As to the point of whether it actually helps or not ...
on gcc 6.3.1 (Fedora 25), yes it does. Seems to be one "jmp *something"
per EEO_NEXT or EEO_JUMP.
on gcc 4.4.7 (RHEL 6), it makes things *WORSE*. We go from about half of
the dispatches getting routed through a common location, to *all* of them
(except one; for some odd reason the first EEO_NEXT in EEOP_NULLIF
survives as a separate jump). This seems like a bug, but there it is.
So this means we'd need some serious research to decide whether to apply
it. And I'm suspecting we'd end up with a compiler version test.
regards, tom lane
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