We previously moved container identification later in CodeGen in order
to preserve information for AlignmentCalc.
However, Flattener needs to know if a class is a container in order to
apply its special handling for this case.
This new approach moves container identification in front of Flattener,
but has Container own a type node, representing its layout. This
underlying type node can be used for calculating a container's
alignment in a later pass.
Leave it to the new mutator pass IdentifyContainers to replace Class
nodes with Container nodes where appropriate.
This will allow us to run passes over the type graph before identifying
containers, and therefore before we have lost information about the
internal details of the container (e.g. alignment of member variables).
Lots of places rely on reference stability of ContainerInfo objects
(CodeGen's deduplication, Container nodes' containerInfo_ member).
In the key capture work, we need to be able to append to this list,
which would invalidate references before this change.
We only want to do the extra work if it's explicitly requested.
chaseRawPointers is already explicitly requested whenever it's needed
and readEnumValues currently isn't needed at all.
These aren't used for anything yet, but should be useful for stable IDs
when printing nodes before and after passes and for faster cycle
detection than the current map of pointers.
The worry about doing this earlier was performance, but on a further
reading of the code, both legacy OICodeGen and new DrgnParser have been
calling into drgn_type_fully_qualified_name() for every class for a long
time already.
