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LibJS/Bytecode: Cache object own property accesses

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The instructions GetById and GetByIdWithThis now remember the last-seen
Shape, and if we see the same object again, we reuse the property offset
from last time without doing a new lookup.

This allows us to use Object::get_direct(), bypassing the entire lookup
machinery and saving lots of time.

~23% speed-up on Kraken/ai-astar.js :^)
This commit is contained in:
Andreas Kling 2023-07-08 17:43:26 +02:00
parent 52cd671163
commit de8e4b1853
8 changed files with 76 additions and 26 deletions
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32
Userland/Libraries/LibJS/Bytecode/Op.cpp
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@ -515,15 +515,19 @@ ThrowCompletionOr<void> SetLocal::execute_impl(Bytecode::Interpreter& interprete
return {};
}
static ThrowCompletionOr<void> get_by_id(Bytecode::Interpreter& interpreter, IdentifierTableIndex property, Value base_value, Value this_value)
static ThrowCompletionOr<void> get_by_id(Bytecode::Interpreter& interpreter, IdentifierTableIndex property, Value base_value, Value this_value, u32 cache_index)
{
auto& vm = interpreter.vm();
auto const& name = interpreter.current_executable().get_identifier(property);
auto& cache = interpreter.current_executable().property_lookup_caches[cache_index];
// OPTIMIZATION: For various primitives we can avoid actually creating a new object for them.
GCPtr<Object> base_obj;
if (base_value.is_string()) {
if (base_value.is_object()) {
// This would be covered by the `else` branch below,
// but let's avoid all the extra checks if it's already an object.
base_obj = base_value.as_object();
} else if (base_value.is_string()) {
auto string_value = TRY(base_value.as_string().get(vm, name));
if (string_value.has_value()) {
interpreter.accumulator() = *string_value;
@ -538,21 +542,37 @@ static ThrowCompletionOr<void> get_by_id(Bytecode::Interpreter& interpreter, Ide
base_obj = TRY(base_value.to_object(vm));
}
interpreter.accumulator() = TRY(base_obj->internal_get(name, this_value));
// OPTIMIZATION: If the shape of the object hasn't changed, we can use the cached property offset.
if (&base_obj->shape() == cache.shape) {
interpreter.accumulator() = base_obj->get_direct(cache.property_offset.value());
return {};
}
CacheablePropertyMetadata cacheable_metadata;
interpreter.accumulator() = TRY(base_obj->internal_get(name, this_value, &cacheable_metadata));
if (cacheable_metadata.type == CacheablePropertyMetadata::Type::OwnProperty) {
cache.shape = &base_obj->shape();
cache.property_offset = cacheable_metadata.property_offset.value();
} else {
cache.shape = nullptr;
cache.property_offset = {};
}
return {};
}
ThrowCompletionOr<void> GetById::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto base_value = interpreter.accumulator();
return get_by_id(interpreter, m_property, base_value, base_value);
return get_by_id(interpreter, m_property, base_value, base_value, m_cache_index);
}
ThrowCompletionOr<void> GetByIdWithThis::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto base_value = interpreter.accumulator();
auto this_value = interpreter.reg(m_this_value);
return get_by_id(interpreter, m_property, base_value, this_value);
return get_by_id(interpreter, m_property, base_value, this_value, m_cache_index);
}
ThrowCompletionOr<void> GetPrivateById::execute_impl(Bytecode::Interpreter& interpreter) const