Subversion Repositories openrisc

/*******************************************************************************

 *

 * Copyright (c) 1993 Intel Corporation

 *

 * Intel hereby grants you permission to copy, modify, and distribute this

 * software and its documentation.  Intel grants this permission provided

 * that the above copyright notice appears in all copies and that both the

 * copyright notice and this permission notice appear in supporting

 * documentation.  In addition, Intel grants this permission provided that

 * you prominently mark as "not part of the original" any modifications

 * made to this software or documentation, and that the name of Intel

 * Corporation not be used in advertising or publicity pertaining to

 * distribution of the software or the documentation without specific,

 * written prior permission.

 *

 * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR

 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY

 * OR FITNESS FOR A PARTICULAR PURPOSE.  Intel makes no guarantee or

 * representations regarding the use of, or the results of the use of,

 * the software and documentation in terms of correctness, accuracy,

 * reliability, currentness, or otherwise; and you rely on the software,

 * documentation and results solely at your own risk.

 *

 * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,

 * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES

 * OF ANY KIND.  IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM

 * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.

 *

 ******************************************************************************/

        .file "memcmp.s"

#ifdef  __PIC

        .pic

#endif

#ifdef  __PID

        .pid

#endif

/*

 * (c) copyright 1988,1993 Intel Corp., all rights reserved

 */

/*

        procedure memcmp  (optimized assembler version for the 80960K series)

        result = memcmp (src1_addr, src2_addr, max_bytes)

        compare the byte array pointed to by src1_addr to the byte array

        pointed to by src2_addr.  Return 0 iff the arrays are equal, -1 iff

        src1_addr is lexicographically less than src2_addr, and 1 iff it is

        lexicographically greater.  Do not compare more than max_bytes bytes.

        Undefined behavior will occur if the end of either source array

        is in the last two words of the program's allocated memory space.

        This is so because memcmp fetches ahead.  Disallowing the fetch ahead

        would impose a severe performance penalty.

        Strategy:

        Fetch the source strings by words and compare the words until either

        a differing word is found or max_bytes is exhausted.  In the former

        case, move through the words to find the differing byte and return

        plus or minus one, appropriately.  In the latter case, return zero

        (equality).

        Tactics:

        1) Do NOT try to fetch the words in a word aligned manner because,

        in my judgement, the performance degradation experienced due to

        non-aligned accesses does NOT outweigh the time and complexity added

        by the preamble that would be necessary to assure alignment.  This

        is supported by the intuition that most source arrays (even more

        true of most big source arrays) will be word aligned to begin with.

        2) Rather than decrementing max_bytes to zero, I calculate the

        address of the byte after the last byte of the source_1 array, and

        quit when the source byte pointer passes that.

*/

        .globl _memcmp

        .globl __memcmp

        .leafproc _memcmp,__memcmp

        .align 2

_memcmp:

#ifndef __PIC

        lda     .Lrett,g14

#else

        lda     .Lrett-(.+8)(ip),g14

#endif

__memcmp:

        mov     g14,g13         # preserve return address

        ldconst 0,g14           # conform to register conventions

        cmpibge 0,g2,Lequal_exit        # quit if max_bytes <= 0

        addo    g0,g2,g2        # calculate byte addr of byte after last in src1

.Lwloop:

        cmpo     g0,g2

        ld      (g0), g5        # fetch word of source_1

        bge      Lequal_exit    # quit (equal) if max_bytes exhausted

        ld      (g1), g3        # fetch word of source_2

        addo     4,g0,g0        # post-increment source_1 byte ptr

        addo     4,g1,g1        # post-increment source_2 byte ptr

        cmpobe   g5,g3,.Lwloop  # branch if source words are equal

        ldconst 0xff,g4         # byte extraction mask

        subo     4,g0,g0        # back up src1 pointer

.Lcloop: and    g4,g5,g7        # extract and compare individual bytes

        and     g4,g3,g6

        cmpobne g7,g6,.diff     # branch if they are different

        shlo    8,g4,g4         # position mask for next extraction

        addo    1,g0,g0

        cmpobl  g0,g2,.Lcloop   # quit if max_bytes is exhausted

Lequal_exit:

        mov     0,g0

        bx      (g13)

.Lrett:

        ret

.diff:  bl      .neg            # arrays differ at current byte.

                                /* return 1 or -1 appropriately */

        mov     1,g0

        bx      (g13)

.neg:   subi    1,0,g0

.Lexit:

        bx      (g13)

/* end or memcmp */