[Runtime] Reference ObjC class objects indirectly in conformance records.

Within conformance records, reference Objective-C class objects
indirectly so the runtime can update those references appropriately.
We don't need to do this for classes with Swift metadata.

Author: DougGregor

include/swift/Runtime/Metadata.h

@@ -2543,12 +2543,12 @@ struct TargetProtocolConformanceRecord {
 
     /// An indirect reference to the metadata.
     RelativeIndirectablePointer<const TargetClassMetadata<Runtime> *>
-    IndirectClass;
+      IndirectClass;
 
     /// The nominal type descriptor for a resilient or generic type which has
     /// instances that conform to the protocol.
     RelativeIndirectablePointer<TargetNominalTypeDescriptor<Runtime>>
-    TypeDescriptor;
+      TypeDescriptor;
   };
 
 

lib/IRGen/GenDecl.cpp

@@ -1354,6 +1354,8 @@ bool LinkEntity::isAvailableExternally(IRGenModule &IGM) const {
     return ::isAvailableExternally(IGM, getProtocolConformance()->getDeclContext());
 
   case Kind::ObjCClassRef:
+    return false;
+
   case Kind::ValueWitness:
   case Kind::TypeMetadataAccessFunction:
   case Kind::TypeMetadataLazyCacheVariable:
@@ -2215,18 +2217,21 @@ getTypeEntityInfo(IRGenModule &IGM, CanType conformingType) {
       defaultTy = IGM.TypeMetadataStructTy;
       defaultPtrTy = IGM.TypeMetadataPtrTy;
     } else {
-      // TODO: We should indirectly reference classes. For now directly
-      // reference the class object, which is totally wrong for ObjC interop.
-
-      typeKind = TypeMetadataRecordKind::UniqueDirectClass;
-      if (hasKnownSwiftMetadata(IGM, clas))
+      if (hasKnownSwiftMetadata(IGM, clas)) {
+        typeKind = TypeMetadataRecordKind::UniqueDirectClass;
         entity = LinkEntity::forTypeMetadata(
                          conformingType,
                          TypeMetadataAddress::AddressPoint,
                          /*isPattern*/ false);
-      else
-        entity = LinkEntity::forObjCClass(clas);
-      defaultTy = IGM.TypeMetadataStructTy;
+        defaultTy = IGM.TypeMetadataStructTy;
+      } else {
+        // Form the class reference.
+        (void)IGM.getAddrOfObjCClassRef(clas);
+
+        typeKind = TypeMetadataRecordKind::UniqueIndirectClass;
+        entity = LinkEntity::forObjCClassRef(clas);
+        defaultTy = IGM.TypeMetadataPtrTy;
+      }
       defaultPtrTy = IGM.TypeMetadataPtrTy;
     }
   } else {

test/IRGen/objc_bridged_generic_conformance.swift

@@ -3,7 +3,7 @@
 
 // CHECK-NOT: _TMnCSo
 
-// CHECK: @"\01l_protocol_conformances" = {{.*}} @"got.OBJC_CLASS_$_Thingy"
+// CHECK: @"\01l_protocol_conformances" = {{.*}} @"OBJC_CLASS_REF_$_Thingy"
 
 // CHECK-NOT: _TMnCSo
 

test/IRGen/protocol_conformance_records_objc.swift

@@ -31,12 +31,12 @@ extension NSRect: Runcible {
 // CHECK:         %swift.protocol_conformance {
 // -- protocol descriptor
 // CHECK:           [[RUNCIBLE]]
-// -- class object (TODO should be class ref variable)
-// CHECK:           @"got.OBJC_CLASS_$_Gizmo"
+// -- class object reference
+// CHECK:           @"OBJC_CLASS_REF_$_Gizmo"
 // -- witness table
 // CHECK:           @_T0So5GizmoC33protocol_conformance_records_objc8RuncibleACWP
-// -- flags 0x01: unique direct metadata (TODO should be 0x03 indirect class)
-// CHECK:           i32 1
+// -- flags 0x03: indirect class metadata
+// CHECK:           i32 3
 // CHECK:         }
 extension Gizmo: Runcible {
   public func runce() {}