Macro threaded_main_loop 

macro_rules! threaded_main_loop {
    ($main:path) => { ... };
    ($main:path, $exit:path) => { ... };
}

Like main_loop!, with cooperative threads (thread, sync): main runs as the first thread, thread::spawn starts more. The frame driver is the thread scheduler. Asyncify only (no gasm_run export): run wasm-opt --asyncify --pass-arg=asyncify-removelist@gasm_frame,gasm_loop_frame on the module.