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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [machine/] [i960/] [strncat.S] - Blame information for rev 207

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1 207 jeremybenn
/*******************************************************************************
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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 "strncat.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 strncat  (optimized assembler version for the 80960K Series)
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        dest_addr = strncat (dest_addr, src_addr, max_bytes)
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        append the null terminated string pointed to by src_addr to the null
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        terminated string pointed to by dest_addr.  Return the original
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        dest_addr.  If the source string is longer than max_bytes, then
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        append only max_bytes bytes, and tack on a null byte on the end.
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        This routine will fail if the source and destination string
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        overlap (in particular, if the end of the source is overlapped
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        by the beginning of the destination).  The behavior is undefined.
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        This is acceptable according to the draft C standard.
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        Undefined behavior will also occur if the end of the 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 strncat fetches
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        ahead.  Disallowing the fetch ahead would impose a severe performance
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        penalty.
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        Strategy:
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        First, skip to the null byte in the destination string.  Then
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        fetch the source string by words and store them by words to the
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        destination string, until there are fewer than three bytes left
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        to copy.  Then, using the last word of the source (the one that
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        contains the remaining 0, 1, 2, or 3 bytes to be copied), store
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        a byte at a time until Ldone.
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        If, before exhausting the max_byte count, the null byte is encountered
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        in the source string, then just copy up thru the null byte.
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        Tactics:
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        1) Do NOT try to fetch and store the words in a word aligned manner
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        because, in my judgement, the performance degradation experienced due
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        to 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 _strncat
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        .globl __strncat
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        .leafproc _strncat,__strncat
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        .align    2
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_strncat:
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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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__strncat:
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        mov     g14,g6
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        cmpibge 0, g2, Lno_operation    # Lexit early if max_bytes <= 0
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        mov     g0, g5
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Lskip_word_loop:
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        ld      (g5), g7        # fetch word of dest string
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        addo    4, g5, g5       # post-increment dest ptr
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        scanbyte 0, g7          # does it contain null byte?
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        bno     Lskip_word_loop # if not, loop
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        subo    5, g5, g5       # adjust dest ptr
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        lda     0xff, g3        # byte extraction mask = 0xff;
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Lskip_byte_loop:
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        and     g7, g3, g14     # extract byte of last word of dest string
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        cmpo    0, g14          # is it null?
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        addo    1, g5, g5       # adjust dest ptr
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        shro    8, g7, g7       # position next byte for extraction
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        bne     Lskip_byte_loop # loop if null not found yet
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        ld      (g1), g7        # fetch first word of source string
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Lwloop:                         # word copying loop
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        cmpo    4, g2           # max_bytes < 4 ?
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        addo    4, g1, g1       # post-increment source ptr
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        bge     Lcloop.a                # branch if less than 4 bytes to move
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        scanbyte 0, g7          # is null byte reached yet?
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        mov     g7, g4          # keep a copy of the source word
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        be      Lcloop          # branch if null byte reached
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        ld      (g1), g7        # pre-fetch next word of source
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        subo    4, g2, g2       # reduce max_byte counter
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        st      g4, (g5)        # store current word
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        addo    4, g5, g5       # post-increment destination ptr
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        b       Lwloop
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Lcloop.b:
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        addo    1, g5, g5       # post-increment destination ptr
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        shro    8, g7, g7       # position next byte for extraction
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Lcloop:                         # character copying loop  (max_byte > 3)
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        and     g3, g7, g4      # extract character
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        cmpo    0, g4           # is it null?
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        stob    g4, (g5)        # store it
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        bne     Lcloop.b                # loop if null not encountered yet
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        bx      (g6)            # g0 = dest string address; g14 = 0
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Lrett:
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        ret
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Lcloop.c:
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        addo    1, g5, g5       # post-increment destination ptr
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        shro    8, g7, g7       # position next byte for extraction
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Lcloop.a:                       # character copying loop  (max_byte <= 3)
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        cmpdeco 0,g2,g2         # max_byte == 0?
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        and     g3, g7, g4      # extract character
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        be      Ldone           # store null and Lexit if max_byte exhausted
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        cmpo    0, g4           # is it null?
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        stob    g4, (g5)        # store it
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        bne     Lcloop.c                # loop if null not encountered yet
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Ldone:  stob    g14, (g5)       # store trailing null
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        bx      (g6)            # g0 = dest string address; g14 = 0
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Lno_operation: mov 0, g14       # conform to register conventions
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        bx      (g6)
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/* end of strncat */

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