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; $Id: ASMAtomicCmpXchgU8.asm $
;; @file
; IPRT - ASMAtomicCmpXchgU8().
;
;
; Copyright (C) 2006-2020 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
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