A question about bytecodes + unsigned load performance ./. add performace
Ulf Zibis
Ulf.Zibis at gmx.de
Mon Jan 12 18:08:44 PST 2009
Wow, these are good news. :-)
So is there a chance, to implement this behaviour in trunk, so we could
get rid of the +128 trick ?
Is it also available for -client VM ?
-Ulf
Am 13.01.2009 02:39, John Rose schrieb:
> On Jan 12, 2009, at 1:52 PM, Tom Rodriguez wrote:
>
>> The ideal for the simple example is something like (StoreC mem2 addr2
>> (AndI (LoadB mem1 addr1) (ConI 0xff))). The code above will break
>> the match at the load, forcing the value into a register. It's seem
>> like an excessively strong cutout but I'm not sure how to phrase it
>> better, particularly since I don't know what exactly what problem it
>> designed to eliminate. I believe it's probably the anti-dep issue
>> but without a concrete failure it's hard to know what exactly it
>> should look like.
>
> That sounds plausible. In general, if a node has a unique user, it
> can be pulled into one of the little spanning trees that the matcher
> places over the ideal DAG. The graph dump Christian sent shows that
> the LoadB has just one user ([[141]]) which means the matcher should
> be able to group the LoadB with the AndI (and transform to loadUB),
> unless there's something else going on, like the anti-deps you mention.
>
> -- John
>
>
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