scalar_memory_pipeline.cc

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#include "gpu-compute/scalar_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/scalar_register_file.hh"
#include "gpu-compute/shader.hh"
#include "gpu-compute/wavefront.hh"
 
namespace gem5
{
 
ScalarMemPipeline::ScalarMemPipeline(const ComputeUnitParams &p,
                                     ComputeUnit &cu)
    : computeUnit(cu), _name(cu.name() + ".ScalarMemPipeline"),
      queueSize(p.scalar_mem_queue_size),
      inflightStores(0), inflightLoads(0)
{
}
 
void
ScalarMemPipeline::exec()
{
    // afind oldest scalar request whose data has arrived
    GPUDynInstPtr m = !returnedLoads.empty() ? returnedLoads.front() :
        !returnedStores.empty() ? returnedStores.front() : nullptr;
 
    Wavefront *w = nullptr;
 
    bool accessSrf = true;
    // check the SRF 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();
 
        accessSrf =
            w->computeUnit->srf[w->simdId]->
                canScheduleWriteOperandsFromLoad(w, m);
    }
 
    if ((!returnedStores.empty() || !returnedLoads.empty()) &&
        m->latency.rdy() && computeUnit.scalarMemToSrfBus.rdy() &&
        accessSrf &&
        (computeUnit.shader->coissue_return ||
         computeUnit.scalarMemUnit.rdy())) {
 
        w = m->wavefront();
 
        if (m->isLoad() || m->isAtomicRet()) {
            w->computeUnit->srf[w->simdId]->
                scheduleWriteOperandsFromLoad(w, m);
        }
 
        m->completeAcc(m);
        w->decLGKMInstsIssued();
 
        if (m->isLoad() || m->isAtomic()) {
            returnedLoads.pop();
            assert(inflightLoads > 0);
            --inflightLoads;
        } else {
            returnedStores.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->scalarOutstandingReqsWrGm,
                                             m->time, -1);
        }
 
        if (m->isLoad() || m->isAtomic()) {
            computeUnit.shader->ScheduleAdd(&w->scalarOutstandingReqsRdGm,
                                             m->time, -1);
        }
 
        // Mark write bus busy for appropriate amount of time
        computeUnit.scalarMemToSrfBus.set(m->time);
        if (!computeUnit.shader->coissue_return)
            w->computeUnit->scalarMemUnit.set(m->time);
    }
 
    // If pipeline has executed a global memory instruction
    // execute global memory packets and issue global
    // memory packets to DTLB
    if (!issuedRequests.empty()) {
        GPUDynInstPtr mp = issuedRequests.front();
        if (mp->isLoad() || mp->isAtomic()) {
 
            if (inflightLoads >= queueSize) {
                return;
            } else {
                ++inflightLoads;
            }
        } else {
            if (inflightStores >= queueSize) {
                return;
            } else {
                ++inflightStores;
            }
        }
        mp->initiateAcc(mp);
        issuedRequests.pop();
 
        DPRINTF(GPUMem, "CU%d: WF[%d][%d] Popping scalar mem_op\n",
                computeUnit.cu_id, mp->simdId, mp->wfSlotId);
    }
}
 
void
ScalarMemPipeline::issueRequest(GPUDynInstPtr gpuDynInst)
{
    Wavefront *wf = gpuDynInst->wavefront();
    if (gpuDynInst->isLoad()) {
        wf->scalarRdGmReqsInPipe--;
        wf->scalarOutstandingReqsRdGm++;
    } else if (gpuDynInst->isStore()) {
        wf->scalarWrGmReqsInPipe--;
        wf->scalarOutstandingReqsWrGm++;
    }
 
    wf->outstandingReqs++;
    wf->validateRequestCounters();
 
    issuedRequests.push(gpuDynInst);
}
 
void
ScalarMemPipeline::injectScalarMemFence(GPUDynInstPtr gpuDynInst,
                                        bool kernelMemSync,
                                        RequestPtr req)
{
    assert(gpuDynInst->isScalar());
 
    if (!req) {
        req = std::make_shared<Request>(
                0, 0, 0, computeUnit.requestorId(), 0, gpuDynInst->wfDynId);
    } else {
        req->requestorId(computeUnit.requestorId());
    }
 
    // When the SQC invalidate instruction is executed, it calls
    // injectScalarMemFence. The instruction does not contain an address
    // as one of its operands. Therefore, set the physical address of the
    // invalidation request to 0 and handle it in the sequencer
    req->setPaddr(0);
 
    PacketPtr sqc_pkt = nullptr;
 
    // If kernelMemSync is true, then the invalidation request is from
    // kernel launch and is an implicit invalidation.If false, then it is
    // due to an S_ICACHE_INV instruction
    if (kernelMemSync) {
        req->setCacheCoherenceFlags(Request::INV_L1);
        req->setReqInstSeqNum(gpuDynInst->seqNum());
        req->setFlags(Request::KERNEL);
        sqc_pkt = new Packet(req, MemCmd::MemSyncReq);
        sqc_pkt->pushSenderState(
                new ComputeUnit::SQCPort::SenderState(
                    gpuDynInst->wavefront(), nullptr));
    } else {
        gpuDynInst->setRequestFlags(req);
 
        req->setReqInstSeqNum(gpuDynInst->seqNum());
 
        sqc_pkt = new Packet(req, MemCmd::MemSyncReq);
        sqc_pkt->pushSenderState(
                new ComputeUnit::SQCPort::SenderState(
                    gpuDynInst->wavefront(), nullptr));
    }
 
    ComputeUnit::SQCPort::MemReqEvent *sqc_event =
            new ComputeUnit::SQCPort::MemReqEvent
            (computeUnit.sqcPort, sqc_pkt);
    computeUnit.schedule(
            sqc_event, curTick() + computeUnit.scalar_req_tick_latency);
 
    // When the SQC is invalidated, perform a scalar cache invalidate as well.
    // The SQC and Scalar cache are implement using the same SLICC SM, so this
    // invalidate is identical to the SQC invalidate, however we need to make
    // a new packet and request as they have different cache destinations.
    PacketPtr scalar_pkt = nullptr;
    RequestPtr scalar_req(req);
 
    if (kernelMemSync) {
        scalar_req->setCacheCoherenceFlags(Request::INV_L1);
        scalar_req->setReqInstSeqNum(gpuDynInst->seqNum());
        scalar_req->setFlags(Request::KERNEL);
        scalar_pkt = new Packet(scalar_req, MemCmd::MemSyncReq);
        scalar_pkt->pushSenderState(
                new ComputeUnit::ScalarDataPort::SenderState(
                    gpuDynInst));
    } else {
        gpuDynInst->setRequestFlags(scalar_req);
 
        scalar_req->setReqInstSeqNum(gpuDynInst->seqNum());
 
        scalar_pkt = new Packet(scalar_req, MemCmd::MemSyncReq);
        scalar_pkt->pushSenderState(
                new ComputeUnit::ScalarDataPort::SenderState(
                    gpuDynInst));
    }
 
    ComputeUnit::ScalarDataPort::MemReqEvent *scalar_event =
            new ComputeUnit::ScalarDataPort::MemReqEvent
            (computeUnit.scalarDataPort, scalar_pkt);
    computeUnit.schedule(
            scalar_event, curTick() + computeUnit.scalar_req_tick_latency);
}
 
} // namespace gem5