1 files changed, 97 insertions, 0 deletions
diff --git a/src/VBox/Devices/BiosCommonCode/__I4M.asm b/src/VBox/Devices/BiosCommonCode/__I4M.asm
new file mode 100644
index 00000000..bdba20ad
--- /dev/null
+++ b/src/VBox/Devices/BiosCommonCode/__I4M.asm
@@ -0,0 +1,97 @@
+; $Id: __I4M.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          __I4M
+
+if VBOX_BIOS_CPU lt 80386
+extrn NeedToImplementOn8086__I4M:near
+endif
+
+; 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
+
+_TEXT           segment public 'CODE' use16
+                assume cs:_TEXT
+
+;;
+; 32-bit signed multiplication.
+;
+; @param    dx:ax   Factor 1.
+; @param    cx:bx   Factor 2.
+; @returns  dx:ax   Result.
+; cx, es may be modified; di is preserved
+;
+__I4M:
+                pushf
+if VBOX_BIOS_CPU ge 80386
+                .386
+                push    eax
+                push    edx
+                push    ecx
+                push    ebx
+
+                rol     eax, 16
+                mov     ax, dx
+                ror     eax, 16
+                xor     edx, edx
+
+                shr     ecx, 16
+                mov     cx, bx
+
+                imul    ecx                 ; eax * ecx -> edx:eax
+
+                pop     ebx
+                pop     ecx
+
+                pop     edx
+                ror     eax, 16
+                mov     dx, ax
+                add     sp, 2
+                pop     ax
+                rol     eax, 16
+ifdef __WASM__
+                .8086
+endif
+
+else
+                call    NeedToImplementOn8086__I4M
+endif
+
+                popf
+                ret
+
+
+_TEXT           ends
+                end
+