1 /* $NetBSD: flt_rounds.c,v 1.5 2015/03/19 21:22:59 joerg 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/cdefs.h>
35 #if defined(LIBC_SCCS) && !defined(lint)
36 __RCSID("$NetBSD: flt_rounds.c,v 1.5 2015/03/19 21:22:59 joerg Exp $");
37 #endif /* LIBC_SCCS and not lint */
38
39 #include "namespace.h"
40 #include <sys/types.h>
41 #include <ieeefp.h>
42
43 static const int map[] = {
44 1, /* round to nearest */
45 2, /* round to positive infinity */
46 3, /* round to negative infinity */
47 0 /* round to zero */
48 };
49
50 /*
51 * Return the current FP rounding mode
52 *
53 * Returns:
54 * 0 - round to zero
55 * 1 - round to nearest
56 * 2 - round to postive infinity
57 * 3 - round to negative infinity
58 *
59 * ok all we need to do is get the current FP rounding mode
60 * index our map table and return the appropriate value.
61 *
62 * HOWEVER:
63 * The ARM FPA codes the rounding mode into the actual FP instructions
64 * so there is no such thing as a global rounding mode.
65 * The default is round to nearest if rounding is not explicitly specified.
66 * FP instructions generated by GCC will not explicitly specify a rounding
67 * mode.
68 *
69 * So the best we can do it to return the rounding mode FP instructions
70 * use if rounding is not specified which is round to nearest.
71 *
72 * This could change in the future with new floating point emulators or
73 * soft float FP libraries.
74 */
75
76 int __flt_rounds(void);
77
78 int
__flt_rounds(void)79 __flt_rounds(void)
80 {
81 return(map[fpgetround()]);
82 }
83