Redesign IRBuilder to BlockBuilder (apache#22)

* init

* update

* update

* test case working

* update and add multi block test case

* check in

* fixes

* fix

* update

* add

* update

* add

* update

* address comments.

Co-authored-by: Altan Haan <ahaan@octoml.ai>

include/tvm/relax/block_builder.h

@@ -0,0 +1,204 @@
+/*
+ * 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/block_builder.h
+ * \brief The utility for constructing Relax binding blocks.
+ */
+#ifndef TVM_RELAX_BLOCK_BUILDER_H_
+#define TVM_RELAX_BLOCK_BUILDER_H_
+
+#include <tvm/ir/expr.h>
+#include <tvm/relax/expr.h>
+#include <tvm/relay/expr.h>
+#include <tvm/runtime/object.h>
+#include <tvm/runtime/registry.h>
+#include <tvm/support/with.h>
+
+#include <memory>
+
+namespace tvm {
+namespace relax {
+
+class BlockBuilder;
+
+/*!
+ * \brief Utility data structure for generating unique names for IR construction.
+ */
+class NameTable {
+ public:
+  /*!
+   * \brief Generate a unique name with a specified prefix.
+   * \param prefix The name prefix.
+   * \return The generated name.
+   */
+  inline std::string GetUniqueName(std::string prefix) {
+    std::replace(prefix.begin(), prefix.end(), '.', '_');
+    std::string unique_prefix = prefix;
+    auto it = alloc_map_.find(prefix);
+    if (it != alloc_map_.end()) {
+      while (alloc_map_.count(unique_prefix = prefix + std::to_string(++it->second)) > 0) {
+      }
+    }
+    alloc_map_[unique_prefix] = 0;
+    return unique_prefix;
+  }
+
+ private:
+  std::unordered_map<std::string, uint32_t> alloc_map_;
+};
+
+/*!
+ * \brief A builder that provides APIs to build Relax binding blocks.
+ */
+class BlockBuilderNode : public Object {
+ public:
+  BlockBuilderNode(std::shared_ptr<NameTable> name_table) : name_table_(name_table) {}
+
+  ~BlockBuilderNode();
+
+  BlockBuilderNode() { name_table_ = std::make_shared<NameTable>(); }
+
+  /*! \brief Begin to build a DataflowBlock. */
+  void BeginDataflowBlock();
+  /*! \brief Begin to build a BindingBlock. */
+  void BeginBindingBlock();
+  /*!
+   * \brief End building a BindingBlock.
+   * \return The BindingBlock being built.
+   */
+  BindingBlock EndBlock();
+  /*!
+   * \brief Check if the block being built is DataflowBlock or not.
+   * \return A boolean that indicates if the block being built is DataflowBlock or not.
+   */
+  inline bool CurrentBlockIsDataFlow() { return CurrentFrame()->is_dataflow; }
+  /*!
+   * \brief Emits an Expr, and returns the variable it is bound to.
+   * \param expr The Expr to be emitted.
+   * \param name_hint Name hint for the bound variable.
+   * \return The new variable that \p expr is bound to.
+   */
+  virtual Var Emit(const Expr& expr, std::string name_hint = "");
+  /*!
+   * \brief Emits a variable binding, and returns the bound Var.
+   * \param binding The variable binding.
+   * \return The bound variable.
+   */
+  virtual Var Emit(const VarBinding& binding);
+  /*!
+   * \brief Emit a MatchShape.
+   * \param value The value of the MatchShape to be emitted.
+   * \param pattern The pattern of the MatchShape to be emitted.
+   * \param name_hint Name hint for the bound variable.
+   * \return The variable bound to the MatchShape.
+   */
+  Var EmitMatchShape(const Expr& value, const Array<PrimExpr>& pattern, std::string name_hint = "");
+  /*!
+   * \brief Emit a MatchShape binding.
+   * \param binding The MatchShape binding to be emitted.
+   * \return The variable bound to the MatchShape.
+   */
+  Var EmitMatchShape(const MatchShape& binding);
+  /*!
+   * \brief Generate an output for the current dataflow block.
+   * \param output The output variable of the block.
+   * \param name_hint Name hint for the bound variable.
+   * \return The variable bound to \p output.
+   */
+  Var EmitOutput(const Expr& output, std::string name_hint = "");
+  /*!
+   * \brief Generate an output for the current dataflow block.
+   * \param binding The output binding to output.
+   * \return The variable bound to \p output.
+   */
+  Var EmitOutput(const VarBinding& binding);
+  /*!
+   * \brief Lookup a var in the binding table \p var_map_.
+   * \param var The input var.
+   * \return The Expr bound to the input \p var.
+   */
+  Expr LookupVar(const Var& var);
+  /*!
+   * \brief Check if two shape expressions can be proven equal at compile time.
+   * \param lhs The input lhs shape.
+   * \param rhs The input rhs shape.
+   * \return Whether we can prove lhs shape is the same as the rhs shape.
+   */
+  bool CanProveShapeEqual(const Expr& lhs, const Expr& rhs);
+  /*!
+   * \brief Normalize an Expr to complete its shape and type.
+   * \param expr The input expr.
+   * \return The expr with normalized shape and type.
+   */
+  Expr Normalize(const Expr& expr);
+  /*!
+   * \brief Create a BlockBuilder.
+   * \return The created BlockBuilder.
+   */
+  TVM_DLL static BlockBuilder Create();
+
+  void VisitAttrs(AttrVisitor* v) {}
+
+  static constexpr const uint32_t _type_index = TypeIndex::kDynamic;
+  static constexpr const char* _type_key = "relax.BlockBuilder";
+  TVM_DECLARE_BASE_OBJECT_INFO(BlockBuilderNode, Object);
+
+ private:
+  Var Emit(const Expr& expr, bool is_dataflow, std::string name_hint);
+
+ protected:
+  /*!
+   * \brief A representation of a block frame.
+   *
+   * A block frame is a record containing the bindings needed
+   * to build a binding block, and a boolean to indicate if the
+   * block being built is a DataflowBlock or not.
+   */
+  struct BlockFrame {
+    Array<Binding> bindings;
+    bool is_dataflow;
+  };
+  friend class BlockBuilder;
+  /*!
+   * \brief Get the current block frame.
+   * \return The current block frame.
+   */
+  BlockFrame* CurrentFrame();
+  /*! \brief A stack to store block frames. */
+  std::stack<BlockFrame> block_stack_;
+  /*! \brief A diagnostic context for reporting errors. */
+  DiagnosticContext diag_ctx_ = DiagnosticContext::Default(IRModule({}, {}));
+  /*! \brief A binding table that maps var to value. */
+  // TODO(@yuchen, @altanh): make var_map_ scoped, and decide if it should be in the builder
+  std::unordered_map<Id, Expr, ObjectPtrHash, ObjectPtrEqual> var_map_;
+  /*! \brief A name table to get unique names for IR construction. */
+  std::shared_ptr<NameTable> name_table_;
+};
+
+class BlockBuilder : public ObjectRef {
+ public:
+  TVM_DLL explicit BlockBuilder(std::shared_ptr<NameTable> name_table);
+  TVM_DEFINE_MUTABLE_OBJECT_REF_METHODS(BlockBuilder, ObjectRef, BlockBuilderNode);
+};
+
+}  // namespace relax
+}  // namespace tvm
+
+#endif  // TVM_RELAX_BLOCK_BUILDER_H_

include/tvm/relax/expr_functor.h

@@ -27,8 +27,8 @@
 
 #include <tvm/ir/error.h>
 #include <tvm/node/functor.h>
+#include <tvm/relax/block_builder.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>
@@ -167,6 +167,9 @@ class ExprVisitor : public ExprFunctor<void(const Expr& n)> {
   virtual void VisitMatchShape(const MatchShape& binding);
   virtual void VisitBindingBlock(const BindingBlock& block);
   virtual void VisitDataflowBlock(const DataflowBlock& block);
+
+ protected:
+  std::unordered_map<const Object*, size_t> visit_counter_;
 };
 
 void PostOrderVisit(const Expr& node, std::function<void(const Expr&)> fvisit);
@@ -180,11 +183,22 @@ void PostOrderVisit(const Expr& node, std::function<void(const Expr&)> fvisit);
  */
 class ExprMutator : public ExprFunctor<Expr(const Expr&)> {
  public:
+  ExprMutator() {
+    name_table_ = std::make_shared<NameTable>();
+    builder_ = BlockBuilder(name_table_);
+  }
+
   /*!
    * \brief Mutate is alias for VisitExpr
    * \return expr.
    */
-  Expr Mutate(const Expr& expr) { return this->VisitExpr(expr); }
+  Expr Mutate(const Expr& expr) {
+    if (memo_.count(expr) == 0) {
+      memo_[expr] = this->VisitExpr(expr);
+    }
+    return Downcast<Expr>(memo_[expr]);
+  }
+
   Expr VisitExpr(const Expr& expr) override;
   Expr VisitExpr_(const ConstantNode* op) override;
   Expr VisitExpr_(const TupleNode* op) override;
@@ -208,28 +222,32 @@ class ExprMutator : public ExprFunctor<Expr(const Expr&)> {
    * visitor for types which transform them appropriately.
    */
   virtual Type VisitType(const Type& t);
-  virtual void VisitBinding(const Binding& binding, IRBuilder& builder);
-  virtual Var VisitVarBinding(const VarBinding& binding, IRBuilder& builder);
-  virtual void VisitMatchShape(const MatchShape& binding, IRBuilder& builder);
+
+  virtual void VisitBinding(const Binding& binding);
+  virtual Var VisitVarBinding(const VarBinding& binding);
+  virtual void VisitMatchShape(const MatchShape& binding);
   virtual BindingBlock VisitBindingBlock(const BindingBlock& block);
   virtual BindingBlock VisitDataflowBlock(const DataflowBlock& block);
 
  protected:
-  IRBuilder builder_;
+  Expr MutateWithPrologue(const Expr& expr, bool is_dataflow);
+  /*! \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> var_remap_;
+  std::unordered_map<ObjectRef, ObjectRef, ObjectPtrHash, ObjectPtrEqual> memo_;
+  std::shared_ptr<NameTable> name_table_;
+  BlockBuilder builder_;
 };
 
+// TODO(@yuchen, @altan): Refactor to enforce dataflow mutator only rewrite stuff in dataflow blocks
 /*! \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& builder);
+  void VisitBinding(const Binding& binding) final;
 
- 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_;
+  virtual Var VisitDataflowVarBinding(const VarBinding& binding);
 };
 
 }  // namespace relax