Give internal classes hidden visibility.

Worth 100k on a linux/x86_64 Release+Asserts clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190534 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DIEHash.h

@@ -19,7 +19,7 @@ class CompileUnit;
 
 /// \brief An object containing the capability of hashing and adding hash
 /// attributes onto a DIE.
-class DIEHash {
+class LLVM_LIBRARY_VISIBILITY DIEHash {
   // The entry for a particular attribute.
   struct AttrEntry {
     const DIEValue *Val;