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LibJS: Move most of Interpreter into VM

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This patch moves the exception state, call stack and scope stack from
Interpreter to VM. I'm doing this to help myself discover what the
split between Interpreter and VM should be, by shuffling things around
and seeing what falls where.

With these changes, we no longer have a persistent lexical environment
for the current global object on the Interpreter's call stack. Instead,
we push/pop that environment on Interpreter::run() enter/exit.
Since it should only be used to find the global "this", and not for
variable storage (that goes directly into the global object instead!),
I had to insert some short-circuiting when walking the environment
parent chain during variable lookup.

Note that this is a "stepping stone" commit, not a final design.
This commit is contained in:
Andreas Kling 2020-09-27 15:18:55 +02:00
parent 838d9fa251
commit 6861c619c6
48 changed files with 765 additions and 726 deletions
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313
Libraries/LibJS/Interpreter.cpp
View file

@ -56,272 +56,22 @@ Interpreter::~Interpreter()
Value Interpreter::run(GlobalObject& global_object, const Program& program)
{
VM::InterpreterExecutionScope scope(*this);
ASSERT(!exception());
if (m_call_stack.is_empty()) {
CallFrame global_call_frame;
global_call_frame.this_value = &global_object;
global_call_frame.function_name = "(global execution context)";
global_call_frame.environment = heap().allocate<LexicalEnvironment>(global_object, LexicalEnvironment::EnvironmentRecordType::Global);
global_call_frame.environment->bind_this_value(&global_object);
if (exception())
return {};
m_call_stack.append(move(global_call_frame));
}
return program.execute(*this, global_object);
}
Value Interpreter::execute_statement(GlobalObject& global_object, const Statement& statement, ArgumentVector arguments, ScopeType scope_type)
{
if (!statement.is_scope_node())
return statement.execute(*this, global_object);
auto& block = static_cast<const ScopeNode&>(statement);
enter_scope(block, move(arguments), scope_type, global_object);
if (block.children().is_empty())
m_last_value = js_undefined();
for (auto& node : block.children()) {
m_last_value = node.execute(*this, global_object);
if (should_unwind()) {
if (!block.label().is_null() && should_unwind_until(ScopeType::Breakable, block.label()))
stop_unwind();
break;
}
}
bool did_return = m_unwind_until == ScopeType::Function;
if (m_unwind_until == scope_type)
m_unwind_until = ScopeType::None;
exit_scope(block);
return did_return ? m_last_value : js_undefined();
}
void Interpreter::enter_scope(const ScopeNode& scope_node, ArgumentVector arguments, ScopeType scope_type, GlobalObject& global_object)
{
for (auto& declaration : scope_node.functions()) {
auto* function = ScriptFunction::create(global_object, declaration.name(), declaration.body(), declaration.parameters(), declaration.function_length(), current_environment());
set_variable(declaration.name(), function, global_object);
}
if (scope_type == ScopeType::Function) {
m_scope_stack.append({ scope_type, scope_node, false });
return;
}
HashMap<FlyString, Variable> scope_variables_with_declaration_kind;
scope_variables_with_declaration_kind.ensure_capacity(16);
for (auto& declaration : scope_node.variables()) {
for (auto& declarator : declaration.declarations()) {
if (scope_node.is_program()) {
global_object.put(declarator.id().string(), js_undefined());
if (exception())
return;
} else {
scope_variables_with_declaration_kind.set(declarator.id().string(), { js_undefined(), declaration.declaration_kind() });
}
}
}
for (auto& argument : arguments) {
scope_variables_with_declaration_kind.set(argument.name, { argument.value, DeclarationKind::Var });
}
bool pushed_lexical_environment = false;
if (!scope_variables_with_declaration_kind.is_empty()) {
auto* block_lexical_environment = heap().allocate<LexicalEnvironment>(global_object, move(scope_variables_with_declaration_kind), current_environment());
m_call_stack.last().environment = block_lexical_environment;
pushed_lexical_environment = true;
}
m_scope_stack.append({ scope_type, scope_node, pushed_lexical_environment });
}
void Interpreter::exit_scope(const ScopeNode& scope_node)
{
while (!m_scope_stack.is_empty()) {
auto popped_scope = m_scope_stack.take_last();
if (popped_scope.pushed_environment)
m_call_stack.last().environment = m_call_stack.last().environment->parent();
if (popped_scope.scope_node.ptr() == &scope_node)
break;
}
// If we unwind all the way, just reset m_unwind_until so that future "return" doesn't break.
if (m_scope_stack.is_empty())
m_unwind_until = ScopeType::None;
}
void Interpreter::set_variable(const FlyString& name, Value value, GlobalObject& global_object, bool first_assignment)
{
if (m_call_stack.size()) {
for (auto* environment = current_environment(); environment; environment = environment->parent()) {
auto possible_match = environment->get(name);
if (possible_match.has_value()) {
if (!first_assignment && possible_match.value().declaration_kind == DeclarationKind::Const) {
throw_exception<TypeError>(ErrorType::InvalidAssignToConst);
return;
}
environment->set(name, { value, possible_match.value().declaration_kind });
return;
}
}
}
global_object.put(move(name), move(value));
}
Value Interpreter::get_variable(const FlyString& name, GlobalObject& global_object)
{
if (m_call_stack.size()) {
for (auto* environment = current_environment(); environment; environment = environment->parent()) {
auto possible_match = environment->get(name);
if (possible_match.has_value())
return possible_match.value().value;
}
}
auto value = global_object.get(name);
if (m_underscore_is_last_value && name == "_" && value.is_empty())
return m_last_value;
return value;
}
Reference Interpreter::get_reference(const FlyString& name)
{
if (m_call_stack.size()) {
for (auto* environment = current_environment(); environment; environment = environment->parent()) {
auto possible_match = environment->get(name);
if (possible_match.has_value())
return { Reference::LocalVariable, name };
}
}
return { Reference::GlobalVariable, name };
}
void Interpreter::gather_roots(HashTable<Cell*>& roots)
{
if (m_last_value.is_cell())
roots.set(m_last_value.as_cell());
for (auto& call_frame : m_call_stack) {
if (call_frame.this_value.is_cell())
roots.set(call_frame.this_value.as_cell());
for (auto& argument : call_frame.arguments) {
if (argument.is_cell())
roots.set(argument.as_cell());
}
roots.set(call_frame.environment);
}
}
Value Interpreter::call_internal(Function& function, Value this_value, Optional<MarkedValueList> arguments)
{
ASSERT(!exception());
ASSERT(!vm().exception());
VM::InterpreterExecutionScope scope(*this);
auto& call_frame = push_call_frame();
call_frame.function_name = function.name();
call_frame.this_value = function.bound_this().value_or(this_value);
call_frame.arguments = function.bound_arguments();
if (arguments.has_value())
call_frame.arguments.append(arguments.value().values());
call_frame.environment = function.create_environment();
ASSERT(call_frame.environment->this_binding_status() == LexicalEnvironment::ThisBindingStatus::Uninitialized);
call_frame.environment->bind_this_value(call_frame.this_value);
auto result = function.call(*this);
pop_call_frame();
return result;
}
Value Interpreter::construct(Function& function, Function& new_target, Optional<MarkedValueList> arguments, GlobalObject& global_object)
{
auto& call_frame = push_call_frame();
call_frame.function_name = function.name();
call_frame.arguments = function.bound_arguments();
if (arguments.has_value())
call_frame.arguments.append(arguments.value().values());
call_frame.environment = function.create_environment();
current_environment()->set_new_target(&new_target);
Object* new_object = nullptr;
if (function.constructor_kind() == Function::ConstructorKind::Base) {
new_object = Object::create_empty(global_object);
current_environment()->bind_this_value(new_object);
if (exception())
return {};
auto prototype = new_target.get("prototype");
if (exception())
return {};
if (prototype.is_object()) {
new_object->set_prototype(&prototype.as_object());
if (exception())
return {};
}
}
// If we are a Derived constructor, |this| has not been constructed before super is called.
Value this_value = function.constructor_kind() == Function::ConstructorKind::Base ? new_object : Value {};
call_frame.this_value = this_value;
auto result = function.construct(*this, new_target);
this_value = current_environment()->get_this_binding();
pop_call_frame();
// If we are constructing an instance of a derived class,
// set the prototype on objects created by constructors that return an object (i.e. NativeFunction subclasses).
if (function.constructor_kind() == Function::ConstructorKind::Base && new_target.constructor_kind() == Function::ConstructorKind::Derived && result.is_object()) {
current_environment()->replace_this_binding(result);
auto prototype = new_target.get("prototype");
if (exception())
return {};
if (prototype.is_object()) {
result.as_object().set_prototype(&prototype.as_object());
if (exception())
return {};
}
return result;
}
if (exception())
CallFrame global_call_frame;
global_call_frame.this_value = &global_object;
global_call_frame.function_name = "(global execution context)";
global_call_frame.environment = heap().allocate<LexicalEnvironment>(global_object, LexicalEnvironment::EnvironmentRecordType::Global);
global_call_frame.environment->bind_this_value(&global_object);
if (vm().exception())
return {};
vm().call_stack().append(move(global_call_frame));
if (result.is_object())
return result;
return this_value;
}
void Interpreter::throw_exception(Exception* exception)
{
#ifdef INTERPRETER_DEBUG
if (exception->value().is_object() && exception->value().as_object().is_error()) {
auto& error = static_cast<Error&>(exception->value().as_object());
dbg() << "Throwing JavaScript Error: " << error.name() << ", " << error.message();
for (ssize_t i = m_call_stack.size() - 1; i >= 0; --i) {
auto function_name = m_call_stack[i].function_name;
if (function_name.is_empty())
function_name = "<anonymous>";
dbg() << " " << function_name;
}
}
#endif
vm().set_exception({}, exception);
unwind(ScopeType::Try);
auto result = program.execute(*this, global_object);
vm().pop_call_frame();
return result;
}
GlobalObject& Interpreter::global_object()
@ -334,35 +84,26 @@ const GlobalObject& Interpreter::global_object() const
return static_cast<const GlobalObject&>(*m_global_object.cell());
}
String Interpreter::join_arguments() const
Value Interpreter::call_internal(Function& function, Value this_value, Optional<MarkedValueList> arguments)
{
StringBuilder joined_arguments;
for (size_t i = 0; i < argument_count(); ++i) {
joined_arguments.append(argument(i).to_string_without_side_effects().characters());
if (i != argument_count() - 1)
joined_arguments.append(' ');
}
return joined_arguments.build();
}
ASSERT(!exception());
Value Interpreter::resolve_this_binding() const
{
return get_this_environment()->get_this_binding();
}
VM::InterpreterExecutionScope scope(*this);
const LexicalEnvironment* Interpreter::get_this_environment() const
{
// We will always return because the Global environment will always be reached, which has a |this| binding.
for (const LexicalEnvironment* environment = current_environment(); environment; environment = environment->parent()) {
if (environment->has_this_binding())
return environment;
}
ASSERT_NOT_REACHED();
}
auto& call_frame = vm().push_call_frame();
call_frame.function_name = function.name();
call_frame.this_value = function.bound_this().value_or(this_value);
call_frame.arguments = function.bound_arguments();
if (arguments.has_value())
call_frame.arguments.append(arguments.value().values());
call_frame.environment = function.create_environment();
Value Interpreter::get_new_target() const
{
return get_this_environment()->new_target();
ASSERT(call_frame.environment->this_binding_status() == LexicalEnvironment::ThisBindingStatus::Uninitialized);
call_frame.environment->bind_this_value(call_frame.this_value);
auto result = function.call(*this);
vm().pop_call_frame();
return result;
}
}