Ensure that no backedges are left after the restructuring of all the
metaregions.
This additional assertion should help ensuring that no entries in the
`Backedges` set are left after the restructuring process, in turn making
it easier to spot bugs if backedges references are not handled correctly
during the steps of the restructuring.
Assign a value to cloned and collapsed nodes in terms of shortest path
from entry, which is a criterion we use to elect region entry.
The shortest path is computed at the beginning for the nodes present in
the CFG, but needs to keep updated for additional nodes that we insert
that may become loop entry candidates.
During the creation of the exit dispatcher, take care of removing from
the `Backedges` set the additional backedge that is collapsed in case
two exiting backedges do target the same destination.
When this is not done, a ghost backedge is left inside the set, making
it not coherent with the state of the graph.
In addition, we add an assertion which ensures that during this phase of
the restructuring dummy nodes are present only as source of retreating
edges, and have one and only one successor.
Now that the late stage of the decompilation pipeline is managed with
revng-pipeline, and we have a standalone tool for decompilation, we
have no need to use LLVM passes anymore for those stages.
This commit also renames the directories to avoid the confusing Pass
suffix, not what LLVM passes are gone.
Giacomo Vercesi