[Mesa-dev] [PATCH v3 013/104] nir: Support deref instructions in remove_dead_variables

[Caio Marcelo de Oliveira Filho]

Hi,

> @@ -144,6 +197,45 @@ remove_dead_var_writes(nir_shader *shader, struct set *live)
>                 nir_instr_remove(instr);
>           }
>        }
> +
> +      /* We walk the list of instructions backwards because we're going to
> +       * delete a deref and all of it's uses and we don't want to end up
> +       * deleting stuff ahead of us.
> +       */
> +      nir_foreach_block(block, function->impl) {
> +         nir_foreach_instr_safe(instr, block) {

The comment says backwards, the loop walks forwards.

It seems to me propagating the mode needs to be forward, e.g. a deref
will be marked mode = 0 because of a variable, then another deref that
has the first as parent marked mode = 0. But I might be missing
something.


> +            switch (instr->type) {
> +            case nir_instr_type_deref: {
> +               /* For deref instructions, propagate modes */
> +               nir_deref_instr *deref = nir_instr_as_deref(instr);
> +               if (deref->deref_type == nir_deref_type_var) {
> +                  deref->mode = deref->var->data.mode;
> +               } else {
> +                  nir_deref_instr *parent = nir_deref_instr_parent(deref);
> +                  deref->mode = parent->mode;
> +               }

Should we write deref->mode only if the new mode is zero?
I.e. deref->var->data.mode == 0 for the first case, and parent->mode
== 0 for the else case.


Thanks,
Caio