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/*
28 *	Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.
29 *	Copyright (c) 1988 AT&T
30 *	  All Rights Reserved
31 */
32
33#pragma ident	"%Z%%M%	%I%	%E% SMI"
34
35/*
36 * Establish the default settings for the floating-point state for a C language
37 * program:
38 *	rounding mode		-- round to nearest default by OS,
39 *	exceptions enabled	-- all masked
40 *	sticky bits		-- all clear by default by OS.
41 *      precision control       -- double extended
42 */
43
44#pragma weak _fpstart = __fpstart
45
46#include "lint.h"
47#include <sys/types.h>
48#include <sys/sysi86.h>	/* for SI86FPHW/SI86FPSTART definitions */
49#include <sys/fp.h>	/* for FPU_CW_INIT and SSE_MXCSR_INIT */
50
51int	__flt_rounds;		/* ANSI rounding mode */
52
53void
54__fpstart()
55{
56	int _fp_hw;		/* default: bss: 0 == no hardware */
57
58	/*
59	 * query OS for HW status and ensure the x87 and (optional)
60	 * SSE control words are (will be) set correctly.
61	 * This "cannot fail".
62	 */
63	(void) sysi86(SI86FPSTART,
64	    &_fp_hw, FPU_CW_INIT, SSE_MXCSR_INIT);
65
66	/*
67	 * At this point the x87 fp environment that has been (or more
68	 * hopefully, will be) established by the kernel is:
69	 *
70	 * affine infinity	0x1000
71	 * round to nearest	0x0000
72	 * 64-bit doubles	0x0300
73	 * precision, underflow, overflow, zero-divide, denorm, invalid masked
74	 *			0x003f
75	 *
76	 * which conforms to the 4th edition i386 ABI definition.
77	 *
78	 * Additionally, if we have SSE hardware, we've also masked all
79	 * the same traps, and have round to nearest.
80	 */
81
82	__flt_rounds = 1;	/* ANSI way of saying round-to-nearest */
83}
84