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 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25 /*
26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
27 * Use is subject to license terms.
28 */
29
30 #pragma weak __logbl = logbl
31
32 #include "libm.h"
33 #include "xpg6.h" /* __xpg6 */
34 #define _C99SUSv3_logb _C99SUSv3_logb_subnormal_is_like_ilogb
35
36 #if defined(__sparc)
37 #define ISNORMALL(k, x) (k != 0x7fff) /* assuming k != 0 */
38 #define X86PDNRM(k, x)
39 #define XSCALE_OFFSET 0x406f /* 0x3fff + 112 */
40 static const long double xscale = 5192296858534827628530496329220096.0L;
41 /* 2^112 */
42 #elif defined(__x86)
43 /*
44 * if pseudo-denormal, replace by the equivalent normal
45 */
46 #define X86PDNRM(k, x) if (k == 0 && (((int *) &x)[1] & 0x80000000) != 0) \
47 ((int *) &x)[2] |= k = 1
48 #if defined(HANDLE_UNSUPPORTED) /* assuming k != 0 */
49 #define ISNORMALL(k, x) (k != 0x7fff && (((int *) &x)[1] & 0x80000000) != 0)
50 #else
51 #define ISNORMALL(k, x) (k != 0x7fff)
52 #endif
53 #define XSCALE_OFFSET 0x403e /* 0x3fff + 63 */
54 static const long double xscale = 9223372036854775808.0L; /* 2^63 */
55 #endif
56
57 static long double
raise_division(long double v)58 raise_division(long double v) {
59 #pragma STDC FENV_ACCESS ON
60 static const long double zero = 0.0L;
61 return (v / zero);
62 }
63
64 long double
logbl(long double x)65 logbl(long double x) {
66 int k = XBIASED_EXP(x);
67
68 X86PDNRM(k, x);
69 if (k == 0) {
70 if (ISZEROL(x))
71 return (raise_division(-1.0L));
72 else if ((__xpg6 & _C99SUSv3_logb) != 0) {
73 x *= xscale; /* scale up by 2^112 or 2^63 */
74 return (long double) (XBIASED_EXP(x) - XSCALE_OFFSET);
75 } else
76 return ((long double) (-16382));
77 } else if (ISNORMALL(k, x))
78 return ((long double) (k - 0x3fff));
79 else
80 return (x * x);
81 }
82