llvm-project

d9d9d9ad - [ARM][MVE] Add shuffle costs for LDn and STn instructions. (#145304)

[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).