memcpy.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 memcpy.
 *
 * 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_MEMCPY
#ifndef CONFIG_OPT_LIB_FUNCTION
void *memcpy(void *v_dst, const void *v_src, __kernel_size_t c)
{
    const char *src = v_src;
    char *dst = v_dst;

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

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

    /* 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.
     */
    const uint32_t *i_src;
    uint32_t *i_dst;

    if (likely(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 1:
            *dst++ = *src++;
            --c;
        case 2:
            *dst++ = *src++;
            --c;
        case 3:
            *dst++ = *src++;
            --c;
        }

        i_dst = (void *)dst;

        /* Choose a copy scheme based on the source */
        /* alignment relative to destination. */
        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 & ~3);
#ifndef __MICROBLAZEEL__
            /* Load the holding buffer */
            buf_hold = *i_src++ << 8;

            for (; c >= 4; c -= 4) {
                value = *i_src++;
                *i_dst++ = buf_hold | value >> 24;
                buf_hold = value << 8;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*i_src++ & 0xFFFFFF00) >>8;

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

            for (; c >= 4; c -= 4) {
                value = *i_src++;
                *i_dst++ = buf_hold | value >> 16;
                buf_hold = value << 16;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*i_src++ & 0xFFFF0000 )>>16;

            for (; c >= 4; c -= 4) {
                value = *i_src++;
                *i_dst++ = buf_hold | ((value & 0xFFFF)<<16);
                buf_hold = (value & 0xFFFF0000) >>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 & ~3);
#ifndef __MICROBLAZEEL__
            /* Load the holding buffer */
            buf_hold = *i_src++ << 24;

            for (; c >= 4; c -= 4) {
                value = *i_src++;
                *i_dst++ = buf_hold | value >> 8;
                buf_hold = value << 24;
            }
#else
            /* Load the holding buffer */
            buf_hold = (*i_src++ & 0xFF000000) >> 24;

            for (; c >= 4; c -= 4) {
                value = *i_src++;
                *i_dst++ = buf_hold | ((value & 0xFFFFFF) << 8);
                buf_hold = (value & 0xFF000000) >> 24;
            }
#endif
            /* Realign the source */
            src = (const void *)i_src;
            src -= 1;
            break;
        }
        dst = (void *)i_dst;
    }

    /* Finish off any remaining bytes */
    /* simple fast copy, ... unless a cache boundary is crossed */
    switch (c) {
    case 3:
        *dst++ = *src++;
    case 2:
        *dst++ = *src++;
    case 1:
        *dst++ = *src++;
    }

    return v_dst;
}
#endif /* CONFIG_OPT_LIB_FUNCTION */
EXPORT_SYMBOL(memcpy);
#endif /* __HAVE_ARCH_MEMCPY */