tree-ssa status (was: Re: Dropping of old loop optimizer)

[Diego Novillo]

On Thu, 2003-02-27 at 15:31, Steven Bosscher wrote:

> It would be interesting to know the total time spent in the RTL
> optimizers for mainline and branch...
> 
Yes, it would.  This is something that Jeff Law has started to do
recently.  Most of the recent compile time improvements come from
profiling the implementation and finding obvious hot spots.  We will be
doing lots of that in the coming weeks/months.

> The worst slowdown is obviously in 179.art.  What's so special about it
> that makes the branch twice as slow?
> 
No idea yet.  This is part of what still needs to be done.

> > - Investigate what can be modified/removed/simplified in the RTL
> >   backend due to the different "flavour" of RTL that the tree
> >   optimizers emit.  I suspect that we could get a big compile
> >   time boost if we could get rid of unnecessary work in the
> >   backend.  We could also find that we need some more additional
> >   passes at the tree level that we still haven't thought of.
> 
> Define "unnecessary"...
> 
If we can make simplifying assumptions in the RTL optimizers, we could
make them run faster.  This of course would need to be predicated.  As
you point out, not all the front ends go through tree-ssa.  It is still
unclear to me whether this is impossible or merely difficult.

> > So, it's a lot of work.  Will it be ready for 3.5's stage1?  I
> > don't know.  Particularly if the list of requirements grows
> > bigger.  The integration work will also be interesting.  I diff'd
> > mainline and the branch a few days ago:
> > 
> >  307 files changed, 80994 insertions(+), 4342 deletions(-)
> 
> How much of those insertions are in new files?
> 
Good point.  About 70000.


Diego.