/* $NetBSD: memmove.S,v 1.3 2011/01/15 07:31:12 matt Exp $ */

/* stropt/memmove.S, pl_string_common, pl_linux 10/11/04 11:45:37
* ==========================================================================
* Optimized memmove implementation for IBM PowerPC 405/440.
*
*      Copyright (c) 2003, IBM Corporation
*      All rights reserved.
*
*      Redistribution and use in source and binary forms, with or
*      without modification, are permitted provided that the following
*      conditions are met:
*
*      * Redistributions of source code must retain the above
*      copyright 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 IBM nor the names of its 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 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
*      PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
*      PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
*      OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
*      (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
*      USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* ==========================================================================
*
* Function: Move memory area (handles overlapping regions)
*
*              void *memmove(void * dest, const void * src, int n)
*
* Input:       r3 - destination address
*       r4 - source address
*       r5 - byte count
* Output: r3 - destination address
*
* ==========================================================================
*/

#include <machine/asm.h>

       .text
       .align 4
#ifdef _BCOPY
/* bcopy = memcpy/memmove with arguments reversed. */
/* LINTSTUB: Func: void bcopy(void *, void *, size_t) */
ENTRY(bcopy)
       mr      %r6, %r3                /* swap src/dst */
       mr      %r3, %r4
       mr      %r4, %r6
#else
/* LINTSTUB: Func: void *memmove(void *, const void *, size_t) */
ENTRY(memmove)
#endif

       mr      %r8, %r3                /* Save dst (return value)      */

       cmpw    %r4, %r8                /* Branch to reverse if         */
       blt     reverse                 /* src < dest. Don't want to    */
                                       /* overwrite end of src with    */
                                       /* start of dest                */

       addi    %r4, %r4, -4            /* Back up src and dst pointers */
       addi    %r8, %r8, -4            /* due to auto-update of 'load' */

       srwi.   %r9,%r5,2                       /* How many words in total cnt  */
       beq-    last1                   /* Handle byte by byte if < 4   */
                                       /* bytes total                  */
       mtctr   %r9                     /* Count of words for loop              */
       lwzu    %r7, 4(%r4)             /* Preload first word           */

       b       g1

g0:                                     /* Main loop                    */

       lwzu    %r7, 4(%r4)             /* Load a new word              */
       stwu    %r6, 4(%r8)             /* Store previous word          */

g1:

       bdz-    last                    /* Dec cnt, and branch if just  */
                                       /* one word to store            */
       lwzu    %r6, 4(%r4)             /* Load another word            */
       stwu    %r7, 4(%r8)             /* Store previous word          */
       bdnz+   g0                      /* Dec cnt, and loop again if   */
                                       /* more words                   */
       mr      %r7, %r6                        /* If word count -> 0, then...  */

last:

       stwu    %r7, 4(%r8)             /* ... store last word          */

last1:                                  /* Byte-by-byte copy            */

       clrlwi. %r5,%r5,30              /* If count -> 0, then ...      */
       beqlr                           /* we're done                   */

       mtctr   %r5                     /* else load count for loop     */

       lbzu    %r6, 4(%r4)             /* 1st byte: update addr by 4   */
       stbu    %r6, 4(%r8)             /* since we pre-adjusted by 4   */
       bdzlr-                          /* in anticipation of main loop */

last2:

       lbzu    %r6, 1(%r4)             /* But handle the rest by               */
       stbu    %r6, 1(%r8)             /* updating addr by 1           */
       bdnz+   last2

       blr

       /* We're here since src < dest. Don't want to overwrite end of  */
       /* src with start of dest                                               */

reverse:

       add     %r4, %r4, %r5           /* Work from end to beginning   */
       add     %r8, %r8, %r5           /* so add count to string ptrs  */
       srwi.   %r9,%r5,2                       /* Words in total count         */
       beq-    rlast1                  /* Handle byte by byte if < 4   */
                                       /* bytes total                  */

       mtctr   %r9                     /* Count of words for loop      */

       lwzu    %r7, -4(%r4)            /* Preload first word           */
       b       rg1

rg0:                                    /* Main loop                    */

       lwzu    %r7, -4(%r4)            /* Load a new word              */
       stwu    %r6, -4(%r8)            /* Store previous word          */

rg1:

       bdz-    rlast                   /* Dec cnt, and branch if just  */
                                       /* one word to store            */

       lwzu    %r6, -4(%r4)            /* Load another word            */
       stwu    %r7, -4(%r8)            /* Store previous word          */

       bdnz+   rg0                     /* Dec cnt, and loop again if   */
                                       /* more words                   */

       mr      %r7, %r6                        /* If word count -> 0, then...  */

rlast:

       stwu    %r7, -4(%r8)            /* ... store last word          */

rlast1:                                 /* Byte-by-byte copy            */

       clrlwi. %r5,%r5,30              /* If count -> 0, then...       */
       beqlr                           /* ... we're done               */

       mtctr   %r5                     /* else load count for loop     */

rlast2:

       lbzu    %r6, -1(%r4)            /* Handle the rest, byte by     */
       stbu    %r6, -1(%r8)            /* byte                         */

       bdnz+   rlast2                  /* Dec ctr, and branch if more  */
                                       /* bytes left                   */
       blr

#ifdef _BCOPY
END(bcopy)
#else
END(memmove)
#endif

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