Relax IRVisitor/IRMuator (apache#10)

* ExprVisitor/ExprMutator for relax nodes.

* Update Visitor & Mutator.

* Update Mutator.

* DataflowMutator interface.

* EwiseFMARewriter.

* Update fma rewrite and add test.

* Update test.

* Fix dataflow block dispatching.

* Construct new dataflow block with IRBuilder.

* VisitBinding return void and mutate internal IRBuilder.

* Simplify.

* Update emit dataflow output.

* Explicit memeory allocation rewrite.

* LazyIRBuilder.

* Update ExplicitMemMutator.

* Overload IRBuilder::Emit to have 3 styles.

* Update IRBuilder/IRMutator interfaces and passes.

* Add MatchShape binding to IRBuilder.

* Improve IRMutator interface; add Normalize and CanProveShapeEqual to IRBuilder

* Update EmitMatchShape.

Co-authored-by: ZihengJiang <ziheng@apache.org>

include/tvm/relax/expr.h

@@ -34,9 +34,15 @@ namespace relax {
 using Expr = RelayExpr;
 using ExprNode = RelayExprNode;
 using relay::Call;
+using relay::CallNode;
+using relay::ConstantNode;
 using relay::Id;
+using relay::If;
+using relay::IfNode;
 using relay::Tuple;
 using relay::TupleGetItem;
+using relay::TupleGetItemNode;
+using relay::TupleNode;
 
 /*! \brief A shape expression which allows users to construct a shape containing PrimExpr.
  */

include/tvm/relax/expr_functor.h

@@ -0,0 +1,237 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/*!
+ * \file tvm/relax/expr_functor.h
+ * \brief A more powerful visitor which enables defining arbitrary function
+ * signatures with type based dispatch on first argument.
+ */
+#ifndef TVM_RELAX_EXPR_FUNCTOR_H_
+#define TVM_RELAX_EXPR_FUNCTOR_H_
+
+#include <tvm/ir/error.h>
+#include <tvm/node/functor.h>
+#include <tvm/relax/expr.h>
+#include <tvm/relax/ir_builder.h>
+#include <tvm/relay/adt.h>
+#include <tvm/relay/expr.h>
+#include <tvm/relay/function.h>
+#include <tvm/relay/op.h>
+
+#include <deque>
+#include <string>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+namespace tvm {
+namespace relax {
+
+/*!
+ * \brief A dynamical functor that dispatches on in the first Expr argument.
+ *  You can use this as a more powerful Visitor, since it allows you to
+ *  define function signatures of Visit Function.
+ *
+ * \sa tvm/ir_functor.h
+ *
+ * \tparam FType function signiture
+ *  This type is only defined for FType with function signature R(const Expr&,
+ * Args...)
+ */
+template <typename FType>
+class ExprFunctor;
+
+// functions to be overriden.
+#define EXPR_FUNCTOR_DEFAULT \
+  { return VisitExprDefault_(op, std::forward<Args>(args)...); }
+
+#define RELAX_EXPR_FUNCTOR_DISPATCH(OP)                                                    \
+  vtable.template set_dispatch<OP>([](const ObjectRef& n, TSelf* self, Args... args) {     \
+    return self->VisitExpr_(static_cast<const OP*>(n.get()), std::forward<Args>(args)...); \
+  });
+
+template <typename R, typename... Args>
+class ExprFunctor<R(const Expr& n, Args...)> {
+ private:
+  using TSelf = ExprFunctor<R(const Expr& n, Args...)>;
+  using FType = tvm::NodeFunctor<R(const ObjectRef& n, TSelf* self, Args...)>;
+
+ public:
+  /*! \brief the result type of this functor */
+  using result_type = R;
+  /*! \brief virtual destructor */
+  virtual ~ExprFunctor() {}
+  /*!
+   * \brief Same as call.
+   * \param n The expression node.
+   * \param args Additional arguments.
+   * \return The result of the call
+   */
+  R operator()(const Expr& n, Args... args) { return VisitExpr(n, std::forward<Args>(args)...); }
+  /*!
+   * \brief The functor call.
+   * \param n The expression node.
+   * \param args Additional arguments.
+   * \return The result of the call
+   */
+  virtual R VisitExpr(const Expr& n, Args... args) {
+    ICHECK(n.defined()) << "Found null pointer node while traversing AST. The previous pass may "
+                           "have generated invalid data.";
+    static FType vtable = InitVTable();
+    return vtable(n, this, std::forward<Args>(args)...);
+  }
+  // Functions that can be overriden by subclass
+  virtual R VisitExpr_(const ConstantNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const TupleNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const VarNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const DataflowVarNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const ShapeExprNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const ExternFuncNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const GlobalVarNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const FunctionNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const CallNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const SeqExprNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const IfNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const OpNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExpr_(const TupleGetItemNode* op, Args... args) EXPR_FUNCTOR_DEFAULT;
+  virtual R VisitExprDefault_(const Object* op, Args...) {
+    LOG(FATAL) << "Do not have a default for " << op->GetTypeKey();
+    throw;
+  }
+
+ private:
+  // initialize the vtable.
+  static FType InitVTable() {
+    FType vtable;
+    // Set dispatch
+    RELAX_EXPR_FUNCTOR_DISPATCH(ConstantNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(TupleNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(VarNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(DataflowVarNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(ShapeExprNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(ExternFuncNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(GlobalVarNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(FunctionNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(CallNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(SeqExprNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(IfNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(OpNode);
+    RELAX_EXPR_FUNCTOR_DISPATCH(TupleGetItemNode);
+    return vtable;
+  }
+};
+
+/*!
+ * \brief A simple visitor wrapper around ExprFunctor.
+ *  Recursively visit the content.
+ *
+ * ExprVisitor treats Expr as dataflow graph,
+ * and only visit each Expr node once.
+ */
+class ExprVisitor : public ExprFunctor<void(const Expr& n)> {
+ public:
+  void VisitExpr(const Expr& expr) override;
+  void VisitExpr_(const ConstantNode* op) override;
+  void VisitExpr_(const TupleNode* op) override;
+  void VisitExpr_(const VarNode* op) override;
+  void VisitExpr_(const DataflowVarNode* op) override;
+  void VisitExpr_(const ShapeExprNode* op) override;
+  void VisitExpr_(const ExternFuncNode* op) override;
+  void VisitExpr_(const GlobalVarNode* op) override;
+  void VisitExpr_(const FunctionNode* op) override;
+  void VisitExpr_(const CallNode* op) override;
+  void VisitExpr_(const SeqExprNode* op) override;
+  void VisitExpr_(const IfNode* op) override;
+  void VisitExpr_(const OpNode* op) override;
+  void VisitExpr_(const TupleGetItemNode* op) override;
+
+  virtual void VisitType(const Type& t);
+  virtual void VisitSpan(const Span& span);
+  virtual void VisitBinding(const Binding& binding);
+  virtual void VisitVarBinding(const VarBinding& binding);
+  virtual void VisitMatchShape(const MatchShape& binding);
+  virtual void VisitBindingBlock(const BindingBlock& block);
+  virtual void VisitDataflowBlock(const DataflowBlock& block);
+};
+
+void PostOrderVisit(const Expr& node, std::function<void(const Expr&)> fvisit);
+
+/*!
+ * \brief A wrapper around ExprFunctor which functionally updates the AST.
+ *
+ * ExprMutator treats Expr as dataflow graph, and only Mutate each Expr once.
+ * The mutated results are memoized in a map and reused so that
+ * local transformation on the dataflow preserves the graph structure.
+ */
+class ExprMutator : public ExprFunctor<Expr(const Expr&)> {
+ public:
+  /*!
+   * \brief Mutate is alias for VisitExpr
+   * \return expr.
+   */
+  Expr Mutate(const Expr& expr) { return this->VisitExpr(expr); }
+  Expr VisitExpr(const Expr& expr) override;
+  Expr VisitExpr_(const ConstantNode* op) override;
+  Expr VisitExpr_(const TupleNode* op) override;
+  Expr VisitExpr_(const VarNode* op) override;
+  Expr VisitExpr_(const DataflowVarNode* op) override;
+  Expr VisitExpr_(const ShapeExprNode* op) override;
+  Expr VisitExpr_(const ExternFuncNode* op) override;
+  Expr VisitExpr_(const GlobalVarNode* op) override;
+  Expr VisitExpr_(const FunctionNode* op) override;
+  Expr VisitExpr_(const CallNode* op) override;
+  Expr VisitExpr_(const SeqExprNode* op) override;
+  Expr VisitExpr_(const IfNode* op) override;
+  Expr VisitExpr_(const OpNode* op) override;
+  Expr VisitExpr_(const TupleGetItemNode* op) override;
+
+  /*!
+   * \brief Used to visit the types inside of expressions.
+   *
+   * Can be overloaded to transform the types in arbitrary
+   * ways, one way would be to define a sub-class of type
+   * visitor for types which transform them appropriately.
+   */
+  virtual Type VisitType(const Type& t);
+  virtual void VisitBinding(const Binding& binding);
+  virtual Var VisitVarBinding(const VarBinding& binding, IRBuilder& ir_builder);
+  virtual void VisitMatchShape(const MatchShape& binding, IRBuilder& ir_builder);
+  virtual BindingBlock VisitBindingBlock(const BindingBlock& block);
+  virtual BindingBlock VisitDataflowBlock(const DataflowBlock& block);
+
+ protected:
+  LazyIRBuilder irbuilder_;
+};
+
+/*! \brief Dataflow Graph Rewriting for Custom Rewriting Passes
+ */
+class DataflowMutator : public ExprMutator {
+ public:
+  virtual BindingBlock VisitDataflowBlock(const DataflowBlock& block);
+  virtual Var VisitVarBinding(const VarBinding& binding, IRBuilder& ir_builder);
+
+ protected:
+  /*! \brief Look up the value binded to a var. */
+  Expr LookupVar(Var var);
+  // A remapping table: pre var -> post var
+  std::unordered_map<Var, Var, ObjectPtrHash, ObjectPtrEqual> pre_post_var_map_;
+};
+
+}  // namespace relax
+}  // namespace tvm
+#endif  // TVM_RELAX_EXPR_FUNCTOR_H_