VirtualBox

source: vbox/trunk/src/VBox/Runtime/common/asm/ASMBitFirstSetU32.asm@ 103795

Last change on this file since 103795 was 98103, checked in by vboxsync, 2 years ago

Copyright year updates by scm.

  • Property svn:eol-style set to native
  • Property svn:keywords set to Author Date Id Revision
File size: 2.9 KB
Line 
1; $Id: ASMBitFirstSetU32.asm 98103 2023-01-17 14:15:46Z vboxsync $
2;; @file
3; IPRT - ASMBitFirstSetU32().
4;
5
6;
7; Copyright (C) 2006-2023 Oracle and/or its affiliates.
8;
9; This file is part of VirtualBox base platform packages, as
10; available from https://www.virtualbox.org.
11;
12; This program is free software; you can redistribute it and/or
13; modify it under the terms of the GNU General Public License
14; as published by the Free Software Foundation, in version 3 of the
15; License.
16;
17; This program is distributed in the hope that it will be useful, but
18; WITHOUT ANY WARRANTY; without even the implied warranty of
19; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20; General Public License for more details.
21;
22; You should have received a copy of the GNU General Public License
23; along with this program; if not, see <https://www.gnu.org/licenses>.
24;
25; The contents of this file may alternatively be used under the terms
26; of the Common Development and Distribution License Version 1.0
27; (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
28; in the VirtualBox distribution, in which case the provisions of the
29; CDDL are applicable instead of those of the GPL.
30;
31; You may elect to license modified versions of this file under the
32; terms and conditions of either the GPL or the CDDL or both.
33;
34; SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
35;
36
37
38;*******************************************************************************
39;* Header Files *
40;*******************************************************************************
41%include "iprt/asmdefs.mac"
42
43BEGINCODE
44
45;;
46; Finds the first bit which is set in the given 32-bit integer.
47;
48; Bits are numbered from 1 (least significant) to 32.
49;
50; @returns (xAX) index [1..32] of the first set bit.
51; @returns (xAX) 0 if all bits are cleared.
52; @param msc:ecx gcc:edi x86:stack u32 Integer to search for set bits.
53;
54; @cproto DECLASM(unsigned) ASMBitFirstSetU32(uint32_t u32);
55;
56RT_BEGINPROC ASMBitFirstSetU32
57%if ARCH_BITS == 16
58 CPU 8086
59 push bp
60 mov bp, sp
61
62 ; 15:0
63 mov ax, 1
64 mov cx, [bp + 2 + 2 + 0]
65 test cx, cx
66 jnz .next_bit
67
68 ; 31:16
69 mov al, 16
70 or cx, [bp + 2 + 2 + 2]
71 jz .return_zero
72
73 ; find the bit that was set.
74.next_bit:
75 shr cx, 1
76 jc .return
77 inc ax
78 jmp .next_bit
79
80.return_zero:
81 xor ax, ax
82.return:
83 pop bp
84 ret
85
86%else
87 %if ARCH_BITS == 64
88 %ifdef ASM_CALL64_GCC
89 bsf eax, esi
90 %else
91 bsf eax, ecx
92 %endif
93 %elif ARCH_BITS == 32
94 bsf eax, dword [esp + 4]
95 %else
96 %error "Missing or invalid ARCH_BITS."
97 %endif
98 jz .return_zero
99 inc eax
100.return:
101 ret
102.return_zero:
103 xor eax, eax
104 ret
105%endif
106ENDPROC ASMBitFirstSetU32
107
Note: See TracBrowser for help on using the repository browser.

© 2024 Oracle Support Privacy / Do Not Sell My Info Terms of Use Trademark Policy Automated Access Etiquette