Text file src/runtime/memmove_plan9_amd64.s
1 // Derived from Inferno's libkern/memmove-386.s (adapted for amd64)
2 // https://bitbucket.org/inferno-os/inferno-os/src/default/libkern/memmove-386.s
3 //
4 // Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 // Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved.
6 // Portions Copyright 2009 The Go Authors. All rights reserved.
7 //
8 // Permission is hereby granted, free of charge, to any person obtaining a copy
9 // of this software and associated documentation files (the "Software"), to deal
10 // in the Software without restriction, including without limitation the rights
11 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
12 // copies of the Software, and to permit persons to whom the Software is
13 // furnished to do so, subject to the following conditions:
14 //
15 // The above copyright notice and this permission notice shall be included in
16 // all copies or substantial portions of the Software.
17 //
18 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
19 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
21 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
22 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
23 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
24 // THE SOFTWARE.
25
26 #include "textflag.h"
27
28 // func memmove(to, from unsafe.Pointer, n uintptr)
29 TEXT runtime·memmove(SB), NOSPLIT, $0-24
30
31 MOVQ to+0(FP), DI
32 MOVQ from+8(FP), SI
33 MOVQ n+16(FP), BX
34
35 // REP instructions have a high startup cost, so we handle small sizes
36 // with some straightline code. The REP MOVSQ instruction is really fast
37 // for large sizes. The cutover is approximately 1K.
38 tail:
39 TESTQ BX, BX
40 JEQ move_0
41 CMPQ BX, $2
42 JBE move_1or2
43 CMPQ BX, $4
44 JBE move_3or4
45 CMPQ BX, $8
46 JB move_5through7
47 JE move_8
48 CMPQ BX, $16
49 JBE move_9through16
50
51 /*
52 * check and set for backwards
53 */
54 CMPQ SI, DI
55 JLS back
56
57 /*
58 * forward copy loop
59 */
60 forward:
61 MOVQ BX, CX
62 SHRQ $3, CX
63 ANDQ $7, BX
64
65 REP; MOVSQ
66 JMP tail
67
68 back:
69 /*
70 * check overlap
71 */
72 MOVQ SI, CX
73 ADDQ BX, CX
74 CMPQ CX, DI
75 JLS forward
76
77 /*
78 * whole thing backwards has
79 * adjusted addresses
80 */
81 ADDQ BX, DI
82 ADDQ BX, SI
83 STD
84
85 /*
86 * copy
87 */
88 MOVQ BX, CX
89 SHRQ $3, CX
90 ANDQ $7, BX
91
92 SUBQ $8, DI
93 SUBQ $8, SI
94 REP; MOVSQ
95
96 CLD
97 ADDQ $8, DI
98 ADDQ $8, SI
99 SUBQ BX, DI
100 SUBQ BX, SI
101 JMP tail
102
103 move_1or2:
104 MOVB (SI), AX
105 MOVB -1(SI)(BX*1), CX
106 MOVB AX, (DI)
107 MOVB CX, -1(DI)(BX*1)
108 RET
109 move_0:
110 RET
111 move_3or4:
112 MOVW (SI), AX
113 MOVW -2(SI)(BX*1), CX
114 MOVW AX, (DI)
115 MOVW CX, -2(DI)(BX*1)
116 RET
117 move_5through7:
118 MOVL (SI), AX
119 MOVL -4(SI)(BX*1), CX
120 MOVL AX, (DI)
121 MOVL CX, -4(DI)(BX*1)
122 RET
123 move_8:
124 // We need a separate case for 8 to make sure we write pointers atomically.
125 MOVQ (SI), AX
126 MOVQ AX, (DI)
127 RET
128 move_9through16:
129 MOVQ (SI), AX
130 MOVQ -8(SI)(BX*1), CX
131 MOVQ AX, (DI)
132 MOVQ CX, -8(DI)(BX*1)
133 RET
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