1 /* s_logbl.c -- long double version of s_logb.c.
2 */
3
4 /*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15 /*
16 * long double logbl(x)
17 * IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
18 * Use ilogb instead.
19 */
20
21 #include <math.h>
22 #include <math_private.h>
23 #include <math_ldbl_opt.h>
24 #include <fix-int-fp-convert-zero.h>
25
26 long double
__logbl(long double x)27 __logbl (long double x)
28 {
29 int64_t hx, hxs, rhx;
30 double xhi, xlo;
31
32 ldbl_unpack (x, &xhi, &xlo);
33 EXTRACT_WORDS64 (hx, xhi);
34 hxs = hx;
35 hx &= 0x7fffffffffffffffLL; /* high |x| */
36 if (hx == 0)
37 return -1.0 / fabs (x);
38 if (hx >= 0x7ff0000000000000LL)
39 return x * x;
40 if (__glibc_unlikely ((rhx = hx >> 52) == 0))
41 {
42 /* POSIX specifies that denormal number is treated as
43 though it were normalized. */
44 rhx -= __builtin_clzll (hx) - 12;
45 }
46 else if ((hx & 0x000fffffffffffffLL) == 0)
47 {
48 /* If the high part is a power of 2, and the low part is nonzero
49 with the opposite sign, the low part affects the
50 exponent. */
51 int64_t lx;
52 EXTRACT_WORDS64 (lx, xlo);
53 if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0)
54 rhx--;
55 }
56 if (FIX_INT_FP_CONVERT_ZERO && rhx == 1023)
57 return 0.0L;
58 return (long double) (rhx - 1023);
59 }
60 #ifndef __logbl
61 long_double_symbol (libm, __logbl, logbl);
62 #endif
63