sysdeps/ieee754/flt-32/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2015 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include <math.h>
  22
  23 #include <math_private.h>
  24
  25 static const float two23[2] =
  26 {
  27   8.3886080000e+06, /* 0x4B000000 */
  28  -8.3886080000e+06, /* 0xCB000000 */
  29 };
  30
  31
  32 long int
  33 __lrintf (float x)
  34 {
  35   int32_t j0;
  36   u_int32_t i0;
  37   volatile float w;
  38   float t;
  39   long int result;
  40   int sx;
  41
  42   GET_FLOAT_WORD (i0, x);
  43
  44   sx = i0 >> 31;
  45   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  46   i0 &= 0x7fffff;
  47   i0 |= 0x800000;
  48
  49   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
  50     {
  51       if (j0 >= 23)
  52         result = (long int) i0 << (j0 - 23);
  53       else
  54         {
  55           w = two23[sx] + x;
  56           t = w - two23[sx];
  57           GET_FLOAT_WORD (i0, t);
  58           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  59           i0 &= 0x7fffff;
  60           i0 |= 0x800000;
  61
  62           result = (j0 < 0 ? 0 : i0 >> (23 - j0));
  63         }
  64     }
  65   else
  66     {
  67       /* The number is too large.  It is left implementation defined
  68          what happens.  */
  69       return (long int) x;
  70     }
  71
  72   return sx ? -result : result;
  73 }
  74
  75 weak_alias (__lrintf, lrintf)