[Mesa-dev] [PATCH] spirv: Fix structure splitting with per-vertex interface arrays.

[Jason Ekstrand]

On Mon, Mar 14, 2016 at 9:13 PM, Kenneth Graunke <kenneth at whitecape.org>
wrote:

> On Monday, March 14, 2016 5:23:44 PM PDT Jason Ekstrand wrote:
> > On Sun, Mar 13, 2016 at 6:08 PM, Kenneth Graunke <kenneth at whitecape.org>
> > wrote:
> >
> > > We want to use interface_type, not vtn_var->type.  They're normally
> > > equivalent, but for geometry/tessellation per-vertex interface arrays,
> > > we need to unwrap a level.
> > >
> > > Otherwise, we tried to iterate a structure members but instead used
> > > an array length.  If the array length was longer than the number of
> > > fields in the structure, we'd crash.
> > > ---
> > >  src/compiler/nir/spirv/vtn_variables.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/src/compiler/nir/spirv/vtn_variables.c
> > > b/src/compiler/nir/spirv/vtn_variables.c
> > > index 31bf416..1628042 100644
> > > --- a/src/compiler/nir/spirv/vtn_variables.c
> > > +++ b/src/compiler/nir/spirv/vtn_variables.c
> > > @@ -923,7 +923,7 @@ var_decoration_cb(struct vtn_builder *b, struct
> > > vtn_value *val, int member,
> > >           vtn_var->var->data.explicit_location = true;
> > >        } else {
> > >           assert(vtn_var->members);
> > > -         unsigned length = glsl_get_length(vtn_var->type->type);
> > > +         unsigned length = glsl_get_length(val->type->type);
> > >
> >
> > Good catch.  What I think we really want here though is a "without_array"
> > helper.  I'm not a huge fan of grabbing the type from the value because
> > that comes in from the client and I don't really trust it.
>
> Hmm...okay.  I suppose that would work, because vtn_var->members
> existing means that it's a struct...or array of structs.
>
> (I was afraid that we'd have to replicate the logic for deciding
> whether it's a normal varying array, or arrayed-interface...but
> I guess we don't...)
>

I looked at the code that handles derefrences of these pre-split variables.
All we do is handle it the first time we hit a struct deref so
glsl_get_length(glsl_type_without_array(vtn_var->type->type)) is
more-or-less exactly what we want.
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