1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
* strrchr - find last position of a character in a string.
*
* Copyright (c) 2020-2023, Arm Limited.
* SPDX-License-Identifier: MIT OR Apache-2.0 WITH LLVM-exception
*/
/* Assumptions:
*
* ARMv8-a, AArch64, Advanced SIMD.
* MTE compatible.
*/
#include "asmdefs.h"
#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_aarch64_mte)
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_aarch64_mte)
|