We no longer need this for anything, so remove it from metadata
altogether. This simplifies logic for emitting type metadata and
makes type metadata smaller.
We still pass the parent metadata pointer to type constructors;
removing that is a separate change.
"minimal" is defined as the set of requirements that would be
passed to a function with the type's generic signature that
takes the thick metadata of the parent type as its only argument.
Build a nominal type descriptor when we emit the metadata or generic metadata pattern for a nominal type, and put a reference into the formerly null slot in the struct or enum metadata. We need to make a place for them in class metadata; that'll come next.
Swift SVN r9492
If a generic type has dynamic layout, the value witness table for its instances is dependent on its generic parameters for size and alignment. Instead of emitting a global symbol for the vwtable in these circumstances, embed the value witness table template in the generic metadata template so that both get instantiated in tandem by the runtime when the generic instance metadata is requested.
Swift SVN r7931
Standardize on the more-common "superclass" and "subclass" terminology
throughout the compiler, rather than the odd mix of base/derived and
super/sub.
Also, have ClassDecl only store the Type of the superclass. Location
information will be part of the inheritance clause for parsed classes.
Swift SVN r6687
The principal difficulty here is that we need accessing the
value witness table for a type to be an efficient operation,
but there (obviously) isn't a VWT field for ObjC classes.
Placing this field after the metatype would tend to bloat
metatypes by quite a bit. Placing it before is best, but
it introduces an unfortunate difference between the address
point of a metatype and the address of the global symbol.
That, however, can be fixed with appropriate linker support.
Still, for now this is rather unfortunately over-subtle.
Swift SVN r3307
towards optimizing generic calls to derive things from the
'this' pointer, which is actually crucial for virtual
dispatch (to get all methods to agree about how the
implicit arguments are passed). Fix a number of assorted
bugs in metadata emission. Lots of assorted enhancements.
This was proving surprisingly difficult to actually tease
apart into smaller patches.
Swift SVN r2927
