1 /* ffs -- find first set bit in a word, counted from least significant end.
2 S/390 version.
3 Copyright (C) 2000-2022 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <https://www.gnu.org/licenses/>. */
19
20 #include <limits.h>
21 #define ffsl __something_else
22 #include <string.h>
23
24 #undef ffs
25
26 /* ffs: find first bit set. This is defined the same way as
27 the libc and compiler builtin ffs routines, therefore
28 differs in spirit from the above ffz (man ffs). */
29
30 int
__ffs(int x)31 __ffs (int x)
32 {
33 int r;
34
35 if (x == 0)
36 return 0;
37 __asm__(" lr %%r1,%1\n"
38 " sr %0,%0\n"
39 " tml %%r1,0xFFFF\n"
40 " jnz 0f\n"
41 " ahi %0,16\n"
42 " srl %%r1,16\n"
43 "0: tml %%r1,0x00FF\n"
44 " jnz 1f\n"
45 " ahi %0,8\n"
46 " srl %%r1,8\n"
47 "1: tml %%r1,0x000F\n"
48 " jnz 2f\n"
49 " ahi %0,4\n"
50 " srl %%r1,4\n"
51 "2: tml %%r1,0x0003\n"
52 " jnz 3f\n"
53 " ahi %0,2\n"
54 " srl %%r1,2\n"
55 "3: tml %%r1,0x0001\n"
56 " jnz 4f\n"
57 " ahi %0,1\n"
58 "4:"
59 : "=&d" (r) : "d" (x) : "cc", "1" );
60 return r+1;
61 }
62
63 weak_alias (__ffs, ffs)
64 libc_hidden_def (__ffs)
65 libc_hidden_builtin_def (ffs)
66 #if ULONG_MAX == UINT_MAX
67 #undef ffsl
68 weak_alias (__ffs, ffsl)
69 #endif
70