1  /* Install given floating-point environment.
       2     Copyright (C) 1997-2023 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  
      21  int
      22  __fesetenv (const fenv_t *envp)
      23  {
      24    union { unsigned long long buf[4]; fenv_t env; } temp;
      25    unsigned long long *bufptr;
      26  
      27    /* Install the environment specified by ENVP.  But there are a few
      28       values which we do not want to come from the saved environment.
      29       Therefore, we get the current environment and replace the values
      30       we want to use from the environment specified by the parameter.  */
      31    bufptr = temp.buf;
      32    __asm__ (
      33  	   "fstd %%fr0,0(%1)\n"
      34  	   : "=m" (temp) : "r" (bufptr) : "%r0");
      35  
      36    temp.env.__status_word &= ~(FE_ALL_EXCEPT
      37  			    | (FE_ALL_EXCEPT << 27)
      38  			    | FE_DOWNWARD);
      39    if (envp == FE_DFL_ENV)
      40      temp.env.__status_word = 0;
      41    else if (envp == FE_NOMASK_ENV)
      42      temp.env.__status_word |= FE_ALL_EXCEPT;
      43    else
      44      temp.env.__status_word |= (envp->__status_word
      45  			       & (FE_ALL_EXCEPT
      46  				  | FE_DOWNWARD
      47  				  | (FE_ALL_EXCEPT << 27)));
      48  
      49    /* Load the new environment. We use bufptr again since the
      50       initial asm has modified the value of the register and here
      51       we take advantage of that to load in reverse order so fr0
      52       is loaded last and T-Bit is enabled. */
      53    __asm__ (
      54  	   "fldd 0(%1),%%fr0\n"
      55  	   : : "m" (temp), "r" (bufptr) : "%r0" );
      56  
      57    /* Success.  */
      58    return 0;
      59  }
      60  libm_hidden_def (__fesetenv)
      61  weak_alias (__fesetenv, fesetenv)
      62  libm_hidden_weak (fesetenv)