[llvm] [AArch64] Switch to soft promoting half types. (PR #80576)

[Harald van Dijk via llvm-commits]

hvdijk wrote:

> Given this is a ABI change should we document this somewhere in the release notes?

Hi David, this is not intended to be an ABI change; code compiled with old and new Clang should be fully interoperable (provided, of course, neither or both are using `-mgeneral-regs-only`). If you tested it and found that it did change ABI, I did something wrong, and in that case I would appreciate it if you could share details so that I can fix that.

https://github.com/llvm/llvm-project/pull/80576