[dict-proto] C++ implementation of SwissNameDictionary, pt. 7

This CL is part of a series that adds the C++ implementation of
SwissNameDictionary, a deterministic property backing store based on
Swiss Tables.

This CL adds an in-place version of Rehash and a small change to
HeapObject::HeapObjectShortPrint.

Bug: v8:11388
Change-Id: I578ef8f5638a6201111602ffef7f2d4a5a257bcd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2720305Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Frank Emrich <emrich@google.com>
Cr-Commit-Position: refs/heads/master@{#73099}

src/objects/objects.cc

@@ -1960,6 +1960,10 @@ void HeapObject::HeapObjectShortPrint(std::ostream& os) {  // NOLINT
     case NAME_DICTIONARY_TYPE:
       os << "<NameDictionary[" << FixedArray::cast(*this).length() << "]>";
       break;
+    case SWISS_NAME_DICTIONARY_TYPE:
+      os << "<SwissNameDictionary["
+         << SwissNameDictionary::cast(*this).Capacity() << "]>";
+      break;
     case GLOBAL_DICTIONARY_TYPE:
       os << "<GlobalDictionary[" << FixedArray::cast(*this).length() << "]>";
       break;
@@ -2351,6 +2355,7 @@ bool HeapObject::NeedsRehashing(InstanceType instance_type) const {
     case SMALL_ORDERED_HASH_MAP_TYPE:
     case SMALL_ORDERED_HASH_SET_TYPE:
     case SMALL_ORDERED_NAME_DICTIONARY_TYPE:
+    case SWISS_NAME_DICTIONARY_TYPE:
     case JS_MAP_TYPE:
     case JS_SET_TYPE:
       return true;
@@ -2374,6 +2379,7 @@ bool HeapObject::CanBeRehashed() const {
     case GLOBAL_DICTIONARY_TYPE:
     case NUMBER_DICTIONARY_TYPE:
     case SIMPLE_NUMBER_DICTIONARY_TYPE:
+    case SWISS_NAME_DICTIONARY_TYPE:
       return true;
     case DESCRIPTOR_ARRAY_TYPE:
     case STRONG_DESCRIPTOR_ARRAY_TYPE:
@@ -2399,6 +2405,9 @@ void HeapObject::RehashBasedOnMap(Isolate* isolate) {
     case NAME_DICTIONARY_TYPE:
       NameDictionary::cast(*this).Rehash(isolate);
       break;
+    case SWISS_NAME_DICTIONARY_TYPE:
+      SwissNameDictionary::cast(*this).Rehash(isolate);
+      break;
     case GLOBAL_DICTIONARY_TYPE:
       GlobalDictionary::cast(*this).Rehash(isolate);
       break;

src/objects/swiss-name-dictionary.cc

@@ -94,6 +94,60 @@ Handle<SwissNameDictionary> SwissNameDictionary::Shrink(
   return Rehash(isolate, table, new_capacity);
 }
 
+// TODO(v8::11388) Copying all data into a std::vector and then re-adding into
+// the table doesn't seem like a good algorithm. Abseil's Swiss Tables come with
+// a clever algorithm for re-hashing in place: It first changes the control
+// table, effectively changing the roles of full, empty and deleted buckets. It
+// then moves each entry to its new bucket by swapping entries (see
+// drop_deletes_without_resize in Abseil's raw_hash_set.h). This algorithm could
+// generally adapted to work on our insertion order preserving implementation,
+// too. However, it would require a mapping from hash table buckets back to
+// enumeration indices. This could either be be created in this function
+// (requiring a vector with Capacity() entries and a separate pass over the
+// enumeration table) or by creating this backwards mapping ahead of time and
+// storing it somewhere in the main table or the meta table, for those
+// SwissNameDictionaries that we know will be in-place rehashed, most notably
+// those stored in the snapshot.
+void SwissNameDictionary::Rehash(Isolate* isolate) {
+  DisallowHeapAllocation no_gc;
+
+  struct Entry {
+    Name key;
+    Object value;
+    PropertyDetails details;
+  };
+
+  if (Capacity() == 0) return;
+
+  Entry dummy{Name(), Object(), PropertyDetails::Empty()};
+  std::vector<Entry> data(NumberOfElements(), dummy);
+
+  ReadOnlyRoots roots(isolate);
+  int data_index = 0;
+  for (int enum_index = 0; enum_index < UsedCapacity(); ++enum_index) {
+    int entry = EntryForEnumerationIndex(enum_index);
+    Object key;
+    if (!ToKey(roots, entry, &key)) continue;
+
+    data[data_index++] =
+        Entry{Name::cast(key), ValueAtRaw(entry), DetailsAt(entry)};
+  }
+
+  Initialize(isolate, meta_table(), Capacity());
+
+  int new_enum_index = 0;
+  SetNumberOfElements(static_cast<int>(data.size()));
+  for (Entry& e : data) {
+    int new_entry = AddInternal(e.key, e.value, e.details);
+
+    // TODO(v8::11388) Investigate ways of hoisting the branching needed to
+    // select the correct meta table entry size (based on the capacity of the
+    // table) out of the loop.
+    SetEntryForEnumerationIndex(new_enum_index, new_entry);
+    ++new_enum_index;
+  }
+}
+
 // The largest value we ever have to store in the enumeration table is
 // Capacity() - 1. The largest value we ever have to store for the present or
 // deleted element count is MaxUsableCapacity(Capacity()). All data in the

src/objects/swiss-name-dictionary.h

@@ -119,6 +119,7 @@ class SwissNameDictionary : public HeapObject {
   static Handle<SwissNameDictionary> Rehash(LocalIsolate* isolate,
                                             Handle<SwissNameDictionary> table,
                                             int new_capacity);
+  void Rehash(Isolate* isolate);
 
   inline void SetHash(int hash);
   inline int Hash();