Function save_as_intervals 

pub fn save_as_intervals<'tcx, N, A>(
    elements: &DenseLocationMap,
    body: &Body<'tcx>,
    analysis: A,
    results: Results<A::Domain>,
) -> SparseIntervalMatrix<N, PointIndex>
where
    N: Idx,
    A: Analysis<'tcx, Domain = DenseBitSet<N>>,

Add points depending on the result of the given dataflow analysis.