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perf(semantic): recycle unresolved references hash maps #4213

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graphite-app merged 1 commit into from
Jul 12, 2024
+39 −28
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perf(semantic): recycle unresolved references hash maps #4213

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67 changes: 39 additions & 28 deletions crates/oxc_semantic/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,9 @@ pub struct SemanticBuilder<'a> {
pub current_node_flags: NodeFlags,
pub current_symbol_flags: SymbolFlags,
pub current_scope_id: ScopeId,
/// Current scope depth.
/// 0 is global scope. 1 is `Program`. Incremented on entering a scope, and decremented on exit.
pub current_scope_depth: usize,
/// Stores current `AstKind::Function` and `AstKind::ArrowFunctionExpression` during AST visit
pub function_stack: Vec<AstNodeId>,
// To make a namespace/module value like
Expand All @@ -70,7 +73,10 @@ pub struct SemanticBuilder<'a> {
pub scope: ScopeTree,
pub symbols: SymbolTable,

// LIFO stack used to accumulate unresolved refs while traversing scopes.
// Stack used to accumulate unresolved refs while traversing scopes.
// Indexed by scope depth. We recycle `UnresolvedReferences` instances during traversal
// to reduce allocations, so the stack grows to maximum scope depth, but never shrinks.
// See: <https://github.com/oxc-project/oxc/issues/4169>
unresolved_references: Vec<UnresolvedReferences>,

pub(crate) module_record: Arc<ModuleRecord>,
Expand Down Expand Up @@ -99,6 +105,13 @@ impl<'a> SemanticBuilder<'a> {
let scope = ScopeTree::default();
let current_scope_id = scope.root_scope_id();

// Most programs will have at least 1 place where scope depth reaches 16,
// so initialize `unresolved_references` with this length, to reduce reallocations as it grows.
// This is just an estimate of a good initial size, but certainly better than
// `Vec`'s default initial capacity of 4.
let mut unresolved_references = vec![];
unresolved_references.resize_with(16, Default::default);

let trivias = Trivias::default();
Self {
source_text,
Expand All @@ -110,12 +123,13 @@ impl<'a> SemanticBuilder<'a> {
current_symbol_flags: SymbolFlags::empty(),
current_reference_flag: ReferenceFlag::empty(),
current_scope_id,
current_scope_depth: 0,
function_stack: vec![],
namespace_stack: vec![],
nodes: AstNodes::default(),
scope,
symbols: SymbolTable::default(),
unresolved_references: vec![],
unresolved_references,
module_record: Arc::new(ModuleRecord::default()),
label_builder: LabelBuilder::default(),
build_jsdoc: false,
Expand Down Expand Up @@ -176,7 +190,6 @@ impl<'a> SemanticBuilder<'a> {
pub fn build(mut self, program: &Program<'a>) -> SemanticBuilderReturn<'a> {
if self.source_type.is_typescript_definition() {
let scope_id = self.scope.add_scope(None, ScopeFlags::Top);
self.unresolved_references.push(UnresolvedReferences::default());
program.scope_id.set(Some(scope_id));
} else {
self.visit_program(program);
Expand All @@ -187,8 +200,9 @@ impl<'a> SemanticBuilder<'a> {
}
}

debug_assert_eq!(self.unresolved_references.len(), 1);
self.scope.root_unresolved_references = self.unresolved_references.pop().unwrap();
debug_assert_eq!(self.current_scope_depth, 0);
self.scope.root_unresolved_references =
self.unresolved_references.into_iter().next().unwrap();

let jsdoc = if self.build_jsdoc { self.jsdoc.build() } else { JSDocFinder::default() };

Expand Down Expand Up @@ -336,9 +350,7 @@ impl<'a> SemanticBuilder<'a> {
let reference_name = reference.name().clone();
let reference_id = self.symbols.create_reference(reference);

self.unresolved_references
.last_mut()
.unwrap()
self.unresolved_references[self.current_scope_depth]
.entry(reference_name)
.or_default()
.push(reference_id);
Expand All @@ -363,30 +375,23 @@ impl<'a> SemanticBuilder<'a> {
}

fn resolve_references_for_current_scope(&mut self) {
// Pop-filter-push current level of unresolved references.
let mut remaining_refs = self.unresolved_references.pop().unwrap();
// `iter_mut` to get mut references to 2 entries of `unresolved_references` simultaneously
let mut iter = self.unresolved_references.iter_mut();
let parent_refs = iter.nth(self.current_scope_depth - 1).unwrap();
let current_refs = iter.next().unwrap();

let is_root_scope = self.current_scope_id == self.scope.root_scope_id();
remaining_refs.retain(|name, reference_ids| {
for (name, reference_ids) in current_refs.drain() {
// Try to resolve a reference.
// If unresolved, try to transfer it to parent scope (if any).
// Otherwise, keep it in the current map.
if let Some(symbol_id) = self.scope.get_binding(self.current_scope_id, name) {
for reference_id in &*reference_ids {
// If unresolved, transfer it to parent scope's unresolved references.
if let Some(symbol_id) = self.scope.get_binding(self.current_scope_id, &name) {
for reference_id in &reference_ids {
self.symbols.references[*reference_id].set_symbol_id(symbol_id);
}
self.symbols.resolved_references[symbol_id].append(reference_ids);
false
} else if !is_root_scope {
let parent_refs = self.unresolved_references.last_mut().unwrap();
parent_refs.entry(name.clone()).or_default().append(reference_ids);
false
self.symbols.resolved_references[symbol_id].extend(reference_ids);
} else {
true
parent_refs.entry(name).or_default().extend(reference_ids);
}
});

self.unresolved_references.push(remaining_refs);
}
}

pub fn add_redeclare_variable(&mut self, symbol_id: SymbolId, span: Span) {
Expand Down Expand Up @@ -431,15 +436,21 @@ impl<'a> Visit<'a> for SemanticBuilder<'a> {

self.current_scope_id = self.scope.add_scope(parent_scope_id, flags);
scope_id.set(Some(self.current_scope_id));
self.unresolved_references.push(UnresolvedReferences::default());

// Increment scope depth, and ensure stack is large enough that
// `self.unresolved_references[self.current_scope_depth]` is initialized
self.current_scope_depth += 1;
if self.unresolved_references.len() <= self.current_scope_depth {
self.unresolved_references.push(UnresolvedReferences::default());
}
}

fn leave_scope(&mut self) {
self.resolve_references_for_current_scope();
if let Some(parent_id) = self.scope.get_parent_id(self.current_scope_id) {
self.unresolved_references.pop();
self.current_scope_id = parent_id;
}
self.current_scope_depth -= 1;
}

// Setup all the context for the binder.
Expand Down