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

   1 /* Round to int 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 __floorl (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       /* Long double arithmetic, including the canonicalisation below,
  39          only works in round-to-nearest mode.  */
  40
  41       /* Convert the high double to integer.  */
  42       hi = ldbl_nearbyint (xh);
  43
  44       /* Subtract integral high part from the value.  */
  45       xh -= hi;
  46       ldbl_canonicalize (&xh, &xl);
  47
  48       /* Now convert the low double, adjusted for any remainder from the
  49          high double.  */
  50       lo = ldbl_nearbyint (xh);
  51
  52       /* Adjust the result when the remainder is non-zero.  nearbyint
  53          rounds values to the nearest integer, and values halfway
  54          between integers to the nearest even integer.  floorl must
  55          round towards -Inf.  */
  56       xh -= lo;
  57       ldbl_canonicalize (&xh, &xl);
  58
  59       if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
  60         lo += -1.0;
  61
  62       /* Ensure the final value is canonical.  In certain cases,
  63          rounding causes hi,lo calculated so far to be non-canonical.  */
  64       xh = hi;
  65       xl = lo;
  66       ldbl_canonicalize (&xh, &xl);
  67     }
  68
  69   return ldbl_pack (xh, xl);
  70 }
  71
  72 long_double_symbol (libm, __floorl, floorl);