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glibc  2.9
fsetexcptflg.c
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00001 /* Set floating-point environment exception handling.
00002    Copyright (C) 2001, 2003 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <fenv.h>
00021 #include <math.h>
00022 
00023 int
00024 fesetexceptflag (const fexcept_t *flagp, int excepts)
00025 {
00026   fenv_t temp;
00027   unsigned int mxcsr;
00028 
00029   /* XXX: Do we really need to set both the exception in both units?
00030      Shouldn't it be enough to set only the SSE unit?  */
00031 
00032   /* Get the current x87 FPU environment.  We have to do this since we
00033      cannot separately set the status word.  */
00034   __asm__ ("fnstenv %0" : "=m" (*&temp));
00035 
00036   temp.__status_word &= ~(excepts & FE_ALL_EXCEPT);
00037   temp.__status_word |= *flagp & excepts & FE_ALL_EXCEPT;
00038 
00039   /* Store the new status word (along with the rest of the environment.
00040      Possibly new exceptions are set but they won't get executed unless
00041      the next floating-point instruction.  */
00042   __asm__ ("fldenv %0" : : "m" (*&temp));
00043 
00044   /* And now the same for SSE.  */
00045   __asm__ ("stmxcsr %0" : "=m" (*&mxcsr));
00046 
00047   mxcsr &= ~(excepts & FE_ALL_EXCEPT);
00048   mxcsr |= *flagp & excepts & FE_ALL_EXCEPT;
00049 
00050   __asm__ ("ldmxcsr %0" : : "m" (*&mxcsr));
00051 
00052   /* Success.  */
00053   return 0;
00054 }