[flang-commits] [flang] [flang] improve DITypeAttr caching with recursive derived types (PR #146543)

[Abid Qadeer via flang-commits]

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

Thanks for the PR. It looks good to me apart from the following 2 points.

It took me sometime to get my head around it. It will be helpful for anybody working on in the future if you can elaborate a bit more how it works. May be take the comments in `debug-cyclic-derived-type-caching-complex.f90`, adds in some more details and make that part of the commit message.

Also when I looked at this part last year, I had a quite smallish patch that removed the limitation from the `mlir` about recursive types. I can't remember why I did not pursue it  further but I think this is one thing we need to explore a bit. It may be much simpler to remove that limitation in `mlir` than to workaround it in `flang`. 

https://github.com/llvm/llvm-project/pull/146543