| // 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. | |
| // 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), R1 // *val | |
| MOVW 4(FP), R2 // old | |
| MOVW 8(FP), R3 // new | |
| l: | |
| LDREX (R1), R0 | |
| CMP R0, R2 | |
| BNE fail | |
| STREX R3, (R1), R0 | |
| CMP $0, R0 | |
| BNE l | |
| MOVW $1, R0 | |
| MOVW R0, 16(SP) | |
| RET | |
| fail: | |
| MOVW $0, R0 | |
| MOVW R0, 16(SP) | |
| RET |