[Mesa-dev] [RFCv0 0/8] gallium: add support for NIR as alternate IR

[Roland Scheidegger]

The overall idea looks quite sane to me.
Albeit obviously as you mentioned you'd really have to support all
shader stages and deal with the variants (though there aren't many left).

Roland

Am 19.10.2015 um 21:54 schrieb Rob Clark:
> From: Rob Clark <robclark at freedesktop.org>
> 
> (grr, resend to the right list..)
> 
> Still quite rough around the edges, but now it's at the point of sorta-
> kinda-working-sometimes.  So I guess time to get wider feedback.
> 
> The initial goal is to figure out things that glsl_to_nir does
> differently from tgsi_to_nir, so we can fix them up and have better
> likelyhood of drivers being able to consume NIR from multiple sources.
> Eventually I'd like to be able to re-use spriv->nir for compute/
> clover support, for example.  And at some point I'd like to be able to
> bypass the conversion from glsl->tgsi for mesa st.  But for now, being
> able to track down and fix differences between glsl_to_nir vs tgsi_to_nir
> is a good start.
> 
> With what I've added to pipe_shader_state (which is, I suppose, missing
> some doc updates), the intention is that drivers can ask for an IR
> other than TGSI.  And what they actually get will be either TGSI or
> their preferred IR.  Drivers will have to always handle the TGSI case,
> so the intention isn't to port all the different state trackers (or
> internally generated shaders, etc).
> 
> I suppose pipe_compute_state needs similar treatment, but I've skipped
> that for now.
> 
> Currently only the direct GLSL->NIR path is implemented for vertex
> shaders, which results in a huge hack at the end of the series.  It
> isn't ever intended for drivers to mix/match glsl->nir vs glsl->tgsi->
> nir across shader stages.  But this is sufficient for now for me to
> debug other issues.
> 
> Shader variant handling will be completely broken at the moment, without
> having a nir_clone()[1]. (Ian, depending on how far that is from the top
> of your TODO list, I can take a stab at that, since I might be the first
> consumer.)
> 
> Also, there is some trivial shader variant handling in mesa st which
> would have to be ported to NIR.  Or, perhaps, just somehow expose the
> shader key to the driver.  (Currently most drivers are doing much more
> variant handling within the driver, and having two levels of variants
> does seem a bit silly.)
> 
> [1] https://bugs.freedesktop.org/show_bug.cgi?id=89436
> 
> (First patch isn't actually RFC.. just an issue that I noticed in the
> process.)
> 
> Rob Clark (8):
>   nir: add nir_var_all enum
>   gallium: refactor pipe_shader_state to support multiple IR's
>   gallium: add NIR as a possible IR
>   mesa/st: add support for NIR as possible driver IR
>   freedreno/ir3: drop tokens arg
>   freedreno/ir3: add support for NIR as preferred IR
>   freedreno/ir3: fix const_index handling for uniforms
>   HACK: freedreno/ir3: hack for mismatch on varying slots for
>     glsl->tgsi->nir vs glsl->nir
> 
>  src/gallium/auxiliary/hud/hud_context.c            |  14 +-
>  src/gallium/auxiliary/postprocess/pp_run.c         |   4 +-
>  src/gallium/auxiliary/tgsi/tgsi_ureg.c             |   6 +-
>  src/gallium/auxiliary/util/u_simple_shaders.c      |  42 +++-
>  src/gallium/auxiliary/util/u_tests.c               |   7 +-
>  src/gallium/drivers/freedreno/freedreno_screen.c   |   5 +-
>  src/gallium/drivers/freedreno/freedreno_util.h     |   1 +
>  .../drivers/freedreno/ir3/ir3_compiler_nir.c       |  38 +++-
>  src/gallium/drivers/freedreno/ir3/ir3_shader.c     |  30 ++-
>  src/gallium/drivers/freedreno/ir3/ir3_shader.h     |   3 +
>  src/gallium/include/pipe/p_defines.h               |  13 +-
>  src/gallium/include/pipe/p_state.h                 |  21 +-
>  src/glsl/nir/nir.c                                 |   4 +
>  src/glsl/nir/nir.h                                 |   1 +
>  src/glsl/nir/nir_lower_io.c                        |   2 +-
>  src/mesa/drivers/dri/i965/brw_nir.c                |   3 +-
>  src/mesa/state_tracker/st_glsl_to_tgsi.cpp         | 223 ++++++++++++++++++++-
>  src/mesa/state_tracker/st_program.c                |  43 +++-
>  18 files changed, 422 insertions(+), 38 deletions(-)
>