/* $NetBSD: memcmp.S,v 1.4 2013/07/04 20:57:59 matt Exp $ */

/* stropt/memcmp.S, pl_string_common, pl_linux 10/11/04 11:45:35
* ==========================================================================
* Optimized memcmp 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: Compare two character strings (up to n characters)
*
*              int memcmp(const char *s1, const char *s2, int n)
*
* Input:       r3 - buffer 1 address
*              r4 - buffer 2 address
*              r5 - maximum characters to compare
* Output: r3 <0 (less), 0 (equal), >0 (greater)
*
* ==========================================================================
*/

#include <machine/asm.h>

       .text
       .align 4
/* LINTSTUB: Func: void *memcmp(const void *, const void *, size_t) */
ENTRY(memcmp)

       /*
        * Check count passed in R5. If zero, return 0; otherwise continue.
        */
       cmpwi   %r5,0
       beq-    ret_0;

       /*
        * Most of the time the difference is found in the first
        * several bytes.  The following code minimizes the number
        * of load operations for short compares.
        */

       mr      %r11, %r3               /* Save buffer 1                */

again:

       not     %r10, %r4               /* buffer 2: bytes to page bdy  */
       rlwinm. %r10, %r10,29,23,31     /* buffer 2: dwords to page bdy */
       beq-    bytebybyte              /* If < 8 bytes to the page bdy */
                                       /* do byte by byte              */
       lwz     %r8, 0(%r4)             /* load 1st buffer 2 word       */

       not     %r12, %r11              /* buffer 1: bytes to page bdy  */
       rlwinm. %r12, %r12,29,23,31     /* buffer 1: dwords to page bdy */
       beq-    bytebybyte              /* If < 8 bytes to the page bdy */
                                       /* do byte by byte              */
       lwz     %r6, 0(%r11)            /* load 1st buffer 1 word       */

       cmpwi   %r5, 4                  /* If remaining count <= 4      */
       ble+    first4                  /* handle specially.    DWG     */

       cmplw   %r8, %r6                /* compare buffer 2 and buffer 1*/
       bne+    all_done                /* different => we're done      */

       lwzu    %r9, 4(%r4)             /* load 2nd buffer 2 word       */
       lwzu    %r7, 4(%r11)            /* load 2nd buffer 1 word       */

       cmpwi   %r5, 8                  /* If remaining count <= 8      */
       ble+    last4                   /* handle specially.    DWG     */

       cmplw   %r9, %r7                /* compare buffer 2 and buffer 1*/
       bne+    all_done                /* different => we're done      */

       addi    %r5, %r5, -8            /* Update character counter DWG */
       addi    %r10, %r4, 0x0004       /* DWG*/
       not     %r10, %r10              /* buffer 2: bytes to page bdy DWG */
       rlwinm. %r10, %r10,29,23,31     /* buffer 2: dwords to page bdy DWG */
       addi    %r12, %r11, 0x0004      /* DWG */
       not     %r12, %r12              /* buffer 1: bytes to page bdy DWG */
       rlwinm. %r12, %r12,29,23,31     /* buffer 1: dwords to page bdy DWG */

       /* The following section prior to loop: figures out whether     */
       /* the buffer 1 or buffer 2 is closer to the page boundary.     */
       /* The main loop count is then set up to reflect the number of  */
       /* double words of the buffer that is closest                   */

       cmpw    %r10, %r12              /* Find closest                 */
       blt     lt

       mr      %r10, %r12

lt:

       srwi    %r12, %r5, 3            /* Double check the total count */
       cmpw    %r10, %r12              /* limitation                   */
       blt     lt2

       mr      %r10, %r12              /* DWG */
lt2:                                    /* DWG */
       cmpwi   %r10, 0                 /* DWG */
       bne     lt3                     /* DWG */
       addi    %r4, %r4, 0x0004        /* DWG */
       addi    %r11,%r11,0x0004        /* DWG */
       b       again                   /* DWG */
lt3:                                    /* DWG */
       mtctr   %r10                    /* dword count for loop         */
       lwzu    %r6, 4(%r11)            /* pre-load buffer 1 word       */

       b       in                      /* To the loop                  */

loop:                                   /* main loop                    */

       cmplw   %r8, %r6                /* Compare first buffer 2 word  */
       bne-    all_done                /* with first buffer 1 word     */
                                       /* If different, we're done     */
       cmplw   %r9, %r7                /* Compare second buffer 2 word */
                                       /* with second buffer 1 word    */
       lwzu    %r6, 4(%r11)            /* pre-load buffer 1 word       */

       bne-    all_done                /* If different, we're done     */

in:

       lwzu    %r7, 4(%r11)            /* pre-load buffer 1 word       */
       lwzu    %r8, 4(%r4)             /* pre-load buffer 2 word       */
       lwzu    %r9, 4(%r4)             /* pre-load buffer 2 word       */

       bdnz+   loop                    /* Do more DW's if cnt > 0      */

       /*mfctr %r12*/ /*DWG*/          /* number of dwords left        */
       /*subf  %r10, %r12, %r10*/ /*DWG*//* number of dwords compared  */
       slwi    %r10, %r10, 3
       subf    %r5, %r10, %r5          /* adjust byte counter          */
       /*bne+  partial*/ /*DWG*/       /* If less than 8 bytes, handle */
                                       /* specially                    */
       /*cmpwi %r5, 8*/                /* Removed.              DWG */
       /*blt   partial*/               /* Removed.              DWG */

       /*addic %r5, %r5, -8*/ /*DWG*/  /* Subtract two words from count*/

       cmplw   %r8, %r6                /* compare last dword           */
       addi    %r4, %r4, 4
       bne-    all_done

       cmplw   %r9, %r7
       addi    %r11, %r11, 4
       bne-    all_done

bytebybyte:

       /* We've gotten close to a page boundary: do a byte-byte-byte
        * compare for the following 8 bytes, and then go back to
        * the full-word compare loop.
        */

       li      %r3, 8                  /* loop count                   */
       cmpw    %r3, %r5                /* take min(8, counter)         */
       ble     f2

       mr.     %r3, %r5

       beqlr

f2:

       mtctr   %r3
       subf    %r5, %r3, %r5           /* adjust counter               */

bbb:

       lbz     %r6, 0(%r11)            /* byte copy loop               */

       addi    %r11, %r11, 1

       lbz     %r8, 0(%r4)

       addi    %r4, %r4, 1

       cmplw   %r8, %r6

       bdnzt   eq, bbb

       bne     all_done

       cmpwi   %r5, 0
       bgt     again                   /* handle the rest              */

       xor     %r3,%r3,%r3

       blr

#if 0 /* Removed code section. DWG */
partial:

       mr.     %r3, %r5

       beqlr                           /* If count -> 0, we're done    */

f1:

       subfic  %r3, %r3, 4             /* zero/end in first word?      */
       cmpwi   %r3, 0
       blt     last4
#endif /* DWG */

first4:
       subfic  %r3, %r5, 4             /* If count <= 4, handle        */
       rlwinm  %r3, %r3, 3, 0, 31      /* count *= 8                   */
       srw     %r6, %r6, %r3           /* align 1st buffer 1 word      */
       srw     %r8, %r8, %r3           /* align 1st buffer 2 word      */

       cmplw   %r8, %r6                /* get result                   */
       bne     all_done
       xor     %r3,%r3,%r3
       blr

last4:
       subfic  %r10, %r5, 8            /*DWG*/
       rlwinm  %r10, %r10, 3, 0, 31    /* count *= 8                   */
       srw     %r7, %r7, %r10          /* align 2nd buffer 1 word      */
       srw     %r9, %r9, %r10          /* align 2nd buffer 2 word      */

       cmplw   %r9, %r7                /* get result                   */
       bne     all_done
ret_0:
       xor     %r3,%r3,%r3             /* Equal result          */
       blr

all_done:

       blt     finish_lt

       addi    %r3,0,-1                /* Less than result             */

       blr

finish_lt:

       addi    %r3,0,1                 /* Greater than result          */

       blr
END(memcmp)

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