From a632a7e6441e5990e1452b49ac52aa926e501816 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sat, 28 Feb 2026 16:35:27 -1000
Subject: [PATCH] [core] Deduplicate ControllerRegistry notify dispatch loop

Each notify_*_update method had an identical loop that only differed
in the vtable offset for the virtual call. Extract the shared loop
into a single noinline notify() function and have each wrapper pass
a small trampoline lambda that dispatches to the correct Controller
virtual method.

Before: 8 copies of the loop at ~56 bytes each = ~448 bytes
After:  1 shared loop (56 B) + 8 wrappers (16 B) + 8 trampolines (8 B) = ~248 bytes

Saves ~200 bytes of flash.
---
 esphome/core/controller_registry.cpp | 15 +++++++++------
 esphome/core/controller_registry.h   | 15 +++++++++++++++
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/esphome/core/controller_registry.cpp b/esphome/core/controller_registry.cpp
index 13b505e8e95..67b964d4aa5 100644
--- a/esphome/core/controller_registry.cpp
+++ b/esphome/core/controller_registry.cpp
@@ -10,20 +10,23 @@ StaticVector<Controller *, CONTROLLER_REGISTRY_MAX> ControllerRegistry::controll
 
 void ControllerRegistry::register_controller(Controller *controller) { controllers.push_back(controller); }
 
+void ControllerRegistry::notify(void *obj, DispatchFunc dispatch) {
+  for (auto *controller : controllers) {
+    dispatch(controller, obj);
+  }
+}
+
 // Macro for standard registry notification dispatch - calls on_<entity_name>_update()
+// Each wrapper passes a small trampoline lambda that calls the correct virtual method.
 #define CONTROLLER_REGISTRY_NOTIFY(entity_type, entity_name) \
   void ControllerRegistry::notify_##entity_name##_update(entity_type *obj) { /* NOLINT(bugprone-macro-parentheses) */ \
-    for (auto *controller : controllers) { \
-      controller->on_##entity_name##_update(obj); \
-    } \
+    notify(obj, [](Controller *c, void *o) { c->on_##entity_name##_update(static_cast<entity_type *>(o)); }); \
   }
 
 // Macro for entities where controller method has no "_update" suffix (Event, Update)
 #define CONTROLLER_REGISTRY_NOTIFY_NO_UPDATE_SUFFIX(entity_type, entity_name) \
   void ControllerRegistry::notify_##entity_name(entity_type *obj) { /* NOLINT(bugprone-macro-parentheses) */ \
-    for (auto *controller : controllers) { \
-      controller->on_##entity_name(obj); \
-    } \
+    notify(obj, [](Controller *c, void *o) { c->on_##entity_name(static_cast<entity_type *>(o)); }); \
   }
 
 #ifdef USE_BINARY_SENSOR
diff --git a/esphome/core/controller_registry.h b/esphome/core/controller_registry.h
index d6452d8827e..0642aacdce4 100644
--- a/esphome/core/controller_registry.h
+++ b/esphome/core/controller_registry.h
@@ -162,6 +162,21 @@ class ControllerRegistry {
    */
   static void register_controller(Controller *controller);
 
+  /** Type-erased dispatch function pointer.
+   *
+   * Each notify method passes a small trampoline that calls the
+   * correct virtual method on Controller. The shared notify() loop
+   * iterates controllers once, calling the trampoline for each.
+   */
+  using DispatchFunc = void (*)(Controller *, void *);
+
+  /** Shared dispatch loop - iterates controllers and calls dispatch for each.
+   *
+   * Marked noinline to ensure only one copy of the loop exists in flash,
+   * rather than being duplicated into each notify_*_update wrapper.
+   */
+  static void __attribute__((noinline)) notify(void *obj, DispatchFunc dispatch);
+
 #ifdef USE_BINARY_SENSOR
   static void notify_binary_sensor_update(binary_sensor::BinarySensor *obj);
 #endif