sysdeps/ieee754/dbl-64/s_llrint.c

   1 /* Round argument to nearest integral value according to current rounding
   2    direction.
   3    Copyright (C) 1997-2023 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 #include <math-use-builtins.h>
  29
  30
  31 long long int
  32 __llrint (double x)
  33 {
  34 #if USE_LLRINT_BUILTIN
  35   return __builtin_llrint (x);
  36 #else
  37   /* Use generic implementation.  */
  38   static const double two52[2] =
  39   {
  40     4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
  41    -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
  42   };
  43
  44   int32_t j0;
  45   uint32_t i1, i0;
  46   long long int result;
  47   double w;
  48   double t;
  49   int sx;
  50
  51   EXTRACT_WORDS (i0, i1, x);
  52   j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  53   sx = i0 >> 31;
  54   i0 &= 0xfffff;
  55   i0 |= 0x100000;
  56
  57   if (j0 < 20)
  58     {
  59       w = math_narrow_eval (two52[sx] + x);
  60       t = w - two52[sx];
  61       EXTRACT_WORDS (i0, i1, t);
  62       j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  63       i0 &= 0xfffff;
  64       i0 |= 0x100000;
  65
  66       result = (j0 < 0 ? 0 : i0 >> (20 - j0));
  67     }
  68   else if (j0 < (int32_t) (8 * sizeof (long long int)) - 1)
  69     {
  70       if (j0 >= 52)
  71         result = (((long long int) i0 << 32) | i1) << (j0 - 52);
  72       else
  73         {
  74           w = math_narrow_eval (two52[sx] + x);
  75           t = w - two52[sx];
  76           EXTRACT_WORDS (i0, i1, t);
  77           j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;
  78           i0 &= 0xfffff;
  79           i0 |= 0x100000;
  80
  81           if (j0 == 20)
  82             result = (long long int) i0;
  83           else
  84             result = ((long long int) i0 << (j0 - 20)) | (i1 >> (52 - j0));
  85         }
  86     }
  87   else
  88     {
  89 #ifdef FE_INVALID
  90       /* The number is too large.  Unless it rounds to LLONG_MIN,
  91          FE_INVALID must be raised and the return value is
  92          unspecified.  */
  93       if (FIX_DBL_LLONG_CONVERT_OVERFLOW && x != (double) LLONG_MIN)
  94         {
  95           feraiseexcept (FE_INVALID);
  96           return sx == 0 ? LLONG_MAX : LLONG_MIN;
  97         }
  98 #endif
  99       return (long long int) x;
 100     }
 101
 102   return sx ? -result : result;
 103 #endif /* ! USE_LLRINT_BUILTIN  */
 104 }
 105
 106 libm_alias_double (__llrint, llrint)