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LibJS: Add inline caching for adding new own properties to objects
We already had IC support in PutById for the following cases:
- Changing an existing own property
- Calling a setter located in the prototype chain
This was enough to speed up code where structurally identical objects
(same shape) are processed in a loop:
```js
const arr = [{ a: 1 }, { a: 2 }, { a: 3 }];
for (let obj of arr) {
obj.a += 1;
}
```
However, creating structurally identical objects in a loop was still
slow:
```js
for (let i = 0; i < 10_000_000; i++) {
const o = {};
o.a = 1;
o.b = 2;
o.c = 3;
}
```
This change addresses that by adding a new IC type that caches both the
source and target shapes, allowing property additions to be fast-pathed
by directly jumping to the shape that already includes the new property.
This commit is contained in:
Aliaksandr Kalenik
Andreas Kling
parent
a54215c07d
commit
d45f8a3081
Notes:
github-actions[bot]
2025-09-17 10:45:37 +00:00
Author: https://github.com/kalenikaliaksandr
Commit: d45f8a3081
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/6204
21 changed files with 162 additions and 75 deletions
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@ -1023,7 +1023,7 @@ inline ThrowCompletionOr<Value> get_by_id(VM& vm, Optional<IdentifierTableIndex>
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}
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}
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CacheablePropertyMetadata cacheable_metadata;
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CacheableGetPropertyMetadata cacheable_metadata;
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auto value = TRY(base_obj->internal_get(executable.get_identifier(property), this_value, &cacheable_metadata));
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// If internal_get() caused object's shape change, we can no longer be sure
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@ -1037,11 +1037,11 @@ inline ThrowCompletionOr<Value> get_by_id(VM& vm, Optional<IdentifierTableIndex>
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cache.entries[0] = {};
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return cache.entries[0];
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};
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if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
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if (cacheable_metadata.type == CacheableGetPropertyMetadata::Type::GetOwnProperty) {
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auto& entry = get_cache_slot();
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entry.shape = shape;
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entry.property_offset = cacheable_metadata.property_offset.value();
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} else if (cacheable_metadata.type == CacheablePropertyMetadata::Type::InPrototypeChain) {
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} else if (cacheable_metadata.type == CacheableGetPropertyMetadata::Type::GetPropertyInPrototypeChain) {
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auto& entry = get_cache_slot();
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entry.shape = &base_obj->shape();
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entry.property_offset = cacheable_metadata.property_offset.value();
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@ -1192,9 +1192,9 @@ inline ThrowCompletionOr<Value> get_global(Interpreter& interpreter, IdentifierT
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}
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if (TRY(binding_object.has_property(identifier))) {
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CacheablePropertyMetadata cacheable_metadata;
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CacheableGetPropertyMetadata cacheable_metadata;
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auto value = TRY(binding_object.internal_get(identifier, js_undefined(), &cacheable_metadata));
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if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
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if (cacheable_metadata.type == CacheableGetPropertyMetadata::Type::GetOwnProperty) {
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cache.entries[0].shape = shape;
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cache.entries[0].property_offset = cacheable_metadata.property_offset.value();
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}
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@ -1236,10 +1236,16 @@ inline ThrowCompletionOr<void> put_by_property_key(VM& vm, Value base, Value thi
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break;
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}
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case Op::PropertyKind::KeyValue: {
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auto& shape = object->shape();
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auto this_value_object = MUST(this_value.to_object(vm));
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auto& from_shape = this_value_object->shape();
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if (caches) {
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for (auto& cache : caches->entries) {
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if (cache.prototype) {
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switch (cache.type) {
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case PropertyLookupCache::Entry::Type::Empty:
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break;
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case PropertyLookupCache::Entry::Type::ChangePropertyInPrototypeChain: {
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if (!cache.prototype)
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break;
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// OPTIMIZATION: If the prototype chain hasn't been mutated in a way that would invalidate the cache, we can use it.
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bool can_use_cache = [&]() -> bool {
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if (&object->shape() != cache.shape)
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@ -1257,7 +1263,11 @@ inline ThrowCompletionOr<void> put_by_property_key(VM& vm, Value base, Value thi
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return {};
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}
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}
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} else if (cache.shape == &object->shape()) {
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break;
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}
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case PropertyLookupCache::Entry::Type::ChangeOwnProperty: {
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if (cache.shape != &object->shape())
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break;
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auto value_in_object = object->get_direct(cache.property_offset.value());
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if (value_in_object.is_accessor()) {
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TRY(call(vm, value_in_object.as_accessor().setter(), this_value, value));
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@ -1266,32 +1276,74 @@ inline ThrowCompletionOr<void> put_by_property_key(VM& vm, Value base, Value thi
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}
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return {};
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}
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case PropertyLookupCache::Entry::Type::AddOwnProperty: {
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// OPTIMIZATION: If the object's shape is the same as the one cached before adding the new property, we can
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// reuse the resulting shape from the cache.
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if (cache.from_shape != &object->shape())
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break;
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if (!cache.shape)
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break;
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// The cache is invalid if the prototype chain has been mutated, since such a mutation could have added a setter for the property.
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if (cache.prototype_chain_validity && !cache.prototype_chain_validity->is_valid())
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break;
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object->unsafe_set_shape(*cache.shape);
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object->put_direct(*cache.property_offset, value);
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return {};
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}
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default:
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VERIFY_NOT_REACHED();
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}
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}
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}
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CacheablePropertyMetadata cacheable_metadata;
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CacheableSetPropertyMetadata cacheable_metadata;
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bool succeeded = TRY(object->internal_set(name, value, this_value, &cacheable_metadata));
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auto get_cache_slot = [&] -> PropertyLookupCache::Entry& {
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for (size_t i = caches->entries.size() - 1; i >= 1; --i) {
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caches->entries[i] = caches->entries[i - 1];
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}
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caches->entries[0] = {};
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return caches->entries[0];
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};
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if (succeeded && caches && cacheable_metadata.type == CacheableSetPropertyMetadata::Type::AddOwnProperty) {
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auto& cache = get_cache_slot();
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cache.type = PropertyLookupCache::Entry::Type::AddOwnProperty;
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cache.from_shape = from_shape;
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cache.property_offset = cacheable_metadata.property_offset.value();
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cache.shape = &object->shape();
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if (cacheable_metadata.prototype) {
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cache.prototype_chain_validity = *cacheable_metadata.prototype->shape().prototype_chain_validity();
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}
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}
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// If internal_set() caused object's shape change, we can no longer be sure
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// that collected metadata is valid, e.g. if setter in prototype chain added
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// property with the same name into the object itself.
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if (succeeded && caches && &shape == &object->shape()) {
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auto get_cache_slot = [&] -> PropertyLookupCache::Entry& {
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for (size_t i = caches->entries.size() - 1; i >= 1; --i) {
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caches->entries[i] = caches->entries[i - 1];
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}
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caches->entries[0] = {};
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return caches->entries[0];
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};
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if (succeeded && caches && &from_shape == &object->shape()) {
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auto& cache = get_cache_slot();
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if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
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switch (cacheable_metadata.type) {
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case CacheableSetPropertyMetadata::Type::AddOwnProperty:
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// Something went wrong if we ended up here, because cacheable addition of a new property should've changed the shape.
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VERIFY_NOT_REACHED();
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break;
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case CacheableSetPropertyMetadata::Type::ChangeOwnProperty:
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cache.type = PropertyLookupCache::Entry::Type::ChangeOwnProperty;
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cache.shape = object->shape();
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cache.property_offset = cacheable_metadata.property_offset.value();
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} else if (cacheable_metadata.type == CacheablePropertyMetadata::Type::InPrototypeChain) {
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break;
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case CacheableSetPropertyMetadata::Type::ChangePropertyInPrototypeChain:
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cache.type = PropertyLookupCache::Entry::Type::ChangePropertyInPrototypeChain;
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cache.shape = object->shape();
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cache.property_offset = cacheable_metadata.property_offset.value();
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cache.prototype = *cacheable_metadata.prototype;
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cache.prototype_chain_validity = *cacheable_metadata.prototype->shape().prototype_chain_validity();
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break;
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case CacheableSetPropertyMetadata::Type::NotCacheable:
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break;
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default:
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VERIFY_NOT_REACHED();
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}
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}
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@ -2366,7 +2418,7 @@ ThrowCompletionOr<void> SetGlobal::execute_impl(Bytecode::Interpreter& interpret
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}
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if (TRY(binding_object.has_property(identifier))) {
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CacheablePropertyMetadata cacheable_metadata;
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CacheableSetPropertyMetadata cacheable_metadata;
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auto success = TRY(binding_object.internal_set(identifier, src, &binding_object, &cacheable_metadata));
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if (!success && vm.in_strict_mode()) {
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// Note: Nothing like this in the spec, this is here to produce nicer errors instead of the generic one thrown by Object::set().
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@ -2380,7 +2432,7 @@ ThrowCompletionOr<void> SetGlobal::execute_impl(Bytecode::Interpreter& interpret
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}
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return vm.throw_completion<TypeError>(ErrorType::ObjectSetReturnedFalse);
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}
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if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
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if (cacheable_metadata.type == CacheableSetPropertyMetadata::Type::ChangeOwnProperty) {
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cache.entries[0].shape = shape;
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cache.entries[0].property_offset = cacheable_metadata.property_offset.value();
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}
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