/* FPU control word bits.  x86 version.

   Copyright (C) 1993-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   Contributed by Olaf Flebbe.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library 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

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#ifndef _FPU_CONTROL_H

#define _FPU_CONTROL_H	1

/* Note that this file sets on x86-64 only the x87 FPU, it does not

   touch the SSE unit.  */

/* 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.

 */

#include <features.h>

/* 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.  "*&" is used to

   work around a bug in older versions of GCC.  __volatile__ is used

   to support combination of writing the control register and reading

   it back.  Without __volatile__, the old value may be used for reading

   back under compiler optimization.

   Note that the use of these macros is not sufficient anymore with

   recent hardware nor on x86-64.  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;

#endif	/* fpu_control.h */