[promises] Reduce bloat for promise_based_filter (#31209)

* [bloat] Rewrite promise_based_filter vtables to maximize code sharing

* moar

src/core/lib/channel/promise_based_filter.h

@@ -157,6 +157,8 @@ class BaseCallData : public Activity, private Wakeable {
     finalization_.Run(final_info);
   }
 
+  virtual void StartBatch(grpc_transport_stream_op_batch* batch) = 0;
+
  protected:
   class ScopedContext
       : public promise_detail::Context<Arena>,
@@ -293,7 +295,7 @@ class ClientCallData : public BaseCallData {
   // Activity implementation.
   void ForceImmediateRepoll() final;
   // Handle one grpc_transport_stream_op_batch
-  void StartBatch(grpc_transport_stream_op_batch* batch);
+  void StartBatch(grpc_transport_stream_op_batch* batch) override;
 
  private:
   // At what stage is our handling of send initial metadata?
@@ -393,7 +395,7 @@ class ServerCallData : public BaseCallData {
   // Activity implementation.
   void ForceImmediateRepoll() final;
   // Handle one grpc_transport_stream_op_batch
-  void StartBatch(grpc_transport_stream_op_batch* batch);
+  void StartBatch(grpc_transport_stream_op_batch* batch) override;
 
  private:
   // At what stage is our handling of recv initial metadata?
@@ -471,23 +473,116 @@ class ServerCallData : public BaseCallData {
 // Specific call data per channel filter.
 // Note that we further specialize for clients and servers since their
 // implementations are very different.
-template <class ChannelFilter, FilterEndpoint endpoint>
+template <FilterEndpoint endpoint>
 class CallData;
 
 // Client implementation of call data.
-template <class ChannelFilter>
-class CallData<ChannelFilter, FilterEndpoint::kClient> : public ClientCallData {
+template <>
+class CallData<FilterEndpoint::kClient> : public ClientCallData {
  public:
   using ClientCallData::ClientCallData;
 };
 
 // Server implementation of call data.
-template <class ChannelFilter>
-class CallData<ChannelFilter, FilterEndpoint::kServer> : public ServerCallData {
+template <>
+class CallData<FilterEndpoint::kServer> : public ServerCallData {
  public:
   using ServerCallData::ServerCallData;
 };
 
+struct BaseCallDataMethods {
+  static void SetPollsetOrPollsetSet(grpc_call_element* elem,
+                                     grpc_polling_entity* pollent) {
+    static_cast<BaseCallData*>(elem->call_data)->set_pollent(pollent);
+  }
+
+  static void DestructCallData(grpc_call_element* elem,
+                               const grpc_call_final_info* final_info) {
+    auto* cd = static_cast<BaseCallData*>(elem->call_data);
+    cd->Finalize(final_info);
+    cd->~BaseCallData();
+  }
+
+  static void StartTransportStreamOpBatch(
+      grpc_call_element* elem, grpc_transport_stream_op_batch* batch) {
+    static_cast<BaseCallData*>(elem->call_data)->StartBatch(batch);
+  }
+};
+
+template <typename CallData, uint8_t kFlags>
+struct CallDataFilterWithFlagsMethods {
+  static absl::Status InitCallElem(grpc_call_element* elem,
+                                   const grpc_call_element_args* args) {
+    new (elem->call_data) CallData(elem, args, kFlags);
+    return absl::OkStatus();
+  }
+
+  static void DestroyCallElem(grpc_call_element* elem,
+                              const grpc_call_final_info* final_info,
+                              grpc_closure* then_schedule_closure) {
+    BaseCallDataMethods::DestructCallData(elem, final_info);
+    if ((kFlags & kFilterIsLast) != 0) {
+      ExecCtx::Run(DEBUG_LOCATION, then_schedule_closure, absl::OkStatus());
+    } else {
+      GPR_ASSERT(then_schedule_closure == nullptr);
+    }
+  }
+};
+
+struct ChannelFilterMethods {
+  static ArenaPromise<ServerMetadataHandle> MakeCallPromise(
+      grpc_channel_element* elem, CallArgs call_args,
+      NextPromiseFactory next_promise_factory) {
+    return static_cast<ChannelFilter*>(elem->channel_data)
+        ->MakeCallPromise(std::move(call_args),
+                          std::move(next_promise_factory));
+  }
+
+  static void StartTransportOp(grpc_channel_element* elem,
+                               grpc_transport_op* op) {
+    if (!static_cast<ChannelFilter*>(elem->channel_data)
+             ->StartTransportOp(op)) {
+      grpc_channel_next_op(elem, op);
+    }
+  }
+
+  static void PostInitChannelElem(grpc_channel_stack*,
+                                  grpc_channel_element* elem) {
+    static_cast<ChannelFilter*>(elem->channel_data)->PostInit();
+  }
+
+  static void DestroyChannelElem(grpc_channel_element* elem) {
+    static_cast<ChannelFilter*>(elem->channel_data)->~ChannelFilter();
+  }
+
+  static void GetChannelInfo(grpc_channel_element* elem,
+                             const grpc_channel_info* info) {
+    if (!static_cast<ChannelFilter*>(elem->channel_data)
+             ->GetChannelInfo(info)) {
+      grpc_channel_next_get_info(elem, info);
+    }
+  }
+};
+
+template <typename F, uint8_t kFlags>
+struct ChannelFilterWithFlagsMethods {
+  static absl::Status InitChannelElem(grpc_channel_element* elem,
+                                      grpc_channel_element_args* args) {
+    GPR_ASSERT(args->is_last == ((kFlags & kFilterIsLast) != 0));
+    auto status = F::Create(ChannelArgs::FromC(args->channel_args),
+                            ChannelFilter::Args(args->channel_stack, elem));
+    if (!status.ok()) {
+      static_assert(
+          sizeof(promise_filter_detail::InvalidChannelFilter) <= sizeof(F),
+          "InvalidChannelFilter must fit in F");
+      new (elem->channel_data) promise_filter_detail::InvalidChannelFilter();
+      return absl_status_to_grpc_error(status.status());
+    }
+    new (elem->channel_data) F(std::move(*status));
+    return absl::OkStatus();
+  }
+};
+
 }  // namespace promise_filter_detail
 
 // F implements ChannelFilter and :
@@ -499,83 +594,36 @@ class CallData<ChannelFilter, FilterEndpoint::kServer> : public ServerCallData {
 template <typename F, FilterEndpoint kEndpoint, uint8_t kFlags = 0>
 absl::enable_if_t<std::is_base_of<ChannelFilter, F>::value, grpc_channel_filter>
 MakePromiseBasedFilter(const char* name) {
-  using CallData = promise_filter_detail::CallData<F, kEndpoint>;
+  using CallData = promise_filter_detail::CallData<kEndpoint>;
 
   return grpc_channel_filter{
       // start_transport_stream_op_batch
-      [](grpc_call_element* elem, grpc_transport_stream_op_batch* batch) {
-        static_cast<CallData*>(elem->call_data)->StartBatch(batch);
-      },
+      promise_filter_detail::BaseCallDataMethods::StartTransportStreamOpBatch,
       // make_call_promise
-      [](grpc_channel_element* elem, CallArgs call_args,
-         NextPromiseFactory next_promise_factory) {
-        return static_cast<ChannelFilter*>(elem->channel_data)
-            ->MakeCallPromise(std::move(call_args),
-                              std::move(next_promise_factory));
-      },
+      promise_filter_detail::ChannelFilterMethods::MakeCallPromise,
       // start_transport_op
-      [](grpc_channel_element* elem, grpc_transport_op* op) {
-        if (!static_cast<ChannelFilter*>(elem->channel_data)
-                 ->StartTransportOp(op)) {
-          grpc_channel_next_op(elem, op);
-        }
-      },
+      promise_filter_detail::ChannelFilterMethods::StartTransportOp,
       // sizeof_call_data
       sizeof(CallData),
       // init_call_elem
-      [](grpc_call_element* elem, const grpc_call_element_args* args) {
-        new (elem->call_data) CallData(elem, args, kFlags);
-        return absl::OkStatus();
-      },
+      promise_filter_detail::CallDataFilterWithFlagsMethods<
+          CallData, kFlags>::InitCallElem,
       // set_pollset_or_pollset_set
-      [](grpc_call_element* elem, grpc_polling_entity* pollent) {
-        static_cast<CallData*>(elem->call_data)->set_pollent(pollent);
-      },
+      promise_filter_detail::BaseCallDataMethods::SetPollsetOrPollsetSet,
       // destroy_call_elem
-      [](grpc_call_element* elem, const grpc_call_final_info* final_info,
-         grpc_closure* then_schedule_closure) {
-        auto* cd = static_cast<CallData*>(elem->call_data);
-        cd->Finalize(final_info);
-        cd->~CallData();
-        if ((kFlags & kFilterIsLast) != 0) {
-          ExecCtx::Run(DEBUG_LOCATION, then_schedule_closure, absl::OkStatus());
-        } else {
-          GPR_ASSERT(then_schedule_closure == nullptr);
-        }
-      },
+      promise_filter_detail::CallDataFilterWithFlagsMethods<
+          CallData, kFlags>::DestroyCallElem,
       // sizeof_channel_data
       sizeof(F),
       // init_channel_elem
-      [](grpc_channel_element* elem, grpc_channel_element_args* args) {
-        GPR_ASSERT(args->is_last == ((kFlags & kFilterIsLast) != 0));
-        auto status = F::Create(ChannelArgs::FromC(args->channel_args),
-                                ChannelFilter::Args(args->channel_stack, elem));
-        if (!status.ok()) {
-          static_assert(
-              sizeof(promise_filter_detail::InvalidChannelFilter) <= sizeof(F),
-              "InvalidChannelFilter must fit in F");
-          new (elem->channel_data)
-              promise_filter_detail::InvalidChannelFilter();
-          return absl_status_to_grpc_error(status.status());
-        }
-        new (elem->channel_data) F(std::move(*status));
-        return absl::OkStatus();
-      },
+      promise_filter_detail::ChannelFilterWithFlagsMethods<
+          F, kFlags>::InitChannelElem,
       // post_init_channel_elem
-      [](grpc_channel_stack*, grpc_channel_element* elem) {
-        static_cast<ChannelFilter*>(elem->channel_data)->PostInit();
-      },
+      promise_filter_detail::ChannelFilterMethods::PostInitChannelElem,
       // destroy_channel_elem
-      [](grpc_channel_element* elem) {
-        static_cast<ChannelFilter*>(elem->channel_data)->~ChannelFilter();
-      },
+      promise_filter_detail::ChannelFilterMethods::DestroyChannelElem,
       // get_channel_info
-      [](grpc_channel_element* elem, const grpc_channel_info* info) {
-        if (!static_cast<ChannelFilter*>(elem->channel_data)
-                 ->GetChannelInfo(info)) {
-          grpc_channel_next_get_info(elem, info);
-        }
-      },
+      promise_filter_detail::ChannelFilterMethods::GetChannelInfo,
       // name
       name,
   };