inst_queue_impl.hh revision 2665:a124942bacb8
1/* 2 * Copyright (c) 2004-2005 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// Todo: 32// Current ordering allows for 0 cycle added-to-scheduled. Could maybe fake 33// it; either do in reverse order, or have added instructions put into a 34// different ready queue that, in scheduleRreadyInsts(), gets put onto the 35// normal ready queue. This would however give only a one cycle delay, 36// but probably is more flexible to actually add in a delay parameter than 37// just running it backwards. 38 39#include <limits> 40#include <vector> 41 42#include "sim/root.hh" 43 44#include "cpu/o3/inst_queue.hh" 45 46// Either compile error or max int due to sign extension. 47// Hack to avoid compile warnings. 48const InstSeqNum MaxInstSeqNum = std::numeric_limits<InstSeqNum>::max(); 49 50template <class Impl> 51InstructionQueue<Impl>::InstructionQueue(Params ¶ms) 52 : memDepUnit(params), 53 numEntries(params.numIQEntries), 54 intWidth(params.executeIntWidth), 55 floatWidth(params.executeFloatWidth), 56 branchWidth(params.executeBranchWidth), 57 memoryWidth(params.executeMemoryWidth), 58 totalWidth(params.issueWidth), 59 numPhysIntRegs(params.numPhysIntRegs), 60 numPhysFloatRegs(params.numPhysFloatRegs), 61 commitToIEWDelay(params.commitToIEWDelay) 62{ 63 // Initialize the number of free IQ entries. 64 freeEntries = numEntries; 65 66 // Set the number of physical registers as the number of int + float 67 numPhysRegs = numPhysIntRegs + numPhysFloatRegs; 68 69 DPRINTF(IQ, "IQ: There are %i physical registers.\n", numPhysRegs); 70 71 //Create an entry for each physical register within the 72 //dependency graph. 73 dependGraph = new DependencyEntry[numPhysRegs]; 74 75 // Resize the register scoreboard. 76 regScoreboard.resize(numPhysRegs); 77 78 // Initialize all the head pointers to point to NULL, and all the 79 // entries as unready. 80 // Note that in actuality, the registers corresponding to the logical 81 // registers start off as ready. However this doesn't matter for the 82 // IQ as the instruction should have been correctly told if those 83 // registers are ready in rename. Thus it can all be initialized as 84 // unready. 85 for (int i = 0; i < numPhysRegs; ++i) 86 { 87 dependGraph[i].next = NULL; 88 dependGraph[i].inst = NULL; 89 regScoreboard[i] = false; 90 } 91 92} 93 94template <class Impl> 95void 96InstructionQueue<Impl>::regStats() 97{ 98 iqInstsAdded 99 .name(name() + ".iqInstsAdded") 100 .desc("Number of instructions added to the IQ (excludes non-spec)") 101 .prereq(iqInstsAdded); 102 103 iqNonSpecInstsAdded 104 .name(name() + ".iqNonSpecInstsAdded") 105 .desc("Number of non-speculative instructions added to the IQ") 106 .prereq(iqNonSpecInstsAdded); 107 108// iqIntInstsAdded; 109 110 iqIntInstsIssued 111 .name(name() + ".iqIntInstsIssued") 112 .desc("Number of integer instructions issued") 113 .prereq(iqIntInstsIssued); 114 115// iqFloatInstsAdded; 116 117 iqFloatInstsIssued 118 .name(name() + ".iqFloatInstsIssued") 119 .desc("Number of float instructions issued") 120 .prereq(iqFloatInstsIssued); 121 122// iqBranchInstsAdded; 123 124 iqBranchInstsIssued 125 .name(name() + ".iqBranchInstsIssued") 126 .desc("Number of branch instructions issued") 127 .prereq(iqBranchInstsIssued); 128 129// iqMemInstsAdded; 130 131 iqMemInstsIssued 132 .name(name() + ".iqMemInstsIssued") 133 .desc("Number of memory instructions issued") 134 .prereq(iqMemInstsIssued); 135 136// iqMiscInstsAdded; 137 138 iqMiscInstsIssued 139 .name(name() + ".iqMiscInstsIssued") 140 .desc("Number of miscellaneous instructions issued") 141 .prereq(iqMiscInstsIssued); 142 143 iqSquashedInstsIssued 144 .name(name() + ".iqSquashedInstsIssued") 145 .desc("Number of squashed instructions issued") 146 .prereq(iqSquashedInstsIssued); 147 148 iqLoopSquashStalls 149 .name(name() + ".iqLoopSquashStalls") 150 .desc("Number of times issue loop had to restart due to squashed " 151 "inst; mainly for profiling") 152 .prereq(iqLoopSquashStalls); 153 154 iqSquashedInstsExamined 155 .name(name() + ".iqSquashedInstsExamined") 156 .desc("Number of squashed instructions iterated over during squash;" 157 " mainly for profiling") 158 .prereq(iqSquashedInstsExamined); 159 160 iqSquashedOperandsExamined 161 .name(name() + ".iqSquashedOperandsExamined") 162 .desc("Number of squashed operands that are examined and possibly " 163 "removed from graph") 164 .prereq(iqSquashedOperandsExamined); 165 166 iqSquashedNonSpecRemoved 167 .name(name() + ".iqSquashedNonSpecRemoved") 168 .desc("Number of squashed non-spec instructions that were removed") 169 .prereq(iqSquashedNonSpecRemoved); 170 171 // Tell mem dependence unit to reg stats as well. 172 memDepUnit.regStats(); 173} 174 175template <class Impl> 176void 177InstructionQueue<Impl>::setCPU(FullCPU *cpu_ptr) 178{ 179 cpu = cpu_ptr; 180 181 tail = cpu->instList.begin(); 182} 183 184template <class Impl> 185void 186InstructionQueue<Impl>::setIssueToExecuteQueue( 187 TimeBuffer<IssueStruct> *i2e_ptr) 188{ 189 DPRINTF(IQ, "IQ: Set the issue to execute queue.\n"); 190 issueToExecuteQueue = i2e_ptr; 191} 192 193template <class Impl> 194void 195InstructionQueue<Impl>::setTimeBuffer(TimeBuffer<TimeStruct> *tb_ptr) 196{ 197 DPRINTF(IQ, "IQ: Set the time buffer.\n"); 198 timeBuffer = tb_ptr; 199 200 fromCommit = timeBuffer->getWire(-commitToIEWDelay); 201} 202 203template <class Impl> 204unsigned 205InstructionQueue<Impl>::numFreeEntries() 206{ 207 return freeEntries; 208} 209 210// Might want to do something more complex if it knows how many instructions 211// will be issued this cycle. 212template <class Impl> 213bool 214InstructionQueue<Impl>::isFull() 215{ 216 if (freeEntries == 0) { 217 return(true); 218 } else { 219 return(false); 220 } 221} 222 223template <class Impl> 224void 225InstructionQueue<Impl>::insert(DynInstPtr &new_inst) 226{ 227 // Make sure the instruction is valid 228 assert(new_inst); 229 230 DPRINTF(IQ, "IQ: Adding instruction PC %#x to the IQ.\n", 231 new_inst->readPC()); 232 233 // Check if there are any free entries. Panic if there are none. 234 // Might want to have this return a fault in the future instead of 235 // panicing. 236 assert(freeEntries != 0); 237 238 // If the IQ currently has nothing in it, then there's a possibility 239 // that the tail iterator is invalid (might have been pointing at an 240 // instruction that was retired). Reset the tail iterator. 241 if (freeEntries == numEntries) { 242 tail = cpu->instList.begin(); 243 } 244 245 // Move the tail iterator. Instructions may not have been issued 246 // to the IQ, so we may have to increment the iterator more than once. 247 while ((*tail) != new_inst) { 248 tail++; 249 250 // Make sure the tail iterator points at something legal. 251 assert(tail != cpu->instList.end()); 252 } 253 254 255 // Decrease the number of free entries. 256 --freeEntries; 257 258 // Look through its source registers (physical regs), and mark any 259 // dependencies. 260 addToDependents(new_inst); 261 262 // Have this instruction set itself as the producer of its destination 263 // register(s). 264 createDependency(new_inst); 265 266 // If it's a memory instruction, add it to the memory dependency 267 // unit. 268 if (new_inst->isMemRef()) { 269 memDepUnit.insert(new_inst); 270 // Uh..forgot to look it up and put it on the proper dependency list 271 // if the instruction should not go yet. 272 } else { 273 // If the instruction is ready then add it to the ready list. 274 addIfReady(new_inst); 275 } 276 277 ++iqInstsAdded; 278 279 assert(freeEntries == (numEntries - countInsts())); 280} 281 282template <class Impl> 283void 284InstructionQueue<Impl>::insertNonSpec(DynInstPtr &inst) 285{ 286 nonSpecInsts[inst->seqNum] = inst; 287 288 // @todo: Clean up this code; can do it by setting inst as unable 289 // to issue, then calling normal insert on the inst. 290 291 // Make sure the instruction is valid 292 assert(inst); 293 294 DPRINTF(IQ, "IQ: Adding instruction PC %#x to the IQ.\n", 295 inst->readPC()); 296 297 // Check if there are any free entries. Panic if there are none. 298 // Might want to have this return a fault in the future instead of 299 // panicing. 300 assert(freeEntries != 0); 301 302 // If the IQ currently has nothing in it, then there's a possibility 303 // that the tail iterator is invalid (might have been pointing at an 304 // instruction that was retired). Reset the tail iterator. 305 if (freeEntries == numEntries) { 306 tail = cpu->instList.begin(); 307 } 308 309 // Move the tail iterator. Instructions may not have been issued 310 // to the IQ, so we may have to increment the iterator more than once. 311 while ((*tail) != inst) { 312 tail++; 313 314 // Make sure the tail iterator points at something legal. 315 assert(tail != cpu->instList.end()); 316 } 317 318 // Decrease the number of free entries. 319 --freeEntries; 320 321 // Have this instruction set itself as the producer of its destination 322 // register(s). 323 createDependency(inst); 324 325 // If it's a memory instruction, add it to the memory dependency 326 // unit. 327 if (inst->isMemRef()) { 328 memDepUnit.insertNonSpec(inst); 329 } 330 331 ++iqNonSpecInstsAdded; 332} 333 334// Slightly hack function to advance the tail iterator in the case that 335// the IEW stage issues an instruction that is not added to the IQ. This 336// is needed in case a long chain of such instructions occurs. 337// I don't think this is used anymore. 338template <class Impl> 339void 340InstructionQueue<Impl>::advanceTail(DynInstPtr &inst) 341{ 342 // Make sure the instruction is valid 343 assert(inst); 344 345 DPRINTF(IQ, "IQ: Adding instruction PC %#x to the IQ.\n", 346 inst->readPC()); 347 348 // Check if there are any free entries. Panic if there are none. 349 // Might want to have this return a fault in the future instead of 350 // panicing. 351 assert(freeEntries != 0); 352 353 // If the IQ currently has nothing in it, then there's a possibility 354 // that the tail iterator is invalid (might have been pointing at an 355 // instruction that was retired). Reset the tail iterator. 356 if (freeEntries == numEntries) { 357 tail = cpu->instList.begin(); 358 } 359 360 // Move the tail iterator. Instructions may not have been issued 361 // to the IQ, so we may have to increment the iterator more than once. 362 while ((*tail) != inst) { 363 tail++; 364 365 // Make sure the tail iterator points at something legal. 366 assert(tail != cpu->instList.end()); 367 } 368 369 assert(freeEntries <= numEntries); 370 371 // Have this instruction set itself as the producer of its destination 372 // register(s). 373 createDependency(inst); 374} 375 376// Need to make sure the number of float and integer instructions 377// issued does not exceed the total issue bandwidth. 378// @todo: Figure out a better way to remove the squashed items from the 379// lists. Checking the top item of each list to see if it's squashed 380// wastes time and forces jumps. 381template <class Impl> 382void 383InstructionQueue<Impl>::scheduleReadyInsts() 384{ 385 DPRINTF(IQ, "IQ: Attempting to schedule ready instructions from " 386 "the IQ.\n"); 387 388 int int_issued = 0; 389 int float_issued = 0; 390 int branch_issued = 0; 391 int memory_issued = 0; 392 int squashed_issued = 0; 393 int total_issued = 0; 394 395 IssueStruct *i2e_info = issueToExecuteQueue->access(0); 396 397 bool insts_available = !readyBranchInsts.empty() || 398 !readyIntInsts.empty() || 399 !readyFloatInsts.empty() || 400 !memDepUnit.empty() || 401 !readyMiscInsts.empty() || 402 !squashedInsts.empty(); 403 404 // Note: Requires a globally defined constant. 405 InstSeqNum oldest_inst = MaxInstSeqNum; 406 InstList list_with_oldest = None; 407 408 // Temporary values. 409 DynInstPtr int_head_inst; 410 DynInstPtr float_head_inst; 411 DynInstPtr branch_head_inst; 412 DynInstPtr mem_head_inst; 413 DynInstPtr misc_head_inst; 414 DynInstPtr squashed_head_inst; 415 416 // Somewhat nasty code to look at all of the lists where issuable 417 // instructions are located, and choose the oldest instruction among 418 // those lists. Consider a rewrite in the future. 419 while (insts_available && total_issued < totalWidth) 420 { 421 // Set this to false. Each if-block is required to set it to true 422 // if there were instructions available this check. This will cause 423 // this loop to run once more than necessary, but avoids extra calls. 424 insts_available = false; 425 426 oldest_inst = MaxInstSeqNum; 427 428 list_with_oldest = None; 429 430 if (!readyIntInsts.empty() && 431 int_issued < intWidth) { 432 433 insts_available = true; 434 435 int_head_inst = readyIntInsts.top(); 436 437 if (int_head_inst->isSquashed()) { 438 readyIntInsts.pop(); 439 440 ++iqLoopSquashStalls; 441 442 continue; 443 } 444 445 oldest_inst = int_head_inst->seqNum; 446 447 list_with_oldest = Int; 448 } 449 450 if (!readyFloatInsts.empty() && 451 float_issued < floatWidth) { 452 453 insts_available = true; 454 455 float_head_inst = readyFloatInsts.top(); 456 457 if (float_head_inst->isSquashed()) { 458 readyFloatInsts.pop(); 459 460 ++iqLoopSquashStalls; 461 462 continue; 463 } else if (float_head_inst->seqNum < oldest_inst) { 464 oldest_inst = float_head_inst->seqNum; 465 466 list_with_oldest = Float; 467 } 468 } 469 470 if (!readyBranchInsts.empty() && 471 branch_issued < branchWidth) { 472 473 insts_available = true; 474 475 branch_head_inst = readyBranchInsts.top(); 476 477 if (branch_head_inst->isSquashed()) { 478 readyBranchInsts.pop(); 479 480 ++iqLoopSquashStalls; 481 482 continue; 483 } else if (branch_head_inst->seqNum < oldest_inst) { 484 oldest_inst = branch_head_inst->seqNum; 485 486 list_with_oldest = Branch; 487 } 488 489 } 490 491 if (!memDepUnit.empty() && 492 memory_issued < memoryWidth) { 493 494 insts_available = true; 495 496 mem_head_inst = memDepUnit.top(); 497 498 if (mem_head_inst->isSquashed()) { 499 memDepUnit.pop(); 500 501 ++iqLoopSquashStalls; 502 503 continue; 504 } else if (mem_head_inst->seqNum < oldest_inst) { 505 oldest_inst = mem_head_inst->seqNum; 506 507 list_with_oldest = Memory; 508 } 509 } 510 511 if (!readyMiscInsts.empty()) { 512 513 insts_available = true; 514 515 misc_head_inst = readyMiscInsts.top(); 516 517 if (misc_head_inst->isSquashed()) { 518 readyMiscInsts.pop(); 519 520 ++iqLoopSquashStalls; 521 522 continue; 523 } else if (misc_head_inst->seqNum < oldest_inst) { 524 oldest_inst = misc_head_inst->seqNum; 525 526 list_with_oldest = Misc; 527 } 528 } 529 530 if (!squashedInsts.empty()) { 531 532 insts_available = true; 533 534 squashed_head_inst = squashedInsts.top(); 535 536 if (squashed_head_inst->seqNum < oldest_inst) { 537 list_with_oldest = Squashed; 538 } 539 540 } 541 542 DynInstPtr issuing_inst = NULL; 543 544 switch (list_with_oldest) { 545 case None: 546 DPRINTF(IQ, "IQ: Not able to schedule any instructions. Issuing " 547 "inst is %#x.\n", issuing_inst); 548 break; 549 550 case Int: 551 issuing_inst = int_head_inst; 552 readyIntInsts.pop(); 553 ++int_issued; 554 DPRINTF(IQ, "IQ: Issuing integer instruction PC %#x.\n", 555 issuing_inst->readPC()); 556 break; 557 558 case Float: 559 issuing_inst = float_head_inst; 560 readyFloatInsts.pop(); 561 ++float_issued; 562 DPRINTF(IQ, "IQ: Issuing float instruction PC %#x.\n", 563 issuing_inst->readPC()); 564 break; 565 566 case Branch: 567 issuing_inst = branch_head_inst; 568 readyBranchInsts.pop(); 569 ++branch_issued; 570 DPRINTF(IQ, "IQ: Issuing branch instruction PC %#x.\n", 571 issuing_inst->readPC()); 572 break; 573 574 case Memory: 575 issuing_inst = mem_head_inst; 576 577 memDepUnit.pop(); 578 ++memory_issued; 579 DPRINTF(IQ, "IQ: Issuing memory instruction PC %#x.\n", 580 issuing_inst->readPC()); 581 break; 582 583 case Misc: 584 issuing_inst = misc_head_inst; 585 readyMiscInsts.pop(); 586 587 ++iqMiscInstsIssued; 588 589 DPRINTF(IQ, "IQ: Issuing a miscellaneous instruction PC %#x.\n", 590 issuing_inst->readPC()); 591 break; 592 593 case Squashed: 594 assert(0 && "Squashed insts should not issue any more!"); 595 squashedInsts.pop(); 596 // Set the squashed instruction as able to commit so that commit 597 // can just drop it from the ROB. This is a bit faked. 598 ++squashed_issued; 599 ++freeEntries; 600 601 DPRINTF(IQ, "IQ: Issuing squashed instruction PC %#x.\n", 602 squashed_head_inst->readPC()); 603 break; 604 } 605 606 if (list_with_oldest != None && list_with_oldest != Squashed) { 607 i2e_info->insts[total_issued] = issuing_inst; 608 i2e_info->size++; 609 610 issuing_inst->setIssued(); 611 612 ++freeEntries; 613 ++total_issued; 614 } 615 616 assert(freeEntries == (numEntries - countInsts())); 617 } 618 619 iqIntInstsIssued += int_issued; 620 iqFloatInstsIssued += float_issued; 621 iqBranchInstsIssued += branch_issued; 622 iqMemInstsIssued += memory_issued; 623 iqSquashedInstsIssued += squashed_issued; 624} 625 626template <class Impl> 627void 628InstructionQueue<Impl>::scheduleNonSpec(const InstSeqNum &inst) 629{ 630 DPRINTF(IQ, "IQ: Marking nonspeculative instruction with sequence " 631 "number %i as ready to execute.\n", inst); 632 633 non_spec_it_t inst_it = nonSpecInsts.find(inst); 634 635 assert(inst_it != nonSpecInsts.end()); 636 637 // Mark this instruction as ready to issue. 638 (*inst_it).second->setCanIssue(); 639 640 // Now schedule the instruction. 641 if (!(*inst_it).second->isMemRef()) { 642 addIfReady((*inst_it).second); 643 } else { 644 memDepUnit.nonSpecInstReady((*inst_it).second); 645 } 646 647 nonSpecInsts.erase(inst_it); 648} 649 650template <class Impl> 651void 652InstructionQueue<Impl>::wakeDependents(DynInstPtr &completed_inst) 653{ 654 DPRINTF(IQ, "IQ: Waking dependents of completed instruction.\n"); 655 //Look at the physical destination register of the DynInst 656 //and look it up on the dependency graph. Then mark as ready 657 //any instructions within the instruction queue. 658 DependencyEntry *curr; 659 660 // Tell the memory dependence unit to wake any dependents on this 661 // instruction if it is a memory instruction. 662 663 if (completed_inst->isMemRef()) { 664 memDepUnit.wakeDependents(completed_inst); 665 } 666 667 for (int dest_reg_idx = 0; 668 dest_reg_idx < completed_inst->numDestRegs(); 669 dest_reg_idx++) 670 { 671 PhysRegIndex dest_reg = 672 completed_inst->renamedDestRegIdx(dest_reg_idx); 673 674 // Special case of uniq or control registers. They are not 675 // handled by the IQ and thus have no dependency graph entry. 676 // @todo Figure out a cleaner way to handle this. 677 if (dest_reg >= numPhysRegs) { 678 continue; 679 } 680 681 DPRINTF(IQ, "IQ: Waking any dependents on register %i.\n", 682 (int) dest_reg); 683 684 //Maybe abstract this part into a function. 685 //Go through the dependency chain, marking the registers as ready 686 //within the waiting instructions. 687 while (dependGraph[dest_reg].next) { 688 689 curr = dependGraph[dest_reg].next; 690 691 DPRINTF(IQ, "IQ: Waking up a dependent instruction, PC%#x.\n", 692 curr->inst->readPC()); 693 694 // Might want to give more information to the instruction 695 // so that it knows which of its source registers is ready. 696 // However that would mean that the dependency graph entries 697 // would need to hold the src_reg_idx. 698 curr->inst->markSrcRegReady(); 699 700 addIfReady(curr->inst); 701 702 dependGraph[dest_reg].next = curr->next; 703 704 DependencyEntry::mem_alloc_counter--; 705 706 curr->inst = NULL; 707 708 delete curr; 709 } 710 711 // Reset the head node now that all of its dependents have been woken 712 // up. 713 dependGraph[dest_reg].next = NULL; 714 dependGraph[dest_reg].inst = NULL; 715 716 // Mark the scoreboard as having that register ready. 717 regScoreboard[dest_reg] = true; 718 } 719} 720 721template <class Impl> 722void 723InstructionQueue<Impl>::violation(DynInstPtr &store, 724 DynInstPtr &faulting_load) 725{ 726 memDepUnit.violation(store, faulting_load); 727} 728 729template <class Impl> 730void 731InstructionQueue<Impl>::squash() 732{ 733 DPRINTF(IQ, "IQ: Starting to squash instructions in the IQ.\n"); 734 735 // Read instruction sequence number of last instruction out of the 736 // time buffer. 737 squashedSeqNum = fromCommit->commitInfo.doneSeqNum; 738 739 // Setup the squash iterator to point to the tail. 740 squashIt = tail; 741 742 // Call doSquash if there are insts in the IQ 743 if (freeEntries != numEntries) { 744 doSquash(); 745 } 746 747 // Also tell the memory dependence unit to squash. 748 memDepUnit.squash(squashedSeqNum); 749} 750 751template <class Impl> 752void 753InstructionQueue<Impl>::doSquash() 754{ 755 // Make sure the squash iterator isn't pointing to nothing. 756 assert(squashIt != cpu->instList.end()); 757 // Make sure the squashed sequence number is valid. 758 assert(squashedSeqNum != 0); 759 760 DPRINTF(IQ, "IQ: Squashing instructions in the IQ.\n"); 761 762 // Squash any instructions younger than the squashed sequence number 763 // given. 764 while ((*squashIt)->seqNum > squashedSeqNum) { 765 DynInstPtr squashed_inst = (*squashIt); 766 767 // Only handle the instruction if it actually is in the IQ and 768 // hasn't already been squashed in the IQ. 769 if (!squashed_inst->isIssued() && 770 !squashed_inst->isSquashedInIQ()) { 771 772 // Remove the instruction from the dependency list. 773 // Hack for now: These below don't add themselves to the 774 // dependency list, so don't try to remove them. 775 if (!squashed_inst->isNonSpeculative()/* && 776 !squashed_inst->isStore()*/ 777 ) { 778 779 for (int src_reg_idx = 0; 780 src_reg_idx < squashed_inst->numSrcRegs(); 781 src_reg_idx++) 782 { 783 PhysRegIndex src_reg = 784 squashed_inst->renamedSrcRegIdx(src_reg_idx); 785 786 // Only remove it from the dependency graph if it was 787 // placed there in the first place. 788 // HACK: This assumes that instructions woken up from the 789 // dependency chain aren't informed that a specific src 790 // register has become ready. This may not always be true 791 // in the future. 792 if (!squashed_inst->isReadySrcRegIdx(src_reg_idx) && 793 src_reg < numPhysRegs) { 794 dependGraph[src_reg].remove(squashed_inst); 795 } 796 797 ++iqSquashedOperandsExamined; 798 } 799 800 // Might want to remove producers as well. 801 } else { 802 nonSpecInsts[squashed_inst->seqNum] = NULL; 803 804 nonSpecInsts.erase(squashed_inst->seqNum); 805 806 ++iqSquashedNonSpecRemoved; 807 } 808 809 // Might want to also clear out the head of the dependency graph. 810 811 // Mark it as squashed within the IQ. 812 squashed_inst->setSquashedInIQ(); 813 814// squashedInsts.push(squashed_inst); 815 squashed_inst->setIssued(); 816 squashed_inst->setCanCommit(); 817 818 ++freeEntries; 819 820 DPRINTF(IQ, "IQ: Instruction PC %#x squashed.\n", 821 squashed_inst->readPC()); 822 } 823 824 --squashIt; 825 ++iqSquashedInstsExamined; 826 } 827 828 assert(freeEntries <= numEntries); 829 830 if (freeEntries == numEntries) { 831 tail = cpu->instList.end(); 832 } 833 834} 835 836template <class Impl> 837void 838InstructionQueue<Impl>::stopSquash() 839{ 840 // Clear up the squash variables to ensure that squashing doesn't 841 // get called improperly. 842 squashedSeqNum = 0; 843 844 squashIt = cpu->instList.end(); 845} 846 847template <class Impl> 848void 849InstructionQueue<Impl>::DependencyEntry::insert(DynInstPtr &new_inst) 850{ 851 //Add this new, dependent instruction at the head of the dependency 852 //chain. 853 854 // First create the entry that will be added to the head of the 855 // dependency chain. 856 DependencyEntry *new_entry = new DependencyEntry; 857 new_entry->next = this->next; 858 new_entry->inst = new_inst; 859 860 // Then actually add it to the chain. 861 this->next = new_entry; 862 863 ++mem_alloc_counter; 864} 865 866template <class Impl> 867void 868InstructionQueue<Impl>::DependencyEntry::remove(DynInstPtr &inst_to_remove) 869{ 870 DependencyEntry *prev = this; 871 DependencyEntry *curr = this->next; 872 873 // Make sure curr isn't NULL. Because this instruction is being 874 // removed from a dependency list, it must have been placed there at 875 // an earlier time. The dependency chain should not be empty, 876 // unless the instruction dependent upon it is already ready. 877 if (curr == NULL) { 878 return; 879 } 880 881 // Find the instruction to remove within the dependency linked list. 882 while(curr->inst != inst_to_remove) 883 { 884 prev = curr; 885 curr = curr->next; 886 887 assert(curr != NULL); 888 } 889 890 // Now remove this instruction from the list. 891 prev->next = curr->next; 892 893 --mem_alloc_counter; 894 895 // Could push this off to the destructor of DependencyEntry 896 curr->inst = NULL; 897 898 delete curr; 899} 900 901template <class Impl> 902bool 903InstructionQueue<Impl>::addToDependents(DynInstPtr &new_inst) 904{ 905 // Loop through the instruction's source registers, adding 906 // them to the dependency list if they are not ready. 907 int8_t total_src_regs = new_inst->numSrcRegs(); 908 bool return_val = false; 909 910 for (int src_reg_idx = 0; 911 src_reg_idx < total_src_regs; 912 src_reg_idx++) 913 { 914 // Only add it to the dependency graph if it's not ready. 915 if (!new_inst->isReadySrcRegIdx(src_reg_idx)) { 916 PhysRegIndex src_reg = new_inst->renamedSrcRegIdx(src_reg_idx); 917 918 // Check the IQ's scoreboard to make sure the register 919 // hasn't become ready while the instruction was in flight 920 // between stages. Only if it really isn't ready should 921 // it be added to the dependency graph. 922 if (src_reg >= numPhysRegs) { 923 continue; 924 } else if (regScoreboard[src_reg] == false) { 925 DPRINTF(IQ, "IQ: Instruction PC %#x has src reg %i that " 926 "is being added to the dependency chain.\n", 927 new_inst->readPC(), src_reg); 928 929 dependGraph[src_reg].insert(new_inst); 930 931 // Change the return value to indicate that something 932 // was added to the dependency graph. 933 return_val = true; 934 } else { 935 DPRINTF(IQ, "IQ: Instruction PC %#x has src reg %i that " 936 "became ready before it reached the IQ.\n", 937 new_inst->readPC(), src_reg); 938 // Mark a register ready within the instruction. 939 new_inst->markSrcRegReady(); 940 } 941 } 942 } 943 944 return return_val; 945} 946 947template <class Impl> 948void 949InstructionQueue<Impl>::createDependency(DynInstPtr &new_inst) 950{ 951 //Actually nothing really needs to be marked when an 952 //instruction becomes the producer of a register's value, 953 //but for convenience a ptr to the producing instruction will 954 //be placed in the head node of the dependency links. 955 int8_t total_dest_regs = new_inst->numDestRegs(); 956 957 for (int dest_reg_idx = 0; 958 dest_reg_idx < total_dest_regs; 959 dest_reg_idx++) 960 { 961 PhysRegIndex dest_reg = new_inst->renamedDestRegIdx(dest_reg_idx); 962 963 // Instructions that use the misc regs will have a reg number 964 // higher than the normal physical registers. In this case these 965 // registers are not renamed, and there is no need to track 966 // dependencies as these instructions must be executed at commit. 967 if (dest_reg >= numPhysRegs) { 968 continue; 969 } 970 971 dependGraph[dest_reg].inst = new_inst; 972 973 if (dependGraph[dest_reg].next) { 974 dumpDependGraph(); 975 panic("IQ: Dependency graph not empty!"); 976 } 977 978 // Mark the scoreboard to say it's not yet ready. 979 regScoreboard[dest_reg] = false; 980 } 981} 982 983template <class Impl> 984void 985InstructionQueue<Impl>::addIfReady(DynInstPtr &inst) 986{ 987 //If the instruction now has all of its source registers 988 // available, then add it to the list of ready instructions. 989 if (inst->readyToIssue()) { 990 991 //Add the instruction to the proper ready list. 992 if (inst->isControl()) { 993 994 DPRINTF(IQ, "IQ: Branch instruction is ready to issue, " 995 "putting it onto the ready list, PC %#x.\n", 996 inst->readPC()); 997 readyBranchInsts.push(inst); 998 999 } else if (inst->isMemRef()) { 1000 1001 DPRINTF(IQ, "IQ: Checking if memory instruction can issue.\n"); 1002 1003 // Message to the mem dependence unit that this instruction has 1004 // its registers ready. 1005 1006 memDepUnit.regsReady(inst); 1007 1008#if 0 1009 if (memDepUnit.readyToIssue(inst)) { 1010 DPRINTF(IQ, "IQ: Memory instruction is ready to issue, " 1011 "putting it onto the ready list, PC %#x.\n", 1012 inst->readPC()); 1013 readyMemInsts.push(inst); 1014 } else { 1015 // Make dependent on the store. 1016 // Will need some way to get the store instruction it should 1017 // be dependent upon; then when the store issues it can 1018 // put the instruction on the ready list. 1019 // Yet another tree? 1020 assert(0 && "Instruction has no way to actually issue"); 1021 } 1022#endif 1023 1024 } else if (inst->isInteger()) { 1025 1026 DPRINTF(IQ, "IQ: Integer instruction is ready to issue, " 1027 "putting it onto the ready list, PC %#x.\n", 1028 inst->readPC()); 1029 readyIntInsts.push(inst); 1030 1031 } else if (inst->isFloating()) { 1032 1033 DPRINTF(IQ, "IQ: Floating instruction is ready to issue, " 1034 "putting it onto the ready list, PC %#x.\n", 1035 inst->readPC()); 1036 readyFloatInsts.push(inst); 1037 1038 } else { 1039 DPRINTF(IQ, "IQ: Miscellaneous instruction is ready to issue, " 1040 "putting it onto the ready list, PC %#x..\n", 1041 inst->readPC()); 1042 1043 readyMiscInsts.push(inst); 1044 } 1045 } 1046} 1047 1048/* 1049 * Caution, this function must not be called prior to tail being updated at 1050 * least once, otherwise it will fail the assertion. This is because 1051 * instList.begin() actually changes upon the insertion of an element into the 1052 * list when the list is empty. 1053 */ 1054template <class Impl> 1055int 1056InstructionQueue<Impl>::countInsts() 1057{ 1058 ListIt count_it = cpu->instList.begin(); 1059 int total_insts = 0; 1060 1061 if (tail == cpu->instList.end()) 1062 return 0; 1063 1064 while (count_it != tail) { 1065 if (!(*count_it)->isIssued()) { 1066 ++total_insts; 1067 } 1068 1069 ++count_it; 1070 1071 assert(count_it != cpu->instList.end()); 1072 } 1073 1074 // Need to count the tail iterator as well. 1075 if (count_it != cpu->instList.end() && 1076 (*count_it) && 1077 !(*count_it)->isIssued()) { 1078 ++total_insts; 1079 } 1080 1081 return total_insts; 1082} 1083 1084template <class Impl> 1085void 1086InstructionQueue<Impl>::dumpDependGraph() 1087{ 1088 DependencyEntry *curr; 1089 1090 for (int i = 0; i < numPhysRegs; ++i) 1091 { 1092 curr = &dependGraph[i]; 1093 1094 if (curr->inst) { 1095 cprintf("dependGraph[%i]: producer: %#x consumer: ", i, 1096 curr->inst->readPC()); 1097 } else { 1098 cprintf("dependGraph[%i]: No producer. consumer: ", i); 1099 } 1100 1101 while (curr->next != NULL) { 1102 curr = curr->next; 1103 1104 cprintf("%#x ", curr->inst->readPC()); 1105 } 1106 1107 cprintf("\n"); 1108 } 1109} 1110 1111template <class Impl> 1112void 1113InstructionQueue<Impl>::dumpLists() 1114{ 1115 cprintf("Ready integer list size: %i\n", readyIntInsts.size()); 1116 1117 cprintf("Ready float list size: %i\n", readyFloatInsts.size()); 1118 1119 cprintf("Ready branch list size: %i\n", readyBranchInsts.size()); 1120 1121 cprintf("Ready misc list size: %i\n", readyMiscInsts.size()); 1122 1123 cprintf("Squashed list size: %i\n", squashedInsts.size()); 1124 1125 cprintf("Non speculative list size: %i\n", nonSpecInsts.size()); 1126 1127 non_spec_it_t non_spec_it = nonSpecInsts.begin(); 1128 1129 cprintf("Non speculative list: "); 1130 1131 while (non_spec_it != nonSpecInsts.end()) { 1132 cprintf("%#x ", (*non_spec_it).second->readPC()); 1133 ++non_spec_it; 1134 } 1135 1136 cprintf("\n"); 1137 1138} 1139