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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 */
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