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LibJS/Bytecode: Add dedicated instruction for getting length property

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By doing this, we can remove all the special-case checks for `length`
from the generic GetById and GetByIdWithThis code paths, making every
other property lookup a bit faster.

Small progressions on most benchmarks, and some larger progressions:

- 12% on Octane/crypto.js
- 6% on Kraken/ai-astar.js
This commit is contained in:
Andreas Kling 2024-05-20 11:53:28 +02:00
commit 448b7ca87b
Notes: sideshowbarker 2024-07-18 02:47:59 +09:00
5 changed files with 124 additions and 7 deletions
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22
Userland/Libraries/LibJS/Bytecode/CommonImplementations.h
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@ -103,19 +103,27 @@ ALWAYS_INLINE ThrowCompletionOr<NonnullGCPtr<Object>> base_object_for_get(VM& vm
return throw_null_or_undefined_property_access(vm, base_value, base_identifier, property_identifier);
}
enum class GetByIdMode {
Normal,
Length,
};
template<GetByIdMode mode = GetByIdMode::Normal>
inline ThrowCompletionOr<Value> get_by_id(VM& vm, Optional<DeprecatedFlyString const&> const& base_identifier, DeprecatedFlyString const& property, Value base_value, Value this_value, PropertyLookupCache& cache)
{
if (base_value.is_string()) {
auto string_value = TRY(base_value.as_string().get(vm, property));
if (string_value.has_value())
return *string_value;
if constexpr (mode == GetByIdMode::Length) {
if (base_value.is_string()) {
return Value(base_value.as_string().utf16_string().length_in_code_units());
}
}
auto base_obj = TRY(base_object_for_get(vm, base_value, base_identifier, property));
// OPTIMIZATION: Fast path for the magical "length" property on Array objects.
if (base_obj->has_magical_length_property() && property == vm.names.length.as_string()) {
return Value { base_obj->indexed_properties().array_like_size() };
if constexpr (mode == GetByIdMode::Length) {
// OPTIMIZATION: Fast path for the magical "length" property on Array objects.
if (base_obj->has_magical_length_property()) {
return Value { base_obj->indexed_properties().array_like_size() };
}
}
auto& shape = base_obj->shape();