[Mesa-dev] [PATCH v4 1/2] glsl: allow any l-value of an input variable as interpolant in interpolateAt*

[Andres Gomez]

Nicolai, this looks like a good candidate to nominate for inclusion in
all the stable queues.

What do you think?

On Tue, 2017-10-10 at 14:09 +0200, Nicolai Hähnle wrote:
> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
> 
> The intended rule has been clarified in GLSL 4.60, Section 8.13.2
> (Interpolation Functions):
> 
>    "For all of the interpolation functions, interpolant must be an l-value
>     from an in declaration; this can include a variable, a block or
>     structure member, an array element, or some combination of these.
>     Component selection operators (e.g., .xy) may be used when specifying
>     interpolant."
> 
> For members of interface blocks, var->data.must_be_shader_input must be
> determined on-the-fly after lowering interface blocks, since we don't want
> to disable varying packing for an entire block just because one input in it
> is used in interpolateAt*.
> 
> v2: keep setting must_be_shader_input in ast_function (Ian)
> v3: follow the relaxed rule of GLSL 4.60
> v4: only apply the relaxed rules to desktop GL
>     (the ES WG decided that the relaxed rules may apply in a future version
>      but not retroactively; see also
>      dEQP-GLES31.functional.shaders.multisample_interpolation.interpolate_at_centroid.negative.*)
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101378
> Reviewed-by: Ian Romanick <ian.d.romanick at intel.com> (v1)
> ---
>  src/compiler/glsl/ast_function.cpp                 | 19 ++++++++++++++-----
>  src/compiler/glsl/lower_named_interface_blocks.cpp | 18 ++++++++++++++++++
>  2 files changed, 32 insertions(+), 5 deletions(-)
> 
> diff --git a/src/compiler/glsl/ast_function.cpp b/src/compiler/glsl/ast_function.cpp
> index 46a61e46fd5..d1596c272e6 100644
> --- a/src/compiler/glsl/ast_function.cpp
> +++ b/src/compiler/glsl/ast_function.cpp
> @@ -220,33 +220,42 @@ verify_parameter_modes(_mesa_glsl_parse_state *state,
>           if (val->ir_type == ir_type_swizzle) {
>              if (!state->is_version(440, 0)) {
>                 _mesa_glsl_error(&loc, state,
>                                  "parameter `%s` must not be swizzled",
>                                  formal->name);
>                 return false;
>              }
>              val = ((ir_swizzle *)val)->val;
>           }
>  
> -         while (val->ir_type == ir_type_dereference_array) {
> -            val = ((ir_dereference_array *)val)->array;
> +         for (;;) {
> +            if (val->ir_type == ir_type_dereference_array) {
> +               val = ((ir_dereference_array *)val)->array;
> +            } else if (val->ir_type == ir_type_dereference_record &&
> +                       !state->es_shader) {
> +               val = ((ir_dereference_record *)val)->record;
> +            } else
> +               break;
>           }
>  
> -         if (!val->as_dereference_variable() ||
> -             val->variable_referenced()->data.mode != ir_var_shader_in) {
> +         ir_variable *var = NULL;
> +         if (const ir_dereference_variable *deref_var = val->as_dereference_variable())
> +            var = deref_var->variable_referenced();
> +
> +         if (!var || var->data.mode != ir_var_shader_in) {
>              _mesa_glsl_error(&loc, state,
>                               "parameter `%s` must be a shader input",
>                               formal->name);
>              return false;
>           }
>  
> -         val->variable_referenced()->data.must_be_shader_input = 1;
> +         var->data.must_be_shader_input = 1;
>        }
>  
>        /* Verify that 'out' and 'inout' actual parameters are lvalues. */
>        if (formal->data.mode == ir_var_function_out
>            || formal->data.mode == ir_var_function_inout) {
>           const char *mode = NULL;
>           switch (formal->data.mode) {
>           case ir_var_function_out:   mode = "out";   break;
>           case ir_var_function_inout: mode = "inout"; break;
>           default:                    assert(false);  break;
> diff --git a/src/compiler/glsl/lower_named_interface_blocks.cpp b/src/compiler/glsl/lower_named_interface_blocks.cpp
> index 064694128bf..136352a131b 100644
> --- a/src/compiler/glsl/lower_named_interface_blocks.cpp
> +++ b/src/compiler/glsl/lower_named_interface_blocks.cpp
> @@ -108,20 +108,21 @@ public:
>  
>     flatten_named_interface_blocks_declarations(void *mem_ctx)
>        : mem_ctx(mem_ctx),
>          interface_namespace(NULL)
>     {
>     }
>  
>     void run(exec_list *instructions);
>  
>     virtual ir_visitor_status visit_leave(ir_assignment *);
> +   virtual ir_visitor_status visit_leave(ir_expression *);
>     virtual void handle_rvalue(ir_rvalue **rvalue);
>  };
>  
>  } /* anonymous namespace */
>  
>  void
>  flatten_named_interface_blocks_declarations::run(exec_list *instructions)
>  {
>     interface_namespace = _mesa_hash_table_create(NULL, _mesa_key_hash_string,
>                                                   _mesa_key_string_equal);
> @@ -231,20 +232,37 @@ flatten_named_interface_blocks_declarations::visit_leave(ir_assignment *ir)
>        }
>  
>        ir_variable *lhs_var =  lhs_rec_tmp->variable_referenced();
>        if (lhs_var) {
>           lhs_var->data.assigned = 1;
>        }
>     }
>     return rvalue_visit(ir);
>  }
>  
> +ir_visitor_status
> +flatten_named_interface_blocks_declarations::visit_leave(ir_expression *ir)
> +{
> +   ir_visitor_status status = rvalue_visit(ir);
> +
> +   if (ir->operation == ir_unop_interpolate_at_centroid ||
> +       ir->operation == ir_binop_interpolate_at_offset ||
> +       ir->operation == ir_binop_interpolate_at_sample) {
> +      const ir_rvalue *val = ir->operands[0];
> +
> +      /* This disables varying packing for this input. */
> +      val->variable_referenced()->data.must_be_shader_input = 1;
> +   }
> +
> +   return status;
> +}
> +
>  void
>  flatten_named_interface_blocks_declarations::handle_rvalue(ir_rvalue **rvalue)
>  {
>     if (*rvalue == NULL)
>        return;
>  
>     ir_dereference_record *ir = (*rvalue)->as_dereference_record();
>     if (ir == NULL)
>        return;
>  
-- 
Br,

Andres