1 /* FPU control word bits. i387 version.
2 Copyright (C) 1993,1995-1998,2000,2001,2003 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Olaf Flebbe.
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
20 #ifndef _FPU_CONTROL_H
21 #define _FPU_CONTROL_H 1
23 /* Here is the dirty part. Set up your 387 through the control word
26 * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0
27 * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM
29 * IM: Invalid operation mask
30 * DM: Denormalized operand mask
31 * ZM: Zero-divide mask
34 * PM: Precision (inexact result) mask
36 * Mask bit is 1 means no interrupt.
38 * PC: Precision control
39 * 11 - round to extended precision
40 * 10 - round to double precision
41 * 00 - round to single precision
43 * RC: Rounding control
44 * 00 - rounding to nearest
45 * 01 - rounding down (toward - infinity)
46 * 10 - rounding up (toward + infinity)
47 * 11 - rounding toward zero
49 * IC: Infinity control
50 * That is for 8087 and 80287 only.
52 * The hardware default is 0x037f which we use.
57 /* masking of interrupts */
58 #define _FPU_MASK_IM 0x01
59 #define _FPU_MASK_DM 0x02
60 #define _FPU_MASK_ZM 0x04
61 #define _FPU_MASK_OM 0x08
62 #define _FPU_MASK_UM 0x10
63 #define _FPU_MASK_PM 0x20
65 /* precision control */
66 #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */
67 #define _FPU_DOUBLE 0x200
68 #define _FPU_SINGLE 0x0
70 /* rounding control */
71 #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */
72 #define _FPU_RC_DOWN 0x400
73 #define _FPU_RC_UP 0x800
74 #define _FPU_RC_ZERO 0xC00
76 #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
79 /* The fdlibm code requires strict IEEE double precision arithmetic,
80 and no interrupts for exceptions, rounding to nearest. */
82 #define _FPU_DEFAULT 0x037f
84 /* IEEE: same as above. */
85 #define _FPU_IEEE 0x037f
87 /* Type of the control word. */
88 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
90 /* Macros for accessing the hardware control word.
92 Note that the use of these macros is no sufficient anymore with
93 recent hardware. Some floating point operations are executed in
94 the SSE/SSE2 engines which have their own control and status register. */
95 #define _FPU_GETCW(cw) __asm__ __volatile__ ("fnstcw %0" : "=m" (*&cw))
96 #define _FPU_SETCW(cw) __asm__ __volatile__ ("fldcw %0" : : "m" (*&cw))
99 /* Default control word set at startup. */
100 extern fpu_control_t __fpu_control;
103 #endif /* fpu_control.h */