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glibc  2.9
feenablxcpt.c
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00001 /* Enable floating-point exceptions.
00002    Copyright (C) 1999, 2000, 2003, 2004 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Andreas Jaeger <aj@suse.de>, 1999.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU Lesser General Public
00017    License along with the GNU C Library; if not, write to the Free
00018    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00019    02111-1307 USA.  */
00020 
00021 #include <fenv.h>
00022 #include <unistd.h>
00023 #include <ldsodefs.h>
00024 #include <dl-procinfo.h>
00025 
00026 int
00027 feenableexcept (int excepts)
00028 {
00029   unsigned short int new_exc;
00030   unsigned short int old_exc;
00031 
00032   /* Get the current control word.  */
00033   __asm__ ("fstcw %0" : "=m" (*&new_exc));
00034 
00035   excepts &= FE_ALL_EXCEPT;
00036   old_exc = (~new_exc) & FE_ALL_EXCEPT;
00037 
00038   new_exc &= ~excepts;
00039   __asm__ ("fldcw %0" : : "m" (*&new_exc));
00040 
00041   /* If the CPU supports SSE we set the MXCSR as well.  */
00042   if ((GLRO(dl_hwcap) & HWCAP_I386_XMM) != 0)
00043     {
00044       unsigned int xnew_exc;
00045 
00046       /* Get the current control word.  */
00047       __asm__ ("stmxcsr %0" : "=m" (*&xnew_exc));
00048 
00049       xnew_exc &= ~(excepts << 7);
00050 
00051       __asm__ ("ldmxcsr %0" : : "m" (*&xnew_exc));
00052     }
00053 
00054   return old_exc;
00055 }