DOSBox-X: include/fpu_control

00001 /* FPU control word bits.  x86-64 version.
00002    Copyright (C) 1993,1995,1996,1997,1998,2000,2001,2002 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004    Contributed by Olaf Flebbe.
00005 
00006    The GNU C Library is free software; you can redistribute it and/or
00007    modify it under the terms of the GNU Lesser General Public
00008    License as published by the Free Software Foundation; either
00009    version 2.1 of the License, or (at your option) any later version.
00010 
00011    The GNU C Library is distributed in the hope that it will be useful,
00012    but WITHOUT ANY WARRANTY; without even the implied warranty of
00013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014    Lesser General Public License for more details.
00015 
00016    You should have received a copy of the GNU General Public License along
00017    with this program; if not, write to the Free Software Foundation, Inc.,
00018    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
00019 
00020 #ifndef _FPU_CONTROL_H
00021 #define _FPU_CONTROL_H  1
00022 
00023 /* Note that this file sets on x86-64 only the x87 FPU, it does not
00024    touch the SSE unit.  */
00025 
00026 /* Here is the dirty part. Set up your 387 through the control word
00027  * (cw) register.
00028  *
00029  *     15-13    12  11-10  9-8     7-6     5    4    3    2    1    0
00030  * | reserved | IC | RC  | PC | reserved | PM | UM | OM | ZM | DM | IM
00031  *
00032  * IM: Invalid operation mask
00033  * DM: Denormalized operand mask
00034  * ZM: Zero-divide mask
00035  * OM: Overflow mask
00036  * UM: Underflow mask
00037  * PM: Precision (inexact result) mask
00038  *
00039  * Mask bit is 1 means no interrupt.
00040  *
00041  * PC: Precision control
00042  * 11 - round to extended precision
00043  * 10 - round to double precision
00044  * 00 - round to single precision
00045  *
00046  * RC: Rounding control
00047  * 00 - rounding to nearest
00048  * 01 - rounding down (toward - infinity)
00049  * 10 - rounding up (toward + infinity)
00050  * 11 - rounding toward zero
00051  *
00052  * IC: Infinity control
00053  * That is for 8087 and 80287 only.
00054  *
00055  * The hardware default is 0x037f which we use.
00056  */
00057 
00058 //#include <features.h>
00059 
00060 /* masking of interrupts */
00061 #define _FPU_MASK_IM  0x01
00062 #define _FPU_MASK_DM  0x02
00063 #define _FPU_MASK_ZM  0x04
00064 #define _FPU_MASK_OM  0x08
00065 #define _FPU_MASK_UM  0x10
00066 #define _FPU_MASK_PM  0x20
00067 
00068 /* precision control */
00069 #define _FPU_EXTENDED 0x300     /* libm requires double extended precision.  */
00070 #define _FPU_DOUBLE   0x200
00071 #define _FPU_SINGLE   0x0
00072 
00073 /* rounding control */
00074 #define _FPU_RC_NEAREST 0x0    /* RECOMMENDED */
00075 #define _FPU_RC_DOWN    0x400
00076 #define _FPU_RC_UP      0x800
00077 #define _FPU_RC_ZERO    0xC00
00078 
00079 #define _FPU_RESERVED 0xF0C0  /* Reserved bits in cw */
00080 
00081 
00082 /* The fdlibm code requires strict IEEE double precision arithmetic,
00083    and no interrupts for exceptions, rounding to nearest.  */
00084 
00085 #define _FPU_DEFAULT  0x037f
00086 
00087 /* IEEE:  same as above.  */
00088 #define _FPU_IEEE     0x037f
00089 
00090 /* Type of the control word.  */
00091 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
00092 
00093 /* Macros for accessing the hardware control word.  */
00094 #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
00095 #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
00096 
00097 /* Default control word set at startup.  */
00098 extern fpu_control_t __fpu_control;
00099 
00100 #endif  /* fpu_control.h */