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feat(semantic): add SemanticBuilder::with_stats (#5757)

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Add `SemanticBuilder::with_stats` method to optionally pass in a `Stats` object. If `Stats` are provided, `SemanticBuilder` skips the AST traversal.
This commit is contained in:
overlookmotel 2024-09-13 12:19:55 +00:00
parent 4b896f1494
commit f3baa49662
1 changed files with 28 additions and 8 deletions
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36
crates/oxc_semantic/src/builder.rs
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@ -98,6 +98,7 @@ pub struct SemanticBuilder<'a> {
unused_labels: UnusedLabels<'a>,
build_jsdoc: bool,
jsdoc: JSDocBuilder<'a>,
stats: Option<Stats>,
/// Should additional syntax checks be performed?
///
@ -144,6 +145,7 @@ impl<'a> SemanticBuilder<'a> {
unused_labels: UnusedLabels::default(),
build_jsdoc: false,
jsdoc: JSDocBuilder::new(source_text, trivias),
stats: None,
check_syntax_error: false,
cfg: None,
class_table_builder: ClassTableBuilder::new(),
@ -193,6 +195,19 @@ impl<'a> SemanticBuilder<'a> {
self
}
/// Provide statistics about AST to optimize memory usage of semantic analysis.
///
/// Accurate statistics can greatly improve performance, especially for large ASTs.
/// If no stats are provided, [`SemanticBuilder::build`] will compile stats by performing
/// a complete AST traversal.
/// If semantic analysis has already been performed on this AST, get the existing stats with
/// [`Semantic::stats`], and pass them in with this method, to avoid the stats collection AST pass.
#[must_use]
pub fn with_stats(mut self, stats: Stats) -> Self {
self.stats = Some(stats);
self
}
/// Get the built module record from `build_module_record`
pub fn module_record(&self) -> Arc<ModuleRecord> {
Arc::clone(&self.module_record)
@ -221,18 +236,23 @@ impl<'a> SemanticBuilder<'a> {
let scope_id = self.scope.add_scope(None, NodeId::DUMMY, ScopeFlags::Top);
program.scope_id.set(Some(scope_id));
} else {
// Count the number of nodes, scopes, symbols, and references.
// Use these counts to reserve sufficient capacity in `AstNodes`, `ScopeTree`
// and `SymbolTable` to store them.
// Use counts of nodes, scopes, symbols, and references to pre-allocate sufficient capacity
// in `AstNodes`, `ScopeTree` and `SymbolTable`.
//
// This means that as we traverse the AST and fill up these structures with data,
// they never need to grow and reallocate - which is an expensive operation as it
// involves copying all the memory from the old allocation to the new one.
// For large source files, these structures are very large, so growth is very costly
// as it involves copying massive chunks of memory.
// Avoiding this growth produces up to 30% perf boost on our benchmarks.
// TODO: It would be even more efficient to calculate counts in parser to avoid
// this extra AST traversal.
let stats = Stats::count(program);
//
// If user did not provide existing `Stats`, calculate them by visiting AST.
let (stats, check_stats) = if let Some(stats) = self.stats {
(stats, false)
} else {
let stats = Stats::count(program);
(stats, true)
};
self.nodes.reserve(stats.nodes as usize);
self.scope.reserve(stats.scopes as usize);
self.symbols.reserve(stats.symbols as usize, stats.references as usize);
@ -240,9 +260,9 @@ impl<'a> SemanticBuilder<'a> {
// Visit AST to generate scopes tree etc
self.visit_program(program);
// Check that estimated counts accurately
// Check that estimated counts accurately (unless in release mode)
#[cfg(debug_assertions)]
{
if check_stats {
#[allow(clippy::cast_possible_truncation)]
let actual_stats = Stats::new(
self.nodes.len() as u32,