spirv, nir: Allow non-Aliased workgroup memory blocks

Allocate space for the aliased region first, then allocate the
non-Aliased blocks in sequence after that.

SPV_KHR_workgroup_memory_explicit_layout extension added support for
having Blocks of workgroup (shared) memory, which include layout
decoration.  For that extension all such blocks must be decorated with
Aliased.

SPV_KHR_untyped_pointers extension lifts that requirement, allowing
blocks that don't alias in workgroup memory.  They are still explicitly
laid out.

The motivation is that untyped pointers provide a different
mechanism to obtain the same effect as the Aliased blocks.  Instead of
having two Aliased variables with different types, have a single
variable and use an untyped pointer with a different type to access it.

This patch is a preparation for supporting untyped pointers.

Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34139>
3 files changed