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f757355f93
As discussed in https://bugs.llvm.org/show_bug.cgi?id=43870, this transform is missing a crucial legality check: the old (non-countable) loop would early-return upon first mismatch, but there is no such guarantee for bcmp/memcmp. We'd need to ensure that [PtrA, PtrA+NBytes) and [PtrB, PtrB+NBytes) are fully dereferenceable memory regions. But that would limit the transform to constant loop trip counts and would further cripple it because dereferenceability analysis is *very* partial. Furthermore, even if all that is done, every single test would need to be rewritten from scratch. So let's just give up.