[AArch64][CodeGen] Add AArch64 support for complex deinterleaving

[NickGuy]

Added context missing from initial patch

[dmgreen]

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

22036

I think ComplxNum requires NEON, so checking for the first should be enough.

22083

There is quite a lot of debug message left here. I assume it will be removed in the final version?

llvm/test/CodeGen/AArch64/ComplexArithmetic/complex-arithmetic-f16-add.ll

1 ↗

(On Diff #442050)

These don't need to be in a "ComplexArithmetic" directory - they are already easy to identify from the file prefix.

6 ↗

(On Diff #442050)

Can you try and clean up these newlines too. There are gaps in places, but some of the functions are a little jammed together.

[NickGuy]

Addressed comments, cleaned up debug outputs, and implemented vector splitting