1 /* @(#)s_scalbn.c 5.1 93/09/24 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
14 * scalbn (double x, int n)
15 * scalbn(x,n) returns x* 2**n computed by exponent
16 * manipulation rather than by actually performing an
17 * exponentiation or a multiplication.
21 #include "math_private.h"
28 two54
= 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
29 twom54
= 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
34 double __scalbln (double x
, long int n
)
36 double __scalbln (x
,n
)
42 EXTRACT_WORDS64(ix
,x
);
43 k
= (ix
>> 52) & 0x7ff; /* extract exponent */
44 if (k
==0) { /* 0 or subnormal x */
45 if ((ix
& UINT64_C(0xfffffffffffff))==0) return x
; /* +-0 */
47 EXTRACT_WORDS64(ix
,x
);
48 k
= ((ix
>> 52) & 0x7ff) - 54;
50 if (k
==0x7ff) return x
+x
; /* NaN or Inf */
52 if (n
> 50000 || k
> 0x7fe)
53 return huge
*__copysign(huge
,x
); /* overflow */
54 if (n
< -50000) return tiny
*__copysign(tiny
,x
); /*underflow*/
55 if (k
> 0) /* normal result */
56 {INSERT_WORDS64(x
,(ix
&UINT64_C(0x800fffffffffffff))|(k
<<52));
59 return tiny
*__copysign(tiny
,x
); /*underflow*/
60 k
+= 54; /* subnormal result */
61 INSERT_WORDS64(x
,(ix
&INT64_C(0x800fffffffffffff))|(k
<<52));
64 weak_alias (__scalbln
, scalbln
)
66 strong_alias (__scalbln
, __scalblnl
)
67 weak_alias (__scalbln
, scalblnl
)