| 1 | ; $Id: U8RS-x86-32.asm 75129 2018-10-28 17:00:27Z vboxsync $
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| 2 | ;; @file
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| 3 | ; BS3Kit - 32-bit Watcom C/C++, 64-bit unsigned integer right shift.
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| 4 | ;
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| 5 |
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| 6 | ;
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| 7 | ; Copyright (C) 2007-2017 Oracle Corporation
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| 8 | ;
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| 9 | ; This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | ; available from http://www.virtualbox.org. This file is free software;
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| 11 | ; you can redistribute it and/or modify it under the terms of the GNU
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| 12 | ; General Public License (GPL) as published by the Free Software
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| 13 | ; Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | ; VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | ; hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | ;
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| 17 | ; The contents of this file may alternatively be used under the terms
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| 18 | ; of the Common Development and Distribution License Version 1.0
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| 19 | ; (CDDL) only, as it comes in the "COPYING.CDDL" file of the
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| 20 | ; VirtualBox OSE distribution, in which case the provisions of the
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| 21 | ; CDDL are applicable instead of those of the GPL.
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| 22 | ;
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| 23 | ; You may elect to license modified versions of this file under the
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| 24 | ; terms and conditions of either the GPL or the CDDL or both.
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| 25 | ;
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| 26 |
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| 27 | %include "iprt/asmdefs.mac"
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| 28 |
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| 29 |
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| 30 | BEGINCODE
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| 31 |
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| 32 |
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| 33 | ;;
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| 34 | ; 64-bit unsigned integer right shift.
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| 35 | ;
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| 36 | ; @returns EDX:EAX
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| 37 | ; @param EDX:EAX Value to shift.
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| 38 | ; @param BL Shift count (it's specified as ECX:EBX, but we only use BL).
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| 39 | ;
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| 40 | global __U8RS
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| 41 | __U8RS:
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| 42 | push ecx ; We're allowed to trash ECX, but why bother.
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| 43 |
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| 44 | mov cl, bl
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| 45 | and cl, 3fh
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| 46 | test cl, 20h
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| 47 | jnz .big_shift
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| 48 |
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| 49 | ; Shifting less than 32.
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| 50 | shrd eax, edx, cl
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| 51 | shr edx, cl
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| 52 |
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| 53 | .return:
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| 54 | pop ecx
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| 55 | ret
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| 56 |
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| 57 | .big_shift:
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| 58 | ; Shifting 32 or more.
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| 59 | mov eax, edx
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| 60 | shr eax, cl ; Only uses lower 5 bits.
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| 61 | xor edx, edx
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| 62 | jmp .return
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| 63 |
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