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Include access functions for the metadata and witness tables
of associated types in protocol witness tables. We use the global access functions when the result isn't dependent, and a simple accessor when the result can be cheaply recovered from the conforming metadata. Otherwise, we add a cache slot to a private section of the witness table, forcing an instantiation per conformance. Like generic type metadata, concrete instantiations of generic conformances are memoized. There's a fair amount of code in this patch that can't be dynamically tested at the moment because of the widespread reliance on recursive expansion of archetypes / dependent types. That's something we're now theoretically in a position to change, and as we do so, we'll test more of this code. This speculatively re-applies 7576a91, i.e. reverts commit 11ab3d5. We have not been able to duplicate the build failure in independent testing; it might have been spurious or unrelated.
1 parent be4bf81 commit 8f30faa

30 files changed

+1606
-250
lines changed

‎docs/ABI.rst

Lines changed: 8 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -743,15 +743,17 @@ Globals
743743
global ::= 'PA' .* // partial application forwarder
744744
global ::= 'PAo' .* // ObjC partial application forwarder
745745
global ::= 'w' value-witness-kind type // value witness
746-
global ::= 'WV' type // value witness table
747-
global ::= 'Wo' entity // witness table offset
748-
global ::= 'Wv' directness entity // field offset
749-
global ::= 'WP' protocol-conformance // protocol witness table
750746
global ::= 'Wa' protocol-conformance // protocol witness table accessor
747+
global ::= 'WG' protocol-conformance // generic protocol witness table
748+
global ::= 'WI' protocol-conformance // generic protocol witness table instantiation function
751749
global ::= 'Wl' type protocol-conformance // lazy protocol witness table accessor
752750
global ::= 'WL' protocol-conformance // lazy protocol witness table cache variable
753-
global ::= 'WD' protocol-conformance // dependent proto witness table generator
754-
global ::= 'Wd' protocol-conformance // dependent proto witness table template
751+
global ::= 'Wo' entity // witness table offset
752+
global ::= 'WP' protocol-conformance // protocol witness table
753+
global ::= 'Wt' protocol-conformance identifier // associated type metadata accessor
754+
global ::= 'WT' protocol-conformance identifier nominal-type // associated type witness table accessor
755+
global ::= 'Wv' directness entity // field offset
756+
global ::= 'WV' type // value witness table
755757
global ::= entity // some identifiable thing
756758
global ::= 'TO' global // ObjC-as-swift thunk
757759
global ::= 'To' global // swift-as-ObjC thunk

‎include/swift/Basic/DemangleNodes.def

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,8 @@ NODE(ArchetypeRef)
3030
NODE(ArgumentTuple)
3131
NODE(AssociatedType)
3232
NODE(AssociatedTypeRef)
33+
NODE(AssociatedTypeMetadataAccessor)
34+
NODE(AssociatedTypeWitnessTableAccessor)
3335
NODE(AutoClosureType)
3436
NODE(BoundGenericClass)
3537
NODE(BoundGenericEnum)
@@ -49,8 +51,6 @@ NODE(DependentGenericSameTypeRequirement)
4951
NODE(DependentGenericType)
5052
NODE(DependentMemberType)
5153
NODE(DependentGenericParamType)
52-
NODE(DependentProtocolWitnessTableGenerator)
53-
NODE(DependentProtocolWitnessTableTemplate)
5454
CONTEXT_NODE(Destructor)
5555
CONTEXT_NODE(DidSet)
5656
NODE(Directness)
@@ -71,6 +71,8 @@ NODE(FunctionSignatureSpecializationParamKind)
7171
NODE(FunctionSignatureSpecializationParamPayload)
7272
NODE(FunctionType)
7373
NODE(Generics)
74+
NODE(GenericProtocolWitnessTable)
75+
NODE(GenericProtocolWitnessTableInstantiationFunction)
7476
NODE(GenericSpecialization)
7577
NODE(GenericSpecializationParam)
7678
NODE(GenericType)

‎include/swift/Basic/RelativePointer.h

Lines changed: 8 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -102,6 +102,10 @@ class RelativeDirectPointerImpl {
102102
return reinterpret_cast<PointerTy>(absolute);
103103
}
104104

105+
/// A zero relative offset encodes a null reference.
106+
bool isNull() const & {
107+
return RelativeOffset == 0;
108+
}
105109
};
106110

107111
/// A direct relative reference to an object.
@@ -122,6 +126,8 @@ class RelativeDirectPointer :
122126
const typename super::ValueTy *operator->() const & {
123127
return this->get();
124128
}
129+
130+
using super::isNull;
125131
};
126132

127133
/// A specialization of RelativeDirectPointer for function pointers,
@@ -139,6 +145,8 @@ class RelativeDirectPointer<RetTy (ArgTy...)> :
139145
RetTy operator()(ArgTy...arg) {
140146
return this->get()(std::forward<ArgTy>(arg)...);
141147
}
148+
149+
using super::isNull;
142150
};
143151

144152
}

‎include/swift/Runtime/Metadata.h

Lines changed: 33 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2106,6 +2106,25 @@ struct GenericMetadata {
21062106
}
21072107
};
21082108

2109+
/// \brief The control structure of a generic protocol conformance.
2110+
struct GenericWitnessTable {
2111+
/// The size of the witness table in words.
2112+
uint16_t WitnessTableSizeInWords;
2113+
2114+
/// The amount to copy from the pattern in words. The rest is zeroed.
2115+
uint16_t WitnessTableSizeInWordsToCopy;
2116+
2117+
/// The pattern.
2118+
RelativeDirectPointer<WitnessTable> Pattern;
2119+
2120+
/// The instantiation function, which is called after the template is copied.
2121+
RelativeDirectPointer<void(WitnessTable *instantiatedTable,
2122+
const Metadata *type,
2123+
void * const *instantiationArgs)> Instantiator;
2124+
2125+
void *PrivateData[swift::NumGenericMetadataPrivateDataWords];
2126+
};
2127+
21092128
/// The structure of a protocol conformance record.
21102129
///
21112130
/// This contains enough static information to recover the witness table for a
@@ -2333,6 +2352,20 @@ swift_allocateGenericClassMetadata(GenericMetadata *pattern,
23332352
extern "C" Metadata *
23342353
swift_allocateGenericValueMetadata(GenericMetadata *pattern,
23352354
const void *arguments);
2355+
2356+
/// Instantiate a generic protocol witness table.
2357+
///
2358+
///
2359+
/// \param instantiationArgs - An opaque pointer that's forwarded to
2360+
/// the instantiation function, used for conditional conformances.
2361+
/// This API implicitly embeds an assumption that these arguments
2362+
/// never form part of the uniquing key for the conformance, which
2363+
/// is ultimately a statement about the user model of overlapping
2364+
/// conformances.
2365+
extern "C" const WitnessTable *
2366+
swift_getGenericWitnessTable(GenericWitnessTable *genericTable,
2367+
const Metadata *type,
2368+
void * const *instantiationArgs);
23362369

23372370
/// \brief Fetch a uniqued metadata for a function type.
23382371
extern "C" const FunctionTypeMetadata *

‎lib/Basic/Demangle.cpp

Lines changed: 51 additions & 20 deletions
Original file line numberDiff line numberDiff line change
@@ -577,6 +577,18 @@ class Demangler {
577577
DEMANGLE_CHILD_OR_RETURN(witnessTable, ProtocolConformance);
578578
return witnessTable;
579579
}
580+
if (Mangled.nextIf('G')) {
581+
auto witnessTable =
582+
NodeFactory::create(Node::Kind::GenericProtocolWitnessTable);
583+
DEMANGLE_CHILD_OR_RETURN(witnessTable, ProtocolConformance);
584+
return witnessTable;
585+
}
586+
if (Mangled.nextIf('I')) {
587+
auto witnessTable = NodeFactory::create(
588+
Node::Kind::GenericProtocolWitnessTableInstantiationFunction);
589+
DEMANGLE_CHILD_OR_RETURN(witnessTable, ProtocolConformance);
590+
return witnessTable;
591+
}
580592
if (Mangled.nextIf('l')) {
581593
auto accessor =
582594
NodeFactory::create(Node::Kind::LazyProtocolWitnessTableAccessor);
@@ -597,17 +609,20 @@ class Demangler {
597609
DEMANGLE_CHILD_OR_RETURN(tableTemplate, ProtocolConformance);
598610
return tableTemplate;
599611
}
600-
if (Mangled.nextIf('D')) {
601-
auto tableGenerator = NodeFactory::create(
602-
Node::Kind::DependentProtocolWitnessTableGenerator);
603-
DEMANGLE_CHILD_OR_RETURN(tableGenerator, ProtocolConformance);
604-
return tableGenerator;
612+
if (Mangled.nextIf('t')) {
613+
auto accessor = NodeFactory::create(
614+
Node::Kind::AssociatedTypeMetadataAccessor);
615+
DEMANGLE_CHILD_OR_RETURN(accessor, ProtocolConformance);
616+
DEMANGLE_CHILD_OR_RETURN(accessor, DeclName);
617+
return accessor;
605618
}
606-
if (Mangled.nextIf('d')) {
607-
auto tableTemplate = NodeFactory::create(
608-
Node::Kind::DependentProtocolWitnessTableTemplate);
609-
DEMANGLE_CHILD_OR_RETURN(tableTemplate, ProtocolConformance);
610-
return tableTemplate;
619+
if (Mangled.nextIf('T')) {
620+
auto accessor = NodeFactory::create(
621+
Node::Kind::AssociatedTypeWitnessTableAccessor);
622+
DEMANGLE_CHILD_OR_RETURN(accessor, ProtocolConformance);
623+
DEMANGLE_CHILD_OR_RETURN(accessor, DeclName);
624+
DEMANGLE_CHILD_OR_RETURN(accessor, ProtocolName);
625+
return accessor;
611626
}
612627
return nullptr;
613628
}
@@ -2352,6 +2367,8 @@ class NodePrinter {
23522367

23532368
case Node::Kind::Allocator:
23542369
case Node::Kind::ArgumentTuple:
2370+
case Node::Kind::AssociatedTypeMetadataAccessor:
2371+
case Node::Kind::AssociatedTypeWitnessTableAccessor:
23552372
case Node::Kind::AutoClosureType:
23562373
case Node::Kind::CFunctionPointer:
23572374
case Node::Kind::Constructor:
@@ -2363,8 +2380,6 @@ class NodePrinter {
23632380
case Node::Kind::DependentGenericParamCount:
23642381
case Node::Kind::DependentGenericConformanceRequirement:
23652382
case Node::Kind::DependentGenericSameTypeRequirement:
2366-
case Node::Kind::DependentProtocolWitnessTableGenerator:
2367-
case Node::Kind::DependentProtocolWitnessTableTemplate:
23682383
case Node::Kind::Destructor:
23692384
case Node::Kind::DidSet:
23702385
case Node::Kind::DirectMethodReferenceAttribute:
@@ -2381,6 +2396,8 @@ class NodePrinter {
23812396
case Node::Kind::FunctionSignatureSpecializationParamPayload:
23822397
case Node::Kind::FunctionType:
23832398
case Node::Kind::Generics:
2399+
case Node::Kind::GenericProtocolWitnessTable:
2400+
case Node::Kind::GenericProtocolWitnessTableInstantiationFunction:
23842401
case Node::Kind::GenericSpecialization:
23852402
case Node::Kind::GenericSpecializationParam:
23862403
case Node::Kind::GenericType:
@@ -3165,14 +3182,6 @@ void NodePrinter::print(NodePointer pointer, bool asContext, bool suppressType)
31653182
case Node::Kind::PostfixOperator:
31663183
Printer << pointer->getText() << " postfix";
31673184
return;
3168-
case Node::Kind::DependentProtocolWitnessTableGenerator:
3169-
Printer << "dependent protocol witness table generator for ";
3170-
print(pointer->getFirstChild());
3171-
return;
3172-
case Node::Kind::DependentProtocolWitnessTableTemplate:
3173-
Printer << "dependent protocol witness table template for ";
3174-
print(pointer->getFirstChild());
3175-
return;
31763185
case Node::Kind::LazyProtocolWitnessTableAccessor:
31773186
Printer << "lazy protocol witness table accessor for type ";
31783187
print(pointer->getChild(0));
@@ -3193,6 +3202,14 @@ void NodePrinter::print(NodePointer pointer, bool asContext, bool suppressType)
31933202
Printer << "protocol witness table for ";
31943203
print(pointer->getFirstChild());
31953204
return;
3205+
case Node::Kind::GenericProtocolWitnessTable:
3206+
Printer << "generic protocol witness table for ";
3207+
print(pointer->getFirstChild());
3208+
return;
3209+
case Node::Kind::GenericProtocolWitnessTableInstantiationFunction:
3210+
Printer << "instantiation function for generic protocol witness table for ";
3211+
print(pointer->getFirstChild());
3212+
return;
31963213
case Node::Kind::ProtocolWitness: {
31973214
Printer << "protocol witness for ";
31983215
print(pointer->getChild(1));
@@ -3279,6 +3296,20 @@ void NodePrinter::print(NodePointer pointer, bool asContext, bool suppressType)
32793296
Printer << "lazy cache variable for type metadata for ";
32803297
print(pointer->getChild(0));
32813298
return;
3299+
case Node::Kind::AssociatedTypeMetadataAccessor:
3300+
Printer << "associated type metadata accessor for ";
3301+
print(pointer->getChild(1));
3302+
Printer << " in ";
3303+
print(pointer->getChild(0));
3304+
return;
3305+
case Node::Kind::AssociatedTypeWitnessTableAccessor:
3306+
Printer << "associated type witness table accessor for ";
3307+
print(pointer->getChild(1));
3308+
Printer << " : ";
3309+
print(pointer->getChild(2));
3310+
Printer << " in ";
3311+
print(pointer->getChild(0));
3312+
return;
32823313
case Node::Kind::NominalTypeDescriptor:
32833314
Printer << "nominal type descriptor for ";
32843315
print(pointer->getChild(0));

‎lib/Basic/Remangle.cpp

Lines changed: 20 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -698,6 +698,17 @@ void Remangler::mangleProtocolWitnessTable(Node *node) {
698698
mangleSingleChildNode(node); // protocol conformance
699699
}
700700

701+
void Remangler::mangleGenericProtocolWitnessTable(Node *node) {
702+
Out << "WG";
703+
mangleSingleChildNode(node); // protocol conformance
704+
}
705+
706+
void Remangler::mangleGenericProtocolWitnessTableInstantiationFunction(
707+
Node *node) {
708+
Out << "WI";
709+
mangleSingleChildNode(node); // protocol conformance
710+
}
711+
701712
void Remangler::mangleProtocolWitnessTableAccessor(Node *node) {
702713
Out << "Wa";
703714
mangleSingleChildNode(node); // protocol conformance
@@ -713,14 +724,17 @@ void Remangler::mangleLazyProtocolWitnessTableCacheVariable(Node *node) {
713724
mangleChildNodes(node); // type, protocol conformance
714725
}
715726

716-
void Remangler::mangleDependentProtocolWitnessTableGenerator(Node *node) {
717-
Out << "WD";
718-
mangleSingleChildNode(node); // protocol conformance
727+
void Remangler::mangleAssociatedTypeMetadataAccessor(Node *node) {
728+
Out << "Wt";
729+
mangleChildNodes(node); // protocol conformance, identifier
719730
}
720731

721-
void Remangler::mangleDependentProtocolWitnessTableTemplate(Node *node) {
722-
Out << "Wd";
723-
mangleSingleChildNode(node); // protocol conformance
732+
void Remangler::mangleAssociatedTypeWitnessTableAccessor(Node *node) {
733+
Out << "WT";
734+
assert(node->getNumChildren() == 3);
735+
mangleChildNode(node, 0); // protocol conformance
736+
mangleChildNode(node, 1); // identifier
737+
mangleProtocolWithoutPrefix(node->begin()[2].get()); // type
724738
}
725739

726740
void Remangler::mangleReabstractionThunkHelper(Node *node) {

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