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

[Paul Walker via llvm-commits]

paulwalker-arm wrote:

I've been blinkered in assume a PTRUE will only be used for an instruction's general predicate and have not yet considered other uses.  I've updated the PR to reflect this original intent but I need to think some more to understand if this just works or if I need additional handling for non-general-predicate uses.

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