memset.S

/* Copyright (c) 2002, 2007 Marek Michalkiewicz
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

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     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
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  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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/* $Id$ */

/** \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__ */