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 __scalbnl = scalbnl
31
32 #include "libm.h"
33 #include <float.h> /* LDBL_MAX, LDBL_MIN */
34 #include <stdlib.h> /* abs */
35
36 #if defined(__sparc)
37 #define XSET_EXP(k, x) ((int *) &x)[0] = (((int *) &x)[0] & ~0x7fff0000) | \
38 (k << 16)
39 #define ISINFNANL(k, x) (k == 0x7fff)
40 #define XTWOT_OFFSET 113
41 static const long double xtwot = 10384593717069655257060992658440192.0L,
42 /* 2^113 */
43 twomtm1 = 4.814824860968089632639944856462318296E-35L; /* 2^-114 */
44 #elif defined(__x86)
45 #define XSET_EXP(k, x) ((int *) &x)[2] = (((int *) &x)[2] & ~0x7fff) | k
46 #if defined(HANDLE_UNSUPPORTED)
47 #define ISINFNANL(k, x) (k == 0x7fff || k != 0 && \
48 (((int *) &x)[1] & 0x80000000) == 0)
49 #else
50 #define ISINFNANL(k, x) (k == 0x7fff)
51 #endif
52 #define XTWOT_OFFSET 64
53 static const long double xtwot = 18446744073709551616.0L, /* 2^64 */
54 twomtm1 = 2.7105054312137610850186E-20L; /* 2^-65 */
55 #endif
56
57 long double
scalbnl(long double x,int n)58 scalbnl(long double x, int n) {
59 int k = XBIASED_EXP(x);
60
61 if (ISINFNANL(k, x))
62 return (x + x);
63 if (ISZEROL(x) || n == 0)
64 return (x);
65 if (k == 0) {
66 x *= xtwot;
67 k = XBIASED_EXP(x) - XTWOT_OFFSET;
68 }
69 if ((unsigned) abs(n) >= 131072) /* cast to unsigned for -2^31 */
70 n >>= 1; /* avoid subsequent integer overflow */
71 k += n;
72 if (k > 0x7ffe)
73 return (LDBL_MAX * copysignl(LDBL_MAX, x));
74 if (k <= -XTWOT_OFFSET - 1)
75 return (LDBL_MIN * copysignl(LDBL_MIN, x));
76 if (k > 0) {
77 XSET_EXP(k, x);
78 return (x);
79 }
80 k += XTWOT_OFFSET + 1;
81 XSET_EXP(k, x);
82 return (x * twomtm1);
83 }
84