[Mesa-dev] [PATCH 1/2] tgsi: add texture-type info to texture instructions

[Rob Clark]

On Thu, Jun 4, 2015 at 3:11 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
> On 04/06/15 19:50, Rob Clark wrote:
>>
>> On Thu, Jun 4, 2015 at 2:14 PM, Jose Fonseca <jfonseca at vmware.com> wrote:
>>>
>>> I think we had a discussion about this on mesa3d-dev a while ago.  I
>>> don't
>>> recall the conclusions but I wish I did.
>>>
>>> We have tgsi_return_type.  Why isn't this enough?  Or better, why isn't
>>> being used for this?
>>
>>
>> mostly arbitrary reasons.. the unorm/snorm values don't really make
>> sense here, so it didn't quite seem to fit (plus would have needed
>> another bit, although I guess that isn't really an issue)
>>
>> Or if the question was, why not include the type information in the
>> decl rather than the instr?  Well.. that at least is more awkward for
>> the implementation, since the information is part of the instruction
>> for both GLSL IR and NIR (and at the end of the day, that is also
>> where I need the info in my compiler)
>
>
> IIUC, GLSL also has this information readily available in the sampler
> declaration:
>
>   uniform  sampler2D ftex;
>   uniform isampler2D itex;
>   uniform usampler2D utex;
>
> So isn't this a double standard?  After all, if the argument here is
>
>   "GLSL IR / NIR has this info readily available, so let's pass it to the
> TGSI",
>
> then the same rationale should apply to
>
>   "GLSL has this info readily available on the sampler declaration, so lets'
> pass it to GLSL IR/NIR 's declarations."
>

ok, possibly GLSL IR has this info also in the decl.. tbh I'm not a
GLSL IR expert.  I just figured out my way around since I know where I
want the info in NIR, and then looked at where it came from in
glsl_to_nir.

But at any rate, NIR only has it on the tex instruction.  So my point
about having it in the decl making it more akward for tgsi-to-nir and
my compiler still stands. ;-)

>
> I want to avoid having two places for this info in TGSI: in decl and in
> instruction, as that's a recipe for bugs and complexity.  _Specially_ when
> the decl is imposed for D3D10 support, while the inst is mere a matter of
> internal Mesa convention...
>

having the information duplicated (or at least in the instruction) is
more convenient for the consumer of tgsi.  If you are worried about
bugs/inconsistencies then something similar to nir_validate_shader()
for tgsi would have seemed like a better direction.

BR,
-R

>
> In short, I'm fine in in principle with piping this info through, but lets
> come up a decent generalization.  In particular, lets try get this in the
> decls so it's consistent.
>
>
> Jose
>