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LibJS: Make Object::internal_get() reveal the used property offset

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This function now takes an optional out parameter for callers who would
like to what kind of property we ended up getting.

This will be used to implement inline caching for property lookups.

Also, to prepare for adding more forms of caching, the out parameter
is a struct CacheablePropertyMetadata rather than just an offset. :^)
This commit is contained in:
Andreas Kling 2023-07-08 17:39:18 +02:00
parent babe924da1
commit 52cd671163
19 changed files with 58 additions and 28 deletions
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23
Userland/Libraries/LibJS/Runtime/Object.cpp
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@ -764,7 +764,7 @@ ThrowCompletionOr<Optional<PropertyDescriptor>> Object::internal_get_own_propert
PropertyDescriptor descriptor;
// 3. Let X be O's own property whose key is P.
auto [value, attributes] = *maybe_storage_entry;
auto [value, attributes, property_offset] = *maybe_storage_entry;
// 4. If X is a data property, then
if (!value.is_accessor()) {
@ -791,6 +791,9 @@ ThrowCompletionOr<Optional<PropertyDescriptor>> Object::internal_get_own_propert
// 7. Set D.[[Configurable]] to the value of X's [[Configurable]] attribute.
descriptor.configurable = attributes.is_configurable();
// Non-standard: Add the property offset to the descriptor. This is used to populate CacheablePropertyMetadata.
descriptor.property_offset = property_offset;
// 8. Return D.
return descriptor;
}
@ -836,7 +839,7 @@ ThrowCompletionOr<bool> Object::internal_has_property(PropertyKey const& propert
}
// 10.1.8 [[Get]] ( P, Receiver ), https://tc39.es/ecma262/#sec-ordinary-object-internal-methods-and-internal-slots-get-p-receiver
ThrowCompletionOr<Value> Object::internal_get(PropertyKey const& property_key, Value receiver) const
ThrowCompletionOr<Value> Object::internal_get(PropertyKey const& property_key, Value receiver, CacheablePropertyMetadata* cacheable_metadata) const
{
VERIFY(!receiver.is_empty());
VERIFY(property_key.is_valid());
@ -860,8 +863,16 @@ ThrowCompletionOr<Value> Object::internal_get(PropertyKey const& property_key, V
}
// 3. If IsDataDescriptor(desc) is true, return desc.[[Value]].
if (descriptor->is_data_descriptor())
if (descriptor->is_data_descriptor()) {
// Non-standard: If the caller has requested cacheable metadata and the property is an own property, fill it in.
if (cacheable_metadata && descriptor->property_offset.has_value()) {
*cacheable_metadata = CacheablePropertyMetadata {
.type = CacheablePropertyMetadata::Type::OwnProperty,
.property_offset = descriptor->property_offset.value(),
};
}
return *descriptor->value;
}
// 4. Assert: IsAccessorDescriptor(desc) is true.
VERIFY(descriptor->is_accessor_descriptor());
@ -1075,6 +1086,7 @@ Optional<ValueAndAttributes> Object::storage_get(PropertyKey const& property_key
Value value;
PropertyAttributes attributes;
Optional<u32> property_offset;
if (property_key.is_number()) {
auto value_and_attributes = m_indexed_properties.get(property_key.as_number());
@ -1094,9 +1106,10 @@ Optional<ValueAndAttributes> Object::storage_get(PropertyKey const& property_key
value = m_storage[metadata->offset];
attributes = metadata->attributes;
property_offset = metadata->offset;
}
return ValueAndAttributes { .value = value, .attributes = attributes };
return ValueAndAttributes { .value = value, .attributes = attributes, .property_offset = property_offset };
}
bool Object::storage_has(PropertyKey const& property_key) const
@ -1111,7 +1124,7 @@ void Object::storage_set(PropertyKey const& property_key, ValueAndAttributes con
{
VERIFY(property_key.is_valid());
auto [value, attributes] = value_and_attributes;
auto [value, attributes, _] = value_and_attributes;
if (property_key.is_number()) {
auto index = property_key.as_number();