[Mesa-dev] [rfc] evergreen/cayman ARB_shader_image_load_store support

[Dave Airlie]

This is my first pass attempt at getting ARB_shader_image_load_store
going on evergreen/cayman hw. I've tested it on a BARTS card, and it
still fails some piglit tests, but it's mostly there and doesn't
hang the GPU at all. The fails are mostly in the invalid tests,
and some bugs in image size I need to workaround like the driver
does for samplers already (cube arrays and buffers).

Major things I'm still thinking about:

* attaching immed buffers to the resources - I couldn't think
of anywhere else that didn't involve wierd lifetime issues.

* binding the resources pretty much 3 times, once to RAT, one
binding to a PS resource, then a binding for the immediate buffer,
I think this is all correct.

* memory barrier - no idea if I'm doing the right thing.

Dave.