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LibJS: Implement generator functions (only in bytecode mode)
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21 changed files with 407 additions and 34 deletions
163
Userland/Libraries/LibJS/Runtime/GeneratorObject.cpp
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163
Userland/Libraries/LibJS/Runtime/GeneratorObject.cpp
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/*
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* Copyright (c) 2021, Ali Mohammad Pur <mpfard@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/TemporaryChange.h>
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#include <LibJS/Bytecode/Generator.h>
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#include <LibJS/Bytecode/Interpreter.h>
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#include <LibJS/Runtime/GeneratorObject.h>
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#include <LibJS/Runtime/GlobalObject.h>
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namespace JS {
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GeneratorObject* GeneratorObject::create(GlobalObject& global_object, Value initial_value, ScriptFunction* generating_function, ScopeObject* generating_scope, Bytecode::RegisterWindow frame)
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{
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auto object = global_object.heap().allocate<GeneratorObject>(global_object, global_object);
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object->m_generating_function = generating_function;
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object->m_scope = generating_scope;
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object->m_frame = move(frame);
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object->m_previous_value = initial_value;
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return object;
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}
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GeneratorObject::GeneratorObject(GlobalObject& global_object)
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: Object(*global_object.object_prototype())
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{
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}
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void GeneratorObject::initialize(GlobalObject& global_object)
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{
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auto& vm = this->vm();
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Object::initialize(global_object);
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define_native_function(vm.names.next, next);
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define_native_function(vm.names.return_, return_);
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define_native_function(vm.names.throw_, throw_);
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}
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GeneratorObject::~GeneratorObject()
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{
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}
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void GeneratorObject::visit_edges(Cell::Visitor& visitor)
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{
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Object::visit_edges(visitor);
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visitor.visit(m_scope);
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visitor.visit(m_generating_function);
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if (m_previous_value.is_object())
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visitor.visit(&m_previous_value.as_object());
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}
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GeneratorObject* GeneratorObject::typed_this(VM& vm, GlobalObject& global_object)
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{
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auto* this_object = vm.this_value(global_object).to_object(global_object);
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if (!this_object)
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return {};
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if (!is<GeneratorObject>(this_object)) {
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vm.throw_exception<TypeError>(global_object, ErrorType::NotA, "Generator");
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return nullptr;
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}
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return static_cast<GeneratorObject*>(this_object);
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}
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Value GeneratorObject::next_impl(VM& vm, GlobalObject& global_object, Optional<Value> value_to_throw)
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{
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auto bytecode_interpreter = Bytecode::Interpreter::current();
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VERIFY(bytecode_interpreter);
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auto generated_value = [](Value value) {
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if (value.is_object())
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return value.as_object().get("result");
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return value.is_empty() ? js_undefined() : value;
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};
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auto generated_continuation = [&](Value value) -> Bytecode::BasicBlock const* {
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if (value.is_object())
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return reinterpret_cast<Bytecode::BasicBlock const*>(static_cast<u64>(value.as_object().get("continuation").to_double(global_object)));
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return nullptr;
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};
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Value previous_generated_value { generated_value(m_previous_value) };
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if (vm.exception())
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return {};
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auto result = Object::create_empty(global_object);
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result->put("value", previous_generated_value);
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if (m_done) {
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result->put("done", Value(true));
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return result;
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}
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// Extract the continuation
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auto next_block = generated_continuation(m_previous_value);
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if (vm.exception())
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return {};
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if (!next_block) {
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// The generator has terminated, now we can simply return done=true.
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m_done = true;
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result->put("done", Value(true));
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return result;
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}
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// Make sure it's an actual block
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VERIFY(!m_generating_function->bytecode_executable()->basic_blocks.find_if([next_block](auto& block) { return block == next_block; }).is_end());
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// Restore the snapshot registers
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bytecode_interpreter->enter_frame(m_frame);
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// Pretend that 'yield' returned the passed value, or threw
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if (value_to_throw.has_value()) {
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vm.throw_exception(global_object, value_to_throw.release_value());
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bytecode_interpreter->accumulator() = js_undefined();
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} else {
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bytecode_interpreter->accumulator() = vm.argument(0);
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}
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// Temporarily switch to the captured scope
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TemporaryChange change { vm.call_frame().scope, m_scope };
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m_previous_value = bytecode_interpreter->run(*m_generating_function->bytecode_executable(), next_block);
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bytecode_interpreter->leave_frame();
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m_done = generated_continuation(m_previous_value) == nullptr;
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result->put("value", generated_value(m_previous_value));
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result->put("done", Value(m_done));
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if (vm.exception())
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return {};
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return result;
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}
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JS_DEFINE_NATIVE_FUNCTION(GeneratorObject::next)
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{
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auto object = typed_this(vm, global_object);
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if (!object)
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return {};
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return object->next_impl(vm, global_object, {});
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}
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JS_DEFINE_NATIVE_FUNCTION(GeneratorObject::return_)
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{
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auto object = typed_this(vm, global_object);
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if (!object)
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return {};
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object->m_done = true;
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return object->next_impl(vm, global_object, {});
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}
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JS_DEFINE_NATIVE_FUNCTION(GeneratorObject::throw_)
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{
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auto object = typed_this(vm, global_object);
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if (!object)
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return {};
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return object->next_impl(vm, global_object, vm.argument(0));
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}
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}
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