let pd_b_but_not_a infos stmt_a stmt_b =
if stmt_a.sid = stmt_b.sid then Stmt.Hptset.empty
else begin
let a_to_ret, postdom_a = PdgPostdom.get infos ~with_s:false stmt_a in
let b_to_ret, postdom_b = PdgPostdom.get infos ~with_s:true stmt_b in
let res = match a_to_ret, b_to_ret with
| true, true | false, false -> Stmt.Hptset.diff postdom_b postdom_a
| true, false -> postdom_b
| false, true ->
Stmt.Hptset.empty
in
Pdg_parameters.debug ~dkey ~level:2
"pd_b_but_not_a for a=sid:%d b=sid:%d = %a"
stmt_a.sid stmt_b.sid Stmt.Hptset.pretty res;
res
end