let backward kf stmt =
try
let nodes = initial_nodes kf stmt in
let res = direct kf stmt in
Security_slicing_parameters.debug
"computing backward indirect component for %d" stmt.sid;
related_nodes_of_nodes Indirect_Backward res nodes
with Pdg.Top | Pdg.Bottom ->
Security_slicing_parameters.warning "PDG is not manageable. skipping.";
M.empty