diff options
Diffstat (limited to 'src/VBox/Runtime/common/asm/ASMBitFirstSet.asm')
| -rw-r--r-- | src/VBox/Runtime/common/asm/ASMBitFirstSet.asm | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/src/VBox/Runtime/common/asm/ASMBitFirstSet.asm b/src/VBox/Runtime/common/asm/ASMBitFirstSet.asm new file mode 100644 index 00000000..0f2c87a0 --- /dev/null +++ b/src/VBox/Runtime/common/asm/ASMBitFirstSet.asm @@ -0,0 +1,137 @@ +; $Id: ASMBitFirstSet.asm $ +;; @file +; IPRT - ASMBitFirstSet(). +; + +; +; Copyright (C) 2006-2022 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>. +; +; 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 set bit in a bitmap. +; +; @returns (32/64:eax, 16:ax+dx) Index of the first zero bit. +; @returns (32/64:eax, 16:ax+dx) -1 if no set bit was found. +; @param msc:rcx gcc:rdi pvBitmap Pointer to the bitmap. +; @param msc:edx gcc:rsi cBits The number of bits in the bitmap. Multiple of 32. +; +RT_BEGINPROC ASMBitFirstSet + ; + ; if (cBits) + ; Put cBits in ecx first. + ; +%if ARCH_BITS == 64 + %ifdef ASM_CALL64_GCC + mov ecx, esi + %else + xchg rcx, rdx ; rdx=pvDst, ecx=cBits + %endif +%elif ARCH_BITS == 32 + mov ecx, [esp + 4 + 4] +%elif ARCH_BITS == 16 + push bp + mov bp, sp + mov ecx, [bp + 4 + 4] +%endif + or ecx, ecx + jz short .failed + ;{ + push xDI + + ; asm {...} +%if ARCH_BITS == 64 + %ifdef ASM_CALL64_GCC + ; rdi = start of scasd - already done + %else + mov rdi, rdx ; rdi = start of scasd (Note! xchg rdx,rcx above) + %endif +%elif ARCH_BITS == 32 + mov edi, [esp + 4] +%elif ARCH_BITS == 16 + mov ax, [bp + 4 + 2] + mov di, [bp + 4] + mov es, ax ; es is volatile, no need to save. +%endif + add ecx, 31 ; 32 bit aligned + shr ecx, 5 ; number of dwords to scan. + mov xDX, xDI ; xDX = saved pvBitmap + xor eax, eax + repe scasd ; Scan for the first dword with any bit set. + je .failed_restore + + ; find the bit in question + sub xDI, 4 ; one step back. +%if ARCH_BITS == 16 + movzx edi, di + mov eax, [es:xDI] +%else + mov eax, [xDI] +%endif + sub xDI, xDX + shl edi, 3 ; calc bit offset. + + bsf ecx, eax + jz .failed_restore ; race paranoia + add ecx, edi + mov eax, ecx + + ; return success + pop xDI +%if ARCH_BITS == 16 + mov edx, eax + shr edx, 16 + leave +%endif + ret + + ; failure + ;} + ;return -1; +.failed_restore: + pop xDI +.failed: +%if ARCH_BITS != 16 + mov eax, 0ffffffffh +%else + mov ax, 0ffffh + mov dx, ax + leave +%endif + ret +ENDPROC ASMBitFirstSet + |