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/*
* Copyright (c) 2012 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
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders 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
* OWNER 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.
*
* Authors: Andreas Hansson
*/
/**
* @file
* ClockedObject declaration and implementation.
*/
#ifndef __SIM_CLOCKED_OBJECT_HH__
#define __SIM_CLOCKED_OBJECT_HH__
#include "base/intmath.hh"
#include "base/misc.hh"
#include "params/ClockedObject.hh"
#include "sim/core.hh"
#include "sim/sim_object.hh"
/**
* The ClockedObject class extends the SimObject with a clock and
* accessor functions to relate ticks to the cycles of the object.
*/
class ClockedObject : public SimObject
{
private:
// the tick value of the next clock edge (>= curTick()) at the
// time of the last call to update()
mutable Tick tick;
// The cycle counter value corresponding to the current value of
// 'tick'
mutable Cycles cycle;
/**
* Prevent inadvertent use of the copy constructor and assignment
* operator by making them private.
*/
ClockedObject(ClockedObject&);
ClockedObject& operator=(ClockedObject&);
/**
* Align cycle and tick to the next clock edge if not already done.
*/
void update() const
{
// both tick and cycle are up-to-date and we are done, note
// that the >= is important as it captures cases where tick
// has already passed curTick()
if (tick >= curTick())
return;
// optimise for the common case and see if the tick should be
// advanced by a single clock period
tick += clock;
++cycle;
// see if we are done at this point
if (tick >= curTick())
return;
// if not, we have to recalculate the cycle and tick, we
// perform the calculations in terms of relative cycles to
// allow changes to the clock period in the future
Cycles elapsedCycles(divCeil(curTick() - tick, clock));
cycle += elapsedCycles;
tick += elapsedCycles * clock;
}
protected:
// Clock period in ticks
Tick clock;
/**
* Create a clocked object and set the clock based on the
* parameters.
*/
ClockedObject(const ClockedObjectParams* p) :
SimObject(p), tick(0), cycle(0), clock(p->clock)
{
if (clock == 0) {
fatal("%s has a clock period of zero\n", name());
}
}
/**
* Virtual destructor due to inheritance.
*/
virtual ~ClockedObject() { }
/**
* Reset the object's clock using the current global tick value. Likely
* to be used only when the global clock is reset. Currently, this done
* only when Ruby is done warming up the memory system.
*/
void resetClock() const
{
Cycles elapsedCycles(divCeil(curTick(), clock));
cycle = elapsedCycles;
tick = elapsedCycles * clock;
}
public:
/**
* Determine the tick when a cycle begins, by default the current
* one, but the argument also enables the caller to determine a
* future cycle.
*
* @param cycles The number of cycles into the future
*
* @return The tick when the clock edge occurs
*/
inline Tick clockEdge(Cycles cycles = Cycles(0)) const
{
// align tick to the next clock edge
update();
// figure out when this future cycle is
return tick + clock * cycles;
}
/**
* Determine the current cycle, corresponding to a tick aligned to
* a clock edge.
*
* @return The current cycle count
*/
inline Cycles curCycle() const
{
// align cycle to the next clock edge.
update();
return cycle;
}
/**
* Based on the clock of the object, determine the tick when the
* next cycle begins, in other words, return the next clock edge.
*
* @return The tick when the next cycle starts
*/
Tick nextCycle() const
{ return clockEdge(); }
inline uint64_t frequency() const { return SimClock::Frequency / clock; }
inline Tick clockPeriod() const { return clock; }
inline Cycles ticksToCycles(Tick tick) const
{ return Cycles(tick / clock); }
};
#endif //__SIM_CLOCKED_OBJECT_HH__
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