On 08/08/2014 12:31 AM, Kenneth Graunke wrote:
> The lower_vertex_id pass converts uses of the gl_VertexID system value
> to the gl_BaseVertex and gl_VertexIDMESA system values. Since
> gl_VertexID is no longer accessed, it would not be considered active.
>
> Of course, it should be, since the shader uses gl_VertexID.
Right... hmm. Between this and your comments on patch 3, I think we're
going to have some additional challenges implementing
GL_ARB_shader_draw_parameters... all surrounding various abuse of
gl_BaseVertex. I have a couple ideas for handling that, but I don't
think it will require enough re-work to warrant delaying this code any
further.
Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>
> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
> ---
> src/mesa/main/shader_query.cpp | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> Avoids regressing Piglit's gl-get-active-attrib-returns-all-inputs when
> enabling lowering later in the series.
>
> diff --git a/src/mesa/main/shader_query.cpp b/src/mesa/main/shader_query.cpp
> index 4871d09..c395a78 100644
> --- a/src/mesa/main/shader_query.cpp
> +++ b/src/mesa/main/shader_query.cpp
> @@ -93,6 +93,7 @@ is_active_attrib(const ir_variable *var)
> * and gl_InstanceID."
> */
> return var->data.location == SYSTEM_VALUE_VERTEX_ID ||
> + var->data.location == SYSTEM_VALUE_VERTEX_ID_ZERO_BASE ||
> var->data.location == SYSTEM_VALUE_INSTANCE_ID;
>
> default:
> @@ -128,12 +129,22 @@ _mesa_GetActiveAttrib(GLhandleARB program, GLuint desired_index,
>
> foreach_in_list(ir_instruction, node, ir) {
> const ir_variable *const var = node->as_variable();
> + const char *var_name = var->name;
>
> if (!is_active_attrib(var))
> continue;
>
> if (current_index == desired_index) {
> - _mesa_copy_string(name, maxLength, length, var->name);
> + /* Since gl_VertexID may be lowered to gl_VertexIDMESA, we need to
> + * consider gl_VertexIDMESA as gl_VertexID for purposes of checking
> + * active attributes.
> + */
> + if (var->data.mode == ir_var_system_value &&
> + var->data.location == SYSTEM_VALUE_VERTEX_ID_ZERO_BASE) {
> + var_name = "gl_VertexID";
> + }
> +
> + _mesa_copy_string(name, maxLength, length, var_name);
>
> if (size)
> *size = (var->type->is_array()) ? var->type->length : 1;
>