diff --git a/.travis.yml b/.travis.yml
index e7110ecb..31d6e49f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,7 @@ language: cpp
 
 os:
   - linux
-  - osx
+  #  - osx
 
 env:
   # code analysis
diff --git a/include/tvm/api_registry.h b/include/tvm/api_registry.h
new file mode 100644
index 00000000..c4c2a42e
--- /dev/null
+++ b/include/tvm/api_registry.h
@@ -0,0 +1,85 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ * \file api_registry.h
+ * \brief This file defines the TVM API registry.
+ *
+ *  The API registry stores type-erased functions.
+ *  Each registered function is automatically exposed
+ *  to front-end language(e.g. python).
+ *  Front-end can also pass callbacks as PackedFunc, or register
+ *  then into the same global registry in C++.
+ *  The goal is to mix the front-end language and the TVM back-end.
+ *
+ * \code
+ *   // register the function as MyAPIFuncName
+ *   TVM_REGISTER_API(MyAPIFuncName)
+ *   .set_body([](TVMArgs args, TVMRetValue* rv) {
+ *     // my code.
+ *   });
+ * \endcode
+ */
+#ifndef TVM_API_REGISTRY_H_
+#define TVM_API_REGISTRY_H_
+
+#include <dmlc/base.h>
+#include <string>
+#include "./base.h"
+#include "./runtime/packed_func.h"
+#include "./packed_func_ext.h"
+
+namespace tvm {
+
+/*! \brief Utility to register API. */
+class APIRegistry {
+ public:
+  /*!
+   * \brief set the body of the function to be f
+   * \param f The body of the function.
+   */
+  APIRegistry& set_body(PackedFunc f);  // NOLINT(*)
+  /*!
+   * \brief set the body of the function to be f
+   * \param f The body of the function.
+   */
+  APIRegistry& set_body(PackedFunc::FType f) {  // NOLINT(*)
+    return set_body(PackedFunc(f));
+  }
+  /*!
+   * \brief Register a function with given name
+   * \param name The name of the function.
+   */
+  static APIRegistry& __REGISTER__(const std::string& name);  // NOLINT(*)
+
+ private:
+  /*! \brief name of the function */
+  std::string name_;
+};
+
+/*!
+ * \brief Get API function by name.
+ *
+ * \param name The name of the function.
+ * \return the corresponding API function.
+ * \note It is really PackedFunc::GetGlobal under the hood.
+ */
+inline PackedFunc GetAPIFunc(const std::string& name) {
+  return PackedFunc::GetGlobal(name);
+}
+
+#define _TVM_REGISTER_VAR_DEF_                                          \
+  static DMLC_ATTRIBUTE_UNUSED ::tvm::APIRegistry& __make_TVMRegistry_
+
+/*!
+ * \brief Register API function globally.
+ * \code
+ *   TVM_REGISTER_API(MyPrint)
+ *   .set_body([](TVMArgs args, TVMRetValue* rv) {
+ *     // my code.
+ *   });
+ * \endcode
+ */
+#define TVM_REGISTER_API(OpName)                                 \
+  DMLC_STR_CONCAT(_TVM_REGISTER_VAR_DEF_, __COUNTER__) =         \
+      ::tvm::APIRegistry::__REGISTER__(#OpName)
+}  // namespace tvm
+#endif  // TVM_API_REGISTRY_H_
diff --git a/include/tvm/c_api.h b/include/tvm/c_api.h
index 30fd3ea1..e8abf552 100644
--- a/include/tvm/c_api.h
+++ b/include/tvm/c_api.h
@@ -2,6 +2,13 @@
  *  Copyright (c) 2016 by Contributors
  * \file c_api.h
  * \brief C API of TVM DSL
+ *
+ * \note The API is designed in a minimum way.
+ *  Most of the API functions are registered and can be pulled out.
+ *
+ *  The common flow is:
+ *   - Use TVMFuncListGlobalNames to get global function name
+ *   - Use TVMFuncCall to call these functions.
  */
 #ifndef TVM_C_API_H_
 #define TVM_C_API_H_
@@ -9,76 +16,9 @@
 #include "./runtime/c_runtime_api.h"
 
 TVM_EXTERN_C {
-/*! \brief handle to functions */
-typedef void* APIFuncHandle;
 /*! \brief handle to node */
 typedef void* NodeHandle;
 
-/*!
- * \brief List all the node function name
- * \param out_size The number of functions
- * \param out_array The array of function names.
- * \return 0 when success, -1 when failure happens
- */
-TVM_DLL int TVMListAPIFuncNames(int *out_size,
-                                const char*** out_array);
-/*!
- * \brief get function handle by name
- * \param name The name of function
- * \param handle The returning function handle
- * \return 0 when success, -1 when failure happens
- */
-TVM_DLL int TVMGetAPIFuncHandle(const char* name,
-                                APIFuncHandle *handle);
-
-/*!
- * \brief Get the detailed information about function.
- * \param handle The operator handle.
- * \param real_name The returned name of the function.
- *   This name is not the alias name of the atomic symbol.
- * \param description The returned description of the symbol.
- * \param num_doc_args Number of arguments that contain documents.
- * \param arg_names Name of the arguments of doc args
- * \param arg_type_infos Type informations about the arguments.
- * \param arg_descriptions Description information about the arguments.
- * \param return_type Return type of the function, if any.
- * \return 0 when success, -1 when failure happens
- */
-TVM_DLL int TVMGetAPIFuncInfo(APIFuncHandle handle,
-                              const char **real_name,
-                              const char **description,
-                              int *num_doc_args,
-                              const char ***arg_names,
-                              const char ***arg_type_infos,
-                              const char ***arg_descriptions,
-                              const char **return_type);
-
-/*!
- * \brief Push an argument to the function calling stack.
- * If push fails, the stack will be reset to empty
- *
- * \param arg The argument
- * \param type_code The type_code of argument as in TVMTypeCode
- * \return 0 when success, -1 when failure happens
- * \note API calls always exchanges with type bits=64, lanes=1
- */
-TVM_DLL int TVMAPIPushStack(TVMValue arg,
-                            int type_code);
-
-/*!
- * \brief call a function by using arguments in the stack.
- * The stack will be cleanup to empty after this call, whether the call is successful.
- *
- * \param handle The function handle
- * \param ret_val The return value.
- * \param ret_type_code the type code of return value.
- * \return 0 when success, -1 when failure happens
- * \note API calls always exchanges with type bits=64, lanes=1
- */
-TVM_DLL int TVMAPIFuncCall(APIFuncHandle handle,
-                           TVMValue* ret_val,
-                           int* ret_type_code);
-
 /*!
  * \brief free the node handle
  * \param handle The node handle to be freed.
diff --git a/include/tvm/expr.h b/include/tvm/expr.h
index e6057b29..67b5dcdd 100644
--- a/include/tvm/expr.h
+++ b/include/tvm/expr.h
@@ -12,6 +12,7 @@
 #include <string>
 #include <algorithm>
 #include "./base.h"
+#include "./runtime/packed_func.h"
 
 namespace tvm {
 
diff --git a/include/tvm/packed_func_ext.h b/include/tvm/packed_func_ext.h
new file mode 100644
index 00000000..edaf43a8
--- /dev/null
+++ b/include/tvm/packed_func_ext.h
@@ -0,0 +1,196 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ * \file packed_func_ext.h
+ * \brief Extension package to PackedFunc
+ *   This enales pass NodeRef types into/from PackedFunc.
+ */
+#ifndef TVM_PACKED_FUNC_EXT_H_
+#define TVM_PACKED_FUNC_EXT_H_
+
+#include <sstream>
+#include <string>
+#include <memory>
+#include <type_traits>
+
+#include "./base.h"
+#include "./expr.h"
+
+namespace tvm {
+using runtime::TVMArgs;
+using runtime::TVMRetValue;
+using runtime::PackedFunc;
+
+namespace runtime {
+/*!
+ * \brief Runtime type checker for node type.
+ * \tparam T the type to be checked.
+ */
+template<typename T>
+struct NodeTypeChecker {
+  static inline bool Check(Node* sptr) {
+    // This is the only place in the project where RTTI is used
+    // It can be turned off, but will make non strict checking.
+    // TODO(tqchen) possibly find alternative to turn of RTTI
+    using ContainerType = typename T::ContainerType;
+    return (dynamic_cast<ContainerType*>(sptr) != nullptr);
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    using ContainerType = typename T::ContainerType;
+    os << ContainerType::_type_key;
+  }
+};
+
+template<typename T>
+struct NodeTypeChecker<Array<T> > {
+  static inline bool Check(Node* sptr) {
+    if (sptr == nullptr) return false;
+    if (!sptr->is_type<ArrayNode>()) return false;
+    ArrayNode* n = static_cast<ArrayNode*>(sptr);
+    for (const auto& p : n->data) {
+      if (!NodeTypeChecker<T>::Check(p.get())) return false;
+    }
+    return true;
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    os << "array<";
+    NodeTypeChecker<T>::PrintName(os);
+    os << ">";
+  }
+};
+
+template<typename K, typename V>
+struct NodeTypeChecker<Map<K, V> > {
+  static inline bool Check(Node* sptr) {
+    if (sptr == nullptr) return false;
+    if (!sptr->is_type<MapNode>()) return false;
+    MapNode* n = static_cast<MapNode*>(sptr);
+    for (const auto& kv : n->data) {
+      if (!NodeTypeChecker<K>::Check(kv.first.get())) return false;
+      if (!NodeTypeChecker<V>::Check(kv.second.get())) return false;
+    }
+    return true;
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    os << "map<";
+    NodeTypeChecker<K>::PrintName(os);
+    os << ',';
+    NodeTypeChecker<V>::PrintName(os);
+    os << '>';
+  }
+};
+
+template<typename T>
+inline std::string NodeTypeName() {
+  std::ostringstream os;
+  NodeTypeChecker<T>::PrintName(os);
+  return os.str();
+}
+
+// extensions for tvm arg value
+
+template<typename TNodeRef, typename>
+inline TVMArgValue::operator TNodeRef() const {
+  static_assert(
+      std::is_base_of<NodeRef, TNodeRef>::value,
+      "Conversion only works for NodeRef");
+  if (type_code_ == kNull) return TNodeRef();
+  TVM_CHECK_TYPE_CODE(type_code_, kNodeHandle);
+  std::shared_ptr<Node>& sptr = *ptr<std::shared_ptr<Node> >();
+  CHECK(NodeTypeChecker<TNodeRef>::Check(sptr.get()))
+      << "Expected type " << NodeTypeName<TNodeRef>()
+      << " but get " << sptr->type_key();
+  return TNodeRef(sptr);
+}
+
+inline TVMArgValue::operator Halide::Expr() const {
+  if (type_code_ == kNull) return Expr();
+  if (type_code_ == kInt) {
+    return Expr(static_cast<int>(value_.v_int64));
+  }
+  if (type_code_ == kFloat) {
+    return Expr(static_cast<float>(value_.v_float64));
+  }
+  TVM_CHECK_TYPE_CODE(type_code_, kNodeHandle);
+  std::shared_ptr<Node>& sptr = *ptr<std::shared_ptr<Node> >();
+  if (sptr->is_type<IterVarNode>()) {
+    return IterVar(sptr)->var;
+  }
+  CHECK(NodeTypeChecker<Expr>::Check(sptr.get()))
+      << "Expected type " << NodeTypeName<Expr>()
+      << " but get " << sptr->type_key();
+  return Expr(sptr);
+}
+
+inline std::shared_ptr<Node>& TVMArgValue::node_sptr() {
+  TVM_CHECK_TYPE_CODE(type_code_, kNodeHandle);
+  return *ptr<std::shared_ptr<Node> >();
+}
+
+
+template<typename TNodeRef, typename>
+inline bool TVMArgValue::IsNodeType() const {
+  TVM_CHECK_TYPE_CODE(type_code_, kNodeHandle);
+  std::shared_ptr<Node>& sptr =
+      *ptr<std::shared_ptr<Node> >();
+  return NodeTypeChecker<TNodeRef>::Check(sptr.get());
+}
+
+// extensions for TVMRetValue
+inline TVMRetValue& TVMRetValue::operator=(
+    const std::shared_ptr<Node>& other) {
+  SwitchToClass<std::shared_ptr<Node> >(kNodeHandle, other);
+  return *this;
+}
+
+inline TVMRetValue& TVMRetValue::operator=(const NodeRef& other) {
+  SwitchToClass<std::shared_ptr<Node> >(kNodeHandle, other.node_);
+  return *this;
+}
+
+template<typename TNodeRef, typename>
+inline TVMRetValue::operator TNodeRef() const {
+  static_assert(
+      std::is_base_of<NodeRef, TNodeRef>::value,
+      "Conversion only works for NodeRef");
+  if (type_code_ == kNull) return TNodeRef();
+  TVM_CHECK_TYPE_CODE(type_code_, kNodeHandle);
+  return TNodeRef(*ptr<std::shared_ptr<Node> >());
+}
+
+inline void TVMArgsSetter::operator()(size_t i, NodeRef& other) const {  // NOLINT(*)
+  values_[i].v_handle = &(other.node_);
+  type_codes_[i] = kNodeHandle;
+}
+
+// Type related stuffs
+inline Type TVMType2Type(TVMType t) {
+  return Type(static_cast<halide_type_code_t>(t.code), t.bits, t.lanes);
+}
+
+inline TVMType Type2TVMType(Type t) {
+  TVMType ret;
+  ret.code = static_cast<uint8_t>(t.code());
+  ret.bits = static_cast<uint8_t>(t.bits());
+  ret.lanes = static_cast<uint16_t>(t.lanes());
+  return ret;
+}
+
+inline TVMRetValue& TVMRetValue::operator=(const Halide::Type& t) {
+  return this->operator=(Type2TVMType(t));
+}
+
+inline TVMRetValue::operator Halide::Type() const {
+  return TVMType2Type(operator TVMType());
+}
+
+inline TVMArgValue::operator Halide::Type() const {
+  return TVMType2Type(operator TVMType());
+}
+
+inline void TVMArgsSetter::operator()(
+    size_t i, const Halide::Type& t) const {
+  this->operator()(i, Type2TVMType(t));
+}
+}  // namespace runtime
+}  // namespace tvm
+#endif  // TVM_PACKED_FUNC_EXT_H_
diff --git a/include/tvm/runtime/c_runtime_api.h b/include/tvm/runtime/c_runtime_api.h
index f3e9eee8..5151fb53 100644
--- a/include/tvm/runtime/c_runtime_api.h
+++ b/include/tvm/runtime/c_runtime_api.h
@@ -36,18 +36,6 @@
 TVM_EXTERN_C {
 /*! \brief type of array index. */
 typedef uint32_t tvm_index_t;
-
-/*!
- * \brief Union type of values
- *  being passed through API and function calls.
- */
-typedef union {
-  int64_t v_int64;
-  double v_float64;
-  void* v_handle;
-  const char* v_str;
-} TVMValue;
-
 /*!
  * \brief The type code in TVMType
  * \note TVMType is used in two places.
@@ -60,9 +48,11 @@ typedef enum {
   // The next few fields are extension types
   // that is used by TVM API calls.
   kNull = 4U,
-  kNodeHandle = 5U,
-  kStr = 6U,
-  kFuncHandle = 7U
+  kArrayHandle = 5U,
+  kTVMType = 6U,
+  kNodeHandle = 7U,
+  kStr = 8U,
+  kFuncHandle = 9U
 } TVMTypeCode;
 
 /*!
@@ -77,13 +67,25 @@ typedef enum {
  */
 typedef struct {
   /*! \brief type code, in TVMTypeCode */
-  uint8_t type_code;
+  uint8_t code;
   /*! \brief number of bits of the type */
   uint8_t bits;
   /*! \brief number of lanes, */
   uint16_t lanes;
 } TVMType;
 
+/*!
+ * \brief Union type of values
+ *  being passed through API and function calls.
+ */
+typedef union {
+  int64_t v_int64;
+  double v_float64;
+  void* v_handle;
+  const char* v_str;
+  TVMType v_type;
+} TVMValue;
+
 /*!
  * \brief The device type
  */
@@ -133,11 +135,10 @@ typedef struct {
  * can be NULL, which indicates the default one.
  */
 typedef void* TVMStreamHandle;
-/*!
- * \brief Pointer to function handle that points to
- * a generated TVM function.
- */
+/*! \brief Handle to packed function handle. */
 typedef void* TVMFunctionHandle;
+/*! \brief Handle to hold return value. */
+typedef void* TVMRetValueHandle;
 /*! \brief the array handle */
 typedef TVMArray* TVMArrayHandle;
 
@@ -228,20 +229,45 @@ TVM_DLL int TVMSynchronize(TVMContext ctx, TVMStreamHandle stream);
 TVM_DLL int TVMFuncFree(TVMFunctionHandle func);
 
 /*!
- * \brief Call a function whose parameters are all packed.
+ * \brief Call a Packed TVM Function.
  *
  * \param func node handle of the function.
- * \param args The arguments
+ * \param arg_values The arguments
  * \param type_codes The type codes of the arguments
  * \param num_args Number of arguments.
  *
+ * \param ret_val The return value.
+ * \param ret_type_code the type code of return value.
+ *
  * \return 0 when success, -1 when failure happens
  * \note TVM calls always exchanges with type bits=64, lanes=1
+ *
+ * \note API calls always exchanges with type bits=64, lanes=1
+ *   If API call returns container handles (e.g. FunctionHandle)
+ *   these handles should be managed by the front-end.
+ *   The front-end need to call free function (e.g. TVMFuncFree)
+ *   to free these handles.
  */
 TVM_DLL int TVMFuncCall(TVMFunctionHandle func,
-                        TVMValue* args,
+                        TVMValue* arg_values,
                         int* type_codes,
-                        int num_args);
+                        int num_args,
+                        TVMValue* ret_val,
+                        int* ret_type_code);
+
+/*!
+ * \brief Set the return value of TVMPackedCFunc.
+ *
+ *  This function is called by TVMPackedCFunc to set the return value.
+ *  When this function is not called, the function returns null by default.
+ *
+ * \param ret The return value handle, pass by ret in TVMPackedCFunc
+ * \param value The value to be returned.
+ * \param type_code The type of the value to be returned.
+ */
+TVM_DLL int TVMCFuncSetReturn(TVMRetValueHandle ret,
+                              TVMValue value,
+                              int type_code);
 
 /*!
  * \brief C type of packed function.
@@ -249,10 +275,17 @@ TVM_DLL int TVMFuncCall(TVMFunctionHandle func,
  * \param args The arguments
  * \param type_codes The type codes of the arguments
  * \param num_args Number of arguments.
+ * \param ret The return value handle.
  * \param resource_handle The handle additional resouce handle from fron-end.
+ *
+ * \sa TVMCFuncSetReturn
  */
 typedef void (*TVMPackedCFunc)(
-    TVMValue* args, int* type_codes, int num_args, void* resource_handle);
+    TVMValue* args,
+    int* type_codes,
+    int num_args,
+    TVMRetValueHandle ret,
+    void* resource_handle);
 
 /*!
  * \brief C callback to free the resource handle in C packed function.
@@ -291,8 +324,20 @@ TVM_DLL int TVMFuncRegisterGlobal(const char* name, TVMFunctionHandle f);
  *
  * \param name The name of the function.
  * \param out the result function pointer.
+ *
+ * \note The function handle of global function is managed by TVM runtime,
+ *  So TVMFuncFree is should not be called when it get deleted.
  */
 TVM_DLL int TVMFuncGetGlobal(const char* name, TVMFunctionHandle* out);
+
+/*!
+ * \brief List all the globally registered function name
+ * \param out_size The number of functions
+ * \param out_array The array of function names.
+ * \return 0 when success, -1 when failure happens
+ */
+TVM_DLL int TVMFuncListGlobalNames(int *out_size,
+                                   const char*** out_array);
 }  // TVM_EXTERN_C
 
 #endif  // TVM_RUNTIME_C_RUNTIME_API_H_
diff --git a/include/tvm/runtime/packed_func.h b/include/tvm/runtime/packed_func.h
index b4868f75..e3a391c8 100644
--- a/include/tvm/runtime/packed_func.h
+++ b/include/tvm/runtime/packed_func.h
@@ -1,19 +1,41 @@
 /*!
- *  Copyright (c) 2016 by Contributors
+ *  Copyright (c) 2017 by Contributors
  * \file packed_func.h
  * \brief Runtime related c++ class.
  */
 #ifndef TVM_RUNTIME_PACKED_FUNC_H_
 #define TVM_RUNTIME_PACKED_FUNC_H_
 
+#include <dmlc/logging.h>
 #include <functional>
 #include <tuple>
 #include <vector>
 #include <string>
+#include <limits>
+#include <memory>
+#include <type_traits>
 #include "./c_runtime_api.h"
 
+namespace Halide {
+// Forward declare type for extensions
+// The header works fine without depending on this.
+struct Type;
+struct Expr;
+}
+
 namespace tvm {
+// Forward declare NodeRef and Node for extensions.
+// This header works fine without depend on NodeRef
+// as long as it is not used.
+class Node;
+class NodeRef;
+
 namespace runtime {
+// forward declarations
+class TVMArgs;
+class TVMArgValue;
+class TVMRetValue;
+class TVMArgsSetter;
 
 /*!
  * \brief Packed function is a type-erased function.
@@ -25,8 +47,25 @@ namespace runtime {
  */
 class PackedFunc {
  public:
-  /*! \brief The internal std::function */
-  using FType = std::function<void(const TVMValue* args, const int* type_codes, int num_args)>;
+  /*!
+   * \brief The internal std::function
+   * \param args The arguments to the function.
+   * \param rv The return value.
+   *
+   * \code
+   *   // Example code on how to implemented FType
+   *   void MyPackedFunc(TVMArgs args, TVMRetValue* rv) {
+   *     // automatically convert arguments to desired type.
+   *     int a0 = args[0];
+   *     float a1 = args[1];
+   *     ...
+   *     // automatically assign values to rv
+   *     std::string my_return_value = "x";
+   *     *rv = my_return_value;
+   *   }
+   * \endcode
+   */
+  using FType = std::function<void (TVMArgs args, TVMRetValue* rv)>;
   /*! \brief default constructor */
   PackedFunc() {}
   /*!
@@ -38,16 +77,24 @@ class PackedFunc {
    * \brief Call packed function by directly passing in unpacked format.
    * \param args Arguments to be passed.
    * \tparam Args arguments to be passed.
+   *
+   * \code
+   *   // Example code on how to call packed function
+   *   void CallPacked(PackedFunc f) {
+   *     // call like normal functions by pass in arguments
+   *     // return value is automatically converted back
+   *     int rvalue = f(1, 2.0);
+   *   }
+   * \endcode
    */
   template<typename... Args>
-  inline void operator()(Args&& ...args) const;
+  inline TVMRetValue operator()(Args&& ...args) const;
   /*!
    * \brief Call the function in packed format.
    * \param args The arguments
-   * \param type_codes The type_codes of the arguments
-   * \param num_args Number of arguments.
+   * \param rv The return value.
    */
-  inline void CallPacked(const TVMValue* args, const int* type_codes, int num_args) const;
+  inline void CallPacked(TVMArgs args, TVMRetValue* rv) const;
   /*! \return the internal body function */
   inline FType body() const;
   /*!
@@ -74,82 +121,552 @@ class PackedFunc {
   FType body_;
 };
 
-// implementations
-inline void PackedFunc::CallPacked(
-    const TVMValue* args, const int* type_codes, int num_args) const {
-  body_(args, type_codes, num_args);
+/*! \brief Arguments into TVM functions. */
+class TVMArgs {
+ public:
+  const TVMValue* values;
+  const int* type_codes;
+  int num_args;
+  /*!
+   * \brief constructor
+   * \param values The argument values
+   * \param type_codes The argument type codes
+   * \param num_args number of arguments.
+   */
+  TVMArgs(const TVMValue* values,
+          const int* type_codes,
+          int num_args)
+      : values(values),
+        type_codes(type_codes),
+        num_args(num_args) { }
+  /*! \return size of the arguments */
+  inline int size() const;
+  /*!
+   * \brief Get i-th argument
+   * \param i the index.
+   * \return the ith argument.
+   */
+  inline TVMArgValue operator[](int i) const;
+};
+
+/*!
+ * \brief Convert type code to its name
+ * \param type_code The type code .
+ * \return The name of type code.
+ */
+inline const char* TypeCode2Str(int type_code);
+
+/*!
+ * \brief convert a string to TVM type.
+ * \param s The string to be converted.
+ * \return The corresponding tvm type.
+ */
+inline TVMType String2TVMType(std::string s);
+
+// macro to check type code.
+#define TVM_CHECK_TYPE_CODE(CODE, T)                           \
+  CHECK_EQ(CODE, T) << " expected "                            \
+  << TypeCode2Str(T) << " but get " << TypeCode2Str(CODE)      \
+
+/*!
+ * \brief Internal base class to
+ *  handle conversion to POD values.
+ */
+class TVMPODValue_ {
+ public:
+  operator double() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kFloat);
+    return value_.v_float64;
+  }
+  operator int64_t() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kInt);
+    return value_.v_int64;
+  }
+  operator uint64_t() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kInt);
+    return value_.v_int64;
+  }
+  operator int() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kInt);
+    CHECK_LE(value_.v_int64,
+             std::numeric_limits<int>::max());
+    return static_cast<int>(value_.v_int64);
+  }
+  operator bool() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kInt);
+    return value_.v_int64 != 0;
+  }
+  operator void*() const {
+    if (type_code_ == kNull) return nullptr;
+    if (type_code_ == kArrayHandle) return value_.v_handle;
+    TVM_CHECK_TYPE_CODE(type_code_, kHandle);
+    return value_.v_handle;
+  }
+  operator TVMArray*() const {
+    if (type_code_ == kNull) return nullptr;
+    TVM_CHECK_TYPE_CODE(type_code_, kArrayHandle);
+    return static_cast<TVMArray*>(value_.v_handle);
+  }
+  int type_code() const {
+    return type_code_;
+  }
+
+ protected:
+  friend class TVMArgsSetter;
+  friend class TVMRetValue;
+  TVMPODValue_() : type_code_(kNull) {}
+  TVMPODValue_(TVMValue value, int type_code)
+      : value_(value), type_code_(type_code) {}
+  /*!
+   * \brief return handle as specific pointer type.
+   * \tparam T the data type.
+   * \return The pointer type.
+   */
+  template<typename T>
+  T* ptr() const {
+    return static_cast<T*>(value_.v_handle);
+  }
+  /*! \brief The value */
+  TVMValue value_;
+  /*! \brief the type code */
+  int type_code_;
+};
+
+/*!
+ * \brief A single argument value to PackedFunc.
+ *  Containing both type_code and TVMValue
+ *
+ *  Provides utilities to do type cast into other types.
+ */
+class TVMArgValue : public TVMPODValue_ {
+ public:
+  /*!
+   * \brief constructor
+   * \param value of the function
+   * \param type_code The type code.
+   */
+  TVMArgValue(TVMValue value, int type_code)
+      : TVMPODValue_(value, type_code) {
+  }
+  // reuse converter from parent
+  using TVMPODValue_::operator double;
+  using TVMPODValue_::operator int64_t;
+  using TVMPODValue_::operator uint64_t;
+  using TVMPODValue_::operator int;
+  using TVMPODValue_::operator bool;
+  using TVMPODValue_::operator void*;
+  using TVMPODValue_::operator TVMArray*;
+  // conversion operator.
+  operator std::string() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kStr);
+    return std::string(value_.v_str);
+  }
+  operator TVMType() const {
+    if (type_code_ == kStr) {
+      return String2TVMType(operator std::string());
+    }
+    TVM_CHECK_TYPE_CODE(type_code_, kTVMType);
+    return value_.v_type;
+  }
+  operator PackedFunc() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kFuncHandle);
+    return *ptr<PackedFunc>();
+  }
+  const TVMValue& value() const {
+    return value_;
+  }
+  // NodeRef related extenstions: in tvm/packed_func_ext.h
+  template<typename TNodeRef,
+           typename = typename std::enable_if<
+             std::is_class<TNodeRef>::value>::type>
+  inline operator TNodeRef() const;
+  template<typename TNodeRef,
+           typename = typename std::enable_if<
+             std::is_class<TNodeRef>::value>::type>
+  inline bool IsNodeType() const;
+  inline operator Halide::Type() const;
+  inline operator Halide::Expr() const;
+  // get internal node ptr, if it is node
+  inline std::shared_ptr<Node>& node_sptr();
+};
+
+/*!
+ * \brief Return Value container,
+ *  Unlike TVMArgValue, which only holds reference and do not delete
+ *  the underlying container during destruction.
+ *
+ *  TVMRetValue holds value and will manage the underlying containers
+ *  when it stores a complicated data type.
+ */
+class TVMRetValue : public TVMPODValue_ {
+ public:
+  /*! \brief default constructor */
+  TVMRetValue() {}
+  /*!
+   * \brief move constructor from anoter return value.
+   * \param other The other return value.
+   */
+  TVMRetValue(TVMRetValue&& other)
+      : TVMPODValue_(other.value_, other.type_code_) {
+    other.type_code_ = kNull;
+  }
+  /*! \brief destructor */
+  ~TVMRetValue() {
+    this->Clear();
+  }
+  // reuse converter from parent
+  using TVMPODValue_::operator double;
+  using TVMPODValue_::operator int64_t;
+  using TVMPODValue_::operator uint64_t;
+  using TVMPODValue_::operator int;
+  using TVMPODValue_::operator bool;
+  using TVMPODValue_::operator void*;
+  using TVMPODValue_::operator TVMArray*;
+  // Disable copy and assign from another value, but allow move.
+  TVMRetValue(const TVMRetValue& other) {
+    this->Assign(other);
+  }
+  // conversion operators
+  operator std::string() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kStr);
+    return *ptr<std::string>();
+  }
+  operator TVMType() const {
+    if (type_code_ == kStr) {
+      return String2TVMType(operator std::string());
+    }
+    TVM_CHECK_TYPE_CODE(type_code_, kTVMType);
+    return value_.v_type;
+  }
+  operator PackedFunc() const {
+    TVM_CHECK_TYPE_CODE(type_code_, kFuncHandle);
+    return *ptr<PackedFunc>();
+  }
+  // Assign operators
+  TVMRetValue& operator=(TVMRetValue&& other) {
+    this->Clear();
+    value_ = other.value_;
+    type_code_ = other.type_code_;
+    other.type_code_ = kNull;
+    return *this;
+  }
+  TVMRetValue& operator=(double value) {
+    this->SwitchToPOD(kFloat);
+    value_.v_float64 = value;
+    return *this;
+  }
+  TVMRetValue& operator=(std::nullptr_t value) {
+    this->SwitchToPOD(kNull);
+    value_.v_handle = value;
+    return *this;
+  }
+  TVMRetValue& operator=(void* value) {
+    this->SwitchToPOD(kHandle);
+    value_.v_handle = value;
+    return *this;
+  }
+  TVMRetValue& operator=(int64_t value) {
+    this->SwitchToPOD(kInt);
+    value_.v_int64 = value;
+    return *this;
+  }
+  TVMRetValue& operator=(int value) {
+    this->SwitchToPOD(kInt);
+    value_.v_int64 = value;
+    return *this;
+  }
+  TVMRetValue& operator=(TVMType t) {
+    this->SwitchToPOD(kTVMType);
+    value_.v_type = t;
+    return *this;
+  }
+  TVMRetValue& operator=(bool value) {
+    this->SwitchToPOD(kInt);
+    value_.v_int64 = value;
+    return *this;
+  }
+  TVMRetValue& operator=(std::string value) {
+    this->SwitchToClass(kStr, value);
+    return *this;
+  }
+  TVMRetValue& operator=(PackedFunc f) {
+    this->SwitchToClass(kFuncHandle, f);
+    return *this;
+  }
+  TVMRetValue& operator=(const TVMRetValue& other) {  // NOLINT(*0
+    this->Assign(other);
+    return *this;
+  }
+  TVMRetValue& operator=(TVMArgValue other) {
+    this->Assign(other);
+    return *this;
+  }
+  /*!
+   * \brief Move the value back to front-end via C API.
+   *  This marks the current container as null.
+   *  The managed resources is moved to front-end and
+   *  the front end should take charge in managing them.
+   *
+   * \param ret_value The return value.
+   * \param ret_type_code The return type code.
+   */
+  void MoveToCHost(TVMValue* ret_value,
+                   int* ret_type_code) {
+    // cannot move str; need specially handle.
+    CHECK(type_code_ != kStr);
+    *ret_value = value_;
+    *ret_type_code = type_code_;
+    type_code_ = kNull;
+  }
+  // NodeRef related extenstions: in tvm/packed_func_ext.h
+  inline TVMRetValue& operator=(const NodeRef& other);
+  inline TVMRetValue& operator=(const std::shared_ptr<Node>& other);
+  template<typename TNodeRef,
+           typename = typename std::enable_if<
+             std::is_class<TNodeRef>::value>::type>
+  inline operator TNodeRef() const;
+  // type related
+  inline operator Halide::Type() const;
+  inline TVMRetValue& operator=(const Halide::Type& other);
+
+ private:
+  template<typename T>
+  void Assign(const T& other) {
+    switch (other.type_code()) {
+      case kStr: {
+        SwitchToClass<std::string>(kStr, other);
+        break;
+      }
+      case kFuncHandle: {
+        SwitchToClass<PackedFunc>(kFuncHandle, other);
+        break;
+      }
+      case kNodeHandle: {
+        SwitchToClass<std::shared_ptr<Node> >(
+            kNodeHandle, *other.template ptr<std::shared_ptr<Node> >());
+        break;
+      }
+      default: {
+        SwitchToPOD(other.type_code());
+        value_ = other.value_;
+        break;
+      }
+    }
+  }
+
+  // get the internal container.
+  void SwitchToPOD(int type_code) {
+    if (type_code_ != type_code) {
+      this->Clear();
+      type_code_ = type_code;
+    }
+  }
+  template<typename T>
+  void SwitchToClass(int type_code, T v) {
+    if (type_code_ != type_code) {
+      this->Clear();
+      type_code_ = type_code;
+      value_.v_handle = new T(v);
+    } else {
+      *static_cast<T*>(value_.v_handle) = v;
+    }
+  }
+  void Clear() {
+    if (type_code_ == kNull) return;
+    switch (type_code_) {
+      case kStr: delete ptr<std::string>(); break;
+      case kFuncHandle: delete ptr<PackedFunc>(); break;
+      case kNodeHandle: delete ptr<std::shared_ptr<Node> >(); break;
+    }
+    type_code_ = kNull;
+  }
+};
+
+// implementation details
+inline const char* TypeCode2Str(int type_code) {
+  switch (type_code) {
+    case kInt: return "int";
+    case kFloat: return "float";
+    case kStr: return "str";
+    case kHandle: return "Handle";
+    case kNull: return "NULL";
+    case kNodeHandle: return "NodeHandle";
+    case kArrayHandle: return "ArrayHandle";
+    case kTVMType: return "TVMType";
+    case kFuncHandle: return "FunctionHandle";
+    default: LOG(FATAL) << "unknown type_code="
+                        << static_cast<int>(type_code); return "";
+  }
+}
+
+inline TVMType String2TVMType(std::string s) {
+  TVMType t;
+  t.bits = 32; t.lanes = 1;
+  const char* scan;
+  if (s.substr(0, 3) == "int") {
+    t.code = kInt;  scan = s.c_str() + 3;
+  } else if (s.substr(0, 4) == "uint") {
+    t.code = kUInt; scan = s.c_str() + 4;
+  } else if (s.substr(0, 5) == "float") {
+    t.code = kFloat; scan = s.c_str() + 5;
+  } else if (s == "handle") {
+    t.code = kHandle;
+    t.bits = 64;  // handle uses 64 bit by default.
+    scan = s.c_str() + 6;
+  } else {
+    scan = s.c_str();
+    LOG(FATAL) << "unknown type " << s;
+  }
+  unsigned bits = t.bits, lanes = t.lanes;
+  sscanf(scan, "%ux%u", &bits, &lanes);
+  t.bits = static_cast<uint8_t>(bits);
+  t.lanes = static_cast<uint16_t>(lanes);
+  return t;
+}
+
+inline TVMArgValue TVMArgs::operator[](int i) const {
+  CHECK_LT(i, num_args)
+      << "not enough argument passed, "
+      << num_args << " passed"
+      << "but request arg" << i;
+  return TVMArgValue(values[i], type_codes[i]);
+}
+
+inline int TVMArgs::size() const {
+  return num_args;
+}
+
+inline void PackedFunc::CallPacked(TVMArgs args, TVMRetValue* rv) const {
+  body_(args, rv);
 }
 
 inline PackedFunc::FType PackedFunc::body() const {
   return body_;
 }
 
+// internal namespace
+namespace detail {
 template<bool stop, std::size_t I, typename F, typename ...Args>
-struct for_each_dispatcher_ {
-  static inline void run(const std::tuple<Args...>& args, F f) {
+struct for_each_dispatcher {
+  static void run(std::tuple<Args...>& args, const F& f) {  // NOLINT(*)
     f(I, std::get<I>(args));
-    for_each_dispatcher_<(I + 1) == sizeof...(Args), (I+1), F, Args...>::run(args, f);
+    for_each_dispatcher<(I + 1) == sizeof...(Args), (I+1), F, Args...>::run(args, f);
   }
 };
 
 template<std::size_t I, typename F, typename ...Args>
-struct for_each_dispatcher_<true, I, F, Args...>  {
-  static inline void run(const std::tuple<Args...>& args, F f) {}
+struct for_each_dispatcher<true, I, F, Args...>  {
+  static void run(std::tuple<Args...>& args, const F& f) {}  // NOLINT(*)
 };
+}  // namespace detail
 
 template<typename F, typename ...Args>
-inline void for_each(const std::tuple<Args...>& args, F f) {
-  for_each_dispatcher_<sizeof...(Args) == 0, 0, F, Args...>::run(args, f);
+inline void for_each(std::tuple<Args...>& args, const F& f) {  // NOLINT(*)
+  detail::for_each_dispatcher<sizeof...(Args) == 0, 0, F, Args...>::run(args, f);
 }
 
-namespace arg_setter {
-template<typename T>
-inline void Set(TVMValue& arg, int& t, T v);  // NOLINT(*)
-template<>
-inline void Set<double>(TVMValue& arg, int& t, double value) {  // NOLINT(*)
-  arg.v_float64 = value;
-  t = kFloat;
-}
-template<>
-inline void Set<int>(TVMValue& arg, int& t, int value) {  // NOLINT(*)
-  arg.v_int64 = value;
-  t = kInt;
-}
-template<>
-inline void Set<long>(TVMValue& arg, int& t, long value) {  // NOLINT(*)
-  arg.v_int64 = value;
-  t = kInt;
-}
-template<>
-inline void Set<TVMArray*>(TVMValue& arg, int& t, TVMArray* value) {  // NOLINT(*)
-  arg.v_handle = value;
-  t = kHandle;
-}
-template<>
-inline void Set<void*>(TVMValue& arg, int& t, void* value) {  // NOLINT(*)
-  arg.v_handle = value;
-  t = kHandle;
-}
-}  // namespace arg_setter
-
-struct PackedFuncArgSetter {
-  TVMValue* args;
-  int* type_codes;
-  template<typename T>
-  inline void operator()(size_t i, T v) const {
-    arg_setter::Set(args[i], type_codes[i], v);
+/* \brief argument settter to PackedFunc */
+class TVMArgsSetter {
+ public:
+  TVMArgsSetter(TVMValue* values, int* type_codes)
+      : values_(values), type_codes_(type_codes) {}
+  // setters for POD types
+  template<typename T,
+           typename = typename std::enable_if<std::is_integral<T>::value>::type>
+  void operator()(size_t i, T value) const {
+    values_[i].v_int64 = static_cast<int64_t>(value);
+    type_codes_[i] = kInt;
   }
+  void operator()(size_t i, uint64_t value) const {
+    values_[i].v_int64 = static_cast<int64_t>(value);
+    CHECK_LE(value,
+             static_cast<uint64_t>(std::numeric_limits<int64_t>::max()));
+    type_codes_[i] = kInt;
+  }
+  void operator()(size_t i, double value) const {
+    values_[i].v_float64 = value;
+    type_codes_[i] = kFloat;
+  }
+  void operator()(size_t i, std::nullptr_t value) const {
+    values_[i].v_handle = value;
+    type_codes_[i] = kNull;
+  }
+  void operator()(size_t i, const TVMArgValue& value) const {
+    values_[i] = value.value_;
+    type_codes_[i] = value.type_code_;
+  }
+  void operator()(size_t i, void* value) const {
+    values_[i].v_handle = value;
+    type_codes_[i] = kHandle;
+  }
+  void operator()(size_t i, TVMArray* value) const {
+    values_[i].v_handle = value;
+    type_codes_[i] = kArrayHandle;
+  }
+  void operator()(size_t i, TVMType value) const {
+    values_[i].v_type = value;
+    type_codes_[i] = kTVMType;
+  }
+  void operator()(size_t i, const char* value) const {
+    values_[i].v_str = value;
+    type_codes_[i] = kStr;
+  }
+  // setters for container type
+  // They must be reference(instead of const ref)
+  // to make sure they are alive in the tuple(instead of getting converted)
+  void operator()(size_t i, std::string& value) const {  // NOLINT(*)
+    values_[i].v_str = value.c_str();
+    type_codes_[i] = kStr;
+  }
+  void operator()(size_t i, PackedFunc& value) const {  // NOLINT(*)
+    values_[i].v_handle = &value;
+    type_codes_[i] = kFuncHandle;
+  }
+  void operator()(size_t i, TVMRetValue& value) const {  // NOLINT(*)
+    if (value.type_code() == kStr) {
+      values_[i].v_str = value.ptr<std::string>()->c_str();
+      type_codes_[i] = kStr;
+    } else {
+      values_[i] = value.value_;
+      type_codes_[i] = value.type_code();
+    }
+  }
+  // NodeRef related extenstions: in tvm/packed_func_ext.h
+  inline void operator()(size_t i, NodeRef& other) const;  // NOLINT(*)
+  inline void operator()(size_t i, const Halide::Type& t) const;
+
+ private:
+  /*! \brief The values fields */
+  TVMValue* values_;
+  /*! \brief The type code fields */
+  int* type_codes_;
+};
+
+class TVMArgsGetter {
+ public:
+  explicit TVMArgsGetter(TVMArgs args)
+      : args_(args) {}
+
+  template<typename T>
+  inline void operator()(size_t i, T& target) const {  // NOLINT(*)
+    target = args_[i].operator T();
+  }
+ private:
+  TVMArgs args_;
 };
 
 template<typename... Args>
-inline void PackedFunc::operator()(Args&& ...args) const {
-  auto targ = std::make_tuple(std::forward<Args>(args)...);
+inline TVMRetValue PackedFunc::operator()(Args&& ...args) const {
+  auto targs = std::make_tuple(std::forward<Args>(args)...);
   const int kNumArgs = sizeof...(Args);
-  TVMValue tvm_args[kNumArgs];
-  int tvm_arg_type_ids[kNumArgs];
-  for_each(targ, PackedFuncArgSetter{tvm_args, tvm_arg_type_ids});
-  body_(tvm_args, tvm_arg_type_ids, kNumArgs);
+  TVMValue values[kNumArgs];
+  int type_codes[kNumArgs];
+  for_each(targs, TVMArgsSetter(values, type_codes));
+  TVMRetValue rv;
+  body_(TVMArgs(values, type_codes, kNumArgs), &rv);
+  return rv;
 }
+
 }  // namespace runtime
 }  // namespace tvm
 #endif  // TVM_RUNTIME_PACKED_FUNC_H_
diff --git a/include/tvm/tvm.h b/include/tvm/tvm.h
index 5b7113df..6272b9d0 100644
--- a/include/tvm/tvm.h
+++ b/include/tvm/tvm.h
@@ -10,5 +10,6 @@
 #include "./expr.h"
 #include "./tensor.h"
 #include "./operation.h"
+#include "./packed_func_ext.h"
 
 #endif  // TVM_TVM_H_
diff --git a/python/tvm/__init__.py b/python/tvm/__init__.py
index 6729a8bd..2bd6359b 100644
--- a/python/tvm/__init__.py
+++ b/python/tvm/__init__.py
@@ -1,7 +1,7 @@
 # pylint: disable=redefined-builtin, wildcard-import
 """C++ backend related python scripts"""
 from __future__ import absolute_import as _abs
-from ._ctypes._api import register_node
+from ._ctypes._node import register_node
 
 from . import tensor
 from . import expr
diff --git a/python/tvm/_base.py b/python/tvm/_base.py
index 33c9848f..530b883c 100644
--- a/python/tvm/_base.py
+++ b/python/tvm/_base.py
@@ -91,45 +91,3 @@ def c_array(ctype, values):
         Created ctypes array
     """
     return (ctype * len(values))(*values)
-
-
-def ctypes2docstring(num_args, arg_names, arg_types, arg_descs, remove_dup=True):
-    """Convert ctypes returned doc string information into parameters docstring.
-
-    num_args : nn_uint
-        Number of arguments.
-
-    arg_names : ctypes.POINTER(ctypes.c_char_p)
-        Argument names.
-
-    arg_types : ctypes.POINTER(ctypes.c_char_p)
-        Argument type information.
-
-    arg_descs : ctypes.POINTER(ctypes.c_char_p)
-        Argument description information.
-
-    remove_dup : boolean, optional
-        Whether remove duplication or not.
-
-    Returns
-    -------
-    docstr : str
-        Python docstring of parameter sections.
-    """
-    param_keys = set()
-    param_str = []
-    for i in range(num_args.value):
-        key = py_str(arg_names[i])
-        if key in param_keys and remove_dup:
-            continue
-        param_keys.add(key)
-        type_info = py_str(arg_types[i])
-        ret = '%s : %s' % (key, type_info)
-        if len(arg_descs[i]) != 0:
-            ret += '\n    ' + py_str(arg_descs[i])
-        param_str.append(ret)
-    doc_str = ('Parameters\n' +
-               '----------\n' +
-               '%s\n')
-    doc_str = doc_str % ('\n'.join(param_str))
-    return doc_str
diff --git a/python/tvm/_ctypes/_api.py b/python/tvm/_ctypes/_api.py
deleted file mode 100644
index f6eb9ac0..00000000
--- a/python/tvm/_ctypes/_api.py
+++ /dev/null
@@ -1,416 +0,0 @@
-# coding: utf-8
-# pylint: disable=invalid-name, protected-access, too-many-arguments, too-many-lines
-# pylint: disable=attribute-defined-outside-init, no-member, missing-docstring, too-many-return-statements
-"""Symbolic configuration API."""
-from __future__ import absolute_import as _abs
-
-import ctypes
-import sys
-from numbers import Number, Integral
-
-from .._base import _LIB
-from .._base import c_str, py_str, string_types
-from .._base import check_call, ctypes2docstring
-from .. import _api_internal
-from . import _runtime_api
-from ._types import TVMValue, TypeCode, TVMPackedCFunc, TVMCFuncFinalizer
-
-# type definitions
-APIFuncHandle = ctypes.c_void_p
-NodeHandle = ctypes.c_void_p
-FunctionHandle = ctypes.c_void_p
-
-class APIType(object):
-    """TVMType used in API calls"""
-    INT = ctypes.c_int(TypeCode.INT)
-    UINT = ctypes.c_int(TypeCode.UINT)
-    FLOAT = ctypes.c_int(TypeCode.FLOAT)
-    HANDLE = ctypes.c_int(TypeCode.HANDLE)
-    NULL = ctypes.c_int(TypeCode.NULL)
-    NODE_HANDLE = ctypes.c_int(TypeCode.NODE_HANDLE)
-    STR = ctypes.c_int(TypeCode.STR)
-    FUNC_HANDLE = ctypes.c_int(TypeCode.FUNC_HANDLE)
-
-
-NODE_TYPE = {
-}
-
-def _return_node(x):
-    handle = x.v_handle
-    if not isinstance(handle, NodeHandle):
-        handle = NodeHandle(handle)
-    ret_val = TVMValue()
-    ret_type_code = ctypes.c_int()
-    ret_success = ctypes.c_int()
-    check_call(_LIB.TVMNodeGetAttr(
-        handle, c_str("type_key"),
-        ctypes.byref(ret_val),
-        ctypes.byref(ret_type_code),
-        ctypes.byref(ret_success)))
-    return NODE_TYPE.get(py_str(ret_val.v_str), NodeBase)(handle)
-
-
-def _return_func(x):
-    handle = x.v_handle
-    if not isinstance(handle, FunctionHandle):
-        handle = FunctionHandle(handle)
-    return _runtime_api._function_cls(handle)
-
-
-def _return_handle(x):
-    handle = x.v_handle
-    if not isinstance(handle, ctypes.c_void_p):
-        handle = ctypes.c_void_p(handle)
-    return handle
-
-
-RET_SWITCH = {
-    TypeCode.NULL: lambda x: None,
-    TypeCode.INT: lambda x: x.v_int64,
-    TypeCode.FLOAT: lambda x: x.v_float64,
-    TypeCode.STR: lambda x: py_str(x.v_str),
-    TypeCode.NODE_HANDLE: _return_node,
-    TypeCode.FUNC_HANDLE: _return_func
-}
-
-PACK_ARG_SWITCH = {
-    TypeCode.NULL: lambda x: None,
-    TypeCode.INT: lambda x: x.v_int64,
-    TypeCode.FLOAT: lambda x: x.v_float64,
-    TypeCode.STR: lambda x: py_str(x.v_str),
-    TypeCode.HANDLE: lambda x: _return_handle,
-}
-
-
-class SliceBase(object):
-    """base class of slice object"""
-    pass
-
-class NodeBase(object):
-    """Symbol is symbolic graph."""
-    __slots__ = ["handle"]
-    # pylint: disable=no-member
-    def __init__(self, handle):
-        """Initialize the function with handle
-
-        Parameters
-        ----------
-        handle : SymbolHandle
-            the handle to the underlying C++ Symbol
-        """
-        self.handle = handle
-
-    def __repr__(self):
-        return _api_internal._format_str(self)
-
-    def __del__(self):
-        check_call(_LIB.TVMNodeFree(self.handle))
-
-    def __getattr__(self, name):
-        ret_val = TVMValue()
-        ret_type_code = ctypes.c_int()
-        ret_success = ctypes.c_int()
-        check_call(_LIB.TVMNodeGetAttr(
-            self.handle, c_str(name),
-            ctypes.byref(ret_val),
-            ctypes.byref(ret_type_code),
-            ctypes.byref(ret_success)))
-        value = RET_SWITCH[ret_type_code.value](ret_val)
-        if not ret_success.value:
-            raise AttributeError(
-                "'%s' object has no attribute '%s'" % (str(type(self)), name))
-        return value
-
-    def __hash__(self):
-        return _api_internal._raw_ptr(self)
-
-    def __eq__(self, other):
-        if not isinstance(other, NodeBase):
-            return False
-        return self.__hash__() == other.__hash__()
-
-    def __ne__(self, other):
-        return not self.__eq__(other)
-
-    def __dir__(self):
-        plist = ctypes.POINTER(ctypes.c_char_p)()
-        size = ctypes.c_uint()
-        check_call(_LIB.TVMNodeListAttrNames(
-            self.handle, ctypes.byref(size), ctypes.byref(plist)))
-        names = []
-        for i in range(size.value):
-            names.append(py_str(plist[i]))
-        return names
-
-    def __reduce__(self):
-        return (type(self), (None,), self.__getstate__())
-
-    def __getstate__(self):
-        handle = self.handle
-        if handle is not None:
-            return {'handle': _api_internal._save_json(self)}
-        else:
-            return {'handle': None}
-
-    def __setstate__(self, state):
-        # pylint: disable=assigning-non-slot
-        handle = state['handle']
-        if handle is not None:
-            json_str = handle
-            _push_arg(json_str)
-            other = _api_internal._load_json(json_str)
-            self.handle = other.handle
-            other.handle = None
-        else:
-            self.handle = None
-
-
-def const(value, dtype=None):
-    """construct a constant"""
-    if dtype is None:
-        if isinstance(value, Integral):
-            dtype = 'int32'
-        else:
-            dtype = 'float32'
-    return _api_internal._const(value, dtype)
-
-
-def _ctypes_free_resource(rhandle):
-    """callback to free resources when it it not needed."""
-    pyobj = ctypes.cast(rhandle, ctypes.py_object)
-    ctypes.pythonapi.Py_DecRef(pyobj)
-
-# Global callback that is always alive
-TVM_FREE_PYOBJ = TVMCFuncFinalizer(_ctypes_free_resource)
-ctypes.pythonapi.Py_IncRef(ctypes.py_object(TVM_FREE_PYOBJ))
-
-def convert_to_tvm_func(pyfunc):
-    """Convert a python function to TVM function
-
-    Parameters
-    ----------
-    pyfunc : python function
-        The python function to be converted.
-
-    Returns
-    -------
-    tvmfunc: tvm.nd.Function
-        The converted tvm function.
-    """
-    local_pyfunc = pyfunc
-    def cfun(args, type_codes, num_args, _):
-        """ ctypes function """
-        num_args = num_args.value if isinstance(num_args, ctypes.c_int) else num_args
-        pyargs = [PACK_ARG_SWITCH[type_codes[i]](args[i]) for i in range(num_args)]
-        local_pyfunc(*pyargs)
-    handle = FunctionHandle()
-    f = TVMPackedCFunc(cfun)
-    # NOTE: We will need to use python-api to increase ref count of the f
-    # TVM_FREE_PYOBJ will be called after it is no longer needed.
-    pyobj = ctypes.py_object(f)
-    ctypes.pythonapi.Py_IncRef(pyobj)
-    check_call(_LIB.TVMFuncCreateFromCFunc(
-        f, pyobj, TVM_FREE_PYOBJ, ctypes.byref(handle)))
-    return _runtime_api._function_cls(handle)
-
-
-def convert(value):
-    """Convert a value to expression."""
-    if isinstance(value, (NodeBase, _runtime_api.FunctionBase)):
-        return value
-    elif isinstance(value, Number):
-        return const(value)
-    elif isinstance(value, string_types):
-        return _api_internal._str(value)
-    elif isinstance(value, (list, tuple)):
-        value = [convert(x) for x in value]
-        return _api_internal._Array(*value)
-    elif isinstance(value, dict):
-        vlist = []
-        for it in value.items():
-            if not isinstance(it[0], NodeBase):
-                raise ValueError("key of map must already been a container type")
-            vlist.append(it[0])
-            vlist.append(convert(it[1]))
-        return _api_internal._Map(*vlist)
-    elif isinstance(value, SliceBase):
-        return value.tensor(*value.indices)
-    elif callable(value):
-        return convert_to_tvm_func(value)
-    else:
-        raise ValueError("don't know how to handle type %s" % type(value))
-    return value
-
-
-def _push_arg(arg):
-    a = TVMValue()
-    if arg is None:
-        _LIB.TVMAPIPushStack(a, APIType.NULL)
-    elif isinstance(arg, NodeBase):
-        a.v_handle = arg.handle
-        _LIB.TVMAPIPushStack(a, APIType.NODE_HANDLE)
-    elif isinstance(arg, Integral):
-        a.v_int64 = ctypes.c_int64(arg)
-        _LIB.TVMAPIPushStack(a, APIType.INT)
-    elif isinstance(arg, Number):
-        a.v_double = ctypes.c_double(arg)
-        _LIB.TVMAPIPushStack(a, APIType.FLOAT)
-    elif isinstance(arg, string_types):
-        a.v_str = c_str(arg)
-        _LIB.TVMAPIPushStack(a, APIType.STR)
-    else:
-        raise TypeError("Don't know how to handle type %s" % type(arg))
-
-
-def _make_function(handle, name):
-    """Create an atomic symbol function by handle and funciton name."""
-    real_name = ctypes.c_char_p()
-    desc = ctypes.c_char_p()
-    num_args = ctypes.c_int()
-    arg_names = ctypes.POINTER(ctypes.c_char_p)()
-    arg_types = ctypes.POINTER(ctypes.c_char_p)()
-    arg_descs = ctypes.POINTER(ctypes.c_char_p)()
-    ret_type = ctypes.c_char_p()
-
-    check_call(_LIB.TVMGetAPIFuncInfo(
-        handle, ctypes.byref(real_name), ctypes.byref(desc),
-        ctypes.byref(num_args),
-        ctypes.byref(arg_names),
-        ctypes.byref(arg_types),
-        ctypes.byref(arg_descs),
-        ctypes.byref(ret_type)))
-
-    param_str = ctypes2docstring(num_args, arg_names, arg_types, arg_descs)
-    func_name = name
-    desc = py_str(desc.value)
-
-    doc_str = ('%s\n\n' +
-               '%s\n')
-    doc_str = doc_str % (desc, param_str)
-    arg_names = [py_str(arg_names[i]) for i in range(num_args.value)]
-
-    def func(*args):
-        """TVM function"""
-        cargs = []
-        for x in args:
-            if isinstance(x, (list, tuple, dict, SliceBase)):
-                cargs.append(convert(x))
-            else:
-                cargs.append(x)
-
-        for arg in cargs:
-            _push_arg(arg)
-        ret_val = TVMValue()
-        ret_type_code = ctypes.c_int()
-        check_call(_LIB.TVMAPIFuncCall(
-            handle, ctypes.byref(ret_val), ctypes.byref(ret_type_code)))
-        return RET_SWITCH[ret_type_code.value](ret_val)
-
-    func.__name__ = func_name
-    func.__doc__ = doc_str
-    return func
-
-
-def register_node(type_key=None):
-    """register node type
-
-    Parameters
-    ----------
-    type_key : str or cls
-        The type key of the node
-    """
-    if isinstance(type_key, str):
-        def register(cls):
-            """internal register function"""
-            NODE_TYPE[type_key] = cls
-            return cls
-        return register
-    else:
-        cls = type_key
-        NODE_TYPE[cls.__name__] = cls
-        return cls
-
-
-def register_func(func_name, f=None):
-    """Register global function
-
-    Parameters
-    ----------
-    func_name : str or function
-        The function name
-
-    f : function
-        The function to be registered.
-
-    Returns
-    -------
-    fregister : function
-        Register function if f is not specified.
-    """
-    if callable(func_name):
-        f = func_name
-        func_name = f.__name__
-
-    if not isinstance(func_name, str):
-        raise ValueError("expect string function name")
-    def register(myf):
-        """internal register function"""
-        if not isinstance(myf, _runtime_api.FunctionBase):
-            myf = convert_to_tvm_func(myf)
-        check_call(_LIB.TVMFuncRegisterGlobal(
-            c_str(func_name), myf.handle))
-    if f:
-        register(f)
-    else:
-        return register
-
-
-def get_global_func(name):
-    """Get a global function by name
-
-    Parameters
-    ----------
-    name : str
-        The name of the global function
-
-    Returns
-    -------
-    func : tvm.nd.Function
-        The function to be returned.
-    """
-    handle = FunctionHandle()
-    check_call(_LIB.TVMFuncGetGlobal(c_str(name), ctypes.byref(handle)))
-    return _runtime_api._function_cls(handle)
-
-
-def _init_api_module(root_namespace):
-    """List and add all the functions to current module."""
-    plist = ctypes.POINTER(ctypes.c_char_p)()
-    size = ctypes.c_uint()
-
-    check_call(_LIB.TVMListAPIFuncNames(ctypes.byref(size),
-                                        ctypes.byref(plist)))
-    op_names = []
-    for i in range(size.value):
-        op_names.append(py_str(plist[i]))
-
-    module_obj = sys.modules["%s.api" % root_namespace]
-    module_internal = sys.modules["%s._api_internal" % root_namespace]
-    namespace_match = {
-        "_make_": sys.modules["%s.make" % root_namespace],
-        "_pass_": sys.modules["%s.ir_pass" % root_namespace],
-        "_codegen_": sys.modules["%s.codegen" % root_namespace],
-        "_schedule_": sys.modules["%s.schedule" % root_namespace]
-    }
-
-    for name in op_names:
-        hdl = APIFuncHandle()
-        check_call(_LIB.TVMGetAPIFuncHandle(c_str(name), ctypes.byref(hdl)))
-        fname = name
-        target_module = module_internal if name.startswith('_') else module_obj
-        for k, v in namespace_match.items():
-            if name.startswith(k):
-                fname = name[len(k):]
-                target_module = v
-        function = _make_function(hdl, fname)
-        setattr(target_module, function.__name__, function)
diff --git a/python/tvm/_ctypes/_function.py b/python/tvm/_ctypes/_function.py
new file mode 100644
index 00000000..3b133e55
--- /dev/null
+++ b/python/tvm/_ctypes/_function.py
@@ -0,0 +1,250 @@
+# coding: utf-8
+# pylint: disable=invalid-name, protected-access
+"""Symbolic configuration API."""
+from __future__ import absolute_import
+
+import ctypes
+import sys
+from numbers import Number, Integral
+
+from .._base import _LIB, check_call
+from .._base import c_str, py_str, string_types
+from ._types import TVMValue, TypeCode, TVMType
+from ._types import TVMPackedCFunc, TVMCFuncFinalizer
+from ._types import RETURN_SWITCH, C_TO_PY_ARG_SWITCH
+from ._node import NodeBase, SliceBase, convert_to_node
+from ._ndarray import NDArrayBase
+
+FunctionHandle = ctypes.c_void_p
+TVMRetValueHandle = ctypes.c_void_p
+
+def _ctypes_free_resource(rhandle):
+    """callback to free resources when it it not needed."""
+    pyobj = ctypes.cast(rhandle, ctypes.py_object)
+    ctypes.pythonapi.Py_DecRef(pyobj)
+
+# Global callback that is always alive
+TVM_FREE_PYOBJ = TVMCFuncFinalizer(_ctypes_free_resource)
+ctypes.pythonapi.Py_IncRef(ctypes.py_object(TVM_FREE_PYOBJ))
+
+def convert_to_tvm_func(pyfunc):
+    """Convert a python function to TVM function
+
+    Parameters
+    ----------
+    pyfunc : python function
+        The python function to be converted.
+
+    Returns
+    -------
+    tvmfunc: tvm.nd.Function
+        The converted tvm function.
+    """
+    local_pyfunc = pyfunc
+    def cfun(args, type_codes, num_args, ret, _):
+        """ ctypes function """
+        num_args = num_args.value if isinstance(num_args, ctypes.c_int) else num_args
+        pyargs = [C_TO_PY_ARG_SWITCH[type_codes[i]](args[i]) for i in range(num_args)]
+        rv = local_pyfunc(*pyargs)
+        if rv is not None:
+            if isinstance(rv, tuple):
+                raise ValueError("PackedFunction can only support one reurn value")
+            temp_args = []
+            values, tcodes, _ = _make_tvm_args((rv,), temp_args)
+            if not isinstance(ret, TVMRetValueHandle):
+                ret = TVMRetValueHandle(ret)
+            check_call(_LIB.TVMCFuncSetReturn(ret, values[0], ctypes.c_int(tcodes[0])))
+            _ = temp_args
+            _ = rv
+
+    handle = FunctionHandle()
+    f = TVMPackedCFunc(cfun)
+    # NOTE: We will need to use python-api to increase ref count of the f
+    # TVM_FREE_PYOBJ will be called after it is no longer needed.
+    pyobj = ctypes.py_object(f)
+    ctypes.pythonapi.Py_IncRef(pyobj)
+    check_call(_LIB.TVMFuncCreateFromCFunc(
+        f, pyobj, TVM_FREE_PYOBJ, ctypes.byref(handle)))
+    return Function(handle)
+
+
+def _make_tvm_args(args, temp_args):
+    """Pack arguments into c args tvm call accept"""
+    num_args = len(args)
+    values = (TVMValue * num_args)()
+    type_codes = (ctypes.c_int * num_args)()
+    for i, arg in enumerate(args):
+        if arg is None:
+            values[i].v_handle = None
+            type_codes[i] = TypeCode.NULL
+        elif isinstance(arg, NDArrayBase):
+            values[i].v_handle = ctypes.cast(arg.handle, ctypes.c_void_p)
+            type_codes[i] = TypeCode.ARRAY_HANDLE
+        elif isinstance(arg, NodeBase):
+            values[i].v_handle = arg.handle
+            type_codes[i] = TypeCode.NODE_HANDLE
+        elif isinstance(arg, Integral):
+            values[i].v_int64 = arg
+            type_codes[i] = TypeCode.INT
+        elif isinstance(arg, Number):
+            values[i].v_float64 = arg
+            type_codes[i] = TypeCode.FLOAT
+        elif isinstance(arg, TVMType):
+            values[i].v_type = arg
+            type_codes[i] = TypeCode.TVM_TYPE
+        elif isinstance(arg, string_types):
+            values[i].v_str = c_str(arg)
+            type_codes[i] = TypeCode.STR
+        elif isinstance(arg, (list, tuple, dict, SliceBase)):
+            arg = convert_to_node(arg)
+            values[i].v_handle = arg.handle
+            type_codes[i] = TypeCode.NODE_HANDLE
+            temp_args.append(arg)
+        elif isinstance(arg, Function):
+            values[i].v_handle = arg.handle
+            type_codes[i] = TypeCode.FUNC_HANDLE
+        elif callable(arg):
+            arg = convert_to_tvm_func(arg)
+            values[i].v_handle = arg.handle
+            type_codes[i] = TypeCode.FUNC_HANDLE
+            temp_args.append(arg)
+        else:
+            raise TypeError("Don't know how to handle type %s" % type(arg))
+    return values, type_codes, num_args
+
+
+class Function(object):
+    """A function object at runtime."""
+    __slots__ = ["handle", "is_global"]
+    # pylint: disable=no-member
+    def __init__(self, handle, is_global=False):
+        """Initialize the function with handle
+
+        Parameters
+        ----------
+        handle : FunctionHandle
+            the handle to the underlying function.
+
+        is_global : bool, optional
+            Whether it is global function
+        """
+        self.handle = handle
+        self.is_global = is_global
+
+    def __del__(self):
+        if not self.is_global:
+            check_call(_LIB.TVMFuncFree(self.handle))
+
+    def __call__(self, *args):
+        temp_args = []
+        values, tcodes, num_args = _make_tvm_args(args, temp_args)
+        ret_val = TVMValue()
+        ret_tcode = ctypes.c_int()
+        check_call(_LIB.TVMFuncCall(
+            self.handle, values, tcodes, ctypes.c_int(num_args),
+            ctypes.byref(ret_val), ctypes.byref(ret_tcode)))
+        _ = temp_args
+        _ = args
+        return RETURN_SWITCH[ret_tcode.value](ret_val)
+
+
+def _handle_return_func(x):
+    """Return function"""
+    handle = x.v_handle
+    if not isinstance(handle, FunctionHandle):
+        handle = FunctionHandle(handle)
+    return Function(handle, False)
+
+# setup return handle for function type
+RETURN_SWITCH[TypeCode.FUNC_HANDLE] = _handle_return_func
+
+def register_func(func_name, f=None):
+    """Register global function
+
+    Parameters
+    ----------
+    func_name : str or function
+        The function name
+
+    f : function
+        The function to be registered.
+
+    Returns
+    -------
+    fregister : function
+        Register function if f is not specified.
+    """
+    if callable(func_name):
+        f = func_name
+        func_name = f.__name__
+
+    if not isinstance(func_name, str):
+        raise ValueError("expect string function name")
+    def register(myf):
+        """internal register function"""
+        if not isinstance(myf, Function):
+            myf = convert_to_tvm_func(myf)
+        check_call(_LIB.TVMFuncRegisterGlobal(
+            c_str(func_name), myf.handle))
+    if f:
+        register(f)
+    else:
+        return register
+
+
+def get_global_func(name):
+    """Get a global function by name
+
+    Parameters
+    ----------
+    name : str
+        The name of the global function
+
+    Returns
+    -------
+    func : tvm.nd.Function
+        The function to be returned.
+    """
+    handle = FunctionHandle()
+    check_call(_LIB.TVMFuncGetGlobal(c_str(name), ctypes.byref(handle)))
+    return Function(handle, True)
+
+
+def list_global_func_names():
+    """Get list of global functions registered.
+
+    Returns
+    -------
+    names : list
+       List of global functions names.
+    """
+    plist = ctypes.POINTER(ctypes.c_char_p)()
+    size = ctypes.c_uint()
+
+    check_call(_LIB.TVMFuncListGlobalNames(ctypes.byref(size),
+                                           ctypes.byref(plist)))
+    fnames = []
+    for i in range(size.value):
+        fnames.append(py_str(plist[i]))
+    return fnames
+
+
+def _init_api_functions(root_namespace):
+    """List and add all the functions to current module."""
+    module_obj = sys.modules["%s.api" % root_namespace]
+    module_internal = sys.modules["%s._api_internal" % root_namespace]
+    namespace_match = {
+        "_make_": sys.modules["%s.make" % root_namespace],
+        "_pass_": sys.modules["%s.ir_pass" % root_namespace],
+        "_codegen_": sys.modules["%s.codegen" % root_namespace],
+        "_schedule_": sys.modules["%s.schedule" % root_namespace]
+    }
+    for name in list_global_func_names():
+        fname = name
+        target_module = module_internal if name.startswith('_') else module_obj
+        for k, v in namespace_match.items():
+            if name.startswith(k):
+                fname = name[len(k):]
+                target_module = v
+        f = get_global_func(name)
+        setattr(target_module, fname, f)
diff --git a/python/tvm/_ctypes/_runtime_api.py b/python/tvm/_ctypes/_ndarray.py
similarity index 78%
rename from python/tvm/_ctypes/_runtime_api.py
rename to python/tvm/_ctypes/_ndarray.py
index dc4a64ee..b6fc4d4d 100644
--- a/python/tvm/_ctypes/_runtime_api.py
+++ b/python/tvm/_ctypes/_ndarray.py
@@ -1,18 +1,15 @@
 # pylint: disable=invalid-name, protected-access, too-many-arguments,  global-statement
 # pylint: disable=attribute-defined-outside-init, no-member, missing-docstring
 """Symbolic configuration API."""
-from __future__ import absolute_import as _abs
+from __future__ import absolute_import
 
 import ctypes
-from numbers import Number, Integral
 import numpy as np
 
-from .._base import _LIB
-from .._base import c_array, c_str, string_types
-from .._base import check_call
-from ._types import TVMValue, TypeCode, TVMType
+from .._base import _LIB, check_call
+from .._base import c_array, c_str
+from ._types import TVMType, tvm_index_t
 
-tvm_index_t = ctypes.c_uint32
 
 class TVMContext(ctypes.Structure):
     """TVM context strucure."""
@@ -39,6 +36,19 @@ class TVMContext(ctypes.Structure):
         return ret.value != 0
 
 
+class TVMArray(ctypes.Structure):
+    """TVMValue in C API"""
+    _fields_ = [("data", ctypes.c_void_p),
+                ("shape", ctypes.POINTER(tvm_index_t)),
+                ("strides", ctypes.POINTER(tvm_index_t)),
+                ("ndim", tvm_index_t),
+                ("dtype", TVMType),
+                ("ctx", TVMContext)]
+
+
+TVMArrayHandle = ctypes.POINTER(TVMArray)
+
+
 def cpu(dev_id=0):
     """Construct a CPU device
 
@@ -72,18 +82,6 @@ def opencl(dev_id=0):
     return TVMContext(4, dev_id)
 
 
-class TVMArray(ctypes.Structure):
-    """TVMValue in C API"""
-    _fields_ = [("data", ctypes.c_void_p),
-                ("shape", ctypes.POINTER(tvm_index_t)),
-                ("strides", ctypes.POINTER(tvm_index_t)),
-                ("ndim", tvm_index_t),
-                ("dtype", TVMType),
-                ("ctx", TVMContext)]
-
-TVMArrayHandle = ctypes.POINTER(TVMArray)
-
-
 def numpyasarray(np_data):
     """Return a TVMArray representation of a numpy array.
     """
@@ -102,7 +100,6 @@ def numpyasarray(np_data):
 
 
 _ndarray_cls = None
-_function_cls = None
 
 
 def empty(shape, dtype="float32", ctx=cpu(0)):
@@ -275,51 +272,6 @@ class NDArrayBase(object):
         return target
 
 
-class FunctionBase(object):
-    """A function object at runtim."""
-    __slots__ = ["handle"]
-    # pylint: disable=no-member
-    def __init__(self, handle):
-        """Initialize the function with handle
-
-        Parameters
-        ----------
-        handle : FunctionHandle
-            the handle to the underlying function.
-        """
-        self.handle = handle
-
-    def __del__(self):
-        check_call(_LIB.TVMFuncFree(self.handle))
-
-    def __call__(self, *args):
-        num_args = len(args)
-        tvm_args = (TVMValue * num_args)()
-        tvm_type_code = (ctypes.c_int * num_args)()
-        for i, arg in enumerate(args):
-            if arg is None:
-                tvm_args[i].v_handle = None
-                tvm_type_code[i] = TypeCode.NULL
-            elif isinstance(arg, NDArrayBase):
-                tvm_args[i].v_handle = ctypes.cast(arg.handle, ctypes.c_void_p)
-                tvm_type_code[i] = TypeCode.HANDLE
-            elif isinstance(arg, Integral):
-                tvm_args[i].v_int64 = arg
-                tvm_type_code[i] = TypeCode.INT
-            elif isinstance(arg, Number):
-                tvm_args[i].v_float64 = arg
-                tvm_type_code[i] = TypeCode.FLOAT
-            elif isinstance(arg, string_types):
-                tvm_args[i].v_str = c_str(arg)
-                tvm_type_code[i] = TypeCode.STR
-            else:
-                raise TypeError("Don't know how to handle type %s" % type(arg))
-        check_call(_LIB.TVMFuncCall(
-            self.handle, tvm_args, tvm_type_code, ctypes.c_int(num_args)))
-
-
-def _init_runtime_module(ndarray_class, function_class):
+def _init_ndarray_module(ndarray_class):
     global _ndarray_cls
-    global _function_cls
     _ndarray_cls = ndarray_class
-    _function_cls = function_class
diff --git a/python/tvm/_ctypes/_node.py b/python/tvm/_ctypes/_node.py
new file mode 100644
index 00000000..d91b9cac
--- /dev/null
+++ b/python/tvm/_ctypes/_node.py
@@ -0,0 +1,184 @@
+# coding: utf-8
+# pylint: disable=invalid-name, protected-access
+# pylint: disable=no-member, missing-docstring
+"""Symbolic configuration API."""
+from __future__ import absolute_import
+
+import ctypes
+from numbers import Number, Integral
+
+from .._base import _LIB, check_call
+from .._base import c_str, py_str, string_types
+from .. import _api_internal
+from ._types import TVMValue, TypeCode, RETURN_SWITCH
+
+NodeHandle = ctypes.c_void_p
+
+"""Maps node type to its constructor"""
+NODE_TYPE = {
+}
+
+def _return_node(x):
+    """Return function"""
+    handle = x.v_handle
+    if not isinstance(handle, NodeHandle):
+        handle = NodeHandle(handle)
+    ret_val = TVMValue()
+    ret_type_code = ctypes.c_int()
+    ret_success = ctypes.c_int()
+    check_call(_LIB.TVMNodeGetAttr(
+        handle, c_str("type_key"),
+        ctypes.byref(ret_val),
+        ctypes.byref(ret_type_code),
+        ctypes.byref(ret_success)))
+    return NODE_TYPE.get(py_str(ret_val.v_str), NodeBase)(handle)
+
+
+RETURN_SWITCH[TypeCode.NODE_HANDLE] = _return_node
+
+
+class SliceBase(object):
+    """base class of slice object"""
+    pass
+
+class NodeBase(object):
+    """Symbol is symbolic graph."""
+    __slots__ = ["handle"]
+    # pylint: disable=no-member
+    def __init__(self, handle):
+        """Initialize the function with handle
+
+        Parameters
+        ----------
+        handle : SymbolHandle
+            the handle to the underlying C++ Symbol
+        """
+        self.handle = handle
+
+    def __repr__(self):
+        return _api_internal._format_str(self)
+
+    def __del__(self):
+        check_call(_LIB.TVMNodeFree(self.handle))
+
+    def __getattr__(self, name):
+        ret_val = TVMValue()
+        ret_type_code = ctypes.c_int()
+        ret_success = ctypes.c_int()
+        check_call(_LIB.TVMNodeGetAttr(
+            self.handle, c_str(name),
+            ctypes.byref(ret_val),
+            ctypes.byref(ret_type_code),
+            ctypes.byref(ret_success)))
+        if not ret_success.value:
+            raise AttributeError(
+                "'%s' object has no attribute '%s'" % (str(type(self)), name))
+        return RETURN_SWITCH[ret_type_code.value](ret_val)
+
+    def __hash__(self):
+        return _api_internal._raw_ptr(self)
+
+    def __eq__(self, other):
+        if not isinstance(other, NodeBase):
+            return False
+        return self.__hash__() == other.__hash__()
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+    def __dir__(self):
+        plist = ctypes.POINTER(ctypes.c_char_p)()
+        size = ctypes.c_uint()
+        check_call(_LIB.TVMNodeListAttrNames(
+            self.handle, ctypes.byref(size), ctypes.byref(plist)))
+        names = []
+        for i in range(size.value):
+            names.append(py_str(plist[i]))
+        return names
+
+    def __reduce__(self):
+        return (type(self), (None,), self.__getstate__())
+
+    def __getstate__(self):
+        handle = self.handle
+        if handle is not None:
+            return {'handle': _api_internal._save_json(self)}
+        else:
+            return {'handle': None}
+
+    def __setstate__(self, state):
+        # pylint: disable=assigning-non-slot
+        handle = state['handle']
+        if handle is not None:
+            json_str = handle
+            other = _api_internal._load_json(json_str)
+            self.handle = other.handle
+            other.handle = None
+        else:
+            self.handle = None
+
+
+def const(value, dtype=None):
+    """construct a constant"""
+    if dtype is None:
+        if isinstance(value, Integral):
+            dtype = 'int32'
+        else:
+            dtype = 'float32'
+    return _api_internal._const(value, dtype)
+
+
+def convert_to_node(value):
+    """Convert a python value to corresponding node type.
+
+    Parameters
+    ----------
+    value : str
+        The value to be inspected.
+
+    Returns
+    -------
+    node : Node
+        The corresponding node value.
+    """
+    if isinstance(value, NodeBase):
+        return value
+    elif isinstance(value, Number):
+        return const(value)
+    elif isinstance(value, string_types):
+        return _api_internal._str(value)
+    elif isinstance(value, (list, tuple)):
+        value = [convert_to_node(x) for x in value]
+        return _api_internal._Array(*value)
+    elif isinstance(value, dict):
+        vlist = []
+        for it in value.items():
+            if not isinstance(it[0], NodeBase):
+                raise ValueError("key of map must already been a container type")
+            vlist.append(it[0])
+            vlist.append(convert_to_node(it[1]))
+        return _api_internal._Map(*vlist)
+    elif isinstance(value, SliceBase):
+        return value.tensor(*value.indices)
+    else:
+        raise ValueError("don't know how to convert type %s to node" % type(value))
+
+
+def register_node(type_key=None):
+    """register node type
+
+    Parameters
+    ----------
+    type_key : str or cls
+        The type key of the node
+    """
+    if isinstance(type_key, str):
+        def register(cls):
+            """internal register function"""
+            NODE_TYPE[type_key] = cls
+            return cls
+        return register
+    else:
+        cls = type_key
+        NODE_TYPE[cls.__name__] = cls
+        return cls
diff --git a/python/tvm/_ctypes/_types.py b/python/tvm/_ctypes/_types.py
index b7d8e353..f6d0f5e7 100644
--- a/python/tvm/_ctypes/_types.py
+++ b/python/tvm/_ctypes/_types.py
@@ -4,13 +4,9 @@ from __future__ import absolute_import as _abs
 
 import ctypes
 import numpy as np
+from .._base import py_str
 
-class TVMValue(ctypes.Union):
-    """TVMValue in C API"""
-    _fields_ = [("v_int64", ctypes.c_int64),
-                ("v_float64", ctypes.c_double),
-                ("v_handle", ctypes.c_void_p),
-                ("v_str", ctypes.c_char_p)]
+tvm_index_t = ctypes.c_uint32
 
 class TypeCode(object):
     """Type code used in API calls"""
@@ -19,9 +15,11 @@ class TypeCode(object):
     FLOAT = 2
     HANDLE = 3
     NULL = 4
-    NODE_HANDLE = 5
-    STR = 6
-    FUNC_HANDLE = 7
+    ARRAY_HANDLE = 5
+    TVM_TYPE = 6
+    NODE_HANDLE = 7
+    STR = 8
+    FUNC_HANDLE = 9
 
 def _api_type(code):
     """create a type accepted by API"""
@@ -40,13 +38,13 @@ class TVMType(ctypes.Structure):
     CODE2STR = {
         0 : 'int',
         1 : 'uint',
-        2 : 'float'
+        2 : 'float',
+        4 : 'handle'
     }
     def __init__(self, type_str, lanes=1):
         super(TVMType, self).__init__()
         if isinstance(type_str, np.dtype):
             type_str = str(type_str)
-
         if type_str.startswith("int"):
             self.type_code = 0
             bits = int(type_str[3:])
@@ -56,6 +54,9 @@ class TVMType(ctypes.Structure):
         elif type_str.startswith("float"):
             self.type_code = 2
             bits = int(type_str[5:])
+        elif type_str.startswith("handle"):
+            self.type_code = 4
+            bits = 64
         else:
             raise ValueError("Donot know how to handle type %s" % type_str)
 
@@ -71,15 +72,61 @@ class TVMType(ctypes.Structure):
             x += "x%d" % self.lanes
         return x
 
+    def __eq__(self, other):
+        return (self.bits == other.bits and
+                self.type_code == other.type_code and
+                self.lanes == other.lanes)
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
+
+class TVMValue(ctypes.Union):
+    """TVMValue in C API"""
+    _fields_ = [("v_int64", ctypes.c_int64),
+                ("v_float64", ctypes.c_double),
+                ("v_handle", ctypes.c_void_p),
+                ("v_str", ctypes.c_char_p),
+                ("v_type", TVMType)]
+
 
 TVMPackedCFunc = ctypes.CFUNCTYPE(
     None,
     ctypes.POINTER(TVMValue),
     ctypes.POINTER(ctypes.c_int),
     ctypes.c_int,
+    ctypes.c_void_p,
     ctypes.c_void_p)
 
 
 TVMCFuncFinalizer = ctypes.CFUNCTYPE(
     None,
     ctypes.c_void_p)
+
+
+def _return_handle(x):
+    """return handle"""
+    handle = x.v_handle
+    if not isinstance(handle, ctypes.c_void_p):
+        handle = ctypes.c_void_p(handle)
+    return handle
+
+
+RETURN_SWITCH = {
+    TypeCode.INT: lambda x: x.v_int64,
+    TypeCode.FLOAT: lambda x: x.v_float64,
+    TypeCode.HANDLE: _return_handle,
+    TypeCode.NULL: lambda x: None,
+    TypeCode.TVM_TYPE: lambda x: x.v_type,
+    TypeCode.STR: lambda x: py_str(x.v_str)
+}
+
+
+C_TO_PY_ARG_SWITCH = {
+    TypeCode.INT: lambda x: x.v_int64,
+    TypeCode.FLOAT: lambda x: x.v_float64,
+    TypeCode.HANDLE: _return_handle,
+    TypeCode.NULL: lambda x: None,
+    TypeCode.TVM_TYPE: lambda x: x.v_type,
+    TypeCode.STR: lambda x: py_str(x.v_str)
+}
diff --git a/python/tvm/api.py b/python/tvm/api.py
index e181db9f..344ea107 100644
--- a/python/tvm/api.py
+++ b/python/tvm/api.py
@@ -2,16 +2,23 @@
 # pylint: disable=redefined-builtin, undefined-variable, unused-import
 """Functions defined in TVM."""
 from __future__ import absolute_import as _abs
+
 from numbers import Integral as _Integral
-from ._ctypes._api import _init_api_module, convert, register_func, get_global_func
+
+from ._ctypes._types import TVMType
+from ._ctypes._node import register_node, NodeBase
+from ._ctypes._node import convert_to_node as _convert_to_node
+from ._ctypes._function import Function
+from ._ctypes._function import _init_api_functions, register_func, get_global_func
+from ._ctypes._function import convert_to_tvm_func as _convert_tvm_func
 from . import _api_internal
 from . import make as _make
 from . import expr as _expr
 from . import collections as _collections
 
-int32 = "int32"
-float32 = "float32"
-handle = "handle"
+int32 = TVMType("int32")
+float32 = TVMType("float32")
+handle = TVMType("handle")
 
 def const(value, dtype=None):
     """construct a constant"""
@@ -266,4 +273,25 @@ def Schedule(ops):
     return _api_internal._Schedule(ops)
 
 
-_init_api_module("tvm")
+def convert(value):
+    """Convert value to TVM node or function.
+
+    Parameters
+    ----------
+    value : python value
+
+    Returns
+    -------
+    tvm_val : Node or function
+        Converted value in TVM
+    """
+    if isinstance(value, (Function, NodeBase)):
+        return value
+
+    if callable(value):
+        return _convert_tvm_func(value)
+    else:
+        return _convert_to_node(value)
+
+
+_init_api_functions("tvm")
diff --git a/python/tvm/collections.py b/python/tvm/collections.py
index 810b726c..b3bff80b 100644
--- a/python/tvm/collections.py
+++ b/python/tvm/collections.py
@@ -1,7 +1,7 @@
 # pylint: disable=protected-access, no-member
 """Collection structure in the high level DSL."""
 from __future__ import absolute_import as _abs
-from ._ctypes._api import NodeBase, register_node
+from ._ctypes._node import NodeBase, register_node
 from . import _api_internal
 from . import expr as _expr
 
diff --git a/python/tvm/expr.py b/python/tvm/expr.py
index 3d75fa4c..c3b0845a 100644
--- a/python/tvm/expr.py
+++ b/python/tvm/expr.py
@@ -1,6 +1,6 @@
 # pylint: disable=protected-access, no-member, missing-docstring
 from __future__ import absolute_import as _abs
-from ._ctypes._api import NodeBase, register_node
+from ._ctypes._node import NodeBase, register_node
 from . import make as _make
 
 class ExprOp(object):
diff --git a/python/tvm/ndarray.py b/python/tvm/ndarray.py
index c3059662..8dbc22fd 100644
--- a/python/tvm/ndarray.py
+++ b/python/tvm/ndarray.py
@@ -6,11 +6,11 @@ This is a simplified runtime API for quick testing and proptyping.
 from __future__ import absolute_import as _abs
 import numpy as _np
 
-from ._ctypes._runtime_api import TVMContext, TVMType, NDArrayBase, FunctionBase
-from ._ctypes._runtime_api import cpu, gpu, opencl, empty, sync
-from ._ctypes._runtime_api import _init_runtime_module
-from ._ctypes._runtime_api import init_opencl
-
+from ._ctypes._ndarray import TVMContext, TVMType, NDArrayBase
+from ._ctypes._ndarray import cpu, gpu, opencl, empty, sync
+from ._ctypes._ndarray import _init_ndarray_module
+from ._ctypes._ndarray import init_opencl
+from ._ctypes._function import Function
 
 class NDArray(NDArrayBase):
     """Lightweight NDArray class of TVM runtime.
@@ -26,11 +26,6 @@ class NDArray(NDArrayBase):
     pass
 
 
-class Function(FunctionBase):
-    """Function class that can executed a generated code."""
-    pass
-
-
 def array(arr, ctx=cpu(0)):
     """Create an array from source arr.
 
@@ -54,4 +49,4 @@ def array(arr, ctx=cpu(0)):
     return ret
 
 
-_init_runtime_module(NDArray, Function)
+_init_ndarray_module(NDArray)
diff --git a/python/tvm/schedule.py b/python/tvm/schedule.py
index 93767b4c..da5413e6 100644
--- a/python/tvm/schedule.py
+++ b/python/tvm/schedule.py
@@ -1,7 +1,7 @@
 # pylint: disable=protected-access, no-member
 """Collection structure in the high level DSL."""
 from __future__ import absolute_import as _abs
-from ._ctypes._api import NodeBase, register_node
+from ._ctypes._node import NodeBase, register_node
 from . import _api_internal
 from . import tensor as _tensor
 
diff --git a/python/tvm/stmt.py b/python/tvm/stmt.py
index 97ef3b6b..49ce8cf9 100644
--- a/python/tvm/stmt.py
+++ b/python/tvm/stmt.py
@@ -1,6 +1,6 @@
 # pylint: disable=protected-access, no-member, missing-docstring
 from __future__ import absolute_import as _abs
-from ._ctypes._api import NodeBase, register_node
+from ._ctypes._node import NodeBase, register_node
 
 class Stmt(NodeBase):
     pass
diff --git a/python/tvm/tensor.py b/python/tvm/tensor.py
index 51767ee3..47a7ec88 100644
--- a/python/tvm/tensor.py
+++ b/python/tvm/tensor.py
@@ -1,7 +1,7 @@
 # pylint: disable=protected-access, no-member, invalid-name
 """Tensor related abstractions"""
 from __future__ import absolute_import as _abs
-from ._ctypes._api import NodeBase, SliceBase, register_node, convert
+from ._ctypes._node import NodeBase, SliceBase, register_node, convert_to_node
 from . import collections as _collections
 from . import _api_internal
 from . import make as _make
@@ -26,7 +26,7 @@ class Tensor(NodeBase):
         ndim = self.ndim
         if len(indices) != ndim:
             raise ValueError("Need to provide %d index in tensor slice" % ndim)
-        indices = convert(indices)
+        indices = convert_to_node(indices)
         args = []
         for x in indices:
             if isinstance(x, _collections.IterVar):
diff --git a/src/api/api_base.cc b/src/api/api_base.cc
new file mode 100644
index 00000000..8f4e6f91
--- /dev/null
+++ b/src/api/api_base.cc
@@ -0,0 +1,37 @@
+/*!
+ *  Copyright (c) 2017 by Contributors
+ *  Implementation of basic API functions
+ * \file api_base.cc
+ */
+#include <tvm/expr.h>
+#include <tvm/tensor.h>
+#include <tvm/api_registry.h>
+
+namespace tvm {
+
+TVM_REGISTER_API(_format_str)
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    CHECK(args[0].type_code() == kNodeHandle);
+    std::ostringstream os;
+    os << args[0].operator NodeRef();
+    *ret = os.str();
+  });
+
+TVM_REGISTER_API(_raw_ptr)
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    CHECK(args[0].type_code() == kNodeHandle);
+    *ret = reinterpret_cast<int64_t>(
+        args[0].node_sptr().get());
+  });
+
+TVM_REGISTER_API(_save_json)
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = SaveJSON(args[0]);
+  });
+
+TVM_REGISTER_API(_load_json)
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = NodeRef(LoadJSON_(args[0]));
+  });
+
+}  // namespace tvm
diff --git a/src/api/api_codegen.cc b/src/api/api_codegen.cc
new file mode 100644
index 00000000..5f2c958c
--- /dev/null
+++ b/src/api/api_codegen.cc
@@ -0,0 +1,57 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ *  Implementation of API functions related to Codegen
+ * \file c_api_codegen.cc
+ */
+#include <tvm/expr.h>
+#include <tvm/ir.h>
+#include <tvm/codegen.h>
+#include <tvm/api_registry.h>
+#include "../codegen/codegen_c.h"
+
+namespace tvm {
+namespace codegen {
+
+TVM_REGISTER_API(_codegen_CompileToC)
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    *ret = CodeGenC().Compile(args[0], args[1]);
+  });
+
+TVM_REGISTER_API(_codegen_MakeAPI)
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    *ret = MakeAPI(
+        args[0], args[1], args[2], args[3]);
+  });
+
+TVM_REGISTER_API(_codegen_SplitHostDevice)
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    *ret = SplitHostDevice(args[0]);
+  });
+
+// generate a dummy packed function for testing
+void DummyHelloFunction(TVMArgs args, TVMRetValue* rv) {
+  LOG(INFO) << args.size() << " arguments";
+  for (int i = 0; i < args.size(); ++i) {
+    switch (args.type_codes[i]) {
+      case kNull: LOG(INFO) << i << ":nullptr"; break;
+      case kFloat: LOG(INFO) << i << ": double=" << args.values[i].v_float64; break;
+      case kInt: LOG(INFO) << i << ": long=" << args.values[i].v_int64; break;
+      case kHandle: LOG(INFO) << i << ": handle=" << args.values[i].v_handle; break;
+      case kArrayHandle: LOG(INFO) << i << ": array_handle=" << args.values[i].v_handle; break;
+      default: LOG(FATAL) << "unhandled type " << runtime::TypeCode2Str(args.type_codes[i]);
+    }
+  }
+}
+
+TVM_REGISTER_API(_codegen_DummyHelloFunction)
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    *ret = runtime::PackedFunc(DummyHelloFunction);
+  });
+
+TVM_REGISTER_API(_codegen_BuildStackVM)
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    *ret = BuildStackVM(args[0]);
+  });
+
+}  // namespace codegen
+}  // namespace tvm
diff --git a/src/c_api/c_api_ir.cc b/src/api/api_ir.cc
similarity index 51%
rename from src/c_api/c_api_ir.cc
rename to src/api/api_ir.cc
index 41739032..af079580 100644
--- a/src/c_api/c_api_ir.cc
+++ b/src/api/api_ir.cc
@@ -1,98 +1,93 @@
 /*!
  *  Copyright (c) 2016 by Contributors
  *  Implementation of API functions related to IR build
- * \file c_api_ir.cc
+ * \file api_ir.cc
  */
 #include <tvm/expr.h>
 #include <tvm/ir.h>
 #include <ir/IROperator.h>
-#include "./c_api_registry.h"
+#include <tvm/api_registry.h>
 
 namespace tvm {
 namespace ir {
 
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
-
 TVM_REGISTER_API(_Var)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = Variable::make(args.at(1), args.at(0));
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = Variable::make(args[1], args[0]);
   });
 
 TVM_REGISTER_API(_make_For)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = For::make(args.at(0),
-                     args.at(1),
-                     args.at(2),
-                     static_cast<ForType>(args.at(3).operator int()),
-                     static_cast<Halide::DeviceAPI>(args.at(4).operator int()),
-                     args.at(5));
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = For::make(args[0],
+                     args[1],
+                     args[2],
+                     static_cast<ForType>(args[3].operator int()),
+                     static_cast<Halide::DeviceAPI>(args[4].operator int()),
+                     args[5]);
   });
 
 TVM_REGISTER_API(_make_Realize)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = Realize::make(args.at(0),
-                         args.at(1),
-                         args.at(2),
-                         args.at(3),
-                         args.at(4),
-                         args.at(5));
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = Realize::make(args[0],
+                         args[1],
+                         args[2],
+                         args[3],
+                         args[4],
+                         args[5]);
   });
 
 
 TVM_REGISTER_API(_make_Call)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = Call::make(args.at(0),
-                      args.at(1),
-                      args.at(2),
-                      static_cast<Call::CallType>(args.at(3).operator int()),
-                      args.at(4),
-                      args.at(5));
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = Call::make(args[0],
+                      args[1],
+                      args[2],
+                      static_cast<Call::CallType>(args[3].operator int()),
+                      args[4],
+                      args[5]);
   });
 
 TVM_REGISTER_API(_make_Allocate)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = Allocate::make(args.at(0),
-                          args.at(1),
-                          args.at(2),
-                          args.at(3),
-                          args.at(4));
+.set_body([](TVMArgs args,  TVMRetValue *ret) {
+    *ret = Allocate::make(args[0],
+                          args[1],
+                          args[2],
+                          args[3],
+                          args[4]);
   });
 
 // make from two arguments
 #define REGISTER_MAKE1(Node)                                 \
   TVM_REGISTER_API(_make_## Node)                            \
-  .set_body([](const ArgStack& args,  RetValue *ret) {       \
-      *ret = Node::make(args.at(0));                         \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {            \
+      *ret = Node::make(args[0]);                            \
     })                                                       \
 
 #define REGISTER_MAKE2(Node)                                 \
   TVM_REGISTER_API(_make_## Node)                            \
-  .set_body([](const ArgStack& args,  RetValue *ret) {       \
-      *ret = Node::make(args.at(0), args.at(1));             \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {       \
+      *ret = Node::make(args[0], args[1]);                   \
     })                                                       \
 
 #define REGISTER_MAKE3(Node)                                 \
   TVM_REGISTER_API(_make_## Node)                            \
-  .set_body([](const ArgStack& args,  RetValue *ret) {       \
-      *ret = Node::make(args.at(0), args.at(1), args.at(2)); \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {            \
+      *ret = Node::make(args[0], args[1], args[2]);          \
     })                                                       \
 
-#define REGISTER_MAKE4(Node)                                 \
+#define REGISTER_MAKE4(Node)                                            \
   TVM_REGISTER_API(_make_## Node)                                       \
-  .set_body([](const ArgStack& args,  RetValue *ret) {                  \
-*ret = Node::make(args.at(0), args.at(1), args.at(2), args.at(3));      \
-    })                                                                  \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                       \
+      *ret = Node::make(args[0], args[1], args[2], args[3]);       \
+    })                                                             \
 
 #define REGISTER_MAKE_BINARY_OP(Node)                        \
   TVM_REGISTER_API(_make_## Node)                            \
-  .set_body([](const ArgStack& args,  RetValue *ret) {       \
-      Expr a = args.at(0), b = args.at(1);                   \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {            \
+      Expr a = args[0], b = args[1];                         \
       match_types(a, b);                                     \
       *ret = Node::make(a, b);                               \
-    })                                                       \
-  .add_argument("lhs", "Expr", "left operand")               \
-  .add_argument("rhs", "Expr", "right operand")
+    })
 
 REGISTER_MAKE3(Reduce);
 REGISTER_MAKE4(AttrStmt);
diff --git a/src/api/api_lang.cc b/src/api/api_lang.cc
new file mode 100644
index 00000000..e570e55c
--- /dev/null
+++ b/src/api/api_lang.cc
@@ -0,0 +1,256 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ *  Implementation of API functions related to Higher DSL build.
+ * \file api_lang.cc
+ */
+#include <tvm/expr.h>
+#include <tvm/ir.h>
+#include <tvm/tensor.h>
+#include <tvm/buffer.h>
+#include <tvm/schedule.h>
+#include <tvm/api_registry.h>
+
+namespace tvm {
+
+TVM_REGISTER_API(_const)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    if (args[0].type_code() == kInt) {
+      *ret = make_const(args[1], args[0].operator int64_t());
+    } else if (args[0].type_code() == kFloat) {
+      *ret = make_const(args[1], args[0].operator double());
+    } else {
+      LOG(FATAL) << "only accept int or float";
+    }
+  });
+
+
+TVM_REGISTER_API(_str)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+  *ret = ir::StringImm::make(args[0]);
+});
+
+
+TVM_REGISTER_API(_Array)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    std::vector<std::shared_ptr<Node> > data;
+    for (int i = 0; i < args.size(); ++i) {
+      data.push_back(args[i].node_sptr());
+    }
+    auto node = std::make_shared<ArrayNode>();
+    node->data = std::move(data);
+    *ret = node;
+  });
+
+TVM_REGISTER_API(_ArrayGetItem)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    int64_t i = args[1];
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<ArrayNode>());
+    auto* n = static_cast<const ArrayNode*>(sptr.get());
+    CHECK_LT(static_cast<size_t>(i), n->data.size())
+        << "out of bound of array";
+    *ret = n->data[i];
+  });
+
+TVM_REGISTER_API(_ArraySize)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<ArrayNode>());
+    *ret = static_cast<int64_t>(
+        static_cast<const ArrayNode*>(sptr.get())->data.size());
+  });
+
+TVM_REGISTER_API(_Map)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    CHECK_EQ(args.size() % 2, 0);
+    MapNode::ContainerType data;
+    for (int i = 0; i < args.num_args; i += 2) {
+      CHECK(args[i].type_code() == kNodeHandle)
+          << "need content of array to be NodeBase";
+      CHECK(args[i + 1].type_code() == kNodeHandle)
+          << "need content of array to be NodeBase";
+      data.emplace(std::make_pair(args[i].node_sptr(),
+                                  args[i + 1].node_sptr()));
+    }
+    auto node = std::make_shared<MapNode>();
+    node->data = std::move(data);
+    *ret = node;
+  });
+
+TVM_REGISTER_API(_MapSize)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<MapNode>());
+    auto* n = static_cast<const MapNode*>(sptr.get());
+    *ret = static_cast<int64_t>(n->data.size());
+  });
+
+TVM_REGISTER_API(_MapGetItem)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    CHECK(args[0].type_code() == kNodeHandle);
+    CHECK(args[1].type_code() == kNodeHandle);
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<MapNode>());
+    auto* n = static_cast<const MapNode*>(sptr.get());
+    auto it = n->data.find(args[1].node_sptr());
+    CHECK(it != n->data.end())
+        << "cannot find the corresponding key in the Map";
+    *ret = (*it).second;
+  });
+
+TVM_REGISTER_API(_MapCount)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    CHECK(args[0].type_code() == kNodeHandle);
+    CHECK(args[1].type_code() == kNodeHandle);
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<MapNode>());
+    auto* n = static_cast<const MapNode*>(sptr.get());
+    *ret = static_cast<int64_t>(
+        n->data.count(args[1].node_sptr()));
+  });
+
+TVM_REGISTER_API(_MapItems)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    auto& sptr = args[0].node_sptr();
+    CHECK(sptr->is_type<MapNode>());
+    auto* n = static_cast<const MapNode*>(sptr.get());
+    auto rkvs = std::make_shared<ArrayNode>();
+    for (const auto& kv : n->data) {
+      rkvs->data.push_back(kv.first);
+      rkvs->data.push_back(kv.second);
+    }
+    *ret = rkvs;
+  });
+
+TVM_REGISTER_API(Range)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    if (args.size() == 1) {
+      *ret = Range(0, args[0]);
+    } else {
+      *ret = Range(args[0], args[1]);
+    }
+  });
+
+TVM_REGISTER_API(_Buffer)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = BufferNode::make(args[0],
+                            args[1],
+                            args[2],
+                            args[3],
+                            args[4]);
+  });
+
+TVM_REGISTER_API(_Tensor)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = TensorNode::make(args[0],
+                            args[1],
+                            args[2],
+                            args[3]);
+  });
+
+TVM_REGISTER_API(_TensorEqual)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = args[0].operator Tensor() == args[1].operator Tensor();
+  });
+
+TVM_REGISTER_API(_TensorHash)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = static_cast<int64_t>(
+        std::hash<Tensor>()(args[0].operator Tensor()));
+  });
+
+TVM_REGISTER_API(_Placeholder)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = Placeholder(args[0],
+                       args[1],
+                       args[2]);
+  });
+
+TVM_REGISTER_API(_ComputeOp)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = ComputeOpNode::make(args[0],
+                               args[1],
+                               args[2]);
+  });
+
+TVM_REGISTER_API(_OpGetOutput)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = args[0].operator Operation().output(
+        args[1].operator int64_t());
+  });
+
+
+TVM_REGISTER_API(_IterVar)
+.set_body([](TVMArgs args,  TVMRetValue* ret) {
+    *ret = IterVar(args[0], args[1], args[2]);
+  });
+
+TVM_REGISTER_API(_Schedule)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    *ret = Schedule(args[0].operator Array<Operation>());
+  });
+
+TVM_REGISTER_API(_StageSetScope)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    args[0].operator Stage()
+        .set_scope(args[1]);
+  });
+
+TVM_REGISTER_API(_StageSplitByFactor)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    IterVar outer, inner;
+    args[0].operator Stage()
+        .split(args[1], &outer, &inner, args[2]);
+    *ret = Array<IterVar>({outer, inner});
+  });
+
+TVM_REGISTER_API(_StageSplitByOuter)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    IterVar inner;
+    args[0].operator Stage()
+        .split(args[1], args[2], &inner, args[3]);
+    *ret = inner;
+  });
+
+TVM_REGISTER_API(_StageFuse)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    IterVar fused;
+    args[0].operator Stage()
+        .split(args[1], args[2], &fused);
+    *ret = fused;
+  });
+
+TVM_REGISTER_API(_StageComputeAt)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    args[0].operator Stage()
+        .compute_at(args[1], args[2]);
+  });
+
+TVM_REGISTER_API(_StageComputeInline)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    args[0].operator Stage()
+        .compute_inline();
+  });
+
+TVM_REGISTER_API(_StageComputeRoot)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    args[0].operator Stage()
+        .compute_root();
+  });
+
+TVM_REGISTER_API(_StageReorder)
+.set_body([](TVMArgs args, TVMRetValue* ret) {
+    args[0].operator Stage()
+        .reorder(args[1]);
+  });
+
+TVM_REGISTER_API(_StageTile)
+  .set_body([](TVMArgs args, TVMRetValue* ret) {
+    IterVar x_outer, y_outer, x_inner, y_inner;
+    args[0].operator Stage()
+        .tile(args[1], args[2], &x_outer, &y_outer,
+              &x_inner, &y_inner, args[3], args[4]);
+    *ret = Array<IterVar>({x_outer, y_outer, x_inner, y_inner});
+  });
+
+}  // namespace tvm
diff --git a/src/c_api/c_api_pass.cc b/src/api/api_pass.cc
similarity index 51%
rename from src/c_api/c_api_pass.cc
rename to src/api/api_pass.cc
index d7d41c4f..0a88e3b1 100644
--- a/src/c_api/c_api_pass.cc
+++ b/src/api/api_pass.cc
@@ -1,53 +1,51 @@
 /*!
- *  Copyright (c) 2016 by Contributors
+ *  Copyright (c) 2017 by Contributors
  *  Exposre of pass functions.
- * \file c_api_pass.cc
+ * \file api_pass.cc
  */
 #include <tvm/expr.h>
 #include <tvm/ir.h>
 #include <tvm/ir_pass.h>
-#include "./c_api_registry.h"
+#include <tvm/api_registry.h>
 
 namespace tvm {
 namespace ir {
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
 
 TVM_REGISTER_API(_pass_Simplify)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    if (NodeTypeChecker<Stmt>::Check(args.at(0).sptr.get())) {
-      *ret = Simplify(args.at(0).operator Stmt());
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    if (args[0].IsNodeType<Stmt>()) {
+      *ret = Simplify(args[0].operator Stmt());
     } else {
-      *ret = Simplify(args.at(0).operator Expr());
+      *ret = Simplify(args[0].operator Expr());
     }
   });
 
 TVM_REGISTER_API(_pass_Equal)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    if (NodeTypeChecker<Stmt>::Check(args.at(0).sptr.get())) {
-      *ret = Equal(args.at(0).operator Stmt(), args.at(1).operator Stmt());
+.set_body([](TVMArgs args, TVMRetValue *ret) {
+    if (args[0].IsNodeType<Stmt>()) {
+      *ret = Equal(args[0].operator Stmt(), args[1].operator Stmt());
     } else {
-      *ret = Equal(args.at(0).operator Expr(), args.at(1).operator Expr());
+      *ret = Equal(args[0].operator Expr(), args[1].operator Expr());
     }
   });
 
 // make from two arguments
 #define REGISTER_PASS1(PassName)                                  \
   TVM_REGISTER_API(_pass_## PassName)                             \
-  .set_body([](const ArgStack& args,  RetValue *ret) {            \
-      *ret = PassName(args.at(0));                                \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                 \
+      *ret = PassName(args[0]);                                   \
     })                                                            \
 
 #define REGISTER_PASS2(PassName)                                  \
   TVM_REGISTER_API(_pass_## PassName)                             \
-  .set_body([](const ArgStack& args,  RetValue *ret) {            \
-      *ret = PassName(args.at(0), args.at(1));                    \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                 \
+      *ret = PassName(args[0], args[1]);                          \
     })                                                            \
 
 #define REGISTER_PASS4(PassName)                                        \
   TVM_REGISTER_API(_pass_## PassName)                                   \
-  .set_body([](const ArgStack& args,  RetValue *ret) {                  \
-      *ret = PassName(args.at(0), args.at(1), args.at(2), args.at(3));  \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                       \
+      *ret = PassName(args[0], args[1], args[2], args[3]);              \
     })                                                                  \
 
 REGISTER_PASS1(ConvertSSA);
diff --git a/src/api/api_registry.cc b/src/api/api_registry.cc
new file mode 100644
index 00000000..d4ab9028
--- /dev/null
+++ b/src/api/api_registry.cc
@@ -0,0 +1,35 @@
+/*!
+ *  Copyright (c) 2017 by Contributors
+ * \file api_registry.cc
+ */
+#include <tvm/expr.h>
+#include <tvm/tensor.h>
+#include <tvm/api_registry.h>
+#include <memory>
+
+namespace tvm {
+
+struct APIManager {
+  std::unordered_map<std::string, std::unique_ptr<APIRegistry> > fmap;
+
+  static APIManager* Global() {
+    static APIManager inst;
+    return &inst;
+  }
+};
+
+APIRegistry& APIRegistry::__REGISTER__(const std::string& name) {  // NOLINT(*)
+  APIManager* m = APIManager::Global();
+  CHECK(!m->fmap.count(name))
+      << "API function " << name << " has already been registered";
+  std::unique_ptr<APIRegistry> p(new APIRegistry());
+  p->name_ = name;
+  m->fmap[name] = std::move(p);
+  return *(m->fmap[name]);
+}
+
+APIRegistry& APIRegistry::set_body(PackedFunc f) {  // NOLINT(*)
+  PackedFunc::RegisterGlobal(name_, f);
+  return *this;
+}
+}  // namespace tvm
diff --git a/src/c_api/c_api_schedule.cc b/src/api/api_schedule.cc
similarity index 65%
rename from src/c_api/c_api_schedule.cc
rename to src/api/api_schedule.cc
index 6ee41b2d..a84642f9 100644
--- a/src/c_api/c_api_schedule.cc
+++ b/src/api/api_schedule.cc
@@ -1,30 +1,28 @@
 /*!
- *  Copyright (c) 2016 by Contributors
+ *  Copyright (c) 2017 by Contributors
  *  Implementation of API functions related to schedule pass.
- * \file c_api_lang.cc
+ * \file api_schedule.cc
  */
 #include <tvm/expr.h>
 #include <tvm/tensor.h>
 #include <tvm/schedule.h>
 #include <tvm/schedule_pass.h>
-#include "./c_api_registry.h"
+#include <tvm/api_registry.h>
 #include "../schedule/graph.h"
 
 namespace tvm {
 namespace schedule {
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
 
 #define REGISTER_SCHEDULE_PASS1(PassName)                         \
   TVM_REGISTER_API(_schedule_## PassName)                         \
-  .set_body([](const ArgStack& args,  RetValue *ret) {            \
-      *ret = PassName(args.at(0));                                \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                 \
+      *ret = PassName(args[0]);                                   \
     })                                                            \
 
 #define REGISTER_SCHEDULE_PASS2(PassName)                         \
   TVM_REGISTER_API(_schedule_## PassName)                         \
-  .set_body([](const ArgStack& args,  RetValue *ret) {            \
-      *ret = PassName(args.at(0), args.at(1));                    \
+  .set_body([](TVMArgs args,  TVMRetValue *ret) {                 \
+      *ret = PassName(args[0], args[1]);                          \
     })                                                            \
 
 
diff --git a/src/api/c_api.cc b/src/api/c_api.cc
new file mode 100644
index 00000000..c4290c57
--- /dev/null
+++ b/src/api/c_api.cc
@@ -0,0 +1,153 @@
+/*!
+ *  Copyright (c) 2016 by Contributors
+ * Implementation of C API
+ * \file c_api.cc
+ */
+#include <dmlc/base.h>
+#include <dmlc/logging.h>
+#include <dmlc/thread_local.h>
+#include <tvm/c_api.h>
+#include <tvm/api_registry.h>
+#include <vector>
+#include <string>
+#include <exception>
+#include "../runtime/runtime_base.h"
+
+
+/*! \brief entry to to easily hold returning information */
+struct TVMAPIThreadLocalEntry {
+  /*! \brief result holder for returning strings */
+  std::vector<std::string> ret_vec_str;
+  /*! \brief result holder for returning string pointers */
+  std::vector<const char *> ret_vec_charp;
+  /*! \brief result holder for retruning string */
+  std::string ret_str;
+};
+
+using namespace tvm;
+
+/*! \brief Thread local store that can be used to hold return values. */
+typedef dmlc::ThreadLocalStore<TVMAPIThreadLocalEntry> TVMAPIThreadLocalStore;
+
+using TVMAPINode = std::shared_ptr<Node>;
+
+struct APIAttrGetter : public AttrVisitor {
+  std::string skey;
+  TVMRetValue* ret;
+  bool found_node_ref{false};
+
+  void Visit(const char* key, double* value) final {
+    if (skey == key) *ret = value[0];
+  }
+  void Visit(const char* key, int64_t* value) final {
+    if (skey == key) *ret = value[0];
+  }
+  void Visit(const char* key, uint64_t* value) final {
+    CHECK_LE(value[0], static_cast<uint64_t>(std::numeric_limits<int64_t>::max()))
+        << "cannot return too big constant";
+    if (skey == key) *ret = static_cast<int64_t>(value[0]);
+  }
+  void Visit(const char* key, int* value) final {
+    if (skey == key) *ret = static_cast<int64_t>(value[0]);
+  }
+  void Visit(const char* key, bool* value) final {
+    if (skey == key) *ret = static_cast<int64_t>(value[0]);
+  }
+  void Visit(const char* key, Type* value) final {
+    if (skey == key) *ret = value[0];
+  }
+  void Visit(const char* key, std::string* value) final {
+    if (skey == key) *ret = value[0];
+  }
+  void Visit(const char* key, NodeRef* value) final {
+    if (skey == key) {
+      *ret = value[0];
+      found_node_ref = true;
+    }
+  }
+};
+
+struct APIAttrDir : public AttrVisitor {
+  std::vector<std::string>* names;
+
+  void Visit(const char* key, double* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, int64_t* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, uint64_t* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, bool* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, int* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, Type* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, std::string* value) final {
+    names->push_back(key);
+  }
+  void Visit(const char* key, NodeRef* value) final {
+    names->push_back(key);
+  }
+};
+
+
+int TVMNodeFree(NodeHandle handle) {
+  API_BEGIN();
+  delete static_cast<TVMAPINode*>(handle);
+  API_END();
+}
+
+int TVMNodeGetAttr(NodeHandle handle,
+                   const char* key,
+                   TVMValue* ret_val,
+                   int* ret_type_code,
+                   int* ret_success) {
+  API_BEGIN();
+  TVMRetValue rv;
+  APIAttrGetter getter;
+  getter.skey = key;
+  getter.ret = &rv;
+  TVMAPINode* tnode = static_cast<TVMAPINode*>(handle);
+  if (getter.skey == "type_key") {
+    ret_val->v_str = (*tnode)->type_key();
+    *ret_type_code = kStr;
+    *ret_success = 1;
+  } else {
+    (*tnode)->VisitAttrs(&getter);
+    *ret_success = getter.found_node_ref || rv.type_code() != kNull;
+    if (rv.type_code() == kStr) {
+      TVMAPIThreadLocalEntry *e = TVMAPIThreadLocalStore::Get();
+      e->ret_str = rv.operator std::string();
+      *ret_type_code = kStr;
+      ret_val->v_str = e->ret_str.c_str();
+    } else {
+      rv.MoveToCHost(ret_val, ret_type_code);
+    }
+  }
+  API_END();
+}
+
+int TVMNodeListAttrNames(NodeHandle handle,
+                         int *out_size,
+                         const char*** out_array) {
+  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
+  API_BEGIN();
+  ret->ret_vec_str.clear();
+  TVMAPINode* tnode = static_cast<TVMAPINode*>(handle);
+  APIAttrDir dir;
+  dir.names = &(ret->ret_vec_str);
+  (*tnode)->VisitAttrs(&dir);
+  ret->ret_vec_charp.clear();
+  for (size_t i = 0; i < ret->ret_vec_str.size(); ++i) {
+    ret->ret_vec_charp.push_back(ret->ret_vec_str[i].c_str());
+  }
+  *out_array = dmlc::BeginPtr(ret->ret_vec_charp);
+  *out_size = static_cast<int>(ret->ret_vec_str.size());
+  API_END();
+}
diff --git a/src/base/common.h b/src/base/common.h
index 432ec74d..4b1c799e 100644
--- a/src/base/common.h
+++ b/src/base/common.h
@@ -42,5 +42,78 @@ inline Type String2Type(std::string s) {
   return Type(code, bits, lanes);
 }
 
+inline const char* TVMTypeCode2Str(int type_code) {
+  switch (type_code) {
+    case kInt: return "int";
+    case kFloat: return "float";
+    case kStr: return "str";
+    case kHandle: return "Handle";
+    case kNull: return "NULL";
+    case kNodeHandle: return "NodeHandle";
+    default: LOG(FATAL) << "unknown type_code="
+                        << static_cast<int>(type_code); return "";
+  }
+}
+template<typename T>
+struct NodeTypeChecker {
+  static inline bool Check(Node* sptr) {
+    // This is the only place in the project where RTTI is used
+    // It can be turned off, but will make non strict checking.
+    // TODO(tqchen) possibly find alternative to turn of RTTI
+    using ContainerType = typename T::ContainerType;
+    return (dynamic_cast<ContainerType*>(sptr) != nullptr);
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    using ContainerType = typename T::ContainerType;
+    os << ContainerType::_type_key;
+  }
+};
+
+template<typename T>
+struct NodeTypeChecker<Array<T> > {
+  static inline bool Check(Node* sptr) {
+    if (sptr == nullptr) return false;
+    if (!sptr->is_type<ArrayNode>()) return false;
+    ArrayNode* n = static_cast<ArrayNode*>(sptr);
+    for (const auto& p : n->data) {
+      if (!NodeTypeChecker<T>::Check(p.get())) return false;
+    }
+    return true;
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    os << "array<";
+    NodeTypeChecker<T>::PrintName(os);
+    os << ">";
+  }
+};
+
+template<typename K, typename V>
+struct NodeTypeChecker<Map<K, V> > {
+  static inline bool Check(Node* sptr) {
+    if (sptr == nullptr) return false;
+    if (!sptr->is_type<MapNode>()) return false;
+    MapNode* n = static_cast<MapNode*>(sptr);
+    for (const auto& kv : n->data) {
+      if (!NodeTypeChecker<K>::Check(kv.first.get())) return false;
+      if (!NodeTypeChecker<V>::Check(kv.second.get())) return false;
+    }
+    return true;
+  }
+  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
+    os << "map<";
+    NodeTypeChecker<K>::PrintName(os);
+    os << ',';
+    NodeTypeChecker<V>::PrintName(os);
+    os << '>';
+  }
+};
+
+template<typename T>
+inline std::string NodeTypeName() {
+  std::ostringstream os;
+  NodeTypeChecker<T>::PrintName(os);
+  return os.str();
+}
+
 }  // namespace tvm
 #endif  // TVM_BASE_COMMON_H_
diff --git a/src/c_api/c_api.cc b/src/c_api/c_api.cc
deleted file mode 100644
index 7b360594..00000000
--- a/src/c_api/c_api.cc
+++ /dev/null
@@ -1,260 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- * Implementation of C API
- * \file c_api.cc
- */
-#include <tvm/c_api.h>
-#include "./c_api_common.h"
-#include "./c_api_registry.h"
-
-/*! \brief entry to to easily hold returning information */
-struct TVMAPIThreadLocalEntry {
-  /*! \brief result holder for returning strings */
-  std::vector<std::string> ret_vec_str;
-  /*! \brief result holder for returning string pointers */
-  std::vector<const char *> ret_vec_charp;
-  /*! \brief argument stack */
-  std::vector<tvm::APIVariantValue> arg_stack;
-  /*! \brief return value */
-  tvm::APIVariantValue ret_value;
-  // clear calling stack
-  inline void Clear() {
-    arg_stack.clear();
-    ret_value.sptr.reset();
-  }
-  inline void SetReturn(TVMValue* ret_val, int* ret_type_code);
-};
-
-using namespace tvm;
-
-/*! \brief Thread local store that can be used to hold return values. */
-typedef dmlc::ThreadLocalStore<TVMAPIThreadLocalEntry> TVMAPIThreadLocalStore;
-
-using TVMAPINode = std::shared_ptr<Node>;
-
-struct APIAttrGetter : public AttrVisitor {
-  std::string skey;
-  APIVariantValue* ret;
-  bool found_node_ref{false};
-
-  void Visit(const char* key, double* value) final {
-    if (skey == key) *ret = value[0];
-  }
-  void Visit(const char* key, int64_t* value) final {
-    if (skey == key) *ret = value[0];
-  }
-  void Visit(const char* key, uint64_t* value) final {
-    CHECK_LE(value[0], static_cast<uint64_t>(std::numeric_limits<int64_t>::max()))
-        << "cannot return too big constant";
-    if (skey == key) *ret = static_cast<int64_t>(value[0]);
-  }
-  void Visit(const char* key, int* value) final {
-    if (skey == key) *ret = static_cast<int64_t>(value[0]);
-  }
-  void Visit(const char* key, bool* value) final {
-    if (skey == key) *ret = static_cast<int64_t>(value[0]);
-  }
-  void Visit(const char* key, Type* value) final {
-    if (skey == key) *ret = value[0];
-  }
-  void Visit(const char* key, std::string* value) final {
-    if (skey == key) *ret = value[0];
-  }
-  void Visit(const char* key, NodeRef* value) final {
-    if (skey == key) {
-      *ret = value[0];
-      found_node_ref = true;
-    }
-  }
-};
-
-struct APIAttrDir : public AttrVisitor {
-  std::vector<std::string>* names;
-
-  void Visit(const char* key, double* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, int64_t* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, uint64_t* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, bool* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, int* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, Type* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, std::string* value) final {
-    names->push_back(key);
-  }
-  void Visit(const char* key, NodeRef* value) final {
-    names->push_back(key);
-  }
-};
-
-int TVMListAPIFuncNames(int *out_size,
-                            const char*** out_array) {
-  API_BEGIN();
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-  ret->ret_vec_str = dmlc::Registry<APIFuncReg>::ListAllNames();
-  ret->ret_vec_charp.clear();
-  for (size_t i = 0; i < ret->ret_vec_str.size(); ++i) {
-    ret->ret_vec_charp.push_back(ret->ret_vec_str[i].c_str());
-  }
-  *out_array = dmlc::BeginPtr(ret->ret_vec_charp);
-  *out_size = static_cast<int>(ret->ret_vec_str.size());
-  API_END();
-}
-
-int TVMGetAPIFuncHandle(const char* fname,
-                            APIFuncHandle* out) {
-  API_BEGIN();
-  const APIFuncReg* reg = dmlc::Registry<APIFuncReg>::Find(fname);
-  CHECK(reg != nullptr) << "cannot find function " << fname;
-  *out = (APIFuncHandle)reg;
-  API_END();
-}
-
-int TVMGetAPIFuncInfo(APIFuncHandle handle,
-                          const char **real_name,
-                          const char **description,
-                          int *num_doc_args,
-                          const char ***arg_names,
-                          const char ***arg_type_infos,
-                          const char ***arg_descriptions,
-                          const char **return_type) {
-  const auto *op = static_cast<const APIFuncReg *>(handle);
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-
-  API_BEGIN();
-  *real_name = op->name.c_str();
-  *description = op->description.c_str();
-  *num_doc_args = static_cast<int>(op->arguments.size());
-  if (return_type) *return_type = nullptr;
-  ret->ret_vec_charp.clear();
-  for (size_t i = 0; i < op->arguments.size(); ++i) {
-    ret->ret_vec_charp.push_back(op->arguments[i].name.c_str());
-  }
-  for (size_t i = 0; i < op->arguments.size(); ++i) {
-    ret->ret_vec_charp.push_back(op->arguments[i].type_info_str.c_str());
-  }
-  for (size_t i = 0; i < op->arguments.size(); ++i) {
-    ret->ret_vec_charp.push_back(op->arguments[i].description.c_str());
-  }
-  *arg_names = dmlc::BeginPtr(ret->ret_vec_charp);
-  *arg_type_infos = dmlc::BeginPtr(ret->ret_vec_charp) + op->arguments.size();
-  *arg_descriptions = dmlc::BeginPtr(ret->ret_vec_charp) + (op->arguments.size() * 2);
-  API_END();
-}
-
-int TVMAPIPushStack(TVMValue arg,
-                    int type_code) {
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-  API_BEGIN();
-  ret->arg_stack.resize(ret->arg_stack.size() + 1);
-  APIVariantValue& v = ret->arg_stack.back();
-
-  v.type_code = type_code;
-  switch (type_code) {
-    case kInt: case kUInt: case kFloat: case kNull: {
-      v.v_union = arg; break;
-    }
-    case kStr: {
-      v.str = arg.v_str; break;
-    }
-    case kNodeHandle: {
-      v.sptr = *static_cast<TVMAPINode*>(arg.v_handle); break;
-    }
-    default: LOG(FATAL) << "TVM API cannot take type " << TVMTypeCode2Str(type_code);
-  }
-  API_END_HANDLE_ERROR(ret->Clear());
-}
-
-int TVMAPIFuncCall(APIFuncHandle handle,
-                   TVMValue* ret_val,
-                   int* ret_type_code) {
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-  API_BEGIN();
-  const auto *op = static_cast<const APIFuncReg *>(handle);
-  op->body(ret->arg_stack, &(ret->ret_value));
-  ret->SetReturn(ret_val, ret_type_code);
-  ret->arg_stack.clear();
-  API_END_HANDLE_ERROR(ret->Clear());
-}
-
-int TVMNodeFree(NodeHandle handle) {
-  API_BEGIN();
-  delete static_cast<TVMAPINode*>(handle);
-  API_END();
-}
-
-int TVMNodeGetAttr(NodeHandle handle,
-                   const char* key,
-                   TVMValue* ret_val,
-                   int* ret_type_code,
-                   int* ret_success) {
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-  API_BEGIN();
-  ret->ret_value.type_code = kNull;
-  APIAttrGetter getter;
-  getter.skey = key;
-  getter.ret = &(ret->ret_value);
-  TVMAPINode* tnode = static_cast<TVMAPINode*>(handle);
-  if (getter.skey == "type_key") {
-    ret_val->v_str = (*tnode)->type_key();
-    *ret_type_code = kStr;
-    *ret_success = 1;
-  } else {
-    (*tnode)->VisitAttrs(&getter);
-    if (ret->ret_value.type_code != kNull) {
-      ret->SetReturn(ret_val, ret_type_code);
-      *ret_success = 1;
-    } else {
-      *ret_success = getter.found_node_ref ? 1 : 0;
-      *ret_type_code = kNull;
-    }
-  }
-  API_END_HANDLE_ERROR(ret->Clear());
-}
-
-int TVMNodeListAttrNames(NodeHandle handle,
-                         int *out_size,
-                         const char*** out_array) {
-  TVMAPIThreadLocalEntry *ret = TVMAPIThreadLocalStore::Get();
-  API_BEGIN();
-  ret->ret_vec_str.clear();
-  TVMAPINode* tnode = static_cast<TVMAPINode*>(handle);
-  APIAttrDir dir;
-  dir.names = &(ret->ret_vec_str);
-  (*tnode)->VisitAttrs(&dir);
-  ret->ret_vec_charp.clear();
-  for (size_t i = 0; i < ret->ret_vec_str.size(); ++i) {
-    ret->ret_vec_charp.push_back(ret->ret_vec_str[i].c_str());
-  }
-  *out_array = dmlc::BeginPtr(ret->ret_vec_charp);
-  *out_size = static_cast<int>(ret->ret_vec_str.size());
-  API_END();
-}
-
-
-inline void TVMAPIThreadLocalEntry::SetReturn(TVMValue* ret_val,
-                                              int* ret_type_code) {
-  APIVariantValue& rv = ret_value;
-  *ret_type_code = rv.type_code;
-  if (rv.type_code == kNodeHandle) {
-    if (rv.sptr.get() != nullptr) {
-      ret_val->v_handle = new TVMAPINode(std::move(rv.sptr));
-    } else {
-      ret_val->v_handle = nullptr;
-    }
-  } else if (rv.type_code == kFuncHandle) {
-    ret_val->v_handle = new runtime::PackedFunc::FType(std::move(rv.func));
-  } else {
-    *ret_val = rv.v_union;
-  }
-}
diff --git a/src/c_api/c_api_codegen.cc b/src/c_api/c_api_codegen.cc
deleted file mode 100644
index a198365f..00000000
--- a/src/c_api/c_api_codegen.cc
+++ /dev/null
@@ -1,61 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- *  Implementation of API functions related to Codegen
- * \file c_api_codegen.cc
- */
-#include <tvm/expr.h>
-#include <tvm/ir.h>
-#include <tvm/codegen.h>
-
-#include "./c_api_registry.h"
-#include "../codegen/codegen_c.h"
-
-namespace tvm {
-namespace codegen {
-
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
-
-TVM_REGISTER_API(_codegen_CompileToC)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = CodeGenC().Compile(args.at(0), args.at(1));
-  });
-
-TVM_REGISTER_API(_codegen_MakeAPI)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = MakeAPI(
-        args.at(0), args.at(1), args.at(2), args.at(3));
-  });
-
-TVM_REGISTER_API(_codegen_SplitHostDevice)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = SplitHostDevice(args.at(0));
-  });
-
-
-// generate a dummy packed function for testing
-void DummyHelloFunction(const TVMValue* args, const int* type_code, int num_args) {
-  LOG(INFO) << num_args << " arguments";
-  for (int i = 0; i < num_args; ++i) {
-    switch (type_code[i]) {
-      case kNull: LOG(INFO) << i << ":nullptr"; break;
-      case kFloat: LOG(INFO) << i << ": double=" << args[i].v_float64; break;
-      case kInt: LOG(INFO) << i << ": long=" << args[i].v_int64; break;
-      case kHandle: LOG(INFO) << i << ": handle=" << args[i].v_handle; break;
-      default: LOG(FATAL) << "unhandled type " << TVMTypeCode2Str(type_code[i]);
-    }
-  }
-}
-
-TVM_REGISTER_API(_codegen_DummyHelloFunction)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = runtime::PackedFunc(DummyHelloFunction);
-  });
-
-TVM_REGISTER_API(_codegen_BuildStackVM)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = BuildStackVM(args.at(0));
-  });
-
-}  // namespace codegen
-}  // namespace tvm
diff --git a/src/c_api/c_api_common.h b/src/c_api/c_api_common.h
deleted file mode 100644
index 55b3fe0b..00000000
--- a/src/c_api/c_api_common.h
+++ /dev/null
@@ -1,19 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- * \file c_api_common.h
- * \brief Common fields of all C APIs
- */
-#ifndef TVM_C_API_C_API_COMMON_H_
-#define TVM_C_API_C_API_COMMON_H_
-
-#include <dmlc/base.h>
-#include <dmlc/logging.h>
-#include <dmlc/thread_local.h>
-#include <tvm/c_api.h>
-#include <vector>
-#include <string>
-#include <exception>
-#include "./c_api_registry.h"
-#include "../runtime/runtime_base.h"
-
-#endif  // TVM_C_API_C_API_COMMON_H_
diff --git a/src/c_api/c_api_function.cc b/src/c_api/c_api_function.cc
deleted file mode 100644
index f550804a..00000000
--- a/src/c_api/c_api_function.cc
+++ /dev/null
@@ -1,47 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- *  Implementation of API functions
- * \file c_api_impl.cc
- */
-#include <tvm/expr.h>
-#include <tvm/tensor.h>
-#include "./c_api_registry.h"
-
-namespace dmlc {
-DMLC_REGISTRY_ENABLE(::tvm::APIFuncReg);
-}  // namespace dmlc
-
-namespace tvm {
-
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
-
-TVM_REGISTER_API(_format_str)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    std::ostringstream os;
-    os << args.at(0).operator NodeRef();
-    *ret = os.str();
-  })
-.add_argument("expr", "Node", "expression to be printed");
-
-TVM_REGISTER_API(_raw_ptr)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    *ret = reinterpret_cast<int64_t>(args.at(0).sptr.get());
-  })
-.add_argument("src", "NodeBase", "the node base");
-
-TVM_REGISTER_API(_save_json)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = SaveJSON(args.at(0));
-  })
-.add_argument("src", "json_str", "the node ");
-
-TVM_REGISTER_API(_load_json)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = NodeRef(LoadJSON_(args.at(0)));
-  })
-.add_argument("src", "NodeBase", "the node");
-
-}  // namespace tvm
diff --git a/src/c_api/c_api_lang.cc b/src/c_api/c_api_lang.cc
deleted file mode 100644
index 2c65d81b..00000000
--- a/src/c_api/c_api_lang.cc
+++ /dev/null
@@ -1,273 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- *  Implementation of API functions related to Higher DSL build.
- * \file c_api_lang.cc
- */
-#include <tvm/expr.h>
-#include <tvm/ir.h>
-#include <tvm/tensor.h>
-#include <tvm/buffer.h>
-#include <tvm/schedule.h>
-#include "./c_api_registry.h"
-
-namespace tvm {
-
-using ArgStack = const std::vector<APIVariantValue>;
-using RetValue = APIVariantValue;
-
-TVM_REGISTER_API(_const)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    if (args.at(0).type_code == kInt) {
-      *ret = make_const(args.at(1), args.at(0).operator int64_t());
-    } else if (args.at(0).type_code == kFloat) {
-      *ret = make_const(args.at(1), args.at(0).operator double());
-    } else {
-      LOG(FATAL) << "only accept int or float";
-    }
-  })
-.add_argument("src", "Number", "source number")
-.add_argument("dtype", "str", "data type");
-
-
-TVM_REGISTER_API(_str)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-  *ret = ir::StringImm::make(args.at(0));
-});
-
-
-TVM_REGISTER_API(_Array)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    std::vector<std::shared_ptr<Node> > data;
-    for (size_t i = 0; i < args.size(); ++i) {
-      CHECK(args.at(i).type_code == kNodeHandle)
-          << "need content of array to be NodeBase";
-      data.push_back(args.at(i).sptr);
-    }
-    auto node = std::make_shared<ArrayNode>();
-    node->data = std::move(data);
-    ret->type_code = kNodeHandle;
-    ret->sptr = node;
-  });
-
-TVM_REGISTER_API(_ArrayGetItem)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    int64_t i = args.at(1);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<ArrayNode>());
-    auto* n = static_cast<const ArrayNode*>(sptr.get());
-    CHECK_LT(static_cast<size_t>(i), n->data.size())
-        << "out of bound of array";
-    ret->sptr = n->data[i];
-    ret->type_code = kNodeHandle;
-  });
-
-TVM_REGISTER_API(_ArraySize)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<ArrayNode>());
-    *ret = static_cast<int64_t>(
-        static_cast<const ArrayNode*>(sptr.get())->data.size());
-  });
-
-TVM_REGISTER_API(_Map)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK_EQ(args.size() % 2, 0U);
-    MapNode::ContainerType data;
-    for (size_t i = 0; i < args.size(); i += 2) {
-      CHECK(args.at(i).type_code == kNodeHandle)
-          << "need content of array to be NodeBase";
-      CHECK(args.at(i + 1).type_code == kNodeHandle)
-          << "need content of array to be NodeBase";
-      data.emplace(std::make_pair(args.at(i).sptr, args.at(i + 1).sptr));
-    }
-    auto node = std::make_shared<MapNode>();
-    node->data = std::move(data);
-    ret->type_code = kNodeHandle;
-    ret->sptr = node;
-  });
-
-TVM_REGISTER_API(_MapSize)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<MapNode>());
-    auto* n = static_cast<const MapNode*>(sptr.get());
-    *ret = static_cast<int64_t>(n->data.size());
-  });
-
-TVM_REGISTER_API(_MapGetItem)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    CHECK(args.at(1).type_code == kNodeHandle);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<MapNode>());
-    auto* n = static_cast<const MapNode*>(sptr.get());
-    auto it = n->data.find(args.at(1).sptr);
-    CHECK(it != n->data.end())
-        << "cannot find the corresponding key in the Map";
-    ret->sptr = (*it).second;
-    ret->type_code = kNodeHandle;
-  });
-
-TVM_REGISTER_API(_MapCount)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    CHECK(args.at(1).type_code == kNodeHandle);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<MapNode>());
-    auto* n = static_cast<const MapNode*>(sptr.get());
-    *ret = static_cast<int64_t>(n->data.count(args.at(1).sptr));
-  });
-
-TVM_REGISTER_API(_MapItems)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    CHECK(args.at(0).type_code == kNodeHandle);
-    auto& sptr = args.at(0).sptr;
-    CHECK(sptr->is_type<MapNode>());
-    auto* n = static_cast<const MapNode*>(sptr.get());
-    auto rkvs = std::make_shared<ArrayNode>();
-    for (const auto& kv : n->data) {
-      rkvs->data.push_back(kv.first);
-      rkvs->data.push_back(kv.second);
-    }
-    ret->sptr = rkvs;
-    ret->type_code = kNodeHandle;
-  });
-
-TVM_REGISTER_API(Range)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    if (args.size() == 1) {
-      *ret = Range(0, args.at(0));
-    } else {
-      *ret = Range(args.at(0), args.at(1));
-    }
-  })
-.describe("create a domain range")
-.add_argument("begin", "Expr", "beginning of the range.")
-.add_argument("end", "Expr", "extent of the range");
-
-TVM_REGISTER_API(_Buffer)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = BufferNode::make(args.at(0),
-                            args.at(1),
-                            args.at(2),
-                            args.at(3),
-                            args.at(4));
-  });
-
-TVM_REGISTER_API(_Tensor)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = TensorNode::make(args.at(0),
-                            args.at(1),
-                            args.at(2),
-                            args.at(3));
-  });
-
-TVM_REGISTER_API(_TensorEqual)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = args.at(0).operator Tensor() == args.at(1).operator Tensor();
-  });
-
-TVM_REGISTER_API(_TensorHash)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = static_cast<int64_t>(
-        std::hash<Tensor>()(args.at(0).operator Tensor()));
-  });
-
-TVM_REGISTER_API(_Placeholder)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = Placeholder(args.at(0),
-                       args.at(1),
-                       args.at(2));
-  });
-
-TVM_REGISTER_API(_ComputeOp)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = ComputeOpNode::make(args.at(0),
-                               args.at(1),
-                               args.at(2));
-  });
-
-TVM_REGISTER_API(_OpGetOutput)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = args.at(0).operator Operation().output(
-        args.at(1).operator int64_t());
-  });
-
-
-TVM_REGISTER_API(_IterVar)
-.set_body([](const ArgStack& args,  RetValue *ret) {
-    *ret = IterVar(args.at(0), args.at(1), args.at(2));
-  });
-
-TVM_REGISTER_API(_Schedule)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    *ret = Schedule(args.at(0).operator Array<Operation>());
-  });
-
-TVM_REGISTER_API(_StageSetScope)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    args.at(0).operator Stage()
-        .set_scope(args.at(1));
-  });
-
-TVM_REGISTER_API(_StageSplitByFactor)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    IterVar outer, inner;
-    args.at(0).operator Stage()
-        .split(args.at(1), &outer, &inner, args.at(2));
-    *ret = Array<IterVar>({outer, inner});
-  });
-
-TVM_REGISTER_API(_StageSplitByOuter)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    IterVar inner;
-    args.at(0).operator Stage()
-        .split(args.at(1), args.at(2), &inner, args.at(3));
-    *ret = inner;
-  });
-
-TVM_REGISTER_API(_StageFuse)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    IterVar fused;
-    args.at(0).operator Stage()
-        .split(args.at(1), args.at(2), &fused);
-    *ret = fused;
-  });
-
-TVM_REGISTER_API(_StageComputeAt)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    args.at(0).operator Stage()
-        .compute_at(args.at(1), args.at(2));
-  });
-
-TVM_REGISTER_API(_StageComputeInline)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    args.at(0).operator Stage()
-        .compute_inline();
-  });
-
-TVM_REGISTER_API(_StageComputeRoot)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    args.at(0).operator Stage()
-        .compute_root();
-  });
-
-TVM_REGISTER_API(_StageReorder)
-.set_body([](const ArgStack& args, RetValue *ret) {
-    args.at(0).operator Stage()
-        .reorder(args.at(1));
-  });
-
-TVM_REGISTER_API(_StageTile)
-  .set_body([](const ArgStack& args, RetValue *ret) {
-    IterVar x_outer, y_outer, x_inner, y_inner;
-    args.at(0).operator Stage()
-        .tile(args.at(1), args.at(2), &x_outer, &y_outer,
-              &x_inner, &y_inner, args.at(3), args.at(4));
-    *ret = Array<IterVar>({x_outer, y_outer, x_inner, y_inner});
-  });
-
-}  // namespace tvm
diff --git a/src/c_api/c_api_registry.h b/src/c_api/c_api_registry.h
deleted file mode 100644
index 8852b937..00000000
--- a/src/c_api/c_api_registry.h
+++ /dev/null
@@ -1,240 +0,0 @@
-/*!
- *  Copyright (c) 2016 by Contributors
- * \file c_api_registry.h
- * \brief Quick registry for C API.
- */
-#ifndef TVM_C_API_C_API_REGISTRY_H_
-#define TVM_C_API_C_API_REGISTRY_H_
-
-#include <tvm/base.h>
-#include <tvm/expr.h>
-#include <tvm/c_api.h>
-#include <tvm/runtime/packed_func.h>
-#include <memory>
-#include <limits>
-#include <string>
-#include <vector>
-#include "../base/common.h"
-
-namespace tvm {
-
-inline const char* TVMTypeCode2Str(int type_code) {
-  switch (type_code) {
-    case kInt: return "int";
-    case kFloat: return "float";
-    case kStr: return "str";
-    case kHandle: return "Handle";
-    case kNull: return "NULL";
-    case kNodeHandle: return "NodeHandle";
-    default: LOG(FATAL) << "unknown type_code="
-                        << static_cast<int>(type_code); return "";
-  }
-}
-
-template<typename T>
-struct NodeTypeChecker {
-  static inline bool Check(Node* sptr) {
-    // This is the only place in the project where RTTI is used
-    // It can be turned off, but will make non strict checking.
-    // TODO(tqchen) possibly find alternative to turn of RTTI
-    using ContainerType = typename T::ContainerType;
-    return (dynamic_cast<ContainerType*>(sptr) != nullptr);
-  }
-  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
-    using ContainerType = typename T::ContainerType;
-    os << ContainerType::_type_key;
-  }
-};
-
-template<typename T>
-struct NodeTypeChecker<Array<T> > {
-  static inline bool Check(Node* sptr) {
-    if (sptr == nullptr) return false;
-    if (!sptr->is_type<ArrayNode>()) return false;
-    ArrayNode* n = static_cast<ArrayNode*>(sptr);
-    for (const auto& p : n->data) {
-      if (!NodeTypeChecker<T>::Check(p.get())) return false;
-    }
-    return true;
-  }
-  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
-    os << "array<";
-    NodeTypeChecker<T>::PrintName(os);
-    os << ">";
-  }
-};
-
-template<typename K, typename V>
-struct NodeTypeChecker<Map<K, V> > {
-  static inline bool Check(Node* sptr) {
-    if (sptr == nullptr) return false;
-    if (!sptr->is_type<MapNode>()) return false;
-    MapNode* n = static_cast<MapNode*>(sptr);
-    for (const auto& kv : n->data) {
-      if (!NodeTypeChecker<K>::Check(kv.first.get())) return false;
-      if (!NodeTypeChecker<V>::Check(kv.second.get())) return false;
-    }
-    return true;
-  }
-  static inline void PrintName(std::ostringstream& os) { // NOLINT(*)
-    os << "map<";
-    NodeTypeChecker<K>::PrintName(os);
-    os << ',';
-    NodeTypeChecker<V>::PrintName(os);
-    os << '>';
-  }
-};
-
-template<typename T>
-inline std::string NodeTypeName() {
-  std::ostringstream os;
-  NodeTypeChecker<T>::PrintName(os);
-  return os.str();
-}
-
-/*! \brief Variant container for API calls */
-class APIVariantValue {
- public:
-  /*! \brief the type id */
-  int type_code{kNull};
-  /*! \brief shared pointer container */
-  std::shared_ptr<Node> sptr;
-  /*! \brief string container */
-  std::string str;
-  /*! \brief the variant holder */
-  TVMValue v_union;
-  /*! \brief std::function */
-  runtime::PackedFunc::FType func;
-  // constructor
-  APIVariantValue() {
-  }
-  // clear value
-  inline void Clear() {
-  }
-  // assign op
-  inline APIVariantValue& operator=(double value) {
-    type_code = kFloat;
-    v_union.v_float64 = value;
-    return *this;
-  }
-  inline APIVariantValue& operator=(std::nullptr_t value) {
-    type_code = kHandle;
-    v_union.v_handle = value;
-    return *this;
-  }
-  inline APIVariantValue& operator=(int64_t value) {
-    type_code = kInt;
-    v_union.v_int64 = value;
-    return *this;
-  }
-  inline APIVariantValue& operator=(bool value) {
-    type_code = kInt;
-    v_union.v_int64 = value;
-    return *this;
-  }
-  inline APIVariantValue& operator=(std::string value) {
-    type_code = kStr;
-    str = std::move(value);
-    v_union.v_str = str.c_str();
-    return *this;
-  }
-  inline APIVariantValue& operator=(const NodeRef& ref) {
-    if (ref.node_.get() == nullptr) {
-      type_code = kNull;
-    } else {
-      type_code = kNodeHandle;
-      this->sptr = ref.node_;
-    }
-    return *this;
-  }
-  inline APIVariantValue& operator=(const runtime::PackedFunc& f) {
-    type_code = kFuncHandle;
-    this->func = f.body();
-    return *this;
-  }
-  inline APIVariantValue& operator=(const Type& value) {
-    return operator=(Type2String(value));
-  }
-  template<typename T,
-           typename = typename std::enable_if<std::is_base_of<NodeRef, T>::value>::type>
-  inline operator T() const {
-    if (type_code == kNull) return T();
-    CHECK_EQ(type_code, kNodeHandle);
-    CHECK(NodeTypeChecker<T>::Check(sptr.get()))
-        << "Did not get expected type " << NodeTypeName<T>();
-    return T(sptr);
-  }
-  inline operator Expr() const {
-    if (type_code == kNull) {
-      return Expr();
-    }
-    if (type_code == kInt) return Expr(operator int());
-    if (type_code == kFloat) {
-      return Expr(static_cast<float>(operator double()));
-    }
-    CHECK_EQ(type_code, kNodeHandle);
-    if (sptr->is_type<IterVarNode>()) {
-      return IterVar(sptr)->var;
-    } else {
-      CHECK(NodeTypeChecker<Expr>::Check(sptr.get()))
-          << "did not pass in Expr in a place need Expr";
-      return Expr(sptr);
-    }
-  }
-  inline operator double() const {
-    CHECK_EQ(type_code, kFloat);
-    return v_union.v_float64;
-  }
-  inline operator int64_t() const {
-    CHECK_EQ(type_code, kInt);
-    return v_union.v_int64;
-  }
-  inline operator uint64_t() const {
-    CHECK_EQ(type_code, kInt);
-    return v_union.v_int64;
-  }
-  inline operator int() const {
-    CHECK_EQ(type_code, kInt);
-    CHECK_LE(v_union.v_int64,
-             std::numeric_limits<int>::max());
-    return v_union.v_int64;
-  }
-  inline operator bool() const {
-    CHECK_EQ(type_code, kInt)
-        << "expect boolean(int) but get "
-        << TVMTypeCode2Str(type_code);
-    return v_union.v_int64 != 0;
-  }
-  inline operator std::string() const {
-    CHECK_EQ(type_code, kStr)
-        << "expect Str but get "
-        << TVMTypeCode2Str(type_code);
-    return str;
-  }
-  inline operator Type() const {
-    return String2Type(operator std::string());
-  }
-  inline operator runtime::PackedFunc() const {
-    CHECK_EQ(type_code, kFuncHandle);
-    return runtime::PackedFunc(func);
-  }
-};
-
-// common defintiion of API function.
-using APIFunc = std::function<
-  void(const std::vector<APIVariantValue> &args, APIVariantValue* ret)>;
-
-/*!
- * \brief Registry entry for DataIterator factory functions.
- */
-struct APIFuncReg
-    : public dmlc::FunctionRegEntryBase<APIFuncReg,
-                                        APIFunc> {
-};
-
-#define TVM_REGISTER_API(TypeName)                                \
-  DMLC_REGISTRY_REGISTER(::tvm::APIFuncReg, APIFuncReg, TypeName) \
-
-}  // namespace tvm
-
-#endif  // TVM_C_API_C_API_REGISTRY_H_
diff --git a/src/codegen/codegen_stack_vm.cc b/src/codegen/codegen_stack_vm.cc
index d9ca3d38..7748504f 100644
--- a/src/codegen/codegen_stack_vm.cc
+++ b/src/codegen/codegen_stack_vm.cc
@@ -12,19 +12,22 @@ using namespace ir;
 
 runtime::PackedFunc BuildStackVM(LoweredFunc func) {
   StackVM vm = codegen::CodeGenStackVM().Compile(func);
-  auto f = [vm](const TVMValue* args, const int* type_codes, int num_args) {
-    LOG(INFO) << "Run stack VM";
+  using runtime::TVMArgs;
+  using runtime::TVMRetValue;
+
+  auto f = [vm](TVMArgs args, TVMRetValue* rv) {
     StackVM::State* s = StackVM::ThreadLocalState();
     s->sp = 0;
     s->pc = 0;
     if (s->heap.size() < vm.heap_size) {
       s->heap.resize(vm.heap_size);
     }
-    s->heap[0].v_handle = (void*)args;  // NOLINT(*)
-    s->heap[1].v_handle = (void*)type_codes;  // NOLINT(*)
-    s->heap[2].v_int64 = num_args;
+    s->heap[0].v_handle = (void*)args.values;  // NOLINT(*)
+    s->heap[1].v_handle = (void*)args.type_codes;  // NOLINT(*)
+    s->heap[2].v_int64 = args.num_args;
     vm.Run(s);
   };
+
   return runtime::PackedFunc(f);
 }
 
@@ -118,6 +121,9 @@ int CodeGenStackVM::GetGlobalFuncID(std::string name) {
   auto it = fun_idmap_.find(name);
   if (it != fun_idmap_.end()) return it->second;
   using runtime::PackedFunc;
+  using runtime::TVMArgs;
+  using runtime::TVMRetValue;
+
   PackedFunc f = PackedFunc::GetGlobal(name);
   auto extern_f = [f](const TVMValue* args, int num_args) {
     CHECK_EQ(num_args % 2, 0);
@@ -128,7 +134,8 @@ int CodeGenStackVM::GetGlobalFuncID(std::string name) {
       int code = (tcode >> (8 * 3)) & 255;
       type_codes[i] = code;
     }
-    f.CallPacked(args, &type_codes[0], num_args);
+    TVMRetValue rv;
+    f.CallPacked(TVMArgs(args, &type_codes[0], num_args), &rv);
     TVMValue r; r.v_int64 = 0;
     return r;
   };
diff --git a/src/codegen/split_host_device.cc b/src/codegen/split_host_device.cc
index 1560fda4..383e307a 100644
--- a/src/codegen/split_host_device.cc
+++ b/src/codegen/split_host_device.cc
@@ -136,7 +136,6 @@ class HostDeviceSplitter : public IRMutator {
  public:
   Stmt Mutate_(const AttrStmt *op, const Stmt& s) final {
     if (op->type_key == "thread_extent") {
-      LOG(INFO) << "??";
       IterVar iv(op->node.node_);
       return SplitDeviceFunc(s);
     }
diff --git a/src/jit/stack_vm.cc b/src/jit/stack_vm.cc
index 7c92b1ee..80c4bcbf 100644
--- a/src/jit/stack_vm.cc
+++ b/src/jit/stack_vm.cc
@@ -302,7 +302,8 @@ void StackVM::Run(State* s) const {
         STACK_VM_TVM_LOAD_ARG(tc == kFloat, "float"); break;
       }
       case TVM_LOAD_ARG_HANDLE: {
-        STACK_VM_TVM_LOAD_ARG(tc == kHandle || tc == kNull, "handle"); break;
+        STACK_VM_TVM_LOAD_ARG(
+            tc == kHandle || tc == kNull || tc == kArrayHandle, "handle"); break;
       }
       case TVM_ARRAY_GET_DATA: {
         STACK_VM_TVM_ARRARY_GET(v_handle, void*, data); break;
@@ -317,7 +318,7 @@ void StackVM::Run(State* s) const {
         STACK_VM_TVM_ARRARY_GET(v_int64, int64_t, ndim); break;
       }
       case TVM_ARRAY_GET_TYPE_CODE: {
-        STACK_VM_TVM_ARRARY_GET(v_int64, int64_t, dtype.type_code); break;
+        STACK_VM_TVM_ARRARY_GET(v_int64, int64_t, dtype.code); break;
       }
       case TVM_ARRAY_GET_TYPE_BITS: {
         STACK_VM_TVM_ARRARY_GET(v_int64, int64_t, dtype.bits); break;
diff --git a/src/runtime/c_runtime_api.cc b/src/runtime/c_runtime_api.cc
index 8bf4ba4b..17fb97de 100644
--- a/src/runtime/c_runtime_api.cc
+++ b/src/runtime/c_runtime_api.cc
@@ -3,9 +3,11 @@
  * \file c_runtime_api.cc
  * \brief Device specific implementations
  */
+#include <dmlc/thread_local.h>
 #include <tvm/runtime/c_runtime_api.h>
 #include <tvm/runtime/packed_func.h>
 #include <algorithm>
+#include <string>
 #include "./runtime_base.h"
 #include "./device_api.h"
 
@@ -37,7 +39,7 @@ inline void TVMArrayFree_(TVMArray* arr) {
 
 inline void VerifyType(TVMType dtype) {
   CHECK_GE(dtype.lanes, 1U);
-  if (dtype.type_code == kFloat) {
+  if (dtype.code == kFloat) {
     CHECK_EQ(dtype.bits % 32U, 0U);
   } else {
     CHECK_EQ(dtype.bits % 8U, 0U);
@@ -65,6 +67,12 @@ inline size_t GetDataAlignment(TVMArray* arr) {
 
 using namespace tvm::runtime;
 
+struct TVMRuntimeEntry {
+  std::string ret_str;
+};
+
+typedef dmlc::ThreadLocalStore<TVMRuntimeEntry> TVMAPIRuntimeStore;
+
 int TVMDeviceInit(int dev_mask,
                   const char** option_keys,
                   const char** option_vals,
@@ -177,10 +185,31 @@ int TVMFuncFree(TVMFunctionHandle func) {
 int TVMFuncCall(TVMFunctionHandle func,
                 TVMValue* args,
                 int* arg_type_codes,
-                int num_args) {
+                int num_args,
+                TVMValue* ret_val,
+                int* ret_type_code) {
   API_BEGIN();
+  TVMRetValue rv;
   (*static_cast<const PackedFunc*>(func)).CallPacked(
-      args, arg_type_codes, num_args);
+      TVMArgs(args, arg_type_codes, num_args), &rv);
+  // handle return string.
+  if (rv.type_code() == kStr) {
+    TVMRuntimeEntry* e = TVMAPIRuntimeStore::Get();
+    e->ret_str = rv.operator std::string();
+    *ret_type_code = kStr;
+    ret_val->v_str = e->ret_str.c_str();
+  } else {
+    rv.MoveToCHost(ret_val, ret_type_code);
+  }
+  API_END();
+}
+
+int TVMCFuncSetReturn(TVMRetValueHandle ret,
+                      TVMValue value,
+                      int type_code) {
+  API_BEGIN();
+  TVMRetValue* rv = static_cast<TVMRetValue*>(ret);
+  *rv = TVMArgValue(value, type_code);
   API_END();
 }
 
@@ -191,22 +220,18 @@ int TVMFuncCreateFromCFunc(TVMPackedCFunc func,
   API_BEGIN();
   if (fin == nullptr) {
     *out = new PackedFunc(
-        [func, resource_handle](const TVMValue* args,
-                                const int* type_codes,
-                                int num_args) {
-          func((TVMValue*)args, (int*)type_codes, // NOLINT(*)
-               num_args, resource_handle);
+        [func, resource_handle](TVMArgs args, TVMRetValue* rv) {
+          func((TVMValue*)args.values, (int*)args.type_codes, // NOLINT(*)
+               args.num_args, rv, resource_handle);
         });
   } else {
     // wrap it in a shared_ptr, with fin as deleter.
     // so fin will be called when the lambda went out of scope.
     std::shared_ptr<void> rpack(resource_handle, fin);
     *out = new PackedFunc(
-        [func, rpack](const TVMValue* args,
-                      const int* type_codes,
-                      int num_args) {
-          func((TVMValue*)args, (int*)type_codes, // NOLINT(*)
-               num_args, rpack.get());
+        [func, rpack](TVMArgs args, TVMRetValue* rv) {
+          func((TVMValue*)args.values, (int*)args.type_codes, // NOLINT(*)
+               args.num_args, rv, rpack.get());
       });
   }
   API_END();
diff --git a/src/runtime/packed_func_registry.cc b/src/runtime/packed_func_registry.cc
index acc09d8a..8a9c6094 100644
--- a/src/runtime/packed_func_registry.cc
+++ b/src/runtime/packed_func_registry.cc
@@ -4,6 +4,7 @@
  * \brief The global registry of packed function.
  */
 #include <dmlc/logging.h>
+#include <dmlc/thread_local.h>
 #include <tvm/runtime/packed_func.h>
 #include <unordered_map>
 #include <memory>
@@ -58,6 +59,18 @@ std::vector<std::string> PackedFunc::ListGlobalNames() {
 }  // namespace runtime
 }  // namespace tvm
 
+/*! \brief entry to to easily hold returning information */
+struct TVMFuncThreadLocalEntry {
+  /*! \brief result holder for returning strings */
+  std::vector<std::string> ret_vec_str;
+  /*! \brief result holder for returning string pointers */
+  std::vector<const char *> ret_vec_charp;
+};
+
+/*! \brief Thread local store that can be used to hold return values. */
+typedef dmlc::ThreadLocalStore<TVMFuncThreadLocalEntry> TVMFuncThreadLocalStore;
+
+
 int TVMFuncRegisterGlobal(const char* name, TVMFunctionHandle f) {
   using tvm::runtime::PackedFunc;
   API_BEGIN();
@@ -68,6 +81,22 @@ int TVMFuncRegisterGlobal(const char* name, TVMFunctionHandle f) {
 int TVMFuncGetGlobal(const char* name, TVMFunctionHandle* out) {
   using tvm::runtime::PackedFunc;
   API_BEGIN();
-  *out = new PackedFunc(PackedFunc::GetGlobal(name));
+  const PackedFunc& f = PackedFunc::GetGlobal(name);
+  *out = (TVMFunctionHandle)(&f);  // NOLINT(*)
+  API_END();
+}
+
+int TVMFuncListGlobalNames(int *out_size,
+                           const char*** out_array) {
+  using tvm::runtime::PackedFunc;
+  API_BEGIN();
+  TVMFuncThreadLocalEntry *ret = TVMFuncThreadLocalStore::Get();
+  ret->ret_vec_str = PackedFunc::ListGlobalNames();
+  ret->ret_vec_charp.clear();
+  for (size_t i = 0; i < ret->ret_vec_str.size(); ++i) {
+    ret->ret_vec_charp.push_back(ret->ret_vec_str[i].c_str());
+  }
+  *out_array = dmlc::BeginPtr(ret->ret_vec_charp);
+  *out_size = static_cast<int>(ret->ret_vec_str.size());
   API_END();
 }
diff --git a/tests/cpp/packed_func_test.cc b/tests/cpp/packed_func_test.cc
index f2a87e48..c801b4c1 100644
--- a/tests/cpp/packed_func_test.cc
+++ b/tests/cpp/packed_func_test.cc
@@ -1,24 +1,116 @@
 #include <dmlc/logging.h>
 #include <gtest/gtest.h>
 #include <tvm/runtime/packed_func.h>
+#include <tvm/tvm.h>
+#include <tvm/ir.h>
 
 TEST(PackedFunc, Basic) {
+  using namespace tvm;
   using namespace tvm::runtime;
   int x = 0;
   void* handle = &x;
   TVMArray a;
 
-  PackedFunc([&](const TVMValue* args, const int* type_codes, int num_args) {
-      CHECK(num_args == 3);
-      CHECK(args[0].v_float64 == 1.0);
-      CHECK(type_codes[0] == kFloat);
-      CHECK(args[1].v_handle == &a);
-      CHECK(type_codes[1] == kHandle);
-      CHECK(args[2].v_handle == &x);
-      CHECK(type_codes[2] == kHandle);
+  Var v = PackedFunc([&](TVMArgs args, TVMRetValue* rv) {
+      CHECK(args.num_args == 3);
+      CHECK(args.values[0].v_float64 == 1.0);
+      CHECK(args.type_codes[0] == kFloat);
+      CHECK(args.values[1].v_handle == &a);
+      CHECK(args.type_codes[1] == kArrayHandle);
+      CHECK(args.values[2].v_handle == &x);
+      CHECK(args.type_codes[2] == kHandle);
+      *rv = Var("a");
     })(1.0, &a, handle);
+  CHECK(v->name_hint == "a");
 }
 
+TEST(PackedFunc, Node) {
+  using namespace tvm;
+  using namespace tvm::runtime;
+  Var x;
+  Var t = PackedFunc([&](TVMArgs args, TVMRetValue* rv) {
+      CHECK(args.num_args == 1);
+      CHECK(args.type_codes[0] == kNodeHandle);
+      Var b = args[0];
+      CHECK(x.same_as(b));
+      *rv = b;
+    })(x);
+  CHECK(t.same_as(x));
+}
+
+TEST(PackedFunc, str) {
+  using namespace tvm;
+  using namespace tvm::runtime;
+  PackedFunc([&](TVMArgs args, TVMRetValue* rv) {
+      CHECK(args.num_args == 1);
+      std::string x = args[0];
+      CHECK(x == "hello");
+      *rv = x;
+    })("hello");
+}
+
+
+TEST(PackedFunc, func) {
+  using namespace tvm;
+  using namespace tvm::runtime;
+  PackedFunc addone([&](TVMArgs args, TVMRetValue* rv) {
+      *rv = args[0].operator int() + 1;
+    });
+  // function as arguments
+  int r0 = PackedFunc([](TVMArgs args, TVMRetValue* rv) {
+      PackedFunc f = args[0];
+      // TVMArgValue -> Arguments as function
+      *rv = f(args[1]).operator int();
+    })(addone, 1);
+  CHECK_EQ(r0, 2);
+
+  int r1 = PackedFunc([](TVMArgs args, TVMRetValue* rv) {
+      // TVMArgValue -> TVMRetValue
+      *rv = args[1];
+    })(2, 100);
+  CHECK_EQ(r1, 100);
+
+  int r2 = PackedFunc([&](TVMArgs args, TVMRetValue* rv) {
+      // re-assignment
+      *rv = args[0];
+      // TVMRetValue -> Function argument
+      *rv = addone(args[0].operator PackedFunc()(args[1], 1));
+    })(addone, 100);
+  CHECK_EQ(r2, 102);
+}
+
+TEST(PackedFunc, Expr) {
+  using namespace tvm;
+  using namespace tvm::runtime;
+  // automatic conversion of int to expr
+  PackedFunc addone([](TVMArgs args, TVMRetValue* rv) {
+      Expr x = args[0];
+      *rv = x.as<tvm::ir::IntImm>()->value + 1;
+  });
+  int r0 = PackedFunc([](TVMArgs args, TVMRetValue* rv) {
+      PackedFunc f = args[0];
+      // TVMArgValue -> Arguments as function
+      *rv = f(args[1]).operator int();
+    })(addone, 1);
+  CHECK_EQ(r0, 2);
+}
+
+TEST(PackedFunc, Type) {
+  using namespace tvm;
+  using namespace tvm::runtime;
+  auto get_type = PackedFunc([](TVMArgs args, TVMRetValue* rv) {
+      Type x = args[0];
+      *rv = x;
+    });
+  auto get_type2 = PackedFunc([](TVMArgs args, TVMRetValue* rv) {
+      *rv = args[0];
+    });
+  CHECK(get_type("int32").operator Type() == Int(32));
+  CHECK(get_type("float").operator Type() == Float(32));
+  CHECK(get_type2("float32x2").operator Type() == Float(32, 2));
+}
+
+
 int main(int argc, char ** argv) {
   testing::InitGoogleTest(&argc, argv);
   testing::FLAGS_gtest_death_test_style = "threadsafe";
diff --git a/tests/python/test_lang_basic.py b/tests/python/test_lang_basic.py
index b1eb2990..b12a94a2 100644
--- a/tests/python/test_lang_basic.py
+++ b/tests/python/test_lang_basic.py
@@ -2,7 +2,8 @@ import tvm
 
 def test_const():
     x = tvm.const(1)
-    assert x.dtype == 'int32'
+    print(x.dtype)
+    assert x.dtype == tvm.int32
     assert isinstance(x, tvm.expr.IntImm)
 
 def test_const_saveload_json():
diff --git a/tests/python/test_runtime_packed_func.py b/tests/python/test_runtime_packed_func.py
index ed123e9b..3332e9a3 100644
--- a/tests/python/test_runtime_packed_func.py
+++ b/tests/python/test_runtime_packed_func.py
@@ -17,10 +17,22 @@ def test_get_global():
     @tvm.register_func
     def my_packed_func(*args):
         assert(tuple(args) == targs)
+        return 10
     # get it out from global function table
     f = tvm.get_global_func("my_packed_func")
     assert isinstance(f, tvm.nd.Function)
-    f(*targs)
+    y = f(*targs)
+    assert y == 10
+
+
+def test_return_func():
+    def addy(y):
+        def add(x):
+            return tvm.convert(x + y)
+        return add
+    myf = tvm.convert(addy)
+    f = myf(10)
+    assert f(11).value == 21
 
 
 def test_convert():
@@ -38,3 +50,4 @@ if __name__ == "__main__":
     test_function()
     test_convert()
     test_get_global()
+    test_return_func()
diff --git a/tests/travis/run_test.sh b/tests/travis/run_test.sh
index f1a070b5..5c332a55 100755
--- a/tests/travis/run_test.sh
+++ b/tests/travis/run_test.sh
@@ -38,10 +38,10 @@ fi
 if [ ${TASK} == "python_test" ] || [ ${TASK} == "all_test" ]; then
     make all || exit -1
     if [ ${TRAVIS_OS_NAME} == "osx" ]; then
-        python -m nose tests/python/ || exit -1
-        python3 -m nose tests/python/ || exit -1
+        python -m nose -v tests/python/ || exit -1
+        python3 -m nose -v tests/python/ || exit -1
     else
-        nosetests tests/python/ || exit -1
-        nosetests3 tests/python/ || exit -1
+        nosetests -v tests/python/ || exit -1
+        nosetests3 -v tests/python/ || exit -1
     fi
 fi