[tree-ssa] CCP inefficiencies

[law@redhat.com]

In message <1045151865.10505.54.camel@frodo>, Diego Novillo writes:
 >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
 >:)
Or a non-destructive simplifier.  I'm not sure which is going to make
more sense, but it's pretty clear we need something better than just
copying the nodes.


Jeff