mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-25 14:30:06 +00:00
130 lines
3.6 KiB
ArmAsm
130 lines
3.6 KiB
ArmAsm
/* strrchr -- find the last occurrence of C in a nul-terminated string
|
|
Copyright (C) 2013-2023 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
|
|
<https://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: ldrb r2, [r3], #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 alignment 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: ldrd r4, r5, [r3], #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)
|