https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38474
--- Comment #90 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Because it says that the whole range is uninitialized, so the store merging code doesn't need to care about pre-existing content in any gaps between the stored values. So say when the whole var is clobbered and then the code stores to every second bitfield, we don't need to read the old content, mask it, or with the stored bits and store that, but can just put some suitable value into the gaps (0 or all ones or whatever is best). For quadratic behavior, I wonder if we just shouldn't see how many chains are we tracking currently and if we have too many (some param), terminate all of them.
