[llvm] [AArch64][InstCombine] Eliminate redundant barrier intrinsics (PR #112023)

[David Sherwood via llvm-commits]

https://github.com/david-arm commented:

This change seems reasonable to me and looks safe, however I'm not completely sure of the performance impact. Logically you'd hope fewer dmbs means better performance and smaller codesize, but I'm not knowledgeable enough to know if effectively delaying the barrier to a later point could potentially be a net negative?

https://github.com/llvm/llvm-project/pull/112023