[llvm] [AArch64] Set predicates for FP/SIMD InstAliases (PR #79033)

[via llvm-commits]

ostannard wrote:

I think that we don't currently support `-mgeneral-regs-only` in the same way that GCC does, so that shouldn't prevent us from handling things consistently. The instructions affected by this change are a random mix, I wouldn't expect this bug to be "useful" to anyone currently using `-mgeneral-regs-only` with clang.

As for how we could implement `-mgeneral-regs-only`, I think we'd need a way to have different Subtargets for the code-generation and assembler. I don't know exactly how that would work, but it would probably be a big change.

https://github.com/llvm/llvm-project/pull/79033