sysdeps/ieee754/dbl-64/s_llrint.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2016 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, see
  19    <http://www.gnu.org/licenses/>.  */
  20
  21 #include <fenv.h>
  22 #include <limits.h>
  23 #include <math.h>
  24
  25 #include <math_private.h>
  26 #include <fix-fp-int-convert-overflow.h>
  27
  28 static const double two52[2] =
  29 {
  30   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  31  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  32 };
  33
  34
  35 long long int
  36 __llrint (double x)
  37 {
  38   int32_t j0;
  39   u_int32_t i1, i0;
  40   long long int result;
  41   double w;
  42   double t;
  43   int sx;
  44
  45   EXTRACT_WORDS (i0, i1, x);
  46   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  47   sx = i0 >> 31;
  48   i0 &= 0xfffff;
  49   i0 |= 0x100000;
  50
  51   if (j0 < 20)
  52     {
  53       w = math_narrow_eval (two52[sx] + x);
  54       t = w - two52[sx];
  55       EXTRACT_WORDS (i0, i1, t);
  56       j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  57       i0 &= 0xfffff;
  58       i0 |= 0x100000;
  59
  60       result = (j0 < 0 ? 0 : i0 >> (20 - j0));
  61     }
  62   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  63     {
  64       if (j0 >= 52)
  65         result = (((long long int) i0 << 32) | i1) << (j0 - 52);
  66       else
  67         {
  68           w = math_narrow_eval (two52[sx] + x);
  69           t = w - two52[sx];
  70           EXTRACT_WORDS (i0, i1, t);
  71           j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  72           i0 &= 0xfffff;
  73           i0 |= 0x100000;
  74
  75           if (j0 == 20)
  76             result = (long long int) i0;
  77           else
  78             result = ((long long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  79         }
  80     }
  81   else
  82     {
  83 #ifdef FE_INVALID
  84       /* The number is too large.  Unless it rounds to LLONG_MIN,
  85          FE_INVALID must be raised and the return value is
  86          unspecified.  */
  87       if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
  88         {
  89           feraiseexcept (FE_INVALID);
  90           return sx == 0 ? LLONG_MAX : LLONG_MIN;
  91         }
  92 #endif
  93       return (long long int) x;
  94     }
  95
  96   return sx ? -result : result;
  97 }
  98
  99 weak_alias (__llrint, llrint)
 100 #ifdef NO_LONG_DOUBLE
 101 strong_alias (__llrint, __llrintl)
 102 weak_alias (__llrint, llrintl)
 103 #endif