- Instead of keeping multiple flags in the type descriptor flags,
just keep a single flag indicating the presence of additional
import information after the name.
- That import information consists of a sequence of null-terminated
C strings, terminated by an empty string (i.e. by a double null
terminator), each prefixed with a character describing its purpose.
- In addition to the symbol namespace and related entity name,
include the ABI name if it differs from the user-facing name of the
type, and make the name the user-facing Swift name.
There's a remaining issue here that isn't great: we don't correctly
represent the parent relationship between error types and their codes,
and instead we just use the Clang module as the parent. But I'll
leave that for a later commit.
- `swift_getForeignTypeMetadata` is now a request/response function.
- The initialization function is now a completion function, and the
pointer to it has moved into the type descriptor.
- The cache variable is no longer part of the ABI; it's an
implementation detail of the access function.
- The two points above mean that there is no special header on foreign
type metadata and therefore that they can be marked constant when
there isn't something about them that needs to be initialized.
The only foreign-metadata initialization we actually do right now is
of the superclass field of a foreign class, and since that relationship
is a proper DAG, it's not actually possible to have recursive
initialization problems. But this is the right long-term thing to do,
and it removes one of the last two clients of once-based initialization.
As part of this, rename TypeMetadataRecordKind to TypeReferenceKind
and consistently give it three bits of storage.
The better modelling of these type references appears to have been
sufficient to make dynamic conformance checks succeed, which is good
but unexpected.
From what I see the only fields are DATA_VALUE_WITNESS which
all have type size_t. I converted them to use the target-dependent
`StoredSize`. While I was around I fixed also isValueInline()
to do the right thing (it was using ValueBuffer instead of
TargetValueBuffer) and all the getters for the data value witnesses.
<rdar://problem/41546568>
Protocols are never generic, so don't inherit from
TrailingGenericContextObjects. Instead, directly use
swift::ABI::TrailingObjects. Since protocols are never generic, this
doesn't actually affect layout at all; it's cleanup.
These were used to encode the “inherited protocols” for Objective-C
Protocol structures. These are no longer a part of either Swift protocol
descriptors or the part of Objective-C Protocol structures that the
Swift runtime inspects.
Reimplement protocol descriptors for Swift protocols as a kind of
context descriptor, dropping the Objective-C protocol compatibility
layout. The new protocol descriptors have several advantages over the
current implementation:
* They drop all of the unused fields required for layout-compatibility
with Objective-C protocols.
* They encode the full requirement signature of the protocol. This
maintains more information about the protocol itself, including
(e.g.) correctly encoding superclass requirements.
* They fit within the general scheme of context descriptors, rather than
being their own thing, which allows us to share more code with
nominal type descriptors.
* They only use relative pointers, so they’re smaller and can be placed
in read-only memory
Implements rdar://problem/38815359.
When reading the protocol metadata from existential type metadata,
check the “isObjC” bit and handle the reading of the Objective-C
protocol name (using TargetObjCProtocolPrefix) separately from the reading the name of a Swift protocol (using TargetProtocolDescriptor).
More preparation for separating the layout of these two entities.
Introduce TargetObjCProtocolPrefix, which describes just enough of the
Objective-C runtime’s Protocol structure to extract the name without
having to call Objective-C’s protocol_getName().
In a generic requirement, distinguish between Swift and
Objective-C protocols using a spare bit within the relative
(indirectable) reference to the protocol.
Switch one entry point in the runtime (swift_getExistentialTypeMetadata)
to use ProtocolDescriptorRef rather than a protocol descriptor. Update
IRGen to produce ProtocolDescriptorRef instances for its calls, setting
the discriminator bit appropriately.
Within the runtime, verify that all instances of ProtocolDescriptorRef have
the right layout, i.e., the discriminator bit is set for @objc protocols
but not Swift protocols.
Use ProtocolDescriptorRefs within the runtime representation of
existential type metadata (TargetExistentialTypeMetadata) instead of
bare protocol descriptor pointers. Start rolling out the use of
ProtocolDescriptorRef in a few places in the runtime that touch this
code. Note that we’re not yet establishing any strong invariants on
the TargetProtocolDescriptorRef instances.
While here, replace TargetExistentialTypeMetadata’s hand-rolled pointer
arithmetic with swift::ABI::TrailingObjects and centralize knowledge of
its layout better.
In our ABI, we’re using some C++ ABI tricks to simplify the
implementation of the runtime. One of them, in FullMetadata, requires
that we inherit from classes that we would also like to make use
TrailingObjects. Remove the “final” assertion from TrailingObjects
so we can do so.
We promise to be careful.
TargetProtocolDescriptorRef provides a reference to either a Swift or
an Objective-C protocol, using a spare bit to indicate which kind of
protocol it is. At present, the protocol descriptor also has this
information (so this is redundant), but that will change shortly.
There are no clients of TargetProtocolDescriptorRef yet.
Clang-importer-synthesized declarations get an extra tag character included in their mangling, which was not being preserved in type context descriptors. This caused runtime lookup for these synthesized types to fail. Fix this by adding the tag information to type context descriptors and teaching the runtime to match it up when fetching metadata by mangled name. Fixes rdar://problem/40878715.
Runtime/Metadata.h collected a large number of metadata data
structures that are actually part of the ABI. Move those data
structures into a new header, ABI/Metadata.h, and keep the in-process,
runtime-specific bits in Runtime/Metadata.h.
And update the existential container's initializeWithTake implementation
in the runtime. After only allowing bitwise takable values in the
inline buffer we can use memcpy to move existential container values.
rdar://31414907
SR-343
We want to be able to potentially introduce new metadata kinds in future Swift compilers, so a runtime ought to be able to degrade gracefully in the face of metadata kinds it doesn't know about. Remove attempts to exhaustively switch over metadata kinds and instead treat unknown metadata kinds as opaque.
There are multiple reasons to do this. Primarily this is
useful as an optimization. Whenever analysis can determine that no
potentially conflicting access occurs within the scope, the access can
be demoted to "nontracking". It is also useful as an escape hatch for
future code deploying to older runtimes. For example, if a future access
scope may cross threads, and the older runtime doesn't know how to
migrate threads.
See <rdar://problem/37507434> add a flag to swift_beginAccess to inform
the runtime that an access might migrate between threads
I de-templated MetadataState and MetadataRequest because we weren't
relying on the template and because using the template was causing
conversion problems due to the inability to directly template an enum
in C++.
Rename it to swift_initClassMetadata() just like we recently did
swift_initStructMetadata(), and add a StructLayoutFlags parameter
so we can version calls to this function in the future.
Maybe at some point this will become a separate ClassLayoutFlags
type, but at this point it doesn't matter because IRGen always
passes a value of 0.
This includes global generic and non-generic global access
functions, protocol associated type access functions,
swift_getGenericMetadata, and generic type completion functions.
The main part of this change is that the functions now need to take
a MetadataRequest and return a MetadataResponse, which is capable
of expressing that the request can fail. The state of the returned
metadata is reported as an second, independent return value; this
allows the caller to easily check the possibility of failure without
having to mask it out from the returned metadata pointer, as well
as allowing it to be easily ignored.
Also, change metadata access functions to use swiftcc to ensure that
this return value is indeed returned in two separate registers.
Also, change protocol associated conformance access functions to use
swiftcc. This isn't really related, but for some reason it snuck in.
Since it's clearly the right thing to do, and since I really didn't
want to retroactively tease that back out from all the rest of the
test changes, I've left it in.
Also, change generic metadata access functions to either pass all
the generic arguments directly or pass them all indirectly. I don't
know how we ended up with the hybrid approach. I needed to change all
the code-generation and calls here anyway in order to pass the request
parameter, and I figured I might as well change the ABI to something
sensible.
The allocation phase is guaranteed to succeed and just puts enough
of the structure together to make things work.
The completion phase does any component metadata lookups that are
necessary (for the superclass, fields, etc.) and performs layout;
it can fail and require restart.
Next up is to support this in the runtime; then we can start the
process of making metadata accessors actually allow incomplete
metadata to be fetched.
The layout changes to become relative-address based. For this to be
truly immutable (at least on Darwin), things like the RO data patterns
must be moved out of the pattern header. Additionally, compress the
pattern header so that we do not include metadata about patterns that
are not needed for the type.
Value metadata patterns just include the metadata kind and VWT.
The design here is meant to accomodate non-default instantiation
patterns should that become an interesting thing to support in the
future, e.g. for v-table specialization.
Minimize the generic class metadata template by removing the
class header and base-class members. Add back the set of
information that's really required for instantiation.
Teach swift_allocateGenericClass how to allocate classes without
superclass metadata. Reorder generic initialization to establish
a stronger phase-ordering between allocation (the part that doesn't
really care about the generic arguments) and initialization (the
part that really does care about the generic arguments and therefore
might need to be delayed to handle metadata cycles).
A similar thing needs to happen for resilient class relocation.
The key path pattern needs to include a reference to the external descriptor, along with hooks for lowering its type arguments and indices, if any. The runtime will need to instantiate and interpolate the external component when the key path object is instantiated.
While we're here, let's also reserve some more component header bytes for future expansion, since this is an ABI we're going to be living with for a while.
