[IRGen JIT] Register Objective-C classes/categories after other metadata.

The instantiation of an Objective-C class or definition of an Objective-C
category can depend (at runtime) on Swift metadata, which is triggered
(only) by mangled name round-trip verification. Teach the JIT to call
the registration functions for Objective-C classes and categories
after we’ve called all of the metadata registration functions.

Author: DougGregor

lib/IRGen/GenDecl.cpp

@@ -613,7 +613,7 @@ void IRGenModule::emitRuntimeRegistration() {
   if (DebugInfo && !Context.LangOpts.DebuggerSupport)
     DebugInfo->emitArtificialFunction(RegIGF, RegistrationFunction);
 
-  // Register ObjC protocols, classes, and extensions we added.
+  // Register ObjC protocols we added.
   if (ObjCInterop) {
     if (!ObjCProtocols.empty()) {
       // We need to initialize ObjC protocols in inheritance order, parents
@@ -649,14 +649,6 @@ void IRGenModule::emitRuntimeRegistration() {
           .visitMembers(proto);
       }
     }
-    
-    for (llvm::WeakTrackingVH &ObjCClass : ObjCClasses) {
-      RegIGF.Builder.CreateCall(getInstantiateObjCClassFn(), {ObjCClass});
-    }
-      
-    for (ExtensionDecl *ext : ObjCCategoryDecls) {
-      CategoryInitializerVisitor(RegIGF, ext).visitMembers(ext);
-    }
   }
 
   // Register Swift protocols if we added any.
@@ -716,6 +708,17 @@ void IRGenModule::emitRuntimeRegistration() {
     RegIGF.Builder.CreateCall(getRegisterTypeMetadataRecordsFn(), {begin, end});
   }
 
+  // Register Objective-C classes and extensions we added.
+  if (ObjCInterop) {
+    for (llvm::WeakTrackingVH &ObjCClass : ObjCClasses) {
+      RegIGF.Builder.CreateCall(getInstantiateObjCClassFn(), {ObjCClass});
+    }
+
+    for (ExtensionDecl *ext : ObjCCategoryDecls) {
+      CategoryInitializerVisitor(RegIGF, ext).visitMembers(ext);
+    }
+  }
+
   if (!FieldDescriptors.empty()) {
     emitFieldDescriptors();
   }