[cxx-interop] use raw pointer metadata for dynamic FRT field metadata

lib/IRGen/MetadataRequest.cpp

@@ -3735,8 +3735,7 @@ namespace {
         llvm_unreachable("classes shouldn't have this kind of refcounting");
       case ReferenceCounting::None:
       case ReferenceCounting::Custom:
-        llvm_unreachable(
-            "Foreign reference types don't conform to 'AnyClass'.");
+        return emitFromValueWitnessTable(IGF.IGM.Context.TheRawPointerType);
       }
 
       llvm_unreachable("Not a valid ReferenceCounting.");

test/Interop/Cxx/foreign-reference/layout-in-opaque-layout-struct.swift

@@ -0,0 +1,67 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+
+// RUN: %target-build-swift %t/struct.swift -emit-module -emit-library -static -module-name OpaqueStruct -emit-module-path %t/Inputs/OpaqueStruct.swiftmodule -enable-library-evolution
+
+// RUN: %target-swift-emit-irgen %t/test.swift -I %t/Inputs -enable-experimental-cxx-interop -disable-availability-checking | %FileCheck %s
+
+//--- Inputs/module.modulemap
+module CxxModule {
+    header "header.h"
+    requires cplusplus
+}
+
+//--- Inputs/header.h
+
+class
+__attribute__((swift_attr("import_reference")))
+__attribute__((swift_attr("retain:immortal")))
+__attribute__((swift_attr("release:immortal")))
+SingletonReference {
+public:
+    SingletonReference(const SingletonReference &) = delete;
+
+    void method();
+};
+
+class
+__attribute__((swift_attr("import_reference")))
+__attribute__((swift_attr("retain:retainS")))
+__attribute__((swift_attr("release:releaseS")))
+SingletonReferenceRef {
+public:
+    SingletonReferenceRef(const SingletonReferenceRef &) = delete;
+
+    void method();
+};
+
+void retainS(SingletonReferenceRef *);
+void releaseS(SingletonReferenceRef *);
+
+//--- struct.swift
+
+public struct ResilientStruct {
+    let x: Int
+}
+
+//--- test.swift
+
+import OpaqueStruct
+import CxxModule
+
+public struct ImmortalFRT_OpaqueLayout {
+    public let y: SingletonReference
+    public let x: ResilientStruct
+}
+
+public struct SharedFRT_OpaqueLayout {
+    public let x: ResilientStruct
+    public let y: SingletonReferenceRef
+}
+
+// CHECK: define{{.*}} @"$s4test24ImmortalFRT_OpaqueLayoutVMr"
+// CHECK: store ptr getelementptr inbounds (ptr, ptr @"$sBpWV", i32
+
+// CHECK: define{{.*}} @"$s4test22SharedFRT_OpaqueLayoutVMr"
+// CHECK: store ptr getelementptr inbounds (ptr, ptr @"$sBpWV", i32

test/Interop/Cxx/foreign-reference/pod.swift

@@ -1,7 +1,6 @@
 // RUN: %target-run-simple-swift(-I %S/Inputs/ -Xfrontend -enable-experimental-cxx-interop -Xfrontend -validate-tbd-against-ir=none -Xfrontend -disable-llvm-verify -g -Xfrontend -disable-availability-checking)
 //
 // REQUIRES: executable_test
-// XFAIL: OS=windows-msvc
 
 import StdlibUnittest
 import POD