sysdeps/i386/fpu/fesetenv.c

   1 /* Install given floating-point environment.
   2    Copyright (C) 1997, 1998, 1999 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 #include <assert.h>
  24
  25
  26 void
  27 fesetenv (const fenv_t *envp)
  28 {
  29   fenv_t temp;
  30
  31   /* The memory block used by fstenv/fldenv has a size of 28 bytes.  */
  32   assert (sizeof (fenv_t) == 28);
  33
  34   /* Install the environment specified by ENVP.  But there are a few
  35      values which we do not want to come from the saved environment.
  36      Therefore, we get the current environment and replace the values
  37      we want to use from the environment specified by the parameter.  */
  38   __asm__ ("fnstenv %0" : "=m" (*&temp));
  39
  40   if (envp == FE_DFL_ENV)
  41     {
  42       temp.__control_word |= FE_ALL_EXCEPT;
  43       temp.__control_word &= ~FE_TOWARDZERO;
  44       temp.__status_word &= ~FE_ALL_EXCEPT;
  45       temp.__eip = 0;
  46       temp.__cs_selector = 0;
  47       temp.__opcode = 0;
  48       temp.__data_offset = 0;
  49       temp.__data_selector = 0;
  50     }
  51   else if (envp == FE_NOMASK_ENV)
  52     {
  53       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
  54       temp.__status_word &= ~FE_ALL_EXCEPT;
  55       temp.__eip = 0;
  56       temp.__cs_selector = 0;
  57       temp.__opcode = 0;
  58       temp.__data_offset = 0;
  59       temp.__data_selector = 0;
  60     }
  61   else
  62     {
  63       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
  64       temp.__control_word |= (envp->__control_word
  65                               & (FE_ALL_EXCEPT | FE_TOWARDZERO));
  66       temp.__status_word &= ~FE_ALL_EXCEPT;
  67       temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT;
  68       temp.__eip = envp->__eip;
  69       temp.__cs_selector = envp->__cs_selector;
  70       temp.__opcode = envp->__opcode;
  71       temp.__data_offset = envp->__data_offset;
  72       temp.__data_selector = envp->__data_selector;
  73     }
  74
  75   __asm__ ("fldenv %0" : : "m" (temp));
  76 }