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I've attached a preliminary patch for `MDLocation` as a follow-up to the RFC [1] last week. It's not commit-ready -- in particular, it squashes a bunch of commits together and doesn't pass `make check` -- but I think it's close enough to indicate the direction and work toward consensus. [1]: http://lists.cs.uiuc.edu/pipermail/llvmdev/2014-October/077715.html IMO, the files to