memmove.c

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/*
 * Copyright (C) 2008-2009 Michal Simek <[email protected]>
 * Copyright (C) 2008-2009 PetaLogix
 * Copyright (C) 2007 John Williams
 *
 * Reasonably optimised generic C-code for memcpy on Microblaze
 * This is generic C code to do efficient, alignment-aware memmove.
 *
 * It is based on demo code originally Copyright 2001 by Intel Corp, taken from
 * http://www.embedded.com/showArticle.jhtml?articleID=19205567
 *
 * Attempts were made, unsuccessfully, to contact the original
 * author of this code (Michael Morrow, Intel).  Below is the original
 * copyright notice.
 *
 * This software has been developed by Intel Corporation.
 * Intel specifically disclaims all warranties, express or
 * implied, and all liability, including consequential and
 * other indirect damages, for the use of this program, including
 * liability for infringement of any proprietary rights,
 * and including the warranties of merchantability and fitness
 * for a particular purpose. Intel does not assume any
 * responsibility for and errors which may appear in this program
 * not any responsibility to update it.
 */

#include <linux/types.h>
#include <linux/stddef.h>
#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/string.h>

#ifdef __HAVE_ARCH_MEMMOVE
#ifndef CONFIG_OPT_LIB_FUNCTION
void *memmove(void *v_dst, const void *v_src, __kernel_size_t c)
{
    const char *src = v_src;
    char *dst = v_dst;

    if (!c)
        return v_dst;

    /* Use memcpy when source is higher than dest */
    if (v_dst <= v_src)
        return memcpy(v_dst, v_src, c);

    /* copy backwards, from end to beginning */
    src += c;
    dst += c;

    /* Simple, byte oriented memmove. */
    while (c--)
        *--dst = *--src;

    return v_dst;
}
#else /* CONFIG_OPT_LIB_FUNCTION */
void *memmove(void *v_dst, const void *v_src, __kernel_size_t c)
{
    const char *src = v_src;
    char *dst = v_dst;
    const uint32_t *i_src;
    uint32_t *i_dst;

    if (!c)
        return v_dst;

    /* Use memcpy when source is higher than dest */
    if (v_dst <= v_src)
        return memcpy(v_dst, v_src, c);

    /* The following code tries to optimize the copy by using unsigned
     * alignment. This will work fine if both source and destination are
     * aligned on the same boundary. However, if they are aligned on
     * different boundaries shifts will be necessary. This might result in
     * bad performance on MicroBlaze systems without a barrel shifter.
     */
    /* FIXME this part needs more test */
    /* Do a descending copy - this is a bit trickier! */
    dst += c;
    src += c;

    if (c >= 4) {
        unsigned  value, buf_hold;

        /* Align the destination to a word boundary. */
        /* This is done in an endian independent manner. */

        switch ((unsigned long)dst & 3) {
        case 3:
            *--dst = *--src;
            --c;
        case 2:
            *--dst = *--src;
            --c;
        case 1:
            *--dst = *--src;
            --c;
        }

        i_dst = (void *)dst;
        /* Choose a copy scheme based on the source */
        /* alignment relative to dstination. */
        switch ((unsigned long)src & 3) {
        case 0x0:   /* Both byte offsets are aligned */

            i_src  = (const void *)src;

            for (; c >= 4; c -= 4)
                *--i_dst = *--i_src;

            src  = (const void *)i_src;
            break;
        case 0x1:   /* Unaligned - Off by 1 */
            /* Word align the source */
            i_src = (const void *) (((unsigned)src + 4) & ~3);
#ifndef __MICROBLAZEEL__
            /* Load the holding buffer */
            buf_hold = *--i_src >> 24;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold << 8 | value;
                buf_hold = value >> 24;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*--i_src & 0xFF) << 24;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold | ((value & 0xFFFFFF00)>>8);
                buf_hold = (value  & 0xFF) << 24;
            }
#endif
            /* Realign the source */
            src = (const void *)i_src;
            src += 1;
            break;
        case 0x2:   /* Unaligned - Off by 2 */
            /* Word align the source */
            i_src = (const void *) (((unsigned)src + 4) & ~3);
#ifndef __MICROBLAZEEL__
            /* Load the holding buffer */
            buf_hold = *--i_src >> 16;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold << 16 | value;
                buf_hold = value >> 16;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*--i_src & 0xFFFF) << 16;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold | ((value & 0xFFFF0000)>>16);
                buf_hold = (value & 0xFFFF) << 16;
            }
#endif
            /* Realign the source */
            src = (const void *)i_src;
            src += 2;
            break;
        case 0x3:   /* Unaligned - Off by 3 */
            /* Word align the source */
            i_src = (const void *) (((unsigned)src + 4) & ~3);
#ifndef __MICROBLAZEEL__
            /* Load the holding buffer */
            buf_hold = *--i_src >> 8;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold << 24 | value;
                buf_hold = value >> 8;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*--i_src & 0xFFFFFF) << 8;

            for (; c >= 4; c -= 4) {
                value = *--i_src;
                *--i_dst = buf_hold | ((value & 0xFF000000)>> 24);
                buf_hold = (value & 0xFFFFFF) << 8;
            }
#endif
            /* Realign the source */
            src = (const void *)i_src;
            src += 3;
            break;
        }
        dst = (void *)i_dst;
    }

    /* simple fast copy, ... unless a cache boundary is crossed */
    /* Finish off any remaining bytes */
    switch (c) {
    case 4:
        *--dst = *--src;
    case 3:
        *--dst = *--src;
    case 2:
        *--dst = *--src;
    case 1:
        *--dst = *--src;
    }
    return v_dst;
}
#endif /* CONFIG_OPT_LIB_FUNCTION */
EXPORT_SYMBOL(memmove);
#endif /* __HAVE_ARCH_MEMMOVE */