[clang] [compiler-rt] [llvm] [SystemZ] Add support for half (fp16) (PR #109164)

[Trevor Gross via cfe-commits]

tgross35 wrote:

Looks like GCC uses option 3 https://gcc.godbolt.org/z/fM1EbK6Mn.

If you only need something to test against locally, I was able to get our s390x rust dist built against your patches https://github.com/rust-lang-ci/rust/actions/runs/13668570835. `rust-std-s390x-unknown-linux-gnu/lib/rustlib/s390x-unknown-linux-gnu/lib/libcompiler_builtins-77321e818a95f60c.rlib` has all six conversion symbols, though I haven't been able to test their correctness on the platform.

https://github.com/llvm/llvm-project/pull/109164