Introduce the Enforce Single Exit pass, whose task is to normalize a
generic `ScopeGraph`, which may have multiple exit blocks (and/or
infinite loop regions), in order to have a single `sink_block` as exit
block.
This is done by adding a new entry block, a `sink_block`, and some
`scope_closer` edges (which are visible only on the `ScopeGraph`) that
enforce the property.
This is done taking inspiration from how the internally the
`PostDominatorTree` pass construct the temporary graph on which the post
dominance information is computed on.
Some unit tests are added in order to verify that the pass works as
expected.
Introduce the `ScopeCloser` and `GotoTarget` annotations in the IR, and
the relative necessary machinery, needed to handle scope closer and goto
edges for the new backend.
A specialization of the `llvm::GraphTraits`, called `ScopeGraph`, that
is able to handle both the above mentioned annotations is provided.
For the `llvm::GraphTraits` implementation, we introduce the
`GeneratorIterator` class, which uses a coroutine to store the status of
the iteration.
A debug logger pass is added, so that we are able to test the
functionality with `FileCheck`.
This commit ensures that parts of the model that must point to code
(specifically `Binary::EntryPoint`, `Binary::ExtraCodeAddresses` and
`Function::Entry`) actually point to a segment mapped as +x.
On the C++ side of revng it is important that LLVM's signal handlers are
registered within the initialization of `revng::InitRevng`, as this
allows downstream users (e.g. `revng daemon`) to preserve its signal
handlers before setting up the C++ infrastructure. In
`Tracing/Runner.cpp` there's `CommandHandler` which is statically
initialized and called `llvm::sys::AddSignalHandler`, this happened at
`dlopen` time, breaking the promise outlined above. Rework the code so
that the function is called lazily instead of statically.
Lauri Vasama