[EXECUTOR] Add GraphHandle (#285)

* [GRAPH] Add GraphHandle

* Move to apps/graph_executor

HalideIR @ 326e2fa1

-Subproject commit 36ecc1eec0898411ae70e98c315b03247d5fb4a0
+Subproject commit 326e2fa18734f0592d257da6b8cfaae90a499c5c

apps/graph_executor/src/graph_handle.cc

+/*!
+ *  Copyright (c) 2017 by Contributors
+ * \file graph_handle.cc
+ */
+#include <tvm/packed_func_ext.h>
+#include "./graph_handle.h"
+
+namespace tvm {
+
+TVM_STATIC_IR_FUNCTOR(IRPrinter, vtable)
+.set_dispatch<GraphHandleNode>([](const GraphHandleNode *op, IRPrinter *p) {
+    p->stream << "graph-handle("
+              << "handle=0x" << std::hex
+              << reinterpret_cast<uint64_t>(op->graph_handle) << ")";
+});
+
+TVM_REGISTER_NODE_TYPE(GraphHandleNode);
+
+}  // namespace tvm

apps/graph_executor/src/graph_handle.h

+/*!
+ *  Copyright (c) 2017 by Contributors
+ * \file graph.h
+ * \brief Data structure about computational graph.
+ */
+#ifndef TVM_GRAPH_HANDLE_H_
+#define TVM_GRAPH_HANDLE_H_
+
+#include <string>
+#include <tvm/base.h>
+
+namespace tvm {
+
+/*!
+ * \brief Computational graph handle.
+ *  Use GraphHandle as its container type
+ */
+struct GraphHandleNode : public Node {
+  void *graph_handle;
+
+  void VisitAttrs(AttrVisitor* v) final {
+    v->Visit("graph_handle", &graph_handle);
+  }
+
+  static constexpr const char* _type_key = "GraphHandle";
+  TVM_DECLARE_NODE_TYPE_INFO(GraphHandleNode, Node);
+};
+
+/*! \brief Defines graph handle */
+TVM_DEFINE_NODE_REF(GraphHandle, GraphHandleNode);
+
+}  // namespace tvm
+#endif  // TVM_GRAPH_HANDLE_H_

apps/graph_executor/src/graph_pass.cc

@@ -523,12 +523,12 @@ nnvm::Graph PruneGraph(nnvm::Graph src) {
     if (can_be_pruned) {
       pruned.emplace(n.get());
     } else {
-      // scan again to find edge nodes
+      // scan again to find edge nodes, skip variables
       for (auto& e : n->inputs) {
-        if (pruned.count(e.node.get())) {
+        if (!e.node->is_variable() && pruned.count(e.node.get())) {
           if (!entry_var.count(e)) {
             nnvm::NodePtr var = nnvm::Node::Create();
-            var->attrs.name = e.node->attrs.name + "_" + std::to_string(e.index);
+            var->attrs.name = e.node->attrs.name + "_output" + std::to_string(e.index);
             entry_var.emplace(e, var);
           }
           e = nnvm::NodeEntry{entry_var.at(e), 0, 0};
@@ -542,6 +542,7 @@ nnvm::Graph PruneGraph(nnvm::Graph src) {
   std::vector<std::string> output_names;
   output_names.reserve(entry_var.size());
   for (auto kv : entry_var) {
+    if (kv.first.node->is_variable()) continue;
     pre_graph.outputs.emplace_back(kv.first);
     output_names.emplace_back(kv.second->attrs.name);
   }

src/api/dsl_api.cc

@@ -51,6 +51,9 @@ struct APIAttrGetter : public AttrVisitor {
   void Visit(const char* key, bool* value) final {
     if (skey == key) *ret = static_cast<int64_t>(value[0]);
   }
+  void Visit(const char* key, void** value) final {
+    if (skey == key) *ret = static_cast<void*>(value[0]);
+  }
   void Visit(const char* key, Type* value) final {
     if (skey == key) *ret = value[0];
   }
@@ -83,6 +86,9 @@ struct APIAttrDir : public AttrVisitor {
   void Visit(const char* key, int* value) final {
     names->push_back(key);
   }
+  void Visit(const char* key, void** value) final {
+    names->push_back(key);
+  }
   void Visit(const char* key, Type* value) final {
     names->push_back(key);
   }

src/lang/reflection.cc

@@ -59,6 +59,7 @@ class NodeIndexer : public AttrVisitor {
   void Visit(const char* key, int* value) final {}
   void Visit(const char* key, bool* value) final {}
   void Visit(const char* key, std::string* value) final {}
+  void Visit(const char* key, void** value) final {}
   void Visit(const char* key, Type* value) final {}
   void Visit(const char* key, NodeRef* value) final {
     MakeIndex(value->node_.get());
@@ -148,6 +149,9 @@ class JSONAttrGetter : public AttrVisitor {
   void Visit(const char* key, std::string* value) final {
     node_->attrs[key] = *value;
   }
+  void Visit(const char* key, void** value) final {
+    LOG(FATAL) << "not allowed to serialize a pointer";
+  }
   void Visit(const char* key, Type* value) final {
     node_->attrs[key] = Type2String(*value);
   }
@@ -223,6 +227,9 @@ class JSONAttrSetter : public AttrVisitor {
   void Visit(const char* key, std::string* value) final {
     *value = GetValue(key);
   }
+  void Visit(const char* key, void** value) final {
+    LOG(FATAL) << "not allowed to deserialize a pointer";
+  }
   void Visit(const char* key, Type* value) final {
     std::string stype = GetValue(key);
     *value = String2Type(stype);
@@ -371,6 +378,9 @@ class NodeAttrSetter : public AttrVisitor {
   void Visit(const char* key, std::string* value) final {
     SetValue(key, value);
   }
+  void Visit(const char* key, void** value) final {
+    SetValue(key, value);
+  }
   void Visit(const char* key, Type* value) final {
     SetValue(key, value);
   }