[llvm] [AArch64][ARM] Optimize more `tbl`/`tbx` calls into `shufflevector` (PR #169748)

[via llvm-commits]

valadaptive wrote:

I've just rebased this on top of main, without rearranging the InstCombine stuff. I'm not really sure how to move that into its own module in a way that works with `BUILD_SHARED_LIBS`.

https://github.com/llvm/llvm-project/pull/169748