fetch.hh revision 9982:b2bfc23f932c
1/* 2 * Copyright (c) 2010-2012 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 * Korey Sewell 42 */ 43 44#ifndef __CPU_O3_FETCH_HH__ 45#define __CPU_O3_FETCH_HH__ 46 47#include "arch/decoder.hh" 48#include "arch/utility.hh" 49#include "base/statistics.hh" 50#include "config/the_isa.hh" 51#include "cpu/pc_event.hh" 52#include "cpu/pred/bpred_unit.hh" 53#include "cpu/timebuf.hh" 54#include "cpu/translation.hh" 55#include "mem/packet.hh" 56#include "mem/port.hh" 57#include "sim/eventq.hh" 58 59struct DerivO3CPUParams; 60 61/** 62 * DefaultFetch class handles both single threaded and SMT fetch. Its 63 * width is specified by the parameters; each cycle it tries to fetch 64 * that many instructions. It supports using a branch predictor to 65 * predict direction and targets. 66 * It supports the idling functionality of the CPU by indicating to 67 * the CPU when it is active and inactive. 68 */ 69template <class Impl> 70class DefaultFetch 71{ 72 public: 73 /** Typedefs from Impl. */ 74 typedef typename Impl::CPUPol CPUPol; 75 typedef typename Impl::DynInst DynInst; 76 typedef typename Impl::DynInstPtr DynInstPtr; 77 typedef typename Impl::O3CPU O3CPU; 78 79 /** Typedefs from the CPU policy. */ 80 typedef typename CPUPol::FetchStruct FetchStruct; 81 typedef typename CPUPol::TimeStruct TimeStruct; 82 83 /** Typedefs from ISA. */ 84 typedef TheISA::MachInst MachInst; 85 typedef TheISA::ExtMachInst ExtMachInst; 86 87 class FetchTranslation : public BaseTLB::Translation 88 { 89 protected: 90 DefaultFetch<Impl> *fetch; 91 92 public: 93 FetchTranslation(DefaultFetch<Impl> *_fetch) 94 : fetch(_fetch) 95 {} 96 97 void 98 markDelayed() 99 {} 100 101 void 102 finish(Fault fault, RequestPtr req, ThreadContext *tc, 103 BaseTLB::Mode mode) 104 { 105 assert(mode == BaseTLB::Execute); 106 fetch->finishTranslation(fault, req); 107 delete this; 108 } 109 }; 110 111 private: 112 /* Event to delay delivery of a fetch translation result in case of 113 * a fault and the nop to carry the fault cannot be generated 114 * immediately */ 115 class FinishTranslationEvent : public Event 116 { 117 private: 118 DefaultFetch<Impl> *fetch; 119 Fault fault; 120 RequestPtr req; 121 122 public: 123 FinishTranslationEvent(DefaultFetch<Impl> *_fetch) 124 : fetch(_fetch) 125 {} 126 127 void setFault(Fault _fault) 128 { 129 fault = _fault; 130 } 131 132 void setReq(RequestPtr _req) 133 { 134 req = _req; 135 } 136 137 /** Process the delayed finish translation */ 138 void process() 139 { 140 assert(fetch->numInst < fetch->fetchWidth); 141 fetch->finishTranslation(fault, req); 142 } 143 144 const char *description() const 145 { 146 return "FullO3CPU FetchFinishTranslation"; 147 } 148 }; 149 150 public: 151 /** Overall fetch status. Used to determine if the CPU can 152 * deschedule itsef due to a lack of activity. 153 */ 154 enum FetchStatus { 155 Active, 156 Inactive 157 }; 158 159 /** Individual thread status. */ 160 enum ThreadStatus { 161 Running, 162 Idle, 163 Squashing, 164 Blocked, 165 Fetching, 166 TrapPending, 167 QuiescePending, 168 ItlbWait, 169 IcacheWaitResponse, 170 IcacheWaitRetry, 171 IcacheAccessComplete, 172 NoGoodAddr 173 }; 174 175 /** Fetching Policy, Add new policies here.*/ 176 enum FetchPriority { 177 SingleThread, 178 RoundRobin, 179 Branch, 180 IQ, 181 LSQ 182 }; 183 184 private: 185 /** Fetch status. */ 186 FetchStatus _status; 187 188 /** Per-thread status. */ 189 ThreadStatus fetchStatus[Impl::MaxThreads]; 190 191 /** Fetch policy. */ 192 FetchPriority fetchPolicy; 193 194 /** List that has the threads organized by priority. */ 195 std::list<ThreadID> priorityList; 196 197 public: 198 /** DefaultFetch constructor. */ 199 DefaultFetch(O3CPU *_cpu, DerivO3CPUParams *params); 200 201 /** Returns the name of fetch. */ 202 std::string name() const; 203 204 /** Registers statistics. */ 205 void regStats(); 206 207 /** Sets the main backwards communication time buffer pointer. */ 208 void setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer); 209 210 /** Sets pointer to list of active threads. */ 211 void setActiveThreads(std::list<ThreadID> *at_ptr); 212 213 /** Sets pointer to time buffer used to communicate to the next stage. */ 214 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr); 215 216 /** Initialize stage. */ 217 void startupStage(); 218 219 /** Handles retrying the fetch access. */ 220 void recvRetry(); 221 222 /** Processes cache completion event. */ 223 void processCacheCompletion(PacketPtr pkt); 224 225 /** Resume after a drain. */ 226 void drainResume(); 227 228 /** Perform sanity checks after a drain. */ 229 void drainSanityCheck() const; 230 231 /** Has the stage drained? */ 232 bool isDrained() const; 233 234 /** Takes over from another CPU's thread. */ 235 void takeOverFrom(); 236 237 /** 238 * Stall the fetch stage after reaching a safe drain point. 239 * 240 * The CPU uses this method to stop fetching instructions from a 241 * thread that has been drained. The drain stall is different from 242 * all other stalls in that it is signaled instantly from the 243 * commit stage (without the normal communication delay) when it 244 * has reached a safe point to drain from. 245 */ 246 void drainStall(ThreadID tid); 247 248 /** Tells fetch to wake up from a quiesce instruction. */ 249 void wakeFromQuiesce(); 250 251 private: 252 /** Reset this pipeline stage */ 253 void resetStage(); 254 255 /** Changes the status of this stage to active, and indicates this 256 * to the CPU. 257 */ 258 inline void switchToActive(); 259 260 /** Changes the status of this stage to inactive, and indicates 261 * this to the CPU. 262 */ 263 inline void switchToInactive(); 264 265 /** 266 * Looks up in the branch predictor to see if the next PC should be 267 * either next PC+=MachInst or a branch target. 268 * @param next_PC Next PC variable passed in by reference. It is 269 * expected to be set to the current PC; it will be updated with what 270 * the next PC will be. 271 * @param next_NPC Used for ISAs which use delay slots. 272 * @return Whether or not a branch was predicted as taken. 273 */ 274 bool lookupAndUpdateNextPC(DynInstPtr &inst, TheISA::PCState &pc); 275 276 /** 277 * Fetches the cache line that contains the fetch PC. Returns any 278 * fault that happened. Puts the data into the class variable 279 * fetchBuffer, which may not hold the entire fetched cache line. 280 * @param vaddr The memory address that is being fetched from. 281 * @param ret_fault The fault reference that will be set to the result of 282 * the icache access. 283 * @param tid Thread id. 284 * @param pc The actual PC of the current instruction. 285 * @return Any fault that occured. 286 */ 287 bool fetchCacheLine(Addr vaddr, ThreadID tid, Addr pc); 288 void finishTranslation(Fault fault, RequestPtr mem_req); 289 290 291 /** Check if an interrupt is pending and that we need to handle 292 */ 293 bool 294 checkInterrupt(Addr pc) 295 { 296 return (interruptPending && (THE_ISA != ALPHA_ISA || !(pc & 0x3))); 297 } 298 299 /** Squashes a specific thread and resets the PC. */ 300 inline void doSquash(const TheISA::PCState &newPC, 301 const DynInstPtr squashInst, ThreadID tid); 302 303 /** Squashes a specific thread and resets the PC. Also tells the CPU to 304 * remove any instructions between fetch and decode that should be sqaushed. 305 */ 306 void squashFromDecode(const TheISA::PCState &newPC, 307 const DynInstPtr squashInst, 308 const InstSeqNum seq_num, ThreadID tid); 309 310 /** Checks if a thread is stalled. */ 311 bool checkStall(ThreadID tid) const; 312 313 /** Updates overall fetch stage status; to be called at the end of each 314 * cycle. */ 315 FetchStatus updateFetchStatus(); 316 317 public: 318 /** Squashes a specific thread and resets the PC. Also tells the CPU to 319 * remove any instructions that are not in the ROB. The source of this 320 * squash should be the commit stage. 321 */ 322 void squash(const TheISA::PCState &newPC, const InstSeqNum seq_num, 323 DynInstPtr squashInst, ThreadID tid); 324 325 /** Ticks the fetch stage, processing all inputs signals and fetching 326 * as many instructions as possible. 327 */ 328 void tick(); 329 330 /** Checks all input signals and updates the status as necessary. 331 * @return: Returns if the status has changed due to input signals. 332 */ 333 bool checkSignalsAndUpdate(ThreadID tid); 334 335 /** Does the actual fetching of instructions and passing them on to the 336 * next stage. 337 * @param status_change fetch() sets this variable if there was a status 338 * change (ie switching to IcacheMissStall). 339 */ 340 void fetch(bool &status_change); 341 342 /** Align a PC to the start of a fetch buffer block. */ 343 Addr fetchBufferAlignPC(Addr addr) 344 { 345 return (addr & ~(fetchBufferMask)); 346 } 347 348 /** The decoder. */ 349 TheISA::Decoder *decoder[Impl::MaxThreads]; 350 351 private: 352 DynInstPtr buildInst(ThreadID tid, StaticInstPtr staticInst, 353 StaticInstPtr curMacroop, TheISA::PCState thisPC, 354 TheISA::PCState nextPC, bool trace); 355 356 /** Returns the appropriate thread to fetch, given the fetch policy. */ 357 ThreadID getFetchingThread(FetchPriority &fetch_priority); 358 359 /** Returns the appropriate thread to fetch using a round robin policy. */ 360 ThreadID roundRobin(); 361 362 /** Returns the appropriate thread to fetch using the IQ count policy. */ 363 ThreadID iqCount(); 364 365 /** Returns the appropriate thread to fetch using the LSQ count policy. */ 366 ThreadID lsqCount(); 367 368 /** Returns the appropriate thread to fetch using the branch count 369 * policy. */ 370 ThreadID branchCount(); 371 372 /** Pipeline the next I-cache access to the current one. */ 373 void pipelineIcacheAccesses(ThreadID tid); 374 375 /** Profile the reasons of fetch stall. */ 376 void profileStall(ThreadID tid); 377 378 private: 379 /** Pointer to the O3CPU. */ 380 O3CPU *cpu; 381 382 /** Time buffer interface. */ 383 TimeBuffer<TimeStruct> *timeBuffer; 384 385 /** Wire to get decode's information from backwards time buffer. */ 386 typename TimeBuffer<TimeStruct>::wire fromDecode; 387 388 /** Wire to get rename's information from backwards time buffer. */ 389 typename TimeBuffer<TimeStruct>::wire fromRename; 390 391 /** Wire to get iew's information from backwards time buffer. */ 392 typename TimeBuffer<TimeStruct>::wire fromIEW; 393 394 /** Wire to get commit's information from backwards time buffer. */ 395 typename TimeBuffer<TimeStruct>::wire fromCommit; 396 397 /** Internal fetch instruction queue. */ 398 TimeBuffer<FetchStruct> *fetchQueue; 399 400 //Might be annoying how this name is different than the queue. 401 /** Wire used to write any information heading to decode. */ 402 typename TimeBuffer<FetchStruct>::wire toDecode; 403 404 /** BPredUnit. */ 405 BPredUnit *branchPred; 406 407 TheISA::PCState pc[Impl::MaxThreads]; 408 409 Addr fetchOffset[Impl::MaxThreads]; 410 411 StaticInstPtr macroop[Impl::MaxThreads]; 412 413 /** Can the fetch stage redirect from an interrupt on this instruction? */ 414 bool delayedCommit[Impl::MaxThreads]; 415 416 /** Memory request used to access cache. */ 417 RequestPtr memReq[Impl::MaxThreads]; 418 419 /** Variable that tracks if fetch has written to the time buffer this 420 * cycle. Used to tell CPU if there is activity this cycle. 421 */ 422 bool wroteToTimeBuffer; 423 424 /** Tracks how many instructions has been fetched this cycle. */ 425 int numInst; 426 427 /** Source of possible stalls. */ 428 struct Stalls { 429 bool decode; 430 bool rename; 431 bool iew; 432 bool commit; 433 bool drain; 434 }; 435 436 /** Tracks which stages are telling fetch to stall. */ 437 Stalls stalls[Impl::MaxThreads]; 438 439 /** Decode to fetch delay. */ 440 Cycles decodeToFetchDelay; 441 442 /** Rename to fetch delay. */ 443 Cycles renameToFetchDelay; 444 445 /** IEW to fetch delay. */ 446 Cycles iewToFetchDelay; 447 448 /** Commit to fetch delay. */ 449 Cycles commitToFetchDelay; 450 451 /** The width of fetch in instructions. */ 452 unsigned fetchWidth; 453 454 /** Is the cache blocked? If so no threads can access it. */ 455 bool cacheBlocked; 456 457 /** The packet that is waiting to be retried. */ 458 PacketPtr retryPkt; 459 460 /** The thread that is waiting on the cache to tell fetch to retry. */ 461 ThreadID retryTid; 462 463 /** Cache block size. */ 464 unsigned int cacheBlkSize; 465 466 /** The size of the fetch buffer in bytes. The fetch buffer 467 * itself may be smaller than a cache line. 468 */ 469 unsigned fetchBufferSize; 470 471 /** Mask to align a fetch address to a fetch buffer boundary. */ 472 Addr fetchBufferMask; 473 474 /** The fetch data that is being fetched and buffered. */ 475 uint8_t *fetchBuffer[Impl::MaxThreads]; 476 477 /** The PC of the first instruction loaded into the fetch buffer. */ 478 Addr fetchBufferPC[Impl::MaxThreads]; 479 480 /** Whether or not the fetch buffer data is valid. */ 481 bool fetchBufferValid[Impl::MaxThreads]; 482 483 /** Size of instructions. */ 484 int instSize; 485 486 /** Icache stall statistics. */ 487 Counter lastIcacheStall[Impl::MaxThreads]; 488 489 /** List of Active Threads */ 490 std::list<ThreadID> *activeThreads; 491 492 /** Number of threads. */ 493 ThreadID numThreads; 494 495 /** Number of threads that are actively fetching. */ 496 ThreadID numFetchingThreads; 497 498 /** Thread ID being fetched. */ 499 ThreadID threadFetched; 500 501 /** Checks if there is an interrupt pending. If there is, fetch 502 * must stop once it is not fetching PAL instructions. 503 */ 504 bool interruptPending; 505 506 /** Set to true if a pipelined I-cache request should be issued. */ 507 bool issuePipelinedIfetch[Impl::MaxThreads]; 508 509 /** Event used to delay fault generation of translation faults */ 510 FinishTranslationEvent finishTranslationEvent; 511 512 // @todo: Consider making these vectors and tracking on a per thread basis. 513 /** Stat for total number of cycles stalled due to an icache miss. */ 514 Stats::Scalar icacheStallCycles; 515 /** Stat for total number of fetched instructions. */ 516 Stats::Scalar fetchedInsts; 517 /** Total number of fetched branches. */ 518 Stats::Scalar fetchedBranches; 519 /** Stat for total number of predicted branches. */ 520 Stats::Scalar predictedBranches; 521 /** Stat for total number of cycles spent fetching. */ 522 Stats::Scalar fetchCycles; 523 /** Stat for total number of cycles spent squashing. */ 524 Stats::Scalar fetchSquashCycles; 525 /** Stat for total number of cycles spent waiting for translation */ 526 Stats::Scalar fetchTlbCycles; 527 /** Stat for total number of cycles spent blocked due to other stages in 528 * the pipeline. 529 */ 530 Stats::Scalar fetchIdleCycles; 531 /** Total number of cycles spent blocked. */ 532 Stats::Scalar fetchBlockedCycles; 533 /** Total number of cycles spent in any other state. */ 534 Stats::Scalar fetchMiscStallCycles; 535 /** Total number of cycles spent in waiting for drains. */ 536 Stats::Scalar fetchPendingDrainCycles; 537 /** Total number of stall cycles caused by no active threads to run. */ 538 Stats::Scalar fetchNoActiveThreadStallCycles; 539 /** Total number of stall cycles caused by pending traps. */ 540 Stats::Scalar fetchPendingTrapStallCycles; 541 /** Total number of stall cycles caused by pending quiesce instructions. */ 542 Stats::Scalar fetchPendingQuiesceStallCycles; 543 /** Total number of stall cycles caused by I-cache wait retrys. */ 544 Stats::Scalar fetchIcacheWaitRetryStallCycles; 545 /** Stat for total number of fetched cache lines. */ 546 Stats::Scalar fetchedCacheLines; 547 /** Total number of outstanding icache accesses that were dropped 548 * due to a squash. 549 */ 550 Stats::Scalar fetchIcacheSquashes; 551 /** Total number of outstanding tlb accesses that were dropped 552 * due to a squash. 553 */ 554 Stats::Scalar fetchTlbSquashes; 555 /** Distribution of number of instructions fetched each cycle. */ 556 Stats::Distribution fetchNisnDist; 557 /** Rate of how often fetch was idle. */ 558 Stats::Formula idleRate; 559 /** Number of branch fetches per cycle. */ 560 Stats::Formula branchRate; 561 /** Number of instruction fetched per cycle. */ 562 Stats::Formula fetchRate; 563}; 564 565#endif //__CPU_O3_FETCH_HH__ 566