sysdeps/ieee754/flt-32/s_roundf.c

   1 /* Round float to integer away from zero.
   2    Copyright (C) 1997-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #define NO_MATH_REDIRECT
  20 #include <math.h>
  21
  22 #include <math_private.h>
  23 #include <libm-alias-float.h>
  24 #include <math-use-builtins.h>
  25
  26
  27 float
  28 __roundf (float x)
  29 {
  30 #if USE_ROUNDF_BUILTIN
  31   return __builtin_roundf (x);
  32 #else
  33   /* Use generic implementation.  */
  34   int32_t i0, j0;
  35
  36   GET_FLOAT_WORD (i0, x);
  37   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  38   if (j0 < 23)
  39     {
  40       if (j0 < 0)
  41         {
  42           i0 &= 0x80000000;
  43           if (j0 == -1)
  44             i0 |= 0x3f800000;
  45         }
  46       else
  47         {
  48           uint32_t i = 0x007fffff >> j0;
  49           if ((i0 & i) == 0)
  50             /* X is integral.  */
  51             return x;
  52
  53           i0 += 0x00400000 >> j0;
  54           i0 &= ~i;
  55         }
  56     }
  57   else
  58     {
  59       if (j0 == 0x80)
  60         /* Inf or NaN.  */
  61         return x + x;
  62       else
  63         return x;
  64     }
  65
  66   SET_FLOAT_WORD (x, i0);
  67   return x;
  68 #endif /* ! USE_ROUNDF_BUILTIN  */
  69 }
  70 libm_alias_float (__round, round)