[clang] [clang][CodeGen] Emit atomic IR instead of libcalls for misaligned po… (PR #73176)

[Alexander Richardson via cfe-commits]

arichardson wrote:

When I first came across this code I found it quite surprising that both clang and LLVM need handling for atomic libcalls. I feel it would be a lot nicer if this could all be handled inside the LLVM backend logic. Would it also be possible to emit the unoptimized libcall from LLVM instead of Clang and always emit the atomic IR operation and let the backend deal with lowering or am I missing something?

https://github.com/llvm/llvm-project/pull/73176