The ProtoEncode helpers took the write cursor by reference and a
bool force flag. At -Os the compiler outlines most of them, so every
call site had to keep pos in a stack slot and pass its address, plus
a constant for the flag. The helpers now take the cursor by value and
return the advanced cursor, so consecutive calls chain through the
return register; forced fields call a _force overload instead of
passing a flag.
The fixed32 writers use __builtin_memcpy, which stays a builtin under
ESP-IDF's -fno-builtin-memcpy, and are outlined on embedded targets so
each fixed32 or float field is a short call instead of an inline
memcpy call. Non-forced float and fixed32 fields with a single-byte
tag share the same writer behind a zero check.
Generated encode bodies shrink by 18 percent on an ESP32 IDF proxy
build (2360 to 1932 bytes for 27 messages); entity messages gain the
most, for example ListEntitiesSensorResponse::encode 190 to 134 bytes
and SensorStateResponse::encode 78 to 49 bytes.
J. Nick Koston