Method descriptors

docs/ABI/Mangling.rst

@@ -115,6 +115,8 @@ field offsets are therefore required when accessing fields in generic
 types where the metadata itself has unknown layout.)
 
 ::
+  global ::= global 'Tj'                 // resilient method dispatch thunk
+  global ::= global 'Tq'                 // method descriptor
 
   global ::= global 'TO'                 // ObjC-as-swift thunk
   global ::= global 'To'                 // swift-as-ObjC thunk

include/swift/AST/ASTMangler.h

@@ -57,7 +57,6 @@ class ASTMangler : public Mangler {
   enum class SymbolKind {
     Default,
     DynamicThunk,
-    SwiftDispatchThunk,
     SwiftAsObjCThunk,
     ObjCAsSwiftThunk,
     DirectMethodReferenceThunk,

include/swift/Demangling/DemangleNodes.def

@@ -203,8 +203,9 @@ NODE(ReflectionMetadataFieldDescriptor)
 NODE(ReflectionMetadataAssocTypeDescriptor)
 NODE(ReflectionMetadataSuperclassDescriptor)
 NODE(GenericTypeParamDecl)
-CONTEXT_NODE(CurryThunk)
-CONTEXT_NODE(DispatchThunk)
+NODE(CurryThunk)
+NODE(DispatchThunk)
+NODE(MethodDescriptor)
 NODE(ThrowsAnnotation)
 NODE(EmptyList)
 NODE(FirstElementMarker)

include/swift/IRGen/Linking.h

@@ -117,6 +117,18 @@ class LinkEntity {
     /// ConstructorDecl* inside a protocol or a class.
     DispatchThunkAllocator,
 
+    /// A method descriptor.  The pointer is a FuncDecl* inside a protocol
+    /// or a class.
+    MethodDescriptor,
+
+    /// A method descriptor for an initializing constructor.  The pointer
+    /// is a ConstructorDecl* inside a class.
+    MethodDescriptorInitializer,
+
+    /// A method descriptor for an allocating constructor.  The pointer is a
+    /// ConstructorDecl* inside a protocol or a class.
+    MethodDescriptorAllocator,
+
     /// A resilient enum tag index. The pointer is a EnumElementDecl*.
     EnumCase,
 
@@ -412,18 +424,22 @@ class LinkEntity {
 
   LinkEntity() = default;
 
+  static bool isValidResilientMethodRef(SILDeclRef declRef) {
+    if (declRef.isForeign ||
+        declRef.isDirectReference ||
+        declRef.isCurried)
+      return false;
+
+    auto *decl = declRef.getDecl();
+    return (isa<ClassDecl>(decl->getDeclContext()) ||
+            isa<ProtocolDecl>(decl->getDeclContext()));
+  }
+
 public:
   static LinkEntity forDispatchThunk(SILDeclRef declRef) {
-    assert(!declRef.isForeign &&
-           !declRef.isDirectReference &&
-           !declRef.isCurried);
+    assert(isValidResilientMethodRef(declRef));
 
     LinkEntity::Kind kind;
-
-    auto *decl = declRef.getDecl();
-    assert(isa<ClassDecl>(decl->getDeclContext()) ||
-           isa<ProtocolDecl>(decl->getDeclContext()));
-
     switch (declRef.kind) {
     case SILDeclRef::Kind::Func:
       kind = Kind::DispatchThunk;
@@ -439,7 +455,30 @@ class LinkEntity {
     }
 
     LinkEntity entity;
-    entity.setForDecl(kind, decl);
+    entity.setForDecl(kind, declRef.getDecl());
+    return entity;
+  }
+
+  static LinkEntity forMethodDescriptor(SILDeclRef declRef) {
+    assert(isValidResilientMethodRef(declRef));
+
+    LinkEntity::Kind kind;
+    switch (declRef.kind) {
+    case SILDeclRef::Kind::Func:
+      kind = Kind::MethodDescriptor;
+      break;
+    case SILDeclRef::Kind::Initializer:
+      kind = Kind::MethodDescriptorInitializer;
+      break;
+    case SILDeclRef::Kind::Allocator:
+      kind = Kind::MethodDescriptorAllocator;
+      break;
+    default:
+      llvm_unreachable("Bad SILDeclRef for method descriptor");
+    }
+
+    LinkEntity entity;
+    entity.setForDecl(kind, declRef.getDecl());
     return entity;
   }
 

lib/AST/ASTMangler.cpp

@@ -535,7 +535,6 @@ void ASTMangler::appendSymbolKind(SymbolKind SKind) {
   switch (SKind) {
     case SymbolKind::Default: return;
     case SymbolKind::DynamicThunk: return appendOperator("TD");
-    case SymbolKind::SwiftDispatchThunk: return appendOperator("Tj");
     case SymbolKind::SwiftAsObjCThunk: return appendOperator("To");
     case SymbolKind::ObjCAsSwiftThunk: return appendOperator("TO");
     case SymbolKind::DirectMethodReferenceThunk: return appendOperator("Td");

lib/Demangling/Demangler.cpp

@@ -1702,6 +1702,7 @@ NodePointer Demangler::demangleThunkOrSpecialization() {
   switch (char c = nextChar()) {
     case 'c': return createWithChild(Node::Kind::CurryThunk, popNode(isEntity));
     case 'j': return createWithChild(Node::Kind::DispatchThunk, popNode(isEntity));
+    case 'q': return createWithChild(Node::Kind::MethodDescriptor, popNode(isEntity));
     case 'o': return createNode(Node::Kind::ObjCAttribute);
     case 'O': return createNode(Node::Kind::NonObjCAttribute);
     case 'D': return createNode(Node::Kind::DynamicAttribute);

lib/Demangling/NodePrinter.cpp

@@ -381,6 +381,7 @@ class NodePrinter {
     case Node::Kind::MaterializeForSet:
     case Node::Kind::MergedFunction:
     case Node::Kind::Metaclass:
+    case Node::Kind::MethodDescriptor:
     case Node::Kind::ModifyAccessor:
     case Node::Kind::NativeOwningAddressor:
     case Node::Kind::NativeOwningMutableAddressor:
@@ -907,6 +908,10 @@ NodePointer NodePrinter::print(NodePointer Node, bool asPrefixContext) {
     Printer << "dispatch thunk of ";
     print(Node->getChild(0));
     return nullptr;
+  case Node::Kind::MethodDescriptor:
+    Printer << "method descriptor for ";
+    print(Node->getChild(0));
+    return nullptr;
   case Node::Kind::OutlinedBridgedMethod:
     Printer << "outlined bridged method (" << Node->getText() << ") of ";
     return nullptr;

lib/Demangling/OldRemangler.cpp

@@ -1931,14 +1931,18 @@ void Remangler::mangleGenericTypeParamDecl(Node *node) {
   unreachable("todo");
 }
 
-void Remangler::mangleCurryThunk(Node *node, EntityContext &ctx) {
+void Remangler::mangleCurryThunk(Node *node) {
   Out << "<curry-thunk>";
 }
 
-void Remangler::mangleDispatchThunk(Node *node, EntityContext &ctx) {
+void Remangler::mangleDispatchThunk(Node *node) {
   Out << "<dispatch-thunk>";
 }
 
+void Remangler::mangleMethodDescriptor(Node *node) {
+  Out << "<method-descriptor>";
+}
+
 void Remangler::mangleEmptyList(Node *node) {
   Out << "<empty>";
 }

lib/Demangling/Remangler.cpp

@@ -1887,6 +1887,11 @@ void Remangler::mangleDispatchThunk(Node *node) {
   Buffer << "Tj";
 }
 
+void Remangler::mangleMethodDescriptor(Node *node) {
+  mangleSingleChildNode(node);
+  Buffer << "Tq";
+}
+
 void Remangler::mangleThrowsAnnotation(Node *node) {
   Buffer << 'K';
 }

lib/IRGen/GenClass.cpp

@@ -1019,36 +1019,6 @@ void IRGenModule::emitClassDecl(ClassDecl *D) {
 
   emitNestedTypeDecls(D->getMembers());
   emitFieldMetadataRecord(D);
-
-  // If the class is resilient, emit dispatch thunks.
-  if (isResilient(D, ResilienceExpansion::Minimal)) {
-    struct ThunkEmitter : public SILVTableVisitor<ThunkEmitter> {
-      IRGenModule &IGM;
-      ClassDecl *D;
-
-      ThunkEmitter(IRGenModule &IGM, ClassDecl *D)
-        : IGM(IGM), D(D) {
-        addVTableEntries(D);
-      }
-
-      void addMethodOverride(SILDeclRef baseRef, SILDeclRef declRef) {}
-
-      void addMethod(SILDeclRef member) {
-        auto *func = cast<AbstractFunctionDecl>(member.getDecl());
-        if (func->getDeclContext() == D &&
-            func->getEffectiveAccess() >= AccessLevel::Public) {
-          IGM.emitDispatchThunk(member);
-        }
-      }
-
-      void addPlaceholder(MissingMemberDecl *m) {
-        assert(m->getNumberOfVTableEntries() == 0
-               && "Should not be emitting class with missing members");
-      }
-    };
-
-    ThunkEmitter emitter(*this, D);
-  }
 }
 
 namespace {

lib/IRGen/GenDecl.cpp

@@ -1378,7 +1378,10 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
   switch (getKind()) {
   case Kind::DispatchThunk:
   case Kind::DispatchThunkInitializer:
-  case Kind::DispatchThunkAllocator: {
+  case Kind::DispatchThunkAllocator:
+  case Kind::MethodDescriptor:
+  case Kind::MethodDescriptorInitializer:
+  case Kind::MethodDescriptorAllocator: {
     auto *decl = getDecl();
 
     // Protocol requirements don't have their own access control
@@ -1586,7 +1589,10 @@ bool LinkEntity::isAvailableExternally(IRGenModule &IGM) const {
   switch (getKind()) {
   case Kind::DispatchThunk:
   case Kind::DispatchThunkInitializer:
-  case Kind::DispatchThunkAllocator: {
+  case Kind::DispatchThunkAllocator:
+  case Kind::MethodDescriptor:
+  case Kind::MethodDescriptorInitializer:
+  case Kind::MethodDescriptorAllocator: {
     auto *decl = getDecl();
 
     // Protocol requirements don't have their own access control
@@ -3268,6 +3274,47 @@ IRGenModule::getAddrOfTypeMetadataSingletonInitializationCache(
   return variable;
 }
 
+llvm::GlobalValue *IRGenModule::defineAlias(LinkEntity entity,
+                                            llvm::Constant *definition) {
+  // Check for an existing forward declaration of the alias.
+  auto &entry = GlobalVars[entity];
+  llvm::GlobalValue *existingVal = nullptr;
+  if (entry) {
+    existingVal = cast<llvm::GlobalValue>(entry);
+    // Clear the existing value's name so we can steal it.
+    existingVal->setName("");
+  }
+
+  LinkInfo link = LinkInfo::get(*this, entity, ForDefinition);
+  auto *ptrTy = cast<llvm::PointerType>(definition->getType());
+  auto *alias = llvm::GlobalAlias::create(
+      ptrTy->getElementType(), ptrTy->getAddressSpace(), link.getLinkage(),
+      link.getName(), definition, &Module);
+  alias->setVisibility(link.getVisibility());
+  alias->setDLLStorageClass(link.getDLLStorage());
+
+  if (link.isUsed()) {
+    addUsedGlobal(alias);
+  }
+
+  // Replace an existing external declaration for the address point.
+  if (entry) {
+    auto existingVal = cast<llvm::GlobalValue>(entry);
+
+    // FIXME: MC breaks when emitting alias references on some platforms
+    // (rdar://problem/22450593 ). Work around this by referring to the aliasee
+    // instead.
+    llvm::Constant *aliasCast = alias->getAliasee();
+    aliasCast = llvm::ConstantExpr::getBitCast(aliasCast,
+                                               entry->getType());
+    existingVal->replaceAllUsesWith(aliasCast);
+    existingVal->eraseFromParent();
+  }
+  entry = alias;
+
+  return alias;
+}
+
 /// Define the metadata for a type.
 ///
 /// Some type metadata has information before the address point that the
@@ -3320,6 +3367,10 @@ llvm::GlobalValue *IRGenModule::defineTypeMetadata(CanType concreteType,
   if (!section.empty())
     var->setSection(section);
 
+  LinkInfo link = LinkInfo::get(*this, entity, ForDefinition);
+  if (link.isUsed())
+    addUsedGlobal(var);
+
   // Keep type metadata around for all types.
   if (auto nominal = concreteType->getAnyNominal())
     addRuntimeResolvableType(nominal);
@@ -3339,47 +3390,7 @@ llvm::GlobalValue *IRGenModule::defineTypeMetadata(CanType concreteType,
                                                         addr, indices);
   }
   addr = llvm::ConstantExpr::getBitCast(addr, TypeMetadataPtrTy);
-
-  // Check for an existing forward declaration of the address point.
-  auto &directEntry = GlobalVars[directEntity];
-  llvm::GlobalValue *existingVal = nullptr;
-  if (directEntry) {
-    existingVal = cast<llvm::GlobalValue>(directEntry);
-    // Clear the existing value's name so we can steal it.
-    existingVal->setName("");
-  }
-
-  LinkInfo link = LinkInfo::get(*this, directEntity, ForDefinition);
-  auto *ptrTy = cast<llvm::PointerType>(addr->getType());
-  auto *alias = llvm::GlobalAlias::create(
-      ptrTy->getElementType(), ptrTy->getAddressSpace(), link.getLinkage(),
-      link.getName(), addr, &Module);
-  alias->setVisibility(link.getVisibility());
-  alias->setDLLStorageClass(link.getDLLStorage());
-
-  // The full metadata is used based on the visibility of the address point,
-  // not the metadata itself.
-  if (link.isUsed()) {
-    addUsedGlobal(var);
-    addUsedGlobal(alias);
-  }
-
-  // Replace an existing external declaration for the address point.
-  if (directEntry) {
-    auto existingVal = cast<llvm::GlobalValue>(directEntry);
-
-    // FIXME: MC breaks when emitting alias references on some platforms
-    // (rdar://problem/22450593 ). Work around this by referring to the aliasee
-    // instead.
-    llvm::Constant *aliasCast = alias->getAliasee();
-    aliasCast = llvm::ConstantExpr::getBitCast(aliasCast,
-                                               directEntry->getType());
-    existingVal->replaceAllUsesWith(aliasCast);
-    existingVal->eraseFromParent();
-  }
-  directEntry = alias;
-
-  return alias;
+  return defineAlias(directEntity, addr);
 }
 
 /// Fetch the declaration of the metadata (or metadata template) for a