[llvm] [DA] remove constraint propagation and coupled/separable subscripts (PR #160924)

[Sjoerd Meijer via llvm-commits]

sjoerdmeijer wrote:

> Ok, let's remove it.
> If in the future we will need it we can always pick up bits and pieces from it.
> I will send out a patch to remove constraint propagation and the separable subscripts printing.

I was going to suggest that putting it under an option would be the polite thing to do. It could be considered a deprecation step for downstream users. This would be the best thing to do if it was easy to compartmentalise the feature, but looking at the code, that might not be so straightforward. Correctness comes first, so I think that makes it okay to remove this feature. 

> To be clear: I am happy with this direction -- it's an alternative to NewDA that I proposed on Discourse. However, I'm not sure how things should proceed in this case. For example, should we submit a separate RFC to propose removing certain features from DA? Especially if we move forward with this way, there are other parts I'd also like to remove.

I don't think we need another RFC, maybe an update to the NewDA would be appropriate. 

https://github.com/llvm/llvm-project/pull/160924