Where do arguments come from?
The GC ABI passes the first integer argument in r3 — the same register used for the return value. So a function that just returns its argument has nothing to do: the value is already sitting in r3.
blr ; r3 already holds x — just return
That single blr is a perfect, if anticlimactic, match. Later arguments go in r4, r5, r6 … up to r10.
Your task
Write identity, which takes an int x and returns it unchanged.