IRGen: Fix for categories on resilient classes from other modules

If a class has resilient metadata from our point of view, it might
still not have a class stub, if its entire inheritance chain is
defined in a single module.

Note that inserting a superclass is still a resilient operation;
the only way to change a class from having static metadata to having
a class stub is to change it's root class, which is not something
we can do resiliently.

Author: slavapestov

lib/IRGen/MetadataRequest.cpp

@@ -522,14 +522,26 @@ irgen::tryEmitConstantHeapMetadataRef(IRGenModule &IGM,
   auto theDecl = type->getClassOrBoundGenericClass();
   assert(theDecl && "emitting constant heap metadata ref for non-class type?");
 
-  switch (IGM.getClassMetadataStrategy(theDecl)) {
-  case ClassMetadataStrategy::Resilient:
+  // Note that getClassMetadataStrategy() will return
+  // ClassMetadataStrategy::Resilient if the class is
+  // from another resilience domain, even if inside that
+  // resilience domain the class has fixed metadata
+  // layout.
+  //
+  // Since a class only has a class stub if its class
+  // hierarchy crosses resilience domains, we use a
+  // slightly different query here.
+  if (theDecl->checkAncestry(AncestryFlags::ResilientOther)) {
     if (allowStub && IGM.Context.LangOpts.EnableObjCResilientClassStubs) {
       return IGM.getAddrOfObjCResilientClassStub(theDecl, NotForDefinition,
                                             TypeMetadataAddress::AddressPoint);
     }
+
     return nullptr;
+  }
 
+  switch (IGM.getClassMetadataStrategy(theDecl)) {
+  case ClassMetadataStrategy::Resilient:
   case ClassMetadataStrategy::Singleton:
     if (!allowDynamicUninitialized)
       return nullptr;

test/IRGen/class_update_callback_with_stub.swift

@@ -91,6 +91,11 @@ import resilient_objc_class
 // CHECK-LABEL: @"_CATEGORY__TtC31class_update_callback_with_stub27FixedLayoutNSObjectSubclass_$_class_update_callback_with_stub" = private constant
 // CHECK-SAME:  @"$s31class_update_callback_with_stub27FixedLayoutNSObjectSubclassCMs"
 
+// -- But not if the entire inheritance chain is in a single module
+
+// CHECK-LABEL: @"_CATEGORY__TtC15resilient_class22ResilientOutsideParent_$_class_update_callback_with_stub" = private constant
+// CHECK-SAME:  @"$s15resilient_class22ResilientOutsideParentCN"
+
 
 // -- Class stubs do not appear in the class list
 
@@ -102,6 +107,7 @@ import resilient_objc_class
 // CHECK-SAME: @"_CATEGORY__TtC31class_update_callback_with_stub17ResilientSubclass_$_class_update_callback_with_stub"
 // CHECK-SAME: @"_CATEGORY__TtC31class_update_callback_with_stub25ResilientNSObjectSubclass_$_class_update_callback_with_stub"
 // CHECK-SAME: @"_CATEGORY__TtC31class_update_callback_with_stub27FixedLayoutNSObjectSubclass_$_class_update_callback_with_stub"
+// CHECK-SAME: @"_CATEGORY__TtC15resilient_class22ResilientOutsideParent_$_class_update_callback_with_stub"
 // CHECK-SAME: , section "__DATA,__objc_catlist,regular,no_dead_strip"
 
 
@@ -153,3 +159,7 @@ extension ResilientNSObjectSubclass {
 extension FixedLayoutNSObjectSubclass {
   @objc public func objcMethod() {}
 }
+
+extension ResilientOutsideParent {
+  @objc public func anObjcMethod() {}
+}