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ladybird/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
Luke Wilde 125a71d36d LibJS/Bytecode: Define named functions as a variable inside their scope 
This allows you to recurse into a named function that is stored in a
variable. For example, this would previously print "wrong" instead of
"right":
```js
function g() { console.log("wrong") }
f = function g(i) { if (i !== 1) g(1); else console.log("right"); }
f()
```
2022-06-13 07:13:03 +04:30

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/*
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
* Copyright (c) 2021, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
* Copyright (c) 2021, Marcin Gasperowicz <xnooga@gmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Format.h>
#include <LibJS/AST.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Op.h>
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Bytecode/StringTable.h>
#include <LibJS/Runtime/Environment.h>
namespace JS {
Bytecode::CodeGenerationErrorOr<void> ASTNode::generate_bytecode(Bytecode::Generator&) const
{
return Bytecode::CodeGenerationError {
this,
"Missing generate_bytecode()"sv,
};
}
Bytecode::CodeGenerationErrorOr<void> ScopeNode::generate_bytecode(Bytecode::Generator& generator) const
{
Optional<Bytecode::CodeGenerationError> maybe_error;
size_t pushed_scope_count = 0;
auto const failing_completion = Completion(Completion::Type::Throw, {}, {});
// Note: SwitchStatement has its own codegen, but still calls into this function to handle the scoping of the switch body.
auto is_switch_statement = is<SwitchStatement>(*this);
if (is<BlockStatement>(*this) || is_switch_statement) {
// Perform the steps of BlockDeclarationInstantiation.
if (has_lexical_declarations()) {
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Block);
pushed_scope_count++;
}
(void)for_each_lexically_scoped_declaration([&](Declaration const& declaration) -> ThrowCompletionOr<void> {
auto is_constant_declaration = declaration.is_constant_declaration();
declaration.for_each_bound_name([&](auto const& name) {
auto index = generator.intern_identifier(name);
if (is_constant_declaration || !generator.has_binding(index)) {
generator.register_binding(index);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Lexical, is_constant_declaration);
}
});
if (is<FunctionDeclaration>(declaration)) {
auto& function_declaration = static_cast<FunctionDeclaration const&>(declaration);
auto const& name = function_declaration.name();
auto index = generator.intern_identifier(name);
generator.emit<Bytecode::Op::NewFunction>(function_declaration);
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::InitializeOrSet);
}
return {};
});
if (is_switch_statement)
return {};
} else if (is<Program>(*this)) {
// Perform the steps of GlobalDeclarationInstantiation.
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Global, Bytecode::Generator::SurroundingScopeKind::Global);
pushed_scope_count++;
// 1. Let lexNames be the LexicallyDeclaredNames of script.
// 2. Let varNames be the VarDeclaredNames of script.
// 3. For each element name of lexNames, do
(void)for_each_lexically_declared_name([&](auto const& name) -> ThrowCompletionOr<void> {
auto identifier = generator.intern_identifier(name);
// a. If env.HasVarDeclaration(name) is true, throw a SyntaxError exception.
// b. If env.HasLexicalDeclaration(name) is true, throw a SyntaxError exception.
if (generator.has_binding(identifier)) {
// FIXME: Throw an actual SyntaxError instance.
generator.emit<Bytecode::Op::NewString>(generator.intern_string(String::formatted("SyntaxError: toplevel variable already declared: {}", name)));
generator.emit<Bytecode::Op::Throw>();
return {};
}
// FIXME: c. If hasRestrictedGlobalProperty is true, throw a SyntaxError exception.
// d. If hasRestrictedGlobal is true, throw a SyntaxError exception.
return {};
});
// 4. For each element name of varNames, do
(void)for_each_var_declared_name([&](auto const& name) -> ThrowCompletionOr<void> {
auto identifier = generator.intern_identifier(name);
// a. If env.HasLexicalDeclaration(name) is true, throw a SyntaxError exception.
if (generator.has_binding(identifier)) {
// FIXME: Throw an actual SyntaxError instance.
generator.emit<Bytecode::Op::NewString>(generator.intern_string(String::formatted("SyntaxError: toplevel variable already declared: {}", name)));
generator.emit<Bytecode::Op::Throw>();
}
return {};
});
// 5. Let varDeclarations be the VarScopedDeclarations of script.
// 6. Let functionsToInitialize be a new empty List.
Vector<FunctionDeclaration const&> functions_to_initialize;
// 7. Let declaredFunctionNames be a new empty List.
HashTable<FlyString> declared_function_names;
// 8. For each element d of varDeclarations, in reverse List order, do
(void)for_each_var_function_declaration_in_reverse_order([&](FunctionDeclaration const& function) -> ThrowCompletionOr<void> {
// a. If d is neither a VariableDeclaration nor a ForBinding nor a BindingIdentifier, then
// i. Assert: d is either a FunctionDeclaration, a GeneratorDeclaration, an AsyncFunctionDeclaration, or an AsyncGeneratorDeclaration.
// Note: This is checked in for_each_var_function_declaration_in_reverse_order.
// ii. NOTE: If there are multiple function declarations for the same name, the last declaration is used.
// iii. Let fn be the sole element of the BoundNames of d.
// iv. If fn is not an element of declaredFunctionNames, then
if (declared_function_names.set(function.name()) != AK::HashSetResult::InsertedNewEntry)
return {};
// FIXME: 1. Let fnDefinable be ? env.CanDeclareGlobalFunction(fn).
// FIXME: 2. If fnDefinable is false, throw a TypeError exception.
// 3. Append fn to declaredFunctionNames.
// Note: Already done in step iv. above.
// 4. Insert d as the first element of functionsToInitialize.
functions_to_initialize.prepend(function);
return {};
});
// 9. Let declaredVarNames be a new empty List.
HashTable<FlyString> declared_var_names;
// 10. For each element d of varDeclarations, do
(void)for_each_var_scoped_variable_declaration([&](Declaration const& declaration) {
// a. If d is a VariableDeclaration, a ForBinding, or a BindingIdentifier, then
// Note: This is done in for_each_var_scoped_variable_declaration.
// i. For each String vn of the BoundNames of d, do
return declaration.for_each_bound_name([&](auto const& name) -> ThrowCompletionOr<void> {
// 1. If vn is not an element of declaredFunctionNames, then
if (declared_function_names.contains(name))
return {};
// FIXME: a. Let vnDefinable be ? env.CanDeclareGlobalVar(vn).
// FIXME: b. If vnDefinable is false, throw a TypeError exception.
// c. If vn is not an element of declaredVarNames, then
// i. Append vn to declaredVarNames.
declared_var_names.set(name);
return {};
});
});
// 11. NOTE: No abnormal terminations occur after this algorithm step if the global object is an ordinary object. However, if the global object is a Proxy exotic object it may exhibit behaviours that cause abnormal terminations in some of the following steps.
// 12. NOTE: Annex B.3.2.2 adds additional steps at this point.
// 12. Let strict be IsStrict of script.
// 13. If strict is false, then
if (!verify_cast<Program>(*this).is_strict_mode()) {
// a. Let declaredFunctionOrVarNames be the list-concatenation of declaredFunctionNames and declaredVarNames.
// b. For each FunctionDeclaration f that is directly contained in the StatementList of a Block, CaseClause, or DefaultClause Contained within script, do
(void)for_each_function_hoistable_with_annexB_extension([&](FunctionDeclaration& function_declaration) {
// i. Let F be StringValue of the BindingIdentifier of f.
auto& function_name = function_declaration.name();
// ii. If replacing the FunctionDeclaration f with a VariableStatement that has F as a BindingIdentifier would not produce any Early Errors for script, then
// Note: This step is already performed during parsing and for_each_function_hoistable_with_annexB_extension so this always passes here.
// 1. If env.HasLexicalDeclaration(F) is false, then
auto index = generator.intern_identifier(function_name);
if (generator.has_binding(index, Bytecode::Generator::BindingMode::Lexical))
return;
// FIXME: a. Let fnDefinable be ? env.CanDeclareGlobalVar(F).
// b. If fnDefinable is true, then
// i. NOTE: A var binding for F is only instantiated here if it is neither a VarDeclaredName nor the name of another FunctionDeclaration.
// ii. If declaredFunctionOrVarNames does not contain F, then
if (!declared_function_names.contains(function_name) && !declared_var_names.contains(function_name)) {
// i. Perform ? env.CreateGlobalVarBinding(F, false).
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Var, false);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::Initialize, Bytecode::Op::EnvironmentMode::Var);
// ii. Append F to declaredFunctionOrVarNames.
declared_function_names.set(function_name);
}
// iii. When the FunctionDeclaration f is evaluated, perform the following steps in place of the FunctionDeclaration Evaluation algorithm provided in 15.2.6:
// i. Let genv be the running execution context's VariableEnvironment.
// ii. Let benv be the running execution context's LexicalEnvironment.
// iii. Let fobj be ! benv.GetBindingValue(F, false).
// iv. Perform ? genv.SetMutableBinding(F, fobj, false).
// v. Return unused.
function_declaration.set_should_do_additional_annexB_steps();
});
}
// 15. For each element d of lexDeclarations, do
(void)for_each_lexically_scoped_declaration([&](Declaration const& declaration) -> ThrowCompletionOr<void> {
// a. NOTE: Lexically declared names are only instantiated here but not initialized.
// b. For each element dn of the BoundNames of d, do
return declaration.for_each_bound_name([&](auto const& name) -> ThrowCompletionOr<void> {
auto identifier = generator.intern_identifier(name);
// i. If IsConstantDeclaration of d is true, then
generator.register_binding(identifier);
if (declaration.is_constant_declaration()) {
// 1. Perform ? env.CreateImmutableBinding(dn, true).
generator.emit<Bytecode::Op::CreateVariable>(identifier, Bytecode::Op::EnvironmentMode::Lexical, true);
} else {
// ii. Else,
// 1. Perform ? env.CreateMutableBinding(dn, false).
generator.emit<Bytecode::Op::CreateVariable>(identifier, Bytecode::Op::EnvironmentMode::Lexical, false);
}
return {};
});
});
// 16. For each Parse Node f of functionsToInitialize, do
for (auto& function_declaration : functions_to_initialize) {
// FIXME: Do this more correctly.
// a. Let fn be the sole element of the BoundNames of f.
// b. Let fo be InstantiateFunctionObject of f with arguments env and privateEnv.
generator.emit<Bytecode::Op::NewFunction>(function_declaration);
// c. Perform ? env.CreateGlobalFunctionBinding(fn, fo, false).
auto const& name = function_declaration.name();
auto index = generator.intern_identifier(name);
if (!generator.has_binding(index)) {
generator.register_binding(index, Bytecode::Generator::BindingMode::Var);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Lexical, false);
}
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::Initialize);
}
// 17. For each String vn of declaredVarNames, do
// a. Perform ? env.CreateGlobalVarBinding(vn, false).
for (auto& var_name : declared_var_names)
generator.register_binding(generator.intern_identifier(var_name), Bytecode::Generator::BindingMode::Var);
} else {
// Perform the steps of FunctionDeclarationInstantiation.
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Var, Bytecode::Generator::SurroundingScopeKind::Function);
pushed_scope_count++;
if (has_lexical_declarations()) {
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Function);
pushed_scope_count++;
}
// FIXME: Implement this boi correctly.
(void)for_each_lexically_scoped_declaration([&](Declaration const& declaration) -> ThrowCompletionOr<void> {
auto is_constant_declaration = declaration.is_constant_declaration();
declaration.for_each_bound_name([&](auto const& name) {
auto index = generator.intern_identifier(name);
if (is_constant_declaration || !generator.has_binding(index)) {
generator.register_binding(index);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Lexical, is_constant_declaration);
}
});
if (is<FunctionDeclaration>(declaration)) {
auto& function_declaration = static_cast<FunctionDeclaration const&>(declaration);
if (auto result = function_declaration.generate_bytecode(generator); result.is_error()) {
maybe_error = result.release_error();
// To make `for_each_lexically_scoped_declaration` happy.
return failing_completion;
}
auto const& name = function_declaration.name();
auto index = generator.intern_identifier(name);
if (!generator.has_binding(index)) {
generator.register_binding(index);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Lexical, false);
}
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::InitializeOrSet);
}
return {};
});
}
if (maybe_error.has_value())
return maybe_error.release_value();
for (auto& child : children()) {
TRY(child.generate_bytecode(generator));
if (generator.is_current_block_terminated())
break;
}
for (size_t i = 0; i < pushed_scope_count; ++i)
generator.end_variable_scope();
return {};
}
Bytecode::CodeGenerationErrorOr<void> EmptyStatement::generate_bytecode(Bytecode::Generator&) const
{
return {};
}
Bytecode::CodeGenerationErrorOr<void> ExpressionStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return m_expression->generate_bytecode(generator);
}
Bytecode::CodeGenerationErrorOr<void> BinaryExpression::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_lhs->generate_bytecode(generator));
auto lhs_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(lhs_reg);
TRY(m_rhs->generate_bytecode(generator));
switch (m_op) {
case BinaryOp::Addition:
generator.emit<Bytecode::Op::Add>(lhs_reg);
break;
case BinaryOp::Subtraction:
generator.emit<Bytecode::Op::Sub>(lhs_reg);
break;
case BinaryOp::Multiplication:
generator.emit<Bytecode::Op::Mul>(lhs_reg);
break;
case BinaryOp::Division:
generator.emit<Bytecode::Op::Div>(lhs_reg);
break;
case BinaryOp::Modulo:
generator.emit<Bytecode::Op::Mod>(lhs_reg);
break;
case BinaryOp::Exponentiation:
generator.emit<Bytecode::Op::Exp>(lhs_reg);
break;
case BinaryOp::GreaterThan:
generator.emit<Bytecode::Op::GreaterThan>(lhs_reg);
break;
case BinaryOp::GreaterThanEquals:
generator.emit<Bytecode::Op::GreaterThanEquals>(lhs_reg);
break;
case BinaryOp::LessThan:
generator.emit<Bytecode::Op::LessThan>(lhs_reg);
break;
case BinaryOp::LessThanEquals:
generator.emit<Bytecode::Op::LessThanEquals>(lhs_reg);
break;
case BinaryOp::LooselyInequals:
generator.emit<Bytecode::Op::LooselyInequals>(lhs_reg);
break;
case BinaryOp::LooselyEquals:
generator.emit<Bytecode::Op::LooselyEquals>(lhs_reg);
break;
case BinaryOp::StrictlyInequals:
generator.emit<Bytecode::Op::StrictlyInequals>(lhs_reg);
break;
case BinaryOp::StrictlyEquals:
generator.emit<Bytecode::Op::StrictlyEquals>(lhs_reg);
break;
case BinaryOp::BitwiseAnd:
generator.emit<Bytecode::Op::BitwiseAnd>(lhs_reg);
break;
case BinaryOp::BitwiseOr:
generator.emit<Bytecode::Op::BitwiseOr>(lhs_reg);
break;
case BinaryOp::BitwiseXor:
generator.emit<Bytecode::Op::BitwiseXor>(lhs_reg);
break;
case BinaryOp::LeftShift:
generator.emit<Bytecode::Op::LeftShift>(lhs_reg);
break;
case BinaryOp::RightShift:
generator.emit<Bytecode::Op::RightShift>(lhs_reg);
break;
case BinaryOp::UnsignedRightShift:
generator.emit<Bytecode::Op::UnsignedRightShift>(lhs_reg);
break;
case BinaryOp::In:
generator.emit<Bytecode::Op::In>(lhs_reg);
break;
case BinaryOp::InstanceOf:
generator.emit<Bytecode::Op::InstanceOf>(lhs_reg);
break;
default:
VERIFY_NOT_REACHED();
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> LogicalExpression::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_lhs->generate_bytecode(generator));
// lhs
// jump op (true) end (false) rhs
// rhs
// jump always (true) end
// end
auto& rhs_block = generator.make_block();
auto& end_block = generator.make_block();
switch (m_op) {
case LogicalOp::And:
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { rhs_block },
Bytecode::Label { end_block });
break;
case LogicalOp::Or:
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { end_block },
Bytecode::Label { rhs_block });
break;
case LogicalOp::NullishCoalescing:
generator.emit<Bytecode::Op::JumpNullish>().set_targets(
Bytecode::Label { rhs_block },
Bytecode::Label { end_block });
break;
default:
VERIFY_NOT_REACHED();
}
generator.switch_to_basic_block(rhs_block);
TRY(m_rhs->generate_bytecode(generator));
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { end_block },
{});
generator.switch_to_basic_block(end_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> UnaryExpression::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_op == UnaryOp::Delete)
return generator.emit_delete_reference(m_lhs);
// Typeof needs some special handling for when the LHS is an Identifier. Namely, it shouldn't throw on unresolvable references, but instead return "undefined".
if (m_op != UnaryOp::Typeof)
TRY(m_lhs->generate_bytecode(generator));
switch (m_op) {
case UnaryOp::BitwiseNot:
generator.emit<Bytecode::Op::BitwiseNot>();
break;
case UnaryOp::Not:
generator.emit<Bytecode::Op::Not>();
break;
case UnaryOp::Plus:
generator.emit<Bytecode::Op::UnaryPlus>();
break;
case UnaryOp::Minus:
generator.emit<Bytecode::Op::UnaryMinus>();
break;
case UnaryOp::Typeof:
if (is<Identifier>(*m_lhs)) {
auto& identifier = static_cast<Identifier const&>(*m_lhs);
generator.emit<Bytecode::Op::TypeofVariable>(generator.intern_identifier(identifier.string()));
break;
}
TRY(m_lhs->generate_bytecode(generator));
generator.emit<Bytecode::Op::Typeof>();
break;
case UnaryOp::Void:
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
break;
case UnaryOp::Delete: // Delete is implemented above.
default:
VERIFY_NOT_REACHED();
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> NumericLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::LoadImmediate>(m_value);
return {};
}
Bytecode::CodeGenerationErrorOr<void> BooleanLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::LoadImmediate>(Value(m_value));
return {};
}
Bytecode::CodeGenerationErrorOr<void> NullLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::LoadImmediate>(js_null());
return {};
}
Bytecode::CodeGenerationErrorOr<void> BigIntLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::NewBigInt>(Crypto::SignedBigInteger::from_base(10, m_value.substring(0, m_value.length() - 1)));
return {};
}
Bytecode::CodeGenerationErrorOr<void> StringLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::NewString>(generator.intern_string(m_value));
return {};
}
Bytecode::CodeGenerationErrorOr<void> RegExpLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
auto source_index = generator.intern_string(m_pattern);
auto flags_index = generator.intern_string(m_flags);
generator.emit<Bytecode::Op::NewRegExp>(source_index, flags_index);
return {};
}
Bytecode::CodeGenerationErrorOr<void> Identifier::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::GetVariable>(generator.intern_identifier(m_string));
return {};
}
Bytecode::CodeGenerationErrorOr<void> AssignmentExpression::generate_bytecode(Bytecode::Generator& generator) const
{
// FIXME: Implement this for BindingPatterns too.
auto& lhs = m_lhs.get<NonnullRefPtr<Expression>>();
if (m_op == AssignmentOp::Assignment) {
TRY(m_rhs->generate_bytecode(generator));
return generator.emit_store_to_reference(lhs);
}
TRY(generator.emit_load_from_reference(lhs));
Bytecode::BasicBlock* rhs_block_ptr { nullptr };
Bytecode::BasicBlock* end_block_ptr { nullptr };
// Logical assignments short circuit.
if (m_op == AssignmentOp::AndAssignment) { // &&=
rhs_block_ptr = &generator.make_block();
end_block_ptr = &generator.make_block();
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { *rhs_block_ptr },
Bytecode::Label { *end_block_ptr });
} else if (m_op == AssignmentOp::OrAssignment) { // ||=
rhs_block_ptr = &generator.make_block();
end_block_ptr = &generator.make_block();
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { *end_block_ptr },
Bytecode::Label { *rhs_block_ptr });
} else if (m_op == AssignmentOp::NullishAssignment) { // ??=
rhs_block_ptr = &generator.make_block();
end_block_ptr = &generator.make_block();
generator.emit<Bytecode::Op::JumpNullish>().set_targets(
Bytecode::Label { *rhs_block_ptr },
Bytecode::Label { *end_block_ptr });
}
if (rhs_block_ptr)
generator.switch_to_basic_block(*rhs_block_ptr);
// lhs_reg is a part of the rhs_block because the store isn't necessary
// if the logical assignment condition fails.
auto lhs_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(lhs_reg);
TRY(m_rhs->generate_bytecode(generator));
switch (m_op) {
case AssignmentOp::AdditionAssignment:
generator.emit<Bytecode::Op::Add>(lhs_reg);
break;
case AssignmentOp::SubtractionAssignment:
generator.emit<Bytecode::Op::Sub>(lhs_reg);
break;
case AssignmentOp::MultiplicationAssignment:
generator.emit<Bytecode::Op::Mul>(lhs_reg);
break;
case AssignmentOp::DivisionAssignment:
generator.emit<Bytecode::Op::Div>(lhs_reg);
break;
case AssignmentOp::ModuloAssignment:
generator.emit<Bytecode::Op::Mod>(lhs_reg);
break;
case AssignmentOp::ExponentiationAssignment:
generator.emit<Bytecode::Op::Exp>(lhs_reg);
break;
case AssignmentOp::BitwiseAndAssignment:
generator.emit<Bytecode::Op::BitwiseAnd>(lhs_reg);
break;
case AssignmentOp::BitwiseOrAssignment:
generator.emit<Bytecode::Op::BitwiseOr>(lhs_reg);
break;
case AssignmentOp::BitwiseXorAssignment:
generator.emit<Bytecode::Op::BitwiseXor>(lhs_reg);
break;
case AssignmentOp::LeftShiftAssignment:
generator.emit<Bytecode::Op::LeftShift>(lhs_reg);
break;
case AssignmentOp::RightShiftAssignment:
generator.emit<Bytecode::Op::RightShift>(lhs_reg);
break;
case AssignmentOp::UnsignedRightShiftAssignment:
generator.emit<Bytecode::Op::UnsignedRightShift>(lhs_reg);
break;
case AssignmentOp::AndAssignment:
case AssignmentOp::OrAssignment:
case AssignmentOp::NullishAssignment:
break; // These are handled above.
default:
return Bytecode::CodeGenerationError {
this,
"Unimplemented operation"sv,
};
}
TRY(generator.emit_store_to_reference(lhs));
if (end_block_ptr) {
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { *end_block_ptr },
{});
generator.switch_to_basic_block(*end_block_ptr);
}
return {};
}
// 14.13.3 Runtime Semantics: Evaluation, https://tc39.es/ecma262/#sec-labelled-statements-runtime-semantics-evaluation
// LabelledStatement : LabelIdentifier : LabelledItem
Bytecode::CodeGenerationErrorOr<void> LabelledStatement::generate_bytecode(Bytecode::Generator& generator) const
{
// Return ? LabelledEvaluation of this LabelledStatement with argument « ».
return generate_labelled_evaluation(generator, {});
}
// 14.13.4 Runtime Semantics: LabelledEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-labelledevaluation
// LabelledStatement : LabelIdentifier : LabelledItem
Bytecode::CodeGenerationErrorOr<void> LabelledStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
// Convert the m_labelled_item NNRP to a reference early so we don't have to do it every single time we want to use it.
auto const& labelled_item = *m_labelled_item;
// 1. Let label be the StringValue of LabelIdentifier.
// NOTE: Not necessary, this is m_label.
// 2. Let newLabelSet be the list-concatenation of labelSet and « label ».
// FIXME: Avoid copy here.
auto new_label_set = label_set;
new_label_set.append(m_label);
// 3. Let stmtResult be LabelledEvaluation of LabelledItem with argument newLabelSet.
// NOTE: stmtResult will be in the accumulator after running the generated bytecode.
if (is<IterationStatement>(labelled_item)) {
auto const& iteration_statement = static_cast<IterationStatement const&>(labelled_item);
TRY(iteration_statement.generate_labelled_evaluation(generator, new_label_set));
} else if (is<SwitchStatement>(labelled_item)) {
auto const& switch_statement = static_cast<SwitchStatement const&>(labelled_item);
TRY(switch_statement.generate_labelled_evaluation(generator, new_label_set));
} else if (is<LabelledStatement>(labelled_item)) {
auto const& labelled_statement = static_cast<LabelledStatement const&>(labelled_item);
TRY(labelled_statement.generate_labelled_evaluation(generator, new_label_set));
} else {
auto& labelled_break_block = generator.make_block();
// NOTE: We do not need a continuable scope as `continue;` is not allowed outside of iteration statements, throwing a SyntaxError in the parser.
generator.begin_breakable_scope(Bytecode::Label { labelled_break_block }, new_label_set);
TRY(labelled_item.generate_bytecode(generator));
generator.end_breakable_scope();
if (!generator.is_current_block_terminated()) {
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { labelled_break_block },
{});
}
generator.switch_to_basic_block(labelled_break_block);
}
// 4. If stmtResult.[[Type]] is break and SameValue(stmtResult.[[Target]], label) is true, then
// a. Set stmtResult to NormalCompletion(stmtResult.[[Value]]).
// NOTE: These steps are performed by making labelled break jump straight to the appropriate break block, which preserves the statement result's value in the accumulator.
// 5. Return Completion(stmtResult).
// NOTE: This is in the accumulator.
return {};
}
Bytecode::CodeGenerationErrorOr<void> IterationStatement::generate_labelled_evaluation(Bytecode::Generator&, Vector<FlyString> const&) const
{
return Bytecode::CodeGenerationError {
this,
"Missing generate_labelled_evaluation()"sv,
};
}
Bytecode::CodeGenerationErrorOr<void> WhileStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
Bytecode::CodeGenerationErrorOr<void> WhileStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
// test
// jump if_false (true) end (false) body
// body
// jump always (true) test
// end
auto& test_block = generator.make_block();
auto& body_block = generator.make_block();
auto& end_block = generator.make_block();
// Init result register
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
auto result_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(result_reg);
// jump to the test block
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { test_block },
{});
generator.switch_to_basic_block(test_block);
TRY(m_test->generate_bytecode(generator));
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { body_block },
Bytecode::Label { end_block });
generator.switch_to_basic_block(body_block);
generator.begin_continuable_scope(Bytecode::Label { test_block }, label_set);
generator.begin_breakable_scope(Bytecode::Label { end_block }, label_set);
TRY(m_body->generate_bytecode(generator));
generator.end_breakable_scope();
generator.end_continuable_scope();
if (!generator.is_current_block_terminated()) {
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { test_block },
{});
generator.switch_to_basic_block(end_block);
generator.emit<Bytecode::Op::Load>(result_reg);
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> DoWhileStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
Bytecode::CodeGenerationErrorOr<void> DoWhileStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
// jump always (true) body
// test
// jump if_false (true) end (false) body
// body
// jump always (true) test
// end
auto& test_block = generator.make_block();
auto& body_block = generator.make_block();
auto& end_block = generator.make_block();
// Init result register
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
auto result_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(result_reg);
// jump to the body block
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { body_block },
{});
generator.switch_to_basic_block(test_block);
TRY(m_test->generate_bytecode(generator));
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { body_block },
Bytecode::Label { end_block });
generator.switch_to_basic_block(body_block);
generator.begin_continuable_scope(Bytecode::Label { test_block }, label_set);
generator.begin_breakable_scope(Bytecode::Label { end_block }, label_set);
TRY(m_body->generate_bytecode(generator));
generator.end_breakable_scope();
generator.end_continuable_scope();
if (!generator.is_current_block_terminated()) {
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { test_block },
{});
generator.switch_to_basic_block(end_block);
generator.emit<Bytecode::Op::Load>(result_reg);
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> ForStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
Bytecode::CodeGenerationErrorOr<void> ForStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
// init
// jump always (true) test
// test
// jump if_true (true) body (false) end
// body
// jump always (true) update
// update
// jump always (true) test
// end
// If 'test' is missing, fuse the 'test' and 'body' basic blocks
// If 'update' is missing, fuse the 'body' and 'update' basic blocks
Bytecode::BasicBlock* test_block_ptr { nullptr };
Bytecode::BasicBlock* body_block_ptr { nullptr };
Bytecode::BasicBlock* update_block_ptr { nullptr };
auto& end_block = generator.make_block();
bool has_lexical_environment = false;
// The breakable scope needs to start here to unwind the potentially created lexical environment for the init bytecode.
generator.begin_breakable_scope(Bytecode::Label { end_block }, label_set);
if (m_init) {
if (m_init->is_variable_declaration()) {
auto& variable_declaration = verify_cast<VariableDeclaration>(*m_init);
if (variable_declaration.is_lexical_declaration()) {
has_lexical_environment = true;
// FIXME: Is Block correct?
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Block);
bool is_const = variable_declaration.is_constant_declaration();
variable_declaration.for_each_bound_name([&](auto const& name) {
auto index = generator.intern_identifier(name);
generator.register_binding(index);
generator.emit<Bytecode::Op::CreateVariable>(index, Bytecode::Op::EnvironmentMode::Lexical, is_const);
});
}
}
TRY(m_init->generate_bytecode(generator));
}
body_block_ptr = &generator.make_block();
if (m_test)
test_block_ptr = &generator.make_block();
else
test_block_ptr = body_block_ptr;
if (m_update)
update_block_ptr = &generator.make_block();
else
update_block_ptr = body_block_ptr;
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
auto result_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(result_reg);
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { *test_block_ptr },
{});
if (m_test) {
generator.switch_to_basic_block(*test_block_ptr);
TRY(m_test->generate_bytecode(generator));
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { *body_block_ptr },
Bytecode::Label { end_block });
}
generator.switch_to_basic_block(*body_block_ptr);
generator.begin_continuable_scope(Bytecode::Label { *update_block_ptr }, label_set);
TRY(m_body->generate_bytecode(generator));
generator.end_continuable_scope();
if (!generator.is_current_block_terminated()) {
if (m_update) {
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { *update_block_ptr },
{});
generator.switch_to_basic_block(*update_block_ptr);
TRY(m_update->generate_bytecode(generator));
}
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { *test_block_ptr },
{});
generator.switch_to_basic_block(end_block);
generator.emit<Bytecode::Op::Load>(result_reg);
}
if (has_lexical_environment)
generator.end_variable_scope();
generator.end_breakable_scope();
return {};
}
Bytecode::CodeGenerationErrorOr<void> ObjectExpression::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::NewObject>();
if (m_properties.is_empty())
return {};
auto object_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(object_reg);
for (auto& property : m_properties) {
Bytecode::Op::PropertyKind property_kind;
switch (property.type()) {
case ObjectProperty::Type::KeyValue:
property_kind = Bytecode::Op::PropertyKind::KeyValue;
break;
case ObjectProperty::Type::Getter:
property_kind = Bytecode::Op::PropertyKind::Getter;
break;
case ObjectProperty::Type::Setter:
property_kind = Bytecode::Op::PropertyKind::Setter;
break;
case ObjectProperty::Type::Spread:
property_kind = Bytecode::Op::PropertyKind::Spread;
break;
case ObjectProperty::Type::ProtoSetter:
property_kind = Bytecode::Op::PropertyKind::ProtoSetter;
break;
}
if (is<StringLiteral>(property.key())) {
auto& string_literal = static_cast<StringLiteral const&>(property.key());
Bytecode::IdentifierTableIndex key_name = generator.intern_identifier(string_literal.value());
if (property_kind != Bytecode::Op::PropertyKind::Spread)
TRY(property.value().generate_bytecode(generator));
generator.emit<Bytecode::Op::PutById>(object_reg, key_name, property_kind);
} else {
TRY(property.key().generate_bytecode(generator));
auto property_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(property_reg);
if (property_kind != Bytecode::Op::PropertyKind::Spread)
TRY(property.value().generate_bytecode(generator));
generator.emit<Bytecode::Op::PutByValue>(object_reg, property_reg, property_kind);
}
}
generator.emit<Bytecode::Op::Load>(object_reg);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ArrayExpression::generate_bytecode(Bytecode::Generator& generator) const
{
Vector<Bytecode::Register> element_regs;
for (auto& element : m_elements) {
if (element && is<SpreadExpression>(*element)) {
return Bytecode::CodeGenerationError {
this,
"Unimplemented element kind: SpreadExpression"sv,
};
}
element_regs.append(generator.allocate_register());
}
size_t i = 0;
for (auto& element : m_elements) {
if (element) {
TRY(element->generate_bytecode(generator));
if (is<SpreadExpression>(*element))
VERIFY_NOT_REACHED();
} else {
generator.emit<Bytecode::Op::LoadImmediate>(Value {});
}
auto& element_reg = element_regs[i++];
generator.emit<Bytecode::Op::Store>(element_reg);
}
if (element_regs.is_empty()) {
generator.emit<Bytecode::Op::NewArray>();
} else {
generator.emit_with_extra_register_slots<Bytecode::Op::NewArray>(2u, AK::Array { element_regs.first(), element_regs.last() });
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> MemberExpression::generate_bytecode(Bytecode::Generator& generator) const
{
return generator.emit_load_from_reference(*this);
}
Bytecode::CodeGenerationErrorOr<void> FunctionDeclaration::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_is_hoisted) {
auto index = generator.intern_identifier(name());
generator.emit<Bytecode::Op::GetVariable>(index);
generator.emit<Bytecode::Op::SetVariable>(index, Bytecode::Op::SetVariable::InitializationMode::Set, Bytecode::Op::EnvironmentMode::Var);
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> FunctionExpression::generate_bytecode(Bytecode::Generator& generator) const
{
bool has_name = !name().is_empty();
Optional<Bytecode::IdentifierTableIndex> name_identifier;
if (has_name) {
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical);
name_identifier = generator.intern_identifier(name());
generator.emit<Bytecode::Op::CreateVariable>(*name_identifier, Bytecode::Op::EnvironmentMode::Lexical, true);
}
generator.emit<Bytecode::Op::NewFunction>(*this);
if (has_name) {
generator.emit<Bytecode::Op::SetVariable>(*name_identifier, Bytecode::Op::SetVariable::InitializationMode::Initialize, Bytecode::Op::EnvironmentMode::Lexical);
generator.end_variable_scope();
}
return {};
}
static Bytecode::CodeGenerationErrorOr<void> generate_binding_pattern_bytecode(Bytecode::Generator& generator, BindingPattern const& pattern, Bytecode::Op::SetVariable::InitializationMode, Bytecode::Register const& value_reg);
static Bytecode::CodeGenerationErrorOr<void> generate_object_binding_pattern_bytecode(Bytecode::Generator& generator, BindingPattern const& pattern, Bytecode::Op::SetVariable::InitializationMode initialization_mode, Bytecode::Register const& value_reg)
{
Vector<Bytecode::Register> excluded_property_names;
auto has_rest = false;
if (pattern.entries.size() > 0)
has_rest = pattern.entries[pattern.entries.size() - 1].is_rest;
for (auto& [name, alias, initializer, is_rest] : pattern.entries) {
if (is_rest) {
VERIFY(name.has<NonnullRefPtr<Identifier>>());
VERIFY(alias.has<Empty>());
VERIFY(!initializer);
auto identifier = name.get<NonnullRefPtr<Identifier>>()->string();
auto interned_identifier = generator.intern_identifier(identifier);
generator.emit_with_extra_register_slots<Bytecode::Op::CopyObjectExcludingProperties>(excluded_property_names.size(), value_reg, excluded_property_names);
generator.emit<Bytecode::Op::SetVariable>(interned_identifier, initialization_mode);
return {};
}
Bytecode::StringTableIndex name_index;
if (name.has<NonnullRefPtr<Identifier>>()) {
auto identifier = name.get<NonnullRefPtr<Identifier>>()->string();
name_index = generator.intern_string(identifier);
if (has_rest) {
auto excluded_name_reg = generator.allocate_register();
excluded_property_names.append(excluded_name_reg);
generator.emit<Bytecode::Op::NewString>(name_index);
generator.emit<Bytecode::Op::Store>(excluded_name_reg);
}
generator.emit<Bytecode::Op::Load>(value_reg);
generator.emit<Bytecode::Op::GetById>(generator.intern_identifier(identifier));
} else {
auto expression = name.get<NonnullRefPtr<Expression>>();
TRY(expression->generate_bytecode(generator));
if (has_rest) {
auto excluded_name_reg = generator.allocate_register();
excluded_property_names.append(excluded_name_reg);
generator.emit<Bytecode::Op::Store>(excluded_name_reg);
}
generator.emit<Bytecode::Op::GetByValue>(value_reg);
}
if (initializer) {
auto& if_undefined_block = generator.make_block();
auto& if_not_undefined_block = generator.make_block();
generator.emit<Bytecode::Op::JumpUndefined>().set_targets(
Bytecode::Label { if_undefined_block },
Bytecode::Label { if_not_undefined_block });
generator.switch_to_basic_block(if_undefined_block);
TRY(initializer->generate_bytecode(generator));
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { if_not_undefined_block },
{});
generator.switch_to_basic_block(if_not_undefined_block);
}
if (alias.has<NonnullRefPtr<BindingPattern>>()) {
auto& binding_pattern = *alias.get<NonnullRefPtr<BindingPattern>>();
auto nested_value_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(nested_value_reg);
TRY(generate_binding_pattern_bytecode(generator, binding_pattern, initialization_mode, nested_value_reg));
} else if (alias.has<Empty>()) {
if (name.has<NonnullRefPtr<Expression>>()) {
// This needs some sort of SetVariableByValue opcode, as it's a runtime binding
return Bytecode::CodeGenerationError {
name.get<NonnullRefPtr<Expression>>().ptr(),
"Unimplemented name/alias pair: Empty/Expression"sv,
};
}
auto& identifier = name.get<NonnullRefPtr<Identifier>>()->string();
generator.emit<Bytecode::Op::SetVariable>(generator.intern_identifier(identifier), initialization_mode);
} else {
auto& identifier = alias.get<NonnullRefPtr<Identifier>>()->string();
generator.emit<Bytecode::Op::SetVariable>(generator.intern_identifier(identifier), initialization_mode);
}
}
return {};
}
static Bytecode::CodeGenerationErrorOr<void> generate_array_binding_pattern_bytecode(Bytecode::Generator& generator, BindingPattern const& pattern, Bytecode::Op::SetVariable::InitializationMode initialization_mode, Bytecode::Register const& value_reg)
{
/*
* Consider the following destructuring assignment:
*
* let [a, b, c, d, e] = o;
*
* It would be fairly trivial to just loop through this iterator, getting the value
* at each step and assigning them to the binding sequentially. However, this is not
* correct: once an iterator is exhausted, it must not be called again. This complicates
* the bytecode. In order to accomplish this, we do the following:
*
* - Reserve a special boolean register which holds 'true' if the iterator is exhausted,
* and false otherwise
* - When we are retrieving the value which should be bound, we first check this register.
* If it is 'true', we load undefined into the accumulator. Otherwise, we grab the next
* value from the iterator and store it into the accumulator.
*
* Note that the is_exhausted register does not need to be loaded with false because the
* first IteratorNext bytecode is _not_ proceeded by an exhausted check, as it is
* unnecessary.
*/
auto is_iterator_exhausted_register = generator.allocate_register();
auto iterator_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Load>(value_reg);
generator.emit<Bytecode::Op::GetIterator>();
generator.emit<Bytecode::Op::Store>(iterator_reg);
bool first = true;
auto temp_iterator_result_reg = generator.allocate_register();
auto assign_accumulator_to_alias = [&](auto& alias) {
return alias.visit(
[&](Empty) -> Bytecode::CodeGenerationErrorOr<void> {
// This element is an elision
return {};
},
[&](NonnullRefPtr<Identifier> const& identifier) -> Bytecode::CodeGenerationErrorOr<void> {
auto interned_index = generator.intern_identifier(identifier->string());
generator.emit<Bytecode::Op::SetVariable>(interned_index, initialization_mode);
return {};
},
[&](NonnullRefPtr<BindingPattern> const& pattern) -> Bytecode::CodeGenerationErrorOr<void> {
// Store the accumulator value in a permanent register
auto target_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(target_reg);
return generate_binding_pattern_bytecode(generator, pattern, initialization_mode, target_reg);
},
[&](NonnullRefPtr<MemberExpression> const& expr) -> Bytecode::CodeGenerationErrorOr<void> {
return generator.emit_store_to_reference(*expr);
});
};
for (auto& [name, alias, initializer, is_rest] : pattern.entries) {
VERIFY(name.has<Empty>());
if (is_rest) {
if (first) {
// The iterator has not been called, and is thus known to be not exhausted
generator.emit<Bytecode::Op::Load>(iterator_reg);
generator.emit<Bytecode::Op::IteratorToArray>();
} else {
auto& if_exhausted_block = generator.make_block();
auto& if_not_exhausted_block = generator.make_block();
auto& continuation_block = generator.make_block();
generator.emit<Bytecode::Op::Load>(is_iterator_exhausted_register);
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { if_exhausted_block },
Bytecode::Label { if_not_exhausted_block });
generator.switch_to_basic_block(if_exhausted_block);
generator.emit<Bytecode::Op::NewArray>();
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { continuation_block },
{});
generator.switch_to_basic_block(if_not_exhausted_block);
generator.emit<Bytecode::Op::Load>(iterator_reg);
generator.emit<Bytecode::Op::IteratorToArray>();
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { continuation_block },
{});
generator.switch_to_basic_block(continuation_block);
}
return assign_accumulator_to_alias(alias);
}
// In the first iteration of the loop, a few things are true which can save
// us some bytecode:
// - the iterator result is still in the accumulator, so we can avoid a load
// - the iterator is not yet exhausted, which can save us a jump and some
// creation
auto& iterator_is_exhausted_block = generator.make_block();
if (!first) {
auto& iterator_is_not_exhausted_block = generator.make_block();
generator.emit<Bytecode::Op::Load>(is_iterator_exhausted_register);
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { iterator_is_exhausted_block },
Bytecode::Label { iterator_is_not_exhausted_block });
generator.switch_to_basic_block(iterator_is_not_exhausted_block);
generator.emit<Bytecode::Op::Load>(iterator_reg);
}
generator.emit<Bytecode::Op::IteratorNext>();
generator.emit<Bytecode::Op::Store>(temp_iterator_result_reg);
generator.emit<Bytecode::Op::IteratorResultDone>();
generator.emit<Bytecode::Op::Store>(is_iterator_exhausted_register);
// We still have to check for exhaustion here. If the iterator is exhausted,
// we need to bail before trying to get the value
auto& no_bail_block = generator.make_block();
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { iterator_is_exhausted_block },
Bytecode::Label { no_bail_block });
generator.switch_to_basic_block(no_bail_block);
// Get the next value in the iterator
generator.emit<Bytecode::Op::Load>(temp_iterator_result_reg);
generator.emit<Bytecode::Op::IteratorResultValue>();
auto& create_binding_block = generator.make_block();
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { create_binding_block },
{});
// The iterator is exhausted, so we just load undefined and continue binding
generator.switch_to_basic_block(iterator_is_exhausted_block);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { create_binding_block },
{});
// Create the actual binding. The value which this entry must bind is now in the
// accumulator. We can proceed, processing the alias as a nested destructuring
// pattern if necessary.
generator.switch_to_basic_block(create_binding_block);
TRY(assign_accumulator_to_alias(alias));
first = false;
}
return {};
}
static Bytecode::CodeGenerationErrorOr<void> generate_binding_pattern_bytecode(Bytecode::Generator& generator, BindingPattern const& pattern, Bytecode::Op::SetVariable::InitializationMode initialization_mode, Bytecode::Register const& value_reg)
{
if (pattern.kind == BindingPattern::Kind::Object)
return generate_object_binding_pattern_bytecode(generator, pattern, initialization_mode, value_reg);
return generate_array_binding_pattern_bytecode(generator, pattern, initialization_mode, value_reg);
}
static Bytecode::CodeGenerationErrorOr<void> assign_accumulator_to_variable_declarator(Bytecode::Generator& generator, VariableDeclarator const& declarator, VariableDeclaration const& declaration)
{
auto initialization_mode = declaration.is_lexical_declaration() ? Bytecode::Op::SetVariable::InitializationMode::Initialize : Bytecode::Op::SetVariable::InitializationMode::Set;
auto environment_mode = declaration.is_lexical_declaration() ? Bytecode::Op::EnvironmentMode::Lexical : Bytecode::Op::EnvironmentMode::Var;
return declarator.target().visit(
[&](NonnullRefPtr<Identifier> const& id) -> Bytecode::CodeGenerationErrorOr<void> {
generator.emit<Bytecode::Op::SetVariable>(generator.intern_identifier(id->string()), initialization_mode, environment_mode);
return {};
},
[&](NonnullRefPtr<BindingPattern> const& pattern) -> Bytecode::CodeGenerationErrorOr<void> {
auto value_register = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(value_register);
return generate_binding_pattern_bytecode(generator, pattern, initialization_mode, value_register);
});
}
Bytecode::CodeGenerationErrorOr<void> VariableDeclaration::generate_bytecode(Bytecode::Generator& generator) const
{
for (auto& declarator : m_declarations) {
if (declarator.init())
TRY(declarator.init()->generate_bytecode(generator));
else
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
TRY(assign_accumulator_to_variable_declarator(generator, declarator, *this));
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> CallExpression::generate_bytecode(Bytecode::Generator& generator) const
{
auto callee_reg = generator.allocate_register();
auto this_reg = generator.allocate_register();
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::Store>(this_reg);
if (is<NewExpression>(this)) {
TRY(m_callee->generate_bytecode(generator));
generator.emit<Bytecode::Op::Store>(callee_reg);
} else if (is<SuperExpression>(*m_callee)) {
return Bytecode::CodeGenerationError {
this,
"Unimplemented callee kind: SuperExpression"sv,
};
} else if (is<MemberExpression>(*m_callee)) {
auto& member_expression = static_cast<MemberExpression const&>(*m_callee);
if (is<SuperExpression>(member_expression.object())) {
return Bytecode::CodeGenerationError {
this,
"Unimplemented callee kind: MemberExpression on SuperExpression"sv,
};
}
TRY(member_expression.object().generate_bytecode(generator));
generator.emit<Bytecode::Op::Store>(this_reg);
if (member_expression.is_computed()) {
TRY(member_expression.property().generate_bytecode(generator));
generator.emit<Bytecode::Op::GetByValue>(this_reg);
} else {
auto identifier_table_ref = generator.intern_identifier(verify_cast<Identifier>(member_expression.property()).string());
generator.emit<Bytecode::Op::GetById>(identifier_table_ref);
}
generator.emit<Bytecode::Op::Store>(callee_reg);
} else {
// FIXME: this = global object in sloppy mode.
TRY(m_callee->generate_bytecode(generator));
generator.emit<Bytecode::Op::Store>(callee_reg);
}
Vector<Bytecode::Register> argument_registers;
for (auto& arg : m_arguments) {
TRY(arg.value->generate_bytecode(generator));
auto arg_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(arg_reg);
argument_registers.append(arg_reg);
}
Bytecode::Op::Call::CallType call_type;
if (is<NewExpression>(*this)) {
call_type = Bytecode::Op::Call::CallType::Construct;
} else {
call_type = Bytecode::Op::Call::CallType::Call;
}
generator.emit_with_extra_register_slots<Bytecode::Op::Call>(argument_registers.size(), call_type, callee_reg, this_reg, argument_registers);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ReturnStatement::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_argument)
TRY(m_argument->generate_bytecode(generator));
else
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
if (generator.is_in_generator_or_async_function()) {
generator.perform_needed_unwinds<Bytecode::Op::Yield>();
generator.emit<Bytecode::Op::Yield>(nullptr);
} else {
generator.perform_needed_unwinds<Bytecode::Op::Return>();
generator.emit<Bytecode::Op::Return>();
}
return {};
}
Bytecode::CodeGenerationErrorOr<void> YieldExpression::generate_bytecode(Bytecode::Generator& generator) const
{
VERIFY(generator.is_in_generator_function());
if (m_is_yield_from) {
return Bytecode::CodeGenerationError {
this,
"Unimplemented form: `yield*`"sv,
};
}
if (m_argument)
TRY(m_argument->generate_bytecode(generator));
auto& continuation_block = generator.make_block();
generator.emit<Bytecode::Op::Yield>(Bytecode::Label { continuation_block });
generator.switch_to_basic_block(continuation_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> IfStatement::generate_bytecode(Bytecode::Generator& generator) const
{
// test
// jump if_true (true) true (false) false
// true
// jump always (true) end
// false
// jump always (true) end
// end
auto& true_block = generator.make_block();
auto& false_block = generator.make_block();
TRY(m_predicate->generate_bytecode(generator));
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { true_block },
Bytecode::Label { false_block });
Bytecode::Op::Jump* true_block_jump { nullptr };
generator.switch_to_basic_block(true_block);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
TRY(m_consequent->generate_bytecode(generator));
if (!generator.is_current_block_terminated())
true_block_jump = &generator.emit<Bytecode::Op::Jump>();
generator.switch_to_basic_block(false_block);
auto& end_block = generator.make_block();
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
if (m_alternate)
TRY(m_alternate->generate_bytecode(generator));
if (!generator.is_current_block_terminated())
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { end_block }, {});
if (true_block_jump)
true_block_jump->set_targets(Bytecode::Label { end_block }, {});
generator.switch_to_basic_block(end_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ContinueStatement::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_target_label.is_null()) {
generator.perform_needed_unwinds<Bytecode::Op::Jump>();
generator.emit<Bytecode::Op::Jump>().set_targets(
generator.nearest_continuable_scope(),
{});
return {};
}
auto target_to_jump_to = generator.perform_needed_unwinds_for_labelled_continue_and_return_target_block(m_target_label);
generator.emit<Bytecode::Op::Jump>().set_targets(
target_to_jump_to,
{});
return {};
}
Bytecode::CodeGenerationErrorOr<void> DebuggerStatement::generate_bytecode(Bytecode::Generator&) const
{
return {};
}
Bytecode::CodeGenerationErrorOr<void> ConditionalExpression::generate_bytecode(Bytecode::Generator& generator) const
{
// test
// jump if_true (true) true (false) false
// true
// jump always (true) end
// false
// jump always (true) end
// end
auto& true_block = generator.make_block();
auto& false_block = generator.make_block();
auto& end_block = generator.make_block();
TRY(m_test->generate_bytecode(generator));
generator.emit<Bytecode::Op::JumpConditional>().set_targets(
Bytecode::Label { true_block },
Bytecode::Label { false_block });
generator.switch_to_basic_block(true_block);
TRY(m_consequent->generate_bytecode(generator));
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { end_block },
{});
generator.switch_to_basic_block(false_block);
TRY(m_alternate->generate_bytecode(generator));
generator.emit<Bytecode::Op::Jump>().set_targets(
Bytecode::Label { end_block },
{});
generator.switch_to_basic_block(end_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> SequenceExpression::generate_bytecode(Bytecode::Generator& generator) const
{
for (auto& expression : m_expressions)
TRY(expression.generate_bytecode(generator));
return {};
}
Bytecode::CodeGenerationErrorOr<void> TemplateLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
auto string_reg = generator.allocate_register();
for (size_t i = 0; i < m_expressions.size(); i++) {
TRY(m_expressions[i].generate_bytecode(generator));
if (i == 0) {
generator.emit<Bytecode::Op::Store>(string_reg);
} else {
generator.emit<Bytecode::Op::ConcatString>(string_reg);
}
}
generator.emit<Bytecode::Op::Load>(string_reg);
return {};
}
Bytecode::CodeGenerationErrorOr<void> TaggedTemplateLiteral::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_tag->generate_bytecode(generator));
auto tag_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(tag_reg);
Vector<Bytecode::Register> string_regs;
auto& expressions = m_template_literal->expressions();
for (size_t i = 0; i < expressions.size(); ++i) {
if (i % 2 != 0)
continue;
string_regs.append(generator.allocate_register());
}
size_t reg_index = 0;
for (size_t i = 0; i < expressions.size(); ++i) {
if (i % 2 != 0)
continue;
TRY(expressions[i].generate_bytecode(generator));
auto string_reg = string_regs[reg_index++];
generator.emit<Bytecode::Op::Store>(string_reg);
}
if (string_regs.is_empty()) {
generator.emit<Bytecode::Op::NewArray>();
} else {
generator.emit_with_extra_register_slots<Bytecode::Op::NewArray>(2u, AK::Array { string_regs.first(), string_regs.last() });
}
auto strings_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(strings_reg);
Vector<Bytecode::Register> argument_regs;
argument_regs.append(strings_reg);
for (size_t i = 0; i < expressions.size(); ++i) {
if (i % 2 == 0)
continue;
TRY(expressions[i].generate_bytecode(generator));
auto string_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(string_reg);
argument_regs.append(string_reg);
}
Vector<Bytecode::Register> raw_string_regs;
for ([[maybe_unused]] auto& raw_string : m_template_literal->raw_strings())
string_regs.append(generator.allocate_register());
reg_index = 0;
for (auto& raw_string : m_template_literal->raw_strings()) {
TRY(raw_string.generate_bytecode(generator));
auto raw_string_reg = string_regs[reg_index++];
generator.emit<Bytecode::Op::Store>(raw_string_reg);
raw_string_regs.append(raw_string_reg);
}
if (raw_string_regs.is_empty()) {
generator.emit<Bytecode::Op::NewArray>();
} else {
generator.emit_with_extra_register_slots<Bytecode::Op::NewArray>(2u, AK::Array { raw_string_regs.first(), raw_string_regs.last() });
}
auto raw_strings_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(raw_strings_reg);
generator.emit<Bytecode::Op::Load>(strings_reg);
generator.emit<Bytecode::Op::PutById>(raw_strings_reg, generator.intern_identifier("raw"));
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
auto this_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(this_reg);
generator.emit_with_extra_register_slots<Bytecode::Op::Call>(argument_regs.size(), Bytecode::Op::Call::CallType::Call, tag_reg, this_reg, move(argument_regs));
return {};
}
Bytecode::CodeGenerationErrorOr<void> UpdateExpression::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(generator.emit_load_from_reference(*m_argument));
Optional<Bytecode::Register> previous_value_for_postfix_reg;
if (!m_prefixed) {
previous_value_for_postfix_reg = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(*previous_value_for_postfix_reg);
}
if (m_op == UpdateOp::Increment)
generator.emit<Bytecode::Op::Increment>();
else
generator.emit<Bytecode::Op::Decrement>();
TRY(generator.emit_store_to_reference(*m_argument));
if (!m_prefixed)
generator.emit<Bytecode::Op::Load>(*previous_value_for_postfix_reg);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ThrowStatement::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_argument->generate_bytecode(generator));
generator.perform_needed_unwinds<Bytecode::Op::Throw>();
generator.emit<Bytecode::Op::Throw>();
return {};
}
Bytecode::CodeGenerationErrorOr<void> BreakStatement::generate_bytecode(Bytecode::Generator& generator) const
{
if (m_target_label.is_null()) {
generator.perform_needed_unwinds<Bytecode::Op::Jump>(true);
generator.emit<Bytecode::Op::Jump>().set_targets(
generator.nearest_breakable_scope(),
{});
return {};
}
auto target_to_jump_to = generator.perform_needed_unwinds_for_labelled_break_and_return_target_block(m_target_label);
generator.emit<Bytecode::Op::Jump>().set_targets(
target_to_jump_to,
{});
return {};
}
Bytecode::CodeGenerationErrorOr<void> TryStatement::generate_bytecode(Bytecode::Generator& generator) const
{
auto& saved_block = generator.current_block();
Optional<Bytecode::Label> handler_target;
Optional<Bytecode::Label> finalizer_target;
Bytecode::BasicBlock* next_block { nullptr };
if (m_finalizer) {
auto& finalizer_block = generator.make_block();
generator.switch_to_basic_block(finalizer_block);
TRY(m_finalizer->generate_bytecode(generator));
if (!generator.is_current_block_terminated()) {
next_block = &generator.make_block();
auto next_target = Bytecode::Label { *next_block };
generator.emit<Bytecode::Op::ContinuePendingUnwind>(next_target);
}
finalizer_target = Bytecode::Label { finalizer_block };
}
if (m_handler) {
auto& handler_block = generator.make_block();
generator.switch_to_basic_block(handler_block);
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Block);
TRY(m_handler->parameter().visit(
[&](FlyString const& parameter) -> Bytecode::CodeGenerationErrorOr<void> {
if (!parameter.is_empty()) {
auto parameter_identifier = generator.intern_identifier(parameter);
generator.register_binding(parameter_identifier);
generator.emit<Bytecode::Op::CreateVariable>(parameter_identifier, Bytecode::Op::EnvironmentMode::Lexical, false);
generator.emit<Bytecode::Op::SetVariable>(parameter_identifier, Bytecode::Op::SetVariable::InitializationMode::Initialize);
}
return {};
},
[&](NonnullRefPtr<BindingPattern> const&) -> Bytecode::CodeGenerationErrorOr<void> {
// FIXME: Implement this path when the above DeclarativeEnvironment issue is dealt with.
return Bytecode::CodeGenerationError {
this,
"Unimplemented catch argument: BindingPattern"sv,
};
}));
TRY(m_handler->body().generate_bytecode(generator));
handler_target = Bytecode::Label { handler_block };
generator.end_variable_scope();
if (!generator.is_current_block_terminated()) {
if (m_finalizer) {
generator.emit<Bytecode::Op::LeaveUnwindContext>();
generator.emit<Bytecode::Op::Jump>(finalizer_target);
} else {
VERIFY(!next_block);
next_block = &generator.make_block();
auto next_target = Bytecode::Label { *next_block };
generator.emit<Bytecode::Op::Jump>(next_target);
}
}
}
auto& target_block = generator.make_block();
generator.switch_to_basic_block(saved_block);
generator.emit<Bytecode::Op::EnterUnwindContext>(Bytecode::Label { target_block }, handler_target, finalizer_target);
generator.start_boundary(Bytecode::Generator::BlockBoundaryType::Unwind);
generator.switch_to_basic_block(target_block);
TRY(m_block->generate_bytecode(generator));
if (!generator.is_current_block_terminated()) {
if (m_finalizer) {
generator.emit<Bytecode::Op::Jump>(finalizer_target);
} else {
auto& block = generator.make_block();
generator.emit<Bytecode::Op::FinishUnwind>(Bytecode::Label { block });
next_block = &block;
}
}
generator.end_boundary(Bytecode::Generator::BlockBoundaryType::Unwind);
generator.switch_to_basic_block(next_block ? *next_block : saved_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> SwitchStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
Bytecode::CodeGenerationErrorOr<void> SwitchStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
auto discriminant_reg = generator.allocate_register();
TRY(m_discriminant->generate_bytecode(generator));
generator.emit<Bytecode::Op::Store>(discriminant_reg);
Vector<Bytecode::BasicBlock&> case_blocks;
Bytecode::BasicBlock* default_block { nullptr };
Bytecode::BasicBlock* next_test_block = &generator.make_block();
auto has_lexical_block = has_lexical_declarations();
// Note: This call ends up calling begin_variable_scope() if has_lexical_block is true, so we need to clean up after it at the end.
TRY(ScopeNode::generate_bytecode(generator));
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { *next_test_block }, {});
for (auto& switch_case : m_cases) {
auto& case_block = generator.make_block();
if (switch_case.test()) {
generator.switch_to_basic_block(*next_test_block);
TRY(switch_case.test()->generate_bytecode(generator));
generator.emit<Bytecode::Op::StrictlyEquals>(discriminant_reg);
next_test_block = &generator.make_block();
generator.emit<Bytecode::Op::JumpConditional>().set_targets(Bytecode::Label { case_block }, Bytecode::Label { *next_test_block });
} else {
default_block = &case_block;
}
case_blocks.append(case_block);
}
generator.switch_to_basic_block(*next_test_block);
auto& end_block = generator.make_block();
if (default_block != nullptr) {
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { *default_block }, {});
} else {
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { end_block }, {});
}
auto current_block = case_blocks.begin();
generator.begin_breakable_scope(Bytecode::Label { end_block }, label_set);
for (auto& switch_case : m_cases) {
generator.switch_to_basic_block(*current_block);
generator.emit<Bytecode::Op::LoadImmediate>(js_undefined());
for (auto& statement : switch_case.children()) {
TRY(statement.generate_bytecode(generator));
if (generator.is_current_block_terminated())
break;
}
if (!generator.is_current_block_terminated()) {
auto next_block = current_block;
next_block++;
if (next_block.is_end()) {
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { end_block }, {});
} else {
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { *next_block }, {});
}
}
current_block++;
}
generator.end_breakable_scope();
if (has_lexical_block)
generator.end_variable_scope();
generator.switch_to_basic_block(end_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ClassDeclaration::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_class_expression->generate_bytecode(generator));
generator.emit<Bytecode::Op::SetVariable>(generator.intern_identifier(m_class_expression.ptr()->name()), Bytecode::Op::SetVariable::InitializationMode::Initialize);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ClassExpression::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::NewClass>(*this);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ThisExpression::generate_bytecode(Bytecode::Generator& generator) const
{
generator.emit<Bytecode::Op::ResolveThisBinding>();
return {};
}
Bytecode::CodeGenerationErrorOr<void> AwaitExpression::generate_bytecode(Bytecode::Generator& generator) const
{
VERIFY(generator.is_in_async_function());
// Transform `await expr` to `yield expr`
TRY(m_argument->generate_bytecode(generator));
auto& continuation_block = generator.make_block();
generator.emit<Bytecode::Op::Yield>(Bytecode::Label { continuation_block });
generator.switch_to_basic_block(continuation_block);
return {};
}
Bytecode::CodeGenerationErrorOr<void> WithStatement::generate_bytecode(Bytecode::Generator& generator) const
{
TRY(m_object->generate_bytecode(generator));
generator.emit<Bytecode::Op::EnterObjectEnvironment>();
// EnterObjectEnvironment sets the running execution context's lexical_environment to a new Object Environment.
generator.start_boundary(Bytecode::Generator::BlockBoundaryType::LeaveLexicalEnvironment);
TRY(m_body->generate_bytecode(generator));
generator.end_boundary(Bytecode::Generator::BlockBoundaryType::LeaveLexicalEnvironment);
if (!generator.is_current_block_terminated())
generator.emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
return {};
}
enum class LHSKind {
Assignment,
VarBinding,
LexicalBinding,
};
enum class IterationKind {
Enumerate,
Iterate,
AsyncIterate,
};
// 14.7.5.6 ForIn/OfHeadEvaluation ( uninitializedBoundNames, expr, iterationKind ), https://tc39.es/ecma262/#sec-runtime-semantics-forinofheadevaluation
struct ForInOfHeadEvaluationResult {
bool is_destructuring { false };
LHSKind lhs_kind { LHSKind::Assignment };
};
static Bytecode::CodeGenerationErrorOr<ForInOfHeadEvaluationResult> for_in_of_head_evaluation(Bytecode::Generator& generator, IterationKind iteration_kind, Variant<NonnullRefPtr<ASTNode>, NonnullRefPtr<BindingPattern>> const& lhs, NonnullRefPtr<ASTNode> const& rhs)
{
ForInOfHeadEvaluationResult result {};
if (auto* ast_ptr = lhs.get_pointer<NonnullRefPtr<ASTNode>>(); ast_ptr && is<VariableDeclaration>(**ast_ptr)) {
// Runtime Semantics: ForInOfLoopEvaluation, for any of:
// ForInOfStatement : for ( var ForBinding in Expression ) Statement
// ForInOfStatement : for ( ForDeclaration in Expression ) Statement
// ForInOfStatement : for ( var ForBinding of AssignmentExpression ) Statement
// ForInOfStatement : for ( ForDeclaration of AssignmentExpression ) Statement
auto& variable_declaration = static_cast<VariableDeclaration const&>(**ast_ptr);
result.is_destructuring = variable_declaration.declarations().first().target().has<NonnullRefPtr<BindingPattern>>();
result.lhs_kind = variable_declaration.is_lexical_declaration() ? LHSKind::LexicalBinding : LHSKind::VarBinding;
// 1. Let oldEnv be the running execution context's LexicalEnvironment.
// NOTE: 'uninitializedBoundNames' refers to the lexical bindings (i.e. Const/Let) present in the second and last form.
// 2. If uninitializedBoundNames is not an empty List, then
bool entered_lexical_scope = false;
if (variable_declaration.declaration_kind() != DeclarationKind::Var) {
entered_lexical_scope = true;
// a. Assert: uninitializedBoundNames has no duplicate entries.
// b. Let newEnv be NewDeclarativeEnvironment(oldEnv).
generator.begin_variable_scope();
// c. For each String name of uninitializedBoundNames, do
variable_declaration.for_each_bound_name([&](auto const& name) {
// i. Perform ! newEnv.CreateMutableBinding(name, false).
auto identifier = generator.intern_identifier(name);
generator.register_binding(identifier);
generator.emit<Bytecode::Op::CreateVariable>(identifier, Bytecode::Op::EnvironmentMode::Lexical, false);
});
// d. Set the running execution context's LexicalEnvironment to newEnv.
// NOTE: Done by CreateEnvironment.
}
// 3. Let exprRef be the result of evaluating expr.
TRY(rhs->generate_bytecode(generator));
// 4. Set the running execution context's LexicalEnvironment to oldEnv.
if (entered_lexical_scope)
generator.end_variable_scope();
// 5. Let exprValue be ? GetValue(exprRef).
// NOTE: No need to store this anywhere.
// 6. If iterationKind is enumerate, then
if (iteration_kind == IterationKind::Enumerate) {
// a. If exprValue is undefined or null, then
auto& nullish_block = generator.make_block();
auto& continuation_block = generator.make_block();
auto& jump = generator.emit<Bytecode::Op::JumpNullish>();
jump.set_targets(Bytecode::Label { nullish_block }, Bytecode::Label { continuation_block });
// i. Return Completion Record { [[Type]]: break, [[Value]]: empty, [[Target]]: empty }.
generator.switch_to_basic_block(nullish_block);
generator.perform_needed_unwinds<Bytecode::Op::Jump>(true);
generator.emit<Bytecode::Op::Jump>().set_targets(generator.nearest_breakable_scope(), {});
generator.switch_to_basic_block(continuation_block);
// b. Let obj be ! ToObject(exprValue).
// NOTE: GetObjectPropertyIterator does this.
// c. Let iterator be EnumerateObjectProperties(obj).
// d. Let nextMethod be ! GetV(iterator, "next").
// e. Return the Iterator Record { [[Iterator]]: iterator, [[NextMethod]]: nextMethod, [[Done]]: false }.
generator.emit<Bytecode::Op::GetObjectPropertyIterator>();
}
// 7. Else,
else {
// a. Assert: iterationKind is iterate or async-iterate.
// b. If iterationKind is async-iterate, let iteratorHint be async.
if (iteration_kind == IterationKind::AsyncIterate) {
return Bytecode::CodeGenerationError {
rhs.ptr(),
"Unimplemented iteration mode: AsyncIterate"sv,
};
}
// c. Else, let iteratorHint be sync.
// d. Return ? GetIterator(exprValue, iteratorHint).
generator.emit<Bytecode::Op::GetIterator>();
}
} else {
// Runtime Semantics: ForInOfLoopEvaluation, for any of:
// ForInOfStatement : for ( LeftHandSideExpression in Expression ) Statement
// ForInOfStatement : for ( LeftHandSideExpression of AssignmentExpression ) Statement
// Skip everything except steps 3, 5 and 7 (see above true branch for listing).
result.lhs_kind = LHSKind::Assignment;
// 3. Let exprRef be the result of evaluating expr.
TRY(rhs->generate_bytecode(generator));
// 5. Let exprValue be ? GetValue(exprRef).
// NOTE: No need to store this anywhere.
// a. Assert: iterationKind is iterate or async-iterate.
// b. If iterationKind is async-iterate, let iteratorHint be async.
if (iteration_kind == IterationKind::AsyncIterate) {
return Bytecode::CodeGenerationError {
rhs.ptr(),
"Unimplemented iteration mode: AsyncIterate"sv,
};
}
// c. Else, let iteratorHint be sync.
// d. Return ? GetIterator(exprValue, iteratorHint).
generator.emit<Bytecode::Op::GetIterator>();
}
return result;
}
// 14.7.5.7 ForIn/OfBodyEvaluation ( lhs, stmt, iteratorRecord, iterationKind, lhsKind, labelSet [ , iteratorKind ] ), https://tc39.es/ecma262/#sec-runtime-semantics-forin-div-ofbodyevaluation-lhs-stmt-iterator-lhskind-labelset
static Bytecode::CodeGenerationErrorOr<void> for_in_of_body_evaluation(Bytecode::Generator& generator, ASTNode const& node, Variant<NonnullRefPtr<ASTNode>, NonnullRefPtr<BindingPattern>> const& lhs, ASTNode const& body, ForInOfHeadEvaluationResult const& head_result, Vector<FlyString> const& label_set, Bytecode::BasicBlock& loop_end, Bytecode::BasicBlock& loop_update)
{
auto iterator_register = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(iterator_register);
// FIXME: Implement this
// 1. If iteratorKind is not present, set iteratorKind to sync.
// 2. Let oldEnv be the running execution context's LexicalEnvironment.
bool has_lexical_binding = false;
// 3. Let V be undefined.
// NOTE: We don't need 'V' as the resulting value will naturally flow through via the accumulator register.
// 4. Let destructuring be IsDestructuring of lhs.
auto destructuring = head_result.is_destructuring;
// 5. If destructuring is true and if lhsKind is assignment, then
if (destructuring) {
// a. Assert: lhs is a LeftHandSideExpression.
// b. Let assignmentPattern be the AssignmentPattern that is covered by lhs.
// FIXME: Implement this.
return Bytecode::CodeGenerationError {
&node,
"Unimplemented: destructuring in for-in/of"sv,
};
}
// 6. Repeat,
generator.emit<Bytecode::Op::Jump>(Bytecode::Label { loop_update });
generator.switch_to_basic_block(loop_update);
generator.begin_continuable_scope(Bytecode::Label { loop_update }, label_set);
// a. Let nextResult be ? Call(iteratorRecord.[[NextMethod]], iteratorRecord.[[Iterator]]).
generator.emit<Bytecode::Op::Load>(iterator_register);
generator.emit<Bytecode::Op::IteratorNext>();
// FIXME: Implement this:
// b. If iteratorKind is async, set nextResult to ? Await(nextResult).
// c. If Type(nextResult) is not Object, throw a TypeError exception.
// NOTE: IteratorComplete already does this.
// d. Let done be ? IteratorComplete(nextResult).
auto iterator_result_register = generator.allocate_register();
generator.emit<Bytecode::Op::Store>(iterator_result_register);
generator.emit<Bytecode::Op::IteratorResultDone>();
// e. If done is true, return V.
auto& loop_continue = generator.make_block();
generator.emit<Bytecode::Op::JumpConditional>().set_targets(Bytecode::Label { loop_end }, Bytecode::Label { loop_continue });
generator.switch_to_basic_block(loop_continue);
// f. Let nextValue be ? IteratorValue(nextResult).
generator.emit<Bytecode::Op::Load>(iterator_result_register);
generator.emit<Bytecode::Op::IteratorResultValue>();
// g. If lhsKind is either assignment or varBinding, then
if (head_result.lhs_kind != LHSKind::LexicalBinding) {
// i. If destructuring is false, then
if (!destructuring) {
// 1. Let lhsRef be the result of evaluating lhs. (It may be evaluated repeatedly.)
// NOTE: We're skipping all the completion stuff that the spec does, as the unwinding mechanism will take case of doing that.
if (head_result.lhs_kind == LHSKind::VarBinding) {
auto& declaration = static_cast<VariableDeclaration const&>(*lhs.get<NonnullRefPtr<ASTNode>>());
VERIFY(declaration.declarations().size() == 1);
TRY(assign_accumulator_to_variable_declarator(generator, declaration.declarations().first(), declaration));
} else {
if (auto ptr = lhs.get_pointer<NonnullRefPtr<ASTNode>>()) {
TRY(generator.emit_store_to_reference(**ptr));
} else {
auto& binding_pattern = lhs.get<NonnullRefPtr<BindingPattern>>();
TRY(generate_binding_pattern_bytecode(generator, *binding_pattern, Bytecode::Op::SetVariable::InitializationMode::Set, Bytecode::Register::accumulator()));
}
}
}
}
// h. Else,
else {
// i. Assert: lhsKind is lexicalBinding.
// ii. Assert: lhs is a ForDeclaration.
// iii. Let iterationEnv be NewDeclarativeEnvironment(oldEnv).
// iv. Perform ForDeclarationBindingInstantiation of lhs with argument iterationEnv.
// v. Set the running execution context's LexicalEnvironment to iterationEnv.
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical);
has_lexical_binding = true;
// 14.7.5.4 Runtime Semantics: ForDeclarationBindingInstantiation, https://tc39.es/ecma262/#sec-runtime-semantics-fordeclarationbindinginstantiation
// 1. Assert: environment is a declarative Environment Record.
// NOTE: We just made it.
auto& variable_declaration = static_cast<VariableDeclaration const&>(*lhs.get<NonnullRefPtr<ASTNode>>());
// 2. For each element name of the BoundNames of ForBinding, do
variable_declaration.for_each_bound_name([&](auto const& name) {
auto identifier = generator.intern_identifier(name);
generator.register_binding(identifier, Bytecode::Generator::BindingMode::Lexical);
// a. If IsConstantDeclaration of LetOrConst is true, then
if (variable_declaration.is_constant_declaration()) {
// i. Perform ! environment.CreateImmutableBinding(name, true).
generator.emit<Bytecode::Op::CreateVariable>(identifier, Bytecode::Op::EnvironmentMode::Lexical, true);
}
// b. Else,
else {
// i. Perform ! environment.CreateMutableBinding(name, false).
generator.emit<Bytecode::Op::CreateVariable>(identifier, Bytecode::Op::EnvironmentMode::Lexical, false);
}
});
// 3. Return unused.
// NOTE: No need to do that as we've inlined this.
// vi. If destructuring is false, then
if (!destructuring) {
// 1. Assert: lhs binds a single name.
// 2. Let lhsName be the sole element of BoundNames of lhs.
auto lhs_name = variable_declaration.declarations().first().target().get<NonnullRefPtr<Identifier>>()->string();
// 3. Let lhsRef be ! ResolveBinding(lhsName).
// NOTE: We're skipping all the completion stuff that the spec does, as the unwinding mechanism will take case of doing that.
auto identifier = generator.intern_identifier(lhs_name);
generator.emit<Bytecode::Op::SetVariable>(identifier, Bytecode::Op::SetVariable::InitializationMode::Initialize, Bytecode::Op::EnvironmentMode::Lexical);
}
}
// i. If destructuring is false, then
if (!destructuring) {
// i. If lhsRef is an abrupt completion, then
// 1. Let status be lhsRef.
// ii. Else if lhsKind is lexicalBinding, then
// 1. Let status be Completion(InitializeReferencedBinding(lhsRef, nextValue)).
// iii. Else,
// 1. Let status be Completion(PutValue(lhsRef, nextValue)).
// NOTE: This is performed above.
}
// j. Else,
else {
// FIXME: Implement destructuring
// i. If lhsKind is assignment, then
// 1. Let status be Completion(DestructuringAssignmentEvaluation of assignmentPattern with argument nextValue).
// ii. Else if lhsKind is varBinding, then
// 1. Assert: lhs is a ForBinding.
// 2. Let status be Completion(BindingInitialization of lhs with arguments nextValue and undefined).
// iii. Else,
// 1. Assert: lhsKind is lexicalBinding.
// 2. Assert: lhs is a ForDeclaration.
// 3. Let status be Completion(ForDeclarationBindingInitialization of lhs with arguments nextValue and iterationEnv).
return Bytecode::CodeGenerationError {
&node,
"Unimplemented: destructuring in for-in/of"sv,
};
}
// FIXME: Implement iteration closure.
// k. If status is an abrupt completion, then
// i. Set the running execution context's LexicalEnvironment to oldEnv.
// ii. If iteratorKind is async, return ? AsyncIteratorClose(iteratorRecord, status).
// iii. If iterationKind is enumerate, then
// 1. Return ? status.
// iv. Else,
// 1. Assert: iterationKind is iterate.
// 2. Return ? IteratorClose(iteratorRecord, status).
// l. Let result be the result of evaluating stmt.
TRY(body.generate_bytecode(generator));
// m. Set the running execution context's LexicalEnvironment to oldEnv.
if (has_lexical_binding)
generator.end_variable_scope();
generator.end_continuable_scope();
generator.end_breakable_scope();
// NOTE: If we're here, then the loop definitely continues.
// n. If LoopContinues(result, labelSet) is false, then
// i. If iterationKind is enumerate, then
// 1. Return ? UpdateEmpty(result, V).
// ii. Else,
// 1. Assert: iterationKind is iterate.
// 2. Set status to Completion(UpdateEmpty(result, V)).
// 3. If iteratorKind is async, return ? AsyncIteratorClose(iteratorRecord, status).
// 4. Return ? IteratorClose(iteratorRecord, status).
// o. If result.[[Value]] is not empty, set V to result.[[Value]].
// The body can contain an unconditional block terminator (e.g. return, throw), so we have to check for that before generating the Jump.
if (!generator.is_current_block_terminated())
generator.emit<Bytecode::Op::Jump>().set_targets(Bytecode::Label { loop_update }, {});
generator.switch_to_basic_block(loop_end);
return {};
}
Bytecode::CodeGenerationErrorOr<void> ForInStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
// 14.7.5.5 Runtime Semantics: ForInOfLoopEvaluation, https://tc39.es/ecma262/#sec-runtime-semantics-forinofloopevaluation
Bytecode::CodeGenerationErrorOr<void> ForInStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
auto& loop_end = generator.make_block();
auto& loop_update = generator.make_block();
generator.begin_breakable_scope(Bytecode::Label { loop_end }, label_set);
auto head_result = TRY(for_in_of_head_evaluation(generator, IterationKind::Enumerate, m_lhs, m_rhs));
// Now perform the rest of ForInOfLoopEvaluation, given that the accumulator holds the iterator we're supposed to iterate over.
return for_in_of_body_evaluation(generator, *this, m_lhs, body(), head_result, label_set, loop_end, loop_update);
}
Bytecode::CodeGenerationErrorOr<void> ForOfStatement::generate_bytecode(Bytecode::Generator& generator) const
{
return generate_labelled_evaluation(generator, {});
}
Bytecode::CodeGenerationErrorOr<void> ForOfStatement::generate_labelled_evaluation(Bytecode::Generator& generator, Vector<FlyString> const& label_set) const
{
auto& loop_end = generator.make_block();
auto& loop_update = generator.make_block();
generator.begin_breakable_scope(Bytecode::Label { loop_end }, label_set);
auto head_result = TRY(for_in_of_head_evaluation(generator, IterationKind::Iterate, m_lhs, m_rhs));
// Now perform the rest of ForInOfLoopEvaluation, given that the accumulator holds the iterator we're supposed to iterate over.
return for_in_of_body_evaluation(generator, *this, m_lhs, body(), head_result, label_set, loop_end, loop_update);
}
// 13.3.12.1 Runtime Semantics: Evaluation, https://tc39.es/ecma262/#sec-meta-properties-runtime-semantics-evaluation
Bytecode::CodeGenerationErrorOr<void> MetaProperty::generate_bytecode(Bytecode::Generator& generator) const
{
// NewTarget : new . target
if (m_type == MetaProperty::Type::NewTarget) {
// 1. Return GetNewTarget().
generator.emit<Bytecode::Op::GetNewTarget>();
return {};
}
// ImportMeta : import . meta
if (m_type == MetaProperty::Type::ImportMeta) {
return Bytecode::CodeGenerationError {
this,
"Unimplemented meta property: import.meta"sv,
};
}
VERIFY_NOT_REACHED();
}
}
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