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|
;/*++
;
;Copyright (c) 2006, Intel Corporation. All rights reserved.<BR>
;This program and the accompanying materials
;are licensed and made available under the terms and conditions of the BSD License
;which accompanies this distribution. The full text of the license may be found at
;http://opensource.org/licenses/bsd-license.php
;
;THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
;WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
;
;Module Name:
;
; Log2.c
;
;Abstract:
;
; 64-bit integer logarithm function for IA-32
;
;--*/
;
;---------------------------------------------------------------------------
.686
.model flat,C
.code
;---------------------------------------------------------------------------
;UINT8
;Log2 (
; IN UINT64 Operand
; )
;/*++
;
;Routine Description:
;
; Calculates and floors logarithms based on 2
;
;Arguments:
;
; Operand - value to calculate logarithm
;
;Returns:
;
; The largest integer that is less than or equal
; to the logarithm of Operand based on 2
;
;--*/
Log2 PROC
mov ecx, 64
cmp dword ptr [esp + 4], 0 ; (UINT32 *(&Operand))
jne _Log2_Wend
cmp dword ptr [esp + 8], 0 ; (UINT32 *(&Operand)) + 1
jne _Log2_Wend
mov cl, 0FFH
jmp _Log2_Done
_Log2_Wend:
dec ecx
cmp ecx, 32
jae _Log2_Higher
bt [esp + 4], ecx ; (UINT32 *(&Operand))
jmp _Log2_Bit
_Log2_Higher:
mov eax, ecx
sub eax, 32
bt [esp + 8], eax ; (UINT32 *(&Operand)) + 1
_Log2_Bit:
jc _Log2_Done
jmp _Log2_Wend
_Log2_Done:
mov al, cl
ret
Log2 ENDP
END
|
