1// Derived from Inferno's libkern/memmove-386.s (adapted for amd64)
2// https://bitbucket.org/inferno-os/inferno-os/src/master/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// See memmove Go doc for important implementation constraints.
29
30// func memmove(to, from unsafe.Pointer, n uintptr)
31TEXT runtime·memmove(SB), NOSPLIT, $0-24
32
33	MOVQ	to+0(FP), DI
34	MOVQ	from+8(FP), SI
35	MOVQ	n+16(FP), BX
36
37	// REP instructions have a high startup cost, so we handle small sizes
38	// with some straightline code. The REP MOVSQ instruction is really fast
39	// for large sizes. The cutover is approximately 1K.
40tail:
41	TESTQ	BX, BX
42	JEQ	move_0
43	CMPQ	BX, $2
44	JBE	move_1or2
45	CMPQ	BX, $4
46	JBE	move_3or4
47	CMPQ	BX, $8
48	JB	move_5through7
49	JE	move_8
50	CMPQ	BX, $16
51	JBE	move_9through16
52
53/*
54 * check and set for backwards
55 */
56	CMPQ	SI, DI
57	JLS	back
58
59/*
60 * forward copy loop
61 */
62forward:
63	MOVQ	BX, CX
64	SHRQ	$3, CX
65	ANDQ	$7, BX
66
67	REP;	MOVSQ
68	JMP	tail
69
70back:
71/*
72 * check overlap
73 */
74	MOVQ	SI, CX
75	ADDQ	BX, CX
76	CMPQ	CX, DI
77	JLS	forward
78
79/*
80 * whole thing backwards has
81 * adjusted addresses
82 */
83	ADDQ	BX, DI
84	ADDQ	BX, SI
85	STD
86
87/*
88 * copy
89 */
90	MOVQ	BX, CX
91	SHRQ	$3, CX
92	ANDQ	$7, BX
93
94	SUBQ	$8, DI
95	SUBQ	$8, SI
96	REP;	MOVSQ
97
98	CLD
99	ADDQ	$8, DI
100	ADDQ	$8, SI
101	SUBQ	BX, DI
102	SUBQ	BX, SI
103	JMP	tail
104
105move_1or2:
106	MOVB	(SI), AX
107	MOVB	-1(SI)(BX*1), CX
108	MOVB	AX, (DI)
109	MOVB	CX, -1(DI)(BX*1)
110	RET
111move_0:
112	RET
113move_3or4:
114	MOVW	(SI), AX
115	MOVW	-2(SI)(BX*1), CX
116	MOVW	AX, (DI)
117	MOVW	CX, -2(DI)(BX*1)
118	RET
119move_5through7:
120	MOVL	(SI), AX
121	MOVL	-4(SI)(BX*1), CX
122	MOVL	AX, (DI)
123	MOVL	CX, -4(DI)(BX*1)
124	RET
125move_8:
126	// We need a separate case for 8 to make sure we write pointers atomically.
127	MOVQ	(SI), AX
128	MOVQ	AX, (DI)
129	RET
130move_9through16:
131	MOVQ	(SI), AX
132	MOVQ	-8(SI)(BX*1), CX
133	MOVQ	AX, (DI)
134	MOVQ	CX, -8(DI)(BX*1)
135	RET
136