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#include <list> 33 34#include "cpu/o3/rob.hh" 35#include "debug/Fetch.hh" 36#include "debug/ROB.hh" 37 38using namespace std; 39 40template <class Impl> 41ROB<Impl>::ROB(O3CPU *_cpu, unsigned _numEntries, unsigned _squashWidth, 42 std::string _smtROBPolicy, unsigned _smtROBThreshold, 43 ThreadID _numThreads) 44 : cpu(_cpu), 45 numEntries(_numEntries), 46 squashWidth(_squashWidth), 47 numInstsInROB(0), 48 numThreads(_numThreads) 49{ 50 for (ThreadID tid = 0; tid < numThreads; tid++) { 51 squashedSeqNum[tid] = 0; 52 doneSquashing[tid] = true; 53 threadEntries[tid] = 0; 54 } 55 56 std::string policy = _smtROBPolicy; 57 58 //Convert string to lowercase 59 std::transform(policy.begin(), policy.end(), policy.begin(), 60 (int(*)(int)) tolower); 61 62 //Figure out rob policy 63 if (policy == "dynamic") { 64 robPolicy = Dynamic; 65 66 //Set Max Entries to Total ROB Capacity 67 for (ThreadID tid = 0; tid < numThreads; tid++) { 68 maxEntries[tid] = numEntries; 69 } 70 71 } else if (policy == "partitioned") { 72 robPolicy = Partitioned; 73 DPRINTF(Fetch, "ROB sharing policy set to Partitioned\n"); 74 75 //@todo:make work if part_amt doesnt divide evenly. 76 int part_amt = numEntries / numThreads; 77 78 //Divide ROB up evenly 79 for (ThreadID tid = 0; tid < numThreads; tid++) { 80 maxEntries[tid] = part_amt; 81 } 82 83 } else if (policy == "threshold") { 84 robPolicy = Threshold; 85 DPRINTF(Fetch, "ROB sharing policy set to Threshold\n"); 86 87 int threshold = _smtROBThreshold;; 88 89 //Divide up by threshold amount 90 for (ThreadID tid = 0; tid < numThreads; tid++) { 91 maxEntries[tid] = threshold; 92 } 93 } else { 94 assert(0 && "Invalid ROB Sharing Policy.Options Are:{Dynamic," 95 "Partitioned, Threshold}"); 96 } 97 98 // Set the per-thread iterators to the end of the instruction list. 99 for (ThreadID tid = 0; tid < numThreads; tid++) { 100 squashIt[tid] = instList[tid].end(); 101 } 102 103 // Initialize the "universal" ROB head & tail point to invalid 104 // pointers 105 head = instList[0].end(); 106 tail = instList[0].end(); 107} 108 109template <class Impl> 110std::string 111ROB<Impl>::name() const 112{ 113 return cpu->name() + ".rob"; 114} 115 116template <class Impl> 117void 118ROB<Impl>::setActiveThreads(list<ThreadID> *at_ptr) 119{ 120 DPRINTF(ROB, "Setting active threads list pointer.\n"); 121 activeThreads = at_ptr; 122} 123 124template <class Impl> 125void 126ROB<Impl>::switchOut() 127{ 128 for (ThreadID tid = 0; tid < numThreads; tid++) { 129 instList[tid].clear(); 130 } 131} 132 133template <class Impl> 134void 135ROB<Impl>::takeOverFrom() 136{ 137 for (ThreadID tid = 0; tid < numThreads; tid++) { 138 doneSquashing[tid] = true; 139 threadEntries[tid] = 0; 140 squashIt[tid] = instList[tid].end(); 141 } 142 numInstsInROB = 0; 143 144 // Initialize the "universal" ROB head & tail point to invalid 145 // pointers 146 head = instList[0].end(); 147 tail = instList[0].end(); 148} 149 150template <class Impl> 151void 152ROB<Impl>::resetEntries() 153{ 154 if (robPolicy != Dynamic || numThreads > 1) { 155 int active_threads = activeThreads->size(); 156 157 list<ThreadID>::iterator threads = activeThreads->begin(); 158 list<ThreadID>::iterator end = activeThreads->end(); 159 160 while (threads != end) { 161 ThreadID tid = *threads++; 162 163 if (robPolicy == Partitioned) { 164 maxEntries[tid] = numEntries / active_threads; 165 } else if (robPolicy == Threshold && active_threads == 1) { 166 maxEntries[tid] = numEntries; 167 } 168 } 169 } 170} 171 172template <class Impl> 173int 174ROB<Impl>::entryAmount(ThreadID num_threads) 175{ 176 if (robPolicy == Partitioned) { 177 return numEntries / num_threads; 178 } else { 179 return 0; 180 } 181} 182 183template <class Impl> 184int 185ROB<Impl>::countInsts() 186{ 187 int total = 0; 188 189 for (ThreadID tid = 0; tid < numThreads; tid++) 190 total += countInsts(tid); 191 192 return total; 193} 194 195template <class Impl> 196int 197ROB<Impl>::countInsts(ThreadID tid) 198{ 199 return instList[tid].size(); 200} 201 202template <class Impl> 203void 204ROB<Impl>::insertInst(DynInstPtr &inst) 205{ 206 assert(inst); 207 208 robWrites++; 209 210 DPRINTF(ROB, "Adding inst PC %s to the ROB.\n", inst->pcState()); 211 212 assert(numInstsInROB != numEntries); 213 214 ThreadID tid = inst->threadNumber; 215 216 instList[tid].push_back(inst); 217 218 //Set Up head iterator if this is the 1st instruction in the ROB 219 if (numInstsInROB == 0) { 220 head = instList[tid].begin(); 221 assert((*head) == inst); 222 } 223 224 //Must Decrement for iterator to actually be valid since __.end() 225 //actually points to 1 after the last inst 226 tail = instList[tid].end(); 227 tail--; 228 229 inst->setInROB(); 230 231 ++numInstsInROB; 232 ++threadEntries[tid]; 233 234 assert((*tail) == inst); 235 236 DPRINTF(ROB, "[tid:%i] Now has %d instructions.\n", tid, threadEntries[tid]); 237} 238 239template <class Impl> 240void 241ROB<Impl>::retireHead(ThreadID tid) 242{ 243 robWrites++; 244 245 assert(numInstsInROB > 0); 246 247 // Get the head ROB instruction. 248 InstIt head_it = instList[tid].begin(); 249 250 DynInstPtr head_inst = (*head_it); 251 252 assert(head_inst->readyToCommit()); 253 254 DPRINTF(ROB, "[tid:%u]: Retiring head instruction, " 255 "instruction PC %s, [sn:%lli]\n", tid, head_inst->pcState(), 256 head_inst->seqNum); 257 258 --numInstsInROB; 259 --threadEntries[tid]; 260 261 head_inst->clearInROB(); 262 head_inst->setCommitted(); 263 264 instList[tid].erase(head_it); 265 266 //Update "Global" Head of ROB 267 updateHead(); 268 269 // @todo: A special case is needed if the instruction being 270 // retired is the only instruction in the ROB; otherwise the tail 271 // iterator will become invalidated. 272 cpu->removeFrontInst(head_inst); 273} 274 275template <class Impl> 276bool 277ROB<Impl>::isHeadReady(ThreadID tid) 278{ 279 robReads++; 280 if (threadEntries[tid] != 0) { 281 return instList[tid].front()->readyToCommit(); 282 } 283 284 return false; 285} 286 287template <class Impl> 288bool 289ROB<Impl>::canCommit() 290{ 291 //@todo: set ActiveThreads through ROB or CPU 292 list<ThreadID>::iterator threads = activeThreads->begin(); 293 list<ThreadID>::iterator end = activeThreads->end(); 294 295 while (threads != end) { 296 ThreadID tid = *threads++; 297 298 if (isHeadReady(tid)) { 299 return true; 300 } 301 } 302 303 return false; 304} 305 306template <class Impl> 307unsigned 308ROB<Impl>::numFreeEntries() 309{ 310 return numEntries - numInstsInROB; 311} 312 313template <class Impl> 314unsigned 315ROB<Impl>::numFreeEntries(ThreadID tid) 316{ 317 return maxEntries[tid] - threadEntries[tid]; 318} 319 320template <class Impl> 321void 322ROB<Impl>::doSquash(ThreadID tid) 323{ 324 robWrites++; 325 DPRINTF(ROB, "[tid:%u]: Squashing instructions until [sn:%i].\n", 326 tid, squashedSeqNum[tid]); 327 328 assert(squashIt[tid] != instList[tid].end()); 329 330 if ((*squashIt[tid])->seqNum < squashedSeqNum[tid]) { 331 DPRINTF(ROB, "[tid:%u]: Done squashing instructions.\n", 332 tid); 333 334 squashIt[tid] = instList[tid].end(); 335 336 doneSquashing[tid] = true; 337 return; 338 } 339 340 bool robTailUpdate = false; 341 342 for (int numSquashed = 0; 343 numSquashed < squashWidth && 344 squashIt[tid] != instList[tid].end() && 345 (*squashIt[tid])->seqNum > squashedSeqNum[tid]; 346 ++numSquashed) 347 { 348 DPRINTF(ROB, "[tid:%u]: Squashing instruction PC %s, seq num %i.\n", 349 (*squashIt[tid])->threadNumber, 350 (*squashIt[tid])->pcState(), 351 (*squashIt[tid])->seqNum); 352 353 // Mark the instruction as squashed, and ready to commit so that 354 // it can drain out of the pipeline. 355 (*squashIt[tid])->setSquashed(); 356 357 (*squashIt[tid])->setCanCommit(); 358 359 360 if (squashIt[tid] == instList[tid].begin()) { 361 DPRINTF(ROB, "Reached head of instruction list while " 362 "squashing.\n"); 363 364 squashIt[tid] = instList[tid].end(); 365 366 doneSquashing[tid] = true; 367 368 return; 369 } 370 371 InstIt tail_thread = instList[tid].end(); 372 tail_thread--; 373 374 if ((*squashIt[tid]) == (*tail_thread)) 375 robTailUpdate = true; 376 377 squashIt[tid]--; 378 } 379 380 381 // Check if ROB is done squashing. 382 if ((*squashIt[tid])->seqNum <= squashedSeqNum[tid]) { 383 DPRINTF(ROB, "[tid:%u]: Done squashing instructions.\n", 384 tid); 385 386 squashIt[tid] = instList[tid].end(); 387 388 doneSquashing[tid] = true; 389 } 390 391 if (robTailUpdate) { 392 updateTail(); 393 } 394} 395 396 397template <class Impl> 398void 399ROB<Impl>::updateHead() 400{ 401 DynInstPtr head_inst; 402 InstSeqNum lowest_num = 0; 403 bool first_valid = true; 404 405 // @todo: set ActiveThreads through ROB or CPU 406 list<ThreadID>::iterator threads = activeThreads->begin(); 407 list<ThreadID>::iterator end = activeThreads->end(); 408 409 while (threads != end) { 410 ThreadID tid = *threads++; 411 412 if (instList[tid].empty()) 413 continue; 414 415 if (first_valid) { 416 head = instList[tid].begin(); 417 lowest_num = (*head)->seqNum; 418 first_valid = false; 419 continue; 420 } 421 422 InstIt head_thread = instList[tid].begin(); 423 424 DynInstPtr head_inst = (*head_thread); 425 426 assert(head_inst != 0); 427 428 if (head_inst->seqNum < lowest_num) { 429 head = head_thread; 430 lowest_num = head_inst->seqNum; 431 } 432 } 433 434 if (first_valid) { 435 head = instList[0].end(); 436 } 437 438} 439 440template <class Impl> 441void 442ROB<Impl>::updateTail() 443{ 444 tail = instList[0].end(); 445 bool first_valid = true; 446 447 list<ThreadID>::iterator threads = activeThreads->begin(); 448 list<ThreadID>::iterator end = activeThreads->end(); 449 450 while (threads != end) { 451 ThreadID tid = *threads++; 452 453 if (instList[tid].empty()) { 454 continue; 455 } 456 457 // If this is the first valid then assign w/out 458 // comparison 459 if (first_valid) { 460 tail = instList[tid].end(); 461 tail--; 462 first_valid = false; 463 continue; 464 } 465 466 // Assign new tail if this thread's tail is younger 467 // than our current "tail high" 468 InstIt tail_thread = instList[tid].end(); 469 tail_thread--; 470 471 if ((*tail_thread)->seqNum > (*tail)->seqNum) { 472 tail = tail_thread; 473 } 474 } 475} 476 477 478template <class Impl> 479void 480ROB<Impl>::squash(InstSeqNum squash_num, ThreadID tid) 481{ 482 if (isEmpty()) { 483 DPRINTF(ROB, "Does not need to squash due to being empty " 484 "[sn:%i]\n", 485 squash_num); 486 487 return; 488 } 489 490 DPRINTF(ROB, "Starting to squash within the ROB.\n"); 491 492 robStatus[tid] = ROBSquashing; 493 494 doneSquashing[tid] = false; 495 496 squashedSeqNum[tid] = squash_num; 497 498 if (!instList[tid].empty()) { 499 InstIt tail_thread = instList[tid].end(); 500 tail_thread--; 501 502 squashIt[tid] = tail_thread; 503 504 doSquash(tid); 505 } 506} 507 508template <class Impl> 509typename Impl::DynInstPtr 510ROB<Impl>::readHeadInst(ThreadID tid) 511{ 512 if (threadEntries[tid] != 0) { 513 InstIt head_thread = instList[tid].begin(); 514 515 assert((*head_thread)->isInROB()==true); 516 517 return *head_thread; 518 } else { 519 return dummyInst; 520 } 521} 522 523template <class Impl> 524typename Impl::DynInstPtr 525ROB<Impl>::readTailInst(ThreadID tid) 526{ 527 InstIt tail_thread = instList[tid].end(); 528 tail_thread--; 529 530 return *tail_thread; 531} 532 533template <class Impl> 534void 535ROB<Impl>::regStats() 536{ 537 using namespace Stats; 538 robReads 539 .name(name() + ".rob_reads") 540 .desc("The number of ROB reads"); 541 542 robWrites 543 .name(name() + ".rob_writes") 544 .desc("The number of ROB writes"); 545} 546
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