The DLAStep SimplifyInstanceAtOffset0 now only triggers if the parent
node has the child-at-offset-0 node as its only successor, or when the
child-at-offset-0 doesn't have other predecessors.
Doing this guarantees that it's impossible for another predecessor of
the child-at-offset-0 to start seeing memory accesses that were
initially relative to the parent.
This condition is slightly more restrictive than the previous one, but
it takes into consideration some far reaching consequences.
If SimplifyInstanceAtOffset0 aggressively like we did before, DLA can
end up inferring types in some memory locations, like executable
segments, for which there aren't clues in the binary.
This isn't bad per se, but if DLA does that, the newly recovered type is
identified as non-executable data, causing misdecompilation because
rev.ng doesn't decompile memory regions that it understands as non
executable.
This commit, making SimplifyInstanceAtOffset0 less aggressive, makes it
play better with the rest of the assumptions of the decompilation
pipeline.
It also relaxes a decompilation test that was previously working by
chance and that was effectively beyond the current expressive power of
reasoning for DLA at the moment.
This commit adds caching for mutual reachability among children of a
node, in SimplifyInstanceAtOffset0.
This makes the DLAStep 10% to 50% faster on real-world benchmarks we
have measured, such as `updatedb.plocate` and `df` for Ubuntu 22.04
x86_64.
Change company name to "rev.ng Labs Srl" in all license headers
to reflect changed company name and legal status
Add missing license headers to files that didn't have one
This step removes redundant instance-at-offset-0, collapsing the child
into the parent, whenever this operation does not induce instance-loops
on the graph.
This is intended to reduce the number of shallow wrapper structs and
unions.
Alessandro Di Federico