This profitability check was added back in rL281160, as a means to fix PR30244.
PR30244, in essence, talks about the fact that this extra sinking is causing
register allocation issues, for example in tsan. I've retried the two-stage
reproduction approach specified there, and i can not reproduce said issue.
A lot of time has passed since then. Perhaps this is no longer a problem?
Does anyone's benchmark still say this is still bad?