rob_impl.hh revision 2665
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#ifndef __CPU_O3_CPU_ROB_IMPL_HH__ 32#define __CPU_O3_CPU_ROB_IMPL_HH__ 33 34#include "config/full_system.hh" 35#include "cpu/o3/rob.hh" 36 37template <class Impl> 38ROB<Impl>::ROB(unsigned _numEntries, unsigned _squashWidth) 39 : numEntries(_numEntries), 40 squashWidth(_squashWidth), 41 numInstsInROB(0), 42 squashedSeqNum(0) 43{ 44 doneSquashing = true; 45} 46 47template <class Impl> 48void 49ROB<Impl>::setCPU(FullCPU *cpu_ptr) 50{ 51 cpu = cpu_ptr; 52 53 // Set the tail to the beginning of the CPU instruction list so that 54 // upon the first instruction being inserted into the ROB, the tail 55 // iterator can simply be incremented. 56 tail = cpu->instList.begin(); 57 58 // Set the squash iterator to the end of the instruction list. 59 squashIt = cpu->instList.end(); 60} 61 62template <class Impl> 63int 64ROB<Impl>::countInsts() 65{ 66 // Start at 1; if the tail matches cpu->instList.begin(), then there is 67 // one inst in the ROB. 68 int return_val = 1; 69 70 // There are quite a few special cases. Do not use this function other 71 // than for debugging purposes. 72 if (cpu->instList.begin() == cpu->instList.end()) { 73 // In this case there are no instructions in the list. The ROB 74 // must be empty. 75 return 0; 76 } else if (tail == cpu->instList.end()) { 77 // In this case, the tail is not yet pointing to anything valid. 78 // The ROB must be empty. 79 return 0; 80 } 81 82 // Iterate through the ROB from the head to the tail, counting the 83 // entries. 84 for (InstIt_t i = cpu->instList.begin(); i != tail; ++i) 85 { 86 assert(i != cpu->instList.end()); 87 ++return_val; 88 } 89 90 return return_val; 91 92 // Because the head won't be tracked properly until the ROB gets the 93 // first instruction, and any time that the ROB is empty and has not 94 // yet gotten the instruction, this function doesn't work. 95// return numInstsInROB; 96} 97 98template <class Impl> 99void 100ROB<Impl>::insertInst(DynInstPtr &inst) 101{ 102 // Make sure we have the right number of instructions. 103 assert(numInstsInROB == countInsts()); 104 // Make sure the instruction is valid. 105 assert(inst); 106 107 DPRINTF(ROB, "ROB: Adding inst PC %#x to the ROB.\n", inst->readPC()); 108 109 // If the ROB is full then exit. 110 assert(numInstsInROB != numEntries); 111 112 ++numInstsInROB; 113 114 // Increment the tail iterator, moving it one instruction back. 115 // There is a special case if the ROB was empty prior to this insertion, 116 // in which case the tail will be pointing at instList.end(). If that 117 // happens, then reset the tail to the beginning of the list. 118 if (tail != cpu->instList.end()) { 119 ++tail; 120 } else { 121 tail = cpu->instList.begin(); 122 } 123 124 // Make sure the tail iterator is actually pointing at the instruction 125 // added. 126 assert((*tail) == inst); 127 128 DPRINTF(ROB, "ROB: Now has %d instructions.\n", numInstsInROB); 129 130} 131 132// Whatever calls this function needs to ensure that it properly frees up 133// registers prior to this function. 134template <class Impl> 135void 136ROB<Impl>::retireHead() 137{ 138 assert(numInstsInROB == countInsts()); 139 assert(numInstsInROB > 0); 140 141 // Get the head ROB instruction. 142 DynInstPtr head_inst = cpu->instList.front(); 143 144 // Make certain this can retire. 145 assert(head_inst->readyToCommit()); 146 147 DPRINTF(ROB, "ROB: Retiring head instruction of the ROB, " 148 "instruction PC %#x, seq num %i\n", head_inst->readPC(), 149 head_inst->seqNum); 150 151 // Keep track of how many instructions are in the ROB. 152 --numInstsInROB; 153 154 // Tell CPU to remove the instruction from the list of instructions. 155 // A special case is needed if the instruction being retired is the 156 // only instruction in the ROB; otherwise the tail iterator will become 157 // invalidated. 158 cpu->removeFrontInst(head_inst); 159 160 if (numInstsInROB == 0) { 161 tail = cpu->instList.end(); 162 } 163} 164 165template <class Impl> 166bool 167ROB<Impl>::isHeadReady() 168{ 169 if (numInstsInROB != 0) { 170 return cpu->instList.front()->readyToCommit(); 171 } 172 173 return false; 174} 175 176template <class Impl> 177unsigned 178ROB<Impl>::numFreeEntries() 179{ 180 assert(numInstsInROB == countInsts()); 181 182 return numEntries - numInstsInROB; 183} 184 185template <class Impl> 186void 187ROB<Impl>::doSquash() 188{ 189 DPRINTF(ROB, "ROB: Squashing instructions.\n"); 190 191 assert(squashIt != cpu->instList.end()); 192 193 for (int numSquashed = 0; 194 numSquashed < squashWidth && (*squashIt)->seqNum != squashedSeqNum; 195 ++numSquashed) 196 { 197 // Ensure that the instruction is younger. 198 assert((*squashIt)->seqNum > squashedSeqNum); 199 200 DPRINTF(ROB, "ROB: Squashing instruction PC %#x, seq num %i.\n", 201 (*squashIt)->readPC(), (*squashIt)->seqNum); 202 203 // Mark the instruction as squashed, and ready to commit so that 204 // it can drain out of the pipeline. 205 (*squashIt)->setSquashed(); 206 207 (*squashIt)->setCanCommit(); 208 209 // Special case for when squashing due to a syscall. It's possible 210 // that the squash happened after the head instruction was already 211 // committed, meaning that (*squashIt)->seqNum != squashedSeqNum 212 // will never be false. Normally the squash would never be able 213 // to go past the head of the ROB; in this case it might, so it 214 // must be handled otherwise it will segfault. 215#if !FULL_SYSTEM 216 if (squashIt == cpu->instList.begin()) { 217 DPRINTF(ROB, "ROB: Reached head of instruction list while " 218 "squashing.\n"); 219 220 squashIt = cpu->instList.end(); 221 222 doneSquashing = true; 223 224 return; 225 } 226#endif 227 228 // Move the tail iterator to the next instruction. 229 squashIt--; 230 } 231 232 233 // Check if ROB is done squashing. 234 if ((*squashIt)->seqNum == squashedSeqNum) { 235 DPRINTF(ROB, "ROB: Done squashing instructions.\n"); 236 237 squashIt = cpu->instList.end(); 238 239 doneSquashing = true; 240 } 241} 242 243template <class Impl> 244void 245ROB<Impl>::squash(InstSeqNum squash_num) 246{ 247 DPRINTF(ROB, "ROB: Starting to squash within the ROB.\n"); 248 doneSquashing = false; 249 250 squashedSeqNum = squash_num; 251 252 assert(tail != cpu->instList.end()); 253 254 squashIt = tail; 255 256 doSquash(); 257} 258 259template <class Impl> 260uint64_t 261ROB<Impl>::readHeadPC() 262{ 263 assert(numInstsInROB == countInsts()); 264 265 DynInstPtr head_inst = cpu->instList.front(); 266 267 return head_inst->readPC(); 268} 269 270template <class Impl> 271uint64_t 272ROB<Impl>::readHeadNextPC() 273{ 274 assert(numInstsInROB == countInsts()); 275 276 DynInstPtr head_inst = cpu->instList.front(); 277 278 return head_inst->readNextPC(); 279} 280 281template <class Impl> 282InstSeqNum 283ROB<Impl>::readHeadSeqNum() 284{ 285 // Return the last sequence number that has not been squashed. Other 286 // stages can use it to squash any instructions younger than the current 287 // tail. 288 DynInstPtr head_inst = cpu->instList.front(); 289 290 return head_inst->seqNum; 291} 292 293template <class Impl> 294uint64_t 295ROB<Impl>::readTailPC() 296{ 297 assert(numInstsInROB == countInsts()); 298 299 assert(tail != cpu->instList.end()); 300 301 return (*tail)->readPC(); 302} 303 304template <class Impl> 305InstSeqNum 306ROB<Impl>::readTailSeqNum() 307{ 308 // Return the last sequence number that has not been squashed. Other 309 // stages can use it to squash any instructions younger than the current 310 // tail. 311 return (*tail)->seqNum; 312} 313 314#endif // __CPU_O3_CPU_ROB_IMPL_HH__ 315