Add Float16 to supported x86 processors (#46499)

[BioTurboNick]

Reopening #51700

[rbvermaa]

There still seem to be an issue with Float16 on this branch:

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   _       _ _(_)_     |  Documentation: https://docs.julialang.org
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   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.9.3 (2023-10-14)
 _/ |\__'_|_|_|\__'_|  |  float16-sapphirerapids/a639fab579 (fork: 3196 commits, 788 days)
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julia> Float16(2.0)
Float16(0.0)

julia> versioninfo()
Julia Version 1.9.3
Commit a639fab579 (2023-10-14 13:38 UTC)
Platform Info:
  OS: Linux (x86_64-unknown-linux-gnu)
  CPU: 8 × Intel(R) Xeon(R) Platinum 8488C
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-14.0.6 (ORCJIT, sapphirerapids)
  Threads: 1 on 8 virtual cores
Environment:
  LD_FOR_TARGET = ld

This was run on a r7i instance on EC2

[vchuravy]

Could you test if backporting #51666 fixes that?

As Tim said in the PR, that's not backportable.

[fingolfin]

What's the status of this PR? Is the issue @rbvermaa reported still there? Is anyone working on it?

[BioTurboNick]

As far as I understand it, a solution pretty much has been identified - Float16 instructions probably need to be turned off on Sapphire Rapids with 1.9. So I think we should look for that to be done once the devs prioritize the next point release of 1.9.

See comment: #51482 (comment) I confirmed that it fixed the problem.