[Mesa-dev] [PATCH v5 45/70] glsl: atomic counters can be declared as buffer-qualified variables

[Francisco Jerez]

Iago Toral <itoral at igalia.com> writes:

> On Mon, 2015-09-28 at 13:13 +0300, Francisco Jerez wrote:
>> Iago Toral Quiroga <itoral at igalia.com> writes:
>> 
>> > From: Kristian Høgsberg <krh at bitplanet.net>
>> >
>> > ---
>> >  src/glsl/ast_to_hir.cpp | 6 +++---
>> >  1 file changed, 3 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
>> > index 566cc87..a364aae 100644
>> > --- a/src/glsl/ast_to_hir.cpp
>> > +++ b/src/glsl/ast_to_hir.cpp
>> > @@ -2789,7 +2789,7 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
>> >     }
>> >  
>> >     if (var->type->contains_atomic()) {
>> > -      if (var->data.mode == ir_var_uniform) {
>> > +      if (var->data.mode == ir_var_uniform || var->data.mode == ir_var_shader_storage) {
>> >           if (var->data.explicit_binding) {
>> >              unsigned *offset =
>> >                 &state->atomic_counter_offsets[var->data.binding];
>> > @@ -2807,8 +2807,8 @@ apply_type_qualifier_to_variable(const struct ast_type_qualifier *qual,
>> >           }
>> >        } else if (var->data.mode != ir_var_function_in) {
>> >           _mesa_glsl_error(loc, state, "atomic counters may only be declared as "
>> > -                          "function parameters or uniform-qualified "
>> > -                          "global variables");
>> > +                          "function parameters, uniform-qualified or "
>> > +                          "buffer-qualified global variables");
>> >        }
>> >     }
>> >  
>> 
>> Spec quote?  Declaring an atomic counter to have buffer storage is
>> illegal AFAIK.
>
> I think you are right, the specs don't seem to include any explicit
> restrictions affecting the allowed types for buffer variables, however,
> the description of opaque types seems to be in conflict with that:
>
> "The opaque types declare variables that are effectively opaque 
> handles to other objects. These objects are
> accessed through built-in functions, not through direct reading or
> writing of the declared variable.
> (...)
> Opaque variables cannot be treated as l-values;(...)"
>
> I am thinking that we probably want to revert this patch and instead
> check that buffer variables do not contain references to any opaque
> types and produce a compile-time error if that is the case. I'll send
> patches for this. Maybe the specs should be amended to mention this
> explicitly too. Ian, what do you think?
>
They mention it explicitly AFAICT (section 4.1.7 of the GL 4.5 spec):

 "[Opaque Types] can only be declared as function parameters or in
  uniform-qualified variables."

> Iago
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