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, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
21 #ifndef _FPU_CONTROL_H
22 #define _FPU_CONTROL_H 1
24 /* Note that this file sets on x86-64 only the x87 FPU, it does not
25 touch the SSE unit. */
27 /* Here is the dirty part. Set up your 387 through the control word
30 * 15-13 12 11-10 9-8 7-6 5 4 3 2 1 0
31 * | reserved | IC | RC | PC | reserved | PM | UM | OM | ZM | DM | IM
33 * IM: Invalid operation mask
34 * DM: Denormalized operand mask
35 * ZM: Zero-divide mask
38 * PM: Precision (inexact result) mask
40 * Mask bit is 1 means no interrupt.
42 * PC: Precision control
43 * 11 - round to extended precision
44 * 10 - round to double precision
45 * 00 - round to single precision
47 * RC: Rounding control
48 * 00 - rounding to nearest
49 * 01 - rounding down (toward - infinity)
50 * 10 - rounding up (toward + infinity)
51 * 11 - rounding toward zero
53 * IC: Infinity control
54 * That is for 8087 and 80287 only.
56 * The hardware default is 0x037f which we use.
61 /* masking of interrupts */
62 #define _FPU_MASK_IM 0x01
63 #define _FPU_MASK_DM 0x02
64 #define _FPU_MASK_ZM 0x04
65 #define _FPU_MASK_OM 0x08
66 #define _FPU_MASK_UM 0x10
67 #define _FPU_MASK_PM 0x20
69 /* precision control */
70 #define _FPU_EXTENDED 0x300 /* libm requires double extended precision. */
71 #define _FPU_DOUBLE 0x200
72 #define _FPU_SINGLE 0x0
74 /* rounding control */
75 #define _FPU_RC_NEAREST 0x0 /* RECOMMENDED */
76 #define _FPU_RC_DOWN 0x400
77 #define _FPU_RC_UP 0x800
78 #define _FPU_RC_ZERO 0xC00
80 #define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
83 /* The fdlibm code requires strict IEEE double precision arithmetic,
84 and no interrupts for exceptions, rounding to nearest. */
86 #define _FPU_DEFAULT 0x037f
88 /* IEEE: same as above. */
89 #define _FPU_IEEE 0x037f
91 /* Type of the control word. */
92 typedef unsigned int fpu_control_t
__attribute__ ((__mode__ (__HI__
)));
94 /* Macros for accessing the hardware control word. */
95 #define _FPU_GETCW(cw) __asm__ ("fnstcw %0" : "=m" (*&cw))
96 #define _FPU_SETCW(cw) __asm__ ("fldcw %0" : : "m" (*&cw))
98 /* Default control word set at startup. */
99 extern fpu_control_t __fpu_control
;
101 #endif /* fpu_control.h */