Need advice on bounds checking approaches

[Jamie Lokier]

Greg McGary wrote:
> > We have kicked around the idea of two levels of RTL where we do some
> > optimizations on the higher level RTL, then drop down to a lower level
> > RTL.
> 
> Perhaps I could do that in a limited way, by adding a BP-specific
> optimization pass after loop optimization that eliminates redundant
> checks and expands "check_bounds" into primitive RTL for targets that
> don't HAVE_check_bounds.  Could that pass muster?

The general idea works ok for constant_p.  But that is removed
relatively early.

-- Jamie