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 * Set _fp_hw according to what floating-point hardware is available.
43 * Set _sse_hw according to what SSE hardware is available.
44 * Set __flt_rounds according to the rounding mode.
45 */
46
47 #pragma weak _fpstart = __fpstart
48
49 #include "lint.h"
50 #include <sys/types.h>
51 #include <sys/sysi86.h> /* for SI86FPHW/SI86FPSTART definitions */
52 #include <sys/fp.h> /* for FPU_CW_INIT and SSE_MXCSR_INIT */
53
54 extern int __fltrounds();
55
56 int _fp_hw; /* default: bss: 0 == no hardware */
57 int _sse_hw; /* default: bss: 0 == no sse */
58 int __flt_rounds; /* ANSI rounding mode */
59
60 void
__fpstart()61 __fpstart()
62 {
63 /*
64 * query OS for HW status and ensure the x87 and (optional)
65 * SSE control words are (will be) set correctly.
66 */
67 if ((_sse_hw = sysi86(SI86FPSTART,
68 &_fp_hw, FPU_CW_INIT, SSE_MXCSR_INIT)) == -1) {
69 extern void _putcw();
70
71 /*
72 * (fallback to old syscall on old kernels)
73 */
74 _sse_hw = 0;
75 (void) sysi86(SI86FPHW, &_fp_hw);
76 _putcw(0x133f);
77 }
78
79 /*
80 * At this point the x87 fp environment that has been (or more
81 * hopefully, will be) established by the kernel is:
82 *
83 * affine infinity 0x1000
84 * round to nearest 0x0000
85 * 64-bit doubles 0x0300
86 * precision, underflow, overflow, zero-divide, denorm, invalid masked
87 * 0x003f
88 *
89 * which conforms to the 4th edition i386 ABI definition.
90 *
91 * Additionally, if we have SSE hardware, we've also masked all
92 * the same traps, and have round to nearest.
93 */
94
95 __flt_rounds = 1; /* ANSI way of saying round-to-nearest */
96 }
97