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LibJS/Bytecode: Reuse bytecode registers

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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.
This commit is contained in:
Andreas Kling
2024-05-07 21:36:56 +02:00
parent f537d0b3cf
commit cea59b6642
10 changed files with 505 additions and 381 deletions
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82
Userland/Libraries/LibJS/Bytecode/Generator.cpp
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@@ -22,6 +22,7 @@ Generator::Generator(VM& vm)
, m_identifier_table(make<IdentifierTable>())
, m_regex_table(make<RegexTable>())
, m_constants(vm.heap())
, m_accumulator(*this, Operand(Register::accumulator()))
{
}
@@ -208,6 +209,8 @@ CodeGenerationErrorOr<NonnullGCPtr<Executable>> Generator::generate(VM& vm, ASTN
executable->basic_block_start_offsets = move(basic_block_start_offsets);
executable->source_map = move(source_map);
generator.m_finished = true;
return executable;
}
@@ -217,10 +220,28 @@ void Generator::grow(size_t additional_size)
m_current_basic_block->grow(additional_size);
}
Register Generator::allocate_register()
ScopedOperand Generator::allocate_sequential_register()
{
VERIFY(m_next_register != NumericLimits<u32>::max());
return Register { m_next_register++ };
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)
@@ -311,10 +332,10 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_super_refere
// https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
// 1. Let env be GetThisEnvironment().
// 2. Let actualThis be ? env.GetThisBinding().
auto actual_this = Operand(allocate_register());
auto actual_this = allocate_register();
emit<Bytecode::Op::ResolveThisBinding>(actual_this);
Optional<Bytecode::Operand> computed_property_value;
Optional<ScopedOperand> computed_property_value;
if (expression.is_computed()) {
// SuperProperty : super [ Expression ]
@@ -329,7 +350,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_super_refere
// 1. Let env be GetThisEnvironment().
// 2. Assert: env.HasSuperBinding() is true.
// 3. Let baseValue be ? env.GetSuperBase().
auto base_value = Operand(allocate_register());
auto base_value = allocate_register();
emit<Bytecode::Op::ResolveSuperBase>(base_value);
// 4. Return the Reference Record { [[Base]]: baseValue, [[ReferencedName]]: propertyKey, [[Strict]]: strict, [[ThisValue]]: actualThis }.
@@ -340,7 +361,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_super_refere
};
}
CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_reference(JS::ASTNode const& node, Optional<Operand> preferred_dst)
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);
@@ -360,7 +381,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
// 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() : Operand(allocate_register());
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
if (super_reference.referenced_name.has_value()) {
// 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
@@ -381,9 +402,9 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
auto saved_property = Operand(allocate_register());
auto saved_property = allocate_register();
emit<Bytecode::Op::Mov>(saved_property, property);
auto dst = preferred_dst.has_value() ? preferred_dst.value() : Operand(allocate_register());
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,
@@ -394,7 +415,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
}
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() : Operand(allocate_register());
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,
@@ -405,7 +426,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
}
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() : Operand(allocate_register());
auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
emit<Bytecode::Op::GetPrivateById>(dst, base, identifier_table_ref);
return ReferenceOperands {
.base = base,
@@ -420,7 +441,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
};
}
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(JS::ASTNode const& node, Operand value)
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(JS::ASTNode const& node, ScopedOperand value)
{
if (is<Identifier>(node)) {
auto& identifier = static_cast<Identifier const&>(node);
@@ -473,7 +494,7 @@ CodeGenerationErrorOr<void> Generator::emit_store_to_reference(JS::ASTNode const
};
}
CodeGenerationErrorOr<void> Generator::emit_store_to_reference(ReferenceOperands const& reference, Operand value)
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);
@@ -493,14 +514,14 @@ CodeGenerationErrorOr<void> Generator::emit_store_to_reference(ReferenceOperands
return {};
}
CodeGenerationErrorOr<Optional<Operand>> Generator::emit_delete_reference(JS::ASTNode const& node)
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 = Operand(allocate_register());
auto dst = allocate_register();
emit<Bytecode::Op::DeleteVariable>(dst, intern_identifier(identifier.string()));
return dst;
}
@@ -520,11 +541,11 @@ CodeGenerationErrorOr<Optional<Operand>> Generator::emit_delete_reference(JS::AS
emit<Bytecode::Op::DeleteByIdWithThis>(dst, *super_reference.base, *super_reference.this_value, identifier_table_ref);
}
return Optional<Operand> {};
return Optional<ScopedOperand> {};
}
auto object = TRY(expression.object().generate_bytecode(*this)).value();
auto dst = Operand(allocate_register());
auto dst = allocate_register();
if (expression.is_computed()) {
auto property = TRY(expression.property().generate_bytecode(*this)).value();
@@ -555,10 +576,10 @@ CodeGenerationErrorOr<Optional<Operand>> Generator::emit_delete_reference(JS::AS
return add_constant(Value(true));
}
void Generator::emit_set_variable(JS::Identifier const& identifier, Operand value, Bytecode::Op::SetVariable::InitializationMode initialization_mode, Bytecode::Op::EnvironmentMode mode)
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.is_local() && value.index() == identifier.local_variable_index()) {
if (value.operand().is_local() && value.operand().index() == identifier.local_variable_index()) {
// Moving a local to itself is a no-op.
return;
}
@@ -730,7 +751,7 @@ void Generator::generate_continue(DeprecatedFlyString const& continue_label)
generate_labelled_jump(JumpType::Continue, continue_label);
}
void Generator::push_home_object(Operand object)
void Generator::push_home_object(ScopedOperand object)
{
m_home_objects.append(object);
}
@@ -740,7 +761,7 @@ void Generator::pop_home_object()
m_home_objects.take_last();
}
void Generator::emit_new_function(Operand dst, FunctionExpression const& function_node, Optional<IdentifierTableIndex> lhs_name)
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);
@@ -749,7 +770,7 @@ void Generator::emit_new_function(Operand dst, FunctionExpression const& functio
}
}
CodeGenerationErrorOr<Optional<Operand>> Generator::emit_named_evaluation_if_anonymous_function(Expression const& expression, Optional<IdentifierTableIndex> lhs_name, Optional<Operand> preferred_dst)
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);
@@ -768,22 +789,22 @@ CodeGenerationErrorOr<Optional<Operand>> Generator::emit_named_evaluation_if_ano
return expression.generate_bytecode(*this, preferred_dst);
}
void Generator::emit_get_by_id(Operand dst, Operand base, IdentifierTableIndex property_identifier, Optional<IdentifierTableIndex> base_identifier)
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(Operand dst, Operand base, IdentifierTableIndex id, Operand this_value)
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(Operand dst, Operand result)
void Generator::emit_iterator_value(ScopedOperand dst, ScopedOperand result)
{
emit_get_by_id(dst, result, intern_identifier("value"sv));
}
void Generator::emit_iterator_complete(Operand dst, Operand result)
void Generator::emit_iterator_complete(ScopedOperand dst, ScopedOperand result)
{
emit_get_by_id(dst, result, intern_identifier("done"sv));
}
@@ -798,7 +819,7 @@ void Generator::set_local_initialized(u32 local_index)
m_initialized_locals.set(local_index);
}
Operand Generator::get_this(Optional<Operand> preferred_dst)
ScopedOperand Generator::get_this(Optional<ScopedOperand> preferred_dst)
{
if (m_current_basic_block->this_().has_value())
return m_current_basic_block->this_().value();
@@ -806,10 +827,15 @@ Operand Generator::get_this(Optional<Operand> preferred_dst)
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() : Operand(allocate_register());
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;
}
}