[llvm] [TableGen] Complete the support for artificial registers (PR #183371)

[Mikael Holmen via llvm-commits]

mikaelholmen wrote:

> > I've also confirmed that this patch may cause llvm-tblgen to use enormous amount of memory. For my downstream target it tried to use 340GB.
> 
> Is there a reproducer?

Not at the moment. I was (maybe naively) hoping that the fix for the EXPENSIVE_CHECKS issues would solve that too. So I'd rather wait for that fix, and if I still run out of memory then I'd have to put the effort in to try to extract a reproducer I can share.

https://github.com/llvm/llvm-project/pull/183371