Add in .S file for GCC tool-chain.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@5537 6f19259b-4bc3-4df7-8a09-765794883524

EdkCompatibilityPkg/Foundation/Library/EfiCommonLib/Ia32/GetPowerOfTwo.S

@@ -0,0 +1,68 @@
+#/*++
+#
+#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 "EfiBind.h"
+#---------------------------------------------------------------------------
+    .686: 
+    #.MODEL flat,C
+    .code: 
+
+#---------------------------------------------------------------------------
+.globl ASM_PFX(GetPowerOfTwo)
+#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_PFX(GetPowerOfTwo):
+    xorl    %eax, %eax
+    movl    %eax, %edx
+    movl    8(%esp), %ecx  # dword ptr Input[4]
+    jecxz   _F
+    bsrl    %ecx, %ecx
+    btsl    %ecx, %edx
+    jmp     _Exit
+_F: 
+    movl    4(%esp), %ecx  # dword ptr Input[0]
+    jecxz   _Exit
+    bsrl    %ecx, %ecx
+    btsl    %ecx, %eax
+_Exit: 
+
+    ret
+#GetPowerOfTwo ENDP
+