[llvm] [IR][Float8] Add two kinds float8 IR type (PR #89900)

[via llvm-commits]

JinjinLi868 wrote:

> You're going to need a new RFC for this. Please check https://discourse.llvm.org/t/add-llvm-type-support-for-fp8-data-types-f8e4m3-and-f8e5m2/67598 and https://reviews.llvm.org/D140088 to get some background on why this has been rejected in this past.

so, we look to accept more stable data types rather than the unstable data types that come from machine learning? @nikic 

https://github.com/llvm/llvm-project/pull/89900