sysdeps/ieee754/ldbl-96/s_lroundl.c

   1 /* Round long double value to long int.
   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 #include <fenv.h>
  20 #include <limits.h>
  21 #include <math.h>
  22
  23 #include <math_private.h>
  24 #include <libm-alias-ldouble.h>
  25
  26
  27 long int
  28 __lroundl (long double x)
  29 {
  30   int32_t j0;
  31   uint32_t se, i1, i0;
  32   long int result;
  33   int sign;
  34
  35   GET_LDOUBLE_WORDS (se, i0, i1, x);
  36   j0 = (se & 0x7fff) - 0x3fff;
  37   sign = (se & 0x8000) != 0 ? -1 : 1;
  38
  39   if (j0 < 31)
  40     {
  41       if (j0 < 0)
  42         return j0 < -1 ? 0 : sign;
  43       else
  44         {
  45           uint32_t j = i0 + (0x40000000 >> j0);
  46           if (j < i0)
  47             {
  48               j >>= 1;
  49               j |= 0x80000000;
  50               ++j0;
  51             }
  52
  53           result = j >> (31 - j0);
  54 #ifdef FE_INVALID
  55           if (sizeof (long int) == 4
  56               && sign == 1
  57               && result == LONG_MIN)
  58             /* Rounding brought the value out of range.  */
  59             feraiseexcept (FE_INVALID);
  60 #endif
  61         }
  62     }
  63   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  64     {
  65       if (j0 >= 63)
  66         result = ((long int) i0 << (j0 - 31)) | (i1 << (j0 - 63));
  67       else
  68         {
  69           uint32_t j = i1 + (0x80000000 >> (j0 - 31));
  70           unsigned long int ures = i0;
  71
  72           if (j < i1)
  73             ++ures;
  74
  75           if (j0 == 31)
  76             result = ures;
  77           else
  78             {
  79               result = (ures << (j0 - 31)) | (j >> (63 - j0));
  80 #ifdef FE_INVALID
  81               if (sizeof (long int) == 8
  82                   && sign == 1
  83                   && result == LONG_MIN)
  84                 /* Rounding brought the value out of range.  */
  85                 feraiseexcept (FE_INVALID);
  86 #endif
  87             }
  88         }
  89     }
  90   else
  91     {
  92       /* The number is too large.  Unless it rounds to LONG_MIN,
  93          FE_INVALID must be raised and the return value is
  94          unspecified.  */
  95 #ifdef FE_INVALID
  96       if (sizeof (long int) == 4
  97           && x <= (long double) LONG_MIN - 0.5L)
  98         {
  99           /* If truncation produces LONG_MIN, the cast will not raise
 100              the exception, but may raise "inexact".  */
 101           feraiseexcept (FE_INVALID);
 102           return LONG_MIN;
 103         }
 104 #endif
 105       return (long int) x;
 106     }
 107
 108   return sign * result;
 109 }
 110
 111 libm_alias_ldouble (__lround, lround)