* 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.
This commits enable the emission of rich types associated with function
signatures. This types are forward-declared in the decompiled C code
before the definition of each decompiled function that uses them.
The types we emit for now are the types that the DLA is able to compute
(if any) for the return values and the arguments of the function.
Such types are not yet used in the body of the function, nor in the
function declaration. These are the next steps to come.
Before this commit, the logic to generate all the emitted C forward
declarations (types, global variables, and functions) that has to be
printed before each decompiled function was scattered across three
classes: FuncDeclCreationAction, TypeDeclCreationAction, and
GlobalDeclCreationAction.
These are all gone now, because the scattered logic was very confusing
to follow. Now we only have a single class that takes care of
declarations with global scope: DeclCreator.
Thanks to this, I was able to drop a bunch of useless layers of software
engineering used to shape the creation of the declaration as if it was
some kind of clang ASTConsumer, which is pointless.
This class handles the creation of type declarations in clang's AST, and
holds the relationships between llvm Types and Values with those clang's
type declarations.
Before this commit, we assigned names to struct types without looking at
the function names of which they were return types.
Now we do, so that the name of the generated type for the function `f`
is `f_ret_type`.
This also fixes errors when reparsing the generated C code, where the
names of the struct types did not match.
Replicate the changes made by this commit
f2a0df309f78e1b5d7c5f81ada5110523644559e perfomed by Pietro on the
branch containing the development fixes for `revng-c`.
Alvise de Faveri