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 __ilogbf = ilogbf
31
32 #include "libm.h"
33 #include "xpg6.h" /* __xpg6 */
34
35 #if defined(__x86)
36 static const float two25 = 33554432.0F;
37 #else
38 /*
39 * v: a non-zero subnormal |x|
40 */
41 static int
ilogbf_subnormal(unsigned v)42 ilogbf_subnormal(unsigned v) {
43 int r = -126 - 23;
44
45 if (v & 0xffff0000)
46 r += 16, v >>= 16;
47 if (v & 0xff00)
48 r += 8, v >>= 8;
49 if (v & 0xf0)
50 r += 4, v >>= 4;
51 v <<= 1;
52 return (r + ((0xffffaa50 >> v) & 0x3));
53 }
54 #endif /* defined(__x86) */
55
56 static int
raise_invalid(int v)57 raise_invalid(int v) { /* SUSv3 requires ilogbf(0,+/-Inf,NaN) raise invalid */
58 #ifndef lint
59 if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) {
60 static const double zero = 0.0;
61 volatile double dummy __unused;
62
63 dummy = zero / zero;
64 }
65 #endif
66 return (v);
67 }
68
69 int
ilogbf(float x)70 ilogbf(float x) {
71 int k = *((int *) &x) & ~0x80000000;
72
73 if (k < 0x00800000) {
74 if (k == 0)
75 return (raise_invalid(0x80000001));
76 else {
77 #if defined(__x86)
78 x *= two25;
79 return (((*((int *) &x) & 0x7f800000) >> 23) - 152);
80 #else
81 return (ilogbf_subnormal(k));
82 #endif
83 }
84 } else if (k < 0x7f800000)
85 return ((k >> 23) - 127);
86 else
87 return (raise_invalid(0x7fffffff));
88 }
89