| /* @(#)s_logb.c 5.1 93/09/24 */ |
| /* |
| * ==================================================== |
| * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| * |
| * Developed at SunPro, a Sun Microsystems, Inc. business. |
| * Permission to use, copy, modify, and distribute this |
| * software is freely granted, provided that this notice |
| * is preserved. |
| * ==================================================== |
| */ |
| |
| /* |
| * double logb(x) |
| * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. |
| * Use ilogb instead. |
| */ |
| |
| #include <math.h> |
| #include <math_private.h> |
| |
| double |
| __logb (double x) |
| { |
| int32_t lx, ix, rix; |
| |
| EXTRACT_WORDS (ix, lx, x); |
| ix &= 0x7fffffff; /* high |x| */ |
| if ((ix | lx) == 0) |
| return -1.0 / fabs (x); |
| if (ix >= 0x7ff00000) |
| return x * x; |
| if (__builtin_expect ((rix = ix >> 20) == 0, 0)) |
| { |
| /* POSIX specifies that denormal number is treated as |
| though it were normalized. */ |
| int ma; |
| if (ix == 0) |
| ma = __builtin_clz (lx) + 32; |
| else |
| ma = __builtin_clz (ix); |
| rix -= ma - 12; |
| } |
| return (double) (rix - 1023); |
| } |
| weak_alias (__logb, logb) |
| #ifdef NO_LONG_DOUBLE |
| strong_alias (__logb, __logbl) weak_alias (__logb, logbl) |
| #endif |
