Annotation of sys/lib/libkern/arch/mips64/bcmp.S, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: bcmp.S,v 1.4 2004/10/08 14:42:09 pefo Exp $ */
2: /*-
3: * Copyright (c) 1991, 1993
4: * The Regents of the University of California. All rights reserved.
5: *
6: * This code is derived from software contributed to Berkeley by
7: * Ralph Campbell.
8: *
9: * Redistribution and use in source and binary forms, with or without
10: * modification, are permitted provided that the following conditions
11: * are met:
12: * 1. Redistributions of source code must retain the above copyright
13: * notice, this list of conditions and the following disclaimer.
14: * 2. Redistributions in binary form must reproduce the above copyright
15: * notice, this list of conditions and the following disclaimer in the
16: * documentation and/or other materials provided with the distribution.
17: * 3. Neither the name of the University nor the names of its contributors
18: * may be used to endorse or promote products derived from this software
19: * without specific prior written permission.
20: *
21: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31: * SUCH DAMAGE.
32: */
33:
34: #include "DEFS.h"
35:
36:
37: /*
38: * bcmp(s1, s2, n)
39: */
40: LEAF(bcmp, 0)
41: .set noreorder
42: blt a2, 16, smallcmp # is it worth any trouble?
43: xor v0, a0, a1 # compare low two bits of addresses
44: and v0, v0, 3
45: PTR_SUBU a3, zero, a1 # compute # bytes to word align address
46: bne v0, zero, unalignedcmp # not possible to align addresses
47: and a3, a3, 3
48:
49: beq a3, zero, 1f
50: PTR_SUBU a2, a2, a3 # subtract from remaining count
51: move v0, v1 # init v0,v1 so unmodified bytes match
52: LWHI v0, 0(a0) # read 1, 2, or 3 bytes
53: LWHI v1, 0(a1)
54: PTR_ADDU a1, a1, a3
55: bne v0, v1, nomatch
56: PTR_ADDU a0, a0, a3
57: 1:
58: and a3, a2, ~3 # compute number of whole words left
59: PTR_SUBU a2, a2, a3 # which has to be >= (16-3) & ~3
60: PTR_ADDU a3, a3, a0 # compute ending address
61: 2:
62: lw v0, 0(a0) # compare words
63: lw v1, 0(a1)
64: PTR_ADDU a0, a0, 4
65: bne v0, v1, nomatch
66: PTR_ADDU a1, a1, 4
67: bne a0, a3, 2b
68: nop
69: b smallcmp # finish remainder
70: nop
71: unalignedcmp:
72: beq a3, zero, 2f
73: PTR_SUBU a2, a2, a3 # subtract from remaining count
74: PTR_ADDU a3, a3, a0 # compute ending address
75: 1:
76: lbu v0, 0(a0) # compare bytes until a1 word aligned
77: lbu v1, 0(a1)
78: PTR_ADDU a0, a0, 1
79: bne v0, v1, nomatch
80: PTR_ADDU a1, a1, 1
81: bne a0, a3, 1b
82: nop
83: 2:
84: and a3, a2, ~3 # compute number of whole words left
85: PTR_SUBU a2, a2, a3 # which has to be >= (16-3) & ~3
86: PTR_ADDU a3, a3, a0 # compute ending address
87: 3:
88: LWHI v0, 0(a0) # compare words a0 unaligned, a1 aligned
89: LWLO v0, 3(a0)
90: lw v1, 0(a1)
91: PTR_ADDU a0, a0, 4
92: bne v0, v1, nomatch
93: PTR_ADDU a1, a1, 4
94: bne a0, a3, 3b
95: nop
96: smallcmp:
97: ble a2, zero, match
98: PTR_ADDU a3, a2, a0 # compute ending address
99: 1:
100: lbu v0, 0(a0)
101: lbu v1, 0(a1)
102: PTR_ADDU a0, a0, 1
103: bne v0, v1, nomatch
104: PTR_ADDU a1, a1, 1
105: bne a0, a3, 1b
106: nop
107: match:
108: j ra
109: move v0, zero
110: nomatch:
111: j ra
112: dli v0, 1
113: END(bcmp)
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