[llvm] [X86][APX] Avoid generating illegal MI_ND ndd instructions (PR #78233)

[Shengchen Kan via llvm-commits]

KanRobert wrote:

Conditional compare/test instructions also have same issues about instruction length limit. I will send a RFC for possible solutions one or two weeks later.

We found this bug when building Node.js with APX features. Such illegal instruction was not emitted when building SPEC17. Maybe we don't need to rush to fix it.

https://github.com/llvm/llvm-project/pull/78233