src/cpu/inorder/resources/execution_unit.cc

   1 /*
   2  * Copyright (c) 2007 MIPS Technologies, Inc.
   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: Korey Sewell
  29  *
  30  */
  31
  32 #include <list>
  33 #include <vector>
  34
  35 #include "cpu/inorder/resources/execution_unit.hh"
  36 #include "cpu/inorder/cpu.hh"
  37 #include "cpu/inorder/resource_pool.hh"
  38 #include "debug/InOrderExecute.hh"
  39 #include "debug/InOrderStall.hh"
  40
  41 using namespace std;
  42 using namespace ThePipeline;
  43
  44 ExecutionUnit::ExecutionUnit(string res_name, int res_id, int res_width,
  45                              int res_latency, InOrderCPU *_cpu,
  46                              ThePipeline::Params *params)
  47     : Resource(res_name, res_id, res_width, res_latency, _cpu),
  48       lastExecuteTick(0), lastControlTick(0), serializeTick(0)
  49 { }
  50
  51 void
  52 ExecutionUnit::regStats()
  53 {
  54     predictedTakenIncorrect
  55         .name(name() + ".predictedTakenIncorrect")
  56         .desc("Number of Branches Incorrectly Predicted As Taken.");
  57
  58     predictedNotTakenIncorrect
  59         .name(name() + ".predictedNotTakenIncorrect")
  60         .desc("Number of Branches Incorrectly Predicted As Not Taken).");
  61
  62     executions
  63         .name(name() + ".executions")
  64         .desc("Number of Instructions Executed.");
  65
  66
  67     predictedIncorrect
  68         .name(name() + ".mispredicted")
  69         .desc("Number of Branches Incorrectly Predicted");
  70
  71     predictedCorrect
  72         .name(name() + ".predicted")
  73         .desc("Number of Branches Incorrectly Predicted");
  74
  75     mispredictPct
  76         .name(name() + ".mispredictPct")
  77         .desc("Percentage of Incorrect Branches Predicts")
  78         .precision(6);
  79     mispredictPct = (predictedIncorrect /
  80                      (predictedCorrect + predictedIncorrect)) * 100;
  81
  82     Resource::regStats();
  83 }
  84
  85 void
  86 ExecutionUnit::execute(int slot_num)
  87 {
  88     ResourceRequest* exec_req = reqs[slot_num];
  89     DynInstPtr inst = reqs[slot_num]->inst;
  90     Fault fault = NoFault;
  91     InstSeqNum seq_num = inst->seqNum;
  92     Tick cur_tick = curTick();
  93
  94     if (cur_tick == serializeTick) {
  95         DPRINTF(InOrderExecute, "Can not execute [tid:%i][sn:%i][PC:%s] %s. "
  96                 "All instructions are being serialized this cycle\n",
  97                 inst->readTid(), seq_num, inst->pcState(), inst->instName());
  98         exec_req->done(false);
  99         return;
 100     }
 101
 102
 103     switch (exec_req->cmd)
 104     {
 105       case ExecuteInst:
 106         {
 107             if (inst->isNop()) {
 108                 DPRINTF(InOrderExecute, "[tid:%i] [sn:%i] [PC:%s] Ignoring execution"
 109                         "of %s.\n", inst->readTid(), seq_num, inst->pcState(),
 110                         inst->instName());
 111                 inst->setExecuted();
 112                 exec_req->done();
 113                 return;
 114             } else {
 115                 DPRINTF(InOrderExecute, "[tid:%i] Executing [sn:%i] [PC:%s] %s.\n",
 116                         inst->readTid(), seq_num, inst->pcState(), inst->instName());
 117             }
 118
 119             if (cur_tick != lastExecuteTick) {
 120                 lastExecuteTick = cur_tick;
 121             }
 122
 123             assert(!inst->isMemRef());
 124
 125             if (inst->isSerializeAfter()) {
 126                 serializeTick = cur_tick;
 127                 DPRINTF(InOrderExecute, "Serializing execution after [tid:%i] "
 128                         "[sn:%i] [PC:%s] %s.\n", inst->readTid(), seq_num,
 129                         inst->pcState(), inst->instName());
 130             }
 131
 132             if (inst->isControl()) {
 133                 if (lastControlTick == cur_tick) {
 134                     DPRINTF(InOrderExecute, "Can not Execute More than One Control "
 135                             "Inst Per Cycle. Blocking Request.\n");
 136                     exec_req->done(false);
 137                     return;
 138                 }
 139                 lastControlTick = curTick();
 140
 141                 // Evaluate Branch
 142                 DPRINTF(IEW, "Pre-Execute %s PC:%s nextPC:%s predPC:%s\n", inst->instName(), inst->pcState(), inst->readPredTarg());
 143                 fault = inst->execute();
 144                 executions++;
 145                 inst->setExecuted();
 146                 DPRINTF(IEW, "Post-Execute %s PC:%s nextPC:%s predPC:%s\n", inst->instName(), inst->pcState(), inst->readPredTarg());
 147
 148                 if (fault == NoFault) {
 149                     // If branch is mispredicted, then signal squash
 150                     // throughout all stages behind the pipeline stage
 151                     // that got squashed.
 152                     if (inst->mispredicted()) {
 153                         int stage_num = exec_req->getStageNum();
 154                         ThreadID tid = inst->readTid();
 155                         // If it's a branch ...
 156                         if (inst->isDirectCtrl()) {
 157                             assert(!inst->isIndirectCtrl());
 158
 159                             TheISA::PCState pc = inst->pcState();
 160                             TheISA::advancePC(pc, inst->staticInst);
 161                             inst->setPredTarg(pc);
 162
 163                             if (inst->predTaken() && inst->isCondDelaySlot()) {
 164                                 assert(0 && "Not Handling Conditional Delay Slots (1)");
 165                                 inst->bdelaySeqNum = seq_num;
 166                                 DPRINTF(InOrderExecute, "[tid:%i]: Conditional"
 167                                         " branch inst [sn:%i] PC %s mis"
 168                                         "predicted as taken.\n", tid,
 169                                         seq_num, inst->pcState());
 170                             } else if (!inst->predTaken() && inst->isCondDelaySlot()) {
 171                                 assert(0 && "Not Handling Conditional Delay Slots (2)");
 172                                 inst->bdelaySeqNum = seq_num;
 173                                 inst->procDelaySlotOnMispred = true;
 174
 175                                 DPRINTF(InOrderExecute, "[tid:%i]: Conditional"
 176                                         " branch inst [sn:%i] PC %s mis"
 177                                         "predicted as not taken.\n", tid,
 178                                         seq_num, inst->pcState());
 179                             } else {
 180                                 inst->bdelaySeqNum = seq_num;
 181
 182                                 DPRINTF(InOrderExecute, "[tid:%i]: "
 183                                         "Misprediction detected at "
 184                                         "[sn:%i] PC %s,\n\t squashing after "
 185                                         "delay slot instruction [sn:%i].\n",
 186                                         tid, seq_num, inst->pcState(),
 187                                         inst->bdelaySeqNum);
 188                                 DPRINTF(InOrderStall, "STALL: [tid:%i]: Branch"
 189                                         " misprediction at %s\n",
 190                                         tid, inst->pcState());
 191                             }
 192
 193                             DPRINTF(InOrderExecute, "[tid:%i] Redirecting "
 194                                     "fetch to %s.\n", tid,
 195                                     inst->readPredTarg());
 196
 197                         } else if (inst->isIndirectCtrl()){
 198                             TheISA::PCState pc = inst->pcState();
 199                             TheISA::advancePC(pc, inst->staticInst);
 200                             inst->seqNum = seq_num;
 201                             inst->setPredTarg(pc);
 202
 203                             inst->bdelaySeqNum = seq_num;
 204
 205                             DPRINTF(InOrderExecute, "[tid:%i] Redirecting"
 206                                     " fetch to %s.\n", tid,
 207                                     inst->readPredTarg());
 208                         } else {
 209                             panic("Non-control instruction (%s) mispredict"
 210                                   "ing?!!", inst->staticInst->getName());
 211                         }
 212
 213                         DPRINTF(InOrderExecute, "[tid:%i] Squashing will "
 214                                 "start from stage %i.\n", tid, stage_num);
 215
 216                         cpu->pipelineStage[stage_num]->squashDueToBranch(inst,
 217                                                                          tid);
 218
 219                         inst->squashingStage = stage_num;
 220
 221                         // Squash throughout other resources
 222                         cpu->resPool->scheduleEvent((InOrderCPU::CPUEventType)
 223                                                     ResourcePool::SquashAll,
 224                                                     inst, 0, 0, tid);
 225
 226                         if (inst->predTaken()) {
 227                             predictedTakenIncorrect++;
 228                             DPRINTF(InOrderExecute, "[tid:%i] [sn:%i] %s ..."
 229                                     "PC %s ... Mispredicts! (Taken)\n",
 230                                     tid, inst->seqNum,
 231                                     inst->staticInst->disassemble(
 232                                         inst->instAddr()),
 233                                     inst->pcState());
 234                         } else {
 235                             predictedNotTakenIncorrect++;
 236                             DPRINTF(InOrderExecute, "[tid:%i] [sn:%i] %s ..."
 237                                     "PC %s ... Mispredicts! (Not Taken)\n",
 238                                     tid, inst->seqNum,
 239                                     inst->staticInst->disassemble(
 240                                         inst->instAddr()),
 241                                     inst->pcState());
 242                         }
 243                         predictedIncorrect++;
 244                     } else {
 245                         DPRINTF(InOrderExecute, "[tid:%i]: [sn:%i]: Prediction"
 246                                 "Correct.\n", inst->readTid(), seq_num);
 247                         predictedCorrect++;
 248                     }
 249
 250                     exec_req->done();
 251                 } else {
 252                     warn("inst [sn:%i] had a %s fault",
 253                          seq_num, fault->name());
 254                 }
 255             } else {
 256                 // Regular ALU instruction
 257                 fault = inst->execute();
 258                 executions++;
 259
 260                 if (fault == NoFault) {
 261                     inst->setExecuted();
 262
 263                     DPRINTF(InOrderExecute, "[tid:%i]: [sn:%i]: The result "
 264                             "of execution is 0x%x.\n", inst->readTid(),
 265                             seq_num,
 266                             (inst->resultType(0) == InOrderDynInst::Float) ?
 267                             inst->readFloatResult(0) : inst->readIntResult(0));
 268                 } else {
 269                     DPRINTF(InOrderExecute, "[tid:%i]: [sn:%i]: had a %s "
 270                             "fault.\n", inst->readTid(), seq_num, fault->name());
 271                     inst->fault = fault;
 272                 }
 273
 274                 exec_req->done();
 275             }
 276         }
 277         break;
 278
 279       default:
 280         fatal("Unrecognized command to %s", resName);
 281     }
 282 }
 283
 284