redundant

[Matthew Fluet]

> > I ported redundant from CPS to SSA.  Seems to work on all of the
> > regressions.  Spot checking a few regressions and benchmarks, it doesn't
> > seem to do much in practice.  Is it really cleaning up after one of the
> > other simplification passes?
> 
> The reason redundant got put in was due to some output of the closure
> converter where the environment record, or components of it, were
> passed around in several places.  That may have been more relevant
> with polyvariant analyses (which are long gone).  But it still seems
> possibly relevant, especially with more aggressive flattening, which
> should reveal some fields in nested closure records that are
> redundant.

Make sense.  I've generally be running either with all the CPS passes
on or all of the CPS passes off, so without all of the SSA passes
implemented, I don't always see interactions.