perf(semantic): calculate number of nodes, scopes, symbols, references before visiting AST

crates/oxc_semantic/src/builder.rs

@@ -100,6 +100,39 @@ pub struct SemanticBuilderReturn<'a> {
     pub errors: Vec<OxcDiagnostic>,
 }
 
+#[derive(Default)]
+pub struct Collector {
+    node: usize,
+    scope: usize,
+    symbol: usize,
+    reference: usize,
+}
+
+impl<'a> Visit<'a> for Collector {
+    #[inline]
+    fn enter_node(&mut self, _: AstKind<'a>) {
+        self.node += 1;
+    }
+    #[inline]
+    fn enter_scope(&mut self, _: ScopeFlags, _: &Cell<Option<ScopeId>>) {
+        self.scope += 1;
+    }
+    #[inline]
+    fn leave_node(&mut self, _: AstKind<'a>) {}
+    #[inline]
+    fn leave_scope(&mut self) {}
+
+    fn visit_binding_identifier(&mut self, _: &BindingIdentifier<'a>) {
+        self.symbol += 1;
+    }
+    fn visit_identifier_reference(&mut self, _: &IdentifierReference<'a>) {
+        self.reference += 1;
+    }
+    fn visit_jsx_identifier(&mut self, _: &JSXIdentifier<'a>) {
+        self.reference += 1;
+    }
+}
+
 impl<'a> SemanticBuilder<'a> {
     pub fn new(source_text: &'a str, source_type: SourceType) -> Self {
         let scope = ScopeTree::default();
@@ -192,6 +225,11 @@ impl<'a> SemanticBuilder<'a> {
             let scope_id = self.scope.add_scope(None, AstNodeId::DUMMY, ScopeFlags::Top);
             program.scope_id.set(Some(scope_id));
         } else {
+            let mut collector = Collector::default();
+            collector.visit_program(program);
+            self.nodes.reserve(collector.node);
+            self.scope.reserve(collector.scope);
+            self.symbols.reserve(collector.symbol, collector.reference);
             self.visit_program(program);
 
             // Checking syntax error on module record requires scope information from the previous AST pass

crates/oxc_semantic/src/node.rs

@@ -162,6 +162,11 @@ impl<'a> AstNodes<'a> {
         self.nodes.push(node);
         ast_node_id
     }
+
+    pub fn reserve(&mut self, additional: usize) {
+        self.nodes.reserve(additional);
+        self.parent_ids.reserve(additional);
+    }
 }
 
 #[derive(Debug)]

crates/oxc_semantic/src/scope.rs

@@ -218,4 +218,12 @@ impl ScopeTree {
     pub fn remove_binding(&mut self, scope_id: ScopeId, name: &CompactStr) {
         self.bindings[scope_id].shift_remove(name);
     }
+
+    pub fn reserve(&mut self, additional: usize) {
+        self.parent_ids.reserve(additional);
+        self.child_ids.reserve(additional);
+        self.flags.reserve(additional);
+        self.bindings.reserve(additional);
+        self.node_ids.reserve(additional);
+    }
 }

crates/oxc_semantic/src/symbol.rs

@@ -193,4 +193,15 @@ impl SymbolTable {
             _ => false,
         }
     }
+
+    pub fn reserve(&mut self, additional: usize, reference: usize) {
+        self.spans.reserve(additional);
+        self.names.reserve(additional);
+        self.flags.reserve(additional);
+        self.scope_ids.reserve(additional);
+        self.declarations.reserve(additional);
+        self.resolved_references.reserve(additional);
+        self.redeclare_variables.reserve(additional);
+        self.references.reserve(reference);
+    }
 }