Order-independent protocol witness table instantiation

docs/ABI/Mangling.rst

@@ -63,9 +63,11 @@ Globals
   global ::= context 'MXX'               // anonymous context descriptor
   global ::= context identifier 'MXY'    // anonymous context descriptor
   global ::= type assoc_type_path 'MXA'  // generic parameter ref
-  global ::= nominal-type 'Mo'           // class metadata immediate member base offset
   global ::= protocol 'Mp'               // protocol descriptor
-  global ::= protocol-conformance 'Mc'   // protocol conformance descriptor
+  global ::= protocol 'WR'               // protocol requirement table
+
+  global ::= nominal-type 'Mo'           // class metadata immediate member base offset
+
   global ::= type 'MF'                   // metadata for remote mirrors: field descriptor
   global ::= type 'MB'                   // metadata for remote mirrors: builtin type descriptor
   global ::= protocol-conformance 'MA'   // metadata for remote mirrors: associated type descriptor
@@ -76,35 +78,27 @@ Globals
   global ::= mangled-name 'Ta'                     // ObjC partial application forwarder
 
   global ::= type 'w' VALUE-WITNESS-KIND // value witness
+
+  global ::= protocol-conformance 'Mc'   // protocol conformance descriptor
+  global ::= protocol-conformance 'WP'   // protocol witness table
   global ::= protocol-conformance 'Wa'   // protocol witness table accessor
+
   global ::= protocol-conformance 'WG'   // generic protocol witness table
+  global ::= protocol-conformance 'Wp'   // protocol witness table pattern
+  global ::= protocol-conformance 'Wr'   // resilient witness table
   global ::= protocol-conformance 'WI'   // generic protocol witness table instantiation function
   global ::= type protocol-conformance 'WL'   // lazy protocol witness table cache variable
-  global ::= entity 'Wo'                 // witness table offset
-  global ::= protocol-conformance 'WP'   // protocol witness table
 
   global ::= protocol-conformance identifier 'Wt' // associated type metadata accessor
   global ::= protocol-conformance assoc_type_path nominal-type 'WT' // associated type witness table accessor
   global ::= type protocol-conformance 'Wl' // lazy protocol witness table accessor
+
   global ::= type 'WV'                   // value witness table
-  global ::= entity 'Wv' DIRECTNESS      // field offset
-  global ::= entity 'WC' // resilient enum tag index
-
-  global ::= type 'Wy' // Outlined Copy Function Type
-  global ::= type 'We' // Outlined Consume Function Type
-  global ::= type 'Wr' // Outlined Retain Function Type
-  global ::= type 'Ws' // Outlined Release Function Type
-  global ::= type 'Wb' INDEX // Outlined InitializeWithTake Function Type
-  global ::= type 'Wc' INDEX // Outlined InitializeWithCopy Function Type
-  global ::= type 'Wd' INDEX // Outlined AssignWithTake Function Type
-  global ::= type 'Wf' INDEX // Outlined AssignWithCopy Function Type
-  global ::= type 'Wh' INDEX // Outlined Destroy Function Type
+  global ::= entity 'Wvd'                // field offset
+  global ::= entity 'WC'                 // resilient enum tag index
 
   assoc_type_path ::= identifier '_' identifier*
 
-  DIRECTNESS ::= 'd'                         // direct
-  DIRECTNESS ::= 'i'                         // indirect
-
 A direct symbol resolves directly to the address of an object.  An
 indirect symbol resolves to the address of a pointer to the object.
 They are distinct manglings to make a certain class of bugs
@@ -175,6 +169,18 @@ The types in a reabstraction thunk helper function are always non-polymorphic
 ``<VALUE-WITNESS-KIND>`` differentiates the kinds of value
 witness functions for a type.
 
+::
+
+  global ::= generic-signature? type 'WOy' // Outlined copy
+  global ::= generic-signature? type 'WOe' // Outlined consume
+  global ::= generic-signature? type 'WOr' // Outlined retain
+  global ::= generic-signature? type 'WOs' // Outlined release
+  global ::= generic-signature? type 'WOb' // Outlined initializeWithTake
+  global ::= generic-signature? type 'WOc' // Outlined initializeWithCopy
+  global ::= generic-signature? type 'WOd' // Outlined assignWithTake
+  global ::= generic-signature? type 'WOf' // Outlined assignWithCopy
+  global ::= generic-signature? type 'WOh' // Outlined destroy
+
 Entities
 ~~~~~~~~
 

include/swift/Demangling/DemangleNodes.def

@@ -81,6 +81,7 @@ NODE(GenericPartialSpecialization)
 NODE(GenericPartialSpecializationNotReAbstracted)
 NODE(GenericProtocolWitnessTable)
 NODE(GenericProtocolWitnessTableInstantiationFunction)
+NODE(ResilientProtocolWitnessTable)
 NODE(GenericSpecialization)
 NODE(GenericSpecializationNotReAbstracted)
 NODE(GenericSpecializationParam)

include/swift/IRGen/Linking.h

@@ -215,6 +215,9 @@ class LinkEntity {
     /// The secondary pointer is a ProtocolConformance*.
     GenericProtocolWitnessTableInstantiationFunction,
 
+    /// A list of key/value pairs that resiliently specify a witness table.
+    ResilientProtocolWitnessTable,
+
     /// A function which returns the type metadata for the associated type
     /// of a protocol.  The secondary pointer is a ProtocolConformance*.
     /// The index of the associated type declaration is stored in the data.
@@ -641,6 +644,13 @@ class LinkEntity {
     return entity;
   }
 
+  static LinkEntity
+  forResilientProtocolWitnessTable(const ProtocolConformance *C) {
+    LinkEntity entity;
+    entity.setForProtocolConformance(Kind::ResilientProtocolWitnessTable, C);
+    return entity;
+  }
+
   static LinkEntity
   forGenericProtocolWitnessTableInstantiationFunction(
                                       const ProtocolConformance *C) {

include/swift/Runtime/Metadata.h

@@ -1991,14 +1991,11 @@ struct TargetProtocolDescriptor {
   /// Additional flags.
   ProtocolDescriptorFlags Flags;
 
-  /// The number of non-defaultable requirements in the protocol.
-  uint16_t NumMandatoryRequirements;
-
   /// The number of requirements described by the Requirements array.
   /// If any requirements beyond MinimumWitnessTableSizeInWords are present
   /// in the witness table template, they will be not be overwritten with
   /// defaults.
-  uint16_t NumRequirements;
+  uint32_t NumRequirements;
 
   /// Requirement descriptions.
   RelativeDirectPointer<TargetProtocolRequirement<Runtime>> Requirements;
@@ -2011,10 +2008,6 @@ struct TargetProtocolDescriptor {
   /// as the requirements.
   RelativeDirectPointer<const char, /*Nullable=*/true> AssociatedTypeNames;
 
-  void *getDefaultWitness(unsigned index) const {
-    return Requirements.get()[index].DefaultImplementation.get();
-  }
-
   // This is only used in unittests/Metadata.cpp.
   constexpr TargetProtocolDescriptor<Runtime>(const char *Name,
                       const TargetProtocolDescriptorList<Runtime> *Inherited,
@@ -2026,7 +2019,6 @@ struct TargetProtocolDescriptor {
       _ObjC_InstanceProperties(nullptr),
       DescriptorSize(sizeof(TargetProtocolDescriptor<Runtime>)),
       Flags(Flags),
-      NumMandatoryRequirements(0),
       NumRequirements(0),
       Requirements(nullptr),
       Superclass(nullptr),
@@ -2277,6 +2269,57 @@ struct TargetGenericBoxHeapMetadata : public TargetBoxHeapMetadata<Runtime> {
 };
 using GenericBoxHeapMetadata = TargetGenericBoxHeapMetadata<InProcess>;
 
+/// \brief The control structure of a generic or resilient protocol
+/// conformance witness.
+///
+/// Resilient conformances must use a pattern where new requirements
+/// with default implementations can be added and the order of existing
+/// requirements can be changed.
+///
+/// This is accomplished by emitting an order-independent series of
+/// relative pointer pairs, consisting of a protocol requirement together
+/// with a witness. The requirement is identified by an indirect relative
+/// pointer to the protocol dispatch thunk.
+template <typename Runtime>
+struct TargetResilientWitness {
+  RelativeIndirectPointer<void> Function;
+  RelativeDirectPointer<void> Witness;
+};
+using ResilientWitness = TargetResilientWitness<InProcess>;
+
+template <typename Runtime>
+struct TargetResilientWitnessTable final
+  : public swift::ABI::TrailingObjects<
+             TargetResilientWitnessTable<Runtime>,
+             TargetResilientWitness<Runtime>> {
+  uint32_t NumWitnesses;
+
+  using TrailingObjects = swift::ABI::TrailingObjects<
+                             TargetResilientWitnessTable<Runtime>,
+                             TargetResilientWitness<Runtime>>;
+  friend TrailingObjects;
+
+  template<typename T>
+  using OverloadToken = typename TrailingObjects::template OverloadToken<T>;
+
+  size_t numTrailingObjects(
+                        OverloadToken<TargetResilientWitness<Runtime>>) const {
+    return NumWitnesses;
+  }
+
+  llvm::ArrayRef<TargetResilientWitness<Runtime>>
+  getWitnesses() const {
+    return {this->template getTrailingObjects<TargetResilientWitness<Runtime>>(),
+            NumWitnesses};
+  }
+
+  const TargetResilientWitness<Runtime> &
+  getWitness(unsigned i) const {
+    return getWitnesses()[i];
+  }
+};
+using ResilientWitnessTable = TargetResilientWitnessTable<InProcess>;
+
 /// \brief The control structure of a generic or resilient protocol
 /// conformance.
 ///
@@ -2306,6 +2349,10 @@ struct TargetGenericWitnessTable {
   /// The pattern.
   RelativeDirectPointer<const TargetWitnessTable<Runtime>> Pattern;
 
+  /// The resilient witness table, if any.
+  RelativeDirectPointer<const TargetResilientWitnessTable<Runtime>,
+                        /*nullable*/ true> ResilientWitnesses;
+
   /// The instantiation function, which is called after the template is copied.
   RelativeDirectPointer<void(TargetWitnessTable<Runtime> *instantiatedTable,
                              const TargetMetadata<Runtime> *type,

include/swift/SIL/SILDefaultWitnessTable.h

@@ -150,33 +150,9 @@ class SILDefaultWitnessTable : public llvm::ilist_node<SILDefaultWitnessTable>,
     }
   }
 
-  /// Return the minimum witness table size, in words.
-  ///
-  /// This will not change if requirements with default implementations are
-  /// added at the end of the protocol.
-  unsigned getMinimumWitnessTableSize() const;
-
-  /// Return the default witness table size, in words.
-  ///
-  /// This is the number of resilient default entries that were known when the
-  /// protocol definition was compiled; at runtime, it may be smaller or larger,
-  /// so this should only be used when emitting metadata for the protocol
-  /// definition itself.
-  unsigned getDefaultWitnessTableSize() const {
-    return Entries.size() - getMinimumWitnessTableSize();
-  }
-
   /// Return all of the default witness table entries.
   ArrayRef<Entry> getEntries() const { return Entries; }
 
-  /// Return all of the resilient default implementations.
-  ///
-  /// This is the array of witnesses actually emitted as part of the protocol's
-  /// metadata; see the comment in getMinimumWitnessTableSize().
-  ArrayRef<Entry> getResilientDefaultEntries() {
-    return Entries.slice(getMinimumWitnessTableSize());
-  }
-
   /// Verify that the default witness table is well-formed.
   void verify(const SILModule &M) const;
 

include/swift/SIL/SILWitnessTable.h

@@ -37,7 +37,6 @@ class SILModule;
 class ProtocolConformance;
 class NormalProtocolConformance;
 enum IsSerialized_t : unsigned char;
-enum class ResilienceStrategy : unsigned;
 
 /// A mapping from each requirement of a protocol to the SIL-level entity
 /// satisfying the requirement for a concrete type.

lib/Demangling/Demangler.cpp

@@ -2087,6 +2087,10 @@ NodePointer Demangler::demangleWitness() {
       return createWithChild(Node::Kind::ProtocolRequirementArray,
                              popProtocol());
 
+    case 'r':
+      return createWithChild(Node::Kind::ResilientProtocolWitnessTable,
+                             popProtocolConformance());
+
     case 'l': {
       NodePointer Conf = popProtocolConformance();
       NodePointer Type = popNode(Node::Kind::Type);

lib/Demangling/NodePrinter.cpp

@@ -443,6 +443,7 @@ class NodePrinter {
     case Node::Kind::ReflectionMetadataFieldDescriptor:
     case Node::Kind::ReflectionMetadataAssocTypeDescriptor:
     case Node::Kind::ReflectionMetadataSuperclassDescriptor:
+    case Node::Kind::ResilientProtocolWitnessTable:
     case Node::Kind::GenericTypeParamDecl:
     case Node::Kind::ThrowsAnnotation:
     case Node::Kind::EmptyList:
@@ -1316,6 +1317,10 @@ NodePointer NodePrinter::print(NodePointer Node, bool asPrefixContext) {
     Printer << "instantiation function for generic protocol witness table for ";
     print(Node->getFirstChild());
     return nullptr;
+  case Node::Kind::ResilientProtocolWitnessTable:
+    Printer << "resilient protocol witness table for ";
+    print(Node->getFirstChild());
+    return nullptr;
   case Node::Kind::VTableThunk: {
     Printer << "vtable thunk for ";
     print(Node->getChild(1));

lib/Demangling/OldRemangler.cpp

@@ -834,6 +834,10 @@ void Remangler::mangleGenericProtocolWitnessTable(Node *node) {
   mangleSingleChildNode(node); // protocol conformance
 }
 
+void Remangler::mangleResilientProtocolWitnessTable(Node *node) {
+  unreachable("todo");
+}
+
 void Remangler::mangleGenericProtocolWitnessTableInstantiationFunction(
                                                                   Node *node) {
   Out << "WI";

lib/Demangling/Remangler.cpp

@@ -1056,6 +1056,11 @@ void Remangler::mangleGenericProtocolWitnessTableInstantiationFunction(Node *nod
   Buffer << "WI";
 }
 
+void Remangler::mangleResilientProtocolWitnessTable(Node *node) {
+  mangleSingleChildNode(node);
+  Buffer << "Wr";
+}
+
 void Remangler::mangleGenericPartialSpecialization(Node *node) {
   for (NodePointer Child : *node) {
     if (Child->getKind() == Node::Kind::GenericSpecializationParam) {