xref: /gem5/src/gpu-compute/global_memory_pipeline.cc

/*
 * Copyright (c) 2014-2015 Advanced Micro Devices, Inc.
 * All rights reserved.
 *
 * For use for simulation and test purposes only
 *
 * 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: John Kalamatianos, Sooraj Puthoor
 */

#include "gpu-compute/global_memory_pipeline.hh"

#include "debug/GPUMem.hh"
#include "debug/GPUReg.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"

GlobalMemPipeline::GlobalMemPipeline(const ComputeUnitParams* p) :
    computeUnit(nullptr), gmQueueSize(p->global_mem_queue_size),
    inflightStores(0), inflightLoads(0)
{
}

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

void
GlobalMemPipeline::exec()
{
    // apply any returned global memory operations
    GPUDynInstPtr m = !gmReturnedLoads.empty() ? gmReturnedLoads.front() :
        !gmReturnedStores.empty() ? gmReturnedStores.front() : nullptr;

    bool accessVrf = true;
    Wavefront *w = nullptr;

    // check the VRF to see if the operands of a load (or load component
    // of an atomic) are accessible
    if ((m) && (m->isLoad() || m->isAtomicRet())) {
        w = m->wavefront();

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

    if ((!gmReturnedStores.empty() || !gmReturnedLoads.empty()) &&
        m->latency.rdy() && computeUnit->glbMemToVrfBus.rdy() &&
        accessVrf && m->statusBitVector == VectorMask(0) &&
        (computeUnit->shader->coissue_return ||
         computeUnit->wfWait.at(m->pipeId).rdy())) {

        w = m->wavefront();

        m->completeAcc(m);

        if (m->isLoad() || m->isAtomic()) {
            gmReturnedLoads.pop();
            assert(inflightLoads > 0);
            --inflightLoads;
        } else {
            assert(m->isStore());
            gmReturnedStores.pop();
            assert(inflightStores > 0);
            --inflightStores;
        }

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

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

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

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

    // If pipeline has executed a global memory instruction
    // execute global memory packets and issue global
    // memory packets to DTLB
    if (!gmIssuedRequests.empty()) {
        GPUDynInstPtr mp = gmIssuedRequests.front();
        if (mp->isLoad() || mp->isAtomic()) {
            if (inflightLoads >= gmQueueSize) {
                return;
            } else {
                ++inflightLoads;
            }
        } else {
            if (inflightStores >= gmQueueSize) {
                return;
            } else if (mp->isStore()) {
                ++inflightStores;
            }
        }

        mp->initiateAcc(mp);
        gmIssuedRequests.pop();

        DPRINTF(GPUMem, "CU%d: WF[%d][%d] Popping 0 mem_op = \n",
                computeUnit->cu_id, mp->simdId, mp->wfSlotId);
    }
}

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