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| author | Ulrich Drepper <drepper@gmail.com> | 2011-09-12 16:21:24 -0400 |
|---|---|---|
| committer | Ulrich Drepper <drepper@gmail.com> | 2011-09-12 16:21:24 -0400 |
| commit | 8682f8b0e4bd3531e82d65332838421e76682956 (patch) | |
| tree | 297cdc5f6903bedd74f67e6a5828e43c31033a26 | |
| parent | 037e9fe21c92216ef7032ea2796781ec27ca182a (diff) | |
| download | glibc-8682f8b0e4bd3531e82d65332838421e76682956.tar.gz | |
Optimize logb code for 64-bit machines
| -rw-r--r-- | ChangeLog | 4 | ||||
| -rw-r--r-- | sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c | 44 |
2 files changed, 48 insertions, 0 deletions
@@ -1,3 +1,7 @@ +2011-09-12 Ulrich Drepper <drepper@gmail.com> + + * sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c: New file. + 2011-09-12 Andreas Schwab <schwab@redhat.com> * sysdeps/unix/sysv/linux/bits/socket.h (__cmsg_nxthdr): Cast to diff --git a/sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c b/sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c new file mode 100644 index 0000000000..7413504365 --- /dev/null +++ b/sysdeps/ieee754/dbl-64/wordsize-64/s_logb.c @@ -0,0 +1,44 @@ +/* Compute radix independent exponent. + Copyright (C) 2011 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@gmail.com>, 2011. + + 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <math.h> + +#include "math_private.h" + + +double +__logb (double x) +{ + int64_t ix; + + EXTRACT_WORDS64 (ix, x); + ix &= UINT64_C(0x7fffffffffffffff); + if (ix == 0) + return -1.0 / fabs (x); + unsigned int ex = ix >> 52; + if (ex == 0x7ff) + return x * x; + return ex == 0 ? -1022.0 : (double) (ex - 1023); +} +weak_alias (__logb, logb) +#ifdef NO_LONG_DOUBLE +strong_alias (__logb, __logbl) +weak_alias (__logb, logbl) +#endif |