[llvm] [GlobalISel] Fall back for bf16 conversions. (PR #71470)

[David Green via llvm-commits]

davemgreen wrote:

OK. Sounds like that should work, so long as it was still simple to keep the types agnostic where its beneficial (load and stores and shuffles and whatnot). There are multiple types of fp8 already, two that get used in Arm, maybe more that 4 in total but I'm not sure how many will need to be supported. There is still a few bits in vector LLTs that could be used currently.

https://github.com/llvm/llvm-project/pull/71470