Protocol conformance descriptors are recorded in witness tables and are
needed to evaluate associated type witnesses. Start creating them for
property behavior conformances, but don’t put them in the section used
for reflection.
This was only used by the integrated REPL, and is now a dead option.
The "StartElem" option for performTypeChecking is still used for
reading SIL files, which have AST and SIL blocks alternate.
For a resilient protocol that has defaulted associated types, emit
default associated conformance witnesses that compute associated
conformances based on that default witness.
This completes the implementation of resilience protocols that
add new, defaulted associated types, rdar://problem/44167982.
For a resilient conformance, emit the associated conformance accessor
functions into the resilient witness table (keyed on the associated
conformance descriptor) rather than in the fixed part of the witness
table. This is another part of resilience for associated conformances,
and a step toward defaults for associated conformances.
When referencing an associated conformance in a witness table for a
resilient protocol, use the associated conformance descriptor to compute
the index into the witness table at run-time.
Another part of rdar://problem/44167982.
Associated conformance descriptors are aliases that refer to associated
conformance requirements within a protocol descriptor’s list of
requirements. They will be used to provide protocol resilience against
the addition of new associated conformance requirements (which only makes
sense for newly-introduced, defaulted associated types).
When an associated type witness has a default, record that as part of
the protocol and emit a default associated type metadata accessor into the
default witness table. This allows a defaulted associated type to be
added to a protocol resiliently.
This is another part of rdar://problem/44167982, but it’s still very
limiting because the new associated type cannot have any conformances.
Generic parameter references, which occur in generic requirement
metadata, were hardcoding associated type indices. Instead, use
relative references to associated type descriptors and perform the
index calculation at runtime.
Associated types can now be reordered resiliently (without relying on
sorting), which is the first main step toward rdar://problem/44167982.
When accessing the associated type witness metadata for a resilient
protocol, compute the index based on the difference between the
associated type’s descriptor and the protocol requirement base descriptor
to determine the offset into the witness table.
Introduce an alias that refers one element prior to the start of a
protocol descriptor’s protocol requirements. This can be subtracted from
an associated type descriptor address to determine the offset of the
associated type accessor within a corresponding witness table. The code
generation for the latter is not yet implemented.
This silences the instances of the warning from Visual Studio about not all
codepaths returning a value. This makes the output more readable and less
likely to lose useful warnings. NFC.
When we define type metadata, the 'full' symbol points at the
entire struct, whereas the 'address point' symbol points at an
offset inside.
The logic for setting this up is a bit tricky because the
'address point' symbol may have been forward declared, and
has to be replaced.
Previously we would emit class metadata for classes with resilient
ancestry, and relocate it at runtime once the correct size was known.
However most of the fields were blank, so it makes more sense to
construct the metadata from scratch, and store the few bits that we
do need in a true-const pattern where we can use relative pointers.
They were, already, but remove the isConstant parameter to
getAddrOfTypeMetadataPattern(), and just assert that its true for
patterns in defineTypeMetadata() instead.
Also, metadata patterns are i8*, not i8**. In fact they don't contain any
absolute pointers at all.
Should be NFC other than the LLVM type change.
Similar to the non-resilient case, except we also emit a 'relocation
function'. The class descriptor now contains this relocation function
if the class has resilient ancestry, and the relocation function
calls the runtime's swift_relocateClassMetadata() entry point.
The metadata completion function calls swift_initClassMetadata() and
does layout, just like the non-resilient case.
Fixes <rdar://problem/40810002>.
In-place initialization means the class has a symbol we can reference
from the category, so there's nothing to do on the IRGen side.
For JIT mode, we just need to realize the class metadata by calling an
accessor instead of directly referencing the symbol though.
- getAsDeclOrDeclExtensionContext -> getAsDecl
This is basically the same as a dyn_cast, so it should use a 'getAs'
name like TypeBase does.
- getAsNominalTypeOrNominalTypeExtensionContext -> getSelfNominalTypeDecl
- getAsClassOrClassExtensionContext -> getSelfClassDecl
- getAsEnumOrEnumExtensionContext -> getSelfEnumDecl
- getAsStructOrStructExtensionContext -> getSelfStructDecl
- getAsProtocolOrProtocolExtensionContext -> getSelfProtocolDecl
- getAsTypeOrTypeExtensionContext -> getSelfTypeDecl (private)
These do /not/ return some form of 'this'; instead, they get the
extended types when 'this' is an extension. They started off life with
'is' names, which makes sense, but changed to this at some point. The
names I went with match up with getSelfInterfaceType and
getSelfTypeInContext, even though strictly speaking they're closer to
what getDeclaredInterfaceType does. But it didn't seem right to claim
that an extension "declares" the ClassDecl here.
- getAsProtocolExtensionContext -> getExtendedProtocolDecl
Like the above, this didn't return the ExtensionDecl; it returned its
extended type.
This entire commit is a mechanical change: find-and-replace, followed
by manual reformatted but no code changes.
This saves us some expensive cross-referencing and caching in the runtime, and lets us reclaim the `isReflectable` bit from the context descriptor flags (since a null field descriptor is a suitable and more accurate indicator of whether a type is reflectable).
Certain uses of protocols only formally need the requirement
signature, not any of the method requirements. This results in IRGen
seeing a protocol where none of the members have been validated except
the associated types. Account for this by allowing ProtocolInfo to
only contain the layout for the base protocols and associated types,
if requested.
Note that this relies on the layout of a witness table always putting
the "requirement signature part" at the front, or at least at offsets
that aren't affected by function requirements.
rdar://problem/43260117
We also use this for field offset globals, which are not always
constant. I think in practice everything was getting set
correctly, but it was hard to follow the logic.
Introduce ExtensionDecl::getExtendedNominal() to provide the nominal
type declaration that the extension declaration extends. Move most
of the existing callers of the callers to getExtendedType() over to
getExtendedNominal(), because they don’t need the full type information.
ExtensionDecl::getExtendedNominal() is itself not very interesting yet,
because it depends on getExtendedType().
Rather than using getAllConformances() to emit all conformances for a
nominal type whenever we emit its type metadata, use
getLocalConformances() consistently--on the nominal type and on any
extension--to emit the conformances in the appropriate source files.
- `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.
- Move the filter checks in SILGen for skipping emitting certain property descriptors into the AbstractStorageDecl::exportsPropertyDescriptor() predicate, to ensure that TBDGen and SILGen are in sync
- Fix the linkage of property descriptors to be based on the getter's linkage rather than the property's, since a property may be internal but have usableFromInline accessors
The central thrust of this patch is to get these metadata initializations
off of `swift_once` and onto the metadata-request system where we can
properly detect and resolve dependencies. We do this by first introducing
runtime support for resolving metadata requests for "in-place"
initializations (committed previously) and then teaching IRGen to actually
generate code to use them (this patch).
A non-trivial amount of this patch is just renaming and refactoring some of
existing infrastructure that was being used for in-place initializations to
try to avoid unnecessary confusion.
The remaining cases that are still using `swift_once` resolution of
metadata initialization are:
- non-generic classes that can't statically fill their superclass or
have resilient internal layout
- foreign type metadata
Classes require more work because I'd like to switch at least the
resilient-superclass case over to using a pattern much more like what
we do with generic class instantiation. That is, I'd like in-place
initialization to be reserved for classes that actually don't need
relocation.
Foreign metadata should also be updated to the request/dependency scheme
before we declare ABI stability. I'm not sure why foreign metadata
would ever require a type to be resolved, but let's assume it's possible.
Fixes part of SR-7876.
