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review.evervolv.com / android_kernel_htc_msm8960 / ae5536d6f7f9b51f7a0451421eade1988cfd7126 / . / arch / alpha / lib / ev6-memcpy.S
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Linus Torvalds1da177e2005-04-16 15:20:36 -0700[diff] [blame]1/*
2 * arch/alpha/lib/ev6-memcpy.S
3 * 21264 version by Rick Gorton <rick.gorton@alpha-processor.com>
4 *
5 * Reasonably optimized memcpy() routine for the Alpha 21264
6 *
7 * - memory accessed as aligned quadwords only
8 * - uses bcmpge to compare 8 bytes in parallel
9 *
10 * Much of the information about 21264 scheduling/coding comes from:
11 * Compiler Writer's Guide for the Alpha 21264
12 * abbreviated as 'CWG' in other comments here
13 * ftp.digital.com/pub/Digital/info/semiconductor/literature/dsc-library.html
14 * Scheduling notation:
15 * E - either cluster
16 * U - upper subcluster; U0 - subcluster U0; U1 - subcluster U1
17 * L - lower subcluster; L0 - subcluster L0; L1 - subcluster L1
18 *
19 * Temp usage notes:
20 * $1,$2, - scratch
21 */
22
23 .set noreorder
24 .set noat
25
26 .align 4
27 .globl memcpy
28 .ent memcpy
29memcpy:
30 .frame $30,0,$26,0
31 .prologue 0
32
33 mov $16, $0 # E : copy dest to return
34 ble $18, $nomoredata # U : done with the copy?
35 xor $16, $17, $1 # E : are source and dest alignments the same?
36 and $1, 7, $1 # E : are they the same mod 8?
37
38 bne $1, $misaligned # U : Nope - gotta do this the slow way
39 /* source and dest are same mod 8 address */
40 and $16, 7, $1 # E : Are both 0mod8?
41 beq $1, $both_0mod8 # U : Yes
42 nop # E :
43
44 /*
45 * source and dest are same misalignment. move a byte at a time
46 * until a 0mod8 alignment for both is reached.
47 * At least one byte more to move
48 */
49
50$head_align:
51 ldbu $1, 0($17) # L : grab a byte
52 subq $18, 1, $18 # E : count--
53 addq $17, 1, $17 # E : src++
54 stb $1, 0($16) # L :
55 addq $16, 1, $16 # E : dest++
56 and $16, 7, $1 # E : Are we at 0mod8 yet?
57 ble $18, $nomoredata # U : done with the copy?
58 bne $1, $head_align # U :
59
60$both_0mod8:
61 cmple $18, 127, $1 # E : Can we unroll the loop?
62 bne $1, $no_unroll # U :
63 and $16, 63, $1 # E : get mod64 alignment
64 beq $1, $do_unroll # U : no single quads to fiddle
65
66$single_head_quad:
67 ldq $1, 0($17) # L : get 8 bytes
68 subq $18, 8, $18 # E : count -= 8
69 addq $17, 8, $17 # E : src += 8
70 nop # E :
71
72 stq $1, 0($16) # L : store
73 addq $16, 8, $16 # E : dest += 8
74 and $16, 63, $1 # E : get mod64 alignment
75 bne $1, $single_head_quad # U : still not fully aligned
76
77$do_unroll:
78 addq $16, 64, $7 # E : Initial (+1 trip) wh64 address
79 cmple $18, 127, $1 # E : Can we go through the unrolled loop?
80 bne $1, $tail_quads # U : Nope
81 nop # E :
82
83$unroll_body:
84 wh64 ($7) # L1 : memory subsystem hint: 64 bytes at
85 # ($7) are about to be over-written
86 ldq $6, 0($17) # L0 : bytes 0..7
87 nop # E :
88 nop # E :
89
90 ldq $4, 8($17) # L : bytes 8..15
91 ldq $5, 16($17) # L : bytes 16..23
92 addq $7, 64, $7 # E : Update next wh64 address
93 nop # E :
94
95 ldq $3, 24($17) # L : bytes 24..31
96 addq $16, 64, $1 # E : fallback value for wh64
97 nop # E :
98 nop # E :
99
100 addq $17, 32, $17 # E : src += 32 bytes
101 stq $6, 0($16) # L : bytes 0..7
102 nop # E :
103 nop # E :
104
105 stq $4, 8($16) # L : bytes 8..15
106 stq $5, 16($16) # L : bytes 16..23
107 subq $18, 192, $2 # E : At least two more trips to go?
108 nop # E :
109
110 stq $3, 24($16) # L : bytes 24..31
111 addq $16, 32, $16 # E : dest += 32 bytes
112 nop # E :
113 nop # E :
114
115 ldq $6, 0($17) # L : bytes 0..7
116 ldq $4, 8($17) # L : bytes 8..15
117 cmovlt $2, $1, $7 # E : Latency 2, extra map slot - Use
118 # fallback wh64 address if < 2 more trips
119 nop # E :
120
121 ldq $5, 16($17) # L : bytes 16..23
122 ldq $3, 24($17) # L : bytes 24..31
123 addq $16, 32, $16 # E : dest += 32
124 subq $18, 64, $18 # E : count -= 64
125
126 addq $17, 32, $17 # E : src += 32
127 stq $6, -32($16) # L : bytes 0..7
128 stq $4, -24($16) # L : bytes 8..15
129 cmple $18, 63, $1 # E : At least one more trip?
130
131 stq $5, -16($16) # L : bytes 16..23
132 stq $3, -8($16) # L : bytes 24..31
133 nop # E :
134 beq $1, $unroll_body
135
136$tail_quads:
137$no_unroll:
138 .align 4
139 subq $18, 8, $18 # E : At least a quad left?
140 blt $18, $less_than_8 # U : Nope
141 nop # E :
142 nop # E :
143
144$move_a_quad:
145 ldq $1, 0($17) # L : fetch 8
146 subq $18, 8, $18 # E : count -= 8
147 addq $17, 8, $17 # E : src += 8
148 nop # E :
149
150 stq $1, 0($16) # L : store 8
151 addq $16, 8, $16 # E : dest += 8
152 bge $18, $move_a_quad # U :
153 nop # E :
154
155$less_than_8:
156 .align 4
157 addq $18, 8, $18 # E : add back for trailing bytes
158 ble $18, $nomoredata # U : All-done
159 nop # E :
160 nop # E :
161
162 /* Trailing bytes */
163$tail_bytes:
164 subq $18, 1, $18 # E : count--
165 ldbu $1, 0($17) # L : fetch a byte
166 addq $17, 1, $17 # E : src++
167 nop # E :
168
169 stb $1, 0($16) # L : store a byte
170 addq $16, 1, $16 # E : dest++
171 bgt $18, $tail_bytes # U : more to be done?
172 nop # E :
173
174 /* branching to exit takes 3 extra cycles, so replicate exit here */
175 ret $31, ($26), 1 # L0 :
176 nop # E :
177 nop # E :
178 nop # E :
179
180$misaligned:
181 mov $0, $4 # E : dest temp
182 and $0, 7, $1 # E : dest alignment mod8
183 beq $1, $dest_0mod8 # U : life doesnt totally suck
184 nop
185
186$aligndest:
187 ble $18, $nomoredata # U :
188 ldbu $1, 0($17) # L : fetch a byte
189 subq $18, 1, $18 # E : count--
190 addq $17, 1, $17 # E : src++
191
192 stb $1, 0($4) # L : store it
193 addq $4, 1, $4 # E : dest++
194 and $4, 7, $1 # E : dest 0mod8 yet?
195 bne $1, $aligndest # U : go until we are aligned.
196
197 /* Source has unknown alignment, but dest is known to be 0mod8 */
198$dest_0mod8:
199 subq $18, 8, $18 # E : At least a quad left?
200 blt $18, $misalign_tail # U : Nope
201 ldq_u $3, 0($17) # L : seed (rotating load) of 8 bytes
202 nop # E :
203
204$mis_quad:
205 ldq_u $16, 8($17) # L : Fetch next 8
206 extql $3, $17, $3 # U : masking
207 extqh $16, $17, $1 # U : masking
208 bis $3, $1, $1 # E : merged bytes to store
209
210 subq $18, 8, $18 # E : count -= 8
211 addq $17, 8, $17 # E : src += 8
212 stq $1, 0($4) # L : store 8 (aligned)
213 mov $16, $3 # E : "rotate" source data
214
215 addq $4, 8, $4 # E : dest += 8
216 bge $18, $mis_quad # U : More quads to move
217 nop
218 nop
219
220$misalign_tail:
221 addq $18, 8, $18 # E : account for tail stuff
222 ble $18, $nomoredata # U :
223 nop
224 nop
225
226$misalign_byte:
227 ldbu $1, 0($17) # L : fetch 1
228 subq $18, 1, $18 # E : count--
229 addq $17, 1, $17 # E : src++
230 nop # E :
231
232 stb $1, 0($4) # L : store
233 addq $4, 1, $4 # E : dest++
234 bgt $18, $misalign_byte # U : more to go?
235 nop
236
237
238$nomoredata:
239 ret $31, ($26), 1 # L0 :
240 nop # E :
241 nop # E :
242 nop # E :
243
244 .end memcpy
245
246/* For backwards module compatibility. */
247__memcpy = memcpy
248.globl __memcpy