SPEAr : Adding README.spear in doc
[oweals/u-boot.git] / lib_blackfin / memcmp.S
1 /*
2  * File: memcmp.S
3  *
4  * Copyright 2004-2007 Analog Devices Inc.
5  * Enter bugs at http://blackfin.uclinux.org/
6  *
7  * This program is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
9  * the Free Software Foundation; either version 2 of the License, or
10  * (at your option) any later version.
11  *
12  * This program is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with this program; if not, see the file COPYING, or write
19  * to the Free Software Foundation, Inc.,
20  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
21  */
22
23 .align 2
24
25 /*
26  * C Library function MEMCMP
27  * R0 = First Address
28  * R1 = Second Address
29  * R2 = count
30  * Favours word aligned data.
31  */
32
33 .globl _memcmp;
34 .type _memcmp, STT_FUNC;
35 _memcmp:
36         I1 = P3;
37         P0 = R0;                        /* P0 = s1 address */
38         P3 = R1;                        /* P3 = s2 Address  */
39         P2 = R2 ;                       /* P2 = count */
40         CC = R2 <= 7(IU);
41         IF CC JUMP  .Ltoo_small;
42         I0 = R1;                        /* s2 */
43         R1 = R1 | R0;           /* OR addresses together */
44         R1 <<= 30;              /* check bottom two bits */
45         CC =  AZ;                       /* AZ set if zero. */
46         IF !CC JUMP  .Lbytes ;  /* Jump if addrs not aligned. */
47
48         P1 = P2 >> 2;           /* count = n/4 */
49         R3 =  3;
50         R2 = R2 & R3;           /* remainder */
51         P2 = R2;                        /* set remainder */
52
53         LSETUP (.Lquad_loop_s , .Lquad_loop_e) LC0=P1;
54 .Lquad_loop_s:
55         NOP;
56         R0 = [P0++];
57         R1 = [I0++];
58         CC = R0 == R1;
59         IF !CC JUMP .Lquad_different;
60 .Lquad_loop_e:
61         NOP;
62
63         P3 = I0;                        /* s2 */
64 .Ltoo_small:
65         CC = P2 == 0;           /* Check zero count*/
66         IF CC JUMP .Lfinished;  /* very unlikely*/
67
68 .Lbytes:
69         LSETUP (.Lbyte_loop_s , .Lbyte_loop_e) LC0=P2;
70 .Lbyte_loop_s:
71         R1 = B[P3++](Z);        /* *s2 */
72         R0 = B[P0++](Z);        /* *s1 */
73         CC = R0 == R1;
74         IF !CC JUMP .Ldifferent;
75 .Lbyte_loop_e:
76         NOP;
77
78 .Ldifferent:
79         R0 = R0 - R1;
80         P3 = I1;
81         RTS;
82
83 .Lquad_different:
84 /* We've read two quads which don't match.
85  * Can't just compare them, because we're
86  * a little-endian machine, so the MSBs of
87  * the regs occur at later addresses in the
88  * string.
89  * Arrange to re-read those two quads again,
90  * byte-by-byte.
91  */
92         P0 += -4;               /* back up to the start of the */
93         P3 = I0;                /* quads, and increase the*/
94         P2 += 4;                /* remainder count*/
95         P3 += -4;
96         JUMP .Lbytes;
97
98 .Lfinished:
99         R0 = 0;
100         P3 = I1;
101         RTS;
102
103 .size _memcmp, .-_memcmp