| blob | 857bf2031f23c3d49a2ca42b2bf3adf27c958495 |
1 /* $NetBSD: bzero.S,v 1.1 2005/12/20 19:28:50 christos Exp $ */
3 /*
4 * Copyright (c) 1992, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
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 * from: Header: bzero.s,v 1.1 92/06/25 12:52:46 torek Exp
36 */
38 #include <machine/asm.h>
39 #if defined(LIBC_SCCS) && !defined(lint)
40 #if 0
41 .asciz "@(#)bzero.s 8.1 (Berkeley) 6/4/93"
42 #else
43 RCSID("$NetBSD: bzero.S,v 1.1 2005/12/20 19:28:50 christos Exp $")
44 #endif
45 #endif /* LIBC_SCCS and not lint */
47 /*
48 * We should unroll the loop, but at the moment this would
49 * gain nothing since the `std' instructions are what limits us.
50 */
52 #ifdef MEMSET
53 /*
54 * void *
55 * memset(void *addr, int pattern, size_t len)
56 */
57 ENTRY(memset)
58 ! %o0 = addr, %o1 = pattern, %o2 = len
59 /*
60 * Expand the byte pattern to fill 64 bits in an even-aligned
61 * register pair; shuffle arguments to match those of bzero.
62 */
63 and %o1, 0xff, %o3
64 mov %o2, %o1 ! shuffle argument
65 sll %o3, 8, %o2
66 or %o2, %o3, %o2
67 mov %o0, %g1 ! save original pointer
68 sll %o2, 16, %o3
69 or %o2, %o3, %o2
70 ! Optimize a common case: addr and len are both multiples of 8.
71 or %o0, %o1, %o5
72 btst 7, %o5 ! ((addr | len) & 7) != 0?
73 bnz 1f ! if so, cannot optimize
74 mov %o2, %o3 ! in any case, complete pat expansion
75 #else
76 /*
77 * void
78 * bzero(void *addr, size_t len)
79 */
80 ENTRY(bzero)
81 ! %o0 = addr, %o1 = len
83 clr %o2
84 ! Optimize a common case: addr and len are both multiples of 8.
85 or %o0, %o1, %o5
86 btst 7, %o5 ! ((addr | len) & 7) != 0?
87 bnz 1f ! if so, cannot optimize
88 clr %o3 ! in any case, we want o3=0
89 #endif
91 /* `Good' operands, can just store doubles. */
92 0:
93 deccc 8, %o1 ! while ((len -= 8) >= 0)
94 bge,a 0b
95 std %o2, [%o0 + %o1] ! *(quad *)(addr + len) = 0;
96 retl
97 nop
99 /*
100 * Either the address is unaligned, or the count is not a
101 * multiple of 8, or both. We will have to align the address
102 * in order to use anything `better' than stb.
103 */
104 1:
105 cmp %o1, 15 ! len >= 15?
106 bge,a Lstd ! yes, use std
107 btst 1, %o0 ! (but first check alignment)
109 ! not enough to bother: do byte-at-a-time loop.
110 2:
111 deccc %o1 ! while (--len >= 0)
112 bge,a 2b
113 stb %o2, [%o0 + %o1] ! addr[len] = 0;
114 retl
115 nop
117 Lstd:
118 /*
119 * There are at least 15 bytes to zero.
120 * We may have to zero some initial stuff to align
121 * the address.
122 */
123 bz,a 1f ! if (addr & 1) {
124 btst 2, %o0
125 stb %o2, [%o0] ! *addr = 0;
126 inc %o0 ! addr++;
127 dec %o1 ! len--;
128 btst 2, %o0 ! }
129 1:
130 bz,a 1f ! if (addr & 2) {
131 btst 4, %o0
132 sth %o2, [%o0] ! *(short *)addr = 0;
133 inc 2, %o0 ! addr += 2;
134 dec 2, %o1 ! len -= 2;
135 btst 4, %o0 ! }
136 1:
137 bz 1f ! if (addr & 4) {
138 dec 8, %o1
139 st %o2, [%o0] ! *(int *)addr = 0;
140 inc 4, %o0 ! addr += 4;
141 dec 4, %o1 ! len -= 4;
142 ! }
143 /*
144 * Address is double word aligned; len is 8 less than
145 * the number of bytes remaining (i.e., len is 0 if
146 * the remaining count is 8, 1 if it is 9, etc.).
147 */
148 1:
149 std %o2, [%o0] ! do {
150 2: ! *(quad *)addr = 0;
151 inc 8, %o0 ! addr += 8;
152 deccc 8, %o1 ! } while ((len -= 8) >= 0);
153 bge,a 2b
154 std %o2, [%o0]
156 /*
157 * Len is in [-8..-1] where -8 => done, -7 => 1 byte to zero,
158 * -6 => two bytes, etc. Mop up this remainder, if any.
159 */
160 btst 4, %o1
161 bz 1f ! if (len & 4) {
162 btst 2, %o1
163 st %o2, [%o0] ! *(int *)addr = 0;
164 inc 4, %o0 ! addr += 4;
165 1:
166 bz 1f ! if (len & 2) {
167 btst 1, %o1
168 sth %o2, [%o0] ! *(short *)addr = 0;
169 inc 2, %o0 ! addr += 2;
170 1:
171 bnz,a 1f ! if (len & 1)
172 stb %o2, [%o0] ! *addr = 0;
173 1:
174 retl
175 #ifdef MEMSET
176 mov %g1, %o0 ! restore original pointer
177 #else
178 nop
179 #endif