[llvm] [TableGen] Add a bitvector of members of CodeGenRegisterClass (PR #149122)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > you might also try using TGTimer to measure any compile-time difference for this area of code.
>
> Yes, I did try that locally. I should clean it up for submission.

#149309

https://github.com/llvm/llvm-project/pull/149122