use a thin function type.
We still need thin-function-to-RawPointer conversions
for generic code, but that's fixable with some sort of
partial_apply_thin_recoverable instruction.
Swift SVN r24364
Teach IRGen and the runtime about the extra inhabitants
of function pointers, and take advantage of that in
thin and thick function types.
Also add runtime entrypoints for thin function type
metadata.
Swift SVN r24346
Per Joe, a low level retained-pointer-with-user-controlled-spare-bits
type would still be useful for space efficiency even on platforms that
don't need ObjC interop.
Swift SVN r22943
This is a type that has ownership of a reference while allowing access to the
spare bits inside the pointer, but which can also safely hold an ObjC tagged pointer
reference (with no spare bits of course). It additionally blesses one
Foundation-coordinated bit with the meaning of "has swift refcounting" in order
to get a faster short-circuit to native refcounting. It supports the following
builtin operations:
- Builtin.castToBridgeObject<T>(ref: T, bits: Builtin.Word) ->
Builtin.BridgeObject
Creates a BridgeObject that contains the bitwise-OR of the bit patterns of
"ref" and "bits". It is the user's responsibility to ensure "bits" doesn't
interfere with the reference identity of the resulting value. In other words,
it is undefined behavior unless:
castReferenceFromBridgeObject(castToBridgeObject(ref, bits)) === ref
This means "bits" must be zero if "ref" is a tagged pointer. If "ref" is a real
object pointer, "bits" must not have any non-spare bits set (unless they're
already set in the pointer value). The native discriminator bit may only be set
if the object is Swift-refcounted.
- Builtin.castReferenceFromBridgeObject<T>(bo: Builtin.BridgeObject) -> T
Extracts the reference from a BridgeObject.
- Builtin.castBitPatternFromBridgeObject(bo: Builtin.BridgeObject) -> Builtin.Word
Presents the bit pattern of a BridgeObject as a Word.
BridgeObject's bits are set up as follows on the various platforms:
i386, armv7:
No ObjC tagged pointers
Swift native refcounting flag bit: 0x0000_0001
Other available spare bits: 0x0000_0002
x86_64:
Reserved for ObjC tagged pointers: 0x8000_0000_0000_0001
Swift native refcounting flag bit: 0x0000_0000_0000_0002
Other available spare bits: 0x7F00_0000_0000_0004
arm64:
Reserved for ObjC tagged pointers: 0x8000_0000_0000_0000
Swift native refcounting flag bit: 0x4000_0000_0000_0000
Other available spare bits: 0x3F00_0000_0000_0007
TODO: BridgeObject doesn't present any extra inhabitants. It ought to at least provide null as an extra inhabitant for Optional.
Swift SVN r22880
refcounting and take advantage of it.
Also, set the Swift1 flag in classes we generate.
Also, initialize a global cache of the non-pointer-isa
mask and use that instead of object_getClass, at least
within the runtime.
Also, centralize the runtime on a _swift_getSuperclass
function and make that use a direct access while we
await word from Greg on the desired ABI requirements.
Swift SVN r21077
initializeBufferWithTakeOfBuffer value witness.
Attempt to use initializeBufferWithTakeOfBuffer in
some appropriate places.
There are some changes enabled by this which are
coming in a follow-up patch.
Swift SVN r20741
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
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
We haven't fully updated references to union cases, and enums still are not
their own thing yet, but "oneof" is gone. Long live "union"!
Swift SVN r6783
