pentiumrtsc.cpp

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/*
    Sheep - A Rigid Body Dynamics Engine
    Copyright (C) 2001-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of Sheep.

    Sheep is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    Sheep is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Sheep; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include "pentiumrtsc.h"    // include first

using namespace sheep;

#pragma optimize("", off)

PentiumRTSC::PentiumRTSC() {
    // Compute the overhead induced by Start() and Stop() methods.
    // Make three warm-up passes to make sure that the timing code
    // and the data are into the L1 cache and that CPUID and RDTSC
    // instructions timing is stable. Only the result of the fourth
    // pass is taken into account.
    for(int i = 0; i < 4; ++i) {
        Start();
        Stop();
    }

    // Calculate the overhead due to the timing code.
    m_overhead =
        (static_cast<int64>(m_stop_h - m_start_h) << 32) +
         static_cast<int64>(m_stop_l - m_start_l);
}

int64 PentiumRTSC::GetResult() const {
    int64 result =
        (static_cast<int64>(m_stop_h - m_start_h) << 32) +
         static_cast<int64>(m_stop_l - m_start_l);

    return result - m_overhead;
}

#pragma optimize("", on)

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