# Copyright (c) 2005-2007 The Regents of The University of Michigan
# Copyright (c) 2010-2013 Advanced Micro Devices, Inc.
# Copyright (c) 2013 Mark D. Hill and David A. Wood
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from m5.SimObject import SimObject
from m5.params import *
from m5.util import fatal

class Root(SimObject):

    _the_instance = None

    def __new__(cls, **kwargs):
        if Root._the_instance:
            fatal("Attempt to allocate multiple instances of Root.")
            return None

        # first call: allocate the unique instance
        #
        # If SimObject ever implements __new__, we may want to pass
        # kwargs here, but for now this goes straight to
        # object.__new__ which prints an ugly warning if you pass it
        # args.  Seems like a bad design but that's the way it is.
        Root._the_instance = SimObject.__new__(cls)
        return Root._the_instance

    @classmethod
    def getInstance(cls):
        return Root._the_instance

    def path(self):
        return 'root'

    type = 'Root'
    cxx_header = "sim/root.hh"
    cxx_class = 'gem5::Root'

    # By default, root sim object and hence all other sim objects schedule
    # event on the eventq with index 0.
    eventq_index = 0

    # Simulation Quantum for multiple main event queue simulation.
    # Needs to be set explicitly for a multi-eventq simulation.
    sim_quantum = Param.Tick(0, "simulation quantum")

    full_system = Param.Bool("if this is a full system simulation")

    # Time syncing prevents the simulation from running faster than real time.
    time_sync_enable = Param.Bool(False, "whether time syncing is enabled")
    time_sync_period = Param.Clock("100ms", "how often to sync with real time")
    time_sync_spin_threshold = \
            Param.Clock("100us", "when less than this much time is left, spin")