mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 00:31:08 +00:00
71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
/* ffs -- find first set bit in a word, counted from least significant end.
|
|
S/390 version.
|
|
Copyright (C) 2000-2020 Free Software Foundation, Inc.
|
|
Contributed by Martin Schwidefsky (schwidefsky@de.ibm.com).
|
|
This file is part of the GNU C Library.
|
|
|
|
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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <limits.h>
|
|
#define ffsl __something_else
|
|
#include <string.h>
|
|
|
|
#undef ffs
|
|
|
|
/* ffs: find first bit set. This is defined the same way as
|
|
the libc and compiler builtin ffs routines, therefore
|
|
differs in spirit from the above ffz (man ffs). */
|
|
|
|
int
|
|
__ffs (int x)
|
|
{
|
|
int r;
|
|
|
|
if (x == 0)
|
|
return 0;
|
|
__asm__(" lr %%r1,%1\n"
|
|
" sr %0,%0\n"
|
|
" tml %%r1,0xFFFF\n"
|
|
" jnz 0f\n"
|
|
" ahi %0,16\n"
|
|
" srl %%r1,16\n"
|
|
"0: tml %%r1,0x00FF\n"
|
|
" jnz 1f\n"
|
|
" ahi %0,8\n"
|
|
" srl %%r1,8\n"
|
|
"1: tml %%r1,0x000F\n"
|
|
" jnz 2f\n"
|
|
" ahi %0,4\n"
|
|
" srl %%r1,4\n"
|
|
"2: tml %%r1,0x0003\n"
|
|
" jnz 3f\n"
|
|
" ahi %0,2\n"
|
|
" srl %%r1,2\n"
|
|
"3: tml %%r1,0x0001\n"
|
|
" jnz 4f\n"
|
|
" ahi %0,1\n"
|
|
"4:"
|
|
: "=&d" (r) : "d" (x) : "cc", "1" );
|
|
return r+1;
|
|
}
|
|
|
|
weak_alias (__ffs, ffs)
|
|
libc_hidden_def (__ffs)
|
|
libc_hidden_builtin_def (ffs)
|
|
#if ULONG_MAX == UINT_MAX
|
|
#undef ffsl
|
|
weak_alias (__ffs, ffsl)
|
|
#endif
|