ffsl.S

/* 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. */

/* $Id$ */

#ifndef __DOXYGEN__

#include "macros.inc"

#define val_lo  r22
#define val_hi  r23
#define val_hlo r24
#define val_hhi r25

#define cntr    r30

    ASSEMBLY_CLIB_SECTION
    .global _U(ffsl)
    .type   _U(ffsl), @function
_U(ffsl):

    ldi cntr, 1
    tst val_lo
    brne    2f
    subi    cntr, -8
    or  val_lo, val_hi
    brne    2f
    subi    cntr, -8
    or  val_lo, val_hlo
    brne    2f
    subi    cntr, -7
    or  val_lo, val_hhi
    breq    9f

1:  inc cntr
2:  ror val_lo
    brcc    1b
    mov r24, cntr
    clr r25
9:  ret

    .size  _U(ffsl), . - _U(ffsl)
    .end
#endif  /* not __DOXYGEN__ */