pipeline.cc

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/*
 * Copyright (c) 2013-2014 ARM Limited
 * All rights reserved
 *
 * The license below extends only to copyright in the software and shall
 * not be construed as granting a license to any other intellectual
 * property including but not limited to intellectual property relating
 * to a hardware implementation of the functionality of the software
 * licensed hereunder.  You may use the software subject to the license
 * terms below provided that you ensure that this notice is replicated
 * unmodified and in its entirety in all distributions of the software,
 * modified or unmodified, in source code or in binary form.
 *
 * 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
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 * 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
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * Authors: Andrew Bardsley
 */

#include "cpu/minor/pipeline.hh"

#include <algorithm>

#include "cpu/minor/decode.hh"
#include "cpu/minor/execute.hh"
#include "cpu/minor/fetch1.hh"
#include "cpu/minor/fetch2.hh"
#include "debug/Drain.hh"
#include "debug/MinorCPU.hh"
#include "debug/MinorTrace.hh"
#include "debug/Quiesce.hh"

namespace Minor
{

Pipeline::Pipeline(MinorCPU &cpu_, MinorCPUParams &params) :
    Ticked(cpu_, &(cpu_.BaseCPU::numCycles)),
    cpu(cpu_),
    allow_idling(params.enableIdling),
    f1ToF2(cpu.name() + ".f1ToF2", "lines",
        params.fetch1ToFetch2ForwardDelay),
    f2ToF1(cpu.name() + ".f2ToF1", "prediction",
        params.fetch1ToFetch2BackwardDelay, true),
    f2ToD(cpu.name() + ".f2ToD", "insts",
        params.fetch2ToDecodeForwardDelay),
    dToE(cpu.name() + ".dToE", "insts",
        params.decodeToExecuteForwardDelay),
    eToF1(cpu.name() + ".eToF1", "branch",
        params.executeBranchDelay),
    execute(cpu.name() + ".execute", cpu, params,
        dToE.output(), eToF1.input()),
    decode(cpu.name() + ".decode", cpu, params,
        f2ToD.output(), dToE.input(), execute.inputBuffer),
    fetch2(cpu.name() + ".fetch2", cpu, params,
        f1ToF2.output(), eToF1.output(), f2ToF1.input(), f2ToD.input(),
        decode.inputBuffer),
    fetch1(cpu.name() + ".fetch1", cpu, params,
        eToF1.output(), f1ToF2.input(), f2ToF1.output(), fetch2.inputBuffer),
    activityRecorder(cpu.name() + ".activity", Num_StageId,
        /* The max depth of inter-stage FIFOs */
        std::max(params.fetch1ToFetch2ForwardDelay,
        std::max(params.fetch2ToDecodeForwardDelay,
        std::max(params.decodeToExecuteForwardDelay,
        params.executeBranchDelay)))),
    needToSignalDrained(false)
{
    if (params.fetch1ToFetch2ForwardDelay < 1) {
        fatal("%s: fetch1ToFetch2ForwardDelay must be >= 1 (%d)\n",
            cpu.name(), params.fetch1ToFetch2ForwardDelay);
    }

    if (params.fetch2ToDecodeForwardDelay < 1) {
        fatal("%s: fetch2ToDecodeForwardDelay must be >= 1 (%d)\n",
            cpu.name(), params.fetch2ToDecodeForwardDelay);
    }

    if (params.decodeToExecuteForwardDelay < 1) {
        fatal("%s: decodeToExecuteForwardDelay must be >= 1 (%d)\n",
            cpu.name(), params.decodeToExecuteForwardDelay);
    }

    if (params.executeBranchDelay < 1) {
        fatal("%s: executeBranchDelay must be >= 1\n",
            cpu.name(), params.executeBranchDelay);
    }
}

void
Pipeline::minorTrace() const
{
    fetch1.minorTrace();
    f1ToF2.minorTrace();
    f2ToF1.minorTrace();
    fetch2.minorTrace();
    f2ToD.minorTrace();
    decode.minorTrace();
    dToE.minorTrace();
    execute.minorTrace();
    eToF1.minorTrace();
    activityRecorder.minorTrace();
}

void
Pipeline::evaluate()
{
    /* Note that it's important to evaluate the stages in order to allow
     *  'immediate', 0-time-offset TimeBuffer activity to be visible from
     *  later stages to earlier ones in the same cycle */
    execute.evaluate();
    decode.evaluate();
    fetch2.evaluate();
    fetch1.evaluate();

    if (DTRACE(MinorTrace))
        minorTrace();

    /* Update the time buffers after the stages */
    f1ToF2.evaluate();
    f2ToF1.evaluate();
    f2ToD.evaluate();
    dToE.evaluate();
    eToF1.evaluate();

    /* The activity recorder must be be called after all the stages and
     *  before the idler (which acts on the advice of the activity recorder */
    activityRecorder.evaluate();

    if (allow_idling) {
        /* Become idle if we can but are not draining */
        if (!activityRecorder.active() && !needToSignalDrained) {
            DPRINTF(Quiesce, "Suspending as the processor is idle\n");
            stop();
        }

        /* Deactivate all stages.  Note that the stages *could*
         *  activate and deactivate themselves but that's fraught
         *  with additional difficulty.
         *  As organised herre */
        activityRecorder.deactivateStage(Pipeline::CPUStageId);
        activityRecorder.deactivateStage(Pipeline::Fetch1StageId);
        activityRecorder.deactivateStage(Pipeline::Fetch2StageId);
        activityRecorder.deactivateStage(Pipeline::DecodeStageId);
        activityRecorder.deactivateStage(Pipeline::ExecuteStageId);
    }

    if (needToSignalDrained) /* Must be draining */
    {
        DPRINTF(Drain, "Still draining\n");
        if (isDrained()) {
            DPRINTF(Drain, "Signalling end of draining\n");
            cpu.signalDrainDone();
            needToSignalDrained = false;
            stop();
        }
    }
}

MinorCPU::MinorCPUPort &
Pipeline::getInstPort()
{
    return fetch1.getIcachePort();
}

MinorCPU::MinorCPUPort &
Pipeline::getDataPort()
{
    return execute.getDcachePort();
}

void
Pipeline::wakeupFetch(ThreadID tid)
{
    fetch1.wakeupFetch(tid);
}

bool
Pipeline::drain()
{
    DPRINTF(MinorCPU, "Draining pipeline by halting inst fetches. "
        " Execution should drain naturally\n");

    execute.drain();

    /* Make sure that needToSignalDrained isn't accidentally set if we
     *  are 'pre-drained' */
    bool drained = isDrained();
    needToSignalDrained = !drained;

    return drained;
}

void
Pipeline::drainResume()
{
    DPRINTF(Drain, "Drain resume\n");

    for (ThreadID tid = 0; tid < cpu.numThreads; tid++) {
        fetch1.wakeupFetch(tid);
    }

    execute.drainResume();
}

bool
Pipeline::isDrained()
{
    bool fetch1_drained = fetch1.isDrained();
    bool fetch2_drained = fetch2.isDrained();
    bool decode_drained = decode.isDrained();
    bool execute_drained = execute.isDrained();

    bool f1_to_f2_drained = f1ToF2.empty();
    bool f2_to_f1_drained = f2ToF1.empty();
    bool f2_to_d_drained = f2ToD.empty();
    bool d_to_e_drained = dToE.empty();

    bool ret = fetch1_drained && fetch2_drained &&
        decode_drained && execute_drained &&
        f1_to_f2_drained && f2_to_f1_drained &&
        f2_to_d_drained && d_to_e_drained;

    DPRINTF(MinorCPU, "Pipeline undrained stages state:%s%s%s%s%s%s%s%s\n",
        (fetch1_drained ? "" : " Fetch1"),
        (fetch2_drained ? "" : " Fetch2"),
        (decode_drained ? "" : " Decode"),
        (execute_drained ? "" : " Execute"),
        (f1_to_f2_drained ? "" : " F1->F2"),
        (f2_to_f1_drained ? "" : " F2->F1"),
        (f2_to_d_drained ? "" : " F2->D"),
        (d_to_e_drained ? "" : " D->E")
        );

    return ret;
}

}