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

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Logikable wrote:

I believe Clang currently does not properly propagate alignment information for certain IR (e.g. atomicrmw and cmpxchg). Look at the definitions of `CreateAtomic*` in Clang. The patches in https://bugs.llvm.org/show_bug.cgi?id=27168 did not address this (thanks @MaskRay for helping me find this).

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