xref: /titanic_44/usr/src/lib/libc/i386/fp/fpsetround.c (revision 7257d1b4d25bfac0c802847390e98a464fd787ac)
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 ident	"%Z%%M%	%I%	%E% SMI"
32 
33 #pragma weak _fpsetround = fpsetround
34 
35 #include "lint.h"
36 #include <ieeefp.h>
37 #include "fp.h"
38 
39 extern int	_sse_hw;
40 extern void	_getmxcsr(int *), _putmxcsr(int);
41 
42 fp_rnd
fpsetround(fp_rnd newrnd)43 fpsetround(fp_rnd newrnd)
44 {
45 	struct _cw87 cw;
46 	fp_rnd oldrnd;
47 	int	mxcsr;
48 	extern int __flt_rounds;  /* ANSI value for rounding */
49 
50 	newrnd &= 0x3;	/* mask off all ubt last 2 bits */
51 	switch (newrnd) {	/* set ANSI rounding mode */
52 	case FP_RN:	__flt_rounds = 1;
53 			break;
54 	case FP_RM:	__flt_rounds = 3;
55 			break;
56 	case FP_RP:	__flt_rounds = 2;
57 			break;
58 	case FP_RZ:	__flt_rounds = 0;
59 			break;
60 	};
61 	_getcw(&cw);
62 	oldrnd = (fp_rnd)cw.rnd;
63 	cw.rnd = newrnd;
64 	_putcw(cw);
65 	if (_sse_hw) {
66 		_getmxcsr(&mxcsr);
67 		mxcsr = (mxcsr & ~0x6000) | ((int)newrnd << 13);
68 		_putmxcsr(mxcsr);
69 	}
70 	return (oldrnd);
71 }
72