fetch_impl.hh revision 8823:ae411fcf4935
1/* 2 * Copyright (c) 2010-2011 ARM Limited 3 * All rights reserved. 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2004-2006 The Regents of The University of Michigan 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions are 19 * met: redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer; 21 * redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution; 24 * neither the name of the copyright holders nor the names of its 25 * contributors may be used to endorse or promote products derived from 26 * this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39 * 40 * Authors: Kevin Lim 41 * Korey Sewell 42 */ 43 44#include <algorithm> 45#include <cstring> 46#include <list> 47#include <map> 48#include <queue> 49 50#include "arch/isa_traits.hh" 51#include "arch/tlb.hh" 52#include "arch/utility.hh" 53#include "arch/vtophys.hh" 54#include "base/types.hh" 55#include "config/the_isa.hh" 56#include "config/use_checker.hh" 57#include "cpu/base.hh" 58#include "cpu/o3/fetch.hh" 59#include "cpu/exetrace.hh" 60#include "debug/Activity.hh" 61#include "debug/Fetch.hh" 62#include "mem/packet.hh" 63#include "mem/request.hh" 64#include "params/DerivO3CPU.hh" 65#include "sim/byteswap.hh" 66#include "sim/core.hh" 67#include "sim/eventq.hh" 68#include "sim/full_system.hh" 69#include "sim/system.hh" 70 71#if USE_CHECKER 72#include "cpu/checker/cpu.hh" 73#endif // USE_CHECKER 74 75using namespace std; 76 77template<class Impl> 78DefaultFetch<Impl>::DefaultFetch(O3CPU *_cpu, DerivO3CPUParams *params) 79 : cpu(_cpu), 80 branchPred(params), 81 predecoder(NULL), 82 numInst(0), 83 decodeToFetchDelay(params->decodeToFetchDelay), 84 renameToFetchDelay(params->renameToFetchDelay), 85 iewToFetchDelay(params->iewToFetchDelay), 86 commitToFetchDelay(params->commitToFetchDelay), 87 fetchWidth(params->fetchWidth), 88 cacheBlocked(false), 89 retryPkt(NULL), 90 retryTid(InvalidThreadID), 91 numThreads(params->numThreads), 92 numFetchingThreads(params->smtNumFetchingThreads), 93 interruptPending(false), 94 drainPending(false), 95 switchedOut(false), 96 finishTranslationEvent(this) 97{ 98 if (numThreads > Impl::MaxThreads) 99 fatal("numThreads (%d) is larger than compiled limit (%d),\n" 100 "\tincrease MaxThreads in src/cpu/o3/impl.hh\n", 101 numThreads, static_cast<int>(Impl::MaxThreads)); 102 103 // Set fetch stage's status to inactive. 104 _status = Inactive; 105 106 std::string policy = params->smtFetchPolicy; 107 108 // Convert string to lowercase 109 std::transform(policy.begin(), policy.end(), policy.begin(), 110 (int(*)(int)) tolower); 111 112 // Figure out fetch policy 113 if (policy == "singlethread") { 114 fetchPolicy = SingleThread; 115 if (numThreads > 1) 116 panic("Invalid Fetch Policy for a SMT workload."); 117 } else if (policy == "roundrobin") { 118 fetchPolicy = RoundRobin; 119 DPRINTF(Fetch, "Fetch policy set to Round Robin\n"); 120 } else if (policy == "branch") { 121 fetchPolicy = Branch; 122 DPRINTF(Fetch, "Fetch policy set to Branch Count\n"); 123 } else if (policy == "iqcount") { 124 fetchPolicy = IQ; 125 DPRINTF(Fetch, "Fetch policy set to IQ count\n"); 126 } else if (policy == "lsqcount") { 127 fetchPolicy = LSQ; 128 DPRINTF(Fetch, "Fetch policy set to LSQ count\n"); 129 } else { 130 fatal("Invalid Fetch Policy. Options Are: {SingleThread," 131 " RoundRobin,LSQcount,IQcount}\n"); 132 } 133 134 // Get the size of an instruction. 135 instSize = sizeof(TheISA::MachInst); 136} 137 138template <class Impl> 139std::string 140DefaultFetch<Impl>::name() const 141{ 142 return cpu->name() + ".fetch"; 143} 144 145template <class Impl> 146void 147DefaultFetch<Impl>::regStats() 148{ 149 icacheStallCycles 150 .name(name() + ".icacheStallCycles") 151 .desc("Number of cycles fetch is stalled on an Icache miss") 152 .prereq(icacheStallCycles); 153 154 fetchedInsts 155 .name(name() + ".Insts") 156 .desc("Number of instructions fetch has processed") 157 .prereq(fetchedInsts); 158 159 fetchedBranches 160 .name(name() + ".Branches") 161 .desc("Number of branches that fetch encountered") 162 .prereq(fetchedBranches); 163 164 predictedBranches 165 .name(name() + ".predictedBranches") 166 .desc("Number of branches that fetch has predicted taken") 167 .prereq(predictedBranches); 168 169 fetchCycles 170 .name(name() + ".Cycles") 171 .desc("Number of cycles fetch has run and was not squashing or" 172 " blocked") 173 .prereq(fetchCycles); 174 175 fetchSquashCycles 176 .name(name() + ".SquashCycles") 177 .desc("Number of cycles fetch has spent squashing") 178 .prereq(fetchSquashCycles); 179 180 fetchTlbCycles 181 .name(name() + ".TlbCycles") 182 .desc("Number of cycles fetch has spent waiting for tlb") 183 .prereq(fetchTlbCycles); 184 185 fetchIdleCycles 186 .name(name() + ".IdleCycles") 187 .desc("Number of cycles fetch was idle") 188 .prereq(fetchIdleCycles); 189 190 fetchBlockedCycles 191 .name(name() + ".BlockedCycles") 192 .desc("Number of cycles fetch has spent blocked") 193 .prereq(fetchBlockedCycles); 194 195 fetchedCacheLines 196 .name(name() + ".CacheLines") 197 .desc("Number of cache lines fetched") 198 .prereq(fetchedCacheLines); 199 200 fetchMiscStallCycles 201 .name(name() + ".MiscStallCycles") 202 .desc("Number of cycles fetch has spent waiting on interrupts, or " 203 "bad addresses, or out of MSHRs") 204 .prereq(fetchMiscStallCycles); 205 206 fetchPendingDrainCycles 207 .name(name() + ".PendingDrainCycles") 208 .desc("Number of cycles fetch has spent waiting on pipes to drain") 209 .prereq(fetchPendingDrainCycles); 210 211 fetchNoActiveThreadStallCycles 212 .name(name() + ".NoActiveThreadStallCycles") 213 .desc("Number of stall cycles due to no active thread to fetch from") 214 .prereq(fetchNoActiveThreadStallCycles); 215 216 fetchPendingTrapStallCycles 217 .name(name() + ".PendingTrapStallCycles") 218 .desc("Number of stall cycles due to pending traps") 219 .prereq(fetchPendingTrapStallCycles); 220 221 fetchPendingQuiesceStallCycles 222 .name(name() + ".PendingQuiesceStallCycles") 223 .desc("Number of stall cycles due to pending quiesce instructions") 224 .prereq(fetchPendingQuiesceStallCycles); 225 226 fetchIcacheWaitRetryStallCycles 227 .name(name() + ".IcacheWaitRetryStallCycles") 228 .desc("Number of stall cycles due to full MSHR") 229 .prereq(fetchIcacheWaitRetryStallCycles); 230 231 fetchIcacheSquashes 232 .name(name() + ".IcacheSquashes") 233 .desc("Number of outstanding Icache misses that were squashed") 234 .prereq(fetchIcacheSquashes); 235 236 fetchTlbSquashes 237 .name(name() + ".ItlbSquashes") 238 .desc("Number of outstanding ITLB misses that were squashed") 239 .prereq(fetchTlbSquashes); 240 241 fetchNisnDist 242 .init(/* base value */ 0, 243 /* last value */ fetchWidth, 244 /* bucket size */ 1) 245 .name(name() + ".rateDist") 246 .desc("Number of instructions fetched each cycle (Total)") 247 .flags(Stats::pdf); 248 249 idleRate 250 .name(name() + ".idleRate") 251 .desc("Percent of cycles fetch was idle") 252 .prereq(idleRate); 253 idleRate = fetchIdleCycles * 100 / cpu->numCycles; 254 255 branchRate 256 .name(name() + ".branchRate") 257 .desc("Number of branch fetches per cycle") 258 .flags(Stats::total); 259 branchRate = fetchedBranches / cpu->numCycles; 260 261 fetchRate 262 .name(name() + ".rate") 263 .desc("Number of inst fetches per cycle") 264 .flags(Stats::total); 265 fetchRate = fetchedInsts / cpu->numCycles; 266 267 branchPred.regStats(); 268} 269 270template<class Impl> 271void 272DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer) 273{ 274 timeBuffer = time_buffer; 275 276 // Create wires to get information from proper places in time buffer. 277 fromDecode = timeBuffer->getWire(-decodeToFetchDelay); 278 fromRename = timeBuffer->getWire(-renameToFetchDelay); 279 fromIEW = timeBuffer->getWire(-iewToFetchDelay); 280 fromCommit = timeBuffer->getWire(-commitToFetchDelay); 281} 282 283template<class Impl> 284void 285DefaultFetch<Impl>::setActiveThreads(std::list<ThreadID> *at_ptr) 286{ 287 activeThreads = at_ptr; 288} 289 290template<class Impl> 291void 292DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr) 293{ 294 fetchQueue = fq_ptr; 295 296 // Create wire to write information to proper place in fetch queue. 297 toDecode = fetchQueue->getWire(0); 298} 299 300template<class Impl> 301void 302DefaultFetch<Impl>::initStage() 303{ 304 // Setup PC and nextPC with initial state. 305 for (ThreadID tid = 0; tid < numThreads; tid++) { 306 pc[tid] = cpu->pcState(tid); 307 fetchOffset[tid] = 0; 308 macroop[tid] = NULL; 309 delayedCommit[tid] = false; 310 } 311 312 for (ThreadID tid = 0; tid < numThreads; tid++) { 313 314 fetchStatus[tid] = Running; 315 316 priorityList.push_back(tid); 317 318 memReq[tid] = NULL; 319 320 stalls[tid].decode = false; 321 stalls[tid].rename = false; 322 stalls[tid].iew = false; 323 stalls[tid].commit = false; 324 } 325 326 // Schedule fetch to get the correct PC from the CPU 327 // scheduleFetchStartupEvent(1); 328 329 // Fetch needs to start fetching instructions at the very beginning, 330 // so it must start up in active state. 331 switchToActive(); 332} 333 334template<class Impl> 335void 336DefaultFetch<Impl>::setIcache() 337{ 338 assert(cpu->getIcachePort()->isConnected()); 339 340 // Size of cache block. 341 cacheBlkSize = cpu->getIcachePort()->peerBlockSize(); 342 343 // Create mask to get rid of offset bits. 344 cacheBlkMask = (cacheBlkSize - 1); 345 346 for (ThreadID tid = 0; tid < numThreads; tid++) { 347 // Create space to store a cache line. 348 cacheData[tid] = new uint8_t[cacheBlkSize]; 349 cacheDataPC[tid] = 0; 350 cacheDataValid[tid] = false; 351 } 352} 353 354template<class Impl> 355void 356DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt) 357{ 358 ThreadID tid = pkt->req->threadId(); 359 360 DPRINTF(Fetch, "[tid:%u] Waking up from cache miss.\n", tid); 361 362 assert(!pkt->wasNacked()); 363 364 // Only change the status if it's still waiting on the icache access 365 // to return. 366 if (fetchStatus[tid] != IcacheWaitResponse || 367 pkt->req != memReq[tid] || 368 isSwitchedOut()) { 369 ++fetchIcacheSquashes; 370 delete pkt->req; 371 delete pkt; 372 return; 373 } 374 375 memcpy(cacheData[tid], pkt->getPtr<uint8_t>(), cacheBlkSize); 376 cacheDataValid[tid] = true; 377 378 if (!drainPending) { 379 // Wake up the CPU (if it went to sleep and was waiting on 380 // this completion event). 381 cpu->wakeCPU(); 382 383 DPRINTF(Activity, "[tid:%u] Activating fetch due to cache completion\n", 384 tid); 385 386 switchToActive(); 387 } 388 389 // Only switch to IcacheAccessComplete if we're not stalled as well. 390 if (checkStall(tid)) { 391 fetchStatus[tid] = Blocked; 392 } else { 393 fetchStatus[tid] = IcacheAccessComplete; 394 } 395 396 // Reset the mem req to NULL. 397 delete pkt->req; 398 delete pkt; 399 memReq[tid] = NULL; 400} 401 402template <class Impl> 403bool 404DefaultFetch<Impl>::drain() 405{ 406 // Fetch is ready to drain at any time. 407 cpu->signalDrained(); 408 drainPending = true; 409 return true; 410} 411 412template <class Impl> 413void 414DefaultFetch<Impl>::resume() 415{ 416 drainPending = false; 417} 418 419template <class Impl> 420void 421DefaultFetch<Impl>::switchOut() 422{ 423 switchedOut = true; 424 // Branch predictor needs to have its state cleared. 425 branchPred.switchOut(); 426} 427 428template <class Impl> 429void 430DefaultFetch<Impl>::takeOverFrom() 431{ 432 // the instruction port is now connected so we can get the block 433 // size 434 setIcache(); 435 436 // Reset all state 437 for (ThreadID i = 0; i < Impl::MaxThreads; ++i) { 438 stalls[i].decode = 0; 439 stalls[i].rename = 0; 440 stalls[i].iew = 0; 441 stalls[i].commit = 0; 442 pc[i] = cpu->pcState(i); 443 fetchStatus[i] = Running; 444 } 445 numInst = 0; 446 wroteToTimeBuffer = false; 447 _status = Inactive; 448 switchedOut = false; 449 interruptPending = false; 450 branchPred.takeOverFrom(); 451} 452 453template <class Impl> 454void 455DefaultFetch<Impl>::wakeFromQuiesce() 456{ 457 DPRINTF(Fetch, "Waking up from quiesce\n"); 458 // Hopefully this is safe 459 // @todo: Allow other threads to wake from quiesce. 460 fetchStatus[0] = Running; 461} 462 463template <class Impl> 464inline void 465DefaultFetch<Impl>::switchToActive() 466{ 467 if (_status == Inactive) { 468 DPRINTF(Activity, "Activating stage.\n"); 469 470 cpu->activateStage(O3CPU::FetchIdx); 471 472 _status = Active; 473 } 474} 475 476template <class Impl> 477inline void 478DefaultFetch<Impl>::switchToInactive() 479{ 480 if (_status == Active) { 481 DPRINTF(Activity, "Deactivating stage.\n"); 482 483 cpu->deactivateStage(O3CPU::FetchIdx); 484 485 _status = Inactive; 486 } 487} 488 489template <class Impl> 490bool 491DefaultFetch<Impl>::lookupAndUpdateNextPC( 492 DynInstPtr &inst, TheISA::PCState &nextPC) 493{ 494 // Do branch prediction check here. 495 // A bit of a misnomer...next_PC is actually the current PC until 496 // this function updates it. 497 bool predict_taken; 498 499 if (!inst->isControl()) { 500 TheISA::advancePC(nextPC, inst->staticInst); 501 inst->setPredTarg(nextPC); 502 inst->setPredTaken(false); 503 return false; 504 } 505 506 ThreadID tid = inst->threadNumber; 507 predict_taken = branchPred.predict(inst, nextPC, tid); 508 509 if (predict_taken) { 510 DPRINTF(Fetch, "[tid:%i]: [sn:%i]: Branch predicted to be taken to %s.\n", 511 tid, inst->seqNum, nextPC); 512 } else { 513 DPRINTF(Fetch, "[tid:%i]: [sn:%i]:Branch predicted to be not taken.\n", 514 tid, inst->seqNum); 515 } 516 517 DPRINTF(Fetch, "[tid:%i]: [sn:%i] Branch predicted to go to %s.\n", 518 tid, inst->seqNum, nextPC); 519 inst->setPredTarg(nextPC); 520 inst->setPredTaken(predict_taken); 521 522 ++fetchedBranches; 523 524 if (predict_taken) { 525 ++predictedBranches; 526 } 527 528 return predict_taken; 529} 530 531template <class Impl> 532bool 533DefaultFetch<Impl>::fetchCacheLine(Addr vaddr, ThreadID tid, Addr pc) 534{ 535 Fault fault = NoFault; 536 537 // @todo: not sure if these should block translation. 538 //AlphaDep 539 if (cacheBlocked) { 540 DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n", 541 tid); 542 return false; 543 } else if (isSwitchedOut()) { 544 DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, switched out\n", 545 tid); 546 return false; 547 } else if (checkInterrupt(pc)) { 548 // Hold off fetch from getting new instructions when: 549 // Cache is blocked, or 550 // while an interrupt is pending and we're not in PAL mode, or 551 // fetch is switched out. 552 DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n", 553 tid); 554 return false; 555 } 556 557 // Align the fetch address so it's at the start of a cache block. 558 Addr block_PC = icacheBlockAlignPC(vaddr); 559 560 DPRINTF(Fetch, "[tid:%i] Fetching cache line %#x for addr %#x\n", 561 tid, block_PC, vaddr); 562 563 // Setup the memReq to do a read of the first instruction's address. 564 // Set the appropriate read size and flags as well. 565 // Build request here. 566 RequestPtr mem_req = 567 new Request(tid, block_PC, cacheBlkSize, Request::INST_FETCH, 568 pc, cpu->thread[tid]->contextId(), tid); 569 570 memReq[tid] = mem_req; 571 572 // Initiate translation of the icache block 573 fetchStatus[tid] = ItlbWait; 574 FetchTranslation *trans = new FetchTranslation(this); 575 cpu->itb->translateTiming(mem_req, cpu->thread[tid]->getTC(), 576 trans, BaseTLB::Execute); 577 return true; 578} 579 580template <class Impl> 581void 582DefaultFetch<Impl>::finishTranslation(Fault fault, RequestPtr mem_req) 583{ 584 ThreadID tid = mem_req->threadId(); 585 Addr block_PC = mem_req->getVaddr(); 586 587 // Wake up CPU if it was idle 588 cpu->wakeCPU(); 589 590 if (fetchStatus[tid] != ItlbWait || mem_req != memReq[tid] || 591 mem_req->getVaddr() != memReq[tid]->getVaddr() || isSwitchedOut()) { 592 DPRINTF(Fetch, "[tid:%i] Ignoring itlb completed after squash\n", 593 tid); 594 ++fetchTlbSquashes; 595 delete mem_req; 596 return; 597 } 598 599 600 // If translation was successful, attempt to read the icache block. 601 if (fault == NoFault) { 602 // Check that we're not going off into random memory 603 // If we have, just wait around for commit to squash something and put 604 // us on the right track 605 if (!cpu->system->isMemory(mem_req->getPaddr())) { 606 warn("Address %#x is outside of physical memory, stopping fetch\n", 607 mem_req->getPaddr()); 608 fetchStatus[tid] = NoGoodAddr; 609 delete mem_req; 610 memReq[tid] = NULL; 611 return; 612 } 613 614 // Build packet here. 615 PacketPtr data_pkt = new Packet(mem_req, 616 MemCmd::ReadReq, Packet::Broadcast); 617 data_pkt->dataDynamicArray(new uint8_t[cacheBlkSize]); 618 619 cacheDataPC[tid] = block_PC; 620 cacheDataValid[tid] = false; 621 DPRINTF(Fetch, "Fetch: Doing instruction read.\n"); 622 623 fetchedCacheLines++; 624 625 // Access the cache. 626 if (!cpu->getIcachePort()->sendTiming(data_pkt)) { 627 assert(retryPkt == NULL); 628 assert(retryTid == InvalidThreadID); 629 DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid); 630 631 fetchStatus[tid] = IcacheWaitRetry; 632 retryPkt = data_pkt; 633 retryTid = tid; 634 cacheBlocked = true; 635 } else { 636 DPRINTF(Fetch, "[tid:%i]: Doing Icache access.\n", tid); 637 DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache " 638 "response.\n", tid); 639 640 lastIcacheStall[tid] = curTick(); 641 fetchStatus[tid] = IcacheWaitResponse; 642 } 643 } else { 644 if (!(numInst < fetchWidth)) { 645 assert(!finishTranslationEvent.scheduled()); 646 finishTranslationEvent.setFault(fault); 647 finishTranslationEvent.setReq(mem_req); 648 cpu->schedule(finishTranslationEvent, cpu->nextCycle(curTick() + cpu->ticks(1))); 649 return; 650 } 651 DPRINTF(Fetch, "[tid:%i] Got back req with addr %#x but expected %#x\n", 652 tid, mem_req->getVaddr(), memReq[tid]->getVaddr()); 653 // Translation faulted, icache request won't be sent. 654 delete mem_req; 655 memReq[tid] = NULL; 656 657 // Send the fault to commit. This thread will not do anything 658 // until commit handles the fault. The only other way it can 659 // wake up is if a squash comes along and changes the PC. 660 TheISA::PCState fetchPC = pc[tid]; 661 662 DPRINTF(Fetch, "[tid:%i]: Translation faulted, building noop.\n", tid); 663 // We will use a nop in ordier to carry the fault. 664 DynInstPtr instruction = buildInst(tid, 665 decoder.decode(TheISA::NoopMachInst, fetchPC.instAddr()), 666 NULL, fetchPC, fetchPC, false); 667 668 instruction->setPredTarg(fetchPC); 669 instruction->fault = fault; 670 wroteToTimeBuffer = true; 671 672 DPRINTF(Activity, "Activity this cycle.\n"); 673 cpu->activityThisCycle(); 674 675 fetchStatus[tid] = TrapPending; 676 677 DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n", tid); 678 DPRINTF(Fetch, "[tid:%i]: fault (%s) detected @ PC %s.\n", 679 tid, fault->name(), pc[tid]); 680 } 681 _status = updateFetchStatus(); 682} 683 684template <class Impl> 685inline void 686DefaultFetch<Impl>::doSquash(const TheISA::PCState &newPC, 687 const DynInstPtr squashInst, ThreadID tid) 688{ 689 DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %s.\n", 690 tid, newPC); 691 692 pc[tid] = newPC; 693 fetchOffset[tid] = 0; 694 if (squashInst && squashInst->pcState().instAddr() == newPC.instAddr()) 695 macroop[tid] = squashInst->macroop; 696 else 697 macroop[tid] = NULL; 698 predecoder.reset(); 699 700 // Clear the icache miss if it's outstanding. 701 if (fetchStatus[tid] == IcacheWaitResponse) { 702 DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n", 703 tid); 704 memReq[tid] = NULL; 705 } else if (fetchStatus[tid] == ItlbWait) { 706 DPRINTF(Fetch, "[tid:%i]: Squashing outstanding ITLB miss.\n", 707 tid); 708 memReq[tid] = NULL; 709 } 710 711 // Get rid of the retrying packet if it was from this thread. 712 if (retryTid == tid) { 713 assert(cacheBlocked); 714 if (retryPkt) { 715 delete retryPkt->req; 716 delete retryPkt; 717 } 718 retryPkt = NULL; 719 retryTid = InvalidThreadID; 720 } 721 722 fetchStatus[tid] = Squashing; 723 724 ++fetchSquashCycles; 725} 726 727template<class Impl> 728void 729DefaultFetch<Impl>::squashFromDecode(const TheISA::PCState &newPC, 730 const DynInstPtr squashInst, 731 const InstSeqNum seq_num, ThreadID tid) 732{ 733 DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n", tid); 734 735 doSquash(newPC, squashInst, tid); 736 737 // Tell the CPU to remove any instructions that are in flight between 738 // fetch and decode. 739 cpu->removeInstsUntil(seq_num, tid); 740} 741 742template<class Impl> 743bool 744DefaultFetch<Impl>::checkStall(ThreadID tid) const 745{ 746 bool ret_val = false; 747 748 if (cpu->contextSwitch) { 749 DPRINTF(Fetch,"[tid:%i]: Stalling for a context switch.\n",tid); 750 ret_val = true; 751 } else if (stalls[tid].decode) { 752 DPRINTF(Fetch,"[tid:%i]: Stall from Decode stage detected.\n",tid); 753 ret_val = true; 754 } else if (stalls[tid].rename) { 755 DPRINTF(Fetch,"[tid:%i]: Stall from Rename stage detected.\n",tid); 756 ret_val = true; 757 } else if (stalls[tid].iew) { 758 DPRINTF(Fetch,"[tid:%i]: Stall from IEW stage detected.\n",tid); 759 ret_val = true; 760 } else if (stalls[tid].commit) { 761 DPRINTF(Fetch,"[tid:%i]: Stall from Commit stage detected.\n",tid); 762 ret_val = true; 763 } 764 765 return ret_val; 766} 767 768template<class Impl> 769typename DefaultFetch<Impl>::FetchStatus 770DefaultFetch<Impl>::updateFetchStatus() 771{ 772 //Check Running 773 list<ThreadID>::iterator threads = activeThreads->begin(); 774 list<ThreadID>::iterator end = activeThreads->end(); 775 776 while (threads != end) { 777 ThreadID tid = *threads++; 778 779 if (fetchStatus[tid] == Running || 780 fetchStatus[tid] == Squashing || 781 fetchStatus[tid] == IcacheAccessComplete) { 782 783 if (_status == Inactive) { 784 DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid); 785 786 if (fetchStatus[tid] == IcacheAccessComplete) { 787 DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache" 788 "completion\n",tid); 789 } 790 791 cpu->activateStage(O3CPU::FetchIdx); 792 } 793 794 return Active; 795 } 796 } 797 798 // Stage is switching from active to inactive, notify CPU of it. 799 if (_status == Active) { 800 DPRINTF(Activity, "Deactivating stage.\n"); 801 802 cpu->deactivateStage(O3CPU::FetchIdx); 803 } 804 805 return Inactive; 806} 807 808template <class Impl> 809void 810DefaultFetch<Impl>::squash(const TheISA::PCState &newPC, 811 const InstSeqNum seq_num, DynInstPtr squashInst, 812 ThreadID tid) 813{ 814 DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n", tid); 815 816 doSquash(newPC, squashInst, tid); 817 818 // Tell the CPU to remove any instructions that are not in the ROB. 819 cpu->removeInstsNotInROB(tid); 820} 821 822template <class Impl> 823void 824DefaultFetch<Impl>::tick() 825{ 826 list<ThreadID>::iterator threads = activeThreads->begin(); 827 list<ThreadID>::iterator end = activeThreads->end(); 828 bool status_change = false; 829 830 wroteToTimeBuffer = false; 831 832 for (ThreadID i = 0; i < Impl::MaxThreads; ++i) { 833 issuePipelinedIfetch[i] = false; 834 } 835 836 while (threads != end) { 837 ThreadID tid = *threads++; 838 839 // Check the signals for each thread to determine the proper status 840 // for each thread. 841 bool updated_status = checkSignalsAndUpdate(tid); 842 status_change = status_change || updated_status; 843 } 844 845 DPRINTF(Fetch, "Running stage.\n"); 846 847 if (FullSystem) { 848 if (fromCommit->commitInfo[0].interruptPending) { 849 interruptPending = true; 850 } 851 852 if (fromCommit->commitInfo[0].clearInterrupt) { 853 interruptPending = false; 854 } 855 } 856 857 for (threadFetched = 0; threadFetched < numFetchingThreads; 858 threadFetched++) { 859 // Fetch each of the actively fetching threads. 860 fetch(status_change); 861 } 862 863 // Record number of instructions fetched this cycle for distribution. 864 fetchNisnDist.sample(numInst); 865 866 if (status_change) { 867 // Change the fetch stage status if there was a status change. 868 _status = updateFetchStatus(); 869 } 870 871 // If there was activity this cycle, inform the CPU of it. 872 if (wroteToTimeBuffer || cpu->contextSwitch) { 873 DPRINTF(Activity, "Activity this cycle.\n"); 874 875 cpu->activityThisCycle(); 876 } 877 878 // Issue the next I-cache request if possible. 879 for (ThreadID i = 0; i < Impl::MaxThreads; ++i) { 880 if (issuePipelinedIfetch[i]) { 881 pipelineIcacheAccesses(i); 882 } 883 } 884 885 // Reset the number of the instruction we've fetched. 886 numInst = 0; 887} 888 889template <class Impl> 890bool 891DefaultFetch<Impl>::checkSignalsAndUpdate(ThreadID tid) 892{ 893 // Update the per thread stall statuses. 894 if (fromDecode->decodeBlock[tid]) { 895 stalls[tid].decode = true; 896 } 897 898 if (fromDecode->decodeUnblock[tid]) { 899 assert(stalls[tid].decode); 900 assert(!fromDecode->decodeBlock[tid]); 901 stalls[tid].decode = false; 902 } 903 904 if (fromRename->renameBlock[tid]) { 905 stalls[tid].rename = true; 906 } 907 908 if (fromRename->renameUnblock[tid]) { 909 assert(stalls[tid].rename); 910 assert(!fromRename->renameBlock[tid]); 911 stalls[tid].rename = false; 912 } 913 914 if (fromIEW->iewBlock[tid]) { 915 stalls[tid].iew = true; 916 } 917 918 if (fromIEW->iewUnblock[tid]) { 919 assert(stalls[tid].iew); 920 assert(!fromIEW->iewBlock[tid]); 921 stalls[tid].iew = false; 922 } 923 924 if (fromCommit->commitBlock[tid]) { 925 stalls[tid].commit = true; 926 } 927 928 if (fromCommit->commitUnblock[tid]) { 929 assert(stalls[tid].commit); 930 assert(!fromCommit->commitBlock[tid]); 931 stalls[tid].commit = false; 932 } 933 934 // Check squash signals from commit. 935 if (fromCommit->commitInfo[tid].squash) { 936 937 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 938 "from commit.\n",tid); 939 // In any case, squash. 940 squash(fromCommit->commitInfo[tid].pc, 941 fromCommit->commitInfo[tid].doneSeqNum, 942 fromCommit->commitInfo[tid].squashInst, tid); 943 944 // If it was a branch mispredict on a control instruction, update the 945 // branch predictor with that instruction, otherwise just kill the 946 // invalid state we generated in after sequence number 947 if (fromCommit->commitInfo[tid].mispredictInst && 948 fromCommit->commitInfo[tid].mispredictInst->isControl()) { 949 branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum, 950 fromCommit->commitInfo[tid].pc, 951 fromCommit->commitInfo[tid].branchTaken, 952 tid); 953 } else { 954 branchPred.squash(fromCommit->commitInfo[tid].doneSeqNum, 955 tid); 956 } 957 958 return true; 959 } else if (fromCommit->commitInfo[tid].doneSeqNum) { 960 // Update the branch predictor if it wasn't a squashed instruction 961 // that was broadcasted. 962 branchPred.update(fromCommit->commitInfo[tid].doneSeqNum, tid); 963 } 964 965 // Check ROB squash signals from commit. 966 if (fromCommit->commitInfo[tid].robSquashing) { 967 DPRINTF(Fetch, "[tid:%u]: ROB is still squashing.\n", tid); 968 969 // Continue to squash. 970 fetchStatus[tid] = Squashing; 971 972 return true; 973 } 974 975 // Check squash signals from decode. 976 if (fromDecode->decodeInfo[tid].squash) { 977 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 978 "from decode.\n",tid); 979 980 // Update the branch predictor. 981 if (fromDecode->decodeInfo[tid].branchMispredict) { 982 branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum, 983 fromDecode->decodeInfo[tid].nextPC, 984 fromDecode->decodeInfo[tid].branchTaken, 985 tid); 986 } else { 987 branchPred.squash(fromDecode->decodeInfo[tid].doneSeqNum, 988 tid); 989 } 990 991 if (fetchStatus[tid] != Squashing) { 992 993 DPRINTF(Fetch, "Squashing from decode with PC = %s\n", 994 fromDecode->decodeInfo[tid].nextPC); 995 // Squash unless we're already squashing 996 squashFromDecode(fromDecode->decodeInfo[tid].nextPC, 997 fromDecode->decodeInfo[tid].squashInst, 998 fromDecode->decodeInfo[tid].doneSeqNum, 999 tid); 1000 1001 return true; 1002 } 1003 } 1004 1005 if (checkStall(tid) && 1006 fetchStatus[tid] != IcacheWaitResponse && 1007 fetchStatus[tid] != IcacheWaitRetry) { 1008 DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid); 1009 1010 fetchStatus[tid] = Blocked; 1011 1012 return true; 1013 } 1014 1015 if (fetchStatus[tid] == Blocked || 1016 fetchStatus[tid] == Squashing) { 1017 // Switch status to running if fetch isn't being told to block or 1018 // squash this cycle. 1019 DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n", 1020 tid); 1021 1022 fetchStatus[tid] = Running; 1023 1024 return true; 1025 } 1026 1027 // If we've reached this point, we have not gotten any signals that 1028 // cause fetch to change its status. Fetch remains the same as before. 1029 return false; 1030} 1031 1032template<class Impl> 1033typename Impl::DynInstPtr 1034DefaultFetch<Impl>::buildInst(ThreadID tid, StaticInstPtr staticInst, 1035 StaticInstPtr curMacroop, TheISA::PCState thisPC, 1036 TheISA::PCState nextPC, bool trace) 1037{ 1038 // Get a sequence number. 1039 InstSeqNum seq = cpu->getAndIncrementInstSeq(); 1040 1041 // Create a new DynInst from the instruction fetched. 1042 DynInstPtr instruction = 1043 new DynInst(staticInst, curMacroop, thisPC, nextPC, seq, cpu); 1044 instruction->setTid(tid); 1045 1046 instruction->setASID(tid); 1047 1048 instruction->setThreadState(cpu->thread[tid]); 1049 1050 DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x (%d) created " 1051 "[sn:%lli].\n", tid, thisPC.instAddr(), 1052 thisPC.microPC(), seq); 1053 1054 DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n", tid, 1055 instruction->staticInst-> 1056 disassemble(thisPC.instAddr())); 1057 1058#if TRACING_ON 1059 if (trace) { 1060 instruction->traceData = 1061 cpu->getTracer()->getInstRecord(curTick(), cpu->tcBase(tid), 1062 instruction->staticInst, thisPC, curMacroop); 1063 } 1064#else 1065 instruction->traceData = NULL; 1066#endif 1067 1068 // Add instruction to the CPU's list of instructions. 1069 instruction->setInstListIt(cpu->addInst(instruction)); 1070 1071 // Write the instruction to the first slot in the queue 1072 // that heads to decode. 1073 assert(numInst < fetchWidth); 1074 toDecode->insts[toDecode->size++] = instruction; 1075 1076 // Keep track of if we can take an interrupt at this boundary 1077 delayedCommit[tid] = instruction->isDelayedCommit(); 1078 1079 return instruction; 1080} 1081 1082template<class Impl> 1083void 1084DefaultFetch<Impl>::fetch(bool &status_change) 1085{ 1086 ////////////////////////////////////////// 1087 // Start actual fetch 1088 ////////////////////////////////////////// 1089 ThreadID tid = getFetchingThread(fetchPolicy); 1090 1091 if (tid == InvalidThreadID || drainPending) { 1092 // Breaks looping condition in tick() 1093 threadFetched = numFetchingThreads; 1094 1095 if (numThreads == 1) { // @todo Per-thread stats 1096 profileStall(0); 1097 } 1098 1099 return; 1100 } 1101 1102 DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid); 1103 1104 // The current PC. 1105 TheISA::PCState thisPC = pc[tid]; 1106 1107 Addr pcOffset = fetchOffset[tid]; 1108 Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1109 1110 bool inRom = isRomMicroPC(thisPC.microPC()); 1111 1112 // If returning from the delay of a cache miss, then update the status 1113 // to running, otherwise do the cache access. Possibly move this up 1114 // to tick() function. 1115 if (fetchStatus[tid] == IcacheAccessComplete) { 1116 DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n", tid); 1117 1118 fetchStatus[tid] = Running; 1119 status_change = true; 1120 } else if (fetchStatus[tid] == Running) { 1121 // Align the fetch PC so its at the start of a cache block. 1122 Addr block_PC = icacheBlockAlignPC(fetchAddr); 1123 1124 // If buffer is no longer valid or fetchAddr has moved to point 1125 // to the next cache block, AND we have no remaining ucode 1126 // from a macro-op, then start fetch from icache. 1127 if (!(cacheDataValid[tid] && block_PC == cacheDataPC[tid]) 1128 && !inRom && !macroop[tid]) { 1129 DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read " 1130 "instruction, starting at PC %s.\n", tid, thisPC); 1131 1132 fetchCacheLine(fetchAddr, tid, thisPC.instAddr()); 1133 1134 if (fetchStatus[tid] == IcacheWaitResponse) 1135 ++icacheStallCycles; 1136 else if (fetchStatus[tid] == ItlbWait) 1137 ++fetchTlbCycles; 1138 else 1139 ++fetchMiscStallCycles; 1140 return; 1141 } else if ((checkInterrupt(thisPC.instAddr()) && !delayedCommit[tid]) 1142 || isSwitchedOut()) { 1143 // Stall CPU if an interrupt is posted and we're not issuing 1144 // an delayed commit micro-op currently (delayed commit instructions 1145 // are not interruptable by interrupts, only faults) 1146 ++fetchMiscStallCycles; 1147 DPRINTF(Fetch, "[tid:%i]: Fetch is stalled!\n", tid); 1148 return; 1149 } 1150 } else { 1151 if (fetchStatus[tid] == Idle) { 1152 ++fetchIdleCycles; 1153 DPRINTF(Fetch, "[tid:%i]: Fetch is idle!\n", tid); 1154 } 1155 1156 // Status is Idle, so fetch should do nothing. 1157 return; 1158 } 1159 1160 ++fetchCycles; 1161 1162 TheISA::PCState nextPC = thisPC; 1163 1164 StaticInstPtr staticInst = NULL; 1165 StaticInstPtr curMacroop = macroop[tid]; 1166 1167 // If the read of the first instruction was successful, then grab the 1168 // instructions from the rest of the cache line and put them into the 1169 // queue heading to decode. 1170 1171 DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to " 1172 "decode.\n", tid); 1173 1174 // Need to keep track of whether or not a predicted branch 1175 // ended this fetch block. 1176 bool predictedBranch = false; 1177 1178 TheISA::MachInst *cacheInsts = 1179 reinterpret_cast<TheISA::MachInst *>(cacheData[tid]); 1180 1181 const unsigned numInsts = cacheBlkSize / instSize; 1182 unsigned blkOffset = (fetchAddr - cacheDataPC[tid]) / instSize; 1183 1184 // Loop through instruction memory from the cache. 1185 // Keep issuing while fetchWidth is available and branch is not 1186 // predicted taken 1187 while (numInst < fetchWidth && !predictedBranch) { 1188 1189 // We need to process more memory if we aren't going to get a 1190 // StaticInst from the rom, the current macroop, or what's already 1191 // in the predecoder. 1192 bool needMem = !inRom && !curMacroop && !predecoder.extMachInstReady(); 1193 fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1194 Addr block_PC = icacheBlockAlignPC(fetchAddr); 1195 1196 if (needMem) { 1197 // If buffer is no longer valid or fetchAddr has moved to point 1198 // to the next cache block then start fetch from icache. 1199 if (!cacheDataValid[tid] || block_PC != cacheDataPC[tid]) 1200 break; 1201 1202 if (blkOffset >= numInsts) { 1203 // We need to process more memory, but we've run out of the 1204 // current block. 1205 break; 1206 } 1207 1208 if (ISA_HAS_DELAY_SLOT && pcOffset == 0) { 1209 // Walk past any annulled delay slot instructions. 1210 Addr pcAddr = thisPC.instAddr() & BaseCPU::PCMask; 1211 while (fetchAddr != pcAddr && blkOffset < numInsts) { 1212 blkOffset++; 1213 fetchAddr += instSize; 1214 } 1215 if (blkOffset >= numInsts) 1216 break; 1217 } 1218 MachInst inst = TheISA::gtoh(cacheInsts[blkOffset]); 1219 1220 predecoder.setTC(cpu->thread[tid]->getTC()); 1221 predecoder.moreBytes(thisPC, fetchAddr, inst); 1222 1223 if (predecoder.needMoreBytes()) { 1224 blkOffset++; 1225 fetchAddr += instSize; 1226 pcOffset += instSize; 1227 } 1228 } 1229 1230 // Extract as many instructions and/or microops as we can from 1231 // the memory we've processed so far. 1232 do { 1233 if (!(curMacroop || inRom)) { 1234 if (predecoder.extMachInstReady()) { 1235 ExtMachInst extMachInst = 1236 predecoder.getExtMachInst(thisPC); 1237 staticInst = 1238 decoder.decode(extMachInst, thisPC.instAddr()); 1239 1240 // Increment stat of fetched instructions. 1241 ++fetchedInsts; 1242 1243 if (staticInst->isMacroop()) { 1244 curMacroop = staticInst; 1245 } else { 1246 pcOffset = 0; 1247 } 1248 } else { 1249 // We need more bytes for this instruction so blkOffset and 1250 // pcOffset will be updated 1251 break; 1252 } 1253 } 1254 // Whether we're moving to a new macroop because we're at the 1255 // end of the current one, or the branch predictor incorrectly 1256 // thinks we are... 1257 bool newMacro = false; 1258 if (curMacroop || inRom) { 1259 if (inRom) { 1260 staticInst = cpu->microcodeRom.fetchMicroop( 1261 thisPC.microPC(), curMacroop); 1262 } else { 1263 staticInst = curMacroop->fetchMicroop(thisPC.microPC()); 1264 } 1265 newMacro |= staticInst->isLastMicroop(); 1266 } 1267 1268 DynInstPtr instruction = 1269 buildInst(tid, staticInst, curMacroop, 1270 thisPC, nextPC, true); 1271 1272 numInst++; 1273 1274#if TRACING_ON 1275 instruction->fetchTick = curTick(); 1276#endif 1277 1278 nextPC = thisPC; 1279 1280 // If we're branching after this instruction, quite fetching 1281 // from the same block then. 1282 predictedBranch |= thisPC.branching(); 1283 predictedBranch |= 1284 lookupAndUpdateNextPC(instruction, nextPC); 1285 if (predictedBranch) { 1286 DPRINTF(Fetch, "Branch detected with PC = %s\n", thisPC); 1287 } 1288 1289 newMacro |= thisPC.instAddr() != nextPC.instAddr(); 1290 1291 // Move to the next instruction, unless we have a branch. 1292 thisPC = nextPC; 1293 inRom = isRomMicroPC(thisPC.microPC()); 1294 1295 if (newMacro) { 1296 fetchAddr = thisPC.instAddr() & BaseCPU::PCMask; 1297 blkOffset = (fetchAddr - cacheDataPC[tid]) / instSize; 1298 pcOffset = 0; 1299 curMacroop = NULL; 1300 } 1301 1302 if (instruction->isQuiesce()) { 1303 DPRINTF(Fetch, 1304 "Quiesce instruction encountered, halting fetch!"); 1305 fetchStatus[tid] = QuiescePending; 1306 status_change = true; 1307 break; 1308 } 1309 } while ((curMacroop || predecoder.extMachInstReady()) && 1310 numInst < fetchWidth); 1311 } 1312 1313 if (predictedBranch) { 1314 DPRINTF(Fetch, "[tid:%i]: Done fetching, predicted branch " 1315 "instruction encountered.\n", tid); 1316 } else if (numInst >= fetchWidth) { 1317 DPRINTF(Fetch, "[tid:%i]: Done fetching, reached fetch bandwidth " 1318 "for this cycle.\n", tid); 1319 } else if (blkOffset >= cacheBlkSize) { 1320 DPRINTF(Fetch, "[tid:%i]: Done fetching, reached the end of cache " 1321 "block.\n", tid); 1322 } 1323 1324 macroop[tid] = curMacroop; 1325 fetchOffset[tid] = pcOffset; 1326 1327 if (numInst > 0) { 1328 wroteToTimeBuffer = true; 1329 } 1330 1331 pc[tid] = thisPC; 1332 1333 // pipeline a fetch if we're crossing a cache boundary and not in 1334 // a state that would preclude fetching 1335 fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1336 Addr block_PC = icacheBlockAlignPC(fetchAddr); 1337 issuePipelinedIfetch[tid] = block_PC != cacheDataPC[tid] && 1338 fetchStatus[tid] != IcacheWaitResponse && 1339 fetchStatus[tid] != ItlbWait && 1340 fetchStatus[tid] != IcacheWaitRetry && 1341 fetchStatus[tid] != QuiescePending && 1342 !curMacroop; 1343} 1344 1345template<class Impl> 1346void 1347DefaultFetch<Impl>::recvRetry() 1348{ 1349 if (retryPkt != NULL) { 1350 assert(cacheBlocked); 1351 assert(retryTid != InvalidThreadID); 1352 assert(fetchStatus[retryTid] == IcacheWaitRetry); 1353 1354 if (cpu->getIcachePort()->sendTiming(retryPkt)) { 1355 fetchStatus[retryTid] = IcacheWaitResponse; 1356 retryPkt = NULL; 1357 retryTid = InvalidThreadID; 1358 cacheBlocked = false; 1359 } 1360 } else { 1361 assert(retryTid == InvalidThreadID); 1362 // Access has been squashed since it was sent out. Just clear 1363 // the cache being blocked. 1364 cacheBlocked = false; 1365 } 1366} 1367 1368/////////////////////////////////////// 1369// // 1370// SMT FETCH POLICY MAINTAINED HERE // 1371// // 1372/////////////////////////////////////// 1373template<class Impl> 1374ThreadID 1375DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority) 1376{ 1377 if (numThreads > 1) { 1378 switch (fetch_priority) { 1379 1380 case SingleThread: 1381 return 0; 1382 1383 case RoundRobin: 1384 return roundRobin(); 1385 1386 case IQ: 1387 return iqCount(); 1388 1389 case LSQ: 1390 return lsqCount(); 1391 1392 case Branch: 1393 return branchCount(); 1394 1395 default: 1396 return InvalidThreadID; 1397 } 1398 } else { 1399 list<ThreadID>::iterator thread = activeThreads->begin(); 1400 if (thread == activeThreads->end()) { 1401 return InvalidThreadID; 1402 } 1403 1404 ThreadID tid = *thread; 1405 1406 if (fetchStatus[tid] == Running || 1407 fetchStatus[tid] == IcacheAccessComplete || 1408 fetchStatus[tid] == Idle) { 1409 return tid; 1410 } else { 1411 return InvalidThreadID; 1412 } 1413 } 1414} 1415 1416 1417template<class Impl> 1418ThreadID 1419DefaultFetch<Impl>::roundRobin() 1420{ 1421 list<ThreadID>::iterator pri_iter = priorityList.begin(); 1422 list<ThreadID>::iterator end = priorityList.end(); 1423 1424 ThreadID high_pri; 1425 1426 while (pri_iter != end) { 1427 high_pri = *pri_iter; 1428 1429 assert(high_pri <= numThreads); 1430 1431 if (fetchStatus[high_pri] == Running || 1432 fetchStatus[high_pri] == IcacheAccessComplete || 1433 fetchStatus[high_pri] == Idle) { 1434 1435 priorityList.erase(pri_iter); 1436 priorityList.push_back(high_pri); 1437 1438 return high_pri; 1439 } 1440 1441 pri_iter++; 1442 } 1443 1444 return InvalidThreadID; 1445} 1446 1447template<class Impl> 1448ThreadID 1449DefaultFetch<Impl>::iqCount() 1450{ 1451 std::priority_queue<unsigned> PQ; 1452 std::map<unsigned, ThreadID> threadMap; 1453 1454 list<ThreadID>::iterator threads = activeThreads->begin(); 1455 list<ThreadID>::iterator end = activeThreads->end(); 1456 1457 while (threads != end) { 1458 ThreadID tid = *threads++; 1459 unsigned iqCount = fromIEW->iewInfo[tid].iqCount; 1460 1461 PQ.push(iqCount); 1462 threadMap[iqCount] = tid; 1463 } 1464 1465 while (!PQ.empty()) { 1466 ThreadID high_pri = threadMap[PQ.top()]; 1467 1468 if (fetchStatus[high_pri] == Running || 1469 fetchStatus[high_pri] == IcacheAccessComplete || 1470 fetchStatus[high_pri] == Idle) 1471 return high_pri; 1472 else 1473 PQ.pop(); 1474 1475 } 1476 1477 return InvalidThreadID; 1478} 1479 1480template<class Impl> 1481ThreadID 1482DefaultFetch<Impl>::lsqCount() 1483{ 1484 std::priority_queue<unsigned> PQ; 1485 std::map<unsigned, ThreadID> threadMap; 1486 1487 list<ThreadID>::iterator threads = activeThreads->begin(); 1488 list<ThreadID>::iterator end = activeThreads->end(); 1489 1490 while (threads != end) { 1491 ThreadID tid = *threads++; 1492 unsigned ldstqCount = fromIEW->iewInfo[tid].ldstqCount; 1493 1494 PQ.push(ldstqCount); 1495 threadMap[ldstqCount] = tid; 1496 } 1497 1498 while (!PQ.empty()) { 1499 ThreadID high_pri = threadMap[PQ.top()]; 1500 1501 if (fetchStatus[high_pri] == Running || 1502 fetchStatus[high_pri] == IcacheAccessComplete || 1503 fetchStatus[high_pri] == Idle) 1504 return high_pri; 1505 else 1506 PQ.pop(); 1507 } 1508 1509 return InvalidThreadID; 1510} 1511 1512template<class Impl> 1513ThreadID 1514DefaultFetch<Impl>::branchCount() 1515{ 1516#if 0 1517 list<ThreadID>::iterator thread = activeThreads->begin(); 1518 assert(thread != activeThreads->end()); 1519 ThreadID tid = *thread; 1520#endif 1521 1522 panic("Branch Count Fetch policy unimplemented\n"); 1523 return InvalidThreadID; 1524} 1525 1526template<class Impl> 1527void 1528DefaultFetch<Impl>::pipelineIcacheAccesses(ThreadID tid) 1529{ 1530 if (!issuePipelinedIfetch[tid]) { 1531 return; 1532 } 1533 1534 // The next PC to access. 1535 TheISA::PCState thisPC = pc[tid]; 1536 1537 if (isRomMicroPC(thisPC.microPC())) { 1538 return; 1539 } 1540 1541 Addr pcOffset = fetchOffset[tid]; 1542 Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1543 1544 // Align the fetch PC so its at the start of a cache block. 1545 Addr block_PC = icacheBlockAlignPC(fetchAddr); 1546 1547 // Unless buffer already got the block, fetch it from icache. 1548 if (!(cacheDataValid[tid] && block_PC == cacheDataPC[tid])) { 1549 DPRINTF(Fetch, "[tid:%i]: Issuing a pipelined I-cache access, " 1550 "starting at PC %s.\n", tid, thisPC); 1551 1552 fetchCacheLine(fetchAddr, tid, thisPC.instAddr()); 1553 } 1554} 1555 1556template<class Impl> 1557void 1558DefaultFetch<Impl>::profileStall(ThreadID tid) { 1559 DPRINTF(Fetch,"There are no more threads available to fetch from.\n"); 1560 1561 // @todo Per-thread stats 1562 1563 if (drainPending) { 1564 ++fetchPendingDrainCycles; 1565 DPRINTF(Fetch, "Fetch is waiting for a drain!\n"); 1566 } else if (activeThreads->empty()) { 1567 ++fetchNoActiveThreadStallCycles; 1568 DPRINTF(Fetch, "Fetch has no active thread!\n"); 1569 } else if (fetchStatus[tid] == Blocked) { 1570 ++fetchBlockedCycles; 1571 DPRINTF(Fetch, "[tid:%i]: Fetch is blocked!\n", tid); 1572 } else if (fetchStatus[tid] == Squashing) { 1573 ++fetchSquashCycles; 1574 DPRINTF(Fetch, "[tid:%i]: Fetch is squashing!\n", tid); 1575 } else if (fetchStatus[tid] == IcacheWaitResponse) { 1576 ++icacheStallCycles; 1577 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting cache response!\n", 1578 tid); 1579 } else if (fetchStatus[tid] == ItlbWait) { 1580 ++fetchTlbCycles; 1581 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting ITLB walk to " 1582 "finish!\n", tid); 1583 } else if (fetchStatus[tid] == TrapPending) { 1584 ++fetchPendingTrapStallCycles; 1585 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for a pending trap!\n", 1586 tid); 1587 } else if (fetchStatus[tid] == QuiescePending) { 1588 ++fetchPendingQuiesceStallCycles; 1589 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for a pending quiesce " 1590 "instruction!\n", tid); 1591 } else if (fetchStatus[tid] == IcacheWaitRetry) { 1592 ++fetchIcacheWaitRetryStallCycles; 1593 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for an I-cache retry!\n", 1594 tid); 1595 } else if (fetchStatus[tid] == NoGoodAddr) { 1596 DPRINTF(Fetch, "[tid:%i]: Fetch predicted non-executable address\n", 1597 tid); 1598 } else { 1599 DPRINTF(Fetch, "[tid:%i]: Unexpected fetch stall reason (Status: %i).\n", 1600 tid, fetchStatus[tid]); 1601 } 1602} 1603