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
|
/*
* ====================================================
* 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.
* ====================================================
*/
/*
* scalbn (double x, int n)
* scalbn(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 double
two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
huge = 1.0e+300,
tiny = 1.0e-300;
double
__scalbln (double x, long int n)
{
int32_t k,hx,lx;
EXTRACT_WORDS(hx,lx,x);
k = (hx&0x7ff00000)>>20; /* extract exponent */
if (__builtin_expect(k==0, 0)) { /* 0 or subnormal x */
if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
x *= two54;
GET_HIGH_WORD(hx,x);
k = ((hx&0x7ff00000)>>20) - 54;
}
if (__builtin_expect(k==0x7ff, 0)) return x+x; /* NaN or Inf */
if (__builtin_expect(n< -50000, 0))
return tiny*__copysign(tiny,x); /*underflow*/
if (__builtin_expect(n> 50000 || k+n > 0x7fe, 0))
return huge*__copysign(huge,x); /* overflow */
/* Now k and n are bounded we know that k = k+n does not
overflow. */
k = k+n;
if (__builtin_expect(k > 0, 1)) /* normal result */
{SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
if (k <= -54)
return tiny*__copysign(tiny,x); /*underflow*/
k += 54; /* subnormal result */
SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
return x*twom54;
}
weak_alias (__scalbln, scalbln)
#ifdef NO_LONG_DOUBLE
strong_alias (__scalbln, __scalblnl)
weak_alias (__scalbln, scalblnl)
#endif
|
