e1aee31878
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19930 a1c6a512-1295-4272-9138-f99709370657
50 lines
1.8 KiB
ArmAsm
50 lines
1.8 KiB
ArmAsm
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2009 by Maurus Cuelenaere
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* based on ffs-arm.S by Michael Sevakis
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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#include "config.h"
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#include "mips.h"
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/****************************************************************************
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* int find_first_set_bit(uint32_t val);
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*
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* Find the index of the least significant set bit in the 32-bit word.
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*
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* return values:
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* 0 - bit 0 is set
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* 1 - bit 1 is set
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* ...
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* 31 - bit 31 is set
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* 32 - no bits set
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****************************************************************************/
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.align 2
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.global find_first_set_bit
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.type find_first_set_bit, %function
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find_first_set_bit:
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negu t0, a0 # t0 = a0 & -a0
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and t0, t0, a0 #
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clz v0, t0 # Get lead 0's count
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li t0, 31 # t0 = 31
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sub v0, t0, v0 # Return value = t0 - v0
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jr ra
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nop
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