In Vulkan, for some variable modes, the generated NIR will have derefs
pointing to resource index intrinsics instead of the variable. This
was letting nir_remove_dead_variables pass remove those variables,
which would lose information relevant for later passes after
spirv2nir.
Add a set to keep track of such variables and prevent them to be
removed when producing the NIR output.
Issue reported by Rhys.
Fixes: c4c9c780b1 ("spirv: Remove more dead variables")
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8706>
(cherry picked from commit 10b3eecd36)
96de6d7754