gcc/libgfortran/config/fpu-387.h

/* FPU-related code for x86 and x86_64 processors.
   Copyright 2005, 2007, 2009 Free Software Foundation, Inc.
   Contributed by Francois-Xavier Coudert <coudert@clipper.ens.fr>

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public
License as published by the Free Software Foundation; either
version 3 of the License, or (at your option) any later version.

Libgfortran 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 General Public License for more details.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  */

#ifndef __x86_64__
#include "cpuid.h"
#endif

static int
has_sse (void)
{
#ifndef __x86_64__
  unsigned int eax, ebx, ecx, edx;

  if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
    return 0;

  return edx & bit_SSE;
#else
  return 1;
#endif
}

/* i387 -- see linux <fpu_control.h> header file for details.  */
#define _FPU_MASK_IM  0x01
#define _FPU_MASK_DM  0x02
#define _FPU_MASK_ZM  0x04
#define _FPU_MASK_OM  0x08
#define _FPU_MASK_UM  0x10
#define _FPU_MASK_PM  0x20

void set_fpu (void)
{
  unsigned short cw;

  asm volatile ("fnstcw %0" : "=m" (cw));

  cw |= (_FPU_MASK_IM | _FPU_MASK_DM | _FPU_MASK_ZM | _FPU_MASK_OM
	 | _FPU_MASK_UM | _FPU_MASK_PM);

  if (options.fpe & GFC_FPE_INVALID) cw &= ~_FPU_MASK_IM;
  if (options.fpe & GFC_FPE_DENORMAL) cw &= ~_FPU_MASK_DM;
  if (options.fpe & GFC_FPE_ZERO) cw &= ~_FPU_MASK_ZM;
  if (options.fpe & GFC_FPE_OVERFLOW) cw &= ~_FPU_MASK_OM;
  if (options.fpe & GFC_FPE_UNDERFLOW) cw &= ~_FPU_MASK_UM;
  if (options.fpe & GFC_FPE_PRECISION) cw &= ~_FPU_MASK_PM;

  asm volatile ("fldcw %0" : : "m" (cw));

  if (has_sse())
    {
      unsigned int cw_sse;

      asm volatile ("stmxcsr %0" : "=m" (cw_sse));

      cw_sse &= 0xffff0000;
      cw_sse |= (_FPU_MASK_IM | _FPU_MASK_DM | _FPU_MASK_ZM | _FPU_MASK_OM
		 | _FPU_MASK_UM | _FPU_MASK_PM ) << 7;

      if (options.fpe & GFC_FPE_INVALID) cw_sse &= ~(_FPU_MASK_IM << 7);
      if (options.fpe & GFC_FPE_DENORMAL) cw_sse &= ~(_FPU_MASK_DM << 7);
      if (options.fpe & GFC_FPE_ZERO) cw_sse &= ~(_FPU_MASK_ZM << 7);
      if (options.fpe & GFC_FPE_OVERFLOW) cw_sse &= ~(_FPU_MASK_OM << 7);
      if (options.fpe & GFC_FPE_UNDERFLOW) cw_sse &= ~(_FPU_MASK_UM << 7);
      if (options.fpe & GFC_FPE_PRECISION) cw_sse &= ~(_FPU_MASK_PM << 7);

      asm volatile ("ldmxcsr %0" : : "m" (cw_sse));
    }
}