sysdeps/ieee754/flt-32/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2019 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 <fenv.h>
  22 #include <limits.h>
  23 #include <math.h>
  24
  25 #include <math-narrow-eval.h>
  26 #include <math_private.h>
  27 #include <libm-alias-float.h>
  28 #include <fix-fp-int-convert-overflow.h>
  29
  30 static const float two23[2] =
  31 {
  32   8.3886080000e+06, /* 0x4B000000 */
  33  -8.3886080000e+06, /* 0xCB000000 */
  34 };
  35
  36
  37 long int
  38 __lrintf (float x)
  39 {
  40   int32_t j0;
  41   uint32_t i0;
  42   float w;
  43   float t;
  44   long int result;
  45   int sx;
  46
  47   GET_FLOAT_WORD (i0, x);
  48
  49   sx = i0 >> 31;
  50   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  51   i0 &= 0x7fffff;
  52   i0 |= 0x800000;
  53
  54   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
  55     {
  56       if (j0 >= 23)
  57         result = (long int) i0 << (j0 - 23);
  58       else
  59         {
  60           w = math_narrow_eval (two23[sx] + x);
  61           t = w - two23[sx];
  62           GET_FLOAT_WORD (i0, t);
  63           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  64           i0 &= 0x7fffff;
  65           i0 |= 0x800000;
  66
  67           result = (j0 < 0 ? 0 : i0 >> (23 - j0));
  68         }
  69     }
  70   else
  71     {
  72 #ifdef FE_INVALID
  73       /* The number is too large.  Unless it rounds to LONG_MIN,
  74          FE_INVALID must be raised and the return value is
  75          unspecified.  */
  76       if (FIX_FLT_LONG_CONVERT_OVERFLOW && x != (float) LONG_MIN)
  77         {
  78           feraiseexcept (FE_INVALID);
  79           return sx == 0 ? LONG_MAX : LONG_MIN;
  80         }
  81 #endif
  82       return (long int) x;
  83     }
  84
  85   return sx ? -result : result;
  86 }
  87
  88 libm_alias_float (__lrint, lrint)