chore: import upstream snapshot with attribution

include/tvm/ir/node_functor.h

@@ -0,0 +1,194 @@
+/*
+ * 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/ir/node_functor.h
+ * \brief Defines the Functor data structures.
+ */
+#ifndef TVM_IR_NODE_FUNCTOR_H_
+#define TVM_IR_NODE_FUNCTOR_H_
+
+#include <tvm/ffi/error.h>
+
+#include <cstring>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+namespace tvm {
+
+/*!
+ * \brief A dynamically dispatched functor on the type of the first argument.
+ *
+ * This is a class that is useful to construct polymorphic dispatching
+ * base on the AST/IR node's type.
+ *
+ * \code
+ *   NodeFunctor<std::string (const ffi::ObjectRef& n, std::string prefix)> tostr;
+ *   tostr.set_dispatch<Add>([](const ffi::ObjectRef& op, std::string prefix) {
+ *     return prefix + "Add";
+ *   });
+ *   tostr.set_dispatch<IntImm>([](const ffi::ObjectRef& op, std::string prefix) {
+ *     return prefix + "IntImm"
+ *   });
+ *
+ *   Expr x = MakeConst(1);
+ *   Expr y = x + x;
+ *   // dispatch to IntImm, outputs "MyIntImm"
+ *   LOG(INFO) << tostr(x, "My");
+ *   // dispatch to IntImm, outputs "MyAdd"
+ *   LOG(INFO) << tostr(y, "My");
+ * \endcode
+ *
+ * \tparam FType function signiture
+ *  This type if only defined for FType with function signature
+ */
+template <typename FType>
+class NodeFunctor;
+
+template <typename R, typename... Args>
+class NodeFunctor<R(const ffi::ObjectRef& n, Args...)> {
+ private:
+  /*! \brief internal function pointer type */
+  typedef R (*FPointer)(const ffi::ObjectRef& n, Args...);
+  /*! \brief refer to itself. */
+  using TSelf = NodeFunctor<R(const ffi::ObjectRef& n, Args...)>;
+  /*! \brief internal function table */
+  std::vector<FPointer> func_;
+  /*! \brief start range of func index */
+  uint32_t begin_type_index_{0};
+
+ public:
+  /*! \brief the result type of this functor */
+  using result_type = R;
+  /*!
+   * \brief Whether the functor can dispatch the corresponding Node
+   * \param n The node to be dispatched
+   * \return Whether dispatching function is registered for n's type.
+   */
+  bool can_dispatch(const ffi::ObjectRef& n) const {
+    uint32_t type_index = n->type_index();
+    if (type_index < begin_type_index_) return false;
+    type_index -= begin_type_index_;
+    return type_index < func_.size() && func_[type_index] != nullptr;
+  }
+  /*!
+   * \brief invoke the functor, dispatch on type of n
+   * \param n The Node argument
+   * \param args The additional arguments
+   * \return The result.
+   */
+  R operator()(const ffi::ObjectRef& n, Args... args) const {
+    TVM_FFI_ICHECK(can_dispatch(n))
+        << "NodeFunctor calls un-registered function on type " << n->GetTypeKey();
+    return (*func_[n->type_index() - begin_type_index_])(n, std::forward<Args>(args)...);
+  }
+  /*!
+   * \brief set the dispatcher for type TNode
+   * \param f The function to be set.
+   * \tparam TNode the type of Node to be dispatched.
+   * \return reference to self.
+   */
+  template <typename TNode>
+  TSelf& set_dispatch(FPointer f) {  // NOLINT(*)
+    uint32_t tindex = TNode::RuntimeTypeIndex();
+    if (func_.size() <= tindex) {
+      func_.resize(tindex + 1, nullptr);
+    }
+    TVM_FFI_ICHECK(func_[tindex] == nullptr)
+        << "Dispatch for " << TNode::_type_key << " is already set";
+    TVM_FFI_ICHECK_EQ(begin_type_index_, 0) << " Cannot call set_dispatch after calling Finalize";
+    func_[tindex] = f;
+    return *this;
+  }
+  /*!
+   * \brief unset the dispatcher for type TNode
+   *
+   * \tparam TNode the type of Node to be dispatched.
+   * \return reference to self.
+   */
+  template <typename TNode>
+  TSelf& clear_dispatch() {  // NOLINT(*)
+    uint32_t tindex = TNode::RuntimeTypeIndex();
+    TVM_FFI_ICHECK_LT(tindex, func_.size()) << "clear_dispatch: index out of range";
+    TVM_FFI_ICHECK_EQ(begin_type_index_, 0) << " Cannot call clear_dispatch after calling Finalize";
+    func_[tindex] = nullptr;
+    return *this;
+  }
+  /*!
+   * \brief Finalize the functor after calling sequence of set_dispatch
+   * This function will attempt to find the min type index that is not null
+   * and optimize the space of the func table so it is more compact
+   */
+  void Finalize() {
+    TVM_FFI_ICHECK_EQ(begin_type_index_, 0) << "Can only call Finalize once";
+    while (begin_type_index_ < func_.size() && func_[begin_type_index_] == nullptr) {
+      ++begin_type_index_;
+    }
+    // shift up the function value
+    size_t new_ftable_size = func_.size() - begin_type_index_;
+    if (begin_type_index_ != 0) {
+      std::memmove(func_.data(), func_.data() + begin_type_index_,
+                   new_ftable_size * sizeof(FPointer));
+    }
+    func_.resize(new_ftable_size);
+    func_.shrink_to_fit();
+  }
+};
+
+#define TVM_REG_FUNC_VAR_DEF(ClsName) [[maybe_unused]] static auto& __make_functor##_##ClsName
+
+/*!
+ * \brief Useful macro to set NodeFunctor dispatch in a global static field.
+ *
+ * \code
+ *  // Use NodeFunctor to implement TVMScriptPrinter similar to Visitor Pattern.
+ *  // vtable allows easy patch of new Node types, without changing
+ *  // the interface of TVMScriptPrinter.
+ *
+ *  class TVMScriptPrinter {
+ *   public:
+ *    // the dispatch function.
+ *    static std::string Script(const ffi::ObjectRef& node, const PrinterConfig& cfg) {
+ *      return vtable()(node, cfg);
+ *    }
+ *    using FType = NodeFunctor<std::string(const ffi::ObjectRef&, const PrinterConfig&)>;
+ *    // function to return global function table
+ *    static FType& vtable();
+ *  };
+ *
+ *  // in cpp/cc file
+ *  TVMScriptPrinter::FType& TVMScriptPrinter::vtable() {
+ *    static FType inst; return inst;
+ *  }
+ *
+ *  TVM_STATIC_IR_FUNCTOR(TVMScriptPrinter, vtable)
+ *  .set_dispatch<AddNode>([](const ffi::ObjectRef& ref, const PrinterConfig& cfg) {
+ *    auto* n = static_cast<const AddNode*>(ref.get());
+ *    return Script(n->a, cfg) + " + " + Script(n->b, cfg);
+ *  });
+ *
+ * \endcode
+ *
+ * \param ClsName The name of the class
+ * \param FField The static function that returns a singleton of NodeFunctor.
+ */
+#define TVM_STATIC_IR_FUNCTOR(ClsName, FField) \
+  TVM_FFI_STR_CONCAT(TVM_REG_FUNC_VAR_DEF(ClsName), __COUNTER__) = ClsName::FField()
+}  // namespace tvm
+#endif  // TVM_IR_NODE_FUNCTOR_H_