[webkit-changes] [WebKit/WebKit] 65023e: [JSC] Clean up JSRopeString::createSubstringOfReso...

[Yusuke Suzuki]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 65023eebf485cd6787614876915c0afa3da15430
      https://github.com/WebKit/WebKit/commit/65023eebf485cd6787614876915c0afa3da15430
  Author: Yusuke Suzuki <ysuzuki at apple.com>
  Date:   2024-04-19 (Fri, 19 Apr 2024)

  Changed paths:
    M Source/JavaScriptCore/runtime/JSString.h
    M Source/JavaScriptCore/runtime/JSStringInlines.h

  Log Message:
  -----------
  [JSC] Clean up JSRopeString::createSubstringOfResolved
https://bugs.webkit.org/show_bug.cgi?id=273008
rdar://126770852

Reviewed by Alexey Shvayka.

We found that this function is **incredibly** hot, and we need to optimize this very aggressively.

1. Use ASSERT. This length() access is recorded as super hot in the profile.
2. Use is8Bit from the base string directly instead of accessing JSString* base. Overall, let's not
   access to JSString* base after allocating a new rope string.
3. Pass length / is8Bit to JSRopeString constructors. Let's not compute this after allocating JSString.

* Source/JavaScriptCore/runtime/JSString.h:
* Source/JavaScriptCore/runtime/JSStringInlines.h:
(JSC::jsSubstringOfResolved):

Canonical link: https://commits.webkit.org/277768@main



To unsubscribe from these emails, change your notification settings at https://github.com/WebKit/WebKit/settings/notifications