xref: /freebsd/lib/msun/src/s_scalbnl.c (revision 29fc4075e69fd27de0cded313ac6000165d99f8b)
1 /*
2  * Copyright (c) 2005-2020 Rich Felker, et al.
3  *
4  * SPDX-License-Identifier: MIT
5  *
6  * Please see https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
7  * for all contributors to musl.
8  */
9 #include <math.h>
10 #include <float.h>
11 #include "math_private.h"
12 #include "fpmath.h"
13 /*
14  * scalbnl (long double x, int n)
15  * scalbnl(x,n) returns x* 2**n  computed by  exponent
16  * manipulation rather than by actually performing an
17  * exponentiation or a multiplication.
18  */
19 #if (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
20 long double scalbnl(long double x, int n)
21 {
22 	union IEEEl2bits u;
23 
24 	if (n > 16383) {
25 		x *= 0x1p16383L;
26 		n -= 16383;
27 		if (n > 16383) {
28 			x *= 0x1p16383L;
29 			n -= 16383;
30 			if (n > 16383)
31 				n = 16383;
32 		}
33 	} else if (n < -16382) {
34 		x *= 0x1p-16382L * 0x1p113L;
35 		n += 16382 - 113;
36 		if (n < -16382) {
37 			x *= 0x1p-16382L * 0x1p113L;
38 			n += 16382 - 113;
39 			if (n < -16382)
40 				n = -16382;
41 		}
42 	}
43 	u.e = 1.0;
44 	u.xbits.expsign = 0x3fff + n;
45 	return x * u.e;
46 }
47 __strong_reference(scalbnl, ldexpl);
48 #endif
49 
50