diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index e815931..3e3b802 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -227,6 +227,14 @@
   return false;
 }
 
+/// isCompileUnit - Return true if the specified tag is DW_TAG_compile_unit.
+bool DIDescriptor::isCompileUnit() const {
+  assert (!isNull() && "Invalid descriptor!");
+  unsigned Tag = getTag();
+
+  return Tag == dwarf::DW_TAG_compile_unit;
+}
+
 //===----------------------------------------------------------------------===//
 // Simple Descriptor Constructors and other Methods
 //===----------------------------------------------------------------------===//