C header including Timer, Unroll, etc

commons.h

#pragma once
#include <stdint.h>

/* -------------------- UNROLL ---------------------- */
/* DO NOT use unroll without braces.                  */
#define X5(inst) inst inst inst inst inst
#define X10(inst) X5(inst) X5(inst)
#define X50(inst) X10(inst) X10(inst) X10(inst) X10(inst) X10(inst)
#define X100(inst) X50(inst) X50(inst)
#define X500(inst) X100(inst) X100(inst) X100(inst) X100(inst) X100(inst)
#define X1000(inst) X500(inst) X500(inst)
#define X2(inst) inst inst
#define X4(inst) X2(inst) X2(inst)
#define X8(inst) X4(inst) X4(inst)

/* --------------------- TIMER ----------------------- */
/* Use TICK TOCK macro to count.                       */

#define TICK(v) { v = high_resolution_timer_ns(); }
#define TOCK(v) { uint64_t w; w = high_resolution_timer_ns(); v = w - v; }

#if defined(__linux)
  #define HAVE_POSIX_TIMER
  #include <time.h>
  #ifdef CLOCK_MONOTONIC
    #define CLOCKID CLOCK_MONOTONIC
  #else
    #define CLOCKID CLOCK_REALTIME
  #endif
#elif defined(__APPLE__)
  #define HAVE_MACH_TIMER
  #include <mach/mach_time.h>
#elif defined(_WIN32)
  #define WIN32_LEAN_AND_MEAN
  #include <windows.h>
#endif

static uint64_t high_resolution_timer_ns() {
  static uint64_t is_init = 0;
#if defined(__linux)
  static struct timespec linux_rate;
  if (0 == is_init) {
    clock_getres(CLOCKID, &linux_rate);
    is_init = 1;
  }
  uint64_t now;
  struct timespec spec;
  clock_gettime(CLOCKID, &spec);
  now = spec.tv_sec * 1.0e9 + spec.tv_nsec;
  return now;
#elif defined(__APPLE__)
  static mach_timebase_info_data_t info;
  if (0 == is_init) {
    mach_timebase_info(&info);
    is_init = 1;
  }
  uint64_t now;
  now = mach_absolute_time();
  now *= info.numer;
  now /= info.denom;
  return now;
#elif defined(_WIN32)
  static LARGE_INTEGER win_frequency;
  if (0 == is_init) {
    QueryPerformanceFrequency(&win_frequency);
    is_init = 1;
  }
  LARGE_INTEGER now;
  QueryPerformanceCounter(&now);
  return (uint64_t) ((1e9 * now.QuadPart)  / win_frequency.QuadPart);
#endif
}