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