[Mesa-dev] [PATCH] Revert "intel/nir: Call nir_lower_io_to_scalar_early"

[Jason Ekstrand]

On Tue, Aug 14, 2018 at 7:25 PM Timothy Arceri <tarceri at itsqueeze.com>
wrote:

> On 09/08/18 05:05, Jason Ekstrand wrote:
> > Commit 4434591bf56a6b0 caused substantially more URB messages in
> > geometry and tessellation shaders.  Before we can really enable this
> > sort of optimization,  We either need some way of combining them back
> > together into vectors or we need to do cross-stage vector element
> > elimination without splitting everything into scalars.
>
> You should be calling:
>
> nir_compact_varyings() after remove_unused_varyings this should do most
> of what you want.
>

Does that turn things back into vectors?  The problem we're hitting is not
that things aren't compacted, it's that we want to read/write whole vectors
at a time as much as possible.  Just reverting the patch isn't quite the
proper solution because we want to be able to compact things and it would
be nice if we could load two variables at a time if they're packed
side-by-side in one vec4.  However, it does solve the perf regression for
now.

--Jason
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