Remove aliases for @_objcImpl type metadata

Author: beccadax

include/swift/IRGen/Linking.h

@@ -810,6 +810,7 @@ class LinkEntity {
 
   static LinkEntity forTypeMetadata(CanType concreteType,
                                     TypeMetadataAddress addr) {
+    assert(!isObjCImplementation(concreteType));
     LinkEntity entity;
     entity.setForType(Kind::TypeMetadata, concreteType);
     entity.Data |= LINKENTITY_SET_FIELD(MetadataAddress, unsigned(addr));
@@ -872,12 +873,14 @@ class LinkEntity {
   }
 
   static LinkEntity forNominalTypeDescriptor(NominalTypeDecl *decl) {
+    assert(!isObjCImplementation(decl));
     LinkEntity entity;
     entity.setForDecl(Kind::NominalTypeDescriptor, decl);
     return entity;
   }
 
   static LinkEntity forNominalTypeDescriptorRecord(NominalTypeDecl *decl) {
+    assert(!isObjCImplementation(decl));
     LinkEntity entity;
     entity.setForDecl(Kind::NominalTypeDescriptorRecord, decl);
     return entity;
@@ -1553,6 +1556,16 @@ class LinkEntity {
   bool isAlwaysSharedLinkage() const;
 #undef LINKENTITY_GET_FIELD
 #undef LINKENTITY_SET_FIELD
+
+private:
+  static bool isObjCImplementation(NominalTypeDecl *NTD) {
+    if (NTD)
+      return !NTD->getObjCImplementationDecls().empty();
+    return false;
+  }
+  static bool isObjCImplementation(CanType ty) {
+    return isObjCImplementation(ty->getClassOrBoundGenericClass());
+  }
 };
 
 struct IRLinkage {

lib/IRGen/GenDecl.cpp

@@ -4714,17 +4714,17 @@ llvm::GlobalValue *IRGenModule::defineTypeMetadata(
     return cast<llvm::GlobalValue>(addr);
   }
 
-  auto swiftEntity =
+  auto entity =
       (isPrespecialized &&
        !irgen::isCanonicalInitializableTypeMetadataStaticallyAddressable(
            *this, concreteType))
           ? LinkEntity::forNoncanonicalSpecializedGenericTypeMetadata(
                 concreteType)
-          : LinkEntity::forTypeMetadata(concreteType,
-                                        TypeMetadataAddress::FullMetadata);
-  auto entity = isObjCImpl
-      ? LinkEntity::forObjCClass(concreteType->getClassOrBoundGenericClass())
-      : swiftEntity;
+          : (isObjCImpl
+                ? LinkEntity::forObjCClass(
+                      concreteType->getClassOrBoundGenericClass())
+                : LinkEntity::forTypeMetadata(
+                      concreteType, TypeMetadataAddress::FullMetadata));
 
   auto DbgTy = DebugTypeInfo::getMetadata(MetatypeType::get(concreteType),
     entity.getDefaultDeclarationType(*this)->getPointerTo(),
@@ -4757,19 +4757,14 @@ llvm::GlobalValue *IRGenModule::defineTypeMetadata(
     if (!isObjCImpl)
       addRuntimeResolvableType(nominal);
 
-    // Don't define the alias for foreign type metadata or prespecialized
-    // generic metadata, since neither is ABI.
-    if (requiresForeignTypeMetadata(nominal) || isPrespecialized)
+    // Don't define the alias for foreign type metadata, prespecialized
+    // generic metadata, or @_objcImplementation classes, since they're not ABI.
+    if (requiresForeignTypeMetadata(nominal) || isPrespecialized || isObjCImpl)
       return var;
 
     // Native Swift class metadata has a destructor before the address point.
     if (isa<ClassDecl>(nominal)) {
       adjustmentIndex = MetadataAdjustmentIndex::Class;
-
-      // But `@_objcImplementation` extensions have nothing at all!
-      if (!cast<ClassDecl>(nominal)->getObjCImplementationDecls().empty()) {
-        adjustmentIndex = MetadataAdjustmentIndex::None;
-      }
     }
   }
 
@@ -4781,17 +4776,9 @@ llvm::GlobalValue *IRGenModule::defineTypeMetadata(
   addr = llvm::ConstantExpr::getBitCast(addr, TypeMetadataPtrTy);
 
   // For concrete metadata, declare the alias to its address point.
-  // FIXME: Should probably skip all of this for @_objcImpl and just use the
-  // ObjC symbol instead.
   auto directEntity = LinkEntity::forTypeMetadata(
       concreteType, TypeMetadataAddress::AddressPoint);
-  auto directAlias = defineAlias(directEntity, addr);
-
-  if (!isObjCImpl)
-    return directAlias;
-
-  defineAlias(swiftEntity, directAlias);
-  return var;
+  return defineAlias(directEntity, addr);
 }
 
 /// Fetch the declaration of the (possibly uninitialized) metadata for a type.

lib/TBDGen/TBDGen.cpp

@@ -870,12 +870,14 @@ void TBDGenVisitor::visitSubscriptDecl(SubscriptDecl *SD) {
 void TBDGenVisitor::visitNominalTypeDecl(NominalTypeDecl *NTD) {
   auto declaredType = NTD->getDeclaredType()->getCanonicalType();
 
-  addSymbol(LinkEntity::forNominalTypeDescriptor(NTD));
+  if (NTD->getObjCImplementationDecls().empty()) {
+    addSymbol(LinkEntity::forNominalTypeDescriptor(NTD));
 
-  // Generic types do not get metadata directly, only through the function.
-  if (!NTD->isGenericContext()) {
-    addSymbol(LinkEntity::forTypeMetadata(declaredType,
-                                          TypeMetadataAddress::AddressPoint));
+    // Generic types do not get metadata directly, only through the function.
+    if (!NTD->isGenericContext()) {
+      addSymbol(LinkEntity::forTypeMetadata(declaredType,
+                                            TypeMetadataAddress::AddressPoint));
+    }
   }
   addSymbol(LinkEntity::forTypeMetadataAccessFunction(declaredType));
 

test/IRGen/objc_implementation.swift

@@ -35,10 +35,6 @@
 // CHECK: @"objc_classes_OBJC_CLASS_$_ImplClass" = internal global i8* bitcast (<{ i64, %objc_class*, %swift.opaque*, %swift.opaque*, { i32, i32, i32, i32, i8*, i8*, { i32, i32, [1 x { i8*, i8*, i8* }] }*, i8*, i8*, i8*, i8* }* }>* @"OBJC_CLASS_$_ImplClass" to i8*), section "__DATA,__objc_classlist,regular,no_dead_strip", align 8
 // CHECK: @objc_categories = internal global [1 x i8*] [i8* bitcast ({ i8*, %objc_class*, { i32, i32, [1 x { i8*, i8*, i8* }] }*, i8*, i8*, i8*, i8*, i32 }* [[_CATEGORY_ImplClass_Category1]] to i8*)], section "__DATA,__objc_catlist,regular,no_dead_strip", align 8
 
-// CHECK: @"$sSo9ImplClassCN" = alias %swift.type, bitcast (<{ i64, %objc_class*, %swift.opaque*, %swift.opaque*, { i32, i32, i32, i32, i8*, i8*, { i32, i32, [1 x { i8*, i8*, i8* }] }*, i8*, i8*, i8*, i8* }* }>* @"OBJC_CLASS_$_ImplClass" to %swift.type*)
-// CHECK: @"$sSo9ImplClassCMf" = internal alias %swift.type, %swift.type* @"$sSo9ImplClassCN"
-// FIXME: Remove these instead of using aliases?
-
 // CHECK: define internal void @"$sSo9ImplClassC19objc_implementationE10mainMethodyys5Int32VFTo"
 // CHECK: define internal void @"$sSo9ImplClassC19objc_implementationE15category1Methodyys5Int32VFTo"
 
@@ -47,3 +43,5 @@
 // NEGATIVE-NOT: OBJC_CLASS_$_ImplClass.{{[0-9]}}
 // NEGATIVE-NOT: $sSo9ImplClassCMn
 // NEGATIVE-NOT: $sSo9ImplClassCHn
+// NEGATIVE-NOT: $sSo9ImplClassCN
+// NEGATIVE-NOT: $sSo9ImplClassCMf