diff --git a/llvm/lib/CodeGen/AsmPrinter/DIE.h b/llvm/lib/CodeGen/AsmPrinter/DIE.h
index dc6a70a6bd6a..cad8b8955024 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DIE.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DIE.h
@@ -274,7 +274,7 @@ namespace llvm {
   };
 
   //===--------------------------------------------------------------------===//
-  /// DIEString - A string value DIE.
+  /// DIEString - A string value DIE. This DIE keeps string reference only.
   ///
   class DIEString : public DIEValue {
     const StringRef Str;
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index dcb5900fe907..da2b9c3682f4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -330,8 +330,8 @@ void DwarfDebug::addSInt(DIE *Die, unsigned Attribute,
   Die->addValue(Attribute, Form, Value);
 }
 
-/// addString - Add a string attribute data and value.
-///
+/// addString - Add a string attribute data and value. DIEString only
+/// keeps string reference. 
 void DwarfDebug::addString(DIE *Die, unsigned Attribute, unsigned Form,
                            const StringRef String) {
   DIEValue *Value = new DIEString(String);