test/binaryen.js/hello-world.js.txt

(module
 (type $0 (func (param i32 i32) (result i32)))
 (export "adder" (func $adder))
 (func $adder (param $0 i32) (param $1 i32) (result i32)
  (return
   (i32.add
    (local.get $0)
    (local.get $1)
   )
  )
 )
)

optimized:

(module
 (type $0 (func (param i32 i32) (result i32)))
 (export "adder" (func $adder))
 (func $adder (param $0 i32) (param $1 i32) (result i32)
  (i32.add
   (local.get $0)
   (local.get $1)
  )
 )
)

binary size: 43

exports: adder

an addition: 42