| /*************************************************************************** |
| * __________ __ ___. |
| * Open \______ \ ____ ____ | | _\_ |__ _______ ___ |
| * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / |
| * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < |
| * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ |
| * \/ \/ \/ \/ \/ |
| * $Id$ |
| * |
| * Copyright (C) 2008 by Michael Sevakis |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License |
| * as published by the Free Software Foundation; either version 2 |
| * of the License, or (at your option) any later version. |
| * |
| * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY |
| * KIND, either express or implied. |
| * |
| ****************************************************************************/ |
| #include "config.h" |
| #include <inttypes.h> |
| |
| /* find_first_set_bit() - this is a C version of the ffs algorithm devised |
| * by D.Seal and posted to comp.sys.arm on 16 Feb 1994. |
| * |
| * Find the index of the least significant set bit in the word. |
| * return values: |
| * 0 - bit 0 is set |
| * 1 - bit 1 is set |
| * ... |
| * 31 - bit 31 is set |
| * 32 - no bits set |
| */ |
| |
| /* Table shared with assembly code */ |
| const uint8_t L_ffs_table[64] ICONST_ATTR = |
| { |
| /* 0 1 2 3 4 5 6 7 */ |
| /* ----------------------------------------- */ |
| 32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */ |
| 3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */ |
| 10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */ |
| 0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */ |
| 31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */ |
| 9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */ |
| 30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */ |
| 29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */ |
| }; |
| |
| #if !defined(CPU_COLDFIRE) |
| int find_first_set_bit(uint32_t val) |
| { |
| return L_ffs_table[((val & -val)*0x0450fbaf) >> 26]; |
| } |
| #endif |