Function load_from_disk_or_invoke_provider_green 

fn load_from_disk_or_invoke_provider_green<'tcx, C: QueryCache>(
    tcx: TyCtxt<'tcx>,
    dep_graph_data: &DepGraphData,
    query: &'tcx QueryVTable<'tcx, C>,
    key: &C::Key,
    dep_node: &DepNode,
    prev_index: SerializedDepNodeIndex,
    dep_node_index: DepNodeIndex,
) -> C::Value

Given that the dep node for this query+key is green, obtain a value for it by loading one from disk if possible, or by invoking its query provider if necessary.