mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-22 13:00:06 +00:00
55599d4804
Use shrn for narrowing the mask which simplifies code and speeds up small strings. Unroll the first search loop to improve performance on large strings. Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
152 lines
3.9 KiB
ArmAsm
152 lines
3.9 KiB
ArmAsm
/* strrchr: find the last instance of a character in a string.
|
|
|
|
Copyright (C) 2014-2023 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>
|
|
|
|
/* Assumptions:
|
|
*
|
|
* ARMv8-a, AArch64, Advanced SIMD.
|
|
* MTE compatible.
|
|
*/
|
|
|
|
#define srcin x0
|
|
#define chrin w1
|
|
#define result x0
|
|
|
|
#define src x2
|
|
#define tmp x3
|
|
#define synd x3
|
|
#define shift x4
|
|
#define src_match x4
|
|
#define nul_match x5
|
|
#define chr_match x6
|
|
|
|
#define vrepchr v0
|
|
#define vdata v1
|
|
#define vhas_nul v2
|
|
#define vhas_chr v3
|
|
#define vrepmask v4
|
|
#define vend v5
|
|
#define dend d5
|
|
|
|
/* Core algorithm.
|
|
|
|
For each 16-byte chunk we calculate a 64-bit syndrome value, with
|
|
four bits per byte (LSB is always in bits 0 and 1, for both big
|
|
and little-endian systems). For each tuple, bits 0-1 are set if
|
|
the relevant byte matched the requested character; bits 2-3 are set
|
|
if the relevant byte matched the NUL end of string. */
|
|
|
|
ENTRY (strrchr)
|
|
PTR_ARG (0)
|
|
bic src, srcin, 15
|
|
dup vrepchr.16b, chrin
|
|
movi vrepmask.16b, 0x33
|
|
ld1 {vdata.16b}, [src]
|
|
cmeq vhas_nul.16b, vdata.16b, 0
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
bit vhas_nul.16b, vhas_chr.16b, vrepmask.16b
|
|
shrn vend.8b, vhas_nul.8h, 4
|
|
lsl shift, srcin, 2
|
|
fmov synd, dend
|
|
lsr synd, synd, shift
|
|
lsl synd, synd, shift
|
|
ands nul_match, synd, 0xcccccccccccccccc
|
|
bne L(tail)
|
|
cbnz synd, L(loop2_start)
|
|
|
|
.p2align 4
|
|
L(loop1):
|
|
ldr q1, [src, 16]
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
cmhs vhas_nul.16b, vhas_chr.16b, vdata.16b
|
|
umaxp vend.16b, vhas_nul.16b, vhas_nul.16b
|
|
fmov synd, dend
|
|
cbnz synd, L(loop1_end)
|
|
ldr q1, [src, 32]!
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
cmhs vhas_nul.16b, vhas_chr.16b, vdata.16b
|
|
umaxp vend.16b, vhas_nul.16b, vhas_nul.16b
|
|
fmov synd, dend
|
|
cbz synd, L(loop1)
|
|
sub src, src, 16
|
|
L(loop1_end):
|
|
add src, src, 16
|
|
cmeq vhas_nul.16b, vdata.16b, 0
|
|
#ifdef __AARCH64EB__
|
|
bif vhas_nul.16b, vhas_chr.16b, vrepmask.16b
|
|
shrn vend.8b, vhas_nul.8h, 4
|
|
fmov synd, dend
|
|
rbit synd, synd
|
|
#else
|
|
bit vhas_nul.16b, vhas_chr.16b, vrepmask.16b
|
|
shrn vend.8b, vhas_nul.8h, 4
|
|
fmov synd, dend
|
|
#endif
|
|
ands nul_match, synd, 0xcccccccccccccccc
|
|
beq L(loop2_start)
|
|
L(tail):
|
|
sub nul_match, nul_match, 1
|
|
and chr_match, synd, 0x3333333333333333
|
|
ands chr_match, chr_match, nul_match
|
|
add result, src, 15
|
|
clz tmp, chr_match
|
|
sub result, result, tmp, lsr 2
|
|
csel result, result, xzr, ne
|
|
ret
|
|
|
|
.p2align 4
|
|
nop
|
|
nop
|
|
L(loop2_start):
|
|
add src, src, 16
|
|
bic vrepmask.8h, 0xf0
|
|
|
|
L(loop2):
|
|
cmp synd, 0
|
|
csel src_match, src, src_match, ne
|
|
csel chr_match, synd, chr_match, ne
|
|
ld1 {vdata.16b}, [src], 16
|
|
cmeq vhas_nul.16b, vdata.16b, 0
|
|
cmeq vhas_chr.16b, vdata.16b, vrepchr.16b
|
|
bit vhas_nul.16b, vhas_chr.16b, vrepmask.16b
|
|
umaxp vend.16b, vhas_nul.16b, vhas_nul.16b
|
|
fmov synd, dend
|
|
tst synd, 0xcccccccccccccccc
|
|
beq L(loop2)
|
|
|
|
bic vhas_nul.8h, 0x0f, lsl 8
|
|
addp vend.16b, vhas_nul.16b, vhas_nul.16b
|
|
fmov synd, dend
|
|
and nul_match, synd, 0xcccccccccccccccc
|
|
sub nul_match, nul_match, 1
|
|
and tmp, synd, 0x3333333333333333
|
|
ands tmp, tmp, nul_match
|
|
csel chr_match, tmp, chr_match, ne
|
|
csel src_match, src, src_match, ne
|
|
sub src_match, src_match, 1
|
|
clz tmp, chr_match
|
|
sub result, src_match, tmp, lsr 2
|
|
ret
|
|
|
|
END(strrchr)
|
|
weak_alias (strrchr, rindex)
|
|
libc_hidden_builtin_def (strrchr)
|