rename.hh revision 12104:edd63f9c6184
1/* 2 * Copyright (c) 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 * Copyright (c) 2013 Advanced Micro Devices, Inc. 16 * All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions are 20 * met: redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer; 22 * redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution; 25 * neither the name of the copyright holders nor the names of its 26 * contributors may be used to endorse or promote products derived from 27 * this software without specific prior written permission. 28 * 29 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 30 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 31 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 32 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 33 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 34 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 35 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 39 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 40 * 41 * Authors: Kevin Lim 42 */ 43 44#ifndef __CPU_O3_RENAME_HH__ 45#define __CPU_O3_RENAME_HH__ 46 47#include <list> 48#include <utility> 49 50#include "base/statistics.hh" 51#include "config/the_isa.hh" 52#include "cpu/timebuf.hh" 53#include "sim/probe/probe.hh" 54 55struct DerivO3CPUParams; 56 57/** 58 * DefaultRename handles both single threaded and SMT rename. Its 59 * width is specified by the parameters; each cycle it tries to rename 60 * that many instructions. It holds onto the rename history of all 61 * instructions with destination registers, storing the 62 * arch. register, the new physical register, and the old physical 63 * register, to allow for undoing of mappings if squashing happens, or 64 * freeing up registers upon commit. Rename handles blocking if the 65 * ROB, IQ, or LSQ is going to be full. Rename also handles barriers, 66 * and does so by stalling on the instruction until the ROB is empty 67 * and there are no instructions in flight to the ROB. 68 */ 69template<class Impl> 70class DefaultRename 71{ 72 public: 73 // Typedefs from the Impl. 74 typedef typename Impl::CPUPol CPUPol; 75 typedef typename Impl::DynInstPtr DynInstPtr; 76 typedef typename Impl::O3CPU O3CPU; 77 78 // Typedefs from the CPUPol 79 typedef typename CPUPol::DecodeStruct DecodeStruct; 80 typedef typename CPUPol::RenameStruct RenameStruct; 81 typedef typename CPUPol::TimeStruct TimeStruct; 82 typedef typename CPUPol::FreeList FreeList; 83 typedef typename CPUPol::RenameMap RenameMap; 84 // These are used only for initialization. 85 typedef typename CPUPol::IEW IEW; 86 typedef typename CPUPol::Commit Commit; 87 88 // A deque is used to queue the instructions. Barrier insts must 89 // be added to the front of the queue, which is the only reason for 90 // using a deque instead of a queue. (Most other stages use a 91 // queue) 92 typedef std::deque<DynInstPtr> InstQueue; 93 94 public: 95 /** Overall rename status. Used to determine if the CPU can 96 * deschedule itself due to a lack of activity. 97 */ 98 enum RenameStatus { 99 Active, 100 Inactive 101 }; 102 103 /** Individual thread status. */ 104 enum ThreadStatus { 105 Running, 106 Idle, 107 StartSquash, 108 Squashing, 109 Blocked, 110 Unblocking, 111 SerializeStall 112 }; 113 114 private: 115 /** Rename status. */ 116 RenameStatus _status; 117 118 /** Per-thread status. */ 119 ThreadStatus renameStatus[Impl::MaxThreads]; 120 121 /** Probe points. */ 122 typedef typename std::pair<InstSeqNum, short int> SeqNumRegPair; 123 /** To probe when register renaming for an instruction is complete */ 124 ProbePointArg<DynInstPtr> *ppRename; 125 /** 126 * To probe when an instruction is squashed and the register mapping 127 * for it needs to be undone 128 */ 129 ProbePointArg<SeqNumRegPair> *ppSquashInRename; 130 131 public: 132 /** DefaultRename constructor. */ 133 DefaultRename(O3CPU *_cpu, DerivO3CPUParams *params); 134 135 /** Returns the name of rename. */ 136 std::string name() const; 137 138 /** Registers statistics. */ 139 void regStats(); 140 141 /** Registers probes. */ 142 void regProbePoints(); 143 144 /** Sets the main backwards communication time buffer pointer. */ 145 void setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr); 146 147 /** Sets pointer to time buffer used to communicate to the next stage. */ 148 void setRenameQueue(TimeBuffer<RenameStruct> *rq_ptr); 149 150 /** Sets pointer to time buffer coming from decode. */ 151 void setDecodeQueue(TimeBuffer<DecodeStruct> *dq_ptr); 152 153 /** Sets pointer to IEW stage. Used only for initialization. */ 154 void setIEWStage(IEW *iew_stage) 155 { iew_ptr = iew_stage; } 156 157 /** Sets pointer to commit stage. Used only for initialization. */ 158 void setCommitStage(Commit *commit_stage) 159 { commit_ptr = commit_stage; } 160 161 private: 162 /** Pointer to IEW stage. Used only for initialization. */ 163 IEW *iew_ptr; 164 165 /** Pointer to commit stage. Used only for initialization. */ 166 Commit *commit_ptr; 167 168 public: 169 /** Initializes variables for the stage. */ 170 void startupStage(); 171 172 /** Sets pointer to list of active threads. */ 173 void setActiveThreads(std::list<ThreadID> *at_ptr); 174 175 /** Sets pointer to rename maps (per-thread structures). */ 176 void setRenameMap(RenameMap rm_ptr[Impl::MaxThreads]); 177 178 /** Sets pointer to the free list. */ 179 void setFreeList(FreeList *fl_ptr); 180 181 /** Sets pointer to the scoreboard. */ 182 void setScoreboard(Scoreboard *_scoreboard); 183 184 /** Perform sanity checks after a drain. */ 185 void drainSanityCheck() const; 186 187 /** Has the stage drained? */ 188 bool isDrained() const; 189 190 /** Takes over from another CPU's thread. */ 191 void takeOverFrom(); 192 193 /** Squashes all instructions in a thread. */ 194 void squash(const InstSeqNum &squash_seq_num, ThreadID tid); 195 196 /** Ticks rename, which processes all input signals and attempts to rename 197 * as many instructions as possible. 198 */ 199 void tick(); 200 201 /** Debugging function used to dump history buffer of renamings. */ 202 void dumpHistory(); 203 204 private: 205 /** Reset this pipeline stage */ 206 void resetStage(); 207 208 /** Determines what to do based on rename's current status. 209 * @param status_change rename() sets this variable if there was a status 210 * change (ie switching from blocking to unblocking). 211 * @param tid Thread id to rename instructions from. 212 */ 213 void rename(bool &status_change, ThreadID tid); 214 215 /** Renames instructions for the given thread. Also handles serializing 216 * instructions. 217 */ 218 void renameInsts(ThreadID tid); 219 220 /** Inserts unused instructions from a given thread into the skid buffer, 221 * to be renamed once rename unblocks. 222 */ 223 void skidInsert(ThreadID tid); 224 225 /** Separates instructions from decode into individual lists of instructions 226 * sorted by thread. 227 */ 228 void sortInsts(); 229 230 /** Returns if all of the skid buffers are empty. */ 231 bool skidsEmpty(); 232 233 /** Updates overall rename status based on all of the threads' statuses. */ 234 void updateStatus(); 235 236 /** Switches rename to blocking, and signals back that rename has become 237 * blocked. 238 * @return Returns true if there is a status change. 239 */ 240 bool block(ThreadID tid); 241 242 /** Switches rename to unblocking if the skid buffer is empty, and signals 243 * back that rename has unblocked. 244 * @return Returns true if there is a status change. 245 */ 246 bool unblock(ThreadID tid); 247 248 /** Executes actual squash, removing squashed instructions. */ 249 void doSquash(const InstSeqNum &squash_seq_num, ThreadID tid); 250 251 /** Removes a committed instruction's rename history. */ 252 void removeFromHistory(InstSeqNum inst_seq_num, ThreadID tid); 253 254 /** Renames the source registers of an instruction. */ 255 inline void renameSrcRegs(DynInstPtr &inst, ThreadID tid); 256 257 /** Renames the destination registers of an instruction. */ 258 inline void renameDestRegs(DynInstPtr &inst, ThreadID tid); 259 260 /** Calculates the number of free ROB entries for a specific thread. */ 261 inline int calcFreeROBEntries(ThreadID tid); 262 263 /** Calculates the number of free IQ entries for a specific thread. */ 264 inline int calcFreeIQEntries(ThreadID tid); 265 266 /** Calculates the number of free LQ entries for a specific thread. */ 267 inline int calcFreeLQEntries(ThreadID tid); 268 269 /** Calculates the number of free SQ entries for a specific thread. */ 270 inline int calcFreeSQEntries(ThreadID tid); 271 272 /** Returns the number of valid instructions coming from decode. */ 273 unsigned validInsts(); 274 275 /** Reads signals telling rename to block/unblock. */ 276 void readStallSignals(ThreadID tid); 277 278 /** Checks if any stages are telling rename to block. */ 279 bool checkStall(ThreadID tid); 280 281 /** Gets the number of free entries for a specific thread. */ 282 void readFreeEntries(ThreadID tid); 283 284 /** Checks the signals and updates the status. */ 285 bool checkSignalsAndUpdate(ThreadID tid); 286 287 /** Either serializes on the next instruction available in the InstQueue, 288 * or records that it must serialize on the next instruction to enter 289 * rename. 290 * @param inst_list The list of younger, unprocessed instructions for the 291 * thread that has the serializeAfter instruction. 292 * @param tid The thread id. 293 */ 294 void serializeAfter(InstQueue &inst_list, ThreadID tid); 295 296 /** Holds the information for each destination register rename. It holds 297 * the instruction's sequence number, the arch register, the old physical 298 * register for that arch. register, and the new physical register. 299 */ 300 struct RenameHistory { 301 RenameHistory(InstSeqNum _instSeqNum, RegId _archReg, 302 PhysRegIndex _newPhysReg, PhysRegIndex _prevPhysReg) 303 : instSeqNum(_instSeqNum), archReg(_archReg), 304 newPhysReg(_newPhysReg), prevPhysReg(_prevPhysReg) 305 { 306 } 307 308 /** The sequence number of the instruction that renamed. */ 309 InstSeqNum instSeqNum; 310 /** The architectural register index that was renamed. */ 311 RegId archReg; 312 /** The new physical register that the arch. register is renamed to. */ 313 PhysRegIndex newPhysReg; 314 /** The old physical register that the arch. register was renamed to. */ 315 PhysRegIndex prevPhysReg; 316 }; 317 318 /** A per-thread list of all destination register renames, used to either 319 * undo rename mappings or free old physical registers. 320 */ 321 std::list<RenameHistory> historyBuffer[Impl::MaxThreads]; 322 323 /** Pointer to CPU. */ 324 O3CPU *cpu; 325 326 /** Pointer to main time buffer used for backwards communication. */ 327 TimeBuffer<TimeStruct> *timeBuffer; 328 329 /** Wire to get IEW's output from backwards time buffer. */ 330 typename TimeBuffer<TimeStruct>::wire fromIEW; 331 332 /** Wire to get commit's output from backwards time buffer. */ 333 typename TimeBuffer<TimeStruct>::wire fromCommit; 334 335 /** Wire to write infromation heading to previous stages. */ 336 typename TimeBuffer<TimeStruct>::wire toDecode; 337 338 /** Rename instruction queue. */ 339 TimeBuffer<RenameStruct> *renameQueue; 340 341 /** Wire to write any information heading to IEW. */ 342 typename TimeBuffer<RenameStruct>::wire toIEW; 343 344 /** Decode instruction queue interface. */ 345 TimeBuffer<DecodeStruct> *decodeQueue; 346 347 /** Wire to get decode's output from decode queue. */ 348 typename TimeBuffer<DecodeStruct>::wire fromDecode; 349 350 /** Queue of all instructions coming from decode this cycle. */ 351 InstQueue insts[Impl::MaxThreads]; 352 353 /** Skid buffer between rename and decode. */ 354 InstQueue skidBuffer[Impl::MaxThreads]; 355 356 /** Rename map interface. */ 357 RenameMap *renameMap[Impl::MaxThreads]; 358 359 /** Free list interface. */ 360 FreeList *freeList; 361 362 /** Pointer to the list of active threads. */ 363 std::list<ThreadID> *activeThreads; 364 365 /** Pointer to the scoreboard. */ 366 Scoreboard *scoreboard; 367 368 /** Count of instructions in progress that have been sent off to the IQ 369 * and ROB, but are not yet included in their occupancy counts. 370 */ 371 int instsInProgress[Impl::MaxThreads]; 372 373 /** Count of Load instructions in progress that have been sent off to the IQ 374 * and ROB, but are not yet included in their occupancy counts. 375 */ 376 int loadsInProgress[Impl::MaxThreads]; 377 378 /** Count of Store instructions in progress that have been sent off to the IQ 379 * and ROB, but are not yet included in their occupancy counts. 380 */ 381 int storesInProgress[Impl::MaxThreads]; 382 383 /** Variable that tracks if decode has written to the time buffer this 384 * cycle. Used to tell CPU if there is activity this cycle. 385 */ 386 bool wroteToTimeBuffer; 387 388 /** Structures whose free entries impact the amount of instructions that 389 * can be renamed. 390 */ 391 struct FreeEntries { 392 unsigned iqEntries; 393 unsigned robEntries; 394 unsigned lqEntries; 395 unsigned sqEntries; 396 }; 397 398 /** Per-thread tracking of the number of free entries of back-end 399 * structures. 400 */ 401 FreeEntries freeEntries[Impl::MaxThreads]; 402 403 /** Records if the ROB is empty. In SMT mode the ROB may be dynamically 404 * partitioned between threads, so the ROB must tell rename when it is 405 * empty. 406 */ 407 bool emptyROB[Impl::MaxThreads]; 408 409 /** Source of possible stalls. */ 410 struct Stalls { 411 bool iew; 412 bool commit; 413 }; 414 415 /** Tracks which stages are telling decode to stall. */ 416 Stalls stalls[Impl::MaxThreads]; 417 418 /** The serialize instruction that rename has stalled on. */ 419 DynInstPtr serializeInst[Impl::MaxThreads]; 420 421 /** Records if rename needs to serialize on the next instruction for any 422 * thread. 423 */ 424 bool serializeOnNextInst[Impl::MaxThreads]; 425 426 /** Delay between iew and rename, in ticks. */ 427 int iewToRenameDelay; 428 429 /** Delay between decode and rename, in ticks. */ 430 int decodeToRenameDelay; 431 432 /** Delay between commit and rename, in ticks. */ 433 unsigned commitToRenameDelay; 434 435 /** Rename width, in instructions. */ 436 unsigned renameWidth; 437 438 /** Commit width, in instructions. Used so rename knows how many 439 * instructions might have freed registers in the previous cycle. 440 */ 441 unsigned commitWidth; 442 443 /** The index of the instruction in the time buffer to IEW that rename is 444 * currently using. 445 */ 446 unsigned toIEWIndex; 447 448 /** Whether or not rename needs to block this cycle. */ 449 bool blockThisCycle; 450 451 /** Whether or not rename needs to resume a serialize instruction 452 * after squashing. */ 453 bool resumeSerialize; 454 455 /** Whether or not rename needs to resume clearing out the skidbuffer 456 * after squashing. */ 457 bool resumeUnblocking; 458 459 /** The number of threads active in rename. */ 460 ThreadID numThreads; 461 462 /** The maximum skid buffer size. */ 463 unsigned skidBufferMax; 464 465 PhysRegIndex maxPhysicalRegs; 466 467 /** Enum to record the source of a structure full stall. Can come from 468 * either ROB, IQ, LSQ, and it is priortized in that order. 469 */ 470 enum FullSource { 471 ROB, 472 IQ, 473 LQ, 474 SQ, 475 NONE 476 }; 477 478 /** Function used to increment the stat that corresponds to the source of 479 * the stall. 480 */ 481 inline void incrFullStat(const FullSource &source); 482 483 /** Stat for total number of cycles spent squashing. */ 484 Stats::Scalar renameSquashCycles; 485 /** Stat for total number of cycles spent idle. */ 486 Stats::Scalar renameIdleCycles; 487 /** Stat for total number of cycles spent blocking. */ 488 Stats::Scalar renameBlockCycles; 489 /** Stat for total number of cycles spent stalling for a serializing inst. */ 490 Stats::Scalar renameSerializeStallCycles; 491 /** Stat for total number of cycles spent running normally. */ 492 Stats::Scalar renameRunCycles; 493 /** Stat for total number of cycles spent unblocking. */ 494 Stats::Scalar renameUnblockCycles; 495 /** Stat for total number of renamed instructions. */ 496 Stats::Scalar renameRenamedInsts; 497 /** Stat for total number of squashed instructions that rename discards. */ 498 Stats::Scalar renameSquashedInsts; 499 /** Stat for total number of times that the ROB starts a stall in rename. */ 500 Stats::Scalar renameROBFullEvents; 501 /** Stat for total number of times that the IQ starts a stall in rename. */ 502 Stats::Scalar renameIQFullEvents; 503 /** Stat for total number of times that the LQ starts a stall in rename. */ 504 Stats::Scalar renameLQFullEvents; 505 /** Stat for total number of times that the SQ starts a stall in rename. */ 506 Stats::Scalar renameSQFullEvents; 507 /** Stat for total number of times that rename runs out of free registers 508 * to use to rename. */ 509 Stats::Scalar renameFullRegistersEvents; 510 /** Stat for total number of renamed destination registers. */ 511 Stats::Scalar renameRenamedOperands; 512 /** Stat for total number of source register rename lookups. */ 513 Stats::Scalar renameRenameLookups; 514 Stats::Scalar intRenameLookups; 515 Stats::Scalar fpRenameLookups; 516 /** Stat for total number of committed renaming mappings. */ 517 Stats::Scalar renameCommittedMaps; 518 /** Stat for total number of mappings that were undone due to a squash. */ 519 Stats::Scalar renameUndoneMaps; 520 /** Number of serialize instructions handled. */ 521 Stats::Scalar renamedSerializing; 522 /** Number of instructions marked as temporarily serializing. */ 523 Stats::Scalar renamedTempSerializing; 524 /** Number of instructions inserted into skid buffers. */ 525 Stats::Scalar renameSkidInsts; 526}; 527 528#endif // __CPU_O3_RENAME_HH__ 529