1  /* Install given floating-point control modes.  i386 version.
       2     Copyright (C) 2016-2023 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 <fpu_control.h>
      21  #include <unistd.h>
      22  #include <ldsodefs.h>
      23  #include <dl-procinfo.h>
      24  
      25  /* All exceptions, including the x86-specific "denormal operand"
      26     exception.  */
      27  #define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
      28  
      29  int
      30  fesetmode (const femode_t *modep)
      31  {
      32    fpu_control_t cw;
      33    if (modep == FE_DFL_MODE)
      34      cw = _FPU_DEFAULT;
      35    else
      36      cw = modep->__control_word;
      37    _FPU_SETCW (cw);
      38    if (CPU_FEATURE_USABLE (SSE))
      39      {
      40        unsigned int mxcsr;
      41        __asm__ ("stmxcsr %0" : "=m" (mxcsr));
      42        /* Preserve SSE exception flags but restore other state in
      43  	 MXCSR.  */
      44        mxcsr &= FE_ALL_EXCEPT_X86;
      45        if (modep == FE_DFL_MODE)
      46  	/* Default MXCSR state has all bits zero except for those
      47  	   masking exceptions.  */
      48  	mxcsr |= FE_ALL_EXCEPT_X86 << 7;
      49        else
      50  	mxcsr |= modep->__mxcsr & ~FE_ALL_EXCEPT_X86;
      51        __asm__ ("ldmxcsr %0" : : "m" (mxcsr));
      52      }
      53    return 0;
      54  }