Before this commit we were using int64_t for Offset, Strides, and
TripCounts.
Originally, this choice was intended because for some time we envisioned
actually having a use for negative values, but in the end we decided
there's no use for those.
This commit switches all to unsigned integers, allowing to remove some
static_cast across the codebase, and overall easing typicall computation
we have to perform on those fields.
When creating the DLA graph, we want to avoid inserting `instanceOf`
edges with huge offsets, so we set a limit to 64K.
This is a workaround to handle cases in which we make wrong decisions
about the base address of a SCEV expression. One of the situations in
which this occurs are expressions such as `&val + BIG_CONST`, for which
we always identify `%val` as the address and `BIG_CONST` as the offset.
When fixing this case, we should still verify that this never happens.
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 DLAStep was moving edges improperly before this commit.
In particular, edges were detected solely looking at source and target
edge, not looking at the edge itself. This was leading to wrong results
whenever a node N1 had many outgoing edges to a child node N2, at
different offsets, where all the edges were moved instead of just the
correct ones.
In order to fix this, this commit:
- reworks the logic of `moveEdges`, switching to iterator-based logic
- reworks the struct OrderedChild used internally by
DLAComputeNonInterferingComponents, so that it is also iterator-based
- re-uses common code for field size computation
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.
Add a step that recognizes if two subtrees of a union node are
topologically equivalent and merges them. This corresponds to removing
duplicate fields in unions.
This deduplication was prevously done while emitting layouts.
A check is inserted into DLAMakeLayouts to assert that, after
constructing unions, no union has only one child, which could be the
case if we didn't deduplicate union fields in the graph.
* Inheritance straight lines are now collapsed by CollapseSingleChild
* Don't collapse if parent has more than one parent or if the child has
more than one parent
* Allow the possibility to construct single-member struct: if this
struct is inherited by many other structs, "flattening" the struct is not
the most sensible thing to do, since inheritance information is something
we want to preserve in these cases.
While doing thie, also drop `printAccessNode()` from DLA DebugPrinter.
The information about which LLVM instruction originated a given access
node is already available in the csv generated by the `dla-accesses-log`
logger.
Pietro Fezzardi