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[/] [or1k/] [trunk/] [newlib/] [newlib/] [libc/] [machine/] [i960/] [strncmp.S] - Blame information for rev 1765

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1 39 lampret
/*******************************************************************************
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 *
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 * Copyright (c) 1993 Intel Corporation
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 *
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 * Intel hereby grants you permission to copy, modify, and distribute this
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 * software and its documentation.  Intel grants this permission provided
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 * that the above copyright notice appears in all copies and that both the
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 * copyright notice and this permission notice appear in supporting
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 * documentation.  In addition, Intel grants this permission provided that
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 * you prominently mark as "not part of the original" any modifications
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 * made to this software or documentation, and that the name of Intel
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 * Corporation not be used in advertising or publicity pertaining to
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 * distribution of the software or the documentation without specific,
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 * written prior permission.
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 *
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 * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
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 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
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 * OR FITNESS FOR A PARTICULAR PURPOSE.  Intel makes no guarantee or
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 * representations regarding the use of, or the results of the use of,
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 * the software and documentation in terms of correctness, accuracy,
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 * reliability, currentness, or otherwise; and you rely on the software,
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 * documentation and results solely at your own risk.
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 *
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 * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
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 * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
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 * OF ANY KIND.  IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
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 * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
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 *
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 ******************************************************************************/
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        .file "strncmp.s"
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#ifdef  __PIC
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        .pic
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#endif
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#ifdef  __PID
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        .pid
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#endif
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/*
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 * (c) copyright 1988,1993 Intel Corp., all rights reserved
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 */
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/*
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        procedure strncmp  (optimized assembler version for the 80960K Series)
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        result = strncmp (src1_addr, src2_addr, max_bytes)
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        compare the null terminated string pointed to by src1_addr to
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        the string pointed to by src2_addr.  Return 0 iff the strings
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        are equal, -1 if src1_addr is lexicographically less than src2_addr,
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        and 1 if it is lexicographically greater.  Do not compare more than
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        max_bytes bytes.
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        Undefined behavior will occur if the end of either source string
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        (i.e. the terminating null byte) is in the last two words of the
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        program's allocated memory space.  This is so because strncmp
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        will fetch ahead.  Disallowing the fetch ahead would impose
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        a severe performance penalty.
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        Strategy:
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        Fetch and compare the strings by words and go to a character
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        comparison loop as soon as a pair of words differ.  If the
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        words are equal up through either the exhaustion of max_bytes
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        or the presence of the null byte, return 0 (equality).  Otherwise,
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        the character comparator will return -1 or 1 for inequality, or
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        exhaustion of max_bytes.
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        Tactics:
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        1) Do NOT try to fetch the words in a word aligned manner because,
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        in my judgement, the performance degradation experienced due to
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        non-aligned accesses does NOT outweigh the time and complexity added
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        by the preamble and convoluted body that would be necessary to assure
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        alignment.
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*/
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        .globl _strncmp
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        .globl __strncmp
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        .leafproc _strncmp,__strncmp
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        .align 2
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_strncmp:
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#ifndef __PIC
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        lda     .Lrett,g14
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#else
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        lda     .Lrett-(.+8)(ip),g14
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#endif
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__strncmp:
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        mov     g14,g13
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        ldconst 0,g14
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        cmpibge 0,g2,Lequal_exit                # Lexit early if max_bytes <= 0
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        addo    g2,g0,g2
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.Lwloop:
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        cmpo    g0,g2           # are max_bytes exhausted?
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        ld      (g0), g5        # fetch word of source_1
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        bge      Lequal_exit    # Lexit (equality) if max_bytes exhausted
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        ld      (g1), g3        # fetch word of source_2
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        addo     4,g0,g0        # post-increment source_1 ptr
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        scanbyte 0,g5           # is a null byte present?
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        addo     4,g1,g1        # post-increment source_1 ptr
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        be      .Lcloop.a       # perform char comparator if null byte found
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        cmpobe   g5,g3,.Lwloop  # perform char comparator if words are unequal
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.Lcloop.a: subo 4,g0,g0         # adjust max_byte counter
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        ldconst 0xff,g4         # byte extraction mask
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.Lcloop: and    g4,g5,g7        # compare individual bytes
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        and     g4,g3,g6
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        cmpobne g7,g6,.diff     # if different, return -1 or 1
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        cmpo    0,g6            # they are equal.  are they null?
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        shlo    8,g4,g4         # position mask to extract next byte
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        be      Lequal_exit     # if they are null, Lexit (equality)
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        addo    1,g0,g0         # is max_bytes exhausted?
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        cmpobl  g0,g2,.Lcloop   # if not, loop.  if so, Lexit (equality)
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Lequal_exit:
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        mov     0,g0
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        bx      (g13)
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.Lrett:
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        ret
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.diff:  bl      .neg
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        mov     1,g0
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        bx      (g13)
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.neg:   subi    1,0,g0
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.Lexit:
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        bx      (g13)
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/* end of strncmp */

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