sysdeps/i386/fpu/fesetround.c

   1 /* Set current rounding direction.
   2    Copyright (C) 1997, 2003, 2004, 2005 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 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 <fenv.h>
  22 #include <unistd.h>
  23 #include <ldsodefs.h>
  24 #include <dl-procinfo.h>
  25
  26 int
  27 fesetround (int round)
  28 {
  29   unsigned short int cw;
  30
  31   if ((round & ~0xc00) != 0)
  32     /* ROUND is no valid rounding mode.  */
  33     return 1;
  34
  35   __asm__ ("fnstcw %0" : "=m" (*&cw));
  36   cw &= ~0xc00;
  37   cw |= round;
  38   __asm__ ("fldcw %0" : : "m" (*&cw));
  39
  40   /* If the CPU supports SSE we set the MXCSR as well.  */
  41   if ((GLRO(dl_hwcap) & HWCAP_I386_XMM) != 0)
  42     {
  43       unsigned int xcw;
  44
  45       __asm__ ("stmxcsr %0" : "=m" (*&xcw));
  46       xcw &= ~0x6000;
  47       xcw |= round << 3;
  48       __asm__ ("ldmxcsr %0" : : "m" (*&xcw));
  49     }
  50
  51   return 0;
  52 }
  53 libm_hidden_def (fesetround)