[Mesa-dev] [PATCH 3/4] nir: support to flatten_all in peephole-select

[Kenneth Graunke]

On Wednesday, April 01, 2015 07:22:40 PM Connor Abbott wrote:
> I think it might be better here if we had a callback that backends can
> fill in that tells you when an instruction can be pulled out by the
> sel peephole. As Jason noted, you won't be able to do this for
> everything (notably, output writes and variable writes) and we'll
> probably need special handling for predicating discards if we want to
> be able to flatten everything. There are also a few cases where on
> i965 we aren't activating it when we could. Even then, I didn't think
> we'd need something this general, but with different backends with
> such varying needs I guess it makes more sense to go with the more
> general solution.

NIR does have nir_intrinsic_discard_if, which performs a conditional
discard.  Assignments can be handled by conditional selects.  In the
absence of other memory writes (atomics, images, etc), that's probably
sufficient, no?

--Ken
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