source: trunk/libs/newlib/src/newlib/libc/machine/i960/memcmp.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: 4.5 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 "memcmp.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        procedure memcmp  (optimized assembler version for the 80960K series)
43
44        result = memcmp (src1_addr, src2_addr, max_bytes)
45
46        compare the byte array pointed to by src1_addr to the byte array
47        pointed to by src2_addr.  Return 0 iff the arrays are equal, -1 iff
48        src1_addr is lexicographically less than src2_addr, and 1 iff it is
49        lexicographically greater.  Do not compare more than max_bytes bytes.
50
51        Undefined behavior will occur if the end of either source array
52        is in the last two words of the program's allocated memory space.
53        This is so because memcmp fetches ahead.  Disallowing the fetch ahead
54        would impose a severe performance penalty.
55
56        Strategy:
57
58        Fetch the source strings by words and compare the words until either
59        a differing word is found or max_bytes is exhausted.  In the former
60        case, move through the words to find the differing byte and return
61        plus or minus one, appropriately.  In the latter case, return zero
62        (equality).
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_1 array, and
75        quit when the source byte pointer passes that. 
76*/
77
78        .globl _memcmp
79        .globl __memcmp
80        .leafproc _memcmp,__memcmp
81        .align 2
82
83_memcmp:
84#ifndef __PIC
85        lda     .Lrett,g14
86#else
87        lda     .Lrett-(.+8)(ip),g14
88#endif
89__memcmp:
90        mov     g14,g13         # preserve return address
91        ldconst 0,g14           # conform to register conventions
92        cmpibge 0,g2,Lequal_exit        # quit if max_bytes <= 0
93        addo    g0,g2,g2        # calculate byte addr of byte after last in src1
94
95.Lwloop:
96        cmpo     g0,g2         
97        ld      (g0), g5        # fetch word of source_1
98        bge      Lequal_exit    # quit (equal) if max_bytes exhausted
99        ld      (g1), g3        # fetch word of source_2
100        addo     4,g0,g0        # post-increment source_1 byte ptr
101        addo     4,g1,g1        # post-increment source_2 byte ptr
102        cmpobe   g5,g3,.Lwloop  # branch if source words are equal
103
104        ldconst 0xff,g4         # byte extraction mask
105        subo     4,g0,g0        # back up src1 pointer
106
107.Lcloop: and    g4,g5,g7        # extract and compare individual bytes
108        and     g4,g3,g6
109        cmpobne g7,g6,.diff     # branch if they are different
110        shlo    8,g4,g4         # position mask for next extraction
111        addo    1,g0,g0
112        cmpobl  g0,g2,.Lcloop   # quit if max_bytes is exhausted
113
114Lequal_exit:
115        mov     0,g0
116        bx      (g13)
117.Lrett:
118        ret
119
120.diff:  bl      .neg            # arrays differ at current byte. 
121                                /* return 1 or -1 appropriately */
122        mov     1,g0
123        bx      (g13)
124.neg:   subi    1,0,g0
125.Lexit:         
126        bx      (g13)
127
128/* end or memcmp */
Note: See TracBrowser for help on using the repository browser.