[Python-Dev] tiny optimization in ceval mainloop

[Tim Peters]

[Jeremy Hylton]
> The difference I saw with only the ticker check in ceval was only
> about 1% for pystone.  Python was always faster with the change, but
> never by much.

[Michael Hudson]
> A bunch of 0.5% improvements add up.  If there's not much cost in
> complexity, why not go for it?

There isn't, and we should <wink>.  I'd do it even if it slowed things by
1%:  reducing the test+branch count on the critical path will *eventually*
pay off.  The SET_LINENO removal worked in the other direction, and that
proved a timing mini-disaster under MSVC6.  Doing even random things in the
right direction may very well nudge MSVC6 back into the local minimum it got
knocked out of.