[llvm] [LLVM] Slay undead copysign code (PR #111269)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

I like the idea of getting rid of target libcalls, linking in runtime libraries in the same TU is still an unsolved problem. Right now the first step was to only keep symbols alive if the backend actually emits them. Next step would probably have the IR transform LLVM IR intrinsics to libcalls during IR linking and then mark them as `nobuiltin` so they don't get transformed again.

Seems weird that this doesn't handle the x86 / ppc cases. They're weird but it should just be copying a bit I would think.

https://github.com/llvm/llvm-project/pull/111269