Change LoadOperation and StoreOperation to use MemRef

[3ulalia]

Currently, LoadOperation and StoreOperation expect the instructions to just be "load" and "store", respectively. This is not possible in current MLIR - indeed, I don't know if it was ever possible. Regardless, since the operations involve MemRef types anyway, this isn't a significant change, and just makes it compliant with modern MLIR.

(fixes the original cause of #42)

Fixes #42.

[3ulalia]

@tbennun Is there anything preventing this from being merged? It doesn't solve #42's root problem, but it does bring pymlir in line with modern MLIR.

[tbennun]

@3ulalia yes, this file is entirely outdated with its "standard" dialect, which doesn't exist anymore. There are many ops here that are no longer written this way (for example, arith.*). I anticipate other issues in the future if this is not addressed.

[tbennun]

@3ulalia The least I would ask is to move this to a separate memref.py file, just like we did with func. Thank you!

[3ulalia]

@tbennun Done; testing on the once-problematic input reveals that it works perfectly.

[3ulalia]

There are rather a lot of operations in standard.py that should be re-namespaced into memref or arith; since I expect to use those quite regularly I'll go through and fix them at some point. For now, this should suffice as a stopgap/skeletal change.

[3ulalia]

Whoops, forgot to remove the old classes from standard.py. Also mistyped a couple of fields in memref.py. @tbennun should be good to merge now.

[3ulalia]

@tbennun bump; is there anything else that needs to be changed here?

[tbennun]

@3ulalia it looks good! We are failing a few tests though.

[3ulalia]

Ah, right, that would be because we need to update the test suites to make them compatible. Will do sometime this week.