Fix a bug in DebugInfo lib, extend a comment for one of the methods

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159707 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/DebugInfo/DWARFCompileUnit.h b/lib/DebugInfo/DWARFCompileUnit.h
index dc558da..e8a97ec 100644
--- a/lib/DebugInfo/DWARFCompileUnit.h
+++ b/lib/DebugInfo/DWARFCompileUnit.h
@@ -43,7 +43,7 @@
                    const DWARFAbbreviationDeclarationSet *abbrevs);
 
   /// extractDIEsIfNeeded - Parses a compile unit and indexes its DIEs if it
-  /// hasn't already been done.
+  /// hasn't already been done. Returns the number of DIEs parsed at this call.
   size_t extractDIEsIfNeeded(bool cu_die_only);
   void clear();
   void dump(raw_ostream &OS);