[plt-scheme] dead code elimination/closure optimization?

Does the bytecode compiler or the jitter do dead code elimination for
closures?

For example in
(let ((foo (lambda () ...))) body ...)
where foo is not referenced in the body (other than perhaps in in
turn unreferenced macros), is the lambda closure construction and variable
assignment code present in bytecode and ultimately in the
code generated by the jit?

What about
(letrec ((foo (lambda () ... (set! foo ...) ...))) body ...) with
similar body conditions for foo?

-- vyzo