[Bug 28606] [r300g]: Compiz focus blur effect does not work. (causes black windows instead)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=28606

--- Comment #5 from Tom Stellard <tstellar at gmail.com> 2010-07-04 16:54:34 PDT ---
(In reply to comment #4)
> The real problem with the r300 compiler is scheduling of TEX blocks, which is
> done against the r300 hardware (r500 is ok here). I've had a closer look at a
> shader from etqw which creates about 10 TEX blocks on r300 even though there
> are NO texture indirections. The instructions just have wrong ordering and that
> is the only reason the shader doesn't fit in hardware.

I think this bug is slightly different from the problem you are seeing with
etqw.  The problem here is that the compiler is handed several TEX blocks and
can't combine them into a single block.  It sounds like the problem with etqw
is the same as https://bugs.freedesktop.org/show_bug.cgi?id=25109 where the
compiler receives a large TEX block and can't keep all the instructions
together.

A possible fix for this bug is to do some kind of register renaming before the
scheduling.  Even though the TEX instructions are independent of each other,
the scheduler can't schedule them together because they all write to the same
register.  If each destination register for these TEX instructions were renamed
to something unique, I think the scheduler would schedule them correctly.

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