[llvm] [GlobalISel][AArch64] Legalize G_FABS and G_FNEG for SVE (PR #114784)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

In my build the GlobalISel instruction selector is at lib/Target/AArch64/AArch64GenGlobalISel.inc. We already sneak quite a bit of SVE patterns out of tablegen.

I think there are two orthogonal issues to discuss:
* How to select predicated SVE/RISCV-V instructions in general?
* How to select predicated SVE/RISCV-V instructions for GlobalISel?

The latter will a have hard tendency for tablegen patterns.

https://github.com/llvm/llvm-project/pull/114784