swift234

[load-store] Refactor load->load and store->load forwarding to use the same underlying method.

Both have the same form of, (Address, Value, Load). For the store->load I pass in
(SI->getDest(), SI->getSrc(), LI) and for the load->load I pass in
(OldLI->getOperand(), OldLI, LI).

This also for free lets our load deduplication support forwarding from casts.

Swift SVN r19133