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f5ad94e0 | 1 | /* strrchr -- find the last occurence of C in a nul-terminated string |
04277e02 | 2 | Copyright (C) 2013-2019 Free Software Foundation, Inc. |
f5ad94e0 RH |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library. If not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
f5ad94e0 RH |
18 | |
19 | #include <sysdep.h> | |
20 | ||
21 | .syntax unified | |
22 | .text | |
23 | ||
24 | ENTRY (strrchr) | |
25 | @ r0 = start of string | |
26 | @ r1 = character to match | |
27 | @ returns NULL for no match, or a pointer to the match | |
28 | ||
29 | mov r3, r0 | |
30 | mov r0, #0 | |
31 | uxtb r1, r1 | |
32 | ||
33 | @ Loop a few times until we're aligned. | |
34 | tst r3, #7 | |
35 | beq 2f | |
81cb7a0b | 36 | 1: ldrb r2, [r3], #1 |
f5ad94e0 RH |
37 | cmp r2, r1 @ Find the character |
38 | it eq | |
39 | subeq r0, r3, #1 | |
40 | cmp r2, #0 @ Find EOS | |
41 | it eq | |
42 | bxeq lr | |
43 | tst r3, #7 @ Find the aligment point | |
44 | bne 1b | |
45 | ||
46 | @ So now we're aligned. Now we actually need a stack frame. | |
47 | 2: push { r4, r5, r6, r7 } | |
48 | cfi_adjust_cfa_offset (16) | |
49 | cfi_rel_offset (r4, 0) | |
50 | cfi_rel_offset (r5, 4) | |
51 | cfi_rel_offset (r6, 8) | |
52 | cfi_rel_offset (r7, 12) | |
53 | ||
54 | orr r1, r1, r1, lsl #8 @ Replicate C to all bytes | |
55 | #ifdef ARCH_HAS_T2 | |
56 | movw ip, #0x0101 | |
57 | movt ip, #0x0101 | |
58 | #else | |
59 | ldr ip, =0x01010101 | |
60 | #endif | |
61 | orr r1, r1, r1, lsl #16 | |
62 | mov r2, #0 @ No found bits yet | |
63 | ||
64 | @ Loop searching for EOS and C, 8 bytes at a time. | |
65 | @ Any time we find a match in a word, we copy the address of | |
66 | @ the word to r0, and the found bits to r2. | |
81cb7a0b | 67 | 3: ldrd r4, r5, [r3], #8 |
f5ad94e0 RH |
68 | @ Subtracting (unsigned saturating) from 1 means result of 1 for |
69 | @ any byte that was originally zero and 0 otherwise. Therefore | |
70 | @ we consider the lsb of each byte the "found" bit. | |
71 | uqsub8 r6, ip, r4 @ Find EOS | |
72 | uqsub8 r7, ip, r5 | |
73 | eor r4, r4, r1 @ Convert C bytes to 0 | |
74 | eor r5, r5, r1 | |
75 | uqsub8 r4, ip, r4 @ Find C | |
76 | uqsub8 r5, ip, r5 | |
77 | cmp r6, #0 @ Found EOS, first word | |
78 | bne 4f | |
79 | cmp r4, #0 @ Handle C, first word | |
80 | itt ne | |
81 | subne r0, r3, #8 | |
82 | movne r2, r4 | |
83 | cmp r7, #0 @ Found EOS, second word | |
84 | bne 5f | |
85 | cmp r5, #0 @ Handle C, second word | |
86 | itt ne | |
87 | subne r0, r3, #4 | |
88 | movne r2, r5 | |
89 | b 3b | |
90 | ||
91 | @ Found EOS in second word; fold to first word. | |
92 | 5: add r3, r3, #4 @ Dec pointer to 2nd word, with below | |
93 | mov r4, r5 @ Overwrite first word C found | |
94 | mov r6, r7 @ Overwrite first word EOS found | |
95 | ||
96 | @ Found EOS. Zap found C after EOS. | |
97 | 4: sub r3, r3, #8 @ Decrement pointer to first word | |
98 | #ifdef __ARMEB__ | |
99 | @ Byte swap to be congruent with LE, which is easier from here on. | |
100 | rev r6, r6 @ Byte swap found EOS, | |
101 | rev r4, r4 @ ... this found C | |
102 | rev r2, r2 @ ... prev found C | |
103 | #endif | |
104 | sub r7, r6, #1 @ Toggle EOS lsb and below | |
105 | eor r6, r6, r7 @ All bits below and including lsb | |
106 | ands r4, r4, r6 @ Zap C above EOS | |
107 | itt ne | |
108 | movne r2, r4 @ Copy to result, if still non-zero | |
109 | movne r0, r3 | |
110 | ||
111 | pop { r4, r5, r6, r7 } | |
112 | cfi_adjust_cfa_offset (-16) | |
113 | cfi_restore (r4) | |
114 | cfi_restore (r5) | |
115 | cfi_restore (r6) | |
116 | cfi_restore (r7) | |
117 | ||
118 | @ Adjust the result pointer if we found a word containing C. | |
119 | cmp r2, #0 | |
120 | clz r2, r2 @ Find the bit offset of the last C | |
121 | itt ne | |
122 | rsbne r2, r2, #32 @ Convert to a count from the right | |
123 | addne r0, r0, r2, lsr #3 @ Convert to byte offset and add. | |
124 | bx lr | |
125 | ||
126 | END (strrchr) | |
127 | ||
128 | weak_alias (strrchr, rindex) | |
129 | libc_hidden_builtin_def (strrchr) |