April 10 2014 Meeting Notes

[Andy Wingo]

On Fri 25 Apr 2014 17:14, Filip Pizlo <fpizlo at apple.com> writes:

> It's just a matter of common sense that JS implementations move to
> totally-free entry/exit into try-catch and a sensible cost model for
> when you throw, regardless of how this proposal goes. The fact that
> either of these things is a performance cliff is simply a bug and it
> will likely be fixed soon, given the pace of JS VM evolution.

You are right.  I can't help but feel nervous, though, at all the
optimization stars that have to align to get good for-of performance.
Scalar replacement, now (maybe) a rework of try/finally (a gnarly
subsystem if there ever was one), and god forbid generators enter the
mix.  How long until we can honestly say "just use for-of, you'll have
great perf"?  I can't see it happening any time within the next couple
of years...

Andy