[llvm] [LLVM][SVE] Add MachineInst pass to coalesce PTRUE instructions. (PR #204820)

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

> Thanks for the changes. I've left a few more comments but this looks good as far as I can tell. Have you run any benchmarks yet? My main concern is coalescing PTRUEs that are far apart.

Is this a real concern though? We mark PTRUEs as rematerialisable so if the predicate usage it high enough for the extended live range to matter then we're likely to end up just regenerating the original PTRUE, albeit with a different (but compatible) element type.

https://github.com/llvm/llvm-project/pull/204820