/*

 * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * published by the Free Software Foundation.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

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 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

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#ifndef CPU_X86_VM_RDTSC_X86_HPP

#define CPU_X86_VM_RDTSC_X86_HPP

#include "memory/allocation.hpp"

#include "utilities/macros.hpp"

// Interface to the x86 rdtsc() time counter, if available.

// Not guaranteed to be synchronized across hardware threads and

// therefore software threads, and can be updated asynchronously

// by software. elapsed_counter() can jump backwards

// as well as jump forward when threads query different cores/sockets.

// Very much not recommended for general use.

// INVTSC is a minimal requirement for auto-enablement.

class Rdtsc : AllStatic {

 public:

  static jlong elapsed_counter(); // provides quick time stamps

  static jlong frequency();       // tsc register

  static bool  is_supported();    // InvariantTSC

  static jlong raw();             // direct rdtsc() access

  static bool  is_elapsed_counter_enabled(); // turn off with -XX:-UseFastUnorderedTimeStamps

  static jlong epoch();

  static bool  initialize();

};

#endif // CPU_X86_VM_RDTSC_X86_HPP