// 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.

// 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), 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
	RET
fail:
	MOVW	$0, R0
	RET