libquadmath/math/lrintq.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 int
  32 lrintq (__float128 x)
  33 {
  34   int32_t j0;
  35   uint64_t i0,i1;
  36   __float128 w;
  37   __float128 t;
  38   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 int)) - 1)
  48     {
  49       if (j0 < 48)
  50         {
  51 #if defined FE_INVALID || defined FE_INEXACT
  52           /* X < LONG_MAX + 1 implied by J0 < 31.  */
  53           if (sizeof (long int) == 4
  54               && x > (__float128) LONG_MAX)
  55             {
  56               /* In the event of overflow we must raise the "invalid"
  57                  exception, but not "inexact".  */
  58               t = nearbyintq (x);
  59 #ifdef USE_FENV_H
  60               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  61 #endif
  62             }
  63           else
  64 #endif
  65             {
  66               w = two112[sx] + x;
  67               t = w - two112[sx];
  68             }
  69           GET_FLT128_WORDS64 (i0, i1, t);
  70           j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
  71           i0 &= 0x0000ffffffffffffLL;
  72           i0 |= 0x0001000000000000LL;
  73
  74           result = (j0 < 0 ? 0 : i0 >> (48 - j0));
  75         }
  76       else if (j0 >= 112)
  77         result = ((long int) i0 << (j0 - 48)) | (i1 << (j0 - 112));
  78       else
  79         {
  80 #if defined FE_INVALID || defined FE_INEXACT
  81           /* X < LONG_MAX + 1 implied by J0 < 63.  */
  82           if (sizeof (long int) == 8
  83               && x > (__float128) LONG_MAX)
  84             {
  85               /* In the event of overflow we must raise the "invalid"
  86                  exception, but not "inexact".  */
  87               t = nearbyintq (x);
  88 #ifdef USE_FENV_H
  89               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  90 #endif
  91             }
  92           else
  93 #endif
  94             {
  95               w = two112[sx] + x;
  96               t = w - two112[sx];
  97             }
  98           GET_FLT128_WORDS64 (i0, i1, t);
  99           j0 = ((i0 >> 48) & 0x7fff) - 0x3fff;
 100           i0 &= 0x0000ffffffffffffLL;
 101           i0 |= 0x0001000000000000LL;
 102
 103           if (j0 == 48)
 104             result = (long int) i0;
 105           else
 106             result = ((long int) i0 << (j0 - 48)) | (i1 >> (112 - j0));
 107         }
 108     }
 109   else
 110     {
 111       /* The number is too large.  Unless it rounds to LONG_MIN,
 112          FE_INVALID must be raised and the return value is
 113          unspecified.  */
 114 #if defined FE_INVALID || defined FE_INEXACT
 115       if (x < (__float128) LONG_MIN
 116           && x > (__float128) LONG_MIN - 1.0Q)
 117         {
 118           /* If truncation produces LONG_MIN, the cast will not raise
 119              the exception, but may raise "inexact".  */
 120           t = nearbyintq (x);
 121 #ifdef USE_FENV_H
 122           feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
 123 #endif
 124           return LONG_MIN;
 125         }
 126 #endif
 127       return (long int) x;
 128     }
 129
 130   return sx ? -result : result;
 131 }