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/* Copyright (c) 2005, 2007 Dmitry Xmelkov
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */
/* $Id: ffs.S,v 1.4.2.1 2009/04/01 23:12:12 arcanum Exp $ */
/** \file */
/** \ingroup avr_string
\fn int ffs (int val);
\brief This function finds the first (least significant) bit set in the input value.
\returns The ffs() function returns the position of the first
(least significant) bit set in the word val, or 0 if no bits are set.
The least significant bit is position 1.
\note For expressions that are constant at compile time, consider
using the \ref _FFS macro instead.
*/
#ifndef __DOXYGEN__
#include "macros.inc"
#define val_lo r24
#define val_hi r25
#define cntr r30
ASSEMBLY_CLIB_SECTION
.global _U(ffs)
.type _U(ffs), @function
_U(ffs):
ldi cntr, 1
tst val_lo
brne 2f
or val_lo, val_hi
breq 9f
ldi cntr, 8
1: inc cntr
2: ror val_lo
brcc 1b
mov r24, cntr
clr r25
9: ret
.size _U(ffs), . - _U(ffs)
.end
#endif /* not __DOXYGEN__ */
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