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#/*++
#
#Copyright (c) 2006, Intel Corporation
#All rights reserved. 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
#
#--*/
#
#---------------------------------------------------------------------------
#include "EfiBind.h" //For ASM_PFX
#---------------------------------------------------------------------------
.globl ASM_PFX(Log2)
#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
#
#--*/
ASM_PFX(Log2):
movl $64, %ecx
cmpl $0, 4(%esp) # (UINT32 *(&Operand))
jne _Log2_Wend
cmpl $0, 8(%esp) # (UINT32 *(&Operand)) + 1
jne _Log2_Wend
movb $0xFF, %cl
jmp _Log2_Done
_Log2_Wend:
decl %ecx
cmpl $32, %ecx
jae _Log2_Higher
btl %ecx, 4(%esp) # (UINT32 *(&Operand))
jmp _Log2_Bit
_Log2_Higher:
movl %ecx, %eax
subl $32, %eax
btl %eax, 8(%esp) # (UINT32 *(&Operand)) + 1
_Log2_Bit:
jc _Log2_Done
jmp _Log2_Wend
_Log2_Done:
movb %cl, %al
ret
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