[llvm] [RISCV] Add C/Zcf/Zcd/Zce implication rules to subtarget construction. (PR #179615)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson commented:

It seems quite unfortunate that we have to duplicate this logic three times for the different ways data is stored (string map for ISA info, feature bits and boolean variables).

I recently adapted ISA info for the new RVY+C rules and this PR shows me that I was missing another two places that need updating. It would be great if we could have the logic in one place abstracted over the data storage but that's obviously too complicated just to save a few lines of duplicate logic. But maybe we can share the logic in this PR by looking at the feature bits? 

https://github.com/llvm/llvm-project/pull/179615