iew.hh revision 8707:489489c67fd9
1/* 2 * Copyright (c) 2010 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_IEW_HH__ 44#define __CPU_O3_IEW_HH__ 45 46#include <queue> 47#include <set> 48 49#include "base/statistics.hh" 50#include "config/full_system.hh" 51#include "cpu/o3/comm.hh" 52#include "cpu/o3/lsq.hh" 53#include "cpu/o3/scoreboard.hh" 54#include "cpu/timebuf.hh" 55#include "debug/IEW.hh" 56 57class DerivO3CPUParams; 58class FUPool; 59 60/** 61 * DefaultIEW handles both single threaded and SMT IEW 62 * (issue/execute/writeback). It handles the dispatching of 63 * instructions to the LSQ/IQ as part of the issue stage, and has the 64 * IQ try to issue instructions each cycle. The execute latency is 65 * actually tied into the issue latency to allow the IQ to be able to 66 * do back-to-back scheduling without having to speculatively schedule 67 * instructions. This happens by having the IQ have access to the 68 * functional units, and the IQ gets the execution latencies from the 69 * FUs when it issues instructions. Instructions reach the execute 70 * stage on the last cycle of their execution, which is when the IQ 71 * knows to wake up any dependent instructions, allowing back to back 72 * scheduling. The execute portion of IEW separates memory 73 * instructions from non-memory instructions, either telling the LSQ 74 * to execute the instruction, or executing the instruction directly. 75 * The writeback portion of IEW completes the instructions by waking 76 * up any dependents, and marking the register ready on the 77 * scoreboard. 78 */ 79template<class Impl> 80class DefaultIEW 81{ 82 private: 83 //Typedefs from Impl 84 typedef typename Impl::CPUPol CPUPol; 85 typedef typename Impl::DynInstPtr DynInstPtr; 86 typedef typename Impl::O3CPU O3CPU; 87 88 typedef typename CPUPol::IQ IQ; 89 typedef typename CPUPol::RenameMap RenameMap; 90 typedef typename CPUPol::LSQ LSQ; 91 92 typedef typename CPUPol::TimeStruct TimeStruct; 93 typedef typename CPUPol::IEWStruct IEWStruct; 94 typedef typename CPUPol::RenameStruct RenameStruct; 95 typedef typename CPUPol::IssueStruct IssueStruct; 96 97 friend class Impl::O3CPU; 98 friend class CPUPol::IQ; 99 100 public: 101 /** Overall IEW stage status. Used to determine if the CPU can 102 * deschedule itself due to a lack of activity. 103 */ 104 enum Status { 105 Active, 106 Inactive 107 }; 108 109 /** Status for Issue, Execute, and Writeback stages. */ 110 enum StageStatus { 111 Running, 112 Blocked, 113 Idle, 114 StartSquash, 115 Squashing, 116 Unblocking 117 }; 118 119 private: 120 /** Overall stage status. */ 121 Status _status; 122 /** Dispatch status. */ 123 StageStatus dispatchStatus[Impl::MaxThreads]; 124 /** Execute status. */ 125 StageStatus exeStatus; 126 /** Writeback status. */ 127 StageStatus wbStatus; 128 129 public: 130 /** Constructs a DefaultIEW with the given parameters. */ 131 DefaultIEW(O3CPU *_cpu, DerivO3CPUParams *params); 132 133 /** Returns the name of the DefaultIEW stage. */ 134 std::string name() const; 135 136 /** Registers statistics. */ 137 void regStats(); 138 139 /** Initializes stage; sends back the number of free IQ and LSQ entries. */ 140 void initStage(); 141 142 /** Sets main time buffer used for backwards communication. */ 143 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 144 145 /** Sets time buffer for getting instructions coming from rename. */ 146 void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr); 147 148 /** Sets time buffer to pass on instructions to commit. */ 149 void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr); 150 151 /** Sets pointer to list of active threads. */ 152 void setActiveThreads(std::list<ThreadID> *at_ptr); 153 154 /** Sets pointer to the scoreboard. */ 155 void setScoreboard(Scoreboard *sb_ptr); 156 157 /** Drains IEW stage. */ 158 bool drain(); 159 160 /** Resumes execution after a drain. */ 161 void resume(); 162 163 /** Completes switch out of IEW stage. */ 164 void switchOut(); 165 166 /** Takes over from another CPU's thread. */ 167 void takeOverFrom(); 168 169 /** Returns if IEW is switched out. */ 170 bool isSwitchedOut() { return switchedOut; } 171 172 /** Squashes instructions in IEW for a specific thread. */ 173 void squash(ThreadID tid); 174 175 /** Wakes all dependents of a completed instruction. */ 176 void wakeDependents(DynInstPtr &inst); 177 178 /** Tells memory dependence unit that a memory instruction needs to be 179 * rescheduled. It will re-execute once replayMemInst() is called. 180 */ 181 void rescheduleMemInst(DynInstPtr &inst); 182 183 /** Re-executes all rescheduled memory instructions. */ 184 void replayMemInst(DynInstPtr &inst); 185 186 /** Sends an instruction to commit through the time buffer. */ 187 void instToCommit(DynInstPtr &inst); 188 189 /** Inserts unused instructions of a thread into the skid buffer. */ 190 void skidInsert(ThreadID tid); 191 192 /** Returns the max of the number of entries in all of the skid buffers. */ 193 int skidCount(); 194 195 /** Returns if all of the skid buffers are empty. */ 196 bool skidsEmpty(); 197 198 /** Updates overall IEW status based on all of the stages' statuses. */ 199 void updateStatus(); 200 201 /** Resets entries of the IQ and the LSQ. */ 202 void resetEntries(); 203 204 /** Tells the CPU to wakeup if it has descheduled itself due to no 205 * activity. Used mainly by the LdWritebackEvent. 206 */ 207 void wakeCPU(); 208 209 /** Reports to the CPU that there is activity this cycle. */ 210 void activityThisCycle(); 211 212 /** Tells CPU that the IEW stage is active and running. */ 213 inline void activateStage(); 214 215 /** Tells CPU that the IEW stage is inactive and idle. */ 216 inline void deactivateStage(); 217 218 /** Returns if the LSQ has any stores to writeback. */ 219 bool hasStoresToWB() { return ldstQueue.hasStoresToWB(); } 220 221 /** Returns if the LSQ has any stores to writeback. */ 222 bool hasStoresToWB(ThreadID tid) { return ldstQueue.hasStoresToWB(tid); } 223 224 void incrWb(InstSeqNum &sn) 225 { 226 if (++wbOutstanding == wbMax) 227 ableToIssue = false; 228 DPRINTF(IEW, "wbOutstanding: %i [sn:%lli]\n", wbOutstanding, sn); 229 assert(wbOutstanding <= wbMax); 230#ifdef DEBUG 231 wbList.insert(sn); 232#endif 233 } 234 235 void decrWb(InstSeqNum &sn) 236 { 237 if (wbOutstanding-- == wbMax) 238 ableToIssue = true; 239 DPRINTF(IEW, "wbOutstanding: %i [sn:%lli]\n", wbOutstanding, sn); 240 assert(wbOutstanding >= 0); 241#ifdef DEBUG 242 assert(wbList.find(sn) != wbList.end()); 243 wbList.erase(sn); 244#endif 245 } 246 247#ifdef DEBUG 248 std::set<InstSeqNum> wbList; 249 250 void dumpWb() 251 { 252 std::set<InstSeqNum>::iterator wb_it = wbList.begin(); 253 while (wb_it != wbList.end()) { 254 cprintf("[sn:%lli]\n", 255 (*wb_it)); 256 wb_it++; 257 } 258 } 259#endif 260 261 bool canIssue() { return ableToIssue; } 262 263 bool ableToIssue; 264 265 /** Check misprediction */ 266 void checkMisprediction(DynInstPtr &inst); 267 268 private: 269 /** Sends commit proper information for a squash due to a branch 270 * mispredict. 271 */ 272 void squashDueToBranch(DynInstPtr &inst, ThreadID tid); 273 274 /** Sends commit proper information for a squash due to a memory order 275 * violation. 276 */ 277 void squashDueToMemOrder(DynInstPtr &inst, ThreadID tid); 278 279 /** Sends commit proper information for a squash due to memory becoming 280 * blocked (younger issued instructions must be retried). 281 */ 282 void squashDueToMemBlocked(DynInstPtr &inst, ThreadID tid); 283 284 /** Sets Dispatch to blocked, and signals back to other stages to block. */ 285 void block(ThreadID tid); 286 287 /** Unblocks Dispatch if the skid buffer is empty, and signals back to 288 * other stages to unblock. 289 */ 290 void unblock(ThreadID tid); 291 292 /** Determines proper actions to take given Dispatch's status. */ 293 void dispatch(ThreadID tid); 294 295 /** Dispatches instructions to IQ and LSQ. */ 296 void dispatchInsts(ThreadID tid); 297 298 /** Executes instructions. In the case of memory operations, it informs the 299 * LSQ to execute the instructions. Also handles any redirects that occur 300 * due to the executed instructions. 301 */ 302 void executeInsts(); 303 304 /** Writebacks instructions. In our model, the instruction's execute() 305 * function atomically reads registers, executes, and writes registers. 306 * Thus this writeback only wakes up dependent instructions, and informs 307 * the scoreboard of registers becoming ready. 308 */ 309 void writebackInsts(); 310 311 /** Returns the number of valid, non-squashed instructions coming from 312 * rename to dispatch. 313 */ 314 unsigned validInstsFromRename(); 315 316 /** Reads the stall signals. */ 317 void readStallSignals(ThreadID tid); 318 319 /** Checks if any of the stall conditions are currently true. */ 320 bool checkStall(ThreadID tid); 321 322 /** Processes inputs and changes state accordingly. */ 323 void checkSignalsAndUpdate(ThreadID tid); 324 325 /** Removes instructions from rename from a thread's instruction list. */ 326 void emptyRenameInsts(ThreadID tid); 327 328 /** Sorts instructions coming from rename into lists separated by thread. */ 329 void sortInsts(); 330 331 public: 332 /** Ticks IEW stage, causing Dispatch, the IQ, the LSQ, Execute, and 333 * Writeback to run for one cycle. 334 */ 335 void tick(); 336 337 private: 338 /** Updates execution stats based on the instruction. */ 339 void updateExeInstStats(DynInstPtr &inst); 340 341 /** Pointer to main time buffer used for backwards communication. */ 342 TimeBuffer<TimeStruct> *timeBuffer; 343 344 /** Wire to write information heading to previous stages. */ 345 typename TimeBuffer<TimeStruct>::wire toFetch; 346 347 /** Wire to get commit's output from backwards time buffer. */ 348 typename TimeBuffer<TimeStruct>::wire fromCommit; 349 350 /** Wire to write information heading to previous stages. */ 351 typename TimeBuffer<TimeStruct>::wire toRename; 352 353 /** Rename instruction queue interface. */ 354 TimeBuffer<RenameStruct> *renameQueue; 355 356 /** Wire to get rename's output from rename queue. */ 357 typename TimeBuffer<RenameStruct>::wire fromRename; 358 359 /** Issue stage queue. */ 360 TimeBuffer<IssueStruct> issueToExecQueue; 361 362 /** Wire to read information from the issue stage time queue. */ 363 typename TimeBuffer<IssueStruct>::wire fromIssue; 364 365 /** 366 * IEW stage time buffer. Holds ROB indices of instructions that 367 * can be marked as completed. 368 */ 369 TimeBuffer<IEWStruct> *iewQueue; 370 371 /** Wire to write infromation heading to commit. */ 372 typename TimeBuffer<IEWStruct>::wire toCommit; 373 374 /** Queue of all instructions coming from rename this cycle. */ 375 std::queue<DynInstPtr> insts[Impl::MaxThreads]; 376 377 /** Skid buffer between rename and IEW. */ 378 std::queue<DynInstPtr> skidBuffer[Impl::MaxThreads]; 379 380 /** Scoreboard pointer. */ 381 Scoreboard* scoreboard; 382 383 private: 384 /** CPU pointer. */ 385 O3CPU *cpu; 386 387 /** Records if IEW has written to the time buffer this cycle, so that the 388 * CPU can deschedule itself if there is no activity. 389 */ 390 bool wroteToTimeBuffer; 391 392 /** Source of possible stalls. */ 393 struct Stalls { 394 bool commit; 395 }; 396 397 /** Stages that are telling IEW to stall. */ 398 Stalls stalls[Impl::MaxThreads]; 399 400 /** Debug function to print instructions that are issued this cycle. */ 401 void printAvailableInsts(); 402 403 public: 404 /** Instruction queue. */ 405 IQ instQueue; 406 407 /** Load / store queue. */ 408 LSQ ldstQueue; 409 410 /** Pointer to the functional unit pool. */ 411 FUPool *fuPool; 412 /** Records if the LSQ needs to be updated on the next cycle, so that 413 * IEW knows if there will be activity on the next cycle. 414 */ 415 bool updateLSQNextCycle; 416 417 private: 418 /** Records if there is a fetch redirect on this cycle for each thread. */ 419 bool fetchRedirect[Impl::MaxThreads]; 420 421 /** Records if the queues have been changed (inserted or issued insts), 422 * so that IEW knows to broadcast the updated amount of free entries. 423 */ 424 bool updatedQueues; 425 426 /** Commit to IEW delay, in ticks. */ 427 unsigned commitToIEWDelay; 428 429 /** Rename to IEW delay, in ticks. */ 430 unsigned renameToIEWDelay; 431 432 /** 433 * Issue to execute delay, in ticks. What this actually represents is 434 * the amount of time it takes for an instruction to wake up, be 435 * scheduled, and sent to a FU for execution. 436 */ 437 unsigned issueToExecuteDelay; 438 439 /** Width of dispatch, in instructions. */ 440 unsigned dispatchWidth; 441 442 /** Width of issue, in instructions. */ 443 unsigned issueWidth; 444 445 /** Index into queue of instructions being written back. */ 446 unsigned wbNumInst; 447 448 /** Cycle number within the queue of instructions being written back. 449 * Used in case there are too many instructions writing back at the current 450 * cycle and writesbacks need to be scheduled for the future. See comments 451 * in instToCommit(). 452 */ 453 unsigned wbCycle; 454 455 /** Number of instructions in flight that will writeback. */ 456 457 /** Number of instructions in flight that will writeback. */ 458 int wbOutstanding; 459 460 /** Writeback width. */ 461 unsigned wbWidth; 462 463 /** Writeback width * writeback depth, where writeback depth is 464 * the number of cycles of writing back instructions that can be 465 * buffered. */ 466 unsigned wbMax; 467 468 /** Number of active threads. */ 469 ThreadID numThreads; 470 471 /** Pointer to list of active threads. */ 472 std::list<ThreadID> *activeThreads; 473 474 /** Maximum size of the skid buffer. */ 475 unsigned skidBufferMax; 476 477 /** Is this stage switched out. */ 478 bool switchedOut; 479 480 /** Stat for total number of idle cycles. */ 481 Stats::Scalar iewIdleCycles; 482 /** Stat for total number of squashing cycles. */ 483 Stats::Scalar iewSquashCycles; 484 /** Stat for total number of blocking cycles. */ 485 Stats::Scalar iewBlockCycles; 486 /** Stat for total number of unblocking cycles. */ 487 Stats::Scalar iewUnblockCycles; 488 /** Stat for total number of instructions dispatched. */ 489 Stats::Scalar iewDispatchedInsts; 490 /** Stat for total number of squashed instructions dispatch skips. */ 491 Stats::Scalar iewDispSquashedInsts; 492 /** Stat for total number of dispatched load instructions. */ 493 Stats::Scalar iewDispLoadInsts; 494 /** Stat for total number of dispatched store instructions. */ 495 Stats::Scalar iewDispStoreInsts; 496 /** Stat for total number of dispatched non speculative instructions. */ 497 Stats::Scalar iewDispNonSpecInsts; 498 /** Stat for number of times the IQ becomes full. */ 499 Stats::Scalar iewIQFullEvents; 500 /** Stat for number of times the LSQ becomes full. */ 501 Stats::Scalar iewLSQFullEvents; 502 /** Stat for total number of memory ordering violation events. */ 503 Stats::Scalar memOrderViolationEvents; 504 /** Stat for total number of incorrect predicted taken branches. */ 505 Stats::Scalar predictedTakenIncorrect; 506 /** Stat for total number of incorrect predicted not taken branches. */ 507 Stats::Scalar predictedNotTakenIncorrect; 508 /** Stat for total number of mispredicted branches detected at execute. */ 509 Stats::Formula branchMispredicts; 510 511 /** Stat for total number of executed instructions. */ 512 Stats::Scalar iewExecutedInsts; 513 /** Stat for total number of executed load instructions. */ 514 Stats::Vector iewExecLoadInsts; 515 /** Stat for total number of executed store instructions. */ 516// Stats::Scalar iewExecStoreInsts; 517 /** Stat for total number of squashed instructions skipped at execute. */ 518 Stats::Scalar iewExecSquashedInsts; 519 /** Number of executed software prefetches. */ 520 Stats::Vector iewExecutedSwp; 521 /** Number of executed nops. */ 522 Stats::Vector iewExecutedNop; 523 /** Number of executed meomory references. */ 524 Stats::Vector iewExecutedRefs; 525 /** Number of executed branches. */ 526 Stats::Vector iewExecutedBranches; 527 /** Number of executed store instructions. */ 528 Stats::Formula iewExecStoreInsts; 529 /** Number of instructions executed per cycle. */ 530 Stats::Formula iewExecRate; 531 532 /** Number of instructions sent to commit. */ 533 Stats::Vector iewInstsToCommit; 534 /** Number of instructions that writeback. */ 535 Stats::Vector writebackCount; 536 /** Number of instructions that wake consumers. */ 537 Stats::Vector producerInst; 538 /** Number of instructions that wake up from producers. */ 539 Stats::Vector consumerInst; 540 /** Number of instructions that were delayed in writing back due 541 * to resource contention. 542 */ 543 Stats::Vector wbPenalized; 544 /** Number of instructions per cycle written back. */ 545 Stats::Formula wbRate; 546 /** Average number of woken instructions per writeback. */ 547 Stats::Formula wbFanout; 548 /** Number of instructions per cycle delayed in writing back . */ 549 Stats::Formula wbPenalizedRate; 550}; 551 552#endif // __CPU_O3_IEW_HH__ 553