[SPIR-V] Support KHR Ray tracing's OpTerminateRayKHR and OpIgnoreIntersectionKHR

[MarijnS95]

These instructions have a different opcode than their NV counterpart, apparently for a reason: both are now terminal instructions.

There is already code in place to emit returns after the NV variant and reorder writes before it, would that be enough to support these functions normally without enforcing AcceptHitAndEndSearch/IgnoreHit to be placed at the end of a shader?

CC @jiaolu for submitting the intial changes.

[jiaolu]

okay. i will take a look.

[jiaolu]

a quick look here. new OpIgnoreIntersectionKHR/OpTerminateRayKHR are block terminator. so it is little more complicated than inserting a instruction.

[MarijnS95]

@jiaolu Correct. I attempted to make a head-start with a test and adding a new "group" for these two terminals, but am still missing a TerminatorInst. Better if someone else looks into it, I'm not familiar with this codebase at all.

[jiaolu]

made a quick pull-request, though the internal spirv validator would mis-report one validation error "OpLabel inside basic block"
though the generated spv can pass the tool spirv-val check.

[MarijnS95]

@jiolu Thanks! The code is pretty much identical to my attempt, goes to show that I ended up understanding it after all, but also ran into the same OpLabel inside basic block error which I assume is the internal validator not knowing that the block ends with that ray tracing terminal?

[ehsannas]

The SPIRV-Tools fix has been picked up by DXC, and that should fix the issue