IRGen: Emit list of Objective-C resilient class stubs in __objc_stublist section

Part of <rdar://problem/55000892>.

Author: slavapestov

lib/IRGen/GenDecl.cpp

@@ -897,6 +897,11 @@ void IRGenModule::addObjCClass(llvm::Constant *classPtr, bool nonlazy) {
     ObjCNonLazyClasses.push_back(classPtr);
 }
 
+/// Add the given global value to the Objective-C resilient class stub list.
+void IRGenModule::addObjCClassStub(llvm::Constant *classPtr) {
+  ObjCClassStubs.push_back(classPtr);
+}
+
 void IRGenModule::addRuntimeResolvableType(GenericTypeDecl *type) {
   // Collect the nominal type records we emit into a special section.
   RuntimeResolvableTypes.push_back(type);
@@ -995,6 +1000,12 @@ void IRGenModule::emitGlobalLists() {
                                       "regular,no_dead_strip"),
                    llvm::GlobalValue::InternalLinkage, Int8PtrTy, false);
 
+    // So do resilient class stubs.
+    emitGlobalList(*this, ObjCClassStubs, "objc_class_stubs",
+                   GetObjCSectionName("__objc_stublist",
+                                      "regular,no_dead_strip"),
+                   llvm::GlobalValue::InternalLinkage, Int8PtrTy, false);
+
     // So do categories.
     emitGlobalList(*this, ObjCCategories, "objc_categories",
                    GetObjCSectionName("__objc_catlist",

lib/IRGen/GenMeta.cpp

@@ -3794,6 +3794,8 @@ void irgen::emitClassMetadata(IRGenModule &IGM, ClassDecl *classDecl,
               classDecl, NotForDefinition,
               TypeMetadataAddress::AddressPoint);
           emitObjCClassSymbol(IGM, classDecl, stub);
+
+          IGM.addObjCClassStub(stub);
         }
       }
       break;

lib/IRGen/IRGenModule.h

@@ -1004,6 +1004,7 @@ class IRGenModule {
   void addUsedGlobal(llvm::GlobalValue *global);
   void addCompilerUsedGlobal(llvm::GlobalValue *global);
   void addObjCClass(llvm::Constant *addr, bool nonlazy);
+  void addObjCClassStub(llvm::Constant *addr);
   void addProtocolConformance(ConformanceDescription &&conformance);
 
   llvm::Constant *emitSwiftProtocols();
@@ -1121,6 +1122,8 @@ class IRGenModule {
   /// List of Objective-C classes that require nonlazy realization, bitcast to
   /// i8*.
   SmallVector<llvm::WeakTrackingVH, 4> ObjCNonLazyClasses;
+  /// List of Objective-C resilient class stubs, bitcast to i8*.
+  SmallVector<llvm::WeakTrackingVH, 4> ObjCClassStubs;
   /// List of Objective-C categories, bitcast to i8*.
   SmallVector<llvm::WeakTrackingVH, 4> ObjCCategories;
   /// List of Objective-C categories on class stubs, bitcast to i8*.

test/IRGen/class_update_callback_with_stub.swift

@@ -102,6 +102,12 @@ import resilient_objc_class
 
 // NEGATIVE-NOT: @objc_classes =
 
+// -- ... but they do appear in the stub list
+
+// CHECK-LABEL: @objc_class_stubs = internal global
+// CHECK-SAME: @"$s31class_update_callback_with_stub25ResilientNSObjectSubclassCMs"
+// CHECK-SAME: , section "__DATA,__objc_stublist,regular,no_dead_strip"
+
 // -- The category list
 
 // CHECK-LABEL: @objc_categories = internal global