1  /* Set current rounding direction.
       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  #include <unistd.h>
      21  #include <ldsodefs.h>
      22  #include <dl-procinfo.h>
      23  
      24  int
      25  __fesetround (int round)
      26  {
      27    unsigned short int cw;
      28  
      29    if ((round & ~0xc00) != 0)
      30      /* ROUND is no valid rounding mode.  */
      31      return 1;
      32  
      33    __asm__ ("fnstcw %0" : "=m" (*&cw));
      34    cw &= ~0xc00;
      35    cw |= round;
      36    __asm__ ("fldcw %0" : : "m" (*&cw));
      37  
      38    /* If the CPU supports SSE we set the MXCSR as well.  */
      39    if (CPU_FEATURE_USABLE (SSE))
      40      {
      41        unsigned int xcw;
      42  
      43        __asm__ ("stmxcsr %0" : "=m" (*&xcw));
      44        xcw &= ~0x6000;
      45        xcw |= round << 3;
      46        __asm__ ("ldmxcsr %0" : : "m" (*&xcw));
      47      }
      48  
      49    return 0;
      50  }
      51  libm_hidden_def (__fesetround)
      52  weak_alias (__fesetround, fesetround)
      53  libm_hidden_weak (fesetround)