sysdeps/ieee754/dbl-64/s_lrint.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2022 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <fenv.h>
  21 #include <limits.h>
  22 #include <math.h>
  23
  24 #include <math-narrow-eval.h>
  25 #include <math_private.h>
  26 #include <libm-alias-double.h>
  27 #include <fix-fp-int-convert-overflow.h>
  28
  29 static const double two52[2] =
  30 {
  31   4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  32  -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  33 };
  34
  35
  36 long int
  37 __lrint (double x)
  38 {
  39   int32_t j0;
  40   uint32_t i0, i1;
  41   double w;
  42   double t;
  43   long int result;
  44   int sx;
  45
  46   EXTRACT_WORDS (i0, i1, x);
  47   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  48   sx = i0 >> 31;
  49   i0 &= 0xfffff;
  50   i0 |= 0x100000;
  51
  52   if (j0 < 20)
  53     {
  54       w = math_narrow_eval (two52[sx] + x);
  55       t = w - two52[sx];
  56       EXTRACT_WORDS (i0, i1, t);
  57       j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  58       i0 &= 0xfffff;
  59       i0 |= 0x100000;
  60
  61       result = (j0 < 0 ? 0 : i0 >> (20 - j0));
  62     }
  63   else if (j0 < (int32_t) (8 * sizeof (long int)) - 1)
  64     {
  65       if (j0 >= 52)
  66         result = ((long int) i0 << (j0 - 20)) | ((long int) i1 << (j0 - 52));
  67       else
  68         {
  69 #if defined FE_INVALID || defined FE_INEXACT
  70           /* X < LONG_MAX + 1 implied by J0 < 31.  */
  71           if (sizeof (long int) == 4
  72               && x > (double) LONG_MAX)
  73             {
  74               /* In the event of overflow we must raise the "invalid"
  75                  exception, but not "inexact".  */
  76               t = __nearbyint (x);
  77               feraiseexcept (t == LONG_MAX ? FE_INEXACT : FE_INVALID);
  78             }
  79           else
  80 #endif
  81             {
  82               w = math_narrow_eval (two52[sx] + x);
  83               t = w - two52[sx];
  84             }
  85           EXTRACT_WORDS (i0, i1, t);
  86           j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  87           i0 &= 0xfffff;
  88           i0 |= 0x100000;
  89
  90           if (j0 == 20)
  91             result = (long int) i0;
  92           else
  93             result = ((long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  94         }
  95     }
  96   else
  97     {
  98       /* The number is too large.  Unless it rounds to LONG_MIN,
  99          FE_INVALID must be raised and the return value is
 100          unspecified.  */
 101 #if defined FE_INVALID || defined FE_INEXACT
 102       if (sizeof (long int) == 4
 103           && x < (double) LONG_MIN
 104           && x > (double) LONG_MIN - 1.0)
 105         {
 106           /* If truncation produces LONG_MIN, the cast will not raise
 107              the exception, but may raise "inexact".  */
 108           t = __nearbyint (x);
 109           feraiseexcept (t == LONG_MIN ? FE_INEXACT : FE_INVALID);
 110           return LONG_MIN;
 111         }
 112       else if (FIX_DBL_LONG_CONVERT_OVERFLOW && x != (double) LONG_MIN)
 113         {
 114           feraiseexcept (FE_INVALID);
 115           return sx == 0 ? LONG_MAX : LONG_MIN;
 116         }
 117 #endif
 118       return (long int) x;
 119     }
 120
 121   return sx ? -result : result;
 122 }
 123
 124 libm_alias_double (__lrint, lrint)