compiler: tidy up double_inputs_read uses

First we move double_inputs_read into a vs struct in the union,
double_inputs_read is only used for vs inputs so this will
save space and also allows us to add a new double_inputs field.

We add the new field because c2acf97fcc changed the behaviour
of double_inputs_read, and while it's no longer used to track
actual reads in i965 we do still want to track this for gallium
drivers.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>

src/compiler/nir/nir_gather_info.c

@@ -234,7 +234,8 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader)
              glsl_type_is_dual_slot(glsl_without_array(var->type))) {
             for (uint i = 0; i < glsl_count_attribute_slots(var->type, false); i++) {
                int idx = var->data.location + i;
-               shader->info.double_inputs_read |= BITFIELD64_BIT(idx);
+               shader->info.vs.double_inputs |= BITFIELD64_BIT(idx);
+               shader->info.vs.double_inputs_read |= BITFIELD64_BIT(idx);
             }
          }
       }
@@ -356,10 +357,13 @@ nir_shader_gather_info(nir_shader *shader, nir_function_impl *entrypoint)
    shader->info.outputs_written = 0;
    shader->info.outputs_read = 0;
    shader->info.patch_outputs_read = 0;
-   shader->info.double_inputs_read = 0;
    shader->info.patch_inputs_read = 0;
    shader->info.patch_outputs_written = 0;
    shader->info.system_values_read = 0;
+   if (shader->info.stage == MESA_SHADER_VERTEX) {
+      shader->info.vs.double_inputs = 0;
+      shader->info.vs.double_inputs_read = 0;
+   }
    if (shader->info.stage == MESA_SHADER_FRAGMENT) {
       shader->info.fs.uses_sample_qualifier = false;
    }