libquadmath/math/llrintq.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 long int
  31 llrintq (__float128 x)
  32 {
  33   int32_t j0;
  34   uint64_t i0,i1;
  35   __float128 w;
  36   __float128 t;
  37   long 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 long int)) - 1)
  47     {
  48 #if defined FE_INVALID || defined FE_INEXACT
  49       /* X < LLONG_MAX + 1 implied by J0 < 63.  */
  50       if (x > (__float128) LLONG_MAX)
  51         {
  52           /* In the event of overflow we must raise the "invalid"
  53              exception, but not "inexact".  */
  54           t = nearbyintq (x);
  55           feraiseexcept (t == LLONG_MAX ? FE_INEXACT : FE_INVALID);
  56         }
  57       else
  58 #endif
  59         {
  60           w = two112[sx] + x;
  61           t = w - two112[sx];
  62         }
  63       GET_FLT128_WORDS64 (i0, i1, t);
  64       j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  65       i0 &= 0x0000ffffffffffffLL;
  66       i0 |= 0x0001000000000000LL;
  67
  68       if (j0 < 0)
  69         result = 0;
  70       else if (j0 <= 48)
  71         result = i0 >> (48 - j0);
  72       else
  73         result = ((long long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
  74     }
  75   else
  76     {
  77       /* The number is too large.  Unless it rounds to LLONG_MIN,
  78          FE_INVALID must be raised and the return value is
  79          unspecified.  */
  80 #if defined FE_INVALID || defined FE_INEXACT
  81       if (x < (__float128) LLONG_MIN
  82           && x > (__float128) LLONG_MIN - 1)
  83         {
  84           /* If truncation produces LLONG_MIN, the cast will not raise
  85              the exception, but may raise "inexact".  */
  86           t = nearbyintq (x);
  87           feraiseexcept (t == LLONG_MIN ? FE_INEXACT : FE_INVALID);
  88           return LLONG_MIN;
  89         }
  90       else if (FIX_FLT128_LLONG_CONVERT_OVERFLOW && x != (__float128) LLONG_MIN)
  91         {
  92           feraiseexcept (FE_INVALID);
  93           return sx == 0 ? LLONG_MAX : LLONG_MIN;
  94         }
  95
  96 #endif
  97       return (long long int) x;
  98     }
  99
 100   return sx ? -result : result;
 101 }