-- | Compute the predecessors of each /reachable/ block
zipPreds :: LastNode l => LGraph m l -> BlockEnv BlockSet
-- | Compute the predecessors of each /reachable/ block
zipPreds :: LastNode l => LGraph m l -> BlockEnv BlockSet
add_pred pair@(single, multi) id =
if elemBlockSet id multi then pair
else if elemBlockSet id single then
add_pred pair@(single, multi) id =
if elemBlockSet id multi then pair
else if elemBlockSet id single then