[llvm] [TableGen] Look up registers directly in the CodeGenRegBank in CompressInstEmitter, rather than indirecting via the name. (PR #161853)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson approved this pull request.

Looks sensible to me but someone more familiar with this code should approve.

https://github.com/llvm/llvm-project/pull/161853