; $Id$

;; @file

; IPRT - ASMAtomicCmpXchgU8().

;

;

; Copyright (C) 2006-2010 Oracle Corporation

;

; This file is part of VirtualBox Open Source Edition (OSE), as

; available from http://www.virtualbox.org. This file is free software;

; you can redistribute it and/or modify it under the terms of the GNU

; General Public License (GPL) as published by the Free Software

; Foundation, in version 2 as it comes in the "COPYING" file of the

; VirtualBox OSE distribution. VirtualBox OSE is distributed in the

; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.

;

; The contents of this file may alternatively be used under the terms

; of the Common Development and Distribution License Version 1.0

; (CDDL) only, as it comes in the "COPYING.CDDL" file of the

; VirtualBox OSE distribution, in which case the provisions of the

; CDDL are applicable instead of those of the GPL.

;

; You may elect to license modified versions of this file under the

; terms and conditions of either the GPL or the CDDL or both.

;

;*******************************************************************************

;* Header Files *

;*******************************************************************************

%include "iprt/asmdefs.mac"

BEGINCODE

;;

; Atomically compares and exchanges an unsigned 8-bit int.

;

; @param pu8 x86:esp+4 msc:rcx gcc:rdi

; @param u8New x86:esp+8 msc:dl gcc:sil

; @param u8Old x86:esp+c msc:r8l gcc:dl

;

; @returns bool result: true if successfully exchanged, false if not.

; x86:al

;

BEGINPROC_EXPORTED ASMAtomicCmpXchgU8

%ifdef RT_ARCH_AMD64

%ifdef ASM_CALL64_MSC

mov al, r8b

lock cmpxchg [rcx], dl

%else

mov al, dl

lock cmpxchg [rdi], sil

%endif

%else

mov ecx, [esp + 04h]

mov dl, [esp + 08h]

mov al, [esp + 0ch]

lock cmpxchg [ecx], dl

%endif

setz al

movzx eax, al

ret

ENDPROC ASMAtomicCmpXchgU8