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