Subversion Repositories openrisc

/*******************************************************************************
 * 
 * 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 "memccpy.s"
#ifdef  __PIC
        .pic
#endif
#ifdef  __PID
        .pid
#endif
/*
 * (c) copyright 1989,1993 Intel Corp., all rights reserved
 */
/*
        procedure memccpy  (optimized assembler version for the 80960K series)

        dest_addr = memccpy (dest_addr, src_addr, char, len)

        copy len bytes pointed to by src_addr to the space pointed to by 
        dest_addr, stopping if char is copied.  If char is copied,
        return address of byte after char in dest string;  else null.


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

        Undefined behavior will also occur if the source and destination
        strings overlap.

        Strategy:

        Fetch the source array by words and store them by words to the
        destination array, until there are fewer than three bytes left
        to copy.  Then, using the last word of the source (the one that
        contains the remaining 0, 1, 2, or 3 bytes to be copied), store
        a byte at a time until Ldone.

        Tactics:

        1) Do NOT try to fetch and store 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 most source and
        destination arrays (even more true of most big source arrays) will 
        be word aligned to begin with.

        2) Rather than decrementing len to zero,
        I calculate the address of the byte after the last byte of the 
        destination array, and quit when the destination byte pointer passes 
        that.  

*/

        .globl _memccpy
        .leafproc _memccpy, __memccpy
        .align    2
_memccpy:
#ifndef __PIC
        lda     Lrett,g14
#else
        lda     Lrett-(.+8)(ip),g14
#endif
__memccpy:
        mov     g14, g13        # preserve return address
        cmpibge 0,g3,Lexit_char_not_found

        addo    g3,g1,g3        # compute beyond end of src
        ld      (g1), g7        # fetch first word of source
        lda     0xff,g5         # mask for char
        and     g5,g2,g2        # extract only char
        shlo    8,g2,g6
        or      g2,g6,g6
        shlo    16,g6,g4
        or      g6,g4,g6        # word of char
        b       Lwloop_b

Lwloop_a:
        ld      (g1), g7        # fetch ahead next word of source
        st      g4, (g0)        # store word to dest
        addo    4, g0, g0       # post-increment dest pointer
Lwloop_b:                       # word copying loop
        addo    4, g1, g1       # pre-increment src pointer
        cmpo    g3, g1          # is len <= 3 ?
        mov     g7, g4          # keep a copy of the current word
        bl      Lcloop_setup    # quit word loop if less than 4 bytes
        scanbyte g6, g7         # check for char
        bno     Lwloop_a                # continue word loop if char not found.

Lcloop_setup:
        subo    4, g1, g1       # back down src pointer
        cmpobe  g1, g3, Lexit_char_not_found

Lcloop_a:                       # character copying loop (len < 3)
        and     g5,g4,g7        # check the byte against char
        cmpo    g7,g2
        stob    g7,(g0)         # store the byte
        addo    1, g0, g0
        be      Lexit_char_found
        addo    1,g1,g1
        cmpo    g1,g3
        shro    8,g4,g4         # position next byte
        bne     Lcloop_a

Lexit_char_not_found:
        mov     0, g0
Lexit_char_found:
        lda     0,g14
        bx      (g13)           # g0 = dest array address; g14 = 0
Lrett:  
        ret


/* end of memccpy */