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LibJS: Do a single pass to prune non-enumerable keys for iteration

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Instead of pruning as-we-go, which means a ton of hash lookups,
we now only do a single pass to prune all non-enumerable keys when
setting up for for..in iteration.
This commit is contained in:
Andreas Kling 2025-03-19 17:08:24 -05:00 • committed by Andreas Kling
parent 660d533b50
commit 37bf083536
Notes: github-actions[bot] 2025-03-20 17:52:38 +00:00
1 changed files with 44 additions and 14 deletions
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58
Libraries/LibJS/Bytecode/Interpreter.cpp
View file

@ -37,6 +37,30 @@
#include <LibJS/Runtime/ValueInlines.h>
#include <LibJS/SourceTextModule.h>
namespace JS {
struct PropertyKeyAndEnumerableFlag {
JS::PropertyKey key;
bool enumerable { false };
};
}
namespace AK {
template<>
struct Traits<JS::PropertyKeyAndEnumerableFlag> : public DefaultTraits<JS::PropertyKeyAndEnumerableFlag> {
static unsigned hash(JS::PropertyKeyAndEnumerableFlag const& entry)
{
return Traits<JS::PropertyKey>::hash(entry.key);
}
static bool equals(JS::PropertyKeyAndEnumerableFlag const& a, JS::PropertyKeyAndEnumerableFlag const& b)
{
return Traits<JS::PropertyKey>::equals(a.key, b.key);
}
};
}
namespace JS::Bytecode {
bool g_dump_bytecode = false;
@ -1713,8 +1737,8 @@ inline ThrowCompletionOr<Object*> get_object_property_iterator(VM& vm, Value val
auto object = TRY(value.to_object(vm));
// Note: While the spec doesn't explicitly require these to be ordered, it says that the values should be retrieved via OwnPropertyKeys,
// so we just keep the order consistent anyway.
OrderedHashTable<PropertyKey> properties;
OrderedHashTable<PropertyKey> non_enumerable_properties;
OrderedHashTable<PropertyKeyAndEnumerableFlag> properties;
HashTable<GC::Ref<Object>> seen_objects;
// Collect all keys immediately (invariant no. 5)
for (auto object_to_check = GC::Ptr { object.ptr() }; object_to_check && !seen_objects.contains(*object_to_check); object_to_check = TRY(object_to_check->internal_get_prototype_of())) {
@ -1722,24 +1746,30 @@ inline ThrowCompletionOr<Object*> get_object_property_iterator(VM& vm, Value val
for (auto& key : TRY(object_to_check->internal_own_property_keys())) {
if (key.is_symbol())
continue;
auto property_key = TRY(PropertyKey::from_value(vm, key));
// If there is a non-enumerable property higher up the prototype chain with the same key,
// we mustn't include this property even if it's enumerable (invariant no. 5 and 6)
if (non_enumerable_properties.contains(property_key))
continue;
if (properties.contains(property_key))
// NOTE: If there is a non-enumerable property higher up the prototype chain with the same key,
// we mustn't include this property even if it's enumerable (invariant no. 5 and 6)
// This is achieved with the PropertyKeyAndEnumerableFlag struct, which doesn't consider
// the enumerable flag when comparing keys.
PropertyKeyAndEnumerableFlag new_entry {
.key = TRY(PropertyKey::from_value(vm, key)),
.enumerable = false,
};
if (properties.contains(new_entry))
continue;
auto descriptor = TRY(object_to_check->internal_get_own_property(property_key));
auto descriptor = TRY(object_to_check->internal_get_own_property(new_entry.key));
if (!descriptor.has_value())
continue;
if (!*descriptor->enumerable)
non_enumerable_properties.set(move(property_key));
else
properties.set(move(property_key));
new_entry.enumerable = *descriptor->enumerable;
properties.set(move(new_entry), AK::HashSetExistingEntryBehavior::Keep);
}
}
properties.remove_all_matching([&](auto& entry) { return !entry.enumerable; });
auto& realm = *vm.current_realm();
auto callback = NativeFunction::create(
*vm.current_realm(), [items = move(properties)](VM& vm) mutable -> ThrowCompletionOr<Value> {
@ -1756,7 +1786,7 @@ inline ThrowCompletionOr<Object*> get_object_property_iterator(VM& vm, Value val
return result_object;
}
auto key = items.take_first();
auto key = move(items.take_first().key);
// If the property is deleted, don't include it (invariant no. 2)
if (!TRY(iterated_object.has_property(key)))