[clang] [llvm] [Clang][AArch64] Implement widening FMMLA intrinsics (PR #165282)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

I'll redirect the discussion to the RFC thread...  I can go into a little more detail about what exactly I'm worried about.

https://github.com/llvm/llvm-project/pull/165282