flt_rounds.c revision 1.1 
1/*	$NetBSD: flt_rounds.c,v 1.1 2000/01/05 14:07:32 msaitoh Exp $	*/
2
3/*
4 * Copyright (c) 1996 Mark Brinicombe
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 *    must display the following acknowledgement:
17 *      This product includes software developed by Mark Brinicombe
18 *	for the NetBSD Project.
19 * 4. The name of the author may not be used to endorse or promote products
20 *    derived from this software without specific prior written permission
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34#include <sys/types.h>
35#include <ieeefp.h>
36
37static const int map[] = {
38	1,	/* round to nearest */
39	2,	/* round to positive infinity */
40	3,	/* round to negative infinity */
41	0	/* round to zero */
42};
43
44/*
45 * Return the current FP rounding mode
46 *
47 * Returns:
48 *	0 - round to zero
49 *	1 - round to nearest
50 *	2 - round to postive infinity
51 *	3 - round to negative infinity
52 *
53 * ok all we need to do is get the current FP rounding mode
54 * index our map table and return the appropriate value.
55 *
56 * HOWEVER:
57 * The ARM FPA codes the rounding mode into the actual FP instructions
58 * so there is no such thing as a global rounding mode.
59 * The default is round to nearest if rounding is not explictly specified.
60 * FP instructions generated by GCC will not explicitly specify a rounding
61 * mode.
62 *
63 * So the best we can do it to return the rounding mode FP instructions
64 * use if rounding is not specified which is round to nearest.
65 *
66 * This could change in the future with new floating point emulators or
67 * soft float FP libraries.
68 */
69
70#include <sys/cdefs.h>
71
72extern int __flt_rounds __P((void));
73
74int
75__flt_rounds()
76{
77	return(map[fpgetround()]);
78}
79