fetch.hh revision 6658
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_FETCH_HH__ 33#define __CPU_O3_FETCH_HH__ 34 35#include "arch/utility.hh" 36#include "arch/predecoder.hh" 37#include "base/statistics.hh" 38#include "base/timebuf.hh" 39#include "config/the_isa.hh" 40#include "cpu/pc_event.hh" 41#include "mem/packet.hh" 42#include "mem/port.hh" 43#include "sim/eventq.hh" 44 45class DerivO3CPUParams; 46 47/** 48 * DefaultFetch class handles both single threaded and SMT fetch. Its 49 * width is specified by the parameters; each cycle it tries to fetch 50 * that many instructions. It supports using a branch predictor to 51 * predict direction and targets. 52 * It supports the idling functionality of the CPU by indicating to 53 * the CPU when it is active and inactive. 54 */ 55template <class Impl> 56class DefaultFetch 57{ 58 public: 59 /** Typedefs from Impl. */ 60 typedef typename Impl::CPUPol CPUPol; 61 typedef typename Impl::DynInst DynInst; 62 typedef typename Impl::DynInstPtr DynInstPtr; 63 typedef typename Impl::O3CPU O3CPU; 64 65 /** Typedefs from the CPU policy. */ 66 typedef typename CPUPol::BPredUnit BPredUnit; 67 typedef typename CPUPol::FetchStruct FetchStruct; 68 typedef typename CPUPol::TimeStruct TimeStruct; 69 70 /** Typedefs from ISA. */ 71 typedef TheISA::MachInst MachInst; 72 typedef TheISA::ExtMachInst ExtMachInst; 73 74 /** IcachePort class for DefaultFetch. Handles doing the 75 * communication with the cache/memory. 76 */ 77 class IcachePort : public Port 78 { 79 protected: 80 /** Pointer to fetch. */ 81 DefaultFetch<Impl> *fetch; 82 83 public: 84 /** Default constructor. */ 85 IcachePort(DefaultFetch<Impl> *_fetch) 86 : Port(_fetch->name() + "-iport", _fetch->cpu), fetch(_fetch) 87 { } 88 89 bool snoopRangeSent; 90 91 virtual void setPeer(Port *port); 92 93 protected: 94 /** Atomic version of receive. Panics. */ 95 virtual Tick recvAtomic(PacketPtr pkt); 96 97 /** Functional version of receive. Panics. */ 98 virtual void recvFunctional(PacketPtr pkt); 99 100 /** Receives status change. Other than range changing, panics. */ 101 virtual void recvStatusChange(Status status); 102 103 /** Returns the address ranges of this device. */ 104 virtual void getDeviceAddressRanges(AddrRangeList &resp, 105 bool &snoop) 106 { resp.clear(); snoop = true; } 107 108 /** Timing version of receive. Handles setting fetch to the 109 * proper status to start fetching. */ 110 virtual bool recvTiming(PacketPtr pkt); 111 112 /** Handles doing a retry of a failed fetch. */ 113 virtual void recvRetry(); 114 }; 115 116 117 public: 118 /** Overall fetch status. Used to determine if the CPU can 119 * deschedule itsef due to a lack of activity. 120 */ 121 enum FetchStatus { 122 Active, 123 Inactive 124 }; 125 126 /** Individual thread status. */ 127 enum ThreadStatus { 128 Running, 129 Idle, 130 Squashing, 131 Blocked, 132 Fetching, 133 TrapPending, 134 QuiescePending, 135 SwitchOut, 136 IcacheWaitResponse, 137 IcacheWaitRetry, 138 IcacheAccessComplete 139 }; 140 141 /** Fetching Policy, Add new policies here.*/ 142 enum FetchPriority { 143 SingleThread, 144 RoundRobin, 145 Branch, 146 IQ, 147 LSQ 148 }; 149 150 private: 151 /** Fetch status. */ 152 FetchStatus _status; 153 154 /** Per-thread status. */ 155 ThreadStatus fetchStatus[Impl::MaxThreads]; 156 157 /** Fetch policy. */ 158 FetchPriority fetchPolicy; 159 160 /** List that has the threads organized by priority. */ 161 std::list<ThreadID> priorityList; 162 163 public: 164 /** DefaultFetch constructor. */ 165 DefaultFetch(O3CPU *_cpu, DerivO3CPUParams *params); 166 167 /** Returns the name of fetch. */ 168 std::string name() const; 169 170 /** Registers statistics. */ 171 void regStats(); 172 173 /** Returns the icache port. */ 174 Port *getIcachePort() { return icachePort; } 175 176 /** Sets the main backwards communication time buffer pointer. */ 177 void setTimeBuffer(TimeBuffer<TimeStruct> *time_buffer); 178 179 /** Sets pointer to list of active threads. */ 180 void setActiveThreads(std::list<ThreadID> *at_ptr); 181 182 /** Sets pointer to time buffer used to communicate to the next stage. */ 183 void setFetchQueue(TimeBuffer<FetchStruct> *fq_ptr); 184 185 /** Initialize stage. */ 186 void initStage(); 187 188 /** Tells the fetch stage that the Icache is set. */ 189 void setIcache(); 190 191 /** Processes cache completion event. */ 192 void processCacheCompletion(PacketPtr pkt); 193 194 /** Begins the drain of the fetch stage. */ 195 bool drain(); 196 197 /** Resumes execution after a drain. */ 198 void resume(); 199 200 /** Tells fetch stage to prepare to be switched out. */ 201 void switchOut(); 202 203 /** Takes over from another CPU's thread. */ 204 void takeOverFrom(); 205 206 /** Checks if the fetch stage is switched out. */ 207 bool isSwitchedOut() { return switchedOut; } 208 209 /** Tells fetch to wake up from a quiesce instruction. */ 210 void wakeFromQuiesce(); 211 212 private: 213 /** Changes the status of this stage to active, and indicates this 214 * to the CPU. 215 */ 216 inline void switchToActive(); 217 218 /** Changes the status of this stage to inactive, and indicates 219 * this to the CPU. 220 */ 221 inline void switchToInactive(); 222 223 /** 224 * Looks up in the branch predictor to see if the next PC should be 225 * either next PC+=MachInst or a branch target. 226 * @param next_PC Next PC variable passed in by reference. It is 227 * expected to be set to the current PC; it will be updated with what 228 * the next PC will be. 229 * @param next_NPC Used for ISAs which use delay slots. 230 * @return Whether or not a branch was predicted as taken. 231 */ 232 bool lookupAndUpdateNextPC(DynInstPtr &inst, Addr &next_PC, Addr &next_NPC, Addr &next_MicroPC); 233 234 /** 235 * Fetches the cache line that contains fetch_PC. Returns any 236 * fault that happened. Puts the data into the class variable 237 * cacheData. 238 * @param fetch_PC The PC address that is being fetched from. 239 * @param ret_fault The fault reference that will be set to the result of 240 * the icache access. 241 * @param tid Thread id. 242 * @return Any fault that occured. 243 */ 244 bool fetchCacheLine(Addr fetch_PC, Fault &ret_fault, ThreadID tid); 245 246 /** Squashes a specific thread and resets the PC. */ 247 inline void doSquash(const Addr &new_PC, const Addr &new_NPC, 248 const Addr &new_MicroPC, ThreadID tid); 249 250 /** Squashes a specific thread and resets the PC. Also tells the CPU to 251 * remove any instructions between fetch and decode that should be sqaushed. 252 */ 253 void squashFromDecode(const Addr &new_PC, const Addr &new_NPC, 254 const Addr &new_MicroPC, 255 const InstSeqNum &seq_num, ThreadID tid); 256 257 /** Checks if a thread is stalled. */ 258 bool checkStall(ThreadID tid) const; 259 260 /** Updates overall fetch stage status; to be called at the end of each 261 * cycle. */ 262 FetchStatus updateFetchStatus(); 263 264 public: 265 /** Squashes a specific thread and resets the PC. Also tells the CPU to 266 * remove any instructions that are not in the ROB. The source of this 267 * squash should be the commit stage. 268 */ 269 void squash(const Addr &new_PC, const Addr &new_NPC, 270 const Addr &new_MicroPC, 271 const InstSeqNum &seq_num, ThreadID tid); 272 273 /** Ticks the fetch stage, processing all inputs signals and fetching 274 * as many instructions as possible. 275 */ 276 void tick(); 277 278 /** Checks all input signals and updates the status as necessary. 279 * @return: Returns if the status has changed due to input signals. 280 */ 281 bool checkSignalsAndUpdate(ThreadID tid); 282 283 /** Does the actual fetching of instructions and passing them on to the 284 * next stage. 285 * @param status_change fetch() sets this variable if there was a status 286 * change (ie switching to IcacheMissStall). 287 */ 288 void fetch(bool &status_change); 289 290 /** Align a PC to the start of an I-cache block. */ 291 Addr icacheBlockAlignPC(Addr addr) 292 { 293 addr = TheISA::realPCToFetchPC(addr); 294 return (addr & ~(cacheBlkMask)); 295 } 296 297 private: 298 /** Handles retrying the fetch access. */ 299 void recvRetry(); 300 301 /** Returns the appropriate thread to fetch, given the fetch policy. */ 302 ThreadID getFetchingThread(FetchPriority &fetch_priority); 303 304 /** Returns the appropriate thread to fetch using a round robin policy. */ 305 ThreadID roundRobin(); 306 307 /** Returns the appropriate thread to fetch using the IQ count policy. */ 308 ThreadID iqCount(); 309 310 /** Returns the appropriate thread to fetch using the LSQ count policy. */ 311 ThreadID lsqCount(); 312 313 /** Returns the appropriate thread to fetch using the branch count 314 * policy. */ 315 ThreadID branchCount(); 316 317 private: 318 /** Pointer to the O3CPU. */ 319 O3CPU *cpu; 320 321 /** Time buffer interface. */ 322 TimeBuffer<TimeStruct> *timeBuffer; 323 324 /** Wire to get decode's information from backwards time buffer. */ 325 typename TimeBuffer<TimeStruct>::wire fromDecode; 326 327 /** Wire to get rename's information from backwards time buffer. */ 328 typename TimeBuffer<TimeStruct>::wire fromRename; 329 330 /** Wire to get iew's information from backwards time buffer. */ 331 typename TimeBuffer<TimeStruct>::wire fromIEW; 332 333 /** Wire to get commit's information from backwards time buffer. */ 334 typename TimeBuffer<TimeStruct>::wire fromCommit; 335 336 /** Internal fetch instruction queue. */ 337 TimeBuffer<FetchStruct> *fetchQueue; 338 339 //Might be annoying how this name is different than the queue. 340 /** Wire used to write any information heading to decode. */ 341 typename TimeBuffer<FetchStruct>::wire toDecode; 342 343 /** Icache interface. */ 344 IcachePort *icachePort; 345 346 /** BPredUnit. */ 347 BPredUnit branchPred; 348 349 /** Predecoder. */ 350 TheISA::Predecoder predecoder; 351 352 /** Per-thread fetch PC. */ 353 Addr PC[Impl::MaxThreads]; 354 355 /** Per-thread fetch micro PC. */ 356 Addr microPC[Impl::MaxThreads]; 357 358 /** Per-thread next PC. */ 359 Addr nextPC[Impl::MaxThreads]; 360 361 /** Memory request used to access cache. */ 362 RequestPtr memReq[Impl::MaxThreads]; 363 364 /** Variable that tracks if fetch has written to the time buffer this 365 * cycle. Used to tell CPU if there is activity this cycle. 366 */ 367 bool wroteToTimeBuffer; 368 369 /** Tracks how many instructions has been fetched this cycle. */ 370 int numInst; 371 372 /** Source of possible stalls. */ 373 struct Stalls { 374 bool decode; 375 bool rename; 376 bool iew; 377 bool commit; 378 }; 379 380 /** Tracks which stages are telling fetch to stall. */ 381 Stalls stalls[Impl::MaxThreads]; 382 383 /** Decode to fetch delay, in ticks. */ 384 unsigned decodeToFetchDelay; 385 386 /** Rename to fetch delay, in ticks. */ 387 unsigned renameToFetchDelay; 388 389 /** IEW to fetch delay, in ticks. */ 390 unsigned iewToFetchDelay; 391 392 /** Commit to fetch delay, in ticks. */ 393 unsigned commitToFetchDelay; 394 395 /** The width of fetch in instructions. */ 396 unsigned fetchWidth; 397 398 /** Is the cache blocked? If so no threads can access it. */ 399 bool cacheBlocked; 400 401 /** The packet that is waiting to be retried. */ 402 PacketPtr retryPkt; 403 404 /** The thread that is waiting on the cache to tell fetch to retry. */ 405 ThreadID retryTid; 406 407 /** Cache block size. */ 408 int cacheBlkSize; 409 410 /** Mask to get a cache block's address. */ 411 Addr cacheBlkMask; 412 413 /** The cache line being fetched. */ 414 uint8_t *cacheData[Impl::MaxThreads]; 415 416 /** The PC of the cacheline that has been loaded. */ 417 Addr cacheDataPC[Impl::MaxThreads]; 418 419 /** Whether or not the cache data is valid. */ 420 bool cacheDataValid[Impl::MaxThreads]; 421 422 /** Size of instructions. */ 423 int instSize; 424 425 /** Icache stall statistics. */ 426 Counter lastIcacheStall[Impl::MaxThreads]; 427 428 /** List of Active Threads */ 429 std::list<ThreadID> *activeThreads; 430 431 /** Number of threads. */ 432 ThreadID numThreads; 433 434 /** Number of threads that are actively fetching. */ 435 ThreadID numFetchingThreads; 436 437 /** Thread ID being fetched. */ 438 ThreadID threadFetched; 439 440 /** Checks if there is an interrupt pending. If there is, fetch 441 * must stop once it is not fetching PAL instructions. 442 */ 443 bool interruptPending; 444 445 /** Is there a drain pending. */ 446 bool drainPending; 447 448 /** Records if fetch is switched out. */ 449 bool switchedOut; 450 451 // @todo: Consider making these vectors and tracking on a per thread basis. 452 /** Stat for total number of cycles stalled due to an icache miss. */ 453 Stats::Scalar icacheStallCycles; 454 /** Stat for total number of fetched instructions. */ 455 Stats::Scalar fetchedInsts; 456 /** Total number of fetched branches. */ 457 Stats::Scalar fetchedBranches; 458 /** Stat for total number of predicted branches. */ 459 Stats::Scalar predictedBranches; 460 /** Stat for total number of cycles spent fetching. */ 461 Stats::Scalar fetchCycles; 462 /** Stat for total number of cycles spent squashing. */ 463 Stats::Scalar fetchSquashCycles; 464 /** Stat for total number of cycles spent blocked due to other stages in 465 * the pipeline. 466 */ 467 Stats::Scalar fetchIdleCycles; 468 /** Total number of cycles spent blocked. */ 469 Stats::Scalar fetchBlockedCycles; 470 /** Total number of cycles spent in any other state. */ 471 Stats::Scalar fetchMiscStallCycles; 472 /** Stat for total number of fetched cache lines. */ 473 Stats::Scalar fetchedCacheLines; 474 /** Total number of outstanding icache accesses that were dropped 475 * due to a squash. 476 */ 477 Stats::Scalar fetchIcacheSquashes; 478 /** Distribution of number of instructions fetched each cycle. */ 479 Stats::Distribution fetchNisnDist; 480 /** Rate of how often fetch was idle. */ 481 Stats::Formula idleRate; 482 /** Number of branch fetches per cycle. */ 483 Stats::Formula branchRate; 484 /** Number of instruction fetched per cycle. */ 485 Stats::Formula fetchRate; 486}; 487 488#endif //__CPU_O3_FETCH_HH__ 489