1 | /* s_scalblnl.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 | * scalblnl (long double x, long int n) |
22 | * scalblnl(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 | |
36 | _Float128 __scalblnl (_Float128 x, long 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 | |