[Mesa-dev] [RFC PATCH 10/12] glsl: add AoA support for an inteface with unsized array members

[Timothy Arceri]

On Sat, 2015-03-21 at 19:57 -0400, Ilia Mirkin wrote:
> On Sat, Mar 21, 2015 at 5:49 AM, Timothy Arceri <t_arceri at yahoo.com.au> wrote:
> > Add support for setting the max access of an unsized member
> > of an interface array of arrays.
> >
> > For example ifc[j][k].foo[i] where foo is unsized.
> > ---
> >  src/glsl/ast_array_index.cpp | 16 ++++++++++++----
> >  1 file changed, 12 insertions(+), 4 deletions(-)
> >
> > diff --git a/src/glsl/ast_array_index.cpp b/src/glsl/ast_array_index.cpp
> > index ecef651..481bba8 100644
> > --- a/src/glsl/ast_array_index.cpp
> > +++ b/src/glsl/ast_array_index.cpp
> > @@ -64,21 +64,29 @@ update_max_array_access(ir_rvalue *ir, int idx, YYLTYPE *loc,
> >        }
> >     } else if (ir_dereference_record *deref_record =
> >                ir->as_dereference_record()) {
> > -      /* There are two possibilities we need to consider:
> > +      /* There are three possibilities we need to consider:
> >         *
> >         * - Accessing an element of an array that is a member of a named
> >         *   interface block (e.g. ifc.foo[i])
> >         *
> >         * - Accessing an element of an array that is a member of a named
> >         *   interface block array (e.g. ifc[j].foo[i]).
> > +       *
> > +       * - Accessing an element of an array that is a member of a named
> > +       *   interface block array of arrays (e.g. ifc[j][k].foo[i]).
> >         */
> >        ir_dereference_variable *deref_var =
> >           deref_record->record->as_dereference_variable();
> >        if (deref_var == NULL) {
> > -         if (ir_dereference_array *deref_array =
> > -             deref_record->record->as_dereference_array()) {
> > -            deref_var = deref_array->array->as_dereference_variable();
> > +         ir_dereference_array *deref_array =
> > +            deref_record->record->as_dereference_array();
> > +         ir_dereference_array *deref_array_prev = NULL;
> > +         while (deref_array != NULL) {
> > +            deref_array_prev = deref_array;
> > +            deref_array = deref_array->array->as_dereference_array();
> >           }
> > +         if (deref_array_prev != NULL)
> > +            deref_var = deref_array_prev->array->as_dereference_variable();
> 
> Hm... what will this variable be? An interface, or a
> dereference_array? I'm guessing the latter, but the code below wants
> the deref_var->var to be an interface. Is that still going to work?
> (Don't know the code well enough... so just asking the question.)

We are going from the inside out like this:

ifc[j][k]
ifc[j]
ifc

So we should end up at the interface which is where the max_array_access
information is stored.

> 
> Also can you just do ->array->as_dereference_array() /
> ->as_dereference_variable() like that and expect it to work? I'd think
> only one of those would ever return non-null, but you end up doing
> both on the value pointed at by deref_array_prev->array...
> 

Yeah the last deref_array->array->as_dereference_array() call is
expected to return null which is how we know that there are no more
arrays and its time to exit the loop and call as_dereference_variable()

> >        }
> >
> >        if (deref_var != NULL) {
> > --
> > 2.1.0
> >
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