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LibJS/Bytecode: Leave BlockDeclarationInstantiation in C++

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Instead of implementing this AO in bytecode, we now have an instruction
for it that simply invokes the C++ implementation.

This allows us to simplify Bytecode::Generator quite a bit by removing
all the variable scope tracking.
This commit is contained in:
Andreas Kling 2023-06-16 16:34:47 +02:00
parent 4684d3fe54
commit ac246d764d
6 changed files with 56 additions and 91 deletions
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54
Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
View file

@ -29,62 +29,30 @@ Bytecode::CodeGenerationErrorOr<void> ASTNode::generate_bytecode(Bytecode::Gener
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);
bool did_create_lexical_environment = false;
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++;
generator.block_declaration_instantiation(*this);
did_create_lexical_environment = true;
}
(void)for_each_lexically_scoped_declaration([&](Declaration const& declaration) -> ThrowCompletionOr<void> {
auto is_constant_declaration = declaration.is_constant_declaration();
// NOTE: Nothing in the callback throws an exception.
MUST(declaration.for_each_bound_name([&](auto const& name) {
auto index = generator.intern_identifier(name);
// NOTE: BlockDeclarationInstantiation takes as input the new lexical environment that was created and checks if there is a binding for the current name only in this new scope.
// For example: `{ let a = 1; { let a = 2; } }`. The second `a` will shadow the first `a` instead of re-initializing or setting it.
if (is_constant_declaration || !generator.has_binding_in_current_scope(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)) {
// GlobalDeclarationInstantiation is handled by the C++ AO.
} else {
// FunctionDeclarationInstantiation is handled by the C++ AO.
}
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)
if (did_create_lexical_environment)
generator.end_variable_scope();
return {};
@ -788,13 +756,12 @@ Bytecode::CodeGenerationErrorOr<void> ForStatement::generate_labelled_evaluation
has_lexical_environment = true;
// FIXME: Is Block correct?
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Block);
generator.begin_variable_scope();
bool is_const = variable_declaration.is_constant_declaration();
// NOTE: Nothing in the callback throws an exception.
MUST(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);
}));
}
@ -994,7 +961,7 @@ Bytecode::CodeGenerationErrorOr<void> FunctionExpression::generate_bytecode(Byte
Optional<Bytecode::IdentifierTableIndex> name_identifier;
if (has_name) {
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical);
generator.begin_variable_scope();
name_identifier = generator.intern_identifier(name());
generator.emit<Bytecode::Op::CreateVariable>(*name_identifier, Bytecode::Op::EnvironmentMode::Lexical, true);
@ -2036,12 +2003,11 @@ Bytecode::CodeGenerationErrorOr<void> TryStatement::generate_bytecode(Bytecode::
if (!m_finalizer)
generator.emit<Bytecode::Op::LeaveUnwindContext>();
generator.begin_variable_scope(Bytecode::Generator::BindingMode::Lexical, Bytecode::Generator::SurroundingScopeKind::Block);
generator.begin_variable_scope();
TRY(m_handler->parameter().visit(
[&](DeprecatedFlyString 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);
}
@ -2313,7 +2279,6 @@ static Bytecode::CodeGenerationErrorOr<ForInOfHeadEvaluationResult> for_in_of_he
MUST(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.
@ -2461,7 +2426,7 @@ static Bytecode::CodeGenerationErrorOr<void> for_in_of_body_evaluation(Bytecode:
// 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);
generator.begin_variable_scope();
has_lexical_binding = true;
// 14.7.5.4 Runtime Semantics: ForDeclarationBindingInstantiation, https://tc39.es/ecma262/#sec-runtime-semantics-fordeclarationbindinginstantiation
@ -2472,7 +2437,6 @@ static Bytecode::CodeGenerationErrorOr<void> for_in_of_body_evaluation(Bytecode:
// NOTE: Nothing in the callback throws an exception.
MUST(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).

30
Userland/Libraries/LibJS/Bytecode/Generator.cpp
View file

@ -87,30 +87,24 @@ Label Generator::nearest_continuable_scope() const
return m_continuable_scopes.last().bytecode_target;
}
void Generator::begin_variable_scope(BindingMode mode, SurroundingScopeKind kind)
void Generator::block_declaration_instantiation(ScopeNode const& scope_node)
{
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);
}
start_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
emit<Bytecode::Op::BlockDeclarationInstantiation>(scope_node);
}
void Generator::begin_variable_scope()
{
start_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
emit<Bytecode::Op::CreateEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
}
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);
end_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
if (!m_current_basic_block->is_terminated()) {
emit<Bytecode::Op::LeaveEnvironment>(
mode == BindingMode::Lexical
? Bytecode::Op::EnvironmentMode::Lexical
: Bytecode::Op::EnvironmentMode::Var);
}
if (!m_current_basic_block->is_terminated()) {
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
}
}

30
Userland/Libraries/LibJS/Bytecode/Generator.h
View file

@ -136,36 +136,11 @@ public:
};
struct LexicalScope {
SurroundingScopeKind kind;
BindingMode mode;
HashTable<IdentifierTableIndex> known_bindings;
};
void register_binding(IdentifierTableIndex identifier, BindingMode mode = BindingMode::Lexical)
{
m_variable_scopes.last_matching([&](auto& x) { return x.mode == BindingMode::Global || x.mode == mode; })->known_bindings.set(identifier);
}
bool has_binding(IdentifierTableIndex identifier, Optional<BindingMode> const& specific_binding_mode = {}) const
{
for (auto index = m_variable_scopes.size(); index > 0; --index) {
auto& scope = m_variable_scopes[index - 1];
void block_declaration_instantiation(ScopeNode const&);
if (scope.mode != BindingMode::Global && specific_binding_mode.value_or(scope.mode) != scope.mode)
continue;
if (scope.known_bindings.contains(identifier))
return true;
}
return false;
}
bool has_binding_in_current_scope(IdentifierTableIndex identifier) const
{
if (m_variable_scopes.is_empty())
return false;
return m_variable_scopes.last().known_bindings.contains(identifier);
}
void begin_variable_scope(BindingMode mode = BindingMode::Lexical, SurroundingScopeKind kind = SurroundingScopeKind::Block);
void begin_variable_scope();
void end_variable_scope();
enum class BlockBoundaryType {
@ -239,7 +214,6 @@ private:
FunctionKind m_enclosing_function_kind { FunctionKind::Normal };
Vector<LabelableScope> m_continuable_scopes;
Vector<LabelableScope> m_breakable_scopes;
Vector<LexicalScope> m_variable_scopes;
Vector<BlockBoundaryType> m_boundaries;
Vector<Register> m_home_objects;
};

1
Userland/Libraries/LibJS/Bytecode/Instruction.h
View file

@ -17,6 +17,7 @@
O(BitwiseNot) \
O(BitwiseOr) \
O(BitwiseXor) \
O(BlockDeclarationInstantiation) \
O(Call) \
O(ConcatString) \
O(ContinuePendingUnwind) \

15
Userland/Libraries/LibJS/Bytecode/Op.cpp
View file

@ -1097,6 +1097,16 @@ ThrowCompletionOr<void> ToNumeric::execute_impl(Bytecode::Interpreter& interpret
return {};
}
ThrowCompletionOr<void> BlockDeclarationInstantiation::execute_impl(Bytecode::Interpreter& interpreter) const
{
auto& vm = interpreter.vm();
auto old_environment = vm.running_execution_context().lexical_environment;
interpreter.saved_lexical_environment_stack().append(old_environment);
vm.running_execution_context().lexical_environment = new_declarative_environment(*old_environment);
m_scope_node.block_declaration_instantiation(vm, vm.running_execution_context().lexical_environment);
return {};
}
DeprecatedString Load::to_deprecated_string_impl(Bytecode::Executable const&) const
{
return DeprecatedString::formatted("Load {}", m_src);
@ -1459,4 +1469,9 @@ DeprecatedString ToNumeric::to_deprecated_string_impl(Bytecode::Executable const
return "ToNumeric"sv;
}
DeprecatedString BlockDeclarationInstantiation::to_deprecated_string_impl(Bytecode::Executable const&) const
{
return "BlockDeclarationInstantiation"sv;
}
}

17
Userland/Libraries/LibJS/Bytecode/Op.h
View file

@ -794,6 +794,23 @@ private:
Optional<Register> m_home_object;
};
class BlockDeclarationInstantiation final : public Instruction {
public:
explicit BlockDeclarationInstantiation(ScopeNode const& scope_node)
: Instruction(Type::BlockDeclarationInstantiation)
, m_scope_node(scope_node)
{
}
ThrowCompletionOr<void> execute_impl(Bytecode::Interpreter&) const;
DeprecatedString to_deprecated_string_impl(Bytecode::Executable const&) const;
void replace_references_impl(BasicBlock const&, BasicBlock const&) { }
void replace_references_impl(Register, Register) { }
private:
ScopeNode const& m_scope_node;
};
class Return final : public Instruction {
public:
constexpr static bool IsTerminator = true;