1/* s_logbl.c -- long double version of s_logb.c.
2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#if defined(LIBM_SCCS) && !defined(lint)
17static char rcsid[] = "NetBSD: ";
18#endif
19
20/*
21 * long double logbq(x)
22 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
23 * Use ilogb instead.
24 */
25
26#include "quadmath-imp.h"
27
28__float128
29logbq (__float128 x)
30{
31  int64_t lx, hx, ex;
32
33  GET_FLT128_WORDS64 (hx, lx, x);
34  hx &= 0x7fffffffffffffffLL;	/* high |x| */
35  if ((hx | lx) == 0)
36    return -1.0 / fabsq (x);
37  if (hx >= 0x7fff000000000000LL)
38    return x * x;
39  if ((ex = hx >> 48) == 0)	/* IEEE 754 logb */
40    {
41      /* POSIX specifies that denormal number is treated as
42         though it were normalized.  */
43      int ma;
44      if (hx == 0)
45	ma = __builtin_clzll (lx) + 64;
46      else
47	ma = __builtin_clzll (hx);
48      ex -= ma - 16;
49    }
50  return (__float128) (ex - 16383);
51}
52