mirror of https://github.com/acidanthera/audk.git
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
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/*++
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Copyright (c) 2006, Intel Corporation
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All rights reserved. This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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Module Name:
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RShiftU64.c
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Abstract:
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64-bit right shift function for IA-32
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--*/
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#include "Tiano.h"
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UINT64
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RShiftU64 (
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IN UINT64 Operand,
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IN UINTN Count
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)
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/*++
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Routine Description:
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This routine allows a 64 bit value to be right shifted by 32 bits and returns the
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shifted value.
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Count is valid up 63. (Only Bits 0-5 is valid for Count)
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Arguments:
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Operand - Value to be shifted
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Count - Number of times to shift right.
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Returns:
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Value shifted right identified by the Count.
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--*/
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{
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__asm {
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mov eax, dword ptr Operand[0]
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mov edx, dword ptr Operand[4]
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;
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; CL is valid from 0 - 31. shld will move EDX:EAX by CL times but EDX is not touched
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; For CL of 32 - 63, it will be shifted 0 - 31 so we will move edx to eax later.
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;
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mov ecx, Count
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and ecx, 63
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shrd eax, edx, cl
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shr edx, cl
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cmp ecx, 32
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jc short _RShiftU64_Done
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;
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; Since Count is 32 - 63, edx will have been shifted by 0 - 31
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; If shifted by 32 or more, set upper 32 bits to zero.
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;
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mov eax, edx
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xor edx, edx
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_RShiftU64_Done:
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}
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}
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