bool SILLinkerVisitor::visitProtocolConformance(
ProtocolConformanceRef ref, const Optional<SILDeclRef> &Member) {
// If an abstract protocol conformance was passed in, just return false.
if (ref.isAbstract())
return false;
// Otherwise try and lookup a witness table for C.
auto C = ref.getConcrete();
SILWitnessTable *WT = Mod.lookUpWitnessTable(C);
// If we don't find any witness table for the conformance, bail and return
// false.
if (!WT) {
Mod.createWitnessTableDeclaration(
C, getLinkageForProtocolConformance(
C->getRootNormalConformance(), NotForDefinition));
return false;
}
// If the looked up witness table is a declaration, there is nothing we can
// do here. Just bail and return false.
if (WT->isDeclaration())
return false;
bool performFuncDeserialization = false;
// For each entry in the witness table...
for (auto &E : WT->getEntries()) {
// If the entry is a witness method...
if (E.getKind() == SILWitnessTable::WitnessKind::Method) {
// And we are only interested in deserializing a specific requirement
// and don't have that requirement, don't deserialize this method.
if (Member.hasValue() && E.getMethodWitness().Requirement != *Member)
continue;
// The witness could be removed by dead function elimination.
if (!E.getMethodWitness().Witness)
continue;
// Otherwise if it is the requirement we are looking for or we just want
// to deserialize everything, add the function to the list of functions
// to deserialize.
performFuncDeserialization = true;
addFunctionToWorklist(E.getMethodWitness().Witness);
}
}
return performFuncDeserialization;
}
void SILLinkerVisitor::visitProtocolConformance(
ProtocolConformanceRef ref, const Optional<SILDeclRef> &Member) {
// If an abstract protocol conformance was passed in, just return false.
if (ref.isAbstract())
return;
bool mustDeserialize = mustDeserializeProtocolConformance(Mod, ref);
// Otherwise try and lookup a witness table for C.
auto C = ref.getConcrete();
if (!VisitedConformances.insert(C).second)
return;
SILWitnessTable *WT = Mod.lookUpWitnessTable(C, true);
// If we don't find any witness table for the conformance, bail and return
// false.
if (!WT) {
Mod.createWitnessTableDeclaration(
C, getLinkageForProtocolConformance(
C->getRootNormalConformance(), NotForDefinition));
// Adding the declaration may allow us to now deserialize the body.
// Force the body if we must deserialize this witness table.
if (mustDeserialize) {
WT = Mod.lookUpWitnessTable(C, true);
assert(WT && WT->isDefinition()
&& "unable to deserialize witness table when we must?!");
} else {
return;
}
}
// If the looked up witness table is a declaration, there is nothing we can
// do here. Just bail and return false.
if (WT->isDeclaration())
return;
auto maybeVisitRelatedConformance = [&](ProtocolConformanceRef c) {
// Formally all conformances referenced by a used conformance are used.
// However, eagerly visiting them all at this point leads to a large blowup
// in the amount of SIL we read in. For optimization purposes we can defer
// reading in most conformances until we need them for devirtualization.
// However, we *must* pull in shared clang-importer-derived conformances
// we potentially use, since we may not otherwise have a local definition.
if (mustDeserializeProtocolConformance(Mod, c))
visitProtocolConformance(c, None);
};
// For each entry in the witness table...
for (auto &E : WT->getEntries()) {
switch (E.getKind()) {
// If the entry is a witness method...
case SILWitnessTable::WitnessKind::Method: {
// And we are only interested in deserializing a specific requirement
// and don't have that requirement, don't deserialize this method.
if (Member.hasValue() && E.getMethodWitness().Requirement != *Member)
continue;
// The witness could be removed by dead function elimination.
if (!E.getMethodWitness().Witness)
continue;
// Otherwise, deserialize the witness if it has shared linkage, or if
// we were asked to deserialize everything.
maybeAddFunctionToWorklist(E.getMethodWitness().Witness);
break;
}
// If the entry is a related witness table, see whether we need to
// eagerly deserialize it.
case SILWitnessTable::WitnessKind::BaseProtocol: {
auto baseConformance = E.getBaseProtocolWitness().Witness;
maybeVisitRelatedConformance(ProtocolConformanceRef(baseConformance));
break;
}
case SILWitnessTable::WitnessKind::AssociatedTypeProtocol: {
auto assocConformance = E.getAssociatedTypeProtocolWitness().Witness;
maybeVisitRelatedConformance(assocConformance);
break;
}
case SILWitnessTable::WitnessKind::AssociatedType:
case SILWitnessTable::WitnessKind::Invalid:
break;
}
}
}