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LibJS: Use [[likely]] annotations for cached environment lookups

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These will generally be cached the vast majority of the time except on
first encounter, and sprinkling [[likely]] gives us a nice boost.

1.10x speed-up on this micro-benchmark:

    (() => {
        var a = 3;
        for (let i = 0; i < 100_000_000; ++i) { a; }
        eval("");
    })();
This commit is contained in:
Andreas Kling 2025-10-07 16:37:22 +02:00 • committed by Jelle Raaijmakers
commit d0df7c8c62
Notes: github-actions[bot] 2025-10-07 21:52:01 +00:00
1 changed files with 9 additions and 9 deletions
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18
Libraries/LibJS/Bytecode/Interpreter.cpp
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@ -1536,11 +1536,11 @@ inline ThrowCompletionOr<CalleeAndThis> get_callee_and_this_from_environment(Byt
Value callee = js_undefined(); Value callee = js_undefined();
Value this_value = js_undefined(); Value this_value = js_undefined();
if (cache.is_valid()) { if (cache.is_valid()) [[likely]] {
auto const* environment = interpreter.running_execution_context().lexical_environment.ptr(); auto const* environment = interpreter.running_execution_context().lexical_environment.ptr();
for (size_t i = 0; i < cache.hops; ++i) for (size_t i = 0; i < cache.hops; ++i)
environment = environment->outer_environment(); environment = environment->outer_environment();
if (!environment->is_permanently_screwed_by_eval()) { if (!environment->is_permanently_screwed_by_eval()) [[likely]] {
callee = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, cache.index)); callee = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, cache.index));
this_value = js_undefined(); this_value = js_undefined();
if (auto base_object = environment->with_base_object()) if (auto base_object = environment->with_base_object())
@ -2297,13 +2297,12 @@ template<BindingIsKnownToBeInitialized binding_is_known_to_be_initialized>
static ThrowCompletionOr<void> get_binding(Interpreter& interpreter, Operand dst, IdentifierTableIndex identifier, EnvironmentCoordinate& cache) static ThrowCompletionOr<void> get_binding(Interpreter& interpreter, Operand dst, IdentifierTableIndex identifier, EnvironmentCoordinate& cache)
{ {
auto& vm = interpreter.vm(); auto& vm = interpreter.vm();
auto& executable = interpreter.current_executable();
if (cache.is_valid()) { if (cache.is_valid()) [[likely]] {
auto const* environment = interpreter.running_execution_context().lexical_environment.ptr(); auto const* environment = interpreter.running_execution_context().lexical_environment.ptr();
for (size_t i = 0; i < cache.hops; ++i) for (size_t i = 0; i < cache.hops; ++i)
environment = environment->outer_environment(); environment = environment->outer_environment();
if (!environment->is_permanently_screwed_by_eval()) { if (!environment->is_permanently_screwed_by_eval()) [[likely]] {
Value value; Value value;
if constexpr (binding_is_known_to_be_initialized == BindingIsKnownToBeInitialized::No) { if constexpr (binding_is_known_to_be_initialized == BindingIsKnownToBeInitialized::No) {
value = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, cache.index)); value = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, cache.index));
@ -2316,6 +2315,7 @@ static ThrowCompletionOr<void> get_binding(Interpreter& interpreter, Operand dst
cache = {}; cache = {};
} }
auto& executable = interpreter.current_executable();
auto reference = TRY(vm.resolve_binding(executable.get_identifier(identifier))); auto reference = TRY(vm.resolve_binding(executable.get_identifier(identifier)));
if (reference.environment_coordinate().has_value()) if (reference.environment_coordinate().has_value())
cache = reference.environment_coordinate().value(); cache = reference.environment_coordinate().value();
@ -2554,10 +2554,10 @@ static ThrowCompletionOr<void> initialize_or_set_binding(Interpreter& interprete
? interpreter.running_execution_context().lexical_environment.ptr() ? interpreter.running_execution_context().lexical_environment.ptr()
: interpreter.running_execution_context().variable_environment.ptr(); : interpreter.running_execution_context().variable_environment.ptr();
if (cache.is_valid()) { if (cache.is_valid()) [[likely]] {
for (size_t i = 0; i < cache.hops; ++i) for (size_t i = 0; i < cache.hops; ++i)
environment = environment->outer_environment(); environment = environment->outer_environment();
if (!environment->is_permanently_screwed_by_eval()) { if (!environment->is_permanently_screwed_by_eval()) [[likely]] {
if constexpr (initialization_mode == BindingInitializationMode::Initialize) { if constexpr (initialization_mode == BindingInitializationMode::Initialize) {
TRY(static_cast<DeclarativeEnvironment&>(*environment).initialize_binding_direct(vm, cache.index, value, Environment::InitializeBindingHint::Normal)); TRY(static_cast<DeclarativeEnvironment&>(*environment).initialize_binding_direct(vm, cache.index, value, Environment::InitializeBindingHint::Normal));
} else { } else {
@ -3349,11 +3349,11 @@ ThrowCompletionOr<void> TypeofBinding::execute_impl(Bytecode::Interpreter& inter
{ {
auto& vm = interpreter.vm(); auto& vm = interpreter.vm();
if (m_cache.is_valid()) { if (m_cache.is_valid()) [[likely]] {
auto const* environment = interpreter.running_execution_context().lexical_environment.ptr(); auto const* environment = interpreter.running_execution_context().lexical_environment.ptr();
for (size_t i = 0; i < m_cache.hops; ++i) for (size_t i = 0; i < m_cache.hops; ++i)
environment = environment->outer_environment(); environment = environment->outer_environment();
if (!environment->is_permanently_screwed_by_eval()) { if (!environment->is_permanently_screwed_by_eval()) [[likely]] {
auto value = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, m_cache.index)); auto value = TRY(static_cast<DeclarativeEnvironment const&>(*environment).get_binding_value_direct(vm, m_cache.index));
interpreter.set(dst(), value.typeof_(vm)); interpreter.set(dst(), value.typeof_(vm));
return {}; return {};