[llvm] [SPIRV] Handle unknown intrinsics (PR #166284)

[Dmitry Sidorov via llvm-commits]

https://github.com/MrSidims commented:

TBH I'm not the greatest fan of this llvm-spirv option. Usually when compilation comes to this point the intrinsics should be resolved by the SPIR-V generator. Also even if the intention is to have them translated back to LLVM IR it opens some uncomfortable questions regarding change of the semantics or intrinsics' postfixes for overloads (for example switch from typed to untyped pointers made some intrinsics incompatible (at least out of a box)).

On the other hand there are vendor specific intrinsics, that might not have a counterpart in the upstream LLVM or that are better not to be emulated.

How do you feel about always requiring a Prefix for --spv-allow-unknown-intrinsics? Like this we could at least create a notion, that 'native' LLVM intrinsics should be lowered to SPIR-V appropriately?

https://github.com/llvm/llvm-project/pull/166284