[llvm] [RFC][SPIR-V] Add llvm.arbitrary.fp.convert intrinsic (PR #164252)

[Eli Friedman via llvm-commits]

https://github.com/efriedma-quic commented:

My quick impressions:

- For non-fp8 types, this adds some new functionality for int-to-fp conversions: an explicit static rounding mode.  CC @spavloff .  The rest of the conversions I think are existing conversions.
- I think, for clarity, I'd prefer to have separate intrinsics for int-to-fp, fp-to-int, and fp-to-fp; they have significantly different semantics, which is hard to describe when they're all mixed together.  (What does it mean for an fp type to saturate? Are the integers signed?  Can you do int-to-int conversions?)

https://github.com/llvm/llvm-project/pull/164252