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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