commit.hh revision 13429:a1e199fd8122
1/* 2 * Copyright (c) 2010-2012, 2014 ARM Limited 3 * All rights reserved. 4 * 5 * The license below extends only to copyright in the software and shall 6 * not be construed as granting a license to any other intellectual 7 * property including but not limited to intellectual property relating 8 * to a hardware implementation of the functionality of the software 9 * licensed hereunder. You may use the software subject to the license 10 * terms below provided that you ensure that this notice is replicated 11 * unmodified and in its entirety in all distributions of the software, 12 * modified or unmodified, in source code or in binary form. 13 * 14 * Copyright (c) 2004-2006 The Regents of The University of Michigan 15 * All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions are 19 * met: redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer; 21 * redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution; 24 * neither the name of the copyright holders nor the names of its 25 * contributors may be used to endorse or promote products derived from 26 * this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 29 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 30 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 31 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 32 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 33 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 34 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 35 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 36 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 37 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 38 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 39 * 40 * Authors: Kevin Lim 41 * Korey Sewell 42 */ 43 44#ifndef __CPU_O3_COMMIT_HH__ 45#define __CPU_O3_COMMIT_HH__ 46 47#include <queue> 48 49#include "base/statistics.hh" 50#include "cpu/exetrace.hh" 51#include "cpu/inst_seq.hh" 52#include "cpu/timebuf.hh" 53#include "sim/probe/probe.hh" 54 55struct DerivO3CPUParams; 56 57template <class> 58struct O3ThreadState; 59 60/** 61 * DefaultCommit handles single threaded and SMT commit. Its width is 62 * specified by the parameters; each cycle it tries to commit that 63 * many instructions. The SMT policy decides which thread it tries to 64 * commit instructions from. Non- speculative instructions must reach 65 * the head of the ROB before they are ready to execute; once they 66 * reach the head, commit will broadcast the instruction's sequence 67 * number to the previous stages so that they can issue/ execute the 68 * instruction. Only one non-speculative instruction is handled per 69 * cycle. Commit is responsible for handling all back-end initiated 70 * redirects. It receives the redirect, and then broadcasts it to all 71 * stages, indicating the sequence number they should squash until, 72 * and any necessary branch misprediction information as well. It 73 * priortizes redirects by instruction's age, only broadcasting a 74 * redirect if it corresponds to an instruction that should currently 75 * be in the ROB. This is done by tracking the sequence number of the 76 * youngest instruction in the ROB, which gets updated to any 77 * squashing instruction's sequence number, and only broadcasting a 78 * redirect if it corresponds to an older instruction. Commit also 79 * supports multiple cycle squashing, to model a ROB that can only 80 * remove a certain number of instructions per cycle. 81 */ 82template<class Impl> 83class DefaultCommit 84{ 85 public: 86 // Typedefs from the Impl. 87 typedef typename Impl::O3CPU O3CPU; 88 typedef typename Impl::DynInstPtr DynInstPtr; 89 typedef typename Impl::CPUPol CPUPol; 90 91 typedef typename CPUPol::RenameMap RenameMap; 92 typedef typename CPUPol::ROB ROB; 93 94 typedef typename CPUPol::TimeStruct TimeStruct; 95 typedef typename CPUPol::FetchStruct FetchStruct; 96 typedef typename CPUPol::IEWStruct IEWStruct; 97 typedef typename CPUPol::RenameStruct RenameStruct; 98 99 typedef typename CPUPol::Fetch Fetch; 100 typedef typename CPUPol::IEW IEW; 101 102 typedef O3ThreadState<Impl> Thread; 103 104 /** Overall commit status. Used to determine if the CPU can deschedule 105 * itself due to a lack of activity. 106 */ 107 enum CommitStatus{ 108 Active, 109 Inactive 110 }; 111 112 /** Individual thread status. */ 113 enum ThreadStatus { 114 Running, 115 Idle, 116 ROBSquashing, 117 TrapPending, 118 FetchTrapPending, 119 SquashAfterPending, //< Committing instructions before a squash. 120 }; 121 122 /** Commit policy for SMT mode. */ 123 enum CommitPolicy { 124 Aggressive, 125 RoundRobin, 126 OldestReady 127 }; 128 129 private: 130 /** Overall commit status. */ 131 CommitStatus _status; 132 /** Next commit status, to be set at the end of the cycle. */ 133 CommitStatus _nextStatus; 134 /** Per-thread status. */ 135 ThreadStatus commitStatus[Impl::MaxThreads]; 136 /** Commit policy used in SMT mode. */ 137 CommitPolicy commitPolicy; 138 139 /** Probe Points. */ 140 ProbePointArg<DynInstPtr> *ppCommit; 141 ProbePointArg<DynInstPtr> *ppCommitStall; 142 /** To probe when an instruction is squashed */ 143 ProbePointArg<DynInstPtr> *ppSquash; 144 145 /** Mark the thread as processing a trap. */ 146 void processTrapEvent(ThreadID tid); 147 148 public: 149 /** Construct a DefaultCommit with the given parameters. */ 150 DefaultCommit(O3CPU *_cpu, DerivO3CPUParams *params); 151 152 /** Returns the name of the DefaultCommit. */ 153 std::string name() const; 154 155 /** Registers statistics. */ 156 void regStats(); 157 158 /** Registers probes. */ 159 void regProbePoints(); 160 161 /** Sets the list of threads. */ 162 void setThreads(std::vector<Thread *> &threads); 163 164 /** Sets the main time buffer pointer, used for backwards communication. */ 165 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 166 167 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr); 168 169 /** Sets the pointer to the queue coming from rename. */ 170 void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr); 171 172 /** Sets the pointer to the queue coming from IEW. */ 173 void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr); 174 175 /** Sets the pointer to the IEW stage. */ 176 void setIEWStage(IEW *iew_stage); 177 178 /** The pointer to the IEW stage. Used solely to ensure that 179 * various events (traps, interrupts, syscalls) do not occur until 180 * all stores have written back. 181 */ 182 IEW *iewStage; 183 184 /** Sets pointer to list of active threads. */ 185 void setActiveThreads(std::list<ThreadID> *at_ptr); 186 187 /** Sets pointer to the commited state rename map. */ 188 void setRenameMap(RenameMap rm_ptr[Impl::MaxThreads]); 189 190 /** Sets pointer to the ROB. */ 191 void setROB(ROB *rob_ptr); 192 193 /** Initializes stage by sending back the number of free entries. */ 194 void startupStage(); 195 196 /** Initializes the draining of commit. */ 197 void drain(); 198 199 /** Resumes execution after draining. */ 200 void drainResume(); 201 202 /** Perform sanity checks after a drain. */ 203 void drainSanityCheck() const; 204 205 /** Has the stage drained? */ 206 bool isDrained() const; 207 208 /** Takes over from another CPU's thread. */ 209 void takeOverFrom(); 210 211 /** Deschedules a thread from scheduling */ 212 void deactivateThread(ThreadID tid); 213 214 /** Ticks the commit stage, which tries to commit instructions. */ 215 void tick(); 216 217 /** Handles any squashes that are sent from IEW, and adds instructions 218 * to the ROB and tries to commit instructions. 219 */ 220 void commit(); 221 222 /** Returns the number of free ROB entries for a specific thread. */ 223 size_t numROBFreeEntries(ThreadID tid); 224 225 /** Generates an event to schedule a squash due to a trap. */ 226 void generateTrapEvent(ThreadID tid, Fault inst_fault); 227 228 /** Records that commit needs to initiate a squash due to an 229 * external state update through the TC. 230 */ 231 void generateTCEvent(ThreadID tid); 232 233 private: 234 /** Updates the overall status of commit with the nextStatus, and 235 * tell the CPU if commit is active/inactive. 236 */ 237 void updateStatus(); 238 239 /** Returns if any of the threads have the number of ROB entries changed 240 * on this cycle. Used to determine if the number of free ROB entries needs 241 * to be sent back to previous stages. 242 */ 243 bool changedROBEntries(); 244 245 /** Squashes all in flight instructions. */ 246 void squashAll(ThreadID tid); 247 248 /** Handles squashing due to a trap. */ 249 void squashFromTrap(ThreadID tid); 250 251 /** Handles squashing due to an TC write. */ 252 void squashFromTC(ThreadID tid); 253 254 /** Handles a squash from a squashAfter() request. */ 255 void squashFromSquashAfter(ThreadID tid); 256 257 /** 258 * Handle squashing from instruction with SquashAfter set. 259 * 260 * This differs from the other squashes as it squashes following 261 * instructions instead of the current instruction and doesn't 262 * clean up various status bits about traps/tc writes 263 * pending. Since there might have been instructions committed by 264 * the commit stage before the squashing instruction was reached 265 * and we can't commit and squash in the same cycle, we have to 266 * squash in two steps: 267 * 268 * <ol> 269 * <li>Immediately set the commit status of the thread of 270 * SquashAfterPending. This forces the thread to stop 271 * committing instructions in this cycle. The last 272 * instruction to be committed in this cycle will be the 273 * SquashAfter instruction. 274 * <li>In the next cycle, commit() checks for the 275 * SquashAfterPending state and squashes <i>all</i> 276 * in-flight instructions. Since the SquashAfter instruction 277 * was the last instruction to be committed in the previous 278 * cycle, this causes all subsequent instructions to be 279 * squashed. 280 * </ol> 281 * 282 * @param tid ID of the thread to squash. 283 * @param head_inst Instruction that requested the squash. 284 */ 285 void squashAfter(ThreadID tid, const DynInstPtr &head_inst); 286 287 /** Handles processing an interrupt. */ 288 void handleInterrupt(); 289 290 /** Get fetch redirecting so we can handle an interrupt */ 291 void propagateInterrupt(); 292 293 /** Commits as many instructions as possible. */ 294 void commitInsts(); 295 296 /** Tries to commit the head ROB instruction passed in. 297 * @param head_inst The instruction to be committed. 298 */ 299 bool commitHead(const DynInstPtr &head_inst, unsigned inst_num); 300 301 /** Gets instructions from rename and inserts them into the ROB. */ 302 void getInsts(); 303 304 /** Marks completed instructions using information sent from IEW. */ 305 void markCompletedInsts(); 306 307 /** Gets the thread to commit, based on the SMT policy. */ 308 ThreadID getCommittingThread(); 309 310 /** Returns the thread ID to use based on a round robin policy. */ 311 ThreadID roundRobin(); 312 313 /** Returns the thread ID to use based on an oldest instruction policy. */ 314 ThreadID oldestReady(); 315 316 public: 317 /** Reads the PC of a specific thread. */ 318 TheISA::PCState pcState(ThreadID tid) { return pc[tid]; } 319 320 /** Sets the PC of a specific thread. */ 321 void pcState(const TheISA::PCState &val, ThreadID tid) 322 { pc[tid] = val; } 323 324 /** Returns the PC of a specific thread. */ 325 Addr instAddr(ThreadID tid) { return pc[tid].instAddr(); } 326 327 /** Returns the next PC of a specific thread. */ 328 Addr nextInstAddr(ThreadID tid) { return pc[tid].nextInstAddr(); } 329 330 /** Reads the micro PC of a specific thread. */ 331 Addr microPC(ThreadID tid) { return pc[tid].microPC(); } 332 333 private: 334 /** Time buffer interface. */ 335 TimeBuffer<TimeStruct> *timeBuffer; 336 337 /** Wire to write information heading to previous stages. */ 338 typename TimeBuffer<TimeStruct>::wire toIEW; 339 340 /** Wire to read information from IEW (for ROB). */ 341 typename TimeBuffer<TimeStruct>::wire robInfoFromIEW; 342 343 TimeBuffer<FetchStruct> *fetchQueue; 344 345 typename TimeBuffer<FetchStruct>::wire fromFetch; 346 347 /** IEW instruction queue interface. */ 348 TimeBuffer<IEWStruct> *iewQueue; 349 350 /** Wire to read information from IEW queue. */ 351 typename TimeBuffer<IEWStruct>::wire fromIEW; 352 353 /** Rename instruction queue interface, for ROB. */ 354 TimeBuffer<RenameStruct> *renameQueue; 355 356 /** Wire to read information from rename queue. */ 357 typename TimeBuffer<RenameStruct>::wire fromRename; 358 359 public: 360 /** ROB interface. */ 361 ROB *rob; 362 363 private: 364 /** Pointer to O3CPU. */ 365 O3CPU *cpu; 366 367 /** Vector of all of the threads. */ 368 std::vector<Thread *> thread; 369 370 /** Records that commit has written to the time buffer this cycle. Used for 371 * the CPU to determine if it can deschedule itself if there is no activity. 372 */ 373 bool wroteToTimeBuffer; 374 375 /** Records if the number of ROB entries has changed this cycle. If it has, 376 * then the number of free entries must be re-broadcast. 377 */ 378 bool changedROBNumEntries[Impl::MaxThreads]; 379 380 /** Records if a thread has to squash this cycle due to a trap. */ 381 bool trapSquash[Impl::MaxThreads]; 382 383 /** Records if a thread has to squash this cycle due to an XC write. */ 384 bool tcSquash[Impl::MaxThreads]; 385 386 /** 387 * Instruction passed to squashAfter(). 388 * 389 * The squash after implementation needs to buffer the instruction 390 * that caused a squash since this needs to be passed to the fetch 391 * stage once squashing starts. 392 */ 393 DynInstPtr squashAfterInst[Impl::MaxThreads]; 394 395 /** Priority List used for Commit Policy */ 396 std::list<ThreadID> priority_list; 397 398 /** IEW to Commit delay. */ 399 const Cycles iewToCommitDelay; 400 401 /** Commit to IEW delay. */ 402 const Cycles commitToIEWDelay; 403 404 /** Rename to ROB delay. */ 405 const Cycles renameToROBDelay; 406 407 const Cycles fetchToCommitDelay; 408 409 /** Rename width, in instructions. Used so ROB knows how many 410 * instructions to get from the rename instruction queue. 411 */ 412 const unsigned renameWidth; 413 414 /** Commit width, in instructions. */ 415 const unsigned commitWidth; 416 417 /** Number of Reorder Buffers */ 418 unsigned numRobs; 419 420 /** Number of Active Threads */ 421 const ThreadID numThreads; 422 423 /** Is a drain pending? Commit is looking for an instruction boundary while 424 * there are no pending interrupts 425 */ 426 bool drainPending; 427 428 /** Is a drain imminent? Commit has found an instruction boundary while no 429 * interrupts were present or in flight. This was the last architecturally 430 * committed instruction. Interrupts disabled and pipeline flushed. 431 * Waiting for structures to finish draining. 432 */ 433 bool drainImminent; 434 435 /** The latency to handle a trap. Used when scheduling trap 436 * squash event. 437 */ 438 const Cycles trapLatency; 439 440 /** The interrupt fault. */ 441 Fault interrupt; 442 443 /** The commit PC state of each thread. Refers to the instruction that 444 * is currently being processed/committed. 445 */ 446 TheISA::PCState pc[Impl::MaxThreads]; 447 448 /** The sequence number of the youngest valid instruction in the ROB. */ 449 InstSeqNum youngestSeqNum[Impl::MaxThreads]; 450 451 /** The sequence number of the last commited instruction. */ 452 InstSeqNum lastCommitedSeqNum[Impl::MaxThreads]; 453 454 /** Records if there is a trap currently in flight. */ 455 bool trapInFlight[Impl::MaxThreads]; 456 457 /** Records if there were any stores committed this cycle. */ 458 bool committedStores[Impl::MaxThreads]; 459 460 /** Records if commit should check if the ROB is truly empty (see 461 commit_impl.hh). */ 462 bool checkEmptyROB[Impl::MaxThreads]; 463 464 /** Pointer to the list of active threads. */ 465 std::list<ThreadID> *activeThreads; 466 467 /** Rename map interface. */ 468 RenameMap *renameMap[Impl::MaxThreads]; 469 470 /** True if last committed microop can be followed by an interrupt */ 471 bool canHandleInterrupts; 472 473 /** Have we had an interrupt pending and then seen it de-asserted because 474 of a masking change? In this case the variable is set and the next time 475 interrupts are enabled and pending the pipeline will squash to avoid 476 a possible livelock senario. */ 477 bool avoidQuiesceLiveLock; 478 479 /** Updates commit stats based on this instruction. */ 480 void updateComInstStats(const DynInstPtr &inst); 481 482 /** Stat for the total number of squashed instructions discarded by commit. 483 */ 484 Stats::Scalar commitSquashedInsts; 485 /** Stat for the total number of times commit has had to stall due to a non- 486 * speculative instruction reaching the head of the ROB. 487 */ 488 Stats::Scalar commitNonSpecStalls; 489 /** Stat for the total number of branch mispredicts that caused a squash. */ 490 Stats::Scalar branchMispredicts; 491 /** Distribution of the number of committed instructions each cycle. */ 492 Stats::Distribution numCommittedDist; 493 494 /** Total number of instructions committed. */ 495 Stats::Vector instsCommitted; 496 /** Total number of ops (including micro ops) committed. */ 497 Stats::Vector opsCommitted; 498 /** Total number of software prefetches committed. */ 499 Stats::Vector statComSwp; 500 /** Stat for the total number of committed memory references. */ 501 Stats::Vector statComRefs; 502 /** Stat for the total number of committed loads. */ 503 Stats::Vector statComLoads; 504 /** Total number of committed memory barriers. */ 505 Stats::Vector statComMembars; 506 /** Total number of committed branches. */ 507 Stats::Vector statComBranches; 508 /** Total number of vector instructions */ 509 Stats::Vector statComVector; 510 /** Total number of floating point instructions */ 511 Stats::Vector statComFloating; 512 /** Total number of integer instructions */ 513 Stats::Vector statComInteger; 514 /** Total number of function calls */ 515 Stats::Vector statComFunctionCalls; 516 /** Committed instructions by instruction type (OpClass) */ 517 Stats::Vector2d statCommittedInstType; 518 519 /** Number of cycles where the commit bandwidth limit is reached. */ 520 Stats::Scalar commitEligibleSamples; 521}; 522 523#endif // __CPU_O3_COMMIT_HH__ 524