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
51 int __flt_rounds; /* ANSI rounding mode */
52
53 void
__fpstart()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