| Michael Sevakis | 27cf677 | 2008-03-25 02:34:12 +0000 | [diff] [blame] | 1 | /*************************************************************************** |
| 2 | * __________ __ ___. |
| 3 | * Open \______ \ ____ ____ | | _\_ |__ _______ ___ |
| 4 | * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / |
| 5 | * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < |
| 6 | * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ |
| 7 | * \/ \/ \/ \/ \/ |
| 8 | * $Id$ |
| 9 | * |
| 10 | * Copyright (C) 2008 by Michael Sevakis |
| 11 | * |
| Daniel Stenberg | 2acc0ac | 2008-06-28 18:10:04 +0000 | [diff] [blame^] | 12 | * This program is free software; you can redistribute it and/or |
| 13 | * modify it under the terms of the GNU General Public License |
| 14 | * as published by the Free Software Foundation; either version 2 |
| 15 | * of the License, or (at your option) any later version. |
| Michael Sevakis | 27cf677 | 2008-03-25 02:34:12 +0000 | [diff] [blame] | 16 | * |
| 17 | * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY |
| 18 | * KIND, either express or implied. |
| 19 | * |
| 20 | ****************************************************************************/ |
| 21 | #include "config.h" |
| 22 | #include <inttypes.h> |
| 23 | |
| 24 | /* find_first_set_bit() - this is a C version of the ffs algorithm devised |
| 25 | * by D.Seal and posted to comp.sys.arm on 16 Feb 1994. |
| 26 | * |
| 27 | * Find the index of the least significant set bit in the word. |
| 28 | * return values: |
| 29 | * 0 - bit 0 is set |
| 30 | * 1 - bit 1 is set |
| 31 | * ... |
| 32 | * 31 - bit 31 is set |
| 33 | * 32 - no bits set |
| 34 | */ |
| 35 | |
| 36 | /* Table shared with assembly code */ |
| 37 | const uint8_t L_ffs_table[64] ICONST_ATTR = |
| 38 | { |
| 39 | /* 0 1 2 3 4 5 6 7 */ |
| 40 | /* ----------------------------------------- */ |
| 41 | 32, 0, 1, 12, 2, 6, 0, 13, /* 0- 7 */ |
| 42 | 3, 0, 7, 0, 0, 0, 0, 14, /* 8-15 */ |
| 43 | 10, 4, 0, 0, 8, 0, 0, 25, /* 16-23 */ |
| 44 | 0, 0, 0, 0, 0, 21, 27, 15, /* 24-31 */ |
| 45 | 31, 11, 5, 0, 0, 0, 0, 0, /* 32-39 */ |
| 46 | 9, 0, 0, 24, 0, 0, 20, 26, /* 40-47 */ |
| 47 | 30, 0, 0, 0, 0, 23, 0, 19, /* 48-55 */ |
| 48 | 29, 0, 22, 18, 28, 17, 16, 0, /* 56-63 */ |
| 49 | }; |
| 50 | |
| 51 | #if !defined(CPU_COLDFIRE) |
| 52 | int find_first_set_bit(uint32_t val) |
| 53 | { |
| 54 | return L_ffs_table[((val & -val)*0x0450fbaf) >> 26]; |
| 55 | } |
| 56 | #endif |