Subversion Repositories openrisc_me

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

 *

 * 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 "strcmp.s"

#ifdef  __PIC

        .pic

#endif

#ifdef  __PID

        .pid

#endif

/*

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

 */

/*

        procedure strcmp  (optimized assembler version for the 80960K Series)

        result = strcmp (src1_addr, src2_addr)

        compare the null terminated string pointed to by src1_addr to

        the string pointed to by src2_addr.  Return 0 iff the strings

        are equal, -1 if src1_addr is lexicographically less than src2_addr,

        and 1 if it is lexicographically greater.

        Undefined behavior will occur if the end of either source string

        (i.e. the terminating null byte) is in the last two words of the

        program's allocated memory space.  This is so because strcmp 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

        differing words are found or the null byte is encountered.  In either

        case, move through the word until either the differing byte if found,

        in which case return -1 or 1 appropriately;  or the null byte is

        encountered, in which 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 and convoluted body that would be necessary to assure

        alignment.  This is supported by the intuition that many source

        strings will be word aligned to begin with.

*/

        .globl _strcmp

        .globl __strcmp

        .leafproc _strcmp,__strcmp

        .align 2

_strcmp:

#ifndef __PIC

        lda     .Lrett,g14

#else

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

#endif

__strcmp:

        ld      (g0), g5        # fetch first word of source_1

        mov     g14,g7          # preserve return address

        ldconst 0,g14           # conform to register conventions

        ldconst 0xff,g4         # byte extraction mask

.Lwloop:

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

        ld      (g1), g3        # fetch word of source_2

        scanbyte 0,g5           # does word have a null byte?

        mov      g5,g2          # save a copy of the source_1 word

        be .Lcloop              # branch if null byte encountered

        cmpo     g2,g3          # are the source words the same?

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

        ld      (g0), g5        # fetch ahead next word of source_1

        be       .Lwloop                # fall thru if words are unequal

.Lcloop: and    g4,g2,g5        # extract and compare individual bytes

        and     g4,g3,g6

        cmpobne g5,g6,.diff     # if they differ, go return 1 or -1

        cmpo    0,g6            # they are the same.  Are they null?

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

        bne     .Lcloop         # loop if null not encountered

        mov     0,g0            # return equality

        bx      (g7)

.Lrett:

        ret

.diff:  bl      .neg

        mov     1,g0

        bx      (g7)

.neg:   subi    1,0,g0

.Lexit:

        bx      (g7)