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Diffstat (limited to 'firmware/asm/sh/strlen.S')
-rw-r--r-- | firmware/asm/sh/strlen.S | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/firmware/asm/sh/strlen.S b/firmware/asm/sh/strlen.S new file mode 100644 index 0000000000..e7169e25db --- /dev/null +++ b/firmware/asm/sh/strlen.S | |||
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1 | /*************************************************************************** | ||
2 | * __________ __ ___. | ||
3 | * Open \______ \ ____ ____ | | _\_ |__ _______ ___ | ||
4 | * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / | ||
5 | * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < | ||
6 | * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ | ||
7 | * \/ \/ \/ \/ \/ | ||
8 | * $Id$ | ||
9 | * | ||
10 | * Copyright (C) 2005 by Jens Arnold | ||
11 | * | ||
12 | * This program is free software; you can redistribute it and/or | ||
13 | * modify it under the terms of the GNU General Public License | ||
14 | * as published by the Free Software Foundation; either version 2 | ||
15 | * of the License, or (at your option) any later version. | ||
16 | * | ||
17 | * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY | ||
18 | * KIND, either express or implied. | ||
19 | * | ||
20 | ****************************************************************************/ | ||
21 | #include "config.h" | ||
22 | |||
23 | .section .icode,"ax",@progbits | ||
24 | |||
25 | .align 2 | ||
26 | .global _strlen | ||
27 | .type _strlen,@function | ||
28 | |||
29 | /* Works out the length of a string | ||
30 | * This version is optimized for speed | ||
31 | * | ||
32 | * arguments: | ||
33 | * r4 - start address | ||
34 | * | ||
35 | * return value: | ||
36 | * r0 - string length | ||
37 | * | ||
38 | * register usage: | ||
39 | * r0 - current address | ||
40 | * r1 - current value (byte/long) | ||
41 | * r2 - mask for alignment / zero (for cmp/str) | ||
42 | * r4 - start address | ||
43 | * | ||
44 | */ | ||
45 | |||
46 | _strlen: | ||
47 | mov r4,r0 /* r0 = start address */ | ||
48 | tst #3,r0 /* long aligned? */ | ||
49 | bt .start_l /* yes, jump directly to the longword loop */ | ||
50 | |||
51 | /* not long aligned: check the first 3 bytes */ | ||
52 | mov.b @r0+,r1 /* fetch first byte */ | ||
53 | tst r1,r1 /* byte == 0 ? */ | ||
54 | bt .hitzero /* yes, string end found */ | ||
55 | mov.b @r0+,r1 /* fetch second byte */ | ||
56 | mov #3,r2 /* prepare mask: r2 = 0..00000011b */ | ||
57 | tst r1,r1 /* byte == 0 ? */ | ||
58 | bt .hitzero /* yes, string end found */ | ||
59 | mov.b @r0+,r1 /* fetch third byte */ | ||
60 | not r2,r2 /* prepare mask: r2 = 1..11111100b */ | ||
61 | tst r1,r1 /* byte == 0 ? */ | ||
62 | bt .hitzero /* yes, string end found */ | ||
63 | |||
64 | /* not yet found, fall through into longword loop */ | ||
65 | and r2,r0 /* align down to long bound */ | ||
66 | |||
67 | /* main loop: check longwords */ | ||
68 | .start_l: | ||
69 | mov #0,r2 /* zero longword for cmp/str */ | ||
70 | .loop_l: | ||
71 | mov.l @r0+,r1 /* fetch long word */ | ||
72 | cmp/str r1,r2 /* any zero byte within? */ | ||
73 | bf .loop_l /* no, loop */ | ||
74 | add #-4,r0 /* set address back to start of this longword */ | ||
75 | |||
76 | /* the last longword contains the string end: figure out the byte */ | ||
77 | mov.b @r0+,r1 /* fetch first byte */ | ||
78 | tst r1,r1 /* byte == 0 ? */ | ||
79 | bt .hitzero /* yes, string end found */ | ||
80 | mov.b @r0+,r1 /* fetch second byte */ | ||
81 | tst r1,r1 /* byte == 0 ? */ | ||
82 | bt .hitzero /* yes, string end found */ | ||
83 | mov.b @r0+,r1 /* fetch third byte */ | ||
84 | tst r1,r1 /* byte == 0 ? */ | ||
85 | bt .hitzero /* yes, string end found */ | ||
86 | rts /* must be the fourth byte */ | ||
87 | sub r4,r0 /* len = string_end - string_start */ | ||
88 | |||
89 | .hitzero: | ||
90 | add #-1,r0 /* undo address increment */ | ||
91 | rts | ||
92 | sub r4,r0 /* len = string_end - string_start */ | ||
93 | |||
94 | .end: | ||
95 | .size _strlen,.end-_strlen | ||
96 | |||