Esempio n. 1
0
long
__lrintl (long double x)
{
  double xh, xl;
  long res, hi, lo;
  int save_round;

  ldbl_unpack (x, &xh, &xl);

  /* Limit the range of values handled by the conversion to long.
     We do this because we aren't sure whether that conversion properly
     raises FE_INVALID.  */
  if (
#if __LONG_MAX__ == 2147483647
      __builtin_expect
      ((__builtin_fabs (xh) <= (double) __LONG_MAX__ + 2), 1)
#else
      __builtin_expect
      ((__builtin_fabs (xh) <= -(double) (-__LONG_MAX__ - 1)), 1)
#endif
#if !defined (FE_INVALID)
      || 1
#endif
    )
    {
      save_round = __fegetround ();

#if __LONG_MAX__ == 2147483647
      long long llhi = (long long) xh;
      if (llhi != (long) llhi)
	hi = llhi < 0 ? -__LONG_MAX__ - 1 : __LONG_MAX__;
      else
	hi = llhi;
      xh -= hi;
#else
      if (__glibc_unlikely ((xh == -(double) (-__LONG_MAX__ - 1))))
	{
	  /* When XH is 9223372036854775808.0, converting to long long will
	     overflow, resulting in an invalid operation.  However, XL might
	     be negative and of sufficient magnitude that the overall long
	     double is in fact in range.  Avoid raising an exception.  In any
	     case we need to convert this value specially, because
	     the converted value is not exactly represented as a double
	     thus subtracting HI from XH suffers rounding error.  */
	  hi = __LONG_MAX__;
	  xh = 1.0;
	}
      else
	{
	  hi = (long) xh;
	  xh -= hi;
	}
#endif
      ldbl_canonicalize (&xh, &xl);

      lo = (long) xh;

      /* Peg at max/min values, assuming that the above conversions do so.
         Strictly speaking, we can return anything for values that overflow,
         but this is more useful.  */
      res = hi + lo;

      /* This is just sign(hi) == sign(lo) && sign(res) != sign(hi).  */
      if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
	goto overflow;

      xh -= lo;
      ldbl_canonicalize (&xh, &xl);

      hi = res;
      switch (save_round)
	{
	case FE_TONEAREST:
	  if (fabs (xh) < 0.5
	      || (fabs (xh) == 0.5
		  && ((xh > 0.0 && xl < 0.0)
		      || (xh < 0.0 && xl > 0.0)
		      || (xl == 0.0 && (res & 1) == 0))))
	    return res;

	  if (xh < 0.0)
	    res -= 1;
	  else
	    res += 1;
	  break;

	case FE_TOWARDZERO:
	  if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
	    res -= 1;
	  else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
	    res += 1;
	  return res;
	  break;

	case FE_UPWARD:
	  if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
	    res += 1;
	  break;

	case FE_DOWNWARD:
	  if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
	    res -= 1;
	  break;
	}

      if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
	goto overflow;

      return res;
    }
  else
    {
      if (xh > 0.0)
	hi = __LONG_MAX__;
      else if (xh < 0.0)
	hi = -__LONG_MAX__ - 1;
      else
	/* Nan */
	hi = 0;
    }

overflow:
#ifdef FE_INVALID
  feraiseexcept (FE_INVALID);
#endif
  return hi;
}
Esempio n. 2
0
double
__ieee754_sqrt (double x)
{
#include "uroot.h"
    static const double
    rt0 = 9.99999999859990725855365213134618E-01,
    rt1 = 4.99999999495955425917856814202739E-01,
    rt2 = 3.75017500867345182581453026130850E-01,
    rt3 = 3.12523626554518656309172508769531E-01;
    static const double big = 134217728.0;
    double y, t, del, res, res1, hy, z, zz, p, hx, tx, ty, s;
    mynumber a, c = { { 0, 0 } };
    int4 k;

    a.x = x;
    k = a.i[HIGH_HALF];
    a.i[HIGH_HALF] = (k & 0x001fffff) | 0x3fe00000;
    t = inroot[(k & 0x001fffff) >> 14];
    s = a.x;
    /*----------------- 2^-1022  <= | x |< 2^1024  -----------------*/
    if (k > 0x000fffff && k < 0x7ff00000)
    {
        int rm = __fegetround ();
        fenv_t env;
        libc_feholdexcept_setround (&env, FE_TONEAREST);
        double ret;
        y = 1.0 - t * (t * s);
        t = t * (rt0 + y * (rt1 + y * (rt2 + y * rt3)));
        c.i[HIGH_HALF] = 0x20000000 + ((k & 0x7fe00000) >> 1);
        y = t * s;
        hy = (y + big) - big;
        del = 0.5 * t * ((s - hy * hy) - (y - hy) * (y + hy));
        res = y + del;
        if (res == (res + 1.002 * ((y - res) + del)))
            ret = res * c.x;
        else
        {
            res1 = res + 1.5 * ((y - res) + del);
            EMULV (res, res1, z, zz, p, hx, tx, hy, ty); /* (z+zz)=res*res1 */
            res = ((((z - s) + zz) < 0) ? max (res, res1) :
                   min (res, res1));
            ret = res * c.x;
        }
        math_force_eval (ret);
        libc_fesetenv (&env);
        double dret = x / ret;
        if (dret != ret)
        {
            double force_inexact = 1.0 / 3.0;
            math_force_eval (force_inexact);
            /* The square root is inexact, ret is the round-to-nearest
               value which may need adjusting for other rounding
               modes.  */
            switch (rm)
            {
#ifdef FE_UPWARD
            case FE_UPWARD:
                if (dret > ret)
                    ret = (res + 0x1p-1022) * c.x;
                break;
#endif

#ifdef FE_DOWNWARD
            case FE_DOWNWARD:
#endif
#ifdef FE_TOWARDZERO
            case FE_TOWARDZERO:
#endif
#if defined FE_DOWNWARD || defined FE_TOWARDZERO
                if (dret < ret)
                    ret = (res - 0x1p-1022) * c.x;
                break;
#endif

            default:
                break;
            }
        }
        /* Otherwise (x / ret == ret), either the square root was exact or
           the division was inexact.  */
        return ret;
    }