It was never really useful to track #iterations, though it helped during
the initial development. What we should track, in a follow up, are
potentially #updates. That is also what we should restrict instead of
the #iterations.
Different offsets can be handled by expansion rather than defaulting to
an unknown offset. Thus, [4,4] & [8,8] will result in [4, 12] rather
than [unknown, unknown].
Derive the mustprogress attribute based on the willreturn attribute
or the fact that all callers are mustprogress.
Differential Revision: https://reviews.llvm.org/D94740
While full support requires more work (see TODOs), this allows us to
handle vector writes with a single constant value properly. For now,
we can handle the same constant values stored to all elements if
everything is of a fixed size.
