Added description about BuildDFG.h

hpvm/include/BuildDFG/BuildDFG.h

@@ -9,6 +9,12 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// This pass defines the BuildDFG pass which uses LLVM IR with HPVM intrinsics
+// to infer information about dataflow graph hierarchy and structure to construct
+// HPVM IR. 
+//
+//===----------------------------------------------------------------------===//
 
 #include "SupportHPVM/DFGraph.h"
 #include "llvm/IR/Function.h"