Reopt can be helped by providing a C header file (for now, just one). This is because we can immediately tell what registers a function will need when called and use when returning just looking at the C signature of a function symbol.
Without it, we must rely on successfully exploring all symbolic paths through the function execution to witness what registers are used, which may fail for a variety of reasons (see Discovery).
The header resolution step builds an AnnDeclarations data type, which contains
two maps:
-
typeDefs, a map resolving Ctypedefs to their C type (anAnnType), -
funDecls, a map resolving function names to their C function type (anAnnFunType).
The former is simply used to resolve the type of typedef-ed type aliases at
their use sites.
The latter is used during discovery to tell what registers a function will use.