sysdeps/ieee754/flt-32/s_lrintf.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2024 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <fenv.h>
  21 #include <limits.h>
  22 #include <math.h>
  23
  24 #include <math-narrow-eval.h>
  25 #include <math_private.h>
  26 #include <libm-alias-float.h>
  27 #include <fix-fp-int-convert-overflow.h>
  28 #include <math-use-builtins.h>
  29
  30
  31 long int
  32 __lrintf (float x)
  33 {
  34 #if USE_LRINTF_BUILTIN
  35   return __builtin_lrintf (x);
  36 #else
  37   /* Use generic implementation.  */
  38   static const float two23[2] =
  39   {
  40     8.3886080000e+06, /* 0x4B000000 */
  41    -8.3886080000e+06, /* 0xCB000000 */
  42   };
  43
  44   int32_t j0;
  45   uint32_t i0;
  46   float w;
  47   float t;
  48   long int result;
  49   int sx;
  50
  51   GET_FLOAT_WORD (i0, x);
  52
  53   sx = i0 >> 31;
  54   j0 = ((i0 >> 23) & 0xff) - 0x7f;
  55   i0 &= 0x7fffff;
  56   i0 |= 0x800000;
  57
  58   if (j0 < (int32_t) (sizeof (long int) * 8) - 1)
  59     {
  60       if (j0 >= 23)
  61         result = (long int) i0 << (j0 - 23);
  62       else
  63         {
  64           w = math_narrow_eval (two23[sx] + x);
  65           t = w - two23[sx];
  66           GET_FLOAT_WORD (i0, t);
  67           j0 = ((i0 >> 23) & 0xff) - 0x7f;
  68           i0 &= 0x7fffff;
  69           i0 |= 0x800000;
  70
  71           result = (j0 < 0 ? 0 : i0 >> (23 - j0));
  72         }
  73     }
  74   else
  75     {
  76 #ifdef FE_INVALID
  77       /* The number is too large.  Unless it rounds to LONG_MIN,
  78          FE_INVALID must be raised and the return value is
  79          unspecified.  */
  80       if (FIX_FLT_LONG_CONVERT_OVERFLOW && x != (float) LONG_MIN)
  81         {
  82           feraiseexcept (FE_INVALID);
  83           return sx == 0 ? LONG_MAX : LONG_MIN;
  84         }
  85 #endif
  86       return (long int) x;
  87     }
  88
  89   return sx ? -result : result;
  90 #endif /* ! USE_LRINTF_BUILTIN  */
  91 }
  92
  93 libm_alias_float (__lrint, lrint)