[llvm] [Hexagon] Add AP register to liveins when used for frame index access (PR #188942)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

Also, adding a live-in to a single basic block is not what you want: if a register is live-in to a block, that means it's live-out from all the predecessors... which might mean the predecessors also need life-in markings.

https://github.com/llvm/llvm-project/pull/188942