source: trunk/libs/newlib/src/newlib/libc/machine/i960/memchr.S @ 444

Last change on this file since 444 was 444, checked in by satin@…, 6 years ago

add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
File size: 4.7 KB
Line 
1/*******************************************************************************
2 *
3 * Copyright (c) 1993 Intel Corporation
4 *
5 * Intel hereby grants you permission to copy, modify, and distribute this
6 * software and its documentation.  Intel grants this permission provided
7 * that the above copyright notice appears in all copies and that both the
8 * copyright notice and this permission notice appear in supporting
9 * documentation.  In addition, Intel grants this permission provided that
10 * you prominently mark as "not part of the original" any modifications
11 * made to this software or documentation, and that the name of Intel
12 * Corporation not be used in advertising or publicity pertaining to
13 * distribution of the software or the documentation without specific,
14 * written prior permission.
15 *
16 * Intel Corporation provides this AS IS, WITHOUT ANY WARRANTY, EXPRESS OR
17 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
18 * OR FITNESS FOR A PARTICULAR PURPOSE.  Intel makes no guarantee or
19 * representations regarding the use of, or the results of the use of,
20 * the software and documentation in terms of correctness, accuracy,
21 * reliability, currentness, or otherwise; and you rely on the software,
22 * documentation and results solely at your own risk.
23 *
24 * IN NO EVENT SHALL INTEL BE LIABLE FOR ANY LOSS OF USE, LOSS OF BUSINESS,
25 * LOSS OF PROFITS, INDIRECT, INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES
26 * OF ANY KIND.  IN NO EVENT SHALL INTEL'S TOTAL LIABILITY EXCEED THE SUM
27 * PAID TO INTEL FOR THE PRODUCT LICENSED HEREUNDER.
28 *
29 ******************************************************************************/
30
31        .file "memchr.s"
32#ifdef  __PIC
33        .pic
34#endif
35#ifdef  __PID
36        .pid
37#endif
38/*
39 * (c) copyright 1988,1993 Intel Corp., all rights reserved
40 */
41
42/*
43        procedure memchr  (optimized assembler version for the 80960K series)
44
45        src_addr = memchr (src_addr, char, max_bytes)
46
47        searching from src_addr for a span of max_bytes bytes, return a
48        pointer to the first byte in the source array that contains the
49        indicated char.  Return null if the char is not found.
50
51        Undefined behavior will occur if the last byte of the source array
52        is in the last two words of the program's allocated memory space.
53        This is so because memchr fetches ahead.  Disallowing the fetch
54        ahead would impose a severe performance penalty.
55
56        Strategy:
57
58        Fetch the source array by words and scanbyte the words for the
59        char until either a word with the byte is found or max_bytes is
60        exhausted.  In the former case, move through the word to find the
61        matching byte and return its memory address.  In the latter case,
62        return zero (null).
63
64        Tactics:
65
66        1) Do NOT try to fetch the words in a word aligned manner because,
67        in my judgement, the performance degradation experienced due to
68        non-aligned accesses does NOT outweigh the time and complexity added
69        by the preamble that would be necessary to assure alignment.  This
70        is supported by the intuition that most source arrays (even more
71        true of most big source arrays) will be word aligned to begin with.
72
73        2) Rather than decrementing max_bytes to zero, I calculate the
74        address of the byte after the last byte of the source array, and
75        quit when the source byte pointer passes that.  Refining, actually
76        I calculate the address of the fifth byte after the last byte of
77        the source array, because the source byte pointer is ahead of the
78        actual examination point due to fetch ahead.
79*/
80
81        .globl  _memchr
82        .globl  __memchr
83        .leafproc       _memchr, __memchr
84        .align  2
85_memchr:
86#ifndef __PIC
87        lda     Lrett,g14
88#else
89        lda     Lrett-(.+8)(ip),g14
90#endif
91__memchr:
92
93        mov     g14,g13         # preserve return address
94        lda     0xff,g7         # byte extraction mask
95        and     g1,g7,g1        # make char an 8-bit ordinal
96        mov     0,g14           # conform to register linkage standard
97        cmpibge 0,g2,Lnot_found # do nothing if max_bytes <= 0
98        addo    4,g0,g6         # post-increment src word pointer
99        addo    g2,g6,g2        # compute ending address from start and len
100        ld      (g0),g4         # fetch first word
101        shlo    8,g1,g3         # broadcast the char to four bytes
102        or      g1,g3,g3
103        shlo    16,g3,g5
104        or      g3,g5,g3
105
106Lsearch_for_word_with_char:
107        mov     g4,g5           # keep a copy of word
108        scanbyte g3,g5          # check for byte with char
109        ld      (g6),g4         # fetch next word of src
110        bo      Lsearch_for_char        # branch if null found
111        addo    4,g6,g6         # post-increment src word pointer
112        cmpobge g2,g6,Lsearch_for_word_with_char        # branch if max_bytes > 3
113
114Lnot_found:
115        mov     0,g0            # char not found.  Return null
116        bx      (g13)           # g0 = addr of char in src (or null);  g14 = 0
117Lrett:
118        ret
119
120Lsearch_for_char:
121        cmpobe.f g6,g2,Lnot_found       # quit if max_bytes exhausted
122        and     g5,g7,g0        # extract byte
123        cmpo    g1,g0           # is it char?
124        addo    1,g6,g6         # bump src byte ptr
125        shro    8,g5,g5         # shift word to position next byte
126        bne.t   Lsearch_for_char
127        subo    5,g6,g0         # back up the byte pointer
128        bx      (g13)
129
130/* end of memchr */
Note: See TracBrowser for help on using the repository browser.