sysdeps/i386/fpu/fesetround.c

   1 /* Set current rounding direction.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    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    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <fenv.h>
  22
  23 int
  24 fesetround (int round)
  25 {
  26   unsigned short int cw;
  27
  28   if ((round & ~0xc00) != 0)
  29     /* ROUND is no valid rounding mode.  */
  30     return 0;
  31
  32   __asm__ ("fnstcw %0" : "=m" (*&cw));
  33   cw &= ~0xc00;
  34   cw |= round;
  35   __asm__ ("fldcw %0" : : "m" (*&cw));
  36
  37   return 1;
  38 }