[tree-ssa] CCP inefficiencies

[Diego Novillo]

On Wed, 2003-02-12 at 18:08, law@redhat.com wrote:

> It looks like a lot of the problem is the over-eager copying of nodes
> so that we can replace their operands and try to fold them.  This is
> in itself rather expensive, but it also creates lots of garbage for
> the collector to clean up.  Ugh.  
> 
Yeah.  Attribute that to Diego being a lazy bum(1).  I originally had
the idea of having some sort of undo buffer so that CCP could try the
replacement and fold, but copying the expression tree was so much easier
:)

In any case, if you implement an undo buffer for CCP, I'll be in your
debt.  Even better, implement an undo buffer for any kind of tree
rewrite we may want to use.


Diego.

(1) The original message had an alternate spelling with bum that started
with 'sh', but this is a public list.