rockbox/firmware/asm/ffs.c
Michael Sevakis 74736fcfc9 find_first_set_bit tweaks
Correct sizing in m68k asm.
Make the gerneric version far more generic.

Change-Id: I32945f7431771979b3fe0da5472bdb110fd054ae
2012-01-27 11:51:25 -05:00

41 lines
1.4 KiB
C

/***************************************************************************
* __________ __ ___.
* 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 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
*/
int find_first_set_bit(uint32_t val)
{
if (val == 0)
return 32;
/* __builtin_ffs(l(l)): Returns one plus the index of the least significant
1-bit of x, or if x is zero, returns zero. */
return __builtin_ffs(val) - 1;
}