[Webkit-unassigned] [Bug 86175] HasCustomWillOrDidRecalcStyleFlag and family should live in a bit.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=86175





--- Comment #2 from Hajime Morrita <morrita at google.com>  2012-05-11 03:55:27 PST ---
(In reply to comment #1)
> (In reply to comment #0)
> > Following flags are used to indicate that the node has some special callback functions.
> > 
> > - HasCustomWillOrDidRecalcStyleFlag
> > - HasCustomStyleForRendererFlag
> > - IsFrameOwnerElementFlag
> > 
> > We can replace them with a flag namely, say, HasCustomCallbacks.
> > And have optional virtual method to check which types of callbacks the node actually has.
> > Since majority of node doesn't have none of them and even single bit can work for early-out check.
> 
> Why do we need those extra bits? Also adding virtual function calls don't seem like a good idea. Do we have any data on how rare these flags are?
I need one for introduce InShadow and I'm expecting one more for another shadow purpose.
Also, this sharing allows us to more aggressive de-virtualization.
FYI elements with these flags are frame, iframe, plugin, form controls and svg.

In general people use flags if it's available. I made 3-4 bits for purpose I mentioned above.
But all bits were taken by other folks before I use it. I hope I could've reserve them.

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