local_memory_pipeline.cc

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/*
 * Copyright (c) 2014-2015 Advanced Micro Devices, Inc.
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 *
 * For use for simulation and test purposes only
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 * 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.
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 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * Author: Sooraj Puthoor
 */

#include "gpu-compute/local_memory_pipeline.hh"

#include "debug/GPUPort.hh"
#include "gpu-compute/compute_unit.hh"
#include "gpu-compute/gpu_dyn_inst.hh"
#include "gpu-compute/shader.hh"
#include "gpu-compute/vector_register_file.hh"
#include "gpu-compute/wavefront.hh"

LocalMemPipeline::LocalMemPipeline(const ComputeUnitParams* p) :
    computeUnit(nullptr), lmQueueSize(p->local_mem_queue_size)
{
}

void
LocalMemPipeline::init(ComputeUnit *cu)
{
    computeUnit = cu;
    _name = computeUnit->name() + ".LocalMemPipeline";
}

void
LocalMemPipeline::exec()
{
    // apply any returned shared (LDS) memory operations
    GPUDynInstPtr m = !lmReturnedRequests.empty() ?
        lmReturnedRequests.front() : nullptr;

    bool accessVrf = true;
    Wavefront *w = nullptr;

    if ((m) && (m->isLoad() || m->isAtomicRet())) {
        w = m->wavefront();

        accessVrf =
            w->computeUnit->vrf[w->simdId]->
            vrfOperandAccessReady(m->seqNum(), w, m,
                                  VrfAccessType::WRITE);
    }

    if (!lmReturnedRequests.empty() && m->latency.rdy() && accessVrf &&
        computeUnit->locMemToVrfBus.rdy() && (computeUnit->shader->coissue_return
                 || computeUnit->wfWait.at(m->pipeId).rdy())) {

        lmReturnedRequests.pop();
        w = m->wavefront();

        m->completeAcc(m);

        // Decrement outstanding request count
        computeUnit->shader->ScheduleAdd(&w->outstandingReqs, m->time, -1);

        if (m->isStore() || m->isAtomic()) {
            computeUnit->shader->ScheduleAdd(&w->outstandingReqsWrLm,
                                             m->time, -1);
        }

        if (m->isLoad() || m->isAtomic()) {
            computeUnit->shader->ScheduleAdd(&w->outstandingReqsRdLm,
                                             m->time, -1);
        }

        // Mark write bus busy for appropriate amount of time
        computeUnit->locMemToVrfBus.set(m->time);
        if (computeUnit->shader->coissue_return == 0)
            w->computeUnit->wfWait.at(m->pipeId).set(m->time);
    }

    // If pipeline has executed a local memory instruction
    // execute local memory packet and issue the packets
    // to LDS
    if (!lmIssuedRequests.empty() && lmReturnedRequests.size() < lmQueueSize) {

        GPUDynInstPtr m = lmIssuedRequests.front();

        bool returnVal = computeUnit->sendToLds(m);
        if (!returnVal) {
            DPRINTF(GPUPort, "packet was nack'd and put in retry queue");
        }
        lmIssuedRequests.pop();
    }
}

void
LocalMemPipeline::regStats()
{
    loadVrfBankConflictCycles
        .name(name() + ".load_vrf_bank_conflict_cycles")
        .desc("total number of cycles LDS data are delayed before updating "
              "the VRF")
        ;
}