2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
9 * ====================================================
13 * scalbn (double x, int n)
14 * scalbn(x,n) returns x* 2**n computed by exponent
15 * manipulation rather than by actually performing an
16 * exponentiation or a multiplication.
20 #include <math_private.h>
23 two54
= 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
24 twom54
= 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
29 __scalbn (double x
, int n
)
33 EXTRACT_WORDS64(ix
,x
);
34 k
= (ix
>> 52) & 0x7ff; /* extract exponent */
35 if (__builtin_expect(k
==0, 0)) { /* 0 or subnormal x */
36 if ((ix
& UINT64_C(0xfffffffffffff))==0) return x
; /* +-0 */
38 EXTRACT_WORDS64(ix
,x
);
39 k
= ((ix
>> 52) & 0x7ff) - 54;
41 if (__builtin_expect(k
==0x7ff, 0)) return x
+x
; /* NaN or Inf */
42 if (__builtin_expect(n
< -50000, 0))
43 return tiny
*__copysign(tiny
,x
); /*underflow*/
44 if (__builtin_expect(n
> 50000 || k
+n
> 0x7fe, 0))
45 return huge
*__copysign(huge
,x
); /* overflow */
46 /* Now k and n are bounded we know that k = k+n does not
49 if (__builtin_expect(k
> 0, 1)) /* normal result */
50 {INSERT_WORDS64(x
,(ix
&UINT64_C(0x800fffffffffffff))|(k
<<52));
53 return tiny
*__copysign(tiny
,x
); /*underflow*/
54 k
+= 54; /* subnormal result */
55 INSERT_WORDS64(x
,(ix
&INT64_C(0x800fffffffffffff))|(k
<<52));
58 weak_alias (__scalbn
, scalbn
)
60 strong_alias (__scalbn
, __scalbnl
)
61 weak_alias (__scalbn
, scalbnl
)