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ladybird/Userland/Libraries/LibJS/Bytecode/Generator.cpp
Andreas Kling cea59b6642 LibJS/Bytecode: Reuse bytecode registers 
This patch adds a register freelist to Bytecode::Generator and switches
all operands inside the generator to a new ScopedOperand type that is
ref-counted and automatically frees the register when nothing uses it.

This dramatically reduces the size of bytecode executable register
windows, which were often in the several thousands of registers for
large functions. Most functions now use less than 100 registers.
2024-05-09 09:12:13 +02:00

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/*
* Copyright (c) 2021-2024, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/QuickSort.h>
#include <AK/TemporaryChange.h>
#include <LibJS/AST.h>
#include <LibJS/Bytecode/BasicBlock.h>
#include <LibJS/Bytecode/Generator.h>
#include <LibJS/Bytecode/Instruction.h>
#include <LibJS/Bytecode/Op.h>
#include <LibJS/Bytecode/Register.h>
#include <LibJS/Runtime/VM.h>
namespace JS::Bytecode {
Generator::Generator(VM& vm)
: m_vm(vm)
, m_string_table(make<StringTable>())
, m_identifier_table(make<IdentifierTable>())
, m_regex_table(make<RegexTable>())
, m_constants(vm.heap())
, m_accumulator(*this, Operand(Register::accumulator()))
{
}
CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::generate(VM& vm, ASTNode const& node, ReadonlySpan<FunctionParameter> parameters, FunctionKind enclosing_function_kind)
{
Generator generator(vm);
for (auto const& parameter : parameters) {
if (auto const* identifier = parameter.binding.get_pointer<NonnullRefPtr<Identifier const>>();
identifier && (*identifier)->is_local()) {
generator.set_local_initialized((*identifier)->local_variable_index());
}
}
generator.switch_to_basic_block(generator.make_block());
SourceLocationScope scope(generator, node);
generator.m_enclosing_function_kind = enclosing_function_kind;
if (generator.is_in_generator_or_async_function()) {
// Immediately yield with no value.
auto& start_block = generator.make_block();
generator.emit<Bytecode::Op::Yield>(Label { start_block }, generator.add_constant(js_undefined()));
generator.switch_to_basic_block(start_block);
// NOTE: This doesn't have to handle received throw/return completions, as GeneratorObject::resume_abrupt
// will not enter the generator from the SuspendedStart state and immediately completes the generator.
}
auto last_value = TRY(node.generate_bytecode(generator));
if (!generator.current_block().is_terminated() && last_value.has_value()) {
generator.emit<Bytecode::Op::End>(last_value.value());
}
if (generator.is_in_generator_or_async_function()) {
// Terminate all unterminated blocks with yield return
for (auto& block : generator.m_root_basic_blocks) {
if (block->is_terminated())
continue;
generator.switch_to_basic_block(*block);
generator.emit<Bytecode::Op::Yield>(nullptr, generator.add_constant(js_undefined()));
}
}
bool is_strict_mode = false;
if (is<Program>(node))
is_strict_mode = static_cast<Program const&>(node).is_strict_mode();
else if (is<FunctionBody>(node))
is_strict_mode = static_cast<FunctionBody const&>(node).in_strict_mode();
else if (is<FunctionDeclaration>(node))
is_strict_mode = static_cast<FunctionDeclaration const&>(node).is_strict_mode();
else if (is<FunctionExpression>(node))
is_strict_mode = static_cast<FunctionExpression const&>(node).is_strict_mode();
size_t size_needed = 0;
for (auto& block : generator.m_root_basic_blocks) {
size_needed += block->size();
}
Vector<u8> bytecode;
bytecode.ensure_capacity(size_needed);
Vector<size_t> basic_block_start_offsets;
basic_block_start_offsets.ensure_capacity(generator.m_root_basic_blocks.size());
HashMap<BasicBlock const*, size_t> block_offsets;
Vector<size_t> label_offsets;
struct UnlinkedExceptionHandlers {
size_t start_offset;
size_t end_offset;
BasicBlock const* handler;
BasicBlock const* finalizer;
};
Vector<UnlinkedExceptionHandlers> unlinked_exception_handlers;
HashMap<size_t, SourceRecord> source_map;
for (auto& block : generator.m_root_basic_blocks) {
basic_block_start_offsets.append(bytecode.size());
if (block->handler() || block->finalizer()) {
unlinked_exception_handlers.append({
.start_offset = bytecode.size(),
.end_offset = 0,
.handler = block->handler(),
.finalizer = block->finalizer(),
});
}
block_offsets.set(block.ptr(), bytecode.size());
for (auto& [offset, source_record] : block->source_map()) {
source_map.set(bytecode.size() + offset, source_record);
}
Bytecode::InstructionStreamIterator it(block->instruction_stream());
while (!it.at_end()) {
auto& instruction = const_cast<Instruction&>(*it);
// OPTIMIZATION: Don't emit jumps that just jump to the next block.
if (instruction.type() == Instruction::Type::Jump) {
auto& jump = static_cast<Bytecode::Op::Jump&>(instruction);
if (jump.target().basic_block_index() == block->index() + 1) {
if (basic_block_start_offsets.last() == bytecode.size()) {
// This block is empty, just skip it.
basic_block_start_offsets.take_last();
}
++it;
continue;
}
}
// OPTIMIZATION: For `JumpIf` where one of the targets is the very next block,
// we can emit a `JumpTrue` or `JumpFalse` (to the other block) instead.
if (instruction.type() == Instruction::Type::JumpIf) {
auto& jump = static_cast<Bytecode::Op::JumpIf&>(instruction);
if (jump.true_target().basic_block_index() == block->index() + 1) {
Op::JumpFalse jump_false(jump.condition(), Label { jump.false_target() });
auto& label = jump_false.target();
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&jump_false));
label_offsets.append(label_offset);
bytecode.append(reinterpret_cast<u8 const*>(&jump_false), jump_false.length());
++it;
continue;
}
if (jump.false_target().basic_block_index() == block->index() + 1) {
Op::JumpTrue jump_true(jump.condition(), Label { jump.true_target() });
auto& label = jump_true.target();
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&jump_true));
label_offsets.append(label_offset);
bytecode.append(reinterpret_cast<u8 const*>(&jump_true), jump_true.length());
++it;
continue;
}
}
instruction.visit_labels([&](Label& label) {
size_t label_offset = bytecode.size() + (bit_cast<FlatPtr>(&label) - bit_cast<FlatPtr>(&instruction));
label_offsets.append(label_offset);
});
bytecode.append(reinterpret_cast<u8 const*>(&instruction), instruction.length());
++it;
}
if (!block->is_terminated()) {
Op::End end(generator.add_constant(js_undefined()));
bytecode.append(reinterpret_cast<u8 const*>(&end), end.length());
}
if (block->handler() || block->finalizer()) {
unlinked_exception_handlers.last().end_offset = bytecode.size();
}
}
for (auto label_offset : label_offsets) {
auto& label = *reinterpret_cast<Label*>(bytecode.data() + label_offset);
auto* block = generator.m_root_basic_blocks[label.basic_block_index()].ptr();
label.set_address(block_offsets.get(block).value());
}
auto executable = vm.heap().allocate_without_realm<Executable>(
move(bytecode),
move(generator.m_identifier_table),
move(generator.m_string_table),
move(generator.m_regex_table),
move(generator.m_constants),
node.source_code(),
generator.m_next_property_lookup_cache,
generator.m_next_global_variable_cache,
generator.m_next_environment_variable_cache,
generator.m_next_register,
is_strict_mode);
Vector<Executable::ExceptionHandlers> linked_exception_handlers;
for (auto& unlinked_handler : unlinked_exception_handlers) {
auto start_offset = unlinked_handler.start_offset;
auto end_offset = unlinked_handler.end_offset;
auto handler_offset = unlinked_handler.handler ? block_offsets.get(unlinked_handler.handler).value() : Optional<size_t> {};
auto finalizer_offset = unlinked_handler.finalizer ? block_offsets.get(unlinked_handler.finalizer).value() : Optional<size_t> {};
linked_exception_handlers.append({ start_offset, end_offset, handler_offset, finalizer_offset });
}
quick_sort(linked_exception_handlers, [](auto const& a, auto const& b) {
return a.start_offset < b.start_offset;
});
executable->exception_handlers = move(linked_exception_handlers);
executable->basic_block_start_offsets = move(basic_block_start_offsets);
executable->source_map = move(source_map);
generator.m_finished = true;
return executable;
}
void Generator::grow(size_t additional_size)
{
VERIFY(m_current_basic_block);
m_current_basic_block->grow(additional_size);
}
ScopedOperand Generator::allocate_sequential_register()
{
VERIFY(m_next_register != NumericLimits<u32>::max());
return ScopedOperand { *this, Operand { Register { m_next_register++ } } };
}
ScopedOperand Generator::allocate_register()
{
if (!m_free_registers.is_empty()) {
return ScopedOperand { *this, Operand { m_free_registers.take_last() } };
}
return allocate_sequential_register();
}
void Generator::free_register(Register reg)
{
m_free_registers.append(reg);
}
ScopedOperand Generator::local(u32 local_index)
{
return ScopedOperand { *this, Operand { Operand::Type::Local, static_cast<u32>(local_index) } };
}
Generator::SourceLocationScope::SourceLocationScope(Generator& generator, ASTNode const& node)
: m_generator(generator)
, m_previous_node(m_generator.m_current_ast_node)
{
m_generator.m_current_ast_node = &node;
}
Generator::SourceLocationScope::~SourceLocationScope()
{
m_generator.m_current_ast_node = m_previous_node;
}
Generator::UnwindContext::UnwindContext(Generator& generator, Optional<Label> finalizer)
: m_generator(generator)
, m_finalizer(finalizer)
, m_previous_context(m_generator.m_current_unwind_context)
{
m_generator.m_current_unwind_context = this;
}
Generator::UnwindContext::~UnwindContext()
{
VERIFY(m_generator.m_current_unwind_context == this);
m_generator.m_current_unwind_context = m_previous_context;
}
Label Generator::nearest_continuable_scope() const
{
return m_continuable_scopes.last().bytecode_target;
}
void Generator::block_declaration_instantiation(ScopeNode const& scope_node)
{
start_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
emit<Bytecode::Op::BlockDeclarationInstantiation>(scope_node);
}
void Generator::begin_variable_scope()
{
start_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
emit<Bytecode::Op::CreateLexicalEnvironment>();
}
void Generator::end_variable_scope()
{
end_boundary(BlockBoundaryType::LeaveLexicalEnvironment);
if (!m_current_basic_block->is_terminated()) {
emit<Bytecode::Op::LeaveLexicalEnvironment>();
}
}
void Generator::begin_continuable_scope(Label continue_target, Vector<DeprecatedFlyString> const& language_label_set)
{
m_continuable_scopes.append({ continue_target, language_label_set });
start_boundary(BlockBoundaryType::Continue);
}
void Generator::end_continuable_scope()
{
m_continuable_scopes.take_last();
end_boundary(BlockBoundaryType::Continue);
}
Label Generator::nearest_breakable_scope() const
{
return m_breakable_scopes.last().bytecode_target;
}
void Generator::begin_breakable_scope(Label breakable_target, Vector<DeprecatedFlyString> const& language_label_set)
{
m_breakable_scopes.append({ breakable_target, language_label_set });
start_boundary(BlockBoundaryType::Break);
}
void Generator::end_breakable_scope()
{
m_breakable_scopes.take_last();
end_boundary(BlockBoundaryType::Break);
}
CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_super_reference(MemberExpression const& expression)
{
VERIFY(is<SuperExpression>(expression.object()));
// https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
// 1. Let env be GetThisEnvironment().
// 2. Let actualThis be ? env.GetThisBinding().
auto actual_this = allocate_register();
emit<Bytecode::Op::ResolveThisBinding>(actual_this);
Optional<ScopedOperand> computed_property_value;
if (expression.is_computed()) {
// SuperProperty : super [ Expression ]
// 3. Let propertyNameReference be ? Evaluation of Expression.
// 4. Let propertyNameValue be ? GetValue(propertyNameReference).
computed_property_value = TRY(expression.property().generate_bytecode(*this)).value();
}
// 5/7. Return ? MakeSuperPropertyReference(actualThis, propertyKey, strict).
// https://tc39.es/ecma262/#sec-makesuperpropertyreference
// 1. Let env be GetThisEnvironment().
// 2. Assert: env.HasSuperBinding() is true.
// 3. Let baseValue be ? env.GetSuperBase().
auto base_value = allocate_register();
emit<Bytecode::Op::ResolveSuperBase>(base_value);
// 4. Return the Reference Record { [[Base]]: baseValue, [[ReferencedName]]: propertyKey, [[Strict]]: strict, [[ThisValue]]: actualThis }.
return ReferenceOperands {
.base = base_value,
.referenced_name = computed_property_value,
.this_value = actual_this,
};
}
CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_reference(JS::ASTNode const& node, Optional<ScopedOperand> preferred_dst)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
auto loaded_value = TRY(identifier.generate_bytecode(*this, preferred_dst)).value();
return ReferenceOperands {
.loaded_value = loaded_value,
};
}
if (!is<MemberExpression>(node)) {
return CodeGenerationError {
&node,
"Unimplemented/invalid node used as a reference"sv
};
}
auto& expression = static_cast<MemberExpression const&>(node);
// https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
if (is<SuperExpression>(expression.object())) {
auto super_reference = TRY(emit_super_reference(expression));
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
if (super_reference.referenced_name.has_value()) {
// 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
// FIXME: This does ToPropertyKey out of order, which is observable by Symbol.toPrimitive!
emit<Bytecode::Op::GetByValueWithThis>(dst, *super_reference.base, *super_reference.referenced_name, *super_reference.this_value);
} else {
// 3. Let propertyKey be StringValue of IdentifierName.
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit_get_by_id_with_this(dst, *super_reference.base, identifier_table_ref, *super_reference.this_value);
}
super_reference.loaded_value = dst;
return super_reference;
}
auto base = TRY(expression.object().generate_bytecode(*this)).value();
auto base_identifier = intern_identifier_for_expression(expression.object());
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
auto saved_property = allocate_register();
emit<Bytecode::Op::Mov>(saved_property, property);
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::GetByValue>(dst, base, property, move(base_identifier));
return ReferenceOperands {
.base = base,
.referenced_name = saved_property,
.this_value = base,
.loaded_value = dst,
};
}
if (expression.property().is_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit_get_by_id(dst, base, identifier_table_ref, move(base_identifier));
return ReferenceOperands {
.base = base,
.referenced_identifier = identifier_table_ref,
.this_value = base,
.loaded_value = dst,
};
}
if (expression.property().is_private_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<PrivateIdentifier>(expression.property()).string());
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::GetPrivateById>(dst, base, identifier_table_ref);
return ReferenceOperands {
.base = base,
.referenced_private_identifier = identifier_table_ref,
.this_value = base,
.loaded_value = dst,
};
}
return CodeGenerationError {
&expression,
"Unimplemented non-computed member expression"sv
};
}
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(JS::ASTNode const& node, ScopedOperand value)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
emit_set_variable(identifier, value);
return {};
}
if (is<MemberExpression>(node)) {
auto& expression = static_cast<MemberExpression const&>(node);
// https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
if (is<SuperExpression>(expression.object())) {
auto super_reference = TRY(emit_super_reference(expression));
// 4. Return the Reference Record { [[Base]]: baseValue, [[ReferencedName]]: propertyKey, [[Strict]]: strict, [[ThisValue]]: actualThis }.
if (super_reference.referenced_name.has_value()) {
// 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
// FIXME: This does ToPropertyKey out of order, which is observable by Symbol.toPrimitive!
emit<Bytecode::Op::PutByValueWithThis>(*super_reference.base, *super_reference.referenced_name, *super_reference.this_value, value);
} else {
// 3. Let propertyKey be StringValue of IdentifierName.
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::PutByIdWithThis>(*super_reference.base, *super_reference.this_value, identifier_table_ref, value, Bytecode::Op::PropertyKind::KeyValue, next_property_lookup_cache());
}
} else {
auto object = TRY(expression.object().generate_bytecode(*this)).value();
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
emit<Bytecode::Op::PutByValue>(object, property, value);
} else if (expression.property().is_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::PutById>(object, identifier_table_ref, value, Bytecode::Op::PropertyKind::KeyValue, next_property_lookup_cache());
} else if (expression.property().is_private_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<PrivateIdentifier>(expression.property()).string());
emit<Bytecode::Op::PutPrivateById>(object, identifier_table_ref, value);
} else {
return CodeGenerationError {
&expression,
"Unimplemented non-computed member expression"sv
};
}
}
return {};
}
return CodeGenerationError {
&node,
"Unimplemented/invalid node used a reference"sv
};
}
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(ReferenceOperands const& reference, ScopedOperand value)
{
if (reference.referenced_private_identifier.has_value()) {
emit<Bytecode::Op::PutPrivateById>(*reference.base, *reference.referenced_private_identifier, value);
return {};
}
if (reference.referenced_identifier.has_value()) {
if (reference.base == reference.this_value)
emit<Bytecode::Op::PutById>(*reference.base, *reference.referenced_identifier, value, Bytecode::Op::PropertyKind::KeyValue, next_property_lookup_cache());
else
emit<Bytecode::Op::PutByIdWithThis>(*reference.base, *reference.this_value, *reference.referenced_identifier, value, Bytecode::Op::PropertyKind::KeyValue, next_property_lookup_cache());
return {};
}
if (reference.base == reference.this_value)
emit<Bytecode::Op::PutByValue>(*reference.base, *reference.referenced_name, value);
else
emit<Bytecode::Op::PutByValueWithThis>(*reference.base, *reference.referenced_name, *reference.this_value, value);
return {};
}
CodeGenerationErrorOr<Optional<ScopedOperand>> Generator::emit_delete_reference(JS::ASTNode const& node)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
if (identifier.is_local()) {
return add_constant(Value(false));
}
auto dst = allocate_register();
emit<Bytecode::Op::DeleteVariable>(dst, intern_identifier(identifier.string()));
return dst;
}
if (is<MemberExpression>(node)) {
auto& expression = static_cast<MemberExpression const&>(node);
// https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
if (is<SuperExpression>(expression.object())) {
auto super_reference = TRY(emit_super_reference(expression));
auto dst = Operand(allocate_register());
if (super_reference.referenced_name.has_value()) {
emit<Bytecode::Op::DeleteByValueWithThis>(dst, *super_reference.base, *super_reference.this_value, *super_reference.referenced_name);
} else {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::DeleteByIdWithThis>(dst, *super_reference.base, *super_reference.this_value, identifier_table_ref);
}
return Optional<ScopedOperand> {};
}
auto object = TRY(expression.object().generate_bytecode(*this)).value();
auto dst = allocate_register();
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
emit<Bytecode::Op::DeleteByValue>(dst, object, property);
} else if (expression.property().is_identifier()) {
auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
emit<Bytecode::Op::DeleteById>(dst, object, identifier_table_ref);
} else {
// NOTE: Trying to delete a private field generates a SyntaxError in the parser.
return CodeGenerationError {
&expression,
"Unimplemented non-computed member expression"sv
};
}
return dst;
}
// Though this will have no deletion effect, we still have to evaluate the node as it can have side effects.
// For example: delete a(); delete ++c.b; etc.
// 13.5.1.2 Runtime Semantics: Evaluation, https://tc39.es/ecma262/#sec-delete-operator-runtime-semantics-evaluation
// 1. Let ref be the result of evaluating UnaryExpression.
// 2. ReturnIfAbrupt(ref).
(void)TRY(node.generate_bytecode(*this));
// 3. If ref is not a Reference Record, return true.
// NOTE: The rest of the steps are handled by Delete{Variable,ByValue,Id}.
return add_constant(Value(true));
}
void Generator::emit_set_variable(JS::Identifier const& identifier, ScopedOperand value, Bytecode::Op::SetVariable::InitializationMode initialization_mode, Bytecode::Op::EnvironmentMode mode)
{
if (identifier.is_local()) {
if (value.operand().is_local() && value.operand().index() == identifier.local_variable_index()) {
// Moving a local to itself is a no-op.
return;
}
emit<Bytecode::Op::SetLocal>(identifier.local_variable_index(), value);
} else {
emit<Bytecode::Op::SetVariable>(intern_identifier(identifier.string()), value, next_environment_variable_cache(), initialization_mode, mode);
}
}
static Optional<ByteString> expression_identifier(Expression const& expression)
{
if (expression.is_identifier()) {
auto const& identifier = static_cast<Identifier const&>(expression);
return identifier.string();
}
if (expression.is_numeric_literal()) {
auto const& literal = static_cast<NumericLiteral const&>(expression);
return literal.value().to_string_without_side_effects().to_byte_string();
}
if (expression.is_string_literal()) {
auto const& literal = static_cast<StringLiteral const&>(expression);
return ByteString::formatted("'{}'", literal.value());
}
if (expression.is_member_expression()) {
auto const& member_expression = static_cast<MemberExpression const&>(expression);
StringBuilder builder;
if (auto identifer = expression_identifier(member_expression.object()); identifer.has_value())
builder.append(*identifer);
if (auto identifer = expression_identifier(member_expression.property()); identifer.has_value()) {
if (member_expression.is_computed())
builder.appendff("[{}]", *identifer);
else
builder.appendff(".{}", *identifer);
}
return builder.to_byte_string();
}
return {};
}
Optional<IdentifierTableIndex> Generator::intern_identifier_for_expression(Expression const& expression)
{
if (auto identifer = expression_identifier(expression); identifer.has_value())
return intern_identifier(identifer.release_value());
return {};
}
void Generator::generate_scoped_jump(JumpType type)
{
TemporaryChange temp { m_current_unwind_context, m_current_unwind_context };
bool last_was_finally = false;
for (size_t i = m_boundaries.size(); i > 0; --i) {
auto boundary = m_boundaries[i - 1];
using enum BlockBoundaryType;
switch (boundary) {
case Break:
if (type == JumpType::Break) {
emit<Op::Jump>(nearest_breakable_scope());
return;
}
break;
case Continue:
if (type == JumpType::Continue) {
emit<Op::Jump>(nearest_continuable_scope());
return;
}
break;
case Unwind:
VERIFY(last_was_finally || !m_current_unwind_context->finalizer().has_value());
if (!last_was_finally) {
VERIFY(m_current_unwind_context && m_current_unwind_context->handler().has_value());
emit<Bytecode::Op::LeaveUnwindContext>();
m_current_unwind_context = m_current_unwind_context->previous();
}
last_was_finally = false;
break;
case LeaveLexicalEnvironment:
emit<Bytecode::Op::LeaveLexicalEnvironment>();
break;
case ReturnToFinally: {
VERIFY(m_current_unwind_context->finalizer().has_value());
m_current_unwind_context = m_current_unwind_context->previous();
auto jump_type_name = type == JumpType::Break ? "break"sv : "continue"sv;
auto block_name = MUST(String::formatted("{}.{}", current_block().name(), jump_type_name));
auto& block = make_block(block_name);
emit<Op::ScheduleJump>(Label { block });
switch_to_basic_block(block);
last_was_finally = true;
break;
}
case LeaveFinally:
emit<Op::LeaveFinally>();
break;
}
}
VERIFY_NOT_REACHED();
}
void Generator::generate_labelled_jump(JumpType type, DeprecatedFlyString const& label)
{
TemporaryChange temp { m_current_unwind_context, m_current_unwind_context };
size_t current_boundary = m_boundaries.size();
bool last_was_finally = false;
auto const& jumpable_scopes = type == JumpType::Continue ? m_continuable_scopes : m_breakable_scopes;
for (auto const& jumpable_scope : jumpable_scopes.in_reverse()) {
for (; current_boundary > 0; --current_boundary) {
auto boundary = m_boundaries[current_boundary - 1];
if (boundary == BlockBoundaryType::Unwind) {
VERIFY(last_was_finally || !m_current_unwind_context->finalizer().has_value());
if (!last_was_finally) {
VERIFY(m_current_unwind_context && m_current_unwind_context->handler().has_value());
emit<Bytecode::Op::LeaveUnwindContext>();
m_current_unwind_context = m_current_unwind_context->previous();
}
last_was_finally = false;
} else if (boundary == BlockBoundaryType::LeaveLexicalEnvironment) {
emit<Bytecode::Op::LeaveLexicalEnvironment>();
} else if (boundary == BlockBoundaryType::ReturnToFinally) {
VERIFY(m_current_unwind_context->finalizer().has_value());
m_current_unwind_context = m_current_unwind_context->previous();
auto jump_type_name = type == JumpType::Break ? "break"sv : "continue"sv;
auto block_name = MUST(String::formatted("{}.{}", current_block().name(), jump_type_name));
auto& block = make_block(block_name);
emit<Op::ScheduleJump>(Label { block });
switch_to_basic_block(block);
last_was_finally = true;
} else if ((type == JumpType::Continue && boundary == BlockBoundaryType::Continue) || (type == JumpType::Break && boundary == BlockBoundaryType::Break)) {
// Make sure we don't process this boundary twice if the current jumpable scope doesn't contain the target label.
--current_boundary;
break;
}
}
if (jumpable_scope.language_label_set.contains_slow(label)) {
emit<Op::Jump>(jumpable_scope.bytecode_target);
return;
}
}
// We must have a jumpable scope available that contains the label, as this should be enforced by the parser.
VERIFY_NOT_REACHED();
}
void Generator::generate_break()
{
generate_scoped_jump(JumpType::Break);
}
void Generator::generate_break(DeprecatedFlyString const& break_label)
{
generate_labelled_jump(JumpType::Break, break_label);
}
void Generator::generate_continue()
{
generate_scoped_jump(JumpType::Continue);
}
void Generator::generate_continue(DeprecatedFlyString const& continue_label)
{
generate_labelled_jump(JumpType::Continue, continue_label);
}
void Generator::push_home_object(ScopedOperand object)
{
m_home_objects.append(object);
}
void Generator::pop_home_object()
{
m_home_objects.take_last();
}
void Generator::emit_new_function(ScopedOperand dst, FunctionExpression const& function_node, Optional<IdentifierTableIndex> lhs_name)
{
if (m_home_objects.is_empty()) {
emit<Op::NewFunction>(dst, function_node, lhs_name);
} else {
emit<Op::NewFunction>(dst, function_node, lhs_name, m_home_objects.last());
}
}
CodeGenerationErrorOr<Optional<ScopedOperand>> Generator::emit_named_evaluation_if_anonymous_function(Expression const& expression, Optional<IdentifierTableIndex> lhs_name, Optional<ScopedOperand> preferred_dst)
{
if (is<FunctionExpression>(expression)) {
auto const& function_expression = static_cast<FunctionExpression const&>(expression);
if (!function_expression.has_name()) {
return TRY(function_expression.generate_bytecode_with_lhs_name(*this, move(lhs_name), preferred_dst)).value();
}
}
if (is<ClassExpression>(expression)) {
auto const& class_expression = static_cast<ClassExpression const&>(expression);
if (!class_expression.has_name()) {
return TRY(class_expression.generate_bytecode_with_lhs_name(*this, move(lhs_name), preferred_dst)).value();
}
}
return expression.generate_bytecode(*this, preferred_dst);
}
void Generator::emit_get_by_id(ScopedOperand dst, ScopedOperand base, IdentifierTableIndex property_identifier, Optional<IdentifierTableIndex> base_identifier)
{
emit<Op::GetById>(dst, base, property_identifier, move(base_identifier), m_next_property_lookup_cache++);
}
void Generator::emit_get_by_id_with_this(ScopedOperand dst, ScopedOperand base, IdentifierTableIndex id, ScopedOperand this_value)
{
emit<Op::GetByIdWithThis>(dst, base, id, this_value, m_next_property_lookup_cache++);
}
void Generator::emit_iterator_value(ScopedOperand dst, ScopedOperand result)
{
emit_get_by_id(dst, result, intern_identifier("value"sv));
}
void Generator::emit_iterator_complete(ScopedOperand dst, ScopedOperand result)
{
emit_get_by_id(dst, result, intern_identifier("done"sv));
}
bool Generator::is_local_initialized(u32 local_index) const
{
return m_initialized_locals.find(local_index) != m_initialized_locals.end();
}
void Generator::set_local_initialized(u32 local_index)
{
m_initialized_locals.set(local_index);
}
ScopedOperand Generator::get_this(Optional<ScopedOperand> preferred_dst)
{
if (m_current_basic_block->this_().has_value())
return m_current_basic_block->this_().value();
if (m_root_basic_blocks[0]->this_().has_value()) {
m_current_basic_block->set_this(m_root_basic_blocks[0]->this_().value());
return m_root_basic_blocks[0]->this_().value();
}
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::ResolveThisBinding>(dst);
m_current_basic_block->set_this(dst);
return dst;
}
ScopedOperand Generator::accumulator()
{
return m_accumulator;
}
}
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