[llvm] [ARM][NEON] Add constraint to vld2 Odd/Even Pseudo instructions. (PR #79287)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

Why does the original code have special cases for vld2dup?  Looking at https://reviews.llvm.org/D48439, it had some special-cases specifically for VLD2... do you think the special-cases were just working around the bug in the definition of the pseudo-instruction?

Can we come up with better names for TableGen classes, so it's more clear how they're different from each other?  In particular, the important thing isn't the constraint itself; it's whether or not there's an input register.

https://github.com/llvm/llvm-project/pull/79287