gcc/libgfortran/config/fpu-387.h

/* FPU-related code for x86 and x86_64 processors.
   Copyright (C) 2005-2014 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 __SSE_MATH__
#include "cpuid.h"
#endif

#if defined(__sun__) && defined(__svr4__)
#include <signal.h>
#include <ucontext.h>

static volatile sig_atomic_t sigill_caught;

static void
sigill_hdlr (int sig __attribute((unused)),
	     siginfo_t *sip __attribute__((unused)),
	     ucontext_t *ucp)
{
  sigill_caught = 1;
  /* Set PC to the instruction after the faulting one to skip over it,
     otherwise we enter an infinite loop.  3 is the size of the movaps
     instruction.  */
  ucp->uc_mcontext.gregs[EIP] += 3;
  setcontext (ucp);
}
#endif

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

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

#if defined(__sun__) && defined(__svr4__)
  /* Solaris 2 before Solaris 9 4/04 cannot execute SSE instructions even
     if the CPU supports them.  Programs receive SIGILL instead, so check
     for that at runtime.  */

  if (edx & bit_SSE)
    {
      struct sigaction act, oact;

      act.sa_handler = sigill_hdlr;
      sigemptyset (&act.sa_mask);
      /* Need to set SA_SIGINFO so a ucontext_t * is passed to the handler.  */
      act.sa_flags = SA_SIGINFO;
      sigaction (SIGILL, &act, &oact);

      /* We need a single SSE instruction here so the handler can safely skip
	 over it.  */
      __asm__ __volatile__ ("movaps\t%xmm0,%xmm0");

      sigaction (SIGILL, &oact, NULL);

      if (sigill_caught)
	return 0;
    }
#endif /* __sun__ && __svr4__ */

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

/* i387 exceptions -- 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
#define _FPU_MASK_ALL 0x3f

#define _FPU_EX_ALL   0x3f

/* i387 rounding modes.  */

#define _FPU_RC_NEAREST 0x0
#define _FPU_RC_DOWN    0x1
#define _FPU_RC_UP      0x2
#define _FPU_RC_ZERO    0x3

#define _FPU_RC_MASK    0x3


void
set_fpu (void)
{
  int excepts = 0;
  unsigned short cw;

  __asm__ __volatile__ ("fstcw\t%0" : "=m" (cw));

  if (options.fpe & GFC_FPE_INVALID) excepts |= _FPU_MASK_IM;
  if (options.fpe & GFC_FPE_DENORMAL) excepts |= _FPU_MASK_DM;
  if (options.fpe & GFC_FPE_ZERO) excepts |= _FPU_MASK_ZM;
  if (options.fpe & GFC_FPE_OVERFLOW) excepts |= _FPU_MASK_OM;
  if (options.fpe & GFC_FPE_UNDERFLOW) excepts |= _FPU_MASK_UM;
  if (options.fpe & GFC_FPE_INEXACT) excepts |= _FPU_MASK_PM;

  cw |= _FPU_MASK_ALL;
  cw &= ~excepts;

  __asm__ __volatile__ ("fnclex\n\tfldcw\t%0" : : "m" (cw));

  if (has_sse())
    {
      unsigned int cw_sse;

      __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (cw_sse));

      /* The SSE exception masks are shifted by 7 bits.  */
      cw_sse |= _FPU_MASK_ALL << 7;
      cw_sse &= ~(excepts << 7);

      /* Clear stalled exception flags.  */
      cw_sse &= ~_FPU_EX_ALL;

      __asm__ __volatile__ ("%vldmxcsr\t%0" : : "m" (cw_sse));
    }
}

int
get_fpu_except_flags (void)
{
  unsigned short cw;
  int excepts;
  int result = 0;

  __asm__ __volatile__ ("fnstsw\t%0" : "=a" (cw));
  excepts = cw;

  if (has_sse())
    {
      unsigned int cw_sse;

      __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (cw_sse));
      excepts |= cw_sse;
    }

  excepts &= _FPU_EX_ALL;

  if (excepts & _FPU_MASK_IM) result |= GFC_FPE_INVALID;
  if (excepts & _FPU_MASK_DM) result |= GFC_FPE_DENORMAL;
  if (excepts & _FPU_MASK_ZM) result |= GFC_FPE_ZERO;
  if (excepts & _FPU_MASK_OM) result |= GFC_FPE_OVERFLOW;
  if (excepts & _FPU_MASK_UM) result |= GFC_FPE_UNDERFLOW;
  if (excepts & _FPU_MASK_PM) result |= GFC_FPE_INEXACT;

  return result;
}

void
set_fpu_rounding_mode (int round)
{
  int round_mode;
  unsigned short cw;

  switch (round)
    {
    case GFC_FPE_TONEAREST:
      round_mode = _FPU_RC_NEAREST;
      break;
    case GFC_FPE_UPWARD:
      round_mode = _FPU_RC_UP;
      break;
    case GFC_FPE_DOWNWARD:
      round_mode = _FPU_RC_DOWN;
      break;
    case GFC_FPE_TOWARDZERO:
      round_mode = _FPU_RC_ZERO;
      break;
    default:
      return; /* Should be unreachable.  */
    }

  __asm__ __volatile__ ("fnstcw\t%0" : "=m" (cw));

  /* The x87 round control bits are shifted by 10 bits.  */
  cw &= ~(_FPU_RC_MASK << 10);
  cw |= round_mode << 10;

  __asm__ __volatile__ ("fldcw\t%0" : : "m" (cw));

  if (has_sse())
    {
      unsigned int cw_sse;

      __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (cw_sse));

      /* The SSE round control bits are shifted by 13 bits.  */
      cw_sse &= ~(_FPU_RC_MASK << 13);
      cw_sse |= round_mode << 13;

      __asm__ __volatile__ ("%vldmxcsr\t%0" : : "m" (cw_sse));
    }
}

int
get_fpu_rounding_mode (void)
{
  int round_mode;

#ifdef __SSE_MATH__
  unsigned int cw;

  __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (cw));

  /* The SSE round control bits are shifted by 13 bits.  */
  round_mode = cw >> 13;
#else
  unsigned short cw;

  __asm__ __volatile__ ("fnstcw\t%0" : "=m" (cw));

  /* The x87 round control bits are shifted by 10 bits.  */
  round_mode = cw >> 10;
#endif

  round_mode &= _FPU_RC_MASK;

  switch (round_mode)
    {
    case _FPU_RC_NEAREST:
      return GFC_FPE_TONEAREST;
    case _FPU_RC_UP:
      return GFC_FPE_UPWARD;
    case _FPU_RC_DOWN:
      return GFC_FPE_DOWNWARD;
    case _FPU_RC_ZERO:
      return GFC_FPE_TOWARDZERO;
    default:
      return GFC_FPE_INVALID; /* Should be unreachable.  */
    }
}