[TVMScript] Printer Registry (apache#12237)

This PR:

- Adds the registry of printing function (traced_object_layered_functor.cc)

Compared to the prototype version, this:
- Consolidates the implementation into a single class, since this class is only for the TVMScript printer.
- Deduces the TObjectRef when calling set_dispatch.

Tracking issue: apache#11912

Co-authored-by: Greg Bonik <gbonik@octoml.ai>

include/tvm/script/printer/traced_object.h

@@ -86,6 +86,8 @@ class TracedObject {
   using ObjectType = typename RefT::ContainerType;
 
  public:
+  using ObjectRefType = RefT;
+
   // Don't use this direcly. For convenience, call MakeTraced() instead.
   explicit TracedObject(const RefT& object_ref, ObjectPath path)
       : ref_(object_ref), path_(std::move(path)) {}

include/tvm/script/printer/traced_object_functor.h

@@ -0,0 +1,183 @@
+/*
+ * 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.
+ */
+#ifndef TVM_SCRIPT_PRINTER_TRACED_OBJECT_FUNCTOR_H_
+#define TVM_SCRIPT_PRINTER_TRACED_OBJECT_FUNCTOR_H_
+
+#include <tvm/node/node.h>
+#include <tvm/runtime/logging.h>
+#include <tvm/runtime/packed_func.h>
+#include <tvm/script/printer/traced_object.h>
+
+#include <string>
+#include <type_traits>
+#include <unordered_map>
+#include <utility>
+#include <vector>
+
+namespace tvm {
+namespace script {
+namespace printer {
+
+namespace {
+
+namespace detail {
+/*!
+ * \brief Helper template class to extract the type of first argument of a function
+ * \tparam FType The function type.
+ */
+template <typename FType>
+struct FirstArgTypeGetter;
+
+template <typename R, typename ArgOne, typename... OtherArgs>
+struct FirstArgTypeGetter<R(ArgOne, OtherArgs...)> {
+  using T = ArgOne;
+};
+
+/*!
+ * \brief Template alias for the type of first argument of a function
+ * \tparam FType The function type.
+ *
+ * The name of public functions are in snake case to be consistent with
+ * tvm/node/functor.h
+ */
+template <typename FType>
+using FirstArgType = typename detail::FirstArgTypeGetter<
+    typename tvm::runtime::detail::function_signature<FType>::FType>::T;
+}  // namespace detail
+
+}  // namespace
+
+/*
+ * This type alias and the following free functions are created to reduce the binary bloat
+ * from template and also hide implementation details from this header
+ */
+using DispatchTable = std::unordered_map<std::string, std::vector<runtime::PackedFunc>>;
+
+/*!
+ * \brief Get function from dispatch table.
+ * \param dispatch_table The dispatch table.
+ * \param token The dispatch token.
+ * \param type_index The type index of the Object type to be dispatched.
+ *
+ * \return The dispatch function.
+ */
+const runtime::PackedFunc& GetDispatchFunction(const DispatchTable& dispatch_table,
+                                               const String& token, uint32_t type_index);
+
+/*!
+ * \brief Set function in dispatch table.
+ * \param dispatch_table The dispatch table.
+ * \param token The dispatch token.
+ * \param type_index The type index of the Object type to be dispatched.
+ * \param f The dispatch function.
+ */
+void SetDispatchFunction(DispatchTable* dispatch_table, const String& token, uint32_t type_index,
+                         runtime::PackedFunc f);
+
+constexpr const char* kDefaultDispatchToken = "";
+
+/*!
+ * \brief Dynamic dispatch functor based on TracedObject.
+ *
+ * This functor dispatches based on the type of object ref inside the input TracedObject,
+ * and the input dispatch token.
+ */
+template <typename R, typename... Args>
+class TracedObjectFunctor {
+ private:
+  using TSelf = TracedObjectFunctor<R, Args...>;
+
+  template <class TObjectRef, class TCallable>
+  using IsDispatchFunction =
+      typename std::is_convertible<TCallable, std::function<R(TracedObject<TObjectRef>, Args...)>>;
+
+ public:
+  /*!
+   * \brief Call the dispatch function.
+   * \param token The dispatch token.
+   * \param traced_object The traced object.
+   * \param args Other args.
+   *
+   * \return The return value of the dispatch function
+   *
+   * If the TObjectRef isn't registered with the token, it will try to find
+   * dispatch function for TObjectRef with kDefaultDispatchToken.
+   */
+  template <class TObjectRef>
+  R operator()(const String& token, TracedObject<TObjectRef> traced_object, Args... args) const {
+    const runtime::PackedFunc& dispatch_function =
+        GetDispatchFunction(dispatch_table_, token, traced_object.Get()->type_index());
+    return dispatch_function(traced_object.Get(), traced_object.GetPath(), args...);
+  }
+
+  /*!
+   * \brief Set the dispatch function
+   * \param token The dispatch token.
+   * \param type_index The TVM object type index for this dispatch function.
+   * \param f The dispatch function.
+   *
+   * This takes a type-erased packed function as input. It should be used
+   * through FFI boundary, for example, registering dispatch function from Python.
+   */
+  TSelf& set_dispatch(String token, uint32_t type_index, runtime::PackedFunc f) {
+    SetDispatchFunction(&dispatch_table_, token, type_index, std::move(f));
+    return *this;
+  }
+
+  /*!
+   * \brief Set the dispatch function
+   * \param token The dispatch token.
+   * \param f The dispatch function.
+   *
+   * The diaptch function should have signature `R(TracedObject<TObjectRef>, Args...)`.
+   */
+  template <typename TCallable,
+            typename TObjectRef = typename detail::FirstArgType<TCallable>::ObjectRefType,
+            typename = std::enable_if_t<IsDispatchFunction<TObjectRef, TCallable>::value>>
+  TSelf& set_dispatch(String token, TCallable f) {
+    return set_dispatch(
+        token,                                          //
+        TObjectRef::ContainerType::RuntimeTypeIndex(),  //
+        runtime::TypedPackedFunc<R(TObjectRef, ObjectPath, Args...)>(
+            [f = std::move(f)](TObjectRef object, ObjectPath path, Args... args) -> R {
+              return f(MakeTraced(object, path), args...);
+            }));
+  }
+  /*!
+   * \brief Set the default dispatch function
+   * \param f The dispatch function.
+   *
+   * Default dispatch function will be used if there is no function registered
+   * with the requested dispatch token.
+   *
+   * Default dispatch function has an empty string as dispatch token.
+   */
+  template <typename TCallable>
+  TSelf& set_dispatch(TCallable&& f) {
+    return set_dispatch(kDefaultDispatchToken, std::forward<TCallable>(f));
+  }
+
+ private:
+  DispatchTable dispatch_table_;
+};
+
+}  // namespace printer
+}  // namespace script
+}  // namespace tvm
+#endif  // TVM_SCRIPT_PRINTER_TRACED_OBJECT_FUNCTOR_H_

src/script/printer/traced_object_functor.cc

@@ -0,0 +1,75 @@
+/*
+ * 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.
+ */
+
+#include <tvm/script/printer/traced_object_functor.h>
+
+namespace tvm {
+namespace script {
+namespace printer {
+
+const runtime::PackedFunc* GetDispatchFunctionForToken(const DispatchTable& table,
+                                                       const String& token, uint32_t type_index) {
+  auto it = table.find(token);
+  if (it == table.end()) {
+    return nullptr;
+  }
+  const std::vector<runtime::PackedFunc>& tab = it->second;
+  if (type_index >= tab.size()) {
+    return nullptr;
+  }
+  const PackedFunc* f = &tab[type_index];
+  if (f->defined()) {
+    return f;
+  } else {
+    return nullptr;
+  }
+}
+
+const runtime::PackedFunc& GetDispatchFunction(const DispatchTable& dispatch_table,
+                                               const String& token, uint32_t type_index) {
+  if (const runtime::PackedFunc* pf =
+          GetDispatchFunctionForToken(dispatch_table, token, type_index)) {
+    return *pf;
+  } else if (const runtime::PackedFunc* pf =
+                 GetDispatchFunctionForToken(dispatch_table, kDefaultDispatchToken, type_index)) {
+    // Fallback to function with the default dispatch token
+    return *pf;
+  } else {
+    ICHECK(false) << "ObjectFunctor calls un-registered function on type: "
+                  << runtime::Object::TypeIndex2Key(type_index) << " (token: " << token << ")";
+    throw;
+  }
+}
+
+void SetDispatchFunction(DispatchTable* dispatch_table, const String& token, uint32_t type_index,
+                         runtime::PackedFunc f) {
+  std::vector<runtime::PackedFunc>* table = &(*dispatch_table)[token];
+  if (table->size() <= type_index) {
+    table->resize(type_index + 1, nullptr);
+  }
+  runtime::PackedFunc& slot = (*table)[type_index];
+  if (slot != nullptr) {
+    ICHECK(false) << "Dispatch for type is already registered: "
+                  << runtime::Object::TypeIndex2Key(type_index);
+  }
+  slot = f;
+}
+}  // namespace printer
+}  // namespace script
+}  // namespace tvm