Where do arguments come from?
On the GameCube's ABI, the first integer argument arrives in r3 — the same register the return value leaves in. That overlap has a funny consequence: some functions need no instructions at all beyond the return.
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One blr and that's a complete, valid function. Further integer and pointer arguments stack up in r4, r5, r6, and so on through r10. Floats play by different rules — they ride in f1–f8 and don't consume an integer slot.
When the assembly is nothing but a blr, with nothing touching r3, ask yourself: what would the input and output have to be for the compiler to need zero work?
Your task
Write identity, taking an int x, to reproduce the assembly above.