[Mesa-dev] NIR, SCons, and Gallium

Ian Romanick idr at freedesktop.org
Mon Jan 11 16:11:24 PST 2016

On 01/11/2016 06:21 AM, Jose Fonseca wrote:
> FWIW, I updated SCons to build NIR, both with GCC and MSVC:
>   http://cgit.freedesktop.org/~jrfonseca/mesa/log/?h=scons-nir
> It was actually simpler than I anticipated.
> But I hit a wall -- there's actually no way to get NIR used with
> softpipe/llvmpipe, not even as an intermediate IR somewhere between GLSL
> IR and TGSI, is there?
> Without this I can't actually test it.  And I'm afraid the scons
> integration will rot again unless it is used.
> I know other gallium drivers already use NIR, but IIUC, they use NIR
> internally, ie., TGSI -> NIR-> HW.
> So what is exactly the long term plan for NIR in Mesa general, and
> Gallium in particular?
> - replace GLSL IR completely?

Not likely.  GLSL IR has a lot of GLSL-specific semantics that aren't
really appropriate for an IR at NIR's level.

> - use NIR as intermediate IR betweem GLSL IR and TGSI, and run
> optimizations in there?
> - use NIR instead of TGSI at the gallium interface?

I think folks have expressed a (slight?) preference for the latter
rather than the former.  However, the former may provide an easier
stepping stone.

I know that Ilia has expressed some concerns about how NIR will effect
nouveau.  I don't recall hearing an opinion expressed by Marek or any of
the other AMD guys, but that probably just means that I wasn't paying
enough attention.

> - be only used internally by drivers?

I think this would be unfortunate, but I'm not working on any of this
code. :)  This seems to be the option that leads to the most code and
the most duplicated effort.

> - something else?
> Jose
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