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diff --git a/src/VBox/Runtime/common/asm/ASMBitFirstSetU32.asm b/src/VBox/Runtime/common/asm/ASMBitFirstSetU32.asm
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+; $Id: ASMBitFirstSetU32.asm $
+;; @file
+; IPRT - ASMBitFirstSetU32().
+;
+
+;
+; Copyright (C) 2006-2023 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
+;
+
+
+;*******************************************************************************
+;* Header Files *
+;*******************************************************************************
+%include "iprt/asmdefs.mac"
+
+BEGINCODE
+
+;;
+; Finds the first bit which is set in the given 32-bit integer.
+;
+; Bits are numbered from 1 (least significant) to 32.
+;
+; @returns (xAX) index [1..32] of the first set bit.
+; @returns (xAX) 0 if all bits are cleared.
+; @param msc:ecx gcc:edi x86:stack u32 Integer to search for set bits.
+;
+; @cproto DECLASM(unsigned) ASMBitFirstSetU32(uint32_t u32);
+;
+RT_BEGINPROC ASMBitFirstSetU32
+%if ARCH_BITS == 16
+ CPU 8086
+ push bp
+ mov bp, sp
+
+ ; 15:0
+ mov ax, 1
+ mov cx, [bp + 2 + 2 + 0]
+ test cx, cx
+ jnz .next_bit
+
+ ; 31:16
+ mov al, 16
+ or cx, [bp + 2 + 2 + 2]
+ jz .return_zero
+
+ ; find the bit that was set.
+.next_bit:
+ shr cx, 1
+ jc .return
+ inc ax
+ jmp .next_bit
+
+.return_zero:
+ xor ax, ax
+.return:
+ pop bp
+ ret
+
+%else
+ %if ARCH_BITS == 64
+ %ifdef ASM_CALL64_GCC
+ bsf eax, esi
+ %else
+ bsf eax, ecx
+ %endif
+ %elif ARCH_BITS == 32
+ bsf eax, dword [esp + 4]
+ %else
+ %error "Missing or invalid ARCH_BITS."
+ %endif
+ jz .return_zero
+ inc eax
+.return:
+ ret
+.return_zero:
+ xor eax, eax
+ ret
+%endif
+ENDPROC ASMBitFirstSetU32
+