xref: /illumos-gate/usr/src/lib/libc/amd64/fp/fpsetround.c (revision 08855964b9970604433f7b19dcd71cf5af5e5f14)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.	*/
28 /*	Copyright (c) 1988 AT&T	*/
29 /*	  All Rights Reserved	*/
30 
31 #pragma weak _fpsetround = fpsetround
32 
33 #include "lint.h"
34 #include <ieeefp.h>
35 #include "fp.h"
36 
37 extern void	_getmxcsr(int *), _putmxcsr(int);
38 
39 fp_rnd
40 fpsetround(fp_rnd newrnd)
41 {
42 	struct _cw87 cw;
43 	fp_rnd oldrnd;
44 	int	mxcsr;
45 
46 	newrnd &= 0x3;	/* mask off all ubt last 2 bits */
47 	_getcw(&cw);
48 	oldrnd = (fp_rnd)cw.rnd;
49 	cw.rnd = newrnd;
50 	_putcw(cw);
51 	_getmxcsr(&mxcsr);
52 	mxcsr = (mxcsr & ~0x6000) | ((int)newrnd << 13);
53 	_putmxcsr(mxcsr);
54 	return (oldrnd);
55 }
56