Function sha512_chain_lane_kernel 

pub fn sha512_chain_lane_kernel<const MASK: usize>(
    _cr: ClockReset,
    input: ChainStepInput,
    q: Sha512ChainLaneQ<MASK>,
) -> (ChainStepOutput, Sha512ChainLaneD<MASK>)

Build and pad the block, hash, keep the first 18 digest bytes.

The input enters the core this cycle; its digest and tag appear [SHA_LATENCY] (82) cycles later. ready is always true.