[llvm] [AArch64] Combine vector FNEG+FMA into `FNML[A|S]` (PR #167900)

[Damian Heaton via llvm-commits]

dheaton-arm wrote:

@gbossu
> Have you checked if we have ISel patterns in .td that could be removed after introducing these DAG combines?

Ah, I had seen some but forgot to remove them. Done :)

> Out of curiosity, have you tried to add more patterns instead of creating a SDAG-specific combiner?

Yes, though the main problem is converting the Neon vectors to scalable, though I might just be unaware of a way to do that in TableGen.

https://github.com/llvm/llvm-project/pull/167900