mirror of https://github.com/acidanthera/audk.git
82 lines
1.9 KiB
NASM
82 lines
1.9 KiB
NASM
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;/*++
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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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;
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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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;
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;Module Name:
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;
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; Log2.c
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;
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;Abstract:
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;
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; 64-bit integer logarithm function for IA-32
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;
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;--*/
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;
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;---------------------------------------------------------------------------
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.686
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.model flat,C
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.code
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;---------------------------------------------------------------------------
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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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;
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;Routine Description:
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;
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; Calculates and floors logarithms based on 2
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;
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;Arguments:
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;
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; Operand - value to calculate logarithm
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;
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;Returns:
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;
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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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Log2 PROC
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mov ecx, 64
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cmp dword ptr [esp + 4], 0 ; (UINT32 *(&Operand))
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jne _Log2_Wend
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cmp dword ptr [esp + 8], 0 ; (UINT32 *(&Operand)) + 1
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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 [esp + 4], ecx ; (UINT32 *(&Operand))
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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 [esp + 8], eax ; (UINT32 *(&Operand)) + 1
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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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ret
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Log2 ENDP
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END
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