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

[Nicolai Hähnle]

On 28.11.2017 14:58, Andres Gomez wrote:
> Nicolai, this looks like a good candidate to nominate for inclusion in
> all the stable queues.
> 
> What do you think?

It's a rare enough use case, but the change is small and there seem to 
have been no regressions, so sure, go ahead for both of them.

Thanks,
Nicolai


> 
> 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;
>>