1 /***************************************************************************
3 * Open \______ \ ____ ____ | | _\_ |__ _______ ___
4 * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
5 * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
6 * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
10 * Copyright (C) 2008 by Michael Sevakis
12 * All files in this archive are subject to the GNU General Public License.
13 * See the file COPYING in the source tree root for full license agreement.
15 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
16 * KIND, either express or implied.
18 ****************************************************************************/
22 /* find_first_set_bit() - this is a C version of the ffs algorithm devised
23 * by D.Seal and posted to comp.sys.arm on 16 Feb 1994.
25 * Find the index of the least significant set bit in the word.
34 /* Table shared with assembly code */
35 const uint8_t L_ffs_table
[64] ICONST_ATTR
=
38 /* ----------------------------------------- */
39 32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */
40 3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */
41 10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */
42 0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */
43 31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */
44 9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */
45 30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */
46 29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */
49 #if !defined(CPU_COLDFIRE)
50 int find_first_set_bit(uint32_t val
)
52 return L_ffs_table
[((val
& -val
)*0x0450fbaf) >> 26];