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Diffstat (limited to 'src/cpu/inorder/resources/branch_predictor.cc')
-rw-r--r-- | src/cpu/inorder/resources/branch_predictor.cc | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/src/cpu/inorder/resources/branch_predictor.cc b/src/cpu/inorder/resources/branch_predictor.cc new file mode 100644 index 000000000..b563a3057 --- /dev/null +++ b/src/cpu/inorder/resources/branch_predictor.cc @@ -0,0 +1,149 @@ +/* + * Copyright (c) 2007 MIPS Technologies, Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution; + * neither the name of the copyright holders nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + * Authors: Korey Sewell + * + */ + +#include "cpu/inorder/resources/branch_predictor.hh" + +using namespace std; +using namespace TheISA; +using namespace ThePipeline; + +BranchPredictor::BranchPredictor(std::string res_name, int res_id, int res_width, + int res_latency, InOrderCPU *_cpu, ThePipeline::Params *params) + : Resource(res_name, res_id, res_width, res_latency, _cpu), + branchPred(params) +{ + instSize = sizeof(MachInst); +} + +void +BranchPredictor::regStats() +{ + predictedTaken + .name(name() + ".predictedTaken") + .desc("Number of Branches Predicted As Taken (True)."); + + predictedNotTaken + .name(name() + ".predictedNotTaken") + .desc("Number of Branches Predicted As Not Taken (False)."); + + Resource::regStats(); +} + +void +BranchPredictor::execute(int slot_num) +{ + // After this is working, change this to a reinterpret cast + // for performance considerations + ResourceRequest* bpred_req = reqMap[slot_num]; + + DynInstPtr inst = bpred_req->inst; + int tid = inst->readTid(); + int seq_num = inst->seqNum; + //int stage_num = bpred_req->getStageNum(); + + bpred_req->fault = NoFault; + + switch (bpred_req->cmd) + { + case PredictBranch: + { + Addr pred_PC = inst->readNextPC(); + + if (inst->isControl()) { + // If predicted, the pred_PC will be updated to new target value + // If not, the pred_PC be updated to pc+8 + bool predict_taken = branchPred.predict(inst, pred_PC, tid); + + if (predict_taken) { + DPRINTF(Resource, "[tid:%i]: [sn:%i]: Branch predicted true.\n", + tid, seq_num); + + inst->setPredTarg(pred_PC); + + predictedTaken++; + } else { + DPRINTF(Resource, "[tid:%i]: [sn:%i]: Branch predicted false.\n", + tid, seq_num); + + if (inst->isCondDelaySlot()) + { + inst->setPredTarg(inst->readPC() + (2 * instSize)); + } else { + inst->setPredTarg(pred_PC); + } + + predictedNotTaken++; + } + + inst->setBranchPred(predict_taken); + + DPRINTF(Resource, "[tid:%i]: [sn:%i]: Predicted PC is %08p.\n", + tid, seq_num, pred_PC); + + } else { + DPRINTF(Resource, "[tid:%i]: Ignoring [sn:%i] because this isn't " + "a control instruction.\n", tid, seq_num); + } + + bpred_req->done(); + } + break; + + case UpdatePredictor: + { + DPRINTF(Resource, "[tid:%i]: [sn:%i]: Updating Branch Predictor.\n", + tid, seq_num); + + + branchPred.update(seq_num, tid); + + bpred_req->done(); + } + break; + + default: + fatal("Unrecognized command to %s", resName); + } +} + +void +BranchPredictor::squash(DynInstPtr inst, int squash_stage, + InstSeqNum squash_seq_num, unsigned tid) +{ + DPRINTF(Resource, "Squashing...\n"); + branchPred.squash(squash_seq_num, tid); +} + +void +BranchPredictor::instGraduated(InstSeqNum seq_num,unsigned tid) +{ + branchPred.update(seq_num, tid); +} |