Give internal classes hidden visibility.

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

llvm-svn: 190534

llvm/lib/Bitcode/Writer/ValueEnumerator.h

@@ -34,7 +34,7 @@ class ValueSymbolTable;
 class MDSymbolTable;
 class raw_ostream;
 
-class ValueEnumerator {
+class LLVM_LIBRARY_VISIBILITY ValueEnumerator {
 public:
   typedef std::vector<Type*> TypeList;