Start using null-page values as extra inhabitants when laying out single-payload enums that contain class pointers as their payload type. Don't use inhabitants that set the lowest bit, to avoid trampling potential ObjC tagged pointer representations. This means that 'T?' for class type T now has a null pointer representation. Enums with multiple empty cases, as well as nested enums like 'T??', should now have optimal representations for class type T as well.
Note that we don't yet expose extra inhabitants for aggregates that contain heap object references, such as structs with class fields, Swift function types, or class-bounded existentials (even when the existential has no witness tables).
Swift SVN r10061
When we need a reference to protocol or protocol composition type metadata, ask for it through the runtime, instead of referencing statically-emitted protocol metadata.
Swift SVN r9871
Same deal as for opaque existentials--pre-instantiate a static witness table for one-witness-table types (the zero-witness-tables case is nicely handled by Builtin.ObjCPointer's value witness), and generate a vwtable using dynamic witness implementations for each different-sized container on demand as necessary.
Swift SVN r9850
The assign-with-copy operation on existentials is complex enough to be emitted as a function call, which is currently generated on-demand by IRGen for every existential layout. We can instead use the implementation out of the runtime. Provide entry points for zero, one, and any number of witness tables.
Swift SVN r9815
Metadata.cpp:1280:26: warning: zero size arrays are an extension [-Wzero-length-array]
const void *_witnesses[NUM_VALUE_WITNESSES];
^~~~~~~~~~~~~~~~~~~
Metadata.cpp:1366:12: note: in instantiation of member class
'<anonymous>::OpaqueExistentialValueWitnesses<0>::Container' requested here
/*size*/ Container::size(),
^
Metadata.cpp:1448:51: note: in instantiation of static data member '<anonymous
namespace>::OpaqueExistentialValueWitnesses<0>::ValueWitnessTable' requested here
return &OpaqueExistentialValueWitnesses<0>::ValueWitnessTable;
^
1 warning generated.
As an aside, putting a template argument in ALL_CAPS is kinda wierd.
Swift SVN r9787
Instantiate static value witness implementations for the common zero- and one-witness-table cases, which correspond to the "Any" type protocol<> and to single-protocol types. For protocol compositions, instantiate a value witness table that uses the layout information from existential metadata to perform the value witness operations.
Swift SVN r9752
Set up a metadata cache for existential type metadata. Instantiate existential metadata by first sorting the protocol list, so that it is order invariant, precomputing the overall witness table count and class constraint of the composition so it can be cached in the existential metadata.
We still need to implement value witnesses for existential containers in the runtime before this is complete. We can at least test the uniquing and flags computations at this point.
Swift SVN r9727
It'd be nice to eventually report some context information, maybe derived from the location info on the originating 'cond_fail' SIL instruction, but this is a start.
Swift SVN r9589
Does what it says on the tin: lays out the fields, storing their offsets into the metadata, and initializes the size, flags, and stride of the value witness table.
Swift SVN r9120
We'll want to use the same logic to lay out generic struct fields at runtime. While we're here, fix a bug where we weren't aligning field offsets prior to storing them in the tuple metadata.
Swift SVN r9117
If a single-payload union doesn't use up all of its payload's extra inhabitants, it can claim the remaining ones as its own. While we're here, specialize the extra inhabitants implementation for no-payload unions to generously (and more efficiently) give out all integer values within its storage type above the largest discriminator as extra inhabitants, instead of relying entirely on the spare bits mask.
Swift SVN r8470
Add functions to dynamically query the extra inhabitants of a single-payload union's payload metadata, then identify or store bit patterns used to represent empty cases, whether they happen to use extra inhabitants or added tag bits.
Swift SVN r8320
