Merge pull request swiftlang#20040 from DougGregor/remove-witness-table-accessor

[ABI] Eliminate witness table accessors.

Author: DougGregor

docs/ABI/Mangling.rst

@@ -128,7 +128,7 @@ Globals
 
   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 'Wa'   // protocol witness table accessor (HISTORICAL)
 
   global ::= protocol-conformance 'WG'   // generic protocol witness table (HISTORICAL)
   global ::= protocol-conformance 'Wp'   // protocol witness table pattern

include/swift/ABI/Metadata.h

@@ -2013,13 +2013,10 @@ struct TargetGenericWitnessTable {
   /// to require instantiation.
   uint16_t WitnessTablePrivateSizeInWordsAndRequiresInstantiation;
 
-  /// The pattern.
-  RelativeDirectPointer<const TargetWitnessTable<Runtime>> Pattern;
-
   /// The instantiation function, which is called after the template is copied.
   RelativeDirectPointer<void(TargetWitnessTable<Runtime> *instantiatedTable,
                              const TargetMetadata<Runtime> *type,
-                             void ** const *instantiationArgs),
+                             const void * const *instantiationArgs),
                         /*nullable*/ true> Instantiator;
 
   using PrivateDataType = void *[swift::NumGenericMetadataPrivateDataWords];
@@ -2036,18 +2033,6 @@ 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>;
 
@@ -2279,15 +2264,8 @@ struct TargetProtocolConformanceDescriptor final
   // Some description of the type that conforms to the protocol.
   TargetTypeReference<Runtime> TypeRef;
 
-  // The conformance, or a generator function for the conformance.
-  union {
-    /// A direct reference to the witness table for the conformance.
-    RelativeDirectPointer<const TargetWitnessTable<Runtime>> WitnessTable;
-    
-    /// A function that produces the witness table given an instance of the
-    /// type.
-    RelativeDirectPointer<WitnessTableAccessorFn> WitnessTableAccessor;
-  };
+  /// The witness table pattern, which may also serve as the witness table.
+  RelativeDirectPointer<const TargetWitnessTable<Runtime>> WitnessTablePattern;
 
   /// Various flags, including the kind of conformance.
   ConformanceFlags Flags;
@@ -2302,10 +2280,6 @@ struct TargetProtocolConformanceDescriptor final
     return Flags.getTypeReferenceKind();
   }
 
-  typename ConformanceFlags::ConformanceKind getConformanceKind() const {
-    return Flags.getConformanceKind();
-  }
-
   const char *getDirectObjCClassName() const {
     return TypeRef.getDirectObjCClassName(getTypeKind());
   }
@@ -2325,6 +2299,18 @@ struct TargetProtocolConformanceDescriptor final
     return this->template getTrailingObjects<RelativeContextPointer<Runtime>>();
   }
 
+  /// Whether this conformance is non-unique because it has been synthesized
+  /// for a foreign type.
+  bool isSynthesizedNonUnique() const {
+    return Flags.isSynthesizedNonUnique();
+  }
+
+  /// Whether this conformance has any conditional requirements that need to
+  /// be evaluated.
+  bool hasConditionalRequirements() const {
+    return Flags.getNumConditionalRequirements() > 0;
+  }
+
   /// Retrieve the conditional requirements that must also be
   /// satisfied
   llvm::ArrayRef<GenericRequirementDescriptor>
@@ -2333,31 +2319,12 @@ struct TargetProtocolConformanceDescriptor final
             Flags.getNumConditionalRequirements()};
   }
 
-  /// Get the directly-referenced static witness table.
-  const swift::TargetWitnessTable<Runtime> *getStaticWitnessTable() const {
-    switch (getConformanceKind()) {
-    case ConformanceFlags::ConformanceKind::WitnessTable:
-      break;
-        
-    case ConformanceFlags::ConformanceKind::WitnessTableAccessor:
-    case ConformanceFlags::ConformanceKind::ConditionalWitnessTableAccessor:
-      assert(false && "not witness table");
-    }
-    return WitnessTable;
+  /// Get the directly-referenced witness table pattern, which may also
+  /// serve as the witness table.
+  const swift::TargetWitnessTable<Runtime> *getWitnessTablePattern() const {
+    return WitnessTablePattern;
   }
-  
-  WitnessTableAccessorFn *getWitnessTableAccessor() const {
-    switch (getConformanceKind()) {
-    case ConformanceFlags::ConformanceKind::WitnessTableAccessor:
-    case ConformanceFlags::ConformanceKind::ConditionalWitnessTableAccessor:
-      break;
-        
-    case ConformanceFlags::ConformanceKind::WitnessTable:
-      assert(false && "not witness table accessor");
-    }
-    return WitnessTableAccessor;
-  }
-  
+
   /// Get the canonical metadata for the type referenced by this record, or
   /// return null if the record references a generic or universal type.
   const TargetMetadata<Runtime> *getCanonicalTypeMetadata() const;

include/swift/ABI/MetadataValues.h

@@ -600,24 +600,9 @@ class ConformanceFlags {
 public:
   typedef uint32_t int_type;
 
-  enum class ConformanceKind {
-    /// A direct reference to a protocol witness table.
-    WitnessTable,
-    /// A function pointer that can be called to access the protocol witness
-    /// table.
-    WitnessTableAccessor,
-    /// A function pointer that can be called to access the protocol witness
-    /// table whose conformance is conditional on additional requirements that
-    /// must first be evaluated and then provided to the accessor function.
-    ConditionalWitnessTableAccessor,
-
-    First_Kind = WitnessTable,
-    Last_Kind = ConditionalWitnessTableAccessor,
-  };
-
 private:
   enum : int_type {
-    ConformanceKindMask = 0x07,      // 8 conformance kinds
+    UnusedLowBits = 0x07,      // historical conformance kind
 
     TypeMetadataKindMask = 0x7 << 3, // 8 type reference kinds
     TypeMetadataKindShift = 3,
@@ -637,10 +622,6 @@ class ConformanceFlags {
 public:
   ConformanceFlags(int_type value = 0) : Value(value) {}
 
-  ConformanceFlags withConformanceKind(ConformanceKind kind) const {
-    return ConformanceFlags((Value & ~ConformanceKindMask) | int_type(kind));
-  }
-
   ConformanceFlags withTypeReferenceKind(TypeReferenceKind kind) const {
     return ConformanceFlags((Value & ~TypeMetadataKindMask)
                             | (int_type(kind) << TypeMetadataKindShift));
@@ -677,11 +658,6 @@ class ConformanceFlags {
                                  : 0));
   }
 
-  /// Retrieve the conformance kind.
-  ConformanceKind getConformanceKind() const {
-    return ConformanceKind(Value & ConformanceKindMask);
-  }
-
   /// Retrieve the type reference kind kind.
   TypeReferenceKind getTypeReferenceKind() const {
     return TypeReferenceKind(

include/swift/AST/ProtocolConformance.h

@@ -258,10 +258,6 @@ class alignas(1 << DeclAlignInBits) ProtocolConformance {
   /// Get the substitutions associated with this conformance.
   SubstitutionMap getSubstitutions(ModuleDecl *M) const;
 
-  /// Determine whether the witness table access function for this conformance
-  /// needs to be passed information when called, or if it stands alone.
-  bool witnessTableAccessorRequiresArguments() const;
-
   /// Get the underlying normal conformance.
   const NormalProtocolConformance *getRootNormalConformance() const;
 

include/swift/IRGen/Linking.h

@@ -244,10 +244,6 @@ class LinkEntity {
     /// ProtocolConformance*.
     ProtocolWitnessTablePattern,
 
-    /// A witness accessor function. The secondary pointer is a
-    /// ProtocolConformance*.
-    ProtocolWitnessTableAccessFunction,
-
     /// The instantiation function for a generic protocol witness table.
     /// The secondary pointer is a ProtocolConformance*.
     GenericProtocolWitnessTableInstantiationFunction,
@@ -727,14 +723,6 @@ class LinkEntity {
     return entity;
   }
 
-  static LinkEntity
-  forProtocolWitnessTableAccessFunction(const ProtocolConformance *C) {
-    LinkEntity entity;
-    entity.setForProtocolConformance(Kind::ProtocolWitnessTableAccessFunction,
-                                     C);
-    return entity;
-  }
-
   static LinkEntity
   forGenericProtocolWitnessTableInstantiationFunction(
                                       const ProtocolConformance *C) {

include/swift/Runtime/Metadata.h

@@ -385,18 +385,13 @@ SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
 MetadataResponse swift_checkMetadataState(MetadataRequest request,
                                           const Metadata *type);
 
-/// Instantiate a resilient or generic protocol witness table.
+/// Retrieve a witness table based on a given conformance.
 ///
 /// \param conformance - The protocol conformance descriptor, which
-///   contains the generic witness table record. It may either have fields
-///   that require runtime initialization, or be missing requirements at the
-///   end for which default witnesses are available.
+///   contains any information required to form the witness table.
 ///
 /// \param type - The conforming type, used to form a uniquing key
-///   for the conformance. If the witness table is not dependent on
-///   the substituted type of the conformance, this can be set to
-///   nullptr, in which case there will only be one instantiated
-///   witness table per witness table template.
+///   for the conformance.
 ///
 /// \param instantiationArgs - An opaque pointer that's forwarded to
 ///   the instantiation function, used for conditional conformances.
@@ -406,9 +401,9 @@ MetadataResponse swift_checkMetadataState(MetadataRequest request,
 ///   conformances.
 SWIFT_RUNTIME_EXPORT
 const WitnessTable *
-swift_instantiateWitnessTable(ProtocolConformanceDescriptor *conformance,
-                              const Metadata *type,
-                              void **const *instantiationArgs);
+swift_getWitnessTable(const ProtocolConformanceDescriptor *conformance,
+                      const Metadata *type,
+                      const void * const *instantiationArgs);
 
 /// Retrieve an associated type witness from the given witness table.
 ///
@@ -490,13 +485,6 @@ MetadataResponse
 swift_getForeignTypeMetadata(MetadataRequest request,
                              ForeignTypeMetadata *nonUnique);
 
-/// \brief Fetch a unique witness table for a foreign witness table.
-SWIFT_RUNTIME_EXPORT
-const WitnessTable *
-swift_getForeignWitnessTable(const WitnessTable *nonUniqueWitnessCandidate,
-                             const TypeContextDescriptor *forForeignType,
-                             const ProtocolDescriptor *forProtocol);
-
 /// \brief Fetch a uniqued metadata for a tuple type.
 ///
 /// The labels argument is null if and only if there are no element

include/swift/Runtime/RuntimeFunctions.def

@@ -585,16 +585,6 @@ FUNCTION(GetForeignTypeMetadata, swift_getForeignTypeMetadata, SwiftCC,
          ARGS(SizeTy, TypeMetadataPtrTy),
          ATTRS(NoUnwind, ReadNone)) // only writes to runtime-private fields
 
-// WitnessTable *swift_getForeignWitnessTable(
-//                                  const WitnessTable *candidate,
-//                                  const TypeContextDescriptor *forType,
-//                                  const ProtocolDescriptor *forProtocol);
-FUNCTION(GetForeignWitnessTable, swift_getForeignWitnessTable, C_CC,
-         RETURNS(WitnessTablePtrTy),
-         ARGS(WitnessTablePtrTy, TypeContextDescriptorPtrTy,
-              ProtocolDescriptorPtrTy),
-         ATTRS(NoUnwind, ReadNone))
-
 // MetadataResponse swift_getSingletonMetadata(MetadataRequest request,
 //                                             TypeContextDescriptor *type);
 FUNCTION(GetSingletonMetadata, swift_getSingletonMetadata, SwiftCC,
@@ -635,10 +625,10 @@ FUNCTION(CheckMetadataState, swift_checkMetadataState, SwiftCC,
          ATTRS(NoUnwind, ReadOnly))
 
 // const ProtocolWitnessTable *
-// swift_instantiateWitnessTable(const ProtocolConformanceDescriptor *conf,
-//                               const Metadata *type,
-//                               void ** const *instantiationArgs);
-FUNCTION(InstantiateWitnessTable, swift_instantiateWitnessTable, C_CC,
+// swift_getWitnessTable(const ProtocolConformanceDescriptor *conf,
+//                       const Metadata *type,
+//                       const void * const *instantiationArgs);
+FUNCTION(GetWitnessTable, swift_getWitnessTable, C_CC,
          RETURNS(WitnessTablePtrTy),
          ARGS(ProtocolConformanceDescriptorPtrTy,
               TypeMetadataPtrTy,

lib/AST/ProtocolConformance.cpp

@@ -1079,10 +1079,6 @@ ProtocolConformance::getRootNormalConformance() const {
   return cast<NormalProtocolConformance>(C);
 }
 
-bool ProtocolConformance::witnessTableAccessorRequiresArguments() const {
-  return getRootNormalConformance()->getDeclContext()->isGenericContext();
-}
-
 bool ProtocolConformance::isVisibleFrom(const DeclContext *dc) const {
   // FIXME: Implement me!
   return true;

lib/IRGen/GenDecl.cpp

@@ -3643,36 +3643,6 @@ IRGenModule::getAddrOfGenericWitnessTableInstantiationFunction(
   return entry;
 }
 
-/// Fetch the witness table access function for a protocol conformance.
-llvm::Function *
-IRGenModule::getAddrOfWitnessTableAccessFunction(
-                                      const NormalProtocolConformance *conf,
-                                              ForDefinition_t forDefinition) {
-  IRGen.addLazyWitnessTable(conf);
-
-  LinkEntity entity = LinkEntity::forProtocolWitnessTableAccessFunction(conf);
-  llvm::Function *&entry = GlobalFuncs[entity];
-  if (entry) {
-    if (forDefinition) updateLinkageForDefinition(*this, entry, entity);
-    return entry;
-  }
-
-  llvm::FunctionType *fnType;
-  if (conf->witnessTableAccessorRequiresArguments()) {
-    // conditional requirements are passed indirectly, as an array of witness
-    // tables.
-    fnType = llvm::FunctionType::get(
-        WitnessTablePtrTy, {TypeMetadataPtrTy, WitnessTablePtrPtrTy}, false);
-  } else {
-    fnType = llvm::FunctionType::get(WitnessTablePtrTy, false);
-  }
-
-  Signature signature(fnType, llvm::AttributeList(), DefaultCC);
-  LinkInfo link = LinkInfo::get(*this, entity, forDefinition);
-  entry = createFunction(*this, link, signature);
-  return entry;
-}
-
 /// Fetch the lazy witness table access function for a protocol conformance.
 llvm::Function *
 IRGenModule::getAddrOfWitnessTableLazyAccessFunction(