sysdeps/ieee754/ldbl-128ibm/s_floorl.c

   1 /* Round to int long double floating-point values.
   2    IBM extended format long double version.
   3    Copyright (C) 2006, 2007 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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <math.h>
  22 #include <math_ldbl_opt.h>
  23 #include <float.h>
  24 #include <ieee754.h>
  25
  26
  27 #ifdef __STDC__
  28 long double
  29 __floorl (long double x)
  30 #else
  31 long double
  32 __floorl (x)
  33      long double x;
  34 #endif
  35 {
  36   double xh, xl, hi, lo;
  37
  38   ldbl_unpack (x, &xh, &xl);
  39
  40   /* Return Inf, Nan, +/-0 unchanged.  */
  41   if (__builtin_expect (xh != 0.0
  42                         && __builtin_isless (__builtin_fabs (xh),
  43                                              __builtin_inf ()), 1))
  44     {
  45       /* Long double arithmetic, including the canonicalisation below,
  46          only works in round-to-nearest mode.  */
  47
  48       /* Convert the high double to integer.  */
  49       hi = ldbl_nearbyint (xh);
  50
  51       /* Subtract integral high part from the value.  */
  52       xh -= hi;
  53       ldbl_canonicalize (&xh, &xl);
  54
  55       /* Now convert the low double, adjusted for any remainder from the
  56          high double.  */
  57       lo = ldbl_nearbyint (xh);
  58
  59       /* Adjust the result when the remainder is non-zero.  nearbyint
  60          rounds values to the nearest integer, and values halfway
  61          between integers to the nearest even integer.  floorl must
  62          round towards -Inf.  */
  63       xh -= lo;
  64       ldbl_canonicalize (&xh, &xl);
  65
  66       if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
  67         lo += -1.0;
  68
  69       /* Ensure the final value is canonical.  In certain cases,
  70          rounding causes hi,lo calculated so far to be non-canonical.  */
  71       xh = hi;
  72       xl = lo;
  73       ldbl_canonicalize (&xh, &xl);
  74     }
  75
  76   return ldbl_pack (xh, xl);
  77 }
  78
  79 long_double_symbol (libm, __floorl, floorl);