1 | /* s_scalbnl.c -- long double version of s_scalbn.c. |
2 | * Conversion to long double by Ulrich Drepper, |
3 | * Cygnus Support, drepper@cygnus.com. |
4 | */ |
5 | |
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 | /* |
18 | * scalbnl (long double x, int n) |
19 | * scalbnl(x,n) returns x* 2**n computed by exponent |
20 | * manipulation rather than by actually performing an |
21 | * exponentiation or a multiplication. |
22 | */ |
23 | |
24 | #include <math.h> |
25 | #include <math_private.h> |
26 | |
27 | static const long double |
28 | two63 = 0x1p63L, |
29 | twom64 = 0x1p-64L, |
30 | huge = 1.0e+4900L, |
31 | tiny = 1.0e-4900L; |
32 | |
33 | long double |
34 | __scalblnl (long double x, long int n) |
35 | { |
36 | int32_t k,es,hx,lx; |
37 | GET_LDOUBLE_WORDS(es,hx,lx,x); |
38 | k = es&0x7fff; /* extract exponent */ |
39 | if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */ |
40 | if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */ |
41 | x *= two63; |
42 | GET_LDOUBLE_EXP(es,x); |
43 | k = (es&0x7fff) - 63; |
44 | } |
45 | if (__builtin_expect(k==0x7fff, 0)) return x+x; /* NaN or Inf */ |
46 | if (__builtin_expect(n< -50000, 0)) |
47 | return tiny*__copysignl(tiny,x); |
48 | if (__builtin_expect(n> 50000 || k+n > 0x7ffe, 0)) |
49 | return huge*__copysignl(huge,x); /* overflow */ |
50 | /* Now k and n are bounded we know that k = k+n does not |
51 | overflow. */ |
52 | k = k+n; |
53 | if (__builtin_expect(k > 0, 1)) /* normal result */ |
54 | {SET_LDOUBLE_EXP(x,(es&0x8000)|k); return x;} |
55 | if (k <= -64) |
56 | return tiny*__copysignl(tiny,x); /*underflow*/ |
57 | k += 64; /* subnormal result */ |
58 | SET_LDOUBLE_EXP(x,(es&0x8000)|k); |
59 | return x*twom64; |
60 | } |
61 | |