1 | /* ffs -- find first set bit in a word, counted from least significant end. |
2 | S/390 version. |
3 | Copyright (C) 2000-2024 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 |
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 | |