[ABI] Move the resilient witness table into the conformance descriptor.

Place resilient witnesses in the protocol conformance descriptor,
tail-allocated after the conditional requirements, so they can be found by
reflection. Drop the resilient witness table and protocol descriptor from
the generic witness table.

Addresses rdar://problem/45228582.

include/swift/ABI/Metadata.h

@@ -2013,17 +2013,9 @@ struct TargetGenericWitnessTable {
   /// to require instantiation.
   uint16_t WitnessTablePrivateSizeInWordsAndRequiresInstantiation;
 
-  /// The protocol descriptor. Only used for resilient conformances.
-  RelativeIndirectablePointer<ProtocolDescriptor,
-                              /*nullable*/ true> Protocol;
-
   /// 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,
@@ -2044,6 +2036,18 @@ struct TargetGenericWitnessTable {
   uint16_t requiresInstantiation() const {
     return WitnessTablePrivateSizeInWordsAndRequiresInstantiation & 0x01;
   }
+
+  /// Retrieve the protocol conformance descriptor.
+  ConstTargetPointer<Runtime, TargetProtocolConformanceDescriptor<Runtime>>
+  getConformance() const {
+    return Pattern->Description;
+  }
+
+  /// Retrieve the protocol.
+  ConstTargetPointer<Runtime, TargetProtocolDescriptor<Runtime>>
+  getProtocol() const {
+    return Pattern->Description->getProtocol();
+  }
 };
 using GenericWitnessTable = TargetGenericWitnessTable<InProcess>;
 
@@ -2222,6 +2226,14 @@ struct TargetTypeReference {
 };
 using TypeReference = TargetTypeReference<InProcess>;
 
+/// Header containing information about the resilient witnesses in a
+/// protocol conformance descriptor.
+template <typename Runtime>
+struct TargetResilientWitnessesHeader {
+  uint32_t NumWitnesses;
+};
+using ResilientWitnessesHeader = TargetResilientWitnessesHeader<InProcess>;
+
 /// The structure of a protocol conformance.
 ///
 /// This contains enough static information to recover the witness table for a
@@ -2231,12 +2243,16 @@ struct TargetProtocolConformanceDescriptor final
   : public swift::ABI::TrailingObjects<
              TargetProtocolConformanceDescriptor<Runtime>,
              RelativeContextPointer<Runtime>,
-             TargetGenericRequirementDescriptor<Runtime>> {
+             TargetGenericRequirementDescriptor<Runtime>,
+             TargetResilientWitnessesHeader<Runtime>,
+             TargetResilientWitness<Runtime>> {
 
   using TrailingObjects = swift::ABI::TrailingObjects<
                              TargetProtocolConformanceDescriptor<Runtime>,
                              RelativeContextPointer<Runtime>,
-                             TargetGenericRequirementDescriptor<Runtime>>;
+                             TargetGenericRequirementDescriptor<Runtime>,
+                             TargetResilientWitnessesHeader<Runtime>,
+                             TargetResilientWitness<Runtime>>;
   friend TrailingObjects;
 
   template<typename T>
@@ -2250,6 +2266,9 @@ struct TargetProtocolConformanceDescriptor final
   using GenericRequirementDescriptor =
     TargetGenericRequirementDescriptor<Runtime>;
 
+  using ResilientWitnessesHeader = TargetResilientWitnessesHeader<Runtime>;
+  using ResilientWitness = TargetResilientWitness<Runtime>;
+
 private:
   /// The protocol being conformed to.
   RelativeIndirectablePointer<ProtocolDescriptor> Protocol;
@@ -2271,7 +2290,8 @@ struct TargetProtocolConformanceDescriptor final
   ConformanceFlags Flags;
 
 public:
-  const ProtocolDescriptor *getProtocol() const {
+  ConstTargetPointer<Runtime, TargetProtocolDescriptor<Runtime>>
+  getProtocol() const {
     return Protocol;
   }
 
@@ -2345,6 +2365,16 @@ struct TargetProtocolConformanceDescriptor final
   const swift::TargetWitnessTable<Runtime> *
   getWitnessTable(const TargetMetadata<Runtime> *type) const;
 
+  /// Retrieve the resilient witnesses.
+  ArrayRef<ResilientWitness> getResilientWitnesses() const{
+    if (!Flags.hasResilientWitnesses())
+      return { };
+
+    return ArrayRef<ResilientWitness>(
+             this->template getTrailingObjects<ResilientWitness>(),
+             numTrailingObjects(OverloadToken<ResilientWitness>()));
+  }
+
 #if !defined(NDEBUG) && SWIFT_OBJC_INTEROP
   void dump() const;
 #endif
@@ -2368,6 +2398,17 @@ struct TargetProtocolConformanceDescriptor final
   size_t numTrailingObjects(OverloadToken<GenericRequirementDescriptor>) const {
     return Flags.getNumConditionalRequirements();
   }
+
+  size_t numTrailingObjects(OverloadToken<ResilientWitnessesHeader>) const {
+    return Flags.hasResilientWitnesses() ? 1 : 0;
+  }
+
+  size_t numTrailingObjects(OverloadToken<ResilientWitness>) const {
+    return Flags.hasResilientWitnesses()
+      ? this->template getTrailingObjects<ResilientWitnessesHeader>()
+          ->NumWitnesses
+      : 0;
+  }
 };
 using ProtocolConformanceDescriptor
   = TargetProtocolConformanceDescriptor<InProcess>;

include/swift/ABI/MetadataValues.h

@@ -627,6 +627,8 @@ class ConformanceFlags {
 
     NumConditionalRequirementsMask = 0xFF << 8,
     NumConditionalRequirementsShift = 8,
+
+    HasResilientWitnessesMask = 0x01 << 16,
   };
 
   int_type Value;
@@ -660,6 +662,12 @@ class ConformanceFlags {
                             | (n << NumConditionalRequirementsShift));
   }
 
+  ConformanceFlags withHasResilientWitnesses(bool hasResilientWitnesses) const {
+    return ConformanceFlags((Value & ~HasResilientWitnessesMask)
+                            | (hasResilientWitnesses? HasResilientWitnessesMask
+                                                    : 0));
+  }
+
   /// Retrieve the conformance kind.
   ConformanceKind getConformanceKind() const {
     return ConformanceKind(Value & ConformanceKindMask);
@@ -696,6 +704,11 @@ class ConformanceFlags {
               >> NumConditionalRequirementsShift;
   }
 
+  /// Whether this conformance has any resilient witnesses.
+  bool hasResilientWitnesses() const {
+    return Value & HasResilientWitnessesMask;
+  }
+
   int_type getIntValue() const { return Value; }
 };
 

lib/IRGen/GenDecl.cpp

@@ -2451,20 +2451,20 @@ llvm::Constant *IRGenModule::emitSwiftProtocols() {
 }
 
 void IRGenModule::addProtocolConformance(
-                                const NormalProtocolConformance *conformance) {
+                                ConformanceDescription record) {
   // Add this protocol conformance.
-  ProtocolConformances.push_back(conformance);
+  ProtocolConformances.push_back(std::move(record));
 }
 
 /// Emit the protocol conformance list and return it.
 llvm::Constant *IRGenModule::emitProtocolConformances() {
   // Emit the conformances.
   bool anyReflectedConformances = false;
-  for (auto *conformance : ProtocolConformances) {
+  for (const auto &record : ProtocolConformances) {
     // Emit the protocol conformance now.
-    emitProtocolConformance(conformance);
+    emitProtocolConformance(record);
 
-    if (conformance->isBehaviorConformance())
+    if (record.conformance->isBehaviorConformance())
       continue;
 
     anyReflectedConformances = true;
@@ -2477,7 +2477,9 @@ llvm::Constant *IRGenModule::emitProtocolConformances() {
   ConstantInitBuilder builder(*this);
   auto descriptorArray = builder.beginArray(RelativeAddressTy);
 
-  for (auto *conformance : ProtocolConformances) {
+  for (const auto &record : ProtocolConformances) {
+    auto conformance = record.conformance;
+
     // Behavior conformances cannot be reflected.
     if (conformance->isBehaviorConformance())
       continue;
@@ -3687,12 +3689,8 @@ llvm::StructType *IRGenModule::getGenericWitnessTableCacheTy() {
       Int16Ty,
       // WitnessTablePrivateSizeInWords + RequiresInstantiation bit
       Int16Ty,
-      // Protocol
-      RelativeAddressTy,
       // Pattern
       RelativeAddressTy,
-      // ResilientWitnesses
-      RelativeAddressTy,
       // Instantiator
       RelativeAddressTy,
       // PrivateData