On Wed, Aug 29, 2018 at 3:19 PM Caio Marcelo de Oliveira Filho <
caio.olive...@intel.com> wrote:
> Jason Ekstrand <ja...@jlekstrand.net> writes:
>
> >> >> +static bool
> >> >> +remove_dead_write_vars_local(struct state *state, nir_block *block)
> >> >> +{
> >> >> + bool progress = false;
> >> >> +
> >> >> + struct util_dynarray unused_writes;
> >> >> + util_dynarray_init(&unused_writes, state->mem_ctx);
> >> >> +
> >> >> + nir_foreach_instr_safe(instr, block) {
> >> >>
> >> >
> >> > It wouldn't hurt to add a case for call instructions which does a
> barrier
> >> > on everything I mentioned below as well as globals and locals.
> >>
> >> Makes sense. But I don't get locals are affect? Is this to cover the
> >> parameters being passed to the call?
> >>
> >
> > Because a deref to a local might be passed in as a parameter. This is
> the
> > way pass-by-reference works for SPIR-V.
>
> Will the parameter appear to the new function as local too? If so, will
> they be tagged in a way I can identify the derefs?
>
They'll appear as writes to casts whose source is a load_param intrinsic.
> I'm thinking about what to do with unused writes for locals at the end
> of a function. If it's the main function, we can just remove them, but
> depending on the answer of the question above, it is not so clear for
> non-main functions.
>
Yeah... That's a bit sticky and I'm not sure what the right answer is. I
guess we could, in theory, have a new "param" mode which is sort-of like a
local only it crosses function boundaries. I haven't given that much
though. However, given that functions are always inlined right now, that's
not something we need to deal with just yet.
--Jason
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