This is essentially a long-belated follow-up to Arnold's #12606.
The key observation here is that the enum-tag-single-payload witnesses
are strictly more powerful than the XI witnesses: you can simulate
the XI witnesses by using an extra case count that's <= the XI count.
Of course the result is less efficient than the XI witnesses, but
that's less important than overall code size, and we can work on
fast-paths for that.
The extra inhabitant count is stored in a 32-bit field (always present)
following the ValueWitnessFlags, which now occupy a fixed 32 bits.
This inflates non-XI VWTs on 32-bit targets by a word, but the net effect
on XI VWTs is to shrink them by two words, which is likely to be the
more important change. Also, being able to access the XI count directly
should be a nice win.
These functions don't accept local variable heap memory, although the names make it sound like they work on anything. When you try, they mistakenly identify such things as ObjC objects, call through to the equivalent objc_* function, and crash confusingly. This adds Object to the name of each one to make it more clear what they accept.
rdar://problem/37285743
- Create the value witness table as a separate global object instead
of concatenating it to the metadata pattern.
- Always pass the metadata to the runtime and let the runtime handle
instantiating or modifying the value witness table.
- Pass the right layout algorithm version to the runtime; currently
this is always "Swift 5".
- Create a runtime function to instantiate single-case enums.
Among other things, this makes the copying of the VWT, and any
modifications of it, explicit and in the runtime, which is more
future-proof.
* IRGen: EmptyBoxType's representation cannot be nil because of a conflict with extra inhabitant assumption in indirect enums
We map nil to the .None case of Optional. Instead use a singleton object.
SR-5148
rdar://32618580
All generic bridgeable types can bridge for all their instantiations now. Removing this ferrets out some now-unnecessary traps that check for unbridgeable parameter types.
It's to be used by code produced by the ReleaseDevirtualizer.
As the function is only used for non-escaping objects, the deallocating bit is set non-atomically.
Instead of directly emitting calls to swift_getGenericMetadata*() and
referencing metadata templates, call a metadata accessor function
corresponding to the UnboundGenericType of the NominalTypeDecl.
The body of this accessor forwards arguments to a runtime metadata
instantiation function, together with the template.
Also, move some code around, so that metadata accesses which are
only done as part of the body of a metadata accessor function are
handled separately in emitTypeMetadataAccessFunction().
Apart from protocol conformances, this means metadata templates are
no longer referenced from outside the module where they were defined.
The runtime entry doesn't just report the error, unlike the other report* functions, it also does the crashing.
Reapplying independent of unrelated reverted patches.
Getting a superclass, instance extents, and whether a class is native-refcounted are all useful type API. De-underscore these functions and give them a consistent `swift[_objc]_class*` naming scheme.
Many of the report* entry points are specific to the stdlib assert implementation, so belong in the stdlib. Keep a single `reportError` entry point in the runtime to handle the CrashReporter/ASL interface, and call down to it from the assert implementation functions.
