1  /* Set current rounding direction.
       2     Copyright (C) 2001-2023 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  __fesetround (int round)
      23  {
      24    unsigned short int cw;
      25    int mxcsr;
      26  
      27    if ((round & ~0xc00) != 0)
      28      /* ROUND is no valid rounding mode.  */
      29      return 1;
      30  
      31    /* First set the x87 FPU.  */
      32    asm ("fnstcw %0" : "=m" (*&cw));
      33    cw &= ~0xc00;
      34    cw |= round;
      35    asm ("fldcw %0" : : "m" (*&cw));
      36  
      37    /* And now the MSCSR register for SSE, the precision is at different bit
      38       positions in the different units, we need to shift it 3 bits.  */
      39    asm ("stmxcsr %0" : "=m" (*&mxcsr));
      40    mxcsr &= ~ 0x6000;
      41    mxcsr |= round << 3;
      42    asm ("ldmxcsr %0" : : "m" (*&mxcsr));
      43  
      44    return 0;
      45  }
      46  libm_hidden_def (__fesetround)
      47  weak_alias (__fesetround, fesetround)
      48  libm_hidden_weak (fesetround)