1 /* strrchr -- find the last occurence of C in a nul-terminated string
2 Copyright (C) 2013-2015 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <http://www.gnu.org/licenses/>. */
25 @ r0 = start of string
26 @ r1 = character to match
27 @ returns NULL for no match, or a pointer to the match
33 @ Loop a few times until we're aligned.
38 cmp r2, r1 @ Find the character
44 tst r3, #7 @ Find the aligment point
47 @ So now we're aligned. Now we actually need a stack frame.
48 2: push { r4, r5, r6, r7 }
49 cfi_adjust_cfa_offset (16)
50 cfi_rel_offset (r4, 0)
51 cfi_rel_offset (r5, 4)
52 cfi_rel_offset (r6, 8)
53 cfi_rel_offset (r7, 12)
55 orr r1, r1, r1, lsl #8 @ Replicate C to all bytes
62 orr r1, r1, r1, lsl #16
63 mov r2, #0 @ No found bits yet
65 @ Loop searching for EOS and C, 8 bytes at a time.
66 @ Any time we find a match in a word, we copy the address of
67 @ the word to r0, and the found bits to r2.
70 @ Subtracting (unsigned saturating) from 1 means result of 1 for
71 @ any byte that was originally zero and 0 otherwise. Therefore
72 @ we consider the lsb of each byte the "found" bit.
73 uqsub8 r6, ip, r4 @ Find EOS
75 eor r4, r4, r1 @ Convert C bytes to 0
77 uqsub8 r4, ip, r4 @ Find C
79 cmp r6, #0 @ Found EOS, first word
81 cmp r4, #0 @ Handle C, first word
85 cmp r7, #0 @ Found EOS, second word
87 cmp r5, #0 @ Handle C, second word
93 @ Found EOS in second word; fold to first word.
94 5: add r3, r3, #4 @ Dec pointer to 2nd word, with below
95 mov r4, r5 @ Overwrite first word C found
96 mov r6, r7 @ Overwrite first word EOS found
98 @ Found EOS. Zap found C after EOS.
99 4: sub r3, r3, #8 @ Decrement pointer to first word
101 @ Byte swap to be congruent with LE, which is easier from here on.
102 rev r6, r6 @ Byte swap found EOS,
103 rev r4, r4 @ ... this found C
104 rev r2, r2 @ ... prev found C
106 sub r7, r6, #1 @ Toggle EOS lsb and below
107 eor r6, r6, r7 @ All bits below and including lsb
108 ands r4, r4, r6 @ Zap C above EOS
110 movne r2, r4 @ Copy to result, if still non-zero
113 pop { r4, r5, r6, r7 }
114 cfi_adjust_cfa_offset (-16)
120 @ Adjust the result pointer if we found a word containing C.
122 clz r2, r2 @ Find the bit offset of the last C
124 rsbne r2, r2, #32 @ Convert to a count from the right
125 addne r0, r0, r2, lsr #3 @ Convert to byte offset and add.
130 weak_alias (strrchr, rindex)
131 libc_hidden_builtin_def (strrchr)