sysdeps/x86_64/fpu/fsetexcptflg.c

   1 /* Set floating-point environment exception handling.
   2    Copyright (C) 2001-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <fenv.h>
  20 #include <math.h>
  21
  22 int
  23 fesetexceptflag (const fexcept_t *flagp, int excepts)
  24 {
  25   /* The flags can be set in the 387 unit or in the SSE unit.
  26      When we need to clear a flag, we need to do so in both units,
  27      due to the way fetestexcept() is implemented.
  28      When we need to set a flag, it is sufficient to do it in the SSE unit,
  29      because that is guaranteed to not trap.  */
  30
  31   fenv_t temp;
  32   unsigned int mxcsr;
  33
  34   excepts &= FE_ALL_EXCEPT;
  35
  36   /* Get the current x87 FPU environment.  We have to do this since we
  37      cannot separately set the status word.  */
  38   __asm__ ("fnstenv %0" : "=m" (*&temp));
  39
  40   /* Clear relevant flags.  */
  41   temp.__status_word &= ~(excepts & ~ *flagp);
  42
  43   /* Store the new status word (along with the rest of the environment).  */
  44   __asm__ ("fldenv %0" : : "m" (*&temp));
  45
  46   /* And now similarly for SSE.  */
  47   __asm__ ("stmxcsr %0" : "=m" (*&mxcsr));
  48
  49   /* Clear or set relevant flags.  */
  50   mxcsr ^= (mxcsr ^ *flagp) & excepts;
  51
  52   /* Put the new data in effect.  */
  53   __asm__ ("ldmxcsr %0" : : "m" (*&mxcsr));
  54
  55   /* Success.  */
  56   return 0;
  57 }