Subversion Repositories openrisc_me

/*******************************************************************************

 *

 * 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_ca.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 CA)

        src_addr = memchr (src_addr, char, max_bytes)

        searching from src_addr for max_bytes bytes, return a pointer to the

        first byte that contains the indicated byte in the source string.

        Return null if the byte is not found.

        Undefined behavior will occur if the end of the source string (i.e.

        the terminating null byte) is in the last two words of the program's

        allocated memory space.  This is so because, in several cases, memchr

        will fetch ahead.  Disallowing the fetch ahead would impose a severe

        performance penalty.

        This program handles two cases:

        1) the argument starts on a word boundary

        2) the argument doesn't start on a word boundary

        At the time of this writing, only g0 thru g7 and g13 are available

        for use in this leafproc;  other registers would have to be saved and

        restored.  These nine registers, plus tricky use of g14 are sufficient

        to implement the routine.  The registers are used as follows:

        g0  src ptr;  upon return it is a pointer to the matching byte, or null

        g1  char to seek

        g2  maximum number of bytes to check

        g3  char to seek, broadcast to all four bytes

        g4  word of the source string

        g5  copy of the word

        g6  mask to avoid unimportant bytes in first word

        g7  byte extraction mask

        g13 return address

        g14

*/

        .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

         lda    0,g14           # conform to register linkage standard

        cmpibge.f 0,g2,Lnot_found       # do nothing if max_bytes <= 0

        addo    g0,g2,g2        # compute ending address from start and len

        and     g0,3,g6         # extract byte offset of src

        notand  g0,3,g0         # extract word addr of start of src

        shlo    8,g1,g3         # broadcast the char to four bytes

         ld     (g0),g4         # fetch word containing at least first byte

        or      g1,g3,g3

        shlo    16,g3,g5

        cmpo    g1,g7           # is char being sought 0xff?

        or      g5,g3,g3

        shlo    3,g6,g6         # get shift count for making mask for first word

        subi    1,0,g5          # mask initially all ones

#if __i960_BIG_ENDIAN__

        shro    g6,g5,g5        # get mask for bytes needed from first word

#else

        shlo    g6,g5,g5        # get mask for bytes needed from first word

#endif

        notor   g4,g5,g4        # set unneeded bytes to all ones

         be.f   Lsearch_for_0xff        # branch if seeking 0xff

Lsearch_for_word_with_char:

        scanbyte g3,g4          # check for byte with char

         lda    4(g0),g0        # pre-increment src word pointer

        mov     g4,g5           # keep a copy of word

        ld      (g0),g4         # fetch next word of src

         bo.f   Lsearch_for_char        # branch if null found

        cmpoble.t g0,g2,Lsearch_for_word_with_char      # branch if not null

Lnot_found:

        mov     0,g0            # char not found.  Return null

Lexit_code:

        bx      (g13)           # g0 = addr of char in src (or null);  g14 = 0

Lrett:

        ret

Lsearch_for_char:

        subo    4,g0,g0         # back up the byte pointer

Lsearch_for_char.a:

        cmpobe.f g0,g2,Lnot_found       # quit if max_bytes exhausted

#if __i960_BIG_ENDIAN__

        rotate  8,g5,g5         # shift word to position next byte

#endif

        and     g5,g7,g6        # extract byte

        cmpo    g1,g6           # is it char?

         lda    1(g0),g0        # bump src byte ptr

#if ! __i960_BIG_ENDIAN__

        shro    8,g5,g5         # shift word to position next byte

#endif

         bne.t  Lsearch_for_char.a

        subo    1,g0,g0         # back up the byte pointer

         b      Lexit_code

Lsearch_for_0xff:

        lda     0xf0f0f0f0,g6   # make first comparison mask for char=-1 case.

        or      g6,g5,g6

        and     g4,g6,g4        # make unimportant bytes of first word 0x0f

         b      Lsearch_for_word_with_char

/* end of memchr */