Added a description for LocalMem pass in LocalMem.cpp

hpvm/lib/Transforms/LocalMem/LocalMem.cpp

@@ -6,6 +6,12 @@
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// This pass traverses the dataflow graph to recognize the allocation nodes which
+// allocate scratch memory. This pass does not make changes to the textual 
+// representation of HPVM IR.
+//
+//===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "LocalMem"
 #include "SupportHPVM/DFG2LLVM.h"