nir/lower_io: Introduce nir_store_per_vertex_output intrinsics.

Similar to nir_load_per_vertex_input, but for outputs.  This is not
useful in geometry shaders, but will be useful in tessellation shaders.

v2: Change stage_uses_per_vertex_outputs() to is_per_vertex_output(),
    taking a nir_variable (requested by Jason Ekstrand).

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
3 files changed