text: #ifndef KMP_STATS_TIMING_H
  #define KMP_STATS_TIMING_H
  
  /** @file kmp_stats_timing.h
   * Access to real time clock and timers.
   */
  
  
  //===----------------------------------------------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is dual licensed under the MIT and the University of Illinois Open
  // Source Licenses. See LICENSE.txt for details.
  //
  //===----------------------------------------------------------------------===//
  
  
  
  #include <stdint.h>
  #include <string>
  #include <limits>
  #include "kmp_os.h"
  #if KMP_HAVE_X86INTRIN_H
  # include <x86intrin.h>
  #endif
  
  class tsc_tick_count {
    private:
      int64_t my_count;
  
    public:
      class tsc_interval_t {
          int64_t value;
          explicit tsc_interval_t(int64_t _value) : value(_value) {}
       public:
          tsc_interval_t() : value(0) {}; // Construct 0 time duration
  #if KMP_HAVE_TICK_TIME
          double seconds() const; // Return the length of a time interval in seconds
  #endif
          double ticks() const { return double(value); }
          int64_t getValue() const { return value; }
          tsc_interval_t& operator=(int64_t nvalue) { value = nvalue; return *this; }
  
          friend class tsc_tick_count;
  
          friend tsc_interval_t operator-(const tsc_tick_count& t1,
                                          const tsc_tick_count& t0);
          friend tsc_interval_t operator-(const tsc_tick_count::tsc_interval_t& i1,
                                          const tsc_tick_count::tsc_interval_t& i0);
          friend tsc_interval_t& operator+=(tsc_tick_count::tsc_interval_t& i1,
                                           const tsc_tick_count::tsc_interval_t& i0);
      };
  
  #if KMP_HAVE___BUILTIN_READCYCLECOUNTER
      tsc_tick_count() : my_count(static_cast<int64_t>(__builtin_readcyclecounter())) {}
  #elif KMP_HAVE___RDTSC
      tsc_tick_count() : my_count(static_cast<int64_t>(__rdtsc())) {};
  #else
  # error Must have high resolution timer defined
  #endif
      tsc_tick_count(int64_t value) : my_count(value) {};
      int64_t getValue() const { return my_count; }
      tsc_tick_count later (tsc_tick_count const other) const {
          return my_count > other.my_count ? (*this) : other;
      }
      tsc_tick_count earlier(tsc_tick_count const other) const {
          return my_count < other.my_count ? (*this) : other;
      }
  #if KMP_HAVE_TICK_TIME
      static double tick_time(); // returns seconds per cycle (period) of clock
  #endif
      static tsc_tick_count now() { return tsc_tick_count(); } // returns the rdtsc register value
      friend tsc_tick_count::tsc_interval_t operator-(const tsc_tick_count& t1, const tsc_tick_count& t0);
  };
  
  inline tsc_tick_count::tsc_interval_t operator-(const tsc_tick_count& t1, const tsc_tick_count& t0)
  {
      return tsc_tick_count::tsc_interval_t( t1.my_count-t0.my_count );
  }
  
  inline tsc_tick_count::tsc_interval_t operator-(const tsc_tick_count::tsc_interval_t& i1, const tsc_tick_count::tsc_interval_t& i0)
  {
      return tsc_tick_count::tsc_interval_t( i1.value-i0.value );
  }
  
  inline tsc_tick_count::tsc_interval_t& operator+=(tsc_tick_count::tsc_interval_t& i1, const tsc_tick_count::tsc_interval_t& i0)
  {
      i1.value += i0.value;
      return i1;
  }
  
  #if KMP_HAVE_TICK_TIME
  inline double tsc_tick_count::tsc_interval_t::seconds() const
  {
      return value*tick_time();
  }
  #endif
  
  extern std::string formatSI(double interval, int width, char unit);
  
  inline std::string formatSeconds(double interval, int width)
  {
      return formatSI(interval, width, 'S');
  }
  
  inline std::string formatTicks(double interval, int width)
  {
      return formatSI(interval, width, 'T');
  }
  
  #endif // KMP_STATS_TIMING_H
  