/* ieee-utils/fp-darwin86.c

 * 

 * Copyright (C) 2006 Erik Schnetter

 * 

 * This program 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.

 * 

 * This program 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.

 * 

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

#include <config.h>

#include <gsl/gsl_ieee_utils.h>

#include <gsl/gsl_errno.h>

/* Here is the dirty part. Set up your 387 through the control word

 * (cw) register.

 *

 *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0

 * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM

 *

 * IM: Invalid operation mask

 * DM: Denormalized operand mask

 * ZM: Zero-divide mask

 * OM: Overflow mask

 * UM: Underflow mask

 * PM: Precision (inexact result) mask

 *

 * Mask bit is 1 means no interrupt.

 *

 * PC: Precision control

 * 11 - round to extended precision

 * 10 - round to double precision

 * 00 - round to single precision

 *

 * RC: Rounding control

 * 00 - rounding to nearest

 * 01 - rounding down (toward - infinity)

 * 10 - rounding up (toward + infinity)

 * 11 - rounding toward zero

 *

 * IC: Infinity control

 * That is for 8087 and 80287 only.

 *

 * The hardware default is 0x037f which we use.

 */

/* masking of interrupts */

#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

/* precision control */

#define _FPU_EXTENDED 0x300	/* libm requires double extended precision.  */

#define _FPU_DOUBLE   0x200

#define _FPU_SINGLE   0x0

/* rounding control */

#define _FPU_RC_NEAREST 0x0    /* RECOMMENDED */

#define _FPU_RC_DOWN    0x400

#define _FPU_RC_UP      0x800

#define _FPU_RC_ZERO    0xC00

#define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */

/* The fdlibm code requires strict IEEE double precision arithmetic,

   and no interrupts for exceptions, rounding to nearest.  */

#define _FPU_DEFAULT  0x037f

/* IEEE:  same as above.  */

#define _FPU_IEEE     0x037f

/* Type of the control word.  */

typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));

/* Macros for accessing the hardware control word.

   Note that the use of these macros is no sufficient anymore with

   recent hardware.  Some floating point operations are executed in

   the SSE/SSE2 engines which have their own control and status register.  */

#define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw))

#define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw))

/* Default control word set at startup.  */

extern fpu_control_t __fpu_control;

#define _FPU_GETMXCSR(cw_sse) asm volatile ("stmxcsr %0" : "=m" (cw_sse))

#define _FPU_SETMXCSR(cw_sse) asm volatile ("ldmxcsr %0" : : "m" (cw_sse))

int

gsl_ieee_set_mode (int precision, int rounding, int exception_mask)

{

  fpu_control_t mode, mode_sse;

  _FPU_GETCW (mode) ;

  mode &= _FPU_RESERVED ;

  switch (precision)

    {

    case GSL_IEEE_SINGLE_PRECISION:

      mode |= _FPU_SINGLE ;

      break ;

    case GSL_IEEE_DOUBLE_PRECISION:

      mode |= _FPU_DOUBLE ;

      break ;

    case GSL_IEEE_EXTENDED_PRECISION:

      mode |= _FPU_EXTENDED ;

      break ;

    default:

      mode |= _FPU_EXTENDED ;

    }

  switch (rounding)

    {

    case GSL_IEEE_ROUND_TO_NEAREST:

      mode |= _FPU_RC_NEAREST ;

      break ;

    case GSL_IEEE_ROUND_DOWN:

      mode |= _FPU_RC_DOWN ;

      break ;

    case GSL_IEEE_ROUND_UP:

      mode |= _FPU_RC_UP ;

      break ;

    case GSL_IEEE_ROUND_TO_ZERO:

      mode |= _FPU_RC_ZERO ;

      break ;

    default:

      mode |= _FPU_RC_NEAREST ;

    }

  if (exception_mask & GSL_IEEE_MASK_INVALID)

    mode |= _FPU_MASK_IM ;

  if (exception_mask & GSL_IEEE_MASK_DENORMALIZED)

    mode |= _FPU_MASK_DM ;

  if (exception_mask & GSL_IEEE_MASK_DIVISION_BY_ZERO)

    mode |= _FPU_MASK_ZM ;

  if (exception_mask & GSL_IEEE_MASK_OVERFLOW)

    mode |= _FPU_MASK_OM ;

  if (exception_mask & GSL_IEEE_MASK_UNDERFLOW)

    mode |= _FPU_MASK_UM ;

  if (exception_mask & GSL_IEEE_TRAP_INEXACT)

    {

      mode &= ~ _FPU_MASK_PM ;

    }

  else

    {

      mode |= _FPU_MASK_PM ;

    }

  _FPU_SETCW (mode) ;

  _FPU_GETMXCSR (mode_sse) ;

  mode_sse &= 0xFFFF0000 ;

  if (exception_mask & GSL_IEEE_MASK_INVALID)

    mode_sse |= _FPU_MASK_IM << 7 ;

  if (exception_mask & GSL_IEEE_MASK_DENORMALIZED)

    mode_sse |= _FPU_MASK_DM << 7 ;

  if (exception_mask & GSL_IEEE_MASK_DIVISION_BY_ZERO)

    mode_sse |= _FPU_MASK_ZM << 7 ;

  if (exception_mask & GSL_IEEE_MASK_OVERFLOW)

    mode_sse |= _FPU_MASK_OM << 7 ;

  if (exception_mask & GSL_IEEE_MASK_UNDERFLOW)

    mode_sse |= _FPU_MASK_UM << 7 ;

  if (exception_mask & GSL_IEEE_TRAP_INEXACT)

    {

      mode_sse &= ~ _FPU_MASK_PM << 7 ;

    }

  else

    {

      mode_sse |= _FPU_MASK_PM << 7 ;

    }

  _FPU_SETMXCSR (mode_sse) ;

  return GSL_SUCCESS ;

}