/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002, 2003 Free Software Foundation, Inc.
 * This file was originally part of the GNU C Library
 * Contributed to glibc by Hartvig Ekner <hartvige@mips.com>, 2002
 * Adapted for Rockbox by Maurus Cuelenaere, 2009
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/

#include "config.h"
#include "mips.h"

/* void *memcpy(void *s1, const void *s2, size_t n);  */

#ifdef ROCKBOX_BIG_ENDIAN
# define LWHI  lwl                /* high part is left in big-endian        */
# define SWHI  swl                /* high part is left in big-endian        */
# define LWLO  lwr                /* low part is right in big-endian        */
# define SWLO  swr                /* low part is right in big-endian        */
#else
# define LWHI  lwr                /* high part is right in little-endian    */
# define SWHI  swr                /* high part is right in little-endian    */
# define LWLO  lwl                /* low part is left in little-endian      */
# define SWLO  swl                /* low part is left in little-endian      */
#endif

    .section   .icode, "ax", %progbits

    .global    memcpy
    .type      memcpy, %function
    
    .set       noreorder

memcpy:
    slti       t0, a2, 8                # Less than 8?
    bne        t0, zero, last8
    move       v0, a0                   # Setup exit value before too late

    xor        t0, a1, a0               # Find a0/a1 displacement
    andi       t0, 0x3
    bne        t0, zero, shift          # Go handle the unaligned case
    subu       t1, zero, a1
    andi       t1, 0x3                  # a0/a1 are aligned, but are we
    beq        t1, zero, chk8w          # starting in the middle of a word?
    subu       a2, t1
    LWHI       t0, 0(a1)                # Yes we are... take care of that
    addu       a1, t1
    SWHI       t0, 0(a0)
    addu       a0, t1

chk8w:       
    andi       t0, a2, 0x1f             # 32 or more bytes left?
    beq        t0, a2, chk1w
    subu       a3, a2, t0               # Yes
    addu       a3, a1                   # a3 = end address of loop
    move       a2, t0                   # a2 = what will be left after loop
lop8w:       
    lw         t0,  0(a1)               # Loop taking 8 words at a time
    lw         t1,  4(a1)
    lw         t2,  8(a1)
    lw         t3, 12(a1)
    lw         t4, 16(a1)
    lw         t5, 20(a1)
    lw         t6, 24(a1)
    lw         t7, 28(a1)
    addiu      a0, 32
    addiu      a1, 32
    sw         t0, -32(a0)
    sw         t1, -28(a0)
    sw         t2, -24(a0)
    sw         t3, -20(a0)
    sw         t4, -16(a0)
    sw         t5, -12(a0)
    sw         t6, -8(a0)
    bne        a1, a3, lop8w
    sw         t7, -4(a0)

chk1w:       
    andi       t0, a2, 0x3              # 4 or more bytes left?
    beq        t0, a2, last8
    subu       a3, a2, t0               # Yes, handle them one word at a time
    addu       a3, a1                   # a3 again end address
    move       a2, t0
lop1w:       
    lw         t0, 0(a1)
    addiu      a0, 4
    addiu      a1, 4
    bne        a1, a3, lop1w
    sw         t0, -4(a0)

last8:       
    blez       a2, lst8e                # Handle last 8 bytes, one at a time
    addu       a3, a2, a1
lst8l:       
    lb         t0, 0(a1)
    addiu      a0, 1
    addiu      a1, 1
    bne        a1, a3, lst8l
    sb         t0, -1(a0)
lst8e:       
    jr         ra                       # Bye, bye
    nop

shift:       
    subu       a3, zero, a0             # Src and Dest unaligned 
    andi       a3, 0x3                  #  (unoptimized case...)
    beq        a3, zero, shft1
    subu       a2, a3                   # a2 = bytes left
    LWHI       t0, 0(a1)                # Take care of first odd part
    LWLO       t0, 3(a1)
    addu       a1, a3
    SWHI       t0, 0(a0)
    addu       a0, a3
shft1:       
    andi       t0, a2, 0x3
    subu       a3, a2, t0
    addu       a3, a1
shfth:       
    LWHI       t1, 0(a1)                # Limp through, word by word
    LWLO       t1, 3(a1)
    addiu      a0, 4
    addiu      a1, 4
    bne        a1, a3, shfth
    sw         t1, -4(a0)
    b          last8                    # Handle anything which may be left
    move       a2, t0

    .set       reorder