sysdeps/ieee754/flt-32/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2018 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 <fenv_private.h>
  28 #include <libm-alias-float.h>
  29 #include <fix-fp-int-convert-overflow.h>
  30
  31 static const float two23[2] =
  32 {
  33   8.3886080000e+06, /* 0x4B000000 */
  34  -8.3886080000e+06, /* 0xCB000000 */
  35 };
  36
  37
  38 long int
  39 __lrintf (float x)
  40 {
  41   int32_t j0;
  42   uint32_t i0;
  43   float w;
  44   float t;
  45   long int result;
  46   int sx;
  47
  48   GET_FLOAT_WORD (i0, x);
  49
  50   sx = i0 >> 31;
  51   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  52   i0 &= 0x7fffff;
  53   i0 |= 0x800000;
  54
  55   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
  56     {
  57       if (j0 >= 23)
  58         result = (long int) i0 << (j0 - 23);
  59       else
  60         {
  61           w = math_narrow_eval (two23[sx] + x);
  62           t = w - two23[sx];
  63           GET_FLOAT_WORD (i0, t);
  64           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  65           i0 &= 0x7fffff;
  66           i0 |= 0x800000;
  67
  68           result = (j0 < 0 ? 0 : i0 >> (23 - j0));
  69         }
  70     }
  71   else
  72     {
  73 #ifdef FE_INVALID
  74       /* The number is too large.  Unless it rounds to LONG_MIN,
  75          FE_INVALID must be raised and the return value is
  76          unspecified.  */
  77       if (FIX_FLT_LONG_CONVERT_OVERFLOW && x != (float) LONG_MIN)
  78         {
  79           feraiseexcept (FE_INVALID);
  80           return sx == 0 ? LONG_MAX : LONG_MIN;
  81         }
  82 #endif
  83       return (long int) x;
  84     }
  85
  86   return sx ? -result : result;
  87 }
  88
  89 libm_alias_float (__lrint, lrint)