Add Memory fence for ARM Architecture (32 and 64 bit)

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>



git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14615 6f19259b-4bc3-4df7-8a09-765794883524

MdePkg/Library/BaseLib/AArch64/MemoryFence.S

@@ -0,0 +1,39 @@
+##------------------------------------------------------------------------------
+#
+# MemoryFence() for AArch64
+#
+# Copyright (c) 2013, ARM Ltd. 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.
+#
+##------------------------------------------------------------------------------
+
+.text
+.p2align 2
+
+GCC_ASM_EXPORT(MemoryFence)
+
+
+#/**
+#  Used to serialize load and store operations.
+#
+#  All loads and stores that proceed calls to this function are guaranteed to be
+#  globally visible when this function returns.
+#
+#**/
+#VOID
+#EFIAPI
+#MemoryFence (
+#  VOID
+#  );
+#
+ASM_PFX(MemoryFence):
+    // System wide Data Memory Barrier.
+    dmb sy
+    ret