[Mesa-dev] [PATCH] mesa/st: add support for dynamic sampler offsets

[Ilia Mirkin]

On Sat, Aug 9, 2014 at 11:12 AM, Roland Scheidegger <sroland at vmware.com> wrote:
> Am 09.08.2014 16:33, schrieb Ilia Mirkin:
>> On Sat, Aug 9, 2014 at 10:14 AM, Roland Scheidegger <sroland at vmware.com> wrote:
>>> On closer look, it looks to me like it wouldn't be all that difficult to
>>> make proper sampler array dcls (as you apparently get them quite easily
>>
>> If you can briefly outline how you think that should be done, I'd be
>> happy to try to do it. Right now the samplers are declared in
>> st_translate_program, which only has the program->samplers_used
>> bitfield (where program is glsl_to_tgsi_visitor).
>>
>> One quick thing that occurs to me is to keep track of samplers in a
>> map of index -> array size (0 if it's not accessed indirectly or not
>> an array), and then using the map to create the declarations. Does
>> that seem reasonable?
>>
> Well I didn't think about it that much but nothing is stopping you from
> putting whatever you need into the glsl_to_tgsi_visitor to keep that
> array information instead of just filling out samplers_used.
>
>> Either way, this seems like a nice-to-have rather than required, so
>> I'm going to push this patch even if the other one isn't ready.
> Agreed. The address thingy is also something which should go away as
> discussed but really separate issue too.
> btw you get the actual sampler type from the constant in the sampler reg
> right? So if you have
> 4: TEX TEMP[1], TEMP[1], SAMP[ADDR[2].x+1], 2D
> that +1 in there says the 2nd declared sampler determines what kind of
> sampler this is (2d, 3d, shadow...).

>From what I can tell, samplers (in TGSI) have no attached semantics...
they're just an index into an array that you're promised was set up
correctly beforehand. For emitting the instructions, we look at the 2D
from the tex instruction.

BTW, I have a follow-up patch that I'll send shortly which generates

FRAG
PROPERTY FS_COLOR0_WRITES_ALL_CBUFS 1
DCL IN[0], GENERIC[0], PERSPECTIVE
DCL OUT[0], COLOR
DCL SAMP[0]
DCL SAMP[1..3]
DCL CONST[4]
DCL TEMP[0..1], LOCAL
DCL ADDR[0..2]
IMM[0] FLT32 {    0.0000,     0.0000,     0.0000,     0.0000}
  0: MOV TEMP[0].xy, IN[0].xyyy
  1: TEX TEMP[0], TEMP[0], SAMP[0], 2D
  2: MOV TEMP[1].xy, IN[0].xyyy
  3: UARL ADDR[2].x, CONST[4].xxxx
  4: TEX TEMP[1], TEMP[1], SAMP[ADDR[2].x+1], 2D
  5: MAD TEMP[0], TEMP[0], IMM[0].xxxx, TEMP[1]
  6: MOV OUT[0], TEMP[0]
  7: END

Is that what you had in mind?