| // 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 | |