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author | Richard Maw <richard.maw@codethink.co.uk> | 2012-01-17 14:43:55 +0000 |
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committer | Richard Maw <richard.maw@codethink.co.uk> | 2012-01-17 14:43:55 +0000 |
commit | 2de9abc5c9d40b3c716307d67d16146f823fd554 (patch) | |
tree | 6979db67934ddc8b564150b465846a383b428ff8 /gnulib/lib/ffs.c | |
parent | 33cc1c6fda6e72a7bae1401e9b2cec495a4d3ff1 (diff) | |
download | patch-baserock/bootstrap.tar.gz |
add the output of bootstrapbaserock/bootstrap-pass2baserock/bootstrap
Diffstat (limited to 'gnulib/lib/ffs.c')
m--------- | gnulib | 0 | ||||
-rw-r--r-- | gnulib/lib/ffs.c | 56 |
2 files changed, 56 insertions, 0 deletions
diff --git a/gnulib b/gnulib deleted file mode 160000 -Subproject 443bc5ffcf7429e557f4a371b0661abe98ddbc1 diff --git a/gnulib/lib/ffs.c b/gnulib/lib/ffs.c new file mode 100644 index 0000000..34916f5 --- /dev/null +++ b/gnulib/lib/ffs.c @@ -0,0 +1,56 @@ +/* ffs.c -- find the first set bit in a word. + Copyright (C) 2011 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +/* Written by Eric Blake. */ + +#include <config.h> + +/* Specification. */ +#include <strings.h> + +#include <limits.h> + +int +ffs (int i) +{ +#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) + return __builtin_ffs (i); +#else + /* http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightMultLookup + gives this deBruijn constant for a branch-less computation, although + that table counted trailing zeros rather than bit position. This + requires 32-bit int, we fall back to a naive algorithm on the rare + platforms where that assumption is not true. */ + if (CHAR_BIT * sizeof i == 32) + { + static unsigned int table[] = { + 1, 2, 29, 3, 30, 15, 25, 4, 31, 23, 21, 16, 26, 18, 5, 9, + 32, 28, 14, 24, 22, 20, 17, 8, 27, 13, 19, 7, 12, 6, 11, 10 + }; + unsigned int u = i; + unsigned int bit = u & -u; + return table[(bit * 0x077cb531U) >> 27] - !i; + } + else + { + unsigned int j; + for (j = 0; j < CHAR_BIT * sizeof i; j++) + if (i & (1U << j)) + return j + 1; + return 0; + } +#endif +} |