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; $Id$
;; @file
; BS3Kit - 32-bit Watcom C/C++, 64-bit unsigned integer division.
;
;
; Copyright (C) 2007-2022 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.
;
%include "iprt/asmdefs.mac"
BEGINCODE
;;
; 64-bit signed & unsigned integer multiplication.
;
; @returns EDX:EAX product
; @param EDX:EAX Factor #1.
; @param ECX:EBX Factor #2.
; @uses ECX, EBX
;
global __U8M
__U8M:
global __I8M
__I8M:
;
; See if this is a pure 32-bit multiplication. We might get lucky.
;
test edx, edx
jnz .complicated
test ecx, ecx
jnz .complicated
mul ebx ; eax * ebx -> edx:eax
ret
.complicated:
push eax
push edx
; ecx = F1.lo * F2.hi (edx contains overflow here can be ignored)
mul ecx
mov ecx, eax
; ecx += F1.hi * F2.lo (edx can be ignored again)
pop eax
mul ebx
add ecx, eax
; edx:eax = F1.lo * F2.lo
pop eax
mul ebx
; Add ecx to the high part (edx).
add edx, ecx
ret
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