[sn:%lli]\n",
1147                    tid, instruction->readPC(), inst_seq);
1148
1149            DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n",
1150                    tid, instruction->staticInst->disassemble(fetch_PC));
1151
1152            instruction->traceData =
1153                Trace::getInstRecord(curTick, cpu->tcBase(tid),
1154                                     instruction->staticInst,
1155                                     instruction->readPC());
1156
1157            predicted_branch = lookupAndUpdateNextPC(instruction, next_PC,
1158                                                     next_NPC);
1159
1160            // Add instruction to the CPU's list of instructions.
1161            instruction->setInstListIt(cpu->addInst(instruction));
1162
1163            // Write the instruction to the first slot in the queue
1164            // that heads to decode.
1165            toDecode->insts[numInst] = instruction;
1166
1167            toDecode->size++;
1168
1169            // Increment stat of fetched instructions.
1170            ++fetchedInsts;
1171
1172            // Move to the next instruction, unless we have a branch.
1173            fetch_PC = next_PC;
1174
1175            if (instruction->isQuiesce()) {
1176                DPRINTF(Fetch, "Quiesce instruction encountered, halting fetch!",
1177                        curTick);
1178                fetchStatus[tid] = QuiescePending;
1179                ++numInst;
1180                status_change = true;
1181                break;
1182            }
1183
1184            offset += instSize;
1185
1186#if ISA_HAS_DELAY_SLOT
1187            if (predicted_branch) {
1188                delaySlotInfo[tid].branchSeqNum = inst_seq;
1189
1190                DPRINTF(Fetch, "[tid:%i]: Delay slot branch set to [sn:%i]\n",
1191                        tid, inst_seq);
1192                continue;
1193            } else if (delaySlotInfo[tid].numInsts > 0) {
1194                --delaySlotInfo[tid].numInsts;
1195
1196                // It's OK to set PC to target of branch
1197                if (delaySlotInfo[tid].numInsts == 0) {
1198                    delaySlotInfo[tid].targetReady = true;
1199
1200                    // Break the looping condition
1201                    predicted_branch = true;
1202                }
1203
1204                DPRINTF(Fetch, "[tid:%i]: %i delay slot inst(s) left to"
1205                        " process.\n", tid, delaySlotInfo[tid].numInsts);
1206            }
1207#endif
1208        }
1209
1210        if (offset >= cacheBlkSize) {
1211            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached the end of cache "
1212                    "block.\n", tid);
1213        } else if (numInst >= fetchWidth) {
1214            DPRINTF(Fetch, "[tid:%i]: Done fetching, reached fetch bandwidth "
1215                    "for this cycle.\n", tid);
1216        } else if (predicted_branch && delaySlotInfo[tid].numInsts <= 0) {
1217            DPRINTF(Fetch, "[tid:%i]: Done fetching, predicted branch "
1218                    "instruction encountered.\n", tid);
1219        }
1220    }
1221
1222    if (numInst > 0) {
1223        wroteToTimeBuffer = true;
1224    }
1225
1226    // Now that fetching is completed, update the PC to signify what the next
1227    // cycle will be.
1228    if (fault == NoFault) {
1229#if ISA_HAS_DELAY_SLOT
1230        if (delaySlotInfo[tid].targetReady &&
1231            delaySlotInfo[tid].numInsts == 0) {
1232            // Set PC to target
1233            PC[tid] = delaySlotInfo[tid].targetAddr; //next_PC
1234            nextPC[tid] = next_PC + instSize;        //next_NPC
1235            nextNPC[tid] = next_PC + (2 * instSize);
1236
1237            delaySlotInfo[tid].targetReady = false;
1238        } else {
1239            PC[tid] = next_PC;
1240            nextPC[tid] = next_NPC;
1241            nextNPC[tid] = next_NPC + instSize;
1242        }
1243
1244        DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n", tid, PC[tid]);
1245#else
1246        DPRINTF(Fetch, "[tid:%i]: Setting PC to %08p.\n",tid, next_PC);
1247        PC[tid] = next_PC;
1248        nextPC[tid] = next_PC + instSize;
1249#endif
1250    } else {
1251        // We shouldn't be in an icache miss and also have a fault (an ITB
1252        // miss)
1253        if (fetchStatus[tid] == IcacheWaitResponse) {
1254            panic("Fetch should have exited prior to this!");
1255        }
1256
1257        // Send the fault to commit.  This thread will not do anything
1258        // until commit handles the fault.  The only other way it can
1259        // wake up is if a squash comes along and changes the PC.
1260#if FULL_SYSTEM
1261        assert(numInst != fetchWidth);
1262        // Get a sequence number.
1263        inst_seq = cpu->getAndIncrementInstSeq();
1264        // We will use a nop in order to carry the fault.
1265        ext_inst = TheISA::NoopMachInst;
1266
1267        // Create a new DynInst from the dummy nop.
1268        DynInstPtr instruction = new DynInst(ext_inst, fetch_PC,
1269                                             next_PC,
1270                                             inst_seq, cpu);
1271        instruction->setPredTarg(next_PC + instSize);
1272        instruction->setTid(tid);
1273
1274        instruction->setASID(tid);
1275
1276        instruction->setThreadState(cpu->thread[tid]);
1277
1278        instruction->traceData = NULL;
1279
1280        instruction->setInstListIt(cpu->addInst(instruction));
1281
1282        instruction->fault = fault;
1283
1284        toDecode->insts[numInst] = instruction;
1285        toDecode->size++;
1286
1287        DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n",tid);
1288
1289        fetchStatus[tid] = TrapPending;
1290        status_change = true;
1291#else // !FULL_SYSTEM
1292        fetchStatus[tid] = TrapPending;
1293        status_change = true;
1294
1295#endif // FULL_SYSTEM
1296        DPRINTF(Fetch, "[tid:%i]: fault (%s) detected @ PC %08p",
1297                tid, fault->name(), PC[tid]);
1298    }
1299}
1300
1301template<class Impl>
1302void
1303DefaultFetch<Impl>::recvRetry()
1304{
1305    if (retryPkt != NULL) {
1306        assert(cacheBlocked);
1307        assert(retryTid != -1);
1308        assert(fetchStatus[retryTid] == IcacheWaitRetry);
1309
1310        if (icachePort->sendTiming(retryPkt)) {
1311            fetchStatus[retryTid] = IcacheWaitResponse;
1312            retryPkt = NULL;
1313            retryTid = -1;
1314            cacheBlocked = false;
1315        }
1316    } else {
1317        assert(retryTid == -1);
1318        // Access has been squashed since it was sent out.  Just clear
1319        // the cache being blocked.
1320        cacheBlocked = false;
1321    }
1322}
1323
1324///////////////////////////////////////
1325//                                   //
1326//  SMT FETCH POLICY MAINTAINED HERE //
1327//                                   //
1328///////////////////////////////////////
1329template<class Impl>
1330int
1331DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority)
1332{
1333    if (numThreads > 1) {
1334        switch (fetch_priority) {
1335
1336          case SingleThread:
1337            return 0;
1338
1339          case RoundRobin:
1340            return roundRobin();
1341
1342          case IQ:
1343            return iqCount();
1344
1345          case LSQ:
1346            return lsqCount();
1347
1348          case Branch:
1349            return branchCount();
1350
1351          default:
1352            return -1;
1353        }
1354    } else {
1355        int tid = *((*activeThreads).begin());
1356
1357        if (fetchStatus[tid] == Running ||
1358            fetchStatus[tid] == IcacheAccessComplete ||
1359            fetchStatus[tid] == Idle) {
1360            return tid;
1361        } else {
1362            return -1;
1363        }
1364    }
1365
1366}
1367
1368
1369template<class Impl>
1370int
1371DefaultFetch<Impl>::roundRobin()
1372{
1373    std::list<unsigned>::iterator pri_iter = priorityList.begin();
1374    std::list<unsigned>::iterator end      = priorityList.end();
1375
1376    int high_pri;
1377
1378    while (pri_iter != end) {
1379        high_pri = *pri_iter;
1380
1381        assert(high_pri <= numThreads);
1382
1383        if (fetchStatus[high_pri] == Running ||
1384            fetchStatus[high_pri] == IcacheAccessComplete ||
1385            fetchStatus[high_pri] == Idle) {
1386
1387            priorityList.erase(pri_iter);
1388            priorityList.push_back(high_pri);
1389
1390            return high_pri;
1391        }
1392
1393        pri_iter++;
1394    }
1395
1396    return -1;
1397}
1398
1399template<class Impl>
1400int
1401DefaultFetch<Impl>::iqCount()
1402{
1403    std::priority_queue<unsigned> PQ;
1404
1405    std::list<unsigned>::iterator threads = (*activeThreads).begin();
1406
1407    while (threads != (*activeThreads).end()) {
1408        unsigned tid = *threads++;
1409
1410        PQ.push(fromIEW->iewInfo[tid].iqCount);
1411    }
1412
1413    while (!PQ.empty()) {
1414
1415        unsigned high_pri = PQ.top();
1416
1417        if (fetchStatus[high_pri] == Running ||
1418            fetchStatus[high_pri] == IcacheAccessComplete ||
1419            fetchStatus[high_pri] == Idle)
1420            return high_pri;
1421        else
1422            PQ.pop();
1423
1424    }
1425
1426    return -1;
1427}
1428
1429template<class Impl>
1430int
1431DefaultFetch<Impl>::lsqCount()
1432{
1433    std::priority_queue<unsigned> PQ;
1434
1435
1436    std::list<unsigned>::iterator threads = (*activeThreads).begin();
1437
1438    while (threads != (*activeThreads).end()) {
1439        unsigned tid = *threads++;
1440
1441        PQ.push(fromIEW->iewInfo[tid].ldstqCount);
1442    }
1443
1444    while (!PQ.empty()) {
1445
1446        unsigned high_pri = PQ.top();
1447
1448        if (fetchStatus[high_pri] == Running ||
1449            fetchStatus[high_pri] == IcacheAccessComplete ||
1450            fetchStatus[high_pri] == Idle)
1451            return high_pri;
1452        else
1453            PQ.pop();
1454
1455    }
1456
1457    return -1;
1458}
1459
1460template<class Impl>
1461int
1462DefaultFetch<Impl>::branchCount()
1463{
1464    std::list<unsigned>::iterator threads = (*activeThreads).begin();
1465    panic("Branch Count Fetch policy unimplemented\n");
1466    return *threads;
1467}
1468