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
|
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This version works on pre v6 architectures
// func cas(val *int32, old, new int32) bool
// Atomically:
// if *val == old {
// *val = new;
// return true;
// }else
// return false;
TEXT ·cas(SB),7,$0
MOVW 0(FP), R0 // *val
MOVW 4(FP), R1 // old
MOVW 8(FP), R2 // new
MOVW $1, R3
MOVW $cas_mutex(SB), R4
l:
SWPW (R4), R3 // acquire mutex
CMP $0, R3
BNE fail0
MOVW (R0), R5
CMP R1, R5
BNE fail1
MOVW R2, (R0)
MOVW R3, (R4) // release mutex
MOVW $1, R0
MOVW R0, 16(SP)
RET
fail1:
MOVW R3, (R4) // release mutex
fail0:
MOVW $0, R0
MOVW R0, 16(SP)
RET
|
