fetch_impl.hh revision 12427:b0611f1ad833
1/* 2 * Copyright (c) 2010-2014 ARM Limited 3 * Copyright (c) 2012-2013 AMD 4 * All rights reserved. 5 * 6 * The license below extends only to copyright in the software and shall 7 * not be construed as granting a license to any other intellectual 8 * property including but not limited to intellectual property relating 9 * to a hardware implementation of the functionality of the software 10 * licensed hereunder. You may use the software subject to the license 11 * terms below provided that you ensure that this notice is replicated 12 * unmodified and in its entirety in all distributions of the software, 13 * modified or unmodified, in source code or in binary form. 14 * 15 * Copyright (c) 2004-2006 The Regents of The University of Michigan 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Kevin Lim 42 * Korey Sewell 43 */ 44 45#ifndef __CPU_O3_FETCH_IMPL_HH__ 46#define __CPU_O3_FETCH_IMPL_HH__ 47 48#include <algorithm> 49#include <cstring> 50#include <list> 51#include <map> 52#include <queue> 53 54#include "arch/generic/tlb.hh" 55#include "arch/isa_traits.hh" 56#include "arch/utility.hh" 57#include "arch/vtophys.hh" 58#include "base/random.hh" 59#include "base/types.hh" 60#include "config/the_isa.hh" 61#include "cpu/base.hh" 62//#include "cpu/checker/cpu.hh" 63#include "cpu/o3/fetch.hh" 64#include "cpu/exetrace.hh" 65#include "debug/Activity.hh" 66#include "debug/Drain.hh" 67#include "debug/Fetch.hh" 68#include "debug/O3PipeView.hh" 69#include "mem/packet.hh" 70#include "params/DerivO3CPU.hh" 71#include "sim/byteswap.hh" 72#include "sim/core.hh" 73#include "sim/eventq.hh" 74#include "sim/full_system.hh" 75#include "sim/system.hh" 76#include "cpu/o3/isa_specific.hh" 77 78using namespace std; 79 80template<class Impl> 81DefaultFetch<Impl>::DefaultFetch(O3CPU *_cpu, DerivO3CPUParams *params) 82 : cpu(_cpu), 83 decodeToFetchDelay(params->decodeToFetchDelay), 84 renameToFetchDelay(params->renameToFetchDelay), 85 iewToFetchDelay(params->iewToFetchDelay), 86 commitToFetchDelay(params->commitToFetchDelay), 87 fetchWidth(params->fetchWidth), 88 decodeWidth(params->decodeWidth), 89 retryPkt(NULL), 90 retryTid(InvalidThreadID), 91 cacheBlkSize(cpu->cacheLineSize()), 92 fetchBufferSize(params->fetchBufferSize), 93 fetchBufferMask(fetchBufferSize - 1), 94 fetchQueueSize(params->fetchQueueSize), 95 numThreads(params->numThreads), 96 numFetchingThreads(params->smtNumFetchingThreads), 97 finishTranslationEvent(this) 98{ 99 if (numThreads > Impl::MaxThreads) 100 fatal("numThreads (%d) is larger than compiled limit (%d),\n" 101 "\tincrease MaxThreads in src/cpu/o3/impl.hh\n", 102 numThreads, static_cast<int>(Impl::MaxThreads)); 103 if (fetchWidth > Impl::MaxWidth) 104 fatal("fetchWidth (%d) is larger than compiled limit (%d),\n" 105 "\tincrease MaxWidth in src/cpu/o3/impl.hh\n", 106 fetchWidth, static_cast<int>(Impl::MaxWidth)); 107 if (fetchBufferSize > cacheBlkSize) 108 fatal("fetch buffer size (%u bytes) is greater than the cache " 109 "block size (%u bytes)\n", fetchBufferSize, cacheBlkSize); 110 if (cacheBlkSize % fetchBufferSize) 111 fatal("cache block (%u bytes) is not a multiple of the " 112 "fetch buffer (%u bytes)\n", cacheBlkSize, fetchBufferSize); 113 114 std::string policy = params->smtFetchPolicy; 115 116 // Convert string to lowercase 117 std::transform(policy.begin(), policy.end(), policy.begin(), 118 (int(*)(int)) tolower); 119 120 // Figure out fetch policy 121 if (policy == "singlethread") { 122 fetchPolicy = SingleThread; 123 if (numThreads > 1) 124 panic("Invalid Fetch Policy for a SMT workload."); 125 } else if (policy == "roundrobin") { 126 fetchPolicy = RoundRobin; 127 DPRINTF(Fetch, "Fetch policy set to Round Robin\n"); 128 } else if (policy == "branch") { 129 fetchPolicy = Branch; 130 DPRINTF(Fetch, "Fetch policy set to Branch Count\n"); 131 } else if (policy == "iqcount") { 132 fetchPolicy = IQ; 133 DPRINTF(Fetch, "Fetch policy set to IQ count\n"); 134 } else if (policy == "lsqcount") { 135 fetchPolicy = LSQ; 136 DPRINTF(Fetch, "Fetch policy set to LSQ count\n"); 137 } else { 138 fatal("Invalid Fetch Policy. Options Are: {SingleThread," 139 " RoundRobin,LSQcount,IQcount}\n"); 140 } 141 142 // Get the size of an instruction. 143 instSize = sizeof(TheISA::MachInst); 144 145 for (int i = 0; i < Impl::MaxThreads; i++) { 146 decoder[i] = NULL; 147 fetchBuffer[i] = NULL; 148 fetchBufferPC[i] = 0; 149 fetchBufferValid[i] = false; 150 } 151 152 branchPred = params->branchPred; 153 154 for (ThreadID tid = 0; tid < numThreads; tid++) { 155 decoder[tid] = new TheISA::Decoder(params->isa[tid]); 156 // Create space to buffer the cache line data, 157 // which may not hold the entire cache line. 158 fetchBuffer[tid] = new uint8_t[fetchBufferSize]; 159 } 160} 161 162template <class Impl> 163std::string 164DefaultFetch<Impl>::name() const 165{ 166 return cpu->name() + ".fetch"; 167} 168 169template <class Impl> 170void 171DefaultFetch<Impl>::regProbePoints() 172{ 173 ppFetch = new ProbePointArg<DynInstPtr>(cpu->getProbeManager(), "Fetch"); 174 ppFetchRequestSent = new ProbePointArg<RequestPtr>(cpu->getProbeManager(), 175 "FetchRequest"); 176 177} 178 179template <class Impl> 180void 181DefaultFetch<Impl>::regStats() 182{ 183 icacheStallCycles 184 .name(name() + ".icacheStallCycles") 185 .desc("Number of cycles fetch is stalled on an Icache miss") 186 .prereq(icacheStallCycles); 187 188 fetchedInsts 189 .name(name() + ".Insts") 190 .desc("Number of instructions fetch has processed") 191 .prereq(fetchedInsts); 192 193 fetchedBranches 194 .name(name() + ".Branches") 195 .desc("Number of branches that fetch encountered") 196 .prereq(fetchedBranches); 197 198 predictedBranches 199 .name(name() + ".predictedBranches") 200 .desc("Number of branches that fetch has predicted taken") 201 .prereq(predictedBranches); 202 203 fetchCycles 204 .name(name() + ".Cycles") 205 .desc("Number of cycles fetch has run and was not squashing or" 206 " blocked") 207 .prereq(fetchCycles); 208 209 fetchSquashCycles 210 .name(name() + ".SquashCycles") 211 .desc("Number of cycles fetch has spent squashing") 212 .prereq(fetchSquashCycles); 213 214 fetchTlbCycles 215 .name(name() + ".TlbCycles") 216 .desc("Number of cycles fetch has spent waiting for tlb") 217 .prereq(fetchTlbCycles); 218 219 fetchIdleCycles 220 .name(name() + ".IdleCycles") 221 .desc("Number of cycles fetch was idle") 222 .prereq(fetchIdleCycles); 223 224 fetchBlockedCycles 225 .name(name() + ".BlockedCycles") 226 .desc("Number of cycles fetch has spent blocked") 227 .prereq(fetchBlockedCycles); 228 229 fetchedCacheLines 230 .name(name() + ".CacheLines") 231 .desc("Number of cache lines fetched") 232 .prereq(fetchedCacheLines); 233 234 fetchMiscStallCycles 235 .name(name() + ".MiscStallCycles") 236 .desc("Number of cycles fetch has spent waiting on interrupts, or " 237 "bad addresses, or out of MSHRs") 238 .prereq(fetchMiscStallCycles); 239 240 fetchPendingDrainCycles 241 .name(name() + ".PendingDrainCycles") 242 .desc("Number of cycles fetch has spent waiting on pipes to drain") 243 .prereq(fetchPendingDrainCycles); 244 245 fetchNoActiveThreadStallCycles 246 .name(name() + ".NoActiveThreadStallCycles") 247 .desc("Number of stall cycles due to no active thread to fetch from") 248 .prereq(fetchNoActiveThreadStallCycles); 249 250 fetchPendingTrapStallCycles 251 .name(name() + ".PendingTrapStallCycles") 252 .desc("Number of stall cycles due to pending traps") 253 .prereq(fetchPendingTrapStallCycles); 254 255 fetchPendingQuiesceStallCycles 256 .name(name() + ".PendingQuiesceStallCycles") 257 .desc("Number of stall cycles due to pending quiesce instructions") 258 .prereq(fetchPendingQuiesceStallCycles); 259 260 fetchIcacheWaitRetryStallCycles 261 .name(name() + ".IcacheWaitRetryStallCycles") 262 .desc("Number of stall cycles due to full MSHR") 263 .prereq(fetchIcacheWaitRetryStallCycles); 264 265 fetchIcacheSquashes 266 .name(name() + ".IcacheSquashes") 267 .desc("Number of outstanding Icache misses that were squashed") 268 .prereq(fetchIcacheSquashes); 269 270 fetchTlbSquashes 271 .name(name() + ".ItlbSquashes") 272 .desc("Number of outstanding ITLB misses that were squashed") 273 .prereq(fetchTlbSquashes); 274 275 fetchNisnDist 276 .init(/* base value */ 0, 277 /* last value */ fetchWidth, 278 /* bucket size */ 1) 279 .name(name() + ".rateDist") 280 .desc("Number of instructions fetched each cycle (Total)") 281 .flags(Stats::pdf); 282 283 idleRate 284 .name(name() + ".idleRate") 285 .desc("Percent of cycles fetch was idle") 286 .prereq(idleRate); 287 idleRate = fetchIdleCycles * 100 / cpu->numCycles; 288 289 branchRate 290 .name(name() + ".branchRate") 291 .desc("Number of branch fetches per cycle") 292 .flags(Stats::total); 293 branchRate = fetchedBranches / cpu->numCycles; 294 295 fetchRate 296 .name(name() + ".rate") 297 .desc("Number of inst fetches per cycle") 298 .flags(Stats::total); 299 fetchRate = fetchedInsts / cpu->numCycles; 300} 301 302template<class Impl> 303void 304DefaultFetch<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer) 305{ 306 timeBuffer = time_buffer; 307 308 // Create wires to get information from proper places in time buffer. 309 fromDecode = timeBuffer->getWire(-decodeToFetchDelay); 310 fromRename = timeBuffer->getWire(-renameToFetchDelay); 311 fromIEW = timeBuffer->getWire(-iewToFetchDelay); 312 fromCommit = timeBuffer->getWire(-commitToFetchDelay); 313} 314 315template<class Impl> 316void 317DefaultFetch<Impl>::setActiveThreads(std::list<ThreadID> *at_ptr) 318{ 319 activeThreads = at_ptr; 320} 321 322template<class Impl> 323void 324DefaultFetch<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *ftb_ptr) 325{ 326 // Create wire to write information to proper place in fetch time buf. 327 toDecode = ftb_ptr->getWire(0); 328} 329 330template<class Impl> 331void 332DefaultFetch<Impl>::startupStage() 333{ 334 assert(priorityList.empty()); 335 resetStage(); 336 337 // Fetch needs to start fetching instructions at the very beginning, 338 // so it must start up in active state. 339 switchToActive(); 340} 341 342template<class Impl> 343void 344DefaultFetch<Impl>::resetStage() 345{ 346 numInst = 0; 347 interruptPending = false; 348 cacheBlocked = false; 349 350 priorityList.clear(); 351 352 // Setup PC and nextPC with initial state. 353 for (ThreadID tid = 0; tid < numThreads; ++tid) { 354 fetchStatus[tid] = Running; 355 pc[tid] = cpu->pcState(tid); 356 fetchOffset[tid] = 0; 357 macroop[tid] = NULL; 358 359 delayedCommit[tid] = false; 360 memReq[tid] = NULL; 361 362 stalls[tid].decode = false; 363 stalls[tid].drain = false; 364 365 fetchBufferPC[tid] = 0; 366 fetchBufferValid[tid] = false; 367 368 fetchQueue[tid].clear(); 369 370 priorityList.push_back(tid); 371 } 372 373 wroteToTimeBuffer = false; 374 _status = Inactive; 375} 376 377template<class Impl> 378void 379DefaultFetch<Impl>::processCacheCompletion(PacketPtr pkt) 380{ 381 ThreadID tid = cpu->contextToThread(pkt->req->contextId()); 382 383 DPRINTF(Fetch, "[tid:%u] Waking up from cache miss.\n", tid); 384 assert(!cpu->switchedOut()); 385 386 // Only change the status if it's still waiting on the icache access 387 // to return. 388 if (fetchStatus[tid] != IcacheWaitResponse || 389 pkt->req != memReq[tid]) { 390 ++fetchIcacheSquashes; 391 delete pkt->req; 392 delete pkt; 393 return; 394 } 395 396 memcpy(fetchBuffer[tid], pkt->getConstPtr<uint8_t>(), fetchBufferSize); 397 fetchBufferValid[tid] = true; 398 399 // Wake up the CPU (if it went to sleep and was waiting on 400 // this completion event). 401 cpu->wakeCPU(); 402 403 DPRINTF(Activity, "[tid:%u] Activating fetch due to cache completion\n", 404 tid); 405 406 switchToActive(); 407 408 // Only switch to IcacheAccessComplete if we're not stalled as well. 409 if (checkStall(tid)) { 410 fetchStatus[tid] = Blocked; 411 } else { 412 fetchStatus[tid] = IcacheAccessComplete; 413 } 414 415 pkt->req->setAccessLatency(); 416 cpu->ppInstAccessComplete->notify(pkt); 417 // Reset the mem req to NULL. 418 delete pkt->req; 419 delete pkt; 420 memReq[tid] = NULL; 421} 422 423template <class Impl> 424void 425DefaultFetch<Impl>::drainResume() 426{ 427 for (ThreadID i = 0; i < numThreads; ++i) { 428 stalls[i].decode = false; 429 stalls[i].drain = false; 430 } 431} 432 433template <class Impl> 434void 435DefaultFetch<Impl>::drainSanityCheck() const 436{ 437 assert(isDrained()); 438 assert(retryPkt == NULL); 439 assert(retryTid == InvalidThreadID); 440 assert(!cacheBlocked); 441 assert(!interruptPending); 442 443 for (ThreadID i = 0; i < numThreads; ++i) { 444 assert(!memReq[i]); 445 assert(fetchStatus[i] == Idle || stalls[i].drain); 446 } 447 448 branchPred->drainSanityCheck(); 449} 450 451template <class Impl> 452bool 453DefaultFetch<Impl>::isDrained() const 454{ 455 /* Make sure that threads are either idle of that the commit stage 456 * has signaled that draining has completed by setting the drain 457 * stall flag. This effectively forces the pipeline to be disabled 458 * until the whole system is drained (simulation may continue to 459 * drain other components). 460 */ 461 for (ThreadID i = 0; i < numThreads; ++i) { 462 // Verify fetch queues are drained 463 if (!fetchQueue[i].empty()) 464 return false; 465 466 // Return false if not idle or drain stalled 467 if (fetchStatus[i] != Idle) { 468 if (fetchStatus[i] == Blocked && stalls[i].drain) 469 continue; 470 else 471 return false; 472 } 473 } 474 475 /* The pipeline might start up again in the middle of the drain 476 * cycle if the finish translation event is scheduled, so make 477 * sure that's not the case. 478 */ 479 return !finishTranslationEvent.scheduled(); 480} 481 482template <class Impl> 483void 484DefaultFetch<Impl>::takeOverFrom() 485{ 486 assert(cpu->getInstPort().isConnected()); 487 resetStage(); 488 489} 490 491template <class Impl> 492void 493DefaultFetch<Impl>::drainStall(ThreadID tid) 494{ 495 assert(cpu->isDraining()); 496 assert(!stalls[tid].drain); 497 DPRINTF(Drain, "%i: Thread drained.\n", tid); 498 stalls[tid].drain = true; 499} 500 501template <class Impl> 502void 503DefaultFetch<Impl>::wakeFromQuiesce() 504{ 505 DPRINTF(Fetch, "Waking up from quiesce\n"); 506 // Hopefully this is safe 507 // @todo: Allow other threads to wake from quiesce. 508 fetchStatus[0] = Running; 509} 510 511template <class Impl> 512inline void 513DefaultFetch<Impl>::switchToActive() 514{ 515 if (_status == Inactive) { 516 DPRINTF(Activity, "Activating stage.\n"); 517 518 cpu->activateStage(O3CPU::FetchIdx); 519 520 _status = Active; 521 } 522} 523 524template <class Impl> 525inline void 526DefaultFetch<Impl>::switchToInactive() 527{ 528 if (_status == Active) { 529 DPRINTF(Activity, "Deactivating stage.\n"); 530 531 cpu->deactivateStage(O3CPU::FetchIdx); 532 533 _status = Inactive; 534 } 535} 536 537template <class Impl> 538void 539DefaultFetch<Impl>::deactivateThread(ThreadID tid) 540{ 541 // Update priority list 542 auto thread_it = std::find(priorityList.begin(), priorityList.end(), tid); 543 if (thread_it != priorityList.end()) { 544 priorityList.erase(thread_it); 545 } 546} 547 548template <class Impl> 549bool 550DefaultFetch<Impl>::lookupAndUpdateNextPC( 551 DynInstPtr &inst, TheISA::PCState &nextPC) 552{ 553 // Do branch prediction check here. 554 // A bit of a misnomer...next_PC is actually the current PC until 555 // this function updates it. 556 bool predict_taken; 557 558 if (!inst->isControl()) { 559 TheISA::advancePC(nextPC, inst->staticInst); 560 inst->setPredTarg(nextPC); 561 inst->setPredTaken(false); 562 return false; 563 } 564 565 ThreadID tid = inst->threadNumber; 566 predict_taken = branchPred->predict(inst->staticInst, inst->seqNum, 567 nextPC, tid); 568 569 if (predict_taken) { 570 DPRINTF(Fetch, "[tid:%i]: [sn:%i]: Branch predicted to be taken to %s.\n", 571 tid, inst->seqNum, nextPC); 572 } else { 573 DPRINTF(Fetch, "[tid:%i]: [sn:%i]:Branch predicted to be not taken.\n", 574 tid, inst->seqNum); 575 } 576 577 DPRINTF(Fetch, "[tid:%i]: [sn:%i] Branch predicted to go to %s.\n", 578 tid, inst->seqNum, nextPC); 579 inst->setPredTarg(nextPC); 580 inst->setPredTaken(predict_taken); 581 582 ++fetchedBranches; 583 584 if (predict_taken) { 585 ++predictedBranches; 586 } 587 588 return predict_taken; 589} 590 591template <class Impl> 592bool 593DefaultFetch<Impl>::fetchCacheLine(Addr vaddr, ThreadID tid, Addr pc) 594{ 595 Fault fault = NoFault; 596 597 assert(!cpu->switchedOut()); 598 599 // @todo: not sure if these should block translation. 600 //AlphaDep 601 if (cacheBlocked) { 602 DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, cache blocked\n", 603 tid); 604 return false; 605 } else if (checkInterrupt(pc) && !delayedCommit[tid]) { 606 // Hold off fetch from getting new instructions when: 607 // Cache is blocked, or 608 // while an interrupt is pending and we're not in PAL mode, or 609 // fetch is switched out. 610 DPRINTF(Fetch, "[tid:%i] Can't fetch cache line, interrupt pending\n", 611 tid); 612 return false; 613 } 614 615 // Align the fetch address to the start of a fetch buffer segment. 616 Addr fetchBufferBlockPC = fetchBufferAlignPC(vaddr); 617 618 DPRINTF(Fetch, "[tid:%i] Fetching cache line %#x for addr %#x\n", 619 tid, fetchBufferBlockPC, vaddr); 620 621 // Setup the memReq to do a read of the first instruction's address. 622 // Set the appropriate read size and flags as well. 623 // Build request here. 624 RequestPtr mem_req = 625 new Request(tid, fetchBufferBlockPC, fetchBufferSize, 626 Request::INST_FETCH, cpu->instMasterId(), pc, 627 cpu->thread[tid]->contextId()); 628 629 mem_req->taskId(cpu->taskId()); 630 631 memReq[tid] = mem_req; 632 633 // Initiate translation of the icache block 634 fetchStatus[tid] = ItlbWait; 635 FetchTranslation *trans = new FetchTranslation(this); 636 cpu->itb->translateTiming(mem_req, cpu->thread[tid]->getTC(), 637 trans, BaseTLB::Execute); 638 return true; 639} 640 641template <class Impl> 642void 643DefaultFetch<Impl>::finishTranslation(const Fault &fault, RequestPtr mem_req) 644{ 645 ThreadID tid = cpu->contextToThread(mem_req->contextId()); 646 Addr fetchBufferBlockPC = mem_req->getVaddr(); 647 648 assert(!cpu->switchedOut()); 649 650 // Wake up CPU if it was idle 651 cpu->wakeCPU(); 652 653 if (fetchStatus[tid] != ItlbWait || mem_req != memReq[tid] || 654 mem_req->getVaddr() != memReq[tid]->getVaddr()) { 655 DPRINTF(Fetch, "[tid:%i] Ignoring itlb completed after squash\n", 656 tid); 657 ++fetchTlbSquashes; 658 delete mem_req; 659 return; 660 } 661 662 663 // If translation was successful, attempt to read the icache block. 664 if (fault == NoFault) { 665 // Check that we're not going off into random memory 666 // If we have, just wait around for commit to squash something and put 667 // us on the right track 668 if (!cpu->system->isMemAddr(mem_req->getPaddr())) { 669 warn("Address %#x is outside of physical memory, stopping fetch\n", 670 mem_req->getPaddr()); 671 fetchStatus[tid] = NoGoodAddr; 672 delete mem_req; 673 memReq[tid] = NULL; 674 return; 675 } 676 677 // Build packet here. 678 PacketPtr data_pkt = new Packet(mem_req, MemCmd::ReadReq); 679 data_pkt->dataDynamic(new uint8_t[fetchBufferSize]); 680 681 fetchBufferPC[tid] = fetchBufferBlockPC; 682 fetchBufferValid[tid] = false; 683 DPRINTF(Fetch, "Fetch: Doing instruction read.\n"); 684 685 fetchedCacheLines++; 686 687 // Access the cache. 688 if (!cpu->getInstPort().sendTimingReq(data_pkt)) { 689 assert(retryPkt == NULL); 690 assert(retryTid == InvalidThreadID); 691 DPRINTF(Fetch, "[tid:%i] Out of MSHRs!\n", tid); 692 693 fetchStatus[tid] = IcacheWaitRetry; 694 retryPkt = data_pkt; 695 retryTid = tid; 696 cacheBlocked = true; 697 } else { 698 DPRINTF(Fetch, "[tid:%i]: Doing Icache access.\n", tid); 699 DPRINTF(Activity, "[tid:%i]: Activity: Waiting on I-cache " 700 "response.\n", tid); 701 lastIcacheStall[tid] = curTick(); 702 fetchStatus[tid] = IcacheWaitResponse; 703 // Notify Fetch Request probe when a packet containing a fetch 704 // request is successfully sent 705 ppFetchRequestSent->notify(mem_req); 706 } 707 } else { 708 // Don't send an instruction to decode if we can't handle it. 709 if (!(numInst < fetchWidth) || !(fetchQueue[tid].size() < fetchQueueSize)) { 710 assert(!finishTranslationEvent.scheduled()); 711 finishTranslationEvent.setFault(fault); 712 finishTranslationEvent.setReq(mem_req); 713 cpu->schedule(finishTranslationEvent, 714 cpu->clockEdge(Cycles(1))); 715 return; 716 } 717 DPRINTF(Fetch, "[tid:%i] Got back req with addr %#x but expected %#x\n", 718 tid, mem_req->getVaddr(), memReq[tid]->getVaddr()); 719 // Translation faulted, icache request won't be sent. 720 delete mem_req; 721 memReq[tid] = NULL; 722 723 // Send the fault to commit. This thread will not do anything 724 // until commit handles the fault. The only other way it can 725 // wake up is if a squash comes along and changes the PC. 726 TheISA::PCState fetchPC = pc[tid]; 727 728 DPRINTF(Fetch, "[tid:%i]: Translation faulted, building noop.\n", tid); 729 // We will use a nop in ordier to carry the fault. 730 DynInstPtr instruction = buildInst(tid, StaticInst::nopStaticInstPtr, 731 NULL, fetchPC, fetchPC, false); 732 instruction->setNotAnInst(); 733 734 instruction->setPredTarg(fetchPC); 735 instruction->fault = fault; 736 wroteToTimeBuffer = true; 737 738 DPRINTF(Activity, "Activity this cycle.\n"); 739 cpu->activityThisCycle(); 740 741 fetchStatus[tid] = TrapPending; 742 743 DPRINTF(Fetch, "[tid:%i]: Blocked, need to handle the trap.\n", tid); 744 DPRINTF(Fetch, "[tid:%i]: fault (%s) detected @ PC %s.\n", 745 tid, fault->name(), pc[tid]); 746 } 747 _status = updateFetchStatus(); 748} 749 750template <class Impl> 751inline void 752DefaultFetch<Impl>::doSquash(const TheISA::PCState &newPC, 753 const DynInstPtr squashInst, ThreadID tid) 754{ 755 DPRINTF(Fetch, "[tid:%i]: Squashing, setting PC to: %s.\n", 756 tid, newPC); 757 758 pc[tid] = newPC; 759 fetchOffset[tid] = 0; 760 if (squashInst && squashInst->pcState().instAddr() == newPC.instAddr()) 761 macroop[tid] = squashInst->macroop; 762 else 763 macroop[tid] = NULL; 764 decoder[tid]->reset(); 765 766 // Clear the icache miss if it's outstanding. 767 if (fetchStatus[tid] == IcacheWaitResponse) { 768 DPRINTF(Fetch, "[tid:%i]: Squashing outstanding Icache miss.\n", 769 tid); 770 memReq[tid] = NULL; 771 } else if (fetchStatus[tid] == ItlbWait) { 772 DPRINTF(Fetch, "[tid:%i]: Squashing outstanding ITLB miss.\n", 773 tid); 774 memReq[tid] = NULL; 775 } 776 777 // Get rid of the retrying packet if it was from this thread. 778 if (retryTid == tid) { 779 assert(cacheBlocked); 780 if (retryPkt) { 781 delete retryPkt->req; 782 delete retryPkt; 783 } 784 retryPkt = NULL; 785 retryTid = InvalidThreadID; 786 } 787 788 fetchStatus[tid] = Squashing; 789 790 // Empty fetch queue 791 fetchQueue[tid].clear(); 792 793 // microops are being squashed, it is not known wheather the 794 // youngest non-squashed microop was marked delayed commit 795 // or not. Setting the flag to true ensures that the 796 // interrupts are not handled when they cannot be, though 797 // some opportunities to handle interrupts may be missed. 798 delayedCommit[tid] = true; 799 800 ++fetchSquashCycles; 801} 802 803template<class Impl> 804void 805DefaultFetch<Impl>::squashFromDecode(const TheISA::PCState &newPC, 806 const DynInstPtr squashInst, 807 const InstSeqNum seq_num, ThreadID tid) 808{ 809 DPRINTF(Fetch, "[tid:%i]: Squashing from decode.\n", tid); 810 811 doSquash(newPC, squashInst, tid); 812 813 // Tell the CPU to remove any instructions that are in flight between 814 // fetch and decode. 815 cpu->removeInstsUntil(seq_num, tid); 816} 817 818template<class Impl> 819bool 820DefaultFetch<Impl>::checkStall(ThreadID tid) const 821{ 822 bool ret_val = false; 823 824 if (stalls[tid].drain) { 825 assert(cpu->isDraining()); 826 DPRINTF(Fetch,"[tid:%i]: Drain stall detected.\n",tid); 827 ret_val = true; 828 } 829 830 return ret_val; 831} 832 833template<class Impl> 834typename DefaultFetch<Impl>::FetchStatus 835DefaultFetch<Impl>::updateFetchStatus() 836{ 837 //Check Running 838 list<ThreadID>::iterator threads = activeThreads->begin(); 839 list<ThreadID>::iterator end = activeThreads->end(); 840 841 while (threads != end) { 842 ThreadID tid = *threads++; 843 844 if (fetchStatus[tid] == Running || 845 fetchStatus[tid] == Squashing || 846 fetchStatus[tid] == IcacheAccessComplete) { 847 848 if (_status == Inactive) { 849 DPRINTF(Activity, "[tid:%i]: Activating stage.\n",tid); 850 851 if (fetchStatus[tid] == IcacheAccessComplete) { 852 DPRINTF(Activity, "[tid:%i]: Activating fetch due to cache" 853 "completion\n",tid); 854 } 855 856 cpu->activateStage(O3CPU::FetchIdx); 857 } 858 859 return Active; 860 } 861 } 862 863 // Stage is switching from active to inactive, notify CPU of it. 864 if (_status == Active) { 865 DPRINTF(Activity, "Deactivating stage.\n"); 866 867 cpu->deactivateStage(O3CPU::FetchIdx); 868 } 869 870 return Inactive; 871} 872 873template <class Impl> 874void 875DefaultFetch<Impl>::squash(const TheISA::PCState &newPC, 876 const InstSeqNum seq_num, DynInstPtr squashInst, 877 ThreadID tid) 878{ 879 DPRINTF(Fetch, "[tid:%u]: Squash from commit.\n", tid); 880 881 doSquash(newPC, squashInst, tid); 882 883 // Tell the CPU to remove any instructions that are not in the ROB. 884 cpu->removeInstsNotInROB(tid); 885} 886 887template <class Impl> 888void 889DefaultFetch<Impl>::tick() 890{ 891 list<ThreadID>::iterator threads = activeThreads->begin(); 892 list<ThreadID>::iterator end = activeThreads->end(); 893 bool status_change = false; 894 895 wroteToTimeBuffer = false; 896 897 for (ThreadID i = 0; i < numThreads; ++i) { 898 issuePipelinedIfetch[i] = false; 899 } 900 901 while (threads != end) { 902 ThreadID tid = *threads++; 903 904 // Check the signals for each thread to determine the proper status 905 // for each thread. 906 bool updated_status = checkSignalsAndUpdate(tid); 907 status_change = status_change || updated_status; 908 } 909 910 DPRINTF(Fetch, "Running stage.\n"); 911 912 if (FullSystem) { 913 if (fromCommit->commitInfo[0].interruptPending) { 914 interruptPending = true; 915 } 916 917 if (fromCommit->commitInfo[0].clearInterrupt) { 918 interruptPending = false; 919 } 920 } 921 922 for (threadFetched = 0; threadFetched < numFetchingThreads; 923 threadFetched++) { 924 // Fetch each of the actively fetching threads. 925 fetch(status_change); 926 } 927 928 // Record number of instructions fetched this cycle for distribution. 929 fetchNisnDist.sample(numInst); 930 931 if (status_change) { 932 // Change the fetch stage status if there was a status change. 933 _status = updateFetchStatus(); 934 } 935 936 // Issue the next I-cache request if possible. 937 for (ThreadID i = 0; i < numThreads; ++i) { 938 if (issuePipelinedIfetch[i]) { 939 pipelineIcacheAccesses(i); 940 } 941 } 942 943 // Send instructions enqueued into the fetch queue to decode. 944 // Limit rate by fetchWidth. Stall if decode is stalled. 945 unsigned insts_to_decode = 0; 946 unsigned available_insts = 0; 947 948 for (auto tid : *activeThreads) { 949 if (!stalls[tid].decode) { 950 available_insts += fetchQueue[tid].size(); 951 } 952 } 953 954 // Pick a random thread to start trying to grab instructions from 955 auto tid_itr = activeThreads->begin(); 956 std::advance(tid_itr, random_mt.random<uint8_t>(0, activeThreads->size() - 1)); 957 958 while (available_insts != 0 && insts_to_decode < decodeWidth) { 959 ThreadID tid = *tid_itr; 960 if (!stalls[tid].decode && !fetchQueue[tid].empty()) { 961 auto inst = fetchQueue[tid].front(); 962 toDecode->insts[toDecode->size++] = inst; 963 DPRINTF(Fetch, "[tid:%i][sn:%i]: Sending instruction to decode from " 964 "fetch queue. Fetch queue size: %i.\n", 965 tid, inst->seqNum, fetchQueue[tid].size()); 966 967 wroteToTimeBuffer = true; 968 fetchQueue[tid].pop_front(); 969 insts_to_decode++; 970 available_insts--; 971 } 972 973 tid_itr++; 974 // Wrap around if at end of active threads list 975 if (tid_itr == activeThreads->end()) 976 tid_itr = activeThreads->begin(); 977 } 978 979 // If there was activity this cycle, inform the CPU of it. 980 if (wroteToTimeBuffer) { 981 DPRINTF(Activity, "Activity this cycle.\n"); 982 cpu->activityThisCycle(); 983 } 984 985 // Reset the number of the instruction we've fetched. 986 numInst = 0; 987} 988 989template <class Impl> 990bool 991DefaultFetch<Impl>::checkSignalsAndUpdate(ThreadID tid) 992{ 993 // Update the per thread stall statuses. 994 if (fromDecode->decodeBlock[tid]) { 995 stalls[tid].decode = true; 996 } 997 998 if (fromDecode->decodeUnblock[tid]) { 999 assert(stalls[tid].decode); 1000 assert(!fromDecode->decodeBlock[tid]); 1001 stalls[tid].decode = false; 1002 } 1003 1004 // Check squash signals from commit. 1005 if (fromCommit->commitInfo[tid].squash) { 1006 1007 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 1008 "from commit.\n",tid); 1009 // In any case, squash. 1010 squash(fromCommit->commitInfo[tid].pc, 1011 fromCommit->commitInfo[tid].doneSeqNum, 1012 fromCommit->commitInfo[tid].squashInst, tid); 1013 1014 // If it was a branch mispredict on a control instruction, update the 1015 // branch predictor with that instruction, otherwise just kill the 1016 // invalid state we generated in after sequence number 1017 if (fromCommit->commitInfo[tid].mispredictInst && 1018 fromCommit->commitInfo[tid].mispredictInst->isControl()) { 1019 branchPred->squash(fromCommit->commitInfo[tid].doneSeqNum, 1020 fromCommit->commitInfo[tid].pc, 1021 fromCommit->commitInfo[tid].branchTaken, 1022 tid); 1023 } else { 1024 branchPred->squash(fromCommit->commitInfo[tid].doneSeqNum, 1025 tid); 1026 } 1027 1028 return true; 1029 } else if (fromCommit->commitInfo[tid].doneSeqNum) { 1030 // Update the branch predictor if it wasn't a squashed instruction 1031 // that was broadcasted. 1032 branchPred->update(fromCommit->commitInfo[tid].doneSeqNum, tid); 1033 } 1034 1035 // Check squash signals from decode. 1036 if (fromDecode->decodeInfo[tid].squash) { 1037 DPRINTF(Fetch, "[tid:%u]: Squashing instructions due to squash " 1038 "from decode.\n",tid); 1039 1040 // Update the branch predictor. 1041 if (fromDecode->decodeInfo[tid].branchMispredict) { 1042 branchPred->squash(fromDecode->decodeInfo[tid].doneSeqNum, 1043 fromDecode->decodeInfo[tid].nextPC, 1044 fromDecode->decodeInfo[tid].branchTaken, 1045 tid); 1046 } else { 1047 branchPred->squash(fromDecode->decodeInfo[tid].doneSeqNum, 1048 tid); 1049 } 1050 1051 if (fetchStatus[tid] != Squashing) { 1052 1053 DPRINTF(Fetch, "Squashing from decode with PC = %s\n", 1054 fromDecode->decodeInfo[tid].nextPC); 1055 // Squash unless we're already squashing 1056 squashFromDecode(fromDecode->decodeInfo[tid].nextPC, 1057 fromDecode->decodeInfo[tid].squashInst, 1058 fromDecode->decodeInfo[tid].doneSeqNum, 1059 tid); 1060 1061 return true; 1062 } 1063 } 1064 1065 if (checkStall(tid) && 1066 fetchStatus[tid] != IcacheWaitResponse && 1067 fetchStatus[tid] != IcacheWaitRetry && 1068 fetchStatus[tid] != ItlbWait && 1069 fetchStatus[tid] != QuiescePending) { 1070 DPRINTF(Fetch, "[tid:%i]: Setting to blocked\n",tid); 1071 1072 fetchStatus[tid] = Blocked; 1073 1074 return true; 1075 } 1076 1077 if (fetchStatus[tid] == Blocked || 1078 fetchStatus[tid] == Squashing) { 1079 // Switch status to running if fetch isn't being told to block or 1080 // squash this cycle. 1081 DPRINTF(Fetch, "[tid:%i]: Done squashing, switching to running.\n", 1082 tid); 1083 1084 fetchStatus[tid] = Running; 1085 1086 return true; 1087 } 1088 1089 // If we've reached this point, we have not gotten any signals that 1090 // cause fetch to change its status. Fetch remains the same as before. 1091 return false; 1092} 1093 1094template<class Impl> 1095typename Impl::DynInstPtr 1096DefaultFetch<Impl>::buildInst(ThreadID tid, StaticInstPtr staticInst, 1097 StaticInstPtr curMacroop, TheISA::PCState thisPC, 1098 TheISA::PCState nextPC, bool trace) 1099{ 1100 // Get a sequence number. 1101 InstSeqNum seq = cpu->getAndIncrementInstSeq(); 1102 1103 // Create a new DynInst from the instruction fetched. 1104 DynInstPtr instruction = 1105 new DynInst(staticInst, curMacroop, thisPC, nextPC, seq, cpu); 1106 instruction->setTid(tid); 1107 1108 instruction->setASID(tid); 1109 1110 instruction->setThreadState(cpu->thread[tid]); 1111 1112 DPRINTF(Fetch, "[tid:%i]: Instruction PC %#x (%d) created " 1113 "[sn:%lli].\n", tid, thisPC.instAddr(), 1114 thisPC.microPC(), seq); 1115 1116 DPRINTF(Fetch, "[tid:%i]: Instruction is: %s\n", tid, 1117 instruction->staticInst-> 1118 disassemble(thisPC.instAddr())); 1119 1120#if TRACING_ON 1121 if (trace) { 1122 instruction->traceData = 1123 cpu->getTracer()->getInstRecord(curTick(), cpu->tcBase(tid), 1124 instruction->staticInst, thisPC, curMacroop); 1125 } 1126#else 1127 instruction->traceData = NULL; 1128#endif 1129 1130 // Add instruction to the CPU's list of instructions. 1131 instruction->setInstListIt(cpu->addInst(instruction)); 1132 1133 // Write the instruction to the first slot in the queue 1134 // that heads to decode. 1135 assert(numInst < fetchWidth); 1136 fetchQueue[tid].push_back(instruction); 1137 assert(fetchQueue[tid].size() <= fetchQueueSize); 1138 DPRINTF(Fetch, "[tid:%i]: Fetch queue entry created (%i/%i).\n", 1139 tid, fetchQueue[tid].size(), fetchQueueSize); 1140 //toDecode->insts[toDecode->size++] = instruction; 1141 1142 // Keep track of if we can take an interrupt at this boundary 1143 delayedCommit[tid] = instruction->isDelayedCommit(); 1144 1145 return instruction; 1146} 1147 1148template<class Impl> 1149void 1150DefaultFetch<Impl>::fetch(bool &status_change) 1151{ 1152 ////////////////////////////////////////// 1153 // Start actual fetch 1154 ////////////////////////////////////////// 1155 ThreadID tid = getFetchingThread(fetchPolicy); 1156 1157 assert(!cpu->switchedOut()); 1158 1159 if (tid == InvalidThreadID) { 1160 // Breaks looping condition in tick() 1161 threadFetched = numFetchingThreads; 1162 1163 if (numThreads == 1) { // @todo Per-thread stats 1164 profileStall(0); 1165 } 1166 1167 return; 1168 } 1169 1170 DPRINTF(Fetch, "Attempting to fetch from [tid:%i]\n", tid); 1171 1172 // The current PC. 1173 TheISA::PCState thisPC = pc[tid]; 1174 1175 Addr pcOffset = fetchOffset[tid]; 1176 Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1177 1178 bool inRom = isRomMicroPC(thisPC.microPC()); 1179 1180 // If returning from the delay of a cache miss, then update the status 1181 // to running, otherwise do the cache access. Possibly move this up 1182 // to tick() function. 1183 if (fetchStatus[tid] == IcacheAccessComplete) { 1184 DPRINTF(Fetch, "[tid:%i]: Icache miss is complete.\n", tid); 1185 1186 fetchStatus[tid] = Running; 1187 status_change = true; 1188 } else if (fetchStatus[tid] == Running) { 1189 // Align the fetch PC so its at the start of a fetch buffer segment. 1190 Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr); 1191 1192 // If buffer is no longer valid or fetchAddr has moved to point 1193 // to the next cache block, AND we have no remaining ucode 1194 // from a macro-op, then start fetch from icache. 1195 if (!(fetchBufferValid[tid] && fetchBufferBlockPC == fetchBufferPC[tid]) 1196 && !inRom && !macroop[tid]) { 1197 DPRINTF(Fetch, "[tid:%i]: Attempting to translate and read " 1198 "instruction, starting at PC %s.\n", tid, thisPC); 1199 1200 fetchCacheLine(fetchAddr, tid, thisPC.instAddr()); 1201 1202 if (fetchStatus[tid] == IcacheWaitResponse) 1203 ++icacheStallCycles; 1204 else if (fetchStatus[tid] == ItlbWait) 1205 ++fetchTlbCycles; 1206 else 1207 ++fetchMiscStallCycles; 1208 return; 1209 } else if ((checkInterrupt(thisPC.instAddr()) && !delayedCommit[tid])) { 1210 // Stall CPU if an interrupt is posted and we're not issuing 1211 // an delayed commit micro-op currently (delayed commit instructions 1212 // are not interruptable by interrupts, only faults) 1213 ++fetchMiscStallCycles; 1214 DPRINTF(Fetch, "[tid:%i]: Fetch is stalled!\n", tid); 1215 return; 1216 } 1217 } else { 1218 if (fetchStatus[tid] == Idle) { 1219 ++fetchIdleCycles; 1220 DPRINTF(Fetch, "[tid:%i]: Fetch is idle!\n", tid); 1221 } 1222 1223 // Status is Idle, so fetch should do nothing. 1224 return; 1225 } 1226 1227 ++fetchCycles; 1228 1229 TheISA::PCState nextPC = thisPC; 1230 1231 StaticInstPtr staticInst = NULL; 1232 StaticInstPtr curMacroop = macroop[tid]; 1233 1234 // If the read of the first instruction was successful, then grab the 1235 // instructions from the rest of the cache line and put them into the 1236 // queue heading to decode. 1237 1238 DPRINTF(Fetch, "[tid:%i]: Adding instructions to queue to " 1239 "decode.\n", tid); 1240 1241 // Need to keep track of whether or not a predicted branch 1242 // ended this fetch block. 1243 bool predictedBranch = false; 1244 1245 // Need to halt fetch if quiesce instruction detected 1246 bool quiesce = false; 1247 1248 TheISA::MachInst *cacheInsts = 1249 reinterpret_cast<TheISA::MachInst *>(fetchBuffer[tid]); 1250 1251 const unsigned numInsts = fetchBufferSize / instSize; 1252 unsigned blkOffset = (fetchAddr - fetchBufferPC[tid]) / instSize; 1253 1254 // Loop through instruction memory from the cache. 1255 // Keep issuing while fetchWidth is available and branch is not 1256 // predicted taken 1257 while (numInst < fetchWidth && fetchQueue[tid].size() < fetchQueueSize 1258 && !predictedBranch && !quiesce) { 1259 // We need to process more memory if we aren't going to get a 1260 // StaticInst from the rom, the current macroop, or what's already 1261 // in the decoder. 1262 bool needMem = !inRom && !curMacroop && 1263 !decoder[tid]->instReady(); 1264 fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1265 Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr); 1266 1267 if (needMem) { 1268 // If buffer is no longer valid or fetchAddr has moved to point 1269 // to the next cache block then start fetch from icache. 1270 if (!fetchBufferValid[tid] || 1271 fetchBufferBlockPC != fetchBufferPC[tid]) 1272 break; 1273 1274 if (blkOffset >= numInsts) { 1275 // We need to process more memory, but we've run out of the 1276 // current block. 1277 break; 1278 } 1279 1280 MachInst inst = TheISA::gtoh(cacheInsts[blkOffset]); 1281 decoder[tid]->moreBytes(thisPC, fetchAddr, inst); 1282 1283 if (decoder[tid]->needMoreBytes()) { 1284 blkOffset++; 1285 fetchAddr += instSize; 1286 pcOffset += instSize; 1287 } 1288 } 1289 1290 // Extract as many instructions and/or microops as we can from 1291 // the memory we've processed so far. 1292 do { 1293 if (!(curMacroop || inRom)) { 1294 if (decoder[tid]->instReady()) { 1295 staticInst = decoder[tid]->decode(thisPC); 1296 1297 // Increment stat of fetched instructions. 1298 ++fetchedInsts; 1299 1300 if (staticInst->isMacroop()) { 1301 curMacroop = staticInst; 1302 } else { 1303 pcOffset = 0; 1304 } 1305 } else { 1306 // We need more bytes for this instruction so blkOffset and 1307 // pcOffset will be updated 1308 break; 1309 } 1310 } 1311 // Whether we're moving to a new macroop because we're at the 1312 // end of the current one, or the branch predictor incorrectly 1313 // thinks we are... 1314 bool newMacro = false; 1315 if (curMacroop || inRom) { 1316 if (inRom) { 1317 staticInst = cpu->microcodeRom.fetchMicroop( 1318 thisPC.microPC(), curMacroop); 1319 } else { 1320 staticInst = curMacroop->fetchMicroop(thisPC.microPC()); 1321 } 1322 newMacro |= staticInst->isLastMicroop(); 1323 } 1324 1325 DynInstPtr instruction = 1326 buildInst(tid, staticInst, curMacroop, 1327 thisPC, nextPC, true); 1328 1329 ppFetch->notify(instruction); 1330 numInst++; 1331 1332#if TRACING_ON 1333 if (DTRACE(O3PipeView)) { 1334 instruction->fetchTick = curTick(); 1335 } 1336#endif 1337 1338 nextPC = thisPC; 1339 1340 // If we're branching after this instruction, quit fetching 1341 // from the same block. 1342 predictedBranch |= thisPC.branching(); 1343 predictedBranch |= 1344 lookupAndUpdateNextPC(instruction, nextPC); 1345 if (predictedBranch) { 1346 DPRINTF(Fetch, "Branch detected with PC = %s\n", thisPC); 1347 } 1348 1349 newMacro |= thisPC.instAddr() != nextPC.instAddr(); 1350 1351 // Move to the next instruction, unless we have a branch. 1352 thisPC = nextPC; 1353 inRom = isRomMicroPC(thisPC.microPC()); 1354 1355 if (newMacro) { 1356 fetchAddr = thisPC.instAddr() & BaseCPU::PCMask; 1357 blkOffset = (fetchAddr - fetchBufferPC[tid]) / instSize; 1358 pcOffset = 0; 1359 curMacroop = NULL; 1360 } 1361 1362 if (instruction->isQuiesce()) { 1363 DPRINTF(Fetch, 1364 "Quiesce instruction encountered, halting fetch!\n"); 1365 fetchStatus[tid] = QuiescePending; 1366 status_change = true; 1367 quiesce = true; 1368 break; 1369 } 1370 } while ((curMacroop || decoder[tid]->instReady()) && 1371 numInst < fetchWidth && 1372 fetchQueue[tid].size() < fetchQueueSize); 1373 1374 // Re-evaluate whether the next instruction to fetch is in micro-op ROM 1375 // or not. 1376 inRom = isRomMicroPC(thisPC.microPC()); 1377 } 1378 1379 if (predictedBranch) { 1380 DPRINTF(Fetch, "[tid:%i]: Done fetching, predicted branch " 1381 "instruction encountered.\n", tid); 1382 } else if (numInst >= fetchWidth) { 1383 DPRINTF(Fetch, "[tid:%i]: Done fetching, reached fetch bandwidth " 1384 "for this cycle.\n", tid); 1385 } else if (blkOffset >= fetchBufferSize) { 1386 DPRINTF(Fetch, "[tid:%i]: Done fetching, reached the end of the" 1387 "fetch buffer.\n", tid); 1388 } 1389 1390 macroop[tid] = curMacroop; 1391 fetchOffset[tid] = pcOffset; 1392 1393 if (numInst > 0) { 1394 wroteToTimeBuffer = true; 1395 } 1396 1397 pc[tid] = thisPC; 1398 1399 // pipeline a fetch if we're crossing a fetch buffer boundary and not in 1400 // a state that would preclude fetching 1401 fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1402 Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr); 1403 issuePipelinedIfetch[tid] = fetchBufferBlockPC != fetchBufferPC[tid] && 1404 fetchStatus[tid] != IcacheWaitResponse && 1405 fetchStatus[tid] != ItlbWait && 1406 fetchStatus[tid] != IcacheWaitRetry && 1407 fetchStatus[tid] != QuiescePending && 1408 !curMacroop; 1409} 1410 1411template<class Impl> 1412void 1413DefaultFetch<Impl>::recvReqRetry() 1414{ 1415 if (retryPkt != NULL) { 1416 assert(cacheBlocked); 1417 assert(retryTid != InvalidThreadID); 1418 assert(fetchStatus[retryTid] == IcacheWaitRetry); 1419 1420 if (cpu->getInstPort().sendTimingReq(retryPkt)) { 1421 fetchStatus[retryTid] = IcacheWaitResponse; 1422 // Notify Fetch Request probe when a retryPkt is successfully sent. 1423 // Note that notify must be called before retryPkt is set to NULL. 1424 ppFetchRequestSent->notify(retryPkt->req); 1425 retryPkt = NULL; 1426 retryTid = InvalidThreadID; 1427 cacheBlocked = false; 1428 } 1429 } else { 1430 assert(retryTid == InvalidThreadID); 1431 // Access has been squashed since it was sent out. Just clear 1432 // the cache being blocked. 1433 cacheBlocked = false; 1434 } 1435} 1436 1437/////////////////////////////////////// 1438// // 1439// SMT FETCH POLICY MAINTAINED HERE // 1440// // 1441/////////////////////////////////////// 1442template<class Impl> 1443ThreadID 1444DefaultFetch<Impl>::getFetchingThread(FetchPriority &fetch_priority) 1445{ 1446 if (numThreads > 1) { 1447 switch (fetch_priority) { 1448 1449 case SingleThread: 1450 return 0; 1451 1452 case RoundRobin: 1453 return roundRobin(); 1454 1455 case IQ: 1456 return iqCount(); 1457 1458 case LSQ: 1459 return lsqCount(); 1460 1461 case Branch: 1462 return branchCount(); 1463 1464 default: 1465 return InvalidThreadID; 1466 } 1467 } else { 1468 list<ThreadID>::iterator thread = activeThreads->begin(); 1469 if (thread == activeThreads->end()) { 1470 return InvalidThreadID; 1471 } 1472 1473 ThreadID tid = *thread; 1474 1475 if (fetchStatus[tid] == Running || 1476 fetchStatus[tid] == IcacheAccessComplete || 1477 fetchStatus[tid] == Idle) { 1478 return tid; 1479 } else { 1480 return InvalidThreadID; 1481 } 1482 } 1483} 1484 1485 1486template<class Impl> 1487ThreadID 1488DefaultFetch<Impl>::roundRobin() 1489{ 1490 list<ThreadID>::iterator pri_iter = priorityList.begin(); 1491 list<ThreadID>::iterator end = priorityList.end(); 1492 1493 ThreadID high_pri; 1494 1495 while (pri_iter != end) { 1496 high_pri = *pri_iter; 1497 1498 assert(high_pri <= numThreads); 1499 1500 if (fetchStatus[high_pri] == Running || 1501 fetchStatus[high_pri] == IcacheAccessComplete || 1502 fetchStatus[high_pri] == Idle) { 1503 1504 priorityList.erase(pri_iter); 1505 priorityList.push_back(high_pri); 1506 1507 return high_pri; 1508 } 1509 1510 pri_iter++; 1511 } 1512 1513 return InvalidThreadID; 1514} 1515 1516template<class Impl> 1517ThreadID 1518DefaultFetch<Impl>::iqCount() 1519{ 1520 //sorted from lowest->highest 1521 std::priority_queue<unsigned,vector<unsigned>, 1522 std::greater<unsigned> > PQ; 1523 std::map<unsigned, ThreadID> threadMap; 1524 1525 list<ThreadID>::iterator threads = activeThreads->begin(); 1526 list<ThreadID>::iterator end = activeThreads->end(); 1527 1528 while (threads != end) { 1529 ThreadID tid = *threads++; 1530 unsigned iqCount = fromIEW->iewInfo[tid].iqCount; 1531 1532 //we can potentially get tid collisions if two threads 1533 //have the same iqCount, but this should be rare. 1534 PQ.push(iqCount); 1535 threadMap[iqCount] = tid; 1536 } 1537 1538 while (!PQ.empty()) { 1539 ThreadID high_pri = threadMap[PQ.top()]; 1540 1541 if (fetchStatus[high_pri] == Running || 1542 fetchStatus[high_pri] == IcacheAccessComplete || 1543 fetchStatus[high_pri] == Idle) 1544 return high_pri; 1545 else 1546 PQ.pop(); 1547 1548 } 1549 1550 return InvalidThreadID; 1551} 1552 1553template<class Impl> 1554ThreadID 1555DefaultFetch<Impl>::lsqCount() 1556{ 1557 //sorted from lowest->highest 1558 std::priority_queue<unsigned,vector<unsigned>, 1559 std::greater<unsigned> > PQ; 1560 std::map<unsigned, ThreadID> threadMap; 1561 1562 list<ThreadID>::iterator threads = activeThreads->begin(); 1563 list<ThreadID>::iterator end = activeThreads->end(); 1564 1565 while (threads != end) { 1566 ThreadID tid = *threads++; 1567 unsigned ldstqCount = fromIEW->iewInfo[tid].ldstqCount; 1568 1569 //we can potentially get tid collisions if two threads 1570 //have the same iqCount, but this should be rare. 1571 PQ.push(ldstqCount); 1572 threadMap[ldstqCount] = tid; 1573 } 1574 1575 while (!PQ.empty()) { 1576 ThreadID high_pri = threadMap[PQ.top()]; 1577 1578 if (fetchStatus[high_pri] == Running || 1579 fetchStatus[high_pri] == IcacheAccessComplete || 1580 fetchStatus[high_pri] == Idle) 1581 return high_pri; 1582 else 1583 PQ.pop(); 1584 } 1585 1586 return InvalidThreadID; 1587} 1588 1589template<class Impl> 1590ThreadID 1591DefaultFetch<Impl>::branchCount() 1592{ 1593#if 0 1594 list<ThreadID>::iterator thread = activeThreads->begin(); 1595 assert(thread != activeThreads->end()); 1596 ThreadID tid = *thread; 1597#endif 1598 1599 panic("Branch Count Fetch policy unimplemented\n"); 1600 return InvalidThreadID; 1601} 1602 1603template<class Impl> 1604void 1605DefaultFetch<Impl>::pipelineIcacheAccesses(ThreadID tid) 1606{ 1607 if (!issuePipelinedIfetch[tid]) { 1608 return; 1609 } 1610 1611 // The next PC to access. 1612 TheISA::PCState thisPC = pc[tid]; 1613 1614 if (isRomMicroPC(thisPC.microPC())) { 1615 return; 1616 } 1617 1618 Addr pcOffset = fetchOffset[tid]; 1619 Addr fetchAddr = (thisPC.instAddr() + pcOffset) & BaseCPU::PCMask; 1620 1621 // Align the fetch PC so its at the start of a fetch buffer segment. 1622 Addr fetchBufferBlockPC = fetchBufferAlignPC(fetchAddr); 1623 1624 // Unless buffer already got the block, fetch it from icache. 1625 if (!(fetchBufferValid[tid] && fetchBufferBlockPC == fetchBufferPC[tid])) { 1626 DPRINTF(Fetch, "[tid:%i]: Issuing a pipelined I-cache access, " 1627 "starting at PC %s.\n", tid, thisPC); 1628 1629 fetchCacheLine(fetchAddr, tid, thisPC.instAddr()); 1630 } 1631} 1632 1633template<class Impl> 1634void 1635DefaultFetch<Impl>::profileStall(ThreadID tid) { 1636 DPRINTF(Fetch,"There are no more threads available to fetch from.\n"); 1637 1638 // @todo Per-thread stats 1639 1640 if (stalls[tid].drain) { 1641 ++fetchPendingDrainCycles; 1642 DPRINTF(Fetch, "Fetch is waiting for a drain!\n"); 1643 } else if (activeThreads->empty()) { 1644 ++fetchNoActiveThreadStallCycles; 1645 DPRINTF(Fetch, "Fetch has no active thread!\n"); 1646 } else if (fetchStatus[tid] == Blocked) { 1647 ++fetchBlockedCycles; 1648 DPRINTF(Fetch, "[tid:%i]: Fetch is blocked!\n", tid); 1649 } else if (fetchStatus[tid] == Squashing) { 1650 ++fetchSquashCycles; 1651 DPRINTF(Fetch, "[tid:%i]: Fetch is squashing!\n", tid); 1652 } else if (fetchStatus[tid] == IcacheWaitResponse) { 1653 ++icacheStallCycles; 1654 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting cache response!\n", 1655 tid); 1656 } else if (fetchStatus[tid] == ItlbWait) { 1657 ++fetchTlbCycles; 1658 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting ITLB walk to " 1659 "finish!\n", tid); 1660 } else if (fetchStatus[tid] == TrapPending) { 1661 ++fetchPendingTrapStallCycles; 1662 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for a pending trap!\n", 1663 tid); 1664 } else if (fetchStatus[tid] == QuiescePending) { 1665 ++fetchPendingQuiesceStallCycles; 1666 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for a pending quiesce " 1667 "instruction!\n", tid); 1668 } else if (fetchStatus[tid] == IcacheWaitRetry) { 1669 ++fetchIcacheWaitRetryStallCycles; 1670 DPRINTF(Fetch, "[tid:%i]: Fetch is waiting for an I-cache retry!\n", 1671 tid); 1672 } else if (fetchStatus[tid] == NoGoodAddr) { 1673 DPRINTF(Fetch, "[tid:%i]: Fetch predicted non-executable address\n", 1674 tid); 1675 } else { 1676 DPRINTF(Fetch, "[tid:%i]: Unexpected fetch stall reason (Status: %i).\n", 1677 tid, fetchStatus[tid]); 1678 } 1679} 1680 1681#endif//__CPU_O3_FETCH_IMPL_HH__ 1682