Merge pull request #3266 from swiftix/relative-pointers-fixes

Remove copy constructors and assignment operators from RelativeDirectPointerImpl

Author: swiftix

include/swift/Basic/RelativePointer.h

@@ -276,6 +276,15 @@ class RelativeDirectPointerImpl {
   /// RelativePointers should appear in statically-generated metadata. They
   /// shouldn't be constructed or copied.
   RelativeDirectPointerImpl() = delete;
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeDirectPointerImpl(RelativeDirectPointerImpl &&) = delete;
+  RelativeDirectPointerImpl(const RelativeDirectPointerImpl &) = delete;
+  RelativeDirectPointerImpl &operator=(RelativeDirectPointerImpl &&)
+    = delete;
+  RelativeDirectPointerImpl &operator=(const RelativeDirectPointerImpl &)
+    = delete;
+
 
 public:
   using ValueTy = T;
@@ -305,12 +314,6 @@ class RelativeDirectPointerImpl {
       : detail::measureRelativeOffset<Offset>(absolute, this);
     return *this;
   }
-  
-  // Can copy-construct by recalculating the relative offset at the new
-  // position.
-  RelativeDirectPointerImpl(const RelativeDirectPointerImpl &p) {
-    *this = p.get();
-  }
 
   PointerTy get() const & {
     // Check for null.

include/swift/Runtime/Metadata.h

@@ -25,6 +25,7 @@
 #include <string>
 #include <type_traits>
 #include <utility>
+#include <string.h>
 #include "swift/Runtime/Config.h"
 #include "swift/ABI/MetadataValues.h"
 #include "swift/ABI/System.h"
@@ -1089,6 +1090,13 @@ template <typename Runtime> struct TargetOpaqueMetadata;
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Winvalid-offsetof"
 
+extern uint64_t RelativeDirectPointerNullPtr;
+
+#define RelativeDirectPointerNullPtrRef                                        \
+  *reinterpret_cast<ConstTargetFarRelativeDirectPointer<                       \
+      Runtime, TargetNominalTypeDescriptor, /*nullable*/ true> *>(             \
+      &RelativeDirectPointerNullPtr)
+
 /// The common structure of all type metadata.
 template <typename Runtime>
 struct TargetMetadata {
@@ -1221,16 +1229,17 @@ struct TargetMetadata {
 
   /// Get the nominal type descriptor if this metadata describes a nominal type,
   /// or return null if it does not.
-  ConstTargetFarRelativeDirectPointer<Runtime, TargetNominalTypeDescriptor,
-                                      /*nullable*/ true>
+  const ConstTargetFarRelativeDirectPointer<Runtime,
+                                            TargetNominalTypeDescriptor,
+                                            /*nullable*/ true> &
   getNominalTypeDescriptor() const {
     switch (getKind()) {
     case MetadataKind::Class: {
       const auto cls = static_cast<const TargetClassMetadata<Runtime> *>(this);
       if (!cls->isTypeMetadata())
-        return 0;
+        return RelativeDirectPointerNullPtrRef;
       if (cls->isArtificialSubclass())
-        return 0;
+        return RelativeDirectPointerNullPtrRef;
       return cls->getDescription();
     }
     case MetadataKind::Struct:
@@ -1248,7 +1257,7 @@ struct TargetMetadata {
     case MetadataKind::HeapLocalVariable:
     case MetadataKind::HeapGenericLocalVariable:
     case MetadataKind::ErrorObject:
-      return 0;
+      return RelativeDirectPointerNullPtrRef;
     }
   }
 
@@ -1559,6 +1568,11 @@ struct TargetClassMetadata : public TargetHeapMetadata<Runtime> {
       Reserved(0), ClassSize(classSize), ClassAddressPoint(classAddressPoint),
       Description(nullptr), IVarDestroyer(ivarDestroyer) {}
 
+  TargetClassMetadata(const TargetClassMetadata& other): Description(other.getDescription().get()) {
+    memcpy(this, &other, sizeof(*this));
+    setDescription(other.getDescription().get());
+  }
+
   /// The metadata for the superclass.  This is null for the root class.
   ConstTargetMetadataPointer<Runtime, swift::TargetClassMetadata> SuperClass;
 
@@ -1634,8 +1648,10 @@ struct TargetClassMetadata : public TargetHeapMetadata<Runtime> {
   //   - "tabulated" virtual methods
 
 public:
-  ConstTargetFarRelativeDirectPointer<Runtime, TargetNominalTypeDescriptor,
-  /*nullable*/ true> getDescription() const {
+  const ConstTargetFarRelativeDirectPointer<Runtime,
+                                            TargetNominalTypeDescriptor,
+                                            /*nullable*/ true> &
+  getDescription() const {
     assert(isTypeMetadata());
     assert(!isArtificialSubclass());
     return Description;

stdlib/public/runtime/Metadata.cpp

@@ -1576,7 +1576,7 @@ static ClassMetadata *_swift_initializeSuperclass(ClassMetadata *theClass,
   auto *classWords = reinterpret_cast<uintptr_t *>(theClass);
   auto *superWords = reinterpret_cast<const uintptr_t *>(theSuperclass);
   while (ancestor && ancestor->isTypeMetadata()) {
-    auto description = ancestor->getDescription();
+    auto &description = ancestor->getDescription();
     auto &genericParams = description->GenericParams;
 
     // Copy the parent type.
@@ -2486,7 +2486,7 @@ swift::swift_getForeignTypeMetadata(ForeignTypeMetadata *nonUnique) {
 
 template<> const GenericMetadata *
 Metadata::getGenericPattern() const {
-  auto ntd = getNominalTypeDescriptor();
+  auto &ntd = getNominalTypeDescriptor();
   if (!ntd)
     return nullptr;
   return ntd->getGenericMetadataPattern();
@@ -2713,3 +2713,5 @@ swift::swift_getGenericWitnessTable(GenericWitnessTable *genericTable,
 
   return entry->get(genericTable);
 }
+
+uint64_t swift::RelativeDirectPointerNullPtr = 0;

stdlib/public/runtime/ProtocolConformance.cpp

@@ -65,7 +65,7 @@ template<> void ProtocolConformanceRecord::dump() const {
       printf("%s direct type ",
              kind == TypeMetadataRecordKind::UniqueDirectType
              ? "unique" : "nonunique");
-      if (auto ntd = getDirectType()->getNominalTypeDescriptor()) {
+      if (auto &ntd = getDirectType()->getNominalTypeDescriptor()) {
         printf("%s", ntd->Name.get());
       } else {
         printf("<structural type>");