Re: prefetch revisited

[Jan Hubicka <jh at suse dot cz>]

> 
> In fact I have implemented simple greedy prefetching pass that looks for loads
> of pointer that are later used as in memory addresses and emits the prefetch
> instructions.  This already works relativly well - only problem it has is the
> fact that I can't figure out the size of object pointed to and thus I don't
> know how much data to fetch, but this should be doable by Richard Kenner's
> memory tracking code.
> 
> The pass is DU/DF chains based and do use profile information to avoid
> unneeded prefetching.

Just to be more specific, the code actually works and is about 2 weeks old.
I just didn't get around to benchmark it and prepare for review.  Also some
of my fixes to df.c are still pending as the bitmap issue and few other
larger patches I would like to see in with higher priority.

Probably some tweaking of the decision heuristics will be needed and I am
not quite sure how much benefit it will bring as the paper itself don't mention
too much.

In case you want to concerntrate on the prefetch instruction representation and
how to describe those tons of various features various I guess our work don't
conflict and I would really like to see it in.  In case you want to implement
the greedy prefetching, we probably should work together.

Honza