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 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <math.h>
  22 #include <fenv_libc.h>
  23 #include <math_ldbl_opt.h>
  24 #include <float.h>
  25 #include <ieee754.h>
  26
  27
  28 #ifdef __STDC__
  29 long double
  30 __ceill (long double x)
  31 #else
  32 long double
  33 __ceill (x)
  34      long double x;
  35 #endif
  36 {
  37   double xh, xl, hi, lo;
  38
  39   ldbl_unpack (x, &xh, &xl);
  40
  41   /* Return Inf, Nan, +/-0 unchanged.  */
  42   if (__builtin_expect (xh != 0.0
  43                         && __builtin_isless (__builtin_fabs (xh),
  44                                              __builtin_inf ()), 1))
  45     {
  46       double orig_xh;
  47       int save_round = fegetround ();
  48
  49       /* Long double arithmetic, including the canonicalisation below,
  50          only works in round-to-nearest mode.  */
  51       fesetround (FE_TONEAREST);
  52
  53       /* Convert the high double to integer.  */
  54       orig_xh = xh;
  55       hi = ldbl_nearbyint (xh);
  56
  57       /* Subtract integral high part from the value.  */
  58       xh -= hi;
  59       ldbl_canonicalize (&xh, &xl);
  60
  61       /* Now convert the low double, adjusted for any remainder from the
  62          high double.  */
  63       lo = ldbl_nearbyint (xh);
  64
  65       /* Adjust the result when the remainder is non-zero.  nearbyint
  66          rounds values to the nearest integer, and values halfway
  67          between integers to the nearest even integer.  ceill must
  68          round towards +Inf.  */
  69       xh -= lo;
  70       ldbl_canonicalize (&xh, &xl);
  71
  72       if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
  73         lo += 1.0;
  74
  75       /* Ensure the final value is canonical.  In certain cases,
  76          rounding causes hi,lo calculated so far to be non-canonical.  */
  77       xh = hi;
  78       xl = lo;
  79       ldbl_canonicalize (&xh, &xl);
  80
  81       /* Ensure we return -0 rather than +0 when appropriate.  */
  82       if (orig_xh < 0.0)
  83         xh = -__builtin_fabs (xh);
  84
  85       fesetround (save_round);
  86     }
  87
  88   return ldbl_pack (xh, xl);
  89 }
  90
  91 long_double_symbol (libm, __ceill, ceill);