[Mesa-dev] [PATCH] util: add u_lowering

[Brian Paul]

On 09/30/2014 03:38 PM, Rob Clark wrote:
> From: Rob Clark <robclark at freedesktop.org>
>
> TGSI->TGSI pass, extracted from freedreno.  Currently provides the
> following lower support, to help drivers emulate unsupported opcodes
> or features:
>
> Individual opcodes:
>    DST, XPD, SCS, LRP, FRC, POW, LIT, EXP, LOG, DP4, DP3, DPH,
>    DP2, DP2A
>
> Also supported, although it is up to the driver to manage it's own
> shader variants:
>   + two-sided-color
>   + texture coord saturate (ie. to emulate GL_CLAMP)
>
> All of the lowering operations are opt-in so a driver can pick and
> choose what it wants.
>
> Signed-off-by: Rob Clark <robclark at freedesktop.org>

Hi Rob, a few thoughts:

How about moving this into the src/gallium/auxiliary/tgsi/ directory 
since this is a very TGSI-specific thing?

I think some of my recent changes to the tgsi_transform code would be 
helpful, like emit_epilog/prolog() and the various 
tgsi_transform_opX_inst() helpers.

There's a lot of tricky code trying to determine the exact size of the 
new shader token buffer.  Why not just use a 2x buffer and then realloc 
to the exact size at the end?

I think the big if/switch statements could be replaced by some kind of 
table-driven system.

FWIW, I have a two-sided lighting transformation function too that I 
haven't pushed to master yet.

-Brian