f47faa4316
Intel hardware does a form of multisample compression that involves an auxilary surface called the MCS. When an MCS is in use, you have to first sample from the MCS with a special opcode and then pass the result of that operation into the next sample instrucion. Normally, we just do this ourselves in the back-end, but we want to expose that functionality to NIR so that we can use MCS values directly in NIR-based blorp. Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>