This will be used to help IRGen record protocol requirements
with resilient default implementations in protocol metadata.
To enable testing before all the Sema support is in place, this
patch adds SIL parser, printer and verifier support for default
witness tables.
For now, SILGen emits empty default witness tables for protocol
declarations in resilient modules, and IRGen ignores them when
emitting protocol metadata.
The main idea here is that we really, really want to be
able to recover the protocol requirement of a conformance
reference even if it's abstract due to the conforming type
being abstract (e.g. an archetype). I've made the conversion
from ProtocolConformance* explicit to discourage casual
contamination of the Ref with a null value.
As part of this change, always make conformance arrays in
Substitutions fully parallel to the requirements, as opposed
to occasionally being empty when the conformances are abstract.
As another part of this, I've tried to proactively fix
prospective bugs with partially-concrete conformances, which I
believe can happen with concretely-bound archetypes.
In addition to just giving us stronger invariants, this is
progress towards the removal of the archetype from Substitution.
If vtable or witness methods are never called, e.g. because they are completely devirtualized,
then they are removed from the tables and eliminated.
Another improvement of the new algorithm is that it is able to eliminate dead function cycles
(e.g. A() calls B() and vice versa).
Swift SVN r22969
This patch adds in the necessary infrastructure for lazily deserializing
witness tables. This is done by following the same approach as the
deserialization/serialization of SILFunction.
Now if one calls SILModule::lookUpWitnessTable and the given witness table is a
definition, the SILModule will attempt to deserialize it from one of the other
modules.
Swift SVN r15403
The importance of this is that we will be able to use this name during
SIL serialization/deserialization to lookup partially deserialized
witness tables.
I left IRGen's original code alone until I can discuss with Joe/John
combining the logic together.
Swift SVN r15400
This will help with ensuring that we do not create multiple witness
table "definitions" one of which is null. That situtation yields an
IRGen assertion to be hit since the external declaration (in the guise
of a definition) has a different type from the actual deserialized
definition.
Swift SVN r14999
In the short term, we need to be able to emit shared symbols for SILWitnessTables corresponding to Clang-imported modules, and soon, the generic specializer will need to be able to reference *_external witness tables deserialized from library modules.
Swift SVN r14887
This will enable the creation of external witness tables whose entries
can be initialized after the witness table itself has been constructed.
This can occur if the table is deserialized later from a different
module.
Swift SVN r14715
Tweak the type lowering code to work when the conforming type is generic. Handle the case of an associated type with protocol requirements being witnessed by an archetype of the conforming type, which results in a null ProtocolConformance pointer in the witnessing substitution.
Swift SVN r11275
When a type conforms to a protocol that refines another protocol, emit the witness table for the base protocol, and drop a reference into the witness table for the derived protocol. Keep track of what conformances we've already emitted so we don't emit redundant witness tables when types conform redundantly to base protocols or have multiple references to a base protocol via a refinement diamond.
Swift SVN r11263
Walk the ProtocolConformances of type and extension decls to produce SILWitnessTables for them. Work out the type of the witness function by applying substitutions from the witness map and lowering it at the abstraction level of the requirement, then emit a symbol for the witness function (but don't emit the body of the witness function just yet).
Swift SVN r11143
We will generate these in SILGen when we see a NormalProtocolConformance, to provide a mapping of method requirements to witnesses for types.
Swift SVN r10900
