| /* strrchr -- find the last occurence of C in a nul-terminated string |
| Copyright (C) 2013-2014 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library. If not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <sysdep.h> |
| |
| .syntax unified |
| .text |
| |
| ENTRY (strrchr) |
| @ r0 = start of string |
| @ r1 = character to match |
| @ returns NULL for no match, or a pointer to the match |
| |
| mov r3, r0 |
| mov r0, #0 |
| uxtb r1, r1 |
| |
| @ Loop a few times until we're aligned. |
| tst r3, #7 |
| beq 2f |
| 1: sfi_breg r3, \ |
| ldrb r2, [\B], #1 |
| cmp r2, r1 @ Find the character |
| it eq |
| subeq r0, r3, #1 |
| cmp r2, #0 @ Find EOS |
| it eq |
| bxeq lr |
| tst r3, #7 @ Find the aligment point |
| bne 1b |
| |
| @ So now we're aligned. Now we actually need a stack frame. |
| 2: push { r4, r5, r6, r7 } |
| cfi_adjust_cfa_offset (16) |
| cfi_rel_offset (r4, 0) |
| cfi_rel_offset (r5, 4) |
| cfi_rel_offset (r6, 8) |
| cfi_rel_offset (r7, 12) |
| |
| orr r1, r1, r1, lsl #8 @ Replicate C to all bytes |
| #ifdef ARCH_HAS_T2 |
| movw ip, #0x0101 |
| movt ip, #0x0101 |
| #else |
| ldr ip, =0x01010101 |
| #endif |
| orr r1, r1, r1, lsl #16 |
| mov r2, #0 @ No found bits yet |
| |
| @ Loop searching for EOS and C, 8 bytes at a time. |
| @ Any time we find a match in a word, we copy the address of |
| @ the word to r0, and the found bits to r2. |
| 3: sfi_breg r3, \ |
| ldrd r4, r5, [\B], #8 |
| @ Subtracting (unsigned saturating) from 1 means result of 1 for |
| @ any byte that was originally zero and 0 otherwise. Therefore |
| @ we consider the lsb of each byte the "found" bit. |
| uqsub8 r6, ip, r4 @ Find EOS |
| uqsub8 r7, ip, r5 |
| eor r4, r4, r1 @ Convert C bytes to 0 |
| eor r5, r5, r1 |
| uqsub8 r4, ip, r4 @ Find C |
| uqsub8 r5, ip, r5 |
| cmp r6, #0 @ Found EOS, first word |
| bne 4f |
| cmp r4, #0 @ Handle C, first word |
| itt ne |
| subne r0, r3, #8 |
| movne r2, r4 |
| cmp r7, #0 @ Found EOS, second word |
| bne 5f |
| cmp r5, #0 @ Handle C, second word |
| itt ne |
| subne r0, r3, #4 |
| movne r2, r5 |
| b 3b |
| |
| @ Found EOS in second word; fold to first word. |
| 5: add r3, r3, #4 @ Dec pointer to 2nd word, with below |
| mov r4, r5 @ Overwrite first word C found |
| mov r6, r7 @ Overwrite first word EOS found |
| |
| @ Found EOS. Zap found C after EOS. |
| 4: sub r3, r3, #8 @ Decrement pointer to first word |
| #ifdef __ARMEB__ |
| @ Byte swap to be congruent with LE, which is easier from here on. |
| rev r6, r6 @ Byte swap found EOS, |
| rev r4, r4 @ ... this found C |
| rev r2, r2 @ ... prev found C |
| #endif |
| sub r7, r6, #1 @ Toggle EOS lsb and below |
| eor r6, r6, r7 @ All bits below and including lsb |
| ands r4, r4, r6 @ Zap C above EOS |
| itt ne |
| movne r2, r4 @ Copy to result, if still non-zero |
| movne r0, r3 |
| |
| pop { r4, r5, r6, r7 } |
| cfi_adjust_cfa_offset (-16) |
| cfi_restore (r4) |
| cfi_restore (r5) |
| cfi_restore (r6) |
| cfi_restore (r7) |
| |
| @ Adjust the result pointer if we found a word containing C. |
| cmp r2, #0 |
| clz r2, r2 @ Find the bit offset of the last C |
| itt ne |
| rsbne r2, r2, #32 @ Convert to a count from the right |
| addne r0, r0, r2, lsr #3 @ Convert to byte offset and add. |
| bx lr |
| |
| END (strrchr) |
| |
| weak_alias (strrchr, rindex) |
| libc_hidden_builtin_def (strrchr) |
