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Remove `arguments_binding` field from `CodeBlock` (#2969) 

* Ensure the "arguments" is the first argument

* Remove `arguments_binding` field from `CodeBlock`
pull/2977/head
Haled Odat 1 year ago committed by GitHub
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4 changed files with 100 additions and 51 deletions
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  1. 20
      boa_engine/src/builtins/function/arguments.rs
  2. 58
      boa_engine/src/bytecompiler/declarations.rs
  3. 5
      boa_engine/src/bytecompiler/mod.rs
  4. 66
      boa_engine/src/vm/code_block.rs

20
boa_engine/src/builtins/function/arguments.rs
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@ -155,18 +155,22 @@ impl Arguments {
// We use indices to access environment bindings at runtime. // We use indices to access environment bindings at runtime.
// To map to function parameters to binding indices, we use the fact, that bindings in a // To map to function parameters to binding indices, we use the fact, that bindings in a
// function environment start with all of the arguments in order: // function environment start with all of the arguments in order:
//
// Note: The first binding (binding 0) is where "arguments" is stored.
//
// `function f (a,b,c)` // `function f (a,b,c)`
// | binding index | `arguments` property key | identifier | // | binding index | `arguments` property key | identifier |
// | 0 | 0 | a | // | 1 | 0 | a |
// | 1 | 1 | b | // | 2 | 1 | b |
// | 2 | 2 | c | // | 3 | 2 | c |
// //
// Notice that the binding index does not correspond to the argument index: // Notice that the binding index does not correspond to the argument index:
// `function f (a,a,b)` => binding indices 0 (a), 1 (b), 2 (c) // `function f (a,a,b)` => binding indices 0 (a), 1 (b), 2 (c)
// | binding index | `arguments` property key | identifier | // | binding index | `arguments` property key | identifier |
// | - | 0 | - | // | - | 0 | - |
// | 0 | 1 | a | // | 1 | 1 | a |
// | 1 | 2 | b | // | 2 | 2 | b |
//
// While the `arguments` object contains all arguments, they must not be all bound. // While the `arguments` object contains all arguments, they must not be all bound.
// In the case of duplicate parameter names, the last one is bound as the environment binding. // In the case of duplicate parameter names, the last one is bound as the environment binding.
// //
@ -178,10 +182,14 @@ impl Arguments {
if property_index >= len { if property_index >= len {
break; break;
} }
let binding_index = bindings.len() as u32;
// NOTE(HalidOdat): Offset by +1 to account for the first binding ("argument").
let binding_index = bindings.len() as u32 + 1;
let entry = bindings let entry = bindings
.entry(name) .entry(name)
.or_insert((binding_index, property_index)); .or_insert((binding_index, property_index));
entry.1 = property_index; entry.1 = property_index;
property_index += 1; property_index += 1;
} }

58
boa_engine/src/bytecompiler/declarations.rs
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@ -1,6 +1,9 @@
use crate::{ use crate::{
bytecompiler::{ByteCompiler, FunctionCompiler, FunctionSpec, Label, NodeKind}, bytecompiler::{ByteCompiler, FunctionCompiler, FunctionSpec, Label, NodeKind},
vm::{create_function_object_fast, create_generator_function_object, BindingOpcode, Opcode}, vm::{
create_function_object_fast, create_generator_function_object, BindingOpcode,
CodeBlockFlags, Opcode,
},
JsNativeError, JsResult, JsNativeError, JsResult,
}; };
use boa_ast::{ use boa_ast::{
@ -882,26 +885,10 @@ impl ByteCompiler<'_, '_> {
additional_env = true; additional_env = true;
} }
// 21. For each String paramName of parameterNames, do
for param_name in &parameter_names {
// a. Let alreadyDeclared be ! env.HasBinding(paramName).
let already_declared = self.has_binding(*param_name);
// b. NOTE: Early errors ensure that duplicate parameter names can only occur in non-strict
// functions that do not have parameter default values or rest parameters.
// c. If alreadyDeclared is false, then
if !already_declared {
// i. Perform ! env.CreateMutableBinding(paramName, false).
self.create_mutable_binding(*param_name, false);
// Note: These steps are not necessary in our implementation.
// ii. If hasDuplicates is true, then
// 1. Perform ! env.InitializeBinding(paramName, undefined).
}
}
// 22. If argumentsObjectNeeded is true, then // 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 arguments_object_needed {
// Note: This happens at runtime. // Note: This happens at runtime.
// a. If strict is true or simpleParameterList is false, then // a. If strict is true or simpleParameterList is false, then
@ -918,21 +905,48 @@ impl ByteCompiler<'_, '_> {
// ii. NOTE: In strict mode code early errors prevent attempting to assign // ii. NOTE: In strict mode code early errors prevent attempting to assign
// to this binding, so its mutability is not observable. // to this binding, so its mutability is not observable.
self.create_immutable_binding(arguments, false); self.create_immutable_binding(arguments, false);
self.arguments_binding = Some(self.initialize_immutable_binding(arguments));
} }
// d. Else, // d. Else,
else { else {
// i. Perform ! env.CreateMutableBinding("arguments", false). // i. Perform ! env.CreateMutableBinding("arguments", false).
self.create_mutable_binding(arguments, false); self.create_mutable_binding(arguments, false);
self.arguments_binding = Some(self.initialize_mutable_binding(arguments, false));
} }
self.code_block_flags |= CodeBlockFlags::NEEDS_ARGUMENTS_OBJECT;
}
// 21. For each String paramName of parameterNames, do
for param_name in &parameter_names {
// a. Let alreadyDeclared be ! env.HasBinding(paramName).
let already_declared = self.has_binding(*param_name);
// b. NOTE: Early errors ensure that duplicate parameter names can only occur in non-strict
// functions that do not have parameter default values or rest parameters.
// c. If alreadyDeclared is false, then
if !already_declared {
// i. Perform ! env.CreateMutableBinding(paramName, false).
self.create_mutable_binding(*param_name, false);
// Note: These steps are not necessary in our implementation.
// ii. If hasDuplicates is true, then
// 1. Perform ! env.InitializeBinding(paramName, undefined).
}
}
// 22. If argumentsObjectNeeded is true, then
if arguments_object_needed {
// MOVED: a-d.
//
// NOTE(HalidOdat): Has been moved up, see comment above.
// Note: This happens at runtime. // Note: This happens at runtime.
// e. Perform ! env.InitializeBinding("arguments", ao). // e. Perform ! env.InitializeBinding("arguments", ao).
// f. Let parameterBindings be the list-concatenation of parameterNames and « "arguments" ». // f. Let parameterBindings be the list-concatenation of parameterNames and « "arguments" ».
parameter_names.push(arguments); parameter_names.push(arguments);
} }
// 23. Else, // 23. Else,
// a. Let parameterBindings be parameterNames. // a. Let parameterBindings be parameterNames.
let parameter_bindings = parameter_names.clone(); let parameter_bindings = parameter_names.clone();

5
boa_engine/src/bytecompiler/mod.rs
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@ -242,9 +242,6 @@ pub struct ByteCompiler<'ctx, 'host> {
/// Functions inside this function /// Functions inside this function
pub(crate) functions: Vec<Gc<CodeBlock>>, pub(crate) functions: Vec<Gc<CodeBlock>>,
/// The `arguments` binding location of the function, if set.
pub(crate) arguments_binding: Option<BindingLocator>,
/// Compile time environments in this function. /// Compile time environments in this function.
pub(crate) compile_environments: Vec<Gc<GcRefCell<CompileTimeEnvironment>>>, pub(crate) compile_environments: Vec<Gc<GcRefCell<CompileTimeEnvironment>>>,
@ -299,7 +296,6 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
functions: Vec::default(), functions: Vec::default(),
this_mode: ThisMode::Global, this_mode: ThisMode::Global,
params: FormalParameterList::default(), params: FormalParameterList::default(),
arguments_binding: None,
compile_environments: Vec::default(), compile_environments: Vec::default(),
class_field_initializer_name: None, class_field_initializer_name: None,
code_block_flags, code_block_flags,
@ -1349,7 +1345,6 @@ impl<'ctx, 'host> ByteCompiler<'ctx, 'host> {
private_names: self.private_names.into_boxed_slice(), private_names: self.private_names.into_boxed_slice(),
bindings: self.bindings.into_boxed_slice(), bindings: self.bindings.into_boxed_slice(),
functions: self.functions.into_boxed_slice(), functions: self.functions.into_boxed_slice(),
arguments_binding: self.arguments_binding,
compile_environments: self.compile_environments.into_boxed_slice(), compile_environments: self.compile_environments.into_boxed_slice(),
class_field_initializer_name: self.class_field_initializer_name, class_field_initializer_name: self.class_field_initializer_name,
flags: Cell::new(self.code_block_flags), flags: Cell::new(self.code_block_flags),

66
boa_engine/src/vm/code_block.rs
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@ -69,6 +69,11 @@ bitflags! {
/// Does this function have a parameters environment. /// Does this function have a parameters environment.
const PARAMETERS_ENV_BINDINGS = 0b0000_1000; const PARAMETERS_ENV_BINDINGS = 0b0000_1000;
/// Does this function need a `"arguments"` object.
///
/// The `"arguments"` binding is the first binding.
const NEEDS_ARGUMENTS_OBJECT = 0b0001_0000;
/// Trace instruction execution to `stdout`. /// Trace instruction execution to `stdout`.
#[cfg(feature = "trace")] #[cfg(feature = "trace")]
const TRACEABLE = 0b1000_0000; const TRACEABLE = 0b1000_0000;
@ -124,10 +129,6 @@ pub struct CodeBlock {
/// Functions inside this function /// Functions inside this function
pub(crate) functions: Box<[Gc<Self>]>, pub(crate) functions: Box<[Gc<Self>]>,
/// The `arguments` binding location of the function, if set.
#[unsafe_ignore_trace]
pub(crate) arguments_binding: Option<BindingLocator>,
/// Compile time environments in this function. /// Compile time environments in this function.
pub(crate) compile_environments: Box<[Gc<GcRefCell<CompileTimeEnvironment>>]>, pub(crate) compile_environments: Box<[Gc<GcRefCell<CompileTimeEnvironment>>]>,
@ -155,7 +156,6 @@ impl CodeBlock {
length, length,
this_mode: ThisMode::Global, this_mode: ThisMode::Global,
params: FormalParameterList::default(), params: FormalParameterList::default(),
arguments_binding: None,
compile_environments: Box::default(), compile_environments: Box::default(),
class_field_initializer_name: None, class_field_initializer_name: None,
} }
@ -206,6 +206,13 @@ impl CodeBlock {
.get() .get()
.contains(CodeBlockFlags::PARAMETERS_ENV_BINDINGS) .contains(CodeBlockFlags::PARAMETERS_ENV_BINDINGS)
} }
/// Does this function need a `"arguments"` object.
pub(crate) fn needs_arguments_object(&self) -> bool {
self.flags
.get()
.contains(CodeBlockFlags::NEEDS_ARGUMENTS_OBJECT)
}
} }
/// ---- `CodeBlock` private API ---- /// ---- `CodeBlock` private API ----
@ -1078,7 +1085,19 @@ impl JsObject {
.push_lexical(code.compile_environments[last_env].clone()); .push_lexical(code.compile_environments[last_env].clone());
} }
if let Some(binding) = code.arguments_binding { // Taken from: `FunctionDeclarationInstantiation` abstract function.
//
// Spec: https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
//
// 22. If argumentsObjectNeeded is true, then
if code.needs_arguments_object() {
// a. If strict is true or simpleParameterList is false, then
// i. Let ao be CreateUnmappedArgumentsObject(argumentsList).
// b. Else,
// i. NOTE: A mapped argument object is only provided for non-strict functions
// that don't have a rest parameter, any parameter
// default value initializers, or any destructured parameters.
// ii. Let ao be CreateMappedArgumentsObject(func, formals, argumentsList, env).
let arguments_obj = if code.strict() || !code.params.is_simple() { let arguments_obj = if code.strict() || !code.params.is_simple() {
Arguments::create_unmapped_arguments_object(args, context) Arguments::create_unmapped_arguments_object(args, context)
} else { } else {
@ -1091,11 +1110,11 @@ impl JsObject {
context, context,
) )
}; };
context.vm.environments.put_lexical_value( let env_index = context.vm.environments.len() as u32 - 1;
binding.environment_index(), context
binding.binding_index(), .vm
arguments_obj.into(), .environments
); .put_lexical_value(env_index, 0, arguments_obj.into());
} }
let argument_count = args.len(); let argument_count = args.len();
@ -1336,7 +1355,19 @@ impl JsObject {
.push_lexical(code.compile_environments[0].clone()); .push_lexical(code.compile_environments[0].clone());
} }
if let Some(binding) = code.arguments_binding { // Taken from: `FunctionDeclarationInstantiation` abstract function.
//
// Spec: https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
//
// 22. If argumentsObjectNeeded is true, then
if code.needs_arguments_object() {
// a. If strict is true or simpleParameterList is false, then
// i. Let ao be CreateUnmappedArgumentsObject(argumentsList).
// b. Else,
// i. NOTE: A mapped argument object is only provided for non-strict functions
// that don't have a rest parameter, any parameter
// default value initializers, or any destructured parameters.
// ii. Let ao be CreateMappedArgumentsObject(func, formals, argumentsList, env).
let arguments_obj = if code.strict() || !code.params.is_simple() { let arguments_obj = if code.strict() || !code.params.is_simple() {
Arguments::create_unmapped_arguments_object(args, context) Arguments::create_unmapped_arguments_object(args, context)
} else { } else {
@ -1349,11 +1380,12 @@ impl JsObject {
context, context,
) )
}; };
context.vm.environments.put_lexical_value(
binding.environment_index(), let env_index = context.vm.environments.len() as u32 - 1;
binding.binding_index(), context
arguments_obj.into(), .vm
); .environments
.put_lexical_value(env_index, 0, arguments_obj.into());
} }
let argument_count = args.len(); let argument_count = args.len();

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