commit.hh revision 2843:19c4c6c2b5b1
1/* 2 * Copyright (c) 2004-2006 The Regents of The University of Michigan 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions are 7 * met: redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer; 9 * redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution; 12 * neither the name of the copyright holders nor the names of its 13 * contributors may be used to endorse or promote products derived from 14 * this software without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 17 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 18 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 19 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 20 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 21 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 22 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 26 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 * 28 * Authors: Kevin Lim 29 * Korey Sewell 30 */ 31 32#ifndef __CPU_O3_COMMIT_HH__ 33#define __CPU_O3_COMMIT_HH__ 34 35#include "arch/faults.hh" 36#include "base/statistics.hh" 37#include "base/timebuf.hh" 38#include "cpu/exetrace.hh" 39#include "cpu/inst_seq.hh" 40 41template <class> 42class O3ThreadState; 43 44/** 45 * DefaultCommit handles single threaded and SMT commit. Its width is 46 * specified by the parameters; each cycle it tries to commit that 47 * many instructions. The SMT policy decides which thread it tries to 48 * commit instructions from. Non- speculative instructions must reach 49 * the head of the ROB before they are ready to execute; once they 50 * reach the head, commit will broadcast the instruction's sequence 51 * number to the previous stages so that they can issue/ execute the 52 * instruction. Only one non-speculative instruction is handled per 53 * cycle. Commit is responsible for handling all back-end initiated 54 * redirects. It receives the redirect, and then broadcasts it to all 55 * stages, indicating the sequence number they should squash until, 56 * and any necessary branch misprediction information as well. It 57 * priortizes redirects by instruction's age, only broadcasting a 58 * redirect if it corresponds to an instruction that should currently 59 * be in the ROB. This is done by tracking the sequence number of the 60 * youngest instruction in the ROB, which gets updated to any 61 * squashing instruction's sequence number, and only broadcasting a 62 * redirect if it corresponds to an older instruction. Commit also 63 * supports multiple cycle squashing, to model a ROB that can only 64 * remove a certain number of instructions per cycle. 65 */ 66template<class Impl> 67class DefaultCommit 68{ 69 public: 70 // Typedefs from the Impl. 71 typedef typename Impl::O3CPU O3CPU; 72 typedef typename Impl::DynInstPtr DynInstPtr; 73 typedef typename Impl::Params Params; 74 typedef typename Impl::CPUPol CPUPol; 75 76 typedef typename CPUPol::RenameMap RenameMap; 77 typedef typename CPUPol::ROB ROB; 78 79 typedef typename CPUPol::TimeStruct TimeStruct; 80 typedef typename CPUPol::FetchStruct FetchStruct; 81 typedef typename CPUPol::IEWStruct IEWStruct; 82 typedef typename CPUPol::RenameStruct RenameStruct; 83 84 typedef typename CPUPol::Fetch Fetch; 85 typedef typename CPUPol::IEW IEW; 86 87 typedef O3ThreadState<Impl> Thread; 88 89 /** Event class used to schedule a squash due to a trap (fault or 90 * interrupt) to happen on a specific cycle. 91 */ 92 class TrapEvent : public Event { 93 private: 94 DefaultCommit<Impl> *commit; 95 unsigned tid; 96 97 public: 98 TrapEvent(DefaultCommit<Impl> *_commit, unsigned _tid); 99 100 void process(); 101 const char *description(); 102 }; 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 }; 120 121 /** Commit policy for SMT mode. */ 122 enum CommitPolicy { 123 Aggressive, 124 RoundRobin, 125 OldestReady 126 }; 127 128 private: 129 /** Overall commit status. */ 130 CommitStatus _status; 131 /** Next commit status, to be set at the end of the cycle. */ 132 CommitStatus _nextStatus; 133 /** Per-thread status. */ 134 ThreadStatus commitStatus[Impl::MaxThreads]; 135 /** Commit policy used in SMT mode. */ 136 CommitPolicy commitPolicy; 137 138 public: 139 /** Construct a DefaultCommit with the given parameters. */ 140 DefaultCommit(Params *params); 141 142 /** Returns the name of the DefaultCommit. */ 143 std::string name() const; 144 145 /** Registers statistics. */ 146 void regStats(); 147 148 /** Sets the CPU pointer. */ 149 void setCPU(O3CPU *cpu_ptr); 150 151 /** Sets the list of threads. */ 152 void setThreads(std::vector<Thread *> &threads); 153 154 /** Sets the main time buffer pointer, used for backwards communication. */ 155 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 156 157 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr); 158 159 /** Sets the pointer to the queue coming from rename. */ 160 void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr); 161 162 /** Sets the pointer to the queue coming from IEW. */ 163 void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr); 164 165 void setFetchStage(Fetch *fetch_stage); 166 167 Fetch *fetchStage; 168 169 /** Sets the pointer to the IEW stage. */ 170 void setIEWStage(IEW *iew_stage); 171 172 /** The pointer to the IEW stage. Used solely to ensure that 173 * various events (traps, interrupts, syscalls) do not occur until 174 * all stores have written back. 175 */ 176 IEW *iewStage; 177 178 /** Sets pointer to list of active threads. */ 179 void setActiveThreads(std::list<unsigned> *at_ptr); 180 181 /** Sets pointer to the commited state rename map. */ 182 void setRenameMap(RenameMap rm_ptr[Impl::MaxThreads]); 183 184 /** Sets pointer to the ROB. */ 185 void setROB(ROB *rob_ptr); 186 187 /** Initializes stage by sending back the number of free entries. */ 188 void initStage(); 189 190 /** Initializes the draining of commit. */ 191 void drain(); 192 193 /** Resumes execution after draining. */ 194 void resume(); 195 196 /** Completes the switch out of commit. */ 197 void switchOut(); 198 199 /** Takes over from another CPU's thread. */ 200 void takeOverFrom(); 201 202 /** Ticks the commit stage, which tries to commit instructions. */ 203 void tick(); 204 205 /** Handles any squashes that are sent from IEW, and adds instructions 206 * to the ROB and tries to commit instructions. 207 */ 208 void commit(); 209 210 /** Returns the number of free ROB entries for a specific thread. */ 211 unsigned numROBFreeEntries(unsigned tid); 212 213 /** Generates an event to schedule a squash due to a trap. */ 214 void generateTrapEvent(unsigned tid); 215 216 /** Records that commit needs to initiate a squash due to an 217 * external state update through the TC. 218 */ 219 void generateTCEvent(unsigned tid); 220 221 private: 222 /** Updates the overall status of commit with the nextStatus, and 223 * tell the CPU if commit is active/inactive. 224 */ 225 void updateStatus(); 226 227 /** Sets the next status based on threads' statuses, which becomes the 228 * current status at the end of the cycle. 229 */ 230 void setNextStatus(); 231 232 /** Checks if the ROB is completed with squashing. This is for the case 233 * where the ROB can take multiple cycles to complete squashing. 234 */ 235 bool robDoneSquashing(); 236 237 /** Returns if any of the threads have the number of ROB entries changed 238 * on this cycle. Used to determine if the number of free ROB entries needs 239 * to be sent back to previous stages. 240 */ 241 bool changedROBEntries(); 242 243 /** Squashes all in flight instructions. */ 244 void squashAll(unsigned tid); 245 246 /** Handles squashing due to a trap. */ 247 void squashFromTrap(unsigned tid); 248 249 /** Handles squashing due to an TC write. */ 250 void squashFromTC(unsigned tid); 251 252 /** Commits as many instructions as possible. */ 253 void commitInsts(); 254 255 /** Tries to commit the head ROB instruction passed in. 256 * @param head_inst The instruction to be committed. 257 */ 258 bool commitHead(DynInstPtr &head_inst, unsigned inst_num); 259 260 /** Gets instructions from rename and inserts them into the ROB. */ 261 void getInsts(); 262 263 /** Marks completed instructions using information sent from IEW. */ 264 void markCompletedInsts(); 265 266 /** Gets the thread to commit, based on the SMT policy. */ 267 int getCommittingThread(); 268 269 /** Returns the thread ID to use based on a round robin policy. */ 270 int roundRobin(); 271 272 /** Returns the thread ID to use based on an oldest instruction policy. */ 273 int oldestReady(); 274 275 public: 276 /** Returns the PC of the head instruction of the ROB. 277 * @todo: Probably remove this function as it returns only thread 0. 278 */ 279 uint64_t readPC() { return PC[0]; } 280 281 /** Returns the PC of a specific thread. */ 282 uint64_t readPC(unsigned tid) { return PC[tid]; } 283 284 /** Sets the PC of a specific thread. */ 285 void setPC(uint64_t val, unsigned tid) { PC[tid] = val; } 286 287 /** Reads the next PC of a specific thread. */ 288 uint64_t readNextPC(unsigned tid) { return nextPC[tid]; } 289 290 /** Sets the next PC of a specific thread. */ 291 void setNextPC(uint64_t val, unsigned tid) { nextPC[tid] = val; } 292 293#if THE_ISA != ALPHA_ISA 294 /** Reads the next NPC of a specific thread. */ 295 uint64_t readNextPC(unsigned tid) { return nextNPC[tid]; } 296 297 /** Sets the next NPC of a specific thread. */ 298 void setNextPC(uint64_t val, unsigned tid) { nextNPC[tid] = val; } 299#endif 300 301 private: 302 /** Time buffer interface. */ 303 TimeBuffer<TimeStruct> *timeBuffer; 304 305 /** Wire to write information heading to previous stages. */ 306 typename TimeBuffer<TimeStruct>::wire toIEW; 307 308 /** Wire to read information from IEW (for ROB). */ 309 typename TimeBuffer<TimeStruct>::wire robInfoFromIEW; 310 311 TimeBuffer<FetchStruct> *fetchQueue; 312 313 typename TimeBuffer<FetchStruct>::wire fromFetch; 314 315 /** IEW instruction queue interface. */ 316 TimeBuffer<IEWStruct> *iewQueue; 317 318 /** Wire to read information from IEW queue. */ 319 typename TimeBuffer<IEWStruct>::wire fromIEW; 320 321 /** Rename instruction queue interface, for ROB. */ 322 TimeBuffer<RenameStruct> *renameQueue; 323 324 /** Wire to read information from rename queue. */ 325 typename TimeBuffer<RenameStruct>::wire fromRename; 326 327 public: 328 /** ROB interface. */ 329 ROB *rob; 330 331 private: 332 /** Pointer to O3CPU. */ 333 O3CPU *cpu; 334 335 /** Vector of all of the threads. */ 336 std::vector<Thread *> thread; 337 338 Fault fetchFault; 339 340 int fetchTrapWait; 341 342 /** Records that commit has written to the time buffer this cycle. Used for 343 * the CPU to determine if it can deschedule itself if there is no activity. 344 */ 345 bool wroteToTimeBuffer; 346 347 /** Records if the number of ROB entries has changed this cycle. If it has, 348 * then the number of free entries must be re-broadcast. 349 */ 350 bool changedROBNumEntries[Impl::MaxThreads]; 351 352 /** A counter of how many threads are currently squashing. */ 353 int squashCounter; 354 355 /** Records if a thread has to squash this cycle due to a trap. */ 356 bool trapSquash[Impl::MaxThreads]; 357 358 /** Records if a thread has to squash this cycle due to an XC write. */ 359 bool tcSquash[Impl::MaxThreads]; 360 361 /** Priority List used for Commit Policy */ 362 std::list<unsigned> priority_list; 363 364 /** IEW to Commit delay, in ticks. */ 365 unsigned iewToCommitDelay; 366 367 /** Commit to IEW delay, in ticks. */ 368 unsigned commitToIEWDelay; 369 370 /** Rename to ROB delay, in ticks. */ 371 unsigned renameToROBDelay; 372 373 unsigned fetchToCommitDelay; 374 375 /** Rename width, in instructions. Used so ROB knows how many 376 * instructions to get from the rename instruction queue. 377 */ 378 unsigned renameWidth; 379 380 /** Commit width, in instructions. */ 381 unsigned commitWidth; 382 383 /** Number of Reorder Buffers */ 384 unsigned numRobs; 385 386 /** Number of Active Threads */ 387 unsigned numThreads; 388 389 /** Is a drain pending. */ 390 bool drainPending; 391 392 /** Is commit switched out. */ 393 bool switchedOut; 394 395 /** The latency to handle a trap. Used when scheduling trap 396 * squash event. 397 */ 398 Tick trapLatency; 399 400 Tick fetchTrapLatency; 401 402 Tick fetchFaultTick; 403 404 /** The commit PC of each thread. Refers to the instruction that 405 * is currently being processed/committed. 406 */ 407 Addr PC[Impl::MaxThreads]; 408 409 /** The next PC of each thread. */ 410 Addr nextPC[Impl::MaxThreads]; 411 412#if THE_ISA != ALPHA_ISA 413 /** The next NPC of each thread. */ 414 Addr nextNPC[Impl::MaxThreads]; 415#endif 416 417 /** The sequence number of the youngest valid instruction in the ROB. */ 418 InstSeqNum youngestSeqNum[Impl::MaxThreads]; 419 420 /** Pointer to the list of active threads. */ 421 std::list<unsigned> *activeThreads; 422 423 /** Rename map interface. */ 424 RenameMap *renameMap[Impl::MaxThreads]; 425 426 /** Updates commit stats based on this instruction. */ 427 void updateComInstStats(DynInstPtr &inst); 428 429 /** Stat for the total number of committed instructions. */ 430 Stats::Scalar<> commitCommittedInsts; 431 /** Stat for the total number of squashed instructions discarded by commit. 432 */ 433 Stats::Scalar<> commitSquashedInsts; 434 /** Stat for the total number of times commit is told to squash. 435 * @todo: Actually increment this stat. 436 */ 437 Stats::Scalar<> commitSquashEvents; 438 /** Stat for the total number of times commit has had to stall due to a non- 439 * speculative instruction reaching the head of the ROB. 440 */ 441 Stats::Scalar<> commitNonSpecStalls; 442 /** Stat for the total number of branch mispredicts that caused a squash. */ 443 Stats::Scalar<> branchMispredicts; 444 /** Distribution of the number of committed instructions each cycle. */ 445 Stats::Distribution<> numCommittedDist; 446 447 /** Total number of instructions committed. */ 448 Stats::Vector<> statComInst; 449 /** Total number of software prefetches committed. */ 450 Stats::Vector<> statComSwp; 451 /** Stat for the total number of committed memory references. */ 452 Stats::Vector<> statComRefs; 453 /** Stat for the total number of committed loads. */ 454 Stats::Vector<> statComLoads; 455 /** Total number of committed memory barriers. */ 456 Stats::Vector<> statComMembars; 457 /** Total number of committed branches. */ 458 Stats::Vector<> statComBranches; 459 460 /** Number of cycles where the commit bandwidth limit is reached. */ 461 Stats::Scalar<> commitEligibleSamples; 462 /** Number of instructions not committed due to bandwidth limits. */ 463 Stats::Vector<> commitEligible; 464}; 465 466#endif // __CPU_O3_COMMIT_HH__ 467