Bug 4435 – speed up JavaScript by tweaking the Identifier class

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Darin Adler]

I was doing some performance work on JavaScript and found some speedups from tweaking UString and 
Identifier a little -- a bit more inlining and a bit less reference count bumping.

[Darin Adler]

Created attachment 3390 [details]
patch that does a bit more inlining and changes reference counting a bit

[Darin Adler]

*** Bug 4418 has been marked as a duplicate of this bug. ***

[Darin Adler]

I'm thinking that the part of this patch that tweaks reference counting isn't really so helpful, since it only 
saves a ref() in the case where the identifier is a new one -- I don't know how common that code path is.

[Maciej Stachowiak]

Comment on attachment 3390 [details]
patch that does a bit more inlining and changes reference counting a bit

I'm not sure I understand this patch - it adds a bunch of calls to ref, but I
guess the few it removes were called more often? I assume you performance
tested this so r=me

[Darin Adler]

The ref change removes a ref from a common code path, and adds it back in all cases but one. I think the 
performance improvement I measured was from the other change. I think I'll land the other part without 
the ref change.

[Darin Adler]

I landed the null and UString() improvements and didn't bother with the questionable ref/deref 
improvement.