sysdeps/libm-ieee754/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997 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 Library General Public License as
   9    published by the Free Software Foundation; either version 2 of the
  10    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    Library General Public License for more details.
  16
  17    You should have received a copy of the GNU Library General Public
  18    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  19    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26 static const double 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 < -1)
  53         return 0;
  54       else if (j0 >= 23)
  55         result = (long int) i0 << (j0 - 23);
  56       else
  57         {
  58           w = two23[sx] + x;
  59           t = w - two23[sx];
  60           GET_FLOAT_WORD (i0, t);
  61           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  62           i0 &= 0x7fffff;
  63           i0 |= 0x800000;
  64
  65           result = i0 >> (23 - j0);
  66         }
  67     }
  68   else
  69     {
  70       /* The number is too large.  It is left implementation defined
  71          what happens.  */
  72       return (long int) x;
  73     }
  74
  75   return sx ? -result : result;
  76 }
  77
  78 weak_alias (__lrintf, lrintf)