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63 pj 1
/* FPU control word bits.  i387 version.
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   Copyright (C) 1993,1995,1996,1997,1998,2000,2001 Free Software Foundation, Inc.
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   This file is part of the GNU C Library.
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   Contributed by Olaf Flebbe.
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   The GNU C Library is free software; you can redistribute it and/or
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   modify it under the terms of the GNU Lesser General Public
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   License as published by the Free Software Foundation; either
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   version 2.1 of the License, or (at your option) any later version.
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   The GNU C Library is distributed in the hope that it will be useful,
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   but WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   Lesser General Public License for more details.
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   You should have received a copy of the GNU Lesser General Public
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   License along with the GNU C Library; if not, write to the Free
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   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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   02111-1307 USA.  */
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#ifndef _FPU_CONTROL_H
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#define _FPU_CONTROL_H  1
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#include "ll/sys/cdefs.h"
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__BEGIN_DECLS
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/* Here is the dirty part. Set up your 387 through the control word
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 * (cw) register.
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 *
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 *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
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 * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
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 *
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 * IM: Invalid operation mask
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 * DM: Denormalized operand mask
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 * ZM: Zero-divide mask
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 * OM: Overflow mask
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 * UM: Underflow mask
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 * PM: Precision (inexact result) mask
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 *
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 * Mask bit is 1 means no interrupt.
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 *
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 * PC: Precision control
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 * 11 - round to extended precision
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 * 10 - round to double precision
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 * 00 - round to single precision
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 *
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 * RC: Rounding control
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 * 00 - rounding to nearest
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 * 01 - rounding down (toward - infinity)
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 * 10 - rounding up (toward + infinity)
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 * 11 - rounding toward zero
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 *
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 * IC: Infinity control
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 * That is for 8087 and 80287 only.
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 *
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 * The hardware default is 0x037f which we use.
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 */
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#include <features.h>
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/* masking of interrupts */
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#define _FPU_MASK_IM  0x01
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#define _FPU_MASK_DM  0x02
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#define _FPU_MASK_ZM  0x04
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#define _FPU_MASK_OM  0x08
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#define _FPU_MASK_UM  0x10
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#define _FPU_MASK_PM  0x20
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/* precision control */
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#define _FPU_EXTENDED 0x300     /* libm requires double extended precision.  */
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#define _FPU_DOUBLE   0x200
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#define _FPU_SINGLE   0x0
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/* rounding control */
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#define _FPU_RC_NEAREST 0x0    /* RECOMMENDED */
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#define _FPU_RC_DOWN    0x400
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#define _FPU_RC_UP      0x800
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#define _FPU_RC_ZERO    0xC00
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#define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
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/* The fdlibm code requires strict IEEE double precision arithmetic,
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   and no interrupts for exceptions, rounding to nearest.  */
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#define _FPU_DEFAULT  0x037f
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/* IEEE:  same as above.  */
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#define _FPU_IEEE     0x037f
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/* Type of the control word.  */
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typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
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/* Macros for accessing the hardware control word.  */
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#define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
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#define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
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/* Default control word set at startup.  */
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extern fpu_control_t __fpu_control;
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__END_DECLS
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#endif  /* fpu_control.h */