sysdeps/arm/feupdateenv.c

   1 /* Install given floating-point environment and raise exceptions.
   2    Copyright (C) 1997-2022 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 <fpu_control.h>
  21 #include <arm-features.h>
  22
  23
  24 int
  25 __feupdateenv (const fenv_t *envp)
  26 {
  27   fpu_control_t fpscr, new_fpscr, updated_fpscr;
  28   int excepts;
  29
  30   /* Fail if a VFP unit isn't present.  */
  31   if (!ARM_HAVE_VFP)
  32     return 1;
  33
  34   _FPU_GETCW (fpscr);
  35   excepts = fpscr & FE_ALL_EXCEPT;
  36
  37   if ((envp != FE_DFL_ENV) && (envp != FE_NOMASK_ENV))
  38     {
  39       /* Merge current exception flags with the saved fenv.  */
  40       new_fpscr = envp->__cw | excepts;
  41
  42       /* Write new FPSCR if different (ignoring NZCV flags).  */
  43       if (((fpscr ^ new_fpscr) & ~_FPU_MASK_NZCV) != 0)
  44         _FPU_SETCW (new_fpscr);
  45
  46       /* Raise the exceptions if enabled in the new FP state.  */
  47       if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT))
  48         return __feraiseexcept (excepts);
  49
  50       return 0;
  51     }
  52
  53   /* Preserve the reserved FPSCR flags.  */
  54   new_fpscr = fpscr & (_FPU_RESERVED | FE_ALL_EXCEPT);
  55   new_fpscr |= (envp == FE_DFL_ENV) ? _FPU_DEFAULT : _FPU_IEEE;
  56
  57   if (((new_fpscr ^ fpscr) & ~_FPU_MASK_NZCV) != 0)
  58     {
  59       _FPU_SETCW (new_fpscr);
  60
  61       /* Not all VFP architectures support trapping exceptions, so
  62          test whether the relevant bits were set and fail if not.  */
  63       _FPU_GETCW (updated_fpscr);
  64
  65       if (new_fpscr & ~updated_fpscr)
  66         return 1;
  67     }
  68
  69   /* Raise the exceptions if enabled in the new FP state.  */
  70   if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT))
  71     return __feraiseexcept (excepts);
  72
  73   return 0;
  74 }
  75 libm_hidden_def (__feupdateenv)
  76 weak_alias (__feupdateenv, feupdateenv)
  77 libm_hidden_weak (feupdateenv)