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[/] [openrisc/] [trunk/] [gnu-old/] [newlib-1.17.0/] [newlib/] [libc/] [machine/] [i960/] [strrchr.S] - Blame information for rev 816

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1 148 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 "strrchr.s"
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#ifdef  __i960_BIG_ENDIAN__
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#error  "This does not work in big-endian"
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#endif
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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 strrchr  (optimized assembler version for the 80960K series)
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        src_addr = strrchr (src_addr, char)
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        return a pointer to the last byte that contains the indicated
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        byte in the source string.  Return null if the byte is not found.
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        Undefined behavior will occur if the end of the source string (i.e.
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        the terminating null byte) is in the last two words of the program's
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        allocated memory space.  This is so because strrchr fetches ahead.
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        Disallowing the fetch ahead would impose a severe performance penalty.
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        Strategy:
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        Fetch the source string by words and scanbyte the words for the
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        char until either a word with the byte is found or the null byte is
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        encountered.  In the former case, move through the word to find the
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        matching byte and save its memory address, then continue the search.
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        In the latter case, return the saved address, or zero (null) if none
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        was ever found to save.
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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 that would be necessary to assure alignment.  This
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        is supported by the intuition that most source arrays (even more
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        true of most big source arrays) will be word aligned to begin with.
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*/
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        .globl  _strrchr
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        .globl  __strrchr
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        .leafproc       _strrchr, __strrchr
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        .align  2
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_strrchr:
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#ifdef __PIC
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        lda     Lrett-(.+8)(ip),g14
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#else
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        lda     Lrett,g14
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#endif
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__strrchr:
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        ld      (g0),g4         # fetch first word
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        lda     0xff,g7         # byte extraction mask
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        and     g1,g7,g1        # make char an 8-bit ordinal
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        shlo    8,g1,g2         # broadcast the char to four bytes
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        or      g1,g2,g2
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        shlo    16,g2,g5
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        or      g2,g5,g3
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        mov     g14,g13         # preserve return address
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        addo    4,g0,g2         # post-increment src pointer
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        mov     1,g0            # prepare to return null pointer
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        mov     g3,g6           # prepare to return null pointer
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Lsearch_for_word_with_char_or_null:
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        mov     g4,g5           # copy word
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        scanbyte 0,g5           # check for null byte
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        ld      (g2),g4         # fetch next word of src
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        bo      Lword_has_null  # branch if null found
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        scanbyte g3,g5          # check for byte with char
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        addo    4,g2,g2         # post-increment src pointer
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        bno     Lsearch_for_word_with_char_or_null   # branch if no copy of char
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        mov     g5,g6           # save word that has char in it (at least once)
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        subo    4,g2,g0         # save addr of byte after word with char
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        b       Lsearch_for_word_with_char_or_null
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Lword_has_null:
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        subo    4,g2,g2         # move src pointer back to word with null
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Lfind_null:
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        addo    1,g2,g2         # advance src pointer to byte after current
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        and     g7,g5,g14       # extract next byte
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        cmpo    g1,g14          # is current byte char?
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        shro    8,g5,g5         # position next byte for extraction
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        bne     1f              # skip if not char sought after
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        mov     g2,g0           # save addr of byte after char
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        mov     g3,g6           # save word of all char to short circuit search
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1:      cmpobne 0,g14,Lfind_null        # is current byte null?
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Lfind_last_char:
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        rotate  8,g6,g6         # position next highest byte
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        and     g7,g6,g5        # extract byte
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        subo    1,g0,g0         # move pointer to that byte (or nullify)
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        cmpobne g5,g1,Lfind_last_char   # branch if not at char
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        bx      (g13)           # g0 = addr of char in src (or null);  g14 = 0
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Lrett:
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        ret
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/* end of strrchr */

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