SSA IL

[Matthew Fluet]

> > 1. in the CPS version, we don't selectively include Dec.Bind's depending
> > on the VarInfo.t of the var; seems that the only thing affected by the
> > VarInfo.t's are globals -- maybe that's correct; unused Dec.Bind's are
> > dead code, and eliminated by shrinks; but globals aren't eliminated by
> > shrink.
> 
> Right.  remove-unused is the combination of three previous separate passes:
> 
> 	remove-unused-globals
> 	remove-unused-functions
> 	remove-unused-constructors

O.k.  But, no harm in having a unified simplifyStatements (that drops
unused statements) for both blocks and globals.