This is another attempt to fix an issue from https://reviews.llvm.org/D57180. I have to create a new review since have no permissions to update diff in original review.
I don't think we actually need to do any additional book keeping (as suggested in D57180). Current algorithm already examines all pairs and in case of dependence will invalidate interleaving group. I think the real issue is WAW dependence (on the same iteration) is not collected by LoopAccessInfo in the first place and as a result canReorderMemAccessesForInterleavedGroups returns wrong answer. The fix is to explicitly check for WAW dependence in canReorderMemAccessesForInterleavedGroups.