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