diff options
Diffstat (limited to 'src/VBox/Runtime/common/asm/ASMBitFirstClear.asm')
| -rw-r--r-- | src/VBox/Runtime/common/asm/ASMBitFirstClear.asm | 127 |
1 files changed, 127 insertions, 0 deletions
diff --git a/src/VBox/Runtime/common/asm/ASMBitFirstClear.asm b/src/VBox/Runtime/common/asm/ASMBitFirstClear.asm new file mode 100644 index 00000000..86cad421 --- /dev/null +++ b/src/VBox/Runtime/common/asm/ASMBitFirstClear.asm @@ -0,0 +1,127 @@ +; $Id: ASMBitFirstClear.asm $ +;; @file +; IPRT - ASMBitFirstClear(). +; + +; +; Copyright (C) 2006-2019 Oracle Corporation +; +; This file is part of VirtualBox Open Source Edition (OSE), as +; available from http://www.virtualbox.org. This file is free software; +; you can redistribute it and/or modify it under the terms of the GNU +; General Public License (GPL) as published by the Free Software +; Foundation, in version 2 as it comes in the "COPYING" file of the +; VirtualBox OSE distribution. VirtualBox OSE is distributed in the +; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind. +; +; The contents of this file may alternatively be used under the terms +; of the Common Development and Distribution License Version 1.0 +; (CDDL) only, as it comes in the "COPYING.CDDL" file of the +; VirtualBox OSE 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. +; + + +;******************************************************************************* +;* Header Files * +;******************************************************************************* +%include "iprt/asmdefs.mac" + +BEGINCODE + +;; +; Finds the first clear 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 clear 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. +; +BEGINPROC_EXPORTED ASMBitFirstClear + ; + ; 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 + 8] +%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 + mov eax, 0ffffffffh + repe scasd ; Scan for the first dword with any clear bit. + je .failed_restore + + ; find the bit in question + sub xDI, 4 ; one step back. +%if ARCH_BITS == 16 + movzx edi, di + xor eax, [es:xDI] ; eax = NOT [rdi] +%else + xor eax, [xDI] ; eax = NOT [rdi] +%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 ASMBitFirstClear + |