libquadmath/math/lrintq.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 and
   6                   Jakub Jelinek <jj@ultra.linux.cz>, 1999.
   7
   8    The GNU C Library is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU Lesser General Public
  10    License as published by the Free Software Foundation; either
  11    version 2.1 of the License, or (at your option) any later version.
  12
  13    The GNU C Library is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16    Lesser General Public License for more details.
  17
  18    You should have received a copy of the GNU Lesser General Public
  19    License along with the GNU C Library; if not, see
  20    <http://www.gnu.org/licenses/>.  */
  21
  22 #include "quadmath-imp.h"
  23
  24 static const __float128 two112[2] =
  25 {
  26   5.19229685853482762853049632922009600E+33Q, /* 0x406F000000000000, 0 */
  27  -5.19229685853482762853049632922009600E+33Q  /* 0xC06F000000000000, 0 */
  28 };
  29
  30 long int
  31 lrintq (__float128 x)
  32 {
  33   int32_t j0;
  34   uint64_t i0,i1;
  35   __float128 w;
  36   __float128 t;
  37   long int result;
  38   int sx;
  39
  40   GET_FLT128_WORDS64 (i0, i1, x);
  41   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  42   sx = i0 >> 63;
  43   i0 &= 0x0000ffffffffffffLL;
  44   i0 |= 0x0001000000000000LL;
  45
  46   if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  47     {
  48       if (j0 < 48)
  49         {
  50 #if defined FE_INVALID || defined FE_INEXACT
  51           /* X < LONG_MAX + 1 implied by J0 < 31.  */
  52           if (sizeof (long int) == 4
  53               && x > (__float128) LONG_MAX)
  54             {
  55               /* In the event of overflow we must raise the "invalid"
  56                  exception, but not "inexact".  */
  57               t = nearbyintq (x);
  58               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  59             }
  60           else
  61 #endif
  62             {
  63               w = two112[sx] + x;
  64               t = w - two112[sx];
  65             }
  66           GET_FLT128_WORDS64 (i0, i1, t);
  67           j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  68           i0 &= 0x0000ffffffffffffLL;
  69           i0 |= 0x0001000000000000LL;
  70
  71           result = (j0 < 0 ? 0 : i0 >> (48 - j0));
  72         }
  73       else if (j0 >= 112)
  74         result = ((long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  75       else
  76         {
  77 #if defined FE_INVALID || defined FE_INEXACT
  78           /* X < LONG_MAX + 1 implied by J0 < 63.  */
  79           if (sizeof (long int) == 8
  80               && x > (__float128) LONG_MAX)
  81             {
  82               /* In the event of overflow we must raise the "invalid"
  83                  exception, but not "inexact".  */
  84               t = nearbyintq (x);
  85               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  86             }
  87           else
  88 #endif
  89             {
  90               w = two112[sx] + x;
  91               t = w - two112[sx];
  92             }
  93           GET_FLT128_WORDS64 (i0, i1, t);
  94           j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  95           i0 &= 0x0000ffffffffffffLL;
  96           i0 |= 0x0001000000000000LL;
  97
  98           if (j0 == 48)
  99             result = (long int) i0;
 100           else
 101             result = ((long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
 102         }
 103     }
 104   else
 105     {
 106       /* The number is too large.  Unless it rounds to LONG_MIN,
 107          FE_INVALID must be raised and the return value is
 108          unspecified.  */
 109 #if defined FE_INVALID || defined FE_INEXACT
 110       if (x < (__float128) LONG_MIN
 111           && x > (__float128) LONG_MIN - 1)
 112         {
 113           /* If truncation produces LONG_MIN, the cast will not raise
 114              the exception, but may raise "inexact".  */
 115           t = nearbyintq (x);
 116           feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
 117           return LONG_MIN;
 118         }
 119       else if (FIX_FLT128_LONG_CONVERT_OVERFLOW && x != (__float128) LONG_MIN)
 120         {
 121           feraiseexcept (FE_INVALID);
 122           return sx == 0 ? LONG_MAX : LONG_MIN;
 123         }
 124
 125 #endif
 126       return (long int) x;
 127     }
 128
 129   return sx ? -result : result;
 130 }