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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/* Copyright (C) 2012-2016 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/>. */
/* Assumptions:
*
* ARMv8-a, AArch64
* Unaligned accesses
*
*/
#include <sysdep.h>
/* By default we assume that the DC instruction can be used to zero
data blocks more efficiently. In some circumstances this might be
unsafe, for example in an asymmetric multiprocessor environment with
different DC clear lengths (neither the upper nor lower lengths are
safe to use). The feature can be disabled by defining DONT_USE_DC.
If code may be run in a virtualized environment, then define
MAYBE_VIRT. This will cause the code to cache the system register
values rather than re-reading them each call. */
#define dstin x0
#define val w1
#define count x2
#define tmp1 x3
#define tmp1w w3
#define tmp2 x4
#define tmp2w w4
#define zva_len_x x5
#define zva_len w5
#define zva_bits_x x6
#define A_l x7
#define A_lw w7
#define dst x8
#define tmp3w w9
ENTRY_ALIGN (__memset, 6)
mov dst, dstin /* Preserve return value. */
ands A_lw, val, #255
#ifndef DONT_USE_DC
b.eq L(zero_mem)
#endif
orr A_lw, A_lw, A_lw, lsl #8
orr A_lw, A_lw, A_lw, lsl #16
orr A_l, A_l, A_l, lsl #32
L(tail_maybe_long):
cmp count, #64
b.ge L(not_short)
L(tail_maybe_tiny):
cmp count, #15
b.le L(tail15tiny)
L(tail63):
ands tmp1, count, #0x30
b.eq L(tail15)
add dst, dst, tmp1
cmp tmp1w, #0x20
b.eq 1f
b.lt 2f
stp A_l, A_l, [dst, #-48]
1:
stp A_l, A_l, [dst, #-32]
2:
stp A_l, A_l, [dst, #-16]
L(tail15):
and count, count, #15
add dst, dst, count
stp A_l, A_l, [dst, #-16] /* Repeat some/all of last store. */
RET
L(tail15tiny):
/* Set up to 15 bytes. Does not assume earlier memory
being set. */
tbz count, #3, 1f
str A_l, [dst], #8
1:
tbz count, #2, 1f
str A_lw, [dst], #4
1:
tbz count, #1, 1f
strh A_lw, [dst], #2
1:
tbz count, #0, 1f
strb A_lw, [dst]
1:
RET
/* Critical loop. Start at a new cache line boundary. Assuming
* 64 bytes per line, this ensures the entire loop is in one line. */
.p2align 6
L(not_short):
neg tmp2, dst
ands tmp2, tmp2, #15
b.eq 2f
/* Bring DST to 128-bit (16-byte) alignment. We know that there's
* more than that to set, so we simply store 16 bytes and advance by
* the amount required to reach alignment. */
sub count, count, tmp2
stp A_l, A_l, [dst]
add dst, dst, tmp2
/* There may be less than 63 bytes to go now. */
cmp count, #63
b.le L(tail63)
2:
sub dst, dst, #16 /* Pre-bias. */
sub count, count, #64
1:
stp A_l, A_l, [dst, #16]
stp A_l, A_l, [dst, #32]
stp A_l, A_l, [dst, #48]
stp A_l, A_l, [dst, #64]!
subs count, count, #64
b.ge 1b
tst count, #0x3f
add dst, dst, #16
b.ne L(tail63)
RET
#ifndef DONT_USE_DC
/* For zeroing memory, check to see if we can use the ZVA feature to
* zero entire 'cache' lines. */
L(zero_mem):
mov A_l, #0
cmp count, #63
b.le L(tail_maybe_tiny)
neg tmp2, dst
ands tmp2, tmp2, #15
b.eq 1f
sub count, count, tmp2
stp A_l, A_l, [dst]
add dst, dst, tmp2
cmp count, #63
b.le L(tail63)
1:
/* For zeroing small amounts of memory, it's not worth setting up
* the line-clear code. */
cmp count, #128
b.lt L(not_short)
#ifdef MAYBE_VIRT
/* For efficiency when virtualized, we cache the ZVA capability. */
adrp tmp2, L(cache_clear)
ldr zva_len, [tmp2, #:lo12:L(cache_clear)]
tbnz zva_len, #31, L(not_short)
cbnz zva_len, L(zero_by_line)
mrs tmp1, dczid_el0
tbz tmp1, #4, 1f
/* ZVA not available. Remember this for next time. */
mov zva_len, #~0
str zva_len, [tmp2, #:lo12:L(cache_clear)]
b L(not_short)
1:
mov tmp3w, #4
and zva_len, tmp1w, #15 /* Safety: other bits reserved. */
lsl zva_len, tmp3w, zva_len
str zva_len, [tmp2, #:lo12:L(cache_clear)]
#else
mrs tmp1, dczid_el0
tbnz tmp1, #4, L(not_short)
mov tmp3w, #4
and zva_len, tmp1w, #15 /* Safety: other bits reserved. */
lsl zva_len, tmp3w, zva_len
#endif
L(zero_by_line):
/* Compute how far we need to go to become suitably aligned. We're
* already at quad-word alignment. */
cmp count, zva_len_x
b.lt L(not_short) /* Not enough to reach alignment. */
sub zva_bits_x, zva_len_x, #1
neg tmp2, dst
ands tmp2, tmp2, zva_bits_x
b.eq 1f /* Already aligned. */
/* Not aligned, check that there's enough to copy after alignment. */
sub tmp1, count, tmp2
cmp tmp1, #64
ccmp tmp1, zva_len_x, #8, ge /* NZCV=0b1000 */
b.lt L(not_short)
/* We know that there's at least 64 bytes to zero and that it's safe
* to overrun by 64 bytes. */
mov count, tmp1
2:
stp A_l, A_l, [dst]
stp A_l, A_l, [dst, #16]
stp A_l, A_l, [dst, #32]
subs tmp2, tmp2, #64
stp A_l, A_l, [dst, #48]
add dst, dst, #64
b.ge 2b
/* We've overrun a bit, so adjust dst downwards. */
add dst, dst, tmp2
1:
sub count, count, zva_len_x
3:
dc zva, dst
add dst, dst, zva_len_x
subs count, count, zva_len_x
b.ge 3b
ands count, count, zva_bits_x
b.ne L(tail_maybe_long)
RET
#ifdef MAYBE_VIRT
.bss
.p2align 2
L(cache_clear):
.space 4
#endif
#endif /* DONT_USE_DC */
END (__memset)
weak_alias (__memset, memset)
libc_hidden_builtin_def (memset)
|
