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/*******************************************************************************
 * 
 * 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 "memchr.s"
#ifdef  __PIC
        .pic
#endif
#ifdef  __PID
        .pid
#endif
/*
 * (c) copyright 1988,1993 Intel Corp., all rights reserved
 */

/*
        procedure memchr  (optimized assembler version for the 80960K series)

        src_addr = memchr (src_addr, char, max_bytes)

        searching from src_addr for a span of max_bytes bytes, return a 
        pointer to the first byte in the source array that contains the 
        indicated char.  Return null if the char is not found.

        Undefined behavior will occur if the last byte of the source array 
        is in the last two words of the program's allocated memory space.
        This is so because memchr fetches ahead.  Disallowing the fetch 
        ahead would impose a severe performance penalty.

        Strategy:

        Fetch the source array by words and scanbyte the words for the 
        char until either a word with the byte is found or max_bytes is
        exhausted.  In the former case, move through the word to find the
        matching byte and return its memory address.  In the latter case, 
        return zero (null).

        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 array, and
        quit when the source byte pointer passes that.  Refining, actually
        I calculate the address of the fifth byte after the last byte of
        the source array, because the source byte pointer is ahead of the
        actual examination point due to fetch ahead.
*/

        .globl  _memchr
        .globl  __memchr
        .leafproc       _memchr, __memchr
        .align  2
_memchr:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__memchr:

        mov     g14,g13         # preserve return address
        lda     0xff,g7         # byte extraction mask
        and     g1,g7,g1        # make char an 8-bit ordinal
        mov     0,g14           # conform to register linkage standard
        cmpibge 0,g2,Lnot_found # do nothing if max_bytes <= 0
        addo    4,g0,g6         # post-increment src word pointer
        addo    g2,g6,g2        # compute ending address from start and len
        ld      (g0),g4         # fetch first word 
        shlo    8,g1,g3         # broadcast the char to four bytes
        or      g1,g3,g3
        shlo    16,g3,g5
        or      g3,g5,g3

Lsearch_for_word_with_char:
        mov     g4,g5           # keep a copy of word
        scanbyte g3,g5          # check for byte with char
        ld      (g6),g4         # fetch next word of src
        bo      Lsearch_for_char        # branch if null found 
        addo    4,g6,g6         # post-increment src word pointer
        cmpobge g2,g6,Lsearch_for_word_with_char        # branch if max_bytes > 3

Lnot_found:
        mov     0,g0            # char not found.  Return null
        bx      (g13)           # g0 = addr of char in src (or null);  g14 = 0
Lrett:
        ret

Lsearch_for_char:
        cmpobe.f g6,g2,Lnot_found       # quit if max_bytes exhausted
        and     g5,g7,g0        # extract byte
        cmpo    g1,g0           # is it char?
        addo    1,g6,g6         # bump src byte ptr
        shro    8,g5,g5         # shift word to position next byte
        bne.t   Lsearch_for_char
        subo    5,g6,g0         # back up the byte pointer
        bx      (g13)

/* end of memchr */