From 73383642197bdfa6c0ee6cbe7a7057c3e0edafa1 Mon Sep 17 00:00:00 2001
From: Boshen <boshenc@gmail.com>
Date: Tue, 7 May 2024 16:43:27 +0800
Subject: [PATCH] perf(lexer): improve comment building performance by using a
 vec instead of btreemap (#3186)

closes #2693
---
 crates/oxc_parser/src/lexer/trivia_builder.rs | 24 +++++++++++++------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/crates/oxc_parser/src/lexer/trivia_builder.rs b/crates/oxc_parser/src/lexer/trivia_builder.rs
index bcecebba3..91fde3627 100644
--- a/crates/oxc_parser/src/lexer/trivia_builder.rs
+++ b/crates/oxc_parser/src/lexer/trivia_builder.rs
@@ -1,28 +1,38 @@
-use std::collections::BTreeMap;
-
-use oxc_ast::{Comment, CommentKind, Trivias};
+use oxc_ast::{Comment, CommentKind, Trivias, TriviasMap};
 use oxc_span::Span;
 
 #[derive(Debug, Default)]
 pub struct TriviaBuilder {
     // Duplicated comments can be added from rewind, use `BTreeMap` to ensure uniqueness
-    comments: BTreeMap<u32, Comment>,
+    comments: Vec<(u32, Comment)>,
     irregular_whitespaces: Vec<Span>,
 }
 
 impl TriviaBuilder {
     pub fn build(self) -> Trivias {
-        Trivias::new(self.comments, self.irregular_whitespaces)
+        let comments = TriviasMap::from_iter(self.comments);
+        Trivias::new(comments, self.irregular_whitespaces)
     }
 
     pub fn add_single_line_comment(&mut self, start: u32, end: u32) {
         // skip leading `//`
-        self.comments.insert(start + 2, Comment::new(end, CommentKind::SingleLine));
+        self.add_comment(start + 2, Comment::new(end, CommentKind::SingleLine));
     }
 
     pub fn add_multi_line_comment(&mut self, start: u32, end: u32) {
         // skip leading `/*` and trailing `*/`
-        self.comments.insert(start + 2, Comment::new(end - 2, CommentKind::MultiLine));
+        self.add_comment(start + 2, Comment::new(end - 2, CommentKind::MultiLine));
+    }
+
+    fn add_comment(&mut self, start: u32, comment: Comment) {
+        // The comments array is an ordered vec, only add the comment if its not added before,
+        // to avoid situations where the parser needs to rewind and reinsert the comment.
+        if let Some(comment) = self.comments.last_mut() {
+            if start <= comment.0 {
+                return;
+            }
+        }
+        self.comments.push((start, comment));
     }
 
     pub fn add_irregular_whitespace(&mut self, start: u32, end: u32) {