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 __scalbln = scalbln
31
32 #include "libm.h"
33 #include <float.h> /* DBL_MAX, DBL_MIN */
34
35 static const double twom54 = 5.5511151231257827021181583404541015625e-17;
36 #if defined(__x86)
37 static const double two52 = 4503599627370496.0;
38 #else
39 /*
40 * Normalize non-zero subnormal x and return biased exponent of x in [-51,0]
41 */
42 static int
ilogb_biased(unsigned * px)43 ilogb_biased(unsigned *px) {
44 int s = 52;
45 unsigned v = px[HIWORD] & ~0x80000000, w = px[LOWORD], t = v;
46
47 if (t)
48 s -= 32;
49 else
50 t = w;
51 if (t & 0xffff0000)
52 s -= 16, t >>= 16;
53 if (t & 0xff00)
54 s -= 8, t >>= 8;
55 if (t & 0xf0)
56 s -= 4, t >>= 4;
57 t <<= 1;
58 s -= (0xffffaa50 >> t) & 0x3;
59 if (s < 32) {
60 v = (v << s) | w >> (32 - s);
61 w <<= s;
62 } else {
63 v = w << (s - 32);
64 w = 0;
65 }
66 px[HIWORD] = (px[HIWORD] & 0x80000000) | v;
67 px[LOWORD] = w;
68 return (1 - s);
69 }
70 #endif /* defined(__x86) */
71
72 double
scalbln(double x,long n)73 scalbln(double x, long n) {
74 int *px = (int *) &x, ix, k;
75
76 ix = px[HIWORD] & ~0x80000000;
77 k = ix >> 20;
78 if (k == 0x7ff)
79 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
80 return ((px[HIWORD] & 0x80000) != 0 ? x : x + x);
81 /* assumes sparc-like QNaN */
82 #else
83 return (x + x);
84 #endif
85 if ((px[LOWORD] | ix) == 0 || n == 0)
86 return (x);
87 if (k == 0) {
88 #if defined(__x86)
89 x *= two52;
90 k = ((px[HIWORD] & ~0x80000000) >> 20) - 52;
91 #else
92 k = ilogb_biased((unsigned *) px);
93 #endif
94 }
95 k += (int) n;
96 if (n > 5000 || k > 0x7fe)
97 return (DBL_MAX * copysign(DBL_MAX, x));
98 if (n < -5000 || k <= -54)
99 return (DBL_MIN * copysign(DBL_MIN, x));
100 if (k > 0) {
101 px[HIWORD] = (px[HIWORD] & ~0x7ff00000) | (k << 20);
102 return (x);
103 }
104 k += 54;
105 px[HIWORD] = (px[HIWORD] & ~0x7ff00000) | (k << 20);
106 return (x * twom54);
107 }
108