[Webkit-unassigned] [Bug 48060] Speed up op_jeq_null and op_jneq_null in JIT

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=48060





--- Comment #8 from Oliver Hunt <oliver at apple.com>  2010-10-22 14:26:28 PST ---
(In reply to comment #4)
> >         enum { Int32Tag =        0xffffffff };
> >         enum { CellTag =         0xfffffffe };
> 
> If my memory seves my correctly a lot of code depend on these two constants.
> 
> Perhaps we can move "down" the "undefined" like constants to the end of the list.

I was going to say we couldn't do this, and then i forgot why, now i remembered -- the goal i had was to reduce the null + undefined check to a single branch with no additional logic.  If we moved them down rather than up we'd need to do a lower+upper bound check as we currently identify doubles simply by doing a < DeletedValueTag check.

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