[RFC] S/390: Alignment peeling prolog generation

[Robin Dapp]

> Note I was very conservative here to allow store bandwidth starved
> CPUs to benefit from aligning a store.
> 
> I think it would be reasonable to apply the same heuristic to the
> store case that we only peel for same cost if peeling would at least
> align two refs.

Do you mean checking if peeling aligns >= 2 refs for sure? (i.e. with a
known misalignment) Or the same as currently via
STMT_VINFO_SAME_ALIGN_REFS just for stores and .length() >= 2?

Is checking via vect_peeling_hash_choose_best_peeling () too costly or
simply unnecessary if we already know the costs for aligned and
unaligned are the same?

Regards
 Robin