1 | /* s_scalblnl.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) |
18 | static char rcsid[] = "$NetBSD: $" ; |
19 | #endif |
20 | |
21 | /* |
22 | * scalblnl (long double x, long int n) |
23 | * scalblnl(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 | |
31 | static const _Float128 |
32 | two114 = L(2.0769187434139310514121985316880384E+34), /* 0x4071000000000000, 0 */ |
33 | twom114 = L(4.8148248609680896326399448564623183E-35), /* 0x3F8D000000000000, 0 */ |
34 | huge = L(1.0E+4900), |
35 | tiny = L(1.0E-4900); |
36 | |
37 | _Float128 __scalblnl (_Float128 x, long 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 | |