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LibJS: Make async functions & generators faster with helper types

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Instead of returning internal generator results as ordinary JS::Objects
with properties, we now use GeneratorResult and CompletionCell which
both inherit from Cell directly and allow efficient access to state.

1.59x speedup on JetStream3/lazy-collections.js :^)
This commit is contained in:
Andreas Kling 2025-03-31 09:32:39 +01:00 • committed by Alexander Kalenik
commit a0bb31f7a0
Notes: github-actions[bot] 2025-04-01 00:31:35 +00:00
12 changed files with 259 additions and 93 deletions
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25
Libraries/LibJS/Runtime/AsyncGenerator.cpp
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@ -8,7 +8,9 @@
#include <LibJS/Runtime/AsyncGenerator.h>
#include <LibJS/Runtime/AsyncGeneratorPrototype.h>
#include <LibJS/Runtime/AsyncGeneratorRequest.h>
#include <LibJS/Runtime/CompletionCell.h>
#include <LibJS/Runtime/ECMAScriptFunctionObject.h>
#include <LibJS/Runtime/GeneratorResult.h>
#include <LibJS/Runtime/GlobalObject.h>
#include <LibJS/Runtime/PromiseConstructor.h>
@ -155,15 +157,15 @@ void AsyncGenerator::execute(VM& vm, Completion completion)
// Loosely based on step 4 of https://tc39.es/ecma262/#sec-asyncgeneratorstart
VERIFY(completion.value().has_value());
auto generated_value = [&vm](Value value) -> Value {
if (value.is_object())
return value.as_object().get_without_side_effects(vm.names.result);
auto generated_value = [](Value value) -> Value {
if (value.is_cell())
return static_cast<GeneratorResult const&>(value.as_cell()).result();
return value.is_empty() ? js_undefined() : value;
};
auto generated_continuation = [&](Value value) -> Optional<size_t> {
if (value.is_object()) {
auto number_value = value.as_object().get_without_side_effects(vm.names.continuation);
if (value.is_cell()) {
auto number_value = static_cast<GeneratorResult const&>(value.as_cell()).continuation();
if (number_value.is_null())
return {};
return static_cast<size_t>(number_value.as_double());
@ -171,16 +173,13 @@ void AsyncGenerator::execute(VM& vm, Completion completion)
return {};
};
auto generated_is_await = [&vm](Value value) -> bool {
if (value.is_object())
return value.as_object().get_without_side_effects(vm.names.isAwait).as_bool();
auto generated_is_await = [](Value value) -> bool {
if (value.is_cell())
return static_cast<GeneratorResult const&>(value.as_cell()).is_await();
return false;
};
auto& realm = *vm.current_realm();
auto completion_object = Object::create(realm, nullptr);
completion_object->define_direct_property(vm.names.type, Value(to_underlying(completion.type())), default_attributes);
completion_object->define_direct_property(vm.names.value, completion.value().value(), default_attributes);
auto completion_cell = heap().allocate<CompletionCell>(completion);
auto& bytecode_interpreter = vm.bytecode_interpreter();
@ -189,7 +188,7 @@ void AsyncGenerator::execute(VM& vm, Completion completion)
// We should never enter `execute` again after the generator is complete.
VERIFY(continuation_address.has_value());
auto next_result = bytecode_interpreter.run_executable(*m_generating_function->bytecode_executable(), continuation_address, completion_object);
auto next_result = bytecode_interpreter.run_executable(*m_generating_function->bytecode_executable(), continuation_address, completion_cell);
auto result_value = move(next_result.value);
if (!result_value.is_throw_completion()) {