From 9a022baa06615441ff2a036a9bcfaae223bdf373 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@home-assistant.io>
Date: Sun, 12 Apr 2026 19:55:30 -1000
Subject: [PATCH] [core] Optimize main loop with -O2

Add __attribute__((optimize("O2"))) to the main loop functions
(loop_task on ESP32, codegen loop() on other platforms) so GCC
inlines scheduler helpers and loop bookkeeping more aggressively.

Under -Os, GCC outlines small functions (Scheduler::call helpers,
millis conversions, etc.) that are called every loop iteration.
With -O2, these get inlined into the loop body, reducing call
overhead on the hottest code path in the firmware.

ESP32: loop_task grows from 303 to 416 bytes (+113 bytes).
ESP8266: no change (already fully inlined via ESPHOME_ALWAYS_INLINE).
---
 esphome/components/esp32/core.cpp  | 2 +-
 esphome/components/host/core.cpp   | 2 +-
 esphome/components/zephyr/core.cpp | 2 +-
 esphome/core/application.h         | 2 +-
 esphome/writer.py                  | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/esphome/components/esp32/core.cpp b/esphome/components/esp32/core.cpp
index add50dcf4d..1fa51f1d9e 100644
--- a/esphome/components/esp32/core.cpp
+++ b/esphome/components/esp32/core.cpp
@@ -65,7 +65,7 @@ static StaticTask_t loop_task_tcb;        // NOLINT(cppcoreguidelines-avoid-non-
 static StackType_t
     loop_task_stack[ESPHOME_LOOP_TASK_STACK_SIZE];  // NOLINT(cppcoreguidelines-avoid-non-const-global-variables)
 
-void loop_task(void *pv_params) {
+void __attribute__((optimize("O2"))) loop_task(void *pv_params) {
   setup();
   while (true) {
     App.loop();
diff --git a/esphome/components/host/core.cpp b/esphome/components/host/core.cpp
index 0ade4274fe..596b46305f 100644
--- a/esphome/components/host/core.cpp
+++ b/esphome/components/host/core.cpp
@@ -77,7 +77,7 @@ uint32_t arch_get_cpu_freq_hz() { return 1000000000U; }
 
 void setup();
 void loop();
-int main() {
+int __attribute__((optimize("O2"))) main() {
   // Install signal handlers for graceful shutdown (flushes preferences to disk)
   std::signal(SIGINT, signal_handler);
   std::signal(SIGTERM, signal_handler);
diff --git a/esphome/components/zephyr/core.cpp b/esphome/components/zephyr/core.cpp
index a3b0471ebc..84dee374f5 100644
--- a/esphome/components/zephyr/core.cpp
+++ b/esphome/components/zephyr/core.cpp
@@ -95,7 +95,7 @@ void get_mac_address_raw(uint8_t *mac) {  // NOLINT(readability-non-const-parame
 void setup();
 void loop();
 
-int main() {
+int __attribute__((optimize("O2"))) main() {
   setup();
   while (true) {
     loop();
diff --git a/esphome/core/application.h b/esphome/core/application.h
index 6b2969b490..5b68146b2d 100644
--- a/esphome/core/application.h
+++ b/esphome/core/application.h
@@ -837,7 +837,7 @@ inline void ESPHOME_ALWAYS_INLINE Application::before_loop_tasks_(uint32_t loop_
   this->in_loop_ = true;
 }
 
-inline void ESPHOME_ALWAYS_INLINE Application::loop() {
+inline void ESPHOME_ALWAYS_INLINE __attribute__((optimize("O2"))) Application::loop() {
   uint8_t new_app_state = 0;
 
   // Get the initial loop time at the start
diff --git a/esphome/writer.py b/esphome/writer.py
index 06a2230118..c2e0d08fa4 100644
--- a/esphome/writer.py
+++ b/esphome/writer.py
@@ -45,7 +45,7 @@ void setup() {
   App.setup();
 }
 
-void loop() {
+void __attribute__((optimize("O2"))) loop() {
   App.loop();
 }
 """,