[Mlir-commits] [mlir] [MLIR][LLVM] add metadata attrs and `llvm.named_metadata` op (PR #186703)

[Tobias Gysi]

gysit wrote:

> Usually we add LLVM import tests when adding new LLVM constructs as well, but I think this might be more complicated in this case... and the status quo doesn't get worse when the metadata is dropped. 

The cyclic metadata limitation seems ok as long as we are just exporting custom metadata from mlir to llvm. The import is indeed more tricky since we already have handling for a lot of LLVM metadata kinds. I am thus supportive to deal with the export only.

There is actually some handling for cyclic debug metadata using DIRecursiveTypeAttrInterface. This is currently limited to DISubprogram and DICompositeType though. IRC the interface could in theory be used to import arbitrary cyclic metadata (the approach is very complex though).

https://github.com/llvm/llvm-project/pull/186703