[api] Add speed_optimized proto option for hot encode paths

Add a new (speed_optimized) message option that emits
__attribute__((optimize("O2"))) on the generated encode() and
calculate_size() methods. Under -Os, GCC does not inline the small
ProtoEncode helpers (write_raw_byte, encode_varint, etc.) into the
generated methods, causing significant overhead on hot paths.

Apply to SensorStateResponse and BluetoothLERawAdvertisementsResponse
which are the highest-frequency encode paths.

esphome/components/api/api.proto

@@ -671,6 +671,7 @@ message SensorStateResponse {
   option (source) = SOURCE_SERVER;
   option (ifdef) = "USE_SENSOR";
   option (no_delay) = true;
+  option (speed_optimized) = true;
 
   fixed32 key = 1 [(force) = true];
   float state = 2;
@@ -1638,6 +1639,7 @@ message BluetoothLERawAdvertisementsResponse {
   option (source) = SOURCE_SERVER;
   option (ifdef) = "USE_BLUETOOTH_PROXY";
   option (no_delay) = true;
+  option (speed_optimized) = true;
 
   repeated BluetoothLERawAdvertisement advertisements = 1 [(fixed_array_with_length_define) = "BLUETOOTH_PROXY_ADVERTISEMENT_BATCH_SIZE"];
 }

esphome/components/api/api_options.proto

@@ -23,6 +23,7 @@ extend google.protobuf.MessageOptions {
     optional bool no_delay = 1040 [default=false];
     optional string base_class = 1041;
     optional bool inline_encode = 1042 [default=false];
+    optional bool speed_optimized = 1043 [default=false];
 }
 
 extend google.protobuf.FieldOptions {

esphome/components/api/api_pb2.cpp

@@ -745,7 +745,8 @@ uint32_t ListEntitiesSensorResponse::calculate_size() const {
 #endif
   return size;
 }
-uint8_t *SensorStateResponse::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
+__attribute__((optimize("O2"))) uint8_t *SensorStateResponse::encode(
+    ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
   uint8_t *__restrict__ pos = buffer.get_pos();
   ProtoEncode::write_tag_and_fixed32(pos PROTO_ENCODE_DEBUG_ARG, 13, this->key);
   ProtoEncode::encode_float(pos PROTO_ENCODE_DEBUG_ARG, 2, this->state);
@@ -755,7 +756,7 @@ uint8_t *SensorStateResponse::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG
 #endif
   return pos;
 }
-uint32_t SensorStateResponse::calculate_size() const {
+__attribute__((optimize("O2"))) uint32_t SensorStateResponse::calculate_size() const {
   uint32_t size = 0;
   size += 5;
   size += ProtoSize::calc_float(1, this->state);
@@ -2328,7 +2329,8 @@ bool SubscribeBluetoothLEAdvertisementsRequest::decode_varint(uint32_t field_id,
   }
   return true;
 }
-uint8_t *BluetoothLERawAdvertisementsResponse::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
+__attribute__((optimize("O2"))) uint8_t *BluetoothLERawAdvertisementsResponse::encode(
+    ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {
   uint8_t *__restrict__ pos = buffer.get_pos();
   for (uint16_t i = 0; i < this->advertisements_len; i++) {
     auto &sub_msg = this->advertisements[i];
@@ -2350,7 +2352,7 @@ uint8_t *BluetoothLERawAdvertisementsResponse::encode(ProtoWriteBuffer &buffer P
   }
   return pos;
 }
-uint32_t BluetoothLERawAdvertisementsResponse::calculate_size() const {
+__attribute__((optimize("O2"))) uint32_t BluetoothLERawAdvertisementsResponse::calculate_size() const {
   uint32_t size = 0;
   for (uint16_t i = 0; i < this->advertisements_len; i++) {
     auto &sub_msg = this->advertisements[i];

script/api_protobuf/api_protobuf.py

@@ -2679,6 +2679,13 @@ def build_message_type(
         and get_opt(desc, inline_opt, False)
     )
 
+    # Check if this message wants speed-optimized encode/calculate_size.
+    # When set, __attribute__((optimize("O2"))) is added to the definitions
+    # so GCC inlines the small ProtoEncode helpers even under -Os.
+    speed_opt = getattr(pb, "speed_optimized", None)
+    is_speed_optimized = speed_opt is not None and get_opt(desc, speed_opt, False)
+    speed_attr = '__attribute__((optimize("O2"))) ' if is_speed_optimized else ""
+
     # Only generate encode method if this message needs encoding and has fields
     if needs_encode and encode and not is_inline_only:
         # Add PROTO_ENCODE_DEBUG_ARG after pos in all proto_* calls
@@ -2688,7 +2695,7 @@ def build_message_type(
             )
             for line in encode
         ]
-        o = f"uint8_t *{desc.name}::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {{\n"
+        o = f"{speed_attr}uint8_t *{desc.name}::encode(ProtoWriteBuffer &buffer PROTO_ENCODE_DEBUG_PARAM) const {{\n"
         o += "  uint8_t *__restrict__ pos = buffer.get_pos();\n"
         o += indent("\n".join(encode_debug)) + "\n"
         o += "  return pos;\n"
@@ -2702,7 +2709,7 @@ def build_message_type(
 
     # Add calculate_size method only if this message needs encoding and has fields
     if needs_encode and size_calc and not is_inline_only:
-        o = f"uint32_t {desc.name}::calculate_size() const {{\n"
+        o = f"{speed_attr}uint32_t {desc.name}::calculate_size() const {{\n"
         o += "  uint32_t size = 0;\n"
         o += indent("\n".join(size_calc)) + "\n"
         o += "  return size;\n"