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Optimization fast local variables #3194

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Optimization fast local variables #3194

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e23ec27
Implement local variable optimization
HalidOdat Jul 27, 2023
f54f79e
Don't create `arguments` object if not used
HalidOdat Oct 4, 2023
d53a0c4
Don't create parameter expressions environment if not used
HalidOdat Oct 4, 2023
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84 changes: 84 additions & 0 deletions boa_ast/src/operations.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2156,3 +2156,87 @@
ControlFlow::Continue(())
}
}

/// Returns `true` if the given statement can optimize local variables.
#[must_use]
pub fn can_optimize_local_variables<'a, N>(node: &'a N, strict: bool) -> (bool, bool)
where
&'a N: Into<NodeRef<'a>>,
{
let mut visitor = CanOptimizeLocalVariables::new(strict);
let can_optimize_locals = visitor.visit(node.into()).is_continue();

(can_optimize_locals, visitor.uses_arguments)
}

/// The [`Visitor`] used for [`returns_value`].
#[derive(Debug)]
struct CanOptimizeLocalVariables {
strict: bool,

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field `strict` is never read

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field `strict` is never read

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field `strict` is never read
uses_arguments: bool,
}

impl CanOptimizeLocalVariables {
const fn new(strict: bool) -> Self {
Self {
strict,
uses_arguments: false,
}
}
}

impl<'ast> Visitor<'ast> for CanOptimizeLocalVariables {
type BreakTy = ();

fn visit_identifier(&mut self, node: &'ast Identifier) -> ControlFlow<Self::BreakTy> {
if node.sym() == Sym::ARGUMENTS {
self.uses_arguments = true;
}

ControlFlow::Continue(())
}

fn visit_with(&mut self, _node: &'ast crate::statement::With) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}

fn visit_call(&mut self, node: &'ast crate::expression::Call) -> ControlFlow<Self::BreakTy> {
if let Expression::Identifier(identifier) = node.function() {
if identifier.sym() == Sym::EVAL {
// Most likely a direct eval.
return ControlFlow::Break(());
}
}

try_break!(node.function().visit_with(self));

for arg in node.args() {
try_break!(arg.visit_with(self));
}

ControlFlow::Continue(())
}

fn visit_function(&mut self, _node: &'ast Function) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}

fn visit_arrow_function(&mut self, _node: &'ast ArrowFunction) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}

fn visit_async_function(&mut self, _node: &'ast AsyncFunction) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}

fn visit_async_arrow_function(
&mut self,
_node: &'ast AsyncArrowFunction,
) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}

fn visit_class(&mut self, _node: &'ast Class) -> ControlFlow<Self::BreakTy> {
ControlFlow::Break(())
}
}
16 changes: 10 additions & 6 deletions boa_engine/src/bytecompiler/class.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,9 @@ impl ByteCompiler<'_, '_> {
Some(name) if class.has_binding_identifier() => {
let env_index = self.push_compile_environment(false);
self.create_immutable_binding(name, true);
self.emit_with_varying_operand(Opcode::PushDeclarativeEnvironment, env_index);
if !self.can_optimize_local_variables {
self.emit_with_varying_operand(Opcode::PushDeclarativeEnvironment, env_index);
}
true
}
_ => false,
Expand All @@ -39,7 +41,7 @@ impl ByteCompiler<'_, '_> {
let mut compiler = ByteCompiler::new(
class_name,
true,
self.json_parse,
self.json_parse(),
self.current_environment.clone(),
self.context,
);
Expand Down Expand Up @@ -276,7 +278,7 @@ impl ByteCompiler<'_, '_> {
let mut field_compiler = ByteCompiler::new(
Sym::EMPTY_STRING,
true,
self.json_parse,
self.json_parse(),
self.current_environment.clone(),
self.context,
);
Expand Down Expand Up @@ -310,7 +312,7 @@ impl ByteCompiler<'_, '_> {
let mut field_compiler = ByteCompiler::new(
class_name,
true,
self.json_parse,
self.json_parse(),
self.current_environment.clone(),
self.context,
);
Expand Down Expand Up @@ -354,7 +356,7 @@ impl ByteCompiler<'_, '_> {
let mut field_compiler = ByteCompiler::new(
class_name,
true,
self.json_parse,
self.json_parse(),
self.current_environment.clone(),
self.context,
);
Expand Down Expand Up @@ -591,7 +593,9 @@ impl ByteCompiler<'_, '_> {

if class_env {
self.pop_compile_environment();
self.emit_opcode(Opcode::PopEnvironment);
if !self.can_optimize_local_variables {
self.emit_opcode(Opcode::PopEnvironment);
}
}

self.emit_opcode(Opcode::PopPrivateEnvironment);
Expand Down
98 changes: 76 additions & 22 deletions boa_engine/src/bytecompiler/declarations.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -570,9 +570,13 @@ impl ByteCompiler<'_, '_> {

// ii. Perform ! varEnv.InitializeBinding(F, undefined).
let binding = self.initialize_mutable_binding(f, true);
let index = self.get_or_insert_binding(binding);
self.emit_opcode(Opcode::PushUndefined);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);
}
}

Expand Down Expand Up @@ -742,10 +746,12 @@ impl ByteCompiler<'_, '_> {
if binding_exists {
// 1. Perform ! varEnv.SetMutableBinding(fn, fo, false).
match self.set_mutable_binding(name) {
Ok(binding) => {
let index = self.get_or_insert_binding(binding);
self.emit_with_varying_operand(Opcode::SetName, index);
}
Ok(binding) => self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::SetName,
self,
),
Err(BindingLocatorError::MutateImmutable) => {
let index = self.get_or_insert_name(name);
self.emit_with_varying_operand(Opcode::ThrowMutateImmutable, index);
Expand All @@ -760,8 +766,12 @@ impl ByteCompiler<'_, '_> {
// 3. Perform ! varEnv.InitializeBinding(fn, fo).
self.create_mutable_binding(name, !strict);
let binding = self.initialize_mutable_binding(name, !strict);
let index = self.get_or_insert_binding(binding);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);
}
}
}
Expand All @@ -785,9 +795,13 @@ impl ByteCompiler<'_, '_> {
// 3. Perform ! varEnv.InitializeBinding(vn, undefined).
self.create_mutable_binding(name, !strict);
let binding = self.initialize_mutable_binding(name, !strict);
let index = self.get_or_insert_binding(binding);
self.emit_opcode(Opcode::PushUndefined);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);
}
}
}
Expand Down Expand Up @@ -898,6 +912,14 @@ impl ByteCompiler<'_, '_> {
}
}

if self.can_optimize_local_variables
&& !self
.flags
.contains(super::ByteCompilerFlags::USES_ARGUMENTS)
{
arguments_object_needed = false;
}

// 19. If strict is true or hasParameterExpressions is false, then
// a. NOTE: Only a single Environment Record is needed for the parameters,
// since calls to eval in strict mode code cannot create new bindings which are visible outside of the eval.
Expand All @@ -910,15 +932,25 @@ impl ByteCompiler<'_, '_> {
// c. Let env be NewDeclarativeEnvironment(calleeEnv).
// d. Assert: The VariableEnvironment of calleeContext is calleeEnv.
// e. Set the LexicalEnvironment of calleeContext to env.
let _ = self.push_compile_environment(false);
additional_env = true;

if self.can_optimize_local_variables {
let _ = self.push_compile_environment(false);
additional_env = true;
}
}

// 22. If argumentsObjectNeeded is true, then
//
// NOTE(HalidOdat): Has been moved up, so "arguments" gets registed as
// the first binding in the environment with index 0.
if arguments_object_needed {
if !strict {
self.can_optimize_local_variables = false;
}

let can_optimize_local_variables = self.can_optimize_local_variables;
self.can_optimize_local_variables = false;

// Note: This happens at runtime.
// a. If strict is true or simpleParameterList is false, then
// i. Let ao be CreateUnmappedArgumentsObject(argumentsList).
Expand All @@ -941,6 +973,10 @@ impl ByteCompiler<'_, '_> {
self.create_mutable_binding(arguments, false);
}

let binding = self.get_binding_value(arguments);
self.get_or_insert_binding(binding);
self.can_optimize_local_variables = can_optimize_local_variables;

self.code_block_flags |= CodeBlockFlags::NEEDS_ARGUMENTS_OBJECT;
}

Expand Down Expand Up @@ -1017,7 +1053,7 @@ impl ByteCompiler<'_, '_> {
}

if generator {
self.emit(Opcode::Generator, &[Operand::U8(self.in_async().into())]);
self.emit(Opcode::Generator, &[Operand::Bool(self.is_async())]);
self.emit_opcode(Opcode::Pop);
}

Expand All @@ -1031,7 +1067,9 @@ impl ByteCompiler<'_, '_> {
// b. Let varEnv be NewDeclarativeEnvironment(env).
// c. Set the VariableEnvironment of calleeContext to varEnv.
let env_index = self.push_compile_environment(false);
self.emit_with_varying_operand(Opcode::PushDeclarativeEnvironment, env_index);
if !self.can_optimize_local_variables {
self.emit_with_varying_operand(Opcode::PushDeclarativeEnvironment, env_index);
}
env_label = true;

// d. Let instantiatedVarNames be a new empty List.
Expand All @@ -1056,15 +1094,23 @@ impl ByteCompiler<'_, '_> {
else {
// a. Let initialValue be ! env.GetBindingValue(n, false).
let binding = self.get_binding_value(n);
let index = self.get_or_insert_binding(binding);
self.emit_with_varying_operand(Opcode::GetName, index);
self.get_or_insert_binding(binding).emit(
Opcode::GetLocal,
Opcode::GetGlobalName,
Opcode::GetName,
self,
);
}

// 5. Perform ! varEnv.InitializeBinding(n, initialValue).
let binding = self.initialize_mutable_binding(n, true);
let index = self.get_or_insert_binding(binding);
self.emit_opcode(Opcode::PushUndefined);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);

// 6. NOTE: A var with the same name as a formal parameter initially has
// the same value as the corresponding initialized parameter.
Expand All @@ -1089,9 +1135,13 @@ impl ByteCompiler<'_, '_> {

// 3. Perform ! env.InitializeBinding(n, undefined).
let binding = self.initialize_mutable_binding(n, true);
let index = self.get_or_insert_binding(binding);
self.emit_opcode(Opcode::PushUndefined);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);
}
}

Expand Down Expand Up @@ -1121,9 +1171,13 @@ impl ByteCompiler<'_, '_> {

// b. Perform ! varEnv.InitializeBinding(F, undefined).
let binding = self.initialize_mutable_binding(f, true);
let index = self.get_or_insert_binding(binding);
self.emit_opcode(Opcode::PushUndefined);
self.emit_with_varying_operand(Opcode::DefInitVar, index);
self.get_or_insert_binding(binding).emit(
Opcode::SetLocal,
Opcode::SetGlobalName,
Opcode::DefInitVar,
self,
);

// c. Append F to instantiatedVarNames.
instantiated_var_names.push(f);
Expand Down
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