I’ve long wanted to be able to unify MachineValueType.h and ValueTypes.td to avoid the duplication and the hard-coding of constants that makes adding MVTs in a fork annoying for merge conflicts. Currently llvm-tblgen depends on MachineValueType.h as some of the GISel backends need to know about MVTs, but moving to a plugin-based approach could allow that to be decoupled and break the circular dependency. I don’t know how you would propose loading plugins for a statically-linked llvm-tblgen though given dlopen only works in dynamically-linked binaries on some OSes (e.g. FreeBSD), as a attractive as it seems for resolving this problem, and I doubt we want to have one full binary per backend.
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