[llvm-dev] AtomicExpandPass and branch weighting

[Kyle Butt via llvm-dev]

I'm working on a change to the layout algorithm, and I noted that
test/CodeGen/ARM/cmpxchg-weak.ll was affected.

Normally, that would be fine, but I noted that the layout changed the
fallthrough from the success case to the failure case. I was surprised to
see that the success case isn't annotated with a branch weight by
AtomicExpandPass.cpp

Would it make sense to annotate the success case as more likely when we
expand the intrinsic to help guarantee that the success case remains the
fallthrough? Even a 2:1 or 3:2 weighting would correct the layout issue I
noted.

Thanks,
Kyle.
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