1 /* FPU control word bits. x86-64 version.
2 Copyright (C) 1993,1995,1996,1997,1998,2000,2001,2002 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 /* Note that this file sets on x86-64 only the x87 FPU, it does not
24 touch the SSE unit. */
26 /* Here is the dirty part. Set up your 387 through the control word
29 * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0
30 * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM
32 * IM: Invalid operation mask
33 * DM: Denormalized operand mask
34 * ZM: Zero-divide mask
37 * PM: Precision (inexact result) mask
39 * Mask bit is 1 means no interrupt.
41 * PC: Precision control
42 * 11 - round to extended precision
43 * 10 - round to double precision
44 * 00 - round to single precision
46 * RC: Rounding control
47 * 00 - rounding to nearest
48 * 01 - rounding down (toward - infinity)
49 * 10 - rounding up (toward + infinity)
50 * 11 - rounding toward zero
52 * IC: Infinity control
53 * That is for 8087 and 80287 only.
55 * The hardware default is 0x037f which we use.
60 /* masking of interrupts */
61 #define _FPU_MASK_IM 0x01
62 #define _FPU_MASK_DM 0x02
63 #define _FPU_MASK_ZM 0x04
64 #define _FPU_MASK_OM 0x08
65 #define _FPU_MASK_UM 0x10
66 #define _FPU_MASK_PM 0x20
68 /* precision control */
69 #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */
70 #define _FPU_DOUBLE 0x200
71 #define _FPU_SINGLE 0x0
73 /* rounding control */
74 #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */
75 #define _FPU_RC_DOWN 0x400
76 #define _FPU_RC_UP 0x800
77 #define _FPU_RC_ZERO 0xC00
79 #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
82 /* The fdlibm code requires strict IEEE double precision arithmetic,
83 and no interrupts for exceptions, rounding to nearest. */
85 #define _FPU_DEFAULT 0x037f
87 /* IEEE: same as above. */
88 #define _FPU_IEEE 0x037f
90 /* Type of the control word. */
91 typedef unsigned int fpu_control_t __attribute__ ((__mode__ (__HI__)));
93 /* Macros for accessing the hardware control word. */
94 #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
95 #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
98 /* Default control word set at startup. */
99 extern fpu_control_t __fpu_control;
102 #endif /* fpu_control.h */