1/* s_scalbnl.c -- long double version of s_scalbn.c.
2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
3 */
4
5/* @(#)s_scalbn.c 5.1 93/09/24 */
6/*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17#if defined(LIBM_SCCS) && !defined(lint)
18static char rcsid[] = "$NetBSD: $";
19#endif
20
21/*
22 * scalbnl (long double x, int n)
23 * scalbnl(x,n) returns x* 2**n computed by exponent
24 * manipulation rather than by actually performing an
25 * exponentiation or a multiplication.
26 */
27
28#include <math.h>
29#include <math_private.h>
30
31static const _Float128
32two114 = L(2.0769187434139310514121985316880384E+34), /* 0x4071000000000000, 0 */
33twom114 = L(4.8148248609680896326399448564623183E-35), /* 0x3F8D000000000000, 0 */
34huge = L(1.0E+4900),
35tiny = L(1.0E-4900);
36
37_Float128 __scalbnl (_Float128 x, int n)
38{
39 int64_t k,hx,lx;
40 GET_LDOUBLE_WORDS64(hx,lx,x);
41 k = (hx>>48)&0x7fff; /* extract exponent */
42 if (k==0) { /* 0 or subnormal x */
43 if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
44 x *= two114;
45 GET_LDOUBLE_MSW64(hx,x);
46 k = ((hx>>48)&0x7fff) - 114;
47 }
48 if (k==0x7fff) return x+x; /* NaN or Inf */
49 if (n< -50000) return tiny*copysignl(tiny,x); /*underflow*/
50 if (n> 50000 || k+n > 0x7ffe)
51 return huge*copysignl(huge,x); /* overflow */
52 /* Now k and n are bounded we know that k = k+n does not
53 overflow. */
54 k = k+n;
55 if (k > 0) /* normal result */
56 {SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
57 if (k <= -114)
58 return tiny*copysignl(tiny,x); /*underflow*/
59 k += 114; /* subnormal result */
60 SET_LDOUBLE_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
61 return x*twom114;
62}
63