xref: /illumos-gate/usr/src/lib/libc/i386/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 int	_sse_hw;
38 extern void	_getmxcsr(int *), _putmxcsr(int);
39 
40 fp_rnd
41 fpsetround(fp_rnd newrnd)
42 {
43 	struct _cw87 cw;
44 	fp_rnd oldrnd;
45 	int	mxcsr;
46 	extern int __flt_rounds;  /* ANSI value for rounding */
47 
48 	newrnd &= 0x3;	/* mask off all ubt last 2 bits */
49 	switch (newrnd) {	/* set ANSI rounding mode */
50 	case FP_RN:	__flt_rounds = 1;
51 			break;
52 	case FP_RM:	__flt_rounds = 3;
53 			break;
54 	case FP_RP:	__flt_rounds = 2;
55 			break;
56 	case FP_RZ:	__flt_rounds = 0;
57 			break;
58 	};
59 	_getcw(&cw);
60 	oldrnd = (fp_rnd)cw.rnd;
61 	cw.rnd = newrnd;
62 	_putcw(cw);
63 	if (_sse_hw) {
64 		_getmxcsr(&mxcsr);
65 		mxcsr = (mxcsr & ~0x6000) | ((int)newrnd << 13);
66 		_putmxcsr(mxcsr);
67 	}
68 	return (oldrnd);
69 }
70