src/cpu/pred/multiperspective_perceptron_tage_8KB.cc

/*
 * Copyright 2019 Texas A&M University
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of the copyright holder 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
 *  HOLDER 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.
 *
 *  Author: Daniel A. Jiménez
 *  Adapted to gem5 by: Javier Bueno Hedo
 *
 */

/*
 * Multiperspective Perceptron Predictor with TAGE (by Daniel A. Jiménez)
 * 8 KB version
 */

#include "cpu/pred/multiperspective_perceptron_tage_8KB.hh"

namespace gem5
{

namespace branch_prediction
{

MPP_StatisticalCorrector_8KB::MPP_StatisticalCorrector_8KB(
        const MPP_StatisticalCorrector_8KBParams &p)
  : MPP_StatisticalCorrector(p)
{
}

MPP_StatisticalCorrector_8KB::SCThreadHistory*
MPP_StatisticalCorrector_8KB::makeThreadHistory()
{
    MPP_SCThreadHistory *sh = new MPP_SCThreadHistory();

    sh->setNumOrdinalHistories(1);
    sh->initLocalHistory(1, numEntriesFirstLocalHistories, 4);

    return sh;
}

void
MPP_StatisticalCorrector_8KB::getBiasLSUM(Addr branch_pc,
        StatisticalCorrector::BranchInfo* bi, int &lsum) const
{
    int8_t ctr = bias[getIndBias(branch_pc, bi, false /* unused */)];
    lsum += 2 * ctr + 1;
    ctr = biasSK[getIndBiasSK(branch_pc, bi)];
    lsum += 2 * ctr + 1;
}

int
MPP_StatisticalCorrector_8KB::gPredictions(ThreadID tid, Addr branch_pc,
        StatisticalCorrector::BranchInfo* bi, int & lsum, int64_t phist)
{
    MPP_SCThreadHistory *sh = static_cast<MPP_SCThreadHistory *>(scHistory);
    unsigned int pc = branch_pc;
    lsum += gPredict((pc << 1) + bi->predBeforeSC, sh->globalHist << 11,
                     gm, ggehl, gnb, logGnb, wg);

    // Local History #1
    lsum += 2 * gPredict(branch_pc, sh->getLocalHistory(1, branch_pc),
                         lm, lgehl, lnb, logLnb, wl);
    if (sh->getLocalHistory(1, branch_pc) == 2047) lsum += 4;
    if (sh->getLocalHistory(1, branch_pc) == 0) lsum -= 4;

    lsum += gPredict(branch_pc, sh->getHistoryStackEntry(),
                     pm, pgehl, pnb, logPnb, wp);

    int thres = pUpdateThreshold[getIndUpd(branch_pc)];

    return thres;
}

void
MPP_StatisticalCorrector_8KB::gUpdates(ThreadID tid, Addr pc, bool taken,
        StatisticalCorrector::BranchInfo* bi, int64_t phist)
{
    MPP_SCThreadHistory *sh = static_cast<MPP_SCThreadHistory *>(scHistory);

    gUpdate((pc << 1) + bi->predBeforeSC, taken, sh->globalHist << 11,
            gm, ggehl, gnb, logGnb, wg, bi);

    gUpdate(pc, taken, sh->getLocalHistory(1, pc),
            lm, lgehl, lnb, logLnb, wl, bi);

    gUpdate(pc, taken, sh->getHistoryStackEntry(),
            pm, pgehl, pnb, logPnb, wp, bi);
}

void
MPP_StatisticalCorrector_8KB::scHistoryUpdate(Addr branch_pc,
        const StaticInstPtr &inst, bool taken,
        StatisticalCorrector::BranchInfo *bi, Addr corrTarget)
{
    int brtype = inst->isDirectCtrl() ? 0 : 2;
    if (! inst->isUncondCtrl()) {
        ++brtype;
    }

    MPP_SCThreadHistory *sh = static_cast<MPP_SCThreadHistory *>(scHistory);

    if (brtype & 1) {
        sh->globalHist = (sh->globalHist << 1) + taken;
    }
    sh->updateHistoryStack(corrTarget, taken, inst->isCall(),
                           inst->isReturn());

    StatisticalCorrector::scHistoryUpdate(branch_pc, inst, taken, bi,
                                          corrTarget);
}

size_t
MPP_StatisticalCorrector_8KB::getSizeInBits() const
{
    size_t bits = 16; //global histories

    bits += (1 << logSizeUp) * pUpdateThresholdWidth;

    bits += scCountersWidth * 2 * (1 << logBias); //2 bias arrays

    bits += (gnb - 2) * (1 << logGnb) * (scCountersWidth - 1) +
            (1 << (logGnb - 1)) * (2 * scCountersWidth - 1);

    bits += (pnb - 2) * (1 << logPnb) * (scCountersWidth - 1) +
            (1 << (logPnb - 1)) * (2 * scCountersWidth - 1);

    bits += (lnb - 2) * (1 << logLnb) * (scCountersWidth - 1) +
            (1 << (logLnb - 1)) * (2 * scCountersWidth - 1);

    bits += numEntriesFirstLocalHistories * lm[0];

    bits += 16 * 16; // History stack
    bits += 4;       // History stack pointer

    bits += 3 * chooserConfWidth; // 3 chooser counters

    return bits;
}

MultiperspectivePerceptronTAGE8KB::MultiperspectivePerceptronTAGE8KB(
        const MultiperspectivePerceptronTAGE8KBParams &p)
    : MultiperspectivePerceptronTAGE(p)
{
}

void
MultiperspectivePerceptronTAGE8KB::createSpecs()
{
    addSpec(new BLURRYPATH(5, 15, -1, 2.25, 0, 6, *this));
    addSpec(new RECENCYPOS(31, 3.5, 0, 6, *this));
    addSpec(new GHISTMODPATH(3, 7, 1, 2.24, 0, 6, *this));
    addSpec(new IMLI(1, 2.23, 0, 6, *this));
    addSpec(new IMLI(4, 1.98, 0, 6, *this));
}

} // namespace branch_prediction
} // namespace gem5