[LSR] Add a flag that overrides the target's preferred addressing mode

This adds a new flag -lsr-preferred-addressing-mode to override the target's
preferred addressing mode. It replaces flag -lsr-backedge-indexing, which is
equivalent to preindexed addressing that is one of the options that
-lsr-preferred-addressing-mode accepts.

Differential Revision: https://reviews.llvm.org/D96855

GitOrigin-RevId: f78aa8b2c2ebe021b09f35a25e60a8688c757638
3 files changed