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|
; $Id: __U4D.asm $
;; @file
; Compiler support routines.
;
;
; Copyright (C) 2012-2022 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>.
;
; SPDX-License-Identifier: GPL-3.0-only
;
;*******************************************************************************
;* Exported Symbols *
;*******************************************************************************
public __U4D
; MASM (ML.EXE) is used for PXE and no longer understands the .8086 directive.
; WASM is used for the BIOS and understands it just fine.
ifdef __WASM__
.8086
endif
if VBOX_BIOS_CPU lt 80386
extrn _DoUInt32Div:near
endif
_TEXT segment public 'CODE' use16
assume cs:_TEXT
;;
; 32-bit unsigned division.
;
; @param dx:ax Dividend.
; @param cx:bx Divisor.
; @returns dx:ax Quotient.
; cx:bx Remainder.
;
__U4D:
pushf
if VBOX_BIOS_CPU ge 80386
.386
push eax
push edx
push ecx
rol eax, 16
mov ax, dx
ror eax, 16
xor edx, edx
shr ecx, 16
mov cx, bx
div ecx ; eax:edx / ecx -> eax=quotient, edx=remainder.
mov bx, dx
pop ecx
shr edx, 16
mov cx, dx
pop edx
ror eax, 16
mov dx, ax
add sp, 2
pop ax
rol eax, 16
ifdef __WASM__
.8086
endif
else
;
; If the divisor is only 16-bit, use a fast path
;
test cx, cx
jnz do_it_the_hard_way
div bx ; dx:ax / bx -> ax=quotient, dx=remainder
mov bx, dx ; remainder in cx:bx, and we know cx=0
xor dx, dx ; quotient in dx:ax, dx must be zero
popf
ret
do_it_the_hard_way:
; Call C function do this.
push ds
push es
;
; Convert to a C __cdecl call - not doing this in assembly.
;
; Set up a frame of sorts, allocating 4 bytes for the result buffer.
push bp
sub sp, 04h
mov bp, sp
; Pointer to the return buffer.
push ss
push bp
add bp, 04h ; Correct bp.
; The divisor.
push cx
push bx
; The dividend.
push dx
push ax
call _DoUInt32Div
; Load the remainder.
mov cx, [bp - 02h]
mov bx, [bp - 04h]
; The quotient is already in dx:ax
mov sp, bp
pop bp
pop es
pop ds
endif
popf
ret
_TEXT ends
end
|
