| // 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. |
| |
| #include "arm/asm.h" |
| |
| // This version works on pre v6 architectures |
| |
| // bool cas(int32 *val, int32 old, int32 new) |
| // Atomically: |
| // if(*val == old){ |
| // *val = new; |
| // return 1; |
| // }else |
| // return 0; |
| |
| 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 |
| RET |
| fail1: |
| MOVW R3, (R4) // release mutex |
| fail0: |
| MOVW $0, R0 |
| RET |
| |
| DATA cas_mutex(SB)/4, $0 |
| GLOBL cas_mutex(SB), $4 |
