diff options
Diffstat (limited to 'sysdeps/ieee754/dbl-64/s_logb.c')
| -rw-r--r-- | sysdeps/ieee754/dbl-64/s_logb.c | 61 |
1 files changed, 29 insertions, 32 deletions
diff --git a/sysdeps/ieee754/dbl-64/s_logb.c b/sysdeps/ieee754/dbl-64/s_logb.c index a6de1f6e49..e336251fda 100644 --- a/sysdeps/ieee754/dbl-64/s_logb.c +++ b/sysdeps/ieee754/dbl-64/s_logb.c @@ -1,22 +1,24 @@ -/* @(#)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. - * ==================================================== - */ +/* Compute radix independent exponent. + Copyright (C) 2011-2019 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@gmail.com>, 2011. -/* - * double logb(x) - * IEEE 754 logb. Included to pass IEEE test suite. Not recommend. - * Use ilogb instead. - */ + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ #include <math.h> + #include <math_private.h> #include <libm-alias-double.h> #include <fix-int-fp-convert-zero.h> @@ -24,28 +26,23 @@ double __logb (double x) { - int32_t lx, ix, rix; + int64_t ix, ex; - EXTRACT_WORDS (ix, lx, x); - ix &= 0x7fffffff; /* high |x| */ - if ((ix | lx) == 0) + EXTRACT_WORDS64 (ix, x); + ix &= UINT64_C(0x7fffffffffffffff); + if (ix == 0) return -1.0 / fabs (x); - if (ix >= 0x7ff00000) + ex = ix >> 52; + if (ex == 0x7ff) return x * x; - if (__glibc_unlikely ((rix = ix >> 20) == 0)) + if (__glibc_unlikely (ex == 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; + int m = __builtin_clzll (ix); + ex -= m - 12; } - if (FIX_INT_FP_CONVERT_ZERO && rix == 1023) + if (FIX_INT_FP_CONVERT_ZERO && ex == 1023) return 0.0; - return (double) (rix - 1023); + return (double) (ex - 1023); } #ifndef __logb libm_alias_double (__logb, logb) |