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LibJS: Generate unwind chains for break in Bytecode

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This uses a newly added instruction `ScheduleJump`
This instruction tells the finally proceeding it, that instead of
jumping to it's next block it should jump to the designated block.
This commit is contained in:
Hendiadyoin1 2022-11-25 16:15:34 +01:00 • committed by Linus Groh
parent 495ba53e46
commit f5376cb282
9 changed files with 123 additions and 19 deletions
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59
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@ -262,23 +262,62 @@ CodeGenerationErrorOr<void> Generator::emit_delete_reference(JS::ASTNode const&
return {};
}
Label Generator::perform_needed_unwinds_for_labelled_break_and_return_target_block(DeprecatedFlyString const& break_label)
void Generator::generate_break()
{
bool last_was_finally = false;
// FIXME: Reduce code duplication
for (size_t i = m_boundaries.size(); i > 0; --i) {
auto boundary = m_boundaries[i - 1];
using enum BlockBoundaryType;
switch (boundary) {
case Break:
emit<Op::Jump>().set_targets(nearest_breakable_scope(), {});
return;
case Unwind:
if (!last_was_finally)
emit<Bytecode::Op::LeaveUnwindContext>();
last_was_finally = false;
break;
case LeaveLexicalEnvironment:
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Lexical);
break;
case LeaveVariableEnvironment:
emit<Bytecode::Op::LeaveEnvironment>(Bytecode::Op::EnvironmentMode::Var);
break;
case Continue:
break;
case ReturnToFinally: {
auto& block = make_block(DeprecatedString::formatted("{}.break", current_block().name()));
emit<Op::ScheduleJump>(Label { block });
switch_to_basic_block(block);
last_was_finally = true;
break;
};
}
}
VERIFY_NOT_REACHED();
}
void Generator::generate_break(DeprecatedFlyString const& break_label)
{
size_t current_boundary = m_boundaries.size();
for (auto& breakable_scope : m_breakable_scopes.in_reverse()) {
bool last_was_finally = false;
for (auto const& breakable_scope : m_breakable_scopes.in_reverse()) {
for (; current_boundary > 0; --current_boundary) {
auto boundary = m_boundaries[current_boundary - 1];
// FIXME: Handle ReturnToFinally in a graceful manner
// We need to execute the finally block, but tell it to resume
// execution at the designated label
if (boundary == BlockBoundaryType::Unwind) {
emit<Bytecode::Op::LeaveUnwindContext>();
if (!last_was_finally)
emit<Bytecode::Op::LeaveUnwindContext>();
last_was_finally = false;
} 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::ReturnToFinally) {
// FIXME: We need to enter the `finally`, while still scheduling the break to happen
auto& block = make_block(DeprecatedString::formatted("{}.break", current_block().name()));
emit<Op::ScheduleJump>(Label { block });
switch_to_basic_block(block);
last_was_finally = true;
} 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;
@ -286,8 +325,10 @@ Label Generator::perform_needed_unwinds_for_labelled_break_and_return_target_blo
}
}
if (breakable_scope.language_label_set.contains_slow(break_label))
return breakable_scope.bytecode_target;
if (breakable_scope.language_label_set.contains_slow(break_label)) {
emit<Op::Jump>().set_targets(breakable_scope.bytecode_target, {});
return;
}
}
// We must have a breakable scope available that contains the label, as this should be enforced by the parser.