1/* 2 * Copyright (c) 2012 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 */ 42 43#ifndef __CPU_O3_DECODE_IMPL_HH__ 44#define __CPU_O3_DECODE_IMPL_HH__ 45 46#include "arch/types.hh" 47#include "base/trace.hh" 48#include "config/the_isa.hh" 49#include "cpu/o3/decode.hh" 50#include "cpu/inst_seq.hh" 51#include "debug/Activity.hh" 52#include "debug/Decode.hh" 53#include "debug/O3PipeView.hh" 54#include "params/DerivO3CPU.hh" 55#include "sim/full_system.hh" 56 57// clang complains about std::set being overloaded with Packet::set if 58// we open up the entire namespace std 59using std::list; 60 61template<class Impl> 62DefaultDecode<Impl>::DefaultDecode(O3CPU *_cpu, DerivO3CPUParams *params) 63 : cpu(_cpu), 64 renameToDecodeDelay(params->renameToDecodeDelay), 65 iewToDecodeDelay(params->iewToDecodeDelay), 66 commitToDecodeDelay(params->commitToDecodeDelay), 67 fetchToDecodeDelay(params->fetchToDecodeDelay), 68 decodeWidth(params->decodeWidth), 69 numThreads(params->numThreads) 70{
| 1/* 2 * Copyright (c) 2012 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 */ 42 43#ifndef __CPU_O3_DECODE_IMPL_HH__ 44#define __CPU_O3_DECODE_IMPL_HH__ 45 46#include "arch/types.hh" 47#include "base/trace.hh" 48#include "config/the_isa.hh" 49#include "cpu/o3/decode.hh" 50#include "cpu/inst_seq.hh" 51#include "debug/Activity.hh" 52#include "debug/Decode.hh" 53#include "debug/O3PipeView.hh" 54#include "params/DerivO3CPU.hh" 55#include "sim/full_system.hh" 56 57// clang complains about std::set being overloaded with Packet::set if 58// we open up the entire namespace std 59using std::list; 60 61template<class Impl> 62DefaultDecode<Impl>::DefaultDecode(O3CPU *_cpu, DerivO3CPUParams *params) 63 : cpu(_cpu), 64 renameToDecodeDelay(params->renameToDecodeDelay), 65 iewToDecodeDelay(params->iewToDecodeDelay), 66 commitToDecodeDelay(params->commitToDecodeDelay), 67 fetchToDecodeDelay(params->fetchToDecodeDelay), 68 decodeWidth(params->decodeWidth), 69 numThreads(params->numThreads) 70{
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71 // @todo: Make into a parameter 72 skidBufferMax = (fetchToDecodeDelay + 1) * params->fetchWidth; 73} 74 75template<class Impl> 76void 77DefaultDecode<Impl>::startupStage() 78{ 79 resetStage(); 80} 81 82template<class Impl> 83void 84DefaultDecode<Impl>::resetStage() 85{ 86 _status = Inactive; 87 88 // Setup status, make sure stall signals are clear. 89 for (ThreadID tid = 0; tid < numThreads; ++tid) { 90 decodeStatus[tid] = Idle; 91 92 stalls[tid].rename = false; 93 stalls[tid].iew = false; 94 stalls[tid].commit = false; 95 } 96} 97 98template <class Impl> 99std::string 100DefaultDecode<Impl>::name() const 101{ 102 return cpu->name() + ".decode"; 103} 104 105template <class Impl> 106void 107DefaultDecode<Impl>::regStats() 108{ 109 decodeIdleCycles 110 .name(name() + ".IdleCycles") 111 .desc("Number of cycles decode is idle") 112 .prereq(decodeIdleCycles); 113 decodeBlockedCycles 114 .name(name() + ".BlockedCycles") 115 .desc("Number of cycles decode is blocked") 116 .prereq(decodeBlockedCycles); 117 decodeRunCycles 118 .name(name() + ".RunCycles") 119 .desc("Number of cycles decode is running") 120 .prereq(decodeRunCycles); 121 decodeUnblockCycles 122 .name(name() + ".UnblockCycles") 123 .desc("Number of cycles decode is unblocking") 124 .prereq(decodeUnblockCycles); 125 decodeSquashCycles 126 .name(name() + ".SquashCycles") 127 .desc("Number of cycles decode is squashing") 128 .prereq(decodeSquashCycles); 129 decodeBranchResolved 130 .name(name() + ".BranchResolved") 131 .desc("Number of times decode resolved a branch") 132 .prereq(decodeBranchResolved); 133 decodeBranchMispred 134 .name(name() + ".BranchMispred") 135 .desc("Number of times decode detected a branch misprediction") 136 .prereq(decodeBranchMispred); 137 decodeControlMispred 138 .name(name() + ".ControlMispred") 139 .desc("Number of times decode detected an instruction incorrectly" 140 " predicted as a control") 141 .prereq(decodeControlMispred); 142 decodeDecodedInsts 143 .name(name() + ".DecodedInsts") 144 .desc("Number of instructions handled by decode") 145 .prereq(decodeDecodedInsts); 146 decodeSquashedInsts 147 .name(name() + ".SquashedInsts") 148 .desc("Number of squashed instructions handled by decode") 149 .prereq(decodeSquashedInsts); 150} 151 152template<class Impl> 153void 154DefaultDecode<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr) 155{ 156 timeBuffer = tb_ptr; 157 158 // Setup wire to write information back to fetch. 159 toFetch = timeBuffer->getWire(0); 160 161 // Create wires to get information from proper places in time buffer. 162 fromRename = timeBuffer->getWire(-renameToDecodeDelay); 163 fromIEW = timeBuffer->getWire(-iewToDecodeDelay); 164 fromCommit = timeBuffer->getWire(-commitToDecodeDelay); 165} 166 167template<class Impl> 168void 169DefaultDecode<Impl>::setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr) 170{ 171 decodeQueue = dq_ptr; 172 173 // Setup wire to write information to proper place in decode queue. 174 toRename = decodeQueue->getWire(0); 175} 176 177template<class Impl> 178void 179DefaultDecode<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr) 180{ 181 fetchQueue = fq_ptr; 182 183 // Setup wire to read information from fetch queue. 184 fromFetch = fetchQueue->getWire(-fetchToDecodeDelay); 185} 186 187template<class Impl> 188void 189DefaultDecode<Impl>::setActiveThreads(std::list<ThreadID> *at_ptr) 190{ 191 activeThreads = at_ptr; 192} 193 194template <class Impl> 195void 196DefaultDecode<Impl>::drainSanityCheck() const 197{ 198 for (ThreadID tid = 0; tid < numThreads; ++tid) { 199 assert(insts[tid].empty()); 200 assert(skidBuffer[tid].empty()); 201 } 202} 203 204template<class Impl> 205bool 206DefaultDecode<Impl>::checkStall(ThreadID tid) const 207{ 208 bool ret_val = false; 209 210 if (stalls[tid].rename) { 211 DPRINTF(Decode,"[tid:%i]: Stall fom Rename stage detected.\n", tid); 212 ret_val = true; 213 } else if (stalls[tid].iew) { 214 DPRINTF(Decode,"[tid:%i]: Stall fom IEW stage detected.\n", tid); 215 ret_val = true; 216 } else if (stalls[tid].commit) { 217 DPRINTF(Decode,"[tid:%i]: Stall fom Commit stage detected.\n", tid); 218 ret_val = true; 219 } 220 221 return ret_val; 222} 223 224template<class Impl> 225inline bool 226DefaultDecode<Impl>::fetchInstsValid() 227{ 228 return fromFetch->size > 0; 229} 230 231template<class Impl> 232bool 233DefaultDecode<Impl>::block(ThreadID tid) 234{ 235 DPRINTF(Decode, "[tid:%u]: Blocking.\n", tid); 236 237 // Add the current inputs to the skid buffer so they can be 238 // reprocessed when this stage unblocks. 239 skidInsert(tid); 240 241 // If the decode status is blocked or unblocking then decode has not yet 242 // signalled fetch to unblock. In that case, there is no need to tell 243 // fetch to block. 244 if (decodeStatus[tid] != Blocked) { 245 // Set the status to Blocked. 246 decodeStatus[tid] = Blocked; 247 248 if (toFetch->decodeUnblock[tid]) { 249 toFetch->decodeUnblock[tid] = false; 250 } else { 251 toFetch->decodeBlock[tid] = true; 252 wroteToTimeBuffer = true; 253 } 254 255 return true; 256 } 257 258 return false; 259} 260 261template<class Impl> 262bool 263DefaultDecode<Impl>::unblock(ThreadID tid) 264{ 265 // Decode is done unblocking only if the skid buffer is empty. 266 if (skidBuffer[tid].empty()) { 267 DPRINTF(Decode, "[tid:%u]: Done unblocking.\n", tid); 268 toFetch->decodeUnblock[tid] = true; 269 wroteToTimeBuffer = true; 270 271 decodeStatus[tid] = Running; 272 return true; 273 } 274 275 DPRINTF(Decode, "[tid:%u]: Currently unblocking.\n", tid); 276 277 return false; 278} 279 280template<class Impl> 281void 282DefaultDecode<Impl>::squash(DynInstPtr &inst, ThreadID tid) 283{ 284 DPRINTF(Decode, "[tid:%i]: [sn:%i] Squashing due to incorrect branch " 285 "prediction detected at decode.\n", tid, inst->seqNum); 286 287 // Send back mispredict information. 288 toFetch->decodeInfo[tid].branchMispredict = true; 289 toFetch->decodeInfo[tid].predIncorrect = true; 290 toFetch->decodeInfo[tid].mispredictInst = inst; 291 toFetch->decodeInfo[tid].squash = true; 292 toFetch->decodeInfo[tid].doneSeqNum = inst->seqNum; 293 toFetch->decodeInfo[tid].nextPC = inst->branchTarget(); 294 toFetch->decodeInfo[tid].branchTaken = inst->pcState().branching(); 295 toFetch->decodeInfo[tid].squashInst = inst; 296 if (toFetch->decodeInfo[tid].mispredictInst->isUncondCtrl()) { 297 toFetch->decodeInfo[tid].branchTaken = true; 298 } 299 300 InstSeqNum squash_seq_num = inst->seqNum; 301 302 // Might have to tell fetch to unblock. 303 if (decodeStatus[tid] == Blocked || 304 decodeStatus[tid] == Unblocking) { 305 toFetch->decodeUnblock[tid] = 1; 306 } 307 308 // Set status to squashing. 309 decodeStatus[tid] = Squashing; 310 311 for (int i=0; i<fromFetch->size; i++) { 312 if (fromFetch->insts[i]->threadNumber == tid && 313 fromFetch->insts[i]->seqNum > squash_seq_num) { 314 fromFetch->insts[i]->setSquashed(); 315 } 316 } 317 318 // Clear the instruction list and skid buffer in case they have any 319 // insts in them. 320 while (!insts[tid].empty()) { 321 insts[tid].pop(); 322 } 323 324 while (!skidBuffer[tid].empty()) { 325 skidBuffer[tid].pop(); 326 } 327 328 // Squash instructions up until this one 329 cpu->removeInstsUntil(squash_seq_num, tid); 330} 331 332template<class Impl> 333unsigned 334DefaultDecode<Impl>::squash(ThreadID tid) 335{ 336 DPRINTF(Decode, "[tid:%i]: Squashing.\n",tid); 337 338 if (decodeStatus[tid] == Blocked || 339 decodeStatus[tid] == Unblocking) { 340 if (FullSystem) { 341 toFetch->decodeUnblock[tid] = 1; 342 } else { 343 // In syscall emulation, we can have both a block and a squash due 344 // to a syscall in the same cycle. This would cause both signals 345 // to be high. This shouldn't happen in full system. 346 // @todo: Determine if this still happens. 347 if (toFetch->decodeBlock[tid]) 348 toFetch->decodeBlock[tid] = 0; 349 else 350 toFetch->decodeUnblock[tid] = 1; 351 } 352 } 353 354 // Set status to squashing. 355 decodeStatus[tid] = Squashing; 356 357 // Go through incoming instructions from fetch and squash them. 358 unsigned squash_count = 0; 359 360 for (int i=0; i<fromFetch->size; i++) { 361 if (fromFetch->insts[i]->threadNumber == tid) { 362 fromFetch->insts[i]->setSquashed(); 363 squash_count++; 364 } 365 } 366 367 // Clear the instruction list and skid buffer in case they have any 368 // insts in them. 369 while (!insts[tid].empty()) { 370 insts[tid].pop(); 371 } 372 373 while (!skidBuffer[tid].empty()) { 374 skidBuffer[tid].pop(); 375 } 376 377 return squash_count; 378} 379 380template<class Impl> 381void 382DefaultDecode<Impl>::skidInsert(ThreadID tid) 383{ 384 DynInstPtr inst = NULL; 385 386 while (!insts[tid].empty()) { 387 inst = insts[tid].front(); 388 389 insts[tid].pop(); 390 391 assert(tid == inst->threadNumber); 392 393 DPRINTF(Decode,"Inserting [sn:%lli] PC: %s into decode skidBuffer %i\n", 394 inst->seqNum, inst->pcState(), inst->threadNumber); 395 396 skidBuffer[tid].push(inst); 397 } 398 399 // @todo: Eventually need to enforce this by not letting a thread 400 // fetch past its skidbuffer 401 assert(skidBuffer[tid].size() <= skidBufferMax); 402} 403 404template<class Impl> 405bool 406DefaultDecode<Impl>::skidsEmpty() 407{ 408 list<ThreadID>::iterator threads = activeThreads->begin(); 409 list<ThreadID>::iterator end = activeThreads->end(); 410 411 while (threads != end) { 412 ThreadID tid = *threads++; 413 if (!skidBuffer[tid].empty()) 414 return false; 415 } 416 417 return true; 418} 419 420template<class Impl> 421void 422DefaultDecode<Impl>::updateStatus() 423{ 424 bool any_unblocking = false; 425 426 list<ThreadID>::iterator threads = activeThreads->begin(); 427 list<ThreadID>::iterator end = activeThreads->end(); 428 429 while (threads != end) { 430 ThreadID tid = *threads++; 431 432 if (decodeStatus[tid] == Unblocking) { 433 any_unblocking = true; 434 break; 435 } 436 } 437 438 // Decode will have activity if it's unblocking. 439 if (any_unblocking) { 440 if (_status == Inactive) { 441 _status = Active; 442 443 DPRINTF(Activity, "Activating stage.\n"); 444 445 cpu->activateStage(O3CPU::DecodeIdx); 446 } 447 } else { 448 // If it's not unblocking, then decode will not have any internal 449 // activity. Switch it to inactive. 450 if (_status == Active) { 451 _status = Inactive; 452 DPRINTF(Activity, "Deactivating stage.\n"); 453 454 cpu->deactivateStage(O3CPU::DecodeIdx); 455 } 456 } 457} 458 459template <class Impl> 460void 461DefaultDecode<Impl>::sortInsts() 462{ 463 int insts_from_fetch = fromFetch->size; 464 for (int i = 0; i < insts_from_fetch; ++i) { 465 insts[fromFetch->insts[i]->threadNumber].push(fromFetch->insts[i]); 466 } 467} 468 469template<class Impl> 470void 471DefaultDecode<Impl>::readStallSignals(ThreadID tid) 472{ 473 if (fromRename->renameBlock[tid]) { 474 stalls[tid].rename = true; 475 } 476 477 if (fromRename->renameUnblock[tid]) { 478 assert(stalls[tid].rename); 479 stalls[tid].rename = false; 480 } 481 482 if (fromIEW->iewBlock[tid]) { 483 stalls[tid].iew = true; 484 } 485 486 if (fromIEW->iewUnblock[tid]) { 487 assert(stalls[tid].iew); 488 stalls[tid].iew = false; 489 } 490 491 if (fromCommit->commitBlock[tid]) { 492 stalls[tid].commit = true; 493 } 494 495 if (fromCommit->commitUnblock[tid]) { 496 assert(stalls[tid].commit); 497 stalls[tid].commit = false; 498 } 499} 500 501template <class Impl> 502bool 503DefaultDecode<Impl>::checkSignalsAndUpdate(ThreadID tid) 504{ 505 // Check if there's a squash signal, squash if there is. 506 // Check stall signals, block if necessary. 507 // If status was blocked 508 // Check if stall conditions have passed 509 // if so then go to unblocking 510 // If status was Squashing 511 // check if squashing is not high. Switch to running this cycle. 512 513 // Update the per thread stall statuses. 514 readStallSignals(tid); 515 516 // Check squash signals from commit. 517 if (fromCommit->commitInfo[tid].squash) { 518 519 DPRINTF(Decode, "[tid:%u]: Squashing instructions due to squash " 520 "from commit.\n", tid); 521 522 squash(tid); 523 524 return true; 525 } 526 527 // Check ROB squash signals from commit. 528 if (fromCommit->commitInfo[tid].robSquashing) { 529 DPRINTF(Decode, "[tid:%u]: ROB is still squashing.\n", tid); 530 531 // Continue to squash. 532 decodeStatus[tid] = Squashing; 533 534 return true; 535 } 536 537 if (checkStall(tid)) { 538 return block(tid); 539 } 540 541 if (decodeStatus[tid] == Blocked) { 542 DPRINTF(Decode, "[tid:%u]: Done blocking, switching to unblocking.\n", 543 tid); 544 545 decodeStatus[tid] = Unblocking; 546 547 unblock(tid); 548 549 return true; 550 } 551 552 if (decodeStatus[tid] == Squashing) { 553 // Switch status to running if decode isn't being told to block or 554 // squash this cycle. 555 DPRINTF(Decode, "[tid:%u]: Done squashing, switching to running.\n", 556 tid); 557 558 decodeStatus[tid] = Running; 559 560 return false; 561 } 562 563 // If we've reached this point, we have not gotten any signals that 564 // cause decode to change its status. Decode remains the same as before. 565 return false; 566} 567 568template<class Impl> 569void 570DefaultDecode<Impl>::tick() 571{ 572 wroteToTimeBuffer = false; 573 574 bool status_change = false; 575 576 toRenameIndex = 0; 577 578 list<ThreadID>::iterator threads = activeThreads->begin(); 579 list<ThreadID>::iterator end = activeThreads->end(); 580 581 sortInsts(); 582 583 //Check stall and squash signals. 584 while (threads != end) { 585 ThreadID tid = *threads++; 586 587 DPRINTF(Decode,"Processing [tid:%i]\n",tid); 588 status_change = checkSignalsAndUpdate(tid) || status_change; 589 590 decode(status_change, tid); 591 } 592 593 if (status_change) { 594 updateStatus(); 595 } 596 597 if (wroteToTimeBuffer) { 598 DPRINTF(Activity, "Activity this cycle.\n"); 599 600 cpu->activityThisCycle(); 601 } 602} 603 604template<class Impl> 605void 606DefaultDecode<Impl>::decode(bool &status_change, ThreadID tid) 607{ 608 // If status is Running or idle, 609 // call decodeInsts() 610 // If status is Unblocking, 611 // buffer any instructions coming from fetch 612 // continue trying to empty skid buffer 613 // check if stall conditions have passed 614 615 if (decodeStatus[tid] == Blocked) { 616 ++decodeBlockedCycles; 617 } else if (decodeStatus[tid] == Squashing) { 618 ++decodeSquashCycles; 619 } 620 621 // Decode should try to decode as many instructions as its bandwidth 622 // will allow, as long as it is not currently blocked. 623 if (decodeStatus[tid] == Running || 624 decodeStatus[tid] == Idle) { 625 DPRINTF(Decode, "[tid:%u]: Not blocked, so attempting to run " 626 "stage.\n",tid); 627 628 decodeInsts(tid); 629 } else if (decodeStatus[tid] == Unblocking) { 630 // Make sure that the skid buffer has something in it if the 631 // status is unblocking. 632 assert(!skidsEmpty()); 633 634 // If the status was unblocking, then instructions from the skid 635 // buffer were used. Remove those instructions and handle 636 // the rest of unblocking. 637 decodeInsts(tid); 638 639 if (fetchInstsValid()) { 640 // Add the current inputs to the skid buffer so they can be 641 // reprocessed when this stage unblocks. 642 skidInsert(tid); 643 } 644 645 status_change = unblock(tid) || status_change; 646 } 647} 648 649template <class Impl> 650void 651DefaultDecode<Impl>::decodeInsts(ThreadID tid) 652{ 653 // Instructions can come either from the skid buffer or the list of 654 // instructions coming from fetch, depending on decode's status. 655 int insts_available = decodeStatus[tid] == Unblocking ? 656 skidBuffer[tid].size() : insts[tid].size(); 657 658 if (insts_available == 0) { 659 DPRINTF(Decode, "[tid:%u] Nothing to do, breaking out" 660 " early.\n",tid); 661 // Should I change the status to idle? 662 ++decodeIdleCycles; 663 return; 664 } else if (decodeStatus[tid] == Unblocking) { 665 DPRINTF(Decode, "[tid:%u] Unblocking, removing insts from skid " 666 "buffer.\n",tid); 667 ++decodeUnblockCycles; 668 } else if (decodeStatus[tid] == Running) { 669 ++decodeRunCycles; 670 } 671 672 DynInstPtr inst; 673 674 std::queue<DynInstPtr> 675 &insts_to_decode = decodeStatus[tid] == Unblocking ? 676 skidBuffer[tid] : insts[tid]; 677 678 DPRINTF(Decode, "[tid:%u]: Sending instruction to rename.\n",tid); 679 680 while (insts_available > 0 && toRenameIndex < decodeWidth) { 681 assert(!insts_to_decode.empty()); 682 683 inst = insts_to_decode.front(); 684 685 insts_to_decode.pop(); 686 687 DPRINTF(Decode, "[tid:%u]: Processing instruction [sn:%lli] with " 688 "PC %s\n", tid, inst->seqNum, inst->pcState()); 689 690 if (inst->isSquashed()) { 691 DPRINTF(Decode, "[tid:%u]: Instruction %i with PC %s is " 692 "squashed, skipping.\n", 693 tid, inst->seqNum, inst->pcState()); 694 695 ++decodeSquashedInsts; 696 697 --insts_available; 698 699 continue; 700 } 701 702 // Also check if instructions have no source registers. Mark 703 // them as ready to issue at any time. Not sure if this check 704 // should exist here or at a later stage; however it doesn't matter 705 // too much for function correctness. 706 if (inst->numSrcRegs() == 0) { 707 inst->setCanIssue(); 708 } 709 710 // This current instruction is valid, so add it into the decode 711 // queue. The next instruction may not be valid, so check to 712 // see if branches were predicted correctly. 713 toRename->insts[toRenameIndex] = inst; 714 715 ++(toRename->size); 716 ++toRenameIndex; 717 ++decodeDecodedInsts; 718 --insts_available; 719 720#if TRACING_ON 721 if (DTRACE(O3PipeView)) { 722 inst->decodeTick = curTick() - inst->fetchTick; 723 } 724#endif 725 726 // Ensure that if it was predicted as a branch, it really is a 727 // branch. 728 if (inst->readPredTaken() && !inst->isControl()) { 729 panic("Instruction predicted as a branch!"); 730 731 ++decodeControlMispred; 732 733 // Might want to set some sort of boolean and just do 734 // a check at the end 735 squash(inst, inst->threadNumber); 736 737 break; 738 } 739 740 // Go ahead and compute any PC-relative branches. 741 if (inst->isDirectCtrl() && inst->isUncondCtrl()) { 742 ++decodeBranchResolved; 743 744 if (!(inst->branchTarget() == inst->readPredTarg())) { 745 ++decodeBranchMispred; 746 747 // Might want to set some sort of boolean and just do 748 // a check at the end 749 squash(inst, inst->threadNumber); 750 TheISA::PCState target = inst->branchTarget(); 751 752 DPRINTF(Decode, "[sn:%i]: Updating predictions: PredPC: %s\n", 753 inst->seqNum, target); 754 //The micro pc after an instruction level branch should be 0 755 inst->setPredTarg(target); 756 break; 757 } 758 } 759 } 760 761 // If we didn't process all instructions, then we will need to block 762 // and put all those instructions into the skid buffer. 763 if (!insts_to_decode.empty()) { 764 block(tid); 765 } 766 767 // Record that decode has written to the time buffer for activity 768 // tracking. 769 if (toRenameIndex) { 770 wroteToTimeBuffer = true; 771 } 772} 773 774#endif//__CPU_O3_DECODE_IMPL_HH__
| 76 // @todo: Make into a parameter 77 skidBufferMax = (fetchToDecodeDelay + 1) * params->fetchWidth; 78} 79 80template<class Impl> 81void 82DefaultDecode<Impl>::startupStage() 83{ 84 resetStage(); 85} 86 87template<class Impl> 88void 89DefaultDecode<Impl>::resetStage() 90{ 91 _status = Inactive; 92 93 // Setup status, make sure stall signals are clear. 94 for (ThreadID tid = 0; tid < numThreads; ++tid) { 95 decodeStatus[tid] = Idle; 96 97 stalls[tid].rename = false; 98 stalls[tid].iew = false; 99 stalls[tid].commit = false; 100 } 101} 102 103template <class Impl> 104std::string 105DefaultDecode<Impl>::name() const 106{ 107 return cpu->name() + ".decode"; 108} 109 110template <class Impl> 111void 112DefaultDecode<Impl>::regStats() 113{ 114 decodeIdleCycles 115 .name(name() + ".IdleCycles") 116 .desc("Number of cycles decode is idle") 117 .prereq(decodeIdleCycles); 118 decodeBlockedCycles 119 .name(name() + ".BlockedCycles") 120 .desc("Number of cycles decode is blocked") 121 .prereq(decodeBlockedCycles); 122 decodeRunCycles 123 .name(name() + ".RunCycles") 124 .desc("Number of cycles decode is running") 125 .prereq(decodeRunCycles); 126 decodeUnblockCycles 127 .name(name() + ".UnblockCycles") 128 .desc("Number of cycles decode is unblocking") 129 .prereq(decodeUnblockCycles); 130 decodeSquashCycles 131 .name(name() + ".SquashCycles") 132 .desc("Number of cycles decode is squashing") 133 .prereq(decodeSquashCycles); 134 decodeBranchResolved 135 .name(name() + ".BranchResolved") 136 .desc("Number of times decode resolved a branch") 137 .prereq(decodeBranchResolved); 138 decodeBranchMispred 139 .name(name() + ".BranchMispred") 140 .desc("Number of times decode detected a branch misprediction") 141 .prereq(decodeBranchMispred); 142 decodeControlMispred 143 .name(name() + ".ControlMispred") 144 .desc("Number of times decode detected an instruction incorrectly" 145 " predicted as a control") 146 .prereq(decodeControlMispred); 147 decodeDecodedInsts 148 .name(name() + ".DecodedInsts") 149 .desc("Number of instructions handled by decode") 150 .prereq(decodeDecodedInsts); 151 decodeSquashedInsts 152 .name(name() + ".SquashedInsts") 153 .desc("Number of squashed instructions handled by decode") 154 .prereq(decodeSquashedInsts); 155} 156 157template<class Impl> 158void 159DefaultDecode<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr) 160{ 161 timeBuffer = tb_ptr; 162 163 // Setup wire to write information back to fetch. 164 toFetch = timeBuffer->getWire(0); 165 166 // Create wires to get information from proper places in time buffer. 167 fromRename = timeBuffer->getWire(-renameToDecodeDelay); 168 fromIEW = timeBuffer->getWire(-iewToDecodeDelay); 169 fromCommit = timeBuffer->getWire(-commitToDecodeDelay); 170} 171 172template<class Impl> 173void 174DefaultDecode<Impl>::setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr) 175{ 176 decodeQueue = dq_ptr; 177 178 // Setup wire to write information to proper place in decode queue. 179 toRename = decodeQueue->getWire(0); 180} 181 182template<class Impl> 183void 184DefaultDecode<Impl>::setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr) 185{ 186 fetchQueue = fq_ptr; 187 188 // Setup wire to read information from fetch queue. 189 fromFetch = fetchQueue->getWire(-fetchToDecodeDelay); 190} 191 192template<class Impl> 193void 194DefaultDecode<Impl>::setActiveThreads(std::list<ThreadID> *at_ptr) 195{ 196 activeThreads = at_ptr; 197} 198 199template <class Impl> 200void 201DefaultDecode<Impl>::drainSanityCheck() const 202{ 203 for (ThreadID tid = 0; tid < numThreads; ++tid) { 204 assert(insts[tid].empty()); 205 assert(skidBuffer[tid].empty()); 206 } 207} 208 209template<class Impl> 210bool 211DefaultDecode<Impl>::checkStall(ThreadID tid) const 212{ 213 bool ret_val = false; 214 215 if (stalls[tid].rename) { 216 DPRINTF(Decode,"[tid:%i]: Stall fom Rename stage detected.\n", tid); 217 ret_val = true; 218 } else if (stalls[tid].iew) { 219 DPRINTF(Decode,"[tid:%i]: Stall fom IEW stage detected.\n", tid); 220 ret_val = true; 221 } else if (stalls[tid].commit) { 222 DPRINTF(Decode,"[tid:%i]: Stall fom Commit stage detected.\n", tid); 223 ret_val = true; 224 } 225 226 return ret_val; 227} 228 229template<class Impl> 230inline bool 231DefaultDecode<Impl>::fetchInstsValid() 232{ 233 return fromFetch->size > 0; 234} 235 236template<class Impl> 237bool 238DefaultDecode<Impl>::block(ThreadID tid) 239{ 240 DPRINTF(Decode, "[tid:%u]: Blocking.\n", tid); 241 242 // Add the current inputs to the skid buffer so they can be 243 // reprocessed when this stage unblocks. 244 skidInsert(tid); 245 246 // If the decode status is blocked or unblocking then decode has not yet 247 // signalled fetch to unblock. In that case, there is no need to tell 248 // fetch to block. 249 if (decodeStatus[tid] != Blocked) { 250 // Set the status to Blocked. 251 decodeStatus[tid] = Blocked; 252 253 if (toFetch->decodeUnblock[tid]) { 254 toFetch->decodeUnblock[tid] = false; 255 } else { 256 toFetch->decodeBlock[tid] = true; 257 wroteToTimeBuffer = true; 258 } 259 260 return true; 261 } 262 263 return false; 264} 265 266template<class Impl> 267bool 268DefaultDecode<Impl>::unblock(ThreadID tid) 269{ 270 // Decode is done unblocking only if the skid buffer is empty. 271 if (skidBuffer[tid].empty()) { 272 DPRINTF(Decode, "[tid:%u]: Done unblocking.\n", tid); 273 toFetch->decodeUnblock[tid] = true; 274 wroteToTimeBuffer = true; 275 276 decodeStatus[tid] = Running; 277 return true; 278 } 279 280 DPRINTF(Decode, "[tid:%u]: Currently unblocking.\n", tid); 281 282 return false; 283} 284 285template<class Impl> 286void 287DefaultDecode<Impl>::squash(DynInstPtr &inst, ThreadID tid) 288{ 289 DPRINTF(Decode, "[tid:%i]: [sn:%i] Squashing due to incorrect branch " 290 "prediction detected at decode.\n", tid, inst->seqNum); 291 292 // Send back mispredict information. 293 toFetch->decodeInfo[tid].branchMispredict = true; 294 toFetch->decodeInfo[tid].predIncorrect = true; 295 toFetch->decodeInfo[tid].mispredictInst = inst; 296 toFetch->decodeInfo[tid].squash = true; 297 toFetch->decodeInfo[tid].doneSeqNum = inst->seqNum; 298 toFetch->decodeInfo[tid].nextPC = inst->branchTarget(); 299 toFetch->decodeInfo[tid].branchTaken = inst->pcState().branching(); 300 toFetch->decodeInfo[tid].squashInst = inst; 301 if (toFetch->decodeInfo[tid].mispredictInst->isUncondCtrl()) { 302 toFetch->decodeInfo[tid].branchTaken = true; 303 } 304 305 InstSeqNum squash_seq_num = inst->seqNum; 306 307 // Might have to tell fetch to unblock. 308 if (decodeStatus[tid] == Blocked || 309 decodeStatus[tid] == Unblocking) { 310 toFetch->decodeUnblock[tid] = 1; 311 } 312 313 // Set status to squashing. 314 decodeStatus[tid] = Squashing; 315 316 for (int i=0; i<fromFetch->size; i++) { 317 if (fromFetch->insts[i]->threadNumber == tid && 318 fromFetch->insts[i]->seqNum > squash_seq_num) { 319 fromFetch->insts[i]->setSquashed(); 320 } 321 } 322 323 // Clear the instruction list and skid buffer in case they have any 324 // insts in them. 325 while (!insts[tid].empty()) { 326 insts[tid].pop(); 327 } 328 329 while (!skidBuffer[tid].empty()) { 330 skidBuffer[tid].pop(); 331 } 332 333 // Squash instructions up until this one 334 cpu->removeInstsUntil(squash_seq_num, tid); 335} 336 337template<class Impl> 338unsigned 339DefaultDecode<Impl>::squash(ThreadID tid) 340{ 341 DPRINTF(Decode, "[tid:%i]: Squashing.\n",tid); 342 343 if (decodeStatus[tid] == Blocked || 344 decodeStatus[tid] == Unblocking) { 345 if (FullSystem) { 346 toFetch->decodeUnblock[tid] = 1; 347 } else { 348 // In syscall emulation, we can have both a block and a squash due 349 // to a syscall in the same cycle. This would cause both signals 350 // to be high. This shouldn't happen in full system. 351 // @todo: Determine if this still happens. 352 if (toFetch->decodeBlock[tid]) 353 toFetch->decodeBlock[tid] = 0; 354 else 355 toFetch->decodeUnblock[tid] = 1; 356 } 357 } 358 359 // Set status to squashing. 360 decodeStatus[tid] = Squashing; 361 362 // Go through incoming instructions from fetch and squash them. 363 unsigned squash_count = 0; 364 365 for (int i=0; i<fromFetch->size; i++) { 366 if (fromFetch->insts[i]->threadNumber == tid) { 367 fromFetch->insts[i]->setSquashed(); 368 squash_count++; 369 } 370 } 371 372 // Clear the instruction list and skid buffer in case they have any 373 // insts in them. 374 while (!insts[tid].empty()) { 375 insts[tid].pop(); 376 } 377 378 while (!skidBuffer[tid].empty()) { 379 skidBuffer[tid].pop(); 380 } 381 382 return squash_count; 383} 384 385template<class Impl> 386void 387DefaultDecode<Impl>::skidInsert(ThreadID tid) 388{ 389 DynInstPtr inst = NULL; 390 391 while (!insts[tid].empty()) { 392 inst = insts[tid].front(); 393 394 insts[tid].pop(); 395 396 assert(tid == inst->threadNumber); 397 398 DPRINTF(Decode,"Inserting [sn:%lli] PC: %s into decode skidBuffer %i\n", 399 inst->seqNum, inst->pcState(), inst->threadNumber); 400 401 skidBuffer[tid].push(inst); 402 } 403 404 // @todo: Eventually need to enforce this by not letting a thread 405 // fetch past its skidbuffer 406 assert(skidBuffer[tid].size() <= skidBufferMax); 407} 408 409template<class Impl> 410bool 411DefaultDecode<Impl>::skidsEmpty() 412{ 413 list<ThreadID>::iterator threads = activeThreads->begin(); 414 list<ThreadID>::iterator end = activeThreads->end(); 415 416 while (threads != end) { 417 ThreadID tid = *threads++; 418 if (!skidBuffer[tid].empty()) 419 return false; 420 } 421 422 return true; 423} 424 425template<class Impl> 426void 427DefaultDecode<Impl>::updateStatus() 428{ 429 bool any_unblocking = false; 430 431 list<ThreadID>::iterator threads = activeThreads->begin(); 432 list<ThreadID>::iterator end = activeThreads->end(); 433 434 while (threads != end) { 435 ThreadID tid = *threads++; 436 437 if (decodeStatus[tid] == Unblocking) { 438 any_unblocking = true; 439 break; 440 } 441 } 442 443 // Decode will have activity if it's unblocking. 444 if (any_unblocking) { 445 if (_status == Inactive) { 446 _status = Active; 447 448 DPRINTF(Activity, "Activating stage.\n"); 449 450 cpu->activateStage(O3CPU::DecodeIdx); 451 } 452 } else { 453 // If it's not unblocking, then decode will not have any internal 454 // activity. Switch it to inactive. 455 if (_status == Active) { 456 _status = Inactive; 457 DPRINTF(Activity, "Deactivating stage.\n"); 458 459 cpu->deactivateStage(O3CPU::DecodeIdx); 460 } 461 } 462} 463 464template <class Impl> 465void 466DefaultDecode<Impl>::sortInsts() 467{ 468 int insts_from_fetch = fromFetch->size; 469 for (int i = 0; i < insts_from_fetch; ++i) { 470 insts[fromFetch->insts[i]->threadNumber].push(fromFetch->insts[i]); 471 } 472} 473 474template<class Impl> 475void 476DefaultDecode<Impl>::readStallSignals(ThreadID tid) 477{ 478 if (fromRename->renameBlock[tid]) { 479 stalls[tid].rename = true; 480 } 481 482 if (fromRename->renameUnblock[tid]) { 483 assert(stalls[tid].rename); 484 stalls[tid].rename = false; 485 } 486 487 if (fromIEW->iewBlock[tid]) { 488 stalls[tid].iew = true; 489 } 490 491 if (fromIEW->iewUnblock[tid]) { 492 assert(stalls[tid].iew); 493 stalls[tid].iew = false; 494 } 495 496 if (fromCommit->commitBlock[tid]) { 497 stalls[tid].commit = true; 498 } 499 500 if (fromCommit->commitUnblock[tid]) { 501 assert(stalls[tid].commit); 502 stalls[tid].commit = false; 503 } 504} 505 506template <class Impl> 507bool 508DefaultDecode<Impl>::checkSignalsAndUpdate(ThreadID tid) 509{ 510 // Check if there's a squash signal, squash if there is. 511 // Check stall signals, block if necessary. 512 // If status was blocked 513 // Check if stall conditions have passed 514 // if so then go to unblocking 515 // If status was Squashing 516 // check if squashing is not high. Switch to running this cycle. 517 518 // Update the per thread stall statuses. 519 readStallSignals(tid); 520 521 // Check squash signals from commit. 522 if (fromCommit->commitInfo[tid].squash) { 523 524 DPRINTF(Decode, "[tid:%u]: Squashing instructions due to squash " 525 "from commit.\n", tid); 526 527 squash(tid); 528 529 return true; 530 } 531 532 // Check ROB squash signals from commit. 533 if (fromCommit->commitInfo[tid].robSquashing) { 534 DPRINTF(Decode, "[tid:%u]: ROB is still squashing.\n", tid); 535 536 // Continue to squash. 537 decodeStatus[tid] = Squashing; 538 539 return true; 540 } 541 542 if (checkStall(tid)) { 543 return block(tid); 544 } 545 546 if (decodeStatus[tid] == Blocked) { 547 DPRINTF(Decode, "[tid:%u]: Done blocking, switching to unblocking.\n", 548 tid); 549 550 decodeStatus[tid] = Unblocking; 551 552 unblock(tid); 553 554 return true; 555 } 556 557 if (decodeStatus[tid] == Squashing) { 558 // Switch status to running if decode isn't being told to block or 559 // squash this cycle. 560 DPRINTF(Decode, "[tid:%u]: Done squashing, switching to running.\n", 561 tid); 562 563 decodeStatus[tid] = Running; 564 565 return false; 566 } 567 568 // If we've reached this point, we have not gotten any signals that 569 // cause decode to change its status. Decode remains the same as before. 570 return false; 571} 572 573template<class Impl> 574void 575DefaultDecode<Impl>::tick() 576{ 577 wroteToTimeBuffer = false; 578 579 bool status_change = false; 580 581 toRenameIndex = 0; 582 583 list<ThreadID>::iterator threads = activeThreads->begin(); 584 list<ThreadID>::iterator end = activeThreads->end(); 585 586 sortInsts(); 587 588 //Check stall and squash signals. 589 while (threads != end) { 590 ThreadID tid = *threads++; 591 592 DPRINTF(Decode,"Processing [tid:%i]\n",tid); 593 status_change = checkSignalsAndUpdate(tid) || status_change; 594 595 decode(status_change, tid); 596 } 597 598 if (status_change) { 599 updateStatus(); 600 } 601 602 if (wroteToTimeBuffer) { 603 DPRINTF(Activity, "Activity this cycle.\n"); 604 605 cpu->activityThisCycle(); 606 } 607} 608 609template<class Impl> 610void 611DefaultDecode<Impl>::decode(bool &status_change, ThreadID tid) 612{ 613 // If status is Running or idle, 614 // call decodeInsts() 615 // If status is Unblocking, 616 // buffer any instructions coming from fetch 617 // continue trying to empty skid buffer 618 // check if stall conditions have passed 619 620 if (decodeStatus[tid] == Blocked) { 621 ++decodeBlockedCycles; 622 } else if (decodeStatus[tid] == Squashing) { 623 ++decodeSquashCycles; 624 } 625 626 // Decode should try to decode as many instructions as its bandwidth 627 // will allow, as long as it is not currently blocked. 628 if (decodeStatus[tid] == Running || 629 decodeStatus[tid] == Idle) { 630 DPRINTF(Decode, "[tid:%u]: Not blocked, so attempting to run " 631 "stage.\n",tid); 632 633 decodeInsts(tid); 634 } else if (decodeStatus[tid] == Unblocking) { 635 // Make sure that the skid buffer has something in it if the 636 // status is unblocking. 637 assert(!skidsEmpty()); 638 639 // If the status was unblocking, then instructions from the skid 640 // buffer were used. Remove those instructions and handle 641 // the rest of unblocking. 642 decodeInsts(tid); 643 644 if (fetchInstsValid()) { 645 // Add the current inputs to the skid buffer so they can be 646 // reprocessed when this stage unblocks. 647 skidInsert(tid); 648 } 649 650 status_change = unblock(tid) || status_change; 651 } 652} 653 654template <class Impl> 655void 656DefaultDecode<Impl>::decodeInsts(ThreadID tid) 657{ 658 // Instructions can come either from the skid buffer or the list of 659 // instructions coming from fetch, depending on decode's status. 660 int insts_available = decodeStatus[tid] == Unblocking ? 661 skidBuffer[tid].size() : insts[tid].size(); 662 663 if (insts_available == 0) { 664 DPRINTF(Decode, "[tid:%u] Nothing to do, breaking out" 665 " early.\n",tid); 666 // Should I change the status to idle? 667 ++decodeIdleCycles; 668 return; 669 } else if (decodeStatus[tid] == Unblocking) { 670 DPRINTF(Decode, "[tid:%u] Unblocking, removing insts from skid " 671 "buffer.\n",tid); 672 ++decodeUnblockCycles; 673 } else if (decodeStatus[tid] == Running) { 674 ++decodeRunCycles; 675 } 676 677 DynInstPtr inst; 678 679 std::queue<DynInstPtr> 680 &insts_to_decode = decodeStatus[tid] == Unblocking ? 681 skidBuffer[tid] : insts[tid]; 682 683 DPRINTF(Decode, "[tid:%u]: Sending instruction to rename.\n",tid); 684 685 while (insts_available > 0 && toRenameIndex < decodeWidth) { 686 assert(!insts_to_decode.empty()); 687 688 inst = insts_to_decode.front(); 689 690 insts_to_decode.pop(); 691 692 DPRINTF(Decode, "[tid:%u]: Processing instruction [sn:%lli] with " 693 "PC %s\n", tid, inst->seqNum, inst->pcState()); 694 695 if (inst->isSquashed()) { 696 DPRINTF(Decode, "[tid:%u]: Instruction %i with PC %s is " 697 "squashed, skipping.\n", 698 tid, inst->seqNum, inst->pcState()); 699 700 ++decodeSquashedInsts; 701 702 --insts_available; 703 704 continue; 705 } 706 707 // Also check if instructions have no source registers. Mark 708 // them as ready to issue at any time. Not sure if this check 709 // should exist here or at a later stage; however it doesn't matter 710 // too much for function correctness. 711 if (inst->numSrcRegs() == 0) { 712 inst->setCanIssue(); 713 } 714 715 // This current instruction is valid, so add it into the decode 716 // queue. The next instruction may not be valid, so check to 717 // see if branches were predicted correctly. 718 toRename->insts[toRenameIndex] = inst; 719 720 ++(toRename->size); 721 ++toRenameIndex; 722 ++decodeDecodedInsts; 723 --insts_available; 724 725#if TRACING_ON 726 if (DTRACE(O3PipeView)) { 727 inst->decodeTick = curTick() - inst->fetchTick; 728 } 729#endif 730 731 // Ensure that if it was predicted as a branch, it really is a 732 // branch. 733 if (inst->readPredTaken() && !inst->isControl()) { 734 panic("Instruction predicted as a branch!"); 735 736 ++decodeControlMispred; 737 738 // Might want to set some sort of boolean and just do 739 // a check at the end 740 squash(inst, inst->threadNumber); 741 742 break; 743 } 744 745 // Go ahead and compute any PC-relative branches. 746 if (inst->isDirectCtrl() && inst->isUncondCtrl()) { 747 ++decodeBranchResolved; 748 749 if (!(inst->branchTarget() == inst->readPredTarg())) { 750 ++decodeBranchMispred; 751 752 // Might want to set some sort of boolean and just do 753 // a check at the end 754 squash(inst, inst->threadNumber); 755 TheISA::PCState target = inst->branchTarget(); 756 757 DPRINTF(Decode, "[sn:%i]: Updating predictions: PredPC: %s\n", 758 inst->seqNum, target); 759 //The micro pc after an instruction level branch should be 0 760 inst->setPredTarg(target); 761 break; 762 } 763 } 764 } 765 766 // If we didn't process all instructions, then we will need to block 767 // and put all those instructions into the skid buffer. 768 if (!insts_to_decode.empty()) { 769 block(tid); 770 } 771 772 // Record that decode has written to the time buffer for activity 773 // tracking. 774 if (toRenameIndex) { 775 wroteToTimeBuffer = true; 776 } 777} 778 779#endif//__CPU_O3_DECODE_IMPL_HH__
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