i965: Move down genX_upload_sbe in profiles.

Avoid looping over all VARYING_SLOT_MAX urb_setup array
entries from genX_upload_sbe. Prepare an array indirection
to the active entries of urb_setup already in the compile
step. On upload only walk the active arrays.

v2: Use uint8_t to store the attribute numbers.
v3: Change loop to build up the array indirection.
v4: Rebase.
v5: Style fix.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/308>

src/intel/compiler/brw_fs_visitor.cpp

@@ -122,6 +122,7 @@ fs_visitor::emit_dummy_fs()
    wm_prog_data->num_varying_inputs = devinfo->gen < 6 ? 1 : 0;
    memset(wm_prog_data->urb_setup, -1,
           sizeof(wm_prog_data->urb_setup[0]) * VARYING_SLOT_MAX);
+   brw_compute_urb_setup_index(wm_prog_data);
 
    /* We don't have any uniforms. */
    stage_prog_data->nr_params = 0;