If someone subtracts something from the stack pointer the result cannot
be a pointer, so we have to ignore the result when trying to adjust the
stack pointer.
These functions can be used in conjunction to dump the Model on a
file during a gdb session, for example:
```
(gdb) p writeToFile(Model->toString(), "/tmp/model.yaml")
```
Without this attribute, newer versions of llvm are not able to
remove calls to `ReadOnly` functions whose return value is unused.
This is instead the expected behavior for the functions that are
generated by `revng` with the `ReadOnly` attribute.
Since in the model a FunctionPrototype can be shared among different
functions or indirect calls, we should take into account this fact when
initializing the DLA.
In particular, if the aforementioned case happens, we want to add
equality edges between the return value(s) and the arguments of all the
functions that have the same prototype. These will then be merged by
later steps in the middle-end, and the resulting information will be
shared among all the merged nodes.
Add `MakeModelTypes` and `UpdateFuncPrototypes` to the DLA backend:
* `MakeModelTypes` adds to the model all the types recovered by the DLA
* `UpdateFuncPrototypes` updates function prototypes in the model that
have generic return values or arguments to use the types recovered by
the DLA
* Changes to the `LayoutTypeSystem` graph
Pointers are identified in the TypeSystem graph as leaf nodes which
have a new type of edge (PointerEdge) that connects them to another
node of the graph. The destination of the edge represents the layout of
the pointed type.
* Changes to the Front-end
Pointer edges, and their destination nodes, are created by the DLA
front-end (`DLACreateIntraProceduralTypes`) whenever an access node has
a size that is compatible with the size of a pointer in the current
Architecture.
Successors might then be added to the newly generated node, if any,
by looking up the llvm::Value it is attached to.
* Changes to the Middle-end
Most of the DLA passes should ignore Pointer Edges, so they are modified
accordingly. Most notably, nodes that represent pointed layouts should
never be merged/pruned-off.
* Changes to the Back-end
The `TypeDeclCreationAction` of the decompiler and the `DLAMakeLayouts`
step of the DLA back-end are modified to take into account the new
information about pointers.
⚠️ There is a known issue with this version of the decompiler,
namely the fact that type loops are not detected and can cause the
emitter to enter an infinite loop.
When deduplicating unions, for each union we compare each successor
with all other successors. However, the same successor node might be
reachable by more than one edge from the parent.
This can cause problems when a node gets merged while the comparison is
still ongoing. In particular, since the comparison is done using a copy
of the successor list, to avoid iterator invalidation, the links in
the worklist are not updated when a node gets merged, causing links to
the merged node to have an invalid destination.
The fix here is to keep a list of **nodes** to visit, and a list of
**edges** that have already been visited, so that, if a node is merged
through one of its links, we are not visiting other links connected to
the same node after the merge.
We introduce a new tile, for matching if node with a single and inlined
then/else. In these case, the not inlined successor should be connected
with the tile node.
Handle switch nodes with all but one case edges inlined, by electing the
not inlined edge as the path conducting to the postdominator, and
avoiding parts of the graph disconnecting during the tiling procedure.
ConcreteTupleTreeKeyWrapper::clone() should cleanup the Target object
befor cloning, otherwise the destructor of the inner Pointer object
is never called.
Before this commit, SerializeModelPass and SerializeModelWrapperPass had
hard dependencies on the passes that load the model from LLVM-IR.
This commit makes this dependency optional. When the passes for model
serialization are executed, if they see that nobody requested to load
the model, they will not try to serialize it.
This prevents them from crashing when running in pipelines that only
contain passes that ignore the model.
This is particularly beneficial because `revng opt` automatically adds
`-serialize-model` at the end of each pipeline and, before this commit,
this meant that `revng opt` could not be used for unit-testing simple
llvm passes that do not use the model.
With this commit, `revng opt` can be used for unit-tests, even on LLVM IR
with missing model.
* Drop outdated portion describing ABI/CFG metadata that are now stored
in the model.
* Introduce MetaAddress concept.
* Describe the four-parts program counter CSVs.
* Update description of the dispatcher.
* Update description of `function_call` and `newpc`.
* Introduce some documentation for the model.
* Improve the way enums are serialized/deserialized.
* Mark certain fields of model data structures as optional.
* introduces some error messages during model validation.
Pietro Fezzardi