about summary refs log tree commit diff
path: root/sysdeps/aarch64/memcpy.S
blob: 304e7eda7f5dd8c599168db578222c468e9e1fac (plain) (blame)
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
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
/* Generic optimized memcpy using SIMD.
   Copyright (C) 2012-2023 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, unaligned accesses.
 *
 */

#define dstin	x0
#define src	x1
#define count	x2
#define dst	x3
#define srcend	x4
#define dstend	x5
#define A_l	x6
#define A_lw	w6
#define A_h	x7
#define B_l	x8
#define B_lw	w8
#define B_h	x9
#define C_lw	w10
#define tmp1	x14

#define A_q	q0
#define B_q	q1
#define C_q	q2
#define D_q	q3
#define E_q	q4
#define F_q	q5
#define G_q	q6
#define H_q	q7

#ifndef MEMMOVE
# define MEMMOVE memmove
#endif
#ifndef MEMCPY
# define MEMCPY memcpy
#endif

/* This implementation supports both memcpy and memmove and shares most code.
   It uses unaligned accesses and branchless sequences to keep the code small,
   simple and improve performance.

   Copies are split into 3 main cases: small copies of up to 32 bytes, medium
   copies of up to 128 bytes, and large copies.  The overhead of the overlap
   check in memmove is negligible since it is only required for large copies.

   Large copies use a software pipelined loop processing 64 bytes per
   iteration.  The destination pointer is 16-byte aligned to minimize
   unaligned accesses.  The loop tail is handled by always copying 64 bytes
   from the end.  */

ENTRY (MEMCPY)
	PTR_ARG (0)
	PTR_ARG (1)
	SIZE_ARG (2)

	add	srcend, src, count
	add	dstend, dstin, count
	cmp	count, 128
	b.hi	L(copy_long)
	cmp	count, 32
	b.hi	L(copy32_128)

	/* Small copies: 0..32 bytes.  */
	cmp	count, 16
	b.lo	L(copy16)
	ldr	A_q, [src]
	ldr	B_q, [srcend, -16]
	str	A_q, [dstin]
	str	B_q, [dstend, -16]
	ret

	/* Copy 8-15 bytes.  */
L(copy16):
	tbz	count, 3, L(copy8)
	ldr	A_l, [src]
	ldr	A_h, [srcend, -8]
	str	A_l, [dstin]
	str	A_h, [dstend, -8]
	ret

	/* Copy 4-7 bytes.  */
L(copy8):
	tbz	count, 2, L(copy4)
	ldr	A_lw, [src]
	ldr	B_lw, [srcend, -4]
	str	A_lw, [dstin]
	str	B_lw, [dstend, -4]
	ret

	/* Copy 0..3 bytes using a branchless sequence.  */
L(copy4):
	cbz	count, L(copy0)
	lsr	tmp1, count, 1
	ldrb	A_lw, [src]
	ldrb	C_lw, [srcend, -1]
	ldrb	B_lw, [src, tmp1]
	strb	A_lw, [dstin]
	strb	B_lw, [dstin, tmp1]
	strb	C_lw, [dstend, -1]
L(copy0):
	ret

	.p2align 4
	/* Medium copies: 33..128 bytes.  */
L(copy32_128):
	ldp	A_q, B_q, [src]
	ldp	C_q, D_q, [srcend, -32]
	cmp	count, 64
	b.hi	L(copy128)
	stp	A_q, B_q, [dstin]
	stp	C_q, D_q, [dstend, -32]
	ret

	.p2align 4
	/* Copy 65..128 bytes.  */
L(copy128):
	ldp	E_q, F_q, [src, 32]
	cmp	count, 96
	b.ls	L(copy96)
	ldp	G_q, H_q, [srcend, -64]
	stp	G_q, H_q, [dstend, -64]
L(copy96):
	stp	A_q, B_q, [dstin]
	stp	E_q, F_q, [dstin, 32]
	stp	C_q, D_q, [dstend, -32]
	ret

	/* Align loop64 below to 16 bytes.  */
	nop

	/* Copy more than 128 bytes.  */
L(copy_long):
	/* Copy 16 bytes and then align src to 16-byte alignment.  */
	ldr	D_q, [src]
	and	tmp1, src, 15
	bic	src, src, 15
	sub	dst, dstin, tmp1
	add	count, count, tmp1	/* Count is now 16 too large.  */
	ldp	A_q, B_q, [src, 16]
	str	D_q, [dstin]
	ldp	C_q, D_q, [src, 48]
	subs	count, count, 128 + 16	/* Test and readjust count.  */
	b.ls	L(copy64_from_end)
L(loop64):
	stp	A_q, B_q, [dst, 16]
	ldp	A_q, B_q, [src, 80]
	stp	C_q, D_q, [dst, 48]
	ldp	C_q, D_q, [src, 112]
	add	src, src, 64
	add	dst, dst, 64
	subs	count, count, 64
	b.hi	L(loop64)

	/* Write the last iteration and copy 64 bytes from the end.  */
L(copy64_from_end):
	ldp	E_q, F_q, [srcend, -64]
	stp	A_q, B_q, [dst, 16]
	ldp	A_q, B_q, [srcend, -32]
	stp	C_q, D_q, [dst, 48]
	stp	E_q, F_q, [dstend, -64]
	stp	A_q, B_q, [dstend, -32]
	ret

END (MEMCPY)
libc_hidden_builtin_def (MEMCPY)


ENTRY (MEMMOVE)
	PTR_ARG (0)
	PTR_ARG (1)
	SIZE_ARG (2)

	add	srcend, src, count
	add	dstend, dstin, count
	cmp	count, 128
	b.hi	L(move_long)
	cmp	count, 32
	b.hi	L(copy32_128)

	/* Small moves: 0..32 bytes.  */
	cmp	count, 16
	b.lo	L(copy16)
	ldr	A_q, [src]
	ldr	B_q, [srcend, -16]
	str	A_q, [dstin]
	str	B_q, [dstend, -16]
	ret

L(move_long):
	/* Only use backward copy if there is an overlap.  */
	sub	tmp1, dstin, src
	cbz	tmp1, L(move0)
	cmp	tmp1, count
	b.hs	L(copy_long)

	/* Large backwards copy for overlapping copies.
	   Copy 16 bytes and then align srcend to 16-byte alignment.  */
L(copy_long_backwards):
	ldr	D_q, [srcend, -16]
	and	tmp1, srcend, 15
	bic	srcend, srcend, 15
	sub	count, count, tmp1
	ldp	A_q, B_q, [srcend, -32]
	str	D_q, [dstend, -16]
	ldp	C_q, D_q, [srcend, -64]
	sub	dstend, dstend, tmp1
	subs	count, count, 128
	b.ls	L(copy64_from_start)

L(loop64_backwards):
	str	B_q, [dstend, -16]
	str	A_q, [dstend, -32]
	ldp	A_q, B_q, [srcend, -96]
	str	D_q, [dstend, -48]
	str	C_q, [dstend, -64]!
	ldp	C_q, D_q, [srcend, -128]
	sub	srcend, srcend, 64
	subs	count, count, 64
	b.hi	L(loop64_backwards)

	/* Write the last iteration and copy 64 bytes from the start.  */
L(copy64_from_start):
	ldp	E_q, F_q, [src, 32]
	stp	A_q, B_q, [dstend, -32]
	ldp	A_q, B_q, [src]
	stp	C_q, D_q, [dstend, -64]
	stp	E_q, F_q, [dstin, 32]
	stp	A_q, B_q, [dstin]
L(move0):
	ret

END (MEMMOVE)
libc_hidden_builtin_def (MEMMOVE)