Sema: Try harder not to page in all members of imported classes

Author: slavapestov

include/swift/AST/Decl.h

@@ -543,7 +543,7 @@ class alignas(1 << DeclAlignInBits) Decl {
     NumRequirementsInSignature : 16
   );
 
-  SWIFT_INLINE_BITFIELD(ClassDecl, NominalTypeDecl, 2+1+2+1+7+1+1+1+1,
+  SWIFT_INLINE_BITFIELD(ClassDecl, NominalTypeDecl, 2+1+2+1+7+1+1+1+1+1+1,
     /// The stage of the inheritance circularity check for this class.
     Circularity : 2,
 
@@ -557,7 +557,10 @@ class alignas(1 << DeclAlignInBits) Decl {
     HasForcedEmittedMembers : 1,     
 
     HasMissingDesignatedInitializers : 1,
+    ComputedHasMissingDesignatedInitializers : 1,
+
     HasMissingVTableEntries : 1,
+    ComputedHasMissingVTableEntries : 1,
 
     /// Whether instances of this class are incompatible
     /// with weak and unowned references.
@@ -3879,6 +3882,7 @@ class ClassDecl final : public NominalTypeDecl {
   bool hasMissingDesignatedInitializers() const;
 
   void setHasMissingDesignatedInitializers(bool newValue = true) {
+    Bits.ClassDecl.ComputedHasMissingDesignatedInitializers = 1;
     Bits.ClassDecl.HasMissingDesignatedInitializers = newValue;
   }
 
@@ -3889,6 +3893,7 @@ class ClassDecl final : public NominalTypeDecl {
   bool hasMissingVTableEntries() const;
 
   void setHasMissingVTableEntries(bool newValue = true) {
+    Bits.ClassDecl.ComputedHasMissingVTableEntries = 1;
     Bits.ClassDecl.HasMissingVTableEntries = newValue;
   }
 

lib/AST/Decl.cpp

@@ -3816,7 +3816,9 @@ ClassDecl::ClassDecl(SourceLoc ClassLoc, Identifier Name, SourceLoc NameLoc,
   Bits.ClassDecl.InheritsSuperclassInits = 0;
   Bits.ClassDecl.RawForeignKind = 0;
   Bits.ClassDecl.HasMissingDesignatedInitializers = 0;
+  Bits.ClassDecl.ComputedHasMissingDesignatedInitializers = 0;
   Bits.ClassDecl.HasMissingVTableEntries = 0;
+  Bits.ClassDecl.ComputedHasMissingVTableEntries = 0;
   Bits.ClassDecl.IsIncompatibleWithWeakReferences = 0;
 }
 
@@ -3901,16 +3903,25 @@ GetDestructorRequest::evaluate(Evaluator &evaluator, ClassDecl *CD) const {
 
 
 bool ClassDecl::hasMissingDesignatedInitializers() const {
-  auto *mutableThis = const_cast<ClassDecl *>(this);
-  auto flags = OptionSet<LookupDirectFlags>();
-  flags |= LookupDirectFlags::IgnoreNewExtensions;
-  (void)mutableThis->lookupDirect(DeclBaseName::createConstructor(),
-                                  flags);
+  if (!Bits.ClassDecl.ComputedHasMissingDesignatedInitializers) {
+    auto *mutableThis = const_cast<ClassDecl *>(this);
+    mutableThis->Bits.ClassDecl.ComputedHasMissingDesignatedInitializers = 1;
+    auto flags = OptionSet<LookupDirectFlags>();
+    flags |= LookupDirectFlags::IgnoreNewExtensions;
+    (void)mutableThis->lookupDirect(DeclBaseName::createConstructor(),
+                                    flags);
+  }
+
   return Bits.ClassDecl.HasMissingDesignatedInitializers;
 }
 
 bool ClassDecl::hasMissingVTableEntries() const {
-  (void)getMembers();
+  if (!Bits.ClassDecl.ComputedHasMissingVTableEntries) {
+    auto *mutableThis = const_cast<ClassDecl *>(this);
+    mutableThis->Bits.ClassDecl.ComputedHasMissingVTableEntries = 1;
+    mutableThis->loadAllMembers();
+  }
+
   return Bits.ClassDecl.HasMissingVTableEntries;
 }
 

lib/ClangImporter/ImportDecl.cpp

@@ -4736,6 +4736,7 @@ namespace {
         result->setCircularityCheck(CircularityCheck::Checked);
         result->setSuperclass(Type());
         result->setAddedImplicitInitializers(); // suppress all initializers
+        result->setHasMissingVTableEntries(false);
         addObjCAttribute(result, Impl.importIdentifier(decl->getIdentifier()));
         return result;
       };
@@ -4903,6 +4904,7 @@ namespace {
       if (decl->isArcWeakrefUnavailable())
         result->setIsIncompatibleWithWeakReferences();
 
+      result->setHasMissingVTableEntries(false);
       result->setMemberLoader(&Impl, 0);
 
       return result;
@@ -5314,6 +5316,7 @@ SwiftDeclConverter::importCFClassType(const clang::TypedefNameDecl *decl,
   theClass->setCircularityCheck(CircularityCheck::Checked);
   theClass->setSuperclass(superclass);
   theClass->setAddedImplicitInitializers(); // suppress all initializers
+  theClass->setHasMissingVTableEntries(false);
   theClass->setForeignClassKind(ClassDecl::ForeignKind::CFType);
   addObjCAttribute(theClass, None);
 

lib/Parse/ParseDecl.cpp

@@ -6119,6 +6119,9 @@ ParserResult<ClassDecl> Parser::parseDeclClass(ParseDeclOptions Flags,
   setLocalDiscriminator(CD);
   CD->getAttrs() = Attributes;
 
+  // Parsed classes never have missing vtable entries.
+  CD->setHasMissingVTableEntries(false);
+
   ContextChange CC(*this, CD);
 
   // Parse optional inheritance clause within the context of the class.

lib/Sema/CodeSynthesis.cpp

@@ -833,7 +833,7 @@ void TypeChecker::addImplicitConstructors(NominalTypeDecl *decl) {
 
   // Bail out if we're validating one of our constructors or stored properties
   // already; we'll revisit the issue later.
-  if (isa<ClassDecl>(decl)) {
+  if (isa<ClassDecl>(decl) && !decl->hasClangNode()) {
     for (auto member : decl->getMembers()) {
       if (auto ctor = dyn_cast<ConstructorDecl>(member)) {
         validateDecl(ctor);

lib/Sema/TypeCheckDecl.cpp

@@ -2756,6 +2756,9 @@ class DeclChecker : public DeclVisitor<DeclChecker> {
     // we're doing here.
     CD->walkSuperclasses(
       [&](ClassDecl *superclass) {
+        if (!superclass->getParentSourceFile())
+          return TypeWalker::Action::Stop;
+
         for (auto *member : superclass->getMembers()) {
           if (auto *vd = dyn_cast<ValueDecl>(member)) {
             if (vd->isPotentiallyOverridable()) {