[embedded] Lazily emit class metadata in embedded mode

Author: aschwaighofer

lib/IRGen/GenClass.cpp

@@ -1051,16 +1051,22 @@ void IRGenModule::emitClassDecl(ClassDecl *D) {
   auto &resilientLayout =
     classTI.getClassLayout(*this, selfType, /*forBackwardDeployment=*/false);
 
+  auto isEmbeddedWithExistentials =
+    Context.LangOpts.hasFeature(Feature::EmbeddedExistentials);
+
   // As a matter of policy, class metadata is never emitted lazily for now.
-  assert(!IRGen.hasLazyMetadata(D));
+  assert(isEmbeddedWithExistentials || !IRGen.hasLazyMetadata(D));
 
   // Emit the class metadata.
   if (!D->getASTContext().LangOpts.hasFeature(Feature::Embedded)) {
     emitClassMetadata(*this, D, fragileLayout, resilientLayout);
     emitFieldDescriptor(D);
   } else {
-    if (!D->isGenericContext()) {
-      emitEmbeddedClassMetadata(*this, D, fragileLayout);
+    if (!isEmbeddedWithExistentials && !D->isGenericContext()) {
+      emitEmbeddedClassMetadata(*this, D);
+    } else {
+      // We create all metadata lazyly in embedded with existentials mode.
+      return;
     }
   }
 

lib/IRGen/GenMeta.cpp

@@ -5398,6 +5398,7 @@ diagnoseUnsupportedObjCImplLayout(IRGenModule &IGM, ClassDecl *classDecl,
 void irgen::emitClassMetadata(IRGenModule &IGM, ClassDecl *classDecl,
                               const ClassLayout &fragileLayout,
                               const ClassLayout &resilientLayout) {
+
   assert(!classDecl->isForeign());
   PrettyStackTraceDecl stackTraceRAII("emitting metadata for", classDecl);
 
@@ -5565,8 +5566,7 @@ static void emitEmbeddedVTable(IRGenModule &IGM, CanType classTy,
   (void)var;
 }
 
-void irgen::emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *classDecl,
-                                      const ClassLayout &fragileLayout) {
+void irgen::emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *classDecl) {
   PrettyStackTraceDecl stackTraceRAII("emitting metadata for", classDecl);
   assert(!classDecl->isForeign());
   CanType declaredType = classDecl->getDeclaredType()->getCanonicalType();
@@ -5578,7 +5578,9 @@ void irgen::emitLazyClassMetadata(IRGenModule &IGM, CanType classTy) {
   // Might already be emitted, skip if that's the case.
   auto entity =
       LinkEntity::forTypeMetadata(classTy, TypeMetadataAddress::AddressPoint);
-  if (IGM.Context.LangOpts.hasFeature(Feature::EmbeddedExistentials)) {
+
+  auto isEmbeddedWithExistentials = IGM.Context.LangOpts.hasFeature(Feature::EmbeddedExistentials);
+  if (isEmbeddedWithExistentials) {
     entity = LinkEntity::forTypeMetadata(classTy, TypeMetadataAddress::FullMetadata);
   }
   auto *existingVar = cast<llvm::GlobalVariable>(
@@ -5587,6 +5589,11 @@ void irgen::emitLazyClassMetadata(IRGenModule &IGM, CanType classTy) {
     return;
   }
 
+  if (isEmbeddedWithExistentials) {
+    emitEmbeddedClassMetadata(IGM, classTy->getClassOrBoundGenericClass());
+    return;
+  }
+
   auto &context = classTy->getNominalOrBoundGenericNominal()->getASTContext();
   PrettyStackTraceType stackTraceRAII(
     context, "emitting lazy class metadata for", classTy);

lib/IRGen/GenMeta.h

@@ -61,8 +61,7 @@ namespace irgen {
 
   /// Emit "embedded Swift" class metadata (a simple vtable) for the given class
   /// declaration.
-  void emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *theClass,
-                                 const ClassLayout &fragileLayout);
+  void emitEmbeddedClassMetadata(IRGenModule &IGM, ClassDecl *theClass);
 
   /// Emit the constant initializer of the type metadata candidate for
   /// the given foreign class declaration.