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Re: [RFC] Catch 11.8% more jump threading opportunities at treelevel.


Hi Jeff,

> > Wow.  Is there any way I could take a peek at it?
> Certainly.  What would probably work best is to attach it to the
> meta-bug we are using to track 4.1 and/or missed jump threading
> issues. (do you have either of those meta-bug id#s handy?)

Thanks.  Yes, PR 19794 is the meta-bug for missed jump threading
opportunities.

>   1. Change the jump thread selection code to allow threading through
>      blocks with side effects that need to be preserved.  This actually
>      simplifies the jump thread selection code and other parts of DOM
>      as it no longer needs to track the current definition of variables
>      anymore.

What criteria do you use for jump threading?  If we duplicate a big
basic block, we might end up increasing code size.  Or maybe I should
wait until I see your patch. :-)

> Oh yea, we're able to thread something like 40% more jumps statically, I
> haven't measured dynamic jump counts yet.

What do you mean by static and dynamic here?  Do you find 40% more
jumps in the first iteration of DOM?

Kazu Hirata


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