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/*

 * Copyright 2010 B Labs.Ltd.

 *

 * Author: Prem Mallappa  

 *

 * Description: Optimized memcpy for ARM

 *

 */

#include  INC_ARCH(asm.h)

/*

void*

_memcpy(void *dst, const void *src, register uint len)

*/

BEGIN_PROC(_memcpy)

                push {r0, r4-r11, lr}

        loop32:

                cmp r2, #32

                blt loop16

                ldmia r1!, {r4 - r11}

                stmia r0!, {r4 - r11}

                sub r2, r2, #32

                b loop32

        loop16:

                cmp r2, #16

                blt loop8

                ldmia   r1!, {r4 - r7}

                stmia   r0!, {r4 - r7}

                sub r2, r2, #16

                b loop16

        loop8:

                cmp r2, #8

                blt loop4

                ldmia   r1!, {r4, r5}

                stmia   r0!, {r4, r5}

                sub r2, r2, #8

                b loop8

        loop4:

                cmp r2, #4

                blt end

                ldmia   r1!, {r4}

                stmia   r0!, {r4}

                sub r2, r2, #4

                b loop4

        end:

        last:

                teq   r2, #0

                ldrgtb r4, [r1]

                strneb r4, [r0]         // V7 supports strneb , [, +/-] !, with write back

                lsrne r4, r4, #8

                subne r2, r2, #1        // Can be reduced to 1 LDR, but has a catch if it is end of memory

                addne r0, r0, #1        // we dont want to fetch 1 byte extra to end up in abort

                addne r1, r1, #1        // so, playing safe, worst case 3 LDRs

                bne last

        1:

        pop {r0, r4 - r11, pc}

END_PROC(_memcpy)