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Diffstat (limited to 'sysdeps/i386/fpu_control.h')
| -rw-r--r-- | sysdeps/i386/fpu_control.h | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/sysdeps/i386/fpu_control.h b/sysdeps/i386/fpu_control.h new file mode 100644 index 0000000000..d72f474eb6 --- /dev/null +++ b/sysdeps/i386/fpu_control.h @@ -0,0 +1,105 @@ +/* FPU control word bits. i387 version. +Copyright (C) 1993, 1995, 1996 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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, +Boston, MA 02111-1307, USA. */ + +#ifndef _FPU_CONTROL_H +#define _FPU_CONTROL_H + +/* Here is the dirty part. Settup 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. I choose 0x1372. + */ + +#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 +#define _FPU_DOUBLE 0x200 /* fdlibm requires double precision */ +#define _FPU_SINGLE 0x0 /* DO NOT USE */ + +/* 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 0x127f + +/* IEEE: same as above, but exceptions */ +#define _FPU_IEEE 0x127f + +/* Type of the control word. */ +typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__))); + +/* Macros for accessing the hardware control word. */ +#define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (cw)) +#define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (cw)) + +/* Default control word set at startup. */ +extern fpu_control_t __fpu_control; + +__BEGIN_DECLS + +/* Called at startup. It can be used to manipulate fpu control register. */ +extern void __setfpucw __P ((fpu_control_t)); + +__END_DECLS + +#endif /* fpu_control.h */ |