memset.S

/* Copyright (c) 2002, 2007 Marek Michalkiewicz

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the documentation and/or other materials provided with the
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* Neither the name of the copyright holders nor the names of
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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
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */

/* $Id$ */

/** \file */
/** \ingroup avr_string
\fn void *memset(void *dest, int val, size_t len)
\brief Fill memory with a constant byte.

The memset() function fills the first len bytes of the memory area pointed
to by dest with the constant byte val.

\returns The memset() function returns a pointer to the memory area dest. */

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define dest_hi r25
#define dest_lo r24
; #define val_hi r23
#define val_lo r22
#define len_hi r21
#define len_lo r20

ASSEMBLY_CLIB_SECTION
.global _U(memset)
.type   _U(memset), @function
_U(memset):
X_movw  XL, dest_lo
#if OPTIMIZE_SPEED
; 11 words, (12 + len * 4 - (len & 1)) cycles
sbrs    len_lo, 0
rjmp    .L_memset_start
rjmp    .L_memset_odd
.L_memset_loop:
st      X+, val_lo
.L_memset_odd:
st      X+, val_lo
.L_memset_start:
subi    len_lo, lo8(2)
sbci    len_hi, hi8(2)
#else
; 8 words, (11 + len * 6) cycles
rjmp    .L_memset_start
.L_memset_loop:
st      X+, val_lo
.L_memset_start:
subi    len_lo, lo8(1)
sbci    len_hi, hi8(1)
#endif
brcc    .L_memset_loop
; return dest (unchanged)
ret
.L_memset_end:
.size   _U(memset), .L_memset_end - _U(memset)

#endif /* not __DOXYGEN__ */