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