Fun thought experiment: Consider how to make a language with null pointers memory-safe in LLVM. Null dereference is UB, so you have to make sure it never happens.
I think you just have to add explicit null checks everywhere before you dereference them…
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Yes, at least in theory, LLVM supports dereferencing NULL. There are probably some bugs where it's assumed that NULL cannot be dereferences, but it's nominally supported and essentially works already which is the same for a lot of sketchy things people already depend on in LLVM.