[ast-optimizer-branch]: tree-cfg.c insertion fixes

[Diego Novillo]

On Tue, 04 Jun 2002, Daniel Berlin wrote:

> I'm saying that if you simplify inserted statements, you need 
> to keep track of which bb's/stmt's are created by 
> simplification (which we don't do now), so that *when* we 
> start incrementally updating SSA, we can actually do it.
> Right now, this information is not tracked.
> 
Ah, yes.  Now I get it.  That brings me to the next topic.  I've
been thinking that once a function is simplified, further code
generation should always generate SIMPLE trees.

However, I can also see cases where it would be easier to
generate some arbitrary tree expression and pass it to the
simplifier to beat it into shape.  In that case, the simplifier
will have to be aware of the CFG and SSA.

There's also the eternal debate of whether we try to keep SSA
incrementally updated or re-compute from scratch.  I'm more
inclined to try and keep it incrementally up to date, but I've
had bad experiences with concurrent SSA in the past.


Diego.