sysdeps/ieee754/ldbl-128ibm/s_ceill.c

   1 /* Ceil (round to +inf) long double floating-point values.
   2    IBM extended format long double version.
   3    Copyright (C) 2006-2014 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21 #include <math_ldbl_opt.h>
  22 #include <float.h>
  23 #include <ieee754.h>
  24
  25
  26 long double
  27 __ceill (long double x)
  28 {
  29   double xh, xl, hi, lo;
  30
  31   ldbl_unpack (x, &xh, &xl);
  32
  33   /* Return Inf, Nan, +/-0 unchanged.  */
  34   if (__builtin_expect (xh != 0.0
  35                         && __builtin_isless (__builtin_fabs (xh),
  36                                              __builtin_inf ()), 1))
  37     {
  38       double orig_xh;
  39
  40       /* Long double arithmetic, including the canonicalisation below,
  41          only works in round-to-nearest mode.  */
  42
  43       /* Convert the high double to integer.  */
  44       orig_xh = xh;
  45       hi = ldbl_nearbyint (xh);
  46
  47       /* Subtract integral high part from the value.  */
  48       xh -= hi;
  49       ldbl_canonicalize (&xh, &xl);
  50
  51       /* Now convert the low double, adjusted for any remainder from the
  52          high double.  */
  53       lo = ldbl_nearbyint (xh);
  54
  55       /* Adjust the result when the remainder is non-zero.  nearbyint
  56          rounds values to the nearest integer, and values halfway
  57          between integers to the nearest even integer.  ceill must
  58          round towards +Inf.  */
  59       xh -= lo;
  60       ldbl_canonicalize (&xh, &xl);
  61
  62       if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
  63         lo += 1.0;
  64
  65       /* Ensure the final value is canonical.  In certain cases,
  66          rounding causes hi,lo calculated so far to be non-canonical.  */
  67       xh = hi;
  68       xl = lo;
  69       ldbl_canonicalize (&xh, &xl);
  70
  71       /* Ensure we return -0 rather than +0 when appropriate.  */
  72       if (orig_xh < 0.0)
  73         xh = -__builtin_fabs (xh);
  74     }
  75
  76   return ldbl_pack (xh, xl);
  77 }
  78
  79 long_double_symbol (libm, __ceill, ceill);