1 /* s_scalblnl.c -- long double version of s_scalbn.c.
2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
3 */
4
5 /* @(#)s_scalbn.c 5.1 93/09/24 */
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 #if defined(LIBM_SCCS) && !defined(lint)
18 static char rcsid[] = "$NetBSD: $";
19 #endif
20
21 /*
22 * scalblnl (long double x, long int n)
23 * scalblnl(x,n) returns x* 2**n computed by exponent
24 * manipulation rather than by actually performing an
25 * exponentiation or a multiplication.
26 */
27
28 #include "quadmath-imp.h"
29
30 static const __float128
31 two114 = 2.0769187434139310514121985316880384E+34Q, /* 0x4071000000000000, 0 */
32 twom114 = 4.8148248609680896326399448564623183E-35Q, /* 0x3F8D000000000000, 0 */
33 huge = 1.0E+4900Q,
34 tiny = 1.0E-4900Q;
35
scalblnq(__float128 x,long int n)36 __float128 scalblnq (__float128 x, long int n)
37 {
38 int64_t k,hx,lx;
39 GET_FLT128_WORDS64(hx,lx,x);
40 k = (hx>>48)&0x7fff; /* extract exponent */
41 if (k==0) { /* 0 or subnormal x */
42 if ((lx|(hx&0x7fffffffffffffffULL))==0) return x; /* +-0 */
43 x *= two114;
44 GET_FLT128_MSW64(hx,x);
45 k = ((hx>>48)&0x7fff) - 114;
46 }
47 if (k==0x7fff) return x+x; /* NaN or Inf */
48 if (n< -50000) return tiny*copysignq(tiny,x); /*underflow*/
49 if (n> 50000 || k+n > 0x7ffe)
50 return huge*copysignq(huge,x); /* overflow */
51 /* Now k and n are bounded we know that k = k+n does not
52 overflow. */
53 k = k+n;
54 if (k > 0) /* normal result */
55 {SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48)); return x;}
56 if (k <= -114)
57 return tiny*copysignq(tiny,x); /*underflow*/
58 k += 114; /* subnormal result */
59 SET_FLT128_MSW64(x,(hx&0x8000ffffffffffffULL)|(k<<48));
60 return x*twom114;
61 }
62