From 722fffa96fe2ff1d32408aa6c3e782736d3d3fd2 Mon Sep 17 00:00:00 2001
From: camc314 <18101008+camc314@users.noreply.github.com>
Date: Sun, 28 Dec 2025 05:00:19 +0000
Subject: [PATCH] perf(codegen): restructure print_comments to avoid index
 comparisons in loop (#17402)

The idea is that this is a hot-ish path, so if we can remove the index checks from within the hot loop, it should be faster
---
 crates/oxc_codegen/src/comment.rs | 61 +++++++++++++++++++------------
 1 file changed, 38 insertions(+), 23 deletions(-)

diff --git a/crates/oxc_codegen/src/comment.rs b/crates/oxc_codegen/src/comment.rs
index d96f732bd3480..1ed404fb68f78 100644
--- a/crates/oxc_codegen/src/comment.rs
+++ b/crates/oxc_codegen/src/comment.rs
@@ -85,40 +85,55 @@ impl Codegen<'_> {
     }
 
     pub(crate) fn print_comments(&mut self, comments: &[Comment]) {
-        for (i, comment) in comments.iter().enumerate() {
-            if i == 0 {
-                if comment.preceded_by_newline() {
-                    // Skip printing newline if this comment is already on a newline.
-                    if let Some(b) = self.last_byte() {
-                        match b {
-                            b'\n' => self.print_indent(),
-                            b'\t' => { /* noop */ }
-                            _ => {
-                                self.print_hard_newline();
-                                self.print_indent();
-                            }
-                        }
+        let Some((first, rest)) = comments.split_first() else {
+            return;
+        };
+
+        if first.preceded_by_newline() {
+            // Skip printing newline if this comment is already on a newline.
+            if let Some(b) = self.last_byte() {
+                match b {
+                    b'\n' => self.print_indent(),
+                    b'\t' => { /* noop */ }
+                    _ => {
+                        self.print_hard_newline();
+                        self.print_indent();
                     }
-                } else {
-                    self.print_indent();
                 }
             }
-            if i >= 1 {
+        } else {
+            self.print_indent();
+        }
+        self.print_comment(first);
+
+        if let Some((last, middle)) = rest.split_last() {
+            for comment in middle {
                 if comment.preceded_by_newline() {
                     self.print_hard_newline();
                     self.print_indent();
                 } else if comment.is_legal() {
                     self.print_hard_newline();
                 }
+                self.print_comment(comment);
             }
-            self.print_comment(comment);
-            if i == comments.len() - 1 {
-                if comment.is_line() || comment.followed_by_newline() {
-                    self.print_hard_newline();
-                } else {
-                    self.print_next_indent_as_space = true;
-                }
+
+            if last.preceded_by_newline() {
+                self.print_hard_newline();
+                self.print_indent();
+            } else if last.is_legal() {
+                self.print_hard_newline();
             }
+            self.print_comment(last);
+
+            if last.is_line() || last.followed_by_newline() {
+                self.print_hard_newline();
+            } else {
+                self.print_next_indent_as_space = true;
+            }
+        } else if first.is_line() || first.followed_by_newline() {
+            self.print_hard_newline();
+        } else {
+            self.print_next_indent_as_space = true;
         }
     }