diff options
Diffstat (limited to 'sysdeps/i386/ffs.c')
| -rw-r--r-- | sysdeps/i386/ffs.c | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/sysdeps/i386/ffs.c b/sysdeps/i386/ffs.c new file mode 100644 index 0000000000..1e21585874 --- /dev/null +++ b/sysdeps/i386/ffs.c @@ -0,0 +1,45 @@ +/* ffs -- find first set bit in a word, counted from least significant end. + For Intel 80x86, x>=3. + Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc. + Contributed by Torbjorn Granlund (tege@sics.se). + +The GNU C Library is free software; you can redistribute it and/or +modify it under the terms of the GNU Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include <ansidecl.h> +#include <string.h> + +#undef ffs + +#ifdef __GNUC__ + +int +DEFUN(ffs, (x), int x) +{ + int cnt; + int tmp; + + asm ("xorl %0,%0\n" /* Set CNT to zero. */ + "bsfl %2,%1\n" /* Count low bits in X and store in %1. */ + "jz nonzero\n" /* Jump if OK, i.e. X was non-zero. */ + "leal 1(%1),%0\n" /* Return bsfl-result plus one on %0. */ + "nonzero:" : "=&a" (cnt), "=r" (tmp) : "rm" (x)); + + return cnt; +} + +#else +#include <sysdeps/generic/ffs.c> +#endif |