embedded: make sure to serialize vtable methods with the right linkage

In embedded mode CrossModuleOptimization must visit all vtable methods to make sure that no private/internal methods are serialized.

Fixes a compiler crash
rdar://143153941

Author: eeckstein

lib/SILOptimizer/IPO/CrossModuleOptimization.cpp

@@ -431,6 +431,15 @@ void CrossModuleOptimization::serializeWitnessTablesInModule() {
 }
 
 void CrossModuleOptimization::serializeVTablesInModule() {
+  if (everything) {
+    for (SILVTable *vt : M.getVTables()) {
+      vt->setSerializedKind(IsSerialized);
+      for (auto &entry : vt->getEntries()) {
+        makeFunctionUsableFromInline(entry.getImplementation());
+      }
+    }
+    return;
+  }
   if (!isPackageCMOEnabled(M.getSwiftModule()))
     return;
 

test/embedded/import-vtables.swift

@@ -0,0 +1,57 @@
+// RUN: %empty-directory(%t)
+// RUN: %{python} %utils/split_file.py -o %t %s
+
+// RUN: %target-swift-frontend -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -enable-experimental-feature Embedded -parse-as-library
+// RUN: %target-swift-frontend -c -I %t %t/Main.swift -enable-experimental-feature Embedded -o %t/a.o
+// RUN: %target-clang -x c -c %S/Inputs/print.c -o %t/print.o
+// RUN: %target-clang %t/a.o %t/print.o -o %t/a.out
+// RUN: %target-run %t/a.out | %FileCheck %s
+
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: OS=macosx || OS=linux-gnu
+// REQUIRES: swift_feature_Embedded
+
+// BEGIN MyModule.swift
+
+public enum MyEnum {
+    case aCase
+}
+
+open class BaseClass {
+    open var type: MyEnum? { nil }
+}
+
+public final class DerivedClass: BaseClass {
+    public override var type: MyEnum { .aCase }
+
+    public override init() {
+    }
+}
+
+open class BaseGenericClass<T> {
+    open var type: MyEnum? { nil }
+}
+
+public final class DerivedGenericClass<T>: BaseGenericClass<T> {
+    public override var type: MyEnum { .aCase }
+
+    public override init() {
+    }
+}
+
+public func createGenClass() -> BaseGenericClass<Bool> {
+  return DerivedGenericClass<Bool>()
+}
+
+// BEGIN Main.swift
+
+import MyModule
+
+let dc = DerivedClass()
+let dgc = DerivedGenericClass<Int>()
+let gc = createGenClass()
+print("OK!")
+
+// CHECK: OK!
+