Annotation of sys/lib/libkern/arch/m68k/bzero.S, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: bzero.S,v 1.3 2003/06/02 23:28:08 millert Exp $ */
2:
3: /*-
4: * Copyright (c) 1990 The Regents of the University of California.
5: * All rights reserved.
6: *
7: * This code is derived from software contributed to Berkeley by
8: * the Systems Programming Group of the University of Utah Computer
9: * Science Department.
10: *
11: * Redistribution and use in source and binary forms, with or without
12: * modification, are permitted provided that the following conditions
13: * are met:
14: * 1. Redistributions of source code must retain the above copyright
15: * notice, this list of conditions and the following disclaimer.
16: * 2. Redistributions in binary form must reproduce the above copyright
17: * notice, this list of conditions and the following disclaimer in the
18: * documentation and/or other materials provided with the distribution.
19: * 3. Neither the name of the University nor the names of its contributors
20: * may be used to endorse or promote products derived from this software
21: * without specific prior written permission.
22: *
23: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33: * SUCH DAMAGE.
34: */
35:
36: #if defined(LIBC_SCCS) && !defined(lint)
37: .text
38: /*.asciz "from: @(#)bzero.s 5.1 (Berkeley) 5/12/90"*/
39: .asciz "$OpenBSD: bzero.S,v 1.3 2003/06/02 23:28:08 millert Exp $"
40: #endif /* LIBC_SCCS and not lint */
41:
42: #include "DEFS.h"
43:
44: /*
45: * This is probably not the best we can do, but it is still much
46: * faster than the C version in the portable gen directory.
47: *
48: * Things that might help:
49: * - unroll the longword loop (might not be good for a 68020)
50: * - longword, as opposed to word, align when possible (only on the 68020)
51: * - use nested DBcc instructions or use one and limit size to 64K
52: */
53: ENTRY(bzero)
54: movl sp@(4),a0 | destination
55: movl sp@(8),d0 | count
56: beq bzdone | nothing to do
57: movl a0,d1
58: btst #0,d1 | address odd?
59: beq bzeven | no, skip alignment
60: clrb a0@+ | yes, clear a byte
61: subql #1,d0 | adjust count
62: beq bzdone | if zero, all done
63: bzeven:
64: movl d0,d1
65: lsrl #2,d1 | convert to longword count
66: beq bzbloop | no longwords, skip loop
67: bzlloop:
68: clrl a0@+ | clear a longword
69: subql #1,d1 | adjust count
70: bne bzlloop | still more, keep going
71: andl #3,d0 | what remains
72: beq bzdone | nothing, all done
73: bzbloop:
74: clrb a0@+ | clear a byte
75: subql #1,d0 | adjust count
76: bne bzbloop | still more, keep going
77: bzdone:
78: rts
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