[Mesa-dev] [PATCH v2 00/31] Nir support for Nouveau

[Karol Herbst]

On Sat, Jan 6, 2018 at 1:34 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On Thursday, January 4, 2018 11:56:44 AM PST Jason Ekstrand wrote:
>> On January 4, 2018 12:51:15 Karol Herbst <kherbst at redhat.com> wrote:
>>
>> > On Thu, Jan 4, 2018 at 7:06 PM, Ilia Mirkin <imirkin at alum.mit.edu> wrote:
>> >> On Thu, Jan 4, 2018 at 10:01 AM, Karol Herbst <kherbst at redhat.com> wrote:
>> >>> significant changes to last series:
>> >>> * arb_gpu_shader5 interpolateat* (those nir ops don't map well to nvir)
>> >>>   no good plan on how to properly implement those
>> >>
>> >> What's the issue? They should map as well as the TGSI ones. (Since the
>> >> TGSI ones are just the GLSL ones.)
>> >>
>> >
>> > it is a bit ugly, because usually all inputs vars are lowered away, so
>> > that they are inputs. So they need special handling;
>> >
>> > lowered (input is centroid):
>> > vec1 32 ssa_25 = intrinsic load_input (ssa_24) () (0, 0) /* base=0 */
>> > /* component=0 */ /* packed:centroid_qualified */
>> > vec1 32 ssa_27 = intrinsic load_input (ssa_26) () (0, 1) /* base=0 */
>> > /* component=1 */ /* packed:centroid_qualified */
>> >
>> > not lowered:
>> > decl_var  INTERP_MODE_NONE vec2 in at unqualified-temp
>> > vec2 32 ssa_11 = intrinsic interp_var_at_centroid () (in at unqualified-temp) ()
>> >
>> > I kind of wished I could have a load_input intrinsic with a flag or
>> > load_input_at_centroid, so that I end up with the same code in the
>> > end.
>>
>> In i965, we use the NIR explicit input interpolation intrinsics.  I'm on my
>> phone so I can't give more details easily.
>
> Setting nir_shader_compiler_options::use_interpolated_input_intrinsics
> will eliminate the need to look at variables.  Instead, you'll get these
> intrinsics:
>
> - load_input (for flat shaded inputs)
> - load_interpolated_input (for non-flat shaded inputs)
>   - load_barycentric_pixel
>   - load_barycentric_centroid
>   - load_barycentric_sample
>   - load_barycentric_at_sample (+ sample ID source)
>   - load_barycentric_at_offset (+ offset.xy source)
>
> The load_interpolated_input intrinsic takes an extra source, which
> should always be one of the load_barycentric_* intrinsics.  That way,
> from the intrinsic, you can see exactly how to interpolate it.
>
> I highly recommend using these.  They're much nicer to work with.

well I already implemented looking at the variables and this is no
issue really. What I am more concerned about are local variables used
in interp_var_at_* intrinsics and those didn't get converted with
use_interpolated_input_intrinsics. I will take a deeper look, maybe
there is some weird condition to actually convert those as well.