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LibJS/Bytecode: Implement break/continue labels

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This is done by keeping track of all the labels that apply to a given
break/continue scope alongside their bytecode target. When a
break/continue with a label is generated, we scan from the most inner
scope to the most outer scope looking for the label, performing any
necessary unwinds on the way. Once the label is found, it is then
jumped to.
This commit is contained in:
Luke Wilde 2022-06-11 23:09:37 +01:00 • committed by Ali Mohammad Pur
parent 455c0b7794
commit c0fadfb9b7
4 changed files with 218 additions and 30 deletions
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68
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@ -69,7 +69,7 @@ Register Generator::allocate_register()
Label Generator::nearest_continuable_scope() const
{
return m_continuable_scopes.last();
return m_continuable_scopes.last().bytecode_target;
}
void Generator::begin_variable_scope(BindingMode mode, SurroundingScopeKind kind)
@ -99,9 +99,9 @@ void Generator::end_variable_scope()
}
}
void Generator::begin_continuable_scope(Label continue_target)
void Generator::begin_continuable_scope(Label continue_target, Vector<FlyString> const& language_label_set)
{
m_continuable_scopes.append(continue_target);
m_continuable_scopes.append({ continue_target, language_label_set });
start_boundary(BlockBoundaryType::Continue);
}
@ -110,13 +110,15 @@ void Generator::end_continuable_scope()
m_continuable_scopes.take_last();
end_boundary(BlockBoundaryType::Continue);
}
Label Generator::nearest_breakable_scope() const
{
return m_breakable_scopes.last();
return m_breakable_scopes.last().bytecode_target;
}
void Generator::begin_breakable_scope(Label breakable_target)
void Generator::begin_breakable_scope(Label breakable_target, Vector<FlyString> const& language_label_set)
{
m_breakable_scopes.append(breakable_target);
m_breakable_scopes.append({ breakable_target, language_label_set });
start_boundary(BlockBoundaryType::Break);
}
@ -246,6 +248,60 @@ CodeGenerationErrorOr<void> Generator::emit_delete_reference(JS::ASTNode const&
return {};
}
Label Generator::perform_needed_unwinds_for_labelled_break_and_return_target_block(FlyString const& break_label)
{
size_t current_boundary = m_boundaries.size();
for (auto& breakable_scope : m_breakable_scopes.in_reverse()) {
for (; current_boundary > 0; --current_boundary) {
auto boundary = m_boundaries[current_boundary - 1];
if (boundary == BlockBoundaryType::Unwind) {
emit<Bytecode::Op::LeaveUnwindContext>();
} else if (boundary == BlockBoundaryType::LeaveLexicalEnvironment) {
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
} else if (boundary == BlockBoundaryType::LeaveVariableEnvironment) {
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Var);
} else if (boundary == BlockBoundaryType::Break) {
// Make sure we don't process this boundary twice if the current breakable scope doesn't contain the target label.
--current_boundary;
break;
}
}
if (breakable_scope.language_label_set.contains_slow(break_label))
return breakable_scope.bytecode_target;
}
// We must have a breakable scope available that contains the label, as this should be enforced by the parser.
VERIFY_NOT_REACHED();
}
Label Generator::perform_needed_unwinds_for_labelled_continue_and_return_target_block(FlyString const& continue_label)
{
size_t current_boundary = m_boundaries.size();
for (auto& continuable_scope : m_continuable_scopes.in_reverse()) {
for (; current_boundary > 0; --current_boundary) {
auto boundary = m_boundaries[current_boundary - 1];
if (boundary == BlockBoundaryType::Unwind) {
emit<Bytecode::Op::LeaveUnwindContext>();
} else if (boundary == BlockBoundaryType::LeaveLexicalEnvironment) {
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
} else if (boundary == BlockBoundaryType::LeaveVariableEnvironment) {
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Var);
} else if (boundary == BlockBoundaryType::Continue) {
// Make sure we don't process this boundary twice if the current continuable scope doesn't contain the target label.
--current_boundary;
break;
}
}
if (continuable_scope.language_label_set.contains_slow(continue_label))
return continuable_scope.bytecode_target;
}
// We must have a continuable scope available that contains the label, as this should be enforced by the parser.
VERIFY_NOT_REACHED();
}
String CodeGenerationError::to_string()
{
return String::formatted("CodeGenerationError in {}: {}", failing_node ? failing_node->class_name() : "<unknown node>", reason_literal);