[llvm] [RFC][BPF] Do atomic_fetch_*() pattern matching with memory ordering (PR #107343)

[via llvm-commits]

yonghong-song wrote:

Just made the change to support seq_cst/acq_rel/acquire/release/monotonic memory ordering. Also fixed the issue where locked insn is used when actual source expects a return value. I will continue to work on llvm BPF backend to process DW_TAG_atomic_type in the next step.

https://github.com/llvm/llvm-project/pull/107343