sysdeps/powerpc/powerpc32/fpu/s_llround.c

   1 /* Round double value to long long int.
   2    Copyright (C) 1997-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <limits.h>
  20 #include <math.h>
  21 #include <math_ldbl_opt.h>
  22 #include <math_private.h>
  23 #include <stdint.h>
  24 #include <libm-alias-double.h>
  25
  26 /* Round to the nearest integer, with values exactly on a 0.5 boundary
  27    rounded away from zero, regardless of the current rounding mode.
  28    If (long long)x, when x is out of range of a long long, clips at
  29    LLONG_MAX or LLONG_MIN, then this implementation also clips.  */
  30
  31 long long int
  32 __llround (double x)
  33 {
  34   long long xr;
  35   if (HAVE_PPC_FCTIDZ)
  36     xr = (long long) x;
  37   else
  38     {
  39       /* Avoid incorrect exceptions from libgcc conversions (as of GCC
  40          5): <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59412>.  */
  41       if (fabs (x) < 0x1p31)
  42         xr = (long long int) (long int) x;
  43       else
  44         {
  45           uint64_t i0;
  46           EXTRACT_WORDS64 (i0, x);
  47           int exponent = ((i0 >> 52) & 0x7ff) - 0x3ff;
  48           if (exponent < 63)
  49             {
  50               unsigned long long int mant
  51                 = (i0 & ((1ULL << 52) - 1)) | (1ULL << 52);
  52               if (exponent < 52)
  53                 /* llround is not required to raise "inexact".  */
  54                 mant >>= 52 - exponent;
  55               else
  56                 mant <<= exponent - 52;
  57               xr = (long long int) ((i0 & (1ULL << 63)) != 0 ? -mant : mant);
  58             }
  59           else if (x == (double) LLONG_MIN)
  60             xr = LLONG_MIN;
  61           else
  62             xr = (long long int) (long int) x << 32;
  63         }
  64     }
  65   /* Avoid spurious "inexact" converting LLONG_MAX to double, and from
  66      subtraction when the result is out of range, by returning early
  67      for arguments large enough that no rounding is needed.  */
  68   if (!(fabs (x) < 0x1p52))
  69     return xr;
  70   double xrf = (double) xr;
  71
  72   if (x >= 0.0)
  73     {
  74       if (x - xrf >= 0.5)
  75         xr += (long long) ((unsigned long long) xr + 1) > 0;
  76     }
  77   else
  78     {
  79       if (xrf - x >= 0.5)
  80         xr -= (long long) ((unsigned long long) xr - 1) < 0;
  81     }
  82   return xr;
  83 }
  84 libm_alias_double (__llround, llround)