[Mesa-dev] [RFC 1/4] nir: Add a new intrinsic 'load_image_stride'

[Bas Nieuwenhuizen]

On Mon, Jan 28, 2019 at 9:38 AM Eduardo Lima Mitev <elima at igalia.com> wrote:
>
> On 1/26/19 5:34 PM, Jason Ekstrand wrote:
> > Mind suffixing it with _ir3 or something since it's a back-end-specific
> > intrinsic?  Incidentally, this looks a lot like load_image_param_intel.
> >
>
> Yes, I felt inclined to add the suffix but wasn't sure how good/bad a
> practice it is, so I deferred it to review :).
>
> Now, I did a quick experiment and it turns out I can reuse
> image_deref_load_param_intel as-is. The semantics are a bit different so
> I would have to fork the comment to explain ir3 too.
>
> So, what about I remove the '_intel' suffix to that one and use if for
> this ir3?

Instructions that have different semantics for different drivers sound
like a lot of potential for confusion and latent bugs to me. Is it
really a problem to have both?
>
> Thanks for the feedback and the tip!
>
> Eduardo
>
> > On January 25, 2019 07:48:54 Eduardo Lima Mitev <elima at igalia.com> wrote:
> >
> >> This is an internal intrinsic intended to be injected by a
> >> (freedreno-specific) 'lower_sampler_io' pass that will be introduced
> >> later in this series; and consumed by ir3_compiler_nir.
> >>
> >> The intrinsic will load in SSA values for various constants
> >> for images (image_dims), namely the format's bytes-per-pixel,
> >> y-stride and z-stride; for which the backend compiler will emit
> >> the corresponding uniforms.
> >>
> >> const_index[0] is the image index, and const_index[1] is the index
> >> into image_dims' register file for a given image: 0 for bpp, 1 to
> >> y-stride and 2 for z-stride.
> >> ---
> >> src/compiler/nir/nir_intrinsics.py | 2 ++
> >> 1 file changed, 2 insertions(+)
> >>
> >> diff --git a/src/compiler/nir/nir_intrinsics.py
> >> b/src/compiler/nir/nir_intrinsics.py
> >> index a5cc3f7401c..169c835d746 100644
> >> --- a/src/compiler/nir/nir_intrinsics.py
> >> +++ b/src/compiler/nir/nir_intrinsics.py
> >> @@ -590,6 +590,8 @@ load("shared", 1, [BASE, ALIGN_MUL, ALIGN_OFFSET],
> >> [CAN_ELIMINATE])
> >> load("push_constant", 1, [BASE, RANGE], [CAN_ELIMINATE, CAN_REORDER])
> >> # src[] = { offset }. const_index[] = { base, range }
> >> load("constant", 1, [BASE, RANGE], [CAN_ELIMINATE, CAN_REORDER])
> >> +# src[] = { offset }. const_index[] = { image_idx, dim_idx }
> >> +load("image_stride", 1, [], [CAN_REORDER])
> >>
> >> # Stores work the same way as loads, except now the first source is
> >> the value
> >> # to store and the second (and possibly third) source specify where to
> >> store
> >> --
> >> 2.20.1
> >>
> >> _______________________________________________
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> >
> >
> >
> >
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