text: /*
   * Copyright (c) 2020 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.
   *
   * Copyright (c) 2011 Advanced Micro Devices, Inc.
   * All rights reserved.
   *
   * 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.
   */
  
  /**
   * @file This file defines the Root simobject and the methods used to control
   * the time syncing mechanism provided through it.
   *
   * Time syncing prevents simulated time from passing faster than real time. It
   * works by scheduling a periodic event that checks to see if its simulated
   * period is shorter than its real period. If it is, it stalls the simulation
   * until they're equal.
   */
  
  #ifndef __SIM_ROOT_HH__
  #define __SIM_ROOT_HH__
  
  #include "base/statistics.hh"
  #include "base/time.hh"
  #include "base/types.hh"
  #include "params/Root.hh"
  #include "sim/eventq.hh"
  #include "sim/sim_object.hh"
  
  class Root : public SimObject
  {
    private:
      static Root *_root;
  
    protected:
      bool _enabled;
      Time _period;
      Tick _periodTick;
      Time _spinThreshold;
  
      Time lastTime;
  
      void timeSync();
      EventFunctionWrapper syncEvent;
  
    public:
      /**
       * Use this function to get a pointer to the single Root object in the
       * simulation. This function asserts that such an object has actual been
       * constructed to avoid having to perform that check everywhere the root
       * is used. This is to allow calling the functions below.
       *
       * @return Pointer to the single root object.
       */
      static Root *
      root()
      {
          assert(_root);
          return _root;
      }
  
    public: // Global statistics
      struct RootStats : public Stats::Group
      {
          void resetStats() override;
  
          Stats::Formula simSeconds;
          Stats::Value simTicks;
          Stats::Value finalTick;
          Stats::Value simFreq;
          Stats::Value hostSeconds;
  
          Stats::Formula hostTickRate;
          Stats::Value hostMemory;
  
          static RootStats instance;
  
        private:
          RootStats();
  
          RootStats(const RootStats &) = delete;
          RootStats &operator=(const RootStats &) = delete;
  
          Time statTime;
          Tick startTick;
      };
  
    public:
  
      /// Check whether time syncing is enabled.
      bool timeSyncEnabled() const { return _enabled; }
      /// Retrieve the period for the sync event.
      const Time timeSyncPeriod() const { return _period; }
      /// Retrieve the threshold for time remaining to spin wait.
      const Time timeSyncSpinThreshold() const { return _spinThreshold; }
  
      /// Enable or disable time syncing.
      void timeSyncEnable(bool en);
      /// Configure the period for time sync events.
      void timeSyncPeriod(Time newPeriod);
      /// Set the threshold for time remaining to spin wait.
      void timeSyncSpinThreshold(Time newThreshold);
  
      typedef RootParams Params;
      const Params &
      params() const
      {
          return dynamic_cast<const Params &>(_params);
      }
  
      Root(const Params &p);
  
      /** Schedule the timesync event at startup().
       */
      void startup() override;
  
      void serialize(CheckpointOut &cp) const override;
  };
  
  /**
   * Global simulator statistics that are not associated with a
   * specific SimObject.
   */
  extern Root::RootStats &rootStats;
  
  #endif // __SIM_ROOT_HH__
  