IRGen: Disable resilient class metadata unless -enable-class-resilience is passed in

Resilient classes are not fully implemented yet, and can cause
crashes at runtime; add a flag disabling them until the code is
done, to unblock standard library testing with resilience
enabled.

Author: slavapestov

include/swift/Basic/LangOptions.h

@@ -141,6 +141,11 @@ namespace swift {
     /// \brief Enable experimental nested generic types feature.
     bool EnableExperimentalNestedGenericTypes = false;
 
+    /// \brief Staging flag for class resilience, which we do not want to enable
+    /// fully until more code is in place, to allow the standard library to be
+    /// tested with value type resilience only.
+    bool EnableClassResilience = false;
+
     /// Should we check the target OSs of serialized modules to see that they're
     /// new enough?
     bool EnableTargetOSChecking = true;

include/swift/Option/FrontendOptions.td

@@ -331,6 +331,10 @@ def enable_resilience : Flag<["-"], "enable-resilience">,
    HelpText<"Compile the module to export resilient interfaces for all "
             "public declarations by default">;
 
+def enable_class_resilience : Flag<["-"], "enable-class-resilience">,
+   HelpText<"Compile the module to export resilient interfaces for all "
+            "public classes by default (doesn't work yet)">;
+
 def group_info_path : Separate<["-"], "group-info-path">,
   HelpText<"The path to collect the group information of the compiled module">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -787,6 +787,9 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
   Opts.EnableExperimentalNestedGenericTypes |=
     Args.hasArg(OPT_enable_experimental_nested_generic_types);
 
+  Opts.EnableClassResilience |=
+    Args.hasArg(OPT_enable_class_resilience);
+
   Opts.DisableAvailabilityChecking |=
       Args.hasArg(OPT_disable_availability_checking);
   if (FrontendOpts.InputKind == InputFileKind::IFK_SIL)

lib/IRGen/ClassMetadataLayout.h

@@ -88,7 +88,8 @@ template <class Impl> class ClassMetadataLayout : public MetadataLayout<Impl> {
       // Skip superclass fields if superclass is resilient.
       // FIXME: Needs runtime support to ensure the field offset vector is
       // populated correctly.
-      if (!IGM.isResilient(superclassDecl, ResilienceExpansion::Maximal)) {
+      if (!IGM.Context.LangOpts.EnableClassResilience ||
+          !IGM.isResilient(superclassDecl, ResilienceExpansion::Maximal)) {
         addClassMembers(superclassDecl, superclass);
       }
     }

lib/IRGen/GenClass.cpp

@@ -242,7 +242,16 @@ namespace {
 
           // If the superclass is resilient to us, we cannot statically
           // know the layout of either its instances or its class objects.
-          ClassHasFixedFieldCount = false;
+          //
+          // FIXME: We need to implement indirect field/vtable entry access
+          // before we can enable this
+          if (IGM.Context.LangOpts.EnableClassResilience) {
+            ClassHasFixedFieldCount = false;
+          } else {
+            addFieldsForClass(superclass, superclassType);
+            NumInherited = Elements.size();
+          }
+
           ClassHasFixedSize = false;
 
           // Furthermore, if the superclass is a generic context, we have to

test/IRGen/class_resilience.swift

@@ -1,5 +1,5 @@
-// RUN: %target-swift-frontend -I %S/../Inputs -enable-source-import -emit-ir -enable-resilience %s | %FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-%target-runtime
-// RUN: %target-swift-frontend -I %S/../Inputs -enable-source-import -emit-ir -enable-resilience -O %s
+// RUN: %target-swift-frontend -I %S/../Inputs -enable-source-import -emit-ir -enable-resilience -enable-class-resilience %s | %FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-%target-runtime
+// RUN: %target-swift-frontend -I %S/../Inputs -enable-source-import -emit-ir -enable-resilience -enable-class-resilience -O %s
 
 // CHECK: %swift.type = type { [[INT:i32|i64]] }