[Mesa-dev] radv variable pointers (nir/spirv/radv)

[Dave Airlie]

This is a bit hacky, (esp not sure about the nir bits).

When we enable variable pointers on radv we don't want to do the
offset lowering stuff, so this fixes up all the fallout from enabling
things.

The big issue is a select followed by a load, since the select
can't have a variable pointer in it's return, the next load_deref
falls over in lots of places due to lack of var, so I fixed up
a bunch of nir to avoid crashing, and fixed spirv to handle
the non lowering offset case.

This passes ./deqp-vk --deqp-case=dEQP-VK.*variable_pointers*
for me on an rx550.

Dave.