Add in the 1st version of ECP.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@2832 6f19259b-4bc3-4df7-8a09-765794883524

EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/Log2.c

@@ -0,0 +1,74 @@
+/*++
+
+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 "Tiano.h"
+
+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 {
+  mov    ecx, 64
+  
+  cmp    dword ptr Operand[0], 0
+  jne    _Log2_Wend 
+  cmp    dword ptr Operand[4], 0
+  jne    _Log2_Wend 
+  mov    cl, 0FFH
+  jmp    _Log2_Done
+  
+_Log2_Wend:
+  dec    ecx
+  cmp    ecx, 32
+  jae    _Log2_Higher
+  bt     dword ptr Operand[0], ecx
+  jmp    _Log2_Bit
+  
+_Log2_Higher:
+  mov    eax, ecx
+  sub    eax, 32
+  bt     dword ptr Operand[4], eax
+  
+_Log2_Bit:
+  jc     _Log2_Done
+  jmp    _Log2_Wend
+      
+_Log2_Done:
+  mov    al, cl
+  }
+}