sysdeps/ieee754/dbl-64/s_lrint.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2019 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    <https://www.gnu.org/licenses/>.  */
  20
  21 #include <fenv.h>
  22 #include <limits.h>
  23 #include <math.h>
  24
  25 #include <math-narrow-eval.h>
  26 #include <math_private.h>
  27 #include <libm-alias-double.h>
  28 #include <fix-fp-int-convert-overflow.h>
  29
  30 static const double two52[2] =
  31 {
  32   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  33  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  34 };
  35
  36
  37 long int
  38 __lrint (double x)
  39 {
  40   int32_t j0;
  41   uint32_t i0, i1;
  42   double w;
  43   double t;
  44   long int result;
  45   int sx;
  46
  47   EXTRACT_WORDS (i0, i1, x);
  48   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  49   sx = i0 >> 31;
  50   i0 &= 0xfffff;
  51   i0 |= 0x100000;
  52
  53   if (j0 < 20)
  54     {
  55       w = math_narrow_eval (two52[sx] + x);
  56       t = w - two52[sx];
  57       EXTRACT_WORDS (i0, i1, t);
  58       j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  59       i0 &= 0xfffff;
  60       i0 |= 0x100000;
  61
  62       result = (j0 < 0 ? 0 : i0 >> (20 - j0));
  63     }
  64   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  65     {
  66       if (j0 >= 52)
  67         result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
  68       else
  69         {
  70 #if defined FE_INVALID || defined FE_INEXACT
  71           /* X < LONG_MAX + 1 implied by J0 < 31.  */
  72           if (sizeof (long int) == 4
  73               && x > (double) LONG_MAX)
  74             {
  75               /* In the event of overflow we must raise the "invalid"
  76                  exception, but not "inexact".  */
  77               t = __nearbyint (x);
  78               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  79             }
  80           else
  81 #endif
  82             {
  83               w = math_narrow_eval (two52[sx] + x);
  84               t = w - two52[sx];
  85             }
  86           EXTRACT_WORDS (i0, i1, t);
  87           j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  88           i0 &= 0xfffff;
  89           i0 |= 0x100000;
  90
  91           if (j0 == 20)
  92             result = (long int) i0;
  93           else
  94             result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  95         }
  96     }
  97   else
  98     {
  99       /* The number is too large.  Unless it rounds to LONG_MIN,
 100          FE_INVALID must be raised and the return value is
 101          unspecified.  */
 102 #if defined FE_INVALID || defined FE_INEXACT
 103       if (sizeof (long int) == 4
 104           && x < (double) LONG_MIN
 105           && x > (double) LONG_MIN - 1.0)
 106         {
 107           /* If truncation produces LONG_MIN, the cast will not raise
 108              the exception, but may raise "inexact".  */
 109           t = __nearbyint (x);
 110           feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
 111           return LONG_MIN;
 112         }
 113       else if (FIX_DBL_LONG_CONVERT_OVERFLOW && x != (double) LONG_MIN)
 114         {
 115           feraiseexcept (FE_INVALID);
 116           return sx == 0 ? LONG_MAX : LONG_MIN;
 117         }
 118 #endif
 119       return (long int) x;
 120     }
 121
 122   return sx ? -result : result;
 123 }
 124
 125 libm_alias_double (__lrint, lrint)