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/GetPowerOfTwo.c

@@ -0,0 +1,62 @@
+/*++
+
+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:
+
+  GetPowerOfTwo.c
+
+Abstract:
+
+  Calculates the largest integer that is both 
+  a power of two and less than Input
+
+--*/
+
+#include "Tiano.h"
+
+UINT64
+GetPowerOfTwo (
+  IN UINT64   Input
+  )
+/*++
+
+Routine Description:
+
+  Calculates the largest integer that is both 
+  a power of two and less than Input
+
+Arguments:
+
+  Input  - value to calculate power of two
+
+Returns:
+
+  the largest integer that is both  a power of 
+  two and less than Input
+
+--*/
+{
+  __asm {
+    xor     eax, eax
+    mov     edx, eax
+    mov     ecx, dword ptr Input[4]
+    jecxz   _F
+    bsr     ecx, ecx
+    bts     edx, ecx
+    jmp     _Exit
+_F:
+    mov     ecx, dword ptr Input[0]
+    jecxz   _Exit
+    bsr     ecx, ecx
+    bts     eax, ecx
+_Exit:
+  }
+}