uclibc-ng/libm/aarch64/feupdateenv.c

/* Copyright (C) 2009-2025 Free Software Foundation, Inc.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <fenv.h>
#include <fpu_control.h>

int
feupdateenv (const fenv_t *envp)
{
  fpu_control_t fpcr;
  fpu_control_t fpcr_new;
  fpu_control_t updated_fpcr;
  fpu_fpsr_t fpsr;
  fpu_fpsr_t fpsr_new;
  int excepts;

  _FPU_GETCW (fpcr);
  _FPU_GETFPSR (fpsr);
  excepts = fpsr & FE_ALL_EXCEPT;

  if ((envp != FE_DFL_ENV) && (envp != FE_NOMASK_ENV))
    {
      fpcr_new = envp->__fpcr;
      fpsr_new = envp->__fpsr | excepts;

      if (fpcr != fpcr_new)
        _FPU_SETCW (fpcr_new);

      if (fpsr != fpsr_new)
        _FPU_SETFPSR (fpsr_new);

      if (excepts & (fpcr_new >> FE_EXCEPT_SHIFT))
        return feraiseexcept (excepts);

      return 0;
    }

  fpcr_new = fpcr & _FPU_RESERVED;
  fpsr_new = fpsr & (_FPU_FPSR_RESERVED | FE_ALL_EXCEPT);

  if (envp == FE_DFL_ENV)
    {
      fpcr_new |= _FPU_DEFAULT;
      fpsr_new |= _FPU_FPSR_DEFAULT;
    }
  else
    {
      fpcr_new |= _FPU_FPCR_IEEE;
      fpsr_new |= _FPU_FPSR_IEEE;
    }

  _FPU_SETFPSR (fpsr_new);

  if (fpcr != fpcr_new)
    {
      _FPU_SETCW (fpcr_new);

      /* Trapping exceptions are optional in AArch64; the relevant enable
	 bits in FPCR are RES0 hence the absence of support can be detected
	 by reading back the FPCR and comparing with the required value.  */
      _FPU_GETCW (updated_fpcr);

      if (fpcr_new & ~updated_fpcr)
        return 1;
    }

  if (excepts & (fpcr_new >> FE_EXCEPT_SHIFT))
    return feraiseexcept (excepts);

  return 0;
}