dblaikie added a comment. In D69230#1727209 <https://reviews.llvm.org/D69230#1727209>, @labath wrote:
> BTW, I was bored on the plane, so I created this proof of concept F10589216: > dense.cc <https://reviews.llvm.org/F10589216>. It needs a lot of cleanup of > course, but it demonstrates one way to generically store some extra data with > some type. It gives each type the option to define a bunch of unused (the > patch calls them "free") values (which can be useful for for Optional<>s, > DenseMaps, etc.). Also each type can say that it is able to store some extra > unrelated bits (like PointerIntPair does), and with a bit of care, one can > even nest these types arbitrarily). the main thing I haven't yet figured out > is the relationship with DenseMapInfo. Theoretically DenseMapInfo could be > implemented on top of DenseInfo, but I am still wondering whether we could > not make that a single type (trait) somehow... Neat - yeah, I'd certainly like to see something along those lines, including unification with/replacement of DenseMapInfo (though DenseMapInfo needs other things like hashing, so I'm not sure we'd necessarily want to replace them - I guess it could be a trait class with "optional" features - no reason an implementation necessarily has to have all 4 functions of DenseMapInfo - but maybe separating it would be better to express intent (DenseMapInfo builds on DenseInfo and adds the requirement for hashing and equality)). I guess there's an open question to me as to whether DenseOptional should just be the only optional we use, and it could fallback to non-dense when the type didn't provide some extra states - or should it be like DenseMap where you just can't use it and have to use std::map or similar once your type doesn't have extra states? I don't know that I feel super strongyl either way - I don't think we have lots of hypergeneric code that wants to DenseOptional<T> over some unknown T that might have spare bits of state and T that might not. Repository: rG LLVM Github Monorepo CHANGES SINCE LAST ACTION https://reviews.llvm.org/D69230/new/ https://reviews.llvm.org/D69230 _______________________________________________ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
