Bug 35941 – [V8] Use a struct instead of an int to indicate the dom wrapper tpye

• Status: RESOLVED
• Resolution: FIXED
• Component: WebCore Misc.

[Nate Chapin]

Currently, when we wrap a WebCore object for use in V8, we insert 2 internal fields: a pointer to the WebCore object itself, and an integer indicating the V8ClassIndex::V8WrapperType.

Instead of the integer, we could use a struct that includes pointers to the appropriate versions of functions that WebCore might need for this object.  I believe the callbacks would be:

* A pointer to the appropriate GetTemplate function
* A pointer to a function that derefs the WebCore object (if it is refcounted, need in V8GCController.cpp)
* A pointer to a function that casts the WebCore object to an ActiveDOMObject if possible (needed for appropriate handling of active objects in DOMData.cpp)

This will allow us to remove any place that we're using a macro'ed switch statement based on the declarations in V8Index.h, as well as delete V8Index.cpp.

Once this change is in, I plan on working toward generating an equivalent to V8Index.h.

[Nate Chapin]

Created attachment 50343 [details]
patch

This appears to be essentially a no-op in terms of Dromaeo performance (within a fraction of 1% from previous results).

[WebKit Review Bot]

Attachment 50343 [details] did not build on chromium:
Build output: http://webkit-commit-queue.appspot.com/results/481007

[Nate Chapin]

Created attachment 50347 [details]
patch with build file changes

[Dimitri Glazkov (Google)]

This is better than peanut butter, jelly and bread put together. Anton, do you have any concerns with this patch?

[Nate Chapin]

(In reply to comment #4)
> This is better than peanut butter, jelly and bread put together. Anton, do you
> have any concerns with this patch?

I'm allergic to peanuts, you insensitive clod!

[Dimitri Glazkov (Google)]

(In reply to comment #5)
> (In reply to comment #4)
> > This is better than peanut butter, jelly and bread put together. Anton, do you
> > have any concerns with this patch?
> 
> I'm allergic to peanuts, you insensitive clod!

Darn it! I've gotta stop falling into this food sensitivity trap.

[Dimitri Glazkov (Google)]

What about sunflower butter? http://www.nutsonline.com/snacks/sunflowerseeds/butter.html?source=googlebase

[Nate Chapin]

(In reply to comment #7)
> What about sunflower butter?
> http://www.nutsonline.com/snacks/sunflowerseeds/butter.html?source=googlebase

I'm generally ok with seeds, so it's probably safe.  However, unlike the individual in their testimonial, I do not crave peanut butter nor any substitute.  It is the Kryptonite to my Superman, the CodeGeneratorV8.pm to my comprehensible codebase.

[Ojan Vafai]

Does this have any memory implications?

[Nate Chapin]

(In reply to comment #9)
> Does this have any memory implications?

AFAICT, no.  I ran chromium's memory_tests, which passed locally.  If you have any recommendations on other tests to run, I would be happy to hear them.

In terms of what is supposed be happening, instead of storing an integer, we're storing a pointer to a static struct that contents an integer and 3 function pointers.  Unless I screwed something up, that should be negligible.

[anton muhin]

LGTM.  And I like it.

[Dimitri Glazkov (Google)]

Comment on attachment 50347 [details]
patch with build file changes

beam me up, Scotty.

[Nate Chapin]

http://trac.webkit.org/changeset/55798