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

[Eric Anholt]

Brian Paul <brianp at vmware.com> writes:

> 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 happened to be writing a series in parallel with Rob to do the same
thing, and I chose tgsi/.  I've rebased my changes on his freedreno fix,
and I'm going to send them out in this thread now.  I don't really care
which location wins, having good history is all I care about (Also,
reviewing his changes, I found style improvements that I propagated to
mine.  So duplicated work ended up having some value).

> 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?

2x isn't nearly the lowest growth factor, right?  How massively
overallocated do you go?

All this calculation of array sizes up front is pretty awful, though --
it seems like token buffers ought to be just growing as you append
tokens.  But I guess that would be a change to do to tgsi_transform in
general.

> I think the big if/switch statements could be replaced by some kind of 
> table-driven system.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 818 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/mesa-dev/attachments/20140930/3d8cf798/attachment.sig>