Bug 77271 – Cut the indirections when accessing CSS properties

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Benjamin Poulain]

Getting a CSS value (e.g. element.style.position) seems to go through many indirections.

From JSCSSStyleDeclaration::getOwnPropertySlot()
->we check if the name is a valid CSS property
-->we encode the name cssPropertyName()
-->we get the property ID from the name: cssPropertyID()
->if there is and ID, the name is valid, we set the PropertySlot
-->From JSCSSStyleDeclaration::nameGetter(), we do exactly the same thing:
-->cssPropertyName() to get a valid name
-->cssPropertyID() to get the ID
-->get the property for real

This seems like a lot of indirection. We can at least cut some fat between cssPropertyName() -> cssPropertyID() (some redundancy between those two)
Ideally, JSCSSStyleDeclaration::getOwnPropertySlot() should keep a reference to the CSS Property ID, and getting the actual value would be cheap.

[Antti Koivisto]

Does this show up in profiles in some benchmark?

[Benjamin Poulain]

(In reply to comment #1)
> Does this show up in profiles in some benchmark?

This shows up in multiple tests of PeaceKeeper.

This is related to:
-https://bugs.webkit.org/show_bug.cgi?id=77158
-https://bugs.webkit.org/show_bug.cgi?id=74782
which gave us some points already.

[Benjamin Poulain]

Created attachment 130494 [details]
Patch

[Benjamin Poulain]

Comment on attachment 130494 [details]
Patch

wrong bug

[Benjamin Poulain]

Closing this meta bug. What is described here is solved.

For the performance of setters, we will need work on the CSS Parser.