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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <LibJS/AST.h>
#include <LibJS/Bytecode/BasicBlock.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Op.h>
#include <LibJS/Bytecode/Register.h>
namespace JS::Bytecode {
Generator::Generator()
: m_string_table(make<StringTable>())
, m_identifier_table(make<IdentifierTable>())
{
}
CodeGenerationErrorOr<NonnullOwnPtr<Executable>> Generator::generate(ASTNode const& node, FunctionKind enclosing_function_kind)
{
Generator generator;
generator.switch_to_basic_block(generator.make_block());
generator.m_enclosing_function_kind = enclosing_function_kind;
if (generator.is_in_generator_or_async_function()) {
// Immediately yield with no value.
auto& start_block = generator.make_block();
generator.emit<Bytecode::Op::Yield>(Label { start_block });
generator.switch_to_basic_block(start_block);
}
TRY(node.generate_bytecode(generator));
if (generator.is_in_generator_or_async_function()) {
// Terminate all unterminated blocks with yield return
for (auto& block : generator.m_root_basic_blocks) {
if (block.is_terminated())
continue;
generator.switch_to_basic_block(block);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::Yield>(nullptr);
}
}
return adopt_own(*new Executable {
.name = {},
.basic_blocks = move(generator.m_root_basic_blocks),
.string_table = move(generator.m_string_table),
.identifier_table = move(generator.m_identifier_table),
.number_of_registers = generator.m_next_register });
}
void Generator::grow(size_t additional_size)
{
VERIFY(m_current_basic_block);
m_current_basic_block->grow(additional_size);
}
void* Generator::next_slot()
{
VERIFY(m_current_basic_block);
return m_current_basic_block->next_slot();
}
Register Generator::allocate_register()
{
VERIFY(m_next_register != NumericLimits<u32>::max());
return Register { m_next_register++ };
}
Label Generator::nearest_continuable_scope() const
{
return m_continuable_scopes.last();
}
void Generator::begin_variable_scope(BindingMode mode, SurroundingScopeKind kind)
{
m_variable_scopes.append({ kind, mode, {} });
if (mode != BindingMode::Global) {
start_boundary(mode == BindingMode::Lexical ? BlockBoundaryType::LeaveLexicalEnvironment : BlockBoundaryType::LeaveVariableEnvironment);
emit<Bytecode::Op::CreateEnvironment>(
mode == BindingMode::Lexical
? Bytecode::Op::EnvironmentMode::Lexical
: Bytecode::Op::EnvironmentMode::Var);
}
}
void Generator::end_variable_scope()
{
auto mode = m_variable_scopes.take_last().mode;
if (mode != BindingMode::Global) {
end_boundary(mode == BindingMode::Lexical ? BlockBoundaryType::LeaveLexicalEnvironment : BlockBoundaryType::LeaveVariableEnvironment);
if (!m_current_basic_block->is_terminated()) {
emit<Bytecode::Op::LeaveEnvironment>(
mode == BindingMode::Lexical
? Bytecode::Op::EnvironmentMode::Lexical
: Bytecode::Op::EnvironmentMode::Var);
}
}
}
void Generator::begin_continuable_scope(Label continue_target)
{
m_continuable_scopes.append(continue_target);
start_boundary(BlockBoundaryType::Continue);
}
void Generator::end_continuable_scope()
{
m_continuable_scopes.take_last();
end_boundary(BlockBoundaryType::Continue);
}
Label Generator::nearest_breakable_scope() const
{
return m_breakable_scopes.last();
}
void Generator::begin_breakable_scope(Label breakable_target)
{
m_breakable_scopes.append(breakable_target);
start_boundary(BlockBoundaryType::Break);
}
void Generator::end_breakable_scope()
{
m_breakable_scopes.take_last();
end_boundary(BlockBoundaryType::Break);
}
CodeGenerationErrorOr<void> Generator::emit_load_from_reference(JS::ASTNode const& node)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
emit<Bytecode::Op::GetVariable>(intern_identifier(identifier.string()));
return {};
}
if (is<MemberExpression>(node)) {
auto& expression = static_cast<MemberExpression const&>(node);
TRY(expression.object().generate_bytecode(*this));
auto object_reg = allocate_register();
emit<Bytecode::Op::Store>(object_reg);
if (expression.is_computed()) {
TRY(expression.property().generate_bytecode(*this));
emit<Bytecode::Op::GetByValue>(object_reg);
} else if (expression.property().is_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::GetById>(identifier_table_ref);
} else {
return CodeGenerationError {
&expression,
"Unimplemented non-computed member expression"sv
};
}
return {};
}
VERIFY_NOT_REACHED();
}
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(JS::ASTNode const& node)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
emit<Bytecode::Op::SetVariable>(intern_identifier(identifier.string()));
return {};
}
if (is<MemberExpression>(node)) {
// NOTE: The value is in the accumulator, so we have to store that away first.
auto value_reg = allocate_register();
emit<Bytecode::Op::Store>(value_reg);
auto& expression = static_cast<MemberExpression const&>(node);
TRY(expression.object().generate_bytecode(*this));
auto object_reg = allocate_register();
emit<Bytecode::Op::Store>(object_reg);
if (expression.is_computed()) {
TRY(expression.property().generate_bytecode(*this));
auto property_reg = allocate_register();
emit<Bytecode::Op::Store>(property_reg);
emit<Bytecode::Op::Load>(value_reg);
emit<Bytecode::Op::PutByValue>(object_reg, property_reg);
} else if (expression.property().is_identifier()) {
emit<Bytecode::Op::Load>(value_reg);
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::PutById>(object_reg, identifier_table_ref);
} else {
return CodeGenerationError {
&expression,
"Unimplemented non-computed member expression"sv
};
}
return {};
}
VERIFY_NOT_REACHED();
}
String CodeGenerationError::to_string()
{
return String::formatted("CodeGenerationError in {}: {}", failing_node ? failing_node->class_name() : "<unknown node>", reason_literal);
}
}
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