[Mesa-dev] [PATCH v3 057/104] nir,spirv: Rework function calls

[Jason Ekstrand]

+ A bunch of potentially interested parties.

On Mon, Apr 9, 2018 at 4:25 PM, Caio Marcelo de Oliveira Filho <
caio.oliveira at intel.com> wrote:

> Hi,
>
> >  typedef struct {
> > -   nir_parameter_type param_type;
> > -   const struct glsl_type *type;
> > +   uint8_t num_components;
> > +   uint8_t bit_size;
> >  } nir_parameter;
>
> (...)
>
> > @@ -683,18 +692,12 @@ validate_tex_instr(nir_tex_instr *instr,
> validate_state *state)
> >  static void
> >  validate_call_instr(nir_call_instr *instr, validate_state *state)
> >  {
> > -   if (instr->return_deref == NULL) {
> > -      validate_assert(state, glsl_type_is_void(instr->
> callee->return_type));
> > -   } else {
> > -      validate_assert(state, instr->return_deref->deref.type ==
> instr->callee->return_type);
> > -      validate_deref_var(instr, instr->return_deref, state);
> > -   }
> > -
> >     validate_assert(state, instr->num_params ==
> instr->callee->num_params);
> >
> >     for (unsigned i = 0; i < instr->num_params; i++) {
> > -      validate_assert(state, instr->callee->params[i].type ==
> instr->params[i]->deref.type);
> > -      validate_deref_var(instr, instr->params[i], state);
> > +      validate_src(&instr->params[i], state,
> > +                   instr->callee->params[i].bit_size,
> > +                   instr->callee->params[i].num_components);
> >     }
> >  }
>
> Question: I might be misreading, but it seems like we are losing the
> type information for functions. Isn't that something worth keeping,
> maybe in some other way, e.g. load_param specifying the expected type?
>

That's a very good question!  To be honest, I'm not sure what the answer
is.  At the moment, the type information is fairly useless for most of what
we use functions for.  Really, all we need is something that NIR can
inline.  As it is, we're not really preserving the types from SPIR-V
because of the gymnastics we're doing to handle pointers.

If we did want to preserve types, we'd need to have more detailed type
information.  In particular, we'd need to be able to provide pointer types
and maybe combined image-sampler types.  And along with those pointer
types, we'd need to somehow express those pointer's storage requirements.

The philosophy behind this commit is that, if we don't have a good match to
SPIR-V anyway, we might as well just chuck that information and do whatever
makes our lives the easiest.  My philosophy here may be flawed and I'm
happy to hear arguments in favor of keeping the information.  The best
argument I can come up with for keeping the information is if we find
ourselves wanting to do some sort of linking in the future where we have to
match functions by both name and type.  If we want to do that, however,
we'll need all the SPIR-V type information.

Thoughts?

--Jason
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