[ARM][MVE] Add shuffle costs for LDn and STn instructions. (#145304)

LD2 is represented in IR as deinterleave-shuffle(load), and ST2 as
store(interleave-shuffle). Whilst the shuffle would be expensive in
general for MVE (it does not have zip/uzp instructions), it should be
treated as cheap when part of the LD2/ST2 pattern. This borrows some
code from the AArch64 backed to produce lower costs. (Some of which
still shows as higher than it should - that just shows how broken the
generic shuffle costs are at the moment, they would be lower if
getShuffleCost was called directly as opposed to going through
getInstructionCost).

0 files changed, 0 insertions, 0 deletions