Move private classes into anonymous namespaces

NFC.

llvm-svn: 232944
diff --git a/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp b/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
index 44d20fc..0a47dcb 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelDAGToDAG.cpp
@@ -1143,6 +1143,7 @@
   return St;
 }
 
+namespace {
 /// WidenVector - Given a value in the V64 register class, produce the
 /// equivalent value in the V128 register class.
 class WidenVector {
@@ -1163,6 +1164,7 @@
     return DAG.getTargetInsertSubreg(AArch64::dsub, DL, WideTy, Undef, V64Reg);
   }
 };
+} // namespace
 
 /// NarrowVector - Given a value in the V128 register class, produce the
 /// equivalent value in the V64 register class.