; $Id: U8M-I8M-x86-32.asm $
;; @file
; BS3Kit - 32-bit Watcom C/C++, 64-bit unsigned integer division.
;

;
; Copyright (C) 2007-2023 Oracle and/or its affiliates.
;
; This file is part of VirtualBox base platform packages, as
; available from https://www.virtualbox.org.
;
; This program is free software; you can redistribute it and/or
; modify it under the terms of the GNU General Public License
; as published by the Free Software Foundation, in version 3 of the
; License.
;
; This program is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
; General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, see <https://www.gnu.org/licenses>.
;
; The contents of this file may alternatively be used under the terms
; of the Common Development and Distribution License Version 1.0
; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
; in the VirtualBox 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.
;
; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
;

%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