libquadmath/math/llrintq.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2017 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, write to the Free
  20    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  21    02111-1307 USA.  */
  22
  23 #include "quadmath-imp.h"
  24
  25 static const __float128 two112[2] =
  26 {
  27   5.19229685853482762853049632922009600E+33Q, /* 0x406F000000000000, 0 */
  28  -5.19229685853482762853049632922009600E+33Q  /* 0xC06F000000000000, 0 */
  29 };
  30
  31 long long int
  32 llrintq (__float128 x)
  33 {
  34   int32_t j0;
  35   uint64_t i0,i1;
  36   __float128 w;
  37   __float128 t;
  38   long long int result;
  39   int sx;
  40
  41   GET_FLT128_WORDS64 (i0, i1, x);
  42   j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  43   sx = i0 >> 63;
  44   i0 &= 0x0000ffffffffffffLL;
  45   i0 |= 0x0001000000000000LL;
  46
  47   if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  48     {
  49 #if defined FE_INVALID || defined FE_INEXACT
  50       /* X < LLONG_MAX + 1 implied by J0 < 63.  */
  51       if (x > (__float128) LLONG_MAX)
  52         {
  53           /* In the event of overflow we must raise the "invalid"
  54              exception, but not "inexact".  */
  55           t = nearbyintq (x);
  56 #ifdef USE_FENV_H
  57           feraiseexcept (t == LLONG_MAX ? FE_INEXACT : FE_INVALID);
  58 #endif
  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       if (j0 < 0)
  72         result = 0;
  73       else if (j0 <= 48)
  74         result = i0 >> (48 - j0);
  75       else
  76         result = ((long long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
  77     }
  78   else
  79     {
  80       /* The number is too large.  Unless it rounds to LLONG_MIN,
  81          FE_INVALID must be raised and the return value is
  82          unspecified.  */
  83 #if defined FE_INVALID || defined FE_INEXACT
  84       if (x < (__float128) LLONG_MIN
  85           && x > (__float128) LLONG_MIN - 1.0Q)
  86         {
  87           /* If truncation produces LLONG_MIN, the cast will not raise
  88              the exception, but may raise "inexact".  */
  89           t = nearbyintq (x);
  90 #ifdef USE_FENV_H
  91           feraiseexcept (t == LLONG_MIN ? FE_INEXACT : FE_INVALID);
  92 #endif
  93           return LLONG_MIN;
  94         }
  95
  96 #endif
  97
  98       /* The number is too large.  It is left implementation defined
  99          what happens.  */
 100       return (long long int) x;
 101     }
 102
 103   return sx ? -result : result;
 104 }