mirror of
https://github.com/autc04/Retro68.git
synced 2024-11-28 21:49:33 +00:00
124 lines
4.3 KiB
ArmAsm
124 lines
4.3 KiB
ArmAsm
/*******************************************************************************
|
|
*
|
|
* 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 "strchr.s"
|
|
#ifdef __PIC
|
|
.pic
|
|
#endif
|
|
#ifdef __PID
|
|
.pid
|
|
#endif
|
|
/*
|
|
* (c) copyright 1988,1993 Intel Corp., all rights reserved
|
|
*/
|
|
|
|
/*
|
|
procedure strchr (optimized assembler version for the 80960K series)
|
|
|
|
src_addr = strchr (src_addr, char)
|
|
|
|
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 strchr fetches ahead.
|
|
Disallowing the fetch ahead would impose a severe performance penalty.
|
|
|
|
Strategy:
|
|
|
|
Fetch the source string by words and scanbyte the words for the
|
|
char until either a word with the byte is found or the null byte is
|
|
encountered. 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.
|
|
*/
|
|
|
|
.globl _strchr
|
|
.globl __strchr
|
|
.leafproc _strchr, __strchr
|
|
.align 2
|
|
_strchr:
|
|
#ifndef __PIC
|
|
lda Lrett,g14
|
|
#else
|
|
lda Lrett-(.+8)(ip),g14
|
|
#endif
|
|
__strchr:
|
|
|
|
ld (g0),g4 # fetch first word
|
|
lda 0xff,g7 # byte extraction mask
|
|
and g1,g7,g1 # make char an 8-bit ordinal
|
|
shlo 8,g1,g2 # broadcast the char to four bytes
|
|
or g1,g2,g2
|
|
shlo 16,g2,g5
|
|
or g2,g5,g3
|
|
mov g14,g13 # preserve return address
|
|
addo 4,g0,g0 # post-increment src pointer
|
|
mov 0,g14 # conform to register linkage standard
|
|
|
|
Lsearch_for_word_with_char_or_null:
|
|
mov g4,g5 # copy word
|
|
scanbyte g3,g5 # check for byte with char
|
|
ld (g0),g4 # fetch next word of src
|
|
bo Lsearch_for_char # branch if char found
|
|
scanbyte 0,g5 # check for null byte
|
|
addo 4,g0,g0 # post-increment src pointer
|
|
bno Lsearch_for_word_with_char_or_null # 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 5,g0,g0 # back up the byte pointer
|
|
Lsearch_for_char.a:
|
|
and g5,g7,g6 # extract byte
|
|
cmpo g1,g6 # is it char?
|
|
addo 1,g0,g0 # bump src byte ptr
|
|
shro 8,g5,g5 # shift word to position next byte
|
|
be Lexit_code
|
|
cmpobne 0,g6,Lsearch_for_char.a # quit if null comes before char
|
|
b Lnot_found
|
|
|
|
/* end of strchr */
|