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4ea9375a2d
git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@10434 6f19259b-4bc3-4df7-8a09-765794883524
75 lines
1.6 KiB
C
75 lines
1.6 KiB
C
/*++
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Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
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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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Log2.c
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Abstract:
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64-bit integer logarithm function for IA-32
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--*/
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#include "Tiano.h"
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UINT8
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Log2 (
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IN UINT64 Operand
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)
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/*++
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Routine Description:
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Calculates and floors logarithms based on 2
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Arguments:
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Operand - value to calculate logarithm
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Returns:
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The largest integer that is less than or equal
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to the logarithm of Operand based on 2
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--*/
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{
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__asm {
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mov ecx, 64
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cmp dword ptr Operand[0], 0
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jne _Log2_Wend
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cmp dword ptr Operand[4], 0
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jne _Log2_Wend
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mov cl, 0FFH
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jmp _Log2_Done
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_Log2_Wend:
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dec ecx
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cmp ecx, 32
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jae _Log2_Higher
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bt dword ptr Operand[0], ecx
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jmp _Log2_Bit
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_Log2_Higher:
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mov eax, ecx
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sub eax, 32
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bt dword ptr Operand[4], eax
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_Log2_Bit:
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jc _Log2_Done
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jmp _Log2_Wend
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_Log2_Done:
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mov al, cl
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}
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}
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