iew.hh revision 4329:52057dbec096
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 */ 30 31#ifndef __CPU_O3_IEW_HH__ 32#define __CPU_O3_IEW_HH__ 33 34#include "config/full_system.hh" 35 36#include <queue> 37 38#include "base/statistics.hh" 39#include "base/timebuf.hh" 40#include "cpu/o3/comm.hh" 41#include "cpu/o3/scoreboard.hh" 42#include "cpu/o3/lsq.hh" 43 44class FUPool; 45 46/** 47 * DefaultIEW handles both single threaded and SMT IEW 48 * (issue/execute/writeback). It handles the dispatching of 49 * instructions to the LSQ/IQ as part of the issue stage, and has the 50 * IQ try to issue instructions each cycle. The execute latency is 51 * actually tied into the issue latency to allow the IQ to be able to 52 * do back-to-back scheduling without having to speculatively schedule 53 * instructions. This happens by having the IQ have access to the 54 * functional units, and the IQ gets the execution latencies from the 55 * FUs when it issues instructions. Instructions reach the execute 56 * stage on the last cycle of their execution, which is when the IQ 57 * knows to wake up any dependent instructions, allowing back to back 58 * scheduling. The execute portion of IEW separates memory 59 * instructions from non-memory instructions, either telling the LSQ 60 * to execute the instruction, or executing the instruction directly. 61 * The writeback portion of IEW completes the instructions by waking 62 * up any dependents, and marking the register ready on the 63 * scoreboard. 64 */ 65template<class Impl> 66class DefaultIEW 67{ 68 private: 69 //Typedefs from Impl 70 typedef typename Impl::CPUPol CPUPol; 71 typedef typename Impl::DynInstPtr DynInstPtr; 72 typedef typename Impl::O3CPU O3CPU; 73 typedef typename Impl::Params Params; 74 75 typedef typename CPUPol::IQ IQ; 76 typedef typename CPUPol::RenameMap RenameMap; 77 typedef typename CPUPol::LSQ LSQ; 78 79 typedef typename CPUPol::TimeStruct TimeStruct; 80 typedef typename CPUPol::IEWStruct IEWStruct; 81 typedef typename CPUPol::RenameStruct RenameStruct; 82 typedef typename CPUPol::IssueStruct IssueStruct; 83 84 friend class Impl::O3CPU; 85 friend class CPUPol::IQ; 86 87 public: 88 /** Overall IEW stage status. Used to determine if the CPU can 89 * deschedule itself due to a lack of activity. 90 */ 91 enum Status { 92 Active, 93 Inactive 94 }; 95 96 /** Status for Issue, Execute, and Writeback stages. */ 97 enum StageStatus { 98 Running, 99 Blocked, 100 Idle, 101 StartSquash, 102 Squashing, 103 Unblocking 104 }; 105 106 private: 107 /** Overall stage status. */ 108 Status _status; 109 /** Dispatch status. */ 110 StageStatus dispatchStatus[Impl::MaxThreads]; 111 /** Execute status. */ 112 StageStatus exeStatus; 113 /** Writeback status. */ 114 StageStatus wbStatus; 115 116 public: 117 /** Constructs a DefaultIEW with the given parameters. */ 118 DefaultIEW(O3CPU *_cpu, Params *params); 119 120 /** Returns the name of the DefaultIEW stage. */ 121 std::string name() const; 122 123 /** Registers statistics. */ 124 void regStats(); 125 126 /** Initializes stage; sends back the number of free IQ and LSQ entries. */ 127 void initStage(); 128 129 /** Returns the dcache port. */ 130 Port *getDcachePort() { return ldstQueue.getDcachePort(); } 131 132 /** Sets main time buffer used for backwards communication. */ 133 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 134 135 /** Sets time buffer for getting instructions coming from rename. */ 136 void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr); 137 138 /** Sets time buffer to pass on instructions to commit. */ 139 void setIEWQueue(TimeBuffer<IEWStruct> *iq_ptr); 140 141 /** Sets pointer to list of active threads. */ 142 void setActiveThreads(std::list<unsigned> *at_ptr); 143 144 /** Sets pointer to the scoreboard. */ 145 void setScoreboard(Scoreboard *sb_ptr); 146 147 /** Drains IEW stage. */ 148 bool drain(); 149 150 /** Resumes execution after a drain. */ 151 void resume(); 152 153 /** Completes switch out of IEW stage. */ 154 void switchOut(); 155 156 /** Takes over from another CPU's thread. */ 157 void takeOverFrom(); 158 159 /** Returns if IEW is switched out. */ 160 bool isSwitchedOut() { return switchedOut; } 161 162 /** Squashes instructions in IEW for a specific thread. */ 163 void squash(unsigned tid); 164 165 /** Wakes all dependents of a completed instruction. */ 166 void wakeDependents(DynInstPtr &inst); 167 168 /** Tells memory dependence unit that a memory instruction needs to be 169 * rescheduled. It will re-execute once replayMemInst() is called. 170 */ 171 void rescheduleMemInst(DynInstPtr &inst); 172 173 /** Re-executes all rescheduled memory instructions. */ 174 void replayMemInst(DynInstPtr &inst); 175 176 /** Sends an instruction to commit through the time buffer. */ 177 void instToCommit(DynInstPtr &inst); 178 179 /** Inserts unused instructions of a thread into the skid buffer. */ 180 void skidInsert(unsigned tid); 181 182 /** Returns the max of the number of entries in all of the skid buffers. */ 183 int skidCount(); 184 185 /** Returns if all of the skid buffers are empty. */ 186 bool skidsEmpty(); 187 188 /** Updates overall IEW status based on all of the stages' statuses. */ 189 void updateStatus(); 190 191 /** Resets entries of the IQ and the LSQ. */ 192 void resetEntries(); 193 194 /** Tells the CPU to wakeup if it has descheduled itself due to no 195 * activity. Used mainly by the LdWritebackEvent. 196 */ 197 void wakeCPU(); 198 199 /** Reports to the CPU that there is activity this cycle. */ 200 void activityThisCycle(); 201 202 /** Tells CPU that the IEW stage is active and running. */ 203 inline void activateStage(); 204 205 /** Tells CPU that the IEW stage is inactive and idle. */ 206 inline void deactivateStage(); 207 208 /** Returns if the LSQ has any stores to writeback. */ 209 bool hasStoresToWB() { return ldstQueue.hasStoresToWB(); } 210 211 void incrWb(InstSeqNum &sn) 212 { 213 if (++wbOutstanding == wbMax) 214 ableToIssue = false; 215 DPRINTF(IEW, "wbOutstanding: %i\n", wbOutstanding); 216 assert(wbOutstanding <= wbMax); 217#ifdef DEBUG 218 wbList.insert(sn); 219#endif 220 } 221 222 void decrWb(InstSeqNum &sn) 223 { 224 if (wbOutstanding-- == wbMax) 225 ableToIssue = true; 226 DPRINTF(IEW, "wbOutstanding: %i\n", wbOutstanding); 227 assert(wbOutstanding >= 0); 228#ifdef DEBUG 229 assert(wbList.find(sn) != wbList.end()); 230 wbList.erase(sn); 231#endif 232 } 233 234#ifdef DEBUG 235 std::set<InstSeqNum> wbList; 236 237 void dumpWb() 238 { 239 std::set<InstSeqNum>::iterator wb_it = wbList.begin(); 240 while (wb_it != wbList.end()) { 241 cprintf("[sn:%lli]\n", 242 (*wb_it)); 243 wb_it++; 244 } 245 } 246#endif 247 248 bool canIssue() { return ableToIssue; } 249 250 bool ableToIssue; 251 252 private: 253 /** Sends commit proper information for a squash due to a branch 254 * mispredict. 255 */ 256 void squashDueToBranch(DynInstPtr &inst, unsigned thread_id); 257 258 /** Sends commit proper information for a squash due to a memory order 259 * violation. 260 */ 261 void squashDueToMemOrder(DynInstPtr &inst, unsigned thread_id); 262 263 /** Sends commit proper information for a squash due to memory becoming 264 * blocked (younger issued instructions must be retried). 265 */ 266 void squashDueToMemBlocked(DynInstPtr &inst, unsigned thread_id); 267 268 /** Sets Dispatch to blocked, and signals back to other stages to block. */ 269 void block(unsigned thread_id); 270 271 /** Unblocks Dispatch if the skid buffer is empty, and signals back to 272 * other stages to unblock. 273 */ 274 void unblock(unsigned thread_id); 275 276 /** Determines proper actions to take given Dispatch's status. */ 277 void dispatch(unsigned tid); 278 279 /** Dispatches instructions to IQ and LSQ. */ 280 void dispatchInsts(unsigned tid); 281 282 /** Executes instructions. In the case of memory operations, it informs the 283 * LSQ to execute the instructions. Also handles any redirects that occur 284 * due to the executed instructions. 285 */ 286 void executeInsts(); 287 288 /** Writebacks instructions. In our model, the instruction's execute() 289 * function atomically reads registers, executes, and writes registers. 290 * Thus this writeback only wakes up dependent instructions, and informs 291 * the scoreboard of registers becoming ready. 292 */ 293 void writebackInsts(); 294 295 /** Returns the number of valid, non-squashed instructions coming from 296 * rename to dispatch. 297 */ 298 unsigned validInstsFromRename(); 299 300 /** Reads the stall signals. */ 301 void readStallSignals(unsigned tid); 302 303 /** Checks if any of the stall conditions are currently true. */ 304 bool checkStall(unsigned tid); 305 306 /** Processes inputs and changes state accordingly. */ 307 void checkSignalsAndUpdate(unsigned tid); 308 309 /** Removes instructions from rename from a thread's instruction list. */ 310 void emptyRenameInsts(unsigned tid); 311 312 /** Sorts instructions coming from rename into lists separated by thread. */ 313 void sortInsts(); 314 315 public: 316 /** Ticks IEW stage, causing Dispatch, the IQ, the LSQ, Execute, and 317 * Writeback to run for one cycle. 318 */ 319 void tick(); 320 321 private: 322 /** Updates execution stats based on the instruction. */ 323 void updateExeInstStats(DynInstPtr &inst); 324 325 /** Pointer to main time buffer used for backwards communication. */ 326 TimeBuffer<TimeStruct> *timeBuffer; 327 328 /** Wire to write information heading to previous stages. */ 329 typename TimeBuffer<TimeStruct>::wire toFetch; 330 331 /** Wire to get commit's output from backwards time buffer. */ 332 typename TimeBuffer<TimeStruct>::wire fromCommit; 333 334 /** Wire to write information heading to previous stages. */ 335 typename TimeBuffer<TimeStruct>::wire toRename; 336 337 /** Rename instruction queue interface. */ 338 TimeBuffer<RenameStruct> *renameQueue; 339 340 /** Wire to get rename's output from rename queue. */ 341 typename TimeBuffer<RenameStruct>::wire fromRename; 342 343 /** Issue stage queue. */ 344 TimeBuffer<IssueStruct> issueToExecQueue; 345 346 /** Wire to read information from the issue stage time queue. */ 347 typename TimeBuffer<IssueStruct>::wire fromIssue; 348 349 /** 350 * IEW stage time buffer. Holds ROB indices of instructions that 351 * can be marked as completed. 352 */ 353 TimeBuffer<IEWStruct> *iewQueue; 354 355 /** Wire to write infromation heading to commit. */ 356 typename TimeBuffer<IEWStruct>::wire toCommit; 357 358 /** Queue of all instructions coming from rename this cycle. */ 359 std::queue<DynInstPtr> insts[Impl::MaxThreads]; 360 361 /** Skid buffer between rename and IEW. */ 362 std::queue<DynInstPtr> skidBuffer[Impl::MaxThreads]; 363 364 /** Scoreboard pointer. */ 365 Scoreboard* scoreboard; 366 367 private: 368 /** CPU pointer. */ 369 O3CPU *cpu; 370 371 /** Records if IEW has written to the time buffer this cycle, so that the 372 * CPU can deschedule itself if there is no activity. 373 */ 374 bool wroteToTimeBuffer; 375 376 /** Source of possible stalls. */ 377 struct Stalls { 378 bool commit; 379 }; 380 381 /** Stages that are telling IEW to stall. */ 382 Stalls stalls[Impl::MaxThreads]; 383 384 /** Debug function to print instructions that are issued this cycle. */ 385 void printAvailableInsts(); 386 387 public: 388 /** Instruction queue. */ 389 IQ instQueue; 390 391 /** Load / store queue. */ 392 LSQ ldstQueue; 393 394 /** Pointer to the functional unit pool. */ 395 FUPool *fuPool; 396 /** Records if the LSQ needs to be updated on the next cycle, so that 397 * IEW knows if there will be activity on the next cycle. 398 */ 399 bool updateLSQNextCycle; 400 401 private: 402 /** Records if there is a fetch redirect on this cycle for each thread. */ 403 bool fetchRedirect[Impl::MaxThreads]; 404 405 /** Keeps track of the last valid branch delay slot instss for threads */ 406 InstSeqNum bdelayDoneSeqNum[Impl::MaxThreads]; 407 408 /** Used to track if all instructions have been dispatched this cycle. 409 * If they have not, then blocking must have occurred, and the instructions 410 * would already be added to the skid buffer. 411 * @todo: Fix this hack. 412 */ 413 bool dispatchedAllInsts; 414 415 /** Records if the queues have been changed (inserted or issued insts), 416 * so that IEW knows to broadcast the updated amount of free entries. 417 */ 418 bool updatedQueues; 419 420 /** Commit to IEW delay, in ticks. */ 421 unsigned commitToIEWDelay; 422 423 /** Rename to IEW delay, in ticks. */ 424 unsigned renameToIEWDelay; 425 426 /** 427 * Issue to execute delay, in ticks. What this actually represents is 428 * the amount of time it takes for an instruction to wake up, be 429 * scheduled, and sent to a FU for execution. 430 */ 431 unsigned issueToExecuteDelay; 432 433 /** Width of dispatch, in instructions. */ 434 unsigned dispatchWidth; 435 436 /** Width of issue, in instructions. */ 437 unsigned issueWidth; 438 439 /** Index into queue of instructions being written back. */ 440 unsigned wbNumInst; 441 442 /** Cycle number within the queue of instructions being written back. 443 * Used in case there are too many instructions writing back at the current 444 * cycle and writesbacks need to be scheduled for the future. See comments 445 * in instToCommit(). 446 */ 447 unsigned wbCycle; 448 449 /** Number of instructions in flight that will writeback. */ 450 451 /** Number of instructions in flight that will writeback. */ 452 int wbOutstanding; 453 454 /** Writeback width. */ 455 unsigned wbWidth; 456 457 /** Writeback width * writeback depth, where writeback depth is 458 * the number of cycles of writing back instructions that can be 459 * buffered. */ 460 unsigned wbMax; 461 462 /** Number of active threads. */ 463 unsigned numThreads; 464 465 /** Pointer to list of active threads. */ 466 std::list<unsigned> *activeThreads; 467 468 /** Maximum size of the skid buffer. */ 469 unsigned skidBufferMax; 470 471 /** Is this stage switched out. */ 472 bool switchedOut; 473 474 /** Stat for total number of idle cycles. */ 475 Stats::Scalar<> iewIdleCycles; 476 /** Stat for total number of squashing cycles. */ 477 Stats::Scalar<> iewSquashCycles; 478 /** Stat for total number of blocking cycles. */ 479 Stats::Scalar<> iewBlockCycles; 480 /** Stat for total number of unblocking cycles. */ 481 Stats::Scalar<> iewUnblockCycles; 482 /** Stat for total number of instructions dispatched. */ 483 Stats::Scalar<> iewDispatchedInsts; 484 /** Stat for total number of squashed instructions dispatch skips. */ 485 Stats::Scalar<> iewDispSquashedInsts; 486 /** Stat for total number of dispatched load instructions. */ 487 Stats::Scalar<> iewDispLoadInsts; 488 /** Stat for total number of dispatched store instructions. */ 489 Stats::Scalar<> iewDispStoreInsts; 490 /** Stat for total number of dispatched non speculative instructions. */ 491 Stats::Scalar<> iewDispNonSpecInsts; 492 /** Stat for number of times the IQ becomes full. */ 493 Stats::Scalar<> iewIQFullEvents; 494 /** Stat for number of times the LSQ becomes full. */ 495 Stats::Scalar<> iewLSQFullEvents; 496 /** Stat for total number of memory ordering violation events. */ 497 Stats::Scalar<> memOrderViolationEvents; 498 /** Stat for total number of incorrect predicted taken branches. */ 499 Stats::Scalar<> predictedTakenIncorrect; 500 /** Stat for total number of incorrect predicted not taken branches. */ 501 Stats::Scalar<> predictedNotTakenIncorrect; 502 /** Stat for total number of mispredicted branches detected at execute. */ 503 Stats::Formula branchMispredicts; 504 505 /** Stat for total number of executed instructions. */ 506 Stats::Scalar<> iewExecutedInsts; 507 /** Stat for total number of executed load instructions. */ 508 Stats::Vector<> iewExecLoadInsts; 509 /** Stat for total number of executed store instructions. */ 510// Stats::Scalar<> iewExecStoreInsts; 511 /** Stat for total number of squashed instructions skipped at execute. */ 512 Stats::Scalar<> iewExecSquashedInsts; 513 /** Number of executed software prefetches. */ 514 Stats::Vector<> iewExecutedSwp; 515 /** Number of executed nops. */ 516 Stats::Vector<> iewExecutedNop; 517 /** Number of executed meomory references. */ 518 Stats::Vector<> iewExecutedRefs; 519 /** Number of executed branches. */ 520 Stats::Vector<> iewExecutedBranches; 521 /** Number of executed store instructions. */ 522 Stats::Formula iewExecStoreInsts; 523 /** Number of instructions executed per cycle. */ 524 Stats::Formula iewExecRate; 525 526 /** Number of instructions sent to commit. */ 527 Stats::Vector<> iewInstsToCommit; 528 /** Number of instructions that writeback. */ 529 Stats::Vector<> writebackCount; 530 /** Number of instructions that wake consumers. */ 531 Stats::Vector<> producerInst; 532 /** Number of instructions that wake up from producers. */ 533 Stats::Vector<> consumerInst; 534 /** Number of instructions that were delayed in writing back due 535 * to resource contention. 536 */ 537 Stats::Vector<> wbPenalized; 538 /** Number of instructions per cycle written back. */ 539 Stats::Formula wbRate; 540 /** Average number of woken instructions per writeback. */ 541 Stats::Formula wbFanout; 542 /** Number of instructions per cycle delayed in writing back . */ 543 Stats::Formula wbPenalizedRate; 544}; 545 546#endif // __CPU_O3_IEW_HH__ 547