* Adjust stack pointer upon returning from call.
In architecture where the return address is pushed on the stack, on
the caller side, we see the the push but not the pop. This means that,
once the stack pointer is no longer global, we need to take this into
account.
This commit fixes this increase the stack pointer of
`FinalStackOffset` right after a function call.
* Drop the size argument from the `revng_init_local_sp` function. We
will have a `revng_stack_frame` function to represent the actual stack
frame pointing to its beginning.
This assertion was conceived to check that DLADeduplicateUnionFields was
doing its job, ensuring that we never created a union with only one
field.
However, the assertion is too strict, and there are situation that union
deduplication cannot handle and that still generate a union with one
single field. Here's an example
Node A, with Interfering Children
Instance Edge -> Node B
Offset 12 Edge -> Node C
Node C
Offset 12 Edge -> Node D
Node C: uint32_t
Node D: uint32_t
Hence we need to remove the assertion.
Integrate results of ABIAnalyses in EarlyFunctionAnalysis
and refine such results by suppressing stack pointer
and callee-saved registers from the analyses.
Architecture-agnostic and ABI-independent data-flow analyses that
traverse the recovered functions in order to detect arguments and
return values registers.
An architecture-agnostic analysis that attempts to detect
boundaries of functions, recover the control-flow graph as
well as function prototypes (arguments and return values)
of the original program. The analysis determines whether
the function jumps to its return address (namely, it is a
regular function), it tracks the evolution of the stack
by determining its height (in order to say if the stack is
left in a correct position upon stackframe destruction),
and it identifies callee-saved registers.
A pass which segregates direct stack accesses from all other
memory accesses through appropriate alias information metadata.
By doing so, we provide a way to say that stack accesses reasonably
do not interfere with any other memory access. This pass also tries
to canonicalize `inttoptr` + `add` instructions into `getelementptr`s
so as to avoid the use of `inttoptr`, which would otherwise inhibit
compiler optimizations.
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.
Alessandro Di Federico