Function rustc_mir_transform::elaborate_drops::compute_dead_unwinds

fn compute_dead_unwinds<'mir, 'tcx>(
    body: &'mir Body<'tcx>,
    flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>
) -> BitSet<BasicBlock>

Records unwind edges which are known to be unreachable, because they are in drop terminators that can’t drop anything.