[Relay] Reference

include/tvm/relay/expr.h

@@ -428,12 +428,78 @@ class TupleGetItemNode : public ExprNode {
 
   TVM_DLL static TupleGetItem make(Expr tuple, int index);
 
-  static constexpr const char * _type_key = "relay.TupleGetItem";
+  static constexpr const char* _type_key = "relay.TupleGetItem";
   TVM_DECLARE_NODE_TYPE_INFO(TupleGetItemNode, ExprNode);
 };
 
 RELAY_DEFINE_NODE_REF(TupleGetItem, TupleGetItemNode, Expr);
 
+/*! \brief Create a new Reference out of initial value. */
+class RefCreate;
+class RefCreateNode : public ExprNode {
+ public:
+  /*! \brief The initial value of the Reference. */
+  Expr value;
+
+  void VisitAttrs(tvm::AttrVisitor* v) final {
+    v->Visit("value", &value);
+    v->Visit("span", &span);
+    v->Visit("_checked_type_", &checked_type_);
+  }
+
+  TVM_DLL static RefCreate make(Expr value);
+
+  static constexpr const char* _type_key = "relay.RefCreate";
+  TVM_DECLARE_NODE_TYPE_INFO(RefCreateNode, ExprNode);
+};
+
+RELAY_DEFINE_NODE_REF(RefCreate, RefCreateNode, Expr);
+
+/*! \brief Get value out of Reference. */
+class RefRead;
+class RefReadNode : public ExprNode {
+ public:
+  /*! \brief The Reference Expression. */
+  Expr ref;
+
+  void VisitAttrs(tvm::AttrVisitor* v) final {
+    v->Visit("ref", &ref);
+    v->Visit("span", &span);
+    v->Visit("_checked_type_", &checked_type_);
+  }
+
+  TVM_DLL static RefRead make(Expr ref);
+
+  static constexpr const char* _type_key = "relay.RefRead";
+  TVM_DECLARE_NODE_TYPE_INFO(RefReadNode, ExprNode);
+};
+
+RELAY_DEFINE_NODE_REF(RefRead, RefReadNode, Expr);
+
+/*! \brief Set value of Reference. The whole expression evaluates to an Empty Tuple. */
+class RefWrite;
+class RefWriteNode : public ExprNode {
+ public:
+  /*! \brief The Reference Expression. */
+  Expr ref;
+  /*! \brief The value to write into. */
+  Expr value;
+
+  void VisitAttrs(tvm::AttrVisitor* v) final {
+    v->Visit("ref", &ref);
+    v->Visit("value", &value);
+    v->Visit("span", &span);
+    v->Visit("_checked_type_", &checked_type_);
+  }
+
+  TVM_DLL static RefWrite make(Expr ref, Expr value);
+
+  static constexpr const char* _type_key = "relay.RefWrite";
+  TVM_DECLARE_NODE_TYPE_INFO(RefWriteNode, ExprNode);
+};
+
+RELAY_DEFINE_NODE_REF(RefWrite, RefWriteNode, Expr);
+
 /*!
  * \brief Base class of the temporary expression.
  *

include/tvm/relay/expr_functor.h

@@ -89,6 +89,9 @@ class ExprFunctor<R(const Expr& n, Args...)> {
   virtual R VisitExpr_(const OpNode* op,
                        Args... args) EXPR_FUNCTOR_DEFAULT;
   virtual R VisitExpr_(const TupleGetItemNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const RefCreateNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const RefReadNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const RefWriteNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
   virtual R VisitExprDefault_(const Node* op, Args...) {
     throw Error(std::string("Do not have a default for ") + op->type_key());
   }
@@ -108,6 +111,9 @@ class ExprFunctor<R(const Expr& n, Args...)> {
     RELAY_EXPR_FUNCTOR_DISPATCH(IfNode);
     RELAY_EXPR_FUNCTOR_DISPATCH(OpNode);
     RELAY_EXPR_FUNCTOR_DISPATCH(TupleGetItemNode);
+    RELAY_EXPR_FUNCTOR_DISPATCH(RefCreateNode);
+    RELAY_EXPR_FUNCTOR_DISPATCH(RefReadNode);
+    RELAY_EXPR_FUNCTOR_DISPATCH(RefWriteNode);
     return vtable;
   }
 };
@@ -133,6 +139,9 @@ class ExprVisitor
   void VisitExpr_(const IfNode* op) override;
   void VisitExpr_(const OpNode* op) override;
   void VisitExpr_(const TupleGetItemNode* op) override;
+  void VisitExpr_(const RefCreateNode* op) override;
+  void VisitExpr_(const RefReadNode* op) override;
+  void VisitExpr_(const RefWriteNode* op) override;
   virtual void VisitType(const Type& t);
 
  protected:
@@ -168,6 +177,9 @@ class ExprMutator
   Expr VisitExpr_(const LetNode* op) override;
   Expr VisitExpr_(const IfNode* op) override;
   Expr VisitExpr_(const TupleGetItemNode* op) override;
+  Expr VisitExpr_(const RefCreateNode* op) override;
+  Expr VisitExpr_(const RefReadNode* op) override;
+  Expr VisitExpr_(const RefWriteNode* op) override;
   /*!
    * \brief Used to visit the types inside of expressions.
    *

include/tvm/relay/interpreter.h

@@ -140,6 +140,25 @@ struct TensorValueNode : ValueNode {
 
 RELAY_DEFINE_NODE_REF(TensorValue, TensorValueNode, Value);
 
+/*! \brief A reference value. */
+class RefValue;
+
+struct RefValueNode : ValueNode {
+  mutable Value value;
+
+  RefValueNode() {}
+
+  void VisitAttrs(tvm::AttrVisitor* v) final {
+    v->Visit("value", &value);
+  }
+
+  TVM_DLL static RefValue make(Value val);
+
+  static constexpr const char* _type_key = "relay.RefValue";
+  TVM_DECLARE_NODE_TYPE_INFO(RefValueNode, ValueNode);
+};
+
+RELAY_DEFINE_NODE_REF(RefValue, RefValueNode, Value);
 
 }  // namespace relay
 }  // namespace tvm

include/tvm/relay/type.h

@@ -262,6 +262,33 @@ class TupleTypeNode : public TypeNode {
 
 RELAY_DEFINE_NODE_REF(TupleType, TupleTypeNode, Type);
 
+/*!
+ * \brief The type of reference values.
+ */
+class RefType;
+/*!
+ * \brief Reference Type in relay.
+ */
+class RefTypeNode : public TypeNode {
+ public:
+  /*! \brief The type of value in the Reference. */
+  Type value;
+
+  RefTypeNode() {}
+
+  void VisitAttrs(tvm::AttrVisitor* v) final {
+    v->Visit("value", &value);
+    v->Visit("span", &span);
+  }
+
+  TVM_DLL static RefType make(Type value);
+
+  static constexpr const char* _type_key = "relay.RefType";
+  TVM_DECLARE_NODE_TYPE_INFO(RefTypeNode, TypeNode);
+};
+
+RELAY_DEFINE_NODE_REF(RefType, RefTypeNode, Type);
+
 class TypeReporter;
 
 /*!

python/tvm/relay/__init__.py

@@ -44,6 +44,7 @@
 TypeRelation = ty.TypeRelation
 IncompleteType = ty.IncompleteType
 scalar_type = ty.scalar_type
+RefType = ty.RefType
 
 # Expr
 Expr = expr.Expr
@@ -56,15 +57,18 @@
 Let = expr.Let
 If = expr.If
 TupleGetItem = expr.TupleGetItem
-
-# ExprFunctor
-ExprFunctor = expr_functor.ExprFunctor
-ExprMutator = expr_functor.ExprMutator
+RefCreate = expr.RefCreate
+RefRead = expr.RefRead
+RefWrite = expr.RefWrite
 
 # helper functions
 var = expr.var
 const = expr.const
 bind = expr.bind
 
+# ExprFunctor
+ExprFunctor = expr_functor.ExprFunctor
+ExprMutator = expr_functor.ExprMutator
+
 # Parser
 fromtext = parser.fromtext

python/tvm/relay/backend/graph_runtime_codegen.py

@@ -283,6 +283,15 @@ def visit_call(self, call):
     def visit_op(self, _):
         raise Exception("can not compile op in non-eta expanded form")
 
+    def visit_ref_create(self, _):
+        raise RuntimeError("reference not supported")
+
+    def visit_ref_read(self, _):
+        raise RuntimeError("reference not supported")
+
+    def visit_ref_write(self, _):
+        raise RuntimeError("reference not supported")
+
     def _get_json(self):
         """
         Convert the sequence of nodes stored by the compiler into the

python/tvm/relay/backend/interpreter.py

@@ -45,6 +45,7 @@ def __repr__(self):
     def __iter__(self):
         return iter(self.fields)
 
+
 @register_relay_node
 class Closure(Value):
     """A closure produced by the interpreter."""
@@ -79,6 +80,13 @@ def __str__(self):
         return str(self.data)
 
 
+@register_relay_node
+class RefValue(Value):
+    def __init__(self, value):
+        self.__init_handle_by_constructor__(
+            _make.RefValue, value)
+
+
 def _arg_to_ast(arg):
     if isinstance(arg, TensorValue):
         return Constant(arg.data.copyto(_nd.cpu(0)))

python/tvm/relay/expr.py

@@ -327,6 +327,46 @@ def __init__(self, tuple_value, index):
             _make.TupleGetItem, tuple_value, index)
 
 
+@register_relay_node
+class RefCreate(Expr):
+    """Create a new reference from initial value.
+    Parameters
+    ----------
+    value: tvm.relay.Expr
+       The initial value.
+    """
+    def __init__(self, value):
+        self.__init_handle_by_constructor__(_make.RefCreate, value)
+
+
+@register_relay_node
+class RefRead(Expr):
+    """Get the value inside the reference.
+    Parameters
+    ----------
+    ref: tvm.relay.Expr
+         The reference.
+    """
+    def __init__(self, ref):
+        self.__init_handle_by_constructor__(_make.RefRead, ref)
+
+
+@register_relay_node
+class RefWrite(Expr):
+    """
+    Update the value inside the reference.
+    The whole expression will evaluate to an empty tuple.
+    Parameters
+    ----------
+    ref: tvm.relay.Expr
+        The reference.
+    value: tvm.relay.Expr
+        The new value.
+    """
+    def __init__(self, ref, value):
+        self.__init_handle_by_constructor__(_make.RefWrite, ref, value)
+
+
 class TempExpr(Expr):
     """Baseclass of all TempExpr.
 

python/tvm/relay/expr_functor.py

@@ -41,6 +41,12 @@ def visit(self, expr):
             res = self.visit_constant(expr)
         elif isinstance(expr, Op):
             res = self.visit_op(expr)
+        elif isinstance(expr, RefCreate):
+            res = self.visit_ref_create(expr)
+        elif isinstance(expr, RefRead):
+            res = self.visit_ref_read(expr)
+        elif isinstance(expr, RefWrite):
+            res = self.visit_ref_write(expr)
         else:
             raise Exception("warning unhandled case: {0}".format(type(expr)))
 
@@ -81,6 +87,14 @@ def visit_op(self, _):
     def visit_constant(self, _):
         raise NotImplementedError()
 
+    def visit_ref_create(self, _):
+        raise NotImplementedError()
+
+    def visit_ref_write(self, _):
+        raise NotImplementedError()
+
+    def visit_ref_read(self, _):
+        raise NotImplementedError()
 
 class ExprMutator(ExprFunctor):
     """
@@ -145,8 +159,8 @@ def visit_constructor(self, con):
     def visit_match(self, m):
         return Match(self.visit(m.data), [Clause(c.lhs, self.visit(c.rhs)) for c in m.pattern])
 
-    def visit_ref_new(self, r):
-        return RefNew(self.visit(r.value))
+    def visit_ref_create(self, r):
+        return RefCreate(self.visit(r.value))
 
     def visit_ref_write(self, r):
         return RefWrite(self.visit(r.ref), self.visit(r.value))

python/tvm/relay/ty.py

@@ -210,6 +210,19 @@ def __init__(self, func, args, num_inputs, attrs):
                                             func, args, num_inputs, attrs)
 
 
+@register_relay_node
+class RefType(Type):
+    """Reference Type in relay.
+
+    Parameters
+    ----------
+    value: Type
+        The value type.
+    """
+    def __init__(self, value):
+        self.__init_handle_by_constructor__(_make.RefType, value)
+
+
 def scalar_type(dtype):
     """Creates a scalar type.