#include <float.h>
#include <malloc.h>
#include <math.h>
#include <stdio.h>
#ifndef _MSC_VER
#include <sys/time.h>
#endif

#define NUM 1048576

#define FUNC gnulib_frexp
#define DOUBLE double
#ifdef _MSC_VER
#define ISNAN _isnan
#else
#define ISNAN __builtin_isnan
#endif
#define DECL_ROUNDING
#define BEGIN_ROUNDING()
#define END_ROUNDING()
#define L_(literal) literal

DOUBLE
FUNC (DOUBLE x, int *expptr)
{
  int sign;
  int exponent;
  DECL_ROUNDING

  /* Test for NaN, infinity, and zero.  */
  if (ISNAN (x) || x + x == x)
    {
      *expptr = 0;
      return x;
    }

  sign = 0;
  if (x < 0)
    {
      x = - x;
      sign = -1;
    }

  BEGIN_ROUNDING ();

  {
    /* Since the exponent is an 'int', it fits in 64 bits.  Therefore the
       loops are executed no more than 64 times.  */
    DOUBLE pow2[64]; /* pow2[i] = 2^2^i */
    DOUBLE powh[64]; /* powh[i] = 2^-2^i */
    int i;

    exponent = 0;
    if (x >= L_(1.0))
      {
        /* A positive exponent.  */
        DOUBLE pow2_i; /* = pow2[i] */
        DOUBLE powh_i; /* = powh[i] */

        /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
           x * 2^exponent = argument, x >= 1.0.  */
        for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
             ;
             i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
          {
            if (x >= pow2_i)
              {
                exponent += (1 << i);
                x *= powh_i;
              }
            else
              break;

            pow2[i] = pow2_i;
            powh[i] = powh_i;
          }
        /* Avoid making x too small, as it could become a denormalized
           number and thus lose precision.  */
        while (i > 0 && x < pow2[i - 1])
          {
            i--;
            powh_i = powh[i];
          }
        exponent += (1 << i);
        x *= powh_i;
        /* Here 2^-2^i <= x < 1.0.  */
      }
    else
      {
        /* A negative or zero exponent.  */
        DOUBLE pow2_i; /* = pow2[i] */
        DOUBLE powh_i; /* = powh[i] */

        /* Invariants: pow2_i = 2^2^i, powh_i = 2^-2^i,
           x * 2^exponent = argument, x < 1.0.  */
        for (i = 0, pow2_i = L_(2.0), powh_i = L_(0.5);
             ;
             i++, pow2_i = pow2_i * pow2_i, powh_i = powh_i * powh_i)
          {
            if (x < powh_i)
              {
                exponent -= (1 << i);
                x *= pow2_i;
              }
            else
              break;

            pow2[i] = pow2_i;
            powh[i] = powh_i;
          }
        /* Here 2^-2^i <= x < 1.0.  */
      }

    /* Invariants: x * 2^exponent = argument, and 2^-2^i <= x < 1.0.  */
    while (i > 0)
      {
        i--;
        if (x < powh[i])
          {
            exponent -= (1 << i);
            x *= pow2[i];
          }
      }
    /* Here 0.5 <= x < 1.0.  */
  }

  if (sign < 0)
    x = - x;

  END_ROUNDING ();

  *expptr = exponent;
  return x;
}

int main (int argc, char **argv)
{
  double x, y;
  int yi, i;
  int n = NUM, use_gnulib = 0;

  if (argc > 1)
    {
      use_gnulib = atoi (argv[1]);
      if (argc > 2)
        n = atoi (argv[2]);
    }

  x = rand ();

  if (use_gnulib)
    {
      for (i = 0; i < n; i++)
        y = gnulib_frexp (x, &yi);
    }
  else
    {
      for (i = 0; i < n; i++)
        y = frexp (x, &yi);
    }

  return 0;
}