Commit 342f6621 authored by Frank Emrich's avatar Frank Emrich Committed by Commit Bot

[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: 's avatarIgor Sheludko <ishell@chromium.org>
Reviewed-by: 's avatarMarja Hölttä <marja@chromium.org>
Commit-Queue: Frank Emrich <emrich@google.com>
Cr-Commit-Position: refs/heads/master@{#73099}
parent ea5ba5db
...@@ -1960,6 +1960,10 @@ void HeapObject::HeapObjectShortPrint(std::ostream& os) { // NOLINT ...@@ -1960,6 +1960,10 @@ void HeapObject::HeapObjectShortPrint(std::ostream& os) { // NOLINT
case NAME_DICTIONARY_TYPE: case NAME_DICTIONARY_TYPE:
os << "<NameDictionary[" << FixedArray::cast(*this).length() << "]>"; os << "<NameDictionary[" << FixedArray::cast(*this).length() << "]>";
break; break;
case SWISS_NAME_DICTIONARY_TYPE:
os << "<SwissNameDictionary["
<< SwissNameDictionary::cast(*this).Capacity() << "]>";
break;
case GLOBAL_DICTIONARY_TYPE: case GLOBAL_DICTIONARY_TYPE:
os << "<GlobalDictionary[" << FixedArray::cast(*this).length() << "]>"; os << "<GlobalDictionary[" << FixedArray::cast(*this).length() << "]>";
break; break;
...@@ -2351,6 +2355,7 @@ bool HeapObject::NeedsRehashing(InstanceType instance_type) const { ...@@ -2351,6 +2355,7 @@ bool HeapObject::NeedsRehashing(InstanceType instance_type) const {
case SMALL_ORDERED_HASH_MAP_TYPE: case SMALL_ORDERED_HASH_MAP_TYPE:
case SMALL_ORDERED_HASH_SET_TYPE: case SMALL_ORDERED_HASH_SET_TYPE:
case SMALL_ORDERED_NAME_DICTIONARY_TYPE: case SMALL_ORDERED_NAME_DICTIONARY_TYPE:
case SWISS_NAME_DICTIONARY_TYPE:
case JS_MAP_TYPE: case JS_MAP_TYPE:
case JS_SET_TYPE: case JS_SET_TYPE:
return true; return true;
...@@ -2374,6 +2379,7 @@ bool HeapObject::CanBeRehashed() const { ...@@ -2374,6 +2379,7 @@ bool HeapObject::CanBeRehashed() const {
case GLOBAL_DICTIONARY_TYPE: case GLOBAL_DICTIONARY_TYPE:
case NUMBER_DICTIONARY_TYPE: case NUMBER_DICTIONARY_TYPE:
case SIMPLE_NUMBER_DICTIONARY_TYPE: case SIMPLE_NUMBER_DICTIONARY_TYPE:
case SWISS_NAME_DICTIONARY_TYPE:
return true; return true;
case DESCRIPTOR_ARRAY_TYPE: case DESCRIPTOR_ARRAY_TYPE:
case STRONG_DESCRIPTOR_ARRAY_TYPE: case STRONG_DESCRIPTOR_ARRAY_TYPE:
...@@ -2399,6 +2405,9 @@ void HeapObject::RehashBasedOnMap(Isolate* isolate) { ...@@ -2399,6 +2405,9 @@ void HeapObject::RehashBasedOnMap(Isolate* isolate) {
case NAME_DICTIONARY_TYPE: case NAME_DICTIONARY_TYPE:
NameDictionary::cast(*this).Rehash(isolate); NameDictionary::cast(*this).Rehash(isolate);
break; break;
case SWISS_NAME_DICTIONARY_TYPE:
SwissNameDictionary::cast(*this).Rehash(isolate);
break;
case GLOBAL_DICTIONARY_TYPE: case GLOBAL_DICTIONARY_TYPE:
GlobalDictionary::cast(*this).Rehash(isolate); GlobalDictionary::cast(*this).Rehash(isolate);
break; break;
......
...@@ -94,6 +94,60 @@ Handle<SwissNameDictionary> SwissNameDictionary::Shrink( ...@@ -94,6 +94,60 @@ Handle<SwissNameDictionary> SwissNameDictionary::Shrink(
return Rehash(isolate, table, new_capacity); 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 // 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 // Capacity() - 1. The largest value we ever have to store for the present or
// deleted element count is MaxUsableCapacity(Capacity()). All data in the // deleted element count is MaxUsableCapacity(Capacity()). All data in the
......
...@@ -119,6 +119,7 @@ class SwissNameDictionary : public HeapObject { ...@@ -119,6 +119,7 @@ class SwissNameDictionary : public HeapObject {
static Handle<SwissNameDictionary> Rehash(LocalIsolate* isolate, static Handle<SwissNameDictionary> Rehash(LocalIsolate* isolate,
Handle<SwissNameDictionary> table, Handle<SwissNameDictionary> table,
int new_capacity); int new_capacity);
void Rehash(Isolate* isolate);
inline void SetHash(int hash); inline void SetHash(int hash);
inline int Hash(); inline int Hash();
......
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