[webkit-changes] [WebKit/WebKit] 60da0a: Have RenderObject subclass CanMakeCheckedPtr

[Chris Dumez]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 60da0af827823f29aa62dd74f9dc71deafab48f8
      https://github.com/WebKit/WebKit/commit/60da0af827823f29aa62dd74f9dc71deafab48f8
  Author: Chris Dumez <cdumez at apple.com>
  Date:   2023-09-21 (Thu, 21 Sep 2023)

  Changed paths:
    M Source/WebCore/rendering/RenderElement.cpp
    M Source/WebCore/rendering/RenderElement.h
    M Source/WebCore/rendering/RenderObject.cpp
    M Source/WebCore/rendering/RenderObject.h

  Log Message:
  -----------
  Have RenderObject subclass CanMakeCheckedPtr
https://bugs.webkit.org/show_bug.cgi?id=261902

Reviewed by Simon Fraser.

Have RenderObject subclass CanMakeCheckedPtr so that we can adopt CheckedPtr / CheckedRef
in rendering code for safety. We were previously relying on WeakPtr but it turned out to
be too costly and cause performance regressions.

This tested as perf-neutral on Speedometer, Membuster and MotionMark.

In order to do this without regressing Membuster, I had to re-order some data members and
rely on PackedPtr<> to not increase the size of renderers.

* Source/WebCore/rendering/RenderElement.cpp:
(WebCore::RenderElement::RenderElement):
(WebCore::RenderElement::attachRendererInternal):
* Source/WebCore/rendering/RenderElement.h:
(WebCore::RenderElement::firstChild const):
(WebCore::RenderElement::lastChild const):
* Source/WebCore/rendering/RenderObject.cpp:
(WebCore::RenderObject::RenderObject):
* Source/WebCore/rendering/RenderObject.h:

Canonical link: https://commits.webkit.org/268298@main