Mesa (master): i965: Add ARB_occlusion_query support.

[Eric Anholt]

On Wed, 2008-10-08 at 09:29 +0100, Keith Whitwell wrote:
> > + * We use before and after counts when drawing during a query so that
> > + * we don't pick up other clients' query data in ours.  To reduce overhead,
> > + * a single BO is used to record the query data for all active queries at
> > + * once.  This also gives us a simple bound on how much batchbuffer space is
> > + * required for handling queries, so that we can be sure that we won't
> > + * have to emit a batchbuffer without getting the ending PS_DEPTH_COUNT.
> 
> Eric,
> 
> Won't using a single BO undermine the ability to asynchronously issue
> new queries and read the results of old ones?
> 
> IE. if I do something like:
> 
> -- start A
> -- render 1
> -- end A
> 
> ... time passes ...
> 
> -- start B
> -- render 2
> -- end B
> -- read results of A
> 
> Will the fact that B has been issued and refers to the same buffer as
> A mean that when you want to read the results of A, you'll end up
> waiting not just on render 1, but also render 2?

When you ended A you emitted the end of the query, flushed the
batchbuffer, and dereferenced the context's query BO for just this case.
I could have skipped emitting the query end, since flushing would also
emit the end.  I also forgot that I had to squeeze the query end into
the batchbuffer pad, which I'll go fix.

However, I had also missed the feature of the spec that you can only
have one query of a certain type active at a time, so things are a bit
overcomplicated.  For 220 lines of code, I'm not too bothered, but I'll
still go clean up my mess.

-- 
Eric Anholt
eric at anholt.net                         eric.anholt at intel.com


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