summaryrefslogtreecommitdiffstats
path: root/arch/alpha/lib/ev6-memcpy.S
blob: b19798b2efc09a30fce801eda1587e817fcb434b (plain)
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
/*
 * arch/alpha/lib/ev6-memcpy.S
 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
 *
 * Reasonably optimized memcpy() routine for the Alpha 21264
 *
 *	- memory accessed as aligned quadwords only
 *	- uses bcmpge to compare 8 bytes in parallel
 *
 * Much of the information about 21264 scheduling/coding comes from:
 *	Compiler Writer's Guide for the Alpha 21264
 *	abbreviated as 'CWG' in other comments here
 *	ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
 * Scheduling notation:
 *	E	- either cluster
 *	U	- upper subcluster; U0 - subcluster U0; U1 - subcluster U1
 *	L	- lower subcluster; L0 - subcluster L0; L1 - subcluster L1
 *
 * Temp usage notes:
 *	$1,$2,		- scratch
 */
#include <asm/export.h>
	.set noreorder
	.set noat

	.align	4
	.globl memcpy
	.ent memcpy
memcpy:
	.frame $30,0,$26,0
	.prologue 0

	mov	$16, $0			# E : copy dest to return
	ble	$18, $nomoredata	# U : done with the copy?
	xor	$16, $17, $1		# E : are source and dest alignments the same?
	and	$1, 7, $1		# E : are they the same mod 8?

	bne	$1, $misaligned		# U : Nope - gotta do this the slow way
	/* source and dest are same mod 8 address */
	and	$16, 7, $1		# E : Are both 0mod8?
	beq	$1, $both_0mod8		# U : Yes
	nop				# E :

	/*
	 * source and dest are same misalignment.  move a byte at a time
	 * until a 0mod8 alignment for both is reached.
	 * At least one byte more to move
	 */

$head_align:
	ldbu	$1, 0($17)		# L : grab a byte
	subq	$18, 1, $18		# E : count--
	addq	$17, 1, $17		# E : src++
	stb	$1, 0($16)		# L :
	addq	$16, 1, $16		# E : dest++
	and	$16, 7, $1		# E : Are we at 0mod8 yet?
	ble	$18, $nomoredata	# U : done with the copy?
	bne	$1, $head_align		# U :

$both_0mod8:
	cmple	$18, 127, $1		# E : Can we unroll the loop?
	bne	$1, $no_unroll		# U :
	and	$16, 63, $1		# E : get mod64 alignment
	beq	$1, $do_unroll		# U : no single quads to fiddle

$single_head_quad:
	ldq	$1, 0($17)		# L : get 8 bytes
	subq	$18, 8, $18		# E : count -= 8
	addq	$17, 8, $17		# E : src += 8
	nop				# E :

	stq	$1, 0($16)		# L : store
	addq	$16, 8, $16		# E : dest += 8
	and	$16, 63, $1		# E : get mod64 alignment
	bne	$1, $single_head_quad	# U : still not fully aligned

$do_unroll:
	addq	$16, 64, $7		# E : Initial (+1 trip) wh64 address
	cmple	$18, 127, $1		# E : Can we go through the unrolled loop?
	bne	$1, $tail_quads		# U : Nope
	nop				# E : 

$unroll_body:
	wh64	($7)			# L1 : memory subsystem hint: 64 bytes at
					# ($7) are about to be over-written
	ldq	$6, 0($17)		# L0 : bytes 0..7
	nop				# E :
	nop				# E :

	ldq	$4, 8($17)		# L : bytes 8..15
	ldq	$5, 16($17)		# L : bytes 16..23
	addq	$7, 64, $7		# E : Update next wh64 address
	nop				# E :

	ldq	$3, 24($17)		# L : bytes 24..31
	addq	$16, 64, $1		# E : fallback value for wh64
	nop				# E :
	nop				# E :

	addq	$17, 32, $17		# E : src += 32 bytes
	stq	$6, 0($16)		# L : bytes 0..7
	nop				# E :
	nop				# E :

	stq	$4, 8($16)		# L : bytes 8..15
	stq	$5, 16($16)		# L : bytes 16..23
	subq	$18, 192, $2		# E : At least two more trips to go?
	nop				# E :

	stq	$3, 24($16)		# L : bytes 24..31
	addq	$16, 32, $16		# E : dest += 32 bytes
	nop				# E :
	nop				# E :

	ldq	$6, 0($17)		# L : bytes 0..7
	ldq	$4, 8($17)		# L : bytes 8..15
	cmovlt	$2, $1, $7		# E : Latency 2, extra map slot - Use
					# fallback wh64 address if < 2 more trips
	nop				# E :

	ldq	$5, 16($17)		# L : bytes 16..23
	ldq	$3, 24($17)		# L : bytes 24..31
	addq	$16, 32, $16		# E : dest += 32
	subq	$18, 64, $18		# E : count -= 64

	addq	$17, 32, $17		# E : src += 32
	stq	$6, -32($16)		# L : bytes 0..7
	stq	$4, -24($16)		# L : bytes 8..15
	cmple	$18, 63, $1		# E : At least one more trip?

	stq	$5, -16($16)		# L : bytes 16..23
	stq	$3, -8($16)		# L : bytes 24..31
	nop				# E :
	beq	$1, $unroll_body

$tail_quads:
$no_unroll:
	.align 4
	subq	$18, 8, $18		# E : At least a quad left?
	blt	$18, $less_than_8	# U : Nope
	nop				# E :
	nop				# E :

$move_a_quad:
	ldq	$1, 0($17)		# L : fetch 8
	subq	$18, 8, $18		# E : count -= 8
	addq	$17, 8, $17		# E : src += 8
	nop				# E :

	stq	$1, 0($16)		# L : store 8
	addq	$16, 8, $16		# E : dest += 8
	bge	$18, $move_a_quad	# U :
	nop				# E :

$less_than_8:
	.align 4
	addq	$18, 8, $18		# E : add back for trailing bytes
	ble	$18, $nomoredata	# U : All-done
	nop				# E :
	nop				# E :

	/* Trailing bytes */
$tail_bytes:
	subq	$18, 1, $18		# E : count--
	ldbu	$1, 0($17)		# L : fetch a byte
	addq	$17, 1, $17		# E : src++
	nop				# E :

	stb	$1, 0($16)		# L : store a byte
	addq	$16, 1, $16		# E : dest++
	bgt	$18, $tail_bytes	# U : more to be done?
	nop				# E :

	/* branching to exit takes 3 extra cycles, so replicate exit here */
	ret	$31, ($26), 1		# L0 :
	nop				# E :
	nop				# E :
	nop				# E :

$misaligned:
	mov	$0, $4			# E : dest temp
	and	$0, 7, $1		# E : dest alignment mod8
	beq	$1, $dest_0mod8		# U : life doesnt totally suck
	nop

$aligndest:
	ble	$18, $nomoredata	# U :
	ldbu	$1, 0($17)		# L : fetch a byte
	subq	$18, 1, $18		# E : count--
	addq	$17, 1, $17		# E : src++

	stb	$1, 0($4)		# L : store it
	addq	$4, 1, $4		# E : dest++
	and	$4, 7, $1		# E : dest 0mod8 yet?
	bne	$1, $aligndest		# U : go until we are aligned.

	/* Source has unknown alignment, but dest is known to be 0mod8 */
$dest_0mod8:
	subq	$18, 8, $18		# E : At least a quad left?
	blt	$18, $misalign_tail	# U : Nope
	ldq_u	$3, 0($17)		# L : seed (rotating load) of 8 bytes
	nop				# E :

$mis_quad:
	ldq_u	$16, 8($17)		# L : Fetch next 8
	extql	$3, $17, $3		# U : masking
	extqh	$16, $17, $1		# U : masking
	bis	$3, $1, $1		# E : merged bytes to store

	subq	$18, 8, $18		# E : count -= 8
	addq	$17, 8, $17		# E : src += 8
	stq	$1, 0($4)		# L : store 8 (aligned)
	mov	$16, $3			# E : "rotate" source data

	addq	$4, 8, $4		# E : dest += 8
	bge	$18, $mis_quad		# U : More quads to move
	nop
	nop

$misalign_tail:
	addq	$18, 8, $18		# E : account for tail stuff
	ble	$18, $nomoredata	# U :
	nop
	nop

$misalign_byte:
	ldbu	$1, 0($17)		# L : fetch 1
	subq	$18, 1, $18		# E : count--
	addq	$17, 1, $17		# E : src++
	nop				# E :

	stb	$1, 0($4)		# L : store
	addq	$4, 1, $4		# E : dest++
	bgt	$18, $misalign_byte	# U : more to go?
	nop


$nomoredata:
	ret	$31, ($26), 1		# L0 :
	nop				# E :
	nop				# E :
	nop				# E :

	.end memcpy
	EXPORT_SYMBOL(memcpy)

/* For backwards module compatibility.  */
__memcpy = memcpy
.globl __memcpy
OpenPOWER on IntegriCloud