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

Eric Anholt eric at anholt.net
Wed Apr 1 13:52:35 PDT 2015


Rob Clark <robdclark at gmail.com> writes:

> From: Rob Clark <robclark at freedesktop.org>
>
> Freedreno and vc4 want this behavior for the time being (until we have
> real flow control).  Even after that, we probably want to turn this into
> some sort of driver tunable threshold, since for at least some hardware,
> reasonably large if/else is best flattend rather than having divergent
> flow control.
>
> NOTE: wasn't sure about some of the additional restrictions in
> block_check_for_allowed_instrs()..  are there some other cases where
> I might need to fix things up in order to be guaranteed to be able to
> flatten?

Interesting.  I'm relying on GLSL IR-level flattening currently, and
this might be better than that.  Not sure.  I'd need flattening of "if
(condition) discard;", too, though.
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