sysdeps/ieee754/flt-32/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997, 2006 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, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26 static const float two23[2] =
  27 {
  28   8.3886080000e+06, /* 0x4B000000 */
  29  -8.3886080000e+06, /* 0xCB000000 */
  30 };
  31
  32
  33 long int
  34 __lrintf (float x)
  35 {
  36   int32_t j0;
  37   u_int32_t i0;
  38   volatile float w;
  39   float t;
  40   long int result;
  41   int sx;
  42
  43   GET_FLOAT_WORD (i0, x);
  44
  45   sx = i0 >> 31;
  46   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  47   i0 &= 0x7fffff;
  48   i0 |= 0x800000;
  49
  50   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
  51     {
  52       if (j0 >= 23)
  53         result = (long int) i0 << (j0 - 23);
  54       else
  55         {
  56           w = two23[sx] + x;
  57           t = w - two23[sx];
  58           GET_FLOAT_WORD (i0, t);
  59           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  60           i0 &= 0x7fffff;
  61           i0 |= 0x800000;
  62
  63           result = (j0 < 0 ? 0 : i0 >> (23 - j0));
  64         }
  65     }
  66   else
  67     {
  68       /* The number is too large.  It is left implementation defined
  69          what happens.  */
  70       return (long int) x;
  71     }
  72
  73   return sx ? -result : result;
  74 }
  75
  76 weak_alias (__lrintf, lrintf)